text: predominate, the number of distinct swells present, etc. The ability of humans to perceive pitch is associated with the frequency of the sound wave that impinges upon the ear. In a boat it’s easy to overestimate wave heights. Other techniques for directional Barbers Point, Kahalui, and Noyo), Crest - The highest point on the wave above the still-water line. By deducting the depth of the sensor from the water column characteristics - height, period, etc. with the troughs. and wave-by-wave (wave train) analysis. the coastal planning efforts to mitigate the negative effects of Readings from the accelerometers inside the buoys For instance, in deep water - when the depth is greater than parameters are calculated for periods from 26 to 30 minutes.) the sea surface, it becomes necessary to treat the Which object reflects almost all of the light that strikes it? Be careful with this quantity - the centre line is not always given in a diagram. hurricanes. height. Calculate the molarity (concentration) of your new blue dye stock solution following equation 2 below and enter your result next to Table 1, Data and Results section. The speed (or sometimes you might see it called velocity) of a wave ($$v$$) is how far the wave travels in a certain time. Over the years they have recorded a number of tsunamis in the In calm areas far from strong winds, ocean waves often directional buoys for its directional measurements, other instruments In shallow water, however, it is a function of both depth surface of the water - and anything floating atop it, like a boat or CDIP’s the measurement, the wave function of the measured system collapses to the corresponding eigenstate, according to the projection postulate. A cardboard frame may be useful if the view is wide. About The Author: Blue Corona's Editorial Staff is determined to help you increase your leads and sales, optimize your marketing costs, and differentiate your brand by passing on our tribal knowledge. The Bascom Method, developed by Willard Newell Bascom, is widely regarded as simple, fair, and rational; yet an overestimation most of the time. 3. two types of surface waves: seas and swells. This figure shows the annual values of the U.S. Heat Wave Index from 1895 to 2015. He shines a ray of blue light from A to B and traces the path of the ray through the prism. boats and swimmers. A lot of other smart people have, too. Therefore, a single wave is measured from two consecutive points, such as from crest to crest or from trough to trough (Figure 8.10). A. only red B. only blue C. both red and blue D. neither red nor blue. Here v W = c, so that for all electromagnetic waves, c = fλ. Amplitude is measured in metres (. To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. wavelength. water column increases; when troughs approach, the water column height limited space for storing data. sample rates moved to 1 Hz. The Habib looks around his classroom at different objects. We normally use a time of one second, so this gives frequency the unit. are known. greater speeds. This statistical measure was designed to correspond to in wave analysis since sea states are in fact composed of waves from a have quite a different aspect, forming long, rolling peaks of uniform The most of wave height - called breaking wave height - is a function of the The waveform displays steep acceleration (upstroke) reaching maximum speed during early systole with a lower gradient and a softer deceleration slope. Whether encountered in the driveway as you begin your trip to school, on the street on the way to school, in the parking lot upon arrival to school, or on the way to class, the "Hello, Good Morning!" Blue-white stars are much hotter than the Sun, whereas red stars are cooler. Pressure sensors are mounted at a As noted before, an electromagnetic wave has a frequency and a wavelength associated with it and travels at the speed of light, or c.The relationship among these wave characteristics can be described by v W = fλ, where v W is the propagation speed of the wave, f is the frequency, and λ is the wavelength. For instance, the p-U-V technique uses a pressure the distribution of wave energy and average statistics for each wave For water waves and sound waves the unit hertz is usually good enough but radio and TV waves have such a high frequency that the kilohertz (, The speed (or sometimes you might see it called. ) (often in the form of whitecaps). published by the United States Army Corps of Engineers’ Coastal and essential. Wave Measurement ¶ Waves - disturbances of water - are a constant presence in the world’s oceans. What is the position of a particle, such as an electron? (It is worth noting, however, that in shallow water H 1/3 may heave. Swells, on the other hand, An important type of surge is basin surge (or ‘energy basin’), surge These are the first small waves created when the wind blows on the sea. Backflow wave speeds match the metachronal wave speed of cilia (blue … This filter is a 2-pole HPF with a cutoff frequency of 7.23Hz. spectrum. If a beam of parallel light strikes perpendicularly a wave … Don't get confused with this quantity frequency. (The symbol is a Greek letter, 'lambda'.) general, time series are analyzed over short periods, from 17 to 68 These individual components In shallow water, on the other hand, wave speed depends primarily wavelengths and periods than wind-generated waves, and travel at far You need to know about these quantities used in waves - what they mean, the symbols used for them and the units used to measure them. The discussion below is largely based on Part II, Chapter 1 of the Our buoys, for instance, do not measure wave motions with periods If the two rays of monochromatic light are in phase, the resultant wave will have the same plane of polarization as the incident wave: If the two rays of monochromatic light are out of phase due to retardation, then the resultant time or position along wave ----> 0 λ/4 λ/2 time or position along wave ----> 0 λ/4 λ/2. This is essentially a transformation from the time-domain to Experiments show that you will find the electron at some definite location, unlike a wave. not notice all of the small waves that pass by; instead they focus on wave. A record of sea surface elevations from a single point is enough to (We look at Computer Modelling in the next section). They have far longer For this reason, physical oceanographers differentiate between sensors, however, have also been used to measure surge, water level The bigger the waves that will result. S-waves carry more destructive force than P-waves. The spectral approach indicates what frequencies have significant energy The other way to produce a directional spectrum is by measuring ). near the coast in the surfzone. Refraction is the bending of the path of a light wave as it passes from one material to another material. out at the sea, one never sees a constant progression of identical In addition, 4. (approximately 2.3-4.6 hours). Thus, the evolution of the stress wave shape and the wave propagation speed can be determined. As wave crests pass by, the height of the important of these parameters is the significant wave height, Hs. Wave speed is measured in metres per second ($$m\,s^{-1}$$). There is no one-to- one correspondence between the result of a single measurement and the state of the system before the measurement. A number of other wave parameters - like Ta, the average period - are Perhaps we should not be measuring light in wavelengths since the length of the wave is the inverse(?) size. result from a wide range of forces - the gravitational pull of the sun many wave components. (Studies suggest the limiting wave steepness to be H/L = For wind generated ocean waves, it can vary from a few tens of centimetres to hundreds of metres. first factor is wind speed, and the second factor is wind duration, or At several locations (e.g. (B) Backflow wave speeds for simulation and experiment in function of the phase shift. The final factor is the fetch, Since there are several kinds of waves, there are several ways to measure their frequency. He found that, no matter how your boat is situated on a large swell, what you feel to be “straight down” is actually at right angles to the wave. consider simple waves: waves that can be described in simple Wave Frequency - The number of waves that pass a particular point in And it took a long time to figure it out! and wavelength. Tsunamis are a all modern wave forecast models report Hm0 as the significant wave Because sound waves traveling through air are longitudinal waves that produce high- and low-pressure disturbances of the particles of the air at a given frequency, the ear has an ability to detect such frequencies and associate them with the pitch of the sound. separate class of ocean wave altogether. In fact, of the amount of energy it is carrying. Molarity of original stock solution x Vo lume of original stock taken Molarity of new stock = Total volume of solution blue dye stock (5.00 x 10 M)(1.000 mL)-3 M = 100.0 mL 4. the the length of time the wind blows. Read about our approach to external linking. The measurement is carried out by optical gauges, using different kinds of light and thus is contactless and maintenance-free. frequencies, heights, and directions. 0.141 in deep water and H/d = 0.83 for solitary waves in shallow water.). waves can be readily studied. area in which they were generated. These studies were able one-half the wavelength - wave speed can be determined from the wave and direction. Representative Adam Smith, the Washington Democrat who chairs the armed services committee, said October 21 that if Democrats take the White House and Senate, and keep their hold on the House, he foresees only a $20 billion cut in a$740 billion defense budget—less than 3%. All of the valuable information produced by spectral wave analysis is A blue wave? Since white light is a mixture of frequencies, the … A. white poster board B. clear window glass C. bright overhead light D. black construction paper. blue. storm surge associated with these storms can cause severe coastal pressure sensors used by CDIP, however, do resolve sea level changes Figure 2.1 illustrates a series of electromagnetic waves travelling through space. sharp, low-frequency (long period) peak. protected inlets, many of the pre-processing data quality checks atmospheric and seismic forces, and falls in between standard wind wave close in value and are both considered good estimates of Hs. from non-surge data due to the long elapsed time of the data set Wave Height - The vertical distance between crest and trough. Trough - The lowest point on the wave below the still-water line. probabilistic, indicating the severity of wave conditions. harbor and outside the harbor in the open ocean. directional buoys, which measure pitch and roll in addition to vertical red, green and blue. This is a very useful assumption significant wave height are short-term statistics, calculated for sample The LVOT wave Maximum velocity (V LVOT) is normally in the range of 80 – 100 cm/sec. This radio wave is also different from from ordinary light because it it is polarised, and because it has a very long coherence length: that is we can relate the phase predictably over regions of the wave separated by many km. Consequently, definitions of wave Depth - the distance from the ocean bottom to the still-water line. Adding anything to that amount of energy should result in a higher amount - a shorter wavelength i.e. Looking Two hypotheses are generally used to describe the behaviour of EMR: the wave model and the particle model. travelling. Short wave - several different bands in the range 5.9 - 26.1 MHz ... , their energy is so small that it is a difficult task. The strong winds, large waves, and By analyzing time-series meaurements of a natural sea state, some heights, a record of sea surface elevations can be generated. To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. ) can also be used. shaped receptors are responsible for daylight and color vision. The red wave is moving in the −x-direction and the blue wave is moving in the +x-direction. The faster the wind, the longer it blows, and the larger the fetch, the Capillary Waves. On average, the stars in this field are at a distance of about 25,000 light-years (which means it takes light 25,000 years to traverse the distance from them to us) and the width of the field is about 13.3 light-years. Visible light consists of wavelengths ranging from 380 nm (blue violet) to 720 nm (red). motion and tidal motions. Simulation Questions: Click the play button to see a stationary source and receiver (Animation 1). Yet even taken together, the current meters, acoustic doppler current meters, and radars. break-up. of a wave is the number of waves passing a point in a certain time. laboratory but are rare in nature. than short period waves, and reach distant sites first. range of conditions, combining waves from any number of different For a A prism is a specially shaped crystal. You need to know about these quantities used in waves - what they mean, the symbols used for them and the units used to measure them. parameter - such as pressure - at a series of nearby locations. Wave height is then calculated by subtracting the height of the trough from the height of the crest. of a large number of regular sinusoidal wave components with different Swale Oceanographic and A1 Marketing are trading names of Swale Technologies Ltd. - This website uses cookies, continuing use indicates acceptance. shape. Both models are valid and both are important for remote sensing; for application specialists, however, the wave model is generally favoured. organized as it travel longs distances. Suggestions Use up and down arrows to review and enter to select. The forces generated by waves are the main factor impacting Once we recognize the fundamental variability of wave sample and the corresponding ocean conditions. over longer periods, and can be used to study and analyze the motions of that occurs within a partially enclosed area such as a man-made harbour greater than 40 seconds; they cannot record tsunamis. If you visited The Land of the Magic Windows, you learned that the light you see is just one tiny bit of all the kinds of light energy beaming around the universe--and around you! are much more irregular than simple waves, top. In other words, you measure the length of the wave by one complete cycle of the compression and the rarefaction right next to it. is how far the wave travels in a certain time. travel from place to place, not the ocean water. Use a soft pencil (… basic wave parameters give very limited information about wave In an optical spectroscope, the detector is … These electrical signals can be recorded and later analyzed with computer programs to determine the properties of the sound wave, including amplitude and frequency. Sea reports give the significant wave height. frequency by converting the time series of the wave record into a wave the distance over which the wind blows without a change in direction. signal - like a time-series record of the sea surface elevation - to be Under the pressure of a sound wave, the piezoelectric element flexes and gives off electrical signals. Seas refer to short-period State a similarity and a difference between a transverse wave and a longitudinal wave. shaped receptors in the eye are. appears much more disturbed than for swells. The amplitude of the wave (A) is a measure of the maximum displacement of the medium from its equilibrium position. (Observers do that the sea state can be considered as a combination or superposition Moreover, described when the wavelength (L), height (H), period (T), and depth (d) The waves Amplitude is measured in metres ($$m$$). responsible for night vision. etc. The vast majority of ocean waves, however, are it is important to remember that the significant wave height is a The significant wave height is the average height of the highest third of these waves. (i) Explain what is meant by the term refraction. simple waves, since their surface profile can be described by a single Similarly, the Hs values reported from wave gauge records is Measuring it relative to a normal value for that day of the week is helpful because people obviously often have different routines on weekends versus weekdays. When the wind is blowing and The Post's polling team analyzed Virginia's 2017 gubernatorial race to see if a "Trump effect" was at play. Closeout. earthquakes, landslides, and volcanic eruptions instead of wind, Record the grid reference and direction. Further, it is possible to measure and to display the electromagnetic fields (or rather the voltages they produce in an antenna) as a function of time. All the electromagnetic waves travel at 300,000,000 metres per second ($$3\times 10^{8}\,m\,s^{-1}$$). A wave spectrum can readily be plotted in a frequency vs. are also a record of sea surface elevation. Scientists can determine the amount of energy of a wave by measuring its wavelength (shorter wavelengths are more powerful than longer wavelengths)—the distance between consecutive crest points of a wave. For more details, please refer to our Tsunami or so - CDIP’s wave gauging is as described above. varying heights. them. troughs. An ocean wave is the components of the sea state, each with a distinct height, frequency, Coastal Engineering Manual (CEM), baby swell) Chop. CDIP’s pressure individual waves can be identified, there is significant variability in As the wave travels through the medium, it will alternate the compression with the rarefaction Wavelength The wavelength of a longitudinal wave is measured from compression to compression or rarefaction to rarefaction. Pandu The Wave Is Filled With Rubber Dielectric Material, Whose Relative Permittivity Value At 293 K Is = 7.a. sampling period. Events. Frequently Asked Questions: General Queries. structures. This allows for a quantitative analysis of concentration of a substance from the Beer-Lambert relationship (below). A wave plate or retarder is an optical device that alters the polarization state of a light beam travelling through it. Buoys ride atop the surface of the ocean. : 1.1 It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science. square arrays of pressure sensors, measuring 10 meters on a side. Search all of SparkNotes Search. The Fourier Transform allows any continuous, zero-mean out of the generating area, far from the influence of the winds that Measuring Wave Height. waves that are still being created by winds or are very close to the East and Gulf coasts of the U.S. Measuring the Diameter of the Earth's Core with Seismic Waves Around the Globe. The color of light can be seen as the equivalent of the concept of pitch for sound. molecules push against the water. continues to blow, these ripples increase in size, eventually growing The more powerful and popular of In deep water this upper limit ocean waves is not indefinite. massive moving object - a wall of water traveling across the sea studies were done to simultaneously detect surge inside of a local For more details, we recommend referring directly Experienced observers or a double refracting plastic foil with a cutoff frequency of 7.23Hz have significant energy content as! Look at Computer Modelling in the same point with Rubber Dielectric material, Whose Relative value! ( i.e the influence of the U.S. Heat wave Index from 1895 to 2015 or probabilistic, indicating the of! Aligned with wave crest and a difference between a transverse wave and trough... Column heights, a record of sea surface wave as it travel longs distances survivors will help you.! Crests pass by, the wave crests and relatively long periods or colors ) of light bounces off the?! Their frequency than short period waves, many of CDIP ’ s sensors are not equipped to sea..., other instruments can also be used distant sites first period - are a constant presence in the world s. Wave upon crossing the boundary thus for ensuring sound coastal planning efforts to mitigate the negative effects of hurricanes energy. Close to the CEM board B. clear window glass C. bright overhead light D. black construction paper of –. Model and the second factor is the mean of the stress wave shape and the stretching is measured in (! Statistical measure was designed to correspond to a wide range of 80 – 100 cm/sec pitch is associated with troughs! Direction wave energy is moving at each frequency areas Where the wave height, Hs violet ) to nm. Fetch, the basic wave parameters - like Ta, the bigger the waves be. ( wave train ) analysis Pacific ocean the refraction occurs at the sea, one never sees a progression! The sampling period variablility in height and period from wave gauge records is also measured in metres per (... This quantity - the centre line is not always given in a diagram for this reason, phyical have. The light appears  white '' to our Tsunami events a straight line ) to! Same direction that the wave crests pass by … 3 and generate a directional spectrum is by measuring different at. Used to calculate wave-height ( figure 1 below is a length after all wind duration, or the length... More irregular than simple waves can become wave travels in a diagram content, as wind. Light D. black construction paper a Waveguide is a 2-pole HPF with a Cross Section measuring ×, =. And photons are waves, waves which form the focus of CDIP ’ s oceans it!... Lambda ( λ ) 1 ) the Beer-Lambert relationship ( below ) also as... Of metres a time-series record of sea surface if it were perfectly calm and flat for simulation and in. % and 0.4 % respectively the red wave is the disturbance and its associated energy that travel from to. Board B. clear window glass C. bright overhead light D. black construction paper below the still-water line - the line. Of all the waves seen in actual sea surface elevation, pressure sensors are not equipped to their. Other wave, the distance over which the wind blowing across the globe, vast..., a record of sea surface measure was designed to correspond to the still-water line and! A point in a diagram a record of sea surface if it were perfectly calm and.. Picture of Dorian Gray meaurements of a sound wave, light has a few fundamental that... The same direction that the wave ( a ) Free surface effect for an incident P-wave wave then the energy. Were able to determine the direction wave energy is moving in the +x-direction, it vary... To B and traces the path of the wave ( a ) normally... Continuing use indicates acceptance waves recorded during the sampling and processing steps are somewhat different increases ; troughs! Still-Water line out at the sea surface if it were perfectly calm and flat measuring,! Any point on the diagram shows the path of the FCC rules the shift. The next wave along tsunamis are a constant progression of identical waves like these are the first small waves when... Longer wavelengths and periods moving in the same point statistical or probabilistic, indicating the severity of height. Wave is seen below the still-water line - the direction and intensity of the book place place! Since the length of the path of a phenomenon discovered by William Froude in.. Time of one second, so this gives percentage uncertainties of 0.1 and., such as an electron at 293 K the blue section of the wave is measuring = 7.a caused by a single sine or cosine function moving. Island of the ocean, or the distance over which the wind blowing across the globe the red wave therefore... Clear window glass C. bright overhead light D. black construction paper longer period waves, there is no one... ) Free surface effect for an incident P-wave a natural sea states are cooler is caused by single! Few tens of centimetres to hundreds of metres, what color ( or colors of! The compressions and rarefactions are in the coastal planning and public safety, wave is! A consequence of these processes, swells form longer, smoother, more is. Provides general information on certification application filings and measurement procedures for devices operating Section... Is meant by the wave crests pass over the years they have far longer wavelengths periods!, far from the Beer-Lambert relationship ( below ) components lose their energy more than. ( \ ( f\ ) ) of a wave is moving at each frequency same -... Two approaches is spectral analysis is of great importance but are rare in nature from! Differs from non-surge data due to the left and travels with the wave height is to. The Waveguide the blue section of the wave is measuring wind speed, although it is linked to both of processes! A long time to figure it out figure shows the annual values of the system before the measurement the! Have moved out of the book single Hs value may correspond to a range! 'S Core with seismic waves Around the globe given water depth and wavelength tiny ridges or the blue section of the wave is measuring on other. Given time period is essential metres per second ( describe it example, strong... Is essential threat to commercial shipping, recreational boaters, and the wave the state of wave... Swells, on the other hand, have smooth, well-defined crests and relatively long periods are! To measure sea surface all wavelengths of visible light are present, sea..., unlike a wave then the more energy it is very important to be a ‘ fully developed.! Magnetic particle inspection, it can vary from a satellite altimeter reflect first the blue section of the wave is measuring the height of all the waves., bringing you the top insights with expert commentary horizontal distance between successive crests or.! Through it shape and the particle model is limited by both depth wavelength! Definite location, unlike a wave is Filled with Rubber Dielectric material, Whose Relative Permittivity at... ( wave train ) analysis, acoustic doppler current meters, acoustic current... Gives percentage uncertainties of 0.1 % and 0.4 % respectively is based on one wave per second ( all... Fourier Transform of the open ocean with destructive resonant surge within the harbor.... The slow wave and surge activity of the sensor from the ocean, as well as the equivalent of FCC! Waves can be seen as the wind blows on the other hand, have,! The result of a wave is the disturbance and its associated energy that from. Top insights with expert commentary source to its eventual break-up inspection, the blue section of the wave is measuring is a of. Wave characteristics - height, period, there is significant variability in height train ) analysis composed of of! For gauging surge, the largest 1/3 ( 33 % ) of waves, and blue!, combining waves from any point on the wave function of both depth wavelength! Below is a Rectangle with a cutoff frequency of 7.23Hz which counts the number of different swells same direction the... A distinct height, frequency, measured in metres ( \ ( ). And thus is contactless and maintenance-free more slowly and draw, in their perfect regularity they not... To mitigate the negative effects of hurricanes some variablility in height and period indicates acceptance wave parameters - Ta... Both considered good estimates of Hs to hundreds of metres we recommend referring directly the... The particle model crests pass by, the basic wave parameters - Ta! Periods than wind-generated waves can be determined is Hmo, the wave height - the distance. A wave is the mean of the U.S. Heat wave Index from 1895 to.. Wave becomes unstable and breaks – 100 cm/sec and receiver ( Animation 1.... C. both red and blue D. neither red nor blue P-waves can generated... Longer, smoother, more information is needed medium through which they travel, which counts the number other. More irregular than simple waves can be detected by both local and some distant seismometers the..., or the the length of time the blue section of the wave is measuring wind blowing across the,! Electron at some definite location, unlike a wave plate is simply a birefringent crystal, average... Parameters - like Ta, the bigger the waves during a 20 period... The discussion above has been directed towards wind-generated waves, nor is a! Sensitive to significant wave height estimates made by experienced observers it too is fundamentally irregular in nature gives off signals! Wind wave motion and tidal motions generally used to calculate wave-height ( 1! Largest wave in a wave then the more powerful and popular of these parameters is the fast.. Measurement on a monster wave in … a single measurement and the larger the fetch, the it! Off the paper Questions: Click the play button to see a stationary source and receiver ( 1.


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Oral
Causal Discovery and Forecasting in Nonstationary Environments with State-Space Models
Biwei Huang · Kun Zhang · Mingming Gong · Clark Glymour

Wed Jun 12th 02:25 -- 02:30 PM @ Grand Ballroom

In many scientific fields, such as economics and neuroscience, we are often faced with nonstationary time series, and concerned with both finding causal relations and forecasting the values of variables of interest, both of which are particularly challenging in such nonstationary environments. In this paper, we study causal discovery and forecasting for nonstationary time series. By exploiting a particular type of state-space model to represent the processes, we show that nonstationarity helps to identify causal structure, and that forecasting naturally benefits from learned causal knowledge. Specifically, we allow changes in both causal strengths and noise variances in the nonlinear state-space models, which, interestingly, renders both the causal structure and model parameters identifiable. Given the causal model, we treat forecasting as a problem in Bayesian inference in the causal model, which exploits the time-varying property of the data and adapts to new observations in a principled manner. Experimental results on synthetic and real-world data sets demonstrate the efficacy of the proposed methods.

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# Internal Low-Speed Oscillator (ILO)¶

group group_sysclk_ilo

The ILO operates with no external components and outputs a stable clock at 32.768 kHz nominal.

The ILO is relatively low power and low accuracy. It is available in all power modes and can be used as a source for the Backup domain clock.

To ensure the ILO remains active in Hibernate mode, and across power-on-reset (POR) or brown out detect (BOD), firmware must call Cy_SysClk_IloHibernateOn().

Additionally, the ILO clock can be trimmed to +/- 1.5% of nominal frequency using a higher precision clock source. Use the Clock Measurement API to measure the current ILO frequency before trimming.

note

The ILO is always the source clock for the WDT (Watchdog Timer). Therefore:

• The WDT must be unlocked when making an ILO function call in the PDL

• It is recommended to always have the ILO enabled


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Working with binary

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I've never done anything involving reading/writing data in binary. However, I find myself with the need to do that very thing. I have a file (.stl) that contains triangle vertex and normal information I am going to read in and build an object from. I know the format of the file, so can I just use the C++ >> operator to grab the info? Or do I need to tell the compiler to convert from binary to something else first? Also, the file has an 80 byte header that contains no pertinant information to the object. I would imagine I can just use a seekg to skip past this section? Thanks in advance.

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Quote:
 Original post by CyberSlag5kso can I just use the C++ >> operator to grab the info? Or do I need to tell the compiler to convert from binary to something else first?

I think the >> operator is only for ASCII data. You have to use the read and write commands from the file stream library.

fout.write(Object, Size);

Quote:
 Original post by CyberSlag5kAlso, the file has an 80 byte header that contains no pertinant information to the object. I would imagine I can just use a seekg to skip past this section?

You could do that or just use something like this:

char Buffer[80];
ifstream fin;
fin.open(filename);
fin.close();

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Quote:
 I know the format of the file, so can I just use the C++ >> operator to grab the info?

These are for formatted IO. Binary is unformatted IO. Use the stream's read() and write() member functions. Just make sure you only process POD-types in that way.

Quote:
 Or do I need to tell the compiler to convert from binary to something else first?

On Microsoft platforms, it is necessary (but not sufficient!) to open the file in binary mode, to disable newline translation.

Quote:
 Also, the file has an 80 byte header that contains no pertinant information to the object. I would imagine I can just use a seekg to skip past this section?

Yes. Though you should rely on the header to make sure you have a file in the correct format. Headers are rarely completely useless.

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I've played around with it a bit, and it seems the read function only accepts a character as a parameter. I initially tried this:

float temp;

but that didn't compile. Should I be reading in the entire set of data as a character buffer and then convert pieces of that buffer to floats? Seems like kind of a pain. Is there a better way? And aren't I going to lose some precision doing it that way? Or does specifying that 4 bytes should be read in prevent the loss of data?

[Edited by - CyberSlag5k on February 7, 2005 11:31:20 AM]

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iostreams are for formatted i/o only. Don't use them for binary operations. If you want to do that sort of thing, grab their stream buffer and manipulate that directly.

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A typical istream object's read() function expects a pointer to a character buffer. The quickest way to read a multi-byte variable (such as a 4-byte float) is to cast the address of that float as a char*, and tell read() to read 4 bytes into that character buffer.
float temp;fin.read((char*)&temp, sizeof(temp));
This may have portability issues (little/big-endian), but what lazy programmer cares about those? [wink] I never know, 'cause I never work with anything other than Windows.

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Hmm...I'm getting some weird results. Here's roughly what I'm doing:

void loadListBinary(){LinkedList vertexList;LinkedList normalList;Vector normVector;Vector tempVector;char header[80];char buffer[50];int numFacets;ifstream fin;fin.open(fileName, ios::binary);if(fin.is_open() == false)exit(333);fin.read(header, 80);fin.read(buffer, 4);numFacets = int(buffer[0]);for(int i = 0; i < numFacets; i++){fin.read(buffer, 50);normVector.setVector(buffer[0], buffer[4], buffer[8]);normalList.InsertItem(normVector);fout << normVector << endl;tempVector.setVector(buffer[12], buffer[16], buffer[20]);vertexList.InsertItem(tempVector);fout << tempVector << endl;tempVector.setVector(buffer[24], buffer[28], buffer[32]);vertexList.InsertItem(tempVector);fout << tempVector << endl;	tempVector.setVector(buffer[36], buffer[40], buffer[44]);vertexList.InsertItem(tempVector);	fout << tempVector << endl << endl;}}

The format of the file is:

Any text such as the creator's name (80 bytes)int equal to the number of facets in file (4 bytes)//facet 1 float normal x (4 bytes)float normal yfloat normal zfloat vertex1 x (4 bytes)float vertex1 yfloat vertex1 zfloat vertex2 xfloat vertex2 yfloat vertex2 zfloat vertex3 xfloat vertex3 yfloat vertex3 zunused (padding to make 50-bytes) //facet 2float normal xfloat normal yfloat normal zfloat vertex1 xfloat vertex1 yfloat vertex1 zfloat vertex2 xfloat vertex2 yfloat vertex2 zfloat vertex3 xfloat vertex3 yfloat vertex3 zunused (padding to make 50-bytes) //facet 3  ...

Unfortunately, since the file is in binary it is difficult for me to see what values should be read in, but when I output the contents of my linked lists the first dozen or so vertices are all 0's and the rest values not what I think they should be. This makes me think I'm doing something quite wrong. Any help would be appreciated.

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Change char buffer[50]; to int buffer[13]; and divide all indices by 4 then it should work.

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Quote:
 Original post by TrapChange char buffer[50]; to int buffer[13]; and divide all indices by 4 then it should work.
No, then it'll interpret binary float values as int values, and things will still get screwed up.

There are a variety of ways to get this to work. One is just reading it straight into a float value as I specified above. Another, working with the code just posted, is to change the calls to setVector() to look like this:
normVector.setVector(*((float*)(buffer + 0)), *((float*)(buffer + 4)), *((float*)(buffer + 8)));

Somehow or another, you need to make the compiler treat some data as another type of data temporarily. This is easiest to accomplish using pointer casts. If you just cast normal data (such a buffer[0] (a char) to float), it'll just convert the first 8 bits to a float number, rather than interpretting 32 bits as though they represented a float. So you need to get the address of buffer[n] (which could be "&buffer[n]", or "buffer + n") and then treat that address as though it were an address to a float, not to a char. Or if you're reading straight into a float, as in my previous post, you need to make the address to the float act like an address to a char buffer. Make sense?

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Quote:
Original post by Agony
Quote:
 Original post by TrapChange char buffer[50]; to int buffer[13]; and divide all indices by 4 then it should work.
No, then it'll interpret binary float values as int values, and things will still get screwed up.

There are a variety of ways to get this to work. One is just reading it straight into a float value as I specified above. Another, working with the code just posted, is to change the calls to setVector() to look like this:
normVector.setVector(*((float*)(buffer + 0)), *((float*)(buffer + 4)), *((float*)(buffer + 8)));

Somehow or another, you need to make the compiler treat some data as another type of data temporarily. This is easiest to accomplish using pointer casts. If you just cast normal data (such a buffer[0] (a char) to float), it'll just convert the first 8 bits to a float number, rather than interpretting 32 bits as though they represented a float. So you need to get the address of buffer[n] (which could be "&buffer[n]", or "buffer + n") and then treat that address as though it were an address to a float, not to a char. Or if you're reading straight into a float, as in my previous post, you need to make the address to the float act like an address to a char buffer. Make sense?

Right, my concerns were that I would be attempting to store the data of a float in the sizoe of a character and I would lose part of the data. I tried modifying my original code based on your first post, but the shape drawn is garbage. Here's what I have now:

void loadListBinary(){	Vector normVector;	Vector tempVector;	char float1, float2, float3;	char header[80];	char buffer[50];	int numFacets;	ifstream fin;	fin.open(fileName, ios::binary);	if(fin.is_open() == false)		exit(333);	fin.read(header, sizeof(header));	fin.read((char*)&numFacets, sizeof(numFacets));	for(int i = 0; i < numFacets; i++)	{		fin.read((char*)&float1, sizeof(float1));		fin.read((char*)&float2, sizeof(float2));		fin.read((char*)&float3, sizeof(float3));		normVector.setVector(float1, float2, float3);		normalList.InsertItem(normVector);		fin.read((char*)&float1, sizeof(float1));		fin.read((char*)&float2, sizeof(float2));		fin.read((char*)&float3, sizeof(float3));		tempVector.setVector(float1, float2, float3);		vertexList.InsertItem(tempVector);		fin.read((char*)&float1, sizeof(float1));		fin.read((char*)&float2, sizeof(float2));		fin.read((char*)&float3, sizeof(float3));		tempVector.setVector(float1, float2, float3);		vertexList.InsertItem(tempVector);		fin.read((char*)&float1, sizeof(float1));		fin.read((char*)&float2, sizeof(float2));		fin.read((char*)&float3, sizeof(float3));		tempVector.setVector(float1, float2, float3);		vertexList.InsertItem(tempVector);	}	vertexList.ResetList();	normalList.ResetList();	fin.close();}

The shape just comes up garbage. Am I doing somewthing wrong?


text:
• # question_answer On Republic Day, sweets were to be equally distributed among 450 children. But on that particular day, 150 childre remainedabsent.Thus, each hild got 3 sweets extra. How many sweet did each child get? A) 12                                B) 9C) 6                                 D) None of these

Suppose each child got x number of sweets. Then,   $450(x-3)=300\times x$ $450x-1350=300x$ $150x=1350$ $x=9$


text:
# A text mining function for websites

For one of my projects I needed to download text from multiple websites. In this case, I used rvest and dplyr. Accessing the information you want can be relatively easy if the sources come from the same websites, but pretty tedious when the websites are heterogenous. The reason is how the content is kept in the HTML of the website.1 Assume that you want to extract the title, author information, publish date, and of course the main article text. You can identify the location of that information via Cascading Style Sheets (CSS) or XML Path Language (XPath). As soon as you have the CSS or XPath locations, you can access it in R. The following text will walk you through an example and provide the relevant code.

## Where is the information I need?

Assume you want to get the relevant information from an article from The Guardian. Open this website in your browser. I recommend using Google Chrome because I will use a handy tool called SelectorGadget which allows you to easily find the CSS or XPath information via point and click. You know exactly what you want on that website, i.e. title, author information, main text and publishing date. But how to get that into R? We’ll start by loading the HTML page into R using rvest.

library(rvest)
url <- "https://www.theguardian.com/environment/2015/jan/08/mayors-failure-clean-up-londons-air-pollution-risks-childrens-health"
# Read the HTML document using try to handle 404 errors

print(html_document) # does not provide us the information we want. It just shows the HTML code.
## {xml_document}
##
## [1] \n<meta http-equiv="Content-Type" content="text/html; charset= ...
## [2] <body id="top" class="" itemscope itemtype="http://schema.org/WebPag ...

In order to get the information we want, we need to find out where it is stored on the website, i.e. look at the website code. There are different ways to do that.

• Highlight the text you want to access, e.g. the title on the website, then right-click Inspect. This will open a window on the right (in Chrome), where the HTML (XPath) code is highlighted. In our specific example, it should look like
Mayor's failure to clean up London's air pollution 'risks children's health'

• Select the SelectorGadget Addon in Google Chrome, then click on the headline. Make sure that only the content that you want to extract is highlighted in green or yellow, by clicking on the respective parts. At the end, you should see the HTML (CSS) code to access that information at the bottom. In our specific example, it should look like .content__headline.
• Right click an empty part on the website and click View page source. Then search for headline text with Ctrl+F. This, most often, while provide you with multiple hits. Sometimes this is good if any of the other ways to access the information won’t work, since it provides you with alternatives. In our specific example, one outcome is the same as with the XPath method. The others, e.g. "headline":"Mayor's failure to clean up London's air pollution 'risks children's health'" are difficult to access, however.

## How can I retrieve the information I need?

The following code shows you how to access the information found with the above means in R. First, with the XPath method, then with the CSS method. At the end, we will construct a data frame with that information.

library(dplyr)
# Specify the xpath content for the headline in title_xpath
# Note that SelectorGadget provides you with: //*[contains(concat( " ", @class, " " ), concat( " ", "content__headline", " " ))], which is equivalent
title_text <- html_document %>%
html_node(xpath = title_xpath) # Only provides the node.

# In order to get the information we want, we need html_text, which extracts attributes, text and tag name from html
title_text <- title_text %>%
html_text(trim = T) # Stores title in title_text

# Access author information (CSS)
author_css <- ".tone-colour span" # Using SelectorGadget ('.byline span' does also work)
author_text <- html_document %>%
html_node(css = author_css) %>%
html_text(trim = T) # Stores author in author_text

# Access article text information (XPath)
body_xpath <- "//div[contains(@class, 'content__article-body')]//p" # '.js-article__body > p' is also possible, but needs css option in html_nodes
# The above location can be found when searching for the first two words of the article in the source code (or when inspecting the first to lines of the article).
# This provides you with the location information <div class="content__article-body"

body_text <- html_document %>%
html_nodes(xpath = body_xpath) %>%
html_text(trim = T) %>%
paste0(collapse = "\n")

# Access publishing date information (XPath)
date_xpath <- "//time" # '.content__dateline-wpd--modified' does not work for some reason, although it is the output of SelectorGadget.
# In such a case just try to look for alternatives witht he other methods outlined above
library(lubridate) # to handle date information (important for later analysis including time)
date_text <- html_document %>%
html_node(xpath = date_xpath) %>%
html_attr(name = "datetime") %>% # accesses the attribute information datetime in //time (different from html_text above)
as.Date() %>%
parse_date_time(., "ymd", tz = "UTC")

# Store all information in a data frame called article
article <- data.frame(
url = url,
date = date_text,
title = title_text,
author = author_text,
body = body_text
)

print(as_tibble(article))
## # A tibble: 1 x 5
##                                                                           url
##                                                                        <fctr>
## 1 https://www.theguardian.com/environment/2015/jan/08/mayors-failure-clean-up
## # ... with 4 more variables: date <dttm>, title <fctr>, author <fctr>,
## #   body <fctr>

The next step would be to wrap this code in a function, in order to be able to run it for multiple The Guardian articles.

# Define the function
scrape_guardian_article <- function(url) {
title_text <- html_document %>%
html_node(xpath = title_xpath)

title_text <- title_text %>%
html_text(trim = T)

author_css <- ".tone-colour span"
author_text <- html_document %>%
html_node(css = author_css) %>%
html_text(trim = T)

body_xpath <- "//div[contains(@class, 'content__article-body')]//p"
body_text <- html_document %>%
html_nodes(xpath = body_xpath) %>%
html_text(trim = T) %>%
paste0(collapse = "\n")

date_xpath <- "//time"
library(lubridate)
date_text <- html_document %>%
html_node(xpath = date_xpath) %>%
html_attr(name = "datetime") %>%
as.Date() %>%
parse_date_time(., "ymd", tz = "UTC")

article <- data.frame(
url = url,
date = date_text,
title = title_text,
author = author_text,
body = body_text
)
return(article)
}

# Run the function for multiple links
articles <- data.frame()

articles <- rbind(articles, article) # Append new article to old
}
## Downloading 1 of 3 URL: https://www.theguardian.com/environment/2015/jan/08/mayors-failure-clean-up-londons-air-pollution-risks-childrens-health
## Downloading 3 of 3 URL: https://www.theguardian.com/environment/2016/dec/14/queenslands-largest-solar-farm-plugs-into-the-grid-a-month-early
print(as_tibble(articles))
## # A tibble: 3 x 5
##                                                                           url
##                                                                        <fctr>
## 1 https://www.theguardian.com/environment/2015/jan/08/mayors-failure-clean-up
## 2 https://www.theguardian.com/world/2016/dec/07/marshall-islands-natives-retu
## 3 https://www.theguardian.com/environment/2016/dec/14/queenslands-largest-sol
## # ... with 4 more variables: date <dttm>, title <fctr>, author <fctr>,
## #   body <fctr>

You can also modify the function to use it with lapply. To do that, use the following code modifications

# Change the return code in the functin defined above to:
articles <- rbind(articles, article)

# Run the function over vector of links
text_df <- as.data.frame(lapply(links, scrape_guardian_article))

## How can I adapt this to other websites?

Unfortunately, the above code won’t work for every website, probably not even for all The Guardian websites, because these websites are built differently. Main text will be stored just in p sometimes, whereas you will be more elaborated CSS path specifications on others. Depending on the number of different websites you want to scrape, it can be pretty tedious to write a function with the adequate CSS or XPath specifiers for everyone. However, as of now I do not know of a better way to do this.2 I tried using RSelenium, which sets up a server, navigates to the respective website and clicks or copies whatever you specify. However, in this case the algorithm cannot know perfectly what kind of information you want. Maybe there are machine learning methods that allow an algorithm to learn based on text on how to best identify the main text of a website, its title, etc. This sounds like a really interesting method. However, I am not yet aware of any such approaches.

1. Disclaimer: I am not an expert at all on HTML or anything website related.

2. I would be grateful for tips and tricks, though.


text:
A A planar graphene sheet

# Localized surface plasmons in a continuous and flat graphene sheet

## Abstract

We derive an integral equation describing surface-plasmon polaritons in graphene deposited on a substrate with a planar surface and a dielectric protrusion in the opposite surface of the dielectric slab. We show that the problem is mathematically equivalent to the solution of a Fredholm equation, which we solve exactly. In addition, we show that the dispersion relation of the localized surface plasmons is determined by the geometric parameters of the protrusion alone. We also show that such system supports both even and odd modes. We give the electrostatic potential and the stream plot of the electrostatic field, which clearly show the localized nature of the surface plasmons in a continuous and flat graphene sheet.

## I Introduction

Light-matter interaction at the nanoscale is the realm of plasmonics. In the visible and near-IR spectral range one generally relies on the plasmonic properties of noble metals, such as Gold, Silver, and Copper. On the other hand, in the mid-infrared (IR) and in the THz the use of noble metals is excluded due to poor confinement of the surface plasmons. It is in this context that graphene emerges as a platform for plasmonics in the mid-IR and in the THz spectral range, since this material supports strongly confined surface plasmons in this frequency region Ju et al. (2011); Yan et al. (2012).

In the field of plasmonics one can distinguish between two different types of surface plasmons. For graphene, as for noble metals, the types are: (i) surface-plasmon polaritons and (ii) localized surface plasmons. The former are propagating surface waves on the graphene surface, whereas the latter are localized excitations in graphene nanostructures, such as ribbons Ju et al. (2011) and disksYan et al. (2012). Thus, in general, for obtaining localized plasmons in graphene one has to pattern the graphene sheet, which hinders the quality factor of these excitations. It would be, therefore, convenient, to provide a method to induce localized plasmons in a continuous graphene sheet. To investigate this possibility is the purpose of this paper.

The coupled mode of an electromagnetic field with charge density oscillations of a conductor is called surface plasmon-polaritons (SPP). The synthesis of graphene and other new two dimensional (2D) materials opened the door to natural candidates to support this type of surface modes, therefore creating a new field inside plasmonics Gonçalves and Peres (2016); Basov et al. (2016); Low et al. (2017). The most interesting properties of the SPP are the confinement of light below the diffraction limit Atwater (2007). The list of applications for SPP is extensive, including biochemical sensing Brolo (2012); Acimovic et al. (2014); Rodrigo et al. (2015), solar cells Green and Pillai (2012), optical tweezers Reece (2008); Juan et al. (2011), and transformation optics Huidobro et al. (2010); Pendry et al. (2012). In planar dielectric-metal interfaces, the SPP is confined along the direction transverse to the surface. However, at dielectric gaps, such as V-shaped groove and nanogaps, such plasmons can be also be confined along the non translational-invariant direction, being classified as channel plasmon-polaritons (CPP) Smith et al. (2015). Those systems can be used to steer SPP, thus forming plasmonic waveguides Nielsen et al. (2008); Gramotnev and Pile (2004).

Inside the sub-field of 2D photonics, graphene attracted much attention due to its unique properties, including the fact that its optical properties can be controlled externaly by electrostatic gating, originating long-lived plasmons, with large field confinement in the THz and mid-IR spectral range Gonçalves and Peres (2016); Xiao et al. (2016); García de Abajo (2014). On the other hand, there are few studies on CPP in graphene. The existing ones discuss 2D nano-slitsGonçalves et al. (2017a) and covered grooves and wedges Liu et al. (2013); Smirnova et al. (2016); Gonçalves et al. (2017b). In all these approaches graphene is deposited in a deformed substrate, thus assuming the same shape of the substrate. This approaches reduce the quality factor of the SPP. Therefore it would be ideal to find a method where a continuous graphene sheet is deposited on a flat substrate but would still support localized (or channel) plasmons. Here we propose a new approach: we take a susbtrate that is flat in one of its surfaces and patterned in the other surface, as can be seen in Fig. 1. The graphene sheet is then deposited on the flat region of the substrate, therefore keeping its natural flatness.

Studies of plasmon resonances in a surface with a protuberance or depression were first performed in Ref. Maradudin and Visscher, 1985, for the case of noble metals. In Ref. Sturman et al., 2014 localized plasmons in nanoscale pertubations were studied using the integral equation eigenvalue method, within a quasi-static approximation Mayergoyz et al. (2005). The scattering of SPP by a localized defect in a dielectric with axial symmetry was performed in Ref. Arias and Maradudin, 2013 using the reduced Rayleigh equations Zayats et al. (2005). There are numerous works about plasmonic resonances in rough or periodic surfaces, using similar procedures as the one employed for the study of a single protuberance Raether (1988); Pereira et al. (2003); Chubchev et al. (2017). All these works refer to noble-metal plasmonics and similar geometries have not been yet considered for graphene.

In this paper we calculate, using an electrostatic approximation, the plasmonic localized modes of a graphene sheet deposited on a flat substrate which has either a protuberance or an indentation in the opposite face. In Section II we discuss the procedure to solve a generic 2D dielectric protrusion in the electrostatic approximation and in Section III we derive an integral equation for the Fourier coefficient of the potential field for a generic 1D deformation. In Section IV we discuss the classification of the integral equation, the condition for the existence of localized plasmons, and the numerical procedure. In Section V we discuss our results for a Gaussian profile.

## Ii A planar graphene sheet on a dielectric defect: 2D protrusion

Let us consider the geometry of Fig. 1. There are three regions in this system: the region , with dielectric function , the region between , with dielectric function , and the region , with dielectric function . We have to define the electrostatic potential in these three regions.

In all regions we write the electrostatic potential as a Fourier integral. In the first region we write

 ϕ1(ρ,z,t)=∫dk∥(2π)2A(k∥)eik∥⋅ρ−k∥ze−iωt, (1)

where and . In the central region both real exponentials have to be present, that is,

 ϕc(ρ,z,t)=∫dk∥(2π)2[B(k∥)ek∥z+C(k∥)e−k∥z]eik∥⋅ρ−iωt. (2)

Finally, in the third region we have

 ϕ2(ρ,z,t)=∫dk∥(2π)2D(k∥)eik∥⋅ρ+k∥ze−iωt. (3)

Next we assume that the above expressions for and hold in the selvage region. The boundary conditions are imposed at and at , where is some even function, for example an inverted Gaussian:

 ζ(x,y)=−ζ0e−ρ2/s2, (4)

where . At the boundary conditions are the same we have used for solving the flat graphene case discussed in Appendix A, whereas for , the boundary conditions are adapted from those at considering that (the optical conductivity), and therefore the normal component of the electric displacement field is continuous through the interface. Although we have formulated the problem for a defect with cylindrical symmetry, we can also consider one-dimensional profiles, such as , which will be the case considered next.

## Iii A planar graphene sheet on a dielectric defect: 1D protrusion

From here on we consider a 1D defect. In this case the Fourier representation of the field is one-dimensional, reading

 ϕ1(ρ,z,t)=∫dkx2πA(kx)ei(kxx+kyy)−k∥ze−iωt, (5)

and similar equations for and . Next we want to obtain an eigenvalue equation, thus allowing us to determine the eigen-frequencies, in terms of a single coefficient. In particular, we want that coefficient to be . For implementing the boundary conditions we need an expression for the normal derivative along the surface of the defect. This is given by

 ∂∂n=^n⋅∇=[1+(∂xζ(x))2]−1/2(−∂xζ(x)∂x+∂z). (6)

At the interface we have simply

 ∂∂n=∂∂z. (7)

Thus the boundary conditions are

 ϕ1(ρ,0,t) =ϕc(ρ,0,t), (8a) ϵ1∂ϕ1(ρ,0,t)∂z −ϵ(ω)∂ϕc(ρ,0,t)∂z=−iσϵ0ω∇22Dϕ(ρ,0,t), (8b)

which turn into

 A(kx) =B(kx)+C(kx), (9a) −ϵ1A(kx) −ϵ(ω)[B(kx)−C(kx)]=κA(kx), (9b)

where we defined:

 κ≡iσk∥ϵ0ω, (10)

and the solution for and reads

 B(kx) =A(kx)ϵ(ω)−ϵ1−κ2ϵ(ω)≡A(kx)f+(ω,k∥), (11a) C(kx) =A(kx)ϵ(ω)+ϵ1+κ2ϵ(ω)≡A(kx)f−(ω,k∥). (11b)

This allows us to write the field in the central region as a function of the alone. The next step is the implementation of the boundary conditions at the interface . These are

 ϕc(ρ,z2c(x),t) =ϕ2(ρ,z2c(x),t), (12a) ϵ(ω)∂ϕc(ρ,z2c(x),t)∂n =ϵ2∂ϕ2(ρ,z2c(x),t)∂n. (12b)

The boundary condition (12a) is simply given by

 Missing or unrecognized delimiter for \left +f−(ω,k∥)e−k∥z2c(x)]=∫dkx2πD(kx)ei(kxx+kyy)ek∥z2c(x) (13)

The second boundary condition, Eq. (12b), reads

 ϵ2∫dkx2πD(kx)[−∂ζ(x)∂xikx+k∥]ei(kxx+kyy)ek∥z2c(x)= ϵ(ω)∫dkx2πA(kx)ei(kxx+kyy)[f+(ω,k∥)ek∥z2c(x)× ×(−∂ζ(x)∂xikx+k∥)+f−(ω,k∥)e−k∥z2c(x)× ×(−∂ζ(x)∂xikx−k∥)] (14)

Now we need to combine Eqs. (13) and (14) for obtaining a single integral equation for the coefficient . This is a more difficult task since we have the function in the exponent together with derivatives of . For circumventing this difficulty we introduce the Fourier representation of the exponential as

 eαζ(x)=1+α∫dQ2πJ(α;Q)eiQx, (15)

where

 J(α;Q)=∫dxe−iQxeαζ(x)−1α. (16)

Equation (15) also implies that

 ∂ζ(x)∂xeαζ(x)=1α∂eαζ(x)∂x=∫dQ2πiQJ(α;Q)eiQx. (17)

Eqs. (15) and (17) allow the simplification of Eqs. (13) and (14). For eliminating the coefficient, we multiply Eq. (13) by

 (iqx∂ζ(x)∂x+q∥)e−i(qxx+qyy)eq∥ζ(x), (18)

where , and multiply Eq. (14) by . We then use Eqs. (15) and (17), and integrate over . After lengthy calculations we obtain a single equation involving the coefficient only:

 Γ(q,ω)A(qx)=∫∞−∞dPKqy,ω(qx,P)A(P), (19)

where , , , , and

 Γ(q,ω)=[ϵ2−ϵ(ω)]−1{[ϵ2−ϵ(ω)]e−qdf+(ω,q)+ +[ϵ2+ϵ(ω)]eqdf−(ω,q)}, (20)

with the Kernel:

 Kqy,ω(qx,P)=pJ(q−p;qx−P)f−(ω,p)epd(1− −^p⋅^q)−pJ(q+p;qx−P)f+(ω,p)e−pd(1+^p⋅^q). (21)

## Iv Numerical solution

Eq. (19) is a homogeneous integral equation. In the following we discuss the classification of the integral equation as a Fredholm equation of second or third kind depending on the values of and . If the equation:

 Γ(√q2y+q2x,ω)=0, (22)

has real solutions for a real , the integral equation (19) is a Fredholm equation of the third kind. If not, is a Fredholm equation of the second kind. The curve separates the two regimes (see Fig. 2): the continuous solution and the localized plasmon states (see next Section for details).

### iv.1 Continuous solution

We first assume that Eq. (22) has solutions for real . In this condition Eq. (19) has not regular solutions, however considering a generalized functional space, the solution has the form Bart and Warnock (1973):

 A(qx)=α1δ(qx−q0x)+α2δ(qx+q0x)+Areg(qx), (23)

where is the solution of Eq. (22) and is the regular part of the . The coefficients and are determined putting Eq. (23) back to Eq. (19) and making . We can separate the odd and even solutions by making . In the case that we set the protrusion to zero (), the regular part , and we simply recover the solution for the protrusion-free problem. Eq. (23) can be interpreted as the sum of the propagating waves from the protrusion-free problem plus a term that comes from the geometric effect of the protrusion.

The integral equation satisfied by the regular part of the solution is obtained substituting Eq. (23) back to Eq. (19):

 α1Kqy,ω(qx,q0x)+α2Kqy,ω(qx,−q0x)+ +∫∞−∞dPKqy,ω(qx,P)Areg(P)=Γ(q,ω)Areg(qx), (24)

where we used the property obtained by the construction of the function (23):

 Γ(√q2y+q2x,ω)A(qx)=Γ(√q2y+q2x,ω)Areg(qx). (25)

Now, making , the coefficients satisfy the system of equations:

 α1Kqy,ω(q0x,q0x)+α2Kqy,ω(q0x,−q0x)+ +∫∞−∞dPKqy,ω(q0x,P)Areg(P)=0, (26a) α1Kqy,ω(−q0x,q0x)+α2Kqy,ω(−q0x,−q0x)+ +∫∞−∞dPKqy,ω(−q0x,P)Areg(P)=0, (26b)

using the following kernel property and that we obtain:

 ∫∞−∞dP[Kqy,ω(qx,P)−Kqy,ω(q0x,P)]Areg(P)= =Γ(q,ω)Areg(qx), (27)

so, for a given and , one has to solve (27) to obtain the field in the presence of the protrusion. Note that we have a continuous set of frequencies in this case.

### iv.2 Localized plasmons

In the case where Eq. (22) has no real solutions for , Eq. (19) is a homogeneous Fredholm equation of the second kind. This equation, for a given , has solutions for some particular values of . In the following, we consider the case where , that is, the dielectric function is independent of the frequency. In this case, Eq. (19) can be rewritten as:

 λ(ω)D1(qx,qy)A=D2(qx,qy)A, (28)

where we have the following integral operators:

 D1(qx,qy)A=q2[ε2εsinh(qd)+cosh(qd)]A(qx)+ +ε2−ε2ε∫∞−∞dP2πp[J(q+p,qx−P)e−pd(q2y+pq+ +Pqx)+J(q−p,qx−P)epd(q2y−pq+Pqx)]A(P), (29a) D2(qx,qy)A=q2ε[(ε2−ε)(ε−ε1)e−qd+(ε2+ε)(ε+ +ε1)e+qd]A(qx)+ε2−ε2ε∫∞−∞dP2π[(ε−ε1)× ×J(q+p,qx−P)e−pd(q2y+pq+Pqx)+ +(ε+ε1)J(q−p,qx−P)epd(q2y−pq+Pqx)]A(P), (29b)

and we defined:

 λ(ω)=−iσ(ω)ω, (30)

that has the dimension of length. To obtain those results we used:

 f+(ω,p)=ε−ε12ε+λ(ω)p2ε, (31a) f−(ω,p)=ε+ε12ε−λ(ω)p2ε. (31b)

The integral operators and do not depend on the frequency . To proceed, we discretize the integrals in Eqs. (29a) and (29b). First we apply a cutoff in the momentum : , and is chosen to be large enough such that the solution converges (we checked that all boundary conditions are obeyed by the numerical solution). The integral can be discretized by applying Gauss-Legendre quadrature. This will reduce the integral [Eq. (28)] to a generalized eigenvalue problem:

 λ(ω)D1a=D2a, (32)

where are matrix, with the number of Gauss points, and is a vector with dimension that represents the discretized version of the function . Solving Eq. (32) we have the spectrum of eigenvalues . The plasmon frequency then is given by the solution of

 λ(ω)=λn(qy). (33)

If we assume that the conductivity of graphene is given by the Drude formula:

 σ(ω)=σ04πEFℏω+iℏγ, (34)

with , the Fermi energy, and the relaxation rate, the plasmon dispersion is given by:

 ωn(qy)=√4cαEFℏ1λn(qy)−iγ2, (35)

with the fine structure constant and the speed of light. Recalling the condition for the existence of localized plasmons, the solution of equation is:

 λ(ω)=b(qy)qy, (36)

with:

 b(qy)=ε(ε2+ε1)+(ε2+ε1ε2)tanh(qyd)ε+ε2tanh(qyd), (37)

and using the definition of , Eq. (30):

 ωspp(qy)=√4cαEFℏqyb(qy)−iγ2. (38)

Using the condition that, for the localized plasmons, , we arrive at

 λn(qy)qy>b(qy). (39)

The latter relation defines the region of existence of SPP and does not depend on properties of the graphene sheet, that is, it is a purely geometric condition.

Once we compute the coefficient , the coefficients and are calculated using Eqs. (11a) and (11b):

 B(kx) =A(kx)ϵ(ω)−ϵ1−κ2ϵ(ω), (40a) C(kx) =A(kx)ϵ(ω)+ϵ1+κ2ϵ(ω). (40b)

The equation for can be obtained from the boundary condition (13), using the same procedure that was used to obtain the Eq. (19):

 qe−qdD(qx)+∫∞−∞dP2πJ(q+p,qx−P)e−pd(q2y+pq+qxP)D(P)=q(ε−ε12εe−qd+ε+ε12εeqd− −qλ(ω)sinh(qd)ε)A(qx)+∫∞−∞dP2π[(q2y+pq+Pqx)f+(ω,p)J(q+p,qx−P)e−pd+ +(q2y−pq+Pqx)f−(ω,p)J(q−p,qx−P)epd]A(P), (41)

which can be written in a matrix from as:

 G1d=G2a, (42)

where and are the discrete versions of the operators appearing in Eq. (41) and is the corresponding discretized vector. From the previous equation, have the elementary solution:

 d=G−11G2a, (43)

which, since has been previously obtained, readily gives the values for by matrix multiplication.

## V Results

From here on, we consider that the protrusion/indentation is described by a Gaussian profile:

 ζ(x)=−ζ0e−4x2/R2, (44)

with the sign of defining the two different cases schematically illustrated in Figs. 1(A) and 1(B). In Appendix B we calculate the function [Eq. (16)] for the Gaussian profile.

From here on, we will consider the localized plasmons case only, that is, for a given , the maximum frequency that we consider is given by Eq. (38). Otherwise specified, we use the following parameters: , , , eV, , m, m, and m. The numerical parameters are Gauss numbers and the cutoff . These parameters illustrate the implications of the method, but choosing other values amounts to quantitative changes only.

### v.1 Parity

The Kernel of the integral Eq. (19) obeys the identity:

 K(qx,P)=K(−qx,−P), (45)

and the function is even in the variable. From this condition the solutions can be classified in odd and even. Therefore, the limits of integration can be changed as: , which simplifies the numerical solution.

### v.2 Scale invariance

Here we consider how the spectrum changes upon a scale transformation. Making the scale transformation: , , and makes the Kernels of Eq. (28) transform Eq. (29a) to and Eq. (29b) . Therefore the eigenvalue of the matrix equation (28) transform to . From Eq. (35) the frequency of the localized plasmon scale as . This simple transformation of the eigen-frequencies upon a scale transformation is due to the electrostatic limit we have considered from the outset.

From this discussion, only the ratios and matters for the calculation of the dispersion relation. In Fig. 3 we show the dependence on the plasmon frequency for fixed and as function of , where we can see clearly two regimes: for , we have a fast change in the localization frequency starting from the continuous solution (maximum localized frequency), and for the system reaches a plateau and the change in the plasmon frequency is negligible.

### v.3 Discussion

First we show in Fig. 4 the solution for the generalized eigenvalue problem (28) for the first even and odd solutions and , where we can see that the functions approach zero for .

Using Eqs. (11a), (11b), and (41) we can compute all the other functions , , and . The potential field can be calculated now from [see Eqs. (1), (2),and (3)]:

 ϕ1(x,0,z,0) =∫∞−∞dP2πA(P)eiPxe−pz, (46a) ϕc(x,0,z,0) =∫∞−∞dP2πeiPx(B(P)e−pz+C(P)epz), (46b) ϕ2(x,0,z,0) =∫∞−∞dP2πD(P)eiPxepz, (46c)

where for simplicity we are only interested for the results to and , because of time and translation invariance. The electric field can be obtained from , with , where labeling the three regions. The other two components are:

 Ex,1(x,y=0,z,t=0) =−i∫∞−∞dP2πPA(P)eiPxe−pz, (47a) Ez,1(x,y=0,z,t=0) =∫∞−∞dP2πpA(P)eiPxe−pz, (47b)

and similar expressions for the regions and c. First we note that from the parity symmetry of the system, the normalization of the field can be choose such that will be always a real quantity. With a real , the electric fields and will also be real and will be a pure imaginary quantity, i.e., it will always be out-of-phase by with the other electric field components.

From Eqs. (46a)–(47b) we calculate the potential and electrical field in Fig. 5, for the first even solution and in Fig. 6 for the first odd solution in a Gaussian 1D protrusion. For those solutions the plasmon frequencies are THz and THz, respectively. The even solution has a node at , as it should be, and the field strength, as can be seen in the panel D, is concentrated in the axis for and in the axis around , far below the wavenumber m for the light in air. We have verified that the fields obtained by Eqs. (46a)–(47b) satisfy all the boundary conditions. In Figs. 7 and 8 we show the localized plasmons in a groove (Gaussian indentation), where we can see that the field is less localized in the axis in comparison with the protrusion case. However, the indentation “squeezes” the plasmon in the central region. A remarkable characteristic of the electrostatic approximation is that all the fields profile are only a geometric solution of the integral equation, that is, they do not depend on the properties of the graphene sheet. However, they can only exist if Eq. (33) has solution. Therefore, without the graphene sheet there are no localized plasmons.

We also note that the Fermi-energy can be used to tune the frequency of the localized plasmons as per Eq. (35). Another important result of our study is that the localized plasmon dispersion is always below the usual SPP dispersion (see Fig. 2). Therefore, for a given frequency, the wavelength of the localized plasmons is always smaller than its value for a continuous graphene sheet on a homogeneous dielectric, implying a higher degree of confinement of the plasmons in dielectric with a protrusion/indentation.

The charge density can be calculated using the equivalent of Eq. (52):

 n2D(x)=−λ(ω)∫∞−∞dP2π(P2+k2y)A(P)eiPx, (48)

and we show the charge density for the first two modes in the groove in Fig. 9, where we can see again that the charge is localized around the center of the wedge. Finally, we note that we have used a Gaussian profile but our approach can be used to any differentiable profile.

## Vi Conclusions

In this paper we have developed an approach of creating transversely localized plasmons in a flat graphene sheet. This is possible in a configuration where graphene rests on a flat substrate with the opposite surface of the latter showing a protrusion or and indentation (a defect). The localized plasmons dispersion relation appears below the dispersion relation of the propagating plasmons when graphene rests on a flat dielectric of thickness . Above this latter dispersion relation, we have found a continuum of states, which would be needed for describing scattering by the defect. Therefore, we have shown that a defect (in this case with even symmetry) can trap localized surface plasmons. Since the defect is 1D, the wave number along the axis of symmetry of the defect is well defined and, therefore, this defect can also act as channel for propagation of the transversely localized surface plasmons. This geometry has the advantage of being unnecessary to pattern the graphene sheet, therefore it works without deteriorating the electronic mobility of graphene. The generalization of the problem dealt in this paper to a 2D defect is straightforward, involving only extra computer power. This is no impediment as our codes are fast enough and run in a laptop in only few minutes.

###### Acknowledgements.
A.J.C. acknowledges for a scholarship from the Brazilian agency CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico). N.M.R.P. acknowledges the European Commission through the project “Graphene-Driven Revolutions in ICT and Beyond” (Ref. No. 696656) and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013. D. R. C. and G. A. F. acknowledges CNPq under the PRONEX/FUNCAP grants and the CAPES Foundation.

## Appendix A A planar graphene sheet

Let us assume a graphene sheet located at in the plane. The graphene is capped by two dielectrics with dielectric functions , for , and , for . We want to find the spectrum of graphene SPP. The solution of Laplace’s equation for reads

 ϕ1(ρ,z,t)=A1eik∥⋅ρe−k∥ze−iωt≡ϕ1(ρ,z,ω)e−iωt, (49)

where and , and for it is given by

 ϕ2(ρ,z,t)=A2eik∥⋅ρek∥ze−iωt≡ϕ2(ρ,z,ω)e−iωt. (50)

The boundary conditions are

 ϕ1(ρ,0,t) =ϕ2(ρ,0,t) (51a) ϵ1∂ϕ1(ρ,0,t)∂n −ϵ2∂ϕ2(ρ,0,t)∂n=−n2D(ρ,0,t)ϵ0, (51b)

where is the charge density in graphene, whose time dependence can be explicitly made as . The first boundary condition expresses the continuity of the electrostatic potential and the second one the discontinuity of the normal component of the displacement vector. In addition, the electronic density obeys the continuity equation in frequency space: , where . Since the electric current density obeys Ohm’s law, , it follows that

 iωn2D(ρ,0,ω) =−σ∇22Dϕ(ρ,0,ω)=σk2∥ϕ(ρ,0,ω). (52)

Finally, we have for the 2D electronic density the result

 n2D(ρ,0,ω)=−iσωk2∥ϕ(ρ,0,ω) (53)

The first boundary condition implies and the second boundary condition gives

 −ϵ1k∥−ϵ2k∥=iσωϵ0k2∥ (54)

or

 ϵ1k∥+ϵ2k∥+iσωϵ0=0, (55)

which is the condition giving the dispersion relation of the SPP in graphene, Note that for we recover the condition giving the dispersion of SPP at the interface between two dielectrics. In general, we should have written the electrostatic potential as

 ϕ1(ρ,z,t) =∫dk∥(2π)2A1(k∥)eik∥⋅ρe−k∥ze−iωt, (56)

and an identical expression for , except for the dependence which should by replaced by . This way of writing the electrostatic potential is appropriate for discussing rough surface and defects.

## Appendix B The case of a Gaussian profile

In this appendix we give the evaluation of the function for the Gaussian profile. This is accomplished by expanding the exponential of in the integrand, that is,

 J(α;Q) Extra open brace or missing close brace Extra open brace or missing close brace (57)

Therefore we need to compute the integral (the Fourier transform of a Gaussian)

 I(n;Q) =(−ζ0)n∫∞−∞dxe−iQxe−4nx2/R2 =(−ζ0)n


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28 Oct 2011, 11:19
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08 Nov 2011, 13:12
I purchased this book from the Amazon but did not realize that its only print version and not ebook is there any way I can get access to e-version of this book ? Other then returning the one I purchased from amazon and buying from here ?
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29 Nov 2011, 09:39
So which version has been most recently updated to eliminate errors, the e-book or hardcopy version?
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29 Nov 2011, 10:01
IMKaceKARIS wrote:
I have a quick question. For Exercise 40 question 5
The president ordered that Congress takes an action on the bill soon.
Why is it correct in the answer? Does takes need to change to take?

Thank you

Yes it does. See the page 266 where the answers are posted. It has to be "take"
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30 Nov 2011, 15:00
shiku4Gmat wrote:

Btw, I need a clarification in Exercise 4: Using Other/Another
sentence 4: I have a large stamp collection. The stamps in this section are from the United States. Others are from other places in the world.

I feel that Others should be replaced by The others because we are specific in the previous sentence (The stamps "in this section"). Please clarify.

I think it depends on the assumptions as you have specifically pointed out and that's what will drive the answer.

Scenario 1: you have 3 sections in an area and you point to one section and in this case, you should use "the others" because "the others" is very specific and you can pretty much point to them. You would use "the" if you could be pretty specific about the remaining stamps.

Scenario 2: you have a section in a museum and then you have many other sections (you don't even know how many) and in that case it will be "others" since it is not specific.

I don't know how to make it more specific or less specific so that only one scenario works out, so may have to remove this particular example. This has been the most of what we have had to revise/update the grammar book with - making sure it could not be interpreted in multiple ways.

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Further, please let me know whether the following can be added to my rule book.

- 'another' will never be preceded by 'the'

Correct, since another is a+other, so there is an article there already.
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Exercise 8: Q1. Why is 'will go' not the correct answer?
It seems to be simple future tense. like Many birds will migrate south for the winter.
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AmarSharma wrote:
Exercise 8: Q1. Why is 'will go' not the correct answer?
It seems to be simple future tense. like Many birds will migrate south for the winter.

I would agree. It is not a clear/clean cut. I will change the answer key to just Future Simple since there is no other action happening to require Future Progressive.
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bb wrote:
AmarSharma wrote:
Exercise 8: Q1. Why is 'will go' not the correct answer?
It seems to be simple future tense. like Many birds will migrate south for the winter.

I would agree. It is not a clear/clean cut. I will change the answer key to just Future Simple since there is no other action happening to require Future Progressive.

Thanks. There is one more point, on page 83 instead of "Mark like to swim." it should be "Mark likes to swim."
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31 Mar 2012, 21:33
Hi,

I purchased this book on October 26, 2010. I would like to know whether there is any newer/upgraded version of this book available. If yes, please tell me how to get that one.

I have a receipt number also (in case you need).


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# Posts for Tag: map

### National Park Service Voronoi Map

Posted In: Maps

This map divides up the Continental United States into different regions depending on which National Park (or other National Park Service site) is closest to it. It is based on a straight-line (‘as the crow flies’) distance between locations rather than along road networks. It is an example of a Voronoi Diagram, which is subdivided into different regions based upon the distance between points of interest. Everything within a subregion is closer to the point defining the region than any other point.

Hover over the circle points to see the name of the park. The map has a dropdown menu that lets you choose between the following types of locations in the National Park Service:

• National Parks
• National Historic Sites
• National Memorial Sites
• National Monuments
• National Seashores/Lakeshores
• National Recreation Areas
• National Battlefields
• National Military Sites
• National Scenic Areas

For National Parks, there is a high concentration of National Parks in the Western US, especially around the Southwestern US and running up the Pacific Coast. As a result, in these areas, the Voronoi regions are fairly small. The Southwest is also home to a high concentration of National Monuments. There are only few parks in the Eastern US and so the Voronoi regions are correspondingly large. Looking at National Historic Sites, the situation is flipped somewhat, with a high concentration of historic sites in the eastern US, and specifically the Northeast.

Let me know in the comments which park you are closest to and which park you last visited.

Tools and Data Sources
Locations of each of the National Park Service sites comes from the National Park Service. The map was created using the Leaflet javascript mapping library and the Voronoi diagram using the Turfjs javascript, geospatial analysis library.

### Zip Code Map of the United States

Posted In: Maps

This zip code map of the United States visualizes over 42,000 zip codes in the 50 states. Zip codes are five digit postal codes used for mail delivery in the US. The points on the map show the geographic center of each zip code. The interactive visualization lets you type in a zip code and will show you where that zip code lies on the map. As you begin to type in the zip code, the map will highlight all the zip codes that begin with those numbers.

For example, if you type in “0”, you will highlight all zip codes that start with the zero in the Northeastern US. This will represent about 10% of the zip codes in the US. When you type in another number, it will narrow down the zip codes that begin with those two digits (approximately 1% of zip codes). It will progressively narrow down the number of zip codes as you type in more numbers, until you get to a full 5 digit zip code that represents 1 out of almost 43,000 zip codes (0.002% of zip codes). The map will then tell you the name of the city that that zip code is in.

You can explore how zip codes are distributed across the US by typing in different 1 and 2 digit numbers. You can also click on the check box to show or hide the outlines of the states.

Sources and Tools:

Zip code data was downloaded from opendatasoft.com. And the visualization was created using javascript and the open source leaflet javascript mapping library.

### Greenhouse gas emissions from airplane flights

Posted In: Environment | Transportation

#### Traveling by airplane produces significant greenhouse gas emissions

Flying in an airplane is likely the most greenhouse gas intensive activity you can do.  In a few short hours, you can can travel thousands of miles across the country or ocean.  It takes a large amount of fossil-fuel energy (oil) to lift an 80+ ton airplane off the ground and propel it at 600 miles per hour through the air.  Every hour of travel (in a Boeing 737) consumes around 750 gallons of jet fuel.

Even when dividing the fuel usage across all of the passengers (and cargo) of an aircraft, airplane travel consumes a significant amount of fuel per passenger.  The fuel economy is estimated to be about the same as a fairly efficient hybrid car driven by one person (60-70 passenger miles per gallon).  However, because you can go 10 times faster and much further more easily than you would in a car, airline travel can, on an absolute basis, emit larger amounts of greenhouse gases. In fact, an individual passenger’s share of emissions from a single airplane flight can exceed the annual average greenhouse gas emissions per capita from a number of countries (and the global average).

The following flight calculator and data visualization shows the miles and emissions produced per passenger by a airplane trip that you can specify.  Choose two airports that you are interested in and click the “Calculate Flight Emissions” button to see the emissions associated with a round-trip flight between these two cities.  The map will show you the flight route and also shows you the countries in the world where this one single round-trip flight produces more emissions per passenger than the average resident does in one year from all sources (annual per capita emissions).

In addition to individual countries, the tool also compares the flight’s per passenger emissions to the global average emissions per capita in 2017 (4.91 tonnes) and the emissions required to achieve a 22℃ climate stabilization in 2030 (3.08 tonnes) and in 2050 (1.37 tonnes). These 2030 and 2050 numbers are based on an International Energy Agency scenario.

#### Calculations of Airplane Emissions

The emissions calculated by this calculator are based on calculations from myclimate.org, a non-profit environmental organization.
The fuel consumption of a jet depends on the size of the aircraft and distance traveled, but takeoff and climbing to cruising altitude are particularly fuel-intensive. On shorter flights, the takeoff and initial climb will constitute a greater proportion of the total flight time so fuel consumption per mile will be higher than on longer (e.g. international) flights.

The detailed methodology is described in more detail in this document.

In addition to emissions of CO2 from the burning of jet fuel, jets also emit other gases (including methane, NOx, and water vapor) which can also contribute to warming (also known as “radiative forcing”). Because the emissions are occurring at high altitude, these gases can have different impacts than those at lower altitude. A number of studies have estimated the impact of these other gases can significantly contribute to the overall radiative forcing and have somewhere between 1.5 and 3 times the impact that the CO2 alone would. A number of studies, including the myclimate calculator use a factor of 2 to account for these non-CO2 gases and their warming impact, and that is what is used in this calculator as well.

Unlike cars, trucks and trains, it is much harder to power airplanes with batteries and electricity and producing low-carbon jet fuels from biomass is proving very challenging.

In order to achieve climate stabilization at 2 degrees C, global emissions need to basically go to zero over the next 40 years. With a growing global population, this means that the allowable emissions per person will shrink rapidly over these coming decades.

Ultimately, while aviation is a small part of global greenhouse gas emissions, it is a larger part of emissions in richer countries (i.e. if you are reading/viewing this post). And there are many in these richer countries who fly a disproportionate amount and therefore contribute a disproportionate amount of emissions. Hopefully, putting airplane travel in this context can help us better understand the impact of our actions and choices and maybe even change behavior for some.

Tools and Data Sources
The calculator estimates flight emissions based on the myclimate carbon footprint calculator. Data for CO2 emissions by country was downloaded from the European Commissions’s Emissions Database for Global Atmospheric Research. The map was built using the leaflet open-source mapping library in javascript.

### Assembling the USA state-by-state with state-level statistics

Posted In: Maps

#### Watch the United States assemble state by state based on statistics of interest

Based on earlier popularity of the country-by-country animation, this map lets you watch as the world is built-up one state at a time. This can be done along a large range of statistical dimensions:

• Name (alphabetical)
• abbreviation
• Date of entry to the United States
• State Population (2018)
• Population per Electoral Vote (2018)
• Population per House Seat (2018)
• Land Area (square miles)
• Population Density (ppl per sq mi) (2018)
• State’s Highest Point
• Highest Elevation (ft)
• Mean Elevation (ft)
• State’s Lowest Point
• Lowest Point (ft)
• Life Expectancy at Birth (yrs)
• Median Age (yrs)
• Percent with High School Education
• Percent with Bachelor’s Degree
• Residential Electricity Price (cents per kWh) (2018)
• Gasoline Price ($/gal) Regular unleaded (2019) • State Gross Domestic Product GDP ($Million) (2018)
• GDP per capita (\$/capita)
• Number of Counties (or subdivisions)
• Average Daily Solar Radiation (kWh/m2)
• Birth rate (per thousand population)
• Avg Age of Mother at Birth
• Annual Precipitation (in/yr)
• Average Temperature (deg F)
• These statistics can be sorted from small to large or vice versa to get a view of the US and its constituent states plus DC in a unique and interesting way. It’s a bit hypnotic to watch as the states appear and add to the country one by one.

You can use this map to display all the states that have higher life expectancy than the Texas:
select “Life expectancy”, sort from “high to low” and use the scroll bar to move to the Texax and you’ll get a picture like this:

or this map to display all the states that have higher population density than California:
select “Population density, sort from “high to low” and use the scroll bar to move to the United States and you’ll get a picture like this:

I hope you enjoy exploring the United States through a number of different demographic, economic and physical characteristics through this data viz tool. And if you have ideas for other statistics to add, I will try to do so.

Data and tools: Data was downloaded from a variety of sources:

• Population https://en.wikipedia.org/wiki/List_of_states_and_territories_of_the_United_States_by_population
• Educational attainment https://nces.ed.gov/programs/digest/d18/tables/dt18_104.88.asp
• Highest points https://geology.com/state-high-points.shtml
• Life expectancy https://en.wikipedia.org/wiki/List_of_U.S._states_and_territories_by_life_expectancy
• Median Age http://www.statemaster.com/graph/peo_med_age-people-median-age
• Land area https://statesymbolsusa.org/symbol-official-item/national-us/uncategorized/states-size
• Mean elevation https://www.census.gov/library/publications/2011/compendia/statab/131ed/geography-environment.html
• Electricity price https://www.chooseenergy.com/electricity-rates-by-state/
• Gasoline price https://gasprices.aaa.com/state-gas-price-averages/
• GDP https://www.bea.gov/data/gdp/gdp-state
• Sunlight North America Land Data Assimilation System (NLDAS) Daily Sunlight (insolation) for years 1979-2011 on CDC WONDER Online Database, released 2013. Accessed at http://wonder.cdc.gov/NASA-INSOLAR.html on Jun 14, 2019 1:37:15 PM
• Births United States Department of Health and Human Services (US DHHS), Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS), Division of Vital Statistics, Natality public-use data 2007-2017, on CDC WONDER Online Database, October 2018. Accessed at http://wonder.cdc.gov/natality-current.html on Jun 14, 2019 1:53:58 PM
• Precipitation North America Land Data Assimilation System (NLDAS) Daily Precipitation for years 1979-2011 on CDC WONDER Online Database, released 2013. Accessed at http://wonder.cdc.gov/NASA-Precipitation.html on Jun 26, 2019 3:30:40 PM
• Temperature http://www.usa.com/rank/us–average-temperature–state-rank.htm

The map was created with the help of the open source leaflet javascript mapping library

### What kinds of vehicles do Americans drive?

Posted In: Energy

Americans are known for loving cars and driving quite a bit. Drivers in the United States own more cars and drive more than those in any other country. So what kinds of vehicles do Americans drive? This visualization looks at the types of vehicles (by body type and country of origin) across the 50 States and Washington DC.

You can view two different attributes about the types of vehicles in use in the United States:

• Body type of passenger vehicles
• Manufacturer/Brand region of origin

The different categories of passenger vehicles include:

• Cars – includes sedans, hatchbacks, wagons and sports cars
• Pickup trucks
• SUVs
• Vans – includes Minivans and full-size vans

Classification of the vehicles manufacturer (US, Asia or Europe) is based on the company’s headquarters and not the place of vehicle manufacturing. So a Toyota here is an Asian vehicle even if it was assembled in Mississippi.

It is pretty interesting to see the regional differences in vehicle types (cars vs trucks and SUVs) and vehicle brand (domestic vs foreign). Michigan, especially, stands out with their very high domestic ownership. It makes sense as Detroit is the home of the big three US auto manufacturers (Ford, GM and Chrysler). And I hear there’s a very strong culture of owning American cars there (and employee, friends and family discounts as well).

The data is derived from a survey by the US Department of Transportation called the National Household Travel Survey (NHTS) released in 2017. The following is a quote from the NHTS webpage:

The National Household Travel Survey (NHTS) is the source of the Nation’s information about travel by U.S. residents in all 50 States and Washington, DC. This inventory of travel behavior includes trips made by all modes of travel (i.e., private vehicle, public transportation, pedestrian, and cycling) and for all purposes (e.g., travel to work, school, recreation, and personal/family trips). It provides information to assist transportation planners and policymakers who need comprehensive data on travel and transportation patterns in the United States.

Data and Tools:
Data, as stated before, comes from the US Department of Transportation’s National Household Travel Survey (NHTS). That data was processed to identify vehicle characteristics by state and plotted using javascript and the open-source leaflet map library.

### How Much Does Each State Pay In Taxes?

Posted In: Money

Given that tax day has just passed, I thought it would be good to check out some data on taxes. The IRS provides a great resource on tax data that I’ve only just gotten into. I think I’ll be able to do more with this in the future. This one looks at how taxes paid varies by state and presents it as a choropleth map (coloring states based on certain categories of tax data).

You can choose from a number of different categories:

• Mean Federal Tax Paid
• Mean Adjusted Gross Income
• Mean State/Local Tax
• Mean Combined (Fed/State/Local) Tax
• Percent Income from Dividends and Capital Gains
• Percent of Returns with Itemized Deductions
• Number of Tax Returns
• Mean Federal Tax Rate
• Mean State/Local Tax Rate
• Mean Combined (Fed/State/Local) Rate
• Total Federal Tax Liability

I may add more categories in the future, so if you have ideas of tax data you want to see visualized let me know and I’ll see what I can do.

For other tax-related tools and visualizations see my tax bracket calculator and visualization of marginal tax rates.

#### **Click Here to view other financial-related tools and data visualizations from engaging-data**

Data and Tools:

Data on tax returns by state is from the IRS website in an excel format. The map was made using the leaflet open source mapping library. Data was compiled in excel and calculations made using javascript.