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40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Category Subject
4875   Fri Jun 24 01:05:32 2011 NicoleSummarySUSTransfer Function Model Analysis Summary and New Posted LED V vs. I Curve

I have updated the TT suspension wiki to include a new page on my transfer function model. In this new page, an introduction and analysis of my transfer function (including a comparison of the transfer functions for a flexibly- and rigidly-supported damper) are included.  This page contains linear and logarithmic bode plots.  Here is a link to the transfer function page.

I have also updated my photosensor page on the TT suspension wiki so that the experimental data points in my current versus voltage plot are plotted against the curve provided by the Hamamtsu data sheet. I have also included an introduction and analysis for my mini-experiment with the forward voltage and forward current of the LED. Here is link to the photsosensor page.

14963   Thu Oct 10 22:11:53 2019 gautamUpdateLSCTrans QPD checkout
1. I removed the flip-mount that was installed on the EY in-air table for the mode-spectroscopy project (see Attachment #1). The Transmon QPD at EY sees IR light again.
2. Dark noise checkout - see Attachment #2.
3. Light-level expectations:
• For the current config, let's say 0.8 W reaches the PRM, and we will have a PRG of 50.
• This implies ~5.5 kW circulating power in the arms.
• This implies ~70mW will get transmitted through the ETM, of which at most half makes it to the QPD.
• In the nominal operating condition, we expect more like 6 W circulating in the arm cavity. So something like 30uW is expected to make it out onto the Trans QPDs.
• But in this condition, we expect to run with the high-gain Thorlabs PD.
• In reality the number is likely to be somewhat smaller. But we should set the transimpedance gain of this photodiode accordingly. Currently, there are a bunch of ND filters installed on this photodiode, which probably should be removed.
4. Angular control
• The other purpose these QPDs are expected to serve is to stabilize the angular motion of the cavities when locked with high circulating power.
• Need to calculate what the sensing noise requirement is.
14626   Mon May 20 21:45:20 2019 MilindUpdate Traditional cv for beam spot motion

Went through all of Pooja's elog posts, her report and am currently cleaning up her code and working on setting up the simulations of spot motion from her work last year. I've also just begun to look at some material sent by Gautam on resonators.

This week, I plan to do the following:

1) Review Gabriele's CNN work for beam spot tracking and get his code running.

2) Since the relation between the angular motion of the optic and beam spot motion can be determined theoretically, I think a neural network is not mandatory for the tracking of beam spot motion. I strongly believe that a more traditional approach such as thresholding, followed by a hough transform ought to do the trick as the contours of the beam spot are circles. I did try a quick and dirty implementation today using opencv and ran into the problem of no detection or detection of spurious circles (the number of which decreased with the increased application of median blur). I will defer a more careful analysis of this until step (1) is done as Gautam has advised.

3) Clean up Pooja's code on beam tracking and obtain the simulated data.

4) Also data like this  (https://drive.google.com/file/d/1VbXcPTfC9GH2ttZNWM7Lg0RqD7qiCZuA/view) is incredibly noisy. I will look up some standard techniques for cleaning such data though I'm not sure if the impact of that can be measured until I figure out an algorithm to track the beam spot.

A more interesting question Gautam raised was the validity of using the beam spot motion for detection of angular motion in the presence of other factors such as surface irregularities. Another question is the relevance of using the beam spot motion when the oplevs are already in place. It is not immediately obvious to me how I can ascertain this and I will put more thought into this.

13398   Tue Oct 24 16:22:53 2017 gautamUpdateCDSToy DARM model setup in c1tst

[alex, gautam]

Alex is going to have an undergrad work on a calibration optimization project on the 40m RTCDS system. For this purpose, we wanted to setup a "Simulated DARM loop". Today, Alex and I set this up. I figured we can use the c1tst model for this purpose. We basically copied the topology from Figure 2 of the h(t) paper. Attached are screenshots of the MEDM screens of the system we setup, and the simulink block diagram - the main screen can be accessed from the "SIM PLANT" tab in the sitemp.

It remains to setup the appropriate filters in the filter banks, and an EPICS channel monitor for monitoring the single excitation testpoint in the model. We also did not set up any DQ channels for the time being, as it is not even clear to me what channels need to be DQ-ed.

5900   Tue Nov 15 22:31:39 2011 MirkoUpdateAdaptive FilteringTowards wiener filtering and improved OAFing

[Jenne, Mirko]

1. We should help the OAF by compensating for the actuator TF:

The actuator TF, from adaptive filter output to MC2, through PD, mixer, Pentek and into C1:IOO looks like this:

If we assume a white-ish error signal that the adaptive code tries to compensate for its job gets extra complicated because it has to invert this TF. So we really should compensate for that. Easiest place for that is the CORR filter directly behind the adaptive code block.

Using the TF measurement from above I used the vectfit (" /cvs/cds/caltech/apps/mDV/extra/firfit_forFotonMirkoComplex.m" ) to get fit a corresponding digital filter:

If we invert swap the zeros and poles in the digital filter we get the inverted TF.
(Todo: Figure out how to invert the TF. Just switching the poles and zeros doesn't work).

2. Wiener filtering

The idea was to use the adaptive filtering only for small corrections to the wiener filtering. So we really should try to get the wiener filtering going.

Howto:

1. Get data for STS1X and GUR1X and MC_F in matlab. E.g. via ligodv
2. Check the MC was in lock the entire time.
3, Filter MC_F with the actuator TF, so the wiener filter knows about that and compensates for it
4. Calculate the wiener filter " h1winolevLigoDV.m "
5. Export the data to the workspace. It is also saved to the disc as "h1filtcoeffTS.mat". Make sure there are first the witnesses, then MC_F
6. Execute " /cvs/cds/caltech/apps/mDV/extras/LHO/firfit_for_FotonMirko.m" while one directory higher.
7. Copy the digital filter in SOS form that is printed into the matlab command line and put it into the corresponding filter in the OAF model via foton.

With data from 11-11-15 04:00 to 05:45. Sampling freq. 256Hz. 8000 Taps => length = 30.2s. Prefiltered to notch the 60Hz line in MC_F, but not compensation the actuator TF. This results in the following wiener filter and corresponding SOS filter to be copied into foton.
STS1X:

GUR1X:

16306   Wed Sep 1 21:55:14 2021 KojiSummaryGeneralTowards the end upgrade

- Sat amp mod and test: on going (Tega)
- Coil driver mod and test: on going (Tega)

- Acromag: almost ready (Yehonathan)

- IDC10-DB9 cable / D2100641 / IDC10F for ribbon in hand / Dsub9M ribbon brought from Downs / QTY 2 for two ends -> Made 2 (stored in the DSUB connector plastic box)
- IDC40-DB9 cable / D2100640 / IDC40F for ribbon in hand / DB9F solder brought from Downs  / QTY 4 for two ends -> Made 4 0.5m cables (stored in the DSUB connector plastic box)

- DB15-DB9 reducer cable / ETMX2+ETMY2+VERTEX16+NewSOS14 = 34 / to be ordered

- End DAC signal adapter with Dewhitening (with DIFF/SE converter) / to be designed & built
- End ADC adapter (with SE/DIFF converter) / to be designed & built

MISC Ordering

• 3.5 x Sat Amp Adapter made (order more DSUB25 conns)
• -> Gave 2 to Tega, 1.5 in the DSUB box
• 5747842-4 A32100-ND -> 5747842-3 A32099-ND Qty40
• 5747846-3 A32125-ND -> 747846-3 A23311-ND Qty40
• Tega's sat amp components
• 499Ω P499BCCT-ND 78 -> Backorder -> RG32P499BCT-ND Qty 100
• 4.99KΩ TNPW12064K99BEEA 56 -> Qty 100
• 75Ω YAG5096CT-ND 180 -> Qty 200
• 1.82KΩ P18391CT-ND 103 -> Qty 120
• 68 nF P10965-ND 209
• Order more DB9s for Tega's sat amp adapter 4 units (look at the AA IO BOM)
• 4x 8x 5747840-4 DB9M PCB A32092-ND -> 6-747840-9 A123182-ND Qty 35
• 4x 5x 5747844-4 A32117-ND -> Qty 25
• 4x 5x DB9M ribbon MMR09K-ND -> 8209-8000 8209-8000-ND Qty 25
• 4x 5x 5746861-4 DB9F ribbon 5746861-4-ND -> 400F0-09-1-00 LFR09H-ND Qty 35
• Order 18bit DAC AI -> 16bit DAC AI components 4 units
• 4x 4x 5747150-8 DSUB9F PCB A34072-ND -> D09S24A4PX00LF609-6357-ND Qty 20
• 4x 1x 787082-7 CONN D-TYPE RCPT 68POS R/A SLDR (SCSI Female) A3321-ND -> 5787082-7 A31814-ND Qty 5
• 4x 1x 22-23-2021 Connector Header Through Hole 2 position 0.100" (2.54mm)    WM4200-ND -> Qty5

16334   Wed Sep 15 23:53:54 2021 KojiSummaryGeneralTowards the end upgrade

Ordered compoenents are in.

- Made 36 more Sat Amp internal boards (Attachment 1). Now we can install the adapters to all the 19 sat amp units.

- Gave Tega the components for the sat amp adapter units. (Attachment 2)

- Gave Tega the componennts for the sat amp / coil driver modifications.

- Made 5 PCBs for the 16bit DAC AI rear panel interface (Attachment 3)

6198   Sat Jan 14 00:50:08 2012 rana, kojiConfigurationIOOTowards coating thermal noise measurement with RefCav / MC beat

Koji asked aloud tonight if we could measure the coating thermal noise of the refcav optics by beating the refcav light with the MC_TRANS light. Then we looked at our calculations for the noises:

Displacement noise of T=200ppm silica/tantala coating on a 1" silica substrate with a 300 micron beam spot = 1e-18 * sqrt(100 Hz / f) m/rHz.

Displacement noise from coating thermal in the MC is roughly smaller by the beam size ratio (1.8 mm / 0.3 mm). Some differences due to 3 mirrors and more layers on MC2 than the others, but those are small factors.

So, the frequency noise from the refcav should by larger than the MC thermal noise by a total factor of (1.8 / 0.3) * (13 m / 8 inches) ~ 400.

Another way to say it is that the effective strain noise in the RC is (1e-18 / 0.200) = 5e-18 /rHz. This translates into (5e-18 * 13) = 6.5e-17 m/rHz in the MC. (in frequency noise its 1.5 mHz/rHz).

I have measured the frequency noise in the LLO MC to be at this level back in 2009, so it seems possible to use our RC + MC to measure coating thermal noise by the length amplification factor and compete with Frank+Tara.

So today we set up the Jenny RC temperature setup to lock the LWE NPRO to the RC and then set up the beat note with the IFO REFL beam on the AS table. By using the 2 laser beat, we are avoiding the VCO phase noise issue which used to limit the PSL frequency noise at ~0.01 Hz/rHz. To do this we have reworked some of the optics on the PSL and AS tables, but I think its been done without disturbing the beams for the regular locking. Beat note has been found, but the NPRO has still not been locked to the RC - next we setup the lockin amp, dither the PZT, and then use the New Focus lock box to lock it to the RC.

You might think that its hard to measure this since the MC has ~1 MHz frequency fluctuations and we want to measure down to 1e-4 Hz. But, in fact, we can just use a 200 m MFD with a LT1128 preamp. Then we use the MFD to stabilize the MC length to the refcav and just use the control + error signal of the MFD setup as the coating thermal noise measurement.

Note: Beat found at ~40deg for the aux laser. The aux laser is on but the shutter is closed.
The AS camera seems to be hosed. Need a bit of alignment. (KA) ==> Fixed. (Jan 15)

10876   Thu Jan 8 03:09:07 2015 JenneUpdateLSCToward variable finesse locking

[Jenne, EricQ, Rana]

Tonight we started prepping for an attempt at variable finesse locking.

The idea is to put in a MICH offset and hold the lock with ASDC/POPDC (so that the offset can be larger than if we were just using RF signals).  This reduces the PRC buildup, which reduces / removes the double cavity resonance problems while reducing the CARM offset.

• So.  Today, I pulled out the POP22 razor blade so that we can use the Thorlabs PD as POPDC, without the yaw coupling.  Our other option is to use the POP QPD SUM, but that would require some model changes and more importantly it's not a particularly low noise readout path.
• We re-set the analog whitening gains for ASDC and POPDC.
• For ASDC, we want the half-fringe in the PRMI case to be not saturating.  We chose 18dB (it had been the default 0dB).
• For POPDC, Rana and I saw that it was saturating all the time with the 33dB that it had when the carrier became resonant.  This was never really a problem in the past, but if we use it for normalization, we get glitches that knock us out of lock every time POPDC saturated.  So, now POPDC is at 0dB.  It still occasionally saturates when the PRMI is flashing, but we can't get lower than 0dB without going and putting an ND filter on the PD.
• We turned off the analog whitening filters and digital unwhitening for both ASDC and POPDC.  We can consider turning them back on later after we have acquired lock if we need them, but we need them off for acquisition.
• Locked MICH with ASDC/POPDC.  Good.  Stays locked even if PRM is flashing.
• Locked PRMI with PRCL on REFL33I and MICH on ASDC/POPDC.
• Locked arms, held off resonance with ALS, lock MICH with ASDC/POPDC.
• Failed to lock PRMI with arms held off resonance, using the new scheme (no transition, trying to directly acquire)
• Locked PRMI on REFL33 I&Q with the arms held off resonance, and tried to transition MICH over to ASDC/POPDC, failed.
• Confusion about the relative phase between REFL33Q and ASDC.  It looks like it is ~45deg at 100 Hz, or ~90 deg at 375 Hz.  Why isn't it 0 or 180?
• Went back to PRMI-only, tried to map out fringe by changing MICH offset (tried while MICH was on both REFL33 and ASDC/POPDC).  Not really sure where we are on the fringe.

MICH locked on ASDC normalized by POPDC, PRM and ETMs (and SRM) all misaligned.

MICH offset of -20

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always triggered on (no triggering for DoF), but FM8 (CLP400) triggered to come on after lock (didn't write down the values).

PRMI locked with MICH on ASDC normalized by POPDC, PRCL on REFL33I, ETMs and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

PRCL input = 1*REFL33I

MICH gain = +5

PRCL gain = -0.4 (factor ten times the regular value)

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Gives POPDC of about 20 counts, POP22 of about 12 counts, ASDC of about 500 counts.

Arms held at 3nm, MICH locked on ASDC/POPDC, PRM and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Arms held at 3nm, attempt at PRMI lock with MICH on ASDC/POPDC.

Failed.  Tried mostly same MICH gains as arms+mich, and PRCL at 10* normal gain.

Arms held at 3nm, PRMI locked with REFL 33 I&Q, attempt at transition to MICH on ASDC/POPDC.

Failed.  At first, I was putting in the TF line at ~375Hz, but we looked at the full transfer function between 100Hz and 1kHz, and there was a weird dip near 300Hz from PRCL-MICH loop coupling.  Here we were seeing that the phase between REFL33Q and ASDC was ~90 degrees.  What?

Tried putting the TF line at ~100 Hz (since MICH UGF is in the few tens of Hz anyway, so 100 is still above that), but still get weird relative phase.  Here it seems to be about 45 degrees when I inject a single line, although it didn't seem like a weird phase when we did the full swept sine earlier.  Maybe I was just not doing something right at that point??

Anyhow, no matter what values I tried to put into the input matrix (starting with REFL33I&Q, trying to get MICH to ASDC/POPDC), I kept losing lock.  This included trying to ramp up the MICH offset simultaneously with the matrix changing, which was meant to help with the PRCL gain change.  Q has since given us MICH and PRCL UGF servos.

Tomorrow:

• Why is there some weirdo phase between REFL33Q and ASDC at 100Hz?  Was I just being a spaz?
• With PRMI-only, figure out how to transition from REFL33 I&Q over to MICH on ASDC/POPDC.
• Then hold the arms off resonance, and do the same transition.  (First make sure we're at a good place on the fringe)
• Lower the CARM and DARM offsets, transition them to RF, engage CARM AO path.
• Reduce MICH offset, transition to RF.
• Celebrate (maybe).
413   Thu Apr 3 19:27:50 2008 AndreySummaryPhotosTour for prospective grad students
Last Friday (March 28), there was a tour of 40-meter lab for prospective graduate students.

Rana showed to the prospective students the interferometer. See pdf-attachment with pictures (two pictures of Rana with undergraduates (I took them) and two old pictures which I discovered on the memory card of Nikon d-40, it was not me who took those two last pictures).
16339   Thu Sep 16 14:08:14 2021 Ian MacMillanFrogs Tour

I gave some of the data analysts a look around because they asked and nothing was currently going on in the 40m. Nothing was changed.

13910   Fri Jun 1 21:47:23 2018 KojiFrogsGeneralTouch screen manipulation of the IFO

[Koji Gautam]

We talked about touch interface of medm. We realized that android (and iOS) has vnc clients. I just installed VNC viewer on my phone and connected to my mac. Typing is tricky but I managed to get into pianosa, then launched sitemap. We could unlock/lock the IMC by screen touch!

Basically we can connect to one of the laptops (or control machines) from a tablet (either android or ipad). It'd be better to put both in a same network. It'd be great if we have a tablet case with a keyboard so that we can type without blocking the screen.

4358   Fri Feb 25 14:35:06 2011 Larisa ThorneUpdateElectronicsTotal harmonic distortion results for +7dBm mixer

This experiment deals with measuring the total harmonic distortion (THD) contribution of mixers in a circuit.

(a circuit diagram is attached) where:

Mixer: ZFM-3-S+ at +7dBm

Attenuator: VAT-7+, at +7dB

Low-pass filter: SLP-1.9+, which is set to DC-1.9MHz

The total harmonic distortion can be calculated by the equation:

$\mbox{THD} = \frac{V_2^2 + V_3^2 + V_4^2 + \cdots + V_\infty^2}{V_1^2}$

where Vn represents the voltage of the signal at a certain harmonic n.

In this experiment, only the voltages of the first three harmonics were measured, with the first harmonic at 400Hz, the second at 800Hz, and the third at 1.2kHz. The corresponding voltages were read off the spectrum analyzer after it had time averaged 16 measurements. (picture of the general shape of the spectrum analyzer output is attached)

(results for this mixer's particular configuration are on the pdf attached)

There really isn't that much correlation between the modulations and the resulting THD.

We won't know how good these numbers are until more experiments on other mixers are done, so they can be compared. Since the rest of the mixers are relatively high levels (+17dBm, +23dBm in comparison to this experiment's +7dBm), an RF amplifier will need to be hooked up first to do any further measurements.

2002   Fri Sep 25 16:45:29 2009 JenneUpdateMOPATotal MOPA power is constant, but the NPRO's power has decreased after last night's activities?

[Koji, Jenne]

Steve pointed this out to me today, and Koji and I just took a look at it together:  The total power coming out of the MOPA box is constant, about 2.7W.  However, the NPRO power (as measured by 126MOPA_126MON) has decreased from where we left it last night.  It's an exponential decay, and Koji and I aren't sure what is causing it.  This may be some misalignment on the PD which actually measures 126MON or something though, because 126MOPA_LMON, which measures the NPRO power inside the NPRO box (that's how it looks on the MEDM screen at least...) has stayed constant.  I'm hesitant to be sure that it's a misalignment issue since the decay is gradual, rather than a jump.

Koji and I are going to keep an eye on the 126MON value.  Perhaps on Monday we'll take a look at maybe aligning the beam onto this PD, and look at the impedance of both this PD, and the AMPMON PD to see why the reading on the DMM changed last night when we had the DAQ cable T-ed in, and not T-ed in.

5569   Wed Sep 28 21:28:34 2011 MirkoUpdateComputersTorturing control computers. Fine again now

[Mirko, Jenne]

We tried to run an extended version of Matt's LMS adaptive filter c-code. We got the extension to compile separately in gcc first. Then after some tweaking of the code we could make-install c1oaf with the c-code.

This killed c1lsc (the FE computer running c1oaf). Not responding to ssh or even pings. We replaced the bad c-code with harmless code, then reset c1lsc via the hardware button. While looking for c1lsc we discovered the problem with c1iscy network card (see previous entry).

After c1lsc reboot, restart of the FB, and a BURT restore not ok yet

5571   Wed Sep 28 22:25:25 2011 JenneUpdateComputersTorturing control computers. Fine again now

 Quote: [Mirko, Jenne] We tried to run an extended version of Matt's LMS adaptive filter c-code. We got the extension to compile separately in gcc first. Then after some tweaking of the code we could make-install c1oaf with the c-code. This killed c1lsc (the FE computer running c1oaf). Not responding to ssh or even pings. We replaced the bad c-code with harmless code, then reset c1lsc via the hardware button. While looking for c1lsc we discovered the problem with c1iscy network card (see previous entry). After c1lsc reboot, restart of the FB, and a BURT restore not ok yet

We had lots of trouble damping the Vertex Suspensions after this craziness.  A symptom was that even if all of the damping servos on an optic were OFF, and I turned the watchdog on (LSC is disabled, so no OAF siganls, no LSC signals), there were signals going to the coils.

We did a reboot of the c1sus computer, did another BURT restore, and the optics started damping happily.   Burt restore, at least for c1susepics and c1mcsepics, seems to not be happening automatically.  I thought it was supposed to happen when the model was restarted?

Things now appear to be normal again.

3186   Fri Jul 9 11:41:58 2010 GopalSummaryOptic StacksTop Optic Layer Complete; Mechanical Tests Giving Problems

For the last week, I have been attempting to determine the mirror stack transfer function which relates mechanical mirror response to a given ground-motion drive. The idea is to model the stacks in COMSOL and ultimately apply mechanical tests for manual calculation.

Procuring the correct drawings to base my 3D models off of was no simple task. There are two binders full of a random assortment of drawings, and some of them are associated with the smaller chambers, while others are appropriate for the main chamber, which is what we're interested in right now. For future workers, I suggest checking that your drawings are appropriate for the task at hand with other people before wasting time beginning the painstaking process of CAD design in COMSOL.

The drawings that I ultimately decided to use are attached below. They detail four layers of stacks, each which arrange 15, 12, 8, and 5 (going from bottom to top) Viton damping springs in an orderly fashion. The numbers have been chosen to keep the load per spring as constant as possible, in order for all springs to oscillate with as close a resonant frequency to each other as possible.

After making some minor simplifications, I have finished modeling the top stack:

After triangular meshing, before my many failed attempts at mechanical testing:

Both the Viton and steel portions have been given their material properties, and so I should be (theoretically ) ready to perform some eigenfrequency calculations on this simplified system. If my predictions are correct, these eigenfrequencies shouldn’t be too far of the eigenfrequencies of the 4-layer stacked system, because of the layout of the springs. I’ve tried doing mechanical tests on the top stack alone, but there hasn’t been much progress yet on this end, mostly because of some boundary value exceptions that COMSOL keeps throwing at me.

In the next couple weeks or so, I plan to extend this model to combine all four layers into one completed stack, along with a simple steel base and mirror platform. I also plan to figure out how to make eigenfrequency and transfer function measurements.

Lastly, to anyone who is experienced with COMSOL, I am facing two major roadblocks and could really use your help:

1) How to import one model into another, merge models together, or copy and paste the same model over and over.

2) Understanding and debugging run-time errors during mechanical testing.

If you have any idea how to attack either of these issues, please talk to me! Thanks!

16784   Mon Apr 18 15:17:31 2022 JancarloUpdateGeneralTool box and Work Station Organization

I cleaned up around the 40 m lab. All the Laser Safety Glasses have been picked up and placed on the rack at the entrance.

Some miscellaneous BNC Connector cables have been arranged and organized along the wall parallel to the Y-Tunnel.

Nitrogen tanks have been swapped out. Current tank is at 1200 psi and the other is at 1850 psi.

The tool box has been organized with each tool in its specified area.

16787   Mon Apr 18 23:22:39 2022 KojiUpdateGeneralTool box and Work Station Organization

Whoa! Thanks!

10195   Mon Jul 14 16:19:41 2014 AndresUpdate40m Xend Table upgradeTook the measurement for the Mode Matching

Nick and I measured the reflected power of the green light in locked and unlocked. I'm working on the calculation of the mode matching. Tonight, I'll be posted my calculation I'm still working on it.

JCD:  Andres forgot to mention that they closed the PSL shutter, so that they could look at the green light that is reflected off the harmonic separator toward the IR trans path.  Also, the Xarm (and the Yarm) were aligned to IR using the ASS, and then ASX was used to align the green beam to the cavity.

3584   Fri Sep 17 14:55:01 2010 josephbUpdateCDSTook 5565 RFM card from IOVME to place in the new IOO chassis

I took the 5565 RFM card out of the IOVME machine to so I could put it in the new IO chassis that will be replacing it.  It is no longer on the RFM network.  This doesn't affect the slow channels associated with the auxilliary crate.

7983   Fri Feb 1 12:34:55 2013 JenneUpdatePSLToo much power injected into vacuum

I noticed (while relocking the MC after Jamie and I zeroed the LSC offsets) that the MC refl power was 4.8 V.  Usually we should be ~4.2, so I closed the PSL shutter and went in to measure the power.  We were injecting ~125mW or a little more.  I had adjusted the power the other day, and through yesterday, it looked fine, but overnight it looks like it drifted up.

17000   Wed Jul 13 17:30:19 2022 KojiUpdateCDSToo huge script_archive

I wanted to check the script archive to see some old settings. I found that the script archive inflated to huge volume (~1TB).
The size of the common NFS volume (/cvs/cds) is 3TB. So it is really significant.

- The scripts living in /opt/rtcds/caltech/c1/scripts are archived daily in /cvs/cds/caltech/scripts_archive as bz2 files. This is done by crontab of megatron (see https://wiki-40m.ligo.caltech.edu/Computers_and_Scripts/CRON)

- In fact, the script folder (say old script folder) /opt/rtcds/caltech/c1/scripts has the size of 10GB. And we have the compressed copy of thi s everyday.

- This large script folder is due to a couple of huge files/folders listed below

• (scripts)/MEDMtab is 5.3GB / This is probably related to the web MEDM view (on nodus) but I don't think the web page is not updated. (i.e. the images are unused)
• (scripts)/MC/logs/AutoLocker.log 2.9GB / This is just the accumulated MC autolocker log.
• (scripts)/GigE 780M / This does not look like scripts but source and object files
• (scripts)/Admin/n2Check.log 224M / This is important but increases every minute.
• (scripts)/ZI 316MB / Zurich Instrument installation. This should not be here.

Here I propose some changes.
For the script archive

• We can remove most of the scripts for the past (say ~2019). We leave an archive file per month.
• For the scripts in 2020, we leave a weekly archive.
• For 2021 and 2022, we leave all the archive files.

For the existing large files/folders

• MEDMtab: the stored files are redundant with the burt snapshots. Remove the image files. Also, we want to move the image-saving location.
• Autolocker.log: simply zap it
• n2Check.log: we should move the saving location
• GigE /ZI: they need a new home where the daily copy is not taken.
17043   Thu Jul 28 15:11:59 2022 KojiUpdateCDSToo huge script_archive

As a result of the following work, the file volume of /cvs/cds was reduced from 3.2TB to 2.2TB, and /opt/rtcds/caltech/c1/scripts was reduced from 10GB to 1.5GB

/cvs/cds/caltech/scripts_archive was cleaned up. Now the archive files are reduced to have:

• every month 1st day from 2005 to 2018/12
• every ten days (1, 11, 21) for 2019 and 2020
• everyday for 2021 and 2022

(scripts)/MEDMtab/image was deleted. I can be restore back from one of the script_archive files.

(scripts)/MC/logs/AutoLocker.log was just deleted and refreshed. For the past settings, we can refer autoburt snapshots or script_archive files.

(scripts)/Admin/n2Check.log

• It turned out that the frequency of the check was reduced to once per 10min on Sep 9th, 2021 (unelogged activity).
• The volume of the text since then was not much volume. So I deleted the lines before this date. And the file size is <7MB now.

(scripts)/ZI was moved to /cvs/cds/apps

/opt/rtcds/caltech/c1/burt/autoburt/snapshots

• 2018, 2019, 2020 snapshots were archived in tar.gz.
• These snapshots were then deleted

5334   Fri Sep 2 04:41:35 2011 KeikoUpdateLSCTolerance of PRC, SRC, MICH length = 5 mm ?

Keiko, Kiwamu

Length tolerance of the vertex part is about 5 mm.

Sorry for my procrastinating update on this topic. In my last post, I reported that the length tolerance of the vertex ifo would be 2mm, based on Kiwamu's code on CVS. Then we noticed that the MICH degrees of freedom was wrong in the code. I modified the code and ran again. You can find the modified codes on CVS (40m folder, analyzeDRMITolerance3f.m and DRMITolerance.m)

In this code, the arm lengths were kept to be ideal while some length offsets of random gaussian distribution were added on PRCL, SRCL and MICH lengths. The iteration was 1000 times for each sigma of the random gaussian distribution. The resulting sensing matrix is shown as histogram. Also, a histogram of the demodulation phase separation between MICH and SRCL is plotted by this code, as these two length degrees of freedom will be obtained by one channel separated by the demodulation phase. We check this separation because you want to make sure that the random length offsets does not make the separation of these two signals close.

The result is a bit different from the previous post, in the better way! The length tolerance is about 5 mm for the vertex ifo. Fig.1 shows the sensing matrix. Although signal levels are changed by the random offsets, only few orders of magnitude is changed in each degrees of freedom. Fig.2 shows that the signal separation between MICH and SRCL at  POP55 varies from  55 to 120 degrees, which may be OK. If you have 1cm sigma, it varies from 50 degrees to 150 degrees.

Fig. 1 Histgram of the sensing matrix including 3f channels, when sigma is 5mm. Please note that the x-axis is in long 10.

Fig. 2 Histogram of the demodulation phase difference between MICH and SRCL, when sigma is 5 mm. To obtain the two signals independently, 90 is ideal. With the random offsets, the demodulation phase difference varies from 55 degrees to 120 degrees.

My next step is to run the similar code for LLO.

5273   Sat Aug 20 00:42:22 2011 KeikoUpdateLSCTolerance of PRC, SRC, MICH length = 2 mm ?

Keiko, Kiwamu

I have run Kiwamu's length tolerance code (in CVS iscmodeling, ArmTolerance.m & analyseArmTorelance.m ) for the vertex ifo.

In his previous post, he monte-carlo-ed the arm lengths and saw the histogram of the sensing matrix and the demodulation phase between POP55 MICH and POP55 SRCL. From these plots, he roughly estimated that the tolerance is about 1 cm (sigma of the rondom gaussian) and in that case POP55 MICH and SRCL is separated by the demodulation phase 60-150 degrees.

This time I put the length displacements of random gaussian on PRC, SRC, MICH lengths at the same time (Fig.1).

Fig. 1. History of random walk in PRC, SRC, MICH lengths parameter space. Same as Kiwamu's previous post, The position of the three degrees are randomly chosen with a Gaussian distribution function in every simulaton. This example was generated when \sigma = 1 cm for all the three lengths, where \sigma is the standard deviation of  the Gaussian function. The number of simulation is 1000 times.

When the sigma is 1 cm, we found that the sensing matrix is quite bad if you look at Fig. 2. In Fig.2 row POP55, although the desired degrees of freedoms are MICH and SRCL, they have quite a bit of variety. Their separation in the demodulation phase is plotted in Fig.3. The separation in the demodulation phase varies from 40 degrees to 140 degrees, and around 270 degrees. It is not good as ideally we want it to be 90.

Fig. 2 Histgram of the sensing signal power in the matrix when 1 cm sigma rondom gaussian is applied on PRC, SRC, MICH lengths. x axis it the signal power in log10.

Fig.3 POP55 MICH and POP55 SRCL separation with the displacement sigma 1 cm.

Kiwamu suspected that PRC length as more strict tolerance than other two (SRC, MICH) for POP55, as 55MHz is fast and can be sensitive to the arm length change. So I ran the same monte-carlo with SRC, MICH displacements but no PRC displacements when sigma is the same, 1cm. The results were almost same as above, nothing obvious difference.

With 2mm sigma, the signal power matrix and the POP55 MICH and POP55 SRCL separation in the demodulation phase look good (Fig. 4 and Fig. 5).

Fig.4 Signal power matrix when PRC, SRC, MICH lengths fractuate with random gaussian distribution with 2mm sigma. The signal powers are shown in log10 in x axis, and they do not vary very much in this case.

Fig.5 POP55 MICH and POP55 SRCL separation with the displacement sigma 2 mm. The separation of the two signal is 60-90 degrees, much better than when sigma is 1 cm. We may need to check 60 degree separation is really ok or not.

PRC SRC MICH lengths tolerances of 2 mm in the real world will be very difficult !

Next I will check what happens on 3f signals.

 Quote: Required arm length = 37.7974 +/- 0.02 [m] This is a preliminary result of the estimation of the Arm length tolerance. This number was obtained from a simulation based on Optickle. Note that the simulation was done by considering misplacements in only the arm lengths while keeping PRCL, SRCL and MICH at the ideal lengths. Therefore the tolerance will be somewhat tighter if misplacements in the central part are taken into account. Next : check 3f signals, and include misplacements in PRCL, SRCL and MICH.         Figure.2  A sensing matrix of the 40-m DRFPMI while changing the position of ETMX/Y by \sigma = 2 cm. For convenience,  only REFL11, AS55, POP11 and POP55 are shown. They are the designed signal ports that mentioned in the aLIGO LSC document (T1000298). In all the histograms, x-axis represents the optical gain in log scale in units of [W/m]. The y-axis is the number of events. The diagonal ports are surrounded by red rectangular window.         (Results2 : demodulation phase of MICH and SRCL on POP55) Now a special attention should be payed on the MICH and SRCL signals on POP55. Since MICH and SRCL are designed to be taken from POP55, they must be nicely separated in their demodulation phases. Therefore the demodulation phase of MICH and SRCL has to be carefully examined. The plot in Figure.3 is the resultant phase difference between MICH and SRCL on POP55 when \sigma_x = \sigma_y = 2 cm. As shown in the plot the phase are always within a range of 60 - 120 deg, which satisfies my requirement (2) mentioned in the last section.          Figure.3 Difference in the demodulation phase of MICH and SRCL on POP55. x-axis is the difference in the demodulation phase of MICH and SRCL, and y-axis the number of events.

5292   Tue Aug 23 17:51:37 2011 KeikoUpdateLSCTolerance of PRC, SRC, MICH length = 2 mm ?

Keiko, Kiwamu

We noticed that we have used wrong code for MICH degree of freedom for both of the ELOG entries on this topic (cavity lengths tolerance search). It will be modified and posted soon.

5076   Sun Jul 31 17:28:34 2011 kiwamuSummaryLSCTolerance of Arm length = 2 cm

Required arm length = 37.7974 +/- 0.02 [m]

This is a preliminary result of the estimation of the Arm length tolerance.

This number was obtained from a simulation based on Optickle.
Note that the simulation was done by considering misplacements in only the arm lengths while keeping PRCL, SRCL and MICH at the ideal lengths.
Therefore the tolerance will be somewhat tighter if misplacements in the central part are taken into account.

Next : check 3f signals, and include misplacements in PRCL, SRCL and MICH.

(Background)
We will re-position the ETMY/Y suspensions to adjust the arm lenghts during the coming vent.
To get a reasonable sensing matrix for LSC, the arm length must be adjisted within a certain precision.
So we need to know the tolerance of the arm lengths.

(How to estimate)
Optickle, a frequency domiain interferomtere simulator, is used to model the response of the 40m interferometer.
I buit a 40m model in Optickle, and in this model every optical distance is adjusted to the perfect length.
Then some offsets are added on the macroscopic position of ETMs to see what will happen in the LSC sensing matrix.
When putting the offsets, the amount of offsets are randomly assigned with a Gaussian distribution (see Figure.1).
Therefore the calculation is a Monte-Calro style, but this doesn't have to be a Monte-Calro
because the parameter space is only 2-dimensions (i.e. X-arm and Y-arm length) and it can be done by simply scanning the 2-dimentional parameter space.
The reason why the Monte-Calro style was chosen is because I wanted to expand this simulation
to a more general simulation which can handle PRCL, SRCL and MICH misplacements as well.
This time I ran the Monte-Calro 1000 times.

Figure.1 History of random walk in X-Y arm lengths parameter space.
The position of ETMY and ETMX are randomly chosen with a Gaussian distribution function in every simulation.
This example was generated when \sigma_x = \sigma_y = 2 cm, where \sigma is the standard deviation of
the Gaussian function. The number of simulation is 1000 times.

(Criteria)
I made two criteria for the acceptable sensing matrix as follows :
(1) The decrease in the optical gain of the important signals (diagonal signals) must be within a factor of 3 (factor of ~ 0.5 in log scale).
(2) MICH and SRCL signals are separated within a range of 60 - 120 deg in their demodulation phases on POP55.

(Results1 : sensing matrix)
Figure.2 shows the resultant sensing matrix with histograms when \sigma_x = \sigma_y = 2,
where \sigma_x, \sigma_y are the given standard deviation in the position of ETMX and ETMY.
The diagonal signals (in red-rectangular window) shows variation in their optical gain within a factor of 0.5 in log scale (factor of 3 in linear scale).
This satisfies my requirement (1) mentioned in the last section.

Figure.2  A sensing matrix of the 40-m DRFPMI while changing the position of ETMX/Y by \sigma = 2 cm.
For convenience,  only REFL11, AS55, POP11 and POP55 are shown. They are the designed signal ports that
mentioned in the aLIGO LSC document (T1000298). In all the histograms, x-axis represents the optical gain in log scale in units of [W/m].
The y-axis is the number of events. The diagonal ports are surrounded by red rectangular window.

(Results2 : demodulation phase of MICH and SRCL on POP55)
Now a special attention should be payed on the MICH and SRCL signals on POP55.
Since MICH and SRCL are designed to be taken from POP55, they must be nicely separated in their demodulation phases.
Therefore the demodulation phase of MICH and SRCL has to be carefully examined.
The plot in Figure.3 is the resultant phase difference between MICH and SRCL on POP55 when \sigma_x = \sigma_y = 2 cm.
As shown in the plot the phase are always within a range of 60 - 120 deg, which satisfies my requirement (2) mentioned in the last section.

Figure.3 Difference in the demodulation phase of MICH and SRCL on POP55.
x-axis is the difference in the demodulation phase of MICH and SRCL, and y-axis the number of events.

(Notes on the Optickle model)
Optickle that I used is the one downloaded from the MIT CVS server and I believe this is the latest version.
In my current simulation I omitted some foldng mirrors including PR3, SR2 and SR3.
If those mirrors are added on the model, loss from those mirrors will affect the build up powers in all the cavities and hence changes the sensinag matrix somewhat.
I assumed that each optic has loss of 50 ppm in its HR surface.
Input power, after the MC, of 1 W is assumed.
The modulation depth are all 0.1 rad for 11MHz and 55MHz.
The model files were uploaded on the MIT CVS server and files reside under /export/cvs/iscmodeling/40m/fullIFO_Optickle.
More information about the CVS server can be found on aLIGO wiki.

5081   Mon Aug 1 11:46:56 2011 ranaSummaryLSCTolerance of Arm length = 2 cm

wow. This Monte-Carlo matrix is one of the most advanced optical modeling things I have ever seen. We never had this for any of the interferometers before.

483   Fri May 16 17:27:55 2008 AndreyOmnistructureGeneralToilets are broken, do not use them !!!

Both toilets in 40-meter were constantly flushing, the leaking water was on the floor inside of the restrooms, so

BOTH RESTROOMS ARE CLOSED TILL MONDAY

I have heard the constant loud sound of flushing water, opened the door, and was unpleasantly surprised because all the floor was under the layer of water and the toilets were constantly flushing. I called security at X5000, a plumber came in and told that a team of plumbers needs to repair the flushing system after the weekend. The plumber today just shut off the flushing water, wiped off the floor and told not to use the restrooms in the weekend. We should expect a team of plumbers on Monday.

Sinks are working, so you can wash your hands.
16485   Wed Nov 24 17:13:31 2021 YehonathanMetaphysicsGeneralToilet tank broken

The toilet tank in the big bathroom stopped refilling. I contacted PPService@caltech.edu and put up an "Out of Order sign".

16487   Tue Nov 30 11:03:44 2021 YehonathanMetaphysicsGeneralToilet tank broken

a plumber came in yesterday and fixed the issue.

 Quote: The toilet tank in the big bathroom stopped refilling. I contacted PPService@caltech.edu and put up an "Out of Order sign".

5214   Fri Aug 12 17:27:49 2011 YoichiSummaryCDSToggle button for RCG
Bottom line: I made an RCG block to realize a toggle button easily.

Read on if you need such a button, or if you want to know how to
write a new RCG block with C.

-----------------
When I was making MEDM screens for FFC, I wanted to have a toggle
button to enable/disable the FFC path.
I wanted to have something like the ON/OFF buttons of the filter bank
screens, the one changes its state every time I click on it.
However, I could not find an easy way to realize that.

From MEDM, I can send a value to an EPICS channel using a "Message Button".
This value is always the same, say 1.
In the RCG model, I used a cdsEpicsMomentary block so that whenever the channel
gets 1, it stays to be 1 for a while and turns back to 0 in a second or so.
This generates a pulse of 1 when I click on a message button on a MEDM screen.
Then I needed a block to keep its internal state (0 or 1), and flips its state
whenever it receives a pulse of 1.
Since I couldn't find such a block in the current RCG library, I implemented one
using the cdsFunctionCall block. It allows you to implement a block with C code.

There is a good explanation of how to use this block in the CDS_PARTS library.
Here is basically what I did.

(1) Drag and drop thee cdsFunctionCall block to my model.

(2) In the "Block Properties", I put the following line in the Description field.
inline cdsToggle /opt/rtcds/caltech/c1/userapps/release/cds/common/src/cdsToggle.c

This means to call a function cdsToggle(), whose code is in the file indicated above.

(3) The contents of the source code is very simple.
void cdsToggle(double *in, int inSize, double *out, int outSize){
static double x = 0;
static double y = 0;

if (*in != y){
y = *in;
if (y == 1){
x = (x == 1) ? 0 : 1;
*out = x;
}
}
}

The function prototype is always the same. *in and *out are the pointers to the arrays of doubles
for input and output signals of the block. In simuLink, the signals have to be
multiplexed so that the RCG can know how many signals are handed to or returned from the function.
In order to keep the internal state of my custom block, I used "static" keyword in the
declaration of the variables. The rest of the code should be obvious.

(4) Just compile the model as usual. The RCG will automatically include the source code and put
a call to the function in the proper place.

I made the block a library so that people can use it.
/opt/rtcds/caltech/c1/userapps/trunk/cds/common/models/cdsToggle.mdl
is the one.
For the usage of it, please have a look at
/opt/rtcds/caltech/c1/userapps/trunk/isc/c1/models/c1lsc
4282   Mon Feb 14 01:19:18 2011 ranaUpdateCDSToday's CDS problems

This is just a listing of  CDS problems I still notice today:

1. MC2-MCL button was left ON due to BURT failure. This, of course, screws up our Green locking investigations because of the unintended feedback. Please fix the BURT/button issue.

2. The GCV - FB0 status is RED. I guess this means there's something wrong? Its really a bad idea to have a bunch of whited out or falsely red indicators. No one will ever use these or trust these in the future.
3. MC1/2/3 Lockins are all white. Also, the MODE switches for the dewhitening are all white.
4. Is the MC SIDE coil dewhitening filter synced with anything? It doesn't seem to switch anything. Maybe the dewhite indicators at the top right of the SUS screens can be made to show the state of the binary output instead of just the digital filter
5. MC WFS is all still broken. We need a volunteer to take this on - align beams, replace diodes, fix code/screens.
4285   Mon Feb 14 07:58:43 2011 SureshUpdateCDSToday's CDS problems

I am concentrating on the RF system just now and will be attending to the RF PDs one by one.  Also plan to work on some of the simpler CDS problems when I overlap with Joe.  Will be available for helping out with the beam alignment.

4309   Wed Feb 16 23:54:34 2011 ranaUpdateCDSToday's CDS problems
1. ETMX cannot load his filter coefficients. Even if I change the file, the load button doesn't work. I tried changing the lockin filters but they won't load.
2. The ETMX filter modules appear to have 2048 for some of the modules and 16384 for some of the others. How come the make script doesn't make them all 16384?
3. There are a bunch of kill/start scripts in the scripts/ directory instead of in the scripts/FE/ directory. Did this get reverted after a new code exchange?
4. I tried restarting the code using c1startscx, but that doesn't work correctly. It cannot find the burtrb and burtwb files even though they are in the normal path.
5. Kiwamu was using a bunch of cockamamie filters I found.
6. I can't get any minute trend data. I tried on rossa, rosalba, and op440m.
 MC damp dataviewer diaggui AWG c1lsc c1ioo c1sus c1iscex c1iscey RFM The Dolphins Sim.Plant Frame builder TDS Cabling
50   Thu Nov 1 19:53:02 2007 Andrey RodionovBureaucracyPhotosTobin's picture
9667   Mon Feb 24 23:43:10 2014 ranaSummaryGeneralToDo

1) Fixup REFL165: remove ND filters, get box for PD, dump diode reflections, put less light on diode, change DC transimpedance (?), max power dissipation on BBPD < 0.5 W w/ 25 V bias. Perhaps replace OP27 with TLE2027.

2) Make plan for fixing fiber layout up and down the arms. Need tubing for the whole run. Don't make it cheesy. Two fibers per arm.

3) Fix LSC model to allow user switching of whitening. Get back to working on AutoLock scripts (not Guardian).

4) Manasa, Q, Jenne, tune Oplev servos Tuesday morning/afternoon.

5) Reconnect the other seismometers (Steve, Jenne). For real.

6) Balance PRMI coils at high frequency.

4199   Tue Jan 25 06:48:55 2011 kiwamuUpdateGreen LockingTo do list

Here are some tasks that I want someone to work on during my absence.

1. Y-arm alignment for IR

Basically we gradually have to move onto the Y-arm locking at some point.

Prior to it we need to align the Y arm for IR. Probably we have to touch PZT1 and PZT2.

It would be very nice if the X-arm alignment also gets improved together with this work.

2. Temperature feedback with a digital control for X end PDH lock

Need a temperature feedback not with an analog way but with a digital way because we want to put an offset and the feedback signal at the same time (#4198).

Right now the temperature control input of the laser is connected to a slow DAC (#3850).

Probably we should plug the feedback signal from the PDH box to the fast ADC (i.e. c1iscex), and then connect a fast DAC to the laser temperature.

This entry maybe helpful.

3. Calibration of optical gain for IR arm locking

In order to evaluate the performance of the green locking, one of the key points is the IR PDH signal.

Because it tells us how much the motion of the X arm is suppressed at IR when the green lock is engaged.

To get this information in m/sqrtHz, we need to know the optical gain.

4. MC servo characterization and PSL frequency noise measurement

SInce the green beat note tells us the frequency difference between the MC and the arm in the current configuration, we should know how the MC servo is.

Along with this work, I need someone to measure the PSL frequency noise, when it is locked to the MC over the frequency range from 0.01Hz to 1kHz.

5. PLL characterization

Solve this issue (#4195) and make it reliable.

14047   Mon Jul 9 17:29:28 2018 Udit KhandelwalSummaryTip-TIltTipTilt mirror holder final changes

Final Summary of changes to mirror holder in Tip-Tilt holder.

Determining minimum range for Side Clamp:

1. The initial distance b/w wire-release point and mirror assembly COM = 0.265 mm

2. But this distance is assuming that wire-release point is at mid-point of clamp. So I'm settling on a range of +/- 1mm. The screenshots below confirm range of ~1mm between (1) side screw & protrusion and (2) clamp screw and clamp.

Determining length of tilt-weight assembly rod at the bottom to get $\pm$ 20mRad range

The tilt-weight assembly is made from following Mcmaster parts:
Rod   - 95412A864 18-8 SS  #2-56 Threaded Rod
Nuts  - 91855A103 18-8 SS #2-56 Acorn Cap Nut

Since the weights are fixed, only rod length can be changed to get the angle range.

$tan \theta =\frac{d}{h}$

$d= h \times tan\theta = 34.25\text{mm} \times tan(20 \text{mRad}) = 0.69 \text{mm}$
So a range of 1 mm between nut's inner face and mirror-holder face should be enough. Since holder is 12 mm thick, rod length = 12mm + 2 x 1mm + 2 x (nut length) = 12 + 2 + 9.6 = 23.6 mm = 0.93 inch. So a 1" rod from Mcmaster will be fine.

6770   Wed Jun 6 19:46:46 2012 SureshSummaryIOOTip-tilt assembly: current status and work remaining

Recent History

The lower blades which I had given to the Physics Workshop for making a vacuum relief hole (using a sinker-EDM process) came back about ten days ago.   Merih Eken <meken@caltech.edu>,  the supervisor at the Physics Dept workshop, handled this matter for us.  The blades were sent to a local EDM machineshop and returned in about three working days ( a weekend intervened).

Bob cleaned and handed them over to me yesterday evening.

Current status

Today I have reassembled the four tip-tilts.  I have repacked them in clean bags (double bagged) shifted them to Clean Optics Cabinet (near the ETMX chamber).  The four tip-tilts are in the bottom-most shelf in the cabinet.  There are also some tip-tilt spares in a separate envelope.

Note:  The mirror holder is now held tightly by the eddy current dampers.  This was done for safety of the wires during transportation from LHO.  The eddy current damper in the front of the mirror has to be retracted to allow the mirror holder to swing free.  It has be to about 1mm away from the suspended mirror holder

Work Remaining

1) We need to install the quadrapus cables.  The connector placement on the BOSEM side will have some issues.  It is best to loosen the BOSEM seating as well as the connector seating screws and then push the cable connector into place.  Caution:  when the connector seating screws on the BOSEM are loosened the flexible ckt could be damaged by the loose connector.

2) Insert the mirrors into the mirror holders and balance the suspension such that the mirror's hang vertical and do not have a large yaw offset.

3) Adjust the wire suspension point height so that the flags are in the center of the BOSEM aperture.  Else they will strike against the

4) We need to adjust the position of the BOSEMs such that the shadow sensor signals are at 50%.  This ensures that all the magnets hang at an appropriate distance from their respective coils.

5) To do (3) we need to set up a shadow sensor read-out set-up for one tip-tilt (four sensors)

14742   Wed Jul 10 10:04:09 2019 gautamUpdateSUSTip-Tilt moved from South clean cabinet to bake lab cleanroom

Arnaud and I moved one of the two spare TT suspensions from the south clean cabinet to the bake lab clean room. The main purpose was to inspect the contents of the packaging. According to the label, this suspension was cleaned to Class A standards, so we tried to be clean while handling it (frocks, gloves, masks etc). We found that the foil wrapping contained one suspension cage, with what looked like all the parts in a semi-assembled state. There were no OSEMs or electronics together with the suspension cage. Pictures were taken and uploaded to gPhoto. Arnaud is going to plan his tests, so in the meantime, this unit has been stored in Cabinet #6 in the bake lab cleanroom.

6756   Tue Jun 5 20:42:59 2012 SureshSummaryIOOTip-Tilt Cabling

I have made a preliminary sketch of the cabling involved in connecting the Tip-tilt coil drivers.   This is a preliminary document.

 Required parts Quantity Solution 1) DAC Card inserted into C1IOO machine 1 buy or borrow from Cymacs 2) SCSI cable from DAC to D080303 box 1 buy or find at the 40m 3) D080303 box (SCSI to IDC breakout box) 1 Jay may have had spare, if not we have to make one 4) 40 pin IDC cables from D080303 to AntiImaging filter 2 Jay may have kept some stock if not make them 5) 10 pin IDC cables from Anti Imaging filters to Whitening filters 2 make 6) sma to lemo cables from Whitening to coil drivers 4x4=16 buy 7) 15pin IDC to 25pin DSub cables from drivers to feedthroughs on the chambers 4  (length?) make 8) 25pin DSub feedthrough on OMC chamber 1 check in 40m stock else buy 9) 25pin DSub  Kapton strip cable from OMC wall to table top 1 check if any spare are available in aLIGO stock 10) 25pin DSub Kapton strip cable from post to tip-tilt 4 aLIGO team said they have a few to spare if not buy 10) Quadrapus cables on the tip-tilts 4 Jamie is negotiating with aLIGO cable team

6759   Tue Jun 5 22:39:06 2012 JenneSummaryIOOTip-Tilt Cabling

2 questions (so far) regarding your diagram / doc:

We are using 3 of the feed-throughs on the BS chamber, and 1 on the OMC chamber, even though we have 2 TTs on the BS table, 1 on the OMC table, and 1 on the IMC table? Just wanted to check.

Does your list / table at the bottom include all of the cables we already have, as well as the ones we need?  (Or maybe we just have nothing so far, so this is a moot question).

6762   Wed Jun 6 01:23:32 2012 SureshSummaryIOOTip-Tilt Cabling

 Quote: 2 questions (so far) regarding your diagram / doc: We are using 3 of the feed-throughs on the BS chamber, and 1 on the OMC chamber, even though we have 2 TTs on the BS table, 1 on the OMC table, and 1 on the IMC table? Just wanted to check. Does your list / table at the bottom include all of the cables we already have, as well as the ones we need?  (Or maybe we just have nothing so far, so this is a moot question).

The scheme currently is to run a 25pin Kapton strip cable from BS to IMC table inside the chamber.  However we cannot do the same for the OMC table since it will cross the bellows which we often remove.  So we need to supply the one tip-tilt on the OMC table from outside.  I could not spot a spare unused feedthough on the OMC chamber.  We will have to swap one of the blank flanges for one with a few feed throughs.

We do not have any of the cables.   So everything listed has to be arranged for.   The pics are from the existing coil driver system on the SUS machine.

7625   Thu Oct 25 20:44:11 2012 JenneUpdateSUSTip tilts in progress

Jamie and I spent some time with tip tilt SN001 this afternoon.  This was installed as SR3, so I was going to put a new LaserOptik mirror in there.  I accidentally snapped one of the wires (I forgot how strong the magnets are - one zipped from the mirror holder and captured the wire).  Jamie and I put the new LaserOptik mirror in, with the wedge correct, but we need to re-resuspend it with the 0.0036" wire tomorrow.  We'll also keep working on re-pitch aligning the other optics.

PR2 needs to be put back as a G&H, and we need to put a LaserOptik mirror into PR3.

7630   Fri Oct 26 10:44:25 2012 JenneUpdateSUSTip tilts in progress

 Quote: Jamie and I spent some time with tip tilt SN001 this afternoon.  This was installed as SR3, so I was going to put a new LaserOptik mirror in there.  I accidentally snapped one of the wires (I forgot how strong the magnets are - one zipped from the mirror holder and captured the wire).  Jamie and I put the new LaserOptik mirror in, with the wedge correct, but we need to re-resuspend it with the 0.0036" wire tomorrow.  We'll also keep working on re-pitch aligning the other optics. PR2 needs to be put back as a G&H, and we need to put a LaserOptik mirror into PR3.

We resuspended SN001 this morning with 0.0036" wire.  We did as Koji suggested, and flipped the wire clamp so the suspension point is a little higher, so we'll see if that helps.  We put LaserOptik mirror SN1 into this TT001.

We put the G&H mirror back into TT004, which is PR2.  We also put a LaserOptik mirror (SN5) into TT005, which is SR3.

Jamie is working on re-pitch aligning TT004 and TT005 (we already did 001), then we can re-install them in the vacuum system later this afternoon.

7631   Fri Oct 26 13:08:14 2012 JenneUpdateSUSTip tilts in progress

Quote:

 Quote:

Jamie is working on re-pitch aligning TT004 and TT005 (we already did 001), then we can re-install them in the vacuum system later this afternoon.

The tip tilts have all been pitch-adjusted now, and they have all been put back onto the tables, with the same serial numbers in the same places as we took them out.  Jamie also re-leveled the BS table.

Raji and I will align things after I finish measuring the MC spot positions.

7601   Tue Oct 23 18:12:18 2012 JenneUpdateAlignmentTip tilt wires - the truth

 Quote: At this point I cried foul.  This is not an acceptable situation.  Very little stimulation to the tip-tilts can repoint the beam inside the PR cavity. Steve says that the TT weights, which will attach to the base of the TT mirror mounts and should help keep the mirrors vertical and not hysteretic, are being baked now and should be available tomorrow.

We also wrote down the serial numbers (top center of each TT, inscribed by hand) for what tip tilt is installed where.  I then went through the elog to determine which TT was suspended with what kind of wire (thick or thin).  Summary: all installed tip tilts have thick wire, 0.0036" diameter.

As noted in elog 3295, we had found that there was similar hysteresis whether we used the thick or the thin wire, so we had decided not to go back and re-suspend every optic.

Also, since we will redo the pitch balance tomorrow with the new hardware tomorrow, I think we should put in the new LaserOptik mirrors at the same time.  We have not yet gotten phase maps of them, but we might as well do this rebalancing once, rather than twice.

 Serial number Installed as Wire thickness Notes, elog reference 001 SR 3 0.0036" See elog 3437 002 SR 2 0.0036" See elog 3295 003 PR 2 0.0036" No elog, but inferred since there were 4 with thick wire, and #004 is the thin wire one.  Elog 3437 has notes on the 4 thick, 1 thin situation. 004 spare, dirty originally 0.0017", but looks redone with thicker wire See elog 3295 005 PR 3 0.0036" Was supposed to be spare according to elog 3437, but was installed.  See elog 3437

3162   Tue Jul 6 17:38:27 2010 JenneUpdateSUSTip Tilt Progress!

[Jenne, Kyung Ha]

We successfully suspended the 4 eddy current dampers for the first Tip Tilt.  We had some lessons learned, including how to carefully get an allen wrench in between the dampers to do up some of the screws, and how to be careful not to bend the wire while tightening the screws.  More tomorrow...

ELOG V3.1.3-


text:
Amazon Polly breathes life into text by converting it into lifelike speech. This empowers developers and businesses to create applications that can converse in real time, thereby offering an enhanced interactive experience. Text-to-speech (TTS) in Amazon Polly supports a variety of languages and locales, which enables you to perform TTS conversion according to your preferences. Multiple factors guide this choice, such as geographic location and language locales.

Amazon Polly uses advanced deep learning technologies to synthesize text to speech in real time in various output formats, such as MP3, ogg vorbis, JSON, or PCM, across standard and neural engines. The Speech Synthesis Markup Language (SSML) support for Amazon Polly further bolsters the service’s capability to customize speech with a plethora of options, including controlling speech rate and volume, adding pauses, emphasizing certain words or phrases, and more.

In today’s world, businesses continue to expand across multiple geographic locations, and they’re continuously looking for mechanisms to improve personalized end-user engagement. For instance, you may require accurate pronunciation of certain words in a specific style pertaining to different geographical locations. Your business may also need to pronounce certain words and phrases in certain ways depending on their intended meaning. You can achieve this with the help of SSML tags provided by Amazon Polly.

This post aims to assist you in customizing pronunciation when dealing with a truly global customer base.

## Modify pronunciation using phonemes

A phoneme can be considered as the smallest unit of speech. The <phoneme> SSML tag in Amazon Polly helps customize pronunciation based on phonemes using the IPA (International Phonetic Alphabets) or X-SAMPA (Extended Speech Assessment Methods Phonetic Alphabet). X-SAMPA is a representation of IPA in ASCII encoding. Phoneme tags are available and fully supported in both the standard and neural TTS engine. For example, the word “lead” can be pronounced as the present tense verb, or it can refer to the chemical element lead. We will discuss this with an example further in this blog post.

### International Phonetic Alphabet

The IPA is used to portray sounds across different languages. For a list of phonemes Amazon Polly supports, refer to Phoneme and Viseme Tables for Supported Languages.

By default, Amazon Polly determines the pronunciation of the word in a specific format. Let’s use the example of the word “lead,” which can have different pronunciations when referring to the chemical element or the verb. In this example, when we provide the word “lead” as input, it’s spoken in the present tense form (without the use of any customizing SSML tags). The default pronunciation for L E A D by Amazon Polly is the present tense form of “lead.”

<speak>
The default pronunciation by Amazon Polly for L E A D is <break time = "300ms"/> lead,
which is the present tense form.
</speak>

To return the pronunciation of the chemical element lead (which can also be the verb in past tense), we can use phonemes along with IPA or X-SAMPA. IPA is generally used to customize the pronunciation of a word in a given language using phonemes:

<speak>
This is the pronunciation using the
<say-as interpret-as="characters">IPA</say-as> attribute
in the <say-as interpret-as="characters">SSML</say-as> tag. The verb form for L E A D is <break time="150ms"/> lead.
The chemical element <break time="150ms"/><phoneme alphabet="ipa" ph="lɛd">lead</phoneme> <break time="300ms"/>also has an identical spelling.
</speak>

## Modify pronunciation by specifying parts of speech

If we consider the same example of pronouncing “lead,” we can also differentiate between the chemical element and the verb by specifying the parts of speech using the <w> SSML tag.

The <w> tag allows us to customize pronunciation by specifying parts of speech. You can configure the pronunciation in terms of verb (present simple or past tense), noun, adjective, preposition, and determiner. See the following example:

<speak>
The word
 <say-as interpret-as="characters">lead</say-as>
 may be interpreted as either the present simple form <w role="amazon:VB">lead</w>, or the chemical element <w role="amazon:SENSE_1">lead</w>.
</speak>

Additionally, you can use the  tag to indicate the pronunciation of acronyms and abbreviations:

<speak>
Polly is an AWS offering providing text-to-Speech service. </speak>

### Extended Speech Assessment Methods Phonetic Alphabet

The X-SAMPA transcription scheme is an extrapolation to the various language-specific SAMPA phoneme sets available.

The following snippet shows how you can use X-SAMPA to pronounce different variations of the word “lead”:

<speak>
This is the pronunciation using the X-SAMPA attribute, in the verb form <break time="1s"/> lead.
The chemical element <break time="1s"/> <phoneme alphabet='x-sampa' ph='lEd'>lead</phoneme> <break time="0.5s"/>
also has an identical spelling.
</speak>

The stress mark in IPA is usually represented by ˈ. We often encounter scenarios in which an apostrophe is used instead, which might give a different output than expected. In X-SAMPA, the stress mark is the double quotation mark, therefore we should use a single quotation mark for the word and specify the phonemic alphabet. See the following example:

<speak>
You say, <phoneme alphabet="ipa" ph="pɪˈkɑːn">pecan</phoneme>. </speak>

In the example above, we can see the character ˈ used for stressing the word. Similarly, the stress mark in X-SAMPA is shown in double quotation below:

<speak>
You say, <phoneme alphabet='x-sampa' ph='pI"kA:n'>pecan</phoneme>.
</speak>

## Modify pronunciations using other SSML tags

You can use the <say as> tag to modify pronunciation by enabling the spell-out or character feature. Furthermore, it enhances pronunciations in terms of digits, fractions, unit, date, time, address, telephone, cardinal, and ordinal, and can also censor the text enclosed within the tag. For more information, refer to Controlling How Special Types of Words Are Spoken. Let’s look at examples of these attributes.

### Date

By default, Amazon Polly speaks out different text inputs. However, for handling specific attributes such as dates, you can use the date attribute to customize pronunciation in the required format, such as month-day-year or day-month-year.

Without the date attribute, Amazon Polly provides the following output when speaking out dates:

<speak>
The default pronunciation when using date is 01-11-1996
</speak>

However, if you want the dates spoken in a specific format, the date attribute in the <say-as> tags helps customize the pronunciation:

<speak>
We will see the examples of different date formats using the date SSML tag.
The following date is written in the day-month-year format.
<say-as interpret-as="date" format="dmy">01-11-1995</say-as><break time="500ms"/>
The following date is written in the month-day-year format.
<say-as interpret-as="date" format="mdy">09-24-1995</say-as>
</speak>

### Cardinal

This attribute represents a number in its cardinal format. For example, 124456 is pronounced “one hundred twenty four thousand four hundred fifty six”:

<speak> The following number is pronounced in it's cardinal form.
<say-as interpret-as="cardinal">124456</say-as>
</speak>

### Ordinal

This attribute represents a number in its ordinal format. Without the ordinal attribute, the number is pronounced in its numerical form:

<speak>
The following number is pronounced in it's ordinal form without the use of any SSML attribute in the say as tag - 1242 </speak>

If we want to pronounce 1242 as “one thousand two hundred forty second,” we can use the ordinal attribute:

<speak>
The following number is pronounced in it's ordinal form.
<say-as interpret-as="ordinal">1242</say-as>
</speak>

### Digits

The digits attribute is used to speak out the numbers. For example, “1234” is pronounced as “one two three four”:

<speak>
The following number is pronounced as individual digits.
<say-as interpret-as="digits">1242</say-as>
</speak>

### Fraction

The fraction attribute is used to customize the pronunciations in the fractional form:

<speak> The following are examples of pronunciations when <prosody volume="loud"> fraction</prosody>
is used as an attribute in the say -as tag. <break time="500ms"/>Seven one by two is pronounced as
<say-as interpret-as="fraction">7 ½ </say-as>
whereas three by twenty is pronounced as <say-as interpret-as="fraction">3/20</say-as>
</speak>

### Time

The time attribute is used to measure the time across minutes and seconds:

<speak>
Polly also supports customizing pronunciation in terms of minutes and seconds. For example, <say-as interpret-as="time">2'42"</say-as>
</speak>

### Expletive

The expletive attribute censors the text enclosed within the tags:

<speak> The value that is going to be censored is
<say-as interpret-as="expletive">this is not good</say-as>
You should have heard the beep sound.
</speak>

### Telephone

To pronounce telephone numbers, you can use the telephone attribute to speak out telephone numbers instead of pronouncing them as standalone digits or as a cardinal number:

<speak>
The telephone number is <say-as interpret-as="telephone">1800 3000 9009</say-as>
</speak>

The address attribute is used to customize the pronunciation of an address aligning to a specific format:

<speak> The address is<break time="1s"/>
<say-as interpret-as="address">440 Terry Avenue North, Seattle
WA 98109 USA</say-as>
</speak>

## Lexicons

We’ve looked at some of the SSML tags readily available in Amazon Polly. Other use cases might require a higher degree of control for customized pronunciations. Lexicons help achieve this requirement. You can use lexicons when certain words need to be pronounced in a certain form that is uncommon to that specific language.

Another use case for lexicons is with the use of numeronyms, which are abbreviations formed with the help of numbers. For example, Y2K is pronounced as the “year 2000.” You can use lexicons to customize these pronunciations.

Amazon Polly supports lexicon files in .pls and .xml formats. For more information, see Managing Lexicons.

## Conclusion

Amazon Polly SSML tags can help you customize pronunciation in a variety of ways. We hope that this post gives you a head start into the world of speech synthesis and powers your applications to provide more lifelike human interactions.

format: plain


text:
A souped-up version of Pardini's theorem and its application to funny curves
Compositio Mathematica, Tome 71 (1989) no. 3, pp. 295-302.
@article{CM_1989__71_3_295_0,
author = {Homma, Masaaki},
title = {A souped-up version of {Pardini's} theorem and its application to funny curves},
journal = {Compositio Mathematica},
pages = {295--302},
publisher = {Kluwer Academic Publishers},
volume = {71},
number = {3},
year = {1989},
zbl = {0703.14017},
mrnumber = {1022047},
language = {en},
url = {http://www.numdam.org/item/CM_1989__71_3_295_0/}
}
TY  - JOUR
AU  - Homma, Masaaki
TI  - A souped-up version of Pardini's theorem and its application to funny curves
JO  - Compositio Mathematica
PY  - 1989
DA  - 1989///
SP  - 295
EP  - 302
VL  - 71
IS  - 3
PB  - Kluwer Academic Publishers
UR  - http://www.numdam.org/item/CM_1989__71_3_295_0/
UR  - https://zbmath.org/?q=an%3A0703.14017
UR  - https://www.ams.org/mathscinet-getitem?mr=1022047
LA  - en
ID  - CM_1989__71_3_295_0
ER  -
Homma, Masaaki. A souped-up version of Pardini's theorem and its application to funny curves. Compositio Mathematica, Tome 71 (1989) no. 3, pp. 295-302. http://www.numdam.org/item/CM_1989__71_3_295_0/

1 M. Homma, Funny plane curves in characteristic p > 0, Comm. Algebra 15 (1987) 1469-1501. | MR 884025 | Zbl 0623.14014

2 H. Kaji, On the Gauss map of space curves in characteristic p, to appear in Comp. Math. | Numdam | MR 996326

3 S.L. Kleiman, Intersection theory and enumerative geometry: A decade review, Proc. of Symposia in Pure Math. 46, Amer. Math. Soc., (1987) 321-370. | MR 927987 | Zbl 0664.14031

4 R. Pardini, Some remarks on plane curves over fields of finite characteristic, Comp. Math. 60 (1986) 3-17. | Numdam | MR 867952 | Zbl 0607.14023

5 F.K. Schmidt, Die Wronskisch Determinante in belebigen differenzierbaren Funktionenkörpern, Math. Z. 45 (1939) 62-74. | JFM 65.0115.02 | MR 1545804 | Zbl 0020.10201


text:
## References

int a = 2;
int c = 3;
int &refA = a; // refA is a reference to the variable a
int b = refA; // has same effect as b = a

refA = 5; // has same effect as a = 5

int &refC1 = c;
int &refC2 = c;  // both refC1 and refC2 refer to c

Open Source Your Knowledge: become a Contributor and help others learn.


text:
# Angel dust of matrices

A matrix ${A}$ with real entries has positive characteristic polynomial if ${\det(tI-A)\ge 0}$ for all real ${t}$. For example,

$\displaystyle A=\begin{pmatrix} 1 & -5 \\ 3 & -2 \end{pmatrix}$

has this property: ${\det (tI-A)=(t-1)(t+2)+15=t^2+t+13}$. For brevity, let’s say that ${A}$ is a PCP matrix.

Clearly, any PCP matrix must be of even size. Incidentally, this implies that the algebraists’ characteristic polynomial ${\det (tI-A)}$ and the analysts’ characteristic polynomial ${\det (A-tI)}$ coincide.

In general, there is no reason for the PCP property to be preserved under either addition or multiplication of matrices. But there are some natural rings of PCP matrices, such as

• complex numbers ${\begin{pmatrix} a & b \\ -b & a \end{pmatrix} }$
• quaternions ${\begin{pmatrix} a & b & c & d \\ -b & a & -d & c \\ -c & d & a & -b \\ -d & -c & b & a \end{pmatrix}}$

A ${2\times 2}$ matrix is PCP if and only if its eigenvalues are either complex or repeated. This is equivalent to ${(\mathrm{tr}\, A)^2 \le 4\det A}$. In general, a matrix of even size is PCP if and only if it has no real eigenvalues of odd algebraic multiplicity.

Is this post merely an excuse for 1995 flashback: Ангельская Пыль by Ария?


text:
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## maybe vs probably

This topic has 3 expert replies and 11 member replies
gmat_ttt Newbie | Next Rank: 10 Posts
Joined
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Posted:
5 messages

#### maybe vs probably

Thu May 15, 2008 5:10 pm
This is a question from OG.

Of all the possible disasters that threaten American agriculture, the possibility of an adverse change in
climate is maybe the more difficult for analysis.
(A) is maybe the more difficult for analysis
(B) is probably the most difficult to analyze
(C) is maybe the most difficult for analysis
(D) is probably the more difficult to analyze
(E) is, it may be, the analysis that is most difficult

OA is b

The OG explanation says that use of maybe is unidiomatic. Why is that?

### GMAT/MBA Expert

lunarpower GMAT Instructor
Joined
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Fri May 16, 2008 11:26 pm
gmat_ttt wrote:
This is a question from OG.

Of all the possible disasters that threaten American agriculture, the possibility of an adverse change in
climate is maybe the more difficult for analysis.
(A) is maybe the more difficult for analysis
(B) is probably the most difficult to analyze
(C) is maybe the most difficult for analysis
(D) is probably the more difficult to analyze
(E) is, it may be, the analysis that is most difficult

OA is b

The OG explanation says that use of maybe is unidiomatic. Why is that?

1) the most important comment i could make here: it doesn't really matter why. you should follow the gmat's rules slavishly, like a seven-year-old who really wants that piece of candy for bein such a good kid. since the o.g. has just told you, in no uncertain terms, that the use of 'maybe' is unacceptable, that's all you really need to know.
this is not to say that' it's pointless ever to think about 'why'; for most sentences the answer explanations are either simply not there (as for gmatprep problems) or are sufficiently vague to merit debate as to the particulars of the gmat's rules. however, in cases such as this one, where there can be no doubt at all about the rules the gmat employs, just follow their rules.

2) i concur with the official opinion on this one: 'maybe' seems much too informal for formal written english. i would never dream of including the word 'maybe' in any sort of formal paper or article, unless it were embedded in some sort of quote.

_________________
Ron has been teaching various standardized tests for 20 years.

--

Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions Ã  Ron en franÃ§ais
Voit esittÃ¤Ã¤ kysymyksiÃ¤ Ron:lle myÃ¶s suomeksi

--

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--

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chidcguy Master | Next Rank: 500 Posts
Joined
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Posted:
438 messages
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Sat May 17, 2008 6:49 am
How about the usage of perhaps?

Is perhaps preferred over may be?

### GMAT/MBA Expert

lunarpower GMAT Instructor
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Fri May 23, 2008 12:00 am
chidcguy wrote:
How about the usage of perhaps?

Is perhaps preferred over may be?
well, we've established that 'maybe' is proihibited, so anything legitimate would be preferred to it.

but yes, 'perhaps' certainly has a suitable degree of formality.

_________________
Ron has been teaching various standardized tests for 20 years.

--

Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions Ã  Ron en franÃ§ais
Voit esittÃ¤Ã¤ kysymyksiÃ¤ Ron:lle myÃ¶s suomeksi

--

Quand on se sent bien dans un vÃªtement, tout peut arriver. Un bon vÃªtement, c'est un passeport pour le bonheur.

Yves Saint-Laurent

--

Free Manhattan Prep online events - The first class of every online Manhattan Prep course is free. Classes start every week.
goelmohit2002 Legendary Member
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Fri Jul 24, 2009 9:40 am
lunarpower wrote:
gmat_ttt wrote:
This is a question from OG.

Of all the possible disasters that threaten American agriculture, the possibility of an adverse change in
climate is maybe the more difficult for analysis.
(A) is maybe the more difficult for analysis
(B) is probably the most difficult to analyze
(C) is maybe the most difficult for analysis
(D) is probably the more difficult to analyze
(E) is, it may be, the analysis that is most difficult

OA is b

The OG explanation says that use of maybe is unidiomatic. Why is that?

1) the most important comment i could make here: it doesn't really matter why. you should follow the gmat's rules slavishly, like a seven-year-old who really wants that piece of candy for bein such a good kid. since the o.g. has just told you, in no uncertain terms, that the use of 'maybe' is unacceptable, that's all you really need to know.
this is not to say that' it's pointless ever to think about 'why'; for most sentences the answer explanations are either simply not there (as for gmatprep problems) or are sufficiently vague to merit debate as to the particulars of the gmat's rules. however, in cases such as this one, where there can be no doubt at all about the rules the gmat employs, just follow their rules.

2) i concur with the official opinion on this one: 'maybe' seems much too informal for formal written english. i would never dream of including the word 'maybe' in any sort of formal paper or article, unless it were embedded in some sort of quote.
Hi Ron,

Thanks for the explanation....

but as far as I remember there are quite a few correct options in OG where they use "may be"...I am really confused why the same is unidiomatic here but idiomatic in other questions of OG...one example below Q15 of OG-10...where the correct answer is C....

In his research paper, Dr. Frosh, medical director of the Payne Whitney Clinic, distinguishes mood swings. which may be violent without their being grounded in mental disease, from genuine manic-depressive
psychosis.

(A) mood swings, which may be violent without their being grounded in mental disease, from genuine manic-depressive psychosis
(B) mood swings, perhaps violent without being grounded in mental disease, and genuine manic-depressive psychosis ,
(C) between mood swings, which may be violent without being grounded in mental disease, and genuine manic-depressive psychosis
(D) between mood swings, perhaps violent without being grounded in mental disease, from genuine manic-depressive psychosis
(E) genuine manic-depressive psychosis and mood swings, which may be violent without being grounded in mental disease

### GMAT/MBA Expert

lunarpower GMAT Instructor
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Fri Jul 24, 2009 3:28 pm
goelmohit2002 wrote:
but as far as I remember there are quite a few correct options in OG where they use "may be"
that's different.

i was saying that they won't use the SINGLE WORD "maybe". they'll opt instead to use more formally acceptable alternatives, such as "perhaps".

the TWO WORDS "may be" are totally fine.

_________________
Ron has been teaching various standardized tests for 20 years.

--

Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions Ã  Ron en franÃ§ais
Voit esittÃ¤Ã¤ kysymyksiÃ¤ Ron:lle myÃ¶s suomeksi

--

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goelmohit2002 Legendary Member
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Sat Jul 25, 2009 12:32 pm
Edited....Deleted....found my mistake.

Last edited by goelmohit2002 on Sun Jul 26, 2009 5:23 am; edited 1 time in total

goelmohit2002 Legendary Member
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Sun Jul 26, 2009 4:46 am
Edited....Deleted....found my mistake !!!

Last edited by goelmohit2002 on Sun Jul 26, 2009 5:27 am; edited 1 time in total

btg760 Senior | Next Rank: 100 Posts
Joined
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Posted:
33 messages
6
Sun Jul 26, 2009 5:13 am
lunarpower wrote:
goelmohit2002 wrote:
but as far as I remember there are quite a few correct options in OG where they use "may be"
that's different.

i was saying that they won't use the SINGLE WORD "maybe". they'll opt instead to use more formally acceptable alternatives, such as "perhaps".

the TWO WORDS "may be" are totally fine.
Hi Ron,

Suppose both options (B) and (C) have used the word "probably" then which one would be preferable?

(B) is probably the most difficult to analyze
(C) is probably the most difficult for analysis

I still feel "to analyze" is suitable then "for analysis".

Any suggestions?

goelmohit2002 Legendary Member
Joined
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Thu Oct 01, 2009 9:18 am
lunarpower wrote:
goelmohit2002 wrote:
but as far as I remember there are quite a few correct options in OG where they use "may be"
that's different.

i was saying that they won't use the SINGLE WORD "maybe". they'll opt instead to use more formally acceptable alternatives, such as "perhaps".

the TWO WORDS "may be" are totally fine.
Hi Ron,

As per the above discussion, Maybe together is wrong....

but if you will see the OG-12 Q4, OG says "Maybe" and "perhaps" are interchangeable.....not sure what indeed is the case....

does it mean that GMAT has changed its stance between OG-10 and OG-12

Following is the question OG-12, Q4.....OA = E

4. of all the vast tides of migration that have swept through history, maybe none is more concentrated as the wave that brought 12 million immigrants onto American shores in little more than three decades.
A. maybe none is more concentrated as
B. it may be that none is more concentrated as
C. perhaps it is none that is more concentrated than
D. maybe it is none that was more concentrated than
E. perhaps none was more concentrated than

tyronetan82 Senior | Next Rank: 100 Posts
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Thu Aug 19, 2010 9:24 am
my confusion was not maybe vs probably.

I am confused by the use of more vs most, it seems that by using MOST would change the meaning of the question, since the question used more.

I obviously had a bad feeling of choosing D, and had an inclination to choose B since it did sound more logical, BUT B changes more to MOST... can someone explain this please... RON?

gmat_perfect Legendary Member
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Thu Aug 19, 2010 12:58 pm
tyronetan82 wrote:
my confusion was not maybe vs probably.

I am confused by the use of more vs most, it seems that by using MOST would change the meaning of the question, since the question used more.

I obviously had a bad feeling of choosing D, and had an inclination to choose B since it did sound more logical, BUT B changes more to MOST... can someone explain this please... RON?
Good question:

Let me try.
Of all the possible disasters that threaten American agriculture, the possibility of an adverse change in
climate is maybe the more difficult for analysis.

(A) is maybe the more difficult for analysis
(B) is probably the most difficult to analyze
(C) is maybe the most difficult for analysis
(D) is probably the more difficult to analyze
(E) is, it may be, the analysis that is most difficult

See some examples:

Of all the boys, he is the best one to solve the problem.

Of the two boys, Karim is more intelligent.

--> See "OF ALL" leads the sentence to superlative degree. That means when we compare among more than two we need to use "best", most etc.

For the same reason, option B has used MOST.

Got it?

Thanks.

tyronetan82 Senior | Next Rank: 100 Posts
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Sun Aug 22, 2010 11:26 pm
got it. Thanks!!

santhoshnanda Newbie | Next Rank: 10 Posts
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Fri Sep 30, 2011 11:14 am
Difference between maybe and probably :

Probably implies a greater degree of certainty than maybe. For example, let's take two sentences
1. "I will probably hit the gym today."
2. "May be I will hit the gym today."

In the first case the chances of it happening is about 80-90% and in the second case it is only 50%.

Speaking about the question from OG, we are trying to narrow down on one option that is the most difficult to analyse. Hence, by using probably over may be, we are pretty much sure it is 'adverse change' that is the causative.

GmatKiss Legendary Member
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Fri Sep 30, 2011 11:48 am
gmat_ttt wrote:
This is a question from OG.

Of all the possible disasters that threaten American agriculture, the possibility of an adverse change in
climate is maybe the more difficult for analysis.
(A) is maybe the more difficult for analysis
(B) is probably the most difficult to analyze
(C) is maybe the most difficult for analysis
(D) is probably the more difficult to analyze
(E) is, it may be, the analysis that is most difficult

OA is b

The OG explanation says that use of maybe is unidiomatic. Why is that?
B is the best choice!

when you compare an entity with all the others, it should be most

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text:
# colortbl is ignoring \\[] in tabular (MiKTeX, Windows 7) [closed]

In the following sample code, the 10pt row separation is ignored if I use the colortbl package. I know this has been an issue and was reported last year and apparently it was fixed. I am running MiKTeX with the latest updates. My version of colortbl is 1.0d Tue Dec 18 13:34:14 2018. I also did a full update of Miktex to make sure I had the latest packages. Are there any other packages, other than colortbl, I need to make sure that are fully updated?

\documentclass[11pt]{article}

\usepackage{colortbl}

\begin{document}

\begin{tabular}{l}
3.4 \\[10pt]
5.6 \\[10pt]
7.8 \\[10pt]
9.0
\end{tabular}

\end{document}

With colortbl:

Without colortbl

## closed as off-topic by egreg, Phelype Oleinik, Sebastiano, user36296, KurtJan 28 at 12:05

• This question does not fall within the scope of TeX, LaTeX or related typesetting systems as defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

• I'm voting to close this question as off-topic because the issue was due to outdated software, solved with an update – egreg Jan 28 at 11:10
• I just want to add that it took we a couple of hours to figure this one out. It was only because I found a clue in another StackOverflow question that I realized one had to update MiKTeX in admin and user mode. For a newbie, this would not be obvious. Hence I decided to include the answer here. You are free to delete if need be, as I know now how to correctly update MiKTeX in future. – rhody Jan 29 at 16:37


text:
# UCB-like algorithms: how do you compute the exploration bonus?

My question concerns Stochastic Combinatorial Multiarmed Bandits. More specifically, the algorithm called CombUCB1 presented in this paper. It is a UCB-like algorithm.

Essentially, in each round of the sequential game the learner chooses a super-arm to play. A super-arm is a $$d$$-dimensional vector $$a \in \mathcal{A}$$ where $$\mathcal{A} \subset \{0,1\}^d$$. In each super-arm $$a$$, when the $$i$$-element equals to $$1$$ ( $$i \in \{0, \dots, d\}, a(i)=1$$ ), that means that the basic action $$i$$ is active. Basically, in each round the learner plays the basic actions that are active in the chosen super-arm. The rewards of the basic actions are stochastics and a super-arm receives as a reward the sum of the rewards of the basic active actions.

The algorithm mentioned above presents a UCB-like algorithm, where with each basic action is associated a UCB-index and in each round the learner plays the super-arm that maximises that index. My question concerns the confidence interval around the mean of the rewards of the basic actions, presented in equation $$2$$ of the mentioned paper. Here, the exploration bonus is

$$c_{t,s} = \sqrt{\frac{1.5 \log t}{s}}$$

I don't understand where that $$1.5$$ is coming from. I've always known that one needs to use Chernoff-Hoeffding inequality to derive the exploration bonus in a UCB-algorithm. Am I wrong and it needs to be computed in other ways? I've always seen the same coefficient but with $$2$$ instead of $$1.5$$ (reference). Could someone explain me where does $$1.5$$ come from, please?

I know there is a similar question here, but I cannot really understand how that works here.

Thank you in advance in case you have time to read and answer my questions.

• The 1.5 seems to arise from the 6. Which seems to arise from 48. In my experience these proofs often uses choices of constants which are clear from hindsight. So I think if you replace all the constants with variables $k_1,k_2,k_3$ you might be able to obtain a general expression which when optimized will give these variables. – user9947 Feb 4 at 10:40
• Do you mean the $6$ from eq. 6 and $48$ from Theorem 2 in (Kveton et al., 2015)? So, you're saying that if I substitute those constants with variables $k_1, k_2, k_3$ and optimise, I should be able to get back to that 1.5. Have I understood correctly? Thank you for your answer, I really appreciate it! – Hoeff Feb 5 at 9:28


text:
# How to solve log equation

For two logarithms of the same base to be equal, their arguments must be equal. In other words, if \log (a)=\log (b) log(a) =log(b) then a a must equal b b \frac {x+1} {x-1}=1000 x −1x +1 = 1000

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## Solving Logarithm Equations

The logarithmic equation is solved using the logarithmic function: x = log b b x which is equivalently x = b l o g b x How to solve the logarithmic equation If we have the equation used in the Logarithm Equation Calculator log b x = y ( 1)

## Solving Log Equations with Exponentials

log(3x−2)−log(2) = log(x+4) log(3x−2 2) = log(x+4) Apply the quotient rule of logarithms. 3x−2 2 = x+4 Apply the one-to-one property. 3x−2 = 2x+8 Multiply both sides of the equation by 2. x = 10 Subtract 2x and add 2.

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