m8ta
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Sketch - Program synthesis by sketching
The essential algorithm, in words: Take the sketch, expand it to a set of parameterized variables, holes, and calling contexts. Convert these to a DAG aka (?) data-code flow graph w/ dependencies. Try to simplify the DAG, one-hot encode integers, and convert to either a conjunctive-normal-form (CNF) SAT problem for MiniSat, or to a boolean circuit for the ABC solver. Apply MiniSat or ABC to the problem to select a set of control values = values for the holes & permutations that satisfy the boolean constraints. Using this solution, use the SAT solver to find a input variable configuration that does not satisfy the problem. This serves as a counter-example. Run this through the validator function (oracle) to see what it does; use the counter-example and (inputs and outputs) to add clauses to the SAT problem. Run several times until either no counter-examples can be found or the problem is `unsat`. Though the thesis describes a system that was academic & relatively small back in 2008, Sketch has enjoyed continuous development, and remains used. I find the work that went into it to be remarkable and impressive -- even with incremental improvements, you need accurate expansion of the language & manipulations to show proof-of-principle. Left wondering what limits its application to even larger problems -- need for a higher-level loop that further subdivides / factorizes the problem, or DFS for filling out elements of the sketch? Interesting links discovered in while reading the dissertation:
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PMID-22388818 Corticostriatal plasticity is necessary for learning intentional neuroprosthetic skills.
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Problem: have a Q-switched Nd:YAG laser, (flashlamp pumped, passively Q-switched) from ebay (see this album). Allegedly it outputs 1J pulses of 8ns duration; in practice, it may put several 100mJ pulses ~ 16ns long while the flashlamp is firing. It was sold as a tattoo removal machine. However, I'm employing it to drill micro-vias in fine polyimide films. When focused through a 10x objective via the camera mount of an Leica microscope, 532nm (KTP doubled, second harmonic generation (SHG)) laser pulses both ablates the material, but does not leave a clean, sharp hole: it looks more like 'blasting': the hole is ragged, more like a crater. This may be from excessive 1064nm heating (partial KTP conversion), or plasma/flame heating & expansion due to absorption of the 532nm / 1064nm light. It may also be due to excessive pulse duration (should the laser not actually be q-switched... photodiode testing suggests otherwise, but I'd like to verify that), excessive pulse power, insufficient pulse intensity, or insufficient polyimide absorption at 532nm. The solution to excessive plasma and insufficient polyimide absorption is to shift the wavelength to 355nm (NUV) via third harmonic generation, 1064 + 532 = 355nm. This requires sum frequency generation (SFG), for which LBO (lithium triborate) or BBO (beta-barium borate) seem the commonly accepted nonlinear optical materials. To get SHG or THG, phase and polarization matching of the incoming light is critical. The output of the Nd:YAG laser is, I assume, non-polarized (or randomly polarized), as the KTP crystal simply screws on the front, and so should be rotationally agnostic (and there are no polarizing elements in the simple laser head -- unless the (presumed) Cr:YAG passive Q-switch induces some polarization.) Output polarization of the KTP crystal will be perpendicular to the incoming beam; if the resulting THG / SFG crystal needs Type-1 phase matching (both in phase and parallel polarization), will need a half-wave plate for 1064nm; for Type-II phase matching, no plate is needed. For noncritical phase matching in LBO (which I just bought), an oven is required to heat the crystal to the correct temperature. This suggests 73C for THG, while this suggests 150C (for SHG?). Third harmonic frequency generation by type-I critically phase-matched LiB3O5 crystal by means of optically active quartz crystal Suggests most lasers operate in Type-1 SHG, and Type-II THG, but this is less efficient than dual Type-1; the quartz crystal is employed to rotate the polarizations to alignment. Both SHG and THG crystals are heated for optimum power output. Finally, Short pulse duration of an extracavity sum-frequency mixing with an LiB3O5 (LBO) crystal suggests that no polarization change is required, nor oven control LBO temperature. Tight focus and high energy density is required, of course (at the expense of reduced crystal lifetime). Likely this is the Type-1,Type-II scheme alluded to in the paper above. I'll try this first before engaging further complexity (efficiency is not very important, as the holes are very small & material removal may be slow.) | |||||
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PMID-21499255[0] Reversible large-scale modification of cortical networks during neuroprosthetic control.
Other notes:
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PMID-19621062 Emergence of a stable cortical map for neuroprosthetic control.
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IEEE-1300783 (pdf) Transmission latencies in a telemetry-linked brain-machine interface
____References____ Bossetti, C.A. and Carmena, J.M. and Nicolelis, M.A.L. and Wolf, P.D. Transmission latencies in a telemetry-linked brain-machine interface Biomedical Engineering, IEEE Transactions on 51 6 919 -924 (2004.06) | |||||
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PMID-14624244[0] Learning to control a brain-machine interface for reaching and grasping by primates.
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IEEE-1634510 (pdf) Continuous shared control for stabilizing reaching and grasping with brain-machine interfaces.
____References____ Kim, H.K. and Biggs, J. and Schloerb, W. and Carmena, M. and Lebedev, M.A. and Nicolelis, M.A.L. and Srinivasan, M.A. Continuous shared control for stabilizing reaching and grasping with brain-machine interfaces Biomedical Engineering, IEEE Transactions on 53 6 1164 -1173 (2006) | |||||
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PMID-17694874[0] The muscle activation method: an approach to impedance control of brain-machine interfaces through a musculoskeletal model of the arm.
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PMID-17978021[0] Biomimetic Brain Machine Interfaces for the Control of Movement.
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PMID-16291944[0] Stable ensemble performance with single-neuron variability during reaching movements in primates.
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ref: -0
tags: Georgopoulos population vector arm motor control
date: 12-20-2011 22:26 gmt
revision:1
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PMID-3139485 Neural integration of movement: role of motor cortex in reaching.
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PMID-15214971[0] Ensemble recordings of human subcortical neurons as a source of motor control signals for a brain-machine interface
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Historical notes from using the Kinarm... this only seems to render properly in firefox / mozilla. To apply cartesian force fields to the arm, the original kinarm PLCC (whatever that stands for) converted joint velocities to cartesian veolocities using the jacobian matrix. All well and good. The equation for endpoint location of the kinarm is:
L_1 = 0.115 meters, l_2 = 0.195 meters in our case. The jacobian of this function is: etc. and (I think!) where tau is the shoulder and elbow torques and F is the cartesian force. The flow of the PLCC is then:
substitute to see if the matrices look similar ...
where
I'm surprised that we got something even like curl and viscous forces - the matrices are not similar. This explains why the forces seemed odd and poorly scaled, and why the constants for the viscious and curl fields were so small (the units should have been N/(cm/s) - 1 newton is a reasonable force, and the monkey moves at around 10cm/sec, so the constant should have been 1/10 or so. Instead, we usually put in a value of 0.0005 ! For typical values of the shoulder and elbow angles, the determinant of the matrix is 200 (the kinarm PLCC works in centimeters, not meters), so the transpose has entries ~ 200 x too big. Foolishly we compensated by making the constant (or entries in A) 200 times to small. i.e. 1/10 * 1/200 = 0.0005 :( The end result is that a density-plot of the space spanned by the cartesian force and velocity is not very clean, as you can see in the picture below. The horizontal line is, of course, when the forces were turned off. A linear relationship between force and velocity should be manifested by a line in these plots - however, there are only suggestions of lines. The null field should have a negative - slope line in upper left and lower right; the curl field should have a positive sloped line in the upper right and negative in the lower left (or vice-vercia). | |||||
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During the GOSH! summit there was an intensive talk about making a open-hardware USBkey-to-television converter/computer/mp4 player, an idea (patented!) by Joshua Kauffman and Gwendolyn Floyd. Since this was a very hands-on workshop, I decided to get an mp4 player in downtown Banff and take it apart to see how it works. The selected device, a RCA Lyra MC4202-A portable media player, is, in accordance with its low price, electrically simple on the inside. What follows is a rough teardown of the internals. -- View of the Lya with the back plastic panel removed.
-- View underneath the main PCB, showing the keypad PCB.
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From the New Yorker, Feb 25:
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so, what's inside a Lego NXT brick? note: this has all been rendered irrelevant -- Lego has published the hardware schematics for the NXT brick & associated sensors. go lego!
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This was written for the plik-l mailing list, Nov 16 2007 I actually had a bit of an argument yesterday with my dentist, no less, about global warming:
Mostly I'd have to agree with the dentist - the oil is going to be burned eventually, because it is just such a cheap source of energy. We are going to have to deal with the consequences. However, for coal - of which we have a far greater supply, and is considerably more dangerous / expensive to obtain - there is good reason to search for alternatives, and putting a tax on oil/natural gas now fund development of alternatives is probably very future-responsible, and will shift the energy climate so we relinquish coal (and maybe some oil) earlier, resulting in less CO2 in the atmosphere. There are infinitely many things more worthy/long-range responsible than the war, but our leaders have not touched on that. Correct me if I'm wrong, but there is little evidence that they even measured the worth of all alternatives, and decided rationally, based on integrating (over time and path probability) best-of-present knowledge of benefits and consequences. Or maybe they decided rationally, but with the worth of alternatives measured *personally*. It is this that truly angers me. Bayes for president 2008! Comments:
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buglabs, makers of plug n' play configurable handheld platform based on open-source technologies
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ref: Chan-2006.12
tags: computational model primate arm musculoskeletal motor_control Moran
date: 04-09-2007 22:35 gmt
revision:1
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PMID-17124337[0] Computational Model of a Primate Arm: from hand position to joint angles, joint torques, and muscle forces ideas:
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PMID-17271543[] http://hardm.ath.cx:88/pdf/sanchez2004.pdf ____References____ | |||||
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PMID-11600665[] Neural Activity in Primary Motor Cortex Related to Mechanical Loads Applied to the Shoulder and Elbow During a Postural Task
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SELECT file, COUNT(file) FROM info2 WHERE unit>1 AND maxinfo/infoshuf > 10 AND analog < 5 GROUP BY file ORDER BY COUNT(file) DESC to count the number of files matching the criteria.. and get aggregate frequentist statistics. |