Kalman Orbit Optimized Loop Tracking

NASA Technical Reports Server (NTRS)

Young, Lawrence E.; Meehan, Thomas K.

2011-01-01

Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

The Ionospheric Scintillation Effects on the BeiDou Signal Receiver

PubMed Central

He, Zhijun; Zhao, Hongbo; Feng, Wenquan

2016-01-01

Irregularities in the Earth’s ionosphere can make the amplitude and phase of radio signals fluctuate rapidly, which is known as ionospheric scintillation. Severe ionospheric scintillation could affect the performance of the Global Navigation Satellite System (GNSS). Currently, the Multiple Phase Screen (MPS) technique is widely used in solving problems caused by weak and strong scintillations. Considering that Southern China is mainly located in the area where moderate and intense scintillation occur frequently, this paper built a model based on the MPS technique and discussed the scintillation impacts on China’s BeiDou navigation system. By using the BeiDou B1I signal, this paper analyzed the scintillation effects on the receiver, which includes the acquisition and tracking process. For acquisition process, this paper focused on the correlation peak and acquisition probability. For the tracking process, this paper focused on the carrier tracking loop and the code tracking loop. Simulation results show that under high scintillation intensity, the phase fluctuation could be −1.13 ± 0.087 rad to 1.40 ± 0.087 rad and the relative amplitude fluctuation could be −10 dB to 8 dB. As the scintillation intensity increased, the average correlation peak would decrease more than 8%, which could thus degrade acquisition performance. On the other hand, when the signal-to-noise ratio (SNR) is comparatively lower, the influence of strong scintillation on the phase locked loop (PLL) is much higher than that of weak scintillation. As the scintillation becomes more intense, PLL variance could consequently results in an error of more than 2.02 cm in carrier-phase based ranging. In addition, the delay locked loop (DLL) simulation results indicated that the pseudo-range error caused by strong scintillation could be more than 4 m and the consequent impact on positioning accuracy could be more than 6 m. PMID:27834867

A complex approach to the blue-loop problem

NASA Astrophysics Data System (ADS)

Ostrowski, Jakub; Daszynska-Daszkiewicz, Jadwiga

2015-08-01

The problem of the blue loops during the core helium burning, outstanding for almost fifty years, is one of the most difficult and poorly understood problems in stellar astrophysics. Most of the work focused on the blue loops done so far has been performed with old stellar evolution codes and with limited computational resources. In the end the obtained conclusions were based on a small sample of models and could not have taken into account more advanced effects and interactions between them.The emergence of the blue loops depends on many details of the evolution calculations, in particular on chemical composition, opacity, mixing processes etc. The non-linear interactions between these factors contribute to the statement that in most cases it is hard to predict without a precise stellar modeling whether a loop will emerge or not. The high sensitivity of the blue loops to even small changes of the internal structure of a star yields one more issue: a sensitivity to numerical problems, which are common in calculations of stellar models on advanced stages of the evolution.To tackle this problem we used a modern stellar evolution code MESA. We calculated a large grid of evolutionary tracks (about 8000 models) with masses in the range of 3.0 - 25.0 solar masses from the zero age main sequence to the depletion of helium in the core. In order to make a comparative analysis, we varied metallicity, helium abundance and different mixing parameters resulting from convective overshooting, rotation etc.The better understanding of the properties of the blue loops is crucial for our knowledge of the population of blue supergiants or pulsating variables such as Cepheids, α-Cygni or Slowly Pulsating B-type supergiants. In case of more massive models it is also of great importance for studies of the progenitors of supernovae.

Study to investigate and evaluate means of optimizing the Ku-band communication function for the space shuttle

NASA Technical Reports Server (NTRS)

Simon, M. K.; Udalov, S.; Huth, G. K.

1976-01-01

The forward link of the overall Ku-band communication system consists of the ground- TDRS-orbiter communication path. Because the last segment of the link is directed towards a relatively low orbiting shuttle, a PN code is used to reduce the spectral density. A method is presented for incorporating code acquisition and tracking functions into the orbiter's Ku-band receiver. Optimization of a three channel multiplexing technique is described. The importance of Costas loop parameters to provide false lock immunity for the receiver, and the advantage of using a sinusoidal subcarrier waveform, rather than square wave, are discussed.

Design study of a HEAO-C spread spectrum transponder telemetry system for use with the TDRSS subnet

NASA Technical Reports Server (NTRS)

Weathers, G.

1975-01-01

The results of a design study of a spread spectrum transponder for use on the HEAO-C satellite were given. The transponder performs the functions of code turn-around for ground range and range-rate determination, ground command receiver, and telemetry data transmitter. The spacecraft transponder and associated communication system components will allow the HEAO-C satellite to utilize the Tracking and Data Relay Satellite System (TDRSS) subnet of the post 1978 STDN. The following areas were discussed in the report: TDRSS Subnet Description, TDRSS-HEAO-C System Configuration, Gold Code Generator, Convolutional Encoder Design and Decoder Algorithm, High Speed Sequence Generators, Statistical Evaluation of Candidate Code Sequences using Amplitude and Phase Moments, Code and Carrier Phase Lock Loops, Total Spread Spectrum Transponder System, and Reference Literature Search.

Decision feedback loop for tracking a polyphase modulated carrier

NASA Technical Reports Server (NTRS)

Simon, M. K. (Inventor)

1974-01-01

A multiple phase modulated carrier tracking loop for use in a frequency shift keying system is described in which carrier tracking efficiency is improved by making use of the decision signals made on the data phase transmitted in each T-second interval. The decision signal is used to produce a pair of decision-feedback quadrature signals for enhancing the loop's performance in developing a loop phase error signal.

Trajectory tracking control for underactuated stratospheric airship

NASA Astrophysics Data System (ADS)

Zheng, Zewei; Huo, Wei; Wu, Zhe

2012-10-01

Stratospheric airship is a new kind of aerospace system which has attracted worldwide developing interests for its broad application prospects. Based on the trajectory linearization control (TLC) theory, a novel trajectory tracking control method for an underactuated stratospheric airship is presented in this paper. Firstly, the TLC theory is described sketchily, and the dynamic model of the stratospheric airship is introduced with kinematics and dynamics equations. Then, the trajectory tracking control strategy is deduced in detail. The designed control system possesses a cascaded structure which consists of desired attitude calculation, position control loop and attitude control loop. Two sub-loops are designed for the position and attitude control loops, respectively, including the kinematics control loop and dynamics control loop. Stability analysis shows that the controlled closed-loop system is exponentially stable. Finally, simulation results for the stratospheric airship to track typical trajectories are illustrated to verify effectiveness of the proposed approach.

A Markov chain technique for determining the acquisition behavior of a digital tracking loop

NASA Technical Reports Server (NTRS)

Chadwick, H. D.

1972-01-01

An iterative procedure is presented for determining the acquisition behavior of discrete or digital implementations of a tracking loop. The technique is based on the theory of Markov chains and provides the cumulative probability of acquisition in the loop as a function of time in the presence of noise and a given set of initial condition probabilities. A digital second-order tracking loop to be used in the Viking command receiver for continuous tracking of the command subcarrier phase was analyzed using this technique, and the results agree closely with experimental data.

Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos Flyby. II. Doppler tracking: Formulation of observed and computed values, and noise budget

NASA Astrophysics Data System (ADS)

Bocanegra-Bahamón, T. M.; Molera Calvés, G.; Gurvits, L. I.; Duev, D. A.; Pogrebenko, S. V.; Cimò, G.; Dirkx, D.; Rosenblatt, P.

2018-01-01

Context. Closed-loop Doppler data obtained by deep space tracking networks, such as the NASA Deep Space Network (DSN) and the ESA tracking station network (Estrack), are routinely used for navigation and science applications. By shadow tracking the spacecraft signal, Earth-based radio telescopes involved in the Planetary Radio Interferometry and Doppler Experiment (PRIDE) can provide open-loop Doppler tracking data only when the dedicated deep space tracking facilities are operating in closed-loop mode. Aims: We explain the data processing pipeline in detail and discuss the capabilities of the technique and its potential applications in planetary science. Methods: We provide the formulation of the observed and computed values of the Doppler data in PRIDE tracking of spacecraft and demonstrate the quality of the results using an experiment with the ESA Mars Express spacecraft as a test case. Results: We find that the Doppler residuals and the corresponding noise budget of the open-loop Doppler detections obtained with the PRIDE stations compare to the closed-loop Doppler detections obtained with dedicated deep space tracking facilities.

Parallel tiled Nussinov RNA folding loop nest generated using both dependence graph transitive closure and loop skewing.

PubMed

Palkowski, Marek; Bielecki, Wlodzimierz

2017-06-02

RNA secondary structure prediction is a compute intensive task that lies at the core of several search algorithms in bioinformatics. Fortunately, the RNA folding approaches, such as the Nussinov base pair maximization, involve mathematical operations over affine control loops whose iteration space can be represented by the polyhedral model. Polyhedral compilation techniques have proven to be a powerful tool for optimization of dense array codes. However, classical affine loop nest transformations used with these techniques do not optimize effectively codes of dynamic programming of RNA structure predictions. The purpose of this paper is to present a novel approach allowing for generation of a parallel tiled Nussinov RNA loop nest exposing significantly higher performance than that of known related code. This effect is achieved due to improving code locality and calculation parallelization. In order to improve code locality, we apply our previously published technique of automatic loop nest tiling to all the three loops of the Nussinov loop nest. This approach first forms original rectangular 3D tiles and then corrects them to establish their validity by means of applying the transitive closure of a dependence graph. To produce parallel code, we apply the loop skewing technique to a tiled Nussinov loop nest. The technique is implemented as a part of the publicly available polyhedral source-to-source TRACO compiler. Generated code was run on modern Intel multi-core processors and coprocessors. We present the speed-up factor of generated Nussinov RNA parallel code and demonstrate that it is considerably faster than related codes in which only the two outer loops of the Nussinov loop nest are tiled.

Digital accumulators in phase and frequency tracking loops

NASA Technical Reports Server (NTRS)

Hinedi, Sami; Statman, Joseph I.

1990-01-01

Results on the effects of digital accumulators in phase and frequency tracking loops are presented. Digital accumulators or summers are used extensively in digital signal processing to perform averaging or to reduce processing rates to acceptable levels. For tracking the Doppler of high-dynamic targets at low carrier-to-noise ratios, it is shown through simulation and experiment that digital accumulators can contribute an additional loss in operating threshold. This loss was not considered in any previous study and needs to be accounted for in performance prediction analysis. Simulation and measurement results are used to characterize the loss due to the digital summers for three different tracking loops: a digital phase-locked loop, a cross-product automatic frequency tracking loop, and an extended Kalman filter. The tracking algorithms are compared with respect to their frequency error performance and their ability to maintain lock during severe maneuvers at various carrier-to-noise ratios. It is shown that failure to account for the effect of accumulators can result in an inaccurate performance prediction, the extent of which depends highly on the algorithm used.

Livermore Compiler Analysis Loop Suite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hornung, R. D.

2013-03-01

LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizations and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermoremore » Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.« less

BeiDou Signal Acquisition with Neumann–Hoffman Code Modulation in a Degraded Channel

PubMed Central

Zhao, Lin; Liu, Aimeng; Ding, Jicheng; Wang, Jing

2017-01-01

With the modernization of global navigation satellite systems (GNSS), secondary codes, also known as the Neumann–Hoffman (NH) codes, are modulated on the satellite signal to obtain a better positioning performance. However, this leads to an attenuation of the acquisition sensitivity of classic integration algorithms because of the frequent bit transitions that refer to the NH codes. Taking weak BeiDou navigation satellite system (BDS) signals as objects, the present study analyzes the side effect of NH codes on acquisition in detail and derives a straightforward formula, which indicates that bit transitions decrease the frequency accuracy. To meet the requirement of carrier-tracking loop initialization, a frequency recalculation algorithm is proposed based on verified fast Fourier transform (FFT) to mitigate the effect, meanwhile, the starting point of NH codes is found. Then, a differential correction is utilized to improve the acquisition accuracy of code phase. Monte Carlo simulations and real BDS data tests demonstrate that the new structure is superior to the conventional algorithms both in detection probability and frequency accuracy in a degraded channel. PMID:28208776

An Iterative Information-Reduced Quadriphase-Shift-Keyed Carrier Synchronization Scheme Using Decision Feedback for Low Signal-to-Noise Ratio Applications

NASA Technical Reports Server (NTRS)

Simon, M.; Tkacenko, A.

2006-01-01

In a previous publication [1], an iterative closed-loop carrier synchronization scheme for binary phase-shift keyed (BPSK) modulation was proposed that was based on feeding back data decisions to the input of the loop, the purpose being to remove the modulation prior to carrier synchronization as opposed to the more conventional decision-feedback schemes that incorporate such feedback inside the loop. The idea there was that, with sufficient independence between the received data and the decisions on it that are fed back (as would occur in an error-correction coding environment with sufficient decoding delay), a pure tone in the presence of noise would ultimately be produced (after sufficient iteration and low enough error probability) and thus could be tracked without any squaring loss. This article demonstrates that, with some modification, the same idea of iterative information reduction through decision feedback can be applied to quadrature phase-shift keyed (QPSK) modulation, something that was mentioned in the previous publication but never pursued.

Finite-time control for nonlinear spacecraft attitude based on terminal sliding mode technique.

PubMed

Song, Zhankui; Li, Hongxing; Sun, Kaibiao

2014-01-01

In this paper, a fast terminal sliding mode control (FTSMC) scheme with double closed loops is proposed for the spacecraft attitude control. The FTSMC laws are included both in an inner control loop and an outer control loop. Firstly, a fast terminal sliding surface (FTSS) is constructed, which can drive the inner loop tracking-error and the outer loop tracking-error on the FTSS to converge to zero in finite time. Secondly, FTSMC strategy is designed by using Lyaponov's method for ensuring the occurrence of the sliding motion in finite time, which can hold the character of fast transient response and improve the tracking accuracy. It is proved that FTSMC can guarantee the convergence of tracking-error in both approaching and sliding mode surface. Finally, simulation results demonstrate the effectiveness of the proposed control scheme. © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Effect of GNSS receiver carrier phase tracking loops on earthquake monitoring performance

NASA Astrophysics Data System (ADS)

Clare, Adam; Lin, Tao; Lachapelle, Gérard

2017-06-01

This research focuses on the performance of GNSS receiver carrier phase tracking loops for early earthquake monitoring systems. An earthquake was simulated using a hardware simulator and position, velocity and acceleration displacements were obtained to recreate the dynamics of the 2011 Tohoku earthquake. Using a software defined receiver, GSNRx, tracking bandwidths of 5, 10, 15, 20, 30, 40 and 50 Hz along with integration times of 1, 5 and 10 ms were tested. Using the phase lock indicator, an adaptive tracking loop was designed and tested to maximize performance for this application.

Integrated Reconfigurable Aperture, Digital Beam Forming, and Software GPS Receiver for UAV Navigation

DTIC Science & Technology

2007-12-11

Implemented both carrier and code phase tracking loop for performance evaluation of a minimum power beam forming algorithm and null steering algorithm...4 Antennal Antenna2 Antenna K RF RF RF ct, Ct~2 ChKx1 X2 ....... Xk A W ~ ~ =Z, x W ,=1 Fig. 5. Schematics of a K-element antenna array spatial...adaptive processor Antennal Antenna K A N-i V/ ( Vil= .i= VK Fig. 6. Schematics of a K-element antenna array space-time adaptive processor Two additional

Lidar-based wake tracking for closed-loop wind farm control

NASA Astrophysics Data System (ADS)

Raach, Steffen; Schlipf, David; Cheng, Po Wen

2016-09-01

This work presents two advancements towards closed-loop wake redirecting of a wind turbine. First, a model-based estimation approach is presented which uses a nacelle-based lidar system facing downwind to obtain information about the wake. A reduced order wake model is described which is then used in the estimation to track the wake. The tracking is demonstrated with lidar measurement data from an offshore campaign and with simulated lidar data from a SOWFA simulation. Second, a controller for closed-loop wake steering is presented. It uses the wake tracking information to set the yaw actuator of the wind turbine to redirect the wake to a desired position. Altogether, this paper aims to present the concept of closed-loop wake redirecting and gives a possible solution to it.

Tracking Architecture Based on Dual-Filter with State Feedback and Its Application in Ultra-Tight GPS/INS Integration

PubMed Central

Zhang, Xi; Miao, Lingjuan; Shao, Haijun

2016-01-01

If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. Compared with the traditional model utilizing a single KF, this structure avoids carrier tracking being subjected to code tracking errors. Meanwhile, as the loop filters are completely removed, state feedback values are adopted to generate local carrier and code. Although local carrier frequency has a wide fluctuation, the accuracy of Doppler shift estimation is improved. In the ultra-tight GPS/Inertial Navigation System (INS) integration, the carrier frequency derived from the external navigation information is not viewed as the local carrier frequency directly. That facilitates retaining the design principle of state feedback. However, under harsh conditions, the GPS outputs may still bear large errors which can destroy the estimation of INS errors. Thus, an innovative integrated navigation filter is constructed by modeling the non-negligible errors in the estimated Doppler shifts, to ensure INS is properly calibrated. Finally, field test and semi-physical simulation based on telemetered missile trajectory validate the effectiveness of methods proposed in this paper. PMID:27144570

Tracking Architecture Based on Dual-Filter with State Feedback and Its Application in Ultra-Tight GPS/INS Integration.

PubMed

Zhang, Xi; Miao, Lingjuan; Shao, Haijun

2016-05-02

If a Kalman Filter (KF) is applied to Global Positioning System (GPS) baseband signal preprocessing, the estimates of signal phase and frequency can have low variance, even in highly dynamic situations. This paper presents a novel preprocessing scheme based on a dual-filter structure. Compared with the traditional model utilizing a single KF, this structure avoids carrier tracking being subjected to code tracking errors. Meanwhile, as the loop filters are completely removed, state feedback values are adopted to generate local carrier and code. Although local carrier frequency has a wide fluctuation, the accuracy of Doppler shift estimation is improved. In the ultra-tight GPS/Inertial Navigation System (INS) integration, the carrier frequency derived from the external navigation information is not viewed as the local carrier frequency directly. That facilitates retaining the design principle of state feedback. However, under harsh conditions, the GPS outputs may still bear large errors which can destroy the estimation of INS errors. Thus, an innovative integrated navigation filter is constructed by modeling the non-negligible errors in the estimated Doppler shifts, to ensure INS is properly calibrated. Finally, field test and semi-physical simulation based on telemetered missile trajectory validate the effectiveness of methods proposed in this paper.

Post-flight trajectory reconstruction of suborbital free-flyers using GPS raw data

NASA Astrophysics Data System (ADS)

Ivchenko, N.; Yuan, Y.; Linden, E.

2017-08-01

This paper describes the reconstruction of postflight trajectories of suborbital free flying units by using logged GPS raw data. We took the reconstruction as a global least squares optimization problem, using both the pseudo-range and Doppler observables, and solved it by using the trust-region-reflective algorithm, which enabled navigational solutions of high accuracy. The code tracking was implemented with a large number of correlators and least squares curve fitting, in order to improve the precision of the code start times, while a more conventional phased lock loop was used for Doppler tracking. We proposed a weighting scheme to account for fast signal strength variation due to free-flier fast rotation, and a penalty for jerk to achieve a smooth solution. We applied these methods to flight data of two suborbital free flying units launched on REXUS 12 sounding rocket, reconstructing the trajectory, receiver clock error and wind up rates. The trajectory exhibits a parabola with the apogee around 80 km, and the velocity profile shows the details of payloadwobbling. The wind up rates obtained match the measurements from onboard angular rate sensors.

Performance of the all-digital data-transition tracking loop in the advanced receiver

NASA Astrophysics Data System (ADS)

Cheng, U.; Hinedi, S.

1989-11-01

The performance of the all-digital data-transition tracking loop (DTTL) with coherent or noncoherent sampling is described. The effects of few samples per symbol and of noncommensurate sampling rates and symbol rates are addressed and analyzed. Their impacts on the loop phase-error variance and the mean time to lose lock (MTLL) are quantified through computer simulations. The analysis and preliminary simulations indicate that with three to four samples per symbol, the DTTL can track with negligible jitter because of the presence of earth Doppler rate. Furthermore, the MTLL is also expected to be large engough to maintain lock over a Deep Space Network track.

Loop-the-Loop: An Easy Experiment, A Challenging Explanation

NASA Astrophysics Data System (ADS)

Asavapibhop, B.; Suwonjandee, N.

2010-07-01

A loop-the-loop built by the Institute for the Promotion of Teaching Science and Technology (IPST) was used in Thai high school teachers training program to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. We took videos using high speed camera to record the motions of a spherical steel ball moving down the aluminum inclined track at different released positions. The ball then moved into the circular loop and underwent a projectile motion upon leaving the track. We then asked the teachers to predict the landing position of the ball if we changed the height of the whole loop-the-loop system. We also analyzed the videos using Tracker, a video analysis software. It turned out that most teachers did not realize the effect of the friction between the ball and the track and could not obtain the correct relationship hence their predictions were inconsistent with the actual landing positions of the ball.

Comparison of Two Coronal Magnetic Field Models to Reconstruct a Sigmoidal Solar Active Region with Coronal Loops

NASA Astrophysics Data System (ADS)

Duan, Aiying; Jiang, Chaowei; Hu, Qiang; Zhang, Huai; Gary, G. Allen; Wu, S. T.; Cao, Jinbin

2017-06-01

Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE-MHD-NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO/AIA. It is found that the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ˜10°. This suggests that the CESE-MHD-NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (˜30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.

Comparison of Two Coronal Magnetic Field Models to Reconstruct a Sigmoidal Solar Active Region with Coronal Loops

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Aiying; Zhang, Huai; Jiang, Chaowei

Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE–MHD–NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from themore » region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO /AIA. It is found that the CESE–MHD–NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ∼10°. This suggests that the CESE–MHD–NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (∼30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.« less

Performance evaluation of digital phase-locked loops for advanced deep space transponders

NASA Technical Reports Server (NTRS)

Nguyen, T. M.; Hinedi, S. M.; Yeh, H.-G.; Kyriacou, C.

1994-01-01

The performances of the digital phase-locked loops (DPLL's) for the advanced deep-space transponders (ADT's) are investigated. DPLL's considered in this article are derived from the analog phase-locked loop, which is currently employed by the NASA standard deep space transponder, using S-domain to Z-domain mapping techniques. Three mappings are used to develop digital approximations of the standard deep space analog phase-locked loop, namely the bilinear transformation (BT), impulse invariant transformation (IIT), and step invariant transformation (SIT) techniques. The performance in terms of the closed loop phase and magnitude responses, carrier tracking jitter, and response of the loop to the phase offset (the difference between in incoming phase and reference phase) is evaluated for each digital approximation. Theoretical results of the carrier tracking jitter for command-on and command-off cases are then validated by computer simulation. Both theoretical and computer simulation results show that at high sampling frequency, the DPLL's approximated by all three transformations have the same tracking jitter. However, at low sampling frequency, the digital approximation using BT outperforms the others. The minimum sampling frequency for adequate tracking performance is determined for each digital approximation of the analog loop. In addition, computer simulation shows that the DPLL developed by BT provides faster response to the phase offset than IIT and SIT.

System and circuitry to provide stable transconductance for biasing

NASA Technical Reports Server (NTRS)

Garverick, Steven L. (Inventor); Yu, Xinyu (Inventor)

2012-01-01

An amplifier system can include an input amplifier configured to receive an analog input signal and provide an amplified signal corresponding to the analog input signal. A tracking loop is configured to employ delta modulation for tracking the amplified signal, the tracking loop providing a corresponding output signal. A biasing circuit is configured to adjust a bias current to maintain stable transconductance over temperature variations, the biasing circuit providing at least one bias signal for biasing at least one of the input amplifier and the tracking loop, whereby the circuitry receiving the at least one bias signal exhibits stable performance over the temperature variations. In another embodiment the biasing circuit can be utilized in other applications.

Ex-vessel neutron dosimetry analysis for westinghouse 4-loop XL pressurized water reactor plant using the RadTrack{sup TM} Code System with the 3D parallel discrete ordinates code RAPTOR-M3G

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, J.; Alpan, F. A.; Fischer, G.A.

2011-07-01

Traditional two-dimensional (2D)/one-dimensional (1D) SYNTHESIS methodology has been widely used to calculate fast neutron (>1.0 MeV) fluence exposure to reactor pressure vessel in the belt-line region. However, it is expected that this methodology cannot provide accurate fast neutron fluence calculation at elevations far above or below the active core region. A three-dimensional (3D) parallel discrete ordinates calculation for ex-vessel neutron dosimetry on a Westinghouse 4-Loop XL Pressurized Water Reactor has been done. It shows good agreement between the calculated results and measured results. Furthermore, the results show very different fast neutron flux values at some of the former plate locationsmore » and elevations above and below an active core than those calculated by a 2D/1D SYNTHESIS method. This indicates that for certain irregular reactor internal structures, where the fast neutron flux has a very strong local effect, it is required to use a 3D transport method to calculate accurate fast neutron exposure. (authors)« less

Experimental investigation of control/display augmentation effects in a compensatory tracking task

NASA Technical Reports Server (NTRS)

Garg, Sanjay; Schmidt, David K.

1988-01-01

The effects of control/display augmentation on human performance and workload have been investigated for closed-loop, continuous-tracking tasks by a real-time, man-in-the-loop simulation study. The experimental results obtained indicate that only limited improvement in actual tracking performance is obtainable through display augmentation alone; with a very high level of display augmentation, tracking error will actually deteriorate. Tracking performance improves when status information is furnished for reasonable levels of display quickening; again, very high quickening levels lead to tracking error deterioration due to the incompatibility between the status information and the quickened signal.

Digital phase-lock loop

NASA Technical Reports Server (NTRS)

Thomas, Jr., Jess B. (Inventor)

1991-01-01

An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.

Speed-constrained three-axes attitude control using kinematic steering

NASA Astrophysics Data System (ADS)

Schaub, Hanspeter; Piggott, Scott

2018-06-01

Spacecraft attitude control solutions typically are torque-level algorithms that simultaneously control both the attitude and angular velocity tracking errors. In contrast, robotic control solutions are kinematic steering commands where rates are treated as the control variable, and a servo-tracking control subsystem is present to achieve the desired control rates. In this paper kinematic attitude steering controls are developed where an outer control loop establishes a desired angular response history to a tracking error, and an inner control loop tracks the commanded body angular rates. The overall stability relies on the separation principle of the inner and outer control loops which must have sufficiently different response time scales. The benefit is that the outer steering law response can be readily shaped to a desired behavior, such as limiting the approach angular velocity when a large tracking error is corrected. A Modified Rodrigues Parameters implementation is presented that smoothly saturates the speed response. A robust nonlinear body rate servo loop is developed which includes integral feedback. This approach provides a convenient modular framework that makes it simple to interchange outer and inner control loops to readily setup new control implementations. Numerical simulations illustrate the expected performance for an aggressive reorientation maneuver subject to an unknown external torque.

Studying NASA's Transition to Ka-Band Communications for Low Earth Orbit

NASA Technical Reports Server (NTRS)

Chelmins, David; Reinhart, Richard; Mortensen, Dale; Welch, Bryan; Downey, Joseph; Evans, Mike

2014-01-01

As the S-band spectrum becomes crowded, future space missions will need to consider moving command and telemetry services to Ka-band. NASAs Space Communications and Navigation (SCaN) Testbed provides a software-defined radio (SDR) platform that is capable of supporting investigation of this service transition. The testbed contains two S-band SDRs and one Ka-band SDR. Over the past year, SCaN Testbed has demonstrated Ka-band communications capabilities with NASAs Tracking and Data Relay Satellite System (TDRSS) using both open- and closed-loop antenna tracking profiles. A number of technical areas need to be addressed for successful transition to Ka-band. The smaller antenna beamwidth at Ka-band increases the criticality of antenna pointing, necessitating closed loop tracking algorithms and new techniques for received power estimation. Additionally, the antenna pointing routines require enhanced knowledge of spacecraft position and attitude for initial acquisition, versus an S-band antenna. Ka-band provides a number of technical advantages for bulk data transfer. Unlike at S-band, a larger bandwidth may be available for space missions, allowing increased data rates. The potential for high rate data transfer can also be extended for direct-to-ground links through use of variable or adaptive coding and modulation. Specific examples of Ka-band research from SCaN Testbeds first year of operation will be cited, such as communications link performance with TDRSS, and the effects of truss flexure on antenna pointing.

Performance comparison of optimal fractional order hybrid fuzzy PID controllers for handling oscillatory fractional order processes with dead time.

PubMed

Das, Saptarshi; Pan, Indranil; Das, Shantanu

2013-07-01

Fuzzy logic based PID controllers have been studied in this paper, considering several combinations of hybrid controllers by grouping the proportional, integral and derivative actions with fuzzy inferencing in different forms. Fractional order (FO) rate of error signal and FO integral of control signal have been used in the design of a family of decomposed hybrid FO fuzzy PID controllers. The input and output scaling factors (SF) along with the integro-differential operators are tuned with real coded genetic algorithm (GA) to produce optimum closed loop performance by simultaneous consideration of the control loop error index and the control signal. Three different classes of fractional order oscillatory processes with various levels of relative dominance between time constant and time delay have been used to test the comparative merits of the proposed family of hybrid fractional order fuzzy PID controllers. Performance comparison of the different FO fuzzy PID controller structures has been done in terms of optimal set-point tracking, load disturbance rejection and minimal variation of manipulated variable or smaller actuator requirement etc. In addition, multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-II) has been used to study the Pareto optimal trade-offs between the set point tracking and control signal, and the set point tracking and load disturbance performance for each of the controller structure to handle the three different types of processes. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Experimental Evaluation of an Invasive Medical Instrument Based on a Displacement Measurement System.

PubMed

Fotiadis, Dimitris A; Astaras, Alexandros; Bamidis, Panagiotis D; Papathanasiou, Kostas; Kalfas, Anestis

2015-09-01

This paper presents a novel method for tracking the position of a medical instrument's tip. The system is based on phase locking a high frequency signal transmitted from the medical instrument's tip to a reference signal. Displacement measurement is established having the loop open, in order to get a low frequency voltage representing the medical instrument's movement; therefore, positioning is established by means of conventional measuring techniques. The voltage-controlled oscillator stage of the phase-locked loop (PLL), combined to an appropriate antenna, comprises the associated transmitter located inside the medical instrument tip. All the other low frequency PLL components, low noise amplifier and mixer, are located outside the human body, forming the receiver part of the system. The operating details of the proposed system were coded in Verilog-AMS. Simulation results indicate robust medical instrument tracking in 1-D. Experimental evaluation of the proposed position tracking system is also presented. The experiments described in this paper are based on a transmitter moving opposite a stationary receiver performing either constant velocity or uniformly accelerated movement, and also together with two stationary receivers performing constant velocity movement again. This latter setup is implemented in order to demonstrate the prototype's accuracy for planar (2-D) motion measurements. Error analysis and time-domain analysis are presented for system performance characterization. Furthermore, preliminary experimental assessment using a saline solution container to more closely approximate the human body as a radio frequency wave transmission medium has proved the system's capability of operating underneath the skin.

Studying NASA's Transition to Ka-Band Communications for Low Earth Orbit

NASA Technical Reports Server (NTRS)

Chelmins, David T.; Reinhart, Richard C.; Mortensen, Dale; Welch, Bryan; Downey, Joseph; Evans, Michael

2014-01-01

As the S-band spectrum becomes crowded, future space missions will need to consider moving command and telemetry services to Ka-band. NASA's Space Communications and Navigation (SCaN) Testbed provides a software-defined radio (SDR) platform that is capable of supporting investigation of this service transition. The testbed contains two S-band SDRs and one Ka-band SDR. Over the past year, SCaN Testbed has demonstrated Ka-band communications capabilities with NASAs Tracking and Data Relay Satellite System (TDRSS) using both open- and closed-loop antenna tracking profiles. A number of technical areas need to be addressed for successful transition to Ka-band. The smaller antenna beamwidth at Ka-band increases the criticality of antenna pointing, necessitating closed loop tracking algorithms and new techniques for received power estimation. Additionally, the antenna pointing routines require enhanced knowledge of spacecraft position and attitude for initial acquisition, versus an S-band antenna. Ka-band provides a number of technical advantages for bulk data transfer. Unlike at S-band, a larger bandwidth may be available for space missions, allowing increased data rates. The potential for high rate data transfer can also be extended for direct-to-ground links through use of variable or adaptive coding and modulation. Specific examples of Ka-band research from SCaN Testbeds first year of operation will be cited, such as communications link performance with TDRSS, and the effects of truss flexure on antenna pointing.

Digital tracking loops for a programmable digital modem

NASA Technical Reports Server (NTRS)

Poklemba, John J.

1992-01-01

In this paper, an analysis and hardware emulation of the tracking loops for a very flexible programmable digital modem (PDM) will be presented. The modem is capable of being programmed for 2, 4, 8, 16-PSK, 16-QAM, MSK, and Offset-QPSK modulation schemes over a range of data rates from 2.34 to 300 Mbps with programmable spectral occupancy from 1.2 to 1.8 times the symbol rate; these operational parameters are executable in burst or continuous mode. All of the critical processing in both the modulator and demodulator is done at baseband with very high-speed digital hardware and memory. Quadrature analog front-ends are used for translation between baseband and the IF center frequency. The modulator is based on a table lookup approach, where precomputed samples are stored in memory and clocked out according to the incoming data pattern. The sample values are predistorted to counteract the effects of the other filtering functions in the link as well as any transmission impairments. The demodulator architecture was adapted from a joint estimator-detector (JED) mathematical analysis. Its structure is applicable to most signalling formats that can be represented in a two-dimensional space. The JED realization uses interdependent, mutually aiding tracking loops with post-detection data feedback. To expedite and provide for more reliable synchronization, initial estimates for these loops are computed in a parallel acquisition processor. The cornerstone of the demodulator realization is the pre-averager received data filter which allows operation over a broad range of data rates without any hardware changes and greatly simplifies the implementation complexity. The emulation results confirmed tracking loop operation over the entire range of operational parameters listed above, as well as the capability of achieving and maintaining synchronization at BER's in excess of 10(exp -1). The emulation results also showed very close agreement with the tracking loop analysis, and validated the resolution apportionment of the various hardware elements in the tracking loops.

Integration of an On-Axis General Sun-Tracking Formula in the Algorithm of an Open-Loop Sun-Tracking System

PubMed Central

Chong, Kok-Keong; Wong, Chee-Woon; Siaw, Fei-Lu; Yew, Tiong-Keat; Ng, See-Seng; Liang, Meng-Suan; Lim, Yun-Seng; Lau, Sing-Liong

2009-01-01

A novel on-axis general sun-tracking formula has been integrated in the algorithm of an open-loop sun-tracking system in order to track the sun accurately and cost effectively. Sun-tracking errors due to installation defects of the 25 m2 prototype solar concentrator have been analyzed from recorded solar images with the use of a CCD camera. With the recorded data, misaligned angles from ideal azimuth-elevation axes have been determined and corrected by a straightforward changing of the parameters' values in the general formula of the tracking algorithm to improve the tracking accuracy to 2.99 mrad, which falls below the encoder resolution limit of 4.13 mrad. PMID:22408483

Engineering evaluations and studies. Report for IUS studies

NASA Technical Reports Server (NTRS)

1981-01-01

The reviews, investigations, and analyses of the Inertial Upper Stage (IUS) Spacecraft Tracking and Data Network (STDN) transponder are reviewed. Carrier lock detector performance for Tracking and Data Relay Satellite System (TDRSS) dual-mode operation is discussed, as is the problem of predicting instantaneous frequency error in the carrier loop. Coastal loop performance analysis is critiqued and the static tracking phase error induced by thermal noise biases is discussed.

Implementation of a vector-based tracking loop receiver in a pseudolite navigation system.

PubMed

So, Hyoungmin; Lee, Taikjin; Jeon, Sanghoon; Kim, Chongwon; Kee, Changdon; Kim, Taehee; Lee, Sanguk

2010-01-01

We propose a vector tracking loop (VTL) algorithm for an asynchronous pseudolite navigation system. It was implemented in a software receiver and experiments in an indoor navigation system were conducted. Test results show that the VTL successfully tracks signals against the near-far problem, one of the major limitations in pseudolite navigation systems, and could improve positioning availability by extending pseudolite navigation coverage.

Enthalpy-Based Thermal Evolution of Loops: II. Improvements to the Model

NASA Technical Reports Server (NTRS)

Cargill, P. J.; Bradshaw, S. J.; Klimchuk, J. A.

2011-01-01

This paper further develops the zero-dimensional (0D) hydrodynamic coronal loop model "Enthalpy-based Thermal Evolution of Loops" (EBTEL) originally proposed by Klimchuk et al (2008), which studies the plasma response to evolving coronal heating. It has typically been applied to impulsive heating events. The basis of EBTEL is the modelling of mass exchange between the corona and transition region and chromosphere in response to heating variations, with the key parameter being the ratio of transition region to coronal radiation. We develop new models for this parameter that now include gravitational stratification and a physically motivated approach to radiative cooling. A number of examples are presented, including nanoflares in short and long loops, and a small flare. It is found that while the evolution of the loop temperature is rather insensitive to the details of the model, accurate tracking of the density requires the inclusion of our new features. In particular, we are able to now obtain highly over-dense loops in the late cooling phase and decreases to the coronal density arising due to stratification. The 0D results are compared to a 1D hydro code (Hydrad). The agreement is acceptable, with the exception of the flare case where some versions of Hydrad can give significantly lower densities. This is attributed to the method used to model the chromosphere in a flare. EBTEL is suitable for general use as a tool for (a) quick-look results of loop evolution in response to a given heating function and (b) situations where the modelling of hundreds or thousands of elemental loops is needed. A single run takes a few seconds on a contemporary laptop.

Combining Charge Couple Devices and Rate Sensors for the Feedforward Control System of a Charge Coupled Device Tracking Loop.

PubMed

Tang, Tao; Tian, Jing; Zhong, Daijun; Fu, Chengyu

2016-06-25

A rate feed forward control-based sensor fusion is proposed to improve the closed-loop performance for a charge couple device (CCD) tracking loop. The target trajectory is recovered by combining line of sight (LOS) errors from the CCD and the angular rate from a fiber-optic gyroscope (FOG). A Kalman filter based on the Singer acceleration model utilizes the reconstructive target trajectory to estimate the target velocity. Different from classical feed forward control, additive feedback loops are inevitably added to the original control loops due to the fact some closed-loop information is used. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability. The bandwidth of the Kalman filter is the major factor affecting the control stability and close-loop performance. Both simulations and experiments are provided to demonstrate the benefits of the proposed algorithm.

Acquisition and Tracking Behavior of Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Viterbi, A. J.

1958-01-01

Phase-locked or APC loops have found increasing applications in recent years as tracking filters, synchronizing devices, and narrowband FM discriminators. Considerable work has been performed to determine the noise-squelching properties of the loop when it is operating in or near phase lock and is functioning as a linear coherent detector. However, insufficient consideration has been devoted to the non-linear behavior of the loop when it is out of lock and in the process of pulling in. Experimental evidence has indicated that there is a strong tendency for phase-locked loops to achieve lock under most circumstances. However, the analysis which has appeared in the literature iis limited to the acquisition of a constant frequency reference signal with only one phase-locked loop filter configuration. This work represents an investigation of frequency acquisition properties of phase-locked loops for a variety of reference-signal behavior and loop configurations

The free-energy cost of interaction between DNA loops.

PubMed

Huang, Lifang; Liu, Peijiang; Yuan, Zhanjiang; Zhou, Tianshou; Yu, Jianshe

2017-10-03

From the viewpoint of thermodynamics, the formation of DNA loops and the interaction between them, which are all non-equilibrium processes, result in the change of free energy, affecting gene expression and further cell-to-cell variability as observed experimentally. However, how these processes dissipate free energy remains largely unclear. Here, by analyzing a mechanic model that maps three fundamental topologies of two interacting DNA loops into a 4-state model of gene transcription, we first show that a longer DNA loop needs more mean free energy consumption. Then, independent of the type of interacting two DNA loops (nested, side-by-side or alternating), the promotion between them always consumes less mean free energy whereas the suppression dissipates more mean free energy. More interestingly, we find that in contrast to the mechanism of direct looping between promoter and enhancer, the facilitated-tracking mechanism dissipates less mean free energy but enhances the mean mRNA expression, justifying the facilitated-tracking hypothesis, a long-standing debate in biology. Based on minimal energy principle, we thus speculate that organisms would utilize the mechanisms of loop-loop promotion and facilitated tracking to survive in complex environments. Our studies provide insights into the understanding of gene expression regulation mechanism from the view of energy consumption.

The performance of a sampled data delay lock loop implemented with a Kalman loop filter

NASA Astrophysics Data System (ADS)

Eilts, H. S.

1980-01-01

The purpose of this study is to evaluate the steady-state and transient (lock-up) performance of a tracking loop implemented with a Kalman filter. Steady-state performance criteria are errors due to measurement noise (jitter) and Doppler errors due to motion of the tracking loop. Trade-offs exist between the two criteria such that increasing performance with respect to either one will cause performance decrease with respect to the other. It is shown that by carefully selecting filter parameters reasonable performance can be obtained for both criteria simultaneously. It is also shown that lock-up performance for the loop is acceptable when these parameters are used.

Automatic vehicle location system

NASA Technical Reports Server (NTRS)

Hansen, G. R., Jr. (Inventor)

1973-01-01

An automatic vehicle detection system is disclosed, in which each vehicle whose location is to be detected carries active means which interact with passive elements at each location to be identified. The passive elements comprise a plurality of passive loops arranged in a sequence along the travel direction. Each of the loops is tuned to a chosen frequency so that the sequence of the frequencies defines the location code. As the vehicle traverses the sequence of the loops as it passes over each loop, signals only at the frequency of the loop being passed over are coupled from a vehicle transmitter to a vehicle receiver. The frequencies of the received signals in the receiver produce outputs which together represent a code of the traversed location. The code location is defined by a painted pattern which reflects light to a vehicle carried detector whose output is used to derive the code defined by the pattern.

Design and Implementation of an RTK-Based Vector Phase Locked Loop

PubMed Central

Shafaati, Ahmad; Lin, Tao; Broumandan, Ali; Lachapelle, Gérard

2018-01-01

This paper introduces a novel double-differential vector phase-locked loop (DD-VPLL) for Global Navigation Satellite Systems (GNSS) that leverages carrier phase position solutions as well as base station measurements in the estimation of rover tracking loop parameters. The use of double differencing alleviates the need for estimating receiver clock dynamics and atmospheric delays; therefore, the navigation filter consists of the baseline dynamic states only. It is shown that using vector processing for carrier phase tracking leads to a significant enhancement in the receiver sensitivity compared to using the conventional scalar-based tracking loop (STL) and vector frequency locked loop (VFLL). The sensitivity improvement of 8 to 10 dB compared to STL, and 7 to 8 dB compared to VFLL, is obtained based on the test cases reported in the paper. Also, an increased probability of ambiguity resolution in the proposed method results in better availability for real time kinematic (RTK) applications. PMID:29533994

Sun Tracking Systems: A Review

PubMed Central

Lee, Chia-Yen; Chou, Po-Cheng; Chiang, Che-Ming; Lin, Chiu-Feng

2009-01-01

The output power produced by high-concentration solar thermal and photovoltaic systems is directly related to the amount of solar energy acquired by the system, and it is therefore necessary to track the sun's position with a high degree of accuracy. Many systems have been proposed to facilitate this task over the past 20 years. Accordingly, this paper commences by providing a high level overview of the sun tracking system field and then describes some of the more significant proposals for closed-loop and open-loop types of sun tracking systems. PMID:22412341

Filter for third order phase locked loops

NASA Technical Reports Server (NTRS)

Crow, R. B.; Tausworthe, R. C. (Inventor)

1973-01-01

Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.

Looping tracks associated with tropical cyclones approaching an isolated mountain. Part I: Essential parameters

NASA Astrophysics Data System (ADS)

Huang, Yi-Chih; Lin, Yuh-Lang

2018-06-01

Essential parameters for making a looping track when a westward-moving tropical cyclone (TC) approaches a mesoscale mountain are investigated by examining several key nondimensional control parameters with a series of systematic, idealized numerical experiments, such as U/ Nh, V max/ Nh, U/ fL x , V max/ fR, h/ L x , and R/ L y . Here U is the uniform zonal wind velocity, N the Brunt-Vaisala frequency, h the mountain height, f the Coriolis parameter, V max the maximum tangential velocity at a radius of R from the cyclone center and L x is the halfwidth of the mountain in the east-west direction. It is found that looping tracks (a) tend to occur under small U/ Nh and U/ fL x , moderate h/ L x , and large V max/ Nh, which correspond to slow movement (leading to subgeostrophic flow associated with strong orographic blocking), moderate steepness, and strong tangential wind associated with TC vortex; (b) are often accompanied by an area of perturbation high pressure to the northeast of the mountain, which lasts for only a short period; and (c) do not require the existence of a northerly jet. The nondimensional control parameters are consolidated into a TC looping index (LI), {U2 R2 }/{V_{max 2 hLy }} , which is tested by several historical looping and non-looping typhoons approaching Taiwan's Central Mountain Range (CMR) from east or southeast. It is found that LI < 0.0125 may serve as a criterion for looping track to occur.

Optimized tracking of RF carriers with phase noise, including Pioneer 10 results

NASA Technical Reports Server (NTRS)

Vilnrotter, V. A.; Hurd, W. J.; Brown, D. H.

1987-01-01

The ability to track very weak signals from distant spacecraft is limited by the phase instabilities of the received signal and of the local oscillator employed by the receiver. These instabilities ultimately limit the minimum loop bandwidth that can be used in a phase-coherent receiver, and hence limit the ratio of received carrier power to noise spectral density which can be tracked phase coherently. A method is presented for near real time estimation of the received carrier phase and additive noise spectrum, and optimization of the phase locked loop bandwidth. The method was used with the breadboard Deep Space Network (DSN) Advanced Receiver to optimize tracking of very weak signals from the Pioneer 10 spacecraft, which is now more distant that the edge of the solar system. Tracking with bandwidths of 0.1 Hz to 1.0 Hz reduces tracking signal threshold and increases carrier loop signal to noise ratio (SNR) by 5 dB to 15 dB compared to the 3 Hz bandwidth of the receivers now used operationally in the DSN. This will enable the DSN to track Pioneer 10 until its power sources fails near the end of the century.

Loop shaping design for tracking performance in machine axes.

PubMed

Schinstock, Dale E; Wei, Zhouhong; Yang, Tao

2006-01-01

A modern interpretation of classical loop shaping control design methods is presented in the context of tracking control for linear motor stages. Target applications include noncontacting machines such as laser cutters and markers, water jet cutters, and adhesive applicators. The methods are directly applicable to the common PID controller and are pertinent to many electromechanical servo actuators other than linear motors. In addition to explicit design techniques a PID tuning algorithm stressing the importance of tracking is described. While the theory behind these techniques is not new, the analysis of their application to modern systems is unique in the research literature. The techniques and results should be important to control practitioners optimizing PID controller designs for tracking and in comparing results from classical designs to modern techniques. The methods stress high-gain controller design and interpret what this means for PID. Nothing in the methods presented precludes the addition of feedforward control methods for added improvements in tracking. Laboratory results from a linear motor stage demonstrate that with large open-loop gain very good tracking performance can be achieved. The resultant tracking errors compare very favorably to results from similar motions on similar systems that utilize much more complicated controllers.

Bandwidth controller for phase-locked-loop

NASA Technical Reports Server (NTRS)

Brockman, Milton H. (Inventor)

1992-01-01

A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.

Maximum-likelihood-based extended-source spatial acquisition and tracking for planetary optical communications

NASA Astrophysics Data System (ADS)

Tsou, Haiping; Yan, Tsun-Yee

1999-04-01

This paper describes an extended-source spatial acquisition and tracking scheme for planetary optical communications. This scheme uses the Sun-lit Earth image as the beacon signal, which can be computed according to the current Sun-Earth-Probe angle from a pre-stored Earth image or a received snapshot taken by other Earth-orbiting satellite. Onboard the spacecraft, the reference image is correlated in the transform domain with the received image obtained from a detector array, which is assumed to have each of its pixels corrupted by an independent additive white Gaussian noise. The coordinate of the ground station is acquired and tracked, respectively, by an open-loop acquisition algorithm and a closed-loop tracking algorithm derived from the maximum likelihood criterion. As shown in the paper, the optimal spatial acquisition requires solving two nonlinear equations, or iteratively solving their linearized variants, to estimate the coordinate when translation in the relative positions of onboard and ground transceivers is considered. Similar assumption of linearization leads to the closed-loop spatial tracking algorithm in which the loop feedback signals can be derived from the weighted transform-domain correlation. Numerical results using a sample Sun-lit Earth image demonstrate that sub-pixel resolutions can be achieved by this scheme in a high disturbance environment.

Closed loop tracked Doppler optical coherence tomography based heart monitor for the Drosophila melanogaster larvae.

PubMed

Zurauskas, Mantas; Bradu, Adrian; Ferguson, Daniel R; Hammer, Daniel X; Podoleanu, Adrian

2016-03-01

This paper presents a novel instrument for biosciences, useful for studies of moving embryos. A dual sequential imaging/measurement channel is assembled via a closed-loop tracking architecture. The dual channel system can operate in two regimes: (i) single-point Doppler signal monitoring or (ii) fast 3-D swept source OCT imaging. The system is demonstrated for characterizing cardiac dynamics in Drosophila melanogaster larva. Closed loop tracking enables long term in vivo monitoring of the larvae heart without anesthetic or physical restraint. Such an instrument can be used to measure subtle variations in the cardiac behavior otherwise obscured by the larvae movements. A fruit fly larva (top) was continuously tracked for continuous remote monitoring. A heartbeat trace of freely moving larva (bottom) was obtained by a low coherence interferometry based doppler sensing technique. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High Torque-to-Inertia Servo System for Stabilizing Sensor Systems. Candidate Systems Include Missile Guidance, Surveillance, and Tracking

DTIC Science & Technology

1980-04-01

specifications ... 3-10 25. Typical isolation curve ... 3-12 26. Servo amp/motor/load frequency response (inner gimbal) ... 4-3 27. Slave loop ( open loop...slave loop ( open loop) frequency response (inner gimbal) . . . 4-4 30. Slave loop (closed loop) frequency response (inner gimbal) ... 4-5 3 . Slave...loop inner gimbal time response ... 4-5 32. Servo amp/motor/load frequency response (outer gimbal) ... 4-6 33. Slave loop ( open loop) uncompensated

Offset quadrature communications with decision-feedback carrier synchronization

NASA Technical Reports Server (NTRS)

Simon, M. K.; Smith, J. G.

1974-01-01

In order to accommodate a quadrature amplitude-shift-keyed (QASK) signal, Simon and Smith (1974) have modified the decision-feedback loop which tracks a quadrature phase-shift-keyed (QPSK). In the investigation reported approaches are considered to modify the loops in such a way that offset QASK signals can be tracked, giving attention to the special case of an offset QPSK. The development of the stochastic integro-differential equation of operation for a decision-feedback offset QASK loop is discussed along with the probability density function of the phase error process.

Integrated Devices and Systems | Grid Modernization | NREL

Science.gov Websites

storage models Microgrids Microgrids Grid Simulation and Power Hardware-in-the-Loop Grid simulation and power hardware-in-the-loop Grid Standards and Codes Standards and codes Contact Barry Mather, Ph.D

Performance constraints and compensation for teleoperation with delay

NASA Technical Reports Server (NTRS)

Mclaughlin, J. S.; Staunton, B. D.

1989-01-01

A classical control perspective is used to characterize performance constraints and evaluate compensation techniques for teleoperation with delay. Use of control concepts such as open and closed loop performance, stability, and bandwidth yield insight to the delay problem. Teleoperator performance constraints are viewed as an open loop time delay lag and as a delay-induced closed loop bandwidth constraint. These constraints are illustrated with a simple analytical tracking example which is corroborated by a real time, 'man-in-the-loop' tracking experiment. The experiment also provides insight to those controller characteristics which are unique to a human operator. Predictive displays and feedforward commands are shown to provide open loop compensation for delay lag. Low pass filtering of telemetry or feedback signals is interpreted as closed loop compensation used to maintain a sufficiently low bandwidth for stability. A new closed loop compensation approach is proposed that uses a reactive (or force feedback) hand controller to restrict system bandwidth by impeding operator inputs.

Fast flux locked loop

DOEpatents

Ganther, Jr., Kenneth R.; Snapp, Lowell D.

2002-09-10

A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

An Enhanced Non-Coherent Pre-Filter Design for Tracking Error Estimation in GNSS Receivers.

PubMed

Luo, Zhibin; Ding, Jicheng; Zhao, Lin; Wu, Mouyan

2017-11-18

Tracking error estimation is of great importance in global navigation satellite system (GNSS) receivers. Any inaccurate estimation for tracking error will decrease the signal tracking ability of signal tracking loops and the accuracies of position fixing, velocity determination, and timing. Tracking error estimation can be done by traditional discriminator, or Kalman filter-based pre-filter. The pre-filter can be divided into two categories: coherent and non-coherent. This paper focuses on the performance improvements of non-coherent pre-filter. Firstly, the signal characteristics of coherent and non-coherent integration-which are the basis of tracking error estimation-are analyzed in detail. After that, the probability distribution of estimation noise of four-quadrant arctangent (ATAN2) discriminator is derived according to the mathematical model of coherent integration. Secondly, the statistical property of observation noise of non-coherent pre-filter is studied through Monte Carlo simulation to set the observation noise variance matrix correctly. Thirdly, a simple fault detection and exclusion (FDE) structure is introduced to the non-coherent pre-filter design, and thus its effective working range for carrier phase error estimation extends from (-0.25 cycle, 0.25 cycle) to (-0.5 cycle, 0.5 cycle). Finally, the estimation accuracies of discriminator, coherent pre-filter, and the enhanced non-coherent pre-filter are evaluated comprehensively through the carefully designed experiment scenario. The pre-filter outperforms traditional discriminator in estimation accuracy. In a highly dynamic scenario, the enhanced non-coherent pre-filter provides accuracy improvements of 41.6%, 46.4%, and 50.36% for carrier phase error, carrier frequency error, and code phase error estimation, respectively, when compared with coherent pre-filter. The enhanced non-coherent pre-filter outperforms the coherent pre-filter in code phase error estimation when carrier-to-noise density ratio is less than 28.8 dB-Hz, in carrier frequency error estimation when carrier-to-noise density ratio is less than 20 dB-Hz, and in carrier phase error estimation when carrier-to-noise density belongs to (15, 23) dB-Hz ∪ (26, 50) dB-Hz.

An Enhanced Non-Coherent Pre-Filter Design for Tracking Error Estimation in GNSS Receivers

PubMed Central

Luo, Zhibin; Ding, Jicheng; Zhao, Lin; Wu, Mouyan

2017-01-01

Tracking error estimation is of great importance in global navigation satellite system (GNSS) receivers. Any inaccurate estimation for tracking error will decrease the signal tracking ability of signal tracking loops and the accuracies of position fixing, velocity determination, and timing. Tracking error estimation can be done by traditional discriminator, or Kalman filter-based pre-filter. The pre-filter can be divided into two categories: coherent and non-coherent. This paper focuses on the performance improvements of non-coherent pre-filter. Firstly, the signal characteristics of coherent and non-coherent integration—which are the basis of tracking error estimation—are analyzed in detail. After that, the probability distribution of estimation noise of four-quadrant arctangent (ATAN2) discriminator is derived according to the mathematical model of coherent integration. Secondly, the statistical property of observation noise of non-coherent pre-filter is studied through Monte Carlo simulation to set the observation noise variance matrix correctly. Thirdly, a simple fault detection and exclusion (FDE) structure is introduced to the non-coherent pre-filter design, and thus its effective working range for carrier phase error estimation extends from (−0.25 cycle, 0.25 cycle) to (−0.5 cycle, 0.5 cycle). Finally, the estimation accuracies of discriminator, coherent pre-filter, and the enhanced non-coherent pre-filter are evaluated comprehensively through the carefully designed experiment scenario. The pre-filter outperforms traditional discriminator in estimation accuracy. In a highly dynamic scenario, the enhanced non-coherent pre-filter provides accuracy improvements of 41.6%, 46.4%, and 50.36% for carrier phase error, carrier frequency error, and code phase error estimation, respectively, when compared with coherent pre-filter. The enhanced non-coherent pre-filter outperforms the coherent pre-filter in code phase error estimation when carrier-to-noise density ratio is less than 28.8 dB-Hz, in carrier frequency error estimation when carrier-to-noise density ratio is less than 20 dB-Hz, and in carrier phase error estimation when carrier-to-noise density belongs to (15, 23) dB-Hz ∪ (26, 50) dB-Hz. PMID:29156581

A proposed technique for the Venus balloon telemetry and Doppler frequency recovery

NASA Technical Reports Server (NTRS)

Jurgens, R. F.; Divsalar, D.

1985-01-01

A technique is proposed to accurately estimate the Doppler frequency and demodulate the digitally encoded telemetry signal that contains the measurements from balloon instruments. Since the data are prerecorded, one can take advantage of noncausal estimators that are both simpler and more computationally efficient than the usual closed-loop or real-time estimators for signal detection and carrier tracking. Algorithms for carrier frequency estimation subcarrier demodulation, bit and frame synchronization are described. A Viterbi decoder algorithm using a branch indexing technique has been devised to decode constraint length 6, rate 1/2 convolutional code that is being used by the balloon transmitter. These algorithms are memory efficient and can be implemented on microcomputer systems.

A second-order frequency-aided digital phase-locked loop for Doppler rate tracking

NASA Astrophysics Data System (ADS)

Chie, C. M.

1980-08-01

A second-order digital phase-locked loop (DPLL) has a finite lock range which is a function of the frequency of the incoming signal to be tracked. For this reason, it is not capable of tracking an input with Doppler rate for an indefinite period of time. In this correspondence, an analytical expression for the hold-in time is derived. In addition, an all-digital scheme to alleviate this problem is proposed based on the information obtained from estimating the input signal frequency.

Enhanced Performance Controller Design for Stochastic Systems by Adding Extra State Estimation onto the Existing Closed Loop Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yuyang; Zhang, Qichun; Wang, Hong

To enhance the performance of the tracking property , this paper presents a novel control algorithm for a class of linear dynamic stochastic systems with unmeasurable states, where the performance enhancement loop is established based on Kalman filter. Without changing the existing closed loop with the PI controller, the compensative controller is designed to minimize the variances of the tracking errors using the estimated states and the propagation of state variances. Moreover, the stability of the closed-loop systems has been analyzed in the mean-square sense. A simulated example is included to show the effectiveness of the presented control algorithm, wheremore » encouraging results have been obtained.« less

H∞ output tracking control of discrete-time nonlinear systems via standard neural network models.

PubMed

Liu, Meiqin; Zhang, Senlin; Chen, Haiyang; Sheng, Weihua

2014-10-01

This brief proposes an output tracking control for a class of discrete-time nonlinear systems with disturbances. A standard neural network model is used to represent discrete-time nonlinear systems whose nonlinearity satisfies the sector conditions. H∞ control performance for the closed-loop system including the standard neural network model, the reference model, and state feedback controller is analyzed using Lyapunov-Krasovskii stability theorem and linear matrix inequality (LMI) approach. The H∞ controller, of which the parameters are obtained by solving LMIs, guarantees that the output of the closed-loop system closely tracks the output of a given reference model well, and reduces the influence of disturbances on the tracking error. Three numerical examples are provided to show the effectiveness of the proposed H∞ output tracking design approach.

Investigation, development and application of optimal output feedback theory. Volume 2: Development of an optimal, limited state feedback outer-loop digital flight control system for 3-D terminal area operation

NASA Technical Reports Server (NTRS)

Broussard, J. R.; Halyo, N.

1984-01-01

This report contains the development of a digital outer-loop three dimensional radio navigation (3-D RNAV) flight control system for a small commercial jet transport. The outer-loop control system is designed using optimal stochastic limited state feedback techniques. Options investigated using the optimal limited state feedback approach include integrated versus hierarchical control loop designs, 20 samples per second versus 5 samples per second outer-loop operation and alternative Type 1 integration command errors. Command generator tracking techniques used in the digital control design enable the jet transport to automatically track arbitrary curved flight paths generated by waypoints. The performance of the design is demonstrated using detailed nonlinear aircraft simulations in the terminal area, frequency domain multi-input sigma plots, frequency domain single-input Bode plots and closed-loop poles. The response of the system to a severe wind shear during a landing approach is also presented.

The High Altitude Balloon Experiment demonstration of acquisition, tracking, and pointing technologies (HABE-ATP)

NASA Astrophysics Data System (ADS)

Dimiduk, D.; Caylor, M.; Williamson, D.; Larson, L.

1995-01-01

The High Altitude Balloon Experiment demonstration of Acquisition, Tracking, and Pointing (HABE-ATP) is a system built around balloon-borne payload which is carried to a nominal 26-km altitude. The goal is laser tracking thrusting theater and strategic missiles, and then pointing a surrogate laser weapon beam, with performance levels end a timeline traceable to operational laser weapon system requirements. This goal leads to an experiment system design which combines hardware from many technology areas: an optical telescope and IR sensors; an advanced angular inertial reference; a flexible multi-level of actuation digital control system; digital tracking processors which incorporate real-time image analysis and a pulsed, diode-pumped solid state tracking laser. The system components have been selected to meet the overall experiment goals of tracking unmodified boosters at 50- 200 km range. The ATP system on HABE must stabilize and control a relative line of sight between the platform and the unmodified target booster to a 1 microrad accuracy. The angular pointing reference system supports both open loop and closed loop track modes; GPS provides absolute position reference. The control system which positions the line of sight for the ATP system must sequence through accepting a state vector handoff, closed-loop passive IR acquisition, passive IR intermediate fine track, active fine track, and then finally aimpoint determination and maintenance modes. Line of sight stabilization to fine accuracy levels is accomplished by actuating wide bandwidth fast steering mirrors (FSM's). These control loops off-load large-amplitude errors to the outer gimbal in order to remain within the limited angular throw of the FSM's. The SWIR acquisition and MWIR intermediate fine track sensors (both PtSi focal planes) image the signature of the rocket plume. After Hard Body Handover (HBHO), active fine tracking is conducted with a visible focal plane viewing the laser-illuminated target rocket body. The track and fire control performance must be developed to the point that an aimpoint can be selected, maintained, and then track performance scored with a low-power 'surrogate' weapon beam. Extensive instrumentation monitors not only the optical sensors and the video data, but all aspects of each of the experiment subsystems such as the control system, the experiment flight vehicle, and the tracker. Because the system is balloon-borne and recoverable, it is expected to fly many times during its development program.

Modeling and Development of INS-Aided PLLs in a GNSS/INS Deeply-Coupled Hardware Prototype for Dynamic Applications

PubMed Central

Zhang, Tisheng; Niu, Xiaoji; Ban, Yalong; Zhang, Hongping; Shi, Chuang; Liu, Jingnan

2015-01-01

A GNSS/INS deeply-coupled system can improve the satellite signals tracking performance by INS aiding tracking loops under dynamics. However, there was no literature available on the complete modeling of the INS branch in the INS-aided tracking loop, which caused the lack of a theoretical tool to guide the selections of inertial sensors, parameter optimization and quantitative analysis of INS-aided PLLs. This paper makes an effort on the INS branch in modeling and parameter optimization of phase-locked loops (PLLs) based on the scalar-based GNSS/INS deeply-coupled system. It establishes the transfer function between all known error sources and the PLL tracking error, which can be used to quantitatively evaluate the candidate inertial measurement unit (IMU) affecting the carrier phase tracking error. Based on that, a steady-state error model is proposed to design INS-aided PLLs and to analyze their tracking performance. Based on the modeling and error analysis, an integrated deeply-coupled hardware prototype is developed, with the optimization of the aiding information. Finally, the performance of the INS-aided PLLs designed based on the proposed steady-state error model is evaluated through the simulation and road tests of the hardware prototype. PMID:25569751

Performance Improvement of Receivers Based on Ultra-Tight Integration in GNSS-Challenged Environments

PubMed Central

Qin, Feng; Zhan, Xingqun; Du, Gang

2013-01-01

Ultra-tight integration was first proposed by Abbott in 2003 with the purpose of integrating a global navigation satellite system (GNSS) and an inertial navigation system (INS). This technology can improve the tracking performances of a receiver by reconfiguring the tracking loops in GNSS-challenged environments. In this paper, the models of all error sources known to date in the phase lock loops (PLLs) of a standard receiver and an ultra-tightly integrated GNSS/INS receiver are built, respectively. Based on these models, the tracking performances of the two receivers are compared to verify the improvement due to the ultra-tight integration. Meanwhile, the PLL error distributions of the two receivers are also depicted to analyze the error changes of the tracking loops. These results show that the tracking error is significantly reduced in the ultra-tightly integrated GNSS/INS receiver since the receiver's dynamics are estimated and compensated by an INS. Moreover, the mathematical relationship between the tracking performances of the ultra-tightly integrated GNSS/INS receiver and the quality of the selected inertial measurement unit (IMU) is derived from the error models and proved by the error comparisons of four ultra-tightly integrated GNSS/INS receivers aided by different grade IMUs.

HIV1 V3 loop hypermutability is enhanced by the guanine usage bias in the part of env gene coding for it.

PubMed

Khrustalev, Vladislav Victorovich

2009-01-01

Guanine is the most mutable nucleotide in HIV genes because of frequently occurring G to A transitions, which are caused by cytosine deamination in viral DNA minus strands catalyzed by APOBEC enzymes. Distribution of guanine between three codon positions should influence the probability for G to A mutation to be nonsynonymous (to occur in first or second codon position). We discovered that nucleotide sequences of env genes coding for third variable regions (V3 loops) of gp120 from HIV1 and HIV2 have different kinds of guanine usage biases. In the HIV1 reference strain and 100 additionally analyzed HIV1 strains the guanine usage bias in V3 loop coding regions (2G>1G>3G) should lead to elevated nonsynonymous G to A transitions occurrence rates. In the HIV2 reference strain and 100 other HIV2 strains guanine usage bias in V3 loop coding regions (3G>2G>1G) should protect V3 loops from hypermutability. According to the HIV1 and HIV2 V3 alignment, insertion of the sequence enriched with 2G (21 codons in length) occurred during the evolution of HIV1 predecessor, while insertion of the different sequence enriched with 3G (19 codons in length) occurred during the evolution of HIV2 predecessor. The higher is the level of 3G in the V3 coding region, the lower should be the immune escaping mutation occurrence rates. This hypothesis was tested in this study by comparing the guanine usage in V3 loop coding regions from HIV1 fast and slow progressors. All calculations have been performed by our algorithms "VVK In length", "VVK Dinucleotides" and "VVK Consensus" (www.barkovsky.hotmail.ru).

Coded excitation ultrasonic needle tracking: An in vivo study.

PubMed

Xia, Wenfeng; Ginsberg, Yuval; West, Simeon J; Nikitichev, Daniil I; Ourselin, Sebastien; David, Anna L; Desjardins, Adrien E

2016-07-01

Accurate and efficient guidance of medical devices to procedural targets lies at the heart of interventional procedures. Ultrasound imaging is commonly used for device guidance, but determining the location of the device tip can be challenging. Various methods have been proposed to track medical devices during ultrasound-guided procedures, but widespread clinical adoption has remained elusive. With ultrasonic tracking, the location of a medical device is determined by ultrasonic communication between the ultrasound imaging probe and a transducer integrated into the medical device. The signal-to-noise ratio (SNR) of the transducer data is an important determinant of the depth in tissue at which tracking can be performed. In this paper, the authors present a new generation of ultrasonic tracking in which coded excitation is used to improve the SNR without spatial averaging. A fiber optic hydrophone was integrated into the cannula of a 20 gauge insertion needle. This transducer received transmissions from the ultrasound imaging probe, and the data were processed to obtain a tracking image of the needle tip. Excitation using Barker or Golay codes was performed to improve the SNR, and conventional bipolar excitation was performed for comparison. The performance of the coded excitation ultrasonic tracking system was evaluated in an in vivo ovine model with insertions to the brachial plexus and the uterine cavity. Coded excitation significantly increased the SNRs of the tracking images, as compared with bipolar excitation. During an insertion to the brachial plexus, the SNR was increased by factors of 3.5 for Barker coding and 7.1 for Golay coding. During insertions into the uterine cavity, these factors ranged from 2.9 to 4.2 for Barker coding and 5.4 to 8.5 for Golay coding. The maximum SNR was 670, which was obtained with Golay coding during needle withdrawal from the brachial plexus. Range sidelobe artifacts were observed in tracking images obtained with Barker coded excitation, and they were visually absent with Golay coded excitation. The spatial tracking accuracy was unaffected by coded excitation. Coded excitation is a viable method for improving the SNR in ultrasonic tracking without compromising spatial accuracy. This method provided SNR increases that are consistent with theoretical expectations, even in the presence of physiological motion. With the ultrasonic tracking system in this study, the SNR increases will have direct clinical implications in a broad range of interventional procedures by improving visibility of medical devices at large depths.

Indoor Autonomous Control of a Two-Wheeled Inverted Pendulum Vehicle Using Ultra Wide Band Technology.

PubMed

Xia, Dunzhu; Yao, Yanhong; Cheng, Limei

2017-06-15

In this paper, we aimed to achieve the indoor tracking control of a two-wheeled inverted pendulum (TWIP) vehicle. The attitude data are acquired from a low cost micro inertial measurement unit (IMU), and the ultra-wideband (UWB) technology is utilized to obtain an accurate estimation of the TWIP's position. We propose a dual-loop control method to realize the simultaneous balance and trajectory tracking control for the TWIP vehicle. A robust adaptive second-order sliding mode control (2-RASMC) method based on an improved super-twisting (STW) algorithm is investigated to obtain the control laws, followed by several simulations to verify its robustness. The outer loop controller is designed using the idea of backstepping. Moreover, three typical trajectories, including a circle, a trifolium and a hexagon, have been designed to prove the adaptability of the control combinations. Six different combinations of inner and outer loop control algorithms have been compared, and the characteristics of inner and outer loop algorithm combinations have been analyzed. Simulation results demonstrate its tracking performance and thus verify the validity of the proposed control methods. Trajectory tracking experiments in a real indoor environment have been performed using our experimental vehicle to further validate the feasibility of the proposed algorithm in practice.

Indoor Autonomous Control of a Two-Wheeled Inverted Pendulum Vehicle Using Ultra Wide Band Technology

PubMed Central

Xia, Dunzhu; Yao, Yanhong; Cheng, Limei

2017-01-01

In this paper, we aimed to achieve the indoor tracking control of a two-wheeled inverted pendulum (TWIP) vehicle. The attitude data are acquired from a low cost micro inertial measurement unit (IMU), and the ultra-wideband (UWB) technology is utilized to obtain an accurate estimation of the TWIP’s position. We propose a dual-loop control method to realize the simultaneous balance and trajectory tracking control for the TWIP vehicle. A robust adaptive second-order sliding mode control (2-RASMC) method based on an improved super-twisting (STW) algorithm is investigated to obtain the control laws, followed by several simulations to verify its robustness. The outer loop controller is designed using the idea of backstepping. Moreover, three typical trajectories, including a circle, a trifolium and a hexagon, have been designed to prove the adaptability of the control combinations. Six different combinations of inner and outer loop control algorithms have been compared, and the characteristics of inner and outer loop algorithm combinations have been analyzed. Simulation results demonstrate its tracking performance and thus verify the validity of the proposed control methods. Trajectory tracking experiments in a real indoor environment have been performed using our experimental vehicle to further validate the feasibility of the proposed algorithm in practice. PMID:28617338

Bar Coding and Tracking in Pathology.

PubMed

Hanna, Matthew G; Pantanowitz, Liron

2016-03-01

Bar coding and specimen tracking are intricately linked to pathology workflow and efficiency. In the pathology laboratory, bar coding facilitates many laboratory practices, including specimen tracking, automation, and quality management. Data obtained from bar coding can be used to identify, locate, standardize, and audit specimens to achieve maximal laboratory efficiency and patient safety. Variables that need to be considered when implementing and maintaining a bar coding and tracking system include assets to be labeled, bar code symbologies, hardware, software, workflow, and laboratory and information technology infrastructure as well as interoperability with the laboratory information system. This article addresses these issues, primarily focusing on surgical pathology. Copyright © 2016 Elsevier Inc. All rights reserved.

Bar Coding and Tracking in Pathology.

PubMed

Hanna, Matthew G; Pantanowitz, Liron

2015-06-01

Bar coding and specimen tracking are intricately linked to pathology workflow and efficiency. In the pathology laboratory, bar coding facilitates many laboratory practices, including specimen tracking, automation, and quality management. Data obtained from bar coding can be used to identify, locate, standardize, and audit specimens to achieve maximal laboratory efficiency and patient safety. Variables that need to be considered when implementing and maintaining a bar coding and tracking system include assets to be labeled, bar code symbologies, hardware, software, workflow, and laboratory and information technology infrastructure as well as interoperability with the laboratory information system. This article addresses these issues, primarily focusing on surgical pathology. Copyright © 2015 Elsevier Inc. All rights reserved.

An investigation of tritium transfer in reactor loops

NASA Astrophysics Data System (ADS)

Ilyasova, O. H.; Mosunova, N. A.

2017-09-01

The work is devoted to the important task of the numerical simulation and analysis of the tritium behaviour in the reactor loops. The simulation was carried out by HYDRA-IBRAE/LM code, which is being developed in Nuclear safety institute of the Russian Academy of Sciences. The code is intended for modeling of the liquid metal flow (sodium, lead and lead-bismuth) on the base of non-homogeneous and non-equilibrium two-fluid model. In order to simulate tritium transfer in the code, the special module has been developed. Module includes the models describing the main phenomena of tritium behaviour in reactor loops: transfer, permeation, leakage, etc. Because of shortage of the experimental data, a lot of analytical tests and comparative calculations were considered. Some of them are presented in this work. The comparison of estimation results and experimental and analytical data demonstrate not only qualitative but also good quantitative agreement. It is possible to confirm that HYDRA-IBRAE/LM code allows modeling tritium transfer in reactor loops.

The 'Brick Wall' radio loss approximation and the performance of strong channel codes for deep space applications at high data rates

NASA Technical Reports Server (NTRS)

Shambayati, Shervin

2001-01-01

In order to evaluate performance of strong channel codes in presence of imperfect carrier phase tracking for residual carrier BPSK modulation in this paper an approximate 'brick wall' model is developed which is independent of the channel code type for high data rates. It is shown that this approximation is reasonably accurate (less than 0.7dB for low FERs for (1784,1/6) code and less than 0.35dB for low FERs for (5920,1/6) code). Based on the approximation's accuracy, it is concluded that the effects of imperfect carrier tracking are more or less independent of the channel code type for strong channel codes. Therefore, the advantage that one strong channel code has over another with perfect carrier tracking translates to nearly the same advantage under imperfect carrier tracking conditions. This will allow the link designers to incorporate projected channel code performance of strong channel codes into their design tables without worrying about their behavior in the face of imperfect carrier phase tracking.

Two AFC Loops For Low CNR And High Dynamics

NASA Technical Reports Server (NTRS)

Hinedi, Sami M.; Aguirre, Sergio

1992-01-01

Two alternative digital automatic-frequency-control (AFC) loops proposed to acquire (or reacquire) and track frequency of received carrier radio signal. Intended for use where carrier-to-noise ratios (CNR's) low and carrier frequency characterized by high Doppler shift and Doppler rate because of high relative speed and acceleration, respectively, between transmitter and receiver. Either AFC loops used in place of phase-locked loop. New loop concepts integrate ideas from classical spectrum-estimation, digital-phase-locked-loop, and Kalman-Filter theories.

Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs

NASA Technical Reports Server (NTRS)

Chen, C.-C.; Win, M. Z.

1991-01-01

The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.

LOOPREF: A Fluid Code for the Simulation of Coronal Loops

NASA Technical Reports Server (NTRS)

deFainchtein, Rosalinda; Antiochos, Spiro; Spicer, Daniel

1998-01-01

This report documents the code LOOPREF. LOOPREF is a semi-one dimensional finite element code that is especially well suited to simulate coronal-loop phenomena. It has a full implementation of adaptive mesh refinement (AMR), which is crucial for this type of simulation. The AMR routines are an improved version of AMR1D. LOOPREF's versatility makes is suitable to simulate a wide variety of problems. In addition to efficiently providing very high resolution in rapidly changing regions of the domain, it is equipped to treat loops of variable cross section, any non-linear form of heat conduction, shocks, gravitational effects, and radiative loss.

Slab track field test and demonstration program for shared freight and high-speed passenger service

DOT National Transportation Integrated Search

2010-08-01

Two types of slab tracks were installed on the High Tonnage Loop at the Facility for Accelerated Service Testing. Direct fixation slab track (DFST) and independent dual block track (IDBT) were installed into a 5-degree curve with 4-inch superelevatio...

Study of a Simulation Tool to Determine Achievable Control Dynamics and Control Power Requirements with Perfect Tracking

NASA Technical Reports Server (NTRS)

Ostroff, Aaron J.

1998-01-01

This paper contains a study of two methods for use in a generic nonlinear simulation tool that could be used to determine achievable control dynamics and control power requirements while performing perfect tracking maneuvers over the entire flight envelope. The two methods are NDI (nonlinear dynamic inversion) and the SOFFT(Stochastic Optimal Feedforward and Feedback Technology) feedforward control structure. Equivalent discrete and continuous SOFFT feedforward controllers have been developed. These equivalent forms clearly show that the closed-loop plant model loop is a plant inversion and is the same as the NDI formulation. The main difference is that the NDI formulation has a closed-loop controller structure whereas SOFFT uses an open-loop command model. Continuous, discrete, and hybrid controller structures have been developed and integrated into the formulation. Linear simulation results show that seven different configurations all give essentially the same response, with the NDI hybrid being slightly different. The SOFFT controller gave better tracking performance compared to the NDI controller when a nonlinear saturation element was added. Future plans include evaluation using a nonlinear simulation.

On the false lock behavior of polarity-type Costas loops with Manchester coded input. [for Space Shuttle Orbiter communication

NASA Technical Reports Server (NTRS)

Simon, M. K.

1977-01-01

A modification of a Costas loop is described, and the false lock behavior of this system is studied. The modified Costas loop hard limits the output of the in-phase channel, replaces the analog multiplier with a chopper-type device, and is equipped with single-pole arm filters in the loop. The false lock behavior associated with the use of Manchester coded data is investigated; the results can be applied to the assessment of the false lock margin on the Ku-band uplink to the Space Shuttle Orbiter through the TURSS.

Temporal Code-Driven Stimulation: Definition and Application to Electric Fish Signaling

PubMed Central

Lareo, Angel; Forlim, Caroline G.; Pinto, Reynaldo D.; Varona, Pablo; Rodriguez, Francisco de Borja

2016-01-01

Closed-loop activity-dependent stimulation is a powerful methodology to assess information processing in biological systems. In this context, the development of novel protocols, their implementation in bioinformatics toolboxes and their application to different description levels open up a wide range of possibilities in the study of biological systems. We developed a methodology for studying biological signals representing them as temporal sequences of binary events. A specific sequence of these events (code) is chosen to deliver a predefined stimulation in a closed-loop manner. The response to this code-driven stimulation can be used to characterize the system. This methodology was implemented in a real time toolbox and tested in the context of electric fish signaling. We show that while there are codes that evoke a response that cannot be distinguished from a control recording without stimulation, other codes evoke a characteristic distinct response. We also compare the code-driven response to open-loop stimulation. The discussed experiments validate the proposed methodology and the software toolbox. PMID:27766078

Temporal Code-Driven Stimulation: Definition and Application to Electric Fish Signaling.

PubMed

Lareo, Angel; Forlim, Caroline G; Pinto, Reynaldo D; Varona, Pablo; Rodriguez, Francisco de Borja

2016-01-01

Closed-loop activity-dependent stimulation is a powerful methodology to assess information processing in biological systems. In this context, the development of novel protocols, their implementation in bioinformatics toolboxes and their application to different description levels open up a wide range of possibilities in the study of biological systems. We developed a methodology for studying biological signals representing them as temporal sequences of binary events. A specific sequence of these events (code) is chosen to deliver a predefined stimulation in a closed-loop manner. The response to this code-driven stimulation can be used to characterize the system. This methodology was implemented in a real time toolbox and tested in the context of electric fish signaling. We show that while there are codes that evoke a response that cannot be distinguished from a control recording without stimulation, other codes evoke a characteristic distinct response. We also compare the code-driven response to open-loop stimulation. The discussed experiments validate the proposed methodology and the software toolbox.

When causality does not imply correlation: more spadework at the foundations of scientific psychology.

PubMed

Marken, Richard S; Horth, Brittany

2011-06-01

Experimental research in psychology is based on an open-loop causal model which assumes that sensory input causes behavioral output. This model was tested in a tracking experiment where participants were asked to control a cursor, keeping it aligned with a target by moving a mouse to compensate for disturbances of differing difficulty. Since cursor movements (inputs) are the only observable cause of mouse movements (outputs), the open-loop model predicts that there will be a correlation between input and output that increases as tracking performance improves. In fact, the correlation between sensory input and motor output is very low regardless of the quality of tracking performance; causality, in terms of the effect of input on output, does not seem to imply correlation in this situation. This surprising result can be explained by a closed-loop model which assumes that input is causing output while output is causing input.

Space Shuttle program communication and tracking systems interface analysis

NASA Technical Reports Server (NTRS)

Dodds, J. G.; Holmes, J. K.; Huth, G. K.; Iwasaki, R. S.; Nilsen, P. W.; Polydoros, A.; Sampaio, D. R.; Udalov, S.

1984-01-01

The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis.

A new modem for microwave time synchronisation via geosynchronous telecommunication satellites

NASA Astrophysics Data System (ADS)

Dienert, Michael

1992-06-01

A study illustrating the two way time transfer technique and describing the use of this technique with the MITREX (Microwave Time and Range Experiment) SATRE (Satellite Time and Range Experiment) modems is presented. The two way time transfer technique via geosynchronous telecom satellites is one of the most accurate methods for synchronization and comparison of remote clocks. Most of the unknown propagation delays can be eliminated by the two way principle. The use of a coherent spread spectrum technique with a truncated pseudonoise code offers a resolution better than 30 ps of the measured time interval. The receiver is built around a Delay Locked Loop (DLL), which correlates the received signal with the known PN sequence to derive the control signal of the loop. In the locked state both PN sequences are synchronous and tracking errors of less than 30 ps are possible. Results showing the accuracy of the modem depending on signal to noise ratio and variation of total input power levels are presented and show that the expected improvement of the jitter of the internal delay by an increase of the chip rate is possible.

Deductive Evaluation: Implicit Code Verification With Low User Burden

NASA Technical Reports Server (NTRS)

Di Vito, Ben L.

2016-01-01

We describe a framework for symbolically evaluating C code using a deductive approach that discovers and proves program properties. The framework applies Floyd-Hoare verification principles in its treatment of loops, with a library of iteration schemes serving to derive loop invariants. During evaluation, theorem proving is performed on-the-fly, obviating the generation of verification conditions normally needed to establish loop properties. A PVS-based prototype is presented along with results for sample C functions.

Low data rate digital space communications

NASA Technical Reports Server (NTRS)

Chen, C. H.

1973-01-01

The low available transmitter power and the large frequency uncertainty constrain the data rate to be low. An all-digital communication receiver is proposed, and its feasibility is established. Although coherent systems should be used whenever practical, the noncoherent MFSK system is more suitable for very low data rates. The effect of Rician fading on the performance of MFSK receiver is studied. Fading characteristics of the Venus channel are examined based on the exponential model and available experimental data on the Venus atmosphere. Because of the requirement of high communication efficiency, three codes are evaluated and compared. The rapidly varying phase error at low data rate has great effects on the tracking loop behaviors which are examined by extensive computer study of the phase plane trajectories.

Adaptive Wavelet Coding Applied in a Wireless Control System.

PubMed

Gama, Felipe O S; Silveira, Luiz F Q; Salazar, Andrés O

2017-12-13

Wireless control systems can sense, control and act on the information exchanged between the wireless sensor nodes in a control loop. However, the exchanged information becomes susceptible to the degenerative effects produced by the multipath propagation. In order to minimize the destructive effects characteristic of wireless channels, several techniques have been investigated recently. Among them, wavelet coding is a good alternative for wireless communications for its robustness to the effects of multipath and its low computational complexity. This work proposes an adaptive wavelet coding whose parameters of code rate and signal constellation can vary according to the fading level and evaluates the use of this transmission system in a control loop implemented by wireless sensor nodes. The performance of the adaptive system was evaluated in terms of bit error rate (BER) versus E b / N 0 and spectral efficiency, considering a time-varying channel with flat Rayleigh fading, and in terms of processing overhead on a control system with wireless communication. The results obtained through computational simulations and experimental tests show performance gains obtained by insertion of the adaptive wavelet coding in a control loop with nodes interconnected by wireless link. These results enable the use of this technique in a wireless link control loop.

Volume accumulator design analysis computer codes

NASA Technical Reports Server (NTRS)

Whitaker, W. D.; Shimazaki, T. T.

1973-01-01

The computer codes, VANEP and VANES, were written and used to aid in the design and performance calculation of the volume accumulator units (VAU) for the 5-kwe reactor thermoelectric system. VANEP computes the VAU design which meets the primary coolant loop VAU volume and pressure performance requirements. VANES computes the performance of the VAU design, determined from the VANEP code, at the conditions of the secondary coolant loop. The codes can also compute the performance characteristics of the VAU's under conditions of possible modes of failure which still permit continued system operation.

Two-motor direct drive control for elevation axis of telescope

NASA Astrophysics Data System (ADS)

Tang, T.; Tan, Y.; Ren, G.

2014-07-01

Two-motor application has become a very attractive filed in important field which high performance is permitted to achieve of position, speed, and acceleration. In the elevation axis of telescope control system, two-motor direct drive is proposed to enhance the high performance of tracking control system. Although there are several dominant strengths such as low size of motors and high torsional structural dynamics, the synchronization control of two motors is a very difficult and important. In this paper, a multi-loop control technique base master-slave current control is used to synchronize two motors, including current control loop, speed control loop and position control loop. First, the direct drive function of two motors is modeled. Compared of single motor direct control system, the resonance frequency of two motor control systems is same; while the anti-resonance frequency of two motors control system is 1.414 times than those of sing motor system. Because of rigid coupling for direct drive, the speed of two motor of the system is same, and the synchronization of torque for motors is critical. The current master-slave control technique is effective to synchronize the torque, which the current loop of the master motors is tracked the other slave motor. The speed feedback into the input of current loop of the master motors. The experiments test the performance of the two motors drive system. The random tracking error is 0.0119" for the line trajectory of 0.01°/s.

Trellis coded modulation for 4800-9600 bps transmission over a fading mobile satellite channel

NASA Technical Reports Server (NTRS)

Divsalar, D.; Simon, M. K.

1986-01-01

The combination of trellis coding and multiple phase-shift-keyed (MPSK) signalling with the addition of asymmetry to the signal set is discussed with regard to its suitability as a modulation/coding scheme for the fading mobile satellite channel. For MPSK, introducing nonuniformity (asymmetry) into the spacing between signal points in the constellation buys a further improvement in performance over that achievable with trellis coded symmetric MPSK, all this without increasing average or peak power, or changing the bandwidth constraints imposed on the system. Whereas previous contributions have considered the performance of trellis coded modulation transmitted over an additive white Gaussian noise (AWGN) channel, the emphasis in the paper is on the performance of trellis coded MPSK in the fading environment. The results will be obtained by using a combination of analysis and simulation. It will be assumed that the effect of the fading on the phase of the received signal is fully compensated for either by tracking it with some form of phase-locked loop or with pilot tone calibration techniques. Thus, results will reflect only the degradation due to the effect of the fading on the amplitude of the received signal. Also, we shall consider only the case where interleaving/deinterleaving is employed to further combat the fading. This allows for considerable simplification of the analysis and is of great practical interest. Finally, the impact of the availability of channel state information on average bit error probability performance is assessed.

All-digital phase-lock loops for noise-free signals

NASA Technical Reports Server (NTRS)

Anderson, T. O.

1973-01-01

Bit-synchronizers utilize all-digital phase-lock loops that are referenced to a high frequency digital clock. Phase-lock loop of first design acquires frequency within nominal range and tracks phase; second design is modified for random binary data by addition of simple transition detector; and third design acquires frequency over wide dynamic range.

Real-time open-loop frequency response analysis of flight test data

NASA Technical Reports Server (NTRS)

Bosworth, J. T.; West, J. C.

1986-01-01

A technique has been developed to compare the open-loop frequency response of a flight test aircraft real time with linear analysis predictions. The result is direct feedback to the flight control systems engineer on the validity of predictions and adds confidence for proceeding with envelope expansion. Further, gain and phase margins can be tracked for trends in a manner similar to the techniques used by structural dynamics engineers in tracking structural modal damping.

An efficient method to compute microlensed light curves for point sources

NASA Technical Reports Server (NTRS)

Witt, Hans J.

1993-01-01

We present a method to compute microlensed light curves for point sources. This method has the general advantage that all microimages contributing to the light curve are found. While a source moves along a straight line, all micro images are located either on the primary image track or on the secondary image tracks (loops). The primary image track extends from - infinity to + infinity and is made of many sequents which are continuously connected. All the secondary image tracks (loops) begin and end on the lensing point masses. The method can be applied to any microlensing situation with point masses in the deflector plane, even for the overcritical case and surface densities close to the critical. Furthermore, we present general rules to evaluate the light curve for a straight track arbitrary placed in the caustic network of a sample of many point masses.

Novel imaging closed loop control strategy for heliostats

NASA Astrophysics Data System (ADS)

Bern, Gregor; Schöttl, Peter; Heimsath, Anna; Nitz, Peter

2017-06-01

Central Receiver Systems use up to thousands of heliostats to concentrate solar radiation. The precise control of heliostat aiming points is crucial not only for efficiency but also for reliable plant operation. Besides the calibration of open loop control systems, closed loop tracking strategies are developed to address a precise and efficient aiming strategy. The need for cost reductions in the heliostat field intensifies the motivation for economic closed loop control systems. This work introduces an approach for a closed loop heliostat tracking strategy using image analysis and signal modulation. The approach aims at the extraction of heliostat focal spot position within the receiver domain by means of a centralized remote vision system decoupled from the rough conditions close to the focal area. Taking an image sequence of the receiver while modulating a signal on different heliostats, their aiming points are retrieved. The work describes the methodology and shows first results from simulations and practical tests performed in small scale, motivating further investigation and deployment.

Robot trajectory tracking with self-tuning predicted control

NASA Technical Reports Server (NTRS)

Cui, Xianzhong; Shin, Kang G.

1988-01-01

A controller that combines self-tuning prediction and control is proposed for robot trajectory tracking. The controller has two feedback loops: one is used to minimize the prediction error, and the other is designed to make the system output track the set point input. Because the velocity and position along the desired trajectory are given and the future output of the system is predictable, a feedforward loop can be designed for robot trajectory tracking with self-tuning predicted control (STPC). Parameters are estimated online to account for the model uncertainty and the time-varying property of the system. The authors describe the principle of STPC, analyze the system performance, and discuss the simplification of the robot dynamic equations. To demonstrate its utility and power, the controller is simulated for a Stanford arm.

Propagating wave in active region-loops, located over the solar disk observed by the Interface Region Imaging Spectrograph

NASA Astrophysics Data System (ADS)

Zhang, B.; Hou, Y. J.; Zhang, J.

2018-03-01

Aims: We aim to ascertain the physical parameters of a propagating wave over the solar disk detected by the Interface Region Imaging Spectrograph (IRIS). Methods: Using imaging data from the IRIS and the Solar Dynamic Observatory (SDO), we tracked bright spots to determine the parameters of a propagating transverse wave in active region (AR) loops triggered by activation of a filament. Deriving the Doppler velocity of Si IV line from spectral observations of IRIS, we have determined the rotating directions of active region loops which are relevant to the wave. Results: On 2015 December 19, a filament was located on the polarity inversion line of the NOAA AR 12470. The filament was activated and then caused a C1.1 two-ribbon flare. Between the flare ribbons, two rotation motions of a set of bright loops were observed to appear in turn with opposite directions. Following the end of the second rotation, a propagating wave and an associated transverse oscillation were detected in these bright loops. In 1400 Å channel, there was bright material flowing along the loops in a wave-like manner, with a period of 128 s and a mean amplitude of 880 km. For the transverse oscillation, we tracked a given loop and determine the transverse positions of the tracking loop in a limited longitudinal range. In both of 1400 Å and 171 Å channels, approximately four periods are distinguished during the transverse oscillation. The mean period of the oscillation is estimated as 143 s and the displacement amplitude as between 1370 km and 690 km. We interpret these oscillations as a propagating kink wave and obtain its speed of 1400 km s-1. Conclusions: Our observations reveal that a flare associated with filament activation could trigger a kink propagating wave in active region loops over the solar disk. Movies associated to Figs. 1-4 are available at http://https://www.aanda.org

An automatic tracking system for phase-noise measurement.

PubMed

Yuen, Chung Ming; Tsang, Kim Fung

2005-05-01

A low cost, automatic tracking system for phase noise measurement has been implemented successfully. The tracking system is accomplished by applying a charge pump phase-locked loop as an external reference source to a digital spectrum analyzer. Measurement of a 2.5 GHz, free-running, voltage-controlled oscillator demonstrated the tracking accuracy, thus verifying the feasibility of the system.

Phase-lock-loop application for fiber optic receiver

NASA Astrophysics Data System (ADS)

Ruggles, Stephen L.; Wills, Robert W.

1991-02-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Phase-lock-loop application for fiber optic receiver

NASA Technical Reports Server (NTRS)

Ruggles, Stephen L.; Wills, Robert W.

1991-01-01

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Integrated Circuit Wear out Prediction and Recycling Detection using Radio Frequency Distinct Native Attribute Features

DTIC Science & Technology

2016-12-22

105 A.1 Main Loop ... loop monitoring for preventative maintenance rather than early replacement based on statistical projections or replacement-after- failure schemes. IC...estimates, RF-DNA may provide a means to track an IC’s physical degradation during actual use. Monitoring an IC’s degradation in a closed loop fashion

Continuous fractional-order Zero Phase Error Tracking Control.

PubMed

Liu, Lu; Tian, Siyuan; Xue, Dingyu; Zhang, Tao; Chen, YangQuan

2018-04-01

A continuous time fractional-order feedforward control algorithm for tracking desired time varying input signals is proposed in this paper. The presented controller cancels the phase shift caused by the zeros and poles of controlled closed-loop fractional-order system, so it is called Fractional-Order Zero Phase Tracking Controller (FZPETC). The controlled systems are divided into two categories i.e. with and without non-cancellable (non-minimum-phase) zeros which stand in unstable region or on stability boundary. Each kinds of systems has a targeted FZPETC design control strategy. The improved tracking performance has been evaluated successfully by applying the proposed controller to three different kinds of fractional-order controlled systems. Besides, a modified quasi-perfect tracking scheme is presented for those systems which may not have available future tracking trajectory information or have problem in high frequency disturbance rejection if the perfect tracking algorithm is applied. A simulation comparison and a hardware-in-the-loop thermal peltier platform are shown to validate the practicality of the proposed quasi-perfect control algorithm. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

The theory, design, and operation of the suppressed carrier data-aided tracking receiver

NASA Technical Reports Server (NTRS)

Simon, M. K.; Springett, J. C.

1973-01-01

A viable, efficient, and easily mechanized carrier regenerating receiver for use in suppressed carrier-tracking system is described. The receiver referred to as a data-aided receiver (DAR) incorporates a data-aided loop (DAL) which provides the required carrier reference signal. The DAL employs the principle of decision feedback and as such is more efficient than other forms of suppressed carrier-tracking loops. The analysis, design, and implementation of the DAR are covered in detail. Performance comparisons and mechanization tradeoffs are made, wherever possible, with discrete carrier systems and other suppressed carrier systems presently in use. Experimental performance verification is given throughout in support of the theory presented.

Ku-band signal design study. [for space shuttle orbiter communication links

NASA Technical Reports Server (NTRS)

Lindsey, W. L.; Woo, K. T.

1977-01-01

The acquisition/tracking performance of a practical squaring loop in which the times two multiplier is mechanized as a limiter/multiplier combination is evaluated. This squaring approach serves to produce the absolute value of the arriving signal as opposed to the perfect square law action which is required in order to render acquisition and tracking performance equivalent to that of a Costas loop. The Ku-Band orbiter signal design for the forward link is assessed. Acquisition time results and acquisition and tracking thresholds are summarized. A tradeoff study which pertains to bit synchronization techniques for the high rate Ku-Band channel is included and an optimum selection is made based upon the appropriate design constraints.

Shuttle S-band communications technical concepts

NASA Technical Reports Server (NTRS)

Seyl, J. W.; Seibert, W. W.; Porter, J. A.; Eggers, D. S.; Novosad, S. W.; Vang, H. A.; Lenett, S. D.; Lewton, W. A.; Pawlowski, J. F.

1985-01-01

Using the S-band communications system, shuttle orbiter can communicate directly with the Earth via the Ground Spaceflight Tracking and Data Network (GSTDN) or via the Tracking and Data Relay Satellite System (TDRSS). The S-band frequencies provide the primary links for direct Earth and TDRSS communications during all launch and entry/landing phases of shuttle missions. On orbit, S-band links are used when TDRSS Ku-band is not available, when conditions require orbiter attitudes unfavorable to Ku-band communications, or when the payload bay doors are closed. the S-band communications functional requirements, the orbiter hardware configuration, and the NASA S-band communications network are described. The requirements and implementation concepts which resulted in techniques for shuttle S-band hardware development discussed include: (1) digital voice delta modulation; (2) convolutional coding/Viterbi decoding; (3) critical modulation index for phase modulation using a Costas loop (phase-shift keying) receiver; (4) optimum digital data modulation parameters for continuous-wave frequency modulation; (5) intermodulation effects of subcarrier ranging and time-division multiplexing data channels; (6) radiofrequency coverage; and (7) despreading techniques under poor signal-to-noise conditions. Channel performance is reviewed.

A keyboard control method for loop measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Z.W.

1994-12-31

This paper describes a keyboard control mode based on the DEC VAX computer. The VAX Keyboard code can be found under running of a program was developed. During the loop measurement or multitask operation, it ables to be distinguished from a keyboard code to stop current operation or transfer to another operation while previous information can be held. The combining of this mode, the author successfully used one key control loop measurement for test Dual Input Memory module which is used in a rearrange Energy Trigger system for LEP 8 Bunch operation.

A dual-loop model of the human controller in single-axis tracking tasks

NASA Technical Reports Server (NTRS)

Hess, R. A.

1977-01-01

A dual loop model of the human controller in single axis compensatory tracking tasks is introduced. This model possesses an inner-loop closure which involves feeding back that portion of the controlled element output rate which is due to control activity. The sensory inputs to the human controller are assumed to be system error and control force. The former is assumed to be sensed via visual, aural, or tactile displays while the latter is assumed to be sensed in kinesthetic fashion. A nonlinear form of the model is briefly discussed. This model is then linearized and parameterized. A set of general adaptive characteristics for the parameterized model is hypothesized. These characteristics describe the manner in which the parameters in the linearized model will vary with such things as display quality. It is demonstrated that the parameterized model can produce controller describing functions which closely approximate those measured in laboratory tracking tasks for a wide variety of controlled elements.

Parameter estimation in a human operator describing function model for a two-dimensional tracking task

NASA Technical Reports Server (NTRS)

Vanlunteren, A.

1977-01-01

A previously described parameter estimation program was applied to a number of control tasks, each involving a human operator model consisting of more than one describing function. One of these experiments is treated in more detail. It consisted of a two dimensional tracking task with identical controlled elements. The tracking errors were presented on one display as two vertically moving horizontal lines. Each loop had its own manipulator. The two forcing functions were mutually independent and consisted each of 9 sine waves. A human operator model was chosen consisting of 4 describing functions, thus taking into account possible linear cross couplings. From the Fourier coefficients of the relevant signals the model parameters were estimated after alignment, averaging over a number of runs and decoupling. The results show that for the elements in the main loops the crossover model applies. A weak linear cross coupling existed with the same dynamics as the elements in the main loops but with a negative sign.

Sliding mode based trajectory linearization control for hypersonic reentry vehicle via extended disturbance observer.

PubMed

Xingling, Shao; Honglun, Wang

2014-11-01

This paper proposes a novel hybrid control framework by combing observer-based sliding mode control (SMC) with trajectory linearization control (TLC) for hypersonic reentry vehicle (HRV) attitude tracking problem. First, fewer control consumption is achieved using nonlinear tracking differentiator (TD) in the attitude loop. Second, a novel SMC that employs extended disturbance observer (EDO) to counteract the effect of uncertainties using a new sliding surface which includes the estimation error is integrated to address the tracking error stabilization issues in the attitude and angular rate loop, respectively. In addition, new results associated with EDO are examined in terms of dynamic response and noise-tolerant performance, as well as estimation accuracy. The key feature of the proposed compound control approach is that chattering free tracking performance with high accuracy can be ensured for HRV in the presence of multiple uncertainties under control constraints. Based on finite time convergence stability theory, the stability of the resulting closed-loop system is well established. Also, comparisons and extensive simulation results are presented to demonstrate the effectiveness of the control strategy. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Characterization and Design of Digital Pointing Subsystem for Optical Communication Demonstrator

NASA Technical Reports Server (NTRS)

Racho, C.; Portillo, A.

1998-01-01

The Optical Communications Demonstrator (OCD) is a laboratory-based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision bearn pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field-of-view acquisition and permits effective platform jitter compensation and point-ahead control using only one steering mirror. This paper describes the detailed design and characterization of the digital control loop system which includes the Fast Steering Mirror (FSM), the CCD image tracker, and the associated electronics. The objective is to improve the overall system performance using laboratory measured data. The. design of the digital control loop is based on a linear time invariant open loop model. The closed loop performance is predicted using the theoretical model. With the digital filter programmed into the OCD control software, data is collected to verify the predictions. This paper presents the results of the, system modeling and performance analysis. It has been shown that measurement data closely matches theoretical predictions. An important part of the laser communication experiment is the ability of FSM to track the laser beacon within the. required tolerances. The pointing must be maintained to an accuracy that is much smaller than the transmit signal beamwidth. For an earth orbit distance, the system must be able to track the receiving station to within a few microradians. The failure. to do so will result in a severely degraded system performance.

Design and evaluation of a computed tomography (CT)-compatible needle insertion device using an electromagnetic tracking system and CT images.

PubMed

Shahriari, Navid; Hekman, Edsko; Oudkerk, Matthijs; Misra, Sarthak

2015-11-01

Percutaneous needle insertion procedures are commonly used for diagnostic and therapeutic purposes. Although current technology allows accurate localization of lesions, they cannot yet be precisely targeted. Lung cancer is the most common cause of cancer-related death, and early detection reduces the mortality rate. Therefore, suspicious lesions are tested for diagnosis by performing needle biopsy. In this paper, we have presented a novel computed tomography (CT)-compatible needle insertion device (NID). The NID is used to steer a flexible needle (φ0.55 mm) with a bevel at the tip in biological tissue. CT images and an electromagnetic (EM) tracking system are used in two separate scenarios to track the needle tip in three-dimensional space during the procedure. Our system uses a control algorithm to steer the needle through a combination of insertion and minimal number of rotations. Noise analysis of CT images has demonstrated the compatibility of the device. The results for three experimental cases (case 1: open-loop control, case 2: closed-loop control using EM tracking system and case 3: closed-loop control using CT images) are presented. Each experimental case is performed five times, and average targeting errors are 2.86 ± 1.14, 1.11 ± 0.14 and 1.94 ± 0.63 mm for case 1, case 2 and case 3, respectively. The achieved results show that our device is CT-compatible and it is able to steer a bevel-tipped needle toward a target. We are able to use intermittent CT images and EM tracking data to control the needle path in a closed-loop manner. These results are promising and suggest that it is possible to accurately target the lesions in real clinical procedures in the future.

Effects of low sampling rate in the digital data-transition tracking loop

NASA Technical Reports Server (NTRS)

Mileant, A.; Million, S.; Hinedi, S.

1994-01-01

This article describes the performance of the all-digital data-transition tracking loop (DTTL) with coherent and noncoherent sampling using nonlinear theory. The effects of few samples per symbol and of noncommensurate sampling and symbol rates are addressed and analyzed. Their impact on the probability density and variance of the phase error are quantified through computer simulations. It is shown that the performance of the all-digital DTTL approaches its analog counterpart when the sampling and symbol rates are noncommensurate (i.e., the number of samples per symbol is an irrational number). The loop signal-to-noise ratio (SNR) (inverse of phase error variance) degrades when the number of samples per symbol is an odd integer but degrades even further for even integers.

Stability Assessment and Tuning of an Adaptively Augmented Classical Controller for Launch Vehicle Flight Control

NASA Technical Reports Server (NTRS)

VanZwieten, Tannen; Zhu, J. Jim; Adami, Tony; Berry, Kyle; Grammar, Alex; Orr, Jeb S.; Best, Eric A.

2014-01-01

Recently, a robust and practical adaptive control scheme for launch vehicles [ [1] has been introduced. It augments a classical controller with a real-time loop-gain adaptation, and it is therefore called Adaptive Augmentation Control (AAC). The loop-gain will be increased from the nominal design when the tracking error between the (filtered) output and the (filtered) command trajectory is large; whereas it will be decreased when excitation of flex or sloshing modes are detected. There is a need to determine the range and rate of the loop-gain adaptation in order to retain (exponential) stability, which is critical in vehicle operation, and to develop some theoretically based heuristic tuning methods for the adaptive law gain parameters. The classical launch vehicle flight controller design technics are based on gain-scheduling, whereby the launch vehicle dynamics model is linearized at selected operating points along the nominal tracking command trajectory, and Linear Time-Invariant (LTI) controller design techniques are employed to ensure asymptotic stability of the tracking error dynamics, typically by meeting some prescribed Gain Margin (GM) and Phase Margin (PM) specifications. The controller gains at the design points are then scheduled, tuned and sometimes interpolated to achieve good performance and stability robustness under external disturbances (e.g. winds) and structural perturbations (e.g. vehicle modeling errors). While the GM does give a bound for loop-gain variation without losing stability, it is for constant dispersions of the loop-gain because the GM is based on frequency-domain analysis, which is applicable only for LTI systems. The real-time adaptive loop-gain variation of the AAC effectively renders the closed-loop system a time-varying system, for which it is well-known that the LTI system stability criterion is neither necessary nor sufficient when applying to a Linear Time-Varying (LTV) system in a frozen-time fashion. Therefore, a generalized stability metric for time-varying loop=gain perturbations is needed for the AAC.

A Role for the Fifth G-Track in G-Quadruplex Forming Oncogene Promoter Sequences during Oxidative Stress: Do These "Spare Tires" Have an Evolved Function?

PubMed

Fleming, Aaron M; Zhou, Jia; Wallace, Susan S; Burrows, Cynthia J

2015-08-26

Uncontrolled inflammation or oxidative stress generates electron-deficient species that oxidize the genome increasing its instability in cancer. The G-quadruplex (G4) sequences regulating the c-MYC , KRAS , VEGF , BCL-2 , HIF-1α , and RET oncogenes, as examples, are targets for oxidation at loop and 5'-core guanines (G) as showcased in this study by CO 3 •- oxidation of the VEGF G4. Products observed include 8-oxo-7,8-dihydroguanine (OG), spiroiminodihydantoin (Sp), and 5-guanidinohydantoin (Gh). Our previous studies found that OG and Gh, when present in the four G-tracks of the solved structure for VEGF and c-MY C, were not substrates for the base excision repair (BER) DNA glycosylases in biologically relevant KCl solutions. We now hypothesize that a fifth G-track found a few nucleotides distant from the G4 tracks involved in folding can act as a "spare tire," facilitating extrusion of a damaged G-run into a large loop that then becomes a substrate for BER. Thermodynamic, spectroscopic, and DMS footprinting studies verified the fifth domain replacing a damaged G-track with OG or Gh at a loop or core position in the VEGF G4. These new "spare tire"-containing strands with Gh in loops are now found to be substrates for initiation of BER with the NEIL1, NEIL2, and NEIL3 DNA glycosylases. The results support a hypothesis in which regulatory G4s carry a "spare-tire" fifth G-track for aiding in the repair process when these sequences are damaged by radical oxygen species, a feature observed in a large number of these sequences. Furthermore, formation and repair of oxidized bases in promoter regions may constitute an additional example of epigenetic modification, in this case of guanine bases, to regulate gene expression in which the G4 sequences act as sensors of oxidative stress.

High-throughput sample adaptive offset hardware architecture for high-efficiency video coding

NASA Astrophysics Data System (ADS)

Zhou, Wei; Yan, Chang; Zhang, Jingzhi; Zhou, Xin

2018-03-01

A high-throughput hardware architecture for a sample adaptive offset (SAO) filter in the high-efficiency video coding video coding standard is presented. First, an implementation-friendly and simplified bitrate estimation method of rate-distortion cost calculation is proposed to reduce the computational complexity in the mode decision of SAO. Then, a high-throughput VLSI architecture for SAO is presented based on the proposed bitrate estimation method. Furthermore, multiparallel VLSI architecture for in-loop filters, which integrates both deblocking filter and SAO filter, is proposed. Six parallel strategies are applied in the proposed in-loop filters architecture to improve the system throughput and filtering speed. Experimental results show that the proposed in-loop filters architecture can achieve up to 48% higher throughput in comparison with prior work. The proposed architecture can reach a high-operating clock frequency of 297 MHz with TSMC 65-nm library and meet the real-time requirement of the in-loop filters for 8 K × 4 K video format at 132 fps.

TrackEtching - A Java based code for etched track profile calculations in SSNTDs

NASA Astrophysics Data System (ADS)

Muraleedhara Varier, K.; Sankar, V.; Gangadathan, M. P.

2017-09-01

A java code incorporating a user friendly GUI has been developed to calculate the parameters of chemically etched track profiles of ion-irradiated solid state nuclear track detectors. Huygen's construction of wavefronts based on secondary wavelets has been used to numerically calculate the etched track profile as a function of the etching time. Provision for normal incidence and oblique incidence on the detector surface has been incorporated. Results in typical cases are presented and compared with experimental data. Different expressions for the variation of track etch rate as a function of the ion energy have been utilized. The best set of values of the parameters in the expressions can be obtained by comparing with available experimental data. Critical angle for track development can also be calculated using the present code.

Improvements in deep-space tracking by use of third-order loops.

NASA Technical Reports Server (NTRS)

Tausworth, R. C.; Crow, R. B.

1972-01-01

Third-order phase-locked receivers have not yet found wide application in deep-space communications systems because the second-order systems now used have performed adequately on past spacecraft missions. However, a survey of the doppler profiles for future missions shows that an unaided second-order loop may be unable to perform within reasonable error bounds. This article discusses the characteristics of a simple third-order extension to present second-order systems that not only extends doppler-tracking capability, but widens the pull-in range and decreases pull-in time as well.

Improved Speech Coding Based on Open-Loop Parameter Estimation

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Chen, Ya-Chin; Longman, Richard W.

2000-01-01

A nonlinear optimization algorithm for linear predictive speech coding was developed early that not only optimizes the linear model coefficients for the open loop predictor, but does the optimization including the effects of quantization of the transmitted residual. It also simultaneously optimizes the quantization levels used for each speech segment. In this paper, we present an improved method for initialization of this nonlinear algorithm, and demonstrate substantial improvements in performance. In addition, the new procedure produces monotonically improving speech quality with increasing numbers of bits used in the transmitted error residual. Examples of speech encoding and decoding are given for 8 speech segments and signal to noise levels as high as 47 dB are produced. As in typical linear predictive coding, the optimization is done on the open loop speech analysis model. Here we demonstrate that minimizing the error of the closed loop speech reconstruction, instead of the simpler open loop optimization, is likely to produce negligible improvement in speech quality. The examples suggest that the algorithm here is close to giving the best performance obtainable from a linear model, for the chosen order with the chosen number of bits for the codebook.

Study on rejection characteristic of current loop to the base disturbance of optical communication system

NASA Astrophysics Data System (ADS)

Mao, Yao; Deng, Chao; Liu, Qiong; Cao, Zheng

2016-10-01

As laser has narrow transmitting beam and small divergence angle, the LOS (Line of Sight) stabilization of optical communication system is a primary precondition of laser communication links. Compound axis control is usually adopted in LOS stabilization of optical communication system, in which coarse tracking and fine tracking are included. Rejection against high frequency disturbance mainly depends on fine tracking LOS stabilization platform. Limited by different factors such as mechanical characteristic of the stabilization platform and bandwidth/noise of the sensor, the control bandwidth of LOS stabilization platform is restricted so that effective rejection of high frequency disturbance cannot be achieved as it mainly depends on the isolation characteristic of the platform itself. It is proposed by this paper that current loop may reject the effect of back-EMF. By adopting the method of electric control, high frequency isolation characteristic of the platform can be improved. The improvement effect is similar to increasing passive vibration reduction devices. Adopting the double closed loop control structure of velocity and current with the combining of the rejection effect of back-EMF caused by current loop is equivalent to reducing back-EMF coefficient, which can enhance the isolation ability of the LOS stabilization platform to high frequency disturbance.

On the Mysterious Propulsion of Synechococcus

PubMed Central

Ehlers, Kurt; Oster, George

2012-01-01

We propose a model for the self-propulsion of the marine bacterium Synechococcus utilizing a continuous looped helical track analogous to that found in Myxobacteria [1]. In our model cargo-carrying protein motors, driven by proton-motive force, move along a continuous looped helical track. The movement of the cargo creates surface distortions in the form of small amplitude traveling ridges along the S-layer above the helical track. The resulting fluid motion adjacent to the helical ribbon provides the propulsive thrust. A variation on the helical rotor model of [1] allows the motors to be anchored to the peptidoglycan layer, where they drive rotation of the track creating traveling helical waves along the S-layer. We derive expressions relating the swimming speed to the amplitude, wavelength, and velocity of the surface waves induced by the helical rotor, and show that they fall in reasonable ranges to explain the velocity and rotation rate of swimming Synechococcus. PMID:22567124

Doublet Pulse Coherent Laser Radar for Tracking of Resident Space Objects

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Rudd, Van; Shald, Scott; Sandford, Stephen; Dimarcantonio, Albert

2014-01-01

In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance modeling and engagement simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar parameters are presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits are discussed.

A dual-loop model of the human controller

NASA Technical Reports Server (NTRS)

Hess, R. A.

1977-01-01

A representative model of the human controller in single-axis compensatory tracking tasks that exhibits an internal feedback loop which is not evident in single-loop models now in common use is presented. This hypothetical inner-loop involves a neuromuscular command signal derived from the time rate of change of controlled element output which is due to control activity. It is not contended that the single-loop human controller models now in use are incorrect, but that they contain an implicit but important internal loop closure, which, if explicitly considered, can account for a good deal of the adaptive nature of the human controller in a systematic manner.

Digital Phase-Locked Loop With Phase And Frequency Feedback

NASA Technical Reports Server (NTRS)

Thomas, J. Brooks

1991-01-01

Advanced design for digital phase-lock loop (DPLL) allows loop gains higher than those used in other designs. Divided into two major components: counterrotation processor and tracking processor. Notable features include use of both phase and rate-of-change-of-phase feedback instead of frequency feedback alone, normalized sine phase extractor, improved method for extracting measured phase, and improved method for "compressing" output rate.

Higgs mass prediction in the MSSM at three-loop level in a pure \\overline{{ {DR}}} context

NASA Astrophysics Data System (ADS)

Harlander, Robert V.; Klappert, Jonas; Voigt, Alexander

2017-12-01

The impact of the three-loop effects of order α _tα _s^2 on the mass of the light CP-even Higgs boson in the { {MSSM}} is studied in a pure \\overline{{ {DR}}} context. For this purpose, we implement the results of Kant et al. (JHEP 08:104, 2010) into the C++ module Himalaya and link it to FlexibleSUSY, a Mathematica and C++ package to create spectrum generators for BSM models. The three-loop result is compared to the fixed-order two-loop calculations of the original FlexibleSUSY and of FeynHiggs, as well as to the result based on an EFT approach. Aside from the expected reduction of the renormalization scale dependence with respect to the lower-order results, we find that the three-loop contributions significantly reduce the difference from the EFT prediction in the TeV-region of the { {SUSY}} scale {M_S}. Himalaya can be linked also to other two-loop \\overline{{ {DR}}} codes, thus allowing for the elevation of these codes to the three-loop level.

Dynamic optimization of ISR sensors using a risk-based reward function applied to ground and space surveillance scenarios

NASA Astrophysics Data System (ADS)

DeSena, J. T.; Martin, S. R.; Clarke, J. C.; Dutrow, D. A.; Newman, A. J.

2012-06-01

As the number and diversity of sensing assets available for intelligence, surveillance and reconnaissance (ISR) operations continues to expand, the limited ability of human operators to effectively manage, control and exploit the ISR ensemble is exceeded, leading to reduced operational effectiveness. Automated support both in the processing of voluminous sensor data and sensor asset control can relieve the burden of human operators to support operation of larger ISR ensembles. In dynamic environments it is essential to react quickly to current information to avoid stale, sub-optimal plans. Our approach is to apply the principles of feedback control to ISR operations, "closing the loop" from the sensor collections through automated processing to ISR asset control. Previous work by the authors demonstrated non-myopic multiple platform trajectory control using a receding horizon controller in a closed feedback loop with a multiple hypothesis tracker applied to multi-target search and track simulation scenarios in the ground and space domains. This paper presents extensions in both size and scope of the previous work, demonstrating closed-loop control, involving both platform routing and sensor pointing, of a multisensor, multi-platform ISR ensemble tasked with providing situational awareness and performing search, track and classification of multiple moving ground targets in irregular warfare scenarios. The closed-loop ISR system is fullyrealized using distributed, asynchronous components that communicate over a network. The closed-loop ISR system has been exercised via a networked simulation test bed against a scenario in the Afghanistan theater implemented using high-fidelity terrain and imagery data. In addition, the system has been applied to space surveillance scenarios requiring tracking of space objects where current deliberative, manually intensive processes for managing sensor assets are insufficiently responsive. Simulation experiment results are presented. The algorithm to jointly optimize sensor schedules against search, track, and classify is based on recent work by Papageorgiou and Raykin on risk-based sensor management. It uses a risk-based objective function and attempts to minimize and balance the risks of misclassifying and losing track on an object. It supports the requirement to generate tasking for metric and feature data concurrently and synergistically, and account for both tracking accuracy and object characterization, jointly, in computing reward and cost for optimizing tasking decisions.

SpalLoop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabau, Adrian; Wright, Ian

Boiler tubes in steam power plants experience tube blockages due to exfoliation of oxide grown on the inner side of the tubes. In extreme cases, significant tube blockages can lead to forced power plant outages. It is thus desired to predict through modeling the amount of tube blockage in order to inform power plant operators of possible forced outages. SpalLoop solves for the stress-strain equations in an axisymmetric geometry, tracking the stress/strain evolution during boiler operation including outages for the entire boiler tube length. At each operational outage, i.e., temperature excursions down to room temperature, the amount of exfoliated areamore » for the entire tube loop is estimated the amount of tube blockage is predicted based assumed blockage geometry and site. The SpaLLoop code contains modules developed for oxide growth, stress analysis, tube loop geometry, blockage area by taking into account the following phenomena and features, (a) Plant operation schedule with periodic alternate full-load and partial-load regimes and shut-downs, i.e., temperature excursions from high-load to room temperature, (b) axisymmetric formulation for cylindrical tubes, (c) oxide growth in a temperature gradient with multiple oxide layers, (d) geometry of a boiler tube with a single tube loop or two tube loops, (e) temperature variation along the tube length based on hot gas temperature distribution outside the tube and inlet steam temperature, (f) non-uniform oxide growth along the tube length according to the local steam tube temperature, (g) exfoliated area module: at each operational outage considered, the amount of exfoliated area and exfoliated volume along the tube is estimated, (h) blockage module: at each operational outage considered, the exfoliated volume/mass for each tube loop is estimated from which the amount of tube blockage is predicted based on given blockage geometry (length, location, and geometry). The computer program is written in FORTRAN90. Its modular structure was sought for allowing the best flexibility in updating the program by implementing new constitutive equations due to availability of new material property data and/or new physical phenomena.« less

A class of all digital phase locked loops - Modeling and analysis

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a nonlinear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step and frequency step inputs for different levels of quantization without loop filter are studied. The analytical results are checked by simulating the actual system on the digital computer.

Impact of Swarm GPS receiver updates on POD performance

NASA Astrophysics Data System (ADS)

van den IJssel, Jose; Forte, Biagio; Montenbruck, Oliver

2016-05-01

The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard GPS receivers deliver high-quality data with an almost continuous data rate. However, the receivers show a slightly degraded performance when flying over the geomagnetic poles and the geomagnetic equator, due to ionospheric scintillation. Furthermore, with only eight channels available for dual-frequency tracking, the amount of collected GPS tracking data is relatively low compared with various other missions. Therefore, several modifications have been implemented to the Swarm GPS receivers. To optimise the amount of collected GPS data, the GPS antenna elevation mask has slowly been reduced from 10° to 2°. To improve the robustness against ionospheric scintillation, the bandwidths of the GPS receiver tracking loops have been widened. Because these modifications were first implemented on Swarm-C, their impact can be assessed by a comparison with the close flying Swarm-A satellite. This shows that both modifications have a positive impact on the GPS receiver performance. The reduced elevation mask increases the amount of GPS tracking data by more than 3 %, while the updated tracking loops lead to around 1.3 % more observations and a significant reduction in tracking losses due to severe equatorial scintillation. The additional observations at low elevation angles increase the average noise of the carrier phase observations, but nonetheless slightly improve the resulting reduced-dynamic and kinematic orbit accuracy as shown by independent satellite laser ranging (SLR) validation. The more robust tracking loops significantly reduce the large carrier phase observation errors at the geomagnetic poles and along the geomagnetic equator and do not degrade the observations at midlatitudes. SLR validation indicates that the updated tracking loops also improve the reduced-dynamic and kinematic orbit accuracy. It is expected that the Swarm gravity field recovery will benefit from the improved kinematic orbit quality and potentially also from the expected improvement of the kinematic baseline determination and the anticipated reduction in the systematic gravity field errors along the geomagnetic equator. Finally, other satellites that carry GPS receivers that encounter similar disturbances might also benefit from this analysis.

Open-loop radio science with a suppressed-carrier signal

NASA Technical Reports Server (NTRS)

Greenhall, C. A.

1980-01-01

When a suppressed-carrier signal is squared, the carrier reappears in doubled form. An open-loop receiver can be used to deliver a recording of a band-limited waveform containing this carrier, whose amplitude and phase can be tracked by the radio science experimenter.

Receiver design and performance characteristics

NASA Technical Reports Server (NTRS)

Simon, M. K.; Yuen, J. H.

1982-01-01

The basic design, principles of operation, and characteristics of deep space communications receivers are examined. In particular, the basic fundamentals of phase-locked loop and Costas loop receivers used for synchronization, tracking, and demodulation of phase-coherent signals in residual carrier and suppressed carrier systems are addressed.

A GPS Phase-Locked Loop Performance Metric Based on the Phase Discriminator Output

PubMed Central

Stevanovic, Stefan; Pervan, Boris

2018-01-01

We propose a novel GPS phase-lock loop (PLL) performance metric based on the standard deviation of tracking error (defined as the discriminator’s estimate of the true phase error), and explain its advantages over the popular phase jitter metric using theory, numerical simulation, and experimental results. We derive an augmented GPS phase-lock loop (PLL) linear model, which includes the effect of coherent averaging, to be used in conjunction with this proposed metric. The augmented linear model allows more accurate calculation of tracking error standard deviation in the presence of additive white Gaussian noise (AWGN) as compared to traditional linear models. The standard deviation of tracking error, with a threshold corresponding to half of the arctangent discriminator pull-in region, is shown to be a more reliable/robust measure of PLL performance under interference conditions than the phase jitter metric. In addition, the augmented linear model is shown to be valid up until this threshold, which facilitates efficient performance prediction, so that time-consuming direct simulations and costly experimental testing can be reserved for PLL designs that are much more likely to be successful. The effect of varying receiver reference oscillator quality on the tracking error metric is also considered. PMID:29351250

Dual-loop model of the human controller

NASA Technical Reports Server (NTRS)

Hess, R. A.

1978-01-01

A dual-loop model of the human controller in single-axis compensatory tracking tasks is introduced. This model possesses an inner-loop closure that involves feeding back that portion of controlled element output rate that is due to control activity. A novel feature of the model is the explicit appearance of the human's internal representation of the manipulator-controlled element dynamics in the inner loop. The sensor inputs to the human controller are assumed to be system error and control force. The former can be sensed via visual, aural, or tactile displays, whereas the latter is assumed to be sensed in kinesthetic fashion. A set of general adaptive characteristics for the model is hypothesized, including a method for selecting simplified internal models of the manipulator-controlled element dynamics. It is demonstrated that the model can produce controller describing functions that closely approximate those measured in four laboratory tracking tasks in which the controlled element dynamics vary considerably in terms of ease of control. An empirically derived expression for the normalized injected error remnant spectrum is introduced.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of formation flying technologies has been developed at NASA s Goddard Space Flight Center. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. A sample scenario has been set up where the autonomous transition of a satellite formation from an initial along-track separation of 800 m to a final distance of 100 m has been demonstrated. As a result, a typical control accuracy of about 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

Antenna Linear-Quadratic-Gaussian (LQG) Controllers: Properties, Limits of Performance, and Tuning Procedure

NASA Technical Reports Server (NTRS)

Gawronski, W.

2004-01-01

Wind gusts are the main disturbances that depreciate tracking precision of microwave antennas and radiotelescopes. The linear-quadratic-Gaussian (LQG) controllers - as compared with the proportional-and-integral (PI) controllers significantly improve the tracking precision in wind disturbances. However, their properties have not been satisfactorily understood; consequently, their tuning is a trial-and-error process. A control engineer has two tools to tune an LQG controller: the choice of coordinate system of the controller model and the selection of weights of the LQG performance index. This article analyzes properties of an open- and closed-loop antenna. It shows that the proper choice of coordinates of the open-loop model simplifies the shaping of the closed-loop performance. The closed-loop properties are influenced by the LQG weights. The article shows the impact of the weights on the antenna closed-loop bandwidth, disturbance rejection properties, and antenna acceleration. The bandwidth and the disturbance rejection characterize the antenna performance, while the acceleration represents the performance limit set by the antenna hardware (motors). The article presents the controller tuning procedure, based on the coordinate selection and the weight properties. The procedure rationally shapes the closed-loop performance, as an alternative to the trial-and-error approach.

21 CFR 1271.290 - Tracking.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TISSUE-BASED PRODUCTS Current Good Tissue Practice § 1271.290 Tracking. (a) General. If you perform any... designed to facilitate effective tracking, using the distinct identification code, from the donor to the... for recording the distinct identification code and type of each HCT/P distributed to a consignee to...

Multiple symbol partially coherent detection of MPSK

NASA Technical Reports Server (NTRS)

Simon, M. K.; Divsalar, D.

1992-01-01

It is shown that by using the known (or estimated) value of carrier tracking loop signal to noise ratio (SNR) in the decision metric, it is possible to improve the error probability performance of a partially coherent multiple phase-shift-keying (MPSK) system relative to that corresponding to the commonly used ideal coherent decision rule. Using a maximum-likeihood approach, an optimum decision metric is derived and shown to take the form of a weighted sum of the ideal coherent decision metric (i.e., correlation) and the noncoherent decision metric which is optimum for differential detection of MPSK. The performance of a receiver based on this optimum decision rule is derived and shown to provide continued improvement with increasing length of observation interval (data symbol sequence length). Unfortunately, increasing the observation length does not eliminate the error floor associated with the finite loop SNR. Nevertheless, in the limit of infinite observation length, the average error probability performance approaches the algebraic sum of the error floor and the performance of ideal coherent detection, i.e., at any error probability above the error floor, there is no degradation due to the partial coherence. It is shown that this limiting behavior is virtually achievable with practical size observation lengths. Furthermore, the performance is quite insensitive to mismatch between the estimate of loop SNR (e.g., obtained from measurement) fed to the decision metric and its true value. These results may be of use in low-cost Earth-orbiting or deep-space missions employing coded modulations.

Phase-locked tracking loops for LORAN-C

NASA Technical Reports Server (NTRS)

Burhans, R. W.

1978-01-01

Portable battery operated LORAN-C receivers were fabricated to evaluate simple envelope detector methods with hybrid analog to digital phase locked loop sensor processors. The receivers are used to evaluate LORAN-C in general aviation applications. Complete circuit details are given for the experimental sensor and readout system.

Autonomous Visual Tracking of Stationary Targets Using Small Unmanned Aerial Vehicles

DTIC Science & Technology

2004-06-01

59 Figure 43. Commanded and Actual Yaw Rates during Simulation ..................................60 Figure 44. Setup for Hardware In Loop Simulation...System with AVDS Figure 44. Setup for Hardware In Loop Simulation with AVDS and PerceptiVU 2. Test Conditions Simulations were conducted for the

Robust guaranteed cost tracking control of quadrotor UAV with uncertainties.

PubMed

Xu, Zhiwei; Nian, Xiaohong; Wang, Haibo; Chen, Yinsheng

2017-07-01

In this paper, a robust guaranteed cost controller (RGCC) is proposed for quadrotor UAV system with uncertainties to address set-point tracking problem. A sufficient condition of the existence for RGCC is derived by Lyapunov stability theorem. The designed RGCC not only guarantees the whole closed-loop system asymptotically stable but also makes the quadratic performance level built for the closed-loop system have an upper bound irrespective to all admissible parameter uncertainties. Then, an optimal robust guaranteed cost controller is developed to minimize the upper bound of performance level. Simulation results verify the presented control algorithms possess small overshoot and short setting time, with which the quadrotor has ability to perform set-point tracking task well. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

SimTrack: A compact c++ code for particle orbit and spin tracking in accelerators

DOE PAGES

Luo, Yun

2015-08-29

SimTrack is a compact c++ code of 6-d symplectic element-by-element particle tracking in accelerators originally designed for head-on beam–beam compensation simulation studies in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It provides a 6-d symplectic orbit tracking with the 4th order symplectic integration for magnet elements and the 6-d symplectic synchro-beam map for beam–beam interaction. Since its inception in 2009, SimTrack has been intensively used for dynamic aperture calculations with beam–beam interaction for RHIC. Recently, proton spin tracking and electron energy loss due to synchrotron radiation were added. In this article, I will present the code architecture,more » physics models, and some selected examples of its applications to RHIC and a future electron-ion collider design eRHIC.« less

Sensory feedback in prosthetics: a standardized test bench for closed-loop control.

PubMed

Dosen, Strahinja; Markovic, Marko; Hartmann, Cornelia; Farina, Dario

2015-03-01

Closing the control loop by providing sensory feedback to the user of a prosthesis is an important challenge, with major impact on the future of prosthetics. Developing and comparing closed-loop systems is a difficult task, since there are many different methods and technologies that can be used to implement each component of the system. Here, we present a test bench developed in Matlab Simulink for configuring and testing the closed-loop human control system in standardized settings. The framework comprises a set of connected generic blocks with normalized inputs and outputs, which can be customized by selecting specific implementations from a library of predefined components. The framework is modular and extensible and it can be used to configure, compare and test different closed-loop system prototypes, thereby guiding the development towards an optimal system configuration. The use of the test bench was demonstrated by investigating two important aspects of closed-loop control: performance of different electrotactile feedback interfaces (spatial versus intensity coding) during a pendulum stabilization task and feedforward methods (joystick versus myocontrol) for force control. The first experiment demonstrated that in the case of trained subjects the intensity coding might be superior to spatial coding. In the second experiment, the control of force was rather poor even with a stable and precise control interface (joystick), demonstrating that inherent characteristics of the prosthesis can be an important limiting factor when considering the overall effectiveness of the closed-loop control. The presented test bench is an important instrument for investigating different aspects of human manual control with sensory feedback.

Flexible and evolutionary optical access networks

NASA Astrophysics Data System (ADS)

Hsueh, Yu-Li

Passive optical networks (PONs) are promising solutions that will open the first-mile bottleneck. Current PONs employ time division multiplexing (TDM) to share bandwidth among users, leading to low cost but limited capacity. In the future, wavelength division multiplexing (WDM) technologies will be deployed to achieve high performance. This dissertation describes several advanced technologies to enhance PON systems. A spectral shaping line coding scheme is developed to allow a simple and cost-effective overlay of high data-rate services in existing PONs, leaving field-deployed fibers and existing services untouched. Spectral shapes of coded signals can be manipulated to adapt to different systems. For a specific tolerable interference level, the optimal line code can be found which maximizes the data throughput. Experiments are conducted to demonstrate and compare several optimized line codes. A novel PON employing dynamic wavelength allocation to provide bandwidth sharing across multiple physical PONs is designed and experimentally demonstrated. Tunable lasers, arrayed waveguide gratings, and coarse/fine filtering combine to create a flexible optical access solution. The network's excellent scalability can bridge the gap between conventional TDM PONs and WDM PONs. Scheduling algorithms with quality of service support are also investigated. Simulation results show that the proposed architecture exhibits significant performance gain over conventional PON systems. Streaming video transmission is demonstrated on the prototype experimental testbed. The powerful architecture is a promising candidate for next-generation optical access networks. A new CDR circuit for receiving the bursty traffic in PONs is designed and analyzed. It detects data transition edges upon arrival of the data burst and quickly selects the best clock phase by a control logic circuit. Then, an analog delay-locked loop (DLL) keeps track of data transitions and removes phase errors throughout the burst. The combination of the fast phase detection mechanism and a feedback loop based on DLL allows both fast response and manageable jitter performance in the burst-mode application. A new efficient numerical algorithm is developed to analyze holey optical fibers. The algorithm has been verified against experimental data, and is exploited to design holey optical fibers optimized for the discrete Raman amplification.

Accelerated Performance Testing on the 2006 NCAT Pavement Test Track

DOT National Transportation Integrated Search

2009-12-01

The original National Center for Asphalt Technology (NCAT) Pavement Test Track was built in 2000 in Opelika, Alabama where it has served as a state-of-the-art, full-scale, closed-loop accelerated loading facility. The construction, operation, and res...

Impact of tracking loop settings of the Swarm GPS receiver on gravity field recovery

NASA Astrophysics Data System (ADS)

Dahle, C.; Arnold, D.; Jäggi, A.

2017-06-01

The Swarm mission consists of three identical satellites equipped with GPS receivers and orbiting in near-polar low Earth orbits. Thus, they can be used to determine the Earth's gravity field by means of high-low satellite-to-satellite tracking (hl-SST). However, first results by several groups have revealed systematic errors both in precise science orbits and resulting gravity field solutions which are caused by ionospheric disturbances affecting the quality of Swarm GPS observations. Looking at gravity field solutions, the errors lead to systematic artefacts located in two bands north and south of the geomagnetic equator. In order to reduce these artefacts, erroneous GPS observations can be identified and rejected before orbit and gravity field processing, but this may also lead to slight degradations of orbit and low degree gravity field coefficient quality. Since the problems were believed to be receiver-specific, the GPS tracking loop bandwidths onboard Swarm have been widened several times starting in May 2015. The influence of these tracking loop updates on Swarm orbits and, particularly, gravity field solutions is investigated in this work. The main findings are that the first updates increasing the bandwidth from 0.25 Hz to 0.5 Hz help to significantly improve the quality of Swarm gravity fields and that the improvements are even larger than those achieved by GPS data rejection. It is also shown that these improvements are indeed due to an improved quality of GPS observations around the geomagnetic equator, and not due to missing observations in these regions. As the ionospheric activity is rather low in the most recent months, the effect of the tracking loop updates in summer 2016 cannot be properly assessed yet. Nevertheless, the quality of Swarm gravity field solutions has already improved after the first updates which is especially beneficial in view of filling the upcoming gap between the GRACE and GRACE Follow-on missions with hl-SST gravity products.

Modular Track System For Positioning Mobile Robots

NASA Technical Reports Server (NTRS)

Miller, Jeff

1995-01-01

Conceptual system for positioning mobile robotic manipulators on large main structure includes modular tracks and ancillary structures assembled easily along with main structure. System, called "tracked robotic location system" (TROLS), originally intended for application to platforms in outer space, but TROLS concept might also prove useful on Earth; for example, to position robots in factories and warehouses. T-cross-section rail keeps mobile robot on track. Bar codes mark locations along track. Each robot equipped with bar-code-recognizing circuitry so it quickly finds way to assigned location.

Digital Filters for Digital Phase-locked Loops

NASA Technical Reports Server (NTRS)

Simon, M.; Mileant, A.

1985-01-01

An s/z hybrid model for a general phase locked loop is proposed. The impact of the loop filter on the stability, gain margin, noise equivalent bandwidth, steady state error and time response is investigated. A specific digital filter is selected which maximizes the overall gain margin of the loop. This filter can have any desired number of integrators. Three integrators are sufficient in order to track a phase jerk with zero steady state error at loop update instants. This filter has one zero near z = 1.0 for each integrator. The total number of poles of the filter is equal to the number of integrators plus two.

A class of all digital phase locked loops - Modelling and analysis.

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1972-01-01

An all digital phase locked loop which tracks the phase of the incoming signal once per carrier cycle is proposed. The different elements and their functions, and the phase lock operation are explained in detail. The general digital loop operation is governed by a non-linear difference equation from which a suitable model is developed. The lock range for the general model is derived. The performance of the digital loop for phase step, and frequency step inputs for different levels of quantization without loop filter, are studied. The analytical results are checked by simulating the actual system on the digital computer.

Simplified formula for mean cycle-slip time of phase-locked loops with steady-state phase error.

NASA Technical Reports Server (NTRS)

Tausworthe, R. C.

1972-01-01

Previous work shows that the mean time from lock to a slipped cycle of a phase-locked loop is given by a certain double integral. Accurate numerical evaluation of this formula for the second-order loop is extremely vexing because the difference between exponentially large quantities is involved. The presented article demonstrates a method in which a much-reduced precision program can be used to obtain the mean first-cycle slip time for a loop of arbitrary degree tracking at a specified SNR and steady-state phase error. It also presents a simple approximate formula that is asymptotically tight at higher loop SNR.

A Role for the Fifth G-Track in G-Quadruplex Forming Oncogene Promoter Sequences during Oxidative Stress: Do These “Spare Tires” Have an Evolved Function?

PubMed Central

2015-01-01

Uncontrolled inflammation or oxidative stress generates electron-deficient species that oxidize the genome increasing its instability in cancer. The G-quadruplex (G4) sequences regulating the c-MYC, KRAS, VEGF, BCL-2, HIF-1α, and RET oncogenes, as examples, are targets for oxidation at loop and 5′-core guanines (G) as showcased in this study by CO3•– oxidation of the VEGF G4. Products observed include 8-oxo-7,8-dihydroguanine (OG), spiroiminodihydantoin (Sp), and 5-guanidinohydantoin (Gh). Our previous studies found that OG and Gh, when present in the four G-tracks of the solved structure for VEGF and c-MYC, were not substrates for the base excision repair (BER) DNA glycosylases in biologically relevant KCl solutions. We now hypothesize that a fifth G-track found a few nucleotides distant from the G4 tracks involved in folding can act as a “spare tire,” facilitating extrusion of a damaged G-run into a large loop that then becomes a substrate for BER. Thermodynamic, spectroscopic, and DMS footprinting studies verified the fifth domain replacing a damaged G-track with OG or Gh at a loop or core position in the VEGF G4. These new “spare tire”-containing strands with Gh in loops are now found to be substrates for initiation of BER with the NEIL1, NEIL2, and NEIL3 DNA glycosylases. The results support a hypothesis in which regulatory G4s carry a “spare-tire” fifth G-track for aiding in the repair process when these sequences are damaged by radical oxygen species, a feature observed in a large number of these sequences. Furthermore, formation and repair of oxidized bases in promoter regions may constitute an additional example of epigenetic modification, in this case of guanine bases, to regulate gene expression in which the G4 sequences act as sensors of oxidative stress. PMID:26405692

The Extended-Image Tracking Technique Based on the Maximum Likelihood Estimation

NASA Technical Reports Server (NTRS)

Tsou, Haiping; Yan, Tsun-Yee

2000-01-01

This paper describes an extended-image tracking technique based on the maximum likelihood estimation. The target image is assume to have a known profile covering more than one element of a focal plane detector array. It is assumed that the relative position between the imager and the target is changing with time and the received target image has each of its pixels disturbed by an independent additive white Gaussian noise. When a rotation-invariant movement between imager and target is considered, the maximum likelihood based image tracking technique described in this paper is a closed-loop structure capable of providing iterative update of the movement estimate by calculating the loop feedback signals from a weighted correlation between the currently received target image and the previously estimated reference image in the transform domain. The movement estimate is then used to direct the imager to closely follow the moving target. This image tracking technique has many potential applications, including free-space optical communications and astronomy where accurate and stabilized optical pointing is essential.

An Adaptive INS-Aided PLL Tracking Method for GNSS Receivers in Harsh Environments.

PubMed

Cong, Li; Li, Xin; Jin, Tian; Yue, Song; Xue, Rui

2016-01-23

As the weak link in global navigation satellite system (GNSS) signal processing, the phase-locked loop (PLL) is easily influenced with frequent cycle slips and loss of lock as a result of higher vehicle dynamics and lower signal-to-noise ratios. With inertial navigation system (INS) aid, PLLs' tracking performance can be improved. However, for harsh environments with high dynamics and signal attenuation, the traditional INS-aided PLL with fixed loop parameters has some limitations to improve the tracking adaptability. In this paper, an adaptive INS-aided PLL capable of adjusting its noise bandwidth and coherent integration time has been proposed. Through theoretical analysis, the relation between INS-aided PLL phase tracking error and carrier to noise density ratio (C/N₀), vehicle dynamics, aiding information update time, noise bandwidth, and coherent integration time has been built. The relation formulae are used to choose the optimal integration time and bandwidth for a given application under the minimum tracking error criterion. Software and hardware simulation results verify the correctness of the theoretical analysis, and demonstrate that the adaptive tracking method can effectively improve the PLL tracking ability and integrated GNSS/INS navigation performance. For harsh environments, the tracking sensitivity is increased by 3 to 5 dB, velocity errors are decreased by 36% to 50% and position errors are decreased by 6% to 24% when compared with other INS-aided PLL methods.

Computational tools and lattice design for the PEP-II B-Factory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Y.; Irwin, J.; Nosochkov, Y.

1997-02-01

Several accelerator codes were used to design the PEP-II lattices, ranging from matrix-based codes, such as MAD and DIMAD, to symplectic-integrator codes, such as TRACY and DESPOT. In addition to element-by-element tracking, we constructed maps to determine aberration strengths. Furthermore, we have developed a fast and reliable method (nPB tracking) to track particles with a one-turn map. This new technique allows us to evaluate performance of the lattices on the entire tune-plane. Recently, we designed and implemented an object-oriented code in C++ called LEGO which integrates and expands upon TRACY and DESPOT. {copyright} {ital 1997 American Institute of Physics.}

Computational tools and lattice design for the PEP-II B-Factory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai Yunhai; Irwin, John; Nosochkov, Yuri

1997-02-01

Several accelerator codes were used to design the PEP-II lattices, ranging from matrix-based codes, such as MAD and DIMAD, to symplectic-integrator codes, such as TRACY and DESPOT. In addition to element-by-element tracking, we constructed maps to determine aberration strengths. Furthermore, we have developed a fast and reliable method (nPB tracking) to track particles with a one-turn map. This new technique allows us to evaluate performance of the lattices on the entire tune-plane. Recently, we designed and implemented an object-oriented code in C++ called LEGO which integrates and expands upon TRACY and DESPOT.

Optimal tracking and second order sliding power control of the DFIG wind turbine

NASA Astrophysics Data System (ADS)

Abdeddaim, S.; Betka, A.; Charrouf, O.

2017-02-01

In the present paper, an optimal operation of a grid-connected variable speed wind turbine equipped with a Doubly Fed Induction Generator (DFIG) is presented. The proposed cascaded nonlinear controller is designed to perform two main objectives. In the outer loop, a maximum power point tracking (MPPT) algorithm based on fuzzy logic theory is designed to permanently extract the optimal aerodynamic energy, whereas in the inner loop, a second order sliding mode control (2-SM) is applied to achieve smooth regulation of both stator active and reactive powers quantities. The obtained simulation results show a permanent track of the MPP point regardless of the turbine power-speed slope moreover the proposed sliding mode control strategy presents attractive features such as chattering-free, compared to the conventional first order sliding technique (1-SM).

Fixed-base simulator study of the effect of time delays in visual cues on pilot tracking performance

NASA Technical Reports Server (NTRS)

Queijo, M. J.; Riley, D. R.

1975-01-01

Factors were examined which determine the amount of time delay acceptable in the visual feedback loop in flight simulators. Acceptable time delays are defined as delays which significantly affect neither the results nor the manner in which the subject 'flies' the simulator. The subject tracked a target aircraft as it oscillated sinusoidally in a vertical plane only. The pursuing aircraft was permitted five degrees of freedom. Time delays of from 0.047 to 0.297 second were inserted in the visual feedback loop. A side task was employed to maintain the workload constant and to insure that the pilot was fully occupied during the experiment. Tracking results were obtained for 17 aircraft configurations having different longitudinal short-period characteristics. Results show a positive correlation between improved handling qualities and a longer acceptable time delay.

Constructing LDPC Codes from Loop-Free Encoding Modules

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Dolinar, Samuel; Jones, Christopher; Thorpe, Jeremy; Andrews, Kenneth

2009-01-01

A method of constructing certain low-density parity-check (LDPC) codes by use of relatively simple loop-free coding modules has been developed. The subclasses of LDPC codes to which the method applies includes accumulate-repeat-accumulate (ARA) codes, accumulate-repeat-check-accumulate codes, and the codes described in Accumulate-Repeat-Accumulate-Accumulate Codes (NPO-41305), NASA Tech Briefs, Vol. 31, No. 9 (September 2007), page 90. All of the affected codes can be characterized as serial/parallel (hybrid) concatenations of such relatively simple modules as accumulators, repetition codes, differentiators, and punctured single-parity check codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. These codes can also be characterized as hybrid turbolike codes that have projected graph or protograph representations (for example see figure); these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The present method comprises two related submethods for constructing LDPC codes from simple loop-free modules with circulant permutations. The first submethod is an iterative encoding method based on the erasure-decoding algorithm. The computations required by this method are well organized because they involve a parity-check matrix having a block-circulant structure. The second submethod involves the use of block-circulant generator matrices. The encoders of this method are very similar to those of recursive convolutional codes. Some encoders according to this second submethod have been implemented in a small field-programmable gate array that operates at a speed of 100 megasymbols per second. By use of density evolution (a computational- simulation technique for analyzing performances of LDPC codes), it has been shown through some examples that as the block size goes to infinity, low iterative decoding thresholds close to channel capacity limits can be achieved for the codes of the type in question having low maximum variable node degrees. The decoding thresholds in these examples are lower than those of the best-known unstructured irregular LDPC codes constrained to have the same maximum node degrees. Furthermore, the present method enables the construction of codes of any desired rate with thresholds that stay uniformly close to their respective channel capacity thresholds.

Tracking data in the office environment.

PubMed

Erickson, Ty B

2010-09-01

Data tracking in the office setting focuses on a narrow spectrum of the entire patient safety arena; however, when properly executed, data tracking increases staff members' awareness of the importance of patient safety. Data tracking is also a high-volume event and thereby continues to loop back on the consciousness of providers in all aspects of their practice. Improvement in date tracking will improve the collateral areas of patient safety such as proper medication usage, legibility of written communication, effective delegation of patient safety initiatives, and a collegial effort at developing teams for safety design processes.

3D Tracking of Mating Events in Wild Swarms of the Malaria Mosquito Anopheles gambiae

PubMed Central

Butail, Sachit; Manoukis, Nicholas; Diallo, Moussa; Yaro, Alpha S.; Dao, Adama; Traoré, Sekou F.; Ribeiro, José M.; Lehmann, Tovi; Paley, Derek A.

2013-01-01

We describe an automated tracking system that allows us to reconstruct the 3D kinematics of individual mosquitoes in swarms of Anopheles gambiae. The inputs to the tracking system are video streams recorded from a stereo camera system. The tracker uses a two-pass procedure to automatically localize and track mosquitoes within the swarm. A human-in-the-loop step verifies the estimates and connects broken tracks. The tracker performance is illustrated using footage of mating events filmed in Mali in August 2010. PMID:22254411

Exploiting loop level parallelism in nonprocedural dataflow programs

NASA Technical Reports Server (NTRS)

Gokhale, Maya B.

1987-01-01

Discussed are how loop level parallelism is detected in a nonprocedural dataflow program, and how a procedural program with concurrent loops is scheduled. Also discussed is a program restructuring technique which may be applied to recursive equations so that concurrent loops may be generated for a seemingly iterative computation. A compiler which generates C code for the language described below has been implemented. The scheduling component of the compiler and the restructuring transformation are described.

FY 2017-Progress Report on the Design and Construction of the Sodium Loop SMT-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natesan, K.; Momozaki, Y.

This report provides an update on the design of a forced-convection sodium loop to be used for the evaluation of sodium compatibility of advanced Alloy 709 with emphasis on long term exposures of tensile, creep, fatigue, creep fatigue, and fracture toughness ASTM-size specimens in support of ASME Code qualification and NRC licensing. The report is a deliverable (Level 4) in FY17 (M4AT-17AN1602094), under the Work Package AT-17AN160209, “Sodium Compatibility” performed by Argonne National Laboratory (ANL), as part of the Advanced Materials Program for the Advanced Reactor Technology. This work package enables the development of advanced structural materials by providing corrosion,more » microstructure, and mechanical property data from the standpoint of sodium compatibility of advanced structural alloys. The first sodium loop (SMT-1) with a single tank was constructed in 2011 at ANL and has been in operation for exposure of subsize sheet specimens of advanced alloys at a single temperature. The second sodium loop with dual tanks (SMT-2) was constructed in 2013 and has been in operation for the exposure of subsize sheet specimens of advanced alloys at two different temperatures. The current loop (SMT-3) has been designed to incorporate sufficient chamber capacity to expose a large number of ASTM-size specimens to evaluate the sodium effects on tensile, creep, fatigue, creep-fatigue, and fracture toughness properties, in support of ASME Code Qualification and USNRC Licensing. The design of individual components for the third sodium loop SMT-3 is almost complete. The design also has been sent to an outside vendor for piping analysis to be in compliance with ASME Code. A purchase order has been placed with an outside vendor for the fabrication of major components such as the specimen exposure tanks. However, we have contracted with another vendor to establish the piping design in compliance with ASME design codes. The piping design was completed in FY2017 and the information is being transmitted to the tank fabricator. The SMT-3 loop will be located in Building 206 adjacent to the currently operating SMT-2 loop. In addition, we have demolished the aged power supply system in Building 206 and installed a new transformer, wiring, and power panels for the new loop. Procurement of some of the long lead items such as valves, EM pumps, EM flowmeters, etc. is in progress and will continue in FY 2018. The construction of components such as cold trap, economizers, piping arrangement etc. will be performed in the central shops at ANL. About 150 liters of sodium for the loop will be procured in early FY2018. The loop system is designed to circulate sodium through the sample tanks and the associated loop without an operator for an extended period of time. With the three sodium loops (with single-tank, dual-tank and four–tanks), materials can be tested at different sodium temperatures, and large tensile, creep, fatigue, creep-fatigue, and fracture toughness specimens can be exposed to sodium for extended periods of time and generate data on mechanical properties in support of ASME Code Qualification and USNRC Licensing of advanced Alloy 709 for use as a structural material in SFRs.« less

AGARD (Advisory Group for Aerospace Research & Development) Index of Publications, 1986-1988

DTIC Science & Technology

1989-08-01

measurements are used in forming the navigation and the baro-inertial loop as well The system communicates with equations to solve for the user position...processing techniques in the tracking ROBERT P. DENARO and G JEFFREY GEIER In AGARD, The loops . and later in the navigation processing ot the Kalman...avionics investigations to predict the dynamic structural response of flexible assessment. The current status of real time, pilot-in-the- loop flight

Critique of a Hughes shuttle Ku-band data sampler/bit synchronizer

NASA Technical Reports Server (NTRS)

Holmes, J. K.

1980-01-01

An alternative bit synchronizer proposed for shuttle was analyzed in a noise-free environment by considering the basic operation of the loop via timing diagrams and by linearizing the bit synchronizer as an equivalent, continuous, phased-lock loop (PLL). The loop is composed of a high-frequency phase-frequency detector which is capable of detecting both phase and frequency errors and is used to track the clock, and a bit transition detector which attempts to track the transitions of the data bits. It was determined that the basic approach was a good design which, with proper implementation of the accumulator, up/down counter and logic should provide accurate mid-bit sampling with symmetric bits. However, when bit asymmetry occurs, the bit synchronizer can lock up with a large timing error, yet be quasi-stable (timing will not change unless the clock and bit sequence drift). This will result in incorrectly detecting some bits.

Performance and operational considerations in the design of vehicle antennas for mobile satellite communications

NASA Technical Reports Server (NTRS)

Milne, R.

1995-01-01

This paper examines the vehicle antenna requirements for mobile satellite systems. The antenna parameters are discussed in the light of the requirements and the limitations in performance imposed by the physical constraints of antenna and by vehicle geometries. Measurements of diffraction and antenna noise temperature in an operational environment are examined, as well as their effects on system margins. Mechanical versus electronic designs are compared with regards to performance, cost, reliability, and design complexity. Comparisons between open-loop and close-loop tracking systems are made and the effects of bandwidth, sidelobe levels, operational constraints, vehicle angular velocity, and acceleration are discussed. Some consideration is given to the use of hybrid systems employing both open and closed-loop tracking. Changes to antenna/terminal specifications are recommended which will provide greater design flexibility and increase the likelihood of meeting the performance and operational requirements.

Modular high-voltage bias generator powered by dual-looped self-adaptive wireless power transmission.

PubMed

Xie, Kai; Huang, An-Feng; Li, Xiao-Ping; Guo, Shi-Zhong; Zhang, Han-Lu

2015-04-01

We proposed a modular high-voltage (HV) bias generator powered by a novel transmitter-sharing inductive coupled wireless power transmission technology, aimed to extend the generator's flexibility and configurability. To solve the problems caused through an uncertain number of modules, a dual-looped self-adaptive control method is proposed that is capable of tracking resonance frequency while maintaining a relatively stable induction voltage for each HV module. The method combines a phase-locked loop and a current feedback loop, which ensures an accurate resonance state and a relatively constant boost ratio for each module, simplifying the architecture of the boost stage and improving the total efficiency. The prototype was built and tested. The input voltage drop of each module is less than 14% if the module number varies from 3 to 10; resonance tracking is completed within 60 ms. The efficiency of the coupling structure reaches up to 95%, whereas the total efficiency approaches 73% for a rated output. Furthermore, this technology can be used in various multi-load wireless power supply applications.

The use of interleaving for reducing radio loss in convolutionally coded systems

NASA Technical Reports Server (NTRS)

Divsalar, D.; Simon, M. K.; Yuen, J. H.

1989-01-01

The use of interleaving after convolutional coding and deinterleaving before Viterbi decoding is proposed. This effectively reduces radio loss at low-loop Signal to Noise Ratios (SNRs) by several decibels and at high-loop SNRs by a few tenths of a decibel. Performance of the coded system can further be enhanced if the modulation index is optimized for this system. This will correspond to a reduction of bit SNR at a certain bit error rate for the overall system. The introduction of interleaving/deinterleaving into communication systems designed for future deep space missions does not substantially complicate their hardware design or increase their system cost.

Performance of DBS-Radio using concatenated coding and equalization

NASA Technical Reports Server (NTRS)

Gevargiz, J.; Bell, D.; Truong, L.; Vaisnys, A.; Suwitra, K.; Henson, P.

1995-01-01

The Direct Broadcast Satellite-Radio (DBS-R) receiver is being developed for operation in a multipath Rayleigh channel. This receiver uses equalization and concatenated coding, in addition to open loop and closed loop architectures for carrier demodulation and symbol synchronization. Performance test results of this receiver are presented in both AWGN and multipath Rayleigh channels. Simulation results show that the performance of the receiver operating in a multipath Rayleigh channel is significantly improved by using equalization. These results show that fractional-symbol equalization offers a performance advantage over full symbol equalization. Also presented is the base-line performance of the DBS-R receiver using concatenated coding and interleaving.

Charged particle tracking through electrostatic wire meshes using the finite element method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devlin, L. J.; Karamyshev, O.; Welsch, C. P., E-mail: carsten.welsch@cockcroft.ac.uk

Wire meshes are used across many disciplines to accelerate and focus charged particles, however, analytical solutions are non-exact and few codes exist which simulate the exact fields around a mesh with physical sizes. A tracking code based in Matlab-Simulink using field maps generated using finite element software has been developed which tracks electrons or ions through electrostatic wire meshes. The fields around such a geometry are presented as an analytical expression using several basic assumptions, however, it is apparent that computational calculations are required to obtain realistic values of electric potential and fields, particularly when multiple wire meshes are deployed.more » The tracking code is flexible in that any quantitatively describable particle distribution can be used for both electrons and ions as well as other benefits such as ease of export to other programs for analysis. The code is made freely available and physical examples are highlighted where this code could be beneficial for different applications.« less

Residual and suppressed-carrier arraying techniques for deep-space communications

NASA Technical Reports Server (NTRS)

Shihabi, M.; Shah, B.; Hinedi, S.; Million, S.

1995-01-01

Three techniques that use carrier information from multiple antennas to enhance carrier acquisition and tracking are presented. These techniques in combination with baseband combining are analyzed and simulated for residual and suppressed-carrier modulation. It is shown that the carrier arraying using a single carrier loop technique can acquire and track the carrier even when any single antenna in the array cannot do so by itself. The carrier aiding and carrier arraying using multiple carrier loop techniques, on the other hand, are shown to lock on the carrier only when one of the array elements has sufficient margin to acquire the carrier on its own.

A flight test method for pilot/aircraft analysis

NASA Technical Reports Server (NTRS)

Koehler, R.; Buchacker, E.

1986-01-01

In high precision flight maneuvres a pilot is a part of a closed loop pilot/aircraft system. The assessment of the flying qualities is highly dependent on the closed loop characteristics related to precision maneuvres like approach, landing, air-to-air tracking, air-to-ground tracking, close formation flying and air-to air refueling of the receiver. The object of a research program at DFVLR is the final flight phase of an air to ground mission. In this flight phase the pilot has to align the aircraft with the target, correct small deviations from the target direction and keep the target in his sights for a specific time period. To investigate the dynamic behavior of the pilot-aircraft system a special ground attack flight test technique with a prolonged tracking maneuvres was developed. By changing the targets during the attack the pilot is forced to react continously on aiming errors in his sights. Thus the closed loop pilot/aircraft system is excited over a wide frequency range of interest, the pilot gets more information about mission oriented aircraft dynamics and suitable flight test data for a pilot/aircraft analysis can be generated.

Antenna Linear-Quadratic-Gaussian (LQG) Ccontrollers: Properties, Limits of Performance, and Tuning

NASA Technical Reports Server (NTRS)

Gawronski, Wodek K.

2004-01-01

The LQG controllers significantly improve antenna tracking precision, but their tuning is a trial-and-error process. A control engineer has two tools to tune an LQG controller: the choice of coordinate system of the controller, and the selection of weights of the LQG performance index. The paper selects the coordinates of the open-loop model that simplify the shaping of the closed-loop performance. and analyzes the impact of thc weights on the antenna closed-loop bandwidth, disturbance rejection properties, and antenna acceleration. Finally, it presents the LQG controller tuning procedure that rationally shapes the closed-loop performance.

A closed-loop system for frequency tracking of piezoresistive cantilever sensors

NASA Astrophysics Data System (ADS)

Wasisto, Hutomo Suryo; Zhang, Qing; Merzsch, Stephan; Waag, Andreas; Peiner, Erwin

2013-05-01

A closed loop circuit capable of tracking resonant frequencies for MEMS-based piezoresistive cantilever resonators is developed in this work. The proposed closed-loop system is mainly based on a phase locked loop (PLL) circuit. In order to lock onto the resonant frequency of the resonator, an actuation signal generated from a voltage-controlled oscillator (VCO) is locked to the phase of the input reference signal of the cantilever sensor. In addition to the PLL component, an instrumentation amplifier and an active low pass filter (LPF) are connected to the system for gaining the amplitude and reducing the noise of the cantilever output signals. The LPF can transform a rectangular signal into a sinusoidal signal with voltage amplitudes ranging from 5 to 10 V which are sufficient for a piezoactuator input (i.e., maintaining a large output signal of the cantilever sensor). To demonstrate the functionality of the system, a self-sensing silicon cantilever resonator with a built-in piezoresistive Wheatstone bridge is fabricated and integrated with the circuit. A piezoactuator is utilized for actuating the cantilever into resonance. Implementation of this closed loop system is used to track the resonant frequency of a silicon cantilever-based sensor resonating at 9.4 kHz under a cross-sensitivity test of ambient temperature. The changes of the resonant frequency are interpreted using a frequency counter connected to the system. From the experimental results, the temperature sensitivity and coefficient of the employed sensor are 0.3 Hz/°C and 32.8 ppm/°C, respectively. The frequency stability of the system can reach up to 0.08 Hz. The development of this system will enable real-time nanoparticle monitoring systems and provide a miniaturization of the instrumentation modules for cantilever-based nanoparticle detectors.

Electronic circuits

NASA Technical Reports Server (NTRS)

1976-01-01

Twenty-nine circuits and circuit techniques developed for communications and instrumentation technology are described. Topics include pulse-code modulation, phase-locked loops, data coding, data recording, detection circuits, logic circuits, oscillators, and amplifiers.

ALARA: The next link in a chain of activation codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, P.P.H.; Henderson, D.L.

1996-12-31

The Adaptive Laplace and Analytic Radioactivity Analysis [ALARA] code has been developed as the next link in the chain of DKR radioactivity codes. Its methods address the criticisms of DKR while retaining its best features. While DKR ignored loops in the transmutation/decay scheme to preserve the exactness of the mathematical solution, ALARA incorporates new computational approaches without jeopardizing the most important features of DKR`s physical modelling and mathematical methods. The physical model uses `straightened-loop, linear chains` to achieve the same accuracy in the loop solutions as is demanded in the rest of the scheme. In cases where a chain hasmore » no loops, the exact DKR solution is used. Otherwise, ALARA adaptively chooses between a direct Laplace inversion technique and a Laplace expansion inversion technique to optimize the accuracy and speed of the solution. All of these methods result in matrix solutions which allow the fastest and most accurate solution of exact pulsing histories. Since the entire history is solved for each chain as it is created, ALARA achieves the optimum combination of high accuracy, high speed and low memory usage. 8 refs., 2 figs.« less

Research on phase locked loop in optical memory servo system

NASA Astrophysics Data System (ADS)

Qin, Liqin; Ma, Jianshe; Zhang, Jianyong; Pan, Longfa; Deng, Ming

2005-09-01

Phase locked loop (PLL) is a closed loop automatic control system, which can track the phase of input signal. It widely applies in each area of electronic technology. This paper research the phase locked loop in optical memory servo area. This paper introduces the configuration of digital phase locked loop (PLL) and phase locked servo system, the control theory, and analyses system's stability. It constructs the phase locked loop experiment system of optical disk spindle servo, which based on special chip. DC motor is main object, this system adopted phase locked servo technique and digital signal processor (DSP) to achieve constant linear velocity (CLV) in controlling optical spindle motor. This paper analyses the factors that affect the stability of phase locked loop in spindle servo system, and discusses the affection to the optical disk readout signal and jitter due to the stability of phase locked loop.

The use of interleaving for reducing radio loss in trellis-coded modulation systems

NASA Technical Reports Server (NTRS)

Divsalar, D.; Simon, M. K.

1989-01-01

It is demonstrated how the use of interleaving/deinterleaving in trellis-coded modulation (TCM) systems can reduce the signal-to-noise ratio loss due to imperfect carrier demodulation references. Both the discrete carrier (phase-locked loop) and suppressed carrier (Costas loop) cases are considered and the differences between the two are clearly demonstrated by numerical results. These results are of great importance for future communication links to the Deep Space Network (DSN), especially from high Earth orbiters, which may be bandwidth limited.

Analytical solutions to optimal underactuated spacecraft formation reconfiguration

NASA Astrophysics Data System (ADS)

Huang, Xu; Yan, Ye; Zhou, Yang

2015-11-01

Underactuated systems can generally be defined as systems with fewer number of control inputs than that of the degrees of freedom to be controlled. In this paper, analytical solutions to optimal underactuated spacecraft formation reconfiguration without either the radial or the in-track control are derived. By using a linear dynamical model of underactuated spacecraft formation in circular orbits, controllability analysis is conducted for either underactuated case. Indirect optimization methods based on the minimum principle are then introduced to generate analytical solutions to optimal open-loop underactuated reconfiguration problems. Both fixed and free final conditions constraints are considered for either underactuated case and comparisons between these two final conditions indicate that the optimal control strategies with free final conditions require less control efforts than those with the fixed ones. Meanwhile, closed-loop adaptive sliding mode controllers for both underactuated cases are designed to guarantee optimal trajectory tracking in the presence of unmatched external perturbations, linearization errors, and system uncertainties. The adaptation laws are designed via a Lyapunov-based method to ensure the overall stability of the closed-loop system. The explicit expressions of the terminal convergent regions of each system states have also been obtained. Numerical simulations demonstrate the validity and feasibility of the proposed open-loop and closed-loop control schemes for optimal underactuated spacecraft formation reconfiguration in circular orbits.

Recent Developments in the Code RITRACKS (Relativistic Ion Tracks)

NASA Technical Reports Server (NTRS)

Plante, Ianik; Ponomarev, Artem L.; Blattnig, Steve R.

2018-01-01

The code RITRACKS (Relativistic Ion Tracks) was developed to simulate detailed stochastic radiation track structures of ions of different types and energies. Many new capabilities were added to the code during the recent years. Several options were added to specify the times at which the tracks appear in the irradiated volume, allowing the simulation of dose-rate effects. The code has been used to simulate energy deposition in several targets: spherical, ellipsoidal and cylindrical. More recently, density changes as well as a spherical shell were implemented for spherical targets, in order to simulate energy deposition in walled tissue equivalent proportional counters. RITRACKS is used as a part of the new program BDSTracks (Biological Damage by Stochastic Tracks) to simulate several types of chromosome aberrations in various irradiation conditions. The simulation of damage to various DNA structures (linear and chromatin fiber) by direct and indirect effects has been improved and is ongoing. Many improvements were also made to the graphic user interface (GUI), including the addition of several labels allowing changes of units. A new GUI has been added to display the electron ejection vectors. The parallel calculation capabilities, notably the pre- and post-simulation processing on Windows and Linux machines have been reviewed to make them more portable between different systems. The calculation part is currently maintained in an Atlassian Stash® repository for code tracking and possibly future collaboration.

Sandia Simple Particle Tracking (Sandia SPT) v. 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anthony, Stephen M.

2015-06-15

Sandia SPT is designed as software to accompany a book chapter being published a methods chapter which provides an introduction on how to label and track individual proteins. The Sandia Simple Particle Tracking code uses techniques common to the image processing community, where its value is that it facilitates implementing the methods described in the book chapter by providing the necessary open-source code. The code performs single particle spot detection (or segmentation and localization) followed by tracking (or connecting the detected particles into trajectories). The book chapter, which along with the headers in each file, constitutes the documentation for themore » code is: Anthony, S.M.; Carroll-Portillo, A.; Timlon, J.A., Dynamics and Interactions of Individual Proteins in the Membrane of Living Cells. In Anup K. Singh (Ed.) Single Cell Protein Analysis Methods in Molecular Biology. Springer« less

Loran digital phase-locked loop and RF front-end system error analysis

NASA Technical Reports Server (NTRS)

Mccall, D. L.

1979-01-01

An analysis of the system performance of the digital phase locked loops (DPLL) and RF front end that are implemented in the MINI-L4 Loran receiver is presented. Three of the four experiments deal with the performance of the digital phase locked loops. The other experiment deals with the RF front end and DPLL system error which arise in the front end due to poor signal to noise ratios. The ability of the DPLLs to track the offsets is studied.

An Investigation Relating Longitudinal Pilot-Induced Oscillation Tendency Rating to Describing Function Predictions for Rate-Limited Actuators

DTIC Science & Technology

2004-03-01

2-15 2-10. Pitch Tracking Closed Loop System for Gap Criterion...................................... 2-16 2-11. Four Resulting Gap ...Level 1 Minimize Resonance Closed Loop Bode Diagram ( ) ( ) s sCommand θ θ ( ) ( ) s sCommand θ θ         BWω 2-16 Gap Criterion...System for Gap Criterion In modern fly-by-wire aircraft, feedback is an integral part of obtaining more desirable closed loop flying qualities

Robust model reference adaptive output feedback tracking for uncertain linear systems with actuator fault based on reinforced dead-zone modification.

PubMed

Bagherpoor, H M; Salmasi, Farzad R

2015-07-01

In this paper, robust model reference adaptive tracking controllers are considered for Single-Input Single-Output (SISO) and Multi-Input Multi-Output (MIMO) linear systems containing modeling uncertainties, unknown additive disturbances and actuator fault. Two new lemmas are proposed for both SISO and MIMO, under which dead-zone modification rule is improved such that the tracking error for any reference signal tends to zero in such systems. In the conventional approach, adaption of the controller parameters is ceased inside the dead-zone region which results tracking error, while preserving the system stability. In the proposed scheme, control signal is reinforced with an additive term based on tracking error inside the dead-zone which results in full reference tracking. In addition, no Fault Detection and Diagnosis (FDD) unit is needed in the proposed approach. Closed loop system stability and zero tracking error are proved by considering a suitable Lyapunov functions candidate. It is shown that the proposed control approach can assure that all the signals of the close loop system are bounded in faulty conditions. Finally, validity and performance of the new schemes have been illustrated through numerical simulations of SISO and MIMO systems in the presence of actuator faults, modeling uncertainty and output disturbance. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Closed-loop analysis and control of a non-inverting buck-boost converter

NASA Astrophysics Data System (ADS)

Chen, Zengshi; Hu, Jiangang; Gao, Wenzhong

2010-11-01

In this article, a cascade controller is designed and analysed for a non-inverting buck-boost converter. The fast inner current loop uses sliding mode control. The slow outer voltage loop uses the proportional-integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics incorporating both the inner and outer loop controllers. The closed-loop system is proven to have a nonminimum phase structure. The voltage transient due to step changes of input voltage or resistance is predictable. The operating range of the reference voltage is discussed. The controller is validated by a simulation circuit. The simulation results show that the reference output voltage is well-tracked under system uncertainties or disturbances, confirming the validity of the proposed controller.

Open-loop GPS signal tracking at low elevation angles from a ground-based observation site

NASA Astrophysics Data System (ADS)

Beyerle, Georg; Zus, Florian

2016-04-01

For more than a decade space-based global navigation satellite system (GNSS) radio occultation (RO) observations are used by meteorological services world-wide for their numerical weather prediction models. In addition, climate studies increasingly rely on validated GNSS-RO data sets of atmospheric parameters. GNSS-RO profiles typically cover an altitude range from the boundary layer up to the upper stratosphere; their highest accuracy and precision, however, are attained at the tropopause level. In the lower troposphere, multipath ray propagation tend to induce signal amplitude and frequency fluctuations which lead to the development and implementation of open-loop signal tracking methods in GNSS-RO receiver firmwares. In open-loop mode the feed-back values for the carrier tracking loop are derived not from measured data, but from a Doppler frequency model which usually is extracted from an atmospheric climatology. In order to ensure that this receiver-internal parameter set, does not bias the carrier phase path observables, dual-channel open-loop GNSS-RO signal tracking was suggested. Following this proposal the ground-based "GLESER" (GPS low-elevation setting event recorder) campaign was established. Its objective was to disproof the existence of model-induced frequency biases using ground-based GPS observations at very low elevation angles. Between January and December 2014 about 2600 validated setting events, starting at geometric elevation angles of +2° and extending to -1°… - 1.5°, were recorded by the single frequency "OpenGPS" GPS receiver at a measurement site located close to Potsdam, Germany (52.3808°N, 13.0642°E). The study is based on the assumption that these ground-based observations may be used as proxies for space-based RO measurements, even if the latter occur on a one order of magnitude faster temporal scale. The "GLESER" data analysis shows that the open-loop Doppler model has negligible influence on the derived frequency profile provided signal-to-noise density ratios remain above about 30 dB Hz. At low signal levels, however, the dual-channel open-loop design, which tracks the same signal using two Doppler models separated by a 10 Hz offset, reveals a notable bias. A significant fraction of this bias is caused by frequency aliasing. The receiver's dual-channel setup, however, allows for unambiguous identification of the affected observation samples. Finally, the repeat patterns in terms of azimuth angle of the GPS orbit traces reveals characteristic signatures in both, signal amplitude and Doppler frequency with respect to the topography close to the observation site. On the other hand, mean vertical refractivity gradients extracted from ECMWF meteorological fields exhibit moderate correlations with observed signal amplitude fluctuations at negative elevation angles emphasizing the information content of low-elevation GPS signals with respect to the atmospheric state in the boundary layer.

Design of a feedback-feedforward steering controller for accurate path tracking and stability at the limits of handling

NASA Astrophysics Data System (ADS)

Kapania, Nitin R.; Gerdes, J. Christian

2015-12-01

This paper presents a feedback-feedforward steering controller that simultaneously maintains vehicle stability at the limits of handling while minimising lateral path tracking deviation. The design begins by considering the performance of a baseline controller with a lookahead feedback scheme and a feedforward algorithm based on a nonlinear vehicle handling diagram. While this initial design exhibits desirable stability properties at the limits of handling, the steady-state path deviation increases significantly at highway speeds. Results from both linear and nonlinear analyses indicate that lateral path tracking deviations are minimised when vehicle sideslip is held tangent to the desired path at all times. Analytical results show that directly incorporating this sideslip tangency condition into the steering feedback dramatically improves lateral path tracking, but at the expense of poor closed-loop stability margins. However, incorporating the desired sideslip behaviour into the feedforward loop creates a robust steering controller capable of accurate path tracking and oversteer correction at the physical limits of tyre friction. Experimental data collected from an Audi TTS test vehicle driving at the handling limits on a full length race circuit demonstrates the improved performance of the final controller design.

Singularity-free backstepping controller for model helicopters.

PubMed

Zou, Yao; Huo, Wei

2016-11-01

This paper develops a backstepping controller for model helicopters to achieve trajectory tracking without singularity, which occurs in the attitude representation when the roll or pitch reaches ±π2. Based on a simplified model with unmodeled dynamics, backstepping technique is introduced to exploit the controller and hyperbolic tangent functions are utilized to compensate the unmodeled dynamics. Firstly, a position loop controller is designed for the position tracking, where an auxiliary dynamic system with suitable parameters is introduced to warrant the singularity-free requirement for the extracted command attitude. Then, a novel attitude loop controller is proposed to obviate singularity. It is demonstrated that, based on the established criteria for selecting controller parameters and desired trajectories, the proposed controller realizes the singularity-free trajectory tracking of the model helicopter. Simulations confirm the theoretical results. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Free-space laser communication technologies IV; Proceedings of the 4th Conference, Los Angeles, CA, Jan. 23, 24, 1992

NASA Technical Reports Server (NTRS)

Begley, David L. (Editor); Seery, Bernard D. (Editor)

1992-01-01

Papers included in this volume are grouped under topics of receivers; laser transmitters; components; system analysis, performance, and applications; and beam control (pointing, acquisition, and tracking). Papers are presented on an experimental determination of power penalty contributions in an optical Costas-type phase-locked loop receiver, a resonant laser receiver for free-space laser communications, a simple low-loss technique for frequency-locking lasers, direct phase modulation of laser diodes, and a silex beacon. Particular attention is given to experimental results on an optical array antenna for nonmechanical beam steering, a potassium Faraday anomalous dispersion optical filter, a 100-Mbps resonant cavity phase modulator for coherent optical communications, a numerical simulation of a 325-Mbit/s QPPM optical communication system, design options for an optical multiple-access data relay terminal, CCD-based optical tracking loop design trades, and an analysis of a spatial-tracking subsystem for optical communications.

Run-time parallelization and scheduling of loops

NASA Technical Reports Server (NTRS)

Saltz, Joel H.; Mirchandaney, Ravi; Crowley, Kay

1991-01-01

Run-time methods are studied to automatically parallelize and schedule iterations of a do loop in certain cases where compile-time information is inadequate. The methods presented involve execution time preprocessing of the loop. At compile-time, these methods set up the framework for performing a loop dependency analysis. At run-time, wavefronts of concurrently executable loop iterations are identified. Using this wavefront information, loop iterations are reordered for increased parallelism. Symbolic transformation rules are used to produce: inspector procedures that perform execution time preprocessing, and executors or transformed versions of source code loop structures. These transformed loop structures carry out the calculations planned in the inspector procedures. Performance results are presented from experiments conducted on the Encore Multimax. These results illustrate that run-time reordering of loop indexes can have a significant impact on performance.

Sliding Mode Control of the X-33 Vehicle in Launch Mode

NASA Technical Reports Server (NTRS)

Shtessel, Yuri; Jackson, Mark; Hall, Charles; Krupp, Don; Hendrix, N. Douglas

1998-01-01

The "nested" structure of the control system for the X33 vehicle in launch mode is developed. Employing backstopping concepts, the outer loop (guidance) and the Inner loop (rates) continuous sliding mode controllers are designed. Simulations of the 3-DOF model of the X33 launch vehicle showed an accurate, robust, de-coupled tracking performance.

Coalescence of two current loops with a kink instability simulated by a three-dimensional electromagnetic particle code

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Sakai, J.-I.; Zhao, Jie; Neubert, T.; Buneman, Oscar

1994-01-01

We have studied the dynamics of a coalescence of current loops using three-dimensional electromagnetic (EM) particle simulation code. Our focus is the investigation of such kinetic processes as energy trasnfer, heating particles, and electromagnetic emissions associated with a current loop coalescence which cannot be studied by MHD simulations. First, the two loops undergo a pinching oscillation due to a pressure imbalance between the inside and outside of the current loop. During the pinching oscillation, a kinetic kink instability is excited and electrons in the loops are heated perpendicularly to an ambient magnetic field. Next, the two current loops collide and coalesce, while at the same time a helical structure grows further. Subsequently, the perturbed current, which is due to these helically bunched electrons, can drive a whistler instability. It should be noted in this case that the whistler wave is excited by the kinetic kink instability and not a beam instability. After the coalescence of two helical loops, tilting motions can be observed in the direction of left-hand rotation, and the helical structure will relax resulting in strong plasma heating mostly in the direction perpendicular to the ambient magnetic field. It is also shown that high-frequency electromagnetic waves can be emitted from the region where the two loops coalesce and propagate strongly in the direction of the electron drift velocity. These processes may be important in understanding heating mechansims for coronal loops as well as radio wave emission mechanisms from active regions of solar plasmas.

Post-test analysis of dryout test 7B' of the W-1 Sodium Loop Safety Facility Experiment with the SABRE-2P code. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, S.D.; Dearing, J.F.

An understanding of conditions that may cause sodium boiling and boiling propagation that may lead to dryout and fuel failure is crucial in liquid-metal fast-breeder reactor safety. In this study, the SABRE-2P subchannel analysis code has been used to analyze the ultimate transient of the in-core W-1 Sodium Loop Safety Facility experiment. This code has a 3-D simple nondynamic boiling model which is able to predict the flow instability which caused dryout. In other analyses dryout has been predicted for out-of-core test bundles and so this study provides additional confirmation of the model.

Real-time fringe pattern demodulation with a second-order digital phase-locked loop.

PubMed

Gdeisat, M A; Burton, D R; Lalor, M J

2000-10-10

The use of a second-order digital phase-locked loop (DPLL) to demodulate fringe patterns is presented. The second-order DPLL has better tracking ability and more noise immunity than the first-order loop. Consequently, the second-order DPLL is capable of demodulating a wider range of fringe patterns than the first-order DPLL. A basic analysis of the first- and the second-order loops is given, and a performance comparison between the first- and the second-order DPLL's in analyzing fringe patterns is presented. The implementation of the second-order loop in real time on a commercial parallel image processing system is described. Fringe patterns are grabbed and processed, and the resultant phase maps are displayed concurrently.

EKF-Based Enhanced Performance Controller Design for Nonlinear Stochastic Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yuyang; Zhang, Qichun; Wang, Hong

In this paper, a novel control algorithm is presented to enhance the performance of tracking property for a class of non-linear dynamic stochastic systems with unmeasurable variables. To minimize the entropy of tracking errors without changing the existing closed loop with PI controller, the enhanced performance loop is constructed based on the state estimation by extended Kalman Filter and the new controller is designed by full state feedback following this presented control algorithm. Besides, the conditions are obtained for the stability analysis in the mean square sense. In the end, the comparative simulation results are given to illustrate the effectivenessmore » of proposed control algorithm.« less

An open-closed-loop iterative learning control approach for nonlinear switched systems with application to freeway traffic control

NASA Astrophysics Data System (ADS)

Sun, Shu-Ting; Li, Xiao-Dong; Zhong, Ren-Xin

2017-10-01

For nonlinear switched discrete-time systems with input constraints, this paper presents an open-closed-loop iterative learning control (ILC) approach, which includes a feedforward ILC part and a feedback control part. Under a given switching rule, the mathematical induction is used to prove the convergence of ILC tracking error in each subsystem. It is demonstrated that the convergence of ILC tracking error is dependent on the feedforward control gain, but the feedback control can speed up the convergence process of ILC by a suitable selection of feedback control gain. A switched freeway traffic system is used to illustrate the effectiveness of the proposed ILC law.

A compact presentation of DSN array telemetry performance

NASA Technical Reports Server (NTRS)

Greenhall, C. A.

1982-01-01

The telemetry performance of an arrayed receiver system, including radio losses, is often given by a family of curves giving bit error rate vs bit SNR, with tracking loop SNR at one receiver held constant along each curve. This study shows how to process this information into a more compact, useful format in which the minimal total signal power and optimal carrier suppression, for a given fixed bit error rate, are plotted vs data rate. Examples for baseband-only combining are given. When appropriate dimensionless variables are used for plotting, receiver arrays with different numbers of antennas and different threshold tracking loop bandwidths look much alike, and a universal curve for optimal carrier suppression emerges.

The feasibility of paper-based Tracking Codes and electronic medical record systems to monitor tobacco-use assessment and intervention in an Individual Practice Association (IPA) Model health maintenance organization (HMO).

PubMed

Bentz, Charles J; Davis, Nancy; Bayley, Bruce

2002-01-01

Despite evidence of its effectiveness, tobacco cessation is not systematically addressed in routine healthcare settings. Its measurement is part of the problem. A pilot study was designed to develop and implement two different tobacco tracking systems in two independent primary care offices that participated in an IPA Model health maintenance organization in Portland, Oregon. The first clinic, which utilized a paper-based charting system, implemented CPT-like tracking codes to measure and report tobacco-cessation activities, which were eventually included in the managed-care organization's (MCO) claims database. The second clinic implemented an electronic tracking system based on its computerized electronic medical record (EMR) charting system. This paper describes the pilot study, including the processes involved in building provider acceptance for the new tracking systems in these two clinics, the barriers and successes encountered during implementation, and the resources expended by the clinics and by the MCO during the pilot. The findings from the 3-month implementation period were that documentation of tobacco-use status remained stable at 42-45% in the paper-based clinic and increased from 79% to 88% in the EMR clinic. This pilot study demonstrated that Tracking Codes are a feasible preventive-care tracking system in paper-based medical offices. However, high levels of effort and support are needed, and a critical mass of insurers and health plans would need to adopt Tracking Codes before widespread use could be expected. Results of the EMR-based tracking system are also reviewed and discussed.

Design of a Solar Tracking Interactive Kiosk

ERIC Educational Resources Information Center

Greene, Nathaniel R.; Brunskill, Jeffrey C.

2017-01-01

A two-axis solar tracker and its interactive kiosk were designed by an interdisciplinary team of students and faculty. The objective was to develop a publicly accessible kiosk that would facilitate the study of energy usage and production on campus. Tracking is accomplished by an open-loop algorithm, microcontroller, and ham radio rotator. Solar…

On the Effects of a Spacecraft Subcarrier Unbalanced Modulator

NASA Technical Reports Server (NTRS)

Nguyen, Tien Manh

1993-01-01

This paper presents mathematical models with associated analysis of the deleterious effects which a spacecraft's subcarrier unbalanced modulator has on the performance of a phase-modulated residual carrier communications link. The undesired spectral components produced by the phase and amplitude imbalances in the subcarrier modulator can cause (1) potential interference to the carrier tracking and (2) degradation in the telemetry bit signal-to-noise ratio (SNR). A suitable model for the unbalanced modulator is developed and the threshold levels of undesired components that fall into the carrier tracking loop are determined. The distribution of the carrier phase error caused by the additive White Gaussian noise (AWGN) and undesired component at the residual RF carrier is derived for the limiting cases. Further, this paper analyses the telemetry bit signal-to-noise ratio degradations due to undesirable spectral components as well as the carrier tracking phase error induced by phase and amplitude imbalances. Numerical results which indicate the sensitivity of the carrier tracking loop and the telemetry symbol-error rate (SER) to various parameters of the models are also provided as a tool in the design of the subcarrier balanced modulator.

User's manual for the Heat Pipe Space Radiator design and analysis Code (HEPSPARC)

NASA Technical Reports Server (NTRS)

Hainley, Donald C.

1991-01-01

A heat pipe space radiatior code (HEPSPARC), was written for the NASA Lewis Research Center and is used for the design and analysis of a radiator that is constructed from a pumped fluid loop that transfers heat to the evaporative section of heat pipes. This manual is designed to familiarize the user with this new code and to serve as a reference for its use. This manual documents the completed work and is intended to be the first step towards verification of the HEPSPARC code. Details are furnished to provide a description of all the requirements and variables used in the design and analysis of a combined pumped loop/heat pipe radiator system. A description of the subroutines used in the program is furnished for those interested in understanding its detailed workings.

Experiences with Cray multi-tasking

NASA Technical Reports Server (NTRS)

Miya, E. N.

1985-01-01

The issues involved in modifying an existing code for multitasking is explored. They include Cray extensions to FORTRAN, an examination of the application code under study, designing workable modifications, specific code modifications to the VAX and Cray versions, performance, and efficiency results. The finished product is a faster, fully synchronous, parallel version of the original program. A production program is partitioned by hand to run on two CPUs. Loop splitting multitasks three key subroutines. Simply dividing subroutine data and control structure down the middle of a subroutine is not safe. Simple division produces results that are inconsistent with uniprocessor runs. The safest way to partition the code is to transfer one block of loops at a time and check the results of each on a test case. Other issues include debugging and performance. Task startup and maintenance (e.g., synchronization) are potentially expensive.

Coded spread spectrum digital transmission system design study

NASA Technical Reports Server (NTRS)

Heller, J. A.; Odenwalder, J. P.; Viterbi, A. J.

1974-01-01

Results are presented of a comprehensive study of the performance of Viterbi-decoded convolutional codes in the presence of nonideal carrier tracking and bit synchronization. A constraint length 7, rate 1/3 convolutional code and parameters suitable for the space shuttle coded communications links are used. Mathematical models are developed and theoretical and simulation results are obtained to determine the tracking and acquisition performance of the system. Pseudorandom sequence spread spectrum techniques are also considered to minimize potential degradation caused by multipath.

Run-time parallelization and scheduling of loops

NASA Technical Reports Server (NTRS)

Saltz, Joel H.; Mirchandaney, Ravi; Crowley, Kay

1990-01-01

Run time methods are studied to automatically parallelize and schedule iterations of a do loop in certain cases, where compile-time information is inadequate. The methods presented involve execution time preprocessing of the loop. At compile-time, these methods set up the framework for performing a loop dependency analysis. At run time, wave fronts of concurrently executable loop iterations are identified. Using this wavefront information, loop iterations are reordered for increased parallelism. Symbolic transformation rules are used to produce: inspector procedures that perform execution time preprocessing and executors or transformed versions of source code loop structures. These transformed loop structures carry out the calculations planned in the inspector procedures. Performance results are presented from experiments conducted on the Encore Multimax. These results illustrate that run time reordering of loop indices can have a significant impact on performance. Furthermore, the overheads associated with this type of reordering are amortized when the loop is executed several times with the same dependency structure.

Derivation of three closed loop kinematic velocity models using normalized quaternion feedback for an autonomous redundant manipulator with application to inverse kinematics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unseren, M.A.

1993-04-01

The report discusses the orientation tracking control problem for a kinematically redundant, autonomous manipulator moving in a three dimensional workspace. The orientation error is derived using the normalized quaternion error method of Ickes, the Luh, Walker, and Paul error method, and a method suggested here utilizing the Rodrigues parameters, all of which are expressed in terms of normalized quaternions. The analytical time derivatives of the orientation errors are determined. The latter, along with the translational velocity error, form a dosed loop kinematic velocity model of the manipulator using normalized quaternion and translational position feedback. An analysis of the singularities associatedmore » with expressing the models in a form suitable for solving the inverse kinematics problem is given. Two redundancy resolution algorithms originally developed using an open loop kinematic velocity model of the manipulator are extended to properly take into account the orientation tracking control problem. This report furnishes the necessary mathematical framework required prior to experimental implementation of the orientation tracking control schemes on the seven axis CESARm research manipulator or on the seven-axis Robotics Research K1207i dexterous manipulator, the latter of which is to be delivered to the Oak Ridge National Laboratory in 1993.« less

A Radiation Chemistry Code Based on the Green's Function of the Diffusion Equation

NASA Technical Reports Server (NTRS)

Plante, Ianik; Wu, Honglu

2014-01-01

Stochastic radiation track structure codes are of great interest for space radiation studies and hadron therapy in medicine. These codes are used for a many purposes, notably for microdosimetry and DNA damage studies. In the last two decades, they were also used with the Independent Reaction Times (IRT) method in the simulation of chemical reactions, to calculate the yield of various radiolytic species produced during the radiolysis of water and in chemical dosimeters. Recently, we have developed a Green's function based code to simulate reversible chemical reactions with an intermediate state, which yielded results in excellent agreement with those obtained by using the IRT method. This code was also used to simulate and the interaction of particles with membrane receptors. We are in the process of including this program for use with the Monte-Carlo track structure code Relativistic Ion Tracks (RITRACKS). This recent addition should greatly expand the capabilities of RITRACKS, notably to simulate DNA damage by both the direct and indirect effect.

Simulations of fully deformed oscillating flux tubes

NASA Astrophysics Data System (ADS)

Karampelas, K.; Van Doorsselaere, T.

2018-02-01

Context. In recent years, a number of numerical studies have been focusing on the significance of the Kelvin-Helmholtz instability in the dynamics of oscillating coronal loops. This process enhances the transfer of energy into smaller scales, and has been connected with heating of coronal loops, when dissipation mechanisms, such as resistivity, are considered. However, the turbulent layer is expected near the outer regions of the loops. Therefore, the effects of wave heating are expected to be confined to the loop's external layers, leaving their denser inner parts without a heating mechanism. Aim. In the current work we aim to study the spatial evolution of wave heating effects from a footpoint driven standing kink wave in a coronal loop. Methods: Using the MPI-AMRVAC code, we performed ideal, three dimensional magnetohydrodynamic simulations of footpoint driven transverse oscillations of a cold, straight coronal flux tube, embedded in a hotter environment. We have also constructed forward models for our simulation using the FoMo code. Results: The developed transverse wave induced Kelvin-Helmholtz (TWIKH) rolls expand throughout the tube cross-section, and cover it entirely. This turbulence significantly alters the initial density profile, leading to a fully deformed cross section. As a consequence, the resistive and viscous heating rate both increase over the entire loop cross section. The resistive heating rate takes its maximum values near the footpoints, while the viscous heating rate at the apex. Conclusions: We conclude that even a monoperiodic driver can spread wave heating over the whole loop cross section, potentially providing a heating source in the inner loop region. Despite the loop's fully deformed structure, forward modelling still shows the structure appearing as a loop. A movie attached to Fig. 1 is available at http://https://www.aanda.org

A wirelessly-powered homecage with animal behavior analysis and closed-loop power control.

PubMed

Yaoyao Jia; Zheyuan Wang; Canales, Daniel; Tinkler, Morgan; Chia-Chun Hsu; Madsen, Teresa E; Mirbozorgi, S Abdollah; Rainnie, Donald; Ghovanloo, Maysam

2016-08-01

This paper presents a new EnerCage-homecage system, EnerCage-HC2, for longitudinal electrophysiology data acquisition experiments on small freely moving animal subjects, such as rodents. EnerCage-HC2 is equipped with multi-coil wireless power transmission (WPT), closed-loop power control, bidirectional data communication via Bluetooth Low Energy (BLE), and Microsoft Kinect® based animal behavior tracking and analysis. The EnerCage-HC2 achieves a homogeneous power transfer efficiency (PTE) of 14% on average, with ~42 mW power delivered to the load (PDL) at a nominal height of 7 cm by the closed-loop power control mechanism. The Microsoft Kinect® behavioral analysis algorithm can not only track the animal position in real-time but also classify 5 different types of rodent behaviors: standstill, walking, grooming, rearing, and rotating. A proof-of-concept in vivo experiment was conducted on two awake freely behaving rats while successfully operating a one-channel stimulator and generating an ethogram.

Adaptive cruise control with stop&go function using the state-dependent nonlinear model predictive control approach.

PubMed

Shakouri, Payman; Ordys, Andrzej; Askari, Mohamad R

2012-09-01

In the design of adaptive cruise control (ACC) system two separate control loops - an outer loop to maintain the safe distance from the vehicle traveling in front and an inner loop to control the brake pedal and throttle opening position - are commonly used. In this paper a different approach is proposed in which a single control loop is utilized. The objective of the distance tracking is incorporated into the single nonlinear model predictive control (NMPC) by extending the original linear time invariant (LTI) models obtained by linearizing the nonlinear dynamic model of the vehicle. This is achieved by introducing the additional states corresponding to the relative distance between leading and following vehicles, and also the velocity of the leading vehicle. Control of the brake and throttle position is implemented by taking the state-dependent approach. The model demonstrates to be more effective in tracking the speed and distance by eliminating the necessity of switching between the two controllers. It also offers smooth variation in brake and throttle controlling signal which subsequently results in a more uniform acceleration of the vehicle. The results of proposed method are compared with other ACC systems using two separate control loops. Furthermore, an ACC simulation results using a stop&go scenario are shown, demonstrating a better fulfillment of the design requirements. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Aviation Human-in-the-Loop Simulation Studies: Experimental Planning, Design, and Data Management

DTIC Science & Technology

2014-01-01

Aviation Human-in-the-Loop Simulation Studies: Experimental Planning, Design , and Data Management Kevin W. Williams1 Bonny Christopher2 Gena...Simulation Studies: Experimental Planning, Design , and Data Management January 2014 6. Performing Organization Code 7. Author(s) 8. Performing...describe the process by which we designed our human-in-the-loop (HITL) simulation study and the methodology used to collect and analyze the results

Theory on the mechanism of distal action of transcription factors: looping of DNA versus tracking along DNA

NASA Astrophysics Data System (ADS)

Murugan, R.

2010-10-01

In this paper, we develop a theory on the mechanism of distal action of the transcription factors, which are bound at their respective cis-regulatory enhancer modules on the promoter-RNA polymerase II (PR) complexes to initiate the transcription event in eukaryotes. We consider both the looping and tracking modes of their distal communication and calculate the mean first passage time that is required for the distal interactions of the complex of enhancer and transcription factor with the PR via both these modes. We further investigate how this mean first passage time is dependent on the length of the DNA segment (L, base-pairs) that connects the cis-regulatory binding site and the respective promoter. When the radius of curvature of this connecting segment of DNA is R that was induced upon binding of the transcription factor at the cis-acting element and RNAPII at the promoter in cis-positions, our calculations indicate that the looping mode of distal action will dominate when L is such that L > 2πR and the tracking mode of distal action will be favored when L < 2πR. The time required for the distal action will be minimum when L = 2πR where the typical value of R for the binding of histones will be R ~ 16 bps and L ~ 102 bps. It seems that the free energy associated with the binding of the transcription factor with its cis-acting element and the distance of this cis-acting element from the corresponding promoter of the gene of interest is negatively correlated. Our results suggest that the looping and tracking modes of distal action are concurrently operating on the transcription activation and the physics that determines the timescales associated with the looping/tracking in the mechanism of action of these transcription factors on the initiation of the transcription event must put a selection pressure on the distribution of the distances of cis-regulatory modules from their respective promoters of the genes. The computational analysis of the upstream sequences of promoters of various genes in the human and mouse genomes for the presence of putative cis-regulatory elements for a set of known transcription factors using the position weight matrices available with the JASPAR database indicates the presence of cis-acting elements with maximum probability at a distance of ~102 bps from the promoters which substantiates our theoretical predictions.

On the suitability of Elekta’s Agility 160 MLC for tracked radiation delivery: closed-loop machine performance

NASA Astrophysics Data System (ADS)

Glitzner, M.; Crijns, S. P. M.; de Senneville, B. Denis; Lagendijk, J. J. W.; Raaymakers, B. W.

2015-03-01

For motion adaptive radiotherapy, dynamic multileaf collimator tracking can be employed to reduce treatment margins by steering the beam according to the organ motion. The Elekta Agility 160 MLC has hitherto not been evaluated for its tracking suitability. Both dosimetric performance and latency are key figures and need to be assessed generically, independent of the used motion sensor. In this paper, we propose the use of harmonic functions directly fed to the MLC to determine its latency during continuous motion. Furthermore, a control variable is extracted from a camera system and fed to the MLC. Using this setup, film dosimetry and subsequent γ statistics are performed, evaluating the response when tracking (MRI)-based physiologic motion in a closed-loop. The delay attributed to the MLC itself was shown to be a minor contributor to the overall feedback chain as compared to the impact of imaging components such as MRI sequences. Delay showed a linear phase behaviour of the MLC employed in continuously dynamic applications, which enables a general MLC-characterization. Using the exemplary feedback chain, dosimetry showed a vast increase in pass rate employing γ statistics. In this early stage, the tracking performance of the Agility using the test bench yielded promising results, making the technique eligible for translation to tracking using clinical imaging modalities.

TRAC-PF1/MOD1 support calculations for the MIST/OTIS program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujita, R.K.; Knight, T.D.

1984-01-01

We are using the Transient Reactor Analysis Code (TRAC), specifically version TRAC-PF1/MOD1, to perform analyses in support of the MultiLoop Integral-System Test (MIST) and the Once-Through Integral-System (OTIS) experiment program. We have analyzed Geradrohr Dampferzeuger Anlage (GERDA) Test 1605AA to benchmark the TRAC-PF1/MOD1 code against phenomena expected to occur in a raised-loop B and W plant during a small-break loss-of-coolant accident (SBLOCA). These results show that the code can calculate both single- and two-phase natural circulation, flow interruption, boiler-condenser-mode (BCM) heat transfer, and primary-system refill in a B and W-type geometry with low-elevation auxiliary feedwater. 19 figures, 7 tables.

The Simpsons program 6-D phase space tracking with acceleration

NASA Astrophysics Data System (ADS)

Machida, S.

1993-12-01

A particle tracking code, Simpsons, in 6-D phase space including energy ramping has been developed to model proton synchrotrons and storage rings. We take time as the independent variable to change machine parameters and diagnose beam quality in a quite similar way as real machines, unlike existing tracking codes for synchrotrons which advance a particle element by element. Arbitrary energy ramping and rf voltage curves as a function of time are read as an input file for defining a machine cycle. The code is used to study beam dynamics with time dependent parameters. Some of the examples from simulations of the Superconducting Super Collider (SSC) boosters are shown.

Track structure in radiation biology: theory and applications.

PubMed

Nikjoo, H; Uehara, S; Wilson, W E; Hoshi, M; Goodhead, D T

1998-04-01

A brief review is presented of the basic concepts in track structure and the relative merit of various theoretical approaches adopted in Monte-Carlo track-structure codes are examined. In the second part of the paper, a formal cluster analysis is introduced to calculate cluster-distance distributions. Total experimental ionization cross-sections were least-square fitted and compared with the calculation by various theoretical methods. Monte-Carlo track-structure code Kurbuc was used to examine and compare the spectrum of the secondary electrons generated by using functions given by Born-Bethe, Jain-Khare, Gryzinsky, Kim-Rudd, Mott and Vriens' theories. The cluster analysis in track structure was carried out using the k-means method and Hartigan algorithm. Data are presented on experimental and calculated total ionization cross-sections: inverse mean free path (IMFP) as a function of electron energy used in Monte-Carlo track-structure codes; the spectrum of secondary electrons generated by different functions for 500 eV primary electrons; cluster analysis for 4 MeV and 20 MeV alpha-particles in terms of the frequency of total cluster energy to the root-mean-square (rms) radius of the cluster and differential distance distributions for a pair of clusters; and finally relative frequency distribution for energy deposited in DNA, single-strand break and double-strand breaks for 10MeV/u protons, alpha-particles and carbon ions. There are a number of Monte-Carlo track-structure codes that have been developed independently and the bench-marking presented in this paper allows a better choice of the theoretical method adopted in a track-structure code to be made. A systematic bench-marking of cross-sections and spectra of the secondary electrons shows differences between the codes at atomic level, but such differences are not significant in biophysical modelling at the macromolecular level. Clustered-damage evaluation shows: that a substantial proportion of dose ( 30%) is deposited by low-energy electrons; the majority of DNA damage lesions are of simple type; the complexity of damage increases with increased LET, while the total yield of strand breaks remains constant; and at high LET values nearly 70% of all double-strand breaks are of complex type.

Spin Rotation of Formalism for Spin Tracking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luccio,A.

The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.

An alternative for presenting interactive dynamic data sets in electronic presentations: a scrollable flash movie loop.

PubMed

Yam, Chun-Shan

2007-11-01

The purpose of this article is to describe an alternative for creating scrollable movie loops for electronic presentations including PowerPoint. The alternative provided in this article enables academic radiologists to present scrollable movie loops in PowerPoint. The scrolling capability is created using Flash ActionScript. A Flash template with the required ActionScript code is provided. Users can simply download the template and follow the step-by-step demonstration to create scrollable movie loops. No previous ActionScript programming knowledge is necessary.

Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon

NASA Astrophysics Data System (ADS)

Trzynadlowski, Bart

The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source code for both models is included. A moment-based model for dislocation loop formation from {311} defects in ion-implanted silicon was also developed and validated against experimental data. Ab initio density functional theory calculations of stacking faults and edge dislocations were performed to extract energies and elastic properties. This allowed the effect of applied stress on the evolution of {311} defects and dislocation loops to be investigated.

TRAC-PF1 code verification with data from the OTIS test facility. [Once-Through Intergral System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Childerson, M.T.; Fujita, R.K.

1985-01-01

A computer code (TRAC-PF1/MOD1) developed for predicting transient thermal and hydraulic integral nuclear steam supply system (NSSS) response was benchmarked. Post-small break loss-of-coolant accident (LOCA) data from a scaled, experimental facility, designated the One-Through Integral System (OTIS), were obtained for the Babcock and Wilcox NSSS and compared to TRAC predictions. The OTIS tests provided a challenging small break LOCA data set for TRAC verification. The major phases of a small break LOCA observed in the OTIS tests included pressurizer draining and loop saturation, intermittent reactor coolant system circulation, boiler-condenser mode, and the initial stages of refill. The TRAC code wasmore » successful in predicting OTIS loop conditions (system pressures and temperatures) after modification of the steam generator model. In particular, the code predicted both pool and auxiliary-feedwater initiated boiler-condenser mode heat transfer.« less

Gravitational and Magnetic Anomaly Inversion Using a Tree-Based Geometry Representation

DTIC Science & Technology

2009-06-01

find successive mini- ized vectors. Throughout this paper, the term iteration refers to a ingle loop through a stage of the global scheme, not...BOX 12211 RESEARCH TRIANGLE PARK NC 27709-2211 5 NAVAL RESEARCH LAB E R FRANCHI CODE 7100 M H ORR CODE 7120 J A BUCARO CODE 7130

Pressurized thermal shock: TEMPEST computer code simulation of thermal mixing in the cold leg and downcomer of a pressurized water reactor. [Creare 61 and 64

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eyler, L.L.; Trent, D.S.

The TEMPEST computer program was used to simulate fluid and thermal mixing in the cold leg and downcomer of a pressurized water reactor under emergency core cooling high-pressure injection (HPI), which is of concern to the pressurized thermal shock (PTS) problem. Application of the code was made in performing an analysis simulation of a full-scale Westinghouse three-loop plant design cold leg and downcomer. Verification/assessment of the code was performed and analysis procedures developed using data from Creare 1/5-scale experimental tests. Results of three simulations are presented. The first is a no-loop-flow case with high-velocity, low-negative-buoyancy HPI in a 1/5-scale modelmore » of a cold leg and downcomer. The second is a no-loop-flow case with low-velocity, high-negative density (modeled with salt water) injection in a 1/5-scale model. Comparison of TEMPEST code predictions with experimental data for these two cases show good agreement. The third simulation is a three-dimensional model of one loop of a full size Westinghouse three-loop plant design. Included in this latter simulation are loop components extending from the steam generator to the reactor vessel and a one-third sector of the vessel downcomer and lower plenum. No data were available for this case. For the Westinghouse plant simulation, thermally coupled conduction heat transfer in structural materials is included. The cold leg pipe and fluid mixing volumes of the primary pump, the stillwell, and the riser to the steam generator are included in the model. In the reactor vessel, the thermal shield, pressure vessel cladding, and pressure vessel wall are thermally coupled to the fluid and thermal mixing in the downcomer. The inlet plenum mixing volume is included in the model. A 10-min (real time) transient beginning at the initiation of HPI is computed to determine temperatures at the beltline of the pressure vessel wall.« less

Geodetic Secor Satellite

DTIC Science & Technology

1974-06-01

retrans- minied modulation signals. A phase-lock loop was used to provide correlation detection, allowing automatic acquisition and phase tracking at...steel strips, 0.5-inch-wide by 0.009-inch-thick, and formed to a 0.75-inch radius. Each antenne -was plated with silver to imprive con- dutivity...Telemetry Requirements k. Phase Detector Output Requirements 1. Primary Power Requirements m. AM Suppression Requirements n. Data Feedback Loop Gain

F-14 modeling study

NASA Technical Reports Server (NTRS)

Levison, W. H.; Baron, S.

1984-01-01

Preliminary results in the application of a closed loop pilot/simulator model to the analysis of some simulator fidelity issues are discussed in the context of an air to air target tracking task. The closed loop model is described briefly. Then, problem simplifications that are employed to reduce computational costs are discussed. Finally, model results showing sensitivity of performance to various assumptions concerning the simulator and/or the pilot are presented.

Experiments and analysis of tunable monolithic 1- μm single-frequency fiber lasers with loop mirror filters

NASA Astrophysics Data System (ADS)

Wang, Qi; Song, Huaqing; Wang, Xingpeng; Wang, Dongdong; Li, Li

2018-03-01

In this paper, we demonstrated thermally tunable 1- μm single-frequency fiber lasers utilizing loop mirror filters (LMFs) with unpumped Yb-doped fibers. The frequency selection and tracking was achieved by combining a fiber Bragg grating (FBG) and a dynamic grating established inside the LMF. The central emission wavelength was at 1064.07 nm with a tuning range of 1.4 nm, and the measured emission linewidth was less than 10 kHz. We also systematically studied the wavelength-tracking thermal stability of the LMF with separate thermal treatment upon the FBG and LMF, respectively. Finally, we presented a selection criterion for the minimum unpumped doped fiber length inside the LMF with experimental verification.

A time domain inverse dynamic method for the end point tracking control of a flexible manipulator

NASA Technical Reports Server (NTRS)

Kwon, Dong-Soo; Book, Wayne J.

1991-01-01

The inverse dynamic equation of a flexible manipulator was solved in the time domain. By dividing the inverse system equation into the causal part and the anticausal part, we calculated the torque and the trajectories of all state variables for a given end point trajectory. The interpretation of this method in the frequency domain was explained in detail using the two-sided Laplace transform and the convolution integral. The open loop control of the inverse dynamic method shows an excellent result in simulation. For real applications, a practical control strategy is proposed by adding a feedback tracking control loop to the inverse dynamic feedforward control, and its good experimental performance is presented.

Smart Braid Feedback for the Closed-Loop Control of Soft Robotic Systems.

PubMed

Felt, Wyatt; Chin, Khai Yi; Remy, C David

2017-09-01

This article experimentally investigates the potential of using flexible, inductance-based contraction sensors in the closed-loop motion control of soft robots. Accurate motion control remains a highly challenging task for soft robotic systems. Precise models of the actuation dynamics and environmental interactions are often unavailable. This renders open-loop control impossible, while closed-loop control suffers from a lack of suitable feedback. Conventional motion sensors, such as linear or rotary encoders, are difficult to adapt to robots that lack discrete mechanical joints. The rigid nature of these sensors runs contrary to the aspirational benefits of soft systems. As truly soft sensor solutions are still in their infancy, motion control of soft robots has so far relied on laboratory-based sensing systems such as motion capture, electromagnetic (EM) tracking, or Fiber Bragg Gratings. In this article, we used embedded flexible sensors known as Smart Braids to sense the contraction of McKibben muscles through changes in inductance. We evaluated closed-loop control on two systems: a revolute joint and a planar, one degree of freedom continuum manipulator. In the revolute joint, our proposed controller compensated for elasticity in the actuator connections. The Smart Braid feedback allowed motion control with a steady-state root-mean-square (RMS) error of [1.5]°. In the continuum manipulator, Smart Braid feedback enabled tracking of the desired tip angle with a steady-state RMS error of [1.25]°. This work demonstrates that Smart Braid sensors can provide accurate position feedback in closed-loop motion control suitable for field applications of soft robotic systems.

Regulated Formation of lncRNA-DNA Hybrids Enables Faster Transcriptional Induction and Environmental Adaptation.

PubMed

Cloutier, Sara C; Wang, Siwen; Ma, Wai Kit; Al Husini, Nadra; Dhoondia, Zuzer; Ansari, Athar; Pascuzzi, Pete E; Tran, Elizabeth J

2016-02-04

Long non-coding (lnc)RNAs, once thought to merely represent noise from imprecise transcription initiation, have now emerged as major regulatory entities in all eukaryotes. In contrast to the rapidly expanding identification of individual lncRNAs, mechanistic characterization has lagged behind. Here we provide evidence that the GAL lncRNAs in the budding yeast S. cerevisiae promote transcriptional induction in trans by formation of lncRNA-DNA hybrids or R-loops. The evolutionarily conserved RNA helicase Dbp2 regulates formation of these R-loops as genomic deletion or nuclear depletion results in accumulation of these structures across the GAL cluster gene promoters and coding regions. Enhanced transcriptional induction is manifested by lncRNA-dependent displacement of the Cyc8 co-repressor and subsequent gene looping, suggesting that these lncRNAs promote induction by altering chromatin architecture. Moreover, the GAL lncRNAs confer a competitive fitness advantage to yeast cells because expression of these non-coding molecules correlates with faster adaptation in response to an environmental switch. Copyright © 2016 Elsevier Inc. All rights reserved.

The foundation of the Melbourne Code Appendices: Announcing a new paradigm for tracking nomenclatural decisions

USDA-ARS?s Scientific Manuscript database

A new expanded digital resource exists for tracking decisions on all nomenclature proposals potentially contributing to Appendices II-VIII of the International Code of Nomenclature. This system owes its origins to the Smithsonian Institution's Proposals and Disposals website created by Dan Nicolson ...

Track-structure simulations for charged particles.

PubMed

Dingfelder, Michael

2012-11-01

Monte Carlo track-structure simulations provide a detailed and accurate picture of radiation transport of charged particles through condensed matter of biological interest. Liquid water serves as a surrogate for soft tissue and is used in most Monte Carlo track-structure codes. Basic theories of radiation transport and track-structure simulations are discussed and differences compared to condensed history codes highlighted. Interaction cross sections for electrons, protons, alpha particles, and light and heavy ions are required input data for track-structure simulations. Different calculation methods, including the plane-wave Born approximation, the dielectric theory, and semi-empirical approaches are presented using liquid water as a target. Low-energy electron transport and light ion transport are discussed as areas of special interest.

Tracking and disturbance rejection of MIMO nonlinear systems with PI controller

NASA Technical Reports Server (NTRS)

Desoer, C. A.; Lin, C. A.

1985-01-01

The tracking and disturbance rejection of a class of MIMO nonlinear systems with a linear proportional plus integral (PI) compensator is studied. Roughly speaking, it is shown that if the given nonlinear plant is exponentially stable and has a strictly increasing dc steady-state I/O map, then a simple PI compensator can be used to yield a stable unity-feedback closed-loop system which asymptotically tracks reference inputs that tend to constant vectors and asymptotically rejects disturbances that tend to constant vectors.

Tracking and disturbance rejection of MIMO nonlinear systems with PI controller

NASA Technical Reports Server (NTRS)

Desoer, C. A.; Lin, C.-A.

1985-01-01

The tracking and disturbance rejection of a class of MIMO nonlinear systems with linear proportional plus integral (PI) compensator is studied. Roughly speaking, it is shown that if the given nonlinear plant is exponentially stable and has a strictly increasing dc steady-state I/O map, then a simple PI compensator can be used to yield a stable unity-feedback closed-loop system which asymptotically tracks reference inputs that tend to constant vectors and asymptotically rejects disturbances that tend to constant vectors.

An All-Digital Fast Tracking Switching Converter with a Programmable Order Loop Controller for Envelope Tracking RF Power Amplifiers

PubMed Central

Anabtawi, Nijad; Ferzli, Rony; Harmanani, Haidar M.

2017-01-01

This paper presents a step down, switched mode power converter for use in multi-standard envelope tracking radio frequency power amplifiers (RFPA). The converter is based on a programmable order sigma delta modulator that can be configured to operate with either 1st, 2nd, 3rd or 4th order loop filters, eliminating the need for a bulky passive output filter. Output ripple, sideband noise and spectral emission requirements of different wireless standards can be met by configuring the modulator’s filter order and converter’s sampling frequency. The proposed converter is entirely digital and is implemented in 14nm bulk CMOS process for post layout verification. For an input voltage of 3.3V, the converter’s output can be regulated to any voltage level from 0.5V to 2.5V, at a nominal switching frequency of 150MHz. It achieves a maximum efficiency of 94% at 1.5 W output power. PMID:28919657

OBSERVATIONAL SIGNATURES OF CORONAL LOOP HEATING AND COOLING DRIVEN BY FOOTPOINT SHUFFLING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahlburg, R. B.; Taylor, B. D.; Einaudi, G.

The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned current sheets: energy is deposited at small scales where heating occurs. Dissipation is nonuniformly distributed so that only a fraction of the coronal mass and volume gets heated at any time. Temperature and density are highly structured at scalesmore » that, in the solar corona, remain observationally unresolved: the plasma of our simulated loop is multithermal, where highly dynamical hotter and cooler plasma strands are scattered throughout the loop at sub-observational scales. Numerical simulations of coronal loops of 50,000 km length and axial magnetic field intensities ranging from 0.01 to 0.04 T are presented. To connect these simulations to observations, we use the computed number densities and temperatures to synthesize the intensities expected in emission lines typically observed with the Extreme Ultraviolet Imaging Spectrometer on Hinode. These intensities are used to compute differential emission measure distributions using the Monte Carlo Markov Chain code, which are very similar to those derived from observations of solar active regions. We conclude that coronal heating is found to be strongly intermittent in space and time, with only small portions of the coronal loop being heated: in fact, at any given time, most of the corona is cooling down.« less

A parallel-vector algorithm for rapid structural analysis on high-performance computers

NASA Technical Reports Server (NTRS)

Storaasli, Olaf O.; Nguyen, Duc T.; Agarwal, Tarun K.

1990-01-01

A fast, accurate Choleski method for the solution of symmetric systems of linear equations is presented. This direct method is based on a variable-band storage scheme and takes advantage of column heights to reduce the number of operations in the Choleski factorization. The method employs parallel computation in the outermost DO-loop and vector computation via the 'loop unrolling' technique in the innermost DO-loop. The method avoids computations with zeros outside the column heights, and as an option, zeros inside the band. The close relationship between Choleski and Gauss elimination methods is examined. The minor changes required to convert the Choleski code to a Gauss code to solve non-positive-definite symmetric systems of equations are identified. The results for two large-scale structural analyses performed on supercomputers, demonstrate the accuracy and speed of the method.

A parallel-vector algorithm for rapid structural analysis on high-performance computers

NASA Technical Reports Server (NTRS)

Storaasli, Olaf O.; Nguyen, Duc T.; Agarwal, Tarun K.

1990-01-01

A fast, accurate Choleski method for the solution of symmetric systems of linear equations is presented. This direct method is based on a variable-band storage scheme and takes advantage of column heights to reduce the number of operations in the Choleski factorization. The method employs parallel computation in the outermost DO-loop and vector computation via the loop unrolling technique in the innermost DO-loop. The method avoids computations with zeros outside the column heights, and as an option, zeros inside the band. The close relationship between Choleski and Gauss elimination methods is examined. The minor changes required to convert the Choleski code to a Gauss code to solve non-positive-definite symmetric systems of equations are identified. The results for two large scale structural analyses performed on supercomputers, demonstrate the accuracy and speed of the method.

Force-Free Magnetic Fields Calculated from Automated Tracing of Coronal Loops with AIA/SDO

NASA Astrophysics Data System (ADS)

Aschwanden, M. J.

2013-12-01

One of the most realistic magnetic field models of the solar corona is a nonlinear force-free field (NLFFF) solution. There exist about a dozen numeric codes that compute NLFFF solutions based on extrapolations of photospheric vector magnetograph data. However, since the photosphere and lower chromosphere is not force-free, a suitable correction has to be applied to the lower boundary condition. Despite of such "pre-processing" corrections, the resulting theoretical magnetic field lines deviate substantially from observed coronal loop geometries. - Here we developed an alternative method that fits an analytical NLFFF approximation to the observed geometry of coronal loops. The 2D coordinates of the geometry of coronal loop structures observed with AIA/SDO are traced with the "Oriented Coronal CUrved Loop Tracing" (OCCULT-2) code, an automated pattern recognition algorithm that has demonstrated the fidelity in loop tracing matching visual perception. A potential magnetic field solution is then derived from a line-of-sight magnetogram observed with HMI/SDO, and an analytical NLFFF approximation is then forward-fitted to the twisted geometry of coronal loops. We demonstrate the performance of this magnetic field modeling method for a number of solar active regions, before and after major flares observed with SDO. The difference of the NLFFF and the potential field energies allows us then to compute the free magnetic energy, which is an upper limit of the energy that is released during a solar flare.

The Murine Norovirus Core Subgenomic RNA Promoter Consists of a Stable Stem-Loop That Can Direct Accurate Initiation of RNA Synthesis

PubMed Central

Yunus, Muhammad Amir; Lin, Xiaoyan; Bailey, Dalan; Karakasiliotis, Ioannis; Chaudhry, Yasmin; Vashist, Surender; Zhang, Guo; Thorne, Lucy; Kao, C. Cheng

2014-01-01

ABSTRACT All members of the Caliciviridae family of viruses produce a subgenomic RNA during infection. The subgenomic RNA typically encodes only the major and minor capsid proteins, but in murine norovirus (MNV), the subgenomic RNA also encodes the VF1 protein, which functions to suppress host innate immune responses. To date, the mechanism of norovirus subgenomic RNA synthesis has not been characterized. We have previously described the presence of an evolutionarily conserved RNA stem-loop structure on the negative-sense RNA, the complementary sequence of which codes for the viral RNA-dependent RNA polymerase (NS7). The conserved stem-loop is positioned 6 nucleotides 3′ of the start site of the subgenomic RNA in all caliciviruses. We demonstrate that the conserved stem-loop is essential for MNV viability. Mutant MNV RNAs with substitutions in the stem-loop replicated poorly until they accumulated mutations that revert to restore the stem-loop sequence and/or structure. The stem-loop sequence functions in a noncoding context, as it was possible to restore the replication of an MNV mutant by introducing an additional copy of the stem-loop between the NS7- and VP1-coding regions. Finally, in vitro biochemical data suggest that the stem-loop sequence is sufficient for the initiation of viral RNA synthesis by the recombinant MNV RNA-dependent RNA polymerase, confirming that the stem-loop forms the core of the norovirus subgenomic promoter. IMPORTANCE Noroviruses are a significant cause of viral gastroenteritis, and it is important to understand the mechanism of norovirus RNA synthesis. Here we describe the identification of an RNA stem-loop structure that functions as the core of the norovirus subgenomic RNA promoter in cells and in vitro. This work provides new insights into the molecular mechanisms of norovirus RNA synthesis and the sequences that determine the recognition of viral RNA by the RNA-dependent RNA polymerase. PMID:25392209

The murine norovirus core subgenomic RNA promoter consists of a stable stem-loop that can direct accurate initiation of RNA synthesis.

PubMed

Yunus, Muhammad Amir; Lin, Xiaoyan; Bailey, Dalan; Karakasiliotis, Ioannis; Chaudhry, Yasmin; Vashist, Surender; Zhang, Guo; Thorne, Lucy; Kao, C Cheng; Goodfellow, Ian

2015-01-15

All members of the Caliciviridae family of viruses produce a subgenomic RNA during infection. The subgenomic RNA typically encodes only the major and minor capsid proteins, but in murine norovirus (MNV), the subgenomic RNA also encodes the VF1 protein, which functions to suppress host innate immune responses. To date, the mechanism of norovirus subgenomic RNA synthesis has not been characterized. We have previously described the presence of an evolutionarily conserved RNA stem-loop structure on the negative-sense RNA, the complementary sequence of which codes for the viral RNA-dependent RNA polymerase (NS7). The conserved stem-loop is positioned 6 nucleotides 3' of the start site of the subgenomic RNA in all caliciviruses. We demonstrate that the conserved stem-loop is essential for MNV viability. Mutant MNV RNAs with substitutions in the stem-loop replicated poorly until they accumulated mutations that revert to restore the stem-loop sequence and/or structure. The stem-loop sequence functions in a noncoding context, as it was possible to restore the replication of an MNV mutant by introducing an additional copy of the stem-loop between the NS7- and VP1-coding regions. Finally, in vitro biochemical data suggest that the stem-loop sequence is sufficient for the initiation of viral RNA synthesis by the recombinant MNV RNA-dependent RNA polymerase, confirming that the stem-loop forms the core of the norovirus subgenomic promoter. Noroviruses are a significant cause of viral gastroenteritis, and it is important to understand the mechanism of norovirus RNA synthesis. Here we describe the identification of an RNA stem-loop structure that functions as the core of the norovirus subgenomic RNA promoter in cells and in vitro. This work provides new insights into the molecular mechanisms of norovirus RNA synthesis and the sequences that determine the recognition of viral RNA by the RNA-dependent RNA polymerase. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Real-time tracking control of electro-hydraulic force servo systems using offline feedback control and adaptive control.

PubMed

Shen, Gang; Zhu, Zhencai; Zhao, Jinsong; Zhu, Weidong; Tang, Yu; Li, Xiang

2017-03-01

This paper focuses on an application of an electro-hydraulic force tracking controller combined with an offline designed feedback controller (ODFC) and an online adaptive compensator in order to improve force tracking performance of an electro-hydraulic force servo system (EHFS). A proportional-integral controller has been employed and a parameter-based force closed-loop transfer function of the EHFS is identified by a continuous system identification algorithm. By taking the identified system model as a nominal plant model, an H ∞ offline design method is employed to establish an optimized feedback controller with consideration of the performance, control efforts, and robustness of the EHFS. In order to overcome the disadvantage of the offline designed controller and cope with the varying dynamics of the EHFS, an online adaptive compensator with a normalized least-mean-square algorithm is cascaded to the force closed-loop system of the EHFS compensated by the ODFC. Some comparative experiments are carried out on a real-time EHFS using an xPC rapid prototype technology, and the proposed controller yields a better force tracking performance improvement. Copyright © 2016. Published by Elsevier Ltd.

Neural network disturbance observer-based distributed finite-time formation tracking control for multiple unmanned helicopters.

PubMed

Wang, Dandan; Zong, Qun; Tian, Bailing; Shao, Shikai; Zhang, Xiuyun; Zhao, Xinyi

2018-02-01

The distributed finite-time formation tracking control problem for multiple unmanned helicopters is investigated in this paper. The control object is to maintain the positions of follower helicopters in formation with external interferences. The helicopter model is divided into a second order outer-loop subsystem and a second order inner-loop subsystem based on multiple-time scale features. Using radial basis function neural network (RBFNN) technique, we first propose a novel finite-time multivariable neural network disturbance observer (FMNNDO) to estimate the external disturbance and model uncertainty, where the neural network (NN) approximation errors can be dynamically compensated by adaptive law. Next, based on FMNNDO, a distributed finite-time formation tracking controller and a finite-time attitude tracking controller are designed using the nonsingular fast terminal sliding mode (NFTSM) method. In order to estimate the second derivative of the virtual desired attitude signal, a novel finite-time sliding mode integral filter is designed. Finally, Lyapunov analysis and multiple-time scale principle ensure the realization of control goal in finite-time. The effectiveness of the proposed FMNNDO and controllers are then verified by numerical simulations. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Ka-band monopulse antenna-pointing systems analysis and simulation

NASA Technical Reports Server (NTRS)

Lo, V. Y.

1996-01-01

NASA 's Deep Space Network (DSN) has been using both 70-m and 34-m reflector antennas to communicate with spacecraft at S-band (2.3 GHz) and X-band (8.45 GHz). To improve the quality of telecommunication and to meet future mission requirements, JPL has been developing 34-m Ka-band (32-GHz) beam waveguide antennas. Presently, antenna pointing operates in either the open-loop mode with blind pointing using navigation predicts or the closed-loop mode with conical scan (conscan). Pointing accuracy under normal conscan operating conditions is in the neighborhood of 5 mdeg. This is acceptable at S- and X-bands, but not enough at Ka-band. Due to the narrow beamwidth at Ka-band, it is important to improve pointing accuracy significantly (approximately 2 mdeg). Monopulse antenna tracking is one scheme being developed to meet the stringent pointing-accuracy requirement at Ka-band. Other advantages of monopulse tracking include low sensitivity to signal amplitude fluctuations as well as single-pulse processing for acquisition and tracking. This article presents system modeling, signal processing, simulation, and implementation of Ka-band monopulse tracking feed for antennas in NASA/DSN ground stations.

Translating MAPGEN to ASPEN for MER

NASA Technical Reports Server (NTRS)

Rabideau, Gregg R.; Knight, Russell L.; Lenda, Matthew; Maldague, Pierre F.

2013-01-01

This software translates MAPGEN (Europa and APGEN) domains to ASPEN, and the resulting domain can be used to perform planning for the Mars Exploration Rover (MER). In other words, this is a conversion of two distinct planning languages (both declarative and procedural) to a third (declarative) planning language in order to solve the problem of faithful translation from mixed-domain representations into the ASPEN Modeling Language. The MAPGEN planning system is an example of a hybrid procedural/declarative system where the advantages of each are leveraged to produce an effective planner/scheduler for MER tactical planning. The adaptation of the planning system (ASPEN) was investigated, and, with some translation, much of the procedural knowledge encoding is amenable to declarative knowledge encoding. The approach was to compose translators from the core languages used for adapting MAGPEN, which consists of Europa and APGEN. Europa is a constraint- based planner/scheduler where domains are encoded using a declarative model. APGEN is also constraint-based, in that it tracks constraints on resources and states and other variables. Domains are encoded in both constraints and code snippets that execute according to a forward sweep through the plan. Europa and APGEN communicate to each other using proxy activities in APGEN that represent constraints and/or tokens in Europa. The composition of a translator from Europa to ASPEN was fairly straightforward, as ASPEN is also a declarative planning system, and the specific uses of Europa for the MER domain matched ASPEN s native encoding fairly closely. On the other hand, translating from APGEN to ASPEN was considerably more involved. On the surface, the types of activities and resources one encodes in APGEN appear to match oneto- one to the activities, state variables, and resources in ASPEN. But, when looking into the definitions of how resources are profiled and activities are expanded, one sees code snippets that access various information available during planning for the moment in time being planned to decide at the time what the appropriate profile or expansion is. APGEN is actually a forward (in time) sweeping discrete event simulator, where the model is composed of code snippets that are artfully interleaved by the engine to produce a plan/schedule. To solve this problem, representative code is simulated as a declarative series of task expansions. Predominantly, three types of procedural models were translated: loops, if statements, and code blocks. Loops and if statements were handled using controlled task expansion, and code blocks were handled using constraint networks that maintained the generation of results based on what the order of execution would be for a procedural representation. One advantage with respect to performance for MAPGEN is the use of APGEN s GUI. This GUI is written in C++ and Motif, and performs very well for large plans.

FAST TRACK COMMUNICATION: A Temperley-Lieb quantum chain with two- and three-site interactions

NASA Astrophysics Data System (ADS)

Ikhlef, Y.; Jacobsen, J. L.; Saleur, H.

2009-07-01

We study the phase diagram of a quantum chain of spin-1/2 particles whose world lines form a dense loop gas with loop weight n. In addition to the usual two-site interaction corresponding to the XXZ spin chain, we introduce a three-site interaction. The resulting model contains a Majumdar-Ghosh-like gapped phase and a new integrable point, which we solve exactly. We also locate a critical line realizing dilute O(n) criticality, without introducing explicit dilution in the loops. Our results have implications for anisotropic spin chains, as well as anyonic quantum chains.

The Melbourne Code Appendices: announcing a new approach for tracking nomenclatural decisions and a analysis of the history of nomenclatural proposals

USDA-ARS?s Scientific Manuscript database

A newly expanded digital resource exists for tracking decisions on all nomenclature proposals potentially contributing to Appendices II-VIII of the International Code of Nomenclature for algae, fungi, and plants. This resource originated with the Smithsonian Institution's Proposals and Disposals web...

B1 field-insensitive transformers for RF-safe transmission lines.

PubMed

Krafft, Axel; Müller, Sven; Umathum, Reiner; Semmler, Wolfhard; Bock, Michael

2006-11-01

Integration of transformers into transmission lines suppresses radiofrequency (RF)-induced heating. New figure-of-eight-shaped transformer coils are compared to conventional loop transformer coils to assess their signal transmission properties and safety profile. The transmission properties of figure-of-eight-shaped transformers were measured and compared to transformers with loop coils. Experiments to quantify the effect of decoupling from the B1 field of the MR system were conducted. Temperature measurements were performed to demonstrate the effective reduction of RF-induced heating. The transformers were investigated during active tracking experiments. Coupling to the B1 field was reduced by 18 dB over conventional loop-shaped transformer coils. MR images showed a significantly reduced artifact for the figure-of-eight- shaped coils generated by local flip-angle amplification. Comparable transmission properties were seen for both transformer types. Temperature measurements showed a maximal temperature increase of 30 K/3.5 K for an unsegmented/segmented cable. With a segmented transmission line a robotic assistance system could be successfully localized using active tracking. The figure-of-eight-shaped transformer design reduces both RF field coupling with the MR system and artifact sizes. Anatomical structure close to the figure-of-eight-shaped transformer may be less obscured as with loop-shaped transformers if these transformers are integrated into e.g. intravascular catheters.

Learning from adaptive neural dynamic surface control of strict-feedback systems.

PubMed

Wang, Min; Wang, Cong

2015-06-01

Learning plays an essential role in autonomous control systems. However, how to achieve learning in the nonstationary environment for nonlinear systems is a challenging problem. In this paper, we present learning method for a class of n th-order strict-feedback systems by adaptive dynamic surface control (DSC) technology, which achieves the human-like ability of learning by doing and doing with learned knowledge. To achieve the learning, this paper first proposes stable adaptive DSC with auxiliary first-order filters, which ensures the boundedness of all the signals in the closed-loop system and the convergence of tracking errors in a finite time. With the help of DSC, the derivative of the filter output variable is used as the neural network (NN) input instead of traditional intermediate variables. As a result, the proposed adaptive DSC method reduces greatly the dimension of NN inputs, especially for high-order systems. After the stable DSC design, we decompose the stable closed-loop system into a series of linear time-varying perturbed subsystems. Using a recursive design, the recurrent property of NN input variables is easily verified since the complexity is overcome using DSC. Subsequently, the partial persistent excitation condition of the radial basis function NN is satisfied. By combining a state transformation, accurate approximations of the closed-loop system dynamics are recursively achieved in a local region along recurrent orbits. Then, the learning control method using the learned knowledge is proposed to achieve the closed-loop stability and the improved control performance. Simulation studies are performed to demonstrate the proposed scheme can not only reuse the learned knowledge to achieve the better control performance with the faster tracking convergence rate and the smaller tracking error but also greatly alleviate the computational burden because of reducing the number and complexity of NN input variables.

Real Time Target Tracking Using Dedicated Vision Hardware

NASA Astrophysics Data System (ADS)

Kambies, Keith; Walsh, Peter

1988-03-01

This paper describes a real-time vision target tracking system developed by Adaptive Automation, Inc. and delivered to NASA's Launch Equipment Test Facility, Kennedy Space Center, Florida. The target tracking system is part of the Robotic Application Development Laboratory (RADL) which was designed to provide NASA with a general purpose robotic research and development test bed for the integration of robot and sensor systems. One of the first RADL system applications is the closing of a position control loop around a six-axis articulated arm industrial robot using a camera and dedicated vision processor as the input sensor so that the robot can locate and track a moving target. The vision system is inside of the loop closure of the robot tracking system, therefore, tight throughput and latency constraints are imposed on the vision system that can only be met with specialized hardware and a concurrent approach to the processing algorithms. State of the art VME based vision boards capable of processing the image at frame rates were used with a real-time, multi-tasking operating system to achieve the performance required. This paper describes the high speed vision based tracking task, the system throughput requirements, the use of dedicated vision hardware architecture, and the implementation design details. Important to the overall philosophy of the complete system was the hierarchical and modular approach applied to all aspects of the system, hardware and software alike, so there is special emphasis placed on this topic in the paper.

Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.

PubMed

Cowen, Stephen L; Nitz, Douglas A

2014-01-01

Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.

Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator

NASA Technical Reports Server (NTRS)

Mileant, A.; Simon, M.

1986-01-01

When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.

A Robust H ∞ Controller for an UAV Flight Control System.

PubMed

López, J; Dormido, R; Dormido, S; Gómez, J P

2015-01-01

The objective of this paper is the implementation and validation of a robust H ∞ controller for an UAV to track all types of manoeuvres in the presence of noisy environment. A robust inner-outer loop strategy is implemented. To design the H ∞ robust controller in the inner loop, H ∞ control methodology is used. The two controllers that conform the outer loop are designed using the H ∞ Loop Shaping technique. The reference vector used in the control architecture formed by vertical velocity, true airspeed, and heading angle, suggests a nontraditional way to pilot the aircraft. The simulation results show that the proposed control scheme works well despite the presence of noise and uncertainties, so the control system satisfies the requirements.

Discriminator aided phase lock acquisition for suppressed carrier signals

NASA Technical Reports Server (NTRS)

Carson, L. M.; Krasin, F. E. (Inventor)

1982-01-01

A discriminator aided technique for acquisition of phase lock to a suppressed carrier signal utilizes a Costas loop which is initially operated open loop and control voltage for its VCXO is derived from a phase detector that compares the VCXO to a reference frequency thus establishing coarse frequency resolution with the received signal. Then the Costas loop is closed with the low-pass filter of the channel having a bandwidth much greater (by a factor of about 10) than in the I channel so that a frequency discriminator effect results to aid carrier resolution. Finally, after carrier acquisition, the Q-channel filter of the Costas loop is switched to a bandwidth substantially equal to that of the I-channel for carrier tracking.

Development of the Code RITRACKS

NASA Technical Reports Server (NTRS)

Plante, Ianik; Cucinotta, Francis A.

2013-01-01

A document discusses the code RITRACKS (Relativistic Ion Tracks), which was developed to simulate heavy ion track structure at the microscopic and nanoscopic scales. It is a Monte-Carlo code that simulates the production of radiolytic species in water, event-by-event, and which may be used to simulate tracks and also to calculate dose in targets and voxels of different sizes. The dose deposited by the radiation can be calculated in nanovolumes (voxels). RITRACKS allows simulation of radiation tracks without the need of extensive knowledge of computer programming or Monte-Carlo simulations. It is installed as a regular application on Windows systems. The main input parameters entered by the user are the type and energy of the ion, the length and size of the irradiated volume, the number of ions impacting the volume, and the number of histories. The simulation can be started after the input parameters are entered in the GUI. The number of each kind of interactions for each track is shown in the result details window. The tracks can be visualized in 3D after the simulation is complete. It is also possible to see the time evolution of the tracks and zoom on specific parts of the tracks. The software RITRACKS can be very useful for radiation scientists to investigate various problems in the fields of radiation physics, radiation chemistry, and radiation biology. For example, it can be used to simulate electron ejection experiments (radiation physics).

Cross Slip of Dislocation Loops in GaN Under Shear

DTIC Science & Technology

2014-03-01

methodology 2.1 Discrete dislocation dynamic ( DDD ) simula- tions In this work, we employ a modified version of the ParaDiS code [15, 16]. First a...plane. 4 Conclusions The cross slip mechanisms of different dislocation loops have been studied via DDD simulations using the type <a> active

Discriminative object tracking via sparse representation and online dictionary learning.

PubMed

Xie, Yuan; Zhang, Wensheng; Li, Cuihua; Lin, Shuyang; Qu, Yanyun; Zhang, Yinghua

2014-04-01

We propose a robust tracking algorithm based on local sparse coding with discriminative dictionary learning and new keypoint matching schema. This algorithm consists of two parts: the local sparse coding with online updated discriminative dictionary for tracking (SOD part), and the keypoint matching refinement for enhancing the tracking performance (KP part). In the SOD part, the local image patches of the target object and background are represented by their sparse codes using an over-complete discriminative dictionary. Such discriminative dictionary, which encodes the information of both the foreground and the background, may provide more discriminative power. Furthermore, in order to adapt the dictionary to the variation of the foreground and background during the tracking, an online learning method is employed to update the dictionary. The KP part utilizes refined keypoint matching schema to improve the performance of the SOD. With the help of sparse representation and online updated discriminative dictionary, the KP part are more robust than the traditional method to reject the incorrect matches and eliminate the outliers. The proposed method is embedded into a Bayesian inference framework for visual tracking. Experimental results on several challenging video sequences demonstrate the effectiveness and robustness of our approach.

A unified perspective on robot control - The energy Lyapunov function approach

NASA Technical Reports Server (NTRS)

Wen, John T.

1990-01-01

A unified framework for the stability analysis of robot tracking control is presented. By using an energy-motivated Lyapunov function candidate, the closed-loop stability is shown for a large family of control laws sharing a common structure of proportional and derivative feedback and a model-based feedforward. The feedforward can be zero, partial or complete linearized dynamics, partial or complete nonlinear dynamics, or linearized or nonlinear dynamics with parameter adaptation. As result, the dichotomous approaches to the robot control problem based on the open-loop linearization and nonlinear Lyapunov analysis are both included in this treatment. Furthermore, quantitative estimates of the trade-offs between different schemes in terms of the tracking performance, steady state error, domain of convergence, realtime computation load and required a prior model information are derived.

Robust Decentralized Nonlinear Control for a Twin Rotor MIMO System

PubMed Central

Belmonte, Lidia María; Morales, Rafael; Fernández-Caballero, Antonio; Somolinos, José Andrés

2016-01-01

This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of the model, which is due to the action-reaction principle originated in the acceleration and deceleration of the motor-propeller groups. The proposed controller is composed of two nested loops that are utilized to achieve stabilization and precise trajectory tracking tasks for the controlled position of the generalized coordinates of the TRMS. The nonlinear internal loop is used to control the electrical dynamics of the platform, and the nonlinear external loop allows the platform to be perfectly stabilized and positioned in space. Finally, we illustrate the theoretical control developments with a set of experiments in order to verify the effectiveness of the proposed nonlinear decentralized feedback controller, in which a comparative study with other controllers is performed, illustrating the excellent performance of the proposed robust decentralized control scheme in both stabilization and trajectory tracking tasks. PMID:27472338

Robust Decentralized Nonlinear Control for a Twin Rotor MIMO System.

PubMed

Belmonte, Lidia María; Morales, Rafael; Fernández-Caballero, Antonio; Somolinos, José Andrés

2016-07-27

This article presents the design of a novel decentralized nonlinear multivariate control scheme for an underactuated, nonlinear and multivariate laboratory helicopter denominated the twin rotor MIMO system (TRMS). The TRMS is characterized by a coupling effect between rotor dynamics and the body of the model, which is due to the action-reaction principle originated in the acceleration and deceleration of the motor-propeller groups. The proposed controller is composed of two nested loops that are utilized to achieve stabilization and precise trajectory tracking tasks for the controlled position of the generalized coordinates of the TRMS. The nonlinear internal loop is used to control the electrical dynamics of the platform, and the nonlinear external loop allows the platform to be perfectly stabilized and positioned in space. Finally, we illustrate the theoretical control developments with a set of experiments in order to verify the effectiveness of the proposed nonlinear decentralized feedback controller, in which a comparative study with other controllers is performed, illustrating the excellent performance of the proposed robust decentralized control scheme in both stabilization and trajectory tracking tasks.

Closed-loop Separation Control Using Oscillatory Flow Excitation

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Juang, Jer-Nan; Raney, David L.; Seifert, Avi; Pack, latunia G.; Brown, Donald E.

2000-01-01

Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.

Microsoft C#.NET program and electromagnetic depth sounding for large loop source

NASA Astrophysics Data System (ADS)

Prabhakar Rao, K.; Ashok Babu, G.

2009-07-01

A program, in the C# (C Sharp) language with Microsoft.NET Framework, is developed to compute the normalized vertical magnetic field of a horizontal rectangular loop source placed on the surface of an n-layered earth. The field can be calculated either inside or outside the loop. Five C# classes with member functions in each class are, designed to compute the kernel, Hankel transform integral, coefficients for cubic spline interpolation between computed values and the normalized vertical magnetic field. The program computes the vertical magnetic field in the frequency domain using the integral expressions evaluated by a combination of straightforward numerical integration and the digital filter technique. The code utilizes different object-oriented programming (OOP) features. It finally computes the amplitude and phase of the normalized vertical magnetic field. The computed results are presented for geometric and parametric soundings. The code is developed in Microsoft.NET visual studio 2003 and uses various system class libraries.

[Study on a wireless energy transmission system for the noninvasive examination micro system inside alimentary tracts].

PubMed

He, Xiu; Yan, Guo-Zheng; Wang, Fu-Min

2008-01-01

A wireless energy transmission system for the MEMS system inside alimentary tracts is reported here in the paper. It consists of an automatic frequency tracking circuit of phase lock loop and phase shift PWM control circuit. Experimental results show that the energy transmission system is capable of automatic frequency-tracking and transmission power-adjusting and has stable received energy.

Observations with the GISMOS Airborne Radio Occultation System

NASA Astrophysics Data System (ADS)

Muradyan, Paytsar; Haase, Jennifer; Garrison, James; Lulich, Tyler; Xie, Feiqin

2010-05-01

The spatial sample density of temperature and moisture profiles derived from the current spaceborne GPS radio occultation (RO) constellation is limited by the number of occultation satellites in operation. With the current RO satellite configuration, only one RO profile per day is typically available in a 160,000 square kilometer area in the mid-latitude and tropics and slightly more in high latitudes. The airborne RO technique, which has the GPS receiver onboard an airplane, offers flexibility and much denser sampling for targeted observation within 400 km of the aircraft, and provides comparable high vertical resolution to that of the spaceborne case. With an airborne system, targeted measurements can be planned in an optimal geometry to study the accuracy of RO measurements in the lower troposphere where strong vertical gradients in moisture might lead to disruption of signal tracking. These dense measurements can also be used to test assimilation techniques of refractivity and lower tropospheric moisture derived from RO data. In February 2008, the GNSS Instrument System for Multistatic and Occultation Sensing (GISMOS), developed at Purdue University, was successfully deployed on the NSF HIAPER aircraft for series of research flights in the Gulf of Mexico coastal region to validate the airborne observing system. During this campaign, occultation observations were collected in conjunction with supplemental radiosonde and dropsonde soundings. RO signals were recorded using side-looking GPS antennas and dual frequency GPS receivers. However, these conventional phase-locked-loop GPS receivers cannot always track the signal in the lower troposphere, where there are rapid phase accelerations caused by highly variable moisture structures. To extend the observations deeper into the atmosphere, the raw signal from occulting satellites is recorded at 10MHz sampling interval by a GPS recording system (GRS). Open-loop (OL) tracking, which replaces the traditional GPS receiver feedback loop using an a priori estimate of Doppler frequency, was implemented in a software receiver and the data was post-processed after the flight. Such an extensive dataset can be of importance in studies aimed at improving signal processing performance for spaceborne as well as airborne RO measurements. We present data from the February 2008 campaign, and show several examples of occultations with clear atmospheric signals in the excess phase and Doppler. Many recordings that were made with conventional receivers descend below 5 km in the atmosphere. With an OL tracking procedure using the data recorded by the GRS, the measurements extended deeper into the atmosphere (~ 2km above surface). Raytracing was used to simulate the atmospheric excess phase profile from a nearby radiosonde sounding. The excess phase profiles acquired with both closed-loop and open-loop tracking show consistent patterns compared to the radiosonde observations.

Optimizing the inner loop of the gravitational force interaction on modern processors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, Michael S

2010-12-08

We have achieved superior performance on multiple generations of the fastest supercomputers in the world with our hashed oct-tree N-body code (HOT), spanning almost two decades and garnering multiple Gordon Bell Prizes for significant achievement in parallel processing. Execution time for our N-body code is largely influenced by the force calculation in the inner loop. Improvements to the inner loop using SSE3 instructions has enabled the calculation of over 200 million gravitational interactions per second per processor on a 2.6 GHz Opteron, for a computational rate of over 7 Gflops in single precision (700/0 of peak). We obtain optimal performancemore » some processors (including the Cell) by decomposing the reciprocal square root function required for a gravitational interaction into a table lookup, Chebychev polynomial interpolation, and Newton-Raphson iteration, using the algorithm of Karp. By unrolling the loop by a factor of six, and using SPU intrinsics to compute on vectors, we obtain performance of over 16 Gflops on a single Cell SPE. Aggregated over the 8 SPEs on a Cell processor, the overall performance is roughly 130 Gflops. In comparison, the ordinary C version of our inner loop only obtains 1.6 Gflops per SPE with the spuxlc compiler.« less

Compensating Unknown Time-Varying Delay in Opto-Electronic Platform Tracking Servo System.

PubMed

Xie, Ruihong; Zhang, Tao; Li, Jiaquan; Dai, Ming

2017-05-09

This paper investigates the problem of compensating miss-distance delay in opto-electronic platform tracking servo system. According to the characteristic of LOS (light-of-sight) motion, we setup the Markovian process model and compensate this unknown time-varying delay by feed-forward forecasting controller based on robust H∞ control. Finally, simulation based on double closed-loop PI (Proportion Integration) control system indicates that the proposed method is effective for compensating unknown time-varying delay. Tracking experiments on the opto-electronic platform indicate that RMS (root-mean-square) error is 1.253 mrad when tracking 10° 0.2 Hz signal.

A real-time sub-μrad laser beam tracking system

NASA Astrophysics Data System (ADS)

Buske, Ivo; Schragner, Ralph; Riede, Wolfgang

2007-10-01

We present a rugged and reliable real-time laser beam tracking system operating with a high speed, high resolution piezo-electric tip/tilt mirror. Characteristics of the piezo mirror and position sensor are investigated. An industrial programmable automation controller is used to develop a real-time digital PID controller. The controller provides a one million field programmable gate array (FPGA) to realize a high closed-loop frequency of 50 kHz. Beam tracking with a root-mean-squared accuracy better than 0.15 μrad has been laboratory confirmed. The system is intended as an add-on module for established mechanical mrad tracking systems.

Sub-μrad laser beam tracking

NASA Astrophysics Data System (ADS)

Buske, Ivo; Riede, Wolfgang

2006-09-01

We compare active optical elements based on different technologies to accomplish the requirements of a 2-dim. fine tracking control system. A cascaded optically and electrically addressable spatial light modulator (OASLM) based on liquid crystals (LC) is used for refractive beam steering. Spatial light modulators provide a controllable phase wedge to generate a beam deflection. Additionally, a tip/tilt mirror approach operating with piezo-electric actuators is investigated. A digital PID controller is implemented for closed-loop control. Beam tracking with a root-mean-squared accuracy of Δα=30 nrad has been laboratory-confirmed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Vishal C.; Gopalakrishnan, Ganesh; Krishnamoorthy, Sriram

The systems resilience research community has developed methods to manually insert additional source-program level assertions to trap errors, and also devised tools to conduct fault injection studies for scalar program codes. In this work, we contribute the first vector oriented LLVM-level fault injector VULFI to help study the effects of faults in vector architectures that are of growing importance, especially for vectorizing loops. Using VULFI, we conduct a resiliency study of nine real-world vector benchmarks using Intel’s AVX and SSE extensions as the target vector instruction sets, and offer the first reported understanding of how faults affect vector instruction sets.more » We take this work further toward automating the insertion of resilience assertions during compilation. This is based on our observation that during intermediate (e.g., LLVM-level) code generation to handle full and partial vectorization, modern compilers exploit (and explicate in their code-documentation) critical invariants. These invariants are turned into error-checking code. We confirm the efficacy of these automatically inserted low-overhead error detectors for vectorized for-loops.« less

An all digital phase locked loop for synchronization of a sinusoidal signal embedded in white Gaussian noise

NASA Technical Reports Server (NTRS)

Reddy, C. P.; Gupta, S. C.

1973-01-01

An all digital phase locked loop which tracks the phase of the incoming sinusoidal signal once per carrier cycle is proposed. The different elements and their functions and the phase lock operation are explained in detail. The nonlinear difference equations which govern the operation of the digital loop when the incoming signal is embedded in white Gaussian noise are derived, and a suitable model is specified. The performance of the digital loop is considered for the synchronization of a sinusoidal signal. For this, the noise term is suitably modelled which allows specification of the output probabilities for the two level quantizer in the loop at any given phase error. The loop filter considered increases the probability of proper phase correction. The phase error states in modulo two-pi forms a finite state Markov chain which enables the calculation of steady state probabilities, RMS phase error, transient response and mean time for cycle skipping.

All-digital signal-processing open-loop fiber-optic gyroscope with enlarged dynamic range.

PubMed

Wang, Qin; Yang, Chuanchuan; Wang, Xinyue; Wang, Ziyu

2013-12-15

We propose and realize a new open-loop fiber-optic gyroscope (FOG) with an all-digital signal-processing (DSP) system where an all-digital phase-locked loop is employed for digital demodulation to eliminate the variation of the source intensity and suppress the bias drift. A Sagnac phase-shift tracking method is proposed to enlarge the dynamic range, and, with its aid, a new open-loop FOG, which can achieve a large dynamic range and high sensitivity at the same time, is realized. The experimental results show that compared with the conventional open-loop FOG with the same fiber coil and optical devices, the proposed FOG reduces the bias instability from 0.259 to 0.018 deg/h, and the angle random walk from 0.031 to 0.006 deg/h(1/2), moreover, enlarges the dynamic range to ±360 deg/s, exceeding the maximum dynamic range ±63 deg/s of the conventional open-loop FOG.

Reading color barcodes using visual snakes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaub, Hanspeter

2004-05-01

Statistical pressure snakes are used to track a mono-color target in an unstructured environment using a video camera. The report discusses an algorithm to extract a bar code signal that is embedded within the target. The target is assumed to be rectangular in shape, with the bar code printed in a slightly different saturation and value in HSV color space. Thus, the visual snake, which primarily weighs hue tracking errors, will not be deterred by the presence of the color bar codes in the target. The bar code is generate with the standard 3 of 9 method. Using this method,more » the numeric bar codes reveal if the target is right-side-up or up-side-down.« less

Experience Paper: Software Engineering and Community Codes Track in ATPESC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubey, Anshu; Riley, Katherine M.

Argonne Training Program in Extreme Scale Computing (ATPESC) was started by the Argonne National Laboratory with the objective of expanding the ranks of better prepared users of high performance computing (HPC) machines. One of the unique aspects of the program was inclusion of software engineering and community codes track. The inclusion was motivated by the observation that the projects with a good scientific and software process were better able to meet their scientific goals. In this paper we present our experience of running the software track from the beginning of the program until now. We discuss the motivations, the reception,more » and the evolution of the track over the years. We welcome discussion and input from the community to enhance the track in ATPESC, and also to facilitate inclusion of similar tracks in other HPC oriented training programs.« less

Physical Models for Particle Tracking Simulations in the RF Gap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shishlo, Andrei P.; Holmes, Jeffrey A.

2015-06-01

This document describes the algorithms that are used in the PyORBIT code to track the particles accelerated in the Radio-Frequency cavities. It gives the mathematical description of the algorithms and the assumptions made in each case. The derived formulas have been implemented in the PyORBIT code. The necessary data for each algorithm are described in detail.

New technologies for advanced three-dimensional optimum shape design in aeronautics

NASA Astrophysics Data System (ADS)

Dervieux, Alain; Lanteri, Stéphane; Malé, Jean-Michel; Marco, Nathalie; Rostaing-Schmidt, Nicole; Stoufflet, Bruno

1999-05-01

The analysis of complex flows around realistic aircraft geometries is becoming more and more predictive. In order to obtain this result, the complexity of flow analysis codes has been constantly increasing, involving more refined fluid models and sophisticated numerical methods. These codes can only run on top computers, exhausting their memory and CPU capabilities. It is, therefore, difficult to introduce best analysis codes in a shape optimization loop: most previous works in the optimum shape design field used only simplified analysis codes. Moreover, as the most popular optimization methods are the gradient-based ones, the more complex the flow solver, the more difficult it is to compute the sensitivity code. However, emerging technologies are contributing to make such an ambitious project, of including a state-of-the-art flow analysis code into an optimisation loop, feasible. Among those technologies, there are three important issues that this paper wishes to address: shape parametrization, automated differentiation and parallel computing. Shape parametrization allows faster optimization by reducing the number of design variable; in this work, it relies on a hierarchical multilevel approach. The sensitivity code can be obtained using automated differentiation. The automated approach is based on software manipulation tools, which allow the differentiation to be quick and the resulting differentiated code to be rather fast and reliable. In addition, the parallel algorithms implemented in this work allow the resulting optimization software to run on increasingly larger geometries. Copyright

Soft-information flipping approach in multi-head multi-track BPMR systems

NASA Astrophysics Data System (ADS)

Warisarn, C.; Busyatras, W.; Myint, L. M. M.

2018-05-01

Inter-track interference is one of the most severe impairments in bit-patterned media recording system. This impairment can be effectively handled by a modulation code and a multi-head array jointly processing multiple tracks; however, such a modulation constraint has never been utilized to improve the soft-information. Therefore, this paper proposes the utilization of modulation codes with an encoded constraint defined by the criteria for soft-information flipping during a three-track data detection process. Moreover, we also investigate the optimal offset position of readheads to provide the most improvement in system performance. The simulation results indicate that the proposed systems with and without position jitter are significantly superior to uncoded systems.

Visual Tracking via Sparse and Local Linear Coding.

PubMed

Wang, Guofeng; Qin, Xueying; Zhong, Fan; Liu, Yue; Li, Hongbo; Peng, Qunsheng; Yang, Ming-Hsuan

2015-11-01

The state search is an important component of any object tracking algorithm. Numerous algorithms have been proposed, but stochastic sampling methods (e.g., particle filters) are arguably one of the most effective approaches. However, the discretization of the state space complicates the search for the precise object location. In this paper, we propose a novel tracking algorithm that extends the state space of particle observations from discrete to continuous. The solution is determined accurately via iterative linear coding between two convex hulls. The algorithm is modeled by an optimal function, which can be efficiently solved by either convex sparse coding or locality constrained linear coding. The algorithm is also very flexible and can be combined with many generic object representations. Thus, we first use sparse representation to achieve an efficient searching mechanism of the algorithm and demonstrate its accuracy. Next, two other object representation models, i.e., least soft-threshold squares and adaptive structural local sparse appearance, are implemented with improved accuracy to demonstrate the flexibility of our algorithm. Qualitative and quantitative experimental results demonstrate that the proposed tracking algorithm performs favorably against the state-of-the-art methods in dynamic scenes.

A Robust H ∞ Controller for an UAV Flight Control System

PubMed Central

López, J.

2015-01-01

The objective of this paper is the implementation and validation of a robust H ∞ controller for an UAV to track all types of manoeuvres in the presence of noisy environment. A robust inner-outer loop strategy is implemented. To design the H ∞ robust controller in the inner loop, H ∞ control methodology is used. The two controllers that conform the outer loop are designed using the H ∞ Loop Shaping technique. The reference vector used in the control architecture formed by vertical velocity, true airspeed, and heading angle, suggests a nontraditional way to pilot the aircraft. The simulation results show that the proposed control scheme works well despite the presence of noise and uncertainties, so the control system satisfies the requirements. PMID:26221622

Does the brain use sliding variables for the control of movements?

PubMed

Hanneton, S; Berthoz, A; Droulez, J; Slotine, J J

1997-12-01

Delays in the transmission of sensory and motor information prevent errors from being instantaneously available to the central nervous system (CNS) and can reduce the stability of a closed-loop control strategy. On the other hand, the use of a pure feedforward control (inverse dynamics) requires a perfect knowledge of the dynamic behavior of the body and of manipulated objects. Sensory feedback is essential both to accommodate unexpected errors and events and to compensate for uncertainties about the dynamics of the body. Experimental observations concerning the control of posture, gaze and limbs have shown that the CNS certainly uses a combination of closed-loop and open-loop control. Feedforward components of movement, such as eye saccades, occur intermittently and present a stereotyped kinematic profile. In visuo-manual tracking tasks, hand movements exhibit velocity peaks that occur intermittently. When a delay or a slow dynamics are inserted in the visuo-manual control loop, intermittent step-and-hold movements appear clearly in the hand trajectory. In this study, we investigated strategies used by human subjects involved in the control of a particular dynamic system. We found strong evidence for substantial nonlinearities in the commands produced. The presence of step-and-hold movements seemed to be the major source of nonlinearities in the control loop. Furthermore, the stereotyped ballistic-like kinematics of these rapid and corrective movements suggests that they were produced in an open-loop way by the CNS. We analyzed the generation of ballistic movements in the light of sliding control theory assuming that they occurred when a sliding variable exceeded a constant threshold. In this framework, a sliding variable is defined as a composite variable (a combination of the instantaneous tracking error and its temporal derivatives) that fulfills a specific stability criterion. Based on this hypothesis and on the assumption of a constant reaction time, the tracking error and its derivatives should be correlated at a particular time lag before movement onset. A peak of correlation was found for a physiologically plausible reaction time, corresponding to a stable composite variable. The direction and amplitude of the ongoing stereotyped movements seemed also be adjusted in order to minimize this variable. These findings suggest that, during visually guided movements, human subjects attempt to minimize such a composite variable and not the instantaneous error. This minimization seems to be obtained by the execution of stereotyped corrective movements.

Cardinal features of involuntary force variability can arise from the closed-loop control of viscoelastic afferented muscles

PubMed Central

Laine, Christopher M.; Valero-Cuevas, Francisco J.

2018-01-01

Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,‘common drive’), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary ‘isometric’ force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease. PMID:29309405

Cardinal features of involuntary force variability can arise from the closed-loop control of viscoelastic afferented muscles.

PubMed

Nagamori, Akira; Laine, Christopher M; Valero-Cuevas, Francisco J

2018-01-01

Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,'common drive'), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary 'isometric' force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease.

Astrometry with A-Track Using Gaia DR1 Catalogue

NASA Astrophysics Data System (ADS)

Kılıç, Yücel; Erece, Orhan; Kaplan, Murat

2018-04-01

In this work, we built all sky index files from Gaia DR1 catalogue for the high-precision astrometric field solution and the precise WCS coordinates of the moving objects. For this, we used build-astrometry-index program as a part of astrometry.net code suit. Additionally, we added astrometry.net's WCS solution tool to our previously developed software which is a fast and robust pipeline for detecting moving objects such as asteroids and comets in sequential FITS images, called A-Track. Moreover, MPC module was added to A-Track. This module is linked to an asteroid database to name the found objects and prepare the MPC file to report the results. After these innovations, we tested a new version of the A-Track code on photometrical data taken by the SI-1100 CCD with 1-meter telescope at TÜBİTAK National Observatory, Antalya. The pipeline can be used to analyse large data archives or daily sequential data. The code is hosted on GitHub under the GNU GPL v3 license.

Evaluation of Grid Modification Methods for On- and Off-Track Sonic Boom Analysis

NASA Technical Reports Server (NTRS)

Nayani, Sudheer N.; Campbell, Richard L.

2013-01-01

Grid modification methods have been under development at NASA to enable better predictions of low boom pressure signatures from supersonic aircraft. As part of this effort, two new codes, Stretched and Sheared Grid - Modified (SSG) and Boom Grid (BG), have been developed in the past year. The CFD results from these codes have been compared with ones from the earlier grid modification codes Stretched and Sheared Grid (SSGRID) and Mach Cone Aligned Prism (MCAP) and also with the available experimental results. NASA's unstructured grid suite of software TetrUSS and the automatic sourcing code AUTOSRC were used for base grid generation and flow solutions. The BG method has been evaluated on three wind tunnel models. Pressure signatures have been obtained up to two body lengths below a Gulfstream aircraft wind tunnel model. Good agreement with the wind tunnel results have been obtained for both on-track and off-track (up to 53 degrees) cases. On-track pressure signatures up to ten body lengths below a Straight Line Segmented Leading Edge (SLSLE) wind tunnel model have been extracted. Good agreement with the wind tunnel results have been obtained. Pressure signatures have been obtained at 1.5 body lengths below a Lockheed Martin aircraft wind tunnel model. Good agreement with the wind tunnel results have been obtained for both on-track and off-track (up to 40 degrees) cases. Grid sensitivity studies have been carried out to investigate any grid size related issues. Methods have been evaluated for fully turbulent, mixed laminar/turbulent and fully laminar flow conditions.

Real-time edge tracking using a tactile sensor

NASA Technical Reports Server (NTRS)

Berger, Alan D.; Volpe, Richard; Khosla, Pradeep K.

1989-01-01

Object recognition through the use of input from multiple sensors is an important aspect of an autonomous manipulation system. In tactile object recognition, it is necessary to determine the location and orientation of object edges and surfaces. A controller is proposed that utilizes a tactile sensor in the feedback loop of a manipulator to track along edges. In the control system, the data from the tactile sensor is first processed to find edges. The parameters of these edges are then used to generate a control signal to a hybrid controller. Theory is presented for tactile edge detection and an edge tracking controller. In addition, experimental verification of the edge tracking controller is presented.

Measurement Techniques for Clock Jitter

NASA Technical Reports Server (NTRS)

Lansdowne, Chatwin; Schlesinger, Adam

2012-01-01

NASA is in the process of modernizing its communications infrastructure to accompany the development of a Crew Exploration Vehicle (CEV) to replace the shuttle. With this effort comes the opportunity to infuse more advanced coded modulation techniques, including low-density parity-check (LDPC) codes that offer greater coding gains than the current capability. However, in order to take full advantage of these codes, the ground segment receiver synchronization loops must be able to operate at a lower signal-to-noise ratio (SNR) than supported by equipment currently in use.

158. ARAIII Reactor building (ARA608) Secondary cooling loop and piping ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

158. ARA-III Reactor building (ARA-608) Secondary cooling loop and piping plan. This drawing was selected as a typical example of piping arrangements within reactor building. Aerojet/general 880-area/GCRE-608-P-16. Date: February 1958. INeel index code no. 063-0608-50-013-102641. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

Digital plus analog output encoder

NASA Technical Reports Server (NTRS)

Hafle, R. S. (Inventor)

1976-01-01

The disclosed encoder is adapted to produce both digital and analog output signals corresponding to the angular position of a rotary shaft, or the position of any other movable member. The digital signals comprise a series of binary signals constituting a multidigit code word which defines the angular position of the shaft with a degree of resolution which depends upon the number of digits in the code word. The basic binary signals are produced by photocells actuated by a series of binary tracks on a code disc or member. The analog signals are in the form of a series of ramp signals which are related in length to the least significant bit of the digital code word. The analog signals are derived from sine and cosine tracks on the code disc.

Two-dimensional magnetohydrodynamic model of emerging magnetic flux in the solar atmosphere

NASA Technical Reports Server (NTRS)

Shibata, K.; Tajima, T.; Steinolfson, R. S.; Matsumoto, R.

1989-01-01

The nonlinear undular mode of the magnetic buoyancy instability in an isolated horizontal magnetic flux embedded in a two-temperature layered atmosphere (solar corona-chromosphere/photosphere) is investigated using a two-dimensional magnetohydrodynamic code. The results show that the flux sheet with beta of about 1 is initially located at the bottom of the photosphere, and that the gas slides down the expanding loop as the instability develops, with the evacuated loop rising as a result of enhanced magnetic buoyancy. The expansion of the magnetic loop in the nonlinear regime displays self-similar behavior. The rise velocity of the magnetic loop in the high chromosphere (10-15 km/s) and the velocity of downflow noted along the loop (30-50 km/s) are consistent with observed values for arch filament systems.

Control Relevant Modeling and Design of Scramjet-Powered Hypersonic Vehicles

NASA Astrophysics Data System (ADS)

Dickeson, Jeffrey James

This report provides an overview of scramjet-powered hypersonic vehicle modeling and control challenges. Such vehicles are characterized by unstable non-minimum phase dynamics with significant coupling and low thrust margins. Recent trends in hypersonic vehicle research are summarized. To illustrate control relevant design issues and tradeoffs, a generic nonlinear 3DOF longitudinal dynamics model capturing aero-elastic-propulsive interactions for wedge-shaped vehicle is used. Limitations of the model are discussed and numerous modifications have been made to address control relevant needs. Two different baseline configurations are examined over a two-stage to orbit ascent trajectory. The report highlights how vehicle level-flight static (trim) and dynamic properties change over the trajectory. Thermal choking constraints are imposed on control system design as a direct consequence of having a finite FER margin. The implication of this state-dependent nonlinear FER margin constraint, the right half plane (RHP) zero, and lightly damped flexible modes, on control system bandwidth (BW) and FPA tracking has been discussed. A control methodology has been proposed that addresses the above dynamics while providing some robustness to modeling uncertainty. Vehicle closure (the ability to fly a trajectory segment subject to constraints) is provided through a proposed vehicle design methodology. The design method attempts to use open loop metrics whenever possible to design the vehicle. The design method is applied to a vehicle/control law closed loop nonlinear simulation for validation. The 3DOF longitudinal modeling results are validated against a newly released NASA 6DOF code.

Combined magnetic and kinetic control of advanced tokamak steady state scenarios based on semi-empirical modelling

NASA Astrophysics Data System (ADS)

Moreau, D.; Artaud, J. F.; Ferron, J. R.; Holcomb, C. T.; Humphreys, D. A.; Liu, F.; Luce, T. C.; Park, J. M.; Prater, R.; Turco, F.; Walker, M. L.

2015-06-01

This paper shows that semi-empirical data-driven models based on a two-time-scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, βN, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off-axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated open-loop data obtained using a rapidly converging plasma transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0D scaling laws and 1.5D ordinary differential equations. The paper discusses the results of closed-loop METIS simulations, using the near-optimal ARTAEMIS control algorithm (Moreau D et al 2013 Nucl. Fusion 53 063020) for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and βN are satisfactorily tracked with a time scale of about 10 s, despite large disturbances applied to the feedforward powers and plasma parameters. The robustness of the control algorithm with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.

A-Track: A new approach for detection of moving objects in FITS images

NASA Astrophysics Data System (ADS)

Atay, T.; Kaplan, M.; Kilic, Y.; Karapinar, N.

2016-10-01

We have developed a fast, open-source, cross-platform pipeline, called A-Track, for detecting the moving objects (asteroids and comets) in sequential telescope images in FITS format. The pipeline is coded in Python 3. The moving objects are detected using a modified line detection algorithm, called MILD. We tested the pipeline on astronomical data acquired by an SI-1100 CCD with a 1-meter telescope. We found that A-Track performs very well in terms of detection efficiency, stability, and processing time. The code is hosted on GitHub under the GNU GPL v3 license.

Interaction of 〈1 0 0〉 dislocation loops with dislocations studied by dislocation dynamics in α-iron

NASA Astrophysics Data System (ADS)

Shi, X. J.; Dupuy, L.; Devincre, B.; Terentyev, D.; Vincent, L.

2015-05-01

Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron under neutron or heavy ion irradiation. As the density and size of these loops increase with radiation dose and temperature, these defects are thought to play a key role in hardening and subsequent embrittlement of iron-based steels. The aim of the present work is to study the pinning strength of the loops on mobile dislocations. Prior to run massive Dislocation Dynamics (DD) simulations involving experimentally representative array of radiation defects and dislocations, the DD code and its parameterization are validated by comparing the individual loop-dislocation reactions with those obtained from direct atomistic Molecular Dynamics (MD) simulations. Several loop-dislocation reaction mechanisms are successfully reproduced as well as the values of the unpinning stress to detach mobile dislocations from the defects.

Man-in-the-loop study of filtering in airborne head tracking tasks

NASA Technical Reports Server (NTRS)

Lifshitz, S.; Merhav, S. J.

1992-01-01

A human-factors study is conducted of problems due to vibrations during the use of a helmet-mounted display (HMD) in tracking tasks whose major factors are target motion and head vibration. A method is proposed for improving aiming accuracy in such tracking tasks on the basis of (1) head-motion measurement and (2) the shifting of the reticle in the HMD in ways that inhibit much of the involuntary apparent motion of the reticle, relative to the target, and the nonvoluntary motion of the teleoperated device. The HMD inherently furnishes the visual feedback required by this scheme.

Flatness-Based Tracking Control and Nonlinear Observer for a Micro Aerial Quadcopter

NASA Astrophysics Data System (ADS)

Rivera, G.; Sawodny, O.

2010-09-01

This paper deals with the design of a nonlinear observer and a differential flat based path tracking controller for a mini aerial quadcopter. Taking into account that only the inertial coordinates and the yaw angle are available for measurements, it is shown, that the system is differentially flat, allowing a systematic design of a nonlinear tracking control in open and closed loop. A nonlinear observer is carried out to estimate the roll and pitch angle as well as all the linear and angular velocities. Finally the performance of the feedback controller and observer are illustrated in a computer simulation.

Adaptive tracking control for a class of stochastic switched systems

NASA Astrophysics Data System (ADS)

Zhang, Hui; Xia, Yuanqing

2018-02-01

The problem of adaptive tracking is considered for a class of stochastic switched systems, in this paper. As preliminaries, the criterion of global asymptotical practical stability in probability is first presented by the aid of common Lyapunov function method. Based on the Lyapunov stability criterion, adaptive backstepping controllers are designed to guarantee that the closed-loop system has a unique global solution, which is globally asymptotically practically stable in probability, and the tracking error in the fourth moment converges to an arbitrarily small neighbourhood of zero. Simulation examples are given to demonstrate the efficiency of the proposed schemes.

Error rate information in attention allocation pilot models

NASA Technical Reports Server (NTRS)

Faulkner, W. H.; Onstott, E. D.

1977-01-01

The Northrop urgency decision pilot model was used in a command tracking task to compare the optimized performance of multiaxis attention allocation pilot models whose urgency functions were (1) based on tracking error alone, and (2) based on both tracking error and error rate. A matrix of system dynamics and command inputs was employed, to create both symmetric and asymmetric two axis compensatory tracking tasks. All tasks were single loop on each axis. Analysis showed that a model that allocates control attention through nonlinear urgency functions using only error information could not achieve performance of the full model whose attention shifting algorithm included both error and error rate terms. Subsequent to this analysis, tracking performance predictions for the full model were verified by piloted flight simulation. Complete model and simulation data are presented.

Neural network robust tracking control with adaptive critic framework for uncertain nonlinear systems.

PubMed

Wang, Ding; Liu, Derong; Zhang, Yun; Li, Hongyi

2018-01-01

In this paper, we aim to tackle the neural robust tracking control problem for a class of nonlinear systems using the adaptive critic technique. The main contribution is that a neural-network-based robust tracking control scheme is established for nonlinear systems involving matched uncertainties. The augmented system considering the tracking error and the reference trajectory is formulated and then addressed under adaptive critic optimal control formulation, where the initial stabilizing controller is not needed. The approximate control law is derived via solving the Hamilton-Jacobi-Bellman equation related to the nominal augmented system, followed by closed-loop stability analysis. The robust tracking control performance is guaranteed theoretically via Lyapunov approach and also verified through simulation illustration. Copyright © 2017 Elsevier Ltd. All rights reserved.

Annual Tropical Cyclone Report 2011

DTIC Science & Technology

2012-05-24

nuclear plant, still reeling after the tsunami disaster just a few months earlier.6 Operations at Kadena Air Base were put on hold 48 with major...conditions. Several of these early to mid-season forming TCs exhibited ―S‖ shaped, looping, or generally erratic tracks, with numerous passages near or over...track errors after -the fact to extend the data base (3) Mean forecast errors for all w arned systems in Northwest Pacific. 120-Hour Along Cross

A numerical study of the thermal stability of low-lying coronal loops

NASA Technical Reports Server (NTRS)

Klimchuk, J. A.; Antiochos, S. K.; Mariska, J. T.

1986-01-01

The nonlinear evolution of loops that are subjected to a variety of small but finite perturbations was studied. Only the low-lying loops are considered. The analysis was performed numerically using a one-dimensional hydrodynamical model developed at the Naval Research Laboratory. The computer codes solve the time-dependent equations for mass, momentum, and energy transport. The primary interest is the active region filaments, hence a geometry appropriate to those structures was considered. The static solutions were subjected to a moderate sized perturbation and allowed to evolve. The results suggest that both hot and cool loops of the geometry considered are thermally stable against amplitude perturbations of all kinds.

Phase-locked loops and their application

NASA Technical Reports Server (NTRS)

Lindsey, W. C. (Editor); Simon, M. K.

1978-01-01

A collection of papers is presented on the characteristics and capabilities of phase-locked loops (PLLs), along with some applications of interest. The discussion covers basic theory (linear and nonlinear); acquisition; threshold; stability; frequency demodulation and detection; tracking; cycle slipping and loss of lock; phase-locked oscillators; operation and performance in the presence of noise; AGC, AFC, and APC circuits and systems; digital PLL; and applications and miscellaneous. With the rapid development of IC technology, PLLs are expected to be used widely in consumer electronics.

Closed-Loop Aeromaneuvering for a Mars Precision Landing

NASA Technical Reports Server (NTRS)

Smith, Roy; Boussalis, Dhemetrios; Hadaegh, Fred Y.

1997-01-01

Controlled aeromaneuvering is considered as a means of achieving a precisely targeted landing on Mars. This paper presents a preliminary study of the control issues. The candidate vehicle is the existing Mars Pathfinder augmented with roll thrusters and a center of mass offset actuator. These allow control of both bank angle and lift force, giving the ability to control the range and cross-track during the aeromaneuvering entry. A preliminary control system structure is proposed and a design simulation illustrates significant targeting improvement under closed-loop control.

Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume

PubMed Central

Jing, Shuai; Zhan, Xingqun; Liu, Baoyu; Chen, Maolin

2016-01-01

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and proves the incompetence of this conventional architecture. Then an adaptive four-state Kalman filter (KF)-based algorithm is introduced to realize the optimization of loop noise bandwidth, which can adaptively regulate its filter gain according to the received signal power and line-of-sight (LOS) dynamics. To overcome the matter of losing lock in weak-signal and high-dynamic environments, an open loop tracking strategy aided by an inertial navigation system (INS) is recommended, and the traditional maximum likelihood estimation (MLE) method is modified in a non-coherent way by reconstructing the likelihood cost function. Furthermore, a typical mission with combined orbital maneuvering and non-maneuvering arcs is taken as a destination object to test the two proposed strategies. Finally, the experiment based on computer simulation identifies the effectiveness of an adaptive four-state KF-based strategy under non-maneuvering conditions and the virtue of INS-assisted methods under maneuvering conditions. PMID:27598164

Weak and Dynamic GNSS Signal Tracking Strategies for Flight Missions in the Space Service Volume.

PubMed

Jing, Shuai; Zhan, Xingqun; Liu, Baoyu; Chen, Maolin

2016-09-02

Weak-signal and high-dynamics are of two primary concerns of space navigation using GNSS (Global Navigation Satellite System) in the space service volume (SSV). The paper firstly defines a reference assumption third-order phase-locked loop (PLL) as the baseline of an onboard GNSS receiver, and proves the incompetence of this conventional architecture. Then an adaptive four-state Kalman filter (KF)-based algorithm is introduced to realize the optimization of loop noise bandwidth, which can adaptively regulate its filter gain according to the received signal power and line-of-sight (LOS) dynamics. To overcome the matter of losing lock in weak-signal and high-dynamic environments, an open loop tracking strategy aided by an inertial navigation system (INS) is recommended, and the traditional maximum likelihood estimation (MLE) method is modified in a non-coherent way by reconstructing the likelihood cost function. Furthermore, a typical mission with combined orbital maneuvering and non-maneuvering arcs is taken as a destination object to test the two proposed strategies. Finally, the experiment based on computer simulation identifies the effectiveness of an adaptive four-state KF-based strategy under non-maneuvering conditions and the virtue of INS-assisted methods under maneuvering conditions.

Horizontal Running Mattress Suture Modified with Intermittent Simple Loops

PubMed Central

Chacon, Anna H; Shiman, Michael I; Strozier, Narissa; Zaiac, Martin N

2013-01-01

Using the combination of a horizontal running mattress suture with intermittent loops achieves both good eversion with the horizontal running mattress plus the ease of removal of the simple loops. This combination technique also avoids the characteristic railroad track marks that result from prolonged non-absorbable suture retention. The unique feature of our technique is the incorporation of one simple running suture after every two runs of the horizontal running mattress suture. To demonstrate its utility, we used the suturing technique on several patients and analyzed the cosmetic outcome with post-operative photographs in comparison to other suturing techniques. In summary, the combination of running horizontal mattress suture with simple intermittent loops demonstrates functional and cosmetic benefits that can be readily taught, comprehended, and employed, leading to desirable aesthetic results and wound edge eversion. PMID:23723610

A high-speed, tunable silicon photonic ring modulator integrated with ultra-efficient active wavelength control.

PubMed

Zheng, Xuezhe; Chang, Eric; Amberg, Philip; Shubin, Ivan; Lexau, Jon; Liu, Frankie; Thacker, Hiren; Djordjevic, Stevan S; Lin, Shiyun; Luo, Ying; Yao, Jin; Lee, Jin-Hyoung; Raj, Kannan; Ho, Ron; Cunningham, John E; Krishnamoorthy, Ashok V

2014-05-19

We report the first complete 10G silicon photonic ring modulator with integrated ultra-efficient CMOS driver and closed-loop wavelength control. A selective substrate removal technique was used to improve the ring tuning efficiency. Limited by the thermal tuner driver output power, a maximum open-loop tuning range of about 4.5nm was measured with about 14mW of total tuning power including the heater driver circuit power consumption. Stable wavelength locking was achieved with a low-power mixed-signal closed-loop wavelength controller. An active wavelength tracking range of > 500GHz was demonstrated with controller energy cost of only 20fJ/bit.

Effects of maneuver dynamics on drag polars of the X-29A forward-swept-wing aircraft with automatic wing camber control

NASA Technical Reports Server (NTRS)

Hicks, John W.; Moulton, Bryan J.

1988-01-01

The camber control loop of the X-29A FSW aircraft was designed to furnish the optimum L/D for trimmed, stabilized flight. A marked difference was noted between automatic wing camber control loop behavior in dynamic maneuvers and in stabilized flight conditions, which in turn affected subsonic aerodynamic performance. The degree of drag level increase was a direct function of maneuver rate. Attention is given to the aircraft flight drag polar effects of maneuver dynamics in light of wing camber control loop schedule. The effect of changing camber scheduling to better track the optimum automatic camber control L/D schedule is discussed.

Supersymmetric and non-supersymmetric models without catastrophic Goldstone bosons

NASA Astrophysics Data System (ADS)

Braathen, Johannes; Goodsell, Mark D.; Staub, Florian

2017-11-01

The calculation of the Higgs mass in general renormalisable field theories has been plagued by the so-called "Goldstone Boson Catastrophe," where light (would-be) Goldstone bosons give infra-red divergent loop integrals. In supersymmetric models, previous approaches included a workaround that ameliorated the problem for most, but not all, parameter space regions; while giving divergent results everywhere for non-supersymmetric models! We present an implementation of a general solution to the problem in the public code SARAH, along with new calculations of some necessary loop integrals and generic expressions. We discuss the validation of our code in the Standard Model, where we find remarkable agreement with the known results. We then show new applications in Split SUSY, the NMSSM, the Two-Higgs-Doublet Model, and the Georgi-Machacek model. In particular, we take some first steps to exploring where the habit of using tree-level mass relations in non-supersymmetric models breaks down, and show that the loop corrections usually become very large well before naive perturbativity bounds are reached.

Closed-loop thrust and pressure profile throttling of a nitrous oxide/hydroxyl-terminated polybutadiene hybrid rocket motor

NASA Astrophysics Data System (ADS)

Peterson, Zachary W.

Hybrid motors that employ non-toxic, non-explosive components with a liquid oxidizer and a solid hydrocarbon fuel grain have inherently safe operating characteristics. The inherent safety of hybrid rocket motors offers the potential to greatly reduce overall operating costs. Another key advantage of hybrid rocket motors is the potential for in-flight shutdown, restart, and throttle by controlling the pressure drop between the oxidizer tank and the injector. This research designed, developed, and ground tested a closed-loop throttle controller for a hybrid rocket motor using nitrous oxide and hydroxyl-terminated polybutadiene as propellants. The research simultaneously developed closed-loop throttle algorithms and lab scale motor hardware to evaluate the fidelity of the throttle simulations and algorithms. Initial open-loop motor tests were performed to better classify system parameters and to validate motor performance values. Deep-throttle open-loop tests evaluated limits of stable thrust that can be achieved on the test hardware. Open-loop tests demonstrated the ability to throttle the motor to less than 10% of maximum thrust with little reduction in effective specific impulse and acoustical stability. Following the open-loop development, closed-loop, hardware-in-the-loop tests were performed. The closed-loop controller successfully tracked prescribed step and ramp command profiles with a high degree of fidelity. Steady-state accuracy was greatly improved over uncontrolled thrust.

Dynamics of a multi-thermal loop in the solar corona

NASA Astrophysics Data System (ADS)

Nisticò, G.; Anfinogentov, S.; Nakariakov, V. M.

2014-10-01

Context. We present an observation of a long-living multi-thermal coronal loop, visible in different extreme ultra-violet wavebands of SDO/AIA in a quiet-Sun region close to the western solar limb. Aims: Analysis of persistent kink displacements of the loop seen in different bandpasses that correspond to different temperatures of the plasma allows sub-resolution structuring of the loop to be revealed. Methods: A vertically oriented slit is taken at the loop top, and time-distance maps are made from it. Loop displacements in time-distance maps are automatically tracked with the Gaussian fitting technique and fitted with a sinusoidal function that is "guessed". Wavelet transforms are further used in order to quantify the periodicity variation in time of the kink oscillations. Results: The loop strands are found to oscillate with the periods ranging between 3 and 15 min. The oscillations are observed in intermittent regime with temporal changes in the period and amplitude. The oscillations are different at three analysed wavelengths. Conclusions: This finding suggests that the loop-like threads seen at different wavelengths are not co-spatial, hence that the loop consists of several multi-thermal strands. The detected irregularity of the oscillations can be associated with a stochastic driver acting at the footpoints of the loop. A movie associated to Fig. 1 is available in electronic form at http://www.aanda.org

Quantization-Based Adaptive Actor-Critic Tracking Control With Tracking Error Constraints.

PubMed

Fan, Quan-Yong; Yang, Guang-Hong; Ye, Dan

2018-04-01

In this paper, the problem of adaptive actor-critic (AC) tracking control is investigated for a class of continuous-time nonlinear systems with unknown nonlinearities and quantized inputs. Different from the existing results based on reinforcement learning, the tracking error constraints are considered and new critic functions are constructed to improve the performance further. To ensure that the tracking errors keep within the predefined time-varying boundaries, a tracking error transformation technique is used to constitute an augmented error system. Specific critic functions, rather than the long-term cost function, are introduced to supervise the tracking performance and tune the weights of the AC neural networks (NNs). A novel adaptive controller with a special structure is designed to reduce the effect of the NN reconstruction errors, input quantization, and disturbances. Based on the Lyapunov stability theory, the boundedness of the closed-loop signals and the desired tracking performance can be guaranteed. Finally, simulations on two connected inverted pendulums are given to illustrate the effectiveness of the proposed method.

The complete mitochondrial genome and its remarkable secondary structure for a stonefly Acroneuria hainana Wu (Insecta: Plecoptera, Perlidae).

PubMed

Huang, Mingchao; Wang, Yuyu; Liu, Xingyue; Li, Weihai; Kang, Zehui; Wang, Kai; Li, Xuankun; Yang, Ding

2015-02-15

The Plecoptera (stoneflies) is a hemimetabolous order of insects, whose larvae are usually used as indicators for fresh water biomonitoring. Herein, we describe the complete mitochondrial (mt) genome of a stonefly species, namely Acroneuria hainana Wu belonging to the family Perlidae. This mt genome contains 13 PCGs, 22 tRNA-coding genes and 2 rRNA-coding genes that are conserved in most insect mt genomes, and it also has the identical gene order with the insect ancestral gene order. However, there are three special initiation codons of ND1, ND5 and COI in PCGs: TTG, GTG and CGA, coding for L, V and R, respectively. Additionally, the 899-bp control region, with 73.30% A+T content, has two long repeated sequences which are found at the 3'-end closing to the tRNA(Ile) gene. Both of them can be folded into a stem-loop structure, whose adjacent upstream and downstream sequences can be also folded into stem-loop structures. It is presumed that the four special structures in series could be associated with the D-loop replication. It might be able to adjust the replication speed of two replicate directions. Copyright © 2014 Elsevier B.V. All rights reserved.

Alfven resonance mode conversion in the Phaedrus-T current drive experiments: Modelling and density fluctuations measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukovic, M.; Harper, M.; Breun, R.

1995-12-31

Current drive experiments on the Phaedrus-T tokamak performed with a low field side two-strap fast wave antenna at frequencies below {omega}{sub cH} show loop volt drops of up to 30% with strap phasing (0, {pi}/2). RF induced density fluctuations in the plasma core have also been observed with a microwave reflectometer. It is believed that they are caused by kinetic Alfven waves generated by mode conversion of fast waves at the Alfven resonance. Correlation of the observed density fluctuations with the magnitude of the {Delta}V{sub loop} suggest that the {Delta}V{sub loop} is attributable to current drive/heating due to mode convertedmore » kinetic Alfven waves. The toroidal cold plasma wave code LION is used to model the Alfven resonance mode conversion surfaces in the experiments while the cylindrical hot plasma kinetic wave code ISMENE is used to model the behavior of kinetic Alfven waves at the Alfven resonance location. Initial results obtained from limited density, magnetic field, antenna phase, and impurity scans show good agreement between the RF induced density fluctuations and the predicted behavior of the kinetic Alfven waves. Detailed comparisons between the density fluctuations and the code predictions are presented.« less

Sum of the Magnitude for Hard Decision Decoding Algorithm Based on Loop Update Detection.

PubMed

Meng, Jiahui; Zhao, Danfeng; Tian, Hai; Zhang, Liang

2018-01-15

In order to improve the performance of non-binary low-density parity check codes (LDPC) hard decision decoding algorithm and to reduce the complexity of decoding, a sum of the magnitude for hard decision decoding algorithm based on loop update detection is proposed. This will also ensure the reliability, stability and high transmission rate of 5G mobile communication. The algorithm is based on the hard decision decoding algorithm (HDA) and uses the soft information from the channel to calculate the reliability, while the sum of the variable nodes' (VN) magnitude is excluded for computing the reliability of the parity checks. At the same time, the reliability information of the variable node is considered and the loop update detection algorithm is introduced. The bit corresponding to the error code word is flipped multiple times, before this is searched in the order of most likely error probability to finally find the correct code word. Simulation results show that the performance of one of the improved schemes is better than the weighted symbol flipping (WSF) algorithm under different hexadecimal numbers by about 2.2 dB and 2.35 dB at the bit error rate (BER) of 10 -5 over an additive white Gaussian noise (AWGN) channel, respectively. Furthermore, the average number of decoding iterations is significantly reduced.

Retargeting of existing FORTRAN program and development of parallel compilers

NASA Technical Reports Server (NTRS)

Agrawal, Dharma P.

1988-01-01

The software models used in implementing the parallelizing compiler for the B-HIVE multiprocessor system are described. The various models and strategies used in the compiler development are: flexible granularity model, which allows a compromise between two extreme granularity models; communication model, which is capable of precisely describing the interprocessor communication timings and patterns; loop type detection strategy, which identifies different types of loops; critical path with coloring scheme, which is a versatile scheduling strategy for any multicomputer with some associated communication costs; and loop allocation strategy, which realizes optimum overlapped operations between computation and communication of the system. Using these models, several sample routines of the AIR3D package are examined and tested. It may be noted that automatically generated codes are highly parallelized to provide the maximized degree of parallelism, obtaining the speedup up to a 28 to 32-processor system. A comparison of parallel codes for both the existing and proposed communication model, is performed and the corresponding expected speedup factors are obtained. The experimentation shows that the B-HIVE compiler produces more efficient codes than existing techniques. Work is progressing well in completing the final phase of the compiler. Numerous enhancements are needed to improve the capabilities of the parallelizing compiler.

OpenGeoSys-GEMS: Hybrid parallelization of a reactive transport code with MPI and threads

NASA Astrophysics Data System (ADS)

Kosakowski, G.; Kulik, D. A.; Shao, H.

2012-04-01

OpenGeoSys-GEMS is a generic purpose reactive transport code based on the operator splitting approach. The code couples the Finite-Element groundwater flow and multi-species transport modules of the OpenGeoSys (OGS) project (http://www.ufz.de/index.php?en=18345) with the GEM-Selektor research package to model thermodynamic equilibrium of aquatic (geo)chemical systems utilizing the Gibbs Energy Minimization approach (http://gems.web.psi.ch/). The combination of OGS and the GEM-Selektor kernel (GEMS3K) is highly flexible due to the object-oriented modular code structures and the well defined (memory based) data exchange modules. Like other reactive transport codes, the practical applicability of OGS-GEMS is often hampered by the long calculation time and large memory requirements. • For realistic geochemical systems which might include dozens of mineral phases and several (non-ideal) solid solutions the time needed to solve the chemical system with GEMS3K may increase exceptionally. • The codes are coupled in a sequential non-iterative loop. In order to keep the accuracy, the time step size is restricted. In combination with a fine spatial discretization the time step size may become very small which increases calculation times drastically even for small 1D problems. • The current version of OGS is not optimized for memory use and the MPI version of OGS does not distribute data between nodes. Even for moderately small 2D problems the number of MPI processes that fit into memory of up-to-date workstations or HPC hardware is limited. One strategy to overcome the above mentioned restrictions of OGS-GEMS is to parallelize the coupled code. For OGS a parallelized version already exists. It is based on a domain decomposition method implemented with MPI and provides a parallel solver for fluid and mass transport processes. In the coupled code, after solving fluid flow and solute transport, geochemical calculations are done in form of a central loop over all finite element nodes with calls to GEMS3K and consecutive calculations of changed material parameters. In a first step the existing MPI implementation was utilized to parallelize this loop. Calculations were split between the MPI processes and afterwards data was synchronized by using MPI communication routines. Furthermore, multi-threaded calculation of the loop was implemented with help of the boost thread library (http://www.boost.org). This implementation provides a flexible environment to distribute calculations between several threads. For each MPI process at least one and up to several dozens of worker threads are spawned. These threads do not replicate the complete OGS-GEM data structure and use only a limited amount of memory. Calculation of the central geochemical loop is shared between all threads. Synchronization between the threads is done by barrier commands. The overall number of local threads times MPI processes should match the number of available computing nodes. The combination of multi-threading and MPI provides an effective and flexible environment to speed up OGS-GEMS calculations while limiting the required memory use. Test calculations on different hardware show that for certain types of applications tremendous speedups are possible.

Interplex modulation and a suppressed-carrier tracking loop for coherent communications systems

NASA Technical Reports Server (NTRS)

Butman, S.; Timor, U.

1974-01-01

Simple addition to hardware and new mode of operation of transmitter and receiver in coherent, PCM/PSK/PM configuration greatly improves channel efficiency. Procedure reduces amount of power lost to intermodulation products.

An Eye-Tracking Study of How Color Coding Affects Multimedia Learning

ERIC Educational Resources Information Center

Ozcelik, Erol; Karakus, Turkan; Kursun, Engin; Cagiltay, Kursat

2009-01-01

Color coding has been proposed to promote more effective learning. However, insufficient evidence currently exists to show how color coding leads to better learning. The goal of this study was to investigate the underlying cause of the color coding effect by utilizing eye movement data. Fifty-two participants studied either a color-coded or…

Integrating Geochemical Reactions with a Particle-Tracking Approach to Simulate Nitrogen Transport and Transformation in Aquifers

NASA Astrophysics Data System (ADS)

Cui, Z.; Welty, C.; Maxwell, R. M.

2011-12-01

Lagrangian, particle-tracking models are commonly used to simulate solute advection and dispersion in aquifers. They are computationally efficient and suffer from much less numerical dispersion than grid-based techniques, especially in heterogeneous and advectively-dominated systems. Although particle-tracking models are capable of simulating geochemical reactions, these reactions are often simplified to first-order decay and/or linear, first-order kinetics. Nitrogen transport and transformation in aquifers involves both biodegradation and higher-order geochemical reactions. In order to take advantage of the particle-tracking approach, we have enhanced an existing particle-tracking code SLIM-FAST, to simulate nitrogen transport and transformation in aquifers. The approach we are taking is a hybrid one: the reactive multispecies transport process is operator split into two steps: (1) the physical movement of the particles including the attachment/detachment to solid surfaces, which is modeled by a Lagrangian random-walk algorithm; and (2) multispecies reactions including biodegradation are modeled by coupling multiple Monod equations with other geochemical reactions. The coupled reaction system is solved by an ordinary differential equation solver. In order to solve the coupled system of equations, after step 1, the particles are converted to grid-based concentrations based on the mass and position of the particles, and after step 2 the newly calculated concentration values are mapped back to particles. The enhanced particle-tracking code is capable of simulating subsurface nitrogen transport and transformation in a three-dimensional domain with variably saturated conditions. Potential application of the enhanced code is to simulate subsurface nitrogen loading to the Chesapeake Bay and its tributaries. Implementation details, verification results of the enhanced code with one-dimensional analytical solutions and other existing numerical models will be presented in addition to a discussion of implementation challenges.

Effective declutter of complex flight displays using stereoptic 3-D cueing

NASA Technical Reports Server (NTRS)

Parrish, Russell V.; Williams, Steven P.; Nold, Dean E.

1994-01-01

The application of stereo technology to new, integrated pictorial display formats has been effective in situational awareness enhancements, and stereo has been postulated to be effective for the declutter of complex informational displays. This paper reports a full-factorial workstation experiment performed to verify the potential benefits of stereo cueing for the declutter function in a simulated tracking task. The experimental symbology was designed similar to that of a conventional flight director, although the format was an intentionally confused presentation that resulted in a very cluttered dynamic display. The subject's task was to use a hand controller to keep a tracking symbol, an 'X', on top of a target symbol, another X, which was being randomly driven. In the basic tracking task, both the target symbol and the tracking symbol were presented as red X's. The presence of color coding was used to provide some declutter, thus making the task more reasonable to perform. For this condition, the target symbol was coded red, and the tracking symbol was coded blue. Noise conditions, or additional clutter, were provided by the inclusion of randomly moving, differently colored X symbols. Stereo depth, which was hypothesized to declutter the display, was utilized by placing any noise in a plane in front of the display monitor, the tracking symbol at screen depth, and the target symbol behind the screen. The results from analyzing the performances of eight subjects revealed that the stereo presentation effectively offsets the cluttering effects of both the noise and the absence of color coding. The potential of stereo cueing to declutter complex informational displays has therefore been verified; this ability to declutter is an additional benefit from the application of stereoptic cueing to pictorial flight displays.

Revised Extended Grid Library

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martz, Roger L.

The Revised Eolus Grid Library (REGL) is a mesh-tracking library that was developed for use with the MCNP6TM computer code so that (radiation) particles can track on an unstructured mesh. The unstructured mesh is a finite element representation of any geometric solid model created with a state-of-the-art CAE/CAD tool. The mesh-tracking library is written using modern Fortran and programming standards; the library is Fortran 2003 compliant. The library was created with a defined application programmer interface (API) so that it could easily integrate with other particle tracking/transport codes. The library does not handle parallel processing via the message passing interfacemore » (mpi), but has been used successfully where the host code handles the mpi calls. The library is thread-safe and supports the OpenMP paradigm. As a library, all features are available through the API and overall a tight coupling between it and the host code is required. Features of the library are summarized with the following list: Can accommodate first and second order 4, 5, and 6-sided polyhedra; any combination of element types may appear in a single geometry model; parts may not contain tetrahedra mixed with other element types; pentahedra and hexahedra can be together in the same part; robust handling of overlaps and gaps; tracks element-to-element to produce path length results at the element level; finds element numbers for a given mesh location; finds intersection points on element faces for the particle tracks; produce a data file for post processing results analysis; reads Abaqus .inp input (ASCII) files to obtain information for the global mesh-model; supports parallel input processing via mpi; and support parallel particle transport by both mpi and OpenMP.« less

Automatic weld torch guidance control system

NASA Technical Reports Server (NTRS)

Smaith, H. E.; Wall, W. A.; Burns, M. R., Jr.

1982-01-01

A highly reliable, fully digital, closed circuit television optical, type automatic weld seam tracking control system was developed. This automatic tracking equipment is used to reduce weld tooling costs and increase overall automatic welding reliability. The system utilizes a charge injection device digital camera which as 60,512 inidividual pixels as the light sensing elements. Through conventional scanning means, each pixel in the focal plane is sequentially scanned, the light level signal digitized, and an 8-bit word transmitted to scratch pad memory. From memory, the microprocessor performs an analysis of the digital signal and computes the tracking error. Lastly, the corrective signal is transmitted to a cross seam actuator digital drive motor controller to complete the closed loop, feedback, tracking system. This weld seam tracking control system is capable of a tracking accuracy of + or - 0.2 mm, or better. As configured, the system is applicable to square butt, V-groove, and lap joint weldments.

Center for Hybrid Communications and Networks

DTIC Science & Technology

2016-09-08

Transmission loop experimental setup to study coded modulation and turbo equalization for metro and long-haul networks, 3) Experimental setup for...undertaking fundamental studies of QKD systems that use ( hyper -) entangled photon pairs or weak coherent states (WCS) as the quantum resources...onlinelibrary.wiley.com/doi/10.1002/047134608X.W8291/abstract] The real-time scope and AWG are also used in fiber-optics transmission loop experiment we

Performance improvement of a binary quantized all-digital phase-locked loop with a new aided-acquisition technique

NASA Astrophysics Data System (ADS)

Sandoz, J.-P.; Steenaart, W.

1984-12-01

The nonuniform sampling digital phase-locked loop (DPLL) with sequential loop filter, in which the correction sizes are controlled by the accumulated differences of two additional phase comparators, is graphically analyzed. In the absence of noise and frequency drift, the analysis gives some physical insight into the acquisition and tracking behavior. Taking noise into account, a mathematical model is derived and a random walk technique is applied to evaluate the rms phase error and the mean acquisition time. Experimental results confirm the appropriate simplifying hypotheses used in the numerical analysis. Two related performance measures defined in terms of the rms phase error and the acquisition time for a given SNR are used. These measures provide a common basis for comparing different digital loops and, to a limited extent, also with a first-order linear loop. Finally, the behavior of a modified DPLL under frequency deviation in the presence of Gaussian noise is tested experimentally and by computer simulation.

Does Mckuer's Law Hold for Heart Rate Control via Biofeedback Display?

NASA Technical Reports Server (NTRS)

Courter, B. J.; Jex, H. R.

1984-01-01

Some persons can control their pulse rate with the aid of a biofeedback display. If the biofeedback display is modified to show the error between a command pulse-rate and the measured rate, a compensatory (error correcting) heart rate tracking control loop can be created. The dynamic response characteristics of this control loop when subjected to step and quasi-random disturbances were measured. The control loop includes a beat-to-beat cardiotachmeter differenced with a forcing function from a quasi-random input generator; the resulting error pulse-rate is displayed as feedback. The subject acts to null the displayed pulse-rate error, thereby closing a compensatory control loop. McRuer's Law should hold for this case. A few subjects already skilled in voluntary pulse-rate control were tested for heart-rate control response. Control-law properties are derived, such as: crossover frequency, stability margins, and closed-loop bandwidth. These are evaluated for a range of forcing functions and for step as well as random disturbances.

Noncoherent Symbol Synchronization Techniques

NASA Technical Reports Server (NTRS)

Simon, Marvin

2005-01-01

Traditional methods for establishing symbol synchronization (sync) in digital communication receivers assume that carrier sync has already been established, i.e., the problem is addressed at the baseband level assuming that a 'perfect' estimate of carrier phase is available. We refer to this approach as coherent symbol sync. Since, for NRZ signaling, a suppressed carrier sync loop such as an I-Q Costas loop includes integrate-and-dump (I and D) filters in its in-phase (1) and quadrature (Q) arms, the traditional approach is to first track the carrier in the absence of symbol sync information, then feed back the symbol sync estimate to these filters, and then iterate between the two to a desirable operating level In this paper, we revisit the symbol sync problem by examining methods for obtaining such sync in the absence of carrier phase information, i.e., so-called noncoherent symbol sync loops. We compare the performance of these loops with that of a well-known coherent symbol sync loop and examine the conditions under which one is preferable over the other.

Evidence-Based Reading and Writing Assessment for Dyslexia in Adolescents and Young Adults

PubMed Central

Nielsen, Kathleen; Abbott, Robert; Griffin, Whitney; Lott, Joe; Raskind, Wendy; Berninger, Virginia W.

2016-01-01

The same working memory and reading and writing achievement phenotypes (behavioral markers of genetic variants) validated in prior research with younger children and older adults in a multi-generational family genetics study of dyslexia were used to study 81 adolescent and young adults (ages 16 to 25) from that study. Dyslexia is impaired word reading and spelling skills below the population mean and ability to use oral language to express thinking. These working memory predictor measures were given and used to predict reading and writing achievement: Coding (storing and processing) heard and spoken words (phonological coding), read and written words (orthographic coding), base words and affixes (morphological coding), and accumulating words over time (syntax coding); Cross-Code Integration (phonological loop for linking phonological name and orthographic letter codes and orthographic loop for linking orthographic letter codes and finger sequencing codes), and Supervisory Attention (focused and switching attention and self-monitoring during written word finding). Multiple regressions showed that most predictors explained individual difference in at least one reading or writing outcome, but which predictors explained unique variance beyond shared variance depended on outcome. ANOVAs confirmed that research-supported criteria for dyslexia validated for younger children and their parents could be used to diagnose which adolescents and young adults did (n=31) or did not (n=50) meet research criteria for dyslexia. Findings are discussed in reference to the heterogeneity of phenotypes (behavioral markers of genetic variables) and their application to assessment for accommodations and ongoing instruction for adolescents and young adults with dyslexia. PMID:26855554

Genesis of Typhoon Nari (2001) from a mesoscale convective system

NASA Astrophysics Data System (ADS)

Zhang, Da-Lin; Tian, Liqing; Yang, Ming-Jen

2011-12-01

In this study, the origin and genesis of Typhoon Nari (2001) as well as its erratic looping track, are examined using large-scale analysis, satellite observations, and a 4 day nested, cloud-resolving simulation with the finest grid size of 1.33 km. Observational analysis reveals that Nari could be traced 5 days back to a diurnally varying mesoscale convective system with growing cyclonic vorticity and relative humidity in the lower troposphere and that it evolved from a mesoscale convective vortex (MCV) as moving over a warm ocean under the influence of a subtropical high, a weak westerly baroclinic disturbance, an approaching-and-departing Typhoon Danas to the east, and the Kuroshio Current. Results show that the model reproduces the genesis, final intensity, looping track, and the general convective activity of Nari during the 4 day period. It also captures two deep subvortices at the eye-eyewall interface that are similar to those previously observed, a few spiral rainbands, and a midget storm size associated with Nari's relatively dry and stable environment. We find that (1) continuous convective overturning within the MCV stretches the low-level vorticity and moistens a deep mesoscale column that are both favorable for genesis; (2) Nari's genesis does not occur until after the passage of the baroclinic disturbance; (3) convective asymmetry induces a smaller-sized vortex circulation from the preexisting MCV; (4) the vortex-vortex interaction with Danas leads to Nari's looping track and temporal weakening; and (5) midlevel convergence associated with the subtropical high and Danas accounts for the generation of a nearly upright eyewall.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of autonomous satellite formation flying technologies using hardware-in-the-loop has been developed. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. The autonomous closed-loop formation acquisition and keeping strategy is based on Lyapunov's direct control method as applied to the standard set of Keplerian elements. This approach not only assures global and asymptotic stability of the control but also maintains valuable physical insight into the applied control vectors. Furthermore, the approach can account for system uncertainties and effectively avoids a computationally expensive solution of the two point boundary problem, which renders the concept particularly attractive for implementation in onboard processors. A guidance law has been developed which strictly separates the relative from the absolute motion, thus avoiding the numerical integration of a target trajectory in the onboard processor. Moreover, upon using precise kinematic relative GPS solutions, a dynamical modeling or filtering is avoided which provides for an efficient implementation of the process on an onboard processor. A sample formation flying scenario has been created aiming at the autonomous transition of a Low Earth Orbit satellite formation from an initial along-track separation of 800 m to a target distance of 100 m. Assuming a low-thrust actuator which may be accommodated on a small satellite, a typical control accuracy of less than 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

Sliding-mode control combined with improved adaptive feedforward for wafer scanner

NASA Astrophysics Data System (ADS)

Li, Xiaojie; Wang, Yiguang

2018-03-01

In this paper, a sliding-mode control method combined with improved adaptive feedforward is proposed for wafer scanner to improve the tracking performance of the closed-loop system. Particularly, In addition to the inverse model, the nonlinear force ripple effect which may degrade the tracking accuracy of permanent magnet linear motor (PMLM) is considered in the proposed method. The dominant position periodicity of force ripple is determined by using the Fast Fourier Transform (FFT) analysis for experimental data and the improved feedforward control is achieved by the online recursive least-squares (RLS) estimation of the inverse model and the force ripple. The improved adaptive feedforward is given in a general form of nth-order model with force ripple effect. This proposed method is motivated by the motion controller design of the long-stroke PMLM and short-stroke voice coil motor for wafer scanner. The stability of the closed-loop control system and the convergence of the motion tracking are guaranteed by the proposed sliding-mode feedback and adaptive feedforward methods theoretically. Comparative experiments on a precision linear motion platform can verify the correctness and effectiveness of the proposed method. The experimental results show that comparing to traditional method the proposed one has better performance of rapidity and robustness, especially for high speed motion trajectory. And, the improvements on both tracking accuracy and settling time can be achieved.

Probability Quantization for Multiplication-Free Binary Arithmetic Coding

NASA Technical Reports Server (NTRS)

Cheung, K. -M.

1995-01-01

A method has been developed to improve on Witten's binary arithmetic coding procedure of tracking a high value and a low value. The new method approximates the probability of the less probable symbol, which improves the worst-case coding efficiency.

Online Hierarchical Sparse Representation of Multifeature for Robust Object Tracking

PubMed Central

Qu, Shiru

2016-01-01

Object tracking based on sparse representation has given promising tracking results in recent years. However, the trackers under the framework of sparse representation always overemphasize the sparse representation and ignore the correlation of visual information. In addition, the sparse coding methods only encode the local region independently and ignore the spatial neighborhood information of the image. In this paper, we propose a robust tracking algorithm. Firstly, multiple complementary features are used to describe the object appearance; the appearance model of the tracked target is modeled by instantaneous and stable appearance features simultaneously. A two-stage sparse-coded method which takes the spatial neighborhood information of the image patch and the computation burden into consideration is used to compute the reconstructed object appearance. Then, the reliability of each tracker is measured by the tracking likelihood function of transient and reconstructed appearance models. Finally, the most reliable tracker is obtained by a well established particle filter framework; the training set and the template library are incrementally updated based on the current tracking results. Experiment results on different challenging video sequences show that the proposed algorithm performs well with superior tracking accuracy and robustness. PMID:27630710

A Novel Real-Time Path Servo Control of a Hardware-in-the-Loop for a Large-Stroke Asymmetric Rod-Less Pneumatic System under Variable Loads.

PubMed

Lin, Hao-Ting

2017-06-04

This project aims to develop a novel large stroke asymmetric pneumatic servo system of a hardware-in-the-loop for path tracking control under variable loads based on the MATLAB Simulink real-time system. High pressure compressed air provided by the air compressor is utilized for the pneumatic proportional servo valve to drive the large stroke asymmetric rod-less pneumatic actuator. Due to the pressure differences between two chambers, the pneumatic actuator will operate. The highly nonlinear mathematical models of the large stroke asymmetric pneumatic system were analyzed and developed. The functional approximation technique based on the sliding mode controller (FASC) is developed as a controller to solve the uncertain time-varying nonlinear system. The MATLAB Simulink real-time system was a main control unit of a hardware-in-the-loop system proposed to establish driver blocks for analog and digital I/O, a linear encoder, a CPU and a large stroke asymmetric pneumatic rod-less system. By the position sensor, the position signals of the cylinder will be measured immediately. The measured signals will be viewed as the feedback signals of the pneumatic servo system for the study of real-time positioning control and path tracking control. Finally, real-time control of a large stroke asymmetric pneumatic servo system with measuring system, a large stroke asymmetric pneumatic servo system, data acquisition system and the control strategy software will be implemented. Thus, upgrading the high position precision and the trajectory tracking performance of the large stroke asymmetric pneumatic servo system will be realized to promote the high position precision and path tracking capability. Experimental results show that fifth order paths in various strokes and the sine wave path are successfully implemented in the test rig. Also, results of variable loads under the different angle were implemented experimentally.

A Novel Real-Time Path Servo Control of a Hardware-in-the-Loop for a Large-Stroke Asymmetric Rod-Less Pneumatic System under Variable Loads

PubMed Central

Lin, Hao-Ting

2017-01-01

This project aims to develop a novel large stroke asymmetric pneumatic servo system of a hardware-in-the-loop for path tracking control under variable loads based on the MATLAB Simulink real-time system. High pressure compressed air provided by the air compressor is utilized for the pneumatic proportional servo valve to drive the large stroke asymmetric rod-less pneumatic actuator. Due to the pressure differences between two chambers, the pneumatic actuator will operate. The highly nonlinear mathematical models of the large stroke asymmetric pneumatic system were analyzed and developed. The functional approximation technique based on the sliding mode controller (FASC) is developed as a controller to solve the uncertain time-varying nonlinear system. The MATLAB Simulink real-time system was a main control unit of a hardware-in-the-loop system proposed to establish driver blocks for analog and digital I/O, a linear encoder, a CPU and a large stroke asymmetric pneumatic rod-less system. By the position sensor, the position signals of the cylinder will be measured immediately. The measured signals will be viewed as the feedback signals of the pneumatic servo system for the study of real-time positioning control and path tracking control. Finally, real-time control of a large stroke asymmetric pneumatic servo system with measuring system, a large stroke asymmetric pneumatic servo system, data acquisition system and the control strategy software will be implemented. Thus, upgrading the high position precision and the trajectory tracking performance of the large stroke asymmetric pneumatic servo system will be realized to promote the high position precision and path tracking capability. Experimental results show that fifth order paths in various strokes and the sine wave path are successfully implemented in the test rig. Also, results of variable loads under the different angle were implemented experimentally. PMID:28587220

Fractional order implementation of Integral Resonant Control - A nanopositioning application.

PubMed

San-Millan, Andres; Feliu-Batlle, Vicente; Aphale, Sumeet S

2017-10-04

By exploiting the co-located sensor-actuator arrangement in typical flexure-based piezoelectric stack actuated nanopositioners, the polezero interlacing exhibited by their axial frequency response can be transformed to a zero-pole interlacing by adding a constant feed-through term. The Integral Resonant Control (IRC) utilizes this unique property to add substantial damping to the dominant resonant mode by the use of a simple integrator implemented in closed loop. IRC used in conjunction with an integral tracking scheme, effectively reduces positioning errors introduced by modelling inaccuracies or parameter uncertainties. Over the past few years, successful application of the IRC control technique to nanopositioning systems has demonstrated performance robustness, easy tunability and versatility. The main drawback has been the relatively small positioning bandwidth achievable. This paper proposes a fractional order implementation of the classical integral tracking scheme employed in tandem with the IRC scheme to deliver damping and tracking. The fractional order integrator introduces an additional design parameter which allows desired pole-placement, resulting in superior closed loop bandwidth. Simulations and experimental results are presented to validate the theory. A 250% improvement in the achievable positioning bandwidth is observed with proposed fractional order scheme. Copyright © 2017. Published by Elsevier Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unseren, M.A.

The report discusses the orientation tracking control problem for a kinematically redundant, autonomous manipulator moving in a three dimensional workspace. The orientation error is derived using the normalized quaternion error method of Ickes, the Luh, Walker, and Paul error method, and a method suggested here utilizing the Rodrigues parameters, all of which are expressed in terms of normalized quaternions. The analytical time derivatives of the orientation errors are determined. The latter, along with the translational velocity error, form a dosed loop kinematic velocity model of the manipulator using normalized quaternion and translational position feedback. An analysis of the singularities associatedmore » with expressing the models in a form suitable for solving the inverse kinematics problem is given. Two redundancy resolution algorithms originally developed using an open loop kinematic velocity model of the manipulator are extended to properly take into account the orientation tracking control problem. This report furnishes the necessary mathematical framework required prior to experimental implementation of the orientation tracking control schemes on the seven axis CESARm research manipulator or on the seven-axis Robotics Research K1207i dexterous manipulator, the latter of which is to be delivered to the Oak Ridge National Laboratory in 1993.« less

Reusable Launch Vehicle Control In Multiple Time Scale Sliding Modes

NASA Technical Reports Server (NTRS)

Shtessel, Yuri; Hall, Charles; Jackson, Mark

2000-01-01

A reusable launch vehicle control problem during ascent is addressed via multiple-time scaled continuous sliding mode control. The proposed sliding mode controller utilizes a two-loop structure and provides robust, de-coupled tracking of both orientation angle command profiles and angular rate command profiles in the presence of bounded external disturbances and plant uncertainties. Sliding mode control causes the angular rate and orientation angle tracking error dynamics to be constrained to linear, de-coupled, homogeneous, and vector valued differential equations with desired eigenvalues placement. Overall stability of a two-loop control system is addressed. An optimal control allocation algorithm is designed that allocates torque commands into end-effector deflection commands, which are executed by the actuators. The dual-time scale sliding mode controller was designed for the X-33 technology demonstration sub-orbital launch vehicle in the launch mode. Simulation results show that the designed controller provides robust, accurate, de-coupled tracking of the orientation angle command profiles in presence of external disturbances and vehicle inertia uncertainties. This is a significant advancement in performance over that achieved with linear, gain scheduled control systems currently being used for launch vehicles.

Optimal fault-tolerant control strategy of a solid oxide fuel cell system

NASA Astrophysics Data System (ADS)

Wu, Xiaojuan; Gao, Danhui

2017-10-01

For solid oxide fuel cell (SOFC) development, load tracking, heat management, air excess ratio constraint, high efficiency, low cost and fault diagnosis are six key issues. However, no literature studies the control techniques combining optimization and fault diagnosis for the SOFC system. An optimal fault-tolerant control strategy is presented in this paper, which involves four parts: a fault diagnosis module, a switching module, two backup optimizers and a controller loop. The fault diagnosis part is presented to identify the SOFC current fault type, and the switching module is used to select the appropriate backup optimizer based on the diagnosis result. NSGA-II and TOPSIS are employed to design the two backup optimizers under normal and air compressor fault states. PID algorithm is proposed to design the control loop, which includes a power tracking controller, an anode inlet temperature controller, a cathode inlet temperature controller and an air excess ratio controller. The simulation results show the proposed optimal fault-tolerant control method can track the power, temperature and air excess ratio at the desired values, simultaneously achieving the maximum efficiency and the minimum unit cost in the case of SOFC normal and even in the air compressor fault.

A new rate-dependent model for high-frequency tracking performance enhancement of piezoactuator system

NASA Astrophysics Data System (ADS)

Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

2017-05-01

Feedforward-feedback control is widely used in motion control of piezoactuator systems. Due to the phase lag caused by incomplete dynamics compensation, the performance of the composite controller is greatly limited at high frequency. This paper proposes a new rate-dependent model to improve the high-frequency tracking performance by reducing dynamics compensation error. The rate-dependent model is designed as a function of the input and input variation rate to describe the input-output relationship of the residual system dynamics which mainly performs as phase lag in a wide frequency band. Then the direct inversion of the proposed rate-dependent model is used to compensate the residual system dynamics. Using the proposed rate-dependent model as feedforward term, the open loop performance can be improved significantly at medium-high frequency. Then, combining the with feedback controller, the composite controller can provide enhanced close loop performance from low frequency to high frequency. At the frequency of 1 Hz, the proposed controller presents the same performance as previous methods. However, at the frequency of 900 Hz, the tracking error is reduced to be 30.7% of the decoupled approach.

Robust adaptive tracking control for nonholonomic mobile manipulator with uncertainties.

PubMed

Peng, Jinzhu; Yu, Jie; Wang, Jie

2014-07-01

In this paper, mobile manipulator is divided into two subsystems, that is, nonholonomic mobile platform subsystem and holonomic manipulator subsystem. First, the kinematic controller of the mobile platform is derived to obtain a desired velocity. Second, regarding the coupling between the two subsystems as disturbances, Lyapunov functions of the two subsystems are designed respectively. Third, a robust adaptive tracking controller is proposed to deal with the unknown upper bounds of parameter uncertainties and disturbances. According to the Lyapunov stability theory, the derived robust adaptive controller guarantees global stability of the closed-loop system, and the tracking errors and adaptive coefficient errors are all bounded. Finally, simulation results show that the proposed robust adaptive tracking controller for nonholonomic mobile manipulator is effective and has good tracking capacity. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Complete sequence and gene organization of the mitochondrial genome of Asio flammeus (Strigiformes, strigidae).

PubMed

Zhang, Yanan; Song, Tao; Pan, Tao; Sun, Xiaonan; Sun, Zhonglou; Qian, Lifu; Zhang, Baowei

2016-07-01

The complete sequence of the mitochondrial genome was determined for Asio flammeus, which is distributed widely in geography. The length of the complete mitochondrial genome was 18,966 bp, containing 2 rRNA genes, 22 tRNA genes, 13 protein-coding genes (PCGs), and 1 non-coding region (D-loop). All the genes were distributed on the H-strand, except for the ND6 subunit gene and eight tRNA genes which were encoded on the L-strand. The D-loop of A. flammeus contained many tandem repeats of varying lengths and repeat numbers. The molecular-based phylogeny showed that our species acted as the sister group to A. capensis and the supported Asio was the monophyletic group.

CoreTSAR: Core Task-Size Adapting Runtime

DOE PAGES

Scogland, Thomas R. W.; Feng, Wu-chun; Rountree, Barry; ...

2014-10-27

Heterogeneity continues to increase at all levels of computing, with the rise of accelerators such as GPUs, FPGAs, and other co-processors into everything from desktops to supercomputers. As a consequence, efficiently managing such disparate resources has become increasingly complex. CoreTSAR seeks to reduce this complexity by adaptively worksharing parallel-loop regions across compute resources without requiring any transformation of the code within the loop. Lastly, our results show performance improvements of up to three-fold over a current state-of-the-art heterogeneous task scheduler as well as linear performance scaling from a single GPU to four GPUs for many codes. In addition, CoreTSAR demonstratesmore » a robust ability to adapt to both a variety of workloads and underlying system configurations.« less

A real-time simulator of a turbofan engine

NASA Technical Reports Server (NTRS)

Litt, Jonathan S.; Delaat, John C.; Merrill, Walter C.

1989-01-01

A real-time digital simulator of a Pratt and Whitney F100 engine has been developed for real-time code verification and for actuator diagnosis during full-scale engine testing. This self-contained unit can operate in an open-loop stand-alone mode or as part of closed-loop control system. It can also be used for control system design and development. Tests conducted in conjunction with the NASA Advanced Detection, Isolation, and Accommodation program show that the simulator is a valuable tool for real-time code verification and as a real-time actuator simulator for actuator fault diagnosis. Although currently a small perturbation model, advances in microprocessor hardware should allow the simulator to evolve into a real-time, full-envelope, full engine simulation.

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver

NASA Astrophysics Data System (ADS)

Aung, M.

1992-11-01

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan, E-mail: shuhongyang@nao.cas.cn

2014-10-01

Using the Hα observations from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we focus on the fine structures of three confined flares and the issue why all the three flares are confined instead of eruptive. All the three confined flares take place successively at the same location and have similar morphologies, so can be termed homologous confined flares. In the simultaneous images obtained by the Solar Dynamics Observatory, many large-scale coronal loops above the confined flares are clearly observed in multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative sunspot, and the dipolar patches aremore » connected by small loops appearing as arch-shaped Hα fibrils. There exists a reconnection between the small loops, and thus the Hα fibrils change their configuration. The reconnection also occurs between a set of emerging Hα fibrils and a set of pre-existing large loops, which are rooted in the negative sunspot, a nearby positive patch, and some remote positive faculae, forming a typical three-legged structure. During the flare processes, the overlying loops, some of which are tracked by activated dark materials, do not break out. These direct observations may illustrate the physical mechanism of confined flares, i.e., magnetic reconnection between the emerging loops and the pre-existing loops triggers flares and the overlying loops prevent the flares from being eruptive.« less

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver

NASA Technical Reports Server (NTRS)

Aung, M.

1992-01-01

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 2: Data

NASA Technical Reports Server (NTRS)

Waszak, M. R.; Schmidt, D. K.

1985-01-01

Two analysis methods are applied to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop modal analysis technique. This method considers the effect of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Both analyses indicated that dynamic aeroelastic effects caused a degradation in vehicle tracking performance, based on the evaluation of some simulation results. Volume 2 consists of the presentation of the state variable models of the flexible aircraft configurations used in the analysis applications mode shape plots for the structural modes, numerical results from the modal analysis frequency response plots from the pilot in the loop analysis and a listing of the modal analysis computer program.

A rationale for human operator pulsive control behavior

NASA Technical Reports Server (NTRS)

Hess, R. A.

1979-01-01

When performing tracking tasks which involve demanding controlled elements such as those with K/s-squared dynamics, the human operator often develops discrete or pulsive control outputs. A dual-loop model of the human operator is discussed, the dominant adaptive feature of which is the explicit appearance of an internal model of the manipulator-controlled element dynamics in an inner feedback loop. Using this model, a rationale for pulsive control behavior is offered which is based upon the assumption that the human attempts to reduce the computational burden associated with time integration of sensory inputs. It is shown that such time integration is a natural consequence of having an internal representation of the K/s-squared-controlled element dynamics in the dual-loop model. A digital simulation is discussed in which a modified form of the dual-loop model is shown to be capable of producing pulsive control behavior qualitively comparable to that obtained in experiment.

Design and simulation of a sensor for heliostat field closed loop control

NASA Astrophysics Data System (ADS)

Collins, Mike; Potter, Daniel; Burton, Alex

2017-06-01

Significant research has been completed in pursuit of capital cost reductions for heliostats [1],[2]. The camera array closed loop control concept has potential to radically alter the way heliostats are controlled and installed by replacing high quality open loop targeting systems with low quality targeting devices that rely on measurement of image position to remove tracking errors during operation. Although the system could be used for any heliostat size, the system significantly benefits small heliostats by reducing actuation costs, enabling large numbers of heliostats to be calibrated simultaneously, and enabling calibration of heliostats that produce low irradiance (similar or less than ambient light images) on Lambertian calibration targets, such as small heliostats that are far from the tower. A simulation method for the camera array has been designed and verified experimentally. The simulation tool demonstrates that closed loop calibration or control is possible using this device.

Latent uncertainties of the precalculated track Monte Carlo method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renaud, Marc-André; Seuntjens, Jan; Roberge, David

Purpose: While significant progress has been made in speeding up Monte Carlo (MC) dose calculation methods, they remain too time-consuming for the purpose of inverse planning. To achieve clinically usable calculation speeds, a precalculated Monte Carlo (PMC) algorithm for proton and electron transport was developed to run on graphics processing units (GPUs). The algorithm utilizes pregenerated particle track data from conventional MC codes for different materials such as water, bone, and lung to produce dose distributions in voxelized phantoms. While PMC methods have been described in the past, an explicit quantification of the latent uncertainty arising from the limited numbermore » of unique tracks in the pregenerated track bank is missing from the paper. With a proper uncertainty analysis, an optimal number of tracks in the pregenerated track bank can be selected for a desired dose calculation uncertainty. Methods: Particle tracks were pregenerated for electrons and protons using EGSnrc and GEANT4 and saved in a database. The PMC algorithm for track selection, rotation, and transport was implemented on the Compute Unified Device Architecture (CUDA) 4.0 programming framework. PMC dose distributions were calculated in a variety of media and compared to benchmark dose distributions simulated from the corresponding general-purpose MC codes in the same conditions. A latent uncertainty metric was defined and analysis was performed by varying the pregenerated track bank size and the number of simulated primary particle histories and comparing dose values to a “ground truth” benchmark dose distribution calculated to 0.04% average uncertainty in voxels with dose greater than 20% of D{sub max}. Efficiency metrics were calculated against benchmark MC codes on a single CPU core with no variance reduction. Results: Dose distributions generated using PMC and benchmark MC codes were compared and found to be within 2% of each other in voxels with dose values greater than 20% of the maximum dose. In proton calculations, a small (≤1 mm) distance-to-agreement error was observed at the Bragg peak. Latent uncertainty was characterized for electrons and found to follow a Poisson distribution with the number of unique tracks per energy. A track bank of 12 energies and 60000 unique tracks per pregenerated energy in water had a size of 2.4 GB and achieved a latent uncertainty of approximately 1% at an optimal efficiency gain over DOSXYZnrc. Larger track banks produced a lower latent uncertainty at the cost of increased memory consumption. Using an NVIDIA GTX 590, efficiency analysis showed a 807 × efficiency increase over DOSXYZnrc for 16 MeV electrons in water and 508 × for 16 MeV electrons in bone. Conclusions: The PMC method can calculate dose distributions for electrons and protons to a statistical uncertainty of 1% with a large efficiency gain over conventional MC codes. Before performing clinical dose calculations, models to calculate dose contributions from uncharged particles must be implemented. Following the successful implementation of these models, the PMC method will be evaluated as a candidate for inverse planning of modulated electron radiation therapy and scanned proton beams.« less

Latent uncertainties of the precalculated track Monte Carlo method.

PubMed

Renaud, Marc-André; Roberge, David; Seuntjens, Jan

2015-01-01

While significant progress has been made in speeding up Monte Carlo (MC) dose calculation methods, they remain too time-consuming for the purpose of inverse planning. To achieve clinically usable calculation speeds, a precalculated Monte Carlo (PMC) algorithm for proton and electron transport was developed to run on graphics processing units (GPUs). The algorithm utilizes pregenerated particle track data from conventional MC codes for different materials such as water, bone, and lung to produce dose distributions in voxelized phantoms. While PMC methods have been described in the past, an explicit quantification of the latent uncertainty arising from the limited number of unique tracks in the pregenerated track bank is missing from the paper. With a proper uncertainty analysis, an optimal number of tracks in the pregenerated track bank can be selected for a desired dose calculation uncertainty. Particle tracks were pregenerated for electrons and protons using EGSnrc and geant4 and saved in a database. The PMC algorithm for track selection, rotation, and transport was implemented on the Compute Unified Device Architecture (cuda) 4.0 programming framework. PMC dose distributions were calculated in a variety of media and compared to benchmark dose distributions simulated from the corresponding general-purpose MC codes in the same conditions. A latent uncertainty metric was defined and analysis was performed by varying the pregenerated track bank size and the number of simulated primary particle histories and comparing dose values to a "ground truth" benchmark dose distribution calculated to 0.04% average uncertainty in voxels with dose greater than 20% of Dmax. Efficiency metrics were calculated against benchmark MC codes on a single CPU core with no variance reduction. Dose distributions generated using PMC and benchmark MC codes were compared and found to be within 2% of each other in voxels with dose values greater than 20% of the maximum dose. In proton calculations, a small (≤ 1 mm) distance-to-agreement error was observed at the Bragg peak. Latent uncertainty was characterized for electrons and found to follow a Poisson distribution with the number of unique tracks per energy. A track bank of 12 energies and 60000 unique tracks per pregenerated energy in water had a size of 2.4 GB and achieved a latent uncertainty of approximately 1% at an optimal efficiency gain over DOSXYZnrc. Larger track banks produced a lower latent uncertainty at the cost of increased memory consumption. Using an NVIDIA GTX 590, efficiency analysis showed a 807 × efficiency increase over DOSXYZnrc for 16 MeV electrons in water and 508 × for 16 MeV electrons in bone. The PMC method can calculate dose distributions for electrons and protons to a statistical uncertainty of 1% with a large efficiency gain over conventional MC codes. Before performing clinical dose calculations, models to calculate dose contributions from uncharged particles must be implemented. Following the successful implementation of these models, the PMC method will be evaluated as a candidate for inverse planning of modulated electron radiation therapy and scanned proton beams.

Visuo‐manual tracking: does intermittent control with aperiodic sampling explain linear power and non‐linear remnant without sensorimotor noise?

PubMed Central

Gawthrop, Peter J.; Lakie, Martin; Loram, Ian D.

2017-01-01

Key points A human controlling an external system is described most easily and conventionally as linearly and continuously translating sensory input to motor output, with the inevitable output remnant, non‐linearly related to the input, attributed to sensorimotor noise.Recent experiments show sustained manual tracking involves repeated refractoriness (insensitivity to sensory information for a certain duration), with the temporary 200–500 ms periods of irresponsiveness to sensory input making the control process intrinsically non‐linear.This evidence calls for re‐examination of the extent to which random sensorimotor noise is required to explain the non‐linear remnant.This investigation of manual tracking shows how the full motor output (linear component and remnant) can be explained mechanistically by aperiodic sampling triggered by prediction error thresholds.Whereas broadband physiological noise is general to all processes, aperiodic sampling is associated with sensorimotor decision making within specific frontal, striatal and parietal networks; we conclude that manual tracking utilises such slow serial decision making pathways up to several times per second. Abstract The human operator is described adequately by linear translation of sensory input to motor output. Motor output also always includes a non‐linear remnant resulting from random sensorimotor noise from multiple sources, and non‐linear input transformations, for example thresholds or refractory periods. Recent evidence showed that manual tracking incurs substantial, serial, refractoriness (insensitivity to sensory information of 350 and 550 ms for 1st and 2nd order systems respectively). Our two questions are: (i) What are the comparative merits of explaining the non‐linear remnant using noise or non‐linear transformations? (ii) Can non‐linear transformations represent serial motor decision making within the sensorimotor feedback loop intrinsic to tracking? Twelve participants (instructed to act in three prescribed ways) manually controlled two systems (1st and 2nd order) subject to a periodic multi‐sine disturbance. Joystick power was analysed using three models, continuous‐linear‐control (CC), continuous‐linear‐control with calculated noise spectrum (CCN), and intermittent control with aperiodic sampling triggered by prediction error thresholds (IC). Unlike the linear mechanism, the intermittent control mechanism explained the majority of total power (linear and remnant) (77–87% vs. 8–48%, IC vs. CC). Between conditions, IC used thresholds and distributions of open loop intervals consistent with, respectively, instructions and previous measured, model independent values; whereas CCN required changes in noise spectrum deviating from broadband, signal dependent noise. We conclude that manual tracking uses open loop predictive control with aperiodic sampling. Because aperiodic sampling is inherent to serial decision making within previously identified, specific frontal, striatal and parietal networks we suggest that these structures are intimately involved in visuo‐manual tracking. PMID:28833126

Determination of multi-GNSS pseudo-absolute code biases and verification of receiver tracking technology

NASA Astrophysics Data System (ADS)

Villiger, Arturo; Schaer, Stefan; Dach, Rolf; Prange, Lars; Jäggi, Adrian

2017-04-01

It is common to handle code biases in the Global Navigation Satellite System (GNSS) data analysis as conventional differential code biases (DCBs): P1-C1, P1-P2, and P2-C2. Due to the increasing number of signals and systems in conjunction with various tracking modes for the different signals (as defined in RINEX3 format), the number of DCBs would increase drastically and the bookkeeping becomes almost unbearable. The Center for Orbit Determination in Europe (CODE) has thus changed its processing scheme to observable-specific signal biases (OSB). This means that for each observation involved all related satellite and receiver biases are considered. The OSB contributions from various ionosphere analyses (geometry-free linear combination) using different observables and frequencies and from clock analyses (ionosphere-free linear combination) are then combined on normal equation level. By this, one consistent set of OSB values per satellite and receiver can be obtained that contains all information needed for GNSS-related processing. This advanced procedure of code bias handling is now also applied to the IGS (International GNSS Service) MGEX (Multi-GNSS Experiment) procedure at CODE. Results for the biases from the legacy IGS solution as well as the CODE MGEX processing (considering GPS, GLONASS, Galileo, BeiDou, and QZSS) are presented. The consistency with the traditional method is confirmed and the new results are discussed regarding the long-term stability. When processing code data, it is essential to know the true observable types in order to correct for the associated biases. CODE has been verifying the receiver tracking technologies for GPS based on estimated DCB multipliers (for the RINEX 2 case). With the change to OSB, the original verification approach was extended to search for the best fitting observable types based on known OSB values. In essence, a multiplier parameter is estimated for each involved GNSS observable type. This implies that we could recover, for receivers tracking a combination of signals, even the factors of these combinations. The verification of the observable types is crucial to identify the correct observable types of RINEX 2 data (which does not contain the signal modulation in comparison to RINEX 3). The correct information of the used observable types is essential for precise point positioning (PPP) applications and GNSS ambiguity resolution. Multi-GNSS OSBs and verified receiver tracking modes are essential to get best possible multi-GNSS solutions for geodynamic purposes and other applications.

Predictions of GPS X-Set Performance during the Places Experiment

DTIC Science & Technology

1979-07-01

previously existing GPS X-set receiver simulation was modified to include the received signal spectrum and the receiver code correlation operation... CORRELATION OPERATION The X-set receiver simulation documented in Reference 3-1 is a direct sampled -data digital implementation of the GPS X-set...ul(t) -sin w2t From Carrier and Code Loops (wit +0 1 (t)) Figure 3-6. Simplified block diagram of code correlator operation and I-Q sampling . 6 I

Pilot-in-the-Loop CFD Method Development

DTIC Science & Technology

2017-04-20

the methods on the NAVAIR Manned Flight Simulator. Activities this period During this report period, we implemented the CRAFT CFD code on the...Penn State VLRCROE Flight simulator and performed the first Pilot-in-the-Loop PILCFD tests at Penn State using the COCOA5 clusters. The initial tests...integration of the flight simulator and Penn State computing infrastructure. Initial tests showed slower performance than real-time (3x slower than real

Design of efficient and simple interface testing equipment for opto-electric tracking system

NASA Astrophysics Data System (ADS)

Liu, Qiong; Deng, Chao; Tian, Jing; Mao, Yao

2016-10-01

Interface testing for opto-electric tracking system is one important work to assure system running performance, aiming to verify the design result of every electronic interface matching the communication protocols or not, by different levels. Opto-electric tracking system nowadays is more complicated, composed of many functional units. Usually, interface testing is executed between units manufactured completely, highly depending on unit design and manufacture progress as well as relative people. As a result, it always takes days or weeks, inefficiently. To solve the problem, this paper promotes an efficient and simple interface testing equipment for opto-electric tracking system, consisting of optional interface circuit card, processor and test program. The hardware cards provide matched hardware interface(s), easily offered from hardware engineer. Automatic code generation technique is imported, providing adaption to new communication protocols. Automatic acquiring items, automatic constructing code architecture and automatic encoding are used to form a new program quickly with adaption. After simple steps, a standard customized new interface testing equipment with matching test program and interface(s) is ready for a waiting-test system in minutes. The efficient and simple interface testing equipment for opto-electric tracking system has worked for many opto-electric tracking system to test entire or part interfaces, reducing test time from days to hours, greatly improving test efficiency, with high software quality and stability, without manual coding. Used as a common tool, the efficient and simple interface testing equipment for opto-electric tracking system promoted by this paper has changed traditional interface testing method and created much higher efficiency.

Symplectic orbit and spin tracking code for all-electric storage rings

NASA Astrophysics Data System (ADS)

Talman, Richard M.; Talman, John D.

2015-07-01

Proposed methods for measuring the electric dipole moment (EDM) of the proton use an intense, polarized proton beam stored in an all-electric storage ring "trap." At the "magic" kinetic energy of 232.792 MeV, proton spins are "frozen," for example always parallel to the instantaneous particle momentum. Energy deviation from the magic value causes in-plane precession of the spin relative to the momentum. Any nonzero EDM value will cause out-of-plane precession—measuring this precession is the basis for the EDM determination. A proposed implementation of this measurement shows that a proton EDM value of 10-29e -cm or greater will produce a statistically significant, measurable precession after multiply repeated runs, assuming small beam depolarization during 1000 s runs, with high enough precision to test models of the early universe developed to account for the present day particle/antiparticle population imbalance. This paper describes an accelerator simulation code, eteapot, a new component of the Unified Accelerator Libraries (ual), to be used for long term tracking of particle orbits and spins in electric bend accelerators, in order to simulate EDM storage ring experiments. Though qualitatively much like magnetic rings, the nonconstant particle velocity in electric rings gives them significantly different properties, especially in weak focusing rings. Like the earlier code teapot (for magnetic ring simulation) this code performs exact tracking in an idealized (approximate) lattice rather than the more conventional approach, which is approximate tracking in a more nearly exact lattice. The Bargmann-Michel-Telegdi (BMT) equation describing the evolution of spin vectors through idealized bend elements is also solved exactly—original to this paper. Furthermore the idealization permits the code to be exactly symplectic (with no artificial "symplectification"). Any residual spurious damping or antidamping is sufficiently small to permit reliable tracking for the long times, such as the 1000 s assumed in estimating the achievable EDM precision. This paper documents in detail the theoretical formulation implemented in eteapot. An accompanying paper describes the practical application of the eteapot code in the Universal Accelerator Libraries (ual) environment to "resurrect," or reverse engineer, the "AGS-analog" all-electric ring built at Brookhaven National Laboratory in 1954. Of the (very few) all-electric rings ever commissioned, the AGS-analog ring is the only relativistic one and is the closest to what is needed for measuring proton (or, even more so, electron) EDM's. The companion paper also describes preliminary lattice studies for the planned proton EDM storage rings as well as testing the code for long time orbit and spin tracking.

An automatic frequency control loop using overlapping DFTs (Discrete Fourier Transforms)

NASA Technical Reports Server (NTRS)

Aguirre, S.

1988-01-01

An automatic frequency control (AFC) loop is introduced and analyzed in detail. The new scheme is a generalization of the well known Cross Product AFC loop that uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve. Linear analysis is included and supported with computer simulations. The algorithm is tested in a low carrier to noise ratio (CNR) dynamic environment, and the probability of loss of lock is estimated via computer simulations. The algorithm discussed is a suboptimum tracking scheme with a larger frequency error variance compared to an optimum strategy, but offers simplicity of implementation and a very low operating threshold CNR. This technique can be applied during the carrier acquisition and re-acquisition process in the Advanced Receiver.

Precorrection concepts for mobile terminals with processing satellites

NASA Astrophysics Data System (ADS)

Nakamoto, F. S.; Oreilly, M. P.; Wolfson, C. R.

It is pointed out that when the spacecraft must process a large number of users simultaneously, it becomes impractical for it to acquire and track each uplink signal. A solution is for the terminals to precorrect their uplink transmissions so that they reach the spacecraft in time and frequency synchronism with the spacecraft receiver. Two dimensions of precorrection, namely time and frequency, are addressed. Precorrection approaches are classified as open loop, pseudo-open loop, or pseudo-closed loop. Performance relationships are established, and the applicability, requirements, advantages, and disadvantages of each class are discussed. It is found that since time and frequency precorrection have opposite sensitivities to the frequency hopping rate, different classes will often be adopted for the two dimensions.

Simulating nanostorm heating in coronal loops using hydrodynamics and non-thermal particle evolution

NASA Astrophysics Data System (ADS)

Migliore, Christina; Winter, Henry; Murphy, Nicholas

2018-01-01

The solar corona is filled with loop-like structures that appear bright against the background when observed in the extreme ultraviolet (EUV). These loops have several remarkable properties that are not yet well understood. Warm loops (∼ 1 MK) appear to be ∼ 2 ‑ 9 times as dense at their apex as the predictions of hydrostatic atmosphere models. These loops also appear to be of constant cross-section despite the fact that the field strength in a potential magnetic field should decrease in the corona, causing the loops to expand. It is not clear why many active region loops appear to be of constant cross-section. Theories range from an internal twist of the magnetic field to observational effects. In this work we simulate active region loops heated by nanoflare storms using a dipolar magnetic field. We calculate the hydrodynamic properties for each loop using advanced hydrodynamics codes to simulate the corona and chromospheric response and basic dipole models to represent the magnetic fields of the loops. We show that even modest variations of the magnetic field strength along the loop can lead to drastic changes in the density profiles of active region loops, and they can also explain the overpressure at the apex of these loops. Synthetic AIA images of each loop are made to show the observable consequences of varying magnetic field strengths along the loop’s axis of symmetry. We also show how this work can lead to improved modeling of larger solar and stellar flares.

Reading the Rover Tracks

NASA Image and Video Library

2012-08-29

The straight lines in Curiosity zigzag track marks are Morse code for JPL. The footprint is an important reference mark that the rover can use to drive more precisely via a system called visual odometry.

Combined actions of multiple hairpin loop structures and sites of rate-limiting endonucleolytic cleavage determine differential degradation rates of individual segments within polycistronic puf operon mRNA.

PubMed Central

Klug, G; Cohen, S N

1990-01-01

Differential expression of the genes within the puf operon of Rhodobacter capsulatus is accomplished in part by differences in the rate of degradation of different segments of the puf transcript. We report here that decay of puf mRNA sequences specifying the light-harvesting I (LHI) and reaction center (RC) photosynthetic membrane peptides is initiated endoribonucleolytically within a discrete 1.4-kilobase segment of the RC-coding region. Deletion of this segment increased the half-life of the RC-coding region from 8 to 20 min while not affecting decay of LHI-coding sequences upstream from an intercistronic hairpin loop structure shown previously to impede 3'-to-5' degradation. Prolongation of RC segment half-life was dependent on the presence of other hairpin structures 3' to the RC region. Inserting the endonuclease-sensitive sites into the LHI-coding segment markedly accelerated its degradation. Our results suggest that differential degradation of the RC- and LHI-coding segments of puf mRNA is accomplished at least in part by the combined actions of RC region-specific endonuclease(s), one or more exonucleases, and several strategically located exonuclease-impeding hairpins. Images PMID:2394682

The chloroplast tRNALys(UUU) gene from mustard (Sinapis alba) contains a class II intron potentially coding for a maturase-related polypeptide.

PubMed

Neuhaus, H; Link, G

1987-01-01

The trnK gene endocing the tRNALys(UUU) has been located on mustard (Sinapis alba) chloroplast DNA, 263 bp upstream of the psbA gene on the same strand. The nucleotide sequence of the trnK gene and its flanking regions as well as the putative transcription start and termination sites are shown. The 5' end of the transcript lies 121 bp upstream of the 5' tRNA coding region and is preceded by procaryotic-type "-10" and "-35" sequence elements, while the 3' end maps 2.77 kb downstream to a DNA region with possible stemloop secondary structure. The anticodon loop of the tRNALys is interrupted by a 2,574 bp intron containing a long open reading frame, which codes for 524 amino acids. Based on conserved stem and loop structures, this intron has characteristic features of a class II intron. A region near the carboxyl terminus of the derived polypeptide appears structurally related to maturases.

A proven approach for more effective software development and maintenance

NASA Technical Reports Server (NTRS)

Pajerski, Rose; Hall, Dana; Sinclair, Craig

1994-01-01

Modern space flight mission operations and associated ground data systems are increasingly dependent upon reliable, quality software. Critical functions such as command load preparation, health and status monitoring, communications link scheduling and conflict resolution, and transparent gateway protocol conversion are routinely performed by software. Given budget constraints and the ever increasing capabilities of processor technology, the next generation of control centers and data systems will be even more dependent upon software across all aspects of performance. A key challenge now is to implement improved engineering, management, and assurance processes for the development and maintenance of that software; processes that cost less, yield higher quality products, and that self-correct for continual improvement evolution. The NASA Goddard Space Flight Center has a unique experience base that can be readily tapped to help solve the software challenge. Over the past eighteen years, the Software Engineering Laboratory within the code 500 Flight Dynamics Division has evolved a software development and maintenance methodology that accommodates the unique characteristics of an organization while optimizing and continually improving the organization's software capabilities. This methodology relies upon measurement, analysis, and feedback much analogous to that of control loop systems. It is an approach with a time-tested track record proven through repeated applications across a broad range of operational software development and maintenance projects. This paper describes the software improvement methodology employed by the Software Engineering Laboratory, and how it has been exploited within the Flight Dynamics Division with GSFC Code 500. Examples of specific improvement in the software itself and its processes are presented to illustrate the effectiveness of the methodology. Finally, the initial findings are given when this methodology was applied across the mission operations and ground data systems software domains throughout Code 500.

Operative team communication during simulated emergencies: Too busy to respond?

PubMed

Davis, W Austin; Jones, Seth; Crowell-Kuhnberg, Adrianna M; O'Keeffe, Dara; Boyle, Kelly M; Klainer, Suzanne B; Smink, Douglas S; Yule, Steven

2017-05-01

Ineffective communication among members of a multidisciplinary team is associated with operative error and failure to rescue. We sought to measure operative team communication in a simulated emergency using an established communication framework called "closed loop communication." We hypothesized that communication directed at a specific recipient would be more likely to elicit a check back or closed loop response and that this relationship would vary with changes in patients' clinical status. We used the closed loop communication framework to code retrospectively the communication behavior of 7 operative teams (each comprising 2 surgeons, anesthesiologists, and nurses) during response to a simulated, postanesthesia care unit "code blue." We identified call outs, check backs, and closed loop episodes and applied descriptive statistics and a mixed-effects negative binomial regression to describe characteristics of communication in individuals and in different specialties. We coded a total of 662 call outs. The frequency and type of initiation and receipt of communication events varied between clinical specialties (P < .001). Surgeons and nurses initiated fewer and received more communication events than anesthesiologists. For the average participant, directed communication increased the likelihood of check back by at least 50% (P = .021) in periods preceding acute changes in the clinical setting, and exerted no significant effect in periods after acute changes in the clinical situation. Communication patterns vary by specialty during a simulated operative emergency, and the effect of directed communication in eliciting a response depends on the clinical status of the patient. Operative training programs should emphasize the importance of quality communication in the period immediately after an acute change in the clinical setting of a patient and recognize that communication patterns and needs vary between members of multidisciplinary operative teams. Copyright © 2016 Elsevier Inc. All rights reserved.

Digital Baseband Architecture For Transponder

NASA Technical Reports Server (NTRS)

Nguyen, Tien M.; Yeh, Hen-Geul

1995-01-01

Proposed advanced transponder for long-distance radio communication system with turnaround ranging contains carrier-signal-tracking loop including baseband digital "front end." For reduced cost, transponder includes analog intermediate-frequency (IF) section and analog automatic gain control (AGC) loop at first of two IF mixers. However, second IF mixer redesigned to ease digitization of baseband functions. To conserve power and provide for simpler and smaller transponder hardware, baseband digital signal-processing circuits designed to implement undersampling scheme. Furthermore, sampling scheme and sampling frequency chosen so redesign involves minimum modification of command-detector unit (CDU).

Modal Filtering for Control of Flexible Aircraft

NASA Technical Reports Server (NTRS)

Suh, Peter M.; Mavris, Dimitri N.

2013-01-01

Modal regulators and deformation trackers are designed for an open-loop fluttering wing model. The regulators are designed with modal coordinate and accelerometer inputs respectively. The modal coordinates are estimated with simulated fiber optics. The robust stability of the closed-loop systems is compared in a structured singular-value vector analysis. Performance is evaluated and compared in a gust alleviation and flutter suppression simulation. For the same wing and flight condition two wing-shape-tracking control architectures are presented, which achieve deformation control at any point on the wing.

Designing and maintaining an effective chargemaster.

PubMed

Abbey, D C

2001-03-01

The chargemaster is the central repository of charges and associated coding information used to develop claims. But this simple description belies the chargemaster's true complexity. The chargemaster's role in the coding process differs from department to department, and not all codes provided on a claim form are necessarily included in the chargemaster, as codes for complex services may need to be developed and reviewed by coding staff. In addition, with the rise of managed care, the chargemaster increasingly is being used to track utilization of supplies and services. To ensure that the chargemaster performs all of its functions effectively, hospitals should appoint a chargemaster coordinator, supported by a chargemaster review team, to oversee the design and maintenance of the chargemaster. Important design issues that should be considered include the principle of "form follows function," static versus dynamic coding, how modifiers should be treated, how charges should be developed, how to incorporate physician fee schedules into the chargemaster, the interface between the chargemaster and cost reports, and how to include statistical information for tracking utilization.

Simulation and experiment of a fuzzy logic based MPPT controller for a small wind turbine system

NASA Astrophysics Data System (ADS)

Petrila, Diana; Muntean, Nicolae

2012-09-01

This paper describes the development of a fuzzy logic based maximum power point tracking (MPPT) strategy for a variable speed wind turbine system (VSWT). For this scope, a fuzzy logic controller (FLC) was described, simulated and tested on a real time "hardware in the loop" wind turbine emulator. Simulation and experimental results show that the controller is able to track the maximum power point for various wind conditions and validate the proposed control strategy.

An AI Approach to Ground Station Autonomy for Deep Space Communications

NASA Technical Reports Server (NTRS)

Fisher, Forest; Estlin, Tara; Mutz, Darren; Paal, Leslie; Law, Emily; Stockett, Mike; Golshan, Nasser; Chien, Steve

1998-01-01

This paper describes an architecture for an autonomous deep space tracking station (DS-T). The architecture targets fully automated routine operations encompassing scheduling and resource allocation, antenna and receiver predict generation. track procedure generation from service requests, and closed loop control and error recovery for the station subsystems. This architecture has been validated by the construction of a prototype DS-T station, which has performed a series of demonstrations of autonomous ground station control for downlink services with NASA's Mars Global Surveyor (MGS).

Beam-dynamics codes used at DARHT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekdahl, Jr., Carl August

Several beam simulation codes are used to help gain a better understanding of beam dynamics in the DARHT LIAs. The most notable of these fall into the following categories: for beam production – Tricomp Trak orbit tracking code, LSP Particle in cell (PIC) code, for beam transport and acceleration – XTR static envelope and centroid code, LAMDA time-resolved envelope and centroid code, LSP-Slice PIC code, for coasting-beam transport to target – LAMDA time-resolved envelope code, LSP-Slice PIC code. These codes are also being used to inform the design of Scorpius.

Braiding by Majorana tracking and long-range CNOT gates with color codes

NASA Astrophysics Data System (ADS)

Litinski, Daniel; von Oppen, Felix

2017-11-01

Color-code quantum computation seamlessly combines Majorana-based hardware with topological error correction. Specifically, as Clifford gates are transversal in two-dimensional color codes, they enable the use of the Majoranas' non-Abelian statistics for gate operations at the code level. Here, we discuss the implementation of color codes in arrays of Majorana nanowires that avoid branched networks such as T junctions, thereby simplifying their realization. We show that, in such implementations, non-Abelian statistics can be exploited without ever performing physical braiding operations. Physical braiding operations are replaced by Majorana tracking, an entirely software-based protocol which appropriately updates the Majoranas involved in the color-code stabilizer measurements. This approach minimizes the required hardware operations for single-qubit Clifford gates. For Clifford completeness, we combine color codes with surface codes, and use color-to-surface-code lattice surgery for long-range multitarget CNOT gates which have a time overhead that grows only logarithmically with the physical distance separating control and target qubits. With the addition of magic state distillation, our architecture describes a fault-tolerant universal quantum computer in systems such as networks of tetrons, hexons, or Majorana box qubits, but can also be applied to nontopological qubit platforms.

Loop heating by D.C. electric current and electromagnetic wave emissions simulated by 3-D EM particle zone

NASA Technical Reports Server (NTRS)

Sakai, J. I.; Zhao, J.; Nishikawa, K.-I.

1994-01-01

We have shown that a current-carrying plasma loop can be heated by magnetic pinch driven by the pressure imbalance between inside and outside the loop, using a 3-dimensional electromagnetic (EM) particle code. Both electrons and ions in the loop can be heated in the direction perpendicular to the ambient magnetic field, therefore the perpendicular temperature can be increased about 10 times compared with the parallel temperature. This temperature anisotropy produced by the magnetic pinch heating can induce a plasma instability, by which high-frequency electromagnetic waves can be excited. The plasma current which is enhanced by the magnetic pinch can also excite a kinetic kink instability, which can heat ions perpendicular to the magnetic field. The heating mechanism of ions as well as the electromagnetic emission could be important for an understanding of the coronal loop heating and the electromagnetic wave emissions from active coronal regions.

Discriminative detection of deposited radon daughters on CR-39 track detectors using TRIAC II code

NASA Astrophysics Data System (ADS)

Patiris, D. L.; Ioannides, K. G.

2009-07-01

A method for detecting deposited 218Po and 214Po by a spectrometric study of CR-39 solid state nuclear track detectors is described. The method is based on the application of software imposed selection criteria, concerning the geometrical and optical properties of the tracks, which correspond to tracks created by alpha particles of specific energy falling on the detector at given angles of incidence. The selection criteria were based on a preliminary study of tracks' parameters (major and minor axes and mean value of brightness), using the TRIAC II code. Since no linear relation was found between the energy and the geometric characteristics of the tracks (major and minor axes), we resorted to the use of an additional parameter in order to classify the tracks according to the particles' energy. Since the brightness of tracks is associated with the tracks' depth, the mean value of brightness was chosen as the parameter of choice. To reduce the energy of the particles, which are emitted by deposited 218Po and 214Po into a quantifiable range, the detectors were covered with an aluminum absorber material. In this way, the discrimination of radon's daughters was finally accomplished by properly selecting amongst all registered tracks. This method could be applied as a low cost tool for the study of the radon's daughters behavior in air.

Robust GPS carrier tracking under ionospheric scintillation

NASA Astrophysics Data System (ADS)

Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

2013-12-01

Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance of the proposed tracking scheme is assessed by using both simulated and real data. Real data have been collected in Vietnam by using a USRP (Universal Software Radio Peripheral) N210 front end connected to a rubidium oscillator. Selected events are exploited in order to challenge the algorithm with strong phase and amplitude variations. Moreover, simulated data have been collected by using the prototype of a digital front end developed by Novatel, namely the 'Firehose'. Since the latter includes a TCXO oscillator, the proposed tracking scheme is also opportunely modified to take in account the clock error contribution. References 1. R.S., Conker, M. B. El-Arini, C. J. Hegarty, and T. Hsiao, Modelling the effects of ionospheric scintillation on GPS/satellite-based augmentation system availability. Radio Sci., 38, 1, 1001, doi: 10.1029/2000RS002604, 2003. 2. B. Bougard et al, 'CIGALA: Challenging the Solar Maximum in Brazil with PolaRxS,' ION GNSS, Portland, Sept. 2011.

Sum of the Magnitude for Hard Decision Decoding Algorithm Based on Loop Update Detection

PubMed Central

Meng, Jiahui; Zhao, Danfeng; Tian, Hai; Zhang, Liang

2018-01-01

In order to improve the performance of non-binary low-density parity check codes (LDPC) hard decision decoding algorithm and to reduce the complexity of decoding, a sum of the magnitude for hard decision decoding algorithm based on loop update detection is proposed. This will also ensure the reliability, stability and high transmission rate of 5G mobile communication. The algorithm is based on the hard decision decoding algorithm (HDA) and uses the soft information from the channel to calculate the reliability, while the sum of the variable nodes’ (VN) magnitude is excluded for computing the reliability of the parity checks. At the same time, the reliability information of the variable node is considered and the loop update detection algorithm is introduced. The bit corresponding to the error code word is flipped multiple times, before this is searched in the order of most likely error probability to finally find the correct code word. Simulation results show that the performance of one of the improved schemes is better than the weighted symbol flipping (WSF) algorithm under different hexadecimal numbers by about 2.2 dB and 2.35 dB at the bit error rate (BER) of 10−5 over an additive white Gaussian noise (AWGN) channel, respectively. Furthermore, the average number of decoding iterations is significantly reduced. PMID:29342963

21 CFR 1271.290 - Tracking.

Code of Federal Regulations, 2011 CFR

2011-04-01

... for recording the distinct identification code and type of each HCT/P distributed to a consignee to... step in the manufacture of an HCT/P in which you handle the HCT/P, you must track each such HCT/P in... communicable disease and take appropriate and timely corrective action. (b) System of HCT/P tracking. (1) You...

Analysis of spacecraft battery charger systems

NASA Astrophysics Data System (ADS)

Kim, Seong J.; Cho, Bo H.

In spacecraft battery charger systems, switching regulators are widely used for bus voltage regulation, charge current regulation, and peak power tracking. Small-signal dynamic characteristics of the battery charging subsystem of direct energy transfer (DET) and peak power tracking (PPT) systems are analyzed to facilitate design of the control loop for optimum performance and stability. Control loop designs of the charger in various modes of operation are discussed. Analyses are verified through simulations. It is shown that when the charger operates in the bus voltage regulation mode, the control-to-voltage transfer function has a negative DC gain and two LHP zeros in both the DET and PPT systems. The control-to-inductor current transfer function also has a negative DC gain and a RHP zero. Thus, in the current-mode control, the current loop can no longer be used to stabilize the system. When the system operates in the charge current regulation mode, the charger operates with a fixed duty cycle which is determined by the regulated bus voltage and the battery voltage. Without an input filter, the converter becomes a first-order system. When the peak power tracker is inactive, the operating point of the solar array output moves to the voltage source region. Thus, the solar array behaves as a stiff voltage source to a constant power load.

A Carrier Estimation Method Based on MLE and KF for Weak GNSS Signals.

PubMed

Zhang, Hongyang; Xu, Luping; Yan, Bo; Zhang, Hua; Luo, Liyan

2017-06-22

Maximum likelihood estimation (MLE) has been researched for some acquisition and tracking applications of global navigation satellite system (GNSS) receivers and shows high performance. However, all current methods are derived and operated based on the sampling data, which results in a large computation burden. This paper proposes a low-complexity MLE carrier tracking loop for weak GNSS signals which processes the coherent integration results instead of the sampling data. First, the cost function of the MLE of signal parameters such as signal amplitude, carrier phase, and Doppler frequency are used to derive a MLE discriminator function. The optimal value of the cost function is searched by an efficient Levenberg-Marquardt (LM) method iteratively. Its performance including Cramér-Rao bound (CRB), dynamic characteristics and computation burden are analyzed by numerical techniques. Second, an adaptive Kalman filter is designed for the MLE discriminator to obtain smooth estimates of carrier phase and frequency. The performance of the proposed loop, in terms of sensitivity, accuracy and bit error rate, is compared with conventional methods by Monte Carlo (MC) simulations both in pedestrian-level and vehicle-level dynamic circumstances. Finally, an optimal loop which combines the proposed method and conventional method is designed to achieve the optimal performance both in weak and strong signal circumstances.

Mathematical Modeling of RNA-Based Architectures for Closed Loop Control of Gene Expression.

PubMed

Agrawal, Deepak K; Tang, Xun; Westbrook, Alexandra; Marshall, Ryan; Maxwell, Colin S; Lucks, Julius; Noireaux, Vincent; Beisel, Chase L; Dunlop, Mary J; Franco, Elisa

2018-05-08

Feedback allows biological systems to control gene expression precisely and reliably, even in the presence of uncertainty, by sensing and processing environmental changes. Taking inspiration from natural architectures, synthetic biologists have engineered feedback loops to tune the dynamics and improve the robustness and predictability of gene expression. However, experimental implementations of biomolecular control systems are still far from satisfying performance specifications typically achieved by electrical or mechanical control systems. To address this gap, we present mathematical models of biomolecular controllers that enable reference tracking, disturbance rejection, and tuning of the temporal response of gene expression. These controllers employ RNA transcriptional regulators to achieve closed loop control where feedback is introduced via molecular sequestration. Sensitivity analysis of the models allows us to identify which parameters influence the transient and steady state response of a target gene expression process, as well as which biologically plausible parameter values enable perfect reference tracking. We quantify performance using typical control theory metrics to characterize response properties and provide clear selection guidelines for practical applications. Our results indicate that RNA regulators are well-suited for building robust and precise feedback controllers for gene expression. Additionally, our approach illustrates several quantitative methods useful for assessing the performance of biomolecular feedback control systems.

Advanced Receiver tracking of Voyager 2 near solar conjunction

NASA Technical Reports Server (NTRS)

Brown, D. H.; Hurd, W. J.; Vilnrotter, V. A.; Wiggins, J. D.

1988-01-01

The Advanced Receiver (ARX) was used to track the Voyager 2 spacecraft at low Sun-Earth-Probe (SEP) angles near solar conjunction in December of 1987. The received carrier signal exhibited strong fluctuations in both phase and amplitude. The ARX used spectral estimation and mathematical modeling of the phase and receiver noise processes to set an optimum carrier tracking bandwidth. This minimized the mean square phase error in tracking carrier phase and thus minimized the loss in the telemetry signal-to-noise ratio due to the carrier loop. Recovered symbol SNRs and errors in decoded engineering data for the ARX are compared with those for the current Block 3 telemetry stream. Optimum bandwidths are plotted against SEP angle. Measurements of the power spectral density of the solar phase and amplitude fluctuations are also given.

Ground Simulation of an Autonomous Satellite Rendezvous and Tracking System Using Dual Robotic Systems

NASA Technical Reports Server (NTRS)

Trube, Matthew J.; Hyslop, Andrew M.; Carignan, Craig R.; Easley, Joseph W.

2012-01-01

A hardware-in-the-loop ground system was developed for simulating a robotic servicer spacecraft tracking a target satellite at short range. A relative navigation sensor package "Argon" is mounted on the end-effector of a Fanuc 430 manipulator, which functions as the base platform of the robotic spacecraft servicer. Machine vision algorithms estimate the pose of the target spacecraft, mounted on a Rotopod R-2000 platform, relay the solution to a simulation of the servicer spacecraft running in "Freespace", which performs guidance, navigation and control functions, integrates dynamics, and issues motion commands to a Fanuc platform controller so that it tracks the simulated servicer spacecraft. Results will be reviewed for several satellite motion scenarios at different ranges. Key words: robotics, satellite, servicing, guidance, navigation, tracking, control, docking.

Quantifying Pilot Visual Attention in Low Visibility Terminal Operations

NASA Technical Reports Server (NTRS)

Ellis, Kyle K.; Arthur, J. J.; Latorella, Kara A.; Kramer, Lynda J.; Shelton, Kevin J.; Norman, Robert M.; Prinzel, Lawrence J.

2012-01-01

Quantifying pilot visual behavior allows researchers to determine not only where a pilot is looking and when, but holds implications for specific behavioral tracking when these data are coupled with flight technical performance. Remote eye tracking systems have been integrated into simulators at NASA Langley with effectively no impact on the pilot environment. This paper discusses the installation and use of a remote eye tracking system. The data collection techniques from a complex human-in-the-loop (HITL) research experiment are discussed; especially, the data reduction algorithms and logic to transform raw eye tracking data into quantified visual behavior metrics, and analysis methods to interpret visual behavior. The findings suggest superior performance for Head-Up Display (HUD) and improved attentional behavior for Head-Down Display (HDD) implementations of Synthetic Vision System (SVS) technologies for low visibility terminal area operations. Keywords: eye tracking, flight deck, NextGen, human machine interface, aviation

Development of a Run Time Math Library for the 1750A Airborne Microcomputer.

DTIC Science & Technology

1985-12-01

premiue CWUTLDK Is R: Integer :a 0; 0: Integer :ul; LNMM: UEM; -Compute the Lado (alpii) for J In 0..Ol.K-1) loop Itf 0(14 1)/ 0. 0...ORGANIZATION (If appiicable) * School of Engineering AFIT/ ENC 6c. ADDRESS (City, State and ZIP Code) 7b. ADDRESS (City. State and ZIP Code) Air Force

NASA One-Dimensional Combustor Simulation--User Manual for S1D_ML

NASA Technical Reports Server (NTRS)

Stueber, Thomas J.; Paxson, Daniel E.

2014-01-01

The work presented in this paper is to promote research leading to a closed-loop control system to actively suppress thermo-acoustic instabilities. To serve as a model for such a closed-loop control system, a one-dimensional combustor simulation composed using MATLAB software tools has been written. This MATLAB based process is similar to a precursor one-dimensional combustor simulation that was formatted as FORTRAN 77 source code. The previous simulation process requires modification to the FORTRAN 77 source code, compiling, and linking when creating a new combustor simulation executable file. The MATLAB based simulation does not require making changes to the source code, recompiling, or linking. Furthermore, the MATLAB based simulation can be run from script files within the MATLAB environment or with a compiled copy of the executable file running in the Command Prompt window without requiring a licensed copy of MATLAB. This report presents a general simulation overview. Details regarding how to setup and initiate a simulation are also presented. Finally, the post-processing section describes the two types of files created while running the simulation and it also includes simulation results for a default simulation included with the source code.

Next generation sequencing yields the complete mitochondrial genome of the Hornlip mullet Plicomugil labiosus (Teleostei: Mugilidae).

PubMed

Shen, Kang-Ning; Chen, Ching-Hung; Hsiao, Chung-Der

2016-05-01

In this study, the complete mitogenome sequence of hornlip mullet Plicomugil labiosus (Teleostei: Mugilidae) has been sequenced by next-generation sequencing method. The assembled mitogenome, consisting of 16,829 bp, had the typical vertebrate mitochondrial gene arrangement, including 13 protein coding genes, 22 transfer RNAs, 2 ribosomal RNAs genes and a non-coding control region of D-loop. D-loop contains 1057 bp length is located between tRNA-Pro and tRNA-Phe. The overall base composition of P. labiosus is 28.0% for A, 29.3% for C, 15.5% for G and 27.2% for T. The complete mitogenome may provide essential and important DNA molecular data for further population, phylogenetic and evolutionary analysis for Mugilidae.

Next generation sequencing yields the complete mitochondrial genome of the largescale mullet, Liza macrolepis (Teleostei: Mugilidae).

PubMed

Shen, Kang-Ning; Tsai, Shiou-Yi; Chen, Ching-Hung; Hsiao, Chung-Der; Durand, Jean-Dominique

2016-11-01

In this study, the complete mitogenome sequence of largescale mullet (Teleostei: Mugilidae) has been sequenced by the next-generation sequencing method. The assembled mitogenome, consisting of 16,832 bp, had the typical vertebrate mitochondrial gene arrangement, including 13 protein-coding genes, 22 transfer RNAs, two ribosomal RNAs genes, and a non-coding control region of D-loop. D-loop which has a length of 1094 bp is located between tRNA-Pro and tRNA-Phe. The overall base composition of largescale mullet is 27.8% for A, 30.1% for C, 16.2% for G, and 25.9% for T. The complete mitogenome may provide essential and important DNA molecular data for further phylogenetic and evolutionary analysis for Mugilidae.

Monte Carlo track structure for radiation biology and space applications

NASA Technical Reports Server (NTRS)

Nikjoo, H.; Uehara, S.; Khvostunov, I. G.; Cucinotta, F. A.; Wilson, W. E.; Goodhead, D. T.

2001-01-01

Over the past two decades event by event Monte Carlo track structure codes have increasingly been used for biophysical modelling and radiotherapy. Advent of these codes has helped to shed light on many aspects of microdosimetry and mechanism of damage by ionising radiation in the cell. These codes have continuously been modified to include new improved cross sections and computational techniques. This paper provides a summary of input data for ionizations, excitations and elastic scattering cross sections for event by event Monte Carlo track structure simulations for electrons and ions in the form of parametric equations, which makes it easy to reproduce the data. Stopping power and radial distribution of dose are presented for ions and compared with experimental data. A model is described for simulation of full slowing down of proton tracks in water in the range 1 keV to 1 MeV. Modelling and calculations are presented for the response of a TEPC proportional counter irradiated with 5 MeV alpha-particles. Distributions are presented for the wall and wall-less counters. Data shows contribution of indirect effects to the lineal energy distribution for the wall counters responses even at such a low ion energy.

Accelerated event-by-event Monte Carlo microdosimetric calculations of electrons and protons tracks on a multi-core CPU and a CUDA-enabled GPU.

PubMed

Kalantzis, Georgios; Tachibana, Hidenobu

2014-01-01

For microdosimetric calculations event-by-event Monte Carlo (MC) methods are considered the most accurate. The main shortcoming of those methods is the extensive requirement for computational time. In this work we present an event-by-event MC code of low projectile energy electron and proton tracks for accelerated microdosimetric MC simulations on a graphic processing unit (GPU). Additionally, a hybrid implementation scheme was realized by employing OpenMP and CUDA in such a way that both GPU and multi-core CPU were utilized simultaneously. The two implementation schemes have been tested and compared with the sequential single threaded MC code on the CPU. Performance comparison was established on the speed-up for a set of benchmarking cases of electron and proton tracks. A maximum speedup of 67.2 was achieved for the GPU-based MC code, while a further improvement of the speedup up to 20% was achieved for the hybrid approach. The results indicate the capability of our CPU-GPU implementation for accelerated MC microdosimetric calculations of both electron and proton tracks without loss of accuracy. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly.

PubMed

Chen, Yi-Ching; Lin, Linda L; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations [Formula: see text], short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13-35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization.

Variations in Static Force Control and Motor Unit Behavior with Error Amplification Feedback in the Elderly

PubMed Central

Chen, Yi-Ching; Lin, Linda L.; Lin, Yen-Ting; Hu, Chia-Ling; Hwang, Ing-Shiou

2017-01-01

Error amplification (EA) feedback is a promising approach to advance visuomotor skill. As error detection and visuomotor processing at short time scales decline with age, this study examined whether older adults could benefit from EA feedback that included higher-frequency information to guide a force-tracking task. Fourteen young and 14 older adults performed low-level static isometric force-tracking with visual guidance of typical visual feedback and EA feedback containing augmented high-frequency errors. Stabilogram diffusion analysis was used to characterize force fluctuation dynamics. Also, the discharge behaviors of motor units and pooled motor unit coherence were assessed following the decomposition of multi-channel surface electromyography (EMG). EA produced different behavioral and neurophysiological impacts on young and older adults. Older adults exhibited inferior task accuracy with EA feedback than with typical visual feedback, but not young adults. Although stabilogram diffusion analysis revealed that EA led to a significant decrease in critical time points for both groups, EA potentiated the critical point of force fluctuations <ΔFc2>, short-term effective diffusion coefficients (Ds), and short-term exponent scaling only for the older adults. Moreover, in older adults, EA added to the size of discharge variability of motor units and discharge regularity of cumulative discharge rate, but suppressed the pooled motor unit coherence in the 13–35 Hz band. Virtual EA alters the strategic balance between open-loop and closed-loop controls for force-tracking. Contrary to expectations, the prevailing use of closed-loop control with EA that contained high-frequency error information enhanced the motor unit discharge variability and undermined the force steadiness in the older group, concerning declines in physiological complexity in the neurobehavioral system and the common drive to the motoneuronal pool against force destabilization. PMID:29167637

Detection of the Second Harmonic of Decay-less Kink Oscillations in the Solar Corona

NASA Astrophysics Data System (ADS)

Duckenfield, T.; Anfinogentov, S. A.; Pascoe, D. J.; Nakariakov, V. M.

2018-02-01

EUV observations of a multi-thermal coronal loop, taken by the Atmospheric Imaging Assembly of the Solar Dynamics Observatory, which exhibits decay-less kink oscillations are presented. The data cube of the quiet-Sun coronal loop was passed through a motion magnification algorithm to accentuate transverse oscillations. Time–distance maps are made from multiple slits evenly spaced along the loop axis and oriented orthogonal to the loop axis. Displacements of the intensity peak are tracked to generate time series of the loop displacement. Fourier analysis on the time series shows the presence of two periods within the loop: {P}1={10.3}-1.7+1.5 minutes and {P}2={7.4}-1.3+1.1 minutes. The longer period component is greatest in amplitude at the apex and remains in phase throughout the loop length. The shorter period component is strongest further down from the apex on both legs and displays an anti-phase behavior between the two loop legs. We interpret these results as the coexistence of the fundamental and second harmonics of the standing kink mode within the loop in the decay-less oscillation regime. An illustration of seismological application using the ratio P 1/2P 2 ∼ 0.7 to estimate the density scale height is presented. The existence of multiple harmonics has implications for understanding the driving and damping mechanisms for decay-less oscillations and adds credence to their interpretation as standing kink mode oscillations.

Simulation of process identification and controller tuning for flow control system

NASA Astrophysics Data System (ADS)

Chew, I. M.; Wong, F.; Bono, A.; Wong, K. I.

2017-06-01

PID controller is undeniably the most popular method used in controlling various industrial processes. The feature to tune the three elements in PID has allowed the controller to deal with specific needs of the industrial processes. This paper discusses the three elements of control actions and improving robustness of controllers through combination of these control actions in various forms. A plant model is simulated using the Process Control Simulator in order to evaluate the controller performance. At first, the open loop response of the plant is studied by applying a step input to the plant and collecting the output data from the plant. Then, FOPDT of physical model is formed by using both Matlab-Simulink and PRC method. Then, calculation of controller’s setting is performed to find the values of Kc and τi that will give satisfactory control in closed loop system. Then, the performance analysis of closed loop system is obtained by set point tracking analysis and disturbance rejection performance. To optimize the overall physical system performance, a refined tuning of PID or detuning is further conducted to ensure a consistent resultant output of closed loop system reaction to the set point changes and disturbances to the physical model. As a result, the PB = 100 (%) and τi = 2.0 (s) is preferably chosen for setpoint tracking while PB = 100 (%) and τi = 2.5 (s) is selected for rejecting the imposed disturbance to the model. In a nutshell, selecting correlation tuning values is likewise depended on the required control’s objective for the stability performance of overall physical model.

Prediction of pilot reserve attention capacity during air-to-air target tracking

NASA Technical Reports Server (NTRS)

Onstott, E. D.; Faulkner, W. H.

1977-01-01

Reserve attention capacity of a pilot was calculated using a pilot model that allocates exclusive model attention according to the ranking of task urgency functions whose variables are tracking error and error rate. The modeled task consisted of tracking a maneuvering target aircraft both vertically and horizontally, and when possible, performing a diverting side task which was simulated by the precise positioning of an electrical stylus and modeled as a task of constant urgency in the attention allocation algorithm. The urgency of the single loop vertical task is simply the magnitude of the vertical tracking error, while the multiloop horizontal task requires a nonlinear urgency measure of error and error rate terms. Comparison of model results with flight simulation data verified the computed model statistics of tracking error of both axes, lateral and longitudinal stick amplitude and rate, and side task episodes. Full data for the simulation tracking statistics as well as the explicit equations and structure of the urgency function multiaxis pilot model are presented.

Accommodating Sensor Bias in MRAC for State Tracking

NASA Technical Reports Server (NTRS)

Patre, Parag; Joshi, Suresh M.

2011-01-01

The problem of accommodating unknown sensor bias is considered in a direct model reference adaptive control (MRAC) setting for state tracking using state feedback. Sensor faults can occur during operation, and if the biased state measurements are directly used with a standard MRAC control law, neither closed-loop signal boundedness, nor asymptotic tracking can be guaranteed and the resulting tracking errors may be unbounded or unacceptably large. A modified MRAC law is proposed, which combines a bias estimator with control gain adaptation, and it is shown that signal boundedness can be accomplished, although the tracking error may not go to zero. Further, for the case wherein an asymptotically stable sensor bias estimator is available, an MRAC control law is proposed to accomplish asymptotic tracking and signal boundedness. Such a sensor bias estimator can be designed if additional sensor measurements are available, as illustrated for the case wherein bias is present in the rate gyro and airspeed measurements. Numerical example results are presented to illustrate each of the schemes.

Curiosity Leaves Its Mark

NASA Image and Video Library

2012-08-29

This image shows a close-up of track marks from the first test drive of NASA Curiosity rover. The rover arm is visible in the foreground. A close inspection of the tracks reveals a unique, repeating pattern: Morse code for JPL.

Combined line-of-sight error and angular position to generate feedforward control for a charge-coupled device-based tracking loop

NASA Astrophysics Data System (ADS)

Tang, Tao; Cai, Huaxiang; Huang, Yongmei; Ren, Ge

2015-10-01

A feedforward control based on data fusion is proposed to enhance closed-loop performance. The target trajectory as the observed value of a Kalman filter is recovered by synthesizing line-of-sight error and angular position from the encoder. A Kalman filter based on a Singer acceleration model is employed to estimate the target velocity. In this control scheme, the control stability is influenced by the bandwidth of the Kalman filter and time misalignment. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability, which shows that the Kalman filter is the major factor that affects the control stability. The feedforward control proposed here is verified through simulations and experiments.

A modular, closed-loop platform for intracranial stimulation in people with neurological disorders.

PubMed

Sarma, Anish A; Crocker, Britni; Cash, Sydney S; Truccolo, Wilson

2016-08-01

Neuromodulation systems based on electrical stimulation can be used to investigate, probe, and potentially treat a range of neurological disorders. The effects of ongoing neural state and dynamics on stimulation response, and of stimulation parameters on neural state, have broad implications for the development of closed-loop neuro-modulation approaches. We describe the development of a modular, low-latency platform for pre-clinical, closed-loop neuromodulation studies with human participants. We illustrate the uses of the platform in a stimulation case study with a person with epilepsy undergoing neuro-monitoring prior to resective surgery. We demonstrate the efficacy of the system by tracking interictal epileptiform discharges in the local field potential to trigger intracranial electrical stimulation, and show that the response to stimulation depends on the neural state.

KU-Band rendezvous radar performance computer simulation model

NASA Technical Reports Server (NTRS)

Griffin, J. W.

1980-01-01

The preparation of a real time computer simulation model of the KU band rendezvous radar to be integrated into the shuttle mission simulator (SMS), the shuttle engineering simulator (SES), and the shuttle avionics integration laboratory (SAIL) simulator is described. To meet crew training requirements a radar tracking performance model, and a target modeling method were developed. The parent simulation/radar simulation interface requirements, and the method selected to model target scattering properties, including an application of this method to the SPAS spacecraft are described. The radar search and acquisition mode performance model and the radar track mode signal processor model are examined and analyzed. The angle, angle rate, range, and range rate tracking loops are also discussed.

Lasercom system architecture with reduced complexity

NASA Technical Reports Server (NTRS)

Lesh, James R. (Inventor); Chen, Chien-Chung (Inventor); Ansari, Homayoon (Inventor)

1994-01-01

Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. In the present invention, a single high bandwidth CCD detector is used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides the means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. The single detector design can lead to a significantly reduced system complexity and a lower system cost.

LaserCom System Architecture With Reduced Complexity

NASA Technical Reports Server (NTRS)

Lesh, James R. (Inventor); Chen, Chien-Chung (Inventor); Ansari, Homa-Yoon (Inventor)

1996-01-01

Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. In the present invention a single high bandwidth CCD detector is used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. The single detector design can lead to a significantly reduced system complexity and a lower system cost.

Role of Oculoproprioception in Coding the Locus of Attention.

PubMed

Odoj, Bartholomaeus; Balslev, Daniela

2016-03-01

The most common neural representations for spatial attention encode locations retinotopically, relative to center of gaze. To keep track of visual objects across saccades or to orient toward sounds, retinotopic representations must be combined with information about the rotation of one's own eyes in the orbits. Although gaze input is critical for a correct allocation of attention, the source of this input has so far remained unidentified. Two main signals are available: corollary discharge (copy of oculomotor command) and oculoproprioception (feedback from extraocular muscles). Here we asked whether the oculoproprioceptive signal relayed from the somatosensory cortex contributes to coding the locus of attention. We used continuous theta burst stimulation (cTBS) over a human oculoproprioceptive area in the postcentral gyrus (S1EYE). S1EYE-cTBS reduces proprioceptive processing, causing ∼1° underestimation of gaze angle. Participants discriminated visual targets whose location was cued in a nonvisual modality. Throughout the visual space, S1EYE-cTBS shifted the locus of attention away from the cue by ∼1°, in the same direction and by the same magnitude as the oculoproprioceptive bias. This systematic shift cannot be attributed to visual mislocalization. Accuracy of open-loop pointing to the same visual targets, a function thought to rely mainly on the corollary discharge, was unchanged. We argue that oculoproprioception is selective for attention maps. By identifying a potential substrate for the coupling between eye and attention, this study contributes to the theoretical models for spatial attention.

Computation of neutron fluxes in clusters of fuel pins arranged in hexagonal assemblies (2D and 3D)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabha, H.; Marleau, G.

2012-07-01

For computations of fluxes, we have used Carvik's method of collision probabilities. This method requires tracking algorithms. An algorithm to compute tracks (in 2D and 3D) has been developed for seven hexagonal geometries with cluster of fuel pins. This has been implemented in the NXT module of the code DRAGON. The flux distribution in cluster of pins has been computed by using this code. For testing the results, they are compared when possible with the EXCELT module of the code DRAGON. Tracks are plotted in the NXT module by using MATLAB, these plots are also presented here. Results are presentedmore » with increasing number of lines to show the convergence of these results. We have numerically computed volumes, surface areas and the percentage errors in these computations. These results show that 2D results converge faster than 3D results. The accuracy on the computation of fluxes up to second decimal is achieved with fewer lines. (authors)« less

User`s and reference guide to the INEL RML/analytical radiochemistry sample tracking database version 1.00

DOE Office of Scientific and Technical Information (OSTI.GOV)

Femec, D.A.

This report discusses the sample tracking database in use at the Idaho National Engineering Laboratory (INEL) by the Radiation Measurements Laboratory (RML) and Analytical Radiochemistry. The database was designed in-house to meet the specific needs of the RML and Analytical Radiochemistry. The report consists of two parts, a user`s guide and a reference guide. The user`s guide presents some of the fundamentals needed by anyone who will be using the database via its user interface. The reference guide describes the design of both the database and the user interface. Briefly mentioned in the reference guide are the code-generating tools, CREATE-SCHEMAmore » and BUILD-SCREEN, written to automatically generate code for the database and its user interface. The appendices contain the input files used by the these tools to create code for the sample tracking database. The output files generated by these tools are also included in the appendices.« less

Visual servoing in medical robotics: a survey. Part I: endoscopic and direct vision imaging - techniques and applications.

PubMed

Azizian, Mahdi; Khoshnam, Mahta; Najmaei, Nima; Patel, Rajni V

2014-09-01

Intra-operative imaging is widely used to provide visual feedback to a clinician when he/she performs a procedure. In visual servoing, surgical instruments and parts of tissue/body are tracked by processing the acquired images. This information is then used within a control loop to manoeuvre a robotic manipulator during a procedure. A comprehensive search of electronic databases was completed for the period 2000-2013 to provide a survey of the visual servoing applications in medical robotics. The focus is on medical applications where image-based tracking is used for closed-loop control of a robotic system. Detailed classification and comparative study of various contributions in visual servoing using endoscopic or direct visual images are presented and summarized in tables and diagrams. The main challenges in using visual servoing for medical robotic applications are identified and potential future directions are suggested. 'Supervised automation of medical robotics' is found to be a major trend in this field. Copyright © 2013 John Wiley & Sons, Ltd.

Sliding mode disturbance observer-based control of a twin rotor MIMO system.

PubMed

Rashad, Ramy; El-Badawy, Ayman; Aboudonia, Ahmed

2017-07-01

This work proposes a robust tracking controller for a helicopter laboratory setup known as the twin rotor MIMO system (TRMS) using an integral sliding mode controller. To eliminate the discontinuity in the control signal, the controller is augmented by a sliding mode disturbance observer. The actuator dynamics is handled using a backstepping approach which is applicable due to the continuous chattering-free nature of the command signals generated using the disturbance observer based controller. To avoid the complexity of analytically differentiating the command signals, a first order sliding mode differentiator is used. Stability analysis of the closed loop system and the ultimate boundedness of the tracking error is proved using Lyapunov stability arguments. The proposed controller is validated by several simulation studies and is compared to other schemes in the literature. Experimental results using a hardware-in-the-loop system validate the robustness and effectiveness of the proposed controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Phylogenetic Network for European mtDNA

PubMed Central

Finnilä, Saara; Lehtonen, Mervi S.; Majamaa, Kari

2001-01-01

The sequence in the first hypervariable segment (HVS-I) of the control region has been used as a source of evolutionary information in most phylogenetic analyses of mtDNA. Population genetic inference would benefit from a better understanding of the variation in the mtDNA coding region, but, thus far, complete mtDNA sequences have been rare. We determined the nucleotide sequence in the coding region of mtDNA from 121 Finns, by conformation-sensitive gel electrophoresis and subsequent sequencing and by direct sequencing of the D loop. Furthermore, 71 sequences from our previous reports were included, so that the samples represented all the mtDNA haplogroups present in the Finnish population. We found a total of 297 variable sites in the coding region, which allowed the compilation of unambiguous phylogenetic networks. The D loop harbored 104 variable sites, and, in most cases, these could be localized within the coding-region networks, without discrepancies. Interestingly, many homoplasies were detected in the coding region. Nucleotide variation in the rRNA and tRNA genes was 6%, and that in the third nucleotide positions of structural genes amounted to 22% of that in the HVS-I. The complete networks enabled the relationships between the mtDNA haplogroups to be analyzed. Phylogenetic networks based on the entire coding-region sequence in mtDNA provide a rich source for further population genetic studies, and complete sequences make it easier to differentiate between disease-causing mutations and rare polymorphisms. PMID:11349229

Use of a Closed-Loop Tracking Algorithm for Orientation Bias Determination of an S-Band Ground Station

NASA Technical Reports Server (NTRS)

Welch, Bryan W.; Piasecki, Marie T.; Schrage, Dean S.

2015-01-01

The Space Communications and Navigation (SCaN) Testbed project completed installation and checkout testing of a new S-Band ground station at the NASA Glenn Research Center in Cleveland, Ohio in 2015. As with all ground stations, a key alignment process must be conducted to obtain offset angles in azimuth (AZ) and elevation (EL). In telescopes with AZ-EL gimbals, this is normally done with a two-star alignment process, where telescope-based pointing vectors are derived from catalogued locations with the AZ-EL bias angles derived from the pointing vector difference. For an antenna, the process is complicated without an optical asset. For the present study, the solution was to utilize the gimbal control algorithms closed-loop tracking capability to acquire the peak received power signal automatically from two distinct NASA Tracking and Data Relay Satellite (TDRS) spacecraft, without a human making the pointing adjustments. Briefly, the TDRS satellite acts as a simulated optical source and the alignment process proceeds exactly the same way as a one-star alignment. The data reduction process, which will be discussed in the paper, results in two bias angles which are retained for future pointing determination. Finally, the paper compares the test results and provides lessons learned from the activity.

GNSS Signal Tracking Performance Improvement for Highly Dynamic Receivers by Gyroscopic Mounting Crystal Oscillator.

PubMed

Abedi, Maryam; Jin, Tian; Sun, Kewen

2015-08-31

In this paper, the efficiency of the gyroscopic mounting method is studied for a highly dynamic GNSS receiver's reference oscillator for reducing signal loss. Analyses are performed separately in two phases, atmospheric and upper atmospheric flights. Results show that the proposed mounting reduces signal loss, especially in parts of the trajectory where its probability is the highest. This reduction effect appears especially for crystal oscillators with a low elevation angle g-sensitivity vector. The gyroscopic mounting influences frequency deviation or jitter caused by dynamic loads on replica carrier and affects the frequency locked loop (FLL) as the dominant tracking loop in highly dynamic GNSS receivers. In terms of steady-state load, the proposed mounting mostly reduces the frequency deviation below the one-sigma threshold of FLL (1σ(FLL)). The mounting method can also reduce the frequency jitter caused by sinusoidal vibrations and reduces the probability of signal loss in parts of the trajectory where the other error sources accompany this vibration load. In the case of random vibration, which is the main disturbance source of FLL, gyroscopic mounting is even able to suppress the disturbances greater than the three-sigma threshold of FLL (3σ(FLL)). In this way, signal tracking performance can be improved by the gyroscopic mounting method for highly dynamic GNSS receivers.

Autonomous Aerial Refueling Ground Test Demonstration—A Sensor-in-the-Loop, Non-Tracking Method

PubMed Central

Chen, Chao-I; Koseluk, Robert; Buchanan, Chase; Duerner, Andrew; Jeppesen, Brian; Laux, Hunter

2015-01-01

An essential capability for an unmanned aerial vehicle (UAV) to extend its airborne duration without increasing the size of the aircraft is called the autonomous aerial refueling (AAR). This paper proposes a sensor-in-the-loop, non-tracking method for probe-and-drogue style autonomous aerial refueling tasks by combining sensitivity adjustments of a 3D Flash LIDAR camera with computer vision based image-processing techniques. The method overcomes the inherit ambiguity issues when reconstructing 3D information from traditional 2D images by taking advantage of ready to use 3D point cloud data from the camera, followed by well-established computer vision techniques. These techniques include curve fitting algorithms and outlier removal with the random sample consensus (RANSAC) algorithm to reliably estimate the drogue center in 3D space, as well as to establish the relative position between the probe and the drogue. To demonstrate the feasibility of the proposed method on a real system, a ground navigation robot was designed and fabricated. Results presented in the paper show that using images acquired from a 3D Flash LIDAR camera as real time visual feedback, the ground robot is able to track a moving simulated drogue and continuously narrow the gap between the robot and the target autonomously. PMID:25970254

Status Report On Preparation of a Revised Longwave Communication Link Vulnerability Code.

DTIC Science & Technology

1981-10-01

Gallery or Earth-Detached) .J.J Cc) ONE ) E BOVTH ANDENA O EVOUDATENN (EE-G GE d.𔄀, (c) O (d) BOVTHbAD GROUND ANTENN (-G - Figre3.Ilusrain te osibl snge...shows simplified flow diagrams for the ionization models re- quired for LOS and ionospheric dependent propagation calculations. The time loop could be...placed outside the path loop for ionospheric dependent propagation but this requires considerable storage in order to perform nonequilibrium ionization

Coding for parallel execution of hardware-in-the-loop millimeter-wave scene generation models on multicore SIMD processor architectures

NASA Astrophysics Data System (ADS)

Olson, Richard F.

2013-05-01

Rendering of point scatterer based radar scenes for millimeter wave (mmW) seeker tests in real-time hardware-in-the-loop (HWIL) scene generation requires efficient algorithms and vector-friendly computer architectures for complex signal synthesis. New processor technology from Intel implements an extended 256-bit vector SIMD instruction set (AVX, AVX2) in a multi-core CPU design providing peak execution rates of hundreds of GigaFLOPS (GFLOPS) on one chip. Real world mmW scene generation code can approach peak SIMD execution rates only after careful algorithm and source code design. An effective software design will maintain high computing intensity emphasizing register-to-register SIMD arithmetic operations over data movement between CPU caches or off-chip memories. Engineers at the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) applied two basic parallel coding methods to assess new 256-bit SIMD multi-core architectures for mmW scene generation in HWIL. These include use of POSIX threads built on vector library functions and more portable, highlevel parallel code based on compiler technology (e.g. OpenMP pragmas and SIMD autovectorization). Since CPU technology is rapidly advancing toward high processor core counts and TeraFLOPS peak SIMD execution rates, it is imperative that coding methods be identified which produce efficient and maintainable parallel code. This paper describes the algorithms used in point scatterer target model rendering, the parallelization of those algorithms, and the execution performance achieved on an AVX multi-core machine using the two basic parallel coding methods. The paper concludes with estimates for scale-up performance on upcoming multi-core technology.

Vfold: a web server for RNA structure and folding thermodynamics prediction.

PubMed

Xu, Xiaojun; Zhao, Peinan; Chen, Shi-Jie

2014-01-01

The ever increasing discovery of non-coding RNAs leads to unprecedented demand for the accurate modeling of RNA folding, including the predictions of two-dimensional (base pair) and three-dimensional all-atom structures and folding stabilities. Accurate modeling of RNA structure and stability has far-reaching impact on our understanding of RNA functions in human health and our ability to design RNA-based therapeutic strategies. The Vfold server offers a web interface to predict (a) RNA two-dimensional structure from the nucleotide sequence, (b) three-dimensional structure from the two-dimensional structure and the sequence, and (c) folding thermodynamics (heat capacity melting curve) from the sequence. To predict the two-dimensional structure (base pairs), the server generates an ensemble of structures, including loop structures with the different intra-loop mismatches, and evaluates the free energies using the experimental parameters for the base stacks and the loop entropy parameters given by a coarse-grained RNA folding model (the Vfold model) for the loops. To predict the three-dimensional structure, the server assembles the motif scaffolds using structure templates extracted from the known PDB structures and refines the structure using all-atom energy minimization. The Vfold-based web server provides a user friendly tool for the prediction of RNA structure and stability. The web server and the source codes are freely accessible for public use at "http://rna.physics.missouri.edu".

Symplectic orbit and spin tracking code for all-electric storage rings

DOE PAGES

Talman, Richard M.; Talman, John D.

2015-07-22

Proposed methods for measuring the electric dipole moment (EDM) of the proton use an intense, polarized proton beam stored in an all-electric storage ring “trap.” At the “magic” kinetic energy of 232.792 MeV, proton spins are “frozen,” for example always parallel to the instantaneous particle momentum. Energy deviation from the magic value causes in-plane precession of the spin relative to the momentum. Any nonzero EDM value will cause out-of-plane precession—measuring this precession is the basis for the EDM determination. A proposed implementation of this measurement shows that a proton EDM value of 10 –29e–cm or greater will produce a statisticallymore » significant, measurable precession after multiply repeated runs, assuming small beam depolarization during 1000 s runs, with high enough precision to test models of the early universe developed to account for the present day particle/antiparticle population imbalance. This paper describes an accelerator simulation code, eteapot, a new component of the Unified Accelerator Libraries (ual), to be used for long term tracking of particle orbits and spins in electric bend accelerators, in order to simulate EDM storage ring experiments. Though qualitatively much like magnetic rings, the nonconstant particle velocity in electric rings gives them significantly different properties, especially in weak focusing rings. Like the earlier code teapot (for magnetic ring simulation) this code performs exact tracking in an idealized (approximate) lattice rather than the more conventional approach, which is approximate tracking in a more nearly exact lattice. The Bargmann-Michel-Telegdi (BMT) equation describing the evolution of spin vectors through idealized bend elements is also solved exactly—original to this paper. Furthermore the idealization permits the code to be exactly symplectic (with no artificial “symplectification”). Any residual spurious damping or antidamping is sufficiently small to permit reliable tracking for the long times, such as the 1000 s assumed in estimating the achievable EDM precision. This paper documents in detail the theoretical formulation implemented in eteapot. An accompanying paper describes the practical application of the eteapot code in the Universal Accelerator Libraries (ual) environment to “resurrect,” or reverse engineer, the “AGS-analog” all-electric ring built at Brookhaven National Laboratory in 1954. Of the (very few) all-electric rings ever commissioned, the AGS-analog ring is the only relativistic one and is the closest to what is needed for measuring proton (or, even more so, electron) EDM’s. As a result, the companion paper also describes preliminary lattice studies for the planned proton EDM storage rings as well as testing the code for long time orbit and spin tracking.« less

The effects of recall-concurrent visual-motor distraction on picture and word recall.

PubMed

Warren, M W

1977-05-01

The dual-coding model (Paivio, 1971, 1975) predicts a larger imaginal component in the recall of pictures relative to words and a larger imaginal component in the recall of concrete words relative to abstract words. These predictions were tested by examining the effect of a recall-concurrent imagery-suppression task (pursuit-rotor tracking) on the recall of pictures vs picture labels and on the recall of concrete words vs abstract words. The results showed that recall-concurrent pursuit-rotor tracking interfered with picture recall, but not word recall (Experiments 1 and 2); however, there was no evidence of an effect of recall-concurrent tracking on the recall of concrete words (Experiment 3). The results suggested a revision of the dual-coding model.

Hazardous Waste State Authorization Tracking System (StATS) Report for Colorado as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Colorado listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Kentucky as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Kentucky listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Alaska as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Alaska listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Washington as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Washington listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Mississippi as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Mississippi listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Nebraska as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Nebraska listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Iowa as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Iowa listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Maine as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Maine listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Guam as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Guam listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Massachusetts as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Massachusetts listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Michigan as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Michigan listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Pennsylvania as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Pennsylvania listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Ohio as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Ohio listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Montana as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Montana listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Indiana as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Indiana listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Alabama as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Alabama listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Missouri as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Missouri listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Arizona as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Arizona listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Vermont as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Vermont listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Oregon as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Oregon listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Kansas as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Kansas listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Connecticut as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Connecticut listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Nevada as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Nevada listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Utah as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Utah listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Virginia as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Virginia listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Oklahoma as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Oklahoma listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Wisconsin as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Wisconsin listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Maryland as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Maryland listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Texas as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Texas listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for California as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for California listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Florida as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Florida listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Idaho as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Idaho listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Tennessee as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Tennessee listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Minnesota as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Minnesota listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Louisiana as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Louisiana listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Hawaii as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Hawaii listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Illinois as of March 31, 2018

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Illinois listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Nebraska as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Nebraska listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Ohio as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Ohio listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Oregon as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Oregon listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Massachusetts as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Massachusetts listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Missouri as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Missouri listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Indiana as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Indiana listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Illinois as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Illinois listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Colorado as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Colorado listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Alabama as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Alabama listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Nevada as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Nevada listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Arkansas as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Arkansas listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Guam as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Guam listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Minnesota as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Minnesota listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Tennessee as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Tennessee listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Maryland as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Maryland listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Texas as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Texas listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Maine as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Maine listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Hawaii as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Hawaii listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Arizona as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Arizona listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Louisiana as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Louisiana listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Mississippi as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Mississippi listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Florida as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Florida listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Georgia as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Georgia listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Vermont as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Vermont listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Oklahoma as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Oklahoma listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Utah as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Utah listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Delaware as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Delaware listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Virginia as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Virginia listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Washington as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Washington listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Kansas as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Kansas listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for Connecticut as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for Connecticut listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.

Hazardous Waste State Authorization Tracking System (StATS) Report for California as of June 30, 2017

EPA Pesticide Factsheets

State Authorization Tracking System (StATS) data for California listing checklist code, Federal Register Reference, promulgation date, rule description, state adopted/effective date, date of Federal Register Notice, and effective date.