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Sample records for gain transient control

  1. Control of transient gain absorption via tunneling and incoherent pumping in triple quantum dots

    NASA Astrophysics Data System (ADS)

    Tian, Si-Cong; Zhang, Xiao-Jun; Wan, Ren-Gang; Wang, Li-Jie; Shu, Shi-Li; Wang, Tao; Lu, Ze-Feng; Sun, Fang-Yuan; Tong, Cun-Zhu

    2017-01-01

    The transient gain-absorption properties of the probe field in vertical triple quantum dots assisted by double tunneling and incoherent pumping are investigated. With a proper intensity value and detuning of the second tunneling, the transient gain in triple quantum dots with incoherent pumping can be completely eliminated. In addition, the incoherent pumping affects both the amplitude of the transient absorption and the steady-state value. The dependence of transient behaviors on other parameters, such as the radiative decay rate and the pure dephasing decay rate of the quantum dots, is also discussed. The scheme may have important applications in quantum information networks and communication.

  2. Transient gain analysis of gain-switched semiconductor lasers during pulse lasing.

    PubMed

    Chen, Shaoqiang; Ito, Takashi; Asahara, Akifumi; Nakamae, Hidekazu; Nakamura, Takahiro; Yoshita, Masahiro; Kim, Changsu; Zhang, Baoping; Yokoyama, Hiroyuki; Suemoto, Tohru; Akiyama, Hidefumi

    2015-12-10

    We analyzed the transient gain properties of three gain-switched semiconductor lasers with different materials and cavity structures during pulse lasing. All the semiconductor lasers were pumped with impulse optical pumping, and all the generated gain-switched output pulses were well described by exponential functions in their rise parts, wherein the transient gains were derived according to the rate-equation theoretical model. In spite of the different laser structures and materials, the results consistently demonstrated that a higher transient gain produces shorter output pulses, indicating the dominant role of higher transient gain in the generation of even shorter gain-switched pulses with semiconductor lasers.

  3. Helicopter high gain control

    NASA Technical Reports Server (NTRS)

    Cunningham, T. B.; Nunn, E. C.

    1979-01-01

    High gain control is explored through a design study of the CH-47B helicopter. The plans are designed to obtain the maximum bandwidth possible given the hardware constraints. Controls are designed with modal control theory to specific bandwidths and closed loop mode shapes. Comparisons are made to an earlier complementary filter approach. Bandwidth improvement by removal of limitations is explored in order to establish hardware and mechanization options. Improvements in the pitch axis control system and in the rate gyro sensor noise characteristics in all axes are discussed. The use of rotor state feedback is assessed.

  4. Direct transient stability assessment with excitation control

    SciTech Connect

    Fouad, A.A.; Vittal, V.; Ni, Y.X.; Pota, H.R.; Nodehi, K.; Zein-Eldin, H.M.; Vaahedi, E.; Kim

    1989-02-01

    Recently the authors incorporated the effect of excitation control on the transient energy of a multi-machine power system during the first swing. The models used are: the generator represented by the two-axis model and the exciter represented by one gain, one time constant and one limiter. In this paper the parameters of the newly developed transient energy function, which assumes a constant average internal EMF, are computed. The critical value of this transient energy is determined and its use in transient stability assessment is investigated. A procedure for transient stability assessment using the new energy function has been developed and successfully applied to fault disturbances in two test networks.

  5. Transient upsets in microprocessor controllers

    NASA Technical Reports Server (NTRS)

    Glaser, R. E.; Masson, G. M.

    1981-01-01

    The modeling and analysis of transient faults in microprocessor based controllers are discussed. Such controllers typically consist of a microprocessor, read only memory storing and application program, random access memory for data storage, and input/output devices for external communications. The effects of transient faults on the performance of the controller are reviewed. An instruction level perspective of performance is taken which is the basis of a useful high level program state description of the microprocessor controller. A transition matrix is defined which determines the controller's response to transient fault arrivals.

  6. Commutated automatic gain control system

    NASA Technical Reports Server (NTRS)

    Yost, S. R.

    1981-01-01

    A commutated automatic gain control system (AGC) was designed and constructed for the prototype Loran C receiver. The AGC is designed to improve the signal-to-signal ratio of the received Loran signals. The AGC design does not require any analog to digital conversion and it utilizes commonly available components. The AGC consists of: (1) a circuit which samples the peak of the envelope of the Loran signal to obtain an AGC voltage for each of three Loran stations, (2) a dc gain circuit to control the overall gain of the AGC system, and (3) an AGC amplification of the input RF signal. The performance of the AGC system was observed in bench and flight tests; it has improved the overall accuracy of the receiver. Improvements in the accuracy of the time difference calculations to within approx. + or - 1.5 microseconds of the observed time differnces for a given position are reported.

  7. Commutated automatic gain control system

    NASA Technical Reports Server (NTRS)

    Yost, S. R.

    1982-01-01

    The commutated automatic gain control (AGC) system was designed and built for the prototype Loran-C receiver is discussed. The current version of the prototype receiver, the Mini L-80, was tested initially in 1980. The receiver uses a super jolt microcomputer to control a memory aided phase loop (MAPLL). The microcomputer also controls the input/output, latitude/longitude conversion, and the recently added AGC system. The AGC control adjusts the level of each station signal, such that the early portion of each envelope rise is about at the same amplitude in the receiver envelope detector.

  8. Commutated automatic gain control system

    NASA Technical Reports Server (NTRS)

    Yost, S. R.

    1982-01-01

    A commutated automatic gain control (AGC) system was designed and built for a prototype Loran C receiver. The receiver uses a microcomputer to control a memory aided phase-locked loop (MAPLL). The microcomputer also controls the input/output, latitude/longitude conversion, and the recently added AGC system. The circuit designed for the AGC is described, and bench and flight test results are presented. The AGC circuit described actually samples starting at a point 40 microseconds after a zero crossing determined by the software lock pulse ultimately generated by a 30 microsecond delay and add network in the receiver front end envelope detector.

  9. Controlling gain one photon at a time.

    PubMed

    Schwartz, Gregory W; Rieke, Fred

    2013-05-14

    Adaptation is a salient property of sensory processing. All adaptational or gain control mechanisms face the challenge of obtaining a reliable estimate of the property of the input to be adapted to and obtaining this estimate sufficiently rapidly to be useful. Here, we explore how the primate retina balances the need to change gain rapidly and reliably when photons arrive rarely at individual rod photoreceptors. We find that the weakest backgrounds that decrease the gain of the retinal output signals are similar to those that increase human behavioral threshold, and identify a novel site of gain control in the retinal circuitry. Thus, surprisingly, the gain of retinal signals begins to decrease essentially as soon as background lights are detectable; under these conditions, gain control does not rely on a highly averaged estimate of the photon count, but instead signals from individual photon absorptions trigger changes in gain. DOI:http://dx.doi.org/10.7554/eLife.00467.001.

  10. Transient-gain photoionization x-ray laser

    NASA Astrophysics Data System (ADS)

    Weninger, Clemens; Rohringer, Nina

    2014-12-01

    We present a generalized theory based on one-dimensional Maxwell-Bloch equations to study the amplification process of an inner-shell photoionization-pumped atomic x-ray laser. Focusing an x-ray free-electron laser beam in an elongated neon-gas target results in a strong exponential amplification of K α fluorescence, as recently demonstrated [N. Rohringer et al., Nature (London) 481, 488 (2012), 10.1038/nature10721; C. Weninger et al., Phys. Rev. Lett. 111, 233902 (2013), 10.1103/PhysRevLett.111.233902]. Here, we present an in-depth theoretical study of the amplification process that goes beyond the previous theory based on a rate-equation approach. We study the evolution of the pulse characteristics during the amplification process for transform-limited Gaussian and broadband self-amplified spontaneous-emission pump pulses. We discuss the impact of the gain-dependent group velocity on the emitted x-ray radiation and the resulting gain-guiding effects. A thorough analysis of the spectral and temporal properties of the emitted radiation is presented, including higher-order field-correlation functions, to characterize the ensemble of emitted x-ray pulses.

  11. Gaining Control Over Fecal Incontinence.

    PubMed

    Gump, Kendra; Schmelzer, Marilee

    2016-01-01

    Strategies that improve the regularity and efficiency of defecation can eliminate or minimize episodes of fecal incontinence. The medical-surgical nurse's role in identifying patients with fecal incontinence is discussed, along with various treatments to control bowel elimination.

  12. Techniques for improving transients in learning control systems

    NASA Technical Reports Server (NTRS)

    Chang, C.-K.; Longman, Richard W.; Phan, Minh

    1992-01-01

    A discrete modern control formulation is used to study the nature of the transient behavior of the learning process during repetitions. Several alternative learning control schemes are developed to improve the transient performance. These include a new method using an alternating sign on the learning gain, which is very effective in limiting peak transients and also very useful in multiple-input, multiple-output systems. Other methods include learning at an increasing number of points progressing with time, or an increasing number of points of increasing density.

  13. Gain optimization with nonlinear controls

    NASA Technical Reports Server (NTRS)

    Slater, G. L.; Kandadai, R. D.

    1982-01-01

    An algorithm has been developed for the analysis and design of controls for nonlinear systems. The technical approach is to use statistical linearization to model the nonlinear dynamics of a system. A covariance analysis is performed to determine the behavior of the dynamical system and a quadratic cost function. Expressions for the cost function and its derivatives are determined so that numerical optimization techniques can be applied to determine optimal feedback laws. The primary application for this report is centered about the design of controls for nominally linear systems but where the controls are saturated or limited by fixed constraints. The analysis is general however and numerical computation requires only that the specific nonlinearity be considered in the analysis.

  14. Gain optimization with nonlinear controls

    NASA Technical Reports Server (NTRS)

    Slater, G. L.; Kandadai, R. D.

    1982-01-01

    An algorithm has been developed for the analysis and design of controls for nonlinear systems. The technical approach is to use statistical linearization to model the nonlinear dynamics of a system. A covariance analysis is performed to determine the behavior of the dynamical system and a quadratic cost function. Expressions for the cost function and its derivatives are determined so that numerical optimization techniques can be applied to determine optimal feedback laws. The primary application for this report is centered about the design of controls for nominally linear systems but where the controls are saturated or limited by fixed constraints. The analysis is general however and numerical computation requires only that the specific nonlinearity be considered in the analysis.

  15. Transient response characteristics in a biomolecular integral controller.

    PubMed

    Sen, Shaunak

    2016-04-01

    The cellular behaviour of perfect adaptation is achieved through the use of an integral control element in the underlying biomolecular circuit. It is generally unclear how integral action affects the important aspect of transient response in these biomolecular systems, especially in light of the fact that it typically deteriorates the transient response in engineering contexts. To address this issue, the authors investigated the transient response in a computational model of a simple biomolecular integral control system involved in bacterial signalling. They find that the transient response can actually speed up as the integral gain parameter increases. On further analysis, they find that the underlying dynamics are composed of slow and fast modes and the speed-up of the transient response is because of the speed-up of the slow-mode dynamics. Finally, they note how an increase in the integral gain parameter also leads to a decrease in the amplitude of the transient response, consistent with the overall improvement in the transient response. These results should be useful in understanding the overall effect of integral action on system dynamics, particularly for biomolecular systems.

  16. Gain variation induced by power transient in thulium-doped fiber amplifier at 2 μm and its reduction by optical gain clamping technique

    NASA Astrophysics Data System (ADS)

    Khamis, M. A.; Ennser, K.

    2017-02-01

    This paper investigates the dynamic behavior of a thulium doped fiber amplifier (TDFA) operating in the 2 μm region for reconfigurable wavelength division multiplexing (WDM) systems. We show deleterious channel power fluctuations may be generated by input power variation at the amplifier and we propose the use of an optical gain-clamping technique. The investigated system consists of 20 channels with -4 dBm total input power. Our findings revealed that the effects of power transients due to channel reconfigurations are significantly reduced by a lasing feedback signal. Simulation results show that a power excursion of 4.3 dB is produced after dropping 19 channels when the amplifier gain is unclamped and only 0.0062 dB when the amplifier gain is clamped. The dynamics of GC-TDFA are mainly influenced by the value of the pump power factor and thus the laser signal achieves a stronger stabilization condition with increasing pump power factor. Hence, optical gain clamping is a simple and robust technique to control the power transient in the thulium-doped fiber amplifier of WDM systems at 2 μm.

  17. Weight Gain Through Self-Control Procedures

    ERIC Educational Resources Information Center

    Gulanick, Nancy; And Others

    1975-01-01

    Underweight subjects were assigned to either a self-reinforcement condition, a self-punishment condition, or to a discussion/reflection control condition. The subjects received one treatment session per week over a five-week period. After treatment, the self-reinforcement groups gained significantly more pounds (kilograms) than either of the other…

  18. Transient gain-versus-absorption laser probing of spin-orbit states, kinetics and dynamics

    NASA Technical Reports Server (NTRS)

    Smedley, John E.; Hess, Wayne P.; Haugen, Harold K.; Leone, Stephen R.

    1986-01-01

    The spin-orbit populations of excited (2P1/2) and ground (2P3/2) state Br atoms at 2714 nm and I atoms at 1315 nm are examined using a tunable F-center laser and a diode laser. The transient laser gain-versus-absorption measurements are utilized to estimate quantum yields of the spin-orbit states in the photodissociation of Br- and I-containing compounds; the continuum yields for Br2 are investigated in terms of temperature. The collisional release, Doppler velocity effects, and differing reactivity of the spin-orbit excited and ground state atoms are studied. It is noted that the transient gain versus absorption technique is applicable to the analysis of kinetic phenomena due to its high sensitivity and excellent time resolution.

  19. LPV Controller Interpolation for Improved Gain-Scheduling Control Performance

    NASA Technical Reports Server (NTRS)

    Wu, Fen; Kim, SungWan

    2002-01-01

    In this paper, a new gain-scheduling control design approach is proposed by combining LPV (linear parameter-varying) control theory with interpolation techniques. The improvement of gain-scheduled controllers can be achieved from local synthesis of Lyapunov functions and continuous construction of a global Lyapunov function by interpolation. It has been shown that this combined LPV control design scheme is capable of improving closed-loop performance derived from local performance improvement. The gain of the LPV controller will also change continuously across parameter space. The advantages of the newly proposed LPV control is demonstrated through a detailed AMB controller design example.

  20. Linac RF control at transient beamloading

    NASA Astrophysics Data System (ADS)

    Chernogubovsky, M. A.; Sugimoto, M.

    1999-06-01

    Effective RF control design is carried out under electrodynamic property analysis of the transient beam excitation, which gives the basic principle and support method for RF control. The main parameters of the RF system are defined under the directional selective coupling application; the beam dynamics with control characteristics are optimized for operating mode electrodynamics.

  1. Contrast Gain Control Model Fits Masking Data

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.; Solomon, Joshua A.; Null, Cynthia H. (Technical Monitor)

    1994-01-01

    We studied the fit of a contrast gain control model to data of Foley (JOSA 1994), consisting of thresholds for a Gabor patch masked by gratings of various orientations, or by compounds of two orientations. Our general model includes models of Foley and Teo & Heeger (IEEE 1994). Our specific model used a bank of Gabor filters with octave bandwidths at 8 orientations. Excitatory and inhibitory nonlinearities were power functions with exponents of 2.4 and 2. Inhibitory pooling was broad in orientation, but narrow in spatial frequency and space. Minkowski pooling used an exponent of 4. All of the data for observer KMF were well fit by the model. We have developed a contrast gain control model that fits masking data. Unlike Foley's, our model accepts images as inputs. Unlike Teo & Heeger's, our model did not require multiple channels for different dynamic ranges.

  2. Automatic Gain Control in Compact Spectrometers.

    PubMed

    Protopopov, Vladimir

    2016-03-01

    An image intensifier installed in the optical path of a compact spectrometer may act not only as a fast gating unit, which is widely used for time-resolved measurements, but also as a variable attenuator-amplifier in a continuous wave mode. This opens the possibility of an automatic gain control, a new feature in spectroscopy. With it, the user is relieved from the necessity to manually adjust signal level at a certain value that it is done automatically by means of an electronic feedback loop. It is even more important that automatic gain control is done without changing exposure time, which is an additional benefit in time-resolved experiments. The concept, algorithm, design considerations, and experimental results are presented. © The Author(s) 2016.

  3. Demonstration of a transient-gain nickel-like xenon-ion x-ray laser.

    PubMed

    Lu, Peixiang; Kawachi, Tetsuya; Kishimoto, Maki; Sukegawa, Kouta; Tanaka, Momoko; Hasegawa, Noboru; Suzuki, Masayuki; Tai, Renzhong; Kado, Masataka; Nagashima, Keisuke; Daido, Hiroyuki; Kato, Yoshiaki; Fiedorowicz, Henryk; Bartnik, Andrzej

    2002-11-01

    We demonstrate a high-gain nickel-like xenon-ion x-ray laser, using a picosecond-laser-irradiated gas-puff target. The elongated x-ray laser plasma column was produced by irradiation of the gas-puff target with line-focused double picosecond laser pulses with a total energy of 18 J in a traveling-wave excitation scheme. Strong lasing at 9.98 nm was observed, and a high gain coefficient of 17.4 cm(-1) was measured on the transient collisionally excited 4d-4p , J=0-1 transition for nickel-like xenon ions with target lengths as great as 0.45 cm. A weak nickel-like lasing line at a shorter wavelength of 9.64 nm was also observed, with a gain coefficient of 5.9 cm(-1) .

  4. Hypoxia drives transient site-specific copy gain and drug-resistant gene expression

    PubMed Central

    Black, Joshua C.; Atabakhsh, Elnaz; Kim, Jaegil; Biette, Kelly M.; Van Rechem, Capucine; Ladd, Brendon; Burrowes, Paul d.; Donado, Carlos; Mattoo, Hamid; Kleinstiver, Benjamin P.; Song, Bing; Andriani, Grasiella; Joung, J. Keith; Iliopoulos, Othon; Montagna, Cristina; Pillai, Shiv; Getz, Gad

    2015-01-01

    Copy number heterogeneity is a prominent feature within tumors. The molecular basis for this heterogeneity remains poorly characterized. Here, we demonstrate that hypoxia induces transient site-specific copy gains (TSSGs) in primary, nontransformed, and transformed human cells. Hypoxia-driven copy gains are not dependent on HIF1α or HIF2α; however, they are dependent on the KDM4A histone demethylase and are blocked by inhibition of KDM4A with a small molecule or the natural metabolite succinate. Furthermore, this response is conserved at a syntenic region in zebrafish cells. Regions with site-specific copy gain are also enriched for amplifications in hypoxic primary tumors. These tumors exhibited amplification and overexpression of the drug resistance gene CKS1B, which we recapitulated in hypoxic breast cancer cells. Our results demonstrate that hypoxia provides a biological stimulus to create transient site-specific copy alterations that could result in heterogeneity within tumors and cell populations. These findings have major implications in our understanding of copy number heterogeneity and the emergence of drug resistance genes in cancer. PMID:25995187

  5. Hypoxia drives transient site-specific copy gain and drug-resistant gene expression.

    PubMed

    Black, Joshua C; Atabakhsh, Elnaz; Kim, Jaegil; Biette, Kelly M; Van Rechem, Capucine; Ladd, Brendon; Burrowes, Paul D; Donado, Carlos; Mattoo, Hamid; Kleinstiver, Benjamin P; Song, Bing; Andriani, Grasiella; Joung, J Keith; Iliopoulos, Othon; Montagna, Cristina; Pillai, Shiv; Getz, Gad; Whetstine, Johnathan R

    2015-05-15

    Copy number heterogeneity is a prominent feature within tumors. The molecular basis for this heterogeneity remains poorly characterized. Here, we demonstrate that hypoxia induces transient site-specific copy gains (TSSGs) in primary, nontransformed, and transformed human cells. Hypoxia-driven copy gains are not dependent on HIF1α or HIF2α; however, they are dependent on the KDM4A histone demethylase and are blocked by inhibition of KDM4A with a small molecule or the natural metabolite succinate. Furthermore, this response is conserved at a syntenic region in zebrafish cells. Regions with site-specific copy gain are also enriched for amplifications in hypoxic primary tumors. These tumors exhibited amplification and overexpression of the drug resistance gene CKS1B, which we recapitulated in hypoxic breast cancer cells. Our results demonstrate that hypoxia provides a biological stimulus to create transient site-specific copy alterations that could result in heterogeneity within tumors and cell populations. These findings have major implications in our understanding of copy number heterogeneity and the emergence of drug resistance genes in cancer. © 2015 Black et al.; Published by Cold Spring Harbor Laboratory Press.

  6. Gain control in the sonar of odontocetes.

    PubMed

    Ya Supin, Alexander; Nachtigall, Paul E

    2013-06-01

    The sonar of odontocetes processes echo-signals within a wide range of echo levels. The level of echoes varies widely by tens of decibels depending on the level of the emitted sonar pulse, the target strength, the distance to the target, and the sound absorption by the water media. The auditory system of odontocetes must be capable of effective perception, analysis, and discrimination of echo-signals within all this variability. The sonar of odontocetes has several mechanisms to compensate for the echo-level variation (gain control). To date, several mechanisms of the biosonar gain control have been revealed in odontocetes: (1) adjustment of emitted sonar pulse levels (the longer the distance to the target, the higher the level of the emitted pulse), (2) short-term variation of hearing sensitivity based on forward masking of the echo by the preceding self-heard emitted pulse and subsequent release from the masking, and (3) active long-term control of hearing sensitivity. Recent investigations with the use of the auditory evoked-potential technique have demonstrated that these mechanisms effectively minimize the variation of the response to the echo when either the emitted sonar pulse level, or the target distance, or both vary within a wide range. A short review of these data is presented herein.

  7. Compensated gain control circuit for buck regulator command charge circuit

    DOEpatents

    Barrett, David M.

    1996-01-01

    A buck regulator command charge circuit includes a compensated-gain control signal for compensating for changes in the component values in order to achieve optimal voltage regulation. The compensated-gain control circuit includes an automatic-gain control circuit for generating a variable-gain control signal. The automatic-gain control circuit is formed of a precision rectifier circuit, a filter network, an error amplifier, and an integrator circuit.

  8. Compensated gain control circuit for buck regulator command charge circuit

    DOEpatents

    Barrett, D.M.

    1996-11-05

    A buck regulator command charge circuit includes a compensated-gain control signal for compensating for changes in the component values in order to achieve optimal voltage regulation. The compensated-gain control circuit includes an automatic-gain control circuit for generating a variable-gain control signal. The automatic-gain control circuit is formed of a precision rectifier circuit, a filter network, an error amplifier, and an integrator circuit. 5 figs.

  9. Controlling noise in plasmonic structures with gain

    NASA Astrophysics Data System (ADS)

    Vyshnevyy, A. A.; Fedyanin, D. Yu.

    2017-09-01

    Loss compensation by gain medium gives the possibility to exploit subwavelength confinement of light in plasmonic nanostructures and construct nanoscale plasmonic circuits. However, due to fundamentally unavoidable spontaneous emission from the gain medium, lossless waveguides suffer from strong photonic noise, which limits their practical applications. Here we demonstrate the possibility of significant decrease of the noise level while preserving physical dimensions of lossless plasmonic waveguides with gain. Our findings are aimed at extending the communication capabilities of on-chip plasmonic networks.

  10. CSR induced microbunching gain estimation including transient effects in transport and recirculation arcs

    SciTech Connect

    Tsai, Cheng; Douglas, David R.; Li, Rui

    2015-09-01

    The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical Vlasov solver to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects derived from upstream beam entering to and exiting from individual dipoles. The resultant microbunching gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.

  11. GD SDR Automatic Gain Control Characterization Testing

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer M.; Briones, Janette C.

    2013-01-01

    The General Dynamics (GD) S-Band software defined radio (SDR) in the Space Communications and Navigation (SCAN) Testbed on the International Space Station (ISS) will provide experimenters an opportunity to develop and demonstrate experimental waveforms in space. The GD SDR platform and initial waveform were characterized on the ground before launch and the data will be compared to the data that will be collected during on-orbit operations. A desired function of the SDR is to estimate the received signal to noise ratio (SNR), which would enable experimenters to better determine on-orbit link conditions. The GD SDR does not have an SNR estimator, but it does have an analog and a digital automatic gain control (AGC). The AGCs can be used to estimate the SDR input power which can be converted into a SNR. Tests were conducted to characterize the AGC response to changes in SDR input power and temperature. This purpose of this paper is to describe the tests that were conducted, discuss the results showing how the AGCs relate to the SDR input power, and provide recommendations for AGC testing and characterization.

  12. GD SDR Automatic Gain Control Characterization Testing

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer M.; Briones, Janette C.

    2013-01-01

    The General Dynamics (GD) S-Band software defined radio (SDR) in the Space Communications and Navigation (SCAN) Testbed on the International Space Station (ISS) will provide experimenters an opportunity to develop and demonstrate experimental waveforms in space. The GD SDR platform and initial waveform were characterized on the ground before launch and the data will be compared to the data that will be collected during on-orbit operations. A desired function of the SDR is to estimate the received signal to noise ratio (SNR), which would enable experimenters to better determine on-orbit link conditions. The GD SDR does not have an SNR estimator, but it does have an analog and a digital automatic gain control (AGC). The AGCs can be used to estimate the SDR input power which can be converted into a SNR. Tests were conducted to characterize the AGC response to changes in SDR input power and temperature. This purpose of this paper is to describe the tests that were conducted, discuss the results showi ng how the AGCs relate to the SDR input power, and provide recommendations for AGC testing and characterization.

  13. Collective Bargaining and Multiple Control Gains in Education.

    ERIC Educational Resources Information Center

    Crisci, Pat E.; Giancola, Joseph M.

    1986-01-01

    Outlines a study of the use of "control gains" in collective bargaining contracts of teacher unions in Ohio. Control gains are contract items that give unions control over some aspect of the work environment in lieu of financial gains. They can be offered in contract negotiations when school boards have limited funds. (MD)

  14. Central Gain Control in Tinnitus and Hyperacusis

    PubMed Central

    Auerbach, Benjamin D.; Rodrigues, Paulo V.; Salvi, Richard J.

    2014-01-01

    Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders. PMID:25386157

  15. A variable-gain output feedback control design methodology

    NASA Technical Reports Server (NTRS)

    Halyo, Nesim; Moerder, Daniel D.; Broussard, John R.; Taylor, Deborah B.

    1989-01-01

    A digital control system design technique is developed in which the control system gain matrix varies with the plant operating point parameters. The design technique is obtained by formulating the problem as an optimal stochastic output feedback control law with variable gains. This approach provides a control theory framework within which the operating range of a control law can be significantly extended. Furthermore, the approach avoids the major shortcomings of the conventional gain-scheduling techniques. The optimal variable gain output feedback control problem is solved by embedding the Multi-Configuration Control (MCC) problem, previously solved at ICS. An algorithm to compute the optimal variable gain output feedback control gain matrices is developed. The algorithm is a modified version of the MCC algorithm improved so as to handle the large dimensionality which arises particularly in variable-gain control problems. The design methodology developed is applied to a reconfigurable aircraft control problem. A variable-gain output feedback control problem was formulated to design a flight control law for an AFTI F-16 aircraft which can automatically reconfigure its control strategy to accommodate failures in the horizontal tail control surface. Simulations of the closed-loop reconfigurable system show that the approach produces a control design which can accommodate such failures with relative ease. The technique can be applied to many other problems including sensor failure accommodation, mode switching control laws and super agility.

  16. Characterization of a high-gain Ne-like Fe transient x-ray laser

    SciTech Connect

    Dunn, J; Facnov, A; Fournier, K B; Moon, S J; Osterheld, A; Pikuz, T; Shlyaptsev, V N

    1999-09-13

    The authors present experimental results of a high efficiency Ne-like Fe transient collisional excitation x-ray laser using the COMET 15 TW table-top laser system at LLNL. The plasma formation, ionization and collision excitation of the x-ray laser have been optimized using two sequential laser pulses: a plasma formation beam with 5 J energy of 600 ps duration and a pump beam with 5 J energy of 1.2 ps duration. Since the observation of strong lasing on the 255 {angstrom} 3p-3s J = 0-1 transition of Ne-like Fe, they have achieved high gains of 35 cm{sup {minus}1} and saturation of the x-ray laser. A five-stage traveling wave excitation enhances the strongest Fe 3p-3s 255 {angstrom} lasing line as well as additional x-ray lines. A careful characterization of the plasma column conditions using L-shell spectroscopy indicates the degree of ionization along the line focus.

  17. Novel L1 neural network adaptive control architecture with guaranteed transient performance.

    PubMed

    Cao, Chengyu; Hovakimyan, Naira

    2007-07-01

    In this paper, we present a novel neural network (NN) adaptive control architecture with guaranteed transient performance. With this new architecture, both input and output signals of an uncertain nonlinear system follow a desired linear system during the transient phase, in addition to stable tracking. This new architecture uses a low-pass filter in the feedback loop, which consequently enables to enforce the desired transient performance by increasing the adaptation gain. For the guaranteed transient performance of both input and output signals of the uncertain nonlinear system, the L1 gain of a cascaded system, comprised of the low-pass filter and the closed-loop desired reference model, is required to be less than the inverse of the Lipschitz constant of the unknown nonlinearities in the system. The tools from this paper can be used to develop a theoretically justified verification and validation framework for NN adaptive controllers. Simulation results illustrate the theoretical findings.

  18. Aircraft nonlinear optimal control using fuzzy gain scheduling

    NASA Astrophysics Data System (ADS)

    Nusyirwan, I. F.; Kung, Z. Y.

    2016-10-01

    Fuzzy gain scheduling is a common solution for nonlinear flight control. The highly nonlinear region of flight dynamics is determined throughout the examination of eigenvalues and the irregular pattern of root locus plots that show the nonlinear characteristic. By using the optimal control for command tracking, the pitch rate stability augmented system is constructed and the longitudinal flight control system is established. The outputs of optimal control for 21 linear systems are fed into the fuzzy gain scheduler. This research explores the capability in using both optimal control and fuzzy gain scheduling to improve the efficiency in finding the optimal control gains and to achieve Level 1 flying qualities. The numerical simulation work is carried out to determine the effectiveness and performance of the entire flight control system. The simulation results show that the fuzzy gain scheduling technique is able to perform in real time to find near optimal control law in various flying conditions.

  19. Serotonin Affects Movement Gain Control in the Spinal Cord

    PubMed Central

    Glaser, Joshua I.; Deng, Linna; Thompson, Christopher K.; Stevenson, Ian H.; Wang, Qining; Hornby, Thomas George; Heckman, Charles J.; Kording, Konrad P.

    2014-01-01

    A fundamental challenge for the nervous system is to encode signals spanning many orders of magnitude with neurons of limited bandwidth. To meet this challenge, perceptual systems use gain control. However, whether the motor system uses an analogous mechanism is essentially unknown. Neuromodulators, such as serotonin, are prime candidates for gain control signals during force production. Serotonergic neurons project diffusely to motor pools, and, therefore, force production by one muscle should change the gain of others. Here we present behavioral and pharmaceutical evidence that serotonin modulates the input–output gain of motoneurons in humans. By selectively changing the efficacy of serotonin with drugs, we systematically modulated the amplitude of spinal reflexes. More importantly, force production in different limbs interacts systematically, as predicted by a spinal gain control mechanism. Psychophysics and pharmacology suggest that the motor system adopts gain control mechanisms, and serotonin is a primary driver for their implementation in force production. PMID:25232107

  20. Analysis of gain scheduled control for nonlinear plants

    NASA Technical Reports Server (NTRS)

    Shamma, Jeff S.; Athans, Michael

    1990-01-01

    Gain scheduling has proven to be a successful design methodology in many engineering applications. In the absence of a sound theoretical analysis, these designs come with no guarantees of the robustness, performance, or even nominal stability of the overall gain-scheduled design. An analysis is presented for two types of nonlinear gain-scheduled control systems: (1) scheduling on a reference trajectory and (2) scheduling on the plant output. Conditions which guarantee stability, robustness, and performance properties of the global gain schedule designs are given. These conditions confirm and formalize popular notions regarding gain-scheduled designs, such as that the scheduling variable should vary slowly and capture the plant's nonlinearities.

  1. Gain optimization with non-linear controls

    NASA Technical Reports Server (NTRS)

    Slater, G. L.; Kandadai, R. D.

    1984-01-01

    An algorithm has been developed for the analysis and design of controls for non-linear systems. The technical approach is to use statistical linearization to model the non-linear dynamics of a system by a quasi-Gaussian model. A covariance analysis is performed to determine the behavior of the dynamical system and a quadratic cost function. Expressions for the cost function and its derivatives are determined so that numerical optimization techniques can be applied to determine optimal feedback laws. The primary application for this paper is centered about the design of controls for nominally linear systems but where the controls are saturated or limited by fixed constraints. The analysis is general, however, and numerical computation requires only that the specific non-linearity be considered in the analysis.

  2. Analysis and design of sliding mode controller gains for boost power factor corrector.

    PubMed

    Kessal, Abdelhalim; Rahmani, Lazhar

    2013-09-01

    This paper presents a systematic procedure to compute the gains of sliding mode controller based on an optimization scheme. This controller is oriented to drive an AC-DC converter operating in continuous mode with power factor near unity, and in order to improve static and dynamic performances with large variations of reference voltage and load. This study shows the great influence of the controller gains on the global performances of the system. Hence, a methodology for choosing the gains is detailed. The sliding surface used in this study contains two state variables, input current and output voltage; the advantage of this surface is getting reactions against various disturbances-at the power source, the reference of the output, or the value of the load. The controller is experimentally confirmed for steady-state performance and transient response.

  3. Gain scheduled control of linear systems with unsymmetrical saturation actuators

    NASA Astrophysics Data System (ADS)

    Wu, Wen-Juan; Duan, Guang-Ren

    2016-11-01

    The problem of stabilisation of a class of nonlinear continuous-time systems with asymmetric saturations on the control is studied in this paper. By combining the parametric Lyapunov equation approach and gain scheduling technique, a state feedback gain scheduling controller is proposed to solve the stabilisation problem of systems with unsymmetrical saturated control. The proposed gain scheduled approach is to increase the value of the design parameter so that the convergence rate of the closed-loop system can be increased. Numerical simulations show the effectiveness of the proposed approach.

  4. Chemotaxis Control of Transient Cell Aggregation.

    PubMed

    Alexandre, Gladys

    2015-10-01

    Chemotaxis affords motile cells the ability to rapidly respond to environmental challenges by navigating cells to niches favoring growth. Such a property results from the activities of dedicated signal transduction systems on the motility apparatus, such as flagella, type IV pili, and gliding machineries. Once cells have reached a niche with favorable conditions, they often stop moving and aggregate into complex communities termed biofilms. An intermediate and reversible stage that precedes commitment to permanent adhesion often includes transient cell-cell contacts between motile cells. Chemotaxis signaling has been implicated in modulating the transient aggregation of motile cells. Evidence further indicates that chemotaxis-dependent transient cell aggregation events are behavioral responses to changes in metabolic cues that temporarily prohibit permanent attachment by maintaining motility and chemotaxis. This minireview discusses a few examples illustrating the role of chemotaxis signaling in the initiation of cell-cell contacts in bacteria moving via flagella, pili, or gliding.

  5. Gain Scheduling for the Orion Launch Abort Vehicle Controller

    NASA Technical Reports Server (NTRS)

    McNamara, Sara J.; Restrepo, Carolina I.; Madsen, Jennifer M.; Medina, Edgar A.; Proud, Ryan W.; Whitley, Ryan J.

    2011-01-01

    One of NASAs challenges for the Orion vehicle is the control system design for the Launch Abort Vehicle (LAV), which is required to abort safely at any time during the atmospheric ascent portion of ight. The focus of this paper is the gain design and scheduling process for a controller that covers the wide range of vehicle configurations and flight conditions experienced during the full envelope of potential abort trajectories from the pad to exo-atmospheric flight. Several factors are taken into account in the automation process for tuning the gains including the abort effectors, the environmental changes and the autopilot modes. Gain scheduling is accomplished using a linear quadratic regulator (LQR) approach for the decoupled, simplified linear model throughout the operational envelope in time, altitude and Mach number. The derived gains are then implemented into the full linear model for controller requirement validation. Finally, the gains are tested and evaluated in a non-linear simulation using the vehicles ight software to ensure performance requirements are met. An overview of the LAV controller design and a description of the linear plant models are presented. Examples of the most significant challenges with the automation of the gain tuning process are then discussed. In conclusion, the paper will consider the lessons learned through out the process, especially in regards to automation, and examine the usefulness of the gain scheduling tool and process developed as applicable to non-Orion vehicles.

  6. Even transient rapid infancy weight gain is associated with higher BMI in young adults and earlier menarche

    PubMed Central

    Salgin, Burak; Norris, Shane A.; Prentice, Philippa; Pettifor, John. M.; Richter, Linda M.; Ong, Ken K.; Dunger, David B.

    2015-01-01

    Background Early postnatal rapid “catch-up” weight gain has been consistently associated with subsequent higher obesity risk and earlier pubertal development. In many low- and middle-income countries, infancy catch-up weight gain is transient and often followed by growth faltering. We explored the hypothesis that even transient catch-up weight gain during infancy is associated with later obesity risk and earlier puberty. Methods 2352 (1151 male, 1201 female) black South African children in the Birth to Twenty (Bt20) prospective birth cohort study (Johannesburg-Soweto) underwent serial measurements of body size and composition from birth to age 18 years. At age 18 years, whole-body fat mass and fat-free mass were determined using dual energy x-ray absorptiometry. Pubertal development was assessed by the research team between ages 9 and 10 years, and recorded annually from age 11 years using a validated self-assessment protocol. Results Catch-up weight gain from birth to age 1 year, despite being followed by growth faltering between ages 1 and 2 years, was associated greater mid-upper arm circumference (p=0.04) and skin fold thickness (p=0.048) at age 8 years, and with higher weight (p<0.001) and BMI (p=0.001) at age 18 years after adjustment for sex, age, smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status. Infancy catch-up weight gain was also associated with younger age at menarche in girls (p<0.001). This association persisted after adjustment for smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status (p=0.005). Conclusion Transient catch-up weight gain from birth to age 1 year among children born in a low-income area of South Africa was associated with earlier menarche and greater adiposity in early adulthood. This observation suggests that modifiable determinants of rapid infancy weight gain may be targeted in order to prevent later obesity

  7. Robust Optimal Adaptive Control Method with Large Adaptive Gain

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2009-01-01

    In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to the implementation of adaptive control with a large adaptive gain to reduce the tracking error rapidly. However, a large adaptive gain can lead to high-frequency oscillations which can adversely affect robustness of an adaptive control law. A new adaptive control modification is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. The modification is based on the minimization of the Y2 norm of the tracking error, which is formulated as an optimal control problem. The optimality condition is used to derive the modification using the gradient method. The optimal control modification results in a stable adaptation and allows a large adaptive gain to be used for better tracking while providing sufficient stability robustness. Simulations were conducted for a damaged generic transport aircraft with both standard adaptive control and the adaptive optimal control modification technique. The results demonstrate the effectiveness of the proposed modification in tracking a reference model while maintaining a sufficient time delay margin.

  8. Remote Robot Control With High Force-Feedback Gain

    NASA Technical Reports Server (NTRS)

    Kim, Won S.

    1993-01-01

    Improved scheme for force-reflecting hand control of remote robotic manipulator provides unprecedently high force-reflection gain, even when dissimilar master and slave arms used. Three feedback loops contained in remote robot control system exerting position-error-based force feedback and compliance control. Outputs of force and torque sensors on robot not used directly for force reflection, but for compliance control, while errors in position used to generate reflected forces.

  9. Remote Robot Control With High Force-Feedback Gain

    NASA Technical Reports Server (NTRS)

    Kim, Won S.

    1993-01-01

    Improved scheme for force-reflecting hand control of remote robotic manipulator provides unprecedently high force-reflection gain, even when dissimilar master and slave arms used. Three feedback loops contained in remote robot control system exerting position-error-based force feedback and compliance control. Outputs of force and torque sensors on robot not used directly for force reflection, but for compliance control, while errors in position used to generate reflected forces.

  10. Application of gain scheduling to the control of batch bioreactors

    NASA Technical Reports Server (NTRS)

    Cardello, Ralph; San, Ka-Yiu

    1987-01-01

    The implementation of control algorithms to batch bioreactors is often complicated by the inherent variations in process dynamics during the course of fermentation. Such a wide operating range may render the performance of fixed gain PID controllers unsatisfactory. In this work, a detailed study on the control of batch fermentation is performed. Furthermore, a simple batch controller design is proposed which incorporates the concept of gain-scheduling, a subclass of adaptive control, with oxygen uptake rate as an auxiliary variable. The control of oxygen tension in the biorector is used as a vehicle to convey the proposed idea, analysis and results. Simulation experiments indicate significant improvement in controller performance can be achieved by the proposed approach even in the presence of measurement noise.

  11. Application of gain scheduling to the control of batch bioreactors

    NASA Technical Reports Server (NTRS)

    Cardello, Ralph; San, Ka-Yiu

    1987-01-01

    The implementation of control algorithms to batch bioreactors is often complicated by the inherent variations in process dynamics during the course of fermentation. Such a wide operating range may render the performance of fixed gain PID controllers unsatisfactory. In this work, a detailed study on the control of batch fermentation is performed. Furthermore, a simple batch controller design is proposed which incorporates the concept of gain-scheduling, a subclass of adaptive control, with oxygen uptake rate as an auxiliary variable. The control of oxygen tension in the biorector is used as a vehicle to convey the proposed idea, analysis and results. Simulation experiments indicate significant improvement in controller performance can be achieved by the proposed approach even in the presence of measurement noise.

  12. Gain Control Network Conditions in Early Sensory Coding

    PubMed Central

    Serrano, Eduardo; Nowotny, Thomas; Levi, Rafael; Smith, Brian H.; Huerta, Ramón

    2013-01-01

    Gain control is essential for the proper function of any sensory system. However, the precise mechanisms for achieving effective gain control in the brain are unknown. Based on our understanding of the existence and strength of connections in the insect olfactory system, we analyze the conditions that lead to controlled gain in a randomly connected network of excitatory and inhibitory neurons. We consider two scenarios for the variation of input into the system. In the first case, the intensity of the sensory input controls the input currents to a fixed proportion of neurons of the excitatory and inhibitory populations. In the second case, increasing intensity of the sensory stimulus will both, recruit an increasing number of neurons that receive input and change the input current that they receive. Using a mean field approximation for the network activity we derive relationships between the parameters of the network that ensure that the overall level of activity of the excitatory population remains unchanged for increasing intensity of the external stimulation. We find that, first, the main parameters that regulate network gain are the probabilities of connections from the inhibitory population to the excitatory population and of the connections within the inhibitory population. Second, we show that strict gain control is not achievable in a random network in the second case, when the input recruits an increasing number of neurons. Finally, we confirm that the gain control conditions derived from the mean field approximation are valid in simulations of firing rate models and Hodgkin-Huxley conductance based models. PMID:23874176

  13. Cognitive Adaptation of Sonar Gain Control in the Bottlenose Dolphin

    PubMed Central

    Kloepper, Laura N.; Smith, Adam B.; Nachtigall, Paul E.; Buck, John R.; Simmons, James A.; Pacini, Aude F.

    2014-01-01

    Echolocating animals adjust the transmit intensity and receive sensitivity of their sonar in order to regulate the sensation level of their echoes; this process is often termed automatic gain control. Gain control is considered not to be under the animal's cognitive control, but previous investigations studied animals ensonifying targets or hydrophone arrays at predictable distances. To test whether animals maintain gain control at a fixed level in uncertain conditions, we measured changes in signal intensity for a bottlenose dolphin (Tursiops truncatus) detecting a target at three target distances (2.5, 4 and 7 m) in two types of sessions: predictable and unpredictable. Predictable sessions presented the target at a constant distance; unpredictable sessions moved the target randomly between the three target positions. In the predictable sessions the dolphin demonstrated intensity distance compensation, increasing the emitted click intensity as the target distance increased. Additionally, as trials within sessions progressed, the animal adjusted its click intensity even from the first click in a click train, which is consistent with the animal expecting a target at a certain range. In the unpredictable sessions there was no significant difference of intensity with target distance until after the 7th click in a click train. Together, these results demonstrate that the bottlenose dolphin uses learning and expectation for sonar gain control. PMID:25153530

  14. Cognitive adaptation of sonar gain control in the bottlenose dolphin.

    PubMed

    Kloepper, Laura N; Smith, Adam B; Nachtigall, Paul E; Buck, John R; Simmons, James A; Pacini, Aude F

    2014-01-01

    Echolocating animals adjust the transmit intensity and receive sensitivity of their sonar in order to regulate the sensation level of their echoes; this process is often termed automatic gain control. Gain control is considered not to be under the animal's cognitive control, but previous investigations studied animals ensonifying targets or hydrophone arrays at predictable distances. To test whether animals maintain gain control at a fixed level in uncertain conditions, we measured changes in signal intensity for a bottlenose dolphin (Tursiops truncatus) detecting a target at three target distances (2.5, 4 and 7 m) in two types of sessions: predictable and unpredictable. Predictable sessions presented the target at a constant distance; unpredictable sessions moved the target randomly between the three target positions. In the predictable sessions the dolphin demonstrated intensity distance compensation, increasing the emitted click intensity as the target distance increased. Additionally, as trials within sessions progressed, the animal adjusted its click intensity even from the first click in a click train, which is consistent with the animal expecting a target at a certain range. In the unpredictable sessions there was no significant difference of intensity with target distance until after the 7th click in a click train. Together, these results demonstrate that the bottlenose dolphin uses learning and expectation for sonar gain control.

  15. Flexible Contrast Gain Control in the Right Hemisphere

    ERIC Educational Resources Information Center

    Okubo, Matia; Nicholls, Michael E. R.

    2005-01-01

    This study investigates whether the right hemisphere has more flexible contrast gain control settings for the identification of spatial frequency. Right-handed participants identified 1 and 9 cycles per degree sinusoidal gratings presented either to the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH).…

  16. Controlled mass pollination in loblolly pine to increase genetic gains

    Treesearch

    F.E. Bridgwater; D.L. Bramlett; T.D. Byram; W.J. Lowe

    1998-01-01

    Controlled mass pollination (CMP) is one way to increase genetic gains from traditional wind-pollinated seed orchards. Methodology is under development by several forestry companies in the southern USA. Costs of CMP depend on the efficient installation, pollination, and removal of inexpensive paper bags. Even in pilot-scale studies these costs seem reasonable. Net...

  17. Flexible Contrast Gain Control in the Right Hemisphere

    ERIC Educational Resources Information Center

    Okubo, Matia; Nicholls, Michael E. R.

    2005-01-01

    This study investigates whether the right hemisphere has more flexible contrast gain control settings for the identification of spatial frequency. Right-handed participants identified 1 and 9 cycles per degree sinusoidal gratings presented either to the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH).…

  18. Motivation by potential gains and losses affects control processes via different mechanisms in the attentional network.

    PubMed

    Paschke, Lena M; Walter, Henrik; Steimke, Rosa; Ludwig, Vera U; Gaschler, Robert; Schubert, Torsten; Stelzel, Christine

    2015-05-01

    Attentional control in demanding cognitive tasks can be improved by manipulating the motivational state. Motivation to obtain gains and motivation to avoid losses both usually result in faster reaction times and stronger activation in relevant brain areas such as the prefrontal cortex, but little is known about differences in the underlying neurocognitive mechanisms of these types of motivation in an attentional control context. In the present functional magnetic resonance imaging (fMRI) study, we tested whether potential gain and loss as motivating incentives lead to overlapping or distinct neural effects in the attentional network, and whether one of these conditions is more effective than the other. A Flanker task with word stimuli as targets and distracters was performed by 115 healthy participants. Using a mixed blocked and event-related design allowed us to investigate transient and sustained motivation-related effects. Participants could either gain money (potential gain) or avoid losing money (potential loss) in different task blocks. Participants showed a congruency effect with increased reaction times for incongruent compared to congruent trials. Potential gain led to generally faster responses compared to the neutral condition and to stronger improvements than potential loss. Potential loss also led to shorter response times compared to the neutral condition, but participants improved mainly during incongruent and not during congruent trials. The event-related fMRI data revealed a main effect of congruency with increased activity in the left inferior frontal gyrus (IFG) and inferior frontal junction area (IFJ), the pre-supplementary motor area (pre-SMA), bilateral insula, intraparietal sulcus (IPS) and visual word form area (VWFA). While potential gain led to increased activity in a cluster of the IFJ and the VWFA only during incongruent trials, potential loss was linked to activity increases in these regions during incongruent and congruent trials. The

  19. A gain-control theory of binocular combination.

    PubMed

    Ding, Jian; Sperling, George

    2006-01-24

    In binocular combination, light images on the two retinas are combined to form a single "cyclopean" perceptual image, in contrast to binocular rivalry which occurs when the two eyes have incompatible ("rivalrous") inputs and only one eye;s stimulus is perceived. We propose a computational theory for binocular combination with two basic principles of interaction: in every spatial neighborhood, each eye (i) exerts gain control on the other eye's signal in proportion to the contrast energy of its own input and (ii) additionally exerts gain control on the other eye's gain control. For stimuli of ordinary contrast, when either eye is stimulated alone, the predicted cyclopean image is the same as when both eyes are stimulated equally, coinciding with an easily observed property of natural vision. The gain-control theory is contrast dependent: Very low-contrast stimuli to the left- and right-eye add linearly to form the predicted cyclopean image. The intrinsic nonlinearity manifests itself only as contrast increases. To test the theory more precisely, a horizontal sine wave grating of 0.68 cycles per degree is presented to each eye. The gratings differ in contrast and phase. The predicted (and perceived) cyclopean grating also is a sine wave; its apparent phase indicates the relative contribution of the two eyes to the cyclopean image. For 48 measured combinations of phase and contrast, the theory with only one estimated parameter accounts for 95% of the variance of the data. Therefore, a simple, robust, physiologically plausible gain-control theory accurately describes an early stage of binocular combination.

  20. Gain, Level, And Exposure Control For A Television Camera

    NASA Technical Reports Server (NTRS)

    Major, Geoffrey J.; Hetherington, Rolfe W.

    1992-01-01

    Automatic-level-control/automatic-gain-control (ALC/AGC) system for charge-coupled-device (CCD) color television camera prevents over-loading in bright scenes using technique for measuring brightness of scene from red, green, and blue output signals and processing these into adjustments of video amplifiers and iris on camera lens. System faster, does not distort video brightness signals, and built with smaller components.

  1. Gain, Level, And Exposure Control For A Television Camera

    NASA Technical Reports Server (NTRS)

    Major, Geoffrey J.; Hetherington, Rolfe W.

    1992-01-01

    Automatic-level-control/automatic-gain-control (ALC/AGC) system for charge-coupled-device (CCD) color television camera prevents over-loading in bright scenes using technique for measuring brightness of scene from red, green, and blue output signals and processing these into adjustments of video amplifiers and iris on camera lens. System faster, does not distort video brightness signals, and built with smaller components.

  2. Gain-Scheduled Controller Design: Variable Weighting Approach

    NASA Astrophysics Data System (ADS)

    Ilka, Adrian; Veselý, Vojtech

    2014-03-01

    Among the most popular approaches to non-linear control is gain-scheduled (GS) controller, which can have better performance than robust and other ones. Our approach is based on a consideration that in linear parameter varying (LPV) system, scheduling parameters and their derivatives with respect to time are supposed to lie in a priori given hyper rectangles. To access the performance quality a new quadratic cost function is used, where weighting matrices are time varying depends on scheduled parameter. The class of control structure includes decentralised fixed order output feedbacks like PID controller. Numerical examples illustrate the effectiveness of the proposed approach.

  3. Fixed gain and adaptive techniques for rotorcraft vibration control

    NASA Technical Reports Server (NTRS)

    Roy, R. H.; Saberi, H. A.; Walker, R. A.

    1985-01-01

    The results of an analysis effort performed to demonstrate the feasibility of employing approximate dynamical models and frequency shaped cost functional control law desgin techniques for helicopter vibration suppression are presented. Both fixed gain and adaptive control designs based on linear second order dynamical models were implemented in a detailed Rotor Systems Research Aircraft (RSRA) simulation to validate these active vibration suppression control laws. Approximate models of fuselage flexibility were included in the RSRA simulation in order to more accurately characterize the structural dynamics. The results for both the fixed gain and adaptive approaches are promising and provide a foundation for pursuing further validation in more extensive simulation studies and in wind tunnel and/or flight tests.

  4. Neural Network Based PID Gain Tuning of Chemical Plant Controller

    NASA Astrophysics Data System (ADS)

    Abe, Yoshihiro; Konishi, Masami; Imai, Jun; Hasegawa, Ryusaku; Watanabe, Masamori; Kamijo, Hiroaki

    In these years, plant control systems are highly automated and applied to many industries. The control performances change with the passage of time, because of the deterioration of plant facilities. This is why human experts tune the control system to improve the total plant performances. In this study, PID control system for the oil refining chemical plant process is treated. In oil refining, there are thousands of the control loops in the plant to keep the product quality at the desired value and to secure the safety of the plant operation. According to the ambiguity of the interference between control loops, it is difficult to estimate the plant dynamical model accurately. Using neuro emulator and recurrent neural networks model (RNN model) for emulation and tuning parameters, PID gain tuning system of chemical plant controller is constructed. Through numerical experiments using actual plant data, effect of the proposed method was ascertained.

  5. Automatic reactor control system for transient operation

    NASA Astrophysics Data System (ADS)

    Lipinski, Walter C.; Bhattacharyya, Samit K.; Hanan, Nelson A.

    Various programmatic considerations have delayed the upgrading of the TREAT reactor and the performance of the control system is not yet experimentally verified. The current schedule calls for the upgrading activities to occur last in the calendar year 1987. Detailed simulation results, coupled with earlier validation of individual components of the control strategy in TREAT, verify the performance of the algorithms. The control system operates within the safety envelope provided by a protection system designed to ensure reactor safety under conditions of spurious reactivity additions. The approach should be directly applicable to MMW systems, with appropriate accounting of temperature rate limitations of key components and of the inertia of the secondary system components.

  6. Automatic gain control. [the Loran-C receiver

    NASA Technical Reports Server (NTRS)

    Roman, J. P.

    1981-01-01

    An automatic gain control (AGC), designed to operate with the prototype Loran-C receiver, is described. The device is used to eliminate error which occurs when signals are received at different magnitudes. The automatic gain control is a three transistor circuit which requires a constant dc voltage of 8 volts. Tests conclude that this value may be in the range of 4 to 12 v without change in circuit performance. Two transistors are cascaded to pass and amplify the input signal. Their gain is controlled by a third transistor which itself is controlled by an external AGC voltage between 0 and 8 volts dc. The integrated circuit used is an 8 pin chip, which is a differential cascade amplifier designed for use in communications operating at frequencies from dc to 120 MHz. The integrated circuit was balanced for AGC capabilities, and has a wide operating current range. The maximum input current at pins 1 and 5 is 0.1 mAmps. AGC testing is described.

  7. Determination of Flux Control Coefficients from transient metabolite concentrations.

    PubMed Central

    Delgado, J; Liao, J C

    1992-01-01

    Flux Control Coefficients have been used in the analysis of metabolic regulation for quantifying the effect of an enzyme on the overall steady-state flux. However, the experimental determination of these coefficients is very time-consuming, involving either determining the individual enzyme kinetics or perturbing the enzyme activity by genetic or other means. We developed a methodology that enables the determination of the Flux Control Coefficients from transient metabolite concentrations without knowing kinetic parameters. The transient states can be generated by changing the incubation conditions or adding the initial substrate. This approach is suitable for investigating metabolic regulation in vivo or multiple enzyme systems in vitro. It is particularly helpful if used in conjunction with n.m.r. measurements. The approach is based on a relationship between transient metabolite concentrations and the Flux Control Coefficients. The methodology has been improved from our previous results, and it is illustrated by three examples with simple pathway topologies. PMID:1554375

  8. Model of visual contrast gain control and pattern masking

    NASA Technical Reports Server (NTRS)

    Watson, A. B.; Solomon, J. A.

    1997-01-01

    We have implemented a model of contrast gain and control in human vision that incorporates a number of key features, including a contrast sensitivity function, multiple oriented bandpass channels, accelerating nonlinearities, and a devisive inhibitory gain control pool. The parameters of this model have been optimized through a fit to the recent data that describe masking of a Gabor function by cosine and Gabor masks [J. M. Foley, "Human luminance pattern mechanisms: masking experiments require a new model," J. Opt. Soc. Am. A 11, 1710 (1994)]. The model achieves a good fit to the data. We also demonstrate how the concept of recruitment may accommodate a variant of this model in which excitatory and inhibitory paths have a common accelerating nonlinearity, but which include multiple channels tuned to different levels of contrast.

  9. Gain control in molecular information processing: lessons from neuroscience

    NASA Astrophysics Data System (ADS)

    Nemenman, Ilya

    2012-04-01

    Statistical properties of environments experienced by biological signaling systems in the real world change, which necessitates adaptive responses to achieve high fidelity information transmission. One form of such adaptive response is gain control. Here, we argue that a certain simple mechanism of gain control, understood well in the context of systems neuroscience, also works for molecular signaling. The mechanism allows us to transmit more than 1 bit (on or off) of information about the signal independent of the signal variance. It does not require additional molecular circuitry beyond that already present in many molecular systems, and in particular, it does not depend on existence of feedback loops. The mechanism provides a potential explanation for abundance of ultrasensitive response curves in biological regulatory networks.

  10. A new adjustable gains for second order sliding mode control of saturated DFIG-based wind turbine

    NASA Astrophysics Data System (ADS)

    Bounadja, E.; Djahbar, A.; Taleb, R.; Boudjema, Z.

    2017-02-01

    The control of Doubly-Fed induction generator (DFIG), used in wind energy conversion, has been given a great deal of interest. Frequently, this control has been dealt with ignoring the magnetic saturation effect in the DFIG model. The aim of the present work is twofold: firstly, the magnetic saturation effect is accounted in the control design model; secondly, a new second order sliding mode control scheme using adjustable-gains (AG-SOSMC) is proposed to control the DFIG via its rotor side converter. This scheme allows the independent control of the generated active and reactive power. Conventionally, the second order sliding mode control (SOSMC) applied to the DFIG, utilize the super-twisting algorithm with fixed gains. In the proposed AG-SOSMC, a simple means by which the controller can adjust its behavior is used. For that, a linear function is used to represent the variation in gain as a function of the absolute value of the discrepancy between the reference rotor current and its measured value. The transient DFIG speed response using the aforementioned characteristic is compared with the one determined by using the conventional SOSMC controller with fixed gains. Simulation results show, accurate dynamic performances, quicker transient response and more accurate control are achieved for different operating conditions.

  11. Feedback shape control for deployable mesh reflectors using gain scheduling method

    NASA Astrophysics Data System (ADS)

    Xie, Yangmin; Shi, Hang; Alleyne, Andrew; Yang, Bingen

    2016-04-01

    This paper presents a theoretical study on the dynamic shape control problem of deployable mesh reflectors (DMRs) via feedback approaches. The reflector structure is simplified from a nonlinear model to be quasi-static with respect to temperature variations but dynamic with respect to mechanical vibrations. The orbital cycle is segmented into multiple temperature zones, and an H∞ robust state feedback controller is designed for each zone to guarantee the local stability of the system under the model uncertainty caused by thermal effects and to reject external force disturbances. At the same time, gain scheduling control method is adopted to compensate thermal distortions and to ensure smooth transition response when switching among the local robust controllers. A DMR model is considered in the case study to show the effectiveness of the control approach. The structural vibrations caused by external force disturbances can be sufficiently suppressed in a much shorter time. The closed loop response of the DMR structure shows that much higher surface accuracy is obtained during the orbiting mission compared to the open-loop configuration, and transient focal length and transient de-focus of the reflector are well controlled within the satisfactory bounds, demonstrating the numerical feasibility of the proposed method to solve the dynamic shape control problem of DMRs.

  12. Electromagnetic transients program (EMTP): Volume 4, Workbook IV (TACS) (Transients Analysis of Control Systems): Final report

    SciTech Connect

    Lasseter, R.H.

    1989-06-01

    This workbook represents an introduction to the use of TACS (Transients Analysis of Control Systems) in the EMTP. The material progresses from an overview of basic TACS concepts and components to a detailed HVDC model. The following application of TACS are covered: a variable load problem, static Var systems, thyristor models, TCR, basic HVDC models and a detailed HVDC model. Complete data files are given for most examples.

  13. Dynamic modulation of visual and electrosensory gains for locomotor control

    PubMed Central

    Sutton, Erin E.; Demir, Alican; Stamper, Sarah A.; Fortune, Eric S.; Cowan, Noah J.

    2016-01-01

    Animal nervous systems resolve sensory conflict for the control of movement. For example, the glass knifefish, Eigenmannia virescens, relies on visual and electrosensory feedback as it swims to maintain position within a moving refuge. To study how signals from these two parallel sensory streams are used in refuge tracking, we constructed a novel augmented reality apparatus that enables the independent manipulation of visual and electrosensory cues to freely swimming fish (n = 5). We evaluated the linearity of multisensory integration, the change to the relative perceptual weights given to vision and electrosense in relation to sensory salience, and the effect of the magnitude of sensory conflict on sensorimotor gain. First, we found that tracking behaviour obeys superposition of the sensory inputs, suggesting linear sensorimotor integration. In addition, fish rely more on vision when electrosensory salience is reduced, suggesting that fish dynamically alter sensorimotor gains in a manner consistent with Bayesian integration. However, the magnitude of sensory conflict did not significantly affect sensorimotor gain. These studies lay the theoretical and experimental groundwork for future work investigating multisensory control of locomotion. PMID:27170650

  14. Gantry cranes gain scheduling feedback control with friction compensation

    NASA Astrophysics Data System (ADS)

    Omar, Hanafy M.; Nayfeh, Ali H.

    2005-03-01

    We designed a controller based on gain-scheduling feedback to move a load on a gantry crane from point to point within one oscillation cycle and without inducing large swings. The settling time of the system is taken to be equal to the period of oscillation of the load. This criterion enables calculation of the controller feedback gains for varying load weight and cable length. Numerical simulations show that the controller is effective in reducing load oscillations and transferring the load in a reasonable time compared with that of optimal control. To experimentally validate the theory, we had to compensate for friction. To this end, we estimated the friction, and then applied an opposite control action to cancel it. To estimate the friction force, we assumed a mathematical model, and then we estimated the model coefficients using an off-line identification technique, such as the method of least squares (LS). First, the process of identification is applied to a theoretical model of a DC motor with known friction coefficients. From this example, some guidelines and rules are deduced for the choice of the LS parameters. Then, the friction coefficients of the gantry crane model are estimated and validated.

  15. Gain-Scheduled Fault Tolerance Control Under False Identification

    NASA Technical Reports Server (NTRS)

    Shin, Jong-Yeob; Belcastro, Christine (Technical Monitor)

    2006-01-01

    An active fault tolerant control (FTC) law is generally sensitive to false identification since the control gain is reconfigured for fault occurrence. In the conventional FTC law design procedure, dynamic variations due to false identification are not considered. In this paper, an FTC synthesis method is developed in order to consider possible variations of closed-loop dynamics under false identification into the control design procedure. An active FTC synthesis problem is formulated into an LMI optimization problem to minimize the upper bound of the induced-L2 norm which can represent the worst-case performance degradation due to false identification. The developed synthesis method is applied for control of the longitudinal motions of FASER (Free-flying Airplane for Subscale Experimental Research). The designed FTC law of the airplane is simulated for pitch angle command tracking under a false identification case.

  16. Feedback control of acoustic disturbance transient growth in triggering thermoacoustic instability

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Reyhanoglu, Mahmut

    2014-08-01

    Transient growth of acoustic disturbances could trigger thermoacoustic instability in a combustion system with non-orthogonal eigenmodes, even with stable eigenvalues. In this work, feedback control of transient growth of flow perturbations in a Rijke-type combustion system is considered. For this, a generalized thermoacoustic model with distributed monopole-like actuators is developed. The model is formulated in state-space to gain insights on the interaction between various eigenmodes and the dynamic response of the system to the actuators. Three critical parameters are identified: (1) the mode number, (2) the number of actuators, and (3) the locations of the actuators. It is shown that in general the number of the actuators K is related to the mode number N as K=N2. For simplicity in illustrating the main results of the paper, two different thermoacoustic systems are considered: system (a) with one mode and system (b) that involves two modes. The actuator location effect is studied in system (a) and it is found that the actuator location plays an important role in determining the control effort. In addition, sensitivity analysis of pressure- and velocity-related control parameters is conducted. In system (b), when the actuators are turned off (i.e., open-loop configuration), it is observed that acoustic energy transfers from the high frequency mode to the lower frequency mode. After some time, the energy is transferred back. Moreover, the high frequency oscillation grows into nonlinear limit cycle with the low frequency oscillation amplified. As a linear-quadratic regulator (LQR) is implemented to tune the actuators, both systems become asymptotically stable. However, the LQR controller fails in eliminating the transient growth, which may potentially trigger thermoacoustic instability. In order to achieve strict dissipativity (i.e., unity maximum transient growth), a transient growth controller is systematically designed and tested in both systems. Comparison is

  17. Small gain stability theory for matched basis function repetitive control

    NASA Astrophysics Data System (ADS)

    Shi, Yunde; Longman, Richard W.; Nagashima, Masaki

    2014-02-01

    Many spacecraft suffer from jitter produced by periodic vibration sources such as momentum wheels, reaction wheels, or control moment gyros. Vibration isolation mounts are needed for fine pointing equipment. Active control methods directly addressing frequencies of interest have the potential to completely cancel the influence of these disturbances. Typical repetitive control methods initially address all frequencies of a given period. Matched basis function repetitive control individually addresses each frequency, finding error components at these frequencies using the projection algorithm, and can converge to zero error, using only frequency response knowledge at addressed frequencies. This results in linear control laws but with periodic coefficients. Frequency domain raising produces a time invariant pole/zero model of the control law. A small gain stability theory is developed, that exhibits very strong stability robustness properties to model error. For convergence to zero tracking error it needs only knowledge of the phase response at addressed frequencies, and it must be known within an accuracy of ±90°. Controllers are then designed by pole-zero placement, bypassing the complexity of original periodic coefficient equations. Compared to the usual repetitive control approaches, the approach here eliminates the need for a robustifying zero phase low pass filter, eliminates the need for interpolation in data, and handles multiple unrelated frequencies easily and naturally.

  18. Micro-Macro Bilateral Control Taking into Account Scaling of Control Gains

    NASA Astrophysics Data System (ADS)

    Susa, Shigeru; Shimono, Tomoyuki; Ohnishi, Kouhei

    In micro-macro bilateral control systems, it is important to use position and force scaling factors that depend on the size of the master and slave system. Moreover, it is vital for control systems to use appropriate control gains depending on the scaling ratio between master and slave response. This paper proposes a micro-macro bilateral control system based on the scaling of control gains. In this system, the control gains of the master and slave system are adjusted to appropriate values by using control gain scaling factors. These scaling factors are obtained by designing a micro-macro bilateral control system to achieve ideal reproducibility. To verify the validity of the proposed system, analytical results for the reproducibility, operationality, and stability of the proposed control system are presented in this paper. Moreover, the proposed system is used in an experimental micro-macro bilateral system, and the results are presented.

  19. Inhibitory control gains from higher-order cognitive strategy training.

    PubMed

    Motes, Michael A; Gamino, Jacquelyn F; Chapman, Sandra B; Rao, Neena K; Maguire, Mandy J; Brier, Matthew R; Kraut, Michael A; Hart, John

    2014-02-01

    The present study examined the transfer of higher-order cognitive strategy training to inhibitory control. Middle school students enrolled in a comprehension- and reasoning-focused cognitive strategy training program and passive controls participated. The training program taught students a set of steps for inferring essential gist or themes from materials. Both before and after training or a comparable duration in the case of the passive controls, participants completed a semantically cued Go/No-Go task that was designed to assess the effects of depth of semantic processing on response inhibition and components of event-related potentials (ERP) related to response inhibition. Depth of semantic processing was manipulated by varying the level of semantic categorization required for response selection and inhibition. The SMART-trained group showed inhibitory control gains and changes in fronto-central P3 ERP amplitudes on inhibition trials; whereas, the control group did not. The results provide evidence of the transfer of higher-order cognitive strategy training to inhibitory control and modulation of ERPs associated with semantically cued inhibitory control. The findings are discussed in terms of implications for cognitive strategy training, models of cognitive abilities, and education. Published by Elsevier Inc.

  20. A Presynaptic Gain Control Mechanism Fine-Tunes Olfactory Behavior

    PubMed Central

    Root, Cory M.; Masuyama, Kaoru; Green, David S.; Enell, Lina E.; Nässel, Dick R.; Lee, Chi-Hon; Wang, Jing W.

    2008-01-01

    Early sensory processing can play a critical role in sensing environmental cues. We have investigated the physiological and behavioral function of gain control at the first synapse of olfactory processing in Drosophila. We report that olfactory receptor neurons (ORNs) express the GABAB receptor (GABABR) and its expression expands the dynamic range of ORN synaptic transmission that is preserved in projection neuron responses. Strikingly, we find that different ORN channels have unique baseline levels of GABABR expression. ORNs that sense the aversive odorant CO2 do not express GABABRs nor exhibit any presynaptic inhibition. In contrast, pheromone-sensing ORNs express a high level of GABABRs and exhibit strong presynaptic inhibition. Furthermore, a behavioral significance of presynaptic inhibition was revealed by a courtship behavior in which pheromone-dependent mate localization is impaired in flies that lack GABABRs in specific ORNs. Together, these findings indicate that different olfactory receptor channels may employ heterogeneous presynaptic gain control as a mechanism to allow an animal’s innate behavioral responses to match its ecological needs. PMID:18667158

  1. LPV gain-scheduled control of SCR aftertreatment systems

    NASA Astrophysics Data System (ADS)

    Meisami-Azad, Mona; Mohammadpour, Javad; Grigoriadis, Karolos M.; Harold, Michael P.; Franchek, Matthew A.

    2012-01-01

    Hydrocarbons, carbon monoxide and some of other polluting emissions produced by diesel engines are usually lower than those produced by gasoline engines. While great strides have been made in the exhaust aftertreatment of vehicular pollutants, the elimination of nitrogen oxide (NO x ) from diesel vehicles is still a challenge. The primary reason is that diesel combustion is a fuel-lean process, and hence there is significant unreacted oxygen in the exhaust. Selective catalytic reduction (SCR) is a well-developed technology for power plants and has been recently employed for reducing NO x emissions from automotive sources and in particular, heavy-duty diesel engines. In this article, we develop a linear parameter-varying (LPV) feedforward/feedback control design method for the SCR aftertreatment system to decrease NO x emissions while keeping ammonia slippage to a desired low level downstream the catalyst. The performance of the closed-loop system obtained from the interconnection of the SCR system and the output feedback LPV control strategy is then compared with other control design methods including sliding mode, and observer-based static state-feedback parameter-varying control. To reduce the computational complexity involved in the control design process, the number of LPV parameters in the developed quasi-LPV (qLPV) model is reduced by applying the principal component analysis technique. An LPV feedback/feedforward controller is then designed for the qLPV model with reduced number of scheduling parameters. The designed full-order controller is further simplified to a first-order transfer function with a parameter-varying gain and pole. Finally, simulation results using both a low-order model and a high-fidelity and high-order model of SCR reactions in GT-POWER interfaced with MATLAB/SIMULINK illustrate the high NO x conversion efficiency of the closed-loop SCR system using the proposed parameter-varying control law.

  2. Electrical and optical control of optical gain in a coupled triple quantum dot system operating in telecommunication window

    NASA Astrophysics Data System (ADS)

    Mehmannavaz, Mohammad Reza; Sattari, Hamed

    2014-12-01

    We investigate the light amplification and gain without inversion (GWI) in triple quantum dot molecules in both steady-state and transient state. We demonstrate that the light amplification and GWI of a light pulse can be controlled through the rates of the incoherent pumping and tunneling between electronic levels. The required switching times for switching of a light pulse from absorption to gain and vice versa is then discussed. We obtain switching time at about 40 ps, which resembles a high-speed optical switch in nanostructure. The proposed approach in QDMs may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  3. Dendritic Excitability and Gain Control in Recurrent Cortical Microcircuits

    PubMed Central

    Hay, Etay; Segev, Idan

    2015-01-01

    Layer 5 thick tufted pyramidal cells (TTCs) in the neocortex are particularly electrically complex, owing to their highly excitable dendrites. The interplay between dendritic nonlinearities and recurrent cortical microcircuit activity in shaping network response is largely unknown. We simulated detailed conductance-based models of TTCs forming recurrent microcircuits that were interconnected as found experimentally; the network was embedded in a realistic background synaptic activity. TTCs microcircuits significantly amplified brief thalamocortical inputs; this cortical gain was mediated by back-propagation activated N-methyl-d-aspartate depolarizations and dendritic back-propagation-activated Ca2+ spike firing, ignited by the coincidence of thalamic-activated somatic spike and local dendritic synaptic inputs, originating from the cortical microcircuit. Surprisingly, dendritic nonlinearities in TTCs microcircuits linearly multiplied thalamic inputs—amplifying them while maintaining input selectivity. Our findings indicate that dendritic nonlinearities are pivotal in controlling the gain and the computational functions of TTCs microcircuits, which serve as a dominant output source for the neocortex. PMID:25205662

  4. On controllability of neuronal networks with constraints on the average of control gains.

    PubMed

    Tang, Yang; Wang, Zidong; Gao, Huijun; Qiao, Hong; Kurths, Jürgen

    2014-12-01

    Control gains play an important role in the control of a natural or a technical system since they reflect how much resource is required to optimize a certain control objective. This paper is concerned with the controllability of neuronal networks with constraints on the average value of the control gains injected in driver nodes, which are in accordance with engineering and biological backgrounds. In order to deal with the constraints on control gains, the controllability problem is transformed into a constrained optimization problem (COP). The introduction of the constraints on the control gains unavoidably leads to substantial difficulty in finding feasible as well as refining solutions. As such, a modified dynamic hybrid framework (MDyHF) is developed to solve this COP, based on an adaptive differential evolution and the concept of Pareto dominance. By comparing with statistical methods and several recently reported constrained optimization evolutionary algorithms (COEAs), we show that our proposed MDyHF is competitive and promising in studying the controllability of neuronal networks. Based on the MDyHF, we proceed to show the controlling regions under different levels of constraints. It is revealed that we should allocate the control gains economically when strong constraints are considered. In addition, it is found that as the constraints become more restrictive, the driver nodes are more likely to be selected from the nodes with a large degree. The results and methods presented in this paper will provide useful insights into developing new techniques to control a realistic complex network efficiently.

  5. A Modified Lunar Reconnaissance Orbiter (LRO) High Gain Antenna (HGA) Controller Based on Flight Performance

    NASA Technical Reports Server (NTRS)

    Shah, Neerav

    2010-01-01

    The National Aeronautics and Space Administration's (NASA) Lunar Reconnaissance Orbiter (LRO) was launched on June 18, 2009 and is currently in a 50 km mean altitude polar orbit around the Moon. LRO was designed and built by the NASA Goddard Space Flight Center in Greenbelt, MD. The spacecraft is three-axis stabilized via the attitude control system (ACS), which is composed of various control modes using different sets of sensors and actuators. In addition to pointing the spacecraft, the ACS is responsible for pointing LRO s two appendages, the Solar Array (SA) and the High Gain Antenna (HGA). This study reviews LRO s HGA control system. Starting with an overview of the HGA system, the paper delves into the single input single output (SISO) linear analysis followed by the controller design. Based on flight results, an alternate control scheme is devised to address inherent features in the flight control system. The modified control scheme couples the HGA loop with the spacecraft pointing control loop, and through analysis is shown to be stable and improve transient performance. Although proposed, the LRO project decided against implementing this modification.

  6. Ionization and transient absorption control with a resonant attosecond clock

    NASA Astrophysics Data System (ADS)

    Argenti, Luca

    2014-04-01

    Metastable states are important actors in the ionisation of atoms and molecules. Sub-femtosecond extreme ultraviolet pulses can coherently populate several transiently bound states at once, thus starting the attosecond clocks which are required to monitor and control ultrafast electronic evolution above the ionisation threshold. Here we illustrate, from a theoretical point of view, the effects coherent superpositions of 1Po doubly excited states in the helium atom have on channel-resolved photoelectron spectra as well as on the transient absorption spectrum of the atom in the extreme ultraviolet region, when they are created by a single-attosecond pulse in the presence of a strong few-cycle near-infrared/visible pulse which acts as a probe. Interference fringes varying rapidly with the pump-probe time delay are visible in both photoelectron and transient absorption spectra. From such fringes, the wave packet itself can conceivably be reconstructed. Conversely, all observables are modulated by the characteristic beating periods of the wave packet, so that control of partial ionisation yields, branching ratios, and light absorption or amplification can be achieved.

  7. Improved energy coupling into the gain region of the Ni-like Pd transient collisional x-ray laser

    SciTech Connect

    Smith, R; Dunn, J; Filevich, J; Moon, S; Nilsen, J; Keenan, R; Shlyaptsev, V; Rocca, J; Hunter, J; Shepherd, R; Booth, R; Marconi, M

    2004-10-05

    We present within this paper a series of experiments, which yield new observations to further our understanding of the transient collisional x-ray laser medium. We use the recently developed technique of picosecond x-ray laser interferometry to probe the plasma conditions in which the x-ray laser is generated and propagates. This yields two dimensional electron density maps of the plasma taken at different times relative to the peak of the 600ps plasma-forming beam. In another experimental campaign, the output of the x-ray laser plasma column is imaged with a spherical multilayer mirror onto a CCD camera to give a two-dimensional intensity map of the x-ray laser output. Near-field imaging gives insights into refraction, output intensity and spatial mode structure. Combining these images with the density maps gives an indication of the electron density at which the x-ray laser is being emitted at (yielding insights into the effect of density gradients on beam propagation). Experimental observations coupled with simulations predict that most effective coupling of laser pump energy occurs when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for Ni-like schemes). This can increase the output intensity by more than an order of magnitude relative to the case were the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). We have also conducted an experiment in which the output of the x-ray laser was imaged onto the entrance slit of a high temporal resolution streak camera. This effectively takes a one-dimensional slice of the x-ray laser spatial profile and sweeps it in time. Under some conditions we observe rapid movement of the x-ray laser ({approx} 3 {micro}m/ps) towards the target surface.

  8. Yeast gain-of-function mutations reveal structure–function relationships conserved among different subfamilies of transient receptor potential channels

    PubMed Central

    Su, Zhenwei; Zhou, Xinliang; Haynes, W. John; Loukin, Stephen H.; Anishkin, Andriy; Saimi, Yoshiro; Kung, Ching

    2007-01-01

    Transient receptor potential (TRP) channels found in animals, protists, and fungi are primary chemo-, thermo-, or mechanosensors. Current research emphasizes the characteristics of individual channels in each animal TRP subfamily but not the mechanisms common across subfamilies. A forward genetic screen of the TrpY1, the yeast TRP channel, recovered gain-of-function (GOF) mutations with phenotype in vivo and in vitro. Single-channel patch-clamp analyses of these GOF-mutant channels show prominent aberrations in open probability and channel kinetics. These mutations revealed functionally important aromatic amino acid residues in four locations: at the intracellular end of the fifth transmembrane helix (TM5), at both ends of TM6, and at the immediate extension of TM6. These aromatics have counterparts in most TRP subfamilies. The one in TM5 (F380L) aligns precisely with an exceptional Drosophila mutant allele (F550I) that causes constitutive activity in the canonical TRP channel, resulting in rapid and severe retinal degeneration beyond mere loss of phototaxis. Thus, this phenylalanine maintains the balance of various functional states (conformations) of a channel for insect phototransduction as well as one for fungal mechanotransduction. This residue is among a small cluster of phenylalanines found in all known subfamilies of TRP channels. This unique case illustrates that GOF mutations can reveal structure–function principles that can be generalized across different TRP subfamilies. It appears that the conserved aromatics in the four locations have conserved functions in most TRP channels. The possible mechanistic roles of these aromatics and the further use of yeast genetics to dissect TRP channels are discussed. PMID:18042709

  9. Improvement of transient stability using unified power flow controller

    SciTech Connect

    Mihalic, R.; Zunko, P.; Povh, D.

    1996-01-01

    The aim of the paper is to analyze the effect of an Unified Power Flow Controller (UPFC) on transient stability margin enhancement of a longitudinal system. To utilize the UPFC possibilities fully, the three controllable UPFC parameters were determined during the digital simulation process performed by the NETOMAC simulation program. The basis for determination of the suitable damping strategy and for determination of the optimal UPFC parameters is a mathematical model, which describes the interdependence between longitudinal transmission system parameters, operating conditions and UPFC parameters in the form of analytical equations. On the basis of the mathematical model, the theoretical UPFC limits were also detected, and their appearance explained.

  10. Phase and gain control policies for robust active vibration control of flexible structures

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Scorletti, G.; Ichchou, M. N.; Mieyeville, F.

    2013-07-01

    The interest of this paper is to develop a general and systematic robust control methodology for active vibration control of flexible structures. For this purpose, first phase and gain control policies are proposed to impose qualitative frequency-dependent requirements on the controller to consider a complete set of control objectives. Then the proposed control methodology is developed by employing phase and gain control policies in the dynamic output feedback H∞ control: according to the set of control objectives, phase and gain control policies incorporate necessary weighting functions and determine them in a rational and systematic way; on the other hand, with the appropriate weighting functions efficient H∞ control algorithms can automatically realize phase and gain control policies and generate a satisfactory H∞ controller. The proposed control methodology can be used for both SISO and MIMO systems with collocated or non-collocated sensors and actuators. In this paper, it is validated on a non-collocated piezoelectric cantilever beam. Both numerical simulations and experimental results demonstrate the effectiveness of the proposed control methodology.

  11. PID Controller Settings Based on a Transient Response Experiment

    ERIC Educational Resources Information Center

    Silva, Carlos M.; Lito, Patricia F.; Neves, Patricia S.; Da Silva, Francisco A.

    2008-01-01

    An experimental work on controller tuning for chemical engineering undergraduate students is proposed using a small heat exchange unit. Based upon process reaction curves in open-loop configuration, system gain and time constant are determined for first order model with time delay with excellent accuracy. Afterwards students calculate PID…

  12. PID Controller Settings Based on a Transient Response Experiment

    ERIC Educational Resources Information Center

    Silva, Carlos M.; Lito, Patricia F.; Neves, Patricia S.; Da Silva, Francisco A.

    2008-01-01

    An experimental work on controller tuning for chemical engineering undergraduate students is proposed using a small heat exchange unit. Based upon process reaction curves in open-loop configuration, system gain and time constant are determined for first order model with time delay with excellent accuracy. Afterwards students calculate PID…

  13. Multidimensional gain control in image representation and processing in vision.

    PubMed

    Furman, S; Zeevi, Y Y

    2015-04-01

    A generic model of automatic gain control (AGC) is proposed as a general framework for multidimensional automatic contrast sensitivity adjustment in vision, as well as in other sensory modalities. We show that a generic feedback AGC mechanism, incorporating a nonlinear synaptic interaction into the feedback loop of a neural network, can enhance and emphasize important image attributes, such as curvature, size, depth, convexity/concavity and more, similar to its role in the adjustment of photoreceptors and retinal network sensitivity over the extremely high dynamic range of environmental light intensities, while enhancing the contrast. We further propose that visual illusions, well established by psychophysical experiments, are a by-product of the multidimensional AGC. This hypothesis is supported by simulations implementing AGC, which reproduce psychophysical data regarding size contrast effects known as the Ebbinghaus illusion, and depth contrast effects. Processing of curvature by an AGC network illustrates that it is an important mechanism of image structure pre-emphasis, which thereby enhances saliency. It is argued that the generic neural network of AGC constitutes a universal, parsimonious, unified mechanism of neurobiological automatic contrast sensitivity control. This mechanism/model can account for a wide range of physiological and psychophysical phenomena, such as visual illusions and contour completion, in cases of occlusion, by a basic neural network. Likewise, and as important, biologically motivated AGC provides attractive new means for the development of intelligent computer vision systems.

  14. Use of a photonic crystal for optical amplifier gain control

    DOEpatents

    Lin, Shawn-Yu; Fleming, James G.; El-Kady, Ihab

    2006-07-18

    An optical amplifier having a uniform gain profile uses a photonic crystal to tune the density-of-states of a gain medium so as to modify the light emission rate between atomic states. The density-of-states of the gain medium is tuned by selecting the size, shape, dielectric constant, and spacing of a plurality of microcavity defects in the photonic crystal. The optical amplifier is particularly useful for the regeneration of DWDM signals in long optical fibers.

  15. Tiso Adjustable Filter with Controllable Controlled-Gain Voltage Differencing Current Conveyor

    NASA Astrophysics Data System (ADS)

    Jerabek, Jan; Sotner, Roman; Vrba, Kamil

    2014-05-01

    The main aim of this paper is to present solution of triple-input single-output (TISO) filter with independently adjustable pole frequency, quality factor, bandwidth and also gain. Filter is universal, operates in current mode and includes only one active element - the so-called Controlled-Gain Voltage Differencing Current Conveyor (CG-VDCC) with two controllable parameters: transconductance (gm) and gain of output currents (BX ). Implementation of CG-VDCC element in 0.18 μm CMOS technology is also included and this model is used in proposed filter simulations.

  16. Polarization-controlled optimal scatter suppression in transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Malý, Pavel; Ravensbergen, Janneke; Kennis, John T. M.; van Grondelle, Rienk; Croce, Roberta; Mančal, Tomáš; van Oort, Bart

    2017-03-01

    Ultrafast transient absorption spectroscopy is a powerful technique to study fast photo-induced processes, such as electron, proton and energy transfer, isomerization and molecular dynamics, in a diverse range of samples, including solid state materials and proteins. Many such experiments suffer from signal distortion by scattered excitation light, in particular close to the excitation (pump) frequency. Scattered light can be effectively suppressed by a polarizer oriented perpendicular to the excitation polarization and positioned behind the sample in the optical path of the probe beam. However, this introduces anisotropic polarization contributions into the recorded signal. We present an approach based on setting specific polarizations of the pump and probe pulses, combined with a polarizer behind the sample. Together, this controls the signal-to-scatter ratio (SSR), while maintaining isotropic signal. We present SSR for the full range of polarizations and analytically derive the optimal configuration at angles of 40.5° between probe and pump and of 66.9° between polarizer and pump polarizations. This improves SSR by (or compared to polarizer parallel to probe). The calculations are validated by transient absorption experiments on the common fluorescent dye Rhodamine B. This approach provides a simple method to considerably improve the SSR in transient absorption spectroscopy.

  17. Polarization-controlled optimal scatter suppression in transient absorption spectroscopy

    PubMed Central

    Malý, Pavel; Ravensbergen, Janneke; Kennis, John T. M.; van Grondelle, Rienk; Croce, Roberta; Mančal, Tomáš; van Oort, Bart

    2017-01-01

    Ultrafast transient absorption spectroscopy is a powerful technique to study fast photo-induced processes, such as electron, proton and energy transfer, isomerization and molecular dynamics, in a diverse range of samples, including solid state materials and proteins. Many such experiments suffer from signal distortion by scattered excitation light, in particular close to the excitation (pump) frequency. Scattered light can be effectively suppressed by a polarizer oriented perpendicular to the excitation polarization and positioned behind the sample in the optical path of the probe beam. However, this introduces anisotropic polarization contributions into the recorded signal. We present an approach based on setting specific polarizations of the pump and probe pulses, combined with a polarizer behind the sample. Together, this controls the signal-to-scatter ratio (SSR), while maintaining isotropic signal. We present SSR for the full range of polarizations and analytically derive the optimal configuration at angles of 40.5° between probe and pump and of 66.9° between polarizer and pump polarizations. This improves SSR by (or compared to polarizer parallel to probe). The calculations are validated by transient absorption experiments on the common fluorescent dye Rhodamine B. This approach provides a simple method to considerably improve the SSR in transient absorption spectroscopy. PMID:28262765

  18. Specification, Measurement, and Control of Electrical Switching Transients

    NASA Technical Reports Server (NTRS)

    Javor, K.

    1999-01-01

    There have been several instances of susceptibility to switching transients. The Space Shuttle Spacelab Remote Acquisition Unit (RAU-A standard interface between Spacelab payloads and the Shuttle communications system) will shut down if the input 28 Vdc bus drops below 22 volts for more than 80 gs. Although a MIL-STD-461 derivative CS06 requirement was levied on the RAU, it failed to find this susceptibility. A heavy payload on one aircraft sags the 28 volt bus below 20 volts for milliseconds. Dc-dc converters have an operating voltage. A typical 28 Vdc-to-5 Vdc converter operates within tolerance when input potential is between 17-40 Vdc, A hold-up capacitor can be used to extend the time this range is presented to the convener when the line potential sags or surges outside this range. The designer must know the range of normal transients in order to choose the correct value of hold-up. This report describes the phenomena of electrical power bus transients induced by the switching of loads both on and off the bus, and control thereof.

  19. Variable Gain Type Internal Model Control-PID Speed Control for Ultrasonic Motors

    NASA Astrophysics Data System (ADS)

    Tanaka, Kanya; Yoshimura, Yoshie; Wakasa, Yuji; Akashi, Takuya

    Ultrasonic motors (USM) causes serious characteristic changes during operation. It is difficult for the conventional internal model control (IMC) proportional integral differential (PID) control to compensate such characteristic changes of the plant. To solve these problems, we propose a method of variable gain type IMC-PID control. In the proposed method, plant parameters are identified on line and these estimated parameters are used for adjusting three gains of PID. Then the proposed method makes it possible to compensate characteristic changes of the plant. The effectiveness of the proposed control method have been confirmed by experiments using the existing ultrasonic motors servo system.

  20. Parameter Transient Behavior Analysis on Fault Tolerant Control System

    NASA Technical Reports Server (NTRS)

    Belcastro, Christine (Technical Monitor); Shin, Jong-Yeob

    2003-01-01

    In a fault tolerant control (FTC) system, a parameter varying FTC law is reconfigured based on fault parameters estimated by fault detection and isolation (FDI) modules. FDI modules require some time to detect fault occurrences in aero-vehicle dynamics. This paper illustrates analysis of a FTC system based on estimated fault parameter transient behavior which may include false fault detections during a short time interval. Using Lyapunov function analysis, the upper bound of an induced-L2 norm of the FTC system performance is calculated as a function of a fault detection time and the exponential decay rate of the Lyapunov function.

  1. Partially controlling transient chaos in the Lorenz equations

    NASA Astrophysics Data System (ADS)

    Capeáns, Rubén; Sabuco, Juan; Sanjuán, Miguel A. F.; Yorke, James A.

    2017-03-01

    Transient chaos is a characteristic behaviour in nonlinear dynamics where trajectories in a certain region of phase space behave chaotically for a while, before escaping to an external attractor. In some situations, the escapes are highly undesirable, so that it would be necessary to avoid such a situation. In this paper, we apply a control method known as partial control that allows one to prevent the escapes of the trajectories to the external attractors, keeping the trajectories in the chaotic region forever. We also show, for the first time, the application of this method in three dimensions, which is the major step forward in this work. To illustrate how the method works, we have chosen the Lorenz system for a choice of parameters where transient chaos appears, as a paradigmatic example in nonlinear dynamics. We analyse three quite different ways to implement the method. First, we apply this method by building an one-dimensional map using the successive maxima of one of the variables. Next, we implement it by building a two-dimensional map through a Poincaré section. Finally, we built a three-dimensional map, which has the advantage of using a fixed time interval between application of the control, which can be useful for practical applications. This article is part of the themed issue 'Horizons of cybernetical physics'.

  2. Partially controlling transient chaos in the Lorenz equations.

    PubMed

    Capeáns, Rubén; Sabuco, Juan; Sanjuán, Miguel A F; Yorke, James A

    2017-03-06

    Transient chaos is a characteristic behaviour in nonlinear dynamics where trajectories in a certain region of phase space behave chaotically for a while, before escaping to an external attractor. In some situations, the escapes are highly undesirable, so that it would be necessary to avoid such a situation. In this paper, we apply a control method known as partial control that allows one to prevent the escapes of the trajectories to the external attractors, keeping the trajectories in the chaotic region forever. We also show, for the first time, the application of this method in three dimensions, which is the major step forward in this work. To illustrate how the method works, we have chosen the Lorenz system for a choice of parameters where transient chaos appears, as a paradigmatic example in nonlinear dynamics. We analyse three quite different ways to implement the method. First, we apply this method by building an one-dimensional map using the successive maxima of one of the variables. Next, we implement it by building a two-dimensional map through a Poincaré section. Finally, we built a three-dimensional map, which has the advantage of using a fixed time interval between application of the control, which can be useful for practical applications.This article is part of the themed issue 'Horizons of cybernetical physics'.

  3. Sustained vs. transient cognitive control: evidence of a behavioral dissociation.

    PubMed

    Funes, María Jesús; Lupiáñez, Juan; Humphreys, Glyn

    2010-03-01

    This study assessed whether two well known effects associated with cognitive control, conflict adaptation (the Gratton effect) and conflict context (proportion congruent effects), reflect a single common or separate control systems. To test this we examined if these two effects generalized from one kind of conflict to another by using a combined-conflict paradigm (involving the Simon and Spatial Stroop tasks) and manipulating the proportion of congruent to incongruent trials for one conflict (Simon) but not the other (Spatial Stroop). We found that conflict adaptation effects did not generalize, but the effect of conflict context did. This contrasting pattern of results strongly suggests the existence of two separate attentional control systems, one transient and responsible of online regulation of performance (conflict adaptation), the other sustained and responsible for conflict context effects. Copyright 2009 Elsevier B.V. All rights reserved.

  4. Solar heat gain control in historic buildings rehabilitation alternatives

    SciTech Connect

    Not Available

    1984-01-01

    Basic information is presented regarding the importance of existing windows and their glazing to historic buildings, the phenomenon of solar heat gain through windows, the properties of commonly available solar glazing types and sympathetic alternatives to the installation of inappropriate darkly tinted or highly reflective solar glazing in historic buildings. Although the basic principles of solar heat gain through windows is the same for both new construction and existing buildings, the recommendations that are included are specifically targeted toward historic buildings.

  5. Efficient control of transient wave forms to prevent spreading depolarizations.

    PubMed

    Dahlem, M A; Schneider, F M; Schöll, E

    2008-03-21

    In various neurological disorders spatio-temporal excitation patterns constitute examples of excitable behavior emerging from pathological pathways. During migraine, seizure, and stroke an initially localized pathological state can temporarily spread indicating a transition from non-excitable to excitable behavior. We investigate these transient wave forms in the generic FitzHugh-Nagumo (FHN) system of excitable media. Our goal is to define an efficient control minimizing the volume of invaded tissue. The general point of such a therapeutic optimization is how to apply control theory in the framework of structures in differential geometry by regarding parameter plane M of the FHN system as a differentiable manifold endowed with a metric. We suggest to equip M with a metric given by pharmacokinetic-pharmacodynamic models of drug receptor interaction.

  6. Dystrobrevin controls neurotransmitter release and muscle Ca2+ transients by localizing BK channels in C. elegans

    PubMed Central

    Chen, Bojun; Liu, Ping; Zhan, Haiying; Wang, Zhao-Wen

    2011-01-01

    Dystrobrevin is a major component of a dystrophin-associated protein complex (DAPC). It is widely expressed in mammalian tissues including the nervous system, where it is localized to the presynaptic nerve terminal with unknown function. In a genetic screen for suppressors of a lethargic phenotype caused by a gain-of-function (gf) isoform of SLO-1 in C. elegans, we isolated multiple loss-of-function (lf) mutants of the dystrobrevin gene dyb-1. dyb-1(lf) phenocopied slo-1(lf), causing increased neurotransmitter release at the neuromuscular junction, increased frequency of Ca2+ transients in body-wall muscle, and abnormal locomotion behavior. Neuron- and muscle-specific rescue experiments suggest that DYB-1 is required for SLO-1 function in both neurons and muscle cells. DYB-1 colocalized with SLO-1 at presynaptic sites in neurons and dense body regions in muscle cells, and dyb-1(lf) caused SLO-1 mislocalization in both types of cells without altering SLO-1 protein level. The neuronal phenotypes of dyb-1(lf) were partially rescued by mouse α-dystrobrevin-1 (αDB1). These observations revealed novel functions of the BK channel in regulating muscle Ca2+ transients, and of dystrobrevin in controlling neurotransmitter release and muscle Ca2+ transients by localizing the BK channel. PMID:22131396

  7. Transient Colloidal Stability Controls the Particle Formation of SBA-15

    PubMed Central

    2012-01-01

    A hypothesis about (transient) colloidal stability as a controlling mechanism for particle formation in SBA-15 is presented. The hypothesis is based on results from both in situ and ex situ investigations, including cryogenic transmission electron microscopy (cryo-TEM), UV–vis spectroscopy, and dynamic light scattering (DLS). Cryo-TEM images show that particles grow via the formation of silica–Pluronic–water “flocs”, which coalesce in a seemingly arbitrary manner. Despite this, the final material consists of well-defined particles with a small size distribution. We argue that the interface between the flocs and surrounding media is covered by Pluronic molecules, which provide steric stabilization. As the flocs grow, the coverage of polymers at the interface is increased until a stable size is reached, and that regulates the particle size. By targeting the characteristics of the Pluronic molecules, during the on-going synthesis, the hypothesis is tested. The results are consistent with the concept of (transient) colloidal stability. PMID:22758927

  8. Computer Models for IRIS Control System Transient Analysis

    SciTech Connect

    Gary D. Storrick; Bojan Petrovic; Luca Oriani

    2007-01-31

    This report presents results of the Westinghouse work performed under Task 3 of this Financial Assistance Award and it satisfies a Level 2 Milestone for the project. Task 3 of the collaborative effort between ORNL, Brazil and Westinghouse for the International Nuclear Energy Research Initiative entitled “Development of Advanced Instrumentation and Control for an Integrated Primary System Reactor” focuses on developing computer models for transient analysis. This report summarizes the work performed under Task 3 on developing control system models. The present state of the IRIS plant design – such as the lack of a detailed secondary system or I&C system designs – makes finalizing models impossible at this time. However, this did not prevent making considerable progress. Westinghouse has several working models in use to further the IRIS design. We expect to continue modifying the models to incorporate the latest design information until the final IRIS unit becomes operational. Section 1.2 outlines the scope of this report. Section 2 describes the approaches we are using for non-safety transient models. It describes the need for non-safety transient analysis and the model characteristics needed to support those analyses. Section 3 presents the RELAP5 model. This is the highest-fidelity model used for benchmark evaluations. However, it is prohibitively slow for routine evaluations and additional lower-fidelity models have been developed. Section 4 discusses the current Matlab/Simulink model. This is a low-fidelity, high-speed model used to quickly evaluate and compare competing control and protection concepts. Section 5 describes the Modelica models developed by POLIMI and Westinghouse. The object-oriented Modelica language provides convenient mechanisms for developing models at several levels of detail. We have used this to develop a high-fidelity model for detailed analyses and a faster-running simplified model to help speed the I&C development process

  9. Plasma conditions for improved energy coupling into the gain region of the Ni-like Pd transient collisional x-ray laser

    SciTech Connect

    Smith, R F; Dunn, J; Filevich, J; Moon, S; Nilsen, J; Keenan, R; Shlyaptsev, V N; Rocca, J J; Hunter, J R; Marconi, M C

    2004-10-04

    We have directly probed the plasma conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates by measuring the near-field image and by utilizing picosecond resolution soft x-ray laser interferometry of the preformed Pd plasma gain medium. The electron density and gain region of the plasma have been determined experimentally and are found to be in good agreement with simulations. We observe a strong dependence of the laser pump-gain medium coupling on the laser pump parameters. The most efficient coupling of laser pump energy into the gain region occurs with the formation of lower density gradients in the pre-formed plasma and when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for mid-Z Ni-like schemes). This increases the output intensity by more than an order of magnitude relative to the commonly utilized case where the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). In contrast, the higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions where steep density gradients limit the effective length of the gain medium.

  10. Robust gain-scheduling energy-to-peak control of vehicle lateral dynamics stabilisation

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zhang, Xinjie; Wang, Junmin

    2014-03-01

    In this paper, we investigate the vehicle lateral dynamics stabilisation problem to enhance vehicle handling by considering time-varying longitudinal velocity. The longitudinal velocity is described by a polytope with finite vertices and a novel technique is proposed to reduce the number of vertices. Since the tyre dynamics is nonlinear, the cornering stiffness is represented via the norm-bounded uncertainty. Concerning the time-varying velocity and the nonlinear tyre model, a linear parameter-varying vehicle model is obtained. As the velocity and the states are measurable, a gain-scheduling state-feedback controller is introduced. In the lateral control, the sideslip angle is required to be as small as possible and the yaw rate is constrained to a certain level. Thus, the control objective is to minimise the sideslip angle while the yaw rate is under a prescribed level or constrain both the sideslip angle and the yaw rate to prescribed levels. To consider the transient response of the closed-loop system, the ?-stability is also employed in the energy-to-peak control. The optimal controller can be obtained by solving a set of linear matrix inequalities. A nonlinear vehicle model is utilised to illustrate the design procedure and the effectiveness of the proposed design method. Finally, simulations and comparisons are carried out to show the significant advantage of the designed controller. Compared to the open-loop system, the closed-loop system with the designed controller can achieve much smaller sideslip angle and the yaw rate is closer to the desired yaw rate from a reference model. Therefore, the vehicle safety and the handling are both improved in our simulation cases.

  11. Control of Transient Slip Weakening During Gypsum Dehydration

    NASA Astrophysics Data System (ADS)

    Leclere, H.; Faulkner, D.; Wheeler, J.; Mariani, E.

    2015-12-01

    The understanding of fault mechanics is of first order importance to unravel earthquake triggering. Among the parameters influencing fault reactivation and earthquake triggering, the influence of pore-fluid pressure and friction on stability of fault zones have been a focus of recent work based on geological, geophysical and experimental analyses. Here, the effects of dehydration reactions on hydraulic and mechanical properties of rock are analysed to better understand the conditions required to trigger earthquakes. Triaxial experiments are conducted using gypsum and a direct shear sample assembly that allows a constant normal stress to be applied and permeability to be measured during sliding. The evolutions of shear stress, pore-fluid pressure and permeability are continuously measured throughout the experiment until dehydration reaction reached completion. Tests are conducted with a temperature ramp from 70 to 150 °C and with different effective confining pressures (50, 100 and 150 MPa) and velocities (0.1 and 0.4 μm.s-1). Results show that gypsum dehydration induces transient stable slip weakening that is controlled by pore-fluid pressure and permeability evolutions followed by unstable slip on fully dehydrated product.The evolution of microstructures and mineralogy during the experiment are inferred from SEM and XRD analyses of deformed samples collected at different key stages during repeated tests. The microstructural analysis shows clear evidence of dehydration reactions related to the development of S-C-C' structures where dehydration product is preferentially localized along shear and schistosity planes. A conceptual model is then proposed to explain transient slip weakening during dehydration reactions incorporating the key role played by permeability, and to provide a framework to define the conditions required to trigger unstable events during dehydration reactions.

  12. Transient analysis of energy Transfer Control (ECT) and compressor bleed concepts of remote lift fan control

    NASA Technical Reports Server (NTRS)

    Sellers, J. F.

    1973-01-01

    The transient performance of two concepts for control of vertical takeoff aircraft remote lift fans is analyzed and discussed. Both concepts employ flow transfer between pairs of lift fans located in separate parts of the aircraft in order to obtain attitude control moments for hover and low-speed flight. The results presented are from a digital computer, dynamic analysis of the YJ97/LF460 remote drive turbofan. The transient responses of the two systems are presented for step demands in lift and moment.

  13. Control of microbial fuel cell voltage using a gain scheduling control strategy

    NASA Astrophysics Data System (ADS)

    Boghani, Hitesh C.; Michie, Iain; Dinsdale, Richard M.; Guwy, Alan J.; Premier, Giuliano C.

    2016-08-01

    Recent microbial fuel cell (MFC) research frequently addresses matters associated with scale and deployability. Modularisation is often needed to reduce ohmic losses with increasing volume. Series/parallel is then often an obvious strategy to enhance power quality during operation, to make best use of generated electricity. Hence, voltage reversal resulting from power and voltage mismatch between cells become virtually unavoidable. Control MFC voltages could be used to stabilise MFC stacks. Here, nonlinear MFCs are controlled using simple gain scheduled Proportional + Integral actions. Parsimonious control may be necessary for implementation in MFC arrays, so minimising costs. Controller parameterisation used several linearised models over the dynamic operating range of the MFCs. Controller gains were then scheduled according to the operating conditions. A digital potentiometer was used to actuate the control, varying the current sourced from the MFC. The results show that the controller was able to control MFC voltages, rejecting the disturbances. It was shown that the controller was transferable between MFCs with different power performances. This study demonstrates that the control of MFCs can be achieved with relatively simple digital approaches, plausibly implementable using low cost microcontrollers, and likely to be useful in the effective deployment of MFCs in large scale arrays.

  14. Gain scheduled continuous-time model predictive controller with experimental validation on AC machine

    NASA Astrophysics Data System (ADS)

    Wang, Liuping; Gan, Lu

    2013-08-01

    Linear controllers with gain scheduling have been successfully used in the control of nonlinear systems for the past several decades. This paper proposes the design of gain scheduled continuous-time model predictive controller with constraints. Using induction machine as an illustrative example, the paper will show the four steps involved in the design of a gain scheduled predictive controller: (i) linearisation of a nonlinear plant according to operating conditions; (ii) the design of linear predictive controllers for the family of linear models; (iii) gain scheduled predictive control law that will optimise a multiple model objective function with constraints, which will also ensure smooth transitions (i.e. bumpless transfer) between the predictive controllers; (iv) experimental validation of the gain scheduled predictive control system with constraints.

  15. Linear-parameter-varying gain-scheduled control of aerospace systems

    NASA Astrophysics Data System (ADS)

    Barker, Jeffrey Michael

    The dynamics of many aerospace systems vary significantly as a function of flight condition. Robust control provides methods of guaranteeing performance and stability goals across flight conditions. In mu-syntthesis, changes to the dynamical system are primarily treated as uncertainty. This method has been successfully applied to many control problems, and here is applied to flutter control. More recently, two techniques for generating robust gain-scheduled controller have been developed. Linear fractional transformation (LFT) gain-scheduled control is an extension of mu-synthesis in which the plant and controller are explicit functions of parameters measurable in real-time. This LFT gain-scheduled control technique is applied to the Benchmark Active Control Technology (BACT) wing, and compared with mu-synthesis control. Linear parameter-varying (LPV) gain-scheduled control is an extension of Hinfinity control to parameter varying systems. LPV gain-scheduled control directly incorporates bounds on the rate of change of the scheduling parameters, and often reduces conservatism inherent in LFT gain-scheduled control. Gain-scheduled LPV control of the BACT wing compares very favorably with the LFT controller. Gain-scheduled LPV controllers are generated for the lateral-directional and longitudinal axes of the Innovative Control Effectors (ICE) aircraft and implemented in nonlinear simulations and real-time piloted nonlinear simulations. Cooper-Harper and pilot-induced oscillation ratings were obtained for an initial design, a reference aircraft and a redesign. Piloted simulation results for the initial LPV gain-scheduled control of the ICE aircraft are compared with results for a conventional fighter aircraft in discrete pitch and roll angle tracking tasks. The results for the redesigned controller are significantly better than both the previous LPV controller and the conventional aircraft.

  16. Hemodynamic variability and cerebrovascular control after transient cerebral ischemia

    PubMed Central

    Allan, Philip D; Faulkner, James; O’Donnell, Terrence; Lanford, Jeremy; Wong, Lai-kin; Saleem, Saqib; Woolley, Brandon; Lambrick, Danielle; Stoner, Lee; Tzeng, Yu-Chieh

    2015-01-01

    We investigated if hemodynamic variability, cerebral blood flow (CBF) regulation, and their interrelationships differ between patients with transient ischemic attack (TIA) and controls. We recorded blood pressure (BP) and bilateral middle cerebral artery flow velocity (MCAv) in a cohort of TIA patients (n = 17), and age-matched controls (n = 15). Spontaneous fluctuations in BP and MCAv were characterized by spectral power analysis, and CBF regulation was assessed by wavelet phase synchronization analysis in the very low- (0.02–0.07 Hz), low- (0.07–0.20 Hz), and high-frequency (0.20–0.40 Hz) ranges. Furthermore, cerebrovascular CO2 reactivity was assessed as a second metric of CBF regulation by inducing hypercapnia with 8% CO2 inhalation followed by hyperventilation driven hypocapnia. We found that TIA was associated with higher BP power (group effect, P < 0.05), but not MCAv power (P = 0.11). CBF regulation (assessed by wavelet phase synchronization and CO2 reactivity) was intact in patients (all P ≥ 0.075) across both hemispheres (all P ≥ 0.51). Pooled data (controls and affected hemisphere of patients) showed that BP and MCAv power were positively correlated at all frequency ranges (R2 = 0.20–0.80, all P < 0.01). Furthermore, LF phase synchronization index was a significant determinant of MCAv power (P < 0.05), while VLF and HF phase synchronization index, and TIA were not (all P ≥ 0.50). These results indicate that CBF stability and control is maintained in TIA patients, but BPV is markedly elevated. BPV attenuation may be an important therapeutic strategy for enhancing secondary stroke prevention in patients who suffer a TIA. PMID:26537345

  17. How to minimize the control frequency to sustain transient chaos using partial control

    NASA Astrophysics Data System (ADS)

    Zambrano, Samuel; Sabuco, Juan; Sanjuán, Miguel A. F.

    2014-03-01

    In any control problem it is desirable to apply the control as infrequently as possible. In this paper we address the problem of how to minimize the frequency of control in presence of external perturbations, that we call disturbances, when the goal is to sustain transient chaos. We show here that the partial control method, that allows to find the minimum control required to sustain transient chaos in presence of disturbances, is the key to find such minimum control frequency. We prove first for the paradigmatic tent map of slope greater than 2 that for a constant value of the disturbances, the control required to sustain transient chaos decreases when the control is applied every k iterates of the map. We show that the combination of this property with the fact that the disturbances grow with k implies that there is a minimum control frequency and we provide a procedure to compute it. Finally we give evidence of the generality of this result showing that the same features are reproduced when considering the Hénon map.

  18. Two stage dual gate MESFET monolithic gain control amplifier for Ka-band

    NASA Astrophysics Data System (ADS)

    Sokolov, V.; Geddes, J.; Contolatis, A.

    A monolithic two stage gain control amplifier has been developed using submicron gate length dual gate MESFETs fabricated on ion implanted material. The amplifier has a gain of 12 dB at 30 GHz with a gain control range of over 30 dB. This ion implanted monolithic IC is readily integrable with other phased array receiver functions such as low noise amplifiers and phase shifters.

  19. Subtractive, divisive and non-monotonic gain control in feedforward nets linearized by noise and delays

    PubMed Central

    Mejias, Jorge F.; Payeur, Alexandre; Selin, Erik; Maler, Leonard; Longtin, André

    2014-01-01

    The control of input-to-output mappings, or gain control, is one of the main strategies used by neural networks for the processing and gating of information. Using a spiking neural network model, we studied the gain control induced by a form of inhibitory feedforward circuitry—also known as “open-loop feedback”—, which has been experimentally observed in a cerebellum-like structure in weakly electric fish. We found, both analytically and numerically, that this network displays three different regimes of gain control: subtractive, divisive, and non-monotonic. Subtractive gain control was obtained when noise is very low in the network. Also, it was possible to change from divisive to non-monotonic gain control by simply modulating the strength of the feedforward inhibition, which may be achieved via long-term synaptic plasticity. The particular case of divisive gain control has been previously observed in vivo in weakly electric fish. These gain control regimes were robust to the presence of temporal delays in the inhibitory feedforward pathway, which were found to linearize the input-to-output mappings (or f-I curves) via a novel variability-increasing mechanism. Our findings highlight the feedforward-induced gain control analyzed here as a highly versatile mechanism of information gating in the brain. PMID:24616694

  20. Time Difference Amplifier with Robust Gain Using Closed-Loop Control

    NASA Astrophysics Data System (ADS)

    Nakura, Toru; Mandai, Shingo; Ikeda, Makoto; Asada, Kunihiro

    This paper presents a Time Difference Amplifier (TDA) that amplifies the input time difference into the output time difference. Cross coupled chains of variable delay cells with the same number of stages are applicable for TDA, and the gain is adjusted via the closed-loop control. The TDA was fabricated using 65nm CMOS and the measurement results show that the time difference gain is 4.78 at a nominal power supply while the designed gain is 4.0. The gain is stable enough to be less than 1.4% gain shift under ±10% power supply voltage fluctuation.

  1. Comparison of gain degradation and deep level transient spectroscopy in pnp Si bipolar junction transistors irradiated with different ion species

    SciTech Connect

    Aguirre, B. A.; Bielejec, E.; Fleming, R. M.; Vizkelethy, G.; Vaandrager, B.; Campbell, J.; Martin, W. J.; King, D. B.

    2016-12-09

    Here, we studied the effect of light ion and heavy ion irradiations on pnp Si BJTs. A mismatch in DLTS deep peak amplitude for devices with same final gain but irradiated with different ion species was observed. Also, different ions cause different gain degradation when the DLTS spectra are matched. Pre-dosed ion-irradiated samples show that ion induced ionization does not account for the differences in DLTS peak height but isochronal annealing studies suggest that light ions produce more VP defects than heavy ions to compensate for the lack of clusters that heavy ions produce. The creation of defect clusters by heavy ions is evident by the higher content of E4 and V*2 defects compared to light ions.

  2. Comparison of gain degradation and deep level transient spectroscopy in pnp Si bipolar junction transistors irradiated with different ion species

    DOE PAGES

    Aguirre, B. A.; Bielejec, E.; Fleming, R. M.; ...

    2016-12-09

    Here, we studied the effect of light ion and heavy ion irradiations on pnp Si BJTs. A mismatch in DLTS deep peak amplitude for devices with same final gain but irradiated with different ion species was observed. Also, different ions cause different gain degradation when the DLTS spectra are matched. Pre-dosed ion-irradiated samples show that ion induced ionization does not account for the differences in DLTS peak height but isochronal annealing studies suggest that light ions produce more VP defects than heavy ions to compensate for the lack of clusters that heavy ions produce. The creation of defect clusters bymore » heavy ions is evident by the higher content of E4 and V*2 defects compared to light ions.« less

  3. Robust Controller Design: Minimizing Peak-to-Peak Gain

    DTIC Science & Technology

    1992-09-01

    Optimality of Feedback Control Systems: The SISO Discrete-Time Case", IEEE Trans. A-C, 35, 1082- 1085, 1990. [18] C.A. Desoer and M. Vidyasagar, Feedback...Systems: Input-Output Properties, Aca- demic Press, Inc, N.Y., 1975. [19] C.A. Desoer , R-W. Liu, J. Murray and R. Saeks. "Feedback System Design: The

  4. Galileo Spacecraft Scan Platform Celestial Pointing Cone Control Gain Redesign

    NASA Technical Reports Server (NTRS)

    In, C-H. C.; Hilbert, K. B.

    1994-01-01

    During September and October 1991, pictures of the Gaspra asteroid and neighboring stars were taken by the Galileo Optical Navigation (OPNAV) Team for the purpose of navigation the spacecraft for a successful Gaspra encounter. The star tracks in these pictures showed that the scan platform celestial pointing cone controller performed poorly in compensating for wobble-induced cone offsets.

  5. L1-gain analysis and control synthesis of positive switched systems

    NASA Astrophysics Data System (ADS)

    Zhang, Junfeng; Han, Zhengzhi; Zhu, Fubo

    2015-09-01

    This paper investigates the problems of L1-gain analysis and control synthesis of positive switched systems. Linear supply rates and L1-gain notations are introduced to analyse the performance of the underlying systems. Stability with a weighted L1-gain for autonomous systems are solved by using multiple linear copositive Lyapunov functions incorporated with the average dwell time approach. Then, state-feedback and output-feedback controllers are designed to guarantee the stabilisation with a weighted L1-gain for non-autonomous systems. All present conditions are solvable in terms of linear programming. Finally, a practical example is given to illustrate the validity of theoretical findings.

  6. Resistive wall mode feedback control in EXTRAP T2R with improved steady-state error and transient response

    NASA Astrophysics Data System (ADS)

    Brunsell, P. R.; Olofsson, K. E. J.; Frassinetti, L.; Drake, J. R.

    2007-10-01

    Experiments in the EXTRAP T2R reversed field pinch [P. R. Brunsell, H. Bergsåker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] on feedback control of m =1 resistive wall modes (RWMs) are compared with simulations using the cylindrical linear magnetohydrodynamic model, including the dynamics of the active coils and power amplifiers. Stabilization of the main RWMs (n=-11,-10,-9,-8,+5,+6) is shown using modest loop gains of the order G ˜1. However, other marginally unstable RWMs (n=-2,-1,+1,+2) driven by external field errors are only partially canceled at these gains. The experimental system stability limit is confirmed by simulations showing that the latency of the digital controller ˜50μs is degrading the system gain margin. The transient response is improved with a proportional-plus-derivative controller, and steady-state error is improved with a proportional-plus-integral controller. Suppression of all modes is obtained at high gain G ˜10 using a proportional-plus-integral-plus-derivative controller.

  7. Transient Receptor Potential Ion Channels Control Thermoregulatory Behaviour in Reptiles

    PubMed Central

    Seebacher, Frank; Murray, Shauna A.

    2007-01-01

    Biological functions are governed by thermodynamics, and animals regulate their body temperature to optimise cellular performance and to avoid harmful extremes. The capacity to sense environmental and internal temperatures is a prerequisite for the evolution of thermoregulation. However, the mechanisms that enable ectothermic vertebrates to sense heat remain unknown. The recently discovered thermal characteristics of transient receptor potential ion channels (TRP) render these proteins suitable to act as temperature sensors. Here we test the hypothesis that TRPs are present in reptiles and function to control thermoregulatory behaviour. We show that the hot-sensing TRPV1 is expressed in a crocodile (Crocodylus porosus), an agamid (Amphibolurus muricatus) and a scincid (Pseudemoia entrecasteauxii) lizard, as well as in the quail and zebrafinch (Coturnix chinensis and Poephila guttata). The TRPV1 genes from all reptiles form a unique clade that is delineated from the mammalian and the ancestral Xenopus sequences by an insertion of two amino acids. TRPV1 and the cool-sensing TRPM8 are expressed in liver, muscle (transversospinalis complex), and heart tissues of the crocodile, and have the potential to act as internal thermometer and as external temperatures sensors. Inhibition of TRPV1 and TRPM8 in C. porosus abolishes the typically reptilian shuttling behaviour between cooling and heating environments, and leads to significantly altered body temperature patterns. Our results provide the proximate mechanism of thermal selection in terrestrial ectotherms, which heralds a fundamental change in interpretation, because TRPs provide the mechanism for a tissue-specific input into the animals' thermoregulatory response. PMID:17356692

  8. Nanoscale transient porosity controls large-scale metamorphic fluid flow

    NASA Astrophysics Data System (ADS)

    Plümper, Oliver; Botan, Alexandru; Los, Catharina; Malthe-Sørenssen, Anders; Jamtveit, Bjørn

    2016-04-01

    investigations we used non-equilibrium thermodynamics and molecular dynamics simulations to investigate the influence of nanoscale pore transport phenomena on metamorphic mineral replacement reactions. Our findings suggest that fluid transport through nanoscale transient pore networks may control regional-scale metamorphism and metasomatism, at least in the feldspar-dominated crust.

  9. A High Efficiency Variable Gain Amplifier Circuit with Controllable Transconductance Amp

    NASA Astrophysics Data System (ADS)

    Okura, Tetsuro; Okura, Shunsuke; Ido, Toru; Taniguchi, Kenji

    A novel power reduction technique for a variable gain amplifier (VGA) with a two-stage operational amplifier is proposed. The technique improves the power consumption of a VGA by optimizing the bandwidth and the phase margin dynamically on all gain range of the VGA through controlling the input transconductance of opamp. A VGA utilizing the proposed technique shows 40% reduction of power consumption against a conventional VGA at the best condition of VGA gain range.

  10. Removing environmental sources of variation to gain insight on symbionts vs. transient microbes in high and low microbial abundance sponges.

    PubMed

    Blanquer, Andrea; Uriz, Maria J; Galand, Pierre E

    2013-11-01

    In this study, we pursue unravelling the bacterial communities of 26 sponges, belonging to several taxonomical orders, and comprising low microbial abundance (LMA) and high microbial abundance (HMA) representatives. Particularly, we searched for species-specific bacteria, which could be considered as symbionts. To reduce temporal and spatial environmentally caused differences between host species, we sampled all the sponge species present in an isolated small rocky area in a single dive. The bacterial communities identified by pyrosequencing the 16S rRNA gene showed that all HMA species clustered separated from LMA sponges and seawater. HMA sponges often had highest diversity, but some LMA sponges had also very diverse bacterial communities. Network analyses indicated that no core bacterial community seemed to exist for the studied sponges, not even for such a space and time-restricted sampling. Most sequences, particularly the most abundant ones in each species, were species-specific for both HMA and LMA sponges. The bacterial sequences retrieved from LMA sponges, despite being phylogenetically more similar to seawater, did not represent transient seawater bacteria. We conclude that sponge bacterial communities depend more on the host affiliation to the HMA or LMA groups than on host phylogeny. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  11. External locus of control contributes to racial disparities in memory and reasoning training gains in ACTIVE.

    PubMed

    Zahodne, Laura B; Meyer, Oanh L; Choi, Eunhee; Thomas, Michael L; Willis, Sherry L; Marsiske, Michael; Gross, Alden L; Rebok, George W; Parisi, Jeanine M

    2015-09-01

    Racial disparities in cognitive outcomes may be partly explained by differences in locus of control. African Americans report more external locus of control than non-Hispanic Whites, and external locus of control is associated with poorer health and cognition. The aims of this study were to compare cognitive training gains between African American and non-Hispanic White participants in the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study and determine whether racial differences in training gains are mediated by locus of control. The sample comprised 2,062 (26% African American) adults aged 65 and older who participated in memory, reasoning, or speed training. Latent growth curve models evaluated predictors of 10-year cognitive trajectories separately by training group. Multiple group modeling examined associations between training gains and locus of control across racial groups. Compared to non-Hispanic Whites, African Americans evidenced less improvement in memory and reasoning performance after training. These effects were partially mediated by locus of control, controlling for age, sex, education, health, depression, testing site, and initial cognitive ability. African Americans reported more external locus of control, which was associated with smaller training gains. External locus of control also had a stronger negative association with reasoning training gain for African Americans than for Whites. No racial difference in training gain was identified for speed training. Future intervention research with African Americans should test whether explicitly targeting external locus of control leads to greater cognitive improvement following cognitive training.

  12. External locus of control contributes to racial disparities in memory and reasoning training gains in ACTIVE

    PubMed Central

    Zahodne, Laura B.; Meyer, Oanh L.; Choi, Eunhee; Thomas, Michael L.; Willis, Sherry L.; Marsiske, Michael; Gross, Alden L.; Rebok, George W.; Parisi, Jeanine M.

    2015-01-01

    Racial disparities in cognitive outcomes may be partly explained by differences in locus of control. African Americans report more external locus of control than non-Hispanic Whites, and external locus of control is associated with poorer health and cognition. The aims of this study were to compare cognitive training gains between African American and non-Hispanic White participants in the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study and determine whether racial differences in training gains are mediated by locus of control. The sample comprised 2,062 (26% African American) adults aged 65 and older who participated in memory, reasoning, or speed training. Latent growth curve models evaluated predictors of 10-year cognitive trajectories separately by training group. Multiple group modeling examined associations between training gains and locus of control across racial groups. Compared to non-Hispanic Whites, African Americans evidenced less improvement in memory and reasoning performance after training. These effects were partially mediated by locus of control, controlling for age, sex, education, health, depression, testing site, and initial cognitive ability. African Americans reported more external locus of control, which was associated with smaller training gains. External locus of control also had a stronger negative association with reasoning training gain for African Americans than for Whites. No racial difference in training gain was identified for speed training. Future intervention research with African Americans should test whether explicitly targeting external locus of control leads to greater cognitive improvement following cognitive training. PMID:26237116

  13. Switched-Observer-Based Adaptive Neural Control of MIMO Switched Nonlinear Systems With Unknown Control Gains.

    PubMed

    Long, Lijun; Zhao, Jun

    2017-07-01

    In this paper, the problem of adaptive neural output-feedback control is addressed for a class of multi-input multioutput (MIMO) switched uncertain nonlinear systems with unknown control gains. Neural networks (NNs) are used to approximate unknown nonlinear functions. In order to avoid the conservativeness caused by adoption of a common observer for all subsystems, an MIMO NN switched observer is designed to estimate unmeasurable states. A new switched observer-based adaptive neural control technique for the problem studied is then provided by exploiting the classical average dwell time (ADT) method and the backstepping method and the Nussbaum gain technique. It effectively handles the obstacle about the coexistence of multiple Nussbaum-type function terms, and improves the classical ADT method, since the exponential decline property of Lyapunov functions for individual subsystems is no longer satisfied. It is shown that the technique proposed is able to guarantee semiglobal uniformly ultimately boundedness of all the signals in the closed-loop system under a class of switching signals with ADT, and the tracking errors converge to a small neighborhood of the origin. The effectiveness of the approach proposed is illustrated by its application to a two inverted pendulum system.

  14. Mechanisms of Gain Control by Voltage-Gated Channels in Intrinsically-Firing Neurons

    PubMed Central

    Patel, Ameera X.; Burdakov, Denis

    2015-01-01

    Gain modulation is a key feature of neural information processing, but underlying mechanisms remain unclear. In single neurons, gain can be measured as the slope of the current-frequency (input-output) relationship over any given range of inputs. While much work has focused on the control of basal firing rates and spike rate adaptation, gain control has been relatively unstudied. Of the limited studies on gain control, some have examined the roles of synaptic noise and passive somatic currents, but the roles of voltage-gated channels present ubiquitously in neurons have been less explored. Here, we systematically examined the relationship between gain and voltage-gated ion channels in a conductance-based, tonically-active, model neuron. Changes in expression (conductance density) of voltage-gated channels increased (Ca2+ channel), reduced (K+ channels), or produced little effect (h-type channel) on gain. We found that the gain-controlling ability of channels increased exponentially with the steepness of their activation within the dynamic voltage window (voltage range associated with firing). For depolarization-activated channels, this produced a greater channel current per action potential at higher firing rates. This allowed these channels to modulate gain by contributing to firing preferentially at states of higher excitation. A finer analysis of the current-voltage relationship during tonic firing identified narrow voltage windows at which the gain-modulating channels exerted their effects. As a proof of concept, we show that h-type channels can be tuned to modulate gain by changing the steepness of their activation within the dynamic voltage window. These results show how the impact of an ion channel on gain can be predicted from the relationship between channel kinetics and the membrane potential during firing. This is potentially relevant to understanding input-output scaling in a wide class of neurons found throughout the brain and other nervous systems

  15. Comparison of gradient methods for gain tuning of a PD controller applied on a quadrotor system

    NASA Astrophysics Data System (ADS)

    Kim, Jinho; Wilkerson, Stephen A.; Gadsden, S. Andrew

    2016-05-01

    Many mechanical and electrical systems have utilized the proportional-integral-derivative (PID) control strategy. The concept of PID control is a classical approach but it is easy to implement and yields a very good tracking performance. Unmanned aerial vehicles (UAVs) are currently experiencing a significant growth in popularity. Due to the advantages of PID controllers, UAVs are implementing PID controllers for improved stability and performance. An important consideration for the system is the selection of PID gain values in order to achieve a safe flight and successful mission. There are a number of different algorithms that can be used for real-time tuning of gains. This paper presents two algorithms for gain tuning, and are based on the method of steepest descent and Newton's minimization of an objective function. This paper compares the results of applying these two gain tuning algorithms in conjunction with a PD controller on a quadrotor system.

  16. Gain-of-function mutations in the transient receptor potential channels TRPV1 and TRPA1: how painful?

    PubMed

    Boukalova, S; Touska, F; Marsakova, L; Hynkova, A; Sura, L; Chvojka, S; Dittert, I; Vlachova, V

    2014-01-01

    Gain-of-function (GOF) mutations in ion channels are rare events, which lead to increased agonist sensitivity or altered gating properties, and may render the channel constitutively active. Uncovering and following characterization of such mutants contribute substantially to the understanding of the molecular basis of ion channel functioning. Here we give an overview of some GOF mutants in polymodal ion channels specifically involved in transduction of painful stimuli--TRPV1 and TRPA1, which are scrutinized by scientists due to their important role in development of some pathological pain states. Remarkably, a substitution of single amino acid in the S4-S5 region of TRPA1 (N855S) has been recently associated with familial episodic pain syndrome. This mutation increases chemical sensitivity of TRPA1, but leaves the voltage sensitivity unchanged. On the other hand, mutations in the analogous region of TRPV1 (R557K and G563S) severely affect all aspects of channel activation and lead to spontaneous activity. Comparison of the effects induced by mutations in homologous positions in different TRP receptors (or more generally in other distantly related ion channels) may elucidate the gating mechanisms conserved during evolution.

  17. Strategies for Voltage Control and Transient Stability Assessment

    SciTech Connect

    Hiskens, Ian A.

    2013-09-25

    As wind generation grows, its influence on power system performance will becoming increasingly noticeable. Wind generation di ffers from traditional forms of generation in numerous ways though, motivating the need to reconsider the usual approaches to power system assessment and performance enhancement. The project has investigated the impact of wind generation on transient stability and voltage control, identifying and addressing issues at three distinct levels of the power system: 1) at the device level, the physical characteristics of wind turbine generators (WTGs) are quite unlike those of synchronous machines, 2) at the wind-farm level, the provision of reactive support is achieved through coordination of numerous dissimilar devices, rather than straightforward generator control, and 3) from a systems perspective, the location of wind-farms on the sub-transmission network, coupled with the variability inherent in their power output, can cause complex voltage control issues. The project has sought to develop a thorough understanding of the dynamic behaviour of type-3 WTGs, and in particular the WECC generic model. The behaviour of such models is governed by interactions between the continuous dynamics of state variables and discrete events associated with limits. It was shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis was proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It was shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model. In order to eliminate the anomalous behaviour revealed through this investigation, WECC has now released a new generic model for type-3 WTGs. Wind-farms typically incorporate a variety of

  18. Widespread inhibition proportional to excitation controls the gain of a leech behavioral circuit

    PubMed Central

    Kristan, William B.

    2014-01-01

    SUMMARY Changing gain in a neuronal system has important functional consequences, but the underlying mechanisms have been elusive. Models have suggested a variety of neuronal and systems properties to accomplish gain control. Here, we show that the gain of the neuronal network underlying local bending behavior in leeches depends on widespread inhibition. Using behavioral analysis, intracellular recordings, and voltage-sensitive dye imaging, we compared the effects of blocking just the known lateral inhibition with blocking all GABAergic inhibition. This revealed an additional source of inhibition, which was widespread and increased in proportion to increasing stimulus intensity. In a model of the input/output functions of the three-layered local bending network, we showed that inhibiting all interneurons in proportion to the stimulus strength produces the experimentally observed change in gain. This relatively simple mechanism for controlling behavioral gain could be prevalent in vertebrate as well as invertebrate nervous systems. PMID:18215624

  19. Reduced state feedback gain computation. [optimization and control theory for aircraft control

    NASA Technical Reports Server (NTRS)

    Kaufman, H.

    1976-01-01

    Because application of conventional optimal linear regulator theory to flight controller design requires the capability of measuring and/or estimating the entire state vector, it is of interest to consider procedures for computing controls which are restricted to be linear feedback functions of a lower dimensional output vector and which take into account the presence of measurement noise and process uncertainty. Therefore, a stochastic linear model that was developed is presented which accounts for aircraft parameter and initial uncertainty, measurement noise, turbulence, pilot command and a restricted number of measurable outputs. Optimization with respect to the corresponding output feedback gains was performed for both finite and infinite time performance indices without gradient computation by using Zangwill's modification of a procedure originally proposed by Powell. Results using a seventh order process show the proposed procedures to be very effective.

  20. Floquet control of the gain and loss in a PT-symmetric optical coupler

    NASA Astrophysics Data System (ADS)

    Wu, Yi; Zhu, Bo; Hu, Shu-Fang; Zhou, Zheng; Zhong, Hong-Hua

    2017-02-01

    Controlling the balanced gain and loss in a PT-symmetric system is a rather challenging task. Utilizing Floquet theory, we explore the constructive role of periodic modulation in controlling the gain and loss of a PT-symmetric optical coupler. It is found that the gain and loss of the system can be manipulated by applying a periodic modulation. Further, such an original non-Hermitian system can even be modulated into an effective Hermitian system derived by the high-frequency Floquet method. Therefore, compared with other PT symmetry control schemes, our protocol can modulate the unbroken PT-symmetric range to a wider parameter region. Our results provide a promising approach for controlling the gain and loss of a realistic system.

  1. Loop gain stabilizing with an all-digital automatic-gain-control method for high-precision fiber-optic gyroscope.

    PubMed

    Zheng, Yue; Zhang, Chunxi; Li, Lijing; Song, Lailiang; Chen, Wen

    2016-06-10

    For a fiber-optic gyroscope (FOG) using electronic dithers to suppress the dead zone, without a fixed loop gain, the deterministic compensation for the dither signals in the control loop of the FOG cannot remain accurate, resulting in the dither residuals in the FOG rotation rate output and the navigation errors in the inertial navigation system. An all-digital automatic-gain-control method for stabilizing the loop gain of the FOG is proposed. By using a perturbation square wave to measure the loop gain of the FOG and adding an automatic gain control loop in the conventional control loop of the FOG, we successfully obtain the actual loop gain and make the loop gain converge to the reference value. The experimental results show that in the case of 20% variation in the loop gain, the dither residuals are successfully eliminated and the standard deviation of the FOG sampling outputs is decreased from 2.00  deg/h to 0.62  deg/h (sampling period 2.5 ms, 10 points smoothing). With this method, the loop gain of the FOG can be stabilized over the operation temperature range and in the long-time application, which provides a solid foundation for the engineering applications of the high-precision FOG.

  2. An ultrasonic transducer transient compensator design based on a simplified Variable Structure Control algorithm.

    PubMed

    Ma, Shaodong; Wilkinson, Antony J; Paulson, Kevin S

    2014-02-01

    A non-linear control method, known as Variable Structure Control (VSC), is employed to reduce the duration of ultrasonic (US) transducer transients. A physically realizable system using a simplified form of the VSC algorithm is proposed for standard piezoelectric transducers and simulated. Results indicate a VSC-controlled transmitter reduces the transient duration to less than a carrier wave cycle. Applications include high capacity ultrasound communication and localization systems.

  3. Effect of Weight Gain on Cardiac Autonomic Control During Wakefulness and Sleep

    PubMed Central

    Adachi, Taro; Sert-Kuniyoshi, Fatima H.; Calvin, Andrew D.; Singh, Prachi; Romero-Corral, Abel; van der Walt, Christelle; Davison, Diane E.; Bukartyk, Jan; Konecny, Tomas; Pusalavidyasagar, Snigdha; Sierra-Johnson, Justo; Somers, Virend K.

    2012-01-01

    Obesity has been associated with increased cardiac sympathetic activation during wakefulness, but the effect on sleep-related sympathetic modulation is not known. The aim of this study was to investigate the effect of fat gain on cardiac autonomic control during wakefulness and sleep in humans. We performed a randomized controlled study to assess the effects of fat gain on heart rate variability (HRV). We recruited 36 healthy volunteers, who were randomized to either a standardized diet to gain approximately 4 kg over 8 weeks followed by an 8 week weight loss period (n=20), or to serve as a weight-maintainer control (n=16). An overnight polysomnogram with power spectral analysis of HRV was performed at baseline, after weight gain, and after weight loss to determine the ratio of low frequency (LF) to high frequency (HF) power, and to examine the relationship between changes in HRV and changes in insulin, leptin and adiponectin levels. Mean weight gain was 3.9 kg in the fat gain group versus 0.1 kg in the maintainer group. LF/HF increased both during wakefulness and sleep after fat gain and returned to baseline after fat loss in the fat gain group, and did not change in the control group. Insulin, leptin and adiponectin also increased after fat gain and fell after fat loss, but no clear pattern of changes were seen that correlated consistently with changes in HRV. Short-term fat gain in healthy subjects is associated with increased cardiac sympathetic activation during wakefulness and sleep but the mechanisms remain unclear. PMID:21357280

  4. Contrast gain-control in stereo depth and cyclopean contrast perception.

    PubMed

    Hou, Fang; Huang, Chang-Bing; Liang, Ju; Zhou, Yifeng; Lu, Zhong-Lin

    2013-01-01

    Although human observers can perceive depth from stereograms with considerable contrast difference between the images presented to the two eyes (Legge & Gu, 1989), how contrast gain control functions in stereo depth perception has not been systematically investigated. Recently, we developed a multipathway contrast gain-control model (MCM) for binocular phase and contrast perception (Huang, Zhou, Lu, & Zhou, 2011; Huang, Zhou, Zhou, & Lu, 2010) based on a contrast gain-control model of binocular phase combination (Ding & Sperling, 2006). To extend the MCM to simultaneously account for stereo depth and cyclopean contrast perception, we manipulated the contrasts (ranging from 0.08 to 0.4) of the dynamic random dot stereograms (RDS) presented to the left and right eyes independently and measured both disparity thresholds for depth perception and perceived contrasts of the cyclopean images. We found that both disparity threshold and perceived contrast depended strongly on the signal contrasts in the two eyes, exhibiting characteristic binocular contrast gain-control properties. The results were well accounted for by an extended MCM model, in which each eye exerts gain control on the other eye's signal in proportion to its own signal contrast energy and also gain control over the other eye's gain control; stereo strength is proportional to the product of the signal strengths in the two eyes after contrast gain control, and perceived contrast is computed by combining contrast energy from the two eyes. The new model provided an excellent account of our data (r(2) = 0.945), as well as some challenging results in the literature.

  5. Contrast gain-control in stereo depth and cyclopean contrast perception

    PubMed Central

    Hou, Fang; Huang, Chang-Bing; Liang, Ju; Zhou, Yifeng; Lu, Zhong-Lin

    2013-01-01

    Although human observers can perceive depth from stereograms with considerable contrast difference between the images presented to the two eyes (Legge & Gu, 1989), how contrast gain control functions in stereo depth perception has not been systematically investigated. Recently, we developed a multipathway contrast gain-control model (MCM) for binocular phase and contrast perception (Huang, Zhou, Lu, & Zhou, 2011; Huang, Zhou, Zhou, & Lu, 2010) based on a contrast gain-control model of binocular phase combination (Ding & Sperling, 2006). To extend the MCM to simultaneously account for stereo depth and cyclopean contrast perception, we manipulated the contrasts (ranging from 0.08 to 0.4) of the dynamic random dot stereograms (RDS) presented to the left and right eyes independently and measured both disparity thresholds for depth perception and perceived contrasts of the cyclopean images. We found that both disparity threshold and perceived contrast depended strongly on the signal contrasts in the two eyes, exhibiting characteristic binocular contrast gain-control properties. The results were well accounted for by an extended MCM model, in which each eye exerts gain control on the other eye's signal in proportion to its own signal contrast energy and also gain control over the other eye's gain control; stereo strength is proportional to the product of the signal strengths in the two eyes after contrast gain control, and perceived contrast is computed by combining contrast energy from the two eyes. The new model provided an excellent account of our data (r2 = 0.945), as well as some challenging results in the literature. PMID:23820024

  6. Gain control of photomultiplier tubes used in detecting differential absorption lidar returns

    NASA Technical Reports Server (NTRS)

    Allen, Robert J. (Inventor)

    1989-01-01

    A technique for controlling the gain of a photomultiplier tube (PMT) 20. A voltage divider (resistors 45-49 in FIG. 1 and zener diodes 60-65 in FIG. 3) is used to control the potentials on dynodes 5, 7, and 9 of PMT 20. Transistor switches 53 and 58 provide the control of the voltage divider in FIG. 1 and photodiodes 66, 67 and 70 provide the control in FIG. 3. The gain control of PMT 20 is in the range from 100% to less than 0.001% (100,000 to 1).

  7. Synthesis of Optimal Constant-Gain Positive-Real Controllers for Passive Systems

    NASA Technical Reports Server (NTRS)

    Mao, Y.; Kelkar, A. G.; Joshi, S. M.

    1999-01-01

    This paper presents synthesis methods for the design of constant-gain positive real controllers for passive systems. The results presented in this paper, in conjunction with the previous work by the authors on passification of non-passive systems, offer a useful synthesis tool for the design of passivity-based robust controllers for non-passive systems as well. Two synthesis approaches are given for minimizing an LQ-type performance index, resulting in optimal controller gains. Two separate algorithms, one for each of these approaches, are given. The synthesis techniques are demonstrated using two numerical examples: control of a flexible structure and longitudinal control of a fighter aircraft.

  8. Synthesis of Optimal Constant-Gain Positive-Real Controllers for Passive Systems

    NASA Technical Reports Server (NTRS)

    Mao, Y.; Kelkar, A. G.; Joshi, S. M.

    1999-01-01

    This paper presents synthesis methods for the design of constant-gain positive real controllers for passive systems. The results presented in this paper, in conjunction with the previous work by the authors on passification of non-passive systems, offer a useful synthesis tool for the design of passivity-based robust controllers for non-passive systems as well. Two synthesis approaches are given for minimizing an LQ-type performance index, resulting in optimal controller gains. Two separate algorithms, one for each of these approaches, are given. The synthesis techniques are demonstrated using two numerical examples: control of a flexible structure and longitudinal control of a fighter aircraft.

  9. Transient Tolerant Automated Control System for the LEDA 75kV Injector

    SciTech Connect

    Thuot, M.E.; Dalesio, L.R.; Harrington, M.; Hodgkins, D.; Kerstiens, D.M.; Stettler, M.W.; Warren, D.S.; Zaugg, T.; Arvin, A.; Bolt, S.; Richards, M.

    1999-03-29

    The Low-Energy Demonstration Accelerator (LEDA) injector is designed to inject 75-keV, 110-mA, proton beams into the LEDA RFQ. The injector operation has been automated to provide long term, high availability operation using the Experimental Physics and Industrial Control System (EPICS). Automated recovery from spark-downs demands reliable spark detection and sequence execution by the injector controller. Reliable computer control in the high-energy transient environment required transient suppression and isolation of hundreds of analog and binary data lines connecting the EPICS computer controller to the injector and it's power supplies and diagnostics. A transient suppression design based on measured and modeled spark transient parameters provides robust injector operation. This paper describes the control system hardware and software design, implementation and operational performance.

  10. Learning to walk with an adaptive gain proportional myoelectric controller for a robotic ankle exoskeleton.

    PubMed

    Koller, Jeffrey R; Jacobs, Daniel A; Ferris, Daniel P; Remy, C David

    2015-11-04

    Robotic ankle exoskeletons can provide assistance to users and reduce metabolic power during walking. Our research group has investigated the use of proportional myoelectric control for controlling robotic ankle exoskeletons. Previously, these controllers have relied on a constant gain to map user's muscle activity to actuation control signals. A constant gain may act as a constraint on the user, so we designed a controller that dynamically adapts the gain to the user's myoelectric amplitude. We hypothesized that an adaptive gain proportional myoelectric controller would reduce metabolic energy expenditure compared to walking with the ankle exoskeleton unpowered because users could choose their preferred control gain. We tested eight healthy subjects walking with the adaptive gain proportional myoelectric controller with bilateral ankle exoskeletons. The adaptive gain was updated each stride such that on average the user's peak muscle activity was mapped to maximal power output of the exoskeleton. All subjects participated in three identical training sessions where they walked on a treadmill for 50 minutes (30 minutes of which the exoskeleton was powered) at 1.2 ms(-1). We calculated and analyzed metabolic energy consumption, muscle recruitment, inverse kinematics, inverse dynamics, and exoskeleton mechanics. Using our controller, subjects achieved a metabolic reduction similar to that seen in previous work in about a third of the training time. The resulting controller gain was lower than that seen in previous work (β=1.50±0.14 versus a constant β=2). The adapted gain allowed users more total ankle joint power than that of unassisted walking, increasing ankle power in exchange for a decrease in hip power. Our findings indicate that humans prefer to walk with greater ankle mechanical power output than their unassisted gait when provided with an ankle exoskeleton using an adaptive controller. This suggests that robotic assistance from an exoskeleton can allow

  11. Non-linear, high-gain and sustained-to-transient signal transmission from rods to amacrine cells in dark-adapted retina of Ambystoma

    PubMed Central

    Yang, Xiong-Li; Gao, Fan; Wu, Samuel M

    2002-01-01

    In darkness, On-Off amacrine cells (ACs) of the tiger salamander retina exhibited large spontaneous transient depolarizing potentials (sTDPs) with average peak amplitude of 5.05 ± 2.5 mV and average frequency of 0.42 ± 0.25 s−1. Under voltage-clamp conditions the cell displayed large spontaneous postsynaptic currents (sPSCs) with average peak amplitude of 98 ± 39 pA and average frequency of 0.45 ± 0.22 s−1. To a light step, ACs gave rise to a transient ‘On’ response at the light onset and a transient ‘Off’ response at light offset, followed by a train of TDPs (‘After’ response). Near the response threshold (0.3 activated rhodopsin molecules per rod per second), light-evoked TDPs (leTDPs) of similar amplitude and kinetics as the large sTDPs observed in darkness were seen, and about half of these leTDPs elicited a regenerative potential (RP). Brighter light steps gave rise to more leTDPs and higher rates of RPs in the On, Off and After responses. Within the linear response range of the rods, the AC response was non-linear, with the highest gain (676 ± 429) near the dark potential. The amplitude of Off responses increased with the duration of the light step, and ACs may use this to encode speeds of moving stimuli: the faster the light object moves, the smaller the AC Off response. Moreover, the number of leTDPs in the AC After response increased with light intensity, and the onset of the After response coincides with bipolar cell tail response recovery. One possible origin of the large sTDPs and leTDPs is the spontaneous and depolarization-induced regenerative calcium potentials (RCaPs) in bipolar cell synaptic terminals. RCaPs in bipolar cell synaptic terminals cause transient glutamate release that results in the sTDPs in darkness, and leTDPs in On, Off and After responses in ACs. PMID:11850516

  12. Effects of visual gain on force control at the elbow and ankle.

    PubMed

    Prodoehl, Janey; Vaillancourt, David E

    2010-01-01

    Visual feedback is essential when minimizing force fluctuations. Varying degrees of somatotopic organization have been shown in different regions of the brain for the upper and lower extremities, and visual feedback may be processed differently based on the body effector where feedback-based corrections are used. This study compared the effect of changes in visual gain on the control of steady-state force at the elbow and ankle. Ten subjects produced steady-state isometric force to targets at 5 and 40% of their maximum voluntary contraction at seven visual gain levels. Visual gain was used effectively at both joints to reduce variability of the force signal and to improve accuracy, with a greater effect of visual gain at the elbow than the ankle. Visual gain significantly decreased the regularity of force output, and this effect was more pronounced at the elbow than the ankle. There were accompanying changes in the proportion of power in the 0-4, 4-8, and 8-12 Hz frequency bins of the force signal across visual gain at the elbow. Changes in visual gain were accompanied by changes in both agonist and antagonist electromyographic (EMG) activation at the elbow. At the ankle joint, there were only changes in agonist EMG. The results suggest better use of visual information in the control of elbow force than ankle force and this improved control may be related to the changes in the pattern of agonist and antagonist activation.

  13. Active control of vortex shedding: an explanation of the gain window.

    PubMed

    Illingworth, Simon J; Naito, Hiroshi; Fukagata, Koji

    2014-10-01

    This paper explains the gain window phenomenon seen in early experimental and computational studies on active, closed-loop control of vortex shedding, whereby shedding is completely suppressed only if the feedback gain lies within some narrow window of stabilizing gains. Using two-dimensional direct numerical simulations and reduced-order modeling techniques, a low-order, linear model of the cylinder wake is formed at a Reynolds number of 60. This model is used to reproduce and to explain the gain window seen in previous studies. It is shown that the gain window is not caused by the destabilization of a higher mode but rather is determined entirely by the behavior of the open-loop unstable mode under the action of the closed-loop controller. It is demonstrated that the time taken for actuated fluid to convect to the sensor location plays an important part in explaining this gain window. A similar analysis at a higher Reynolds number of 80 reveals that the wake remains unstable for all choices of the feedback gain. The study illustrates the limitations of closed-loop suppression of vortex shedding when a very simple control strategy is used.

  14. Adaptation as a mechanism for gain control in cockroach ON and OFF olfactory receptor neurons.

    PubMed

    Burgstaller, Maria; Tichy, Harald

    2012-02-01

    In many sensory systems adaptation acts as a gain control mechanism that optimizes sensory performance by trading increased sensitivity to low stimulus intensity for decreased sensitivity to high stimulus intensity. Adaptation of insect antennal olfactory receptor neurons (ORNs) has been studied for strong odour concentrations, either pulsed or constant. Here, we report that during slowly oscillating changes in the concentration of the odour of lemon oil, the ON and OFF ORNs on the antenna of the cockroach Periplaneta americana adapt to the actual odour concentration and the rate at which concentration changes. When odour concentration oscillates rapidly with brief periods, adaptation improves gain for instantaneous odour concentration and reduces gain for the rate of concentration change. Conversely, when odour concentration oscillates slowly with long periods, adaptation increases gain for the rate of change at the expense of instantaneous concentration. Without this gain control the ON and OFF ORNs would, at brief oscillation periods, soon reach their saturation level and become insensitive to further concentration increments and decrements. At long oscillation periods, on the other hand, the cue would simply be that the discharge begins to change. Because of the high gain for the rate of change, the cockroach will receive creeping changes in odour concentration, even if they persist in one direction. Gain control permits a high degree of precision at small rates when it counts most, without sacrificing the range of detection and without extending the measuring scale.

  15. Transient dynamics in motor control of patients with Parkinson's disease

    NASA Astrophysics Data System (ADS)

    Beuter, Anne; Labrie, Christiane; Vasilakos, Konstantinon

    1991-10-01

    Experimental observations of movement disorders including tremor and voluntary microdisplacements recorded in patients with Parkinson's disease (PD) during a simple visuomotor tracking task are analyzed. The performance of patients with PD having a very large amplitude tremor is characterized either by the intermittent appearance of transient dynamics or by the presence of sudden transitions in the amplitude or frequency of the signal. The need to develop new tools to characterize changes in dynamics (i.e., transitions) and to redefine neurological degeneration, such as Parkinson's disease, in terms of qualitative changes in oscillatory behaviors is emphasized.

  16. Controlling Chaos of Magnetic-Domain-Wall Motion by using Delayed-Feedback-Control with Automatic Gain-Adjustment

    NASA Astrophysics Data System (ADS)

    Utsumi, Takuya; Okuno, Hikaru

    In this research, the chaotic motion of magnetic domain wall is controlled by using Delayed-Feedback-Control (DFC) with automatic gain-adjustment, modified by Nakajima and Ueda in 1995. The method of automatic gain-adjustment is newly applied to Extended-DFC (E-DFC) for more highly performance. It is clearly confirmed that the control-gain was automatically adjusted on each results. But, in this case, the response of E-DFC has not been improved. It is found that the delayed time has strongly influenced on the response. The selective E-DFC is proposed and the response was best.

  17. Contrast gain control in first- and second-order motion perception.

    PubMed

    Lu, Z L; Sperling, G

    1996-12-01

    A novel pedestal-plus-test paradigm is used to determine the nonlinear gain-control properties of the first-order (luminance) and the second-order (texture-contrast) motion systems, that is, how these systems' responses to motion stimuli are reduced by pedestals and other masking stimuli. Motion-direction thresholds were measured for test stimuli consisting of drifting luminance and texture-contrast-modulation stimuli superimposed on pedestals of various amplitudes. (A pedestal is a static sine-wave grating of the same type and same spatial frequency as the moving test grating.) It was found that first-order motion-direction thresholds are unaffected by small pedestals, but at pedestal contrasts above 1-2% (5-10 x pedestal threshold), motion thresholds increase proportionally to pedestal amplitude (a Weber law). For first-order stimuli, pedestal masking is specific to the spatial frequency of the test. On the other hand, motion-direction thresholds for texture-contrast stimuli are independent of pedestal amplitude (no gain control whatever) throughout the accessible pedestal amplitude range (from 0 to 40%). However, when baseline carrier contrast increases (with constant pedestal modulation amplitude), motion thresholds increase, showing that gain control in second-order motion is determined not by the modulator (as in first-order motion) but by the carrier. Note that baseline contrast of the carrier is inherently independent of spatial frequency of the modulator. The drastically different gain-control properties of the two motion systems and prior observations of motion masking and motion saturation are all encompassed in a functional theory. The stimulus inputs to both first- and second-order motion process are normalized by feedforward, shunting gain control. The different properties arise because the modulator is used to control the first-order gain and the carrier is used to control the second-order gain.

  18. The new theorem of stability and gain convergence in simple adaptive control

    NASA Astrophysics Data System (ADS)

    Barkana, Itzhak

    2017-01-01

    Convergence of the adaptive control gains when the presence of sufficient excitation is not available has remained an open question for more than 30 years. The rather common opinion that in these cases the adaptive control gains do not actually converge and may continue wandering without reaching any limit at all, even when asymptotically perfect tracking is reached, is disturbing to practitioners and potential users of adaptive control. Recent publications have provided solutions to various aspects of this open question within the particular frame of so-called Simple Adaptive Control methodology. However, a thorough review of the problem shows that the solution to the ultimate behavior of the adaptive gains when sufficient excitation is not available may still be considered incomplete. The present paper revisits the issue in order to finally show that a new Theorem of Stability, which greatly simplifies stability analysis for nonautonomous nonlinear systems, in combination with Gronwall-Bellman Lemma provide the solution of the gain convergence problem. It is shown that the control gains do reach a constant value at the end of adaptation process, thus allowing the conclusion that simple and robust adaptive control systems can successfully be implemented in real-world systems.

  19. Metabolic control analysis using transient metabolite concentrations. Determination of metabolite concentration control coefficients.

    PubMed Central

    Delgado, J; Liao, J C

    1992-01-01

    The methodology previously developed for determining the Flux Control Coefficients [Delgado & Liao (1992) Biochem. J. 282, 919-927] is extended to the calculation of metabolite Concentration Control Coefficients. It is shown that the transient metabolite concentrations are related by a few algebraic equations, attributed to mass balance, stoichiometric constraints, quasi-equilibrium or quasi-steady states, and kinetic regulations. The coefficients in these relations can be estimated using linear regression, and can be used to calculate the Control Coefficients. The theoretical basis and two examples are discussed. Although the methodology is derived based on the linear approximation of enzyme kinetics, it yields reasonably good estimates of the Control Coefficients for systems with non-linear kinetics. PMID:1497632

  20. Reliable gain-scheduled control of discrete-time systems and its application to CSTR model

    NASA Astrophysics Data System (ADS)

    Sakthivel, R.; Selvi, S.; Mathiyalagan, K.; Shi, Y.

    2016-10-01

    This paper is focused on reliable gain-scheduled controller design for a class of discrete-time systems with randomly occurring nonlinearities and actuator fault. Further, the nonlinearity in the system model is assumed to occur randomly according to a Bernoulli distribution with measurable time-varying probability in real time. The main purpose of this paper is to design a gain-scheduled controller by implementing a probability-dependent Lyapunov function and linear matrix inequality (LMI) approach such that the closed-loop discrete-time system is stochastically stable for all admissible randomly occurring nonlinearities. The existence conditions for the reliable controller is formulated in terms of LMI constraints. Finally, the proposed reliable gain-scheduled control scheme is applied on continuously stirred tank reactor model to demonstrate the effectiveness and applicability of the proposed design technique.

  1. Adaptive fuzzy dynamic surface control for the chaotic permanent magnet synchronous motor using Nussbaum gain.

    PubMed

    Luo, Shaohua

    2014-09-01

    This paper is concerned with the problem of adaptive fuzzy dynamic surface control (DSC) for the permanent magnet synchronous motor (PMSM) system with chaotic behavior, disturbance and unknown control gain and parameters. Nussbaum gain is adopted to cope with the situation that the control gain is unknown. And the unknown items can be estimated by fuzzy logic system. The proposed controller guarantees that all the signals in the closed-loop system are bounded and the system output eventually converges to a small neighborhood of the desired reference signal. Finally, the numerical simulations indicate that the proposed scheme can suppress the chaos of PMSM and show the effectiveness and robustness of the proposed method.

  2. Adaptive fuzzy dynamic surface control for the chaotic permanent magnet synchronous motor using Nussbaum gain

    SciTech Connect

    Luo, Shaohua

    2014-09-01

    This paper is concerned with the problem of adaptive fuzzy dynamic surface control (DSC) for the permanent magnet synchronous motor (PMSM) system with chaotic behavior, disturbance and unknown control gain and parameters. Nussbaum gain is adopted to cope with the situation that the control gain is unknown. And the unknown items can be estimated by fuzzy logic system. The proposed controller guarantees that all the signals in the closed-loop system are bounded and the system output eventually converges to a small neighborhood of the desired reference signal. Finally, the numerical simulations indicate that the proposed scheme can suppress the chaos of PMSM and show the effectiveness and robustness of the proposed method.

  3. Adaptive tuning of feedback gain in time-delayed feedback control.

    PubMed

    Lehnert, J; Hövel, P; Flunkert, V; Guzenko, P Yu; Fradkov, A L; Schöll, E

    2011-12-01

    We demonstrate that time-delayed feedback control can be improved by adaptively tuning the feedback gain. This adaptive controller is applied to the stabilization of an unstable fixed point and an unstable periodic orbit embedded in a chaotic attractor. The adaptation algorithm is constructed using the speed-gradient method of control theory. Our computer simulations show that the adaptation algorithm can find an appropriate value of the feedback gain for single and multiple delays. Furthermore, we show that our method is robust to noise and different initial conditions.

  4. Modifying the gain of the visual feedback affects undisturbed upright stance control.

    PubMed

    Rougier, P; Farenc, I; Berger, L

    2004-10-01

    To assess the effects of visual feedback gain, which express the amplitudes of the displacements of the centre of pressure displayed on a computer screen. The controlling variable, the centre of pressure trajectories, recorded using a force platform, were decomposed into two elementary motions: (1) the horizontal displacements of the centre of gravity and (2) the vertical projection of the difference between centre of pressure and the centre of gravity. These motions were processed through frequency analysis and modelled as fractional Brownian motion to assess their spatio-temporal linkage and their degree of control. Although tests to modify the feedback gain have already been carried out, the specific effects from a biomechanical and motor control point of view need to be assessed. Thirteen healthy adults were tested through various visual feedback gains performed in random order. By increasing the visual feedback gain, no difference is observed between centre of pressure and centre of gravity motions whereas a progressive diminution of centre of gravity horizontal motions is seen. This latter effect is principally explained by a reinforcement of control during corrective processes. When the control of centre of gravity constitutes the main flaw in undisturbed stance maintenance, the efficiency of a visual feedback rehabilitation protocol should be largely improved by using an enhanced gain.

  5. Class A/AB second-generation current conveyor with controlled current gain

    NASA Astrophysics Data System (ADS)

    Fabre, A.; Mimeche, N.

    1994-08-01

    A new second-generation current conveyor whose current transfer from X to Z is controlled by a current, is introduced. It functions in class A/AB and uses a mixed translinear loop and two complementary current mirrors with controlled gain. SPICE simulation results, are given. They underline the high potential of the circuit.

  6. The role of the kidney in canine blood pressure control: direct assessment of the closed-loop gain.

    PubMed Central

    Persson, P B; Ehmke, H; Kirchheim, H R; Lempinen, M; Nafz, B

    1993-01-01

    1. The feedback control of arterial blood pressure by the kidney in the range of hours was investigated in resting, conscious foxhounds. 2. A servo-control device (connected to an aortic occlusive cuff implanted above both renal arteries) was used to maintain a constant pressure difference of 20 mmHg between aortic pressure measured proximal (mean arterial blood pressure: MAP) and distal (renal artery pressure: RAP) to the aortic cuff. 3. Protocol 1 (n = 6) served as a 4 h time control without intervention, protocol 2 (n = 6) consisted of three periods: after a control of 20 min duration, the servo-control device was activated for 180 min; this was followed by a recovery period of 40 min. Protocol 3 (n = 6) was as protocol 2, but during converting-enzyme inhibition. 4. Servo-control increased plasma renin activity (PRA) transiently from 0.5 ng angiotensin I (AI) ml-1 h-1 to a peak value of 2.4 ng AI ml-1 h-1, subsequently both RAP and MAP rose to reach a new steady state. During this increase in RAP, PRA declined to 1.4 ng AI ml-1 h-1. 5. On average, the compensation of the pressure decrease sensed by the kidney amounted to 63% of the error signal (closed-loop gain of 0.63 +/- 0.1). 6. Converting-enzyme inhibition reduced this closed-loop gain significantly (protocol 2 vs. protocol 3, 0.63 +/- 0.1 vs. 0.15 +/- 0.1; P < 0.05). 7. It is concluded, that the kidney plays an important role in medium-term blood pressure regulation, most probably via the renin-angiotensin system. Images Fig. 3 PMID:8229794

  7. Transient Control of Synchronous Machine Active and Reactive Power in Micro-grid Power Systems

    NASA Astrophysics Data System (ADS)

    Weber, Luke G.

    There are two main topics associated with this dissertation. The first is to investigate phase-to-neutral fault current magnitude occurring in generators with multiple zero-sequence current sources. The second is to design, model, and tune a linear control system for operating a micro-grid in the event of a separation from the electric power system. In the former case, detailed generator, AC8B excitation system, and four-wire electric power system models are constructed. Where available, manufacturers data is used to validate the generator and exciter models. A gain-delay with frequency droop control is used to model an internal combustion engine and governor. The four wire system is connected through a transformer impedance to an infinite bus. Phase-to-neutral faults are imposed on the system, and fault magnitudes analyzed against three-phase faults to gauge their severity. In the latter case, a balanced three-phase system is assumed. The model structure from the former case - but using data for a different generator - is incorporated with a model for an energy storage device and a net load model to form a micro-grid. The primary control model for the energy storage device has a high level of detail, as does the energy storage device plant model in describing the LC filter and transformer. A gain-delay battery and inverter model is used at the front end. The net load model is intended to be the difference between renewable energy sources and load within a micro-grid system that has separated from the grid. Given the variability of both renewable generation and load, frequency and voltage stability are not guaranteed. This work is an attempt to model components of a proposed micro-grid system at the University of Wisconsin Milwaukee, and design, model, and tune a linear control system for operation in the event of a separation from the electric power system. The control module is responsible for management of frequency and active power, and voltage and reactive

  8. Visual angle is the critical variable mediating gain-related effects in manual control

    PubMed Central

    Haibach, Pamela. S.; Newell, Karl. M.

    2008-01-01

    Theoretically visual gain has been identified as a control variable in models of isometric force. However, visual gain is typically confounded with visual angle and distance, and the relative contribution of visual gain, distance, and angle to the control of force remains unclear. This study manipulated visual gain, distance, and angle in three experiments to examine the visual information properties used to regulate the control of a constant level of isometric force. Young adults performed a flexion motion of the index finger of the dominant hand in 20 s trials under a range of parameter values of the three visual variables. The findings demonstrate that the amount and structure of the force fluctuations were organized around the variable of visual angle, rather than gain or distance. Furthermore, the amount and structure of the force fluctuations changed considerably up to 1°, with little change higher than a 1° visual angle. Visual angle is the critical informational variable for the visuomotor system during the control of isometric force. PMID:16604313

  9. Optimal feedback gains of a delayed proportional-derivative (PD) control for balancing an inverted pendulum

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Wang, Zaihua

    2017-06-01

    In the dynamics analysis and synthesis of a controlled system, it is important to know for what feedback gains can the controlled system decay to the demanded steady state as fast as possible. This article presents a systematic method for finding the optimal feedback gains by taking the stability of an inverted pendulum system with a delayed proportional-derivative controller as an example. First, the condition for the existence and uniqueness of the stable region in the gain plane is obtained by using the D-subdivision method and the method of stability switch. Then the same procedure is used repeatedly to shrink the stable region by decreasing the real part of the rightmost characteristic root. Finally, the optimal feedback gains within the stable region that minimizes the real part of the rightmost root are expressed by an explicit formula. With the optimal feedback gains, the controlled inverted pendulum decays to its trivial equilibrium at the fastest speed when the initial values around the origin are fixed. The main results are checked by numerical simulation.

  10. Optimal feedback gains of a delayed proportional-derivative (PD) control for balancing an inverted pendulum

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Wang, Zaihua

    2017-03-01

    In the dynamics analysis and synthesis of a controlled system, it is important to know for what feedback gains can the controlled system decay to the demanded steady state as fast as possible. This article presents a systematic method for finding the optimal feedback gains by taking the stability of an inverted pendulum system with a delayed proportional-derivative controller as an example. First, the condition for the existence and uniqueness of the stable region in the gain plane is obtained by using the D-subdivision method and the method of stability switch. Then the same procedure is used repeatedly to shrink the stable region by decreasing the real part of the rightmost characteristic root. Finally, the optimal feedback gains within the stable region that minimizes the real part of the rightmost root are expressed by an explicit formula. With the optimal feedback gains, the controlled inverted pendulum decays to its trivial equilibrium at the fastest speed when the initial values around the origin are fixed. The main results are checked by numerical simulation.

  11. Cochlear Gain Control Estimated from Distortion Product Otoacoustic Emissions Evoked by Amplitude Modulated Tones

    NASA Astrophysics Data System (ADS)

    Chen, Shixiong; Bian, Lin

    2011-11-01

    It is known that cochlear outer hair cells (OHCs) can provide dynamic feedback to the basilar membrane vibration. Nonlinearities in OHC activities can generate distortion product otoacoustic emissions (DPOAEs) measurable in the ear canal. If evoked by amplitude modulation (AM) signals, DPOAEs could provide a means to access the dynamic gain control of the cochlea. In this study, one of the primary stimuli was replaced with an AM tone to evoke DPOAEs in human ears. The results showed that the estimated cochlear gain decreased with the increase in stimulus level and the gain functions obtained from different AM tone levels were continuous. However, there was a difference in the gain functions depending on which primary was modulated. The gain showed a stronger compression when f2 was modulated. Considering that DPOAEs are mainly generated at the f2 place, it suggests that the cochlear gain control is more nonlinear for on-frequency signals. Using AM stimulus could provide clues on how dynamic signals are processed in the cochlea.

  12. Controlled fundamental supermode operation of phase-locked arrays of gain-guided diode lasers

    NASA Technical Reports Server (NTRS)

    Kapon, E.; Margalit, S.; Yariv, A.; Katz, J.

    1984-01-01

    Uniform semiconductor laser arrays tend to oscillate in a superposition of their supermodes, thus leading to large beam divergence and spectral spread. Discrimination among the supermodes in phase-locked arrays is discussed theoretically. It is shown that supermode discrimination in gain-guided arrays, in favor of the fundamental supermode, is made possible by the near-field interference patterns which result from the complex optical fields of the gain-guided lasers. A fundamental supermode operation is demonstrated, for the first time, in GaAlAs/GaAs gain-guided laser arrays. This is achieved by control of the current (gain) profile across the array by means of individual laser contacts.

  13. Sensory gain control (amplification) as a mechanism of selective attention: electrophysiological and neuroimaging evidence.

    PubMed Central

    Hillyard, S A; Vogel, E K; Luck, S J

    1998-01-01

    Both physiological and behavioral studies have suggested that stimulus-driven neural activity in the sensory pathways can be modulated in amplitude during selective attention. Recordings of event-related brain potentials indicate that such sensory gain control or amplification processes play an important role in visual-spatial attention. Combined event-related brain potential and neuroimaging experiments provide strong evidence that attentional gain control operates at an early stage of visual processing in extrastriate cortical areas. These data support early selection theories of attention and provide a basis for distinguishing between separate mechanisms of attentional suppression (of unattended inputs) and attentional facilitation (of attended inputs). PMID:9770220

  14. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    NASA Astrophysics Data System (ADS)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  15. Presynaptic gain control by endogenous cotransmission of dopamine and GABA in the olfactory bulb.

    PubMed

    Vaaga, Christopher E; Yorgason, Jordan T; Williams, John T; Westbrook, Gary L

    2017-03-01

    In the olfactory bulb, lateral inhibition mediated by local juxtaglomerular interneurons has been proposed as a gain control mechanism, important for decorrelating odorant responses. Among juxtaglomerular interneurons, short axon cells are unique as dual-transmitter neurons that release dopamine and GABA. To examine their intraglomerular function, we expressed channelrhodopsin under control of the DAT-cre promoter and activated olfactory afferents within individual glomeruli. Optical stimulation of labeled cells triggered endogenous dopamine release as measured by cyclic voltammetry and GABA release as measured by whole cell GABAA receptor currents. Activation of short axon cells reduced the afferent presynaptic release probability via D2 and GABAB receptor activation, resulting in reduced spiking in both mitral and external tufted cells. Our results suggest that short axon cells influence glomerular activity not only by direct inhibition of external tufted cells but also by inhibition of afferent inputs to external tufted and mitral cells.NEW & NOTEWORTHY Sensory systems, including the olfactory system, encode information across a large dynamic range, making synaptic mechanisms of gain control critical to proper function. Here we demonstrate that a dual-transmitter interneuron in the olfactory bulb controls the gain of intraglomerular afferent input via two distinct mechanisms, presynaptic inhibition as well as inhibition of a principal neuron subtype, and thereby potently controls the synaptic gain of afferent inputs. Copyright © 2017 the American Physiological Society.

  16. Gain scheduling of aircraft pitch attitude and control of discrete, affine, linear parametrically varying systems

    NASA Astrophysics Data System (ADS)

    Lin, Zhe

    This research is motivated by gain scheduling, a technique which has been successfully applied to many nonlinear control problems. In flight controls, the wide variations in the characteristics of the aircraft dynamics throughout the flight envelope make gain scheduling a particularly suitable design strategy. This research consists of two parts: (1) aircraft pitch attitude scheduling scheme designs, and (2) control of a class of linear parametrically varying (LPV) systems. In the first part, the classical gain scheduling technique and the single quadratic Lyapunov function (SQLF) based LPV technique are investigated. In the classical gain scheduling design, the Hinfinity mixed sensitivity GS/T method is chosen for local linear time invariant (LTI) designs to provide robustness to unmodeled dynamics and parametric uncertainties. Following a model reduction procedure that exploits the optimal controller structure, LTI controllers designed at the selected equilibrium points are reduced to second order controllers and realized in a feedback path configuration. Such controllers are shown to retain the superior robust performance at each flight condition, while having a low order that is amenable to scheduling. A gain-scheduling law is developed and simulation results verify that the closed-loop performance specifications are met. In the LPV design, the mixed sensitivity S/KS/T design setup is used. An approximation to the original LPV controller using the linear fractional transformation (LFT) representation is constructed. Our design exhibits potential applications of the LPV technique to commercial aircraft gain scheduling designs. In the second part, we consider a class of discrete, affine, linear parametrically varying (DALPV) systems. For this type of systems, the parameters are assumed to vary in a polytope and the state space matrices are assumed to depend affinely on the varying parameters. A sufficient condition is derived to analyze the stability and the

  17. Analysis and design of gain scheduled control systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Shamma, Jeff S.

    1988-01-01

    Gain scheduling, as an idea, is to construct a global feedback control system for a time varying and/or nonlinear plant from a collection of local time invariant designs. However in the absence of a sound analysis, these designs come with no guarantees on the robustness, performance, or even nominal stability of the overall gain schedule design. Such an analysis is presented for three types of gain scheduling situations: (1) a linear parameter varying plant scheduling on its exogenous parameters, (2) a nonlinear plant scheduling on a prescribed reference trajectory, and (3) a nonlinear plant scheduling on the current plant output. Conditions are given which guarantee that the stability, robustness, and performance properties of the fixed operating point designs carry over to the global gain scheduled designs, such as the scheduling variable should vary slowly and capture the plants nonlinearities. Finally, an alternate design framework is proposed which removes the slowing varying restriction or gain scheduled systems. This framework addresses some fundamental feedback issues previously ignored in standard gain.

  18. Automatic control systems satisfying certain general criterions on transient behavior

    NASA Technical Reports Server (NTRS)

    Boksenbom, Aaron S; Hood, Richard

    1952-01-01

    An analytic method for the design of automatic controls is developed that starts from certain arbitrary criterions on the behavior of the controlled system and gives those physically realizable equations that the control system can follow in order to realize this behavior. The criterions used are developed in the form of certain time integrals. General results are shown for systems of second order and of any number of degrees of freedom. Detailed examples for several cases in the control of a turbojet engine are presented.

  19. Transient hydrogeological controls on the chemistry of a seepage lake

    USGS Publications Warehouse

    Krabbenhoft, David P.; Webster, Katherine E.

    1995-01-01

    A solute mass balance method was used to estimate groundwater inflow and outflow rates for Nevins Lake, Michigan, a seepage lake in the upper peninsula that historically has shown extremely variable water chemistry compared with most other seepage lakes. A 4-year study (1989–1992) of the hydrology and geochemistry of Nevins Lake and its contiguous groundwater system revealed that changes in the mass of dissolved solutes are the result of annual hydraulic gradient reversals. A pronounced acidification of Nevins Lake from 1986 to 1988 was likely caused by drought-induced diminished groundwater inflow rates. In this study, dissolved calcium (the major cation in water of Nevins Lake, groundwater, and precipitation) was used for estimating mass flow rates. During the 1989–1992 period, Nevins Lake showed a reproducible annual cycle in calcium mass. Immediately following spring snowmelt and the resulting hydraulic gradient reversal, the mass of dissolved calcium in the lake increases rapidly, and then it decreases steadily throughout the summer and early fall, at which time the lake becomes hydraulically mounded and receives no groundwater inflow. Groundwater flow rates estimated by the solute mass balance method are sensitive to assumed solute concentrations in discharging groundwater. Pore water samples from the lake bed are shown to be more representative of water discharging to the lake than are samples from piezometers near the lake shore, but spatial and temporal variability in pore water chemistry must be considered. Stable isotope analyses (18O and 2H) of lake water, groundwater, and pore water samples show that water discharging to Nevins Lake in the spring is entirely recycled lake water, and no groundwater derived from terrestrial recharge reaches the lake. The conceptual model formulated during this study linking lake chemistry and the contiguous groundwater system and general groundwater flow patterns surrounding highly transient lake systems are likely

  20. Research on transient hysteresis current control strategy of DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Wang, Zu-liang; Zhao, Yu-kai

    2017-01-01

    In order to improve the dynamic performance of DC-DC converter, transient hysteresis current control strategy is proposed which is based on parallel computing and combinational logic. By making a comparison between the real-time inductor current and the threshold inductor current, the switch is controlled more accurately. Under the Matlab/Simulink environment, the process of the Buck-Boost converter was simulated. The simulation results show that the transient hysteresis current control strategy can effectively overcome the disadvantages when load changes or input voltage disturbance occurs, it posses high load regulation and short dynamic response time, and it verifies the feasibility of the proposed strategy.

  1. A predictive controller based on transient simulations for controlling a power plant

    NASA Astrophysics Data System (ADS)

    Svingen, B.

    2016-11-01

    A predictive governor based on an embedded, online transient simulation was commissioned at Tonstad power plant in Norway in December 2014. This governor controls each individual turbine governor by feeding them modified setpoints. Tonstad power plant consists of 4 × 160 MW + 1 × 320 MW high head Francis turbines. With a yearly production of 3888 GWh, it is the largest in Norway. The plant is a typical high head Norwegian plant with very long tunnels and correspondingly active dynamic behaviour. This new governor system continuously simulates the entire plant, and appropriate actions are taken automatically by special algorithms. The simulations are based on the method of characteristics (MOC). The governing system has been in full operational mode since December 19 2014. The testing period also included special acceptance tests to be able to deliver FRR, both on the Nordic grid and on DC cable to Denmark. Although in full operational mode, this system is still a prototype under constant development. It shows a new way of using transient analysis that may become increasingly important in the future with added power from un-regulated sources such as wind, solar and bio.

  2. Sustained vs. Transient Cognitive Control: Evidence of a Behavioral Dissociation

    ERIC Educational Resources Information Center

    Funes, Maria Jesus; Lupianez, Juan; Humphreys, Glyn

    2010-01-01

    This study assessed whether two well known effects associated with cognitive control, conflict adaptation (the Gratton effect) and conflict context (proportion congruent effects), reflect a single common or separate control systems. To test this we examined if these two effects generalized from one kind of conflict to another by using a…

  3. Sustained vs. Transient Cognitive Control: Evidence of a Behavioral Dissociation

    ERIC Educational Resources Information Center

    Funes, Maria Jesus; Lupianez, Juan; Humphreys, Glyn

    2010-01-01

    This study assessed whether two well known effects associated with cognitive control, conflict adaptation (the Gratton effect) and conflict context (proportion congruent effects), reflect a single common or separate control systems. To test this we examined if these two effects generalized from one kind of conflict to another by using a…

  4. Light-controlled resistors provide quadrature signal rejection for high-gain servo systems

    NASA Technical Reports Server (NTRS)

    Mc Cauley, D. D.

    1967-01-01

    Servo amplifier feedback system, in which the phase sensitive detection, low pass filtering, and multiplication functions required for quadrature rejection, are preformed by light-controlled photoresistors, eliminates complex circuitry. System increases gain, improves signal-to-noise ratio, and eliminates the necessity for compensation.

  5. Computer simulation of magnetization-controlled shunt reactors for calculating electromagnetic transients in power systems

    SciTech Connect

    Karpov, A. S.

    2013-01-15

    A computer procedure for simulating magnetization-controlled dc shunt reactors is described, which enables the electromagnetic transients in electric power systems to be calculated. It is shown that, by taking technically simple measures in the control system, one can obtain high-speed reactors sufficient for many purposes, and dispense with the use of high-power devices for compensating higher harmonic components.

  6. Precision motion control with a high gain disturbance compensator for linear motors.

    PubMed

    Tan, Kok Kiong; Zhao, Shao

    2004-07-01

    In this paper, we address the problem relating to the precision control of permanent magnet linear motors to track repeated motion trajectories. A high gain disturbance compensator is developed to improve the control performance degraded due to the presence of significant disturbances. An inverse gain of the overall system model is used to set up a disturbance observer. The observed disturbance is then used to generate a "knocker" signal, to be augmented to the control signal, which can provide the additional energy necessary to overcome the effects of the disturbances. A learning scheme is used to adjust the knocker signal iteratively over the repeated cycles. Simulation and experimental results are furnished to demonstrate the effectiveness of the proposed control scheme.

  7. A Nonlinear Excitation Controller Design Method for Terminal Voltage Regulation and Transient Stability Enhancement

    NASA Astrophysics Data System (ADS)

    Huang, Chongxin; Zhang, Kaifeng; Dai, Xianzhong; Zang, Qiang

    2014-06-01

    This paper proposes a cascade control method to design a nonlinear excitation controller to guarantee the terminal voltage regulation and the transient stability. Firstly, a nonlinear automatic voltage regulator (NAVR) in the inner loop is designed to control the terminal voltage exactly. Secondly, the generator model including the NAVR is transformed to be a reduced one. Subsequently, based on the reduced generator model, the nonlinear power system stabilizer in the external loop is designed to enhance the transient stability of the power systems. Furthermore, a coordination strategy is presented to improve the performances of the terminal voltage regulation in the steady state and the stability in the transient state. Finally, the proposed method is verified by numerous simulation results.

  8. Weight gain prevention in young adults: design of the study of novel approaches to weight gain prevention (SNAP) randomized controlled trial

    PubMed Central

    2013-01-01

    Background Weight gain during young adulthood is common and is associated with increased cardiovascular risk. Preventing this weight gain from occurring may be critical to improving long-term health. Few studies have focused on weight gain prevention, and these studies have had limited success. SNAP (Study of Novel Approaches to Weight Gain Prevention) is an NIH-funded randomized clinical trial examining the efficacy of two novel self-regulation approaches to weight gain prevention in young adults compared to a minimal treatment control. The interventions focus on either small, consistent changes in eating and exercise behaviors, or larger, periodic changes to buffer against expected weight gains. Methods/Design SNAP targets recruitment of six hundred young adults (18–35 years) with a body mass index between 21.0-30.0 kg/m2, who will be randomly assigned with equal probability to: (1) minimal intervention control; (2) self-regulation with Small Changes; or (3) self-regulation with Large Changes. Both interventions receive 8 weekly face-to-face group sessions, followed by 2 monthly sessions, with two 4-week refresher courses in each of subsequent years. Participants are instructed to report weight via web at least monthly thereafter, and receive monthly email feedback. Participants in Small Changes are taught to make small daily changes (~100 calorie changes) in how much or what they eat and to accumulate 2000 additional steps per day. Participants in Large Changes are taught to create a weight loss buffer of 5–10 pounds once per year to protect against anticipated weight gains. Both groups are encouraged to self-weigh daily and taught a self-regulation color zone system that specifies action depending on weight gain prevention success. Individualized treatment contact is offered to participants who report weight gains. Participants are assessed at baseline, 4 months, and then annually. The primary outcome is weight gain over an average of 3 years of follow

  9. LNA with wide range of gain control and wideband interference rejection

    NASA Astrophysics Data System (ADS)

    Wang, Jhen-Ji; Chen, Duan-Yu

    2016-10-01

    This work presents a low-noise amplifier (LNA) design with a wide-range gain control characteristic that integrates adjustable current distribution and output impedance techniques. For a given gain characteristic, the proposed LNA provides better wideband interference rejection performance than conventional LNA. Moreover, the proposed LNA also has a wider gain control range than conventional LNA. Therefore, it is suitable for satellite communications systems. The simulation results demonstrate that the voltage gain control range is between 14.5 and 34.2 dB for such applications (2600 MHz); the input reflection coefficient is less than -18.9 dB; the noise figure (NF) is 1.25 dB; and the third-order intercept point (IIP3) is 4.52 dBm. The proposed LNA consumes 23.85-28.17 mW at a supply voltage of 1.8 V. It is implemented by using TSMC 0.18-um RF CMOS process technology.

  10. Interaural Level Difference Dependent Gain Control and Synaptic Scaling Underlying Binaural Computation

    PubMed Central

    Xiong, Xiaorui R.; Liang, Feixue; Li, Haifu; Mesik, Lukas; Zhang, Ke K.; Polley, Daniel B.; Tao, Huizhong W.; Xiao, Zhongju; Zhang, Li I.

    2013-01-01

    Binaural integration in the central nucleus of inferior colliculus (ICC) plays a critical role in sound localization. However, its arithmetic nature and underlying synaptic mechanisms remain unclear. Here, we showed in mouse ICC neurons that the contralateral dominance is created by a “push-pull”-like mechanism, with contralaterally dominant excitation and more bilaterally balanced inhibition. Importantly, binaural spiking response is generated apparently from an ipsilaterally-mediated scaling of contralateral response, leaving frequency tuning unchanged. This scaling effect is attributed to a divisive attenuation of contralaterally-evoked synaptic excitation onto ICC neurons with their inhibition largely unaffected. Thus, a gain control mediates the linear transformation from monaural to binaural spike responses. The gain value is modulated by interaural level difference (ILD) primarily through scaling excitation to different levels. The ILD-dependent synaptic scaling and gain adjustment allow ICC neurons to dynamically encode interaural sound localization cues while maintaining an invariant representation of other independent sound attributes. PMID:23972599

  11. Non-Geiger mode single photon detector with multiple amplification and gain control mechanisms

    SciTech Connect

    Nawar Rahman, Samia Hall, David; Lo, Yu-Hwa

    2014-05-07

    A new type of single photon detector, Multiple Amplification Gain with Internal Control (MAGIC), is proposed and analyzed using Monte Carlo simulations based on a physical model of the device. The MAGIC detector has two coupled amplification mechanisms, avalanche multiplication and bipolar gain, and the net gain is regulated by a built-in feedback mechanism. Compared to conventional Geiger mode single photon avalanche detectors (SPADs), the MAGIC detector produces a much greater single photon detection efficiency of nearly 100%, low bit-error-ratio for single photon signals, and a large dynamic range. All these properties are highly desirable for applications that require single photon sensitivity and are absent for conventional Geiger-mode SPADs.

  12. Application of variable-gain output feedback for high-alpha control

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1990-01-01

    A variable-gain, optimal, discrete, output feedback design approach that is applied to a nonlinear flight regime is described. The flight regime covers a wide angle-of-attack range that includes stall and post stall. The paper includes brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high performance airplane model used in the application. Both linear and nonlinear analysis are shown for a longitudinal four-model design case with angles of attack of 5, 15, 35, and 60 deg. Linear and nonlinear simulations are compared for a single-point longitudinal design at 60 deg angle of attack. Nonlinear simulations for the four-model, multi-mode, variable-gain design include a longitudinal pitch-up and pitch-down maneuver and high angle-of-attack regulation during a lateral maneuver.

  13. Stomatal dynamics and its importance to carbon gain in two rainforest Piper species : I. VPD effects on the transient stomatal response to lightflecks.

    PubMed

    Tinoco-Ojanguren, Clara; Pearcy, Robert W

    1993-06-01

    The effects of leaf-air vapor pressure deficit (VPD) on the transient and steady-state stomatal responses to photon flux density (PFD) were evaluated in Piper auritum, a pioneer tree, and Piper aequale, a shade tolerant shrub, that are both native to tropical forests at Los Tuxtlas, Veracruz, México. Under constant high-PFD conditions, the stomata of shade-acclimated plants of both species were sensitive to VPD, exhibiting a nearly uniform decrease in gs as VPD increased. Acclimation of P. auritum to high light increased the stomatal sensitivity to VPD that was sufflcient to cause a reduction in transpiration at high VPD's. At low PFD, where gs was already reduced, there was little additional absolute change with VPD for any species or growth condition. The stomatal response to 8-min duration lightflecks was strongly modulated by VPD and varied between the species and growth light conditions. In P. aequale shade plants, increased VPD had no effect on the extent of stomatal opening but caused the rate of closure after the lightfleck to be faster. Thus, the overall response to a lightfleck changed from hysteretic (faster opening than closure) to symmetric (similar opening and closing rates). Either high or low VPD caused gs not to return to the steady-state value present before the lightfleck. At high VPD the value after was considerably less than the value before whereas at low VPD the opposite occurred. Shade-acclimated plants of P. auritum showed only a small gs response to lightflecks, which was not affected by VPD. Under sunfleck regimes in the understory, the stomatal response of P. aequale at low VPD may function to enhance carbon gain by increasing the induction state. At high VPD, the shift in the response enhances water use efficiency but at the cost of reduced assimilation.

  14. Optoelectronic gain control of a microwave single stage GaAs MESFET amplifier

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.

    1988-01-01

    Gain control of a single stage GaAs MESFET amplifier is demonstrated by the use of optical illumination of photon energy greater than the GaAs bandgap. The optical illumination is supplied by a semiconductor laser diode and is coupled to the Schottky gate of the MESFET by an optical fiber. The increase in gain is observed to be as much as 5.15 dB when the MESFET is biased close to pinchoff, that is, V(sub gs) equals -1.5 V and with optical illumination of 1.5 mW. The computed maximum available gain (MAG) and current gain (bar h sub 21 bar) from the de-embedded s-parameters show that MAG is unaffected by optical illumination, however, bar h(sub 21)bar increases by more than 2 dB under optical illumination of 1.5 mW. The maximum frequency of oscillation (F sub max) and the unity current gain cut-off frequency (F sub t) obtained by extrapolating the MAG and bar h(sub 21)bar curves, respectively, show that the F(sub max) is insensitive to optical illumination but F(sub t) increases by 5 GHz.

  15. Design and evaluation of controls for drift, video gain, and color balance in spaceborne facsimile cameras

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.; Kelly, W. L., IV; Rowland, C. W.; Burcher, E. E.

    1973-01-01

    The facsimile camera is an optical-mechanical scanning device which has become an attractive candidate as an imaging system for planetary landers and rovers. This paper presents electronic techniques which permit the acquisition and reconstruction of high quality images with this device, even under varying lighting conditions. These techniques include a control for low frequency noise and drift, an automatic gain control, a pulse-duration light modulation scheme, and a relative spectral gain control. Taken together, these techniques allow the reconstruction of radiometrically accurate and properly balanced color images from facsimile camera video data. These techniques have been incorporated into a facsimile camera and reproduction system, and experimental results are presented for each technique and for the complete system.

  16. Auto gain control of EMCCD in Shack-Hartmann wavefront sensor for adaptive optics

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaoyi; Li, Dayu; Hu, Lifa; Mu, QuanQuan; Cao, Zhaoliang; Wang, Yukun; Wang, Shaoxin; Xuan, Li

    2016-12-01

    Electron multiplying charge-coupled-device (EMCCD) applied in Shack-Hartmann wavefront sensor (S-H WFS) makes the wavefront sensing more efficient for adaptive optics (AO). However when the brightness of the observed target changes in large ranges in a few minutes, a fixed electron multiplying (EM) gain may not be optimum. Thus an auto-gain-control (AGC) method based on the spots image of the S-H WFS is proposed. The designed control value is the average value of the maximum signals of all the light spots in a frame. It has been demonstrated in the experiments that the control value is sensitive to the change of the target brightness, and is stable in the presence of detecting noises and turbulence influence. The goal value for control is predetermined based on the linear relation of the signal with the EM gain and the number of photons collected in sub-apertures. The conditions of the self-protection of the EMCCD are also considered for the goal value. Simulations and experiments indicate that the proposed control method is efficient, and keeps the sensing in a high SNR which reaches the upper SNR limit when sensing with EMCCD. The self-protection of the EMCCD is avoided during the whole sensing process.

  17. Optimal control of transient dynamics in balanced networks supports generation of complex movements.

    PubMed

    Hennequin, Guillaume; Vogels, Tim P; Gerstner, Wulfram

    2014-06-18

    Populations of neurons in motor cortex engage in complex transient dynamics of large amplitude during the execution of limb movements. Traditional network models with stochastically assigned synapses cannot reproduce this behavior. Here we introduce a class of cortical architectures with strong and random excitatory recurrence that is stabilized by intricate, fine-tuned inhibition, optimized from a control theory perspective. Such networks transiently amplify specific activity states and can be used to reliably execute multidimensional movement patterns. Similar to the experimental observations, these transients must be preceded by a steady-state initialization phase from which the network relaxes back into the background state by way of complex internal dynamics. In our networks, excitation and inhibition are as tightly balanced as recently reported in experiments across several brain areas, suggesting inhibitory control of complex excitatory recurrence as a generic organizational principle in cortex. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Transient Adverse Side Effects During Neurofeedback Training: A Randomized, Sham-Controlled, Double Blind Study.

    PubMed

    Rogel, Ainat; Guez, Jonathan; Getter, Nir; Keha, Eldad; Cohen, Tzlil; Amor, Tali; Todder, Doron

    2015-09-01

    The benefits of clinical neurofeedback training are well known, however, its adverse side-effects are less studied. This research focuses on the transient adverse side effects of neurofeedback training via a double-blind, sham/controlled methodology. Thirty healthy undergraduate students volunteers were randomly divided into three treatment groups: increasing a modified Sensory Motor Rhythm, increasing Upper Alpha, and Sham/control group who receive a random reward. The training sessions were administered for a total of ten sessions. Questionnaires of transient adverse side effects were completed by all volunteers before each session. The results suggest that similar to most medical treatments, neurofeedback can cause transient adverse side effects. Moreover, most participants reported experiencing some side effects. The side effects can be divided into non-specific side effect, associated with the neurofeedback training in general and specific ones associated with the particular protocol. Sensory Motor Rhythm protocol seems to be the most sensitive to side effects.

  19. An optimal output feedback gain variation scheme for the control of plants exhibiting gross parameter changes

    NASA Technical Reports Server (NTRS)

    Moerder, Daniel D.

    1987-01-01

    A concept for optimally designing output feedback controllers for plants whose dynamics exhibit gross changes over their operating regimes was developed. This was to formulate the design problem in such a way that the implemented feedback gains vary as the output of a dynamical system whose independent variable is a scalar parameterization of the plant operating point. The results of this effort include derivation of necessary conditions for optimality for the general problem formulation, and for several simplified cases. The question of existence of a solution to the design problem was also examined, and it was shown that the class of gain variation schemes developed are capable of achieving gain variation histories which are arbitrarily close to the unconstrained gain solution for each point in the plant operating range. The theory was implemented in a feedback design algorithm, which was exercised in a numerical example. The results are applicable to the design of practical high-performance feedback controllers for plants whose dynamics vary significanly during operation. Many aerospace systems fall into this category.

  20. Effect of olive oil massage on weight gain in preterm infants: A randomized controlled clinical trial

    PubMed Central

    Jabraeile, Mahnaz; Rasooly, Alehe Seyyed; Farshi, Mahni Rahkar; Malakouti, Jamileh

    2016-01-01

    Background: Despite the fact that effect of massage with or without oil on the baby's weight gain is not clear, but recent studies have shown that massage with essential oils make lipid absorption through the skin. The aim of this study was to evaluate the effect of olive oil massage on weight gain in preterm infants. Materials and Methods: This study was a single-blind, randomized controlled clinical trial. In this study, infants who met inclusion criteria for the study were divided into two groups by using random numbers table. Newborns in intervention group were under massage for 10 days and 3 times for 15 min daily; the mother of these newborns had been trained already using olive oil. Moreover, the infants of the control group were under massaging without oil same as the above-mentioned method. Researchers weighed babies daily during 10 days and recorded it at the checklist. Data from the study were reviewed and analyzed by descriptive statistics and repeated measure test using the statistical software SPSS/13. Results: This study showed that the neonatal weight gain in the infants with the oil massage was 21 g daily in average, whereas the increase in infant massage without oil was 7 g. This difference was statistically significant (P < 0.001). Conclusion: Considering the positive effect of infant massage on weight gain in premature infants with olive oil, it is recommended that nurses use oil in infant massage in the neonatal units. PMID:27397955

  1. Transient PrOx carbon monoxide measurement, control, and optimization

    SciTech Connect

    Inbody, M. A.; Borup, R. L.; Tafoya, J.

    2002-01-01

    Fuel processing systems for low temperature polymer electrolyte membrane (PEM) fuel cell systems require control of the carbon monoxide concentration to less than 100 ppm to 10 ppm in the anode feed. Conventional hydrocarbon fuel processors use a water-gas shift (WGS) reactor to react CO with water to form H2 and reduce the CO concentration. The CO conversion is limited by equilibrium at the outlet temperature of the WGS reactor. The WGS outlet CO concentration can range from over 1% to 2000 ppm depending on the system and its operating parameters. At these concentrations, CO poisons low temperature PEM fuel cells and the concentrations needs to be reduced further.

  2. Innovative Self-Regulation Strategies Reduce Weight Gain in Young Adults: The Study of Novel Approaches to Weight Gain Prevention (SNAP) Randomized Controlled Trial

    PubMed Central

    Wing, Rena R.; Tate, Deborah F.; Espeland, Mark A.; Lewis, Cora E.; LaRose, Jessica Gokee; Gorin, Amy A.; Bahnson, Judy; Perdue, Letitia H.; Hatley, Karen E.; Ferguson, Erica; Garcia, Katelyn R.; Lang, Wei

    2017-01-01

    Importance Weight gain occurs commonly in young adults and has adverse effects on health. Reducing weight gain in young adults would have significant public health impact. Objective To compare two self-regulation interventions versus control in reducing weight gain in young adults over an average follow-up of 3 years. Design Randomized controlled trial Setting Two academic settings Participants 599 participants (22% men; 27% minority), age 18–35 (27.7 (4.4)), BMI 21–30 kg/m2 (25.4 (2.6)), recruited via mailings and e-mails between August 2010 and February 2012. Interventions Participants were randomly assigned to: Control, Self-Regulation plus Small Changes or Self-Regulation plus Large Changes. The interventions focused on frequent self-weighing and using this information to know when behavior changes were needed. “Small Changes” taught participants to reduce intake and increase activity, both by approximately 100 calories per day. “Large Changes” focused on losing 5–10 pounds initially to buffer against expected weight gain. Interventions were delivered via 10 in-person group sessions during months 1–4 and then primarily online. Assessments occurred at randomization, 4 months, and then annually for 2–4 years (depending on time of recruitment). Main outcome Changes in weight from baseline over average follow-up of 3 years. Secondary outcomes: proportion gaining ≥1 pound from baseline, proportion developing obesity (BMI ≥30 kg/m2), weight change baseline to 2 years (last assessment reached by all cohorts) Results Mean (SE) weight changes over an average follow-up of 3 years were +0.26 kg (0.22), −0.56 kg (0.22), and −2.37 kg (0.22) in Control, Small Changes and Large Changes, respectively (p=0.001). Differences among all three groups were significant (Large Changes vs Control, p<.001; Small Changes vs Control, p<.02 and Large Changes vs Small Changes, p<.001). Both interventions significantly reduced incidence of obesity (p<.05) relative

  3. Determinants of weight gain in the action to control cardiovascular risk in diabetes trial.

    PubMed

    Fonseca, Vivian; McDuffie, Roberta; Calles, Jorge; Cohen, Robert M; Feeney, Patricia; Feinglos, Mark; Gerstein, Hertzel C; Ismail-Beigi, Faramarz; Morgan, Timothy M; Pop-Busui, Rodica; Riddle, Matthew C

    2013-08-01

    Identify determinants of weight gain in people with type 2 diabetes mellitus (T2DM) allocated to intensive versus standard glycemic control in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. We studied determinants of weight gain over 2 years in 8,929 participants (4,425 intensive arm and 4,504 standard arm) with T2DM in the ACCORD trial. We used general linear models to examine the association between each baseline characteristic and weight change at the 2-year visit. We fit a linear regression of change in weight and A1C and used general linear models to examine the association between each medication at baseline and weight change at the 2-year visit, stratified by glycemia allocation. There was significantly more weight gain in the intensive glycemia arm of the trial compared with the standard arm (3.0 ± 7.0 vs. 0.3 ± 6.3 kg). On multivariate analysis, younger age, male sex, Asian race, no smoking history, high A1C, baseline BMI of 25-35, high waist circumference, baseline insulin use, and baseline metformin use were independently associated with weight gain over 2 years. Reduction of A1C from baseline was consistently associated with weight gain only when baseline A1C was elevated. Medication usage accounted for <15% of the variability of weight change, with initiation of thiazolidinedione (TZD) use the most prominent factor. Intensive participants who never took insulin or a TZD had an average weight loss of 2.9 kg during the first 2 years of the trial. In contrast, intensive participants who had never previously used insulin or TZD but began this combination after enrolling in the ACCORD trial had a weight gain of 4.6-5.3 kg at 2 years. Weight gain in ACCORD was greater with intensive than with standard treatment and generally associated with reduction of A1C from elevated baseline values. Initiation of TZD and/or insulin therapy was the most important medication-related factor associated with weight gain.

  4. Temporal Control over Transient Chemical Systems using Structurally Diverse Chemical Fuels.

    PubMed

    Chen, Jack L-Y; Maiti, Subhabrata; Fortunati, Ilaria; Ferrante, Camilla; Prins, Leonard J

    2017-08-25

    The next generation of adaptive, intelligent chemical systems will rely on a continuous supply of energy to maintain the functional state. Such systems will require chemical methodology that provides precise control over the energy dissipation process, and thus, the lifetime of the transiently activated function. This manuscript reports on the use of structurally diverse chemical fuels to control the lifetime of two different systems under dissipative conditions: transient signal generation and the transient formation of self-assembled aggregates. The energy stored in the fuels is dissipated at different rates by an enzyme, which installs a dependence of the lifetime of the active system on the chemical structure of the fuel. In the case of transient signal generation, it is shown that different chemical fuels can be used to generate a vast range of signal profiles, allowing temporal control over two orders of magnitude. Regarding self-assembly under dissipative conditions, the ability to control the lifetime using different fuels turns out to be particularly important as stable aggregates are formed only at well-defined surfactant/fuel ratios, meaning that temporal control cannot be achieved by simply changing the fuel concentration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A Simple Control Strategy Using Speedy Transient Response for Multiphase Buck Converter

    NASA Astrophysics Data System (ADS)

    Sasikala, K.; Ravikumar, D.; Rubini, B.

    2017-03-01

    The high performance of recent originating digital processors requires power supply for transient output, firm voltage regulation and high current. Industry has taken up interleaved multiphase synchronous buck converters for meeting such demands. Application of the voltage mode (ripple) hysteretic strategy to multiphase Voltage Regulator Units (VRU) would help satisfying many of the upcoming digital processors and IC’s powering demands. This arises from the use of the various advantages that can be obtained from this technique. This current division method is known for several benefits it provides: easy accessibility in application to all control methods, with freedom from the prime control technique in voltage regulation loop, absence of any necessity for current reference, better accuracy in current division of equal magnitude at almost every load conditions in standstill and transients. As against this, there are several challenges that involve distribution of multiple control signals, current sharing and sensitivity to noise, high speed comparators, hysteretic band accuracy and stable at large load transients. In addition, application of the current division technique presented was made to a multiphase voltage mode ripple controlled Buck Converter that produced a novel and easy control strategy having minimum output voltage ripples and speedy transient output.

  6. Gain Control in Predictive Smooth Pursuit Eye Movements: Evidence for an Acceleration-Based Predictive Mechanism

    PubMed Central

    Eggert, Thomas

    2017-01-01

    Abstract The smooth pursuit eye movement system incorporates various control features enabling adaptation to specific tracking situations. In this work, we analyzed the interplay between two of these mechanisms: gain control and predictive pursuit. We tested human responses to high-frequency perturbations during step-ramp pursuit, as well as the pursuit of a periodically moving target. For the latter task, we found a nonlinear interaction between perturbation response and carrier acceleration. Responses to perturbations where the initial perturbation acceleration was contradirectional to carrier acceleration increased with carrier velocity, in a manner similar to that observed during step-ramp pursuit. In contrast, responses to perturbations with ipsidirectional initial perturbation and carrier acceleration were large for all carrier velocities. Modeling the pursuit system suggests that gain control and short-term prediction are separable elements. The observed effect may be explained by combining the standard gain control mechanism with a derivative-based short-term predictive mechanism. The nonlinear interaction between perturbation and carrier acceleration can be reproduced by assuming a signal saturation, which is acting on the derivative of the target velocity signal. Our results therefore argue for the existence of an internal estimate of target acceleration as a basis for a simple yet efficient short-term predictive mechanism. PMID:28560317

  7. Gain control of synaptic transfer from second- to third-order neurons of cockroach ocelli

    PubMed Central

    1996-01-01

    Synaptic transmission from second- to third-order neurons of cockroach ocelli occurs in an exponentially rising part of the overall sigmoidal characteristic curve relating pre- and postsynaptic voltage. Because of the nonlinear nature of the synapse, linear responses of second-order neurons to changes in ligh intensity are half-wave rectified, i.e., the response to a decrement in light is amplified whereas that to an increment in light is compressed. Here I report that the gain of synaptic transmission from second- to third-order neurons changes by ambient light levels and by wind stimulation applied to the cerci. Transfer characteristics of the synapse were studied by simultaneous intracellular recordings of second- and third-order neurons. Potential changes were evoked in second-order neurons by a sinusoidally modulated light with various mean luminances. With a decrease in the mean luminance (a) the mean membrane potential of second-order neurons was depolarized, (b) the synapse between the second- and third-order neurons operated in a steeper range of the exponential characteristic curve, where the gain to transmit modulatory signals was higher, and (c) the gain of third-order neurons to detect a decrement in light increased. Second-order neurons were depolarized when a wind or tactile stimulus was applied to various parts of the body including the cerci. During a wind-evoked depolarization, the synapse operated in a steeper range of the characteristic curve, which resulted in an increased gain of third-order neurons to detect light decrements. I conclude that the nonlinear nature of the synapse between the second- and third-order neurons provides an opportunity for an adjustment of gain to transmit signals of intensity change. The possibility that a similar gain control occurs in other visual systems and underlies a more advanced visual function, i.e., detection of motion, is discussed. PMID:8741734

  8. Extended Horizon Liftings for Periodic Gain Adjustments in Control Systems, and for Equalization of Communication Channels

    NASA Technical Reports Server (NTRS)

    Bayard, David S. (Inventor)

    1996-01-01

    Periodic gain adjustment in plants of irreducible order, n, or for equalization of communications channels is effected in such a way that the plant (system) appears to be minimum phase by choosing a horizon time N greater then n of liftings in periodic input and output windows Pu and Py, respectively, where N is an integer chosen to define the extent (length) of each of the windows Pu and Py, and n is the order of an irreducible input/output plant. The plant may be an electrical, mechanical or chemical system, in which case output tracking (OT) is carried out for feedback control or a communication channel, in which case input tracking (IT) is carried out. Conditions for OT are distinct from IT in terms of zero annihilation, namely for OT and of IT, where the OT conditions are intended for gain adjustments in the control system, and IT conditions are intended for equalization for communication channels.

  9. Spatially precise visual gain control mediated by a cholinergic circuit in the midbrain attention network

    PubMed Central

    Asadollahi, Ali; Knudsen, Eric I.

    2016-01-01

    A primary function of the midbrain stimulus selection network is to compute the highest-priority location for attention and gaze. Here we report the contribution of a specific cholinergic circuit to this computation. We functionally disconnected the tegmental cholinergic nucleus isthmi pars parvocellularis (Ipc) from the optic tectum (OT) in barn owls by reversibly blocking excitatory transmission in the Ipc. Focal blockade in the Ipc decreases the gain and spatial discrimination of OT units specifically for the locations represented by the visual receptive fields (VRFs) of the disconnected Ipc units, and causes OT VRFs to shift away from that location. The results demonstrate mechanisms by which this cholinergic circuit controls bottom-up stimulus competition and by which top-down signals can bias this competition, and they establish causal linkages between a particular circuit, gain control and dynamic shifts of VRFs. This circuit may perform the same function in all vertebrate species. PMID:27853140

  10. Decentralized PI/PID controllers based on gain and phase margin specifications for TITO processes.

    PubMed

    Maghade, D K; Patre, B M

    2012-07-01

    In this paper, a decentralized PI/PID controller design method based on gain and phase margin specifications for two-input-two-output (TITO) interactive processes is proposed. The decouplers are designed for systems to minimize the interaction between the loops, and the first order plus dead time (FOPDT) model is achieved for each decoupled subsystem based on the frequency response fitting. An independent PI/PID controller is designed for each reduced order decoupled subsystem to obtain the desired gain and phase margins, and the performance is verified on the original interactive system to show the effectiveness of the proposed design method for the general class of TITO systems. Simulation examples are incorporated to validate the usefulness of the presented algorithm. An experimentation is performed on the Level-Temperature reactor process to show the practical applicability of the proposed method for the interactive system. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

  11. Impacts of P-f & Q-V Droop Control on MicroGrids Transient Stability

    NASA Astrophysics Data System (ADS)

    Zhao-xia, Xiao; Hong-wei, Fang

    Impacts of P-f & Q-V droop control on MicroGrid transient stability was investigated with a wind unit of asynchronous generator in the MicroGrid. The system frequency stability was explored when the motor load starts and its load power changes, and faults of different types and different locations occurs. The simulations were done by PSCAD/EMTDC.

  12. The Neural Basis of Sustained and Transient Attentional Control in Young Adults with ADHD

    ERIC Educational Resources Information Center

    Banich, Marie T.; Burgess, Gregory C.; Depue, Brendan E.; Ruzic, Luka; Bidwell, L. Cinnamon; Hitt-Laustsen, Sena; Du, Yiping P.; Willcutt, Erik G.

    2009-01-01

    Differences in neural activation during performance on an attentionally demanding Stroop task were examined between 23 young adults with ADHD carefully selected to not be co-morbid for other psychiatric disorders and 23 matched controls. A hybrid blocked/single-trial design allowed for examination of more sustained vs. more transient aspects of…

  13. Phase control of the transient resonance of the automatic ball balancer

    NASA Astrophysics Data System (ADS)

    Michalczyk, Jerzy; Pakuła, Sebastian

    2016-05-01

    Hazards related to undesired increases of vibration amplitudes in transient resonance of vibroinsulated rotor systems with automatic ball balancer (ABB) are discussed in the paper. The application of the phase control method with taking into account the limited drive power is proposed for these amplitudes reduction. The high efficiency of this approach is indicated.

  14. The Neural Basis of Sustained and Transient Attentional Control in Young Adults with ADHD

    ERIC Educational Resources Information Center

    Banich, Marie T.; Burgess, Gregory C.; Depue, Brendan E.; Ruzic, Luka; Bidwell, L. Cinnamon; Hitt-Laustsen, Sena; Du, Yiping P.; Willcutt, Erik G.

    2009-01-01

    Differences in neural activation during performance on an attentionally demanding Stroop task were examined between 23 young adults with ADHD carefully selected to not be co-morbid for other psychiatric disorders and 23 matched controls. A hybrid blocked/single-trial design allowed for examination of more sustained vs. more transient aspects of…

  15. Robust Gain-Scheduled Fault Tolerant Control for a Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Shin, Jong-Yeob; Gregory, Irene

    2007-01-01

    This paper presents an application of robust gain-scheduled control concepts using a linear parameter-varying (LPV) control synthesis method to design fault tolerant controllers for a civil transport aircraft. To apply the robust LPV control synthesis method, the nonlinear dynamics must be represented by an LPV model, which is developed using the function substitution method over the entire flight envelope. The developed LPV model associated with the aerodynamic coefficient uncertainties represents nonlinear dynamics including those outside the equilibrium manifold. Passive and active fault tolerant controllers (FTC) are designed for the longitudinal dynamics of the Boeing 747-100/200 aircraft in the presence of elevator failure. Both FTC laws are evaluated in the full nonlinear aircraft simulation in the presence of the elevator fault and the results are compared to show pros and cons of each control law.

  16. Post-Stall Aerodynamic Modeling and Gain-Scheduled Control Design

    NASA Technical Reports Server (NTRS)

    Wu, Fen; Gopalarathnam, Ashok; Kim, Sungwan

    2005-01-01

    A multidisciplinary research e.ort that combines aerodynamic modeling and gain-scheduled control design for aircraft flight at post-stall conditions is described. The aerodynamic modeling uses a decambering approach for rapid prediction of post-stall aerodynamic characteristics of multiple-wing con.gurations using known section data. The approach is successful in bringing to light multiple solutions at post-stall angles of attack right during the iteration process. The predictions agree fairly well with experimental results from wind tunnel tests. The control research was focused on actuator saturation and .ight transition between low and high angles of attack regions for near- and post-stall aircraft using advanced LPV control techniques. The new control approaches maintain adequate control capability to handle high angle of attack aircraft control with stability and performance guarantee.

  17. Visualization of calcium transients controlling orientation of ciliary beat.

    PubMed

    Tamm, S L; Terasaki, M

    1994-06-01

    To image changes in intraciliary Ca controlling ciliary motility, we microinjected Ca Green dextran, a visible wavelength fluorescent Ca indicator, into eggs or two cell stages of the ctenophore Mnemiopsis leidyi. The embryos developed normally into free-swimming, approximately 0.5 mm cydippid larvae with cells and ciliary comb plates (approximately 100 microns long) loaded with the dye. Comb plates of larvae, like those of adult ctenophores, undergo spontaneous or electrically stimulated reversal of beat direction, triggered by Ca influx through voltage-sensitive Ca channels. Comb plates of larvae loaded with Ca Green dextran emit spontaneous or electrically stimulated fluorescent flashes along the entire length of their cilia, correlated with ciliary reversal. Fluorescence intensity peaks rapidly (34-50 ms), then slowly falls to resting level in approximately 1 s. Electrically stimulated Ca Green emissions often increase in steps to a maximum value near the end of the stimulus pulse train, and slowly decline in 1-2 s. In both spontaneous and electrically stimulated flashes, measurements at multiple sites along a single comb plate show that Ca Green fluorescence rises within 17 ms (1 video field) and to a similar relative extent above resting level from base to tip of the cilia. The decline of fluorescence intensity also begins simultaneously and proceeds at similar rates along the ciliary length. Ca-free sea water reversibly abolishes spontaneous and electrically stimulated Ca Green ciliary emissions as well as reversed beating. Calculations of Ca diffusion from the ciliary base show that Ca must enter the comb plate along the entire length of the ciliary membranes. The voltage-dependent Ca channels mediating changes in beat direction are therefore distributed over the length of the comb plate cilia. The observed rapid and virtually instantaneous Ca signal throughout the intraciliary space may be necessary for reprogramming the pattern of dynein activity

  18. Bilateral gain control; an “innate predisposition” for all sorts of things

    PubMed Central

    Wilkinson, Nicholas; Metta, Giorgio

    2014-01-01

    Empirical studies have revealed remarkable perceptual organization in neonates. Newborn behavioral distinctions have often been interpreted as implying functionally specific modular adaptations, and are widely cited as evidence supporting the nativist agenda. In this theoretical paper, we approach newborn perception and attention from an embodied, developmental perspective. At the mechanistic level, we argue that a generative mechanism based on mutual gain control between bilaterally corresponding points may underly a number of functionally defined “innate predispositions” related to spatial-configural perception. At the computational level, bilateral gain control implements beamforming, which enables spatial-configural tuning at the front end sampling stage. At the psychophysical level, we predict that selective attention in newborns will favor contrast energy which projects to bilaterally corresponding points on the neonate subject's sensor array. The current work extends and generalizes previous work to formalize the bilateral correlation model of newborn attention at a high level, and demonstrate in minimal agent-based simulations how bilateral gain control can enable a simple, robust and “social” attentional bias. PMID:24611045

  19. A wavelet neural network based on genetic algorithm and its application to gain scheduling flight control

    NASA Astrophysics Data System (ADS)

    Sun, Xun; Zhang, Weiguo; Yin, Wei; Li, Aijun

    2006-11-01

    As enlarging of the flight envelop, the aerodynamic derivative of the airplane varies enormous. The gain scheduling method is usually used to deal with it. But the workload is enormously and the stability is difficulty to be assured. To solve the above problem, a large envelope wavelet neural network gain scheduling flight control law design method based on genetic algorithm is presented in this paper. Wavelet has good time accuracy in high frequency-domain and the good frequency accuracy in low frequency-domain. Neural network has the self-learning character. In this method, wavelet function instead of Sigmoid function as the excitation function. So the two merits are merged and the high nonlinear function approximation capability could be achieved. In order to obtain higher accuracy and faster speed, genetic algorithm is used to optimize the parameters of the wavelet neural network. This method is used in design the large envelope gain scheduling flight control law. This simulation results show that good control capability could be achieved in large envelope and the system is still stable when modeling error is 20%. In the situation of 20% modeling error, the maximum overshoot is only 12m and it is 35% of the maximum overshoot using normal method.

  20. Presynaptic gain control drives sweet and bitter taste integration in Drosophila.

    PubMed

    Chu, Bonnie; Chui, Vincent; Mann, Kevin; Gordon, Michael D

    2014-09-08

    The sense of taste is critical in determining the nutritional suitability of foods. Sweet and bitter are primary taste modalities in mammals, and their behavioral relevance is similar in flies. Sweet taste drives the appetitive response to energy sources, whereas bitter taste drives avoidance of potential toxins and also suppresses the sweet response [1, 2]. Despite their importance to survival, little is known about the neural circuit mechanisms underlying integration of sweet and bitter taste. Here, we describe a presynaptic gain control mechanism in Drosophila that differentially affects sweet and bitter taste channels and mediates integration of these opposing stimuli. Gain control is known to play an important role in fly olfaction, where GABAB receptor (GABABR) mediates intra- and interglomerular presynaptic inhibition of sensory neuron output [3-5]. In the taste system, we find that gustatory receptor neurons (GRNs) responding to sweet compounds express GABABR, whereas those that respond to bitter do not. GABABR mediates presynaptic inhibition of calcium responses in sweet GRNs, and both sweet and bitter stimuli evoke GABAergic neuron activity in the vicinity of GRN axon terminals. Pharmacological blockade and genetic reduction of GABABR both lead to increased sugar responses and decreased suppression of the sweet response by bitter compounds. We propose a model in which GABA acts via GABABR to expand the dynamic range of sweet GRNs through presynaptic gain control and suppress the output of sweet GRNs in the presence of opposing bitter stimuli. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Electric-field-assisted gain control in a high-power picosecond laser diode

    NASA Astrophysics Data System (ADS)

    Vainshtein, Sergey N.; Yuferev, Valentin; Kostamovaara, Juha T.

    2003-03-01

    A laser diode structure has lately been reported that is capable of generating high-power picosecond optical pulses (~ 50 W / 20 ps) in the near-infrared range for laser radars and other applications. The physical idea consists of achieving fast gain control through the effect of a transverse electric field on the carrier distribution across the active region, which controls the local gain and local absorption at each instant. The mechanism of field-assisted gain control, which has so far been formulated only as a qualitative idea, is justified in this work by simulations of the carrier transport and laser response using the semiconductor device simulator "Atlas" (Silvaco Inc.). A simplified approach is adopted which replaces photon-assisted carrier transport with carrier penetration over the lowered potential barrier. This points to reasonably good agreement between the experimental and simulation results for picosecond pulse generation, provided that the carrier mobilities are assumed to be higher than those in the heavily doped semiconductor structure by a factor of ~ 4. One important conclusion is that comprehensive modelling of the operation of the experimental laser diode is not possible without considering photon-assisted carrier transport, which has not been studied so far at very high carrier densities (exceeding the transparency concentration).

  2. Modeling lateral geniculate nucleus response with contrast gain control. Part 2: analysis.

    PubMed

    Cope, Davis; Blakeslee, Barbara; McCourt, Mark E

    2014-02-01

    Cope et al. [J. Opt. Soc. Am. A30, 2401 (2013)] proposed a class of models for lateral geniculate nucleus (LGN) ON-cell behavior consisting of a linear response with divisive normalization by local stimulus contrast. Here, we analyze a specific model with the linear response defined by a difference-of-Gaussians filter, and a circular Gaussian for the gain pool weighting function. For sinusoidal grating stimuli, the parameter region for bandpass behavior of the linear response is determined, and the gain control response is shown to act as a switch (changing from "off" to "on" with increasing spatial frequency). It is also shown that large gain pools stabilize the optimal spatial frequency of the total nonlinear response at a fixed value independent of contrast and stimulus magnitude. Under- and super-saturation, as well as contrast saturation, occur as typical effects of stimulus magnitude. For circular spot stimuli, it is shown that large gain pools stabilize the spot size that yields the maximum response.

  3. Control Systems Engineering for Optimizing a Prenatal Weight Gain Intervention to Regulate Infant Birth Weight

    PubMed Central

    Downs, Danielle Symons; Dong, Yuwen; Rivera, Daniel E.

    2014-01-01

    Objectives. We used dynamical systems modeling to describe how a prenatal behavioral intervention that adapts to the needs of each pregnant woman may help manage gestational weight gain and alter the obesogenic intrauterine environment to regulate infant birth weight. Methods. This approach relies on integrating mechanistic energy balance, theory of planned behavior, and self-regulation models to describe how internal processes can be impacted by intervention dosages, and reinforce positive outcomes (e.g., healthy eating and physical activity) to moderate gestational weight gain and affect birth weight. Results. A simulated hypothetical case study from MATLAB with Simulink showed how, in response to our adaptive intervention, self-regulation helps adjust perceived behavioral control. This, in turn, changes the woman’s intention and behavior with respect to healthy eating and physical activity during pregnancy, affecting gestational weight gain and infant birth weight. Conclusions. This article demonstrates the potential for real-world applications of an adaptive intervention to manage gestational weight gain and moderate infant birth weight. This model could be expanded to examine the long-term sustainable impacts of an intervention that varies according to the participant’s needs on maternal postpartum weight retention and child postnatal eating behavior. PMID:24832411

  4. Adaptive gain control for spike-based map communication in a neuromorphic vision system.

    PubMed

    Meng, Yicong; Shi, Bertram E

    2008-06-01

    To support large numbers of model neurons, neuromorphic vision systems are increasingly adopting a distributed architecture, where different arrays of neurons are located on different chips or processors. Spike-based protocols are used to communicate activity between processors. The spike activity in the arrays depends on the input statistics as well as internal parameters such as time constants and gains. In this paper, we investigate strategies for automatically adapting these parameters to maintain a constant firing rate in response to changes in the input statistics. We find that under the constraint of maintaining a fixed firing rate, a strategy based upon updating the gain alone performs as well as an optimal strategy where both the gain and the time constant are allowed to vary. We discuss how to choose the time constant and propose an adaptive gain control mechanism whose operation is robust to changes in the input statistics. Our experimental results on a mobile robotic platform validate the analysis and efficacy of the proposed strategy.

  5. Binocular combination of phase and contrast explained by a gain-control and gain-enhancement model

    PubMed Central

    Ding, Jian; Klein, Stanley A.; Levi, Dennis M.

    2013-01-01

    We investigated suprathreshold binocular combination, measuring both the perceived phase and perceived contrast of a cyclopean sine wave. We used a paradigm adapted from Ding and Sperling (2006, 2007) to measure the perceived phase by indicating the apparent location (phase) of the dark trough in the horizontal cyclopean sine wave relative to a black horizontal reference line, and we used the same stimuli to measure perceived contrast by matching the binocular combined contrast to a standard contrast presented to one eye. We found that under normal viewing conditions (high contrast and long stimulus duration), perceived contrast is constant, independent of the interocular contrast ratio and the interocular phase difference, while the perceived phase shifts smoothly from one eye to the other eye depending on the contrast ratios. However, at low contrasts and short stimulus durations, binocular combination is more linear and contrast summation is phase-dependent. To account for phase-dependent contrast summation, we incorporated a fusion remapping mechanism into our model, using disparity energy to shift the monocular phases towards the cyclopean phase in order to align the two eyes' images through motor/sensory fusion. The Ding-Sperling model with motor/sensory fusion mechanism gives a reasonable account of the phase dependence of binocular contrast combination and can account for either the perceived phase or the perceived contrast of a cyclopean sine wave separately; however it requires different model parameters for the two. However, when fit to both phase and contrast data simultaneously, the Ding-Sperling model fails. Incorporating interocular gain enhancement into the model results in a significant improvement in fitting both phase and contrast data simultaneously, successfully accounting for both linear summation at low contrast energy and strong nonlinearity at high contrast energy. PMID:23397038

  6. Binocular combination of phase and contrast explained by a gain-control and gain-enhancement model.

    PubMed

    Ding, Jian; Klein, Stanley A; Levi, Dennis M

    2013-02-08

    We investigated suprathreshold binocular combination, measuring both the perceived phase and perceived contrast of a cyclopean sine wave. We used a paradigm adapted from Ding and Sperling (2006, 2007) to measure the perceived phase by indicating the apparent location (phase) of the dark trough in the horizontal cyclopean sine wave relative to a black horizontal reference line, and we used the same stimuli to measure perceived contrast by matching the binocular combined contrast to a standard contrast presented to one eye. We found that under normal viewing conditions (high contrast and long stimulus duration), perceived contrast is constant, independent of the interocular contrast ratio and the interocular phase difference, while the perceived phase shifts smoothly from one eye to the other eye depending on the contrast ratios. However, at low contrasts and short stimulus durations, binocular combination is more linear and contrast summation is phase-dependent. To account for phase-dependent contrast summation, we incorporated a fusion remapping mechanism into our model, using disparity energy to shift the monocular phases towards the cyclopean phase in order to align the two eyes' images through motor/sensory fusion. The Ding-Sperling model with motor/sensory fusion mechanism gives a reasonable account of the phase dependence of binocular contrast combination and can account for either the perceived phase or the perceived contrast of a cyclopean sine wave separately; however it requires different model parameters for the two. However, when fit to both phase and contrast data simultaneously, the Ding-Sperling model fails. Incorporating interocular gain enhancement into the model results in a significant improvement in fitting both phase and contrast data simultaneously, successfully accounting for both linear summation at low contrast energy and strong nonlinearity at high contrast energy.

  7. Active control of the forced and transient response of a finite beam. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Post, John T.

    1990-01-01

    Structural vibrations from a point force are modelled on a finite beam. This research explores the theoretical limit on controlling beam vibrations utilizing another point source as an active controller. Three different types of excitation are considered, harmonic, random, and transient. For harmonic excitation, control over the entire beam length is possible only when the excitation frequency is near a resonant frequency of the beam. Control over a subregion may be obtained even between resonant frequencies at the cost of increasing the vibration outside of the control region. For random excitation, integrating the expected value of the displacement squared over the required interval, is shown to yield the identical cost function as obtained by integrating the cost function for harmonic excitation over all excitation frequencies. As a result, it is always possible to reduce the cost function for random excitation whether controlling the entire beam or just a subregion, without ever increasing the vibration outside the region in which control is desired. The last type of excitation considered is a single, transient pulse. The form of the controller is specified as either one or two delayed pulses, thus constraining the controller to be casual. The best possible control is examined while varying the region of control and the controller location. It is found that control is always possible using either one or two control pulses.

  8. Vehicle rollover avoidance by application of gain-scheduled LQR controllers using state observers

    NASA Astrophysics Data System (ADS)

    Dal Poggetto, Vinicius F.; Serpa, Alberto L.

    2016-02-01

    Many researches have been conducted in the area of control applied to vehicle dynamics, aiming at reducing the possibility of the occurrence of the type of accident known as rollover. In this research, based on a common nonlinear model and its linearisation, a method for properly selecting matrices for solving the Riccati equation considering different speeds was proposed. The method showed in which ways speed really influences the choice of controller gains. By developing the dynamic equations for the yaw- and roll-coupled motions and modelling of controllers and state observers, it is possible to compare the efficacy of this control strategy using both linear and nonlinear simulations using Matlab. Significant results were obtained regarding the reduction of the rollover coefficient for a double-lane change manoeuvre at different speeds, thus indicating advantages of using this controller in practical cases.

  9. Static control logic for microfluidic devices using pressure-gain valves

    NASA Astrophysics Data System (ADS)

    Weaver, James A.; Melin, Jessica; Stark, Don; Quake, Stephen R.; Horowitz, Mark A.

    2010-03-01

    Microfluidic technology has developed greatly in recent years, enabling multiple analysis systems to be placed on a microfluidic chip. However, microfluidic large-scale integration of control elements analogous to those achieved in the microelectronics industry is still a challenge. We present an integrated microfluidic valve, compatible with standard soft-lithography processes, which has a pressure gain much greater than unity. We show that this enables integration of fully static digital control logic and state storage directly on-chip, ultimately enabling microfluidic-state machines to be designed. Outputs from this digital control logic can then be used to control traditional analyte flow valves. This strategy enables much of the bulky external hardware at present used to control pneumatically driven microfluidic chips in the laboratory to be transferred onto the microfluidic chip, which drastically reduces the required number of external chip connections.

  10. H∞ and H2 control of multi-agent systems with transient performance improvement

    NASA Astrophysics Data System (ADS)

    Wang, Jingyao; Duan, Zhisheng; Zhao, Yu; Qin, Guozheng; Yan, Yingxin

    2013-12-01

    In this paper, the H∞ consensus control and H2 robust control synthesised with transient performance problems are investigated for a group of autonomous agents with linear or linearised dynamics. Based on the relative information between neighbouring agents and a subset of absolute information of the agents, distributed controllers are proposed for both H∞ and H2 cases. Compared with the existing protocols, the one presented in this article focuses on improving the transient performance of the consensus problem. By using the tools from matrix analysis and robust control theory, conditions for the existence of controllers to those problems under an undirected communication topology are provided. Then, it is shown that the H2 performance limit of uncertain systems under a distributed controller equals the minimum H∞ consensus index synthesised with transient performance of a single agent by using a state feedback controller, independent of the communication topology. Finally, a simulation example as an application in Raptor-90 helicopter is proposed to illustrate the effectiveness of the theoretical results.

  11. Tonic Firing Rate Controls Dendritic Ca2+ Signaling and Synaptic Gain in Substantia Nigra Dopamine Neurons

    PubMed Central

    Hage, Travis A.

    2015-01-01

    Substantia nigra dopamine neurons fire tonically resulting in action potential backpropagation and dendritic Ca2+ influx. Using Ca2+ imaging in acute mouse brain slices, we find a surprisingly steep relationship between tonic firing rate and dendritic Ca2+. Increasing the tonic rate from 1 to 6 Hz generated Ca2+ signals up to fivefold greater than predicted by linear summation of single spike-evoked Ca2+-transients. This “Ca2+ supralinearity” was produced largely by depolarization of the interspike voltage leading to activation of subthreshold Ca2+ channels and was present throughout the proximal and distal dendrites. Two-photon glutamate uncaging experiments show somatic depolarization enhances NMDA receptor-mediated Ca2+ signals >400 μm distal to the soma, due to unusually tight electrotonic coupling of the soma to distal dendrites. Consequently, we find that fast tonic firing intensifies synaptically driven burst firing output in dopamine neurons. These results show that modulation of background firing rate precisely tunes dendritic Ca2+ signaling and provides a simple yet powerful mechanism to dynamically regulate the gain of synaptic input. PMID:25855191

  12. A novel analog power supply for gain control of the Multi-Pixel Photon Counter (MPPC)

    NASA Astrophysics Data System (ADS)

    Li, Zhengwei; Liu, Congzhan; Xu, Yupeng; Yan, Bo; Li, Yanguo; Lu, Xuefeng; Li, Xufang; Zhang, Shuo; Chang, Zhi; Li, Jicheng; Gao, He; Zhang, Yifei; Zhao, Jianling

    2017-04-01

    Silicon Photo-Multipliers (SiPM) are regarded as novel photo-detectors to replace conventional Photo-Multiplier Tubes (PMTs). However, the breakdown voltage dependence on the ambient temperature results in a gain variation of ∼3%/°C. This severely limits the application of this device in experiments with wide range of operating temperature, especially in space missions. An experimental setup was established to investigate the temperature and bias voltage dependence of gain for the Multi-Pixel Photon Counter (MPPC). The gain and breakdown voltage dependence on operating temperature of an MPPC can be approximated by a linear function, which is similar to the behavior of a zener diode. The measured temperature coefficient of the breakdown voltage is (59.4±0.4 mV)/°C. According to this fact, an analog power supply based on two zener diodes and an operational amplifier was designed with a positive temperature coefficient. The measured temperature dependence for the designed power supply is between 63.65-64.61 mV/°C at different output voltages. The designed power supply can bias the MPPC at an over-voltage with a temperature variation of ∼5 mV/°C. The gain variation of the MPPC biased at over-voltage of 2 V was reduced from 2.8 % / ° C to 0.3 % / ° C when biased the MPPC with the designed power supply for gain control. Detailed design and performance of the analog power supply in the temperature range from - 42.7 ° C to 20.9 ° C will be discussed in this paper.

  13. Excess Weight Gain Prevention in Adolescents: Three-year Outcome following a Randomized-Controlled Trial

    PubMed Central

    Tanofsky-Kraff, Marian; Shomaker, Lauren B.; Wilfley, Denise E.; Young, Jami F.; Sbrocco, Tracy; Stephens, Mark; Brady, Sheila M.; Galescu, Ovidiu; Demidowich, Andrew; Olsen, Cara H.; Kozlosky, Merel; Reynolds, James C.; Yanovski, Jack A.

    2016-01-01

    Objective Interpersonal psychotherapy (IPT) prevents weight gain in adults with obesity and binge-eating-disorder, and is especially effective among those with increased psychosocial problems. However, IPT was not superior to health-education (HE) to prevent excess weight gain at 1-year follow-up in 113 adolescent girls at high-risk for excess weight gain because of loss-of-control (LOC)-eating and high BMI (kg/m2) (Tanofsky-Kraff et al., 2014). Method Participants from the original trial were re-contacted 3-years later for assessment. At baseline, adolescent- and parent-reported social-adjustment problems and trait-anxiety were evaluated. At baseline and follow-ups, BMIz and adiposity by dual-energy X-ray absorptiometry were obtained. Results Nearly 60% were re-assessed at 3-years, with no group differences in participation (ps≥.70). Consistent with 1-year, there was no main effect of group on change in BMIz/adiposity (ps≥.18). In exploratory analyses, baseline social-adjustment problems and trait-anxiety moderated outcome (ps<.01). Among girls with high self-reported baseline social-adjustment problems or anxiety, IPT, compared to HE, was associated with the steepest declines in BMIz (p<.001). For adiposity, girls with high- or low-anxiety in HE, and girls with low-anxiety in IPT experienced gains (ps≤.03), while girls in IPT with high-anxiety stabilized. Parent-reports yielded complementary findings. Conclusion In obesity-prone adolescent girls, IPT was not superior to HE in preventing excess weight gain at 3-years. Consistent with theory, exploratory analyses suggested that IPT was associated with improvements in BMIz over 3-years among youth with high social-adjustment problems or trait-anxiety. Future studies should test the efficacy of IPT for obesity prevention among at-risk girls with social-adjustment problems and/or anxiety. PMID:27808536

  14. Excess weight gain prevention in adolescents: Three-year outcome following a randomized controlled trial.

    PubMed

    Tanofsky-Kraff, Marian; Shomaker, Lauren B; Wilfley, Denise E; Young, Jami F; Sbrocco, Tracy; Stephens, Mark; Brady, Sheila M; Galescu, Ovidiu; Demidowich, Andrew; Olsen, Cara H; Kozlosky, Merel; Reynolds, James C; Yanovski, Jack A

    2017-03-01

    Interpersonal psychotherapy (IPT) prevents weight gain in adults with obesity and binge-eating-disorder, and is especially effective among those with increased psychosocial problems. However, IPT was not superior to health education (HE) to prevent excess weight gain at 1-year follow-up in 113 adolescent girls at high-risk for excess weight gain because of loss-of-control eating and high body mass index (BMI; kg/m2; Tanofsky-Kraff et al., 2014). Participants from the original trial were recontacted 3 years later for assessment. At baseline, adolescent- and parent-reported social-adjustment problems and trait anxiety were evaluated. At baseline and follow-ups, BMIz and adiposity by dual-energy x-ray absorptiometry were obtained. Nearly 60% were reassessed at 3 years, with no group differences in participation (ps ≥ .70). Consistent with 1 year, there was no main effect of group on change in BMIz/adiposity (ps ≥ .18). In exploratory analyses, baseline social-adjustment problems and trait-anxiety moderated outcome (ps < .01). Among girls with high self-reported baseline social-adjustment problems or anxiety, IPT, compared to HE, was associated with the steepest declines in BMIz (p < .001). For adiposity, girls with high or low anxiety in HE and girls with low anxiety in IPT experienced gains (ps ≤ .03), while girls in IPT with high anxiety stabilized. Parent-reports yielded complementary findings. In obesity-prone adolescent girls, IPT was not superior to HE in preventing excess weight gain at 3 years. Consistent with theory, exploratory analyses suggested that IPT was associated with improvements in BMIz over 3 years among youth with high social-adjustment problems or trait anxiety. Future studies should test the efficacy of IPT for obesity prevention among at-risk girls with social-adjustment problems and/or anxiety. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  15. Distributed adaptive output consensus control of second-order systems containing unknown non-linear control gains

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Wang, Chaoli; Du, Qinghui; Cai, Xuan

    2016-10-01

    In this paper, we address the output consensus problem of tracking a desired trajectory for a group of second-order agents on a directed graph with a fixed topology. Each agent is modelled by a second-order non-linear system with unknown non-linear dynamics and unknown non-linear control gains. Only a subset of the agents is given access to the desired trajectory information directly. A distributed adaptive consensus protocol driving all agents to track the desired trajectory is presented using the backstepping technique and approximation technique of Fourier series (FSs). The FS structure is taken not only for tracking the non-linear dynamics but also the unknown portion in the controller design procedure, which can avoid virtual controllers containing the uncertain terms. Stability analysis and parameter convergence of the proposed algorithm are conducted based on the Lyapunov theory and the algebraic graph theory. It is also demonstrated that arbitrary small tracking errors can be achieved by appropriately choosing design parameters. Though the proposed work is applicable for second-order non-linear systems containing unknown non-linear control gains, the proposed controller design can be easily extended to higher-order non-linear systems containing unknown non-linear control gains. Simulation results show the effectiveness of the proposed schemes.

  16. Design of Constant Gain Dissipative Controllers for Eigensystem Assignment in Passive Systems

    NASA Technical Reports Server (NTRS)

    Maghami, Peiman G.; Gupta, Sandeep

    1998-01-01

    Partial eigensystem assignment with output feedback can lead to an unstable closed-loop system. However, output feedback with passive linear time-invariant systems, such as flexible space structures, is guaranteed to be stable if the controller is dissipative. This paper presents a novel approach for synthesis of dissipative output feedback gain matrices for assigning a selected number of closed-loop poles. Dissipativity of a gain matrix is known to be equivalent to positive semidefiniteness of the symmetric part of the matrix. A sequential procedure is presented to assign one self-conjugate pair of closed-loop eigenvalues at each step using dissipative output feedback gain matrices, while ensuring that the eigenvalues assigned in the previous steps are not disturbed. The problem of assigning one closed-loop pair is reduced to a constrained solution of a system of quadratic equations, and necessary and sufficient conditions for the existence of a solution are presented. A minimax approach is presented for determining parameters which satisfy these conditions. This method can assign as many closed-loop system poles as the number of control inputs. A numerical example of damping enhancement for a flexible structure is presented to demonstrate the approach.

  17. Feedback control of transient energy growth in subcritical plane Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Martinelli, Fulvio; Quadrio, Maurizio; McKernan, John; Whidborne, James F.

    Subcritical flows may experience large transient perturbation energy amplifications, that could trigger nonlinear mechanisms and eventually lead to transition to turbulence. In plane Poiseuille flow, controlled via wall blowing/suction with zero net mass flux, optimal and robust control theory has been recently applied to a state-space representation of the Orr-Sommerfeld-Squire equations, leading to reduced transient growth as well as increased transition thresholds. However, to date no feedback control law has been found that is capable of ensuring the closed-loop Poiseuille flow to be monotonically stable. The present paper addresses first the possibility of complete feedback suppression of the transient growth mechanism in subcritical plane Poiseuille flow when wall actuation is available, and demonstrates that closed-loop monotonic stability cannot be achieved in such a case. Secondly, a Linear Matrix Inequality (LMI) technique is employed to design controllers that directly target the energy growth mechanism. The performance of such control laws is quantified by using Direct Numerical Simulations of transitional plane Poiseuille flow, and the increase in transition thresholds due to the control action is assessed.

  18. SO2 control by electric utilities: What are the gains from trade?

    SciTech Connect

    Burtraw, D.; Carlson, C.; Cropper, M.; Palmer, K.

    1997-12-31

    Title IV of the 1990 Clean Air Act Amendments, which establishes a market for transferrable sulfur dioxide discharge permits (SO{sub 2} allowances), has been hailed by economists as a triumph of economic incentives over command and control regulation. The gains from using economic incentives are a reduction in the costs of pollution control: Firms operating at high marginal pollution abatement costs are supposed to purchase the right to emit SO{sub 2} from firms operating at low marginal abatement costs, with cost savings resulting as abatement shifts from high-to-low marginal cost firms. flow large are the potential cost savings from SO{sub 2} allowance trading? How many of these gains have been realized during the first year of operation of the allowance market? To answer these questions requires estimates of the marginal cost of abating SO{sub 2} emissions for all generating units affected by Title IV of the CAAA. While there have been various engineering cost estimates of abatement costs and of the gains from trade, there have been no estimates based on the actual responses of plants to changes in emissions standards and input prices. The purpose of this paper is to provide such estimates. To provide econometric estimates of marginal abatement costs and the potential gains from trade we have assembled a database covering the years 1985-94, that contains over 800 coal-fired generating units. In 1994 these units produced 87 percent of the SO{sub 2} emissions generated by all coal-fired power plants in the United States and accounted for 77 percent of the heat input consumed by all coal-fired power plants. For each generating unit we have annual observations on labor, generating capital, abatement capital, and inputs of high- and low-sulfur coal. We also know the emissions standard facing the generator, as well as its output and mean annual emissions rate. Data on input prices complete the dataset.

  19. A small-gain method for integrated guidance and control in terminal phase of reentry

    NASA Astrophysics Data System (ADS)

    Yan, Han; Tan, Shuping; He, Yingzi

    2017-03-01

    The guidance and control systems of reentry vehicles are usually designed separately and then integrated, but the scheme can be argued that synergistic relationships between the two subsystems are not fully exploited. In order to improve the performance of reusable launch vehicles (RLVs), this paper proposes an integrated guidance and control law for approach and landing of a RLV. According to the idea of reference-trajectory guidance, the angle of attack and bank angle commands are designed using sliding mode control (SMC) method to make the reference-trajectory tacking error converge into a small neighborhood of zero. An integrated guidance and control (IGC) law is developed utilizing generalized small-gain theorem to enforce the commands, and theoretical analysis shows that the law can guarantee the stability of the overall system. The Monte Carlo simulation confirms the effectiveness of the proposed design approach.

  20. ATC Enhancement Considering Transient Stability by Optimal Power Flow Control Using UPFC

    NASA Astrophysics Data System (ADS)

    Masuta, Taisuke; Motoki, Hiroaki; Yokoyama, Akihiko

    With recent development of power electronics technology, power system stability enhancement and optimal power flow control by using Flexible AC Transmission System (FACTS) devices have so far been studied. The FACTS devices to relieve multiple constraints can also make it possible to enhance Available Transfer Capability (ATC) without construction of new transmission lines. In this paper, a new method for improving transient stability by Unified Power Flow Controller (UPFC) is proposed. Then the proposed method is applied to an OPF control method by using UPFC for relieving multiple constraints. The new OPF method is used for enhancement of ATC taking into account Transient stability constraints as well as overload and steady-state stability constraints. The OPF problem is formulated to minimize total capacity of inverters of UPFC. Effectiveness of the proposed method is shown by numerical examples for IEEJ East-10-machine test system.

  1. The inhibitory microcircuit of the substantia nigra provides feedback gain control of the basal ganglia output

    PubMed Central

    Brown, Jennifer; Pan, Wei-Xing; Dudman, Joshua Tate

    2014-01-01

    Dysfunction of the basal ganglia produces severe deficits in the timing, initiation, and vigor of movement. These diverse impairments suggest a control system gone awry. In engineered systems, feedback is critical for control. By contrast, models of the basal ganglia highlight feedforward circuitry and ignore intrinsic feedback circuits. In this study, we show that feedback via axon collaterals of substantia nigra projection neurons control the gain of the basal ganglia output. Through a combination of physiology, optogenetics, anatomy, and circuit mapping, we elaborate a general circuit mechanism for gain control in a microcircuit lacking interneurons. Our data suggest that diverse tonic firing rates, weak unitary connections and a spatially diffuse collateral circuit with distinct topography and kinetics from feedforward input is sufficient to implement divisive feedback inhibition. The importance of feedback for engineered systems implies that the intranigral microcircuit, despite its absence from canonical models, could be essential to basal ganglia function. DOI: http://dx.doi.org/10.7554/eLife.02397.001 PMID:24849626

  2. The effects of control-display gain on performance of race car drivers in an isometric braking task.

    PubMed

    de Winter, J C F; de Groot, S

    2012-12-01

    To minimise lap times during car racing, it is important to build up brake forces rapidly and maintain precise control. We examined the effect of the amplification factor (gain) between brake pedal force and a visually represented output value on a driver's ability to track a target value. The test setup was a formula racing car cockpit fitted with an isometric brake pedal. Thirteen racing drivers performed tracking tasks with four control-display gains and two target functions: a step function (35 trials per gain) and a multisine function (15 trials per gain). The control-display gain had only minor effects on root mean-squared error between output value and target value, but it had large effects on build-up speed, overshoot, within-participants variability, and self-reported physical load. The results confirm the hypothesis that choosing an optimum gain involves balancing stability against physical effort.

  3. Improving transient performance of adaptive control architectures using frequency-limited system error dynamics

    NASA Astrophysics Data System (ADS)

    Yucelen, Tansel; De La Torre, Gerardo; Johnson, Eric N.

    2014-11-01

    Although adaptive control theory offers mathematical tools to achieve system performance without excessive reliance on dynamical system models, its applications to safety-critical systems can be limited due to poor transient performance and robustness. In this paper, we develop an adaptive control architecture to achieve stabilisation and command following of uncertain dynamical systems with improved transient performance. Our framework consists of a new reference system and an adaptive controller. The proposed reference system captures a desired closed-loop dynamical system behaviour modified by a mismatch term representing the high-frequency content between the uncertain dynamical system and this reference system, i.e., the system error. In particular, this mismatch term allows the frequency content of the system error dynamics to be limited, which is used to drive the adaptive controller. It is shown that this key feature of our framework yields fast adaptation without incurring high-frequency oscillations in the transient performance. We further show the effects of design parameters on the system performance, analyse closeness of the uncertain dynamical system to the unmodified (ideal) reference system, discuss robustness of the proposed approach with respect to time-varying uncertainties and disturbances, and make connections to gradient minimisation and classical control theory. A numerical example is provided to demonstrate the efficacy of the proposed architecture.

  4. How does a specific learning and memory system in the mammalian brain gain control of behavior?

    PubMed

    McDonald, Robert J; Hong, Nancy S

    2013-11-01

    This review addresses a fundamental, yet poorly understood set of issues in systems neuroscience. The issues revolve around conceptualizations of the organization of learning and memory in the mammalian brain. One intriguing, and somewhat popular, conceptualization is the idea that there are multiple learning and memory systems in the mammalian brain and they interact in different ways to influence and/or control behavior. This approach has generated interesting empirical and theoretical work supporting this view. One issue that needs to be addressed is how these systems influence or gain control of voluntary behavior. To address this issue, we clearly specify what we mean by a learning and memory system. We then review two types of processes that might influence which memory system gains control of behavior. One set of processes are external factors that can affect which system controls behavior in a given situation including task parameters like the kind of information available to the subject, types of training experience, and amount of training. The second set of processes are brain mechanisms that might influence what memory system controls behavior in a given situation including executive functions mediated by the prefrontal cortex; switching mechanisms mediated by ascending neurotransmitter systems, the unique role of the hippocampus during learning. The issue of trait differences in control of different learning and memory systems will also be considered in which trait differences in learning and memory function are thought to potentially emerge from differences in level of prefrontal influence, differences in plasticity processes, differences in ascending neurotransmitter control, differential access to effector systems like motivational and motor systems. Finally, we present scenarios in which different mechanisms might interact. This review was conceived to become a jumping off point for new work directed at understanding these issues. The outcome of

  5. Redesign of a Variable-Gain Output Feedback Longitudinal Controller Flown on the High-Alpha Research Vehicle (HARV)

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1998-01-01

    This paper describes a redesigned longitudinal controller that flew on the High-Alpha Research Vehicle (HARV) during calendar years (CY) 1995 and 1996. Linear models are developed for both the modified controller and a baseline controller that was flown in CY 1994. The modified controller was developed with three gain sets for flight evaluation, and several linear analysis results are shown comparing the gain sets. A Neal-Smith flying qualities analysis shows that performance for the low- and medium-gain sets is near the level 1 boundary, depending upon the bandwidth assumed, whereas the high-gain set indicates a sensitivity problem. A newly developed high-alpha Bode envelope criterion indicates that the control system gains may be slightly high, even for the low-gain set. A large motion-base simulator in the United Kingdom was used to evaluate the various controllers. Desired performance, which appeared to be satisfactory for flight, was generally met with both the low- and medium-gain sets. Both the high-gain set and the baseline controller were very sensitive, and it was easy to generate pilot-induced oscillation (PIO) in some of the target-tracking maneuvers. Flight target-tracking results varied from level 1 to level 3 and from no sensitivity to PIO. These results were related to pilot technique and whether actuator rate saturation was encountered.

  6. Interaural level difference-dependent gain control and synaptic scaling underlying binaural computation.

    PubMed

    Xiong, Xiaorui R; Liang, Feixue; Li, Haifu; Mesik, Lukas; Zhang, Ke K; Polley, Daniel B; Tao, Huizhong W; Xiao, Zhongju; Zhang, Li I

    2013-08-21

    Binaural integration in the central nucleus of inferior colliculus (ICC) plays a critical role in sound localization. However, its arithmetic nature and underlying synaptic mechanisms remain unclear. Here, we showed in mouse ICC neurons that the contralateral dominance is created by a "push-pull"-like mechanism, with contralaterally dominant excitation and more bilaterally balanced inhibition. Importantly, binaural spiking response is generated apparently from an ipsilaterally mediated scaling of contralateral response, leaving frequency tuning unchanged. This scaling effect is attributed to a divisive attenuation of contralaterally evoked synaptic excitation onto ICC neurons with their inhibition largely unaffected. Thus, a gain control mediates the linear transformation from monaural to binaural spike responses. The gain value is modulated by interaural level difference (ILD) primarily through scaling excitation to different levels. The ILD-dependent synaptic scaling and gain adjustment allow ICC neurons to dynamically encode interaural sound localization cues while maintaining an invariant representation of other independent sound attributes. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Active Control of the Forced and Transient Response of a Finite Beam. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Post, John Theodore

    1989-01-01

    When studying structural vibrations resulting from a concentrated source, many structures may be modelled as a finite beam excited by a point source. The theoretical limit on cancelling the resulting beam vibrations by utilizing another point source as an active controller is explored. Three different types of excitation are considered, harmonic, random, and transient. In each case, a cost function is defined and minimized for numerous parameter variations. For the case of harmonic excitation, the cost function is obtained by integrating the mean squared displacement over a region of the beam in which control is desired. A controller is then found to minimize this cost function in the control interval. The control interval and controller location are continuously varied for several frequencies of excitation. The results show that control over the entire beam length is possible only when the excitation frequency is near a resonant frequency of the beam, but control over a subregion may be obtained even between resonant frequencies at the cost of increasing the vibration outside of the control region. For random excitation, the cost function is realized by integrating the expected value of the displacement squared over the interval of the beam in which control is desired. This is shown to yield the identical cost function as obtained by integrating the cost function for harmonic excitation over all excitation frequencies. As a result, it is always possible to reduce the cost function for random excitation whether controlling the entire beam or just a subregion, without ever increasing the vibration outside the region in which control is desired. The last type of excitation considered is a single, transient pulse. A cost function representative of the beam vibration is obtained by integrating the transient displacement squared over a region of the beam and over all time. The form of the controller is chosen a priori as either one or two delayed pulses. Delays

  8. Quinine controls body weight gain without affecting food intake in male C57BL6 mice.

    PubMed

    Cettour-Rose, Philippe; Bezençon, Carole; Darimont, Christian; le Coutre, Johannes; Damak, Sami

    2013-02-08

    Quinine is a natural molecule commonly used as a flavouring agent in tonic water. Diet supplementation with quinine leads to decreased body weight and food intake in rats. Quinine is an in vitro inhibitor of Trpm5, a cation channel expressed in taste bud cells, the gastrointestinal tract and pancreas. The objective of this work is to determine the effect of diet supplementation with quinine on body weight and body composition in male mice, to investigate its mechanism of action, and whether the effect is mediated through Trpm5. Compared with mice consuming AIN, a regular balanced diet, mice consuming AIN diet supplemented with 0.1% quinine gained less weight (2.89 ± 0.30 g vs 5.39 ± 0.50 g) and less fat mass (2.22 ± 0.26 g vs 4.33 ± 0.43 g) after 13 weeks of diet, and had lower blood glucose and plasma triglycerides. There was no difference in food intake between the mice consuming quinine supplemented diet and those consuming control diet. Trpm5 knockout mice gained less fat mass than wild-type mice. There was a trend for a diet-genotype interaction for body weight and body weight gain, with the effect of quinine less pronounced in the Trpm5 KO than in the WT background. Faecal weight, energy and lipid contents were higher in quinine fed mice compared to regular AIN fed mice and in Trpm5 KO mice compared to wild type mice. Quinine contributes to weight control in male C57BL6 mice without affecting food intake. A partial contribution of Trpm5 to quinine dependent body weight control is suggested.

  9. Quinine controls body weight gain without affecting food intake in male C57BL6 mice

    PubMed Central

    2013-01-01

    Background Quinine is a natural molecule commonly used as a flavouring agent in tonic water. Diet supplementation with quinine leads to decreased body weight and food intake in rats. Quinine is an in vitro inhibitor of Trpm5, a cation channel expressed in taste bud cells, the gastrointestinal tract and pancreas. The objective of this work is to determine the effect of diet supplementation with quinine on body weight and body composition in male mice, to investigate its mechanism of action, and whether the effect is mediated through Trpm5. Results Compared with mice consuming AIN, a regular balanced diet, mice consuming AIN diet supplemented with 0.1% quinine gained less weight (2.89 ± 0.30 g vs 5.39 ± 0.50 g) and less fat mass (2.22 ± 0.26 g vs 4.33 ± 0.43 g) after 13 weeks of diet, and had lower blood glucose and plasma triglycerides. There was no difference in food intake between the mice consuming quinine supplemented diet and those consuming control diet. Trpm5 knockout mice gained less fat mass than wild-type mice. There was a trend for a diet-genotype interaction for body weight and body weight gain, with the effect of quinine less pronounced in the Trpm5 KO than in the WT background. Faecal weight, energy and lipid contents were higher in quinine fed mice compared to regular AIN fed mice and in Trpm5 KO mice compared to wild type mice. Conclusion Quinine contributes to weight control in male C57BL6 mice without affecting food intake. A partial contribution of Trpm5 to quinine dependent body weight control is suggested. PMID:23394313

  10. Gain-scheduling multivariable LPV control of an irrigation canal system.

    PubMed

    Bolea, Yolanda; Puig, Vicenç

    2016-07-01

    The purpose of this paper is to present a multivariable linear parameter varying (LPV) controller with a gain scheduling Smith Predictor (SP) scheme applicable to open-flow canal systems. This LPV controller based on SP is designed taking into account the uncertainty in the estimation of delay and the variation of plant parameters according to the operating point. This new methodology can be applied to a class of delay systems that can be represented by a set of models that can be factorized into a rational multivariable model in series with left/right diagonal (multiple) delays, such as, the case of irrigation canals. A multiple pool canal system is used to test and validate the proposed control approach. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  11. Adaptive control and noise suppression by a variable-gain gradient algorithm

    NASA Technical Reports Server (NTRS)

    Merhav, S. J.; Mehta, R. S.

    1987-01-01

    An adaptive control system based on normalized LMS filters is investigated. The finite impulse response of the nonparametric controller is adaptively estimated using a given reference model. Specifically, the following issues are addressed: The stability of the closed loop system is analyzed and heuristically established. Next, the adaptation process is studied for piecewise constant plant parameters. It is shown that by introducing a variable-gain in the gradient algorithm, a substantial reduction in the LMS adaptation rate can be achieved. Finally, process noise at the plant output generally causes a biased estimate of the controller. By introducing a noise suppression scheme, this bias can be substantially reduced and the response of the adapted system becomes very close to that of the reference model. Extensive computer simulations validate these and demonstrate assertions that the system can rapidly adapt to random jumps in plant parameters.

  12. A gain of function polymorphism controlling complex traits and fitness in nature

    PubMed Central

    Prasad, Kasavajhala V. S. K.; Song, Bao-Hua; Olson-Manning, Carrie; Anderson, Jill T.; Lee, Cheng-Ruei; Schranz, M. Eric; Windsor, Aaron J.; Clauss, Maria J.; Manzaneda, Antonio J.; Naqvi, Ibtehaj; Reichelt, Michael; Gershenzon, Jonathan; Rupasinghe, Sanjeewa G.; Schuler, Mary A.; Mitchell-Olds, Thomas

    2013-01-01

    Identifying the causal genes that control complex trait variation remains challenging, limiting our appreciation of the evolutionary processes that influence polymorphisms in nature. We cloned a QTL that controls plant defensive chemistry, damage by insect herbivores, survival, and reproduction in the natural environments where this polymorphism evolved. These ecological effects are driven by duplications in the BCMA loci controlling this QTL and by two selectively favored amino acid changes in the glucosinolate-biosynthetic P450s that they encode. These changes cause a gain of novel enzyme function, modulated by allelic differences in catalytic rate and gene copy number. Ecological interactions in diverse environments likely contribute to the widespread polymorphism of this biochemical function. PMID:22936775

  13. Floating-point scaling technique for sources separation automatic gain control

    NASA Astrophysics Data System (ADS)

    Fermas, A.; Belouchrani, A.; Ait-Mohamed, O.

    2012-07-01

    Based on the floating-point representation and taking advantage of scaling factor indetermination in blind source separation (BSS) processing, we propose a scaling technique applied to the separation matrix, to avoid the saturation or the weakness in the recovered source signals. This technique performs an automatic gain control in an on-line BSS environment. We demonstrate the effectiveness of this technique by using the implementation of a division-free BSS algorithm with two inputs, two outputs. The proposed technique is computationally cheaper and efficient for a hardware implementation compared to the Euclidean normalisation.

  14. Application of particle swarm optimization in gas turbine engine fuel controller gain tuning

    NASA Astrophysics Data System (ADS)

    Montazeri-Gh, M.; Jafari, S.; Ilkhani, M. R.

    2012-02-01

    This article presents the application of particle swarm optimization (PSO) for gain tuning of the gas turbine engine (GTE) fuel controller. For this purpose, the structure of a fuel controller is firstly designed based on the GTE control requirements and constraints. The controller gains are then tuned by PSO where the tuning process is formulated as an engineering optimization problem. In this study, the response time during engine acceleration and deceleration as well as the engine fuel consumption are considered as the objective functions. A computer simulation is also developed to evaluate the objective values for a single spool GTE. The GTE model employed for the simulation is a Wiener model, the parameters of which are extracted from experimental tests. In addition, the effect of neighbour acceleration on PSO results is studied. The results show that the neighbour acceleration factor has a considerable effect on the convergence rate of the PSO process. The PSO results are also compared with the results obtained through a genetic algorithm (GA) to show the relative merits of PSO. Moreover, the PSO results are compared with the results obtained from the dynamic programming (DP) method in order to illustrate the ability of proposed method in finding the global optimal solution. Furthermore, the objective function is also defined in multi-objective manner and the multi-objective particle swarm optimization (MOPSO) is applied to find the Pareto-front for the problem. Finally, the results obtained from the simulation of the optimized controller confirm the effectiveness of the proposed approach to design an optimal fuel controller resulting in an improved GTE performance as well as protection against the physical limitations.

  15. Fast prediction of transient stability margin in systems with SVC control and HVDC link

    SciTech Connect

    Tso, S.K.; Cheung, S.P.

    1995-12-31

    Recent developments in transient stability margin (TSM) prediction using the energy-based direct method have included excitation controllers, power system stabilizers (PSSs) and/or static VAr compensators (SVCs). These devices can be represented in their detailed dynamic models to desired degrees of complexity while the proposed extended equal-area criterion can still be effectively applied. This paper describes further development of this technique to incorporate an HVDC transmission into the test network for TSM prediction. The method is examined with a practical 17-machine power network representing the South China/Hong Kong system. An SVC control scheme is also installed in a weak bus of the test network for transient stability improvement. The results obtained show that there is no sacrifice in accuracy, speed or reliability of the TSM method with SVC and HVDC realistically incorporated into the study.

  16. Augmentor transient capability of an F100 engine equipped with a digital electronic engine control

    NASA Technical Reports Server (NTRS)

    Burcham, F. W., Jr.; Pai, G. D.

    1984-01-01

    An F100 augmented turbofan engine equipped with digital electronic engine control (DEEC) system was evaluated. The engine was equipped with a specially modified augmentor to provide improved steady state and transient augmentor capability. The combination of the DEEC and the modified augmentor was evaluated in sea level and altitude facility tests and then in four different flight phases in an F-15 aircraft. The augmentor configuration, logic, and test results are presented.

  17. Calculation of the transient motion of elastic airfoils forced by control surface motion and gusts

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.; Edwards, J. W.

    1980-01-01

    The time-domain equations of motion of elastic airfoil sections forced by control surface motions and gusts were developed for the case of incompressible flow. Extensive use was made of special functions related to the inverse transform of Theodorsen's function. Approximations for the special cases of zero stream velocity, small time, large and time are given. A numerical solution technique for the solution of the general case is given. Examples of the exact transient response of an airfoil are presented.

  18. A pilot rating scale for evaluating failure transients in electronic flight control systems

    NASA Technical Reports Server (NTRS)

    Hindson, William S.; Schroeder, Jeffery A.; Eshow, Michelle M.

    1990-01-01

    A pilot rating scale was developed to describe the effects of transients in helicopter flight-control systems on safety-of-flight and on pilot recovery action. The scale was applied to the evaluation of hardovers that could potentially occur in the digital flight-control system being designed for a variable-stability UH-60A research helicopter. Tests were conducted in a large moving-base simulator and in flight. The results of the investigation were combined with existing airworthiness criteria to determine quantitative reliability design goals for the control system.

  19. A pilot rating scale for evaluating failure transients in electronic flight control systems

    NASA Technical Reports Server (NTRS)

    Hindson, William S.; Schroeder, Jeffery A.; Eshow, Michelle M.

    1990-01-01

    A pilot rating scale was developed to describe the effects of transients in helicopter flight-control systems on safety-of-flight and on pilot recovery action. The scale was applied to the evaluation of hardovers that could potentially occur in the digital flight-control system being designed for a variable-stability UH-60A research helicopter. Tests were conducted in a large moving-base simulator and in flight. The results of the investigation were combined with existing airworthiness criteria to determine quantitative reliability design goals for the control system.

  20. Modeling of boron control during power transients in a pressurized water reactor

    SciTech Connect

    Mathieu, P.; Distexhe, E.

    1986-02-01

    Accurate control instructions in a reactor control aid computer are included in order to realize the boron makeup throughput, which is required to obtain the boron concentration in the primary coolant loop, predicted by a neutronic code. A modeling of the transfer function between the makeup and the primary loop is proposed. The chemical and volumetric control system, the pressurizer, and the primary loop are modeled as instantaneous diffusion cells. The pipes are modeled as time lag lines. The model provides the unstationary boron distributions in the different elements of the setup. A numerical code is developed to calculate the time evolutions of the makeup throughput during power transients.

  1. Reward value-based gain control: divisive normalization in parietal cortex.

    PubMed

    Louie, Kenway; Grattan, Lauren E; Glimcher, Paul W

    2011-07-20

    The representation of value is a critical component of decision making. Rational choice theory assumes that options are assigned absolute values, independent of the value or existence of other alternatives. However, context-dependent choice behavior in both animals and humans violates this assumption, suggesting that biological decision processes rely on comparative evaluation. Here we show that neurons in the monkey lateral intraparietal cortex encode a relative form of saccadic value, explicitly dependent on the values of the other available alternatives. Analogous to extra-classical receptive field effects in visual cortex, this relative representation incorporates target values outside the response field and is observed in both stimulus-driven activity and baseline firing rates. This context-dependent modulation is precisely described by divisive normalization, indicating that this standard form of sensory gain control may be a general mechanism of cortical computation. Such normalization in decision circuits effectively implements an adaptive gain control for value coding and provides a possible mechanistic basis for behavioral context-dependent violations of rationality.

  2. Direction discrimination thresholds in binocular, monocular, and dichoptic viewing: Motion opponency and contrast gain control.

    PubMed

    Maehara, Goro; Hess, Robert F; Georgeson, Mark A

    2017-01-01

    We studied the binocular organization of motion opponency and its relationship to contrast gain control. Luminance contrast thresholds for discriminating direction of motion were measured for drifting Gabor patterns (target) presented on counterphase flickering Gabor patterns (pedestal). There were four presentation conditions: binocular, monocular, dichoptic, and half-binocular. For the half-binocular presentation, the target was presented to one eye while pedestals were presented to both eyes. In addition, to test for motion opponency, we studied two increment and decrement conditions, in which the target increased contrast for one direction of movement but decreased it for the opposite moving component of the pedestal. Threshold versus pedestal contrast functions showed a dipper shape, and there was a strong interaction between pedestal contrast and test condition. Binocular thresholds were lower than monocular thresholds but only at low pedestal contrasts. Monocular and half-binocular thresholds were similar at low pedestal contrasts, but half-binocular thresholds became higher and closer to dichoptic thresholds as pedestal contrast increased. Adding the decremental target reduced thresholds by a factor of two or more-a strong sign of opponency-when the decrement was in the same eye as the increment or the opposite eye. We compared several computational models fitted to the data. Converging evidence from the present and previous studies (Gorea, Conway, & Blake, 2001) suggests that motion opponency is most likely to be monocular, occurring before direction-specific binocular summation and before divisive, binocular gain control.

  3. Extended horizon lifting for periodic gain adjustment in control systems, and for equalization of communication channels

    NASA Technical Reports Server (NTRS)

    Bayard, David S. (Inventor)

    1994-01-01

    Periodic gain adjustment in plants of irreducible order, n, or for equalization of communications channels is effected in such a way that the plant (system) appears to be minimum phase by choosing a horizon time N is greater than n of liftings in periodic input and output windows rho sub u and rho sub y, respectively, where N is an integer chosen to define the extent (length) of each of the windows rho sub u and rho sub y, and n is the order of an irreducible input/output plant. The plant may be an electrical, mechanical, or chemical system, in which case output tracking (OT) is carried out for feedback control or a communication channel, in which case input tracking (IT) is performed. Conditions for OT are distinct from IT in terms of zero annihilation, namely H(sub s)H(sub s)(sup +) = I for OT and H(sub s)H(sub s)(sup +) = I of IT, where the OT conditions are intended for gain adjustments in the control system, and IT conditions are intended for equalization for communication channels.

  4. Olfactory receptor neurons use gain control and complementary kinetics to encode intermittent odorant stimuli

    PubMed Central

    Gorur-Shandilya, Srinivas; Demir, Mahmut; Long, Junjiajia; Clark, Damon A; Emonet, Thierry

    2017-01-01

    Insects find food and mates by navigating odorant plumes that can be highly intermittent, with intensities and durations that vary rapidly over orders of magnitude. Much is known about olfactory responses to pulses and steps, but it remains unclear how olfactory receptor neurons (ORNs) detect the intensity and timing of natural stimuli, where the absence of scale in the signal makes detection a formidable olfactory task. By stimulating Drosophila ORNs in vivo with naturalistic and Gaussian stimuli, we show that ORNs adapt to stimulus mean and variance, and that adaptation and saturation contribute to naturalistic sensing. Mean-dependent gain control followed the Weber-Fechner relation and occurred primarily at odor transduction, while variance-dependent gain control occurred at both transduction and spiking. Transduction and spike generation possessed complementary kinetic properties, that together preserved the timing of odorant encounters in ORN spiking, regardless of intensity. Such scale-invariance could be critical during odor plume navigation. DOI: http://dx.doi.org/10.7554/eLife.27670.001 PMID:28653907

  5. Analysis of sensorless control of brushless DC motor using unknown input observer with different gains

    NASA Astrophysics Data System (ADS)

    Astik, Mitesh B.; Bhatt, Praghnesh; Bhalja, Bhavesh R.

    2017-03-01

    A sensorless control scheme based on an unknown input observer is presented in this paper in which back EMF of the Brushless DC Motor (BLDC) is continuously estimated from available line voltages and currents. During negative rotation of motor, actual and estimated speed fail to track the reference speed and if the corrective action is not taken by the observer, the motor goes into saturation. To overcome this problem, the speed estimation algorithm has been implemented in this paper to control the dynamic behavior of the motor during negative rotation. The Ackermans method was used to calculate the gains of an unknown input observer which is based on the appropriate choice of the eigenvalues in advance. The criteria to choose eigenvalue is to obtain a balance between faster convergence rate and the least noise level. Simulations have been carried out for different disturbances such as step changes in motor reference speed and load torque. The comparative simulation results clearly depict that the disturbance effects in actual and estimated responses minimizes as observer gain setting increases.

  6. Stability of asthma control with regular treatment: an analysis of the Gaining Optimal Asthma controL (GOAL) study.

    PubMed

    Bateman, E D; Bousquet, J; Busse, W W; Clark, T J H; Gul, N; Gibbs, M; Pedersen, S

    2008-07-01

    Uncontrolled asthma is characterized by variability. Current asthma guidelines recommend focussing on the achievement and maintenance of control but few studies have examined in detail, using composite measures of control, the stability and potential duration of control once achieved. In this post-hoc analysis of the results of the Gaining Optimal Asthma controL (GOAL) study, we examine the association between the level of asthma control achieved during the step-up phase of the study and the stability of control experienced during the maintenance phase. GOAL was a 1-year, randomized, stratified, double-blind study of 3421 patients with uncontrolled asthma, which compared salmeterol/fluticasone propionate combination with fluticasone propionate in achieving two composite, guideline-based measures of control: totally controlled and well-controlled asthma. We analysed the proportion and duration of time spent in control, the effect of treatment on asthma stability, and the impact of asthma control stability on unscheduled use of healthcare resources. In patients achieving well-controlled or totally controlled asthma, at least well-controlled asthma was maintained for a median of almost 3 and 6 months, and for more than 85% and 95% of weeks of follow-up, respectively. A high level of stability was confirmed in a Markov analysis investigating transitional probability of change in control status. Variability in control was associated with increased probability of an unscheduled healthcare resource use (odds ratio: 1.06, P < 0.001). Most patients achieving guideline-defined control can maintain at least a similar level of control with regular, stable dosing, with little likelihood of losing control.

  7. Distributed Hierarchical Control Architecture for Transient Dynamics Improvement in Power Systems

    SciTech Connect

    Marinovici, Laurentiu D.; Lian, Jianming; Kalsi, Karanjit; Du, Pengwei; Elizondo, Marcelo A.

    2013-08-24

    In this paper, a novel distributed hierarchical coordinated control architecture is proposed for large scale power systems. The newly considered architecture facilitates frequency restoration and power balancing functions to be decoupled and implemented at different levels. At the local level, decentralized robust generator controllers are designed to quickly restore frequency after large faults and disturbances in the system. The controllers presented herein are shown to improve transient stability performance, as compared to conventional governor and excitation control. At the area level, Automatic Generation Control (AGC) is modified and coordinates with the decentralized robust controllers to reach the interchange schedule in the tie lines. The interaction of local and zonal controllers is validated through detailed simulations.

  8. Control methods for aiding a pilot during STOL engine failure transients

    NASA Technical Reports Server (NTRS)

    Nelson, E. R.; Debra, D. B.

    1976-01-01

    Candidate autopilot control laws that control the engine failure transient sink rates by demonstrating the engineering application of modern state variable control theory were defined. The results of approximate modal analysis were compared to those derived from full state analyses provided from computer design solutions. The aircraft was described, and a state variable model of its longitudinal dynamic motion due to engine and control variations was defined. The classical fast and slow modes were assumed to be sufficiently different to define reduced order approximations of the aircraft motion amendable to hand analysis control definition methods. The original state equations of motion were also applied to a large scale state variable control design program, in particular OPTSYS. The resulting control laws were compared with respect to their relative responses, ease of application, and meeting the desired performance objectives.

  9. Anfis Approach for Sssc Controller Design for the Improvement of Transient Stability Performance

    NASA Astrophysics Data System (ADS)

    Khuntia, Swasti R.; Panda, Sidhartha

    2011-06-01

    In this paper, Adaptive Neuro-Fuzzy Inference System (ANFIS) method based on the Artificial Neural Network (ANN) is applied to design a Static Synchronous Series Compensator (SSSC)-based controller for improvement of transient stability. The proposed ANFIS controller combines the advantages of fuzzy controller and quick response and adaptability nature of ANN. The ANFIS structures were trained using the generated database by fuzzy controller of SSSC. It is observed that the proposed SSSC controller improves greatly the voltage profile of the system under severe disturbances. The results prove that the proposed SSSC-based ANFIS controller is found to be robust to fault location and change in operating conditions. Further, the results obtained are compared with the conventional lead-lag controllers for SSSC.

  10. Climate variability and vadose zone controls on damping of transient recharge

    USGS Publications Warehouse

    Corona, Claudia R.; Gurdak, Jason J.; Dickinson, Jesse; Ferré, T.P.A.; Maurer, Edwin P.

    2017-01-01

    Increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve. Here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global-scale climate variability and fluctuations in groundwater levels. We use hundreds of HYDRUS-1D simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous United States (U.S). Although the models were parameterized based on U.S. aquifers, findings from this study are applicable elsewhere that have mean recharge rates between 3.65 and 730 mm yr–1. We find that mean infiltration flux, period of time varying infiltration, and hydraulic conductivity are statistically significant predictors of damping depth. The resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone, resulting in steady-state recharge, while other periodic surface fluxes do not dampen with depth, resulting in transient recharge. We find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most U.S. aquifers. Our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations. The implications are that relatively simple, homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate-varying transient recharge in some complex, layered vadose zone profiles.

  11. Gain control of synaptic response function in cerebellar nuclear neurons by a calcium activated potassium conductance

    PubMed Central

    Feng, Steven Si; Lin, Risa; Gauck, Volker; Jaeger, Dieter

    2013-01-01

    Small conductance Ca2+ activated potassium (SK) current provides an important modulator of excitatory synaptic transmission, which undergoes plastic regulation via multiple mechanisms. We examined whether inhibitory input processing is also dependent on SK current in the cerebellar nuclei (CN), where inhibition provides the only route of information transfer from the cerebellar cortical Purkinje cells. We employed dynamic clamping in conjunction with computer simulations to address this question. We found that SK current plays a critical role in the inhibitory synaptic control of spiking output. Specifically, regulation of SK current density resulted in a gain control of spiking output, such that low SK current promoted large output signaling for large inhibitory cell input fluctuations due to Purkinje cell synchronization. In contrast, smaller non-synchronized Purkinje cell input fluctuations were not amplified. Regulation of SK density in the CN therefore would likely lead to important consequences for the transmission of synchronized Purkinje cell activity to the motor system. PMID:23605187

  12. Climate Variability and Vadose Zone Controls on Damping of Transient Recharge Fluxes

    NASA Astrophysics Data System (ADS)

    Corona, C.; Gurdak, J. J.; Dickinson, J.; Ferré, T. P. A.

    2015-12-01

    We investigate the effects of interannual to multidecadal climate variability on groundwater resources by exploring the physical processes in the vadose zone that partially control transient infiltration and recharge fluxes. The vadose zone connects climate variability modes to groundwater systems by influencing infiltration events. Infiltration events become time-varying water flux through the vadose zone and are controlled by highly nonlinear, complex interactions between mean infiltration flux, infiltration period, soil textures, and depth to water table. We focus on the behavior and damping depth of water flux in the vadose zone. The damping depth is defined as the depth that the flux variation damps to 5% of the land surface variation. When the damping depth is above the water table, recharge may be considered steady; when the damping depth is below the water table, recharge may be considered transient. Previous work shows that the damping depth is sensitive to the frequency of the infiltration pattern and the unsaturated hydraulic properties of the media. We examine controls on the damping depth by modeling transient water fluxes at the land surface using the Gardner-Kozeny soil model for diffuse unsaturated flow in HYDRUS 1-D. Results for homogeneous profiles show that shorter-period oscillations, smaller mean fluxes, and finer-grained soil textures generally produce damping depths closer to land surface. Modeling layered soil textures indicates similar, but more complicated responses in the damping depth. Model results indicate that finer-textured layers in a coarser soil profile generally result in damping depths closer to land surface, while coarser-textured layers in a coarser soil profile result in damping depths deeper in the vadose zone. Findings from this study will enhance understanding of the vadose zone's influence on transient water flux and improve the simulation of recharge processes and climate variability effects in groundwater models.

  13. Concerted Efforts to Control or Eliminate Neglected Tropical Diseases: How Much Health Will Be Gained?

    PubMed Central

    Hontelez, Jan A. C.; Bakker, Roel; Blok, David J.; Cai, Rui; Houweling, Tanja A. J.; Kulik, Margarete C.; Lenk, Edeltraud J.; Luyendijk, Marianne; Matthijsse, Suzette M.; Redekop, William K.; Wagenaar, Inge; Jacobson, Julie; Nagelkerke, Nico J. D.; Richardus, Jan H.

    2016-01-01

    Background The London Declaration (2012) was formulated to support and focus the control and elimination of ten neglected tropical diseases (NTDs), with targets for 2020 as formulated by the WHO Roadmap. Five NTDs (lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminths and trachoma) are to be controlled by preventive chemotherapy (PCT), and four (Chagas’ disease, human African trypanosomiasis, leprosy and visceral leishmaniasis) by innovative and intensified disease management (IDM). Guinea worm, virtually eradicated, is not considered here. We aim to estimate the global health impact of meeting these targets in terms of averted morbidity, mortality, and disability adjusted life years (DALYs). Methods The Global Burden of Disease (GBD) 2010 study provides prevalence and burden estimates for all nine NTDs in 1990 and 2010, by country, age and sex, which were taken as the basis for our calculations. Estimates for other years were obtained by interpolating between 1990 (or the start-year of large-scale control efforts) and 2010, and further extrapolating until 2030, such that the 2020 targets were met. The NTD disease manifestations considered in the GBD study were analyzed as either reversible or irreversible. Health impacts were assessed by comparing the results of achieving the targets with the counterfactual, construed as the health burden had the 1990 (or 2010 if higher) situation continued unabated. Principle Findings/Conclusions Our calculations show that meeting the targets will lead to about 600 million averted DALYs in the period 2011–2030, nearly equally distributed between PCT and IDM-NTDs, with the health gain amongst PCT-NTDs mostly (96%) due to averted disability and amongst IDM-NTDs largely (95%) from averted mortality. These health gains include about 150 million averted irreversible disease manifestations (e.g. blindness) and 5 million averted deaths. Control of soil-transmitted helminths accounts for one third of all

  14. Concerted Efforts to Control or Eliminate Neglected Tropical Diseases: How Much Health Will Be Gained?

    PubMed

    de Vlas, Sake J; Stolk, Wilma A; le Rutte, Epke A; Hontelez, Jan A C; Bakker, Roel; Blok, David J; Cai, Rui; Houweling, Tanja A J; Kulik, Margarete C; Lenk, Edeltraud J; Luyendijk, Marianne; Matthijsse, Suzette M; Redekop, William K; Wagenaar, Inge; Jacobson, Julie; Nagelkerke, Nico J D; Richardus, Jan H

    2016-02-01

    The London Declaration (2012) was formulated to support and focus the control and elimination of ten neglected tropical diseases (NTDs), with targets for 2020 as formulated by the WHO Roadmap. Five NTDs (lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminths and trachoma) are to be controlled by preventive chemotherapy (PCT), and four (Chagas' disease, human African trypanosomiasis, leprosy and visceral leishmaniasis) by innovative and intensified disease management (IDM). Guinea worm, virtually eradicated, is not considered here. We aim to estimate the global health impact of meeting these targets in terms of averted morbidity, mortality, and disability adjusted life years (DALYs). The Global Burden of Disease (GBD) 2010 study provides prevalence and burden estimates for all nine NTDs in 1990 and 2010, by country, age and sex, which were taken as the basis for our calculations. Estimates for other years were obtained by interpolating between 1990 (or the start-year of large-scale control efforts) and 2010, and further extrapolating until 2030, such that the 2020 targets were met. The NTD disease manifestations considered in the GBD study were analyzed as either reversible or irreversible. Health impacts were assessed by comparing the results of achieving the targets with the counterfactual, construed as the health burden had the 1990 (or 2010 if higher) situation continued unabated. Our calculations show that meeting the targets will lead to about 600 million averted DALYs in the period 2011-2030, nearly equally distributed between PCT and IDM-NTDs, with the health gain amongst PCT-NTDs mostly (96%) due to averted disability and amongst IDM-NTDs largely (95%) from averted mortality. These health gains include about 150 million averted irreversible disease manifestations (e.g. blindness) and 5 million averted deaths. Control of soil-transmitted helminths accounts for one third of all averted DALYs. We conclude that the projected health

  15. Feedback control of slowly-varying transient growth by an array of plasma actuators

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald E.; Bade, Kyle M.; Belson, Brandt A.; Lavoie, Philippe; Naguib, Ahmed M.; Rowley, Clarence W.

    2014-02-01

    Closed-loop feedback control of boundary layer streaks embedded in a laminar boundary layer and experiencing transient growth, which is inherent to bypass boundary layer transition, is experimentally investigated. Streaky disturbances are introduced by a spanwise array of cylindrical roughness elements, and a counter disturbance is provided by a spanwise array of plasma actuators, which are capable of generating spanwise-periodic counter rotating vortices in the boundary layer. Feedback is provided by a spanwise array of shear stress sensors. An input/output model of the system is obtained from measurements of the boundary layer response to steady forcing, and used to design and analyze a proportional-integral controller, which targets a specific spanwise wavenumber of the disturbance. Attention is directed towards a quasi-steady case in which the controller update is slower than the convective time scale. This choice enables addressing issues pertinent to sensing, actuation, and control strategy that are also relevant to the control of unsteady disturbances but without the full complexity of transient effects. The feedback controller and plasma actuators perform well, attenuating the streamwise streaks both in the vicinity of the sensors and farther downstream. The controller remains effective for a range of off-design flow conditions, such as when the free-stream velocity is varied.

  16. Visual Landmark Information Gains Control of the Head Direction Signal at the Lateral Mammillary Nuclei

    PubMed Central

    Yoder, Ryan M.; Peck, James R.

    2015-01-01

    The neural representation of directional heading is conveyed by head direction (HD) cells located in an ascending circuit that includes projections from the lateral mammillary nuclei (LMN) to the anterodorsal thalamus (ADN) to the postsubiculum (PoS). The PoS provides return projections to LMN and ADN and is responsible for the landmark control of HD cells in ADN. However, the functional role of the PoS projection to LMN has not been tested. The present study recorded HD cells from LMN after bilateral PoS lesions to determine whether the PoS provides landmark control to LMN HD cells. After the lesion and implantation of electrodes, HD cell activity was recorded while rats navigated within a cylindrical arena containing a single visual landmark or while they navigated between familiar and novel arenas of a dual-chamber apparatus. PoS lesions disrupted the landmark control of HD cells and also disrupted the stability of the preferred firing direction of the cells in darkness. Furthermore, PoS lesions impaired the stable HD cell representation maintained by path integration mechanisms when the rat walked between familiar and novel arenas. These results suggest that visual information first gains control of the HD cell signal in the LMN, presumably via the direct PoS → LMN projection. This visual landmark information then controls HD cells throughout the HD cell circuit. PMID:25632114

  17. The Effect of Automatic Gain Control Structure and Release Time on Cochlear Implant Speech Intelligibility

    PubMed Central

    Khing, Phyu P.; Swanson, Brett A.; Ambikairajah, Eliathamby

    2013-01-01

    Nucleus cochlear implant systems incorporate a fast-acting front-end automatic gain control (AGC), sometimes called a compression limiter. The objective of the present study was to determine the effect of replacing the front-end compression limiter with a newly proposed envelope profile limiter. A secondary objective was to investigate the effect of AGC speed on cochlear implant speech intelligibility. The envelope profile limiter was located after the filter bank and reduced the gain when the largest of the filter bank envelopes exceeded the compression threshold. The compression threshold was set equal to the saturation level of the loudness growth function (i.e. the envelope level that mapped to the maximum comfortable current level), ensuring that no envelope clipping occurred. To preserve the spectral profile, the same gain was applied to all channels. Experiment 1 compared sentence recognition with the front-end limiter and with the envelope profile limiter, each with two release times (75 and 625 ms). Six implant recipients were tested in quiet and in four-talker babble noise, at a high presentation level of 89 dB SPL. Overall, release time had a larger effect than the AGC type. With both AGC types, speech intelligibility was lower for the 75 ms release time than for the 625 ms release time. With the shorter release time, the envelope profile limiter provided higher group mean scores than the front-end limiter in quiet, but there was no significant difference in noise. Experiment 2 measured sentence recognition in noise as a function of presentation level, from 55 to 89 dB SPL. The envelope profile limiter with 625 ms release time yielded better scores than the front-end limiter with 75 ms release time. A take-home study showed no clear pattern of preferences. It is concluded that the envelope profile limiter is a feasible alternative to a front-end compression limiter. PMID:24312408

  18. Steady-state and Transient Characteristics of a New Constant V/f Controlled Induction Motor

    NASA Astrophysics Data System (ADS)

    Tsuji, Mineo; Zhao, Xiaodan; Hamasaki, Shin-Ichi

    This paper presents a new constant V/f control method for induction motors and discusses the speed characteristics for steady-state and transient operations. In the proposed method, vector control is applied, and auto-boost voltage compensation for the voltage drop across the stator impedance and slip frequency compensation for improving speed control accuracy are included. The feasible operating region of the proposed method is discussed by using a vector locus. A linear model is proposed, and the stability of the V/f control system is analyzed by using the root locus to design a control parameter. The effectiveness of proposed V/f control method is demonstrated by simulation and experiment for motoring and regenerating operations.

  19. Method and apparatus for controlling combustor temperature during transient load changes

    DOEpatents

    Clingerman, Bruce J.; Chalfant, Robert W.

    2002-01-01

    A method and apparatus for controlling the temperature of a combustor in a fuel cell apparatus includes a fast acting air bypass valve connected in parallel with an air inlet to the combustor. A predetermined excess quantity of air is supplied from an air source to a series connected fuel cell and combustor. The predetermined excess quantity of air is provided in a sufficient amount to control the temperature of the combustor during start-up of the fuel processor when the load on the fuel cell is zero and to accommodate any temperature transients during operation of the fuel cell.

  20. Transient Stability Enhancement of Power Systems by Lyapunov-Based Recurrent Neural Networks UPFC Controllers

    NASA Astrophysics Data System (ADS)

    Chu, Chia-Chi; Tsai, Hung-Chi; Chang, Wei-Neng

    A Lyapunov-based recurrent neural networks unified power flow controller (UPFC) is developed for improving transient stability of power systems. First, a simple UPFC dynamical model, composed of a controllable shunt susceptance on the shunt side and an ideal complex transformer on the series side, is utilized to analyze UPFC dynamical characteristics. Secondly, we study the control configuration of the UPFC with two major blocks: the primary control, and the supplementary control. The primary control is implemented by standard PI techniques when the power system is operated in a normal condition. The supplementary control will be effective only when the power system is subjected by large disturbances. We propose a new Lyapunov-based UPFC controller of the classical single-machine-infinite-bus system for damping enhancement. In order to consider more complicated detailed generator models, we also propose a Lyapunov-based adaptive recurrent neural network controller to deal with such model uncertainties. This controller can be treated as neural network approximations of Lyapunov control actions. In addition, this controller also provides online learning ability to adjust the corresponding weights with the back propagation algorithm built in the hidden layer. The proposed control scheme has been tested on two simple power systems. Simulation results demonstrate that the proposed control strategy is very effective for suppressing power swing even under severe system conditions.

  1. Modeling and Control Systems Design for Air Intake System of Diesel Engines for Improvement of Transient Characteristic

    NASA Astrophysics Data System (ADS)

    Ejiri, Arata; Sasaki, Jun; Kinoshita, Yusuke; Fujimoto, Junya; Maruyama, Tsugito; Shimotani, Keiji

    For the purpose of contributing to global environment protection, several research studies have been conducted involving clean-burning diesel engines. In recent diesel engines with Exhaust Gas Recirculation (EGR) systems and a Variable Nozzle Turbocharger (VNT), mutual interference between EGR and VNT has been noted. Hence, designing and adjusting control of the conventional PID controller is particularly difficult at the transient state in which the engine speed and fuel injection rate change. In this paper, we formulate 1st principal model of air intake system of diesel engines and transform it to control oriented model including an engine steady state model and a transient model. And we propose a model-based control system with the LQR Controller, Saturation Compensator, the Dynamic Feed-forward and Disturbance Observer using a transient model. Using this method, we achieved precise reference tracking and emission reduction in transient mode test with the real engine evaluations.

  2. Analysis of Space Shuttle Primary Reaction-Control Engine-Exhaust Transients

    DTIC Science & Technology

    2008-10-01

    function, W • sr~’ • cm-2 • Hz-1 p .vap = vapor pressure, torr Q = heat gain rate, W £? Earth = Earthshine heating rate, W 9n,d = radiative cooling...sensi- tivity in the spectral range of 0.4 to 0.9 /xm. The sensor gain was set to limit the size of the spot attributable to saturation by the solar...setting of the LAAT sensor . Table 1 lists the pertinent parameters for 22 attitude-control bums for which quality (30 frames per second) video footage was

  3. Engineering studies related to Skylab program. [assessment of automatic gain control data

    NASA Technical Reports Server (NTRS)

    Hayne, G. S.

    1973-01-01

    The relationship between the S-193 Automatic Gain Control data and the magnitude of received signal power was studied in order to characterize performance parameters for Skylab equipment. The r-factor was used for the assessment and is defined to be less than unity, and a function of off-nadir angle, ocean surface roughness, and receiver signal to noise ratio. A digital computer simulation was also used to assess to additive receiver, or white noise. The system model for the digital simulation is described, along with intermediate frequency and video impulse response functions used, details of the input waveforms, and results to date. Specific discussion of the digital computer programs used is also provided.

  4. First principles view on chemical compound space: Gaining rigorous atomistic control of molecular properties

    SciTech Connect

    von Lilienfeld, O. Anatole

    2013-02-26

    A well-defined notion of chemical compound space (CCS) is essential for gaining rigorous control of properties through variation of elemental composition and atomic configurations. Here, we give an introduction to an atomistic first principles perspective on CCS. First, CCS is discussed in terms of variational nuclear charges in the context of conceptual density functional and molecular grand-canonical ensemble theory. Thereafter, we revisit the notion of compound pairs, related to each other via “alchemical” interpolations involving fractional nuclear charges in the electronic Hamiltonian. We address Taylor expansions in CCS, property nonlinearity, improved predictions using reference compound pairs, and the ounce-of-gold prize challenge to linearize CCS. Finally, we turn to machine learning of analytical structure property relationships in CCS. Here, these relationships correspond to inferred, rather than derived through variational principle, solutions of the electronic Schrödinger equation.

  5. First principles view on chemical compound space: Gaining rigorous atomistic control of molecular properties

    DOE PAGES

    von Lilienfeld, O. Anatole

    2013-02-26

    A well-defined notion of chemical compound space (CCS) is essential for gaining rigorous control of properties through variation of elemental composition and atomic configurations. Here, we give an introduction to an atomistic first principles perspective on CCS. First, CCS is discussed in terms of variational nuclear charges in the context of conceptual density functional and molecular grand-canonical ensemble theory. Thereafter, we revisit the notion of compound pairs, related to each other via “alchemical” interpolations involving fractional nuclear charges in the electronic Hamiltonian. We address Taylor expansions in CCS, property nonlinearity, improved predictions using reference compound pairs, and the ounce-of-gold prizemore » challenge to linearize CCS. Finally, we turn to machine learning of analytical structure property relationships in CCS. Here, these relationships correspond to inferred, rather than derived through variational principle, solutions of the electronic Schrödinger equation.« less

  6. An analog neural hardware implementation using charge-injection multipliers and neutron-specific gain control.

    PubMed

    Massengill, L W; Mundie, D B

    1992-01-01

    A neural network IC based on a dynamic charge injection is described. The hardware design is space and power efficient, and achieves massive parallelism of analog inner products via charge-based multipliers and spatially distributed summing buses. Basic synaptic cells are constructed of exponential pulse-decay modulation (EPDM) dynamic injection multipliers operating sequentially on propagating signal vectors and locally stored analog weights. Individually adjustable gain controls on each neutron reduce the effects of limited weight dynamic range. A hardware simulator/trainer has been developed which incorporates the physical (nonideal) characteristics of actual circuit components into the training process, thus absorbing nonlinearities and parametric deviations into the macroscopic performance of the network. Results show that charge-based techniques may achieve a high degree of neural density and throughput using standard CMOS processes.

  7. Automated Gain Control Ion Funnel Trap for Orthogonal Time-of-Flight Mass Spectrometry

    PubMed Central

    Ibrahim, Yehia M.; Belov, Mikhail E.; Liyu, Andrei V.; Smith, Richard D.

    2009-01-01

    Time-of-flight mass spectrometry (TOF MS) is increasingly used in proteomics research. Herein, we report on the development and characterization of a TOF MS instrument with improved sensitivity equipped with an electrodynamic ion funnel trap (IFT) that employs an automated gain control (AGC) capability. The IFT-TOF MS was coupled to a reversed-phase capillary liquid chromatography (RPLC) separation and evaluated in experiments with complex proteolytic digests. When applied to a global tryptic digest of Shewanella oneidensis proteins, an order-of-magnitude increase in sensitivity compared to that of the conventional continuous mode of operation was achieved due to efficient ion accumulation prior to TOF MS analysis. As a result of this sensitivity improvement and related improvement in mass measurement accuracy, the number of unique peptides identified in the AGC-IFT mode was 5-fold greater than that obtained in the continuous mode. PMID:18512944

  8. Parafoveal Target Detectability Reversal Predicted by Local Luminance and Contrast Gain Control

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Beard, Bettina L.; Null, Cynthia H. (Technical Monitor)

    1996-01-01

    This project is part of a program to develop image discrimination models for the prediction of the detectability of objects in a range of backgrounds. We wanted to see if the models could predict parafoveal object detection as well as they predict detection in foveal vision. We also wanted to make our simplified models more general by local computation of luminance and contrast gain control. A signal image (0.78 x 0.17 deg) was made by subtracting a simulated airport runway scene background image (2.7 deg square) from the same scene containing an obstructing aircraft. Signal visibility contrast thresholds were measured in a fully crossed factorial design with three factors: eccentricity (0 deg or 4 deg), background (uniform or runway scene background), and fixed-pattern white noise contrast (0%, 5%, or 10%). Three experienced observers responded to three repetitions of 60 2IFC trials in each condition and thresholds were estimated by maximum likelihood probit analysis. In the fovea the average detection contrast threshold was 4 dB lower for the runway background than for the uniform background, but in the parafovea, the average threshold was 6 dB higher for the runway background than for the uniform background. This interaction was similar across the different noise levels and for all three observers. A likely reason for the runway background giving a lower threshold in the fovea is the low luminance near the signal in that scene. In our model, the local luminance computation is controlled by a spatial spread parameter. When this parameter and a corresponding parameter for the spatial spread of contrast gain were increased for the parafoveal predictions, the model predicts the interaction of background with eccentricity.

  9. The 40-Something randomized controlled trial to prevent weight gain in mid-age women

    PubMed Central

    2013-01-01

    Background Obesity prevention is a major public health priority. Despite the health risks associated with weight gain, there has been a distinct lack of research into effective interventions to prevent, rather than treat, obesity particularly at high risk life stages such as menopause in women. This paper describes the rationale for and design of a 2-year randomized controlled trial (RCT) (the 40-Something Study) aimed at testing the feasibility and efficacy of a relatively low intensity intervention designed to achieve weight control in non-obese women about to enter the menopause transition. Methods and design The study is a parallel-group RCT consisting of 12 months of intervention (Phase 1) and 12 months of monitoring (Phase 2). Non-obese pre-menopausal healthy females 44–50 years of age were screened, stratified according to Body Mass Index (BMI) category (18.5-24.9 and 25–29.9 kg/m2) and randomly assigned to one of two groups: motivational interviewing (MI) intervention (n = 28), or a self-directed intervention (SDI) (control) (n = 26). The MI intervention consisted of five consultations with health professionals (four with a Dietitian and one with an Exercise Physiologist) who applied components of MI counselling to consultations with the women over a 12 month period. The SDI was developed as a control and these participants received print materials only. Outcome measures were collected at baseline, three, 12, 18 and 24 months and included weight (primary outcome), waist circumference, body composition, blood pressure, plasma markers of metabolic syndrome risk, dietary intake, physical activity and quality of life. Analysis of covariance will be used to investigate outcomes according to intervention type and duration (comparing baseline, 12 and 24 months). Discussion The 40-Something study is the first RCT aimed at preventing menopausal weight gain in Australian women. Importantly, this paper describes the methods used to evaluate whether

  10. The 40-Something randomized controlled trial to prevent weight gain in mid-age women.

    PubMed

    Williams, Lauren T; Hollis, Jenna L; Collins, Clare E; Morgan, Philip J

    2013-10-25

    Obesity prevention is a major public health priority. Despite the health risks associated with weight gain, there has been a distinct lack of research into effective interventions to prevent, rather than treat, obesity particularly at high risk life stages such as menopause in women. This paper describes the rationale for and design of a 2-year randomized controlled trial (RCT) (the 40-Something Study) aimed at testing the feasibility and efficacy of a relatively low intensity intervention designed to achieve weight control in non-obese women about to enter the menopause transition. The study is a parallel-group RCT consisting of 12 months of intervention (Phase 1) and 12 months of monitoring (Phase 2). Non-obese pre-menopausal healthy females 44-50 years of age were screened, stratified according to Body Mass Index (BMI) category (18.5-24.9 and 25-29.9 kg/m²) and randomly assigned to one of two groups: motivational interviewing (MI) intervention (n = 28), or a self-directed intervention (SDI) (control) (n = 26). The MI intervention consisted of five consultations with health professionals (four with a Dietitian and one with an Exercise Physiologist) who applied components of MI counselling to consultations with the women over a 12 month period. The SDI was developed as a control and these participants received print materials only. Outcome measures were collected at baseline, three, 12, 18 and 24 months and included weight (primary outcome), waist circumference, body composition, blood pressure, plasma markers of metabolic syndrome risk, dietary intake, physical activity and quality of life. Analysis of covariance will be used to investigate outcomes according to intervention type and duration (comparing baseline, 12 and 24 months). The 40-Something study is the first RCT aimed at preventing menopausal weight gain in Australian women. Importantly, this paper describes the methods used to evaluate whether a relatively low intensity, health professional led

  11. Tangentially migrating transient glutamatergic neurons control neurogenesis and maintenance of cerebral cortical progenitor pools.

    PubMed

    Teissier, A; Waclaw, R R; Griveau, A; Campbell, K; Pierani, A

    2012-02-01

    The relative contribution of intrinsic and extrinsic cues in the regulation of cortical neurogenesis remains a crucial challenge in developmental neurobiology. We previously reported that a transient population of glutamatergic neurons, the cortical plate (CP) transient neurons, migrates from the ventral pallium (VP) over long distances and participate in neocortical development. Here, we show that the genetic ablation of this population leads to a reduction in the number of cortical neurons especially fated to superficial layers. These defects result from precocious neurogenesis followed by a depletion of the progenitor pools. Notably, these changes progress from caudolateral to rostrodorsal pallial territories between E12.5 and E14.5 along the expected trajectory of the ablated cells. Conversely, we describe enhanced proliferation resulting in an increase in the number of cortical neurons in the Gsx2 mutants which present an expansion of the VP and a higher number of CP transient neurons migrating into the pallium. Our findings indicate that these neurons act to maintain the proliferative state of neocortical progenitors and delay differentiation during their migration from extraneocortical regions and, thus, participate in the extrinsic control of cortical neuronal numbers.

  12. Guaranteed properties of gain scheduled control for linear parameter-varying plants

    NASA Technical Reports Server (NTRS)

    Shamma, Jeff S.; Athans, Michael

    1991-01-01

    Gain scheduling has proven to be a successful design methodology in many engineering applications. However, in the absence of a sound theoretical analysis, these designs come with no guarantees on the robustness, performance, or even nominal stability of the overall gain scheduled design. This paper presents such an analysis for one type of gain scheduled system, namely, a linear parameter-varying plant scheduling on its exogenous parameters. Conditions are given which guarantee that the stability, robustness, and performance properties of the fixed operating point designs carry over to the global gain scheduled design. These conditions confirm and formalize popular notions regarding gain scheduled design, such as the scheduling variable should 'vary slowly'.

  13. Gaining control: reform, reimbursement and politics in New York's community hospitals, 1890--1915.

    PubMed Central

    Rosner, D

    1980-01-01

    This is an historical study of an early twentieth century political struggle regarding hospital reimbursement in New York City. During a period called the "Progressive Era" (1895--1915), administrators in the City's Comptroller's office sought to gain control over small, locally run community hospitals by dismantling the long-standing practice of flat-grant payments to institutions. Central office planners felt that these payments gave too much control to trustees. In its place, the Comptroller initiated a system of per-capita, per-diem reimbursement. Inspectors now judged for the institutions which services and which clients were appropriate for municipal reimbursement. From the perspective of the Comptroller's office, this change was an attempt to put rationality into the system of municipal support for charitable institutions. From the perspective of trustees and community representatives, however, this change was a political attack on the rights of institutions and local communities to control their own fate. Within the context of the larger Progressive Era "good government" movement to centralize decision-making in the hands of experts who believed strongly in the efficiency of larger institutions, it was generally the smallest, most financially troubled community institutions which felt the brunt of these changes. PMID:6990801

  14. Thermo-Mechanical Analysis of Coated Particle Fuel Experiencing a Fast Control Rod Ejection Transient

    SciTech Connect

    Ortensi, J.; Brian Boer; Abderrafi M. Ougouag

    2010-10-01

    A rapid increase of the temperature and the mechanical stress is expected in TRISO coated particle fuel that experiences a fast Total Control Rod Ejection (CRE) transient event. During this event the reactor power in the pebble bed core increases significantly for a short time interval. The power is deposited instantly and locally in the fuel kernel. This could result in a rapid increase of the pressure in the buffer layer of the coated fuel particle and, consequently, in an increase of the coating stresses. These stresses determine the mechanical failure probability of the coatings, which serve as the containment of radioactive fission products in the Pebble Bed Reactor (PBR). A new calculation procedure has been implemented at the Idaho National Laboratory (INL), which analyzes the transient fuel performance behavior of TRISO fuel particles in PBRs. This early capability can easily be extended to prismatic designs, given the availability of neutronic and thermal-fluid solvers. The full-core coupled neutronic and thermal-fluid analysis has been modeled with CYNOD-THERMIX. The temperature fields for the fuel kernel and the particle coatings, as well as the gas pressures in the buffer layer, are calculated with the THETRIS module explicitly during the transient calculation. Results from this module are part of the feedback loop within the neutronic-thermal fluid iterations performed for each time step. The temperature and internal pressure values for each pebble type in each region of the core are then input to the PArticle STress Analysis (PASTA) code, which determines the particle coating stresses and the fraction of failed particles. This paper presents an investigation of a Total Control Rod Ejection (TCRE) incident in the 400 MWth Pebble Bed Modular reactor design using the above described calculation procedure. The transient corresponds to a reactivity insertion of $3 (~2000 pcm) reaching 35 times the nominal power in 0.5 seconds. For each position in the core

  15. Neural network-based self-organizing fuzzy controller for transient stability of multimachine power systems

    SciTech Connect

    Chang, H.C.; Wang, M.H.

    1995-06-01

    An efficient self-organizing neural fuzzy controller (SONFC) is designed to improve the transient stability of multimachine power systems. First, an artificial neural network (ANN)-based model is introduced for fuzzy logic control. The characteristic rules and their membership functions of fuzzy systems are represented as the processing nodes in the ANN model. With the excellent learning capability inherent in the ANN, the traditional heuristic fuzzy control rules and input-output fuzzy membership functions can be optimally tuned from training examples by the back propagation learning algorithm. Considerable rule-matching times of the inference engine in the traditional fuzzy system can be saved. To illustrate the performance and usefulness of the SONFC, comparative studies with a bang-bang controller are performed on the 34-generator Taipower system with rather encouraging results.

  16. A New Turbo-shaft Engine Control Law during Variable Rotor Speed Transient Process

    NASA Astrophysics Data System (ADS)

    Hua, Wei; Miao, Lizhen; Zhang, Haibo; Huang, Jinquan

    2015-12-01

    A closed-loop control law employing compressor guided vanes is firstly investigated to solve unacceptable fuel flow dynamic change in single fuel control for turbo-shaft engine here, especially for rotorcraft in variable rotor speed process. Based on an Augmented Linear Quadratic Regulator (ALQR) algorithm, a dual-input, single-output robust control scheme is proposed for a turbo-shaft engine, involving not only the closed loop adjustment of fuel flow but also that of compressor guided vanes. Furthermore, compared to single fuel control, some digital simulation cases using this new scheme about variable rotor speed have been implemented on the basis of an integrated system of helicopter and engine model. The results depict that the command tracking performance to the free turbine rotor speed can be asymptotically realized. Moreover, the fuel flow transient process has been significantly improved, and the fuel consumption has been dramatically cut down by more than 2% while keeping the helicopter level fight unchanged.

  17. Transient stability enhancement of modern power grid using predictive Wide-Area Monitoring and Control

    NASA Astrophysics Data System (ADS)

    Yousefian, Reza

    This dissertation presents a real-time Wide-Area Control (WAC) designed based on artificial intelligence for large scale modern power systems transient stability enhancement. The WAC using the measurements available from Phasor Measurement Units (PMUs) at generator buses, monitors the global oscillations in the system and optimally augments the local excitation system of the synchronous generators. The complexity of the power system stability problem along with uncertainties and nonlinearities makes the conventional modeling non-practical or inaccurate. In this work Reinforcement Learning (RL) algorithm on the benchmark of Neural Networks (NNs) is used to map the nonlinearities of the system in real-time. This method different from both the centralized and the decentralized control schemes, employs a number of semi-autonomous agents to collaborate with each other to perform optimal control theory well-suited for WAC applications. Also, to handle the delays in Wide-Area Monitoring (WAM) and adapt the RL toward the robust control design, Temporal Difference (TD) is proposed as a solver for RL problem or optimal cost function. However, the main drawback of such WAC design is that it is challenging to determine if an offline trained network is valid to assess the stability of the power system once the system is evolved to a different operating state or network topology. In order to address the generality issue of NNs, a value priority scheme is proposed in this work to design a hybrid linear and nonlinear controllers. The algorithm so-called supervised RL is based on mixture of experts, where it is initialized by linear controller and as the performance and identification of the RL controller improves in real-time switches to the other controller. This work also focuses on transient stability and develops Lyapunov energy functions for synchronous generators to monitor the stability stress of the system. Using such energies as a cost function guarantees the convergence

  18. Tactical missile autopilots: Gain-scheduled H(infinity) control and dynamic inversion

    NASA Astrophysics Data System (ADS)

    Schumacher, Corey Joseph

    Autopilot design for a bank-to-turn (BTT) tactical missile is inherently nonlinear, with highly coupled dynamics. These difficulties create a need for the use of multivariable and nonlinear control techniques. This dissertation studies the application of two distinct modern control methods, {cal H}sb{infty} control with {cal D}-implementation gain-scheduling and nonlinear dynamic inversion using the assumption of a two-time-scale separation, for the autopilot design of a BTT air-to-air missile. The first portion of the work presents an analysis of the stability of the closed-loop missile system with a dynamic inversion controller to verify the validity of the time-scale separation assumption. It is proven under certain reasonable assumptions that the closed-loop system can be made exponentially stable about commanded constant state values by choosing a sufficiently large inner-loop frequency. The method used in the proof allows the calculation of a sufficiently large inner loop frequency to guarantee stability with a substantial domain of attraction which is used to show command following. This result is applied to the complete longitudinal/lateral missile dynamics. The proof is derived using two Lyapunov functions that take advantage of the two-time-scale structure the dynamic inversion controller imposes on the system dynamics. The dissertation also contains a generalization of the stability theorem to a general nonlinear system of a certain form, stating that the dynamic inversion controller using the two-time-scale separation can exponentially stabilize the closed-loop system about the commanded values. The second portion of the work examines the design of {cal H}sb{infty} and dynamic inversion controllers for the complete missile system. The performance of the two controllers is compared for nominal performance, robustness to aerodynamic uncertainty, and sensitivity to measurement noise. The performance comparison is carried out on a six degree

  19. Design and performance of an Automatic Gain Control system for the High Energy X-Ray Timing Experiment

    NASA Technical Reports Server (NTRS)

    Pelling, Michael R.; Rothschild, Richard E.; Macdonald, Daniel R.; Hertel, Robert; Nishiie, Edward

    1991-01-01

    The High Energy X-Ray Timing Experiment (HEXTE), currently under development for the X-Ray Timing Explorer (XTE) mission, employs a closed loop gain control system to attain 0.5 percent stabilization of each of eight-phoswich detector gains. This Automatic Gain Control (AGC) system utilizes a split window discriminator scheme to control the response of each detector pulse height analyzer to gated Am-241 X-ray events at 60 keV. A prototype AGC system has been implemented and tested within the gain perturbation environment expected to be experienced by the HEXTE instrument in flight. The AGC system and test configuration are described. Response, stability and noise characteristics are measured and compared with theoretical predictions. The system is found to be generally suitable for the HEXTE application.

  20. Hearing-aid automatic gain control adapting to two sound sources in the environment, using three time constants.

    PubMed

    Nordqvist, Peter; Leijon, Arne

    2004-11-01

    A hearing aid AGC algorithm is presented that uses a richer representation of the sound environment than previous algorithms. The proposed algorithm is designed to (1) adapt slowly (in approximately 10 s) between different listening environments, e.g., when the user leaves a single talker lecture for a multi-babble coffee-break; (2) switch rapidly (about 100 ms) between different dominant sound sources within one listening situation, such as the change from the user's own voice to a distant speaker's voice in a quiet conference room; (3) instantly reduce gain for strong transient sounds and then quickly return to the previous gain setting; and (4) not change the gain in silent pauses but instead keep the gain setting of the previous sound source. An acoustic evaluation showed that the algorithm worked as intended. The algorithm was evaluated together with a reference algorithm in a pilot field test. When evaluated by nine users in a set of speech recognition tests, the algorithm showed similar results to the reference algorithm.

  1. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, Michael

    2011-01-01

    We have learned it is conceivable that the Neutral Mass Spectrometer on board the Lunarr Atmosphere Dust Environment Explorer (LADEE) could measure gases from surface-reflected Attitude Control System (ACS) thruster plume. At minimum altitude, the measurement would be maximized, and gravitational influence minimized ("short" time-of-flight (TOF) situation) Could use to verify aspects of thruster plume modeling Model the transient disturbance to NMS measurements due to ACS gases reflected from lunar surface Observe evolution of various model characteristics as measured by NMS Species magnitudes, TOF measurements, angular distribution, species separation effects

  2. Cannabis, ischemic stroke, and transient ischemic attack: a case-control study.

    PubMed

    Barber, Peter Alan; Pridmore, Heidi M; Krishnamurthy, Venkatesh; Roberts, Sally; Spriggs, David A; Carter, Kristie N; Anderson, Neil E

    2013-08-01

    There is a temporal relationship between cannabis use and stroke in case series and population-based studies. Consecutive stroke patients, aged 18 to 55 years, who had urine screens for cannabis were compared with a cohort of control patients admitted to hospital without cardiovascular or neurological diagnoses. One hundred sixty of 218 (73%) ischemic stroke/transient ischemic attack patients had urine drug screens (100 men; mean [SD] age, 44.8 [8.7] years). Twenty-five (15.6%) patients had positive cannabis drug screens. These patients were more likely to be men (84% versus 59%; χ2: P=0.016) and tobacco smokers (88% versus 28%; χ2: P<0.001). Control urine samples were obtained from 160 patients matched for age, sex, and ethnicity. Thirteen (8.1%) control participants tested positive for cannabis. In a logistic regression analysis adjusted for age, sex, and ethnicity, cannabis use was associated with increased risk of ischemic stroke/transient ischemic attack (odds ratio, 2.30; 95% confidence interval, 1.08-5.08). However after adjusting for tobacco use, an association independent of tobacco could not be confirmed (odds ratio, 1.59; 95% confidence interval, 0.71-3.70). This study provides evidence of an association between a cannabis lifestyle that includes tobacco and ischemic stroke. Further research is required to clarify whether there is an association between cannabis and stroke independent of tobacco. http://www.anzctr.org.au. Unique identifier: ACTRN12610000198022.

  3. Gain-scheduled H∞ control via parameter-dependent Lyapunov functions

    NASA Astrophysics Data System (ADS)

    Chumalee, Sunan; Whidborne, James F.

    2015-01-01

    Synthesising a gain-scheduled output feedback H∞ controller via parameter-dependent Lyapunov functions for linear parameter-varying (LPV) plant models involves solving an infinite number of linear matrix inequalities (LMIs). In practice, for affine LPV models, a finite number of LMIs can be achieved using convexifying techniques. This paper proposes an alternative approach to achieve a finite number of LMIs. By simple manipulations on the bounded real lemma inequality, a symmetric matrix polytope inequality can be formed. Hence, the LMIs need only to be evaluated at all vertices of such a symmetric matrix polytope. In addition, a construction technique of the intermediate controller variables is also proposed as an affine matrix-valued function in the polytopic coordinates of the scheduled parameters. Computational results on a numerical example using the approach were compared with those from a multi-convexity approach in order to demonstrate the impacts of the approach on parameter-dependent Lyapunov-based stability and performance analysis. Furthermore, numerical simulation results show the effectiveness of these proposed techniques.

  4. Knowledge-Driven Contrast Gain Control is Characterized by Two Distinct Electrocortical Markers

    PubMed Central

    Mišić, Bratislav V.; Schneider, Bruce A.; McIntosh, Anthony R.

    2009-01-01

    Sensitivity to variations in luminance (contrast) is fundamental to perception because contrasts define the edges and textures of visual objects. Recent research has shown that contrast sensitivity, in addition to being controlled by purely stimulus-driven mechanisms, is also affected by expectations and prior knowledge about the contrast of upcoming stimuli. The ability to adjust contrast sensitivity based on expectations and prior knowledge could help to maximize the information extracted when scanning familiar visual scenes. In the present study we used the event-related potentials (ERP) technique to resolve the stages that mediate knowledge-driven aspects of contrast gain control. Using groupwise independent components analysis and multivariate partial least squares, we isolated two robust spatiotemporal patterns of electrical brain activity associated with preparation for upcoming targets whose contrast was predicted by a cue. The patterns were sensitive to the informative value of the cue. When the cues were informative, these patterns were also able to differentiate among cues that predicted low-contrast targets and cues that predicted high-contrast targets. Both patterns were localized to parts of occipitotemporal cortex, and their morphology, latency, and topography resembled P2/N2 and P3 potentials. These two patterns provide electrophysiological markers of knowledge-driven preparation for impending changes in contrast and shed new light on the manner in which top-down factors modulate sensory processing. PMID:20140269

  5. Sulfur dioxide control by electric utilities: What are the gains from trade?

    NASA Astrophysics Data System (ADS)

    Carlson, Curtis Paul

    1999-11-01

    Title IV of the 1990 Clean Air Act Amendments (CAAA) established a market for transferable sulfur dioxide (SO2) emission allowances among electric utilities. This market offers firms facing high marginal pollution abatement costs the opportunity to purchase the tight to emit SO2 from firms with lower costs; as such, it is expected to yield cost savings compared to a command-and-control approach to environmental regulation. This thesis uses econometrically estimated marginal abatement cost functions for power plants affected by Title IV of the CAAA to evaluate the performance of the SO2 allowance market. Specifically, I investigate whether the much-heralded fall in the cost of abating SO2, compared to original estimates, can be attributed to allowance trading. I demonstrate that, for plants that use low-sulfur coal to reduce SO2 emissions, technical change and the fall in low sulfur coal prices have lowered marginal abatement cost curves by over 50% since 1985. This is the main source of cost reductions rather than trading per se. In the long run, allowance trading may achieve cost savings of 700-800 million per year compared to an "enlightened" command and control program characterized by a uniform emission rate standard. However, a comparison of potential cost savings in 1995 and 1996 with actual emissions costs suggest that most trading gains were unrealized in the first two years of the program.

  6. Forward-masking based gain control in odontocete biosonar: an evoked-potential study.

    PubMed

    Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

    2009-04-01

    Auditory evoked potentials (AEPs) were recorded during echolocation in a false killer whale Pseudorca crassidens. An electronically synthesized and played-back ("phantom") echo was used. Each electronic echo was triggered by an emitted biosonar pulse. The echo had a spectrum similar to that of the emitted biosonar clicks, and its intensity was proportional to that of the emitted click. The attenuation of the echo relative to the emitted click and its delay was controlled by the experimenter. Four combinations of echo attenuation and delay were tested (-31 dB, 2 ms), (-40 dB, 4 ms), (-49 dB, 8 ms), and (-58 dB, 16 ms); thus, attenuation and delay were associated with a rate of 9 dB of increased attenuation per delay doubling. AEPs related to emitted clicks displayed a regular amplitude dependence on the click level. Echo-related AEPs did not feature amplitude dependence on echo attenuation or emitted click levels, except in a few combinations of the lowest values of these two variables. The results are explained by a hypothesis that partial forward masking of the echoes by the preceding emitted sonar pulses serves as a kind of automatic gain control in the auditory system of echolocating odontocetes.

  7. Damage detection and gain-scheduled control of CFRP smart board mounting the metal core assisted piezoelectric fiber

    NASA Astrophysics Data System (ADS)

    Takagi, Kiyoshi; Sato, Hiroshi; Saigo, Muneharu

    2005-05-01

    This paper reports damage detection and vibration control of a new smart board designed by mounting piezoelectric fibers with metal cores on the surface of a CFRP composite. Damage to the board is identified on the assumption that the piezoelectric fibers used as sensors and actuators are broken simultaneously at the damaged location. When such damage-induced breakage occurs, the piezoelectric fibers expand and contract between the root and the damaged position on the cantilever beam. Damaged positions are detected by focusing attention on this property. Furthermore, this deterioration of sensors and actuators caused by breaks in the piezoelectric fibers is a consideration in the design of the gain-scheduled controller. First, the length of the piezoelectric fibers is measured to derive a finite-element method (FEM) model of the cantilever beam. If the fiber length is shortened due to a break, there is a decrease not only in actuator performance but also in the sensor output. Thus, peak gain of the FEM model is calculated for the length of every piezoelectric fiber. Damage detection is based on the computed relation between peak gain and the damage position. Furthermore, a reduced-order model that considers only the first mode is derived for the controller design and transformed into a linear fractional transformation (LFT) representation for the gain-scheduled controller design. The position of the damage is the contributing parameter in the variation. Next, the gain-scheduled controller is designed using LFT representation. Finally, the simulation and experimental results of the damage detection and the gain-scheduled control are presented. These results show that our gain-scheduled controller can improve control performance when damage cause a break in the piezoelectric fiber.

  8. The 2kW Mini-BRU Electrical Controls Concept and Transient Performance

    NASA Technical Reports Server (NTRS)

    Birchenough, Arthur G.

    2006-01-01

    The proposed Jupiter Icy Moon Orbiter, JIMO, mission selected a Brayton power conversion system as its electrical power generator. Although the JIMO mission power conversion system was expected to produce in the order of 100 kW, an available 2 kW Brayton system was used to develop control system strategies for the JIMO mission. This report describes the shunt loading voltage/speed regulation control concept developed for the 2 kW system, and the transient performance of controls. The 2 kW alternator is a permanent magnet alternator as proposed for the JIMO mission, and operates at a similar speed and internal impedance, allowing it to be used as an accurate model for performance of the larger system. The JIMO mission was cancelled in September 2005.

  9. Migraine aura or transient ischemic attacks? A five-year follow-up case-control study of women with transient central nervous system disorders in pregnancy

    PubMed Central

    Ertresvg, Janne Marit; Stovner, Lars Jacob; Kvavik, Lene Ekern; Johnsen, Hans-Jorgen; Zwart, John-Anker; Helde, Grethe; Bovim, Gunnar

    2007-01-01

    Background Migraine aura may be difficult to differentiate from transient ischemic attacks and other transient neurological disorders in pregnant women. The aims of the present study were to investigate and diagnose all pregnant women with transient neurological disorders of suspected central nervous system origin, and to compare this group with a control group of pregnant women with regard to vascular risk factors and prognosis. Methods During a 28 month period, 41 patients were detected with transient neurological symptoms during pregnancy. These were studied in detail with thorough clinical and laboratory investigations in order to make a certain diagnosis and to evaluate whether the episodes might be of a vascular nature. For comparison, the same investigations were performed in 41 pregnant controls. To assess the prognosis, both patients and controls were followed with questionnaires every year for five years. Results Migraine with aura was the most common cause of symptoms during pregnancy, occurring in 34 patients, while 2 were diagnosed with stroke, 2 with carpal tunnel syndrome, 1 with partial epilepsy, 1 with multiple sclerosis and 1 with presyncope. Patients had more headache before pregnancy than controls, but the average levels of vascular risk factors were similar. None of the patients or the controls reported cerebrovascular episodes during the five-year follow-up. Conclusion The diagnosis of migraine aura was difficult because for many patients it was their first ever attack and headache tended to be absent or of non-migraineous type. The aura features were more complex, with several aura symptoms and a higher prevalence of sensory and dysphasic aura than usual. Gradually developing aura symptoms, or different aura symptoms occurring in succession as described in the International Classification of Headache Disorders, seem to be useful for differentiating aura from other transient disorders. A meticulous history and clinical neurological examination

  10. The afterhyperpolarization conductance exerts the same control over the gain and variability of motoneurone firing in anaesthetized cats

    PubMed Central

    Manuel, Marin; Meunier, Claude; Donnet, Maud; Zytnicki, Daniel

    2006-01-01

    Does the afterhyperpolarization current control the gain and discharge variability of motoneurones according to the same law? We investigated this issue in lumbar motoneurones of anaesthetized cats. Using dynamic clamp, we measured the conductance, time constant and driving force of the AHP current in a sample of motoneurones and studied how the gain was correlated to these quantities. To study the action of the AHP on the discharge variability and to compare it to its action on the gain, we injected an artificial AHP-like current in motoneurones. This increased the natural AHP. In three motoneurones, we abolished most of the natural AHP with the calcium chelator BAPTA to investigate the condition where the discharge was essentially controlled by the artificial AHP. Our results demonstrate that both the gain and the coefficient of variation of the firing rate are inversely proportional to the magnitude and to the time constant of the artificial AHP conductance. This indicates that the AHP exerts the same control over the gain and the variability. This mechanism ensures that the variability of the discharge is modulated with the gain. This guarantees a great regularity of the discharge when the motoneurone is in a low excitability state and hence good control of the force produced. PMID:16931549

  11. Weight-gain inhibition by lactose in Australian Aboriginal children. A controlled trial of normal and lactose hydrolysed milk.

    PubMed

    Mitchell, J D; Brand, J; Halbisch, J

    1977-03-05

    Weight-gain in 35 slightly undernourished Australian Aboriginal infants was studied in hospital (49 admissions) during a blind controlled trial of a pre-hydrolysed low-lactose milk preparation and reconstituted full-cream milk powder. Infants fed the lactose hydrolysed milk gained 70% more weight than those receiving normal milk. Better weight-gains were achieved in those on the lactose hydrolysed milk irrespective of percentage standard weight for age, the presence of diarrhoea on admission to the trial, and stool sugar concentrations. The use of low-lactose milk should be considered in nutritional aid programmes for undernourished children throughout the world.

  12. Modeling of capacitance transients of thin-film solar cells: A valuable tool to gain information on perturbing layers or interfaces

    SciTech Connect

    Lauwaert, Johan Van Puyvelde, Lisanne; Vrielinck, Henk; Lauwaert, Jeroen; Thybaut, Joris W.

    2014-02-03

    Thin-film electronic and photovoltaic devices often comprise, in addition to the anticipated p-n junctions, additional non-ideal ohmic contacts between layers. This may give rise to additional signals in capacitance spectroscopy techniques that are not directly related to defects in the structure. In this paper, we present a fitting algorithm for transient signals arising from such an additional junction. The fitting results are in excellent agreement with the diode characteristics extracted from static measurements on individual components. Finally, the algorithm is applied for determining the barriers associated with anomalous signals reported for selected CuIn{sub 1–x}Ga{sub x}Se{sub 2} and CdTe solar cells.

  13. Multivariate processing of controlled source (CSEM) and transient (TDEM) electromagnetic data

    NASA Astrophysics Data System (ADS)

    Smirnov, Maxim

    2017-04-01

    Multivariate techniques proved to be a superior tool when dealing with simultaneous multichannel data. Previously we developed and validated a scheme (MsDEMPCA, for Missing data EM Principal Components Analysis) to process large synoptic magnetotelluric arrays. Here we focus on applications of MsDEMPCA to controlled source (CSEM) and transient electromagnetic (TDEM) data with a goal to demonstrate how the MV approach can clarify signal and noise characteristics, improve estimates of transfer functions and decay curves. As discussed in Smirnov and Egbert (2012) one can apply MV statistical methods to EM data having missing data to reduce bias, improve signal- to-noise ratios, and provide better control over coherent noise contamination. New approach was used to process Long-offset Transient Electromagnetic (LOTEM) data set, which consisted of several sites recorded simultaneously, having five channels each (two electric components and three magnetic components). The data are courtesy of KMS Technologies. Combined with robust stacking procedure we were able to derive more stable decay curves.

  14. Gaining greater control and understanding of processing plasmas through Tailored Voltage Waveforms

    NASA Astrophysics Data System (ADS)

    Johnson, Erik

    2015-09-01

    The use of multiple harmonics of an RF frequency to generate the exciting voltage waveform for a capacitively coupled plasma has in recent years become a rich and diverse field of research. Initially proposed, observed, and named as the Electrical Asymmetry Effect by the Bochum group, the use of such Tailored Voltage Waveforms to sustain a plasma has gone beyond asymmetrizing the ion bombardment energy and flux to the electrodes. It is now clear that one can gain control over such plasma features as localization of ionization events and composition of species flux by using more counterintuitive waveforms. In this talk, progress in this field in three areas is discussed: (1) identification of new TVW's that give rise to more complex asymmetries (namely ``slope-asymmetric'' waveforms), (2) identifying applications of TVW's in plasma processing and metrology, and finally, (3) solving the technical challenges of using the technique in an industrially feasible way. The talk will focus on work done at the LPICM and LPP CNRS laboratories at the Ecole Polytechnique, but in collaboration with a number of partners from other institutes.

  15. A Neural Circuit That Controls Cortical State, Plasticity, and the Gain of Sensory Responses in Mouse.

    PubMed

    Stryker, Michael P

    2014-01-01

    Neurons in the visual cortex were first found to be exquisitely selective for particular properties of visual stimuli in anesthetized animals, including mice. Studies of alert mice in an apparatus that allowed them to stand or run revealed that locomotion causes a change in cortical state that dramatically increases the magnitude of responses in neurons of the visual cortex without altering selectivity, effectively changing the gain of sensory responses. Locomotion also dramatically enhances adult plasticity in the recovery from long-term visual deprivation. We have studied the elements and operation of the neural circuit responsible for the enhancement of activity and shown that it enhances plasticity even in mice not free to run. The circuit consists of projections ascending from the midbrain locomotor region (MLR) to the basal forebrain, activating cholinergic and perhaps other projections to excite inhibitory interneurons expressing vasoactive intestinal peptide (VIP) in the visual cortex. VIP cells activated by locomotion inhibit interneurons that express somatostatin (SST), thereby disinhibiting the excitatory principal neurons and allowing them to respond more strongly to effective visual stimuli. These findings reveal in alert animals how the ascending reticular activating system described in anesthetized animals 50 years ago operates to control cortical state.

  16. Keeping returns optimal: gain control exerted through sensitivity adjustments in the harbour porpoise auditory system

    PubMed Central

    Linnenschmidt, Meike; Beedholm, Kristian; Wahlberg, Magnus; Højer-Kristensen, Jakob; Nachtigall, Paul E.

    2012-01-01

    Animals that use echolocation (biosonar) listen to acoustic signals with a large range of intensities, because echo levels vary with the fourth power of the animal's distance to the target. In man-made sonar, engineers apply automatic gain control to stabilize the echo energy levels, thereby rendering them independent of distance to the target. Both toothed whales and bats vary the level of their echolocation clicks to compensate for the distance-related energy loss. By monitoring the auditory brainstem response (ABR) during a psychophysical task, we found that a harbour porpoise (Phocoena phocoena), in addition to adjusting the sound level of the outgoing signals up to 5.4 dB, also reduces its ABR threshold by 6 dB when the target distance doubles. This self-induced threshold shift increases the dynamic range of the biosonar system and compensates for half of the variation of energy that is caused by changes in the distance to the target. In combination with an increased source level as a function of target range, this helps the porpoise to maintain a stable echo-evoked ABR amplitude irrespective of target range, and is therefore probably an important tool enabling porpoises to efficiently analyse and classify received echoes. PMID:22279169

  17. Transient river flow into a fjord and its control of plume energy partitioning

    NASA Astrophysics Data System (ADS)

    O'Callaghan, J. M.; Stevens, C. L.

    2015-05-01

    The influence of variable inflows on near-field plume dynamics and energy partitioning was examined using observations of a controlled flow into Doubtful Sound, New Zealand. The high temporal changes in flows passing through the Manapouri hydroelectric power station mimic the magnitude and variability seen in small mountainous river systems (SMRS) globally. The variable flow coupled with strong vertical density gradients akin to ambient conditions in coastal systems enabled plume behavior to be characterized for differing flow, wind, and tidal inputs in a quasi-idealized "laboratory" system. Comparisons of the frequency distributions of energy for different forcing conditions showed that baroclinic and barotropic processes were closely intertwined for transient forcing. The periodicity of density due to tidal oscillations was initially absent; headwaters of the fjord absorbed the momentum when inflows were substantially increased from the mean of ˜420 m3 s-1. From the buoyancy frequency squared N2, six events were identified when N2 was greater than 0.07 s-2. Seven occurrences of supercritical flow (Froude number, Fri > 1) and associated transitions to subcritical flow were observed over the duration of mooring deployment. Transient inflows induced internal hydraulic jumps in the near-field region which lead to a rapid breakdown of vertical stratification. The horizontal length scale of an internal hydraulic jump is O (1 km). Not all transitions from Fri > 1 to <1 are explained by transient forcing and the role of strong, up-fjord wind stress is likely to initiate supercritical flows via setup at the head of the fjord.

  18. Integrated model of G189A and Aspen-plus for the transient modeling of extravehicular activity atmospheric control systems

    NASA Technical Reports Server (NTRS)

    Kolodney, Matthew; Conger, Bruce C.

    1990-01-01

    A computerized modeling tool, under development for the transient modeling of an extravehicular activity atmospheric control subsystem is described. This subsystem includes the astronaut, temperature control, moisture control, CO2 removal, and oxygen make-up components. Trade studies evaluating competing components and subsystems to guide the selection and development of hardware for lunar and Martian missions will use this modeling tool. The integrated modeling tool uses the Advanced System for Process Engineering (ASPEN) to accomplish pseudosteady-state simulations, and the general environmental thermal control and life support program (G189A) to manage overall control of the run and transient input output, as well as transient modeling computations and database functions. Flow charts and flow diagrams are included.

  19. pH-dependent transient conformational states control optical properties in cyan fluorescent protein.

    PubMed

    Laricheva, Elena N; Goh, Garrett B; Dickson, Alex; Brooks, Charles L

    2015-03-04

    (namely, local solvation at the deprotonation site and a partial flexibility of the protein β-barrel structure) and provide the first evidence that transient conformational states can control optical properties of fluorescent proteins.

  20. Controllable optical response by modifying the gain and loss of a mechanical resonator and cavity mode in an optomechanical system

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Long; Wu, Rebing; Zhang, Jing; Özdemir, Şahin Kaya; Yang, Lan; Nori, Franco; Liu, Yu-xi

    2017-01-01

    We theoretically study a strongly driven optomechanical system which consists of a passive optical cavity and an active mechanical resonator. When the optomechanical coupling strength is varied, phase transitions, which are similar to those observed in PT -symmetric systems, are observed. We show that the optical transmission can be controlled by changing the gain of the mechanical resonator and loss of the optical cavity mode. Especially, we find that (i) for balanced gain and loss, optical amplification and absorption can be tuned by changing the optomechanical coupling strength through a control field; (ii) for unbalanced gain and loss, even with a tiny mechanical gain, both optomechanically induced transparency and anomalous dispersion can be observed around a critical point, which exhibits an ultralong group delay. The time delay τ can be optimized by regulating the optomechanical coupling strength through the control field, and it can be improved up to several orders of magnitude (τ ˜2 ms ) compared to that of conventional optomechanical systems (τ ˜1 μ s ). The presence of mechanical gain makes the group delay more robust to environmental perturbations. Our proposal provides a powerful platform to control light transport using a PT -symmetric-like optomechanical system.

  1. Exercise Training and Weight Gain in Obese Pregnant Women: A Randomized Controlled Trial (ETIP Trial).

    PubMed

    Garnæs, Kirsti Krohn; Mørkved, Siv; Salvesen, Øyvind; Moholdt, Trine

    2016-07-01

    The effectiveness of exercise training for preventing excessive gestational weight gain (GWG) and gestational diabetes mellitus (GDM) is still uncertain. As maternal obesity is associated with both GWG and GDM, there is a special need to assess whether prenatal exercise training programs provided to obese women reduce the risk of adverse pregnancy outcomes. Our primary aim was to assess whether regular supervised exercise training in pregnancy could reduce GWG in women with prepregnancy overweight/obesity. Secondary aims were to examine the effects of exercise in pregnancy on 30 outcomes including GDM incidence, blood pressure, blood measurements, skinfold thickness, and body composition. This was a single-center study where we randomized (1:1) 91 pregnant women with a prepregnancy body mass index (BMI) ≥ 28 kg/m2 to exercise training (n = 46) or control (standard maternity care) (n = 45). Assessments were done at baseline (pregnancy week 12-18) and in late pregnancy (week 34-37), as well as at delivery. The exercise group was offered thrice weekly supervised sessions of 35 min of moderate intensity endurance exercise and 25 min of strength training. Seventeen women were lost to follow-up (eight in the exercise group and nine in the control group). Our primary endpoint was GWG from baseline testing to delivery. The principal analyses were done as intention-to-treat analyses, with supplementary per protocol analyses where we assessed outcomes in the women who adhered to the exercise program (n = 19) compared to the control group. Mean GWG from baseline to delivery was 10.5 kg in the exercise group and 9.2 kg in the control group, with a mean difference of 0.92 kg (95% CI -1.35, 3.18; p = 0.43). Among the 30 secondary outcomes in late pregnancy, an apparent reduction was recorded in the incidence of GDM (2009 WHO definition) in the exercise group (2 cases; 6.1%) compared to the control group (9 cases; 27.3%), with an odds ratio of 0.1 (95% CI 0.02, 0.95; p = 0

  2. Cross-Axis Proportional Gains Used to Control Gyroscopic Effects in a Magnetic- Bearing-Supported Flywheel

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Kascak, Albert F.

    2001-01-01

    For magnetic-bearing-supported high-speed machines with significant gyroscopic effects, it is necessary to stabilize both forward and backward tilt whirling modes. Instability or the low damping of these modes can prevent the attainment of desired shaft speeds. Previous work elsewhere showed that cross-axis derivative gain in the magnetic bearing control law can improve the stability of the forward whirl mode, but it is commonly recognized that derivative gains amplify high-frequency noise and increase the required control effort. At the NASA Glenn Research Center, it has been shown previously that a simple cross-axis proportional gain can add stability (without adding noise) to either forward whirl or backward whirl, depending on the sign of the gain, but that such a gain destabilizes the other mode. It has been predicted by Glenn analysis that both modes can be stabilized by cross-axis proportional gains by utilizing the large-frequency separation of the two modes at speeds where the gyroscopic effects are significant. We use a modal controller that decouples the tilt and center-of-mass-translation modes. Only the tilt modes exhibit speed-dependent gyroscopic effects. The key to controlling them by the present method is to stabilize the backward whirl tilt mode with the appropriate sign of cross-axis proportional gain in the control law, but to include a low-pass filter on that gain term to restrict its effect only to the low-frequency backward-whirl mode. A second cross-axis term with the opposite sign and a high-pass filter stabilizes the forward whirl, which can have a frequency one or two orders of magnitude higher than the backward whirl, permitting very independent action of the two terms. Because the physical gyroscopic torques are proportional to the spinning speed of the shaft, it is convenient to gain-schedule the cross-axis control terms by making them proportional to shaft speed. This has the added benefit of avoiding a somewhat awkward zero

  3. Decision-directed automatic gain control for MAPSK systems. [M-ary Amplitude and Phase Shift Keying

    NASA Technical Reports Server (NTRS)

    Weber, W. J., III

    1974-01-01

    An automatic gain control (AGC) loop is presented for use with M-ary amplitude and phase shift keying (MAPSK) systems. The gain control amplifier is regulated by an error signal formed by the difference between the estimated amplitude level and the received amplitude level. The AGC performance is thus independent of the short-term average received signal energy. AGC loop analysis and simulation is presented for M-ary amplitude shift keying and quadrature amplitude shift keying. The AGC is shown to have a negligible degradation on the symbol probability of error for most practical cases. A generalized AGC for an arbitrary MAPSK system is presented.

  4. The Transient Aerodynamic Forces Effected by Trailing Edge Active Flow Control

    NASA Astrophysics Data System (ADS)

    Brzozowski, Dan; Culp, John; Glezer, Ari

    2012-11-01

    The transient aerodynamic forces effected by trailing edge flow control are investigated in wind tunnel experiments using a 2-DOF traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the surface using hybrid synthetic jet actuators. The time-histories of surface pressure and aerodynamic lift and pitching moment immediately following the application of flow control are measured using simultaneous pressure, force and velocity measurements that are taken phase-locked to the commanded actuation waveform. Circulation time history that is estimated from a PIV wake survey shows that the entire flow over the airfoil readjusts within about 1 . 5TCONV , which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.

  5. Random Photon Absorption Model Elucidates How Early Gain Control in Fly Photoreceptors Arises from Quantal Sampling.

    PubMed

    Song, Zhuoyi; Zhou, Yu; Juusola, Mikko

    2016-01-01

    Many diurnal photoreceptors encode vast real-world light changes effectively, but how this performance originates from photon sampling is unclear. A 4-module biophysically-realistic fly photoreceptor model, in which information capture is limited by the number of its sampling units (microvilli) and their photon-hit recovery time (refractoriness), can accurately simulate real recordings and their information content. However, sublinear summation in quantum bump production (quantum-gain-nonlinearity) may also cause adaptation by reducing the bump/photon gain when multiple photons hit the same microvillus simultaneously. Here, we use a Random Photon Absorption Model (RandPAM), which is the 1st module of the 4-module fly photoreceptor model, to quantify the contribution of quantum-gain-nonlinearity in light adaptation. We show how quantum-gain-nonlinearity already results from photon sampling alone. In the extreme case, when two or more simultaneous photon-hits reduce to a single sublinear value, quantum-gain-nonlinearity is preset before the phototransduction reactions adapt the quantum bump waveform. However, the contribution of quantum-gain-nonlinearity in light adaptation depends upon the likelihood of multi-photon-hits, which is strictly determined by the number of microvilli and light intensity. Specifically, its contribution to light-adaptation is marginal (≤ 1%) in fly photoreceptors with many thousands of microvilli, because the probability of simultaneous multi-photon-hits on any one microvillus is low even during daylight conditions. However, in cells with fewer sampling units, the impact of quantum-gain-nonlinearity increases with brightening light.

  6. Random Photon Absorption Model Elucidates How Early Gain Control in Fly Photoreceptors Arises from Quantal Sampling

    PubMed Central

    Song, Zhuoyi; Zhou, Yu; Juusola, Mikko

    2016-01-01

    Many diurnal photoreceptors encode vast real-world light changes effectively, but how this performance originates from photon sampling is unclear. A 4-module biophysically-realistic fly photoreceptor model, in which information capture is limited by the number of its sampling units (microvilli) and their photon-hit recovery time (refractoriness), can accurately simulate real recordings and their information content. However, sublinear summation in quantum bump production (quantum-gain-nonlinearity) may also cause adaptation by reducing the bump/photon gain when multiple photons hit the same microvillus simultaneously. Here, we use a Random Photon Absorption Model (RandPAM), which is the 1st module of the 4-module fly photoreceptor model, to quantify the contribution of quantum-gain-nonlinearity in light adaptation. We show how quantum-gain-nonlinearity already results from photon sampling alone. In the extreme case, when two or more simultaneous photon-hits reduce to a single sublinear value, quantum-gain-nonlinearity is preset before the phototransduction reactions adapt the quantum bump waveform. However, the contribution of quantum-gain-nonlinearity in light adaptation depends upon the likelihood of multi-photon-hits, which is strictly determined by the number of microvilli and light intensity. Specifically, its contribution to light-adaptation is marginal (≤ 1%) in fly photoreceptors with many thousands of microvilli, because the probability of simultaneous multi-photon-hits on any one microvillus is low even during daylight conditions. However, in cells with fewer sampling units, the impact of quantum-gain-nonlinearity increases with brightening light. PMID:27445779

  7. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Technical Reports Server (NTRS)

    Woronowicz, M. S.

    2010-01-01

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cu cm. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  8. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    SciTech Connect

    Woronowicz, M. S.

    2011-05-20

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm{sup 3}. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  9. Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

    NASA Astrophysics Data System (ADS)

    Woronowicz, M. S.

    2011-05-01

    The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm3. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

  10. Continuous higher-order sliding mode control with time-varying gain for a class of uncertain nonlinear systems.

    PubMed

    Han, Yaozhen; Liu, Xiangjie

    2016-05-01

    This paper presents a continuous higher-order sliding mode (HOSM) control scheme with time-varying gain for a class of uncertain nonlinear systems. The proposed controller is derived from the concept of geometric homogeneity and super-twisting algorithm, and includes two parts, the first part of which achieves smooth finite time stabilization of pure integrator chains. The second part conquers the twice differentiable uncertainty and realizes system robustness by employing super-twisting algorithm. Particularly, time-varying switching control gain is constructed to reduce the switching control action magnitude to the minimum possible value while keeping the property of finite time convergence. Examples concerning the perturbed triple integrator chains and excitation control for single-machine infinite bus power system are simulated respectively to demonstrate the effectiveness and applicability of the proposed approach. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  11. New results on the robust stability of PID controllers with gain and phase margins for UFOPTD processes.

    PubMed

    Jin, Q B; Liu, Q; Huang, B

    2016-03-01

    This paper considers the problem of determining all the robust PID (proportional-integral-derivative) controllers in terms of the gain and phase margins (GPM) for open-loop unstable first order plus time delay (UFOPTD) processes. It is the first time that the feasible ranges of the GPM specifications provided by a PID controller are given for UFOPTD processes. A gain and phase margin tester is used to modify the original model, and the ranges of the margin specifications are derived such that the modified model can be stabilized by a stabilizing PID controller based on Hermite-Biehlers Theorem. Furthermore, we obtain all the controllers satisfying a given margin specification. Simulation studies show how to use the results to design a robust PID controller.

  12. Multi-axis transient vibration testing of space objects: Test philosophy, test facility, and control strategy

    NASA Technical Reports Server (NTRS)

    Lachenmayr, Georg

    1992-01-01

    IABG has been using various servohydraulic test facilities for many years for the reproduction of service loads and environmental loads on all kinds of test objects. For more than 15 years, a multi-axis vibration test facility has been under service, originally designed for earthquake simulation but being upgraded to the demands of space testing. First tests with the DFS/STM showed good reproduction accuracy and demonstrated the feasibility of transient vibration testing of space objects on a multi-axis hydraulic shaker. An approach to structural qualification is possible by using this test philosophy. It will be outlined and its obvious advantages over the state-of-the-art single-axis test will be demonstrated by example results. The new test technique has some special requirements to the test facility exceeding those of earthquake testing. Most important is the high reproduction accuracy demanded for a sophisticated control system. The state-of-the-art approach of analog closed-loop control circuits for each actuator combined with a static decoupling network and an off-line iterative waveform control is not able to meet all the demands. Therefore, the future over-all control system is implemented as hierarchical full digital closed-loop system on a highly parallel transputer network. The innermost layer is the digital actuator controller, the second one is the MDOF-control of the table movement. The outermost layer would be the off-line iterative waveform control, which is dedicated only to deal with the interaction of test table and test object or non-linear effects. The outline of the system will be presented.

  13. Determinants of Weight Gain Prevention in Young Adult and Midlife Women: Study Design and Protocol of a Randomized Controlled Trial

    PubMed Central

    2015-01-01

    Background Treatment of overweight and obesity through body weight reduction has been monumentally ineffective as few individuals are able to sustain weight loss. Rather than treating weight gain once it has become problematic, prevention of weight gain over time may be more effective. Objective The aim of this research is to preclude the burden of adult obesity in women by identifying the determinants of weight gain prevention. The objective of this randomized controlled trial (RCT) is to compare a weight gain prevention intervention delivered by the registered dietitian versus counselor. Methods This is a 12-month parallel-arm weight gain prevention RCT designed to increase self-efficacy, self-regulation, outcome expectations and family and social support through the use of a nutrition education intervention in women, aged 18-45 years, from the Urbana-Champaign (Illinois, USA) area. Women have been randomized to registered dietitian, counselor or wait-list control groups (August 2014) and are undergoing weekly nutrition education sessions for four months, followed by monthly sessions for eight months (through August 2015). Outcome measures, including: (1) dietary intake, (2) physical activity, (3) anthropometric and blood pressure measurements, (4) biochemical markers of health, (5) eating behaviors and health perceptions, and (6) mediators of behavior change, were collected before the intervention began (baseline) and will be collected at 3, 6, 9, and 12 months of the study. Results In total, 87 women have been randomized to intervention groups, and 81 women have completed first week of the study. Results are expected in early 2016. Conclusions This RCT is one of the first to examine weight gain prevention in women across normal, overweight, and obese body mass index categories. Results of this research are expected to have application to evidence-based practice in weight gain prevention for women and possibly have implication for policy regarding decreasing the

  14. An analytical method for PID controller tuning with specified gain and phase margins for integral plus time delay processes.

    PubMed

    Hu, Wuhua; Xiao, Gaoxi; Li, Xiumin

    2011-04-01

    In this paper, an analytical method is proposed for proportional-integral/proportional-derivative/proportional-integral-derivative (PI/PD/PID) controller tuning with specified gain and phase margins (GPMs) for integral plus time delay (IPTD) processes. Explicit formulas are also obtained for estimating the GPMs resulting from given PI/PD/PID controllers. The proposed method indicates a general form of the PID parameters and unifies a large number of existing rules as PI/PD/PID controller tuning with various GPM specifications. The GPMs realized by existing PID tuning rules are computed and documented as a reference for control engineers to tune the PID controllers.

  15. [Grazing systems, rotenone and parasites control in crossbred calves: effect on live weight gain and on parasites burdens].

    PubMed

    Catto, João B; Bianchin, Ivo; Santurio, Jânio M; Feijó, Gelson L D; Kichel, Armindo N; Silva, José M da

    2009-01-01

    Practices for endo and ectoparasite control in beef cattle were evaluated in two independent experiments. First, the effects of rotenone on Rhipicephalus (Boophilus) microplus ticks were evaluated in vitro and in experimentally infected calves. In the second trial, the effects of grazing systems associated with endo and ectoparasite treatments on parasite burden and weight gain of naturally parasited animals were evaluated. Rotenone showed acaricide action on larvae and engorged ticks during in vitro tests and on larvae in experimentally infected calves. Three treatments with endectocide decreased (P < .05) the number of EPG and ticks and increased (P < .05) the weight gain in the dry season. Animals treated with only one application of levamisole showed EPG intermediate and different (P < .05) from the groups treated with endectocide (lower) and control (higher) in the dry season, but the weight gain obtained with this treatment did not differ from the control group. During the raining season the animals treated with fipronil were significantly less parasited by horn fly, tick and larvae of Dermatobia hominis and the group treated with rotenone were significantly less parasited by horn fly in relation to control. Animals under rotational grazing showed significantly higher EPG than those under continuous grazing. Three treatments with endectocide in the dry season plus three acaricide treatments with fipronil in the raining season reduced EPG, tick, and screw worm larva counts, and provided a significant increase (23 kg) of live weight gain in relation to untreated animals.

  16. Control of Growth Efficiency in Young Plantation Loblolly Pine and Sweetgum through Irrigation and Fertigation Enhancement of Leaf Carbon Gain

    SciTech Connect

    L. Samuelson

    1999-07-07

    The overall objective of this study was to determine if growth efficiency of young plantation loblolly pine and sweetgum can be maintained by intensive forest management and whether increased carbon gain is the mechanism controlling growth efficiency response to resource augmentation. Key leaf physiological processes were examined over two growing seasons in response to irrigation, fertigation (irrigation with a fertilizer solution), and fertigation plus pest control (pine only). Although irrigation improved leaf net photosynthesis in pine and decreased stomatal sensitivity to vapor pressure deficit in sweetgum, no consistent physiological responses to fertigation were detected in either species. After 4 years of treatment, a 3-fold increase in woody net primary productivity was observed in both species in response to fertigation. Trees supplemented with fertigation and fertigation plus pest control exhibited the largest increases in growth and biomass. Furthermore, growth efficiency was maintained by fertigation and fertigation plus pest control, despite large increases in crown development and self-shading. Greater growth in response to intensive culture was facilitated by significant gains in leaf mass and whole tree carbon gain rather than detectable increases in leaf level processes. Growth efficiency was not maintained by significant increases in leaf level carbon gain but was possibly influenced by changes in carbon allocation to root versus shoot processes.

  17. Exercise Training and Weight Gain in Obese Pregnant Women: A Randomized Controlled Trial (ETIP Trial)

    PubMed Central

    Garnæs, Kirsti Krohn; Mørkved, Siv; Salvesen, Øyvind; Moholdt, Trine

    2016-01-01

    Background The effectiveness of exercise training for preventing excessive gestational weight gain (GWG) and gestational diabetes mellitus (GDM) is still uncertain. As maternal obesity is associated with both GWG and GDM, there is a special need to assess whether prenatal exercise training programs provided to obese women reduce the risk of adverse pregnancy outcomes. Our primary aim was to assess whether regular supervised exercise training in pregnancy could reduce GWG in women with prepregnancy overweight/obesity. Secondary aims were to examine the effects of exercise in pregnancy on 30 outcomes including GDM incidence, blood pressure, blood measurements, skinfold thickness, and body composition. Methods and Findings This was a single-center study where we randomized (1:1) 91 pregnant women with a prepregnancy body mass index (BMI) ≥ 28 kg/m2 to exercise training (n = 46) or control (standard maternity care) (n = 45). Assessments were done at baseline (pregnancy week 12–18) and in late pregnancy (week 34–37), as well as at delivery. The exercise group was offered thrice weekly supervised sessions of 35 min of moderate intensity endurance exercise and 25 min of strength training. Seventeen women were lost to follow-up (eight in the exercise group and nine in the control group). Our primary endpoint was GWG from baseline testing to delivery. The principal analyses were done as intention-to-treat analyses, with supplementary per protocol analyses where we assessed outcomes in the women who adhered to the exercise program (n = 19) compared to the control group. Mean GWG from baseline to delivery was 10.5 kg in the exercise group and 9.2 kg in the control group, with a mean difference of 0.92 kg (95% CI −1.35, 3.18; p = 0.43). Among the 30 secondary outcomes in late pregnancy, an apparent reduction was recorded in the incidence of GDM (2009 WHO definition) in the exercise group (2 cases; 6.1%) compared to the control group (9 cases; 27.3%), with an odds ratio

  18. Risk of excess weight gain in university women: a three-year community controlled analysis.

    PubMed

    Hovell, M F; Mewborn, C R; Randle, Y; Fowler-Johnson, S

    1985-01-01

    A representative sample of university freshman women were compared to same-aged community women for rate of weight change. University women were found to gain a mean of .73 lbs/month, 36 times faster than community women. Analysis of variance showed that university women gained significantly more excess weight than did community women. The incidence of developing "treatable" excess weight was 26% and 9% for university and community women, respectively. University women were 2.6 to 5.2 times as likely as community women to gain 15% or more above ideal weight. Three-year follow-up of university women showed a stabilization and reduction in mean weight for sophomore and junior years. By the junior year, average weight returned to near baseline levels as entering freshman. Mean excess weight loss was associated with a move from mandatory dormitory housing and cafeteria food services. Young adult university women (and men) may be especially important nonclinical study populations for identifying behavioral factors involved in weight gain and self-correcting weight loss, which could be valuable for development of more effective obesity prevention programs.

  19. Application variables and their influence on forest herbicide efficacy and selectivity: gaining understanding and control

    Treesearch

    James H. Miller

    1998-01-01

    Available research is reviewed on the interactions of application variables, herbicides, and species. Objectives of this review are to gain insights into why variation occurs with herbicide performance, how current knowledge might be applied to enhance efficacy and consistency, and research pathways that should foster integration of application-efficacy models. A...

  20. Visual signal detection in structured backgrounds. II. Effects of contrast gain control, background variations, and white noise

    NASA Technical Reports Server (NTRS)

    Eckstein, M. P.; Ahumada, A. J. Jr; Watson, A. B.

    1997-01-01

    Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal. To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to inhibit (divisively) the response of the receptor sensitive to the signal. In tasks in which the observer has to detect a known signal added to one of M different backgrounds grounds due to added visual noise, the main sources of degradation are the stochastic noise in the image and the suboptimal visual processing. We investigate how these two sources of degradation (contrast gain control and variations in the background) interact in a task in which the signal is embedded in one of M locations in a complex spatially varying background (structured background). We use backgrounds extracted from patient digital medical images. To isolate effects of the fixed deterministic background (the contrast gain control) from the effects of the background variations, we conduct detection experiments with three different background conditions: (1) uniform background, (2) a repeated sample of structured background, and (3) different samples of structured background. Results show that human visual detection degrades from the uniform background condition to the repeated background condition and degrades even further in the different backgrounds condition. These results suggest that both the contrast gain control mechanism and the background random variations degrade human performance in detection of a signal in a complex, spatially varying background. A filter model and added white noise are used to generate estimates of sampling efficiencies, an equivalent internal noise, an equivalent contrast-gain-control-induced noise, and an equivalent noise due to the variations in the structured background.

  1. Visual signal detection in structured backgrounds. II. Effects of contrast gain control, background variations, and white noise

    NASA Technical Reports Server (NTRS)

    Eckstein, M. P.; Ahumada, A. J. Jr; Watson, A. B.

    1997-01-01

    Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal. To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to inhibit (divisively) the response of the receptor sensitive to the signal. In tasks in which the observer has to detect a known signal added to one of M different backgrounds grounds due to added visual noise, the main sources of degradation are the stochastic noise in the image and the suboptimal visual processing. We investigate how these two sources of degradation (contrast gain control and variations in the background) interact in a task in which the signal is embedded in one of M locations in a complex spatially varying background (structured background). We use backgrounds extracted from patient digital medical images. To isolate effects of the fixed deterministic background (the contrast gain control) from the effects of the background variations, we conduct detection experiments with three different background conditions: (1) uniform background, (2) a repeated sample of structured background, and (3) different samples of structured background. Results show that human visual detection degrades from the uniform background condition to the repeated background condition and degrades even further in the different backgrounds condition. These results suggest that both the contrast gain control mechanism and the background random variations degrade human performance in detection of a signal in a complex, spatially varying background. A filter model and added white noise are used to generate estimates of sampling efficiencies, an equivalent internal noise, an equivalent contrast-gain-control-induced noise, and an equivalent noise due to the variations in the structured background.

  2. Optimal camera exposure for video surveillance systems by predictive control of shutter speed, aperture, and gain

    NASA Astrophysics Data System (ADS)

    Torres, Juan; Menéndez, José Manuel

    2015-02-01

    This paper establishes a real-time auto-exposure method to guarantee that surveillance cameras in uncontrolled light conditions take advantage of their whole dynamic range while provide neither under nor overexposed images. State-of-the-art auto-exposure methods base their control on the brightness of the image measured in a limited region where the foreground objects are mostly located. Unlike these methods, the proposed algorithm establishes a set of indicators based on the image histogram that defines its shape and position. Furthermore, the location of the objects to be inspected is likely unknown in surveillance applications. Thus, the whole image is monitored in this approach. To control the camera settings, we defined a parameters function (Ef ) that linearly depends on the shutter speed and the electronic gain; and is inversely proportional to the square of the lens aperture diameter. When the current acquired image is not overexposed, our algorithm computes the value of Ef that would move the histogram to the maximum value that does not overexpose the capture. When the current acquired image is overexposed, it computes the value of Ef that would move the histogram to a value that does not underexpose the capture and remains close to the overexposed region. If the image is under and overexposed, the whole dynamic range of the camera is therefore used, and a default value of the Ef that does not overexpose the capture is selected. This decision follows the idea that to get underexposed images is better than to get overexposed ones, because the noise produced in the lower regions of the histogram can be removed in a post-processing step while the saturated pixels of the higher regions cannot be recovered. The proposed algorithm was tested in a video surveillance camera placed at an outdoor parking lot surrounded by buildings and trees which produce moving shadows in the ground. During the daytime of seven days, the algorithm was running alternatively together

  3. Male, but not Female, Alcohol-Dependent African Americans Discount Delayed Gains More Steeply than Propensity-Score Matched Controls

    PubMed Central

    Myerson, Joel; Green, Leonard; van den Berk-Clark, Carissa; Grucza, Richard A.

    2015-01-01

    Rationale Alcohol dependence is known to be associated with steep discounting of delayed rewards, but its relation to the discounting of delayed losses and probabilistic rewards is unclear. Moreover, patterns of alcohol consumption vary considerably between communities, but previous research has not examined the relation between discounting and alcohol dependence in low-income African Americans. Objectives The goal of the present study was to determine whether low-income, alcohol-dependent African Americans differ from controls in the degree to which they discount delayed rewards, delayed losses, or probabilistic rewards. Methods African American participants, both cases and controls, were recruited from the same low-income neighborhoods, and propensity-score matching was used to further control for demographic differences. Participants performed three tasks that assessed their discounting of hypothetical monetary outcomes: delayed rewards, delayed losses, and probabilistic rewards. Results Alcohol-dependent cases discounted delayed gains, but not delayed losses or probabilistic gains, more steeply than their matched controls. The difference in discounting of delayed gains was localized to the male cases, whose discounting was steeper than either the male controls or the female cases; no gender difference was observed between male and female controls. Conclusions The present results extend findings regarding discounting by substance abusers to a previously unstudied group, low-income African Americans, and suggest that in this group at least, alcohol dependence, particularly in males, may be more a reflection of choosing immediate rewards than of ignoring their delayed negative consequences. PMID:26387518

  4. Pregnancy-associated transient osteoporosis of the hip: results of a case-control study.

    PubMed

    Hadji, Peyman; Boekhoff, Jelena; Hahn, Melitta; Hellmeyer, Lars; Hars, Olaf; Kyvernitakis, Ioannis

    2017-12-01

    The etiology and underlying mechanisms of transient of osteoporosis of the hip (TOH) during pregnancy are still unclear, since no systematic analyses exist. Our results support the hypothesis that TOH is a multifactorial disease, which is associated with immobility, dental problems, and lack of exercise in childhood. Pregnancy-associated transient osteoporosis of the hip (TOH) is a rare but severe form of osteoporosis, which may affect a subgroup of women in the last trimester of pregnancy or immediately postpartum. Common symptoms include acute pain of the hip(s) due to bone marrow edema or even hip fractures. The exact underlining mechanisms of this disorder are still unknown since no published systematic analyses exist. Out of a total of 52 TOH patients, 33 TOH patients could be matched with 33 healthy controls according to age, region, and gravity. The aim of this retrospective case-control study was to evaluate the risk factors for TOH in a homogenous population of women. The baseline characteristics of the two study groups were similar. Overall, 12.1% of the TOH patients sustained a hip fracture. Expectedly, 90.9% of the TOH patients complained about pain of the hip (p ≤ 0.001). TOH patients suffered more frequently from severe dental problems during childhood (p = 0.023) and performed less often sports before and after puberty (p ≤ 0.001), whereas the frequency of immobilization during pregnancy was threefold higher compared to the control group (p = 0.007). We found a significant increase of the TOH risk in patients with dental problems in childhood (OR 3.7; CI 1.3-10.7) as well as in patients with lack of exercise during childhood (OR 4.2; CI 1.3-12.9). Our results support the hypothesis that pregnancy-associated TOH is a multifactorial disease, to which several individual factors may contribute. Hereby, we found significant associations with immobility, dental problems, and lack of exercise in childhood.

  5. Operational, control and protective system transient analyses of the closed-cycle GT-HTGR power plant

    SciTech Connect

    Openshaw, F.L.; Chan, T.W.

    1980-07-01

    This paper presents a description of the analyses of the control/protective system preliminary designs for the gas turbine high-temperature gas-cooled reactor (GT-HTGR) power plant. The control system is designed to regulate reactor power, control electric load and turbine speed, control the temperature of the helium delivered to the turbines, and control thermal transients experienced by the system components. In addition, it provides the required control programming for startup, shutdown, load ramp, and other expected operations. The control system also handles conditions imposed on the system during upset and emergency conditions such as loop trip, reactor trip, or electrical load rejection.

  6. A temperature-dependent gain control system for improving the stability of Si-PM-based PET systems

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Satomi, Junkichi; Watabe, Tadashi; Watabe, Hiroshi; Kanai, Yasukazu; Imaizumi, Masao; Shimosegawa, Eku; Hatazawa, Jun

    2011-05-01

    The silicon-photomultiplier (Si-PM) is a promising photodetector for the development of new PET systems due to its small size, high gain and relatively low sensitivity to the static magnetic field. One drawback of the Si-PM is that it has significant temperature-dependent gain that poses a problem for the stability of the Si-PM-based PET system. To reduce this problem, we developed and tested a temperature-dependent gain control system for the Si-PM-based PET system. The system consists of a thermometer, analog-to-digital converter, personal computer, digital-to-analog converter and variable gain amplifiers in the weight summing board of the PET system. Temperature characteristics of the Si-PM array are measured and the calculated correction factor is sent to the variable gain amplifier. Without this correction, the temperature-dependent peak channel shifts of the block detector were -55% from 20 °C to 35 °C. With the correction, the peak channel variations were corrected within ±8%. The coincidence count rate of the Si-PM-based PET system was measured using a Na-22 point source while monitoring the room temperature. Without the correction, the count rate inversely changed with the room temperature by 10% for 1.5° C temperature changes. With the correction, the count rate variation was reduced to within 3.7%. These results indicate that the developed temperature-dependent gain control system can contribute to improving the stability of Si-PM-based PET systems.

  7. A temperature-dependent gain control system for improving the stability of Si-PM-based PET systems.

    PubMed

    Yamamoto, Seiichi; Satomi, Junkichi; Watabe, Tadashi; Watabe, Hiroshi; Kanai, Yasukazu; Imaizumi, Masao; Shimosegawa, Eku; Hatazawa, Jun

    2011-05-07

    The silicon-photomultiplier (Si-PM) is a promising photodetector for the development of new PET systems due to its small size, high gain and relatively low sensitivity to the static magnetic field. One drawback of the Si-PM is that it has significant temperature-dependent gain that poses a problem for the stability of the Si-PM-based PET system. To reduce this problem, we developed and tested a temperature-dependent gain control system for the Si-PM-based PET system. The system consists of a thermometer, analog-to-digital converter, personal computer, digital-to-analog converter and variable gain amplifiers in the weight summing board of the PET system. Temperature characteristics of the Si-PM array are measured and the calculated correction factor is sent to the variable gain amplifier. Without this correction, the temperature-dependent peak channel shifts of the block detector were -55% from 20 °C to 35 °C. With the correction, the peak channel variations were corrected within ±8%. The coincidence count rate of the Si-PM-based PET system was measured using a Na-22 point source while monitoring the room temperature. Without the correction, the count rate inversely changed with the room temperature by 10% for 1.5° C temperature changes. With the correction, the count rate variation was reduced to within 3.7%. These results indicate that the developed temperature-dependent gain control system can contribute to improving the stability of Si-PM-based PET systems.

  8. Turbulent Boundary Layer Drag Reduction by Active Control of Streak Transient Growth

    NASA Astrophysics Data System (ADS)

    Thomas, Flint; Corke, Thomas; Hussain, Fazle; Duong, Alan; McGowan, Ryan; Jasinski, Chrisotpher; Simmons, Daniel

    2016-11-01

    Experiments are reported employing a novel method of large-scale active flow control that was designed to intervene in Streak Transient Growth (STG) which was first postulated by Schoppa and Hussain as the primary mechanism in the production of streamwise vorticity in wall-bounded turbulence. We term the actuator SLIPPS ("Smart Longitudinal Instability Prevention via Plasma Surface). It consists of a new pulsed-DC plasma actuator array that is mounted flush with the wall in a zero pressure gradient, high Reynolds number turbulent boundary layer. The array induces a near-wall spanwise mean velocity component that is comparable in magnitude to the local friction velocity. This prevents the lift-up of low-speed streaks, thereby limiting their flanking wall-normal vorticity, which has been shown to be a critical parameter is STG. Experiments demonstrate friction drag reduction of up to 68%. Measured drag reduction is found to scale with the actuator array spanwise inter-electrode spacing, with the maximum drag reduction corresponding to the simultaneous control of approximately 8-10 low-speed streaks. Due to the unique voltage-current characteristics of the pulsed-DC actuator, the drag reduction is obtained with net power savings. Supported by NASA Langley under NNX15CL65P.

  9. Mode control in a high gain relativistic klystron amplifier with 3 GW output power

    NASA Astrophysics Data System (ADS)

    Wu, Yang; Xie, Hong-Quan; Xu, Zhou

    2014-01-01

    Higher mode excitation is very serious in the relativistic klystron amplifier, especially for the high gain relativistic amplifier working at tens of kilo-amperes. The mechanism of higher mode excitation is explored in the PIC simulation and it is shown that insufficient separation of adjacent cavities is the main cause of higher mode excitation. So RF lossy material mounted on the drift tube wall is adopted to suppress higher mode excitation. A high gain S-band relativistic klystron amplifier is designed for the beam current of 13 kA and the voltage of 1 MV. PIC simulation shows that the output power is 3.2 GW when the input power is only 2.8 kW.

  10. A Technology-Mediated Behavioral Weight Gain Prevention Intervention for College Students: Controlled, Quasi-Experimental Study

    PubMed Central

    Monroe, Courtney M; Turner-McGrievy, Gabrielle; Sundstrom, Beth; Larsen, Chelsea; Magradey, Karen; Wilcox, Sara; Brandt, Heather M

    2016-01-01

    Background Both men and women are vulnerable to weight gain during the college years, and this phenomenon is linked to an increased risk of several chronic diseases and mortality. Technology represents an attractive medium for the delivery of weight control interventions focused on college students, given its reach and appeal among this population. However, few technology-mediated weight gain prevention interventions have been evaluated for college students. Objective This study examined a new technology-based, social media-facilitated weight gain prevention intervention for college students. Methods Undergraduates (n =58) in two sections of a public university course were allocated to either a behavioral weight gain prevention intervention (Healthy Weight, HW; N=29) or a human papillomavirus (HPV) vaccination awareness intervention (control; N=29). All students were enrolled, regardless of initial body weight or expressed interest in weight management. The interventions delivered 8 lessons via electronic newsletters and Facebook postings over 9 weeks, which were designed to foster social support and introduce relevant educational content. The HW intervention targeted behavioral strategies to prevent weight gain and provided participants with a Wi-Fi-enabled scale and an electronic physical activity tracker to facilitate weight regulation. A repeated-measures analysis of variance was conducted to examine within- and between-group differences in measures of self-reported weight control practices and objectively measured weight. Use of each intervention medium and device was objectively tracked, and intervention satisfaction measures were obtained. Results Students remained weight stable (HW: −0.48+1.9 kg; control: −0.45+1.4 kg), with no significant difference between groups over 9 weeks (P =.94). However, HW students reported a significantly greater increase in the number of appropriate weight control strategies than did controls (2.1+4.5 vs −1

  11. A Technology-Mediated Behavioral Weight Gain Prevention Intervention for College Students: Controlled, Quasi-Experimental Study.

    PubMed

    West, Delia Smith; Monroe, Courtney M; Turner-McGrievy, Gabrielle; Sundstrom, Beth; Larsen, Chelsea; Magradey, Karen; Wilcox, Sara; Brandt, Heather M

    2016-06-13

    Both men and women are vulnerable to weight gain during the college years, and this phenomenon is linked to an increased risk of several chronic diseases and mortality. Technology represents an attractive medium for the delivery of weight control interventions focused on college students, given its reach and appeal among this population. However, few technology-mediated weight gain prevention interventions have been evaluated for college students. This study examined a new technology-based, social media-facilitated weight gain prevention intervention for college students. Undergraduates (n =58) in two sections of a public university course were allocated to either a behavioral weight gain prevention intervention (Healthy Weight, HW; N=29) or a human papillomavirus (HPV) vaccination awareness intervention (control; N=29). All students were enrolled, regardless of initial body weight or expressed interest in weight management. The interventions delivered 8 lessons via electronic newsletters and Facebook postings over 9 weeks, which were designed to foster social support and introduce relevant educational content. The HW intervention targeted behavioral strategies to prevent weight gain and provided participants with a Wi-Fi-enabled scale and an electronic physical activity tracker to facilitate weight regulation. A repeated-measures analysis of variance was conducted to examine within- and between-group differences in measures of self-reported weight control practices and objectively measured weight. Use of each intervention medium and device was objectively tracked, and intervention satisfaction measures were obtained. Students remained weight stable (HW: -0.48+1.9 kg; control: -0.45+1.4 kg), with no significant difference between groups over 9 weeks (P =.94). However, HW students reported a significantly greater increase in the number of appropriate weight control strategies than did controls (2.1+4.5 vs -1.1+3.4, respectively; P =.003) and there was no increase in

  12. Independent effects of attentional gain control and competitive interactions on visual stimulus processing.

    PubMed

    Keitel, Christian; Andersen, Søren K; Quigley, Cliodhna; Müller, Matthias M

    2013-04-01

    Attention filters behaviorally relevant stimuli from the constant stream of sensory information comprising our environment. Research into underlying neural mechanisms in humans suggests that visual attention biases mutual suppression between stimuli resulting from competition for limited processing resources. As a consequence, processing of an attended stimulus is facilitated. This account makes 2 assumptions: 1) An attended stimulus is released from mutual suppression with competing stimuli and 2) an attended stimulus experiences greater gain in the presence of competing stimuli than when it is presented alone. Here, we tested these assumptions by recording frequency-tagged potentials elicited in early visual cortex that index stimulus-specific processing. We contrasted the processing of a given stimulus when its location was attended or unattended and in the presence or the absence of a nearby competing stimulus. At variance with previous findings, competition similarly suppressed processing of attended and unattended stimuli. Moreover, the magnitude of attentional gain was comparable in the presence or the absence of competing stimuli. We conclude that visuospatial selective attention does not directly modulate mutual suppression between stimuli but instead acts as a signal gain, which biases processing toward attended stimuli independent of competition.

  13. Coaxial GaAs-AlGaAs core-multishell nanowire lasers with epitaxial gain control

    SciTech Connect

    Stettner, T. E-mail: Gregor.Koblmueller@wsi.tum.de Zimmermann, P.; Loitsch, B.; Regler, A.; Mayer, B.; Winnerl, J.; Matich, S.; Riedl, H.; Kaniber, M.; Abstreiter, G.; Koblmüller, G. E-mail: Gregor.Koblmueller@wsi.tum.de Finley, J. J. E-mail: Gregor.Koblmueller@wsi.tum.de; Döblinger, M.

    2016-01-04

    We demonstrate the growth and single-mode lasing operation of GaAs-AlGaAs core-multishell nanowires (NW) with radial single and multiple GaAs quantum wells (QWs) as active gain media. When subject to optical pumping lasing emission with distinct s-shaped input-output characteristics, linewidth narrowing and emission energies associated with the confined QWs are observed. Comparing the low temperature performance of QW NW laser structures having 7 coaxial QWs with a nominally identical structure having only a single QW shows that the threshold power density reduces several-fold, down to values as low as ∼2.4 kW/cm{sup 2} for the multiple QW NW laser. This confirms that the individual radial QWs are electronically weakly coupled and that epitaxial design can be used to optimize the gain characteristics of the devices. Temperature-dependent investigations show that lasing prevails up to 300 K, opening promising new avenues for efficient III–V semiconductor NW lasers with embedded low-dimensional gain media.

  14. Raman gain induced mode evolution and on-demand coupling control in whispering-gallery-mode microcavities.

    PubMed

    Yang, Xu; Özdemir, Şahin Kaya; Peng, Bo; Yilmaz, Huzeyfe; Lei, Fu-Chuan; Long, Gui-Lu; Yang, Lan

    2015-11-16

    Waveguide-coupled optical resonators have played an important role in a wide range of applications including optical communication, sensing, nonlinear optics, slow/fast light, and cavity QED. In such a system, the coupling regimes strongly affect the resonance feature in the light transmission spectra, and hence the performance and outcomes of the applications. Therefore it is crucial to control the coupling between the waveguide and the microresonator. In this work, we investigated a fiber-taper coupled whispering-gallery-mode microresonator system, in which the coupling regime is traditionally controlled by adjusting the distance between the resonator and the fiber-taper mechanically. We propose and experimentally demonstrate that by utilizing Raman gain one can achieve on-demand control of the coupling regime without any mechanical movement in the resonator system. Particularly, the application of Raman gain is accompanied by Q enhancement. We also show that with the help of Raman gain control, the transitions between various coupling regimes can affect the light transmission spectra so as to provide better resolvability and signal amplification. This all-optical approach is also suitable for monolithically integrated and packaged waveguide-resonator systems, whose coupling regime is fixed at the time of manufacturing. It provides an effective route to control the light transmission in a waveguide-couple resonator system without mechanically moving individual optical components.

  15. Adaptive-gain fast super-twisting sliding mode fault tolerant control for a reusable launch vehicle in reentry phase.

    PubMed

    Zhang, Yao; Tang, Shengjing; Guo, Jie

    2017-09-04

    In this paper, a novel adaptive-gain fast super-twisting (AGFST) sliding mode attitude control synthesis is carried out for a reusable launch vehicle subject to actuator faults and unknown disturbances. According to the fast nonsingular terminal sliding mode surface (FNTSMS) and adaptive-gain fast super-twisting algorithm, an adaptive fault tolerant control law for the attitude stabilization is derived to protect against the actuator faults and unknown uncertainties. Firstly, a second-order nonlinear control-oriented model for the RLV is established by feedback linearization method. And on the basis a fast nonsingular terminal sliding mode (FNTSM) manifold is designed, which provides fast finite-time global convergence and avoids singularity problem as well as chattering phenomenon. Based on the merits of the standard super-twisting (ST) algorithm and fast reaching law with adaption, a novel adaptive-gain fast super-twisting (AGFST) algorithm is proposed for the finite-time fault tolerant attitude control problem of the RLV without any knowledge of the bounds of uncertainties and actuator faults. The important feature of the AGFST algorithm includes non-overestimating the values of the control gains and faster convergence speed than the standard ST algorithm. A formal proof of the finite-time stability of the closed-loop system is derived using the Lyapunov function technique. An estimation of the convergence time and accurate expression of convergence region are also provided. Finally, simulations are presented to illustrate the effectiveness and superiority of the proposed control scheme. Copyright © 2017. Published by Elsevier Ltd.

  16. Reason's Enemy Is Not Emotion: Engagement of Cognitive Control Networks Explains Biases in Gain/Loss Framing.

    PubMed

    Li, Rosa; Smith, David V; Clithero, John A; Venkatraman, Vinod; Carter, R McKell; Huettel, Scott A

    2017-03-29

    In the classic gain/loss framing effect, describing a gamble as a potential gain or loss biases people to make risk-averse or risk-seeking decisions, respectively. The canonical explanation for this effect is that frames differentially modulate emotional processes, which in turn leads to irrational choice behavior. Here, we evaluate the source of framing biases by integrating functional magnetic resonance imaging data from 143 human participants performing a gain/loss framing task with meta-analytic data from >8000 neuroimaging studies. We found that activation during choices consistent with the framing effect were most correlated with activation associated with the resting or default brain, while activation during choices inconsistent with the framing effect was most correlated with the task-engaged brain. Our findings argue against the common interpretation of gain/loss framing as a competition between emotion and control. Instead, our study indicates that this effect results from differential cognitive engagement across decision frames.SIGNIFICANCE STATEMENT The biases frequently exhibited by human decision makers have often been attributed to the presence of emotion. Using a large fMRI sample and analysis of whole-brain networks defined with the meta-analytic tool Neurosynth, we find that neural activity during frame-biased decisions was more significantly associated with default behaviors (and the absence of executive control) than with emotion. These findings point to a role for neuroscience in shaping long-standing psychological theories in decision science.

  17. Reason's Enemy Is Not Emotion: Engagement of Cognitive Control Networks Explains Biases in Gain/Loss Framing

    PubMed Central

    2017-01-01

    In the classic gain/loss framing effect, describing a gamble as a potential gain or loss biases people to make risk-averse or risk-seeking decisions, respectively. The canonical explanation for this effect is that frames differentially modulate emotional processes, which in turn leads to irrational choice behavior. Here, we evaluate the source of framing biases by integrating functional magnetic resonance imaging data from 143 human participants performing a gain/loss framing task with meta-analytic data from >8000 neuroimaging studies. We found that activation during choices consistent with the framing effect were most correlated with activation associated with the resting or default brain, while activation during choices inconsistent with the framing effect was most correlated with the task-engaged brain. Our findings argue against the common interpretation of gain/loss framing as a competition between emotion and control. Instead, our study indicates that this effect results from differential cognitive engagement across decision frames. SIGNIFICANCE STATEMENT The biases frequently exhibited by human decision makers have often been attributed to the presence of emotion. Using a large fMRI sample and analysis of whole-brain networks defined with the meta-analytic tool Neurosynth, we find that neural activity during frame-biased decisions was more significantly associated with default behaviors (and the absence of executive control) than with emotion. These findings point to a role for neuroscience in shaping long-standing psychological theories in decision science. PMID:28264981

  18. High Efficiency Automatic-Power-Controlled and Gain-Clamped EDFA for Broadband Passive Optical Networking Systems

    NASA Astrophysics Data System (ADS)

    Shen, Jyi-Lai; Wei, Shui-Ken; Lin, Chin-Yuan; Iong Li, Ssu; Huang, Chih-Chuan

    2010-04-01

    The configuration of a simple improved high efficiency automatic-power-controlled and gain-clamped EDFA (APC-GC-EDFA) for broadband passive optical networking systems (BPON) is presented here. In order to compensate the phase and amplitude variation due to the different distance between the optical line terminal (OLT) and optical network units (ONU), the APC-GC-EDFA need to be employed. A single 980 nm laser module is employed as the primary pump. To extend the bandwidth, all C-band ASE is recycled as the secondary pump to enhance the gain efficiency. An electrical feedback circuit is used as a multi-wavelength channel transmitter monitor for the automatic power control to improve the gain-flattened flatness for stable amplification. The experimental results prove that the EDFA system can provide flatter clamped gain in both C-band and L-band configurations. The gain flatness wavelength ranging from 1530 to 1610 nm is within 32.83 ± 0.64 dB, i.e. below 1.95 %. The gains are clamped at 33.85 ± 0.65 dB for the input signal power of -40 dBm to -10 dBm. The range of noise figure is between 6.37 and 6.56, which is slightly lower compared to that of unclamped amplifiers. This will be very useful for measuring the gain flatness of APC-GC-EDFA. Finally, we have also demonstrated the records of the overall simultaneous dynamics measurements for the new system stabilization. The carrier to noise ratio (CNR) is 49.5 to 50.8 dBc which is above the National Television System Committee (NTSC) standard of 43 dBc, and both composite second order (CSO) 69.2 to 71.5 dBc and composite triple beat (CTB) of 69.8 to 72.2 dBc are above 53 dBc. The recorded corresponding rise-time of 1.087 ms indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse.

  19. Automatic Ship Handling of the Maritime Search Mission using a Self-Tuning Fuzzy Gain Scheduling PD Controller

    NASA Astrophysics Data System (ADS)

    Yu, Ker-Wei; Hwang, Rey-Chue; Hsieh, Jer-Guang

    In this paper, the ship manoeuvring problems particular to maritime search and rescue are investigated. A solution to such problems is necessary for successful ship handling to save human life. A fuzzy gain scheduling Proportional Derivative (PD) controller, using a back-propagation algorithm, is developed to solve these maritime search and rescue problems. The parameters of the proposed PD controller are determined on-line by fuzzy rules and adjustable fuzzy reasons. The proposed controller is self-adaptive and can accommodate the effects caused by wave or wind disturbance. Some computer simulations are provided to illustrate the use of the main ideas.

  20. Lasing threshold control in two-dimensional photonic crystals with gain

    SciTech Connect

    Droulias, Sotiris; Fietz, Chris; Zhang, Peng; Koschny, Thomas; Soukoulis, Costas M

    2014-01-01

    We demonstrate how the lasing threshold of a two dimensional photonic crystal containing a four-level gain medium is modified, as a result of the interplay between the group velocity and the modal reflectivity at the interface between the cavity and the exterior. Depending on their relative strength and the optical density of states, we show how the lasing threshold may be dramatically altered inside a band or, most importantly, close to the band edge. The idea is realized via self-consistent calculations based on a finite-difference time-domain method. The simulations are in good agreement with theoretical predictions.

  1. Randomized Controlled Trial of Restrictive Fluid Management in Transient Tachypnea of the Newborn

    PubMed Central

    Stroustrup, Annemarie; Trasande, Leonardo; Holzman, Ian R.

    2011-01-01

    Objective To determine the effect of mild fluid restriction on the hospital course of neonates with transient tachypnea of the newborn (TTN). Study design This is a pilot prospective randomized controlled trial of 64 late preterm and term neonates diagnosed with TTN at a single tertiary-care hospital in the United States. Patients were randomized to receive standard fluid management or mild fluid restriction. Primary outcome was duration of respiratory support. Secondary outcomes were duration of admission to the ICU, time to first enteral feed, and total and composite hospital charges. Results were analyzed by t-test, chi-square, Kaplan-Meier estimation and proportional hazards regression. Results Fluid restriction did not cause adverse events or unsafe dehydration. Fluid management strategy did not affect primary or secondary outcomes in the broad study population. Fluid restriction significantly reduced duration of respiratory support (p=0.008) and hospitalization costs (p=0.017) for neonates with severe TTN. Conclusions Mild fluid restriction appears safe in late preterm and term neonates with uncomplicated TTN. Fluid restriction may be of benefit in decreasing duration of respiratory support and hospitalization charges in term and late preterm neonates with uncomplicated severe TTN. PMID:21839467

  2. Improved synthetic-heterodyne Michelson interferometer vibrometer using phase and gain control feedback.

    PubMed

    Galeti, José Henrique; Kitano, Cláudio; Connelly, Michael J

    2015-12-10

    Synthetic-heterodyne demodulation is a useful technique for dynamic displacement and velocity measurement using interferometric sensors as it can provide an output signal which is immune to interferometric drift. With the advent of cost effective, high-speed real-time signal processing systems and software, processing of the complex signals encountered in interferometry has become more feasible. In conventional synthetic-heterodyne demodulation schemes, to obtain the dynamic displacement or vibration of the object under test requires knowledge of the interferometer visibility and also the argument of two Bessel functions. In this paper, a new synthetic-heterodyne demodulation method is described leading to an expression for the dynamic displacement and velocity of the object under test that is significantly less sensitive to the received optical power. In addition, the application of two independent phase and gain feedback loops is used to compensate for the nonideal gain and phase response of the anti-aliasing filter required for the signal acquisition of the received wideband interferometer signal. The efficacy of the improved system is demonstrated by measuring the displacement sensitivity frequency response and linearity of a Piezoelectric Mirror-Shifter (PMS) over a range of 200 Hz-9 kHz. In addition, the system is used to measure the response of the PMS to triangular and impulse type stimuli. The experimental results show excellent agreement with measurements taken using two independent industry standard calibration methods.

  3. A decision tree-based on-line preventive control strategy for power system transient instability prevention

    NASA Astrophysics Data System (ADS)

    Xu, Yan; Dong, Zhao Yang; Zhang, Rui; Wong, Kit Po

    2014-02-01

    Maintaining transient stability is a basic requirement for secure power system operations. Preventive control deals with modifying the system operating point to withstand probable contingencies. In this article, a decision tree (DT)-based on-line preventive control strategy is proposed for transient instability prevention of power systems. Given a stability database, a distance-based feature estimation algorithm is first applied to identify the critical generators, which are then used as features to develop a DT. By interpreting the splitting rules of DT, preventive control is realised by formulating the rules in a standard optimal power flow model and solving it. The proposed method is transparent in control mechanism, on-line computation compatible and convenient to deal with multi-contingency. The effectiveness and efficiency of the method has been verified on New England 10-machine 39-bus test system.

  4. Weight Gain Prevention among Midlife Women: A Randomized Controlled Trial to Address Needs Related to the Physical and Social Environment

    PubMed Central

    Perry, Courtney D.; Degeneffe, Dennis; Davey, Cynthia; Kollannoor-Samuel, Grace; Reicks, Marla

    2016-01-01

    Women tend to gain weight at midlife (40–60 years) increasing risk of obesity-related chronic diseases. Within specific eating occasions, needs related to the physical and social environment may result in less healthy eating behavior, which can lead to weight gain over time. The purpose of this study was to determine if a dietitian-delivered nutrition counseling intervention tailored to eating occasion needs could improve diet and prevent weight gain among midlife women over two years. A randomized controlled trial was conducted with healthy midlife women (n = 354) in one U.S. metropolitan area. The intervention group (n = 185) received ten hours of individual nutrition counseling from dietitians over six months, while women in a control group (n = 169) received no counseling. Measured height, weight and waist circumference, and dietary intakes were collected at baseline and every six months over two years. Mixed linear models were used to test for intervention effect on change in outcome variables over time. Dietary intakes of fruit, reduced/low-fat dairy foods and refined grains were significantly improved over time in the intervention compared to control group. However, the intervention had no effect on weight over time (p = 0.48). Nutrition counseling tailored to address eating occasion needs improved self-reported diet but did not significantly affect weight change. PMID:27231927

  5. Locus of Control, Psychopathology, and Weight Gain in Juvenile Anorexia Nervosa.

    ERIC Educational Resources Information Center

    Strober, Michael

    1982-01-01

    Based on a hypothesized disturbance in personal control and efficacy in anorexia nervosa, locus of control score in female adolescents with anorexia nervosa was compared to scores obtained from depressed and conduct-disordered controls and to adolescent female standardization norms. (Author/CL)

  6. Locus of Control, Psychopathology, and Weight Gain in Juvenile Anorexia Nervosa.

    ERIC Educational Resources Information Center

    Strober, Michael

    1982-01-01

    Based on a hypothesized disturbance in personal control and efficacy in anorexia nervosa, locus of control score in female adolescents with anorexia nervosa was compared to scores obtained from depressed and conduct-disordered controls and to adolescent female standardization norms. (Author/CL)

  7. A Semi-Automatic, Remote-Controlled Video Observation System for Transient Luminous Events

    NASA Astrophysics Data System (ADS)

    Allin, T.; Neubert, T.; Laursen, S.; Rasmussen, I. L.; Soula, S.

    2003-12-01

    In support for global ELF/VLF observations, HF measurements in France, and conjugate photometry/VLF observations in South Africa, we developed and operated a semi-automatic, remotely controlled video system for the observation of middle-atmospheric transient luminous events (TLEs). Installed at the Pic du Midi Observatory in Southern France, the system was operational during the period from July 18 to September 15, 2003. The video system, based two low-light, non-intensified CCD video cameras, was mounted on top of a motorized pan/tilt unit. The cameras and the pan/tilt unit were controlled over serial links from a local computer, and the video outputs were distributed to a pair of PCI frame grabbers in the computer. This setup allowed remote users to log in and operate the system over the internet. Event detection software provided means of recording and time-stamping single TLE video fields and thus eliminated the need for continuous human monitoring of TLE activity. The computer recorded and analyzed two parallel video streams at the full 50 Hz field rate, while uploading status images, TLE images, and system logs to a remote web server. The system detected more than 130 TLEs - mostly sprites - distributed over 9 active evenings. We have thus demonstrated the feasibility of remote agents for TLE observations, which are likely to find use in future ground-based TLE observation campaigns, or to be installed at remote sites in support for space-borne or other global TLE observation efforts.

  8. An implantable neural activity monitor with nonlinear gain-controlled amplifier.

    PubMed

    Kyoso, Masaki; Takeda, Takahiro

    2013-01-01

    An implantable neural spike monitor with nonlinear amplifier was proposed for robust measurement against noise. In embedded electrophysiological signal processing systems, detection performance depends on signal to noise ratio (SNR), however, it is getting worth after implantation because of neoformation surrounding the electrodes and so on. We proposed a spike enhancer in this study. It has two remarkable function; automatic gain optimization with feedback loop and SNR improvement by nonlinear amplifier. In this report, the system performance was evaluated without feedback loop. A prototype circuit is prepared with small number of parts and tested on input-output characteristics. For the final evaluation, neural spike signal from somatosensory cortex of a rat was applied to the circuit. The test results show that system can expand SNR on neural spike signal from rat. It indicates that the spike enhancer can improve total performance of neural activity processing system.

  9. Satisfaction and gains perceived by nursing students with medium and high-fidelity simulation: A randomized controlled trial.

    PubMed

    Baptista, Rui C N; Paiva, Luís A R; Gonçalves, Rui F L; Oliveira, Luís M N; Pereira, Maria de Fátima C R; Martins, José C A

    2016-11-01

    The use of simulation to reproduce the experience of health care settings and its use as a strategy in the teaching of nurses has grown at an unprecedented rate. There is little scientific evidence to examine the differences in satisfaction and gains perceived by the students with the use of medium and high fidelity. To analyse and benchmark gains and satisfaction perceived by nursing students, according to their participation in medium- and high-fidelity simulated practice. Randomized control trial post-test only design with control group. Students of the 4th year of the Bachelor's Degree in Nursing who performed medium and high-fidelity simulated practice in a Simulation Centre environment. A satisfaction scale and a scale of perceived gains from the simulation were applied to the students who underwent simulated practice in a medium-fidelity environment (control group) and high-fidelity environment (experimental group). Statistical analysis was performed and a significance level of p<0.05 was established. Of the 85 students who participated in the study, the majority were female (92.94%), with an average age of 21.89years (SD=2.81years). Satisfaction is statistically significant in the realism dimension and overall satisfaction. In the gains perceived with the simulation there is a statistically significant difference in the dimension recognition/decision. Students are very satisfied with the realism of high-fidelity simulated practice and consider that this helps them more with recognition and decision compared with the medium-fidelity simulation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Adaptive control based on fast online algebraic identification and GPI control for magnetic levitation systems with time-varying input gain

    NASA Astrophysics Data System (ADS)

    Morales, R.; Sira-Ramírez, H.; Feliu, V.

    2014-08-01

    This paper considers the position tracking problem of a voltage-controlled magnetic levitation system (MLS) in the presence of modelling errors caused by uncertainties in the system's physical parameters. An adaptive control based on fast online algebraic parameter estimation and generalised proportional integral (GPI) output feedback control is considered as a control scheme candidate. The GPI controller guarantees an asymptotically exponentially stable behaviour of the controlled ball position and the possibilities of carrying out rest-to-rest trajectory tracking tasks. The nature of the control input gain in an MLS is that of a state-dependent time-varying gain, reflecting the nonlinear character of the magnetic force with regard to the distance and the properties of the metallic ball. The system gain has therefore been locally approximated using a periodically updated time polynomial function (of second degree), where the coefficients of the polynomial are estimated during a very short period of time. This estimation is achieved using the recently introduced algebraic online parameter estimation approach. The stability of the closed-loop system is demonstrated under the assumption that no external factors cause changes in the parameter during the time interval in which the stability is analysed. Finally, experimental results are presented for the controlled MLS demonstrating the excellent stabilisation and position tracking performance of the control system designed in the presence of significant nonlinearities and uncertainties of the underlying system.

  11. Gain Scheduling Control of Gas Turbine Engines: Stability by Computing a Single Quadratic Lyapunov Function

    DTIC Science & Technology

    2013-06-01

    engine control and monitoring systems with a dual interest in both turbofan and turboshaft engines has been covered in [3]. An application of robust...plication of the Linear-Quadratic-Gaussian with Loop-Transfer- Recovery methodology to design a control system for the F-100 turbofan engine is presented in...5], and for a simplified turbofan engine model is considered in [6]. A unified robust multivari- able approach to propulsion control design has been

  12. Control of linear modes in cylindrical resistive magnetohydrodynamics with a resistive wall, plasma rotation, and complex gain

    SciTech Connect

    Brennan, D. P.; Finn, J. M.

    2014-10-15

    Feedback stabilization of magnetohydrodynamic (MHD) modes in a tokamak is studied in a cylindrical model with a resistive wall, plasma resistivity, viscosity, and toroidal rotation. The control is based on a linear combination of the normal and tangential components of the magnetic field just inside the resistive wall. The feedback includes complex gain, for both the normal and for the tangential components, and it is known that the imaginary part of the feedback for the former is equivalent to plasma rotation [J. M. Finn and L. Chacon, Phys. Plasmas 11, 1866 (2004)]. The work includes (1) analysis with a reduced resistive MHD model for a tokamak with finite β and with stepfunction current density and pressure profiles, and (2) computations with a full compressible visco-resistive MHD model with smooth decreasing profiles of current density and pressure. The equilibria are stable for β = 0 and the marginal stability values β{sub rp,rw} < β{sub rp,iw} < β{sub ip,rw} < β{sub ip,iw} (resistive plasma, resistive wall; resistive plasma, ideal wall; ideal plasma, resistive wall; and ideal plasma, ideal wall) are computed for both models. The main results are: (a) imaginary gain with normal sensors or plasma rotation stabilizes below β{sub rp,iw} because rotation suppresses the diffusion of flux from the plasma out through the wall and, more surprisingly, (b) rotation or imaginary gain with normal sensors destabilizes above β{sub rp,iw} because it prevents the feedback flux from entering the plasma through the resistive wall to form a virtual wall. A method of using complex gain G{sub i} to optimize in the presence of rotation in this regime with β > β{sub rp,iw} is presented. The effect of imaginary gain with tangential sensors is more complicated but essentially destabilizes above and below β{sub rp,iw}.

  13. Naltrexone Reduction of Long-Term Smoking Cessation Weight Gain in Women But Not Men: A Randomized Controlled Trial

    PubMed Central

    King, Andrea C.; Cao, Dingcai; Zhang, Lingjiao; O’Malley, Stephanie S.

    2012-01-01

    Background The opioid antagonist naltrexone has shown promise to reduce weight gain during active treatment, but longer-term studies have not been conducted. The goal was to examine effects of naltrexone on weight gain over long-term follow-up in men and women who quit smoking. Methods Weight was examined at baseline and 6- and 12-month follow-up in the two largest randomized, double-blind, placebo-controlled trials of naltrexone in nicotine dependence. For 6–12 weeks after the quit date, participants were randomly assigned to receive naltrexone or placebo. Behavioral counseling and open-label nicotine patch were also included for the first 4–6 weeks. Of the 700 participants in the combined intent-to-treat sample, there were 159 (77 women) biochemically verified abstinent smokers at 6 months, and 115 (57 women) of them remained abstinent at 12 months. Changes in weight (in kilograms or in percentage) and body mass index from baseline to the follow-ups were assessed for these participants. Results Weight gain was significantly lower for women treated with naltrexone compared with placebo (6 months, 3.3 vs. 5.5 kg; 12 months, 5.9 vs. 7.4 kg, respectively). Increases in body mass index and percentage body weight gain were also significantly lower in women treated with naltrexone versus placebo. These effects were not observed in men. Conclusion The results provide evidence for naltrexone as the first pharmacotherapy to reduce postsmoking cessation weight gain among women. PMID:23177384

  14. Toward a Psychophysics of Agency: Detecting Gain and Loss of Control over Auditory Action Effects

    ERIC Educational Resources Information Center

    Repp, Bruno H.; Knoblich, Gunther

    2007-01-01

    Theories of agency--the feeling of being in control of one's actions and their effects--emphasize either perceptual or cognitive aspects. This study addresses both aspects simultaneously in a finger-tapping paradigm. The tasks required participants to detect when synchronization of their taps with computer-controlled tones changed to…

  15. Toward a Psychophysics of Agency: Detecting Gain and Loss of Control over Auditory Action Effects

    ERIC Educational Resources Information Center

    Repp, Bruno H.; Knoblich, Gunther

    2007-01-01

    Theories of agency--the feeling of being in control of one's actions and their effects--emphasize either perceptual or cognitive aspects. This study addresses both aspects simultaneously in a finger-tapping paradigm. The tasks required participants to detect when synchronization of their taps with computer-controlled tones changed to…

  16. Transient stability and control of renewable generators based on Hamiltonian surface shaping and power flow control. Part II, analysis.

    SciTech Connect

    Robinett, Rush D., III; Wilson, David Gerald

    2010-11-01

    The swing equations for renewable generators connected to the grid are developed and a wind turbine is used as an example. The swing equations for the renewable generators are formulated as a natural Hamiltonian system with externally applied non-conservative forces. A two-step process referred to as Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) is used to analyze and design feedback controllers for the renewable generators system. This formulation extends previous results on the analytical verification of the Potential Energy Boundary Surface (PEBS) method to nonlinear control analysis and design and justifies the decomposition of the system into conservative and non-conservative systems to enable a two-step, serial analysis and design procedure. The first step is to analyze the system as a conservative natural Hamiltonian system with no externally applied non-conservative forces. The Hamiltonian surface of the swing equations is related to the Equal-Area Criterion and the PEBS method to formulate the nonlinear transient stability problem. This formulation demonstrates the effectiveness of proportional feedback control to expand the stability region. The second step is to analyze the system as natural Hamiltonian system with externally applied non-conservative forces. The time derivative of the Hamiltonian produces the work/rate (power flow) equation which is used to ensure balanced power flows from the renewable generators to the loads. The Second Law of Thermodynamics is applied to the power flow equations to determine the stability boundaries (limit cycles) of the renewable generators system and enable design of feedback controllers that meet stability requirements while maximizing the power generation and flow to the load. Necessary and sufficient conditions for stability of renewable generators systems are determined based on the concepts of Hamiltonian systems, power flow, exergy (the maximum work that can be extracted from an energy flow) rate

  17. Storage for free: a surprising property of a simple gain-control model of motion aftereffects.

    PubMed

    van de Grind, Wim A; van der Smagt, Maarten J; Verstraten, Frans A J

    2004-01-01

    If a motion aftereffect (MAE) for given adaptation conditions has a duration T s, and the eyes are closed after adaptation during a waiting period tw=T s before testing, an unexpected MAE of a 'residual' duration TrT s is experienced. This effect is called 'storage' and it is often quantified by a storage factor sigma=TrT/T, which can reach values up to about 0.7-0.8. The phenomenon and its name have invited explanations in terms of inhibition of recovery during darkness. We present a model based on the opposite idea, that an effective test stimulus quickens recovery relative to darkness or other ineffective test stimuli. The model is worked out in mathematical detail and proves to explain 'storage' data from the literature, on the static MAE (sMAE: an MAE experienced for static test stimuli). We also present results of a psychophysical experiment with moving random pixel arrays, quantifying storage phenomena both for the sMAE and the dynamic MAE (dMAE: an MAE experienced for a random dynamic noise test stimulus). Storage factors for the dMAE are lower than for the sMAE. Our model also gives an excellent description of these new data on storage of the dMAE. The term 'storage' might therefore be a misnomer. If an effective test stimulus influences all direction tuned motion sensors indiscriminately and thus speeds up equalization of gains, one gets the storage phenomenon for free.

  18. Gain control through divisive inhibition prevents abrupt transition to chaos in a neural mass model

    PubMed Central

    Papasavvas, Christoforos A.; Wang, Yujiang; Trevelyan, Andrew J.; Kaiser, Marcus

    2016-01-01

    Experimental results suggest that there are two distinct mechanisms of inhibition in cortical neuronal networks: subtractive and divisive inhibition. They modulate the input-output function of their target neurons either by increasing the input that is needed to reach maximum output or by reducing the gain and the value of maximum output itself, respectively. However, the role of these mechanisms on the dynamics of the network is poorly understood. We introduce a novel population model and numerically investigate the influence of divisive inhibition on network dynamics. Specifically, we focus on the transitions from a state of regular oscillations to a state of chaotic dynamics via period-doubling bifurcations. The model with divisive inhibition exhibits a universal transition rate to chaos (Feigenbaum behavior). In contrast, in an equivalent model without divisive inhibition, transition rates to chaos are not bounded by the universal constant (non-Feigenbaum behavior). This non-Feigenbaum behavior, when only subtractive inhibition is present, is linked to the interaction of bifurcation curves in the parameter space. Indeed, searching the parameter space showed that such interactions are impossible when divisive inhibition is included. Therefore, divisive inhibition prevents non-Feigenbaum behavior and, consequently, any abrupt transition to chaos. The results suggest that the divisive inhibition in neuronal networks could play a crucial role in keeping the states of order and chaos well separated and in preventing the onset of pathological neural dynamics. PMID:26465514

  19. Gain control through divisive inhibition prevents abrupt transition to chaos in a neural mass model

    NASA Astrophysics Data System (ADS)

    Papasavvas, Christoforos A.; Wang, Yujiang; Trevelyan, Andrew J.; Kaiser, Marcus

    2015-09-01

    Experimental results suggest that there are two distinct mechanisms of inhibition in cortical neuronal networks: subtractive and divisive inhibition. They modulate the input-output function of their target neurons either by increasing the input that is needed to reach maximum output or by reducing the gain and the value of maximum output itself, respectively. However, the role of these mechanisms on the dynamics of the network is poorly understood. We introduce a novel population model and numerically investigate the influence of divisive inhibition on network dynamics. Specifically, we focus on the transitions from a state of regular oscillations to a state of chaotic dynamics via period-doubling bifurcations. The model with divisive inhibition exhibits a universal transition rate to chaos (Feigenbaum behavior). In contrast, in an equivalent model without divisive inhibition, transition rates to chaos are not bounded by the universal constant (non-Feigenbaum behavior). This non-Feigenbaum behavior, when only subtractive inhibition is present, is linked to the interaction of bifurcation curves in the parameter space. Indeed, searching the parameter space showed that such interactions are impossible when divisive inhibition is included. Therefore, divisive inhibition prevents non-Feigenbaum behavior and, consequently, any abrupt transition to chaos. The results suggest that the divisive inhibition in neuronal networks could play a crucial role in keeping the states of order and chaos well separated and in preventing the onset of pathological neural dynamics.

  20. More pain, more gain: Blocking the opioid system boosts adaptive cognitive control.

    PubMed

    van Steenbergen, Henk; Weissman, Daniel H; Stein, Dan J; Malcolm-Smith, Susan; van Honk, Jack

    2017-03-07

    The ability to adaptively increase cognitive control in response to cognitive challenges is crucial for goal-directed behavior. Recent findings suggest that aversive arousal triggers adaptive increases of control, but the neurochemical mechanisms underlying these effects remain unclear. Given the known contributions of the opioid system to hedonic states, we investigated whether blocking this system increases adaptive control modulations. To do so, we conducted a double-blind, placebo-controlled psychopharmacological study (n=52 females) involving a Stroop-like task. Specifically, we assessed the effect of naltrexone, an opioid blocker most selective to the mu-opioid system, on two measures of adaptive control that are thought to depend differentially on aversive arousal: post-error slowing and conflict adaptation. Consistent with our hypothesis, relative to placebo, naltrexone increased post-error slowing without influencing conflict adaptation. This finding not only supports the view that aversive arousal triggers adaptive control but also reveals a novel role for the opioid system in modulating such effects.

  1. Simple adaptive pH control in bioreactors using gain-scheduling methods.

    PubMed

    Gnoth, S; Kuprijanov, A; Simutis, R; Lübbert, A

    2010-01-01

    A simple well-performing adaptive control technique for pH control in fermentations of recombinant protein production processes is described and its design procedure is explained. First, the entire control algorithm was simulated and parameterized. Afterwards it was tested in real cultivation processes. The results show that this simple technique leads to significant reductions in the fluctuations of the pH values in microbial cultures at a minimum of expenditures. The signal-to-noise ratio and thus the information captured by the pH signal were increased by about an order of magnitude. This leads to a substantial improvement in the noise of many other process signals that are used to monitor and control the process. For instance, respiratory off-gas data of CO(2) and its derived carbon dioxide production rate signals from the cultures carry much less noise as compared to those values obtained with conventional pH control. Detailed process analysis revealed that even very small pH jumps of 0.03 values during the fermentation were shown to result in pronounced deflections in CO(2)-volume fraction of 8% (peak to peak). The proposed controller, maintaining the pH within the interval of 0.01 around the setpoint, reduces the noise considerably.

  2. Transient Elastography and Controlled Attenuation Parameter for Diagnosing Liver Fibrosis and Steatosis in Ontario: An Economic Analysis

    PubMed Central

    Thavorn, K; Coyle, D

    2015-01-01

    Background Liver fibrosis is characterized by a buildup of connective tissue due to chronic liver damage. Steatosis is the collection of excessive amounts of fat inside liver cells. Liver biopsy remains the gold standard for the diagnosis of liver fibrosis and steatosis, but its use as a diagnostic tool is limited by its invasive nature and high cost. Objectives To evaluate the cost-effectiveness and budget impact of transient elastography (TE) with and without controlled attenuation parameter (CAP) for the diagnosis of liver fibrosis or steatosis in patients with hepatitis B, hepatitis C, alcoholic liver disease, and nonalcoholic fatty liver disease. Data Sources An economic literature search was performed using computerized databases. For primary economic and budget impact analyses, we obtained data from various sources, such as the Health Quality Ontario evidence-based analysis, published literature, and the Institute for Clinical Evaluative Sciences. Review Methods A systematic review of existing TE cost-effectiveness studies was conducted, and a primary economic evaluation was undertaken from the perspective of the Ontario Ministry of Health and Long-Term Care. Decision analytic models were used to compare short-term costs and outcomes of TE compared to liver biopsy. Outcomes were expressed as incremental cost per correctly diagnosed cases gained. A budget impact analysis was also conducted. Results We included 10 relevant studies that evaluated the cost-effectiveness of TE compared to other noninvasive tests and to liver biopsy; no cost-effectiveness studies of TE with CAP were identified. All studies showed that TE was less expensive but associated with a decrease in the number of correctly diagnosed cases. TE also improved quality-adjusted life-years in patients with hepatitis B and hepatitis C. Our primary economic analysis suggested that TE led to cost savings but was less effective than liver biopsy in the diagnosis of liver fibrosis. TE became more

  3. Transient stability enhancement of wind farms using power electronics and facts controllers

    NASA Astrophysics Data System (ADS)

    Mohammadpour, Hossein Ali

    network, and the frequency of the exchanged energy is below the fundamental frequency of the system. This phenomenon may cause severe damage in the wind farm, if not prevented. Therefore, this dissertation deals with the SSR phenomena in a capacitive series compensated wind farm. A DFIG-based wind farm, which is connected to a series compensated transmission line, is considered as a case study. The small-signal stability analysis of the system is presented, and the eigenvalues of the system are obtained. Using both modal analysis and time-domain simulation, it is shown that the system is potentially unstable due to the SSR mode. Then, three different possibilities for the addition of SSR damping controller (SSRDC) are investigated. The SSRDC can be added to (1) gate-controlled series capacitor (GCSC), (2) thyristor-controlled series capacitor (TCSC), or (3) DFIG rotor-side converter (RSC) and grid-side converter (GSC) controllers. The first and second cases are related to the series flexible AC transmission systems (FACTS) family, and the third case uses the DFIG back-to-back converters to damp the SSR. The SSRDC is designed using residue-based analysis and root locus diagrams. Using residue-based analysis, the optimal input control signal (ICS) to the SSRDC is identified that can damp the SSR mode without destabilizing other modes, and using root-locus analysis, the required gain for the SSRDC is determined. Moreover, two methods are discussed in order to estimate the optimum input signal to the SSRDC, without measuring it directly. In this dissertation, MATLAB/Simulink is used as a tool for modeling and design of the SSRDC, and PSCAD/EMTDC is used to perform time-domain simulation in order to verify the design process.

  4. A computer-controlled transient needle-probe thermal conductivity instrument for liquids

    SciTech Connect

    Asher, G.B.; Graboski, M.S.; Sloan, E.D.; Hauley, H.J.M.; Cezairliyan, A.

    1986-03-01

    A computerized system utilizing the transient needle-probe technique has been developed for thermal conductivity measurements on solids and liquids. Thermal conductivities are determined to an accuracy of better than 5%. The instrument is unique in that it uses ''off the shelf'' components such as a personal computer and analog-to-digital conversion devices, together with software developed in our laboratory. The initial expense and time required to begin measurements are less than 20% of those for normal transient hot-wire measurements. Typical results are presented for liquid tertiary butyl alcohol, 1methylnaphthalene, and glycerin.

  5. Permeability control on transient slip weakening during gypsum dehydration: Implications for earthquakes in subduction zones

    NASA Astrophysics Data System (ADS)

    Leclère, Henri; Faulkner, Daniel; Wheeler, John; Mariani, Elisabetta

    2016-05-01

    A conflict has emerged from recent laboratory experiments regarding the question of whether or not dehydration reactions can promote unstable slip in subduction zones leading to earthquakes. Although reactions produce mechanical weakening due to pore-fluid pressure increase, this weakening has been associated with both stable and unstable slip. Here, new results monitoring strength, permeability, pore-fluid pressure, reaction progress and microstructural evolution during dehydration reactions are presented to identify the conditions necessary for mechanical instability. Triaxial experiments are conducted using gypsum and a direct shear sample assembly with constant normal stress that allows the measurement of permeability during sliding. Tests are conducted with temperature ramp from 70 to 150 °C and with different effective confining pressures (50, 100 and 150 MPa) and velocities (0.1 and 0.4 μm s-1). Results show that gypsum dehydration to bassanite induces transient stable-slip weakening that is controlled by pore-fluid pressure and permeability evolution. At the onset of dehydration, the low permeability promoted by pore compaction induces pore-fluid pressure build-up and stable slip weakening. The increase of bassanite content during the reaction shows clear evidence of dehydration related with the development of R1 Riedel shears and P foliation planes where bassanite is preferentially localized along these structures. The continued production of bassanite, which is stronger than gypsum, provides a supporting framework for newly formed pores, thus resulting in permeability increase, pore-fluid pressure drop and fault strength increase. After dehydration reaction, deformation is characterized by unstable slip on the fully dehydrated reaction product, controlled by the transition from velocity-strengthening to velocity-weakening behaviour of bassanite at temperature above ∼140 °C and the localization of deformation along narrow Y-shear planes. This study

  6. Development and application of a generalized transient computer program for Shuttle atmospheric pressure and composition control analysis

    NASA Technical Reports Server (NTRS)

    Lafuse, S. A.

    1984-01-01

    A generalized computer program for analysis of pressure and composition in a multiple-volume system has been developed by NASA. This paper describes the development of the program, outlines the program's capabilities, and illustrates the application of the program to Space Shuttle-related atmospheric pressure and composition control analyses. The program's features include the calculation of transient partial pressures of four gases in four volumes, an option for either isothermal or temperature-transient analyses, simulation of pressure and composition control hardware, and simulation involving 0-10 crewmembers. This computer program has been used successfully for a variety of Shuttle-related analyses to support hardware design, develop operating procedures, and provide real-time Shuttle mission support. Due to the versatility of this computer program, it will be utilized for Space Station program analyses.

  7. Stability, Transient Response, Control, and Safety of a High-Power Electric Grid for Turboelectric Propulsion of Aircraft

    NASA Technical Reports Server (NTRS)

    Armstrong, Michael; Ross, Christine; Phillips, Danny; Blackwelder, Mark

    2013-01-01

    This document contains the deliverables for the NASA Research and Technology for Aerospace Propulsion Systems (RTAPS) regarding the stability, transient response, control, and safety study for a high power cryogenic turboelectric distributed propulsion (TeDP) system. The objective of this research effort is to enumerate, characterize, and evaluate the critical issues facing the development of the N3-X concept aircraft. This includes the proposal of electrical grid architecture concepts and an evaluation of any needs for energy storage.

  8. Environment Control to Improve Recombinant Protein Yields in Plants Based on Agrobacterium-Mediated Transient Gene Expression

    PubMed Central

    Fujiuchi, Naomichi; Matoba, Nobuyuki; Matsuda, Ryo

    2016-01-01

    Agrobacterium-mediated transient expression systems enable plants to produce a wide range of recombinant proteins on a rapid timescale. To achieve economically feasible upstream production and downstream processing, two yield parameters should be considered: (1) recombinant protein content per unit biomass and (2) recombinant protein productivity per unit area–time at the end of the upstream production. Because environmental factors in the upstream production have impacts on these parameters, environment control is important to maximize the recombinant protein yield. In this review, we summarize the effects of pre- and postinoculation environmental factors in the upstream production on the yield parameters and discuss the basic concept of environment control for plant-based transient expression systems. Preinoculation environmental factors associated with planting density, light quality, and nutrient supply affect plant characteristics, such as biomass and morphology, which in turn affect recombinant protein content and productivity. Accordingly, environment control for such plant characteristics has significant implications to achieve a high yield. On the other hand, postinoculation environmental factors, such as temperature, light intensity, and humidity, have been shown to affect recombinant protein content. Considering that recombinant protein production in Agrobacterium-mediated transient expression systems is a result of a series of complex biological events starting from T-DNA transfer from Agrobacterium tumefaciens to protein biosynthesis and accumulation in leaf tissue, we propose that dynamic environment control during the postinoculation process, i.e., changing environmental conditions at an appropriate timing for each event, may be a promising approach to obtain a high yield. Detailed descriptions of plant growth conditions and careful examination of environmental effects will significantly contribute to our knowledge to stably obtain high recombinant

  9. Environment Control to Improve Recombinant Protein Yields in Plants Based on Agrobacterium-Mediated Transient Gene Expression.

    PubMed

    Fujiuchi, Naomichi; Matoba, Nobuyuki; Matsuda, Ryo

    2016-01-01

    Agrobacterium-mediated transient expression systems enable plants to produce a wide range of recombinant proteins on a rapid timescale. To achieve economically feasible upstream production and downstream processing, two yield parameters should be considered: (1) recombinant protein content per unit biomass and (2) recombinant protein productivity per unit area-time at the end of the upstream production. Because environmental factors in the upstream production have impacts on these parameters, environment control is important to maximize the recombinant protein yield. In this review, we summarize the effects of pre- and postinoculation environmental factors in the upstream production on the yield parameters and discuss the basic concept of environment control for plant-based transient expression systems. Preinoculation environmental factors associated with planting density, light quality, and nutrient supply affect plant characteristics, such as biomass and morphology, which in turn affect recombinant protein content and productivity. Accordingly, environment control for such plant characteristics has significant implications to achieve a high yield. On the other hand, postinoculation environmental factors, such as temperature, light intensity, and humidity, have been shown to affect recombinant protein content. Considering that recombinant protein production in Agrobacterium-mediated transient expression systems is a result of a series of complex biological events starting from T-DNA transfer from Agrobacterium tumefaciens to protein biosynthesis and accumulation in leaf tissue, we propose that dynamic environment control during the postinoculation process, i.e., changing environmental conditions at an appropriate timing for each event, may be a promising approach to obtain a high yield. Detailed descriptions of plant growth conditions and careful examination of environmental effects will significantly contribute to our knowledge to stably obtain high recombinant

  10. Formal specification and verification of a fault-masking and transient-recovery model for digital flight-control systems

    NASA Technical Reports Server (NTRS)

    Rushby, John

    1991-01-01

    The formal specification and mechanically checked verification for a model of fault-masking and transient-recovery among the replicated computers of digital flight-control systems are presented. The verification establishes, subject to certain carefully stated assumptions, that faults among the component computers are masked so that commands sent to the actuators are the same as those that would be sent by a single computer that suffers no failures.

  11. Some Stress and Lots of Control: The "No Pain, No Gain" Recipe for Personal Competence.

    ERIC Educational Resources Information Center

    Carbone, Dominic J.

    This study examined the role of perceived control in mediating the effects of job stress on personal and occupational outcomes, and on enhancing the positive effects of stress on personal and organizational outcomes. Civil service employees working in Child Protective Services in Upstate New York (N=129) completed questionnaires measuring their…

  12. Determination of Reduced Number and Suitable Locations of Fuzzy Logic Controlled Braking Resistors for Transient Stability Enhancement

    NASA Astrophysics Data System (ADS)

    Ali, Mohd. Hasan; Murata, Toshiaki; Tamura, Junji

    Braking resistor is known to be a very powerful tool for transient stability improvement in electric power systems. Usually, in a large power system braking resistors are placed at each generator terminal bus which requires a high installation as well as operation cost. Also, heavy computation is required for the controllers used for the switching of the resistors. From these viewpoints, this paper directs to the study of installation of reduced number of fuzzy logic controlled braking resistors at suitable locations for transient stability enhancement. Groups of coherent generators in the power system are determined. Then one braking resistor is installed in each of the coherent group and at each of the remaining generator terminal bus. Thus, the number of braking resistors is reduced and hence the installation and operation cost as well as computational burden for the controllers are minimized. The suitable location for the braking resistor in each coherent group of generators is determined according to the values of the transient stability index as calculated for a 3LG (Three-phase-to-ground) fault at the points near the generators of the coherent group without considering the braking resistors in the system. The effectiveness of the proposed method is demonstrated through EMTP simulations for the IEEJ West-10 machine model system.

  13. Sliding mode attitude control with L 2-gain performance and vibration reduction of flexible spacecraft with actuator dynamics

    NASA Astrophysics Data System (ADS)

    Hu, Qinglei

    2010-09-01

    This paper presents a dual-stage control system design method for the rotational maneuver control and vibration stabilization of a flexible spacecraft. In this design approach, the sub-systems of attitude control and vibration suppression are designed separately using the low order model. Based on the sliding mode control (SMC) theory, a discontinuous attitude control law in the form of the input voltage of the reaction wheel is derived to control the orientation of the spacecraft, incorporating the L 2-gain performance criterion constraint. The resulting closed-loop system is proven to be uniformly ultimately bounded stability and the effect of the external disturbance on both attitude quaternion and angular velocity can be attenuated to the prescribed level as well. In addition, an adaptive version of the control law is designed for adapting the unknown upper bounds of the lumped disturbance such that the limitation of knowing the bound of the disturbance in advance is released. For actively suppressing the induced vibration, strain rate feedback control method is also investigated by using piezoelectric materials as additional sensors and actuators bonded on the surface of the flexible appendages. Numerical simulations are performed to show that rotational maneuver and vibration suppression are accomplished in spite of the presence of disturbance and uncertainty.

  14. Robust stability analysis and dynamic gain-scheduled controller design for point time-delay systems with parametrical uncertainties

    NASA Astrophysics Data System (ADS)

    De la Sen, M.

    2008-08-01

    This paper discusses linear fractional representations (LFR) of parameter-dependent nonlinear systems with real-rational nonlinearities and point-delayed dynamics. Sufficient conditions for robust global asymptotic stability independent of the delays and the existence of a robust stabilizing gain-scheduled dynamic controller are investigated via linear matrix inequalities. Such inequalities are obtained from the values of the time-derivatives of appropriate Lyapunov functions at all the vertices of the polytope which contains the parametrized uncertainties. The synthesized stabilizing controller consists of an interpolation being performed with the stabilizing controllers at the set of vertices of a certain polytope where the nonlinear-rational parametrization belongs to. Some extensions are also given concerning robust global asymptotic stability dependent of the delays. Numerical examples corroborate the usefulness of the proposed formalism and its applicability to practical related problems.

  15. Design and performance testing of an avalanche photodiode receiver with multiplication gain control algorithm for intersatellite laser communication

    NASA Astrophysics Data System (ADS)

    Yu, Xiaonan; Tong, Shoufeng; Dong, Yan; Song, Yansong; Hao, Shicong; Lu, Jing

    2016-06-01

    An avalanche photodiode (APD) receiver for intersatellite laser communication links is proposed and its performance is experimentally demonstrated. In the proposed system, a series of analog circuits are used not only to adjust the temperature and control the bias voltage but also to monitor the current and recover the clock from the communication data. In addition, the temperature compensation and multiplication gain control algorithm are embedded in the microcontroller to improve the performance of the receiver. As shown in the experiment, with the change of communication rate from 10 to 2000 Mbps, the detection sensitivity of the APD receiver varies from -47 to -34 dBm. Moreover, due to the existence of the multiplication gain control algorithm, the dynamic range of the APD receiver is effectively improved, while the dynamic range at 10, 100, and 1000 Mbps is 38.7, 37.7, and 32.8 dB, respectively. As a result, the experimental results agree well with the theoretical predictions, and the receiver will improve the flexibility of the intersatellite links without increasing the cost.

  16. Modeling and distributed gain scheduling strategy for load frequency control in smart grids with communication topology changes.

    PubMed

    Liu, Shichao; Liu, Xiaoping P; El Saddik, Abdulmotaleb

    2014-03-01

    In this paper, we investigate the modeling and distributed control problems for the load frequency control (LFC) in a smart grid. In contrast with existing works, we consider more practical and real scenarios, where the communication topology of the smart grid changes because of either link failures or packet losses. These topology changes are modeled as a time-varying communication topology matrix. By using this matrix, a new closed-loop power system model is proposed to integrate the communication topology changes into the dynamics of a physical power system. The globally asymptotical stability of this closed-loop power system is analyzed. A distributed gain scheduling LFC strategy is proposed to compensate for the potential degradation of dynamic performance (mean square errors of state vectors) of the power system under communication topology changes. In comparison to conventional centralized control approaches, the proposed method can improve the robustness of the smart grid to the variation of the communication network as well as to reduce computation load. Simulation results show that the proposed distributed gain scheduling approach is capable to improve the robustness of the smart grid to communication topology changes. © 2013 ISA. Published by ISA. All rights reserved.

  17. Application of stochastic optimal reduced state feedback gain computation procedures to the design of aircraft gust alleviation controllers

    NASA Technical Reports Server (NTRS)

    Sobel, K.; Kaufman, H.

    1979-01-01

    A stochastic linear model that accounts for process parameter and initial uncertainty, measurement noise, and a restricted number of measurable outputs was used to determine feedback gains useful for reducing the vertical acceleration which results from the presence of a vertical wind gust. Considered in the study were the influence of various feedback configurations, the effects of sensor noise, flight condition changes, and initialization procedures. Results showed that for sixth order linearized longitudinal motion, a controller with feedback on three states could be designed for effective gust alleviation taking into account both sensor noise and flight condition variation.

  18. Transient dynamics and their control in time-delay autonomous Boolean ring networks.

    PubMed

    Lohmann, Johannes; D'Huys, Otti; Haynes, Nicholas D; Schöll, Eckehard; Gauthier, Daniel J

    2017-02-01

    Biochemical systems with switch-like interactions, such as gene regulatory networks, are well modeled by autonomous Boolean networks. Specifically, the topology and logic of gene interactions can be described by systems of continuous piecewise-linear differential equations, enabling analytical predictions of the dynamics of specific networks. However, most models do not account for time delays along links associated with spatial transport, mRNA transcription, and translation. To address this issue, we have developed an experimental test bed to realize a time-delay autonomous Boolean network with three inhibitory nodes, known as a repressilator, and use it to study the dynamics that arise as time delays along the links vary. We observe various nearly periodic oscillatory transient patterns with extremely long lifetime, which emerge in small network motifs due to the delay, and which are distinct from the eventual asymptotically stable periodic attractors. For repeated experiments with a given network, we find that stochastic processes give rise to a broad distribution of transient times with an exponential tail. In some cases, the transients are so long that it is doubtful the attractors will ever be approached in a biological system that has a finite lifetime. To counteract the long transients, we show experimentally that small, occasional perturbations applied to the time delays can force the trajectories to rapidly approach the attractors.

  19. Transient dynamics and their control in time-delay autonomous Boolean ring networks

    NASA Astrophysics Data System (ADS)

    Lohmann, Johannes; D'Huys, Otti; Haynes, Nicholas D.; Schöll, Eckehard; Gauthier, Daniel J.

    2017-02-01

    Biochemical systems with switch-like interactions, such as gene regulatory networks, are well modeled by autonomous Boolean networks. Specifically, the topology and logic of gene interactions can be described by systems of continuous piecewise-linear differential equations, enabling analytical predictions of the dynamics of specific networks. However, most models do not account for time delays along links associated with spatial transport, mRNA transcription, and translation. To address this issue, we have developed an experimental test bed to realize a time-delay autonomous Boolean network with three inhibitory nodes, known as a repressilator, and use it to study the dynamics that arise as time delays along the links vary. We observe various nearly periodic oscillatory transient patterns with extremely long lifetime, which emerge in small network motifs due to the delay, and which are distinct from the eventual asymptotically stable periodic attractors. For repeated experiments with a given network, we find that stochastic processes give rise to a broad distribution of transient times with an exponential tail. In some cases, the transients are so long that it is doubtful the attractors will ever be approached in a biological system that has a finite lifetime. To counteract the long transients, we show experimentally that small, occasional perturbations applied to the time delays can force the trajectories to rapidly approach the attractors.

  20. Hard gains through soft contracts: productive engagement of private providers in tuberculosis control.

    PubMed Central

    Lönnroth, Knut; Uplekar, Mukund; Blanc, Léopold

    2006-01-01

    Over the past decade, there has been a rapid increase in the number of initiatives involving "for-profit" private health care providers in national tuberculosis (TB) control efforts. We reviewed 15 such initiatives with respect to contractual arrangements, quality of care and success achieved in TB control. In seven initiatives, the National TB Programme (NTP) interacted directly with for-profit providers; while in the remaining eight, the NTP collaborated with for-profit providers through intermediary not-for-profit nongovernmental organizations. All but one of the initiatives used relational "drugs-for-performance contracts" to engage for-profit providers, i.e. drugs were provided free of charge by the NTP emphasizing that providers dispense them free of charge to patients and follow national guidelines for diagnosis and treatment. We found that 90% (range 61-96%) of new smear-positive pulmonary TB cases were successfully treated across all initiatives and TB case detection rates increased between 10% and 36%. We conclude that for-profit providers can be effectively involved in TB control through informal, but well defined drugs-for-performance contracts. The contracting party should be able to reach a common understanding concerning goals and role division with for-profit providers and monitor them for content and quality. Relational drugs-for-performance contracts minimize the need for handling the legal and financial aspects of classical contracting. We opine that further analysis is required to assess if such "soft" contracts are sufficient to scale up private for-profit provider involvement in TB control and other priority health interventions. PMID:17143461

  1. A model-based gain scheduling approach for controlling the common-rail system for GDI engines

    NASA Astrophysics Data System (ADS)

    di Gaeta, Alessandro; Montanaro, Umberto; Fiengo, Giovanni; Palladino, Angelo; Giglio, Veniero

    2012-04-01

    The progressive reduction in vehicle emission requirements have forced the automotive industry to invest in research for developing alternative and more efficient control strategies. All control features and resources are permanently active in an electronic control unit (ECU), ensuring the best performance with respect to emissions, fuel economy, driveability and diagnostics, independently from engine working point. In this article, a considerable step forward has been achieved by the common-rail technology which has made possible to vary the injection pressure over the entire engine speed range. As a consequence, the injection of a fixed amount of fuel is more precise and multiple injections in a combustion cycle can be made. In this article, a novel gain scheduling pressure controller for gasoline direct injection (GDI) engine is designed to stabilise the mean fuel pressure into the rail and to track demanded pressure trajectories. By exploiting a simple control-oriented model describing the mean pressure dynamics in the rail, the control structure turns to be simple enough to be effectively implemented in commercial ECUs. Experimental results in a wide range of operating points confirm the effectiveness of the proposed control method to tame efficiently the mean value pressure dynamics of the plant showing a good accuracy and robustness with respect to unavoidable parameters uncertainties, unmodelled dynamics, and hidden coupling terms.

  2. Measuring Ability, Speed, or Both? Challenges, Psychometric Solutions, and What Can Be Gained From Experimental Control

    PubMed Central

    Goldhammer, Frank

    2015-01-01

    The main challenge of ability tests relates to the difficulty of items, whereas speed tests demand that test takers complete very easy items quickly. This article proposes a conceptual framework to represent how performance depends on both between-person differences in speed and ability and the speed-ability compromise within persons. Related measurement challenges and psychometric models that have been proposed to deal with the challenges are discussed. It is argued that addressing individual differences in the speed-ability trade-off requires the control of item response times. In this way, response behavior can be captured exclusively with the response variable remedying problems in traditional measurement approaches. PMID:26807063

  3. Scalar Modal Control of a Nonlinear System Using Time Varying Gain.

    DTIC Science & Technology

    1984-12-01

    not be an overall improvement but a hinderence. This certainly is a lessor criterion but should be kept in mind when developing - controllers. 14 -- a...zeroes for each period. With this in mind , gi(t) was examined and two restrictions I to finding k(t) were established: (1) a maximum value of 10 units was...11i. TITLE (Include Security Clasification ) see block 19_________________ 17. PERSONAL AUTHOR(S) Nici. RF.8ario Captain USAF 113a. TYPE OF REPORT 13b

  4. Achieving and Maintaining Deep Space 1 Spacecraft High-Gain Antenna Pointing Control by Data Monitoring and Immediate Corrective Commanding

    NASA Astrophysics Data System (ADS)

    Taylor, J.; Ko, P.

    2000-10-01

    The Deep Space 1 (DS1) onboard stellar reference unit failed in November 1999, leaving the spacecraft able to achieve only Sun point, with 8.4 GHz (X-band) communications reduced to the low rates supportable via a low-gain antenna. By January 2000, the DS1 project fight team implemented an interim three-axis pointing concept called the "HGA activity" because it made the high-gain antenna (HGA) usable again. The HGA activity involves the telecommunications analyst as an integral part of a closed-loop ground--spacecraft pointing control system. The HGA activity initiates pointing of the high-gain antenna toward the Earth and subsequently maintains pointing for the duration of one or two passes. The concept requires the tracking station to lock its receiver on the X-band carrier and provide carrier signal-to-noise ratio in monitor data in real time. The project telecommunications analyst uses the data to prepare accurate event timing predictions and to assess performance through rapid and precise comparisons of monitor and prediction data. Use of this labor-intensive and real-time process enabled the project to receive high-rate telemetry data from 14 passes through May 2000. Finally, another 14 HGA activities in June 2000 enabled the project to reload several megabytes of flight software at a high rate. The new software brought to an end the routine use of the HGA activity because it operates the science camera to generate star data for onboard pointing control. With full three-axis pointing capability restored for ion-propulsion subsystem thrusting, DS1 has resumed its science mission with a flyby of the comet Borrelly planned for September 2001.

  5. The effect of intensive nutrition interventions on weight gain after kidney transplantation: protocol of a randomised controlled trial.

    PubMed

    Ryan, Kristin J; Casas, Jessie M Segedin; Mash, Laura E; McLellan, Sandra L; Lloyd, Lyn E; Stinear, James W; Plank, Lindsay D; Collins, Michael G

    2014-09-09

    Weight gain and obesity are common after kidney transplantation, particularly during the first year. Obesity is a risk factor for the development of new-onset diabetes after transplantation, and is associated with reduced graft survival. There is a lack of evidence for effective interventions to prevent weight gain after kidney transplantation. The effect of INTEnsive Nutrition interventions on weight gain after kidney Transplantation (INTENT) trial is a single-blind (outcomes assessor), randomised controlled trial to assess the effect of intensive nutrition interventions, including exercise advice, on weight gain and metabolic parameters in the first year after transplantation. Participants will be randomised during the first post-transplant month to either standard care (four visits with a renal dietitian over twelve months) or intensive nutrition intervention (eight visits with a renal dietitian over the first six months, four visits over the second six months, and three visits over the first six months with an exercise physiologist). In the intensive intervention group, nutrition counselling will be provided using motivational interviewing techniques to encourage quality engagement. Collaborative goal setting will be used to develop personalised nutrition care plans. Individualised advice regarding physical activity will be provided by an exercise physiologist. The primary outcome of the study is weight at six months after transplant, adjusted for baseline (one month post-transplant) weight, obesity and gender. Secondary outcomes will include changes in weight and other anthropometric measures over 12 months, body composition (in vivo neutron activation analysis, total body potassium, dual-energy X-ray absorptiometry, and bioelectrical impedance), biochemistry (fasting glucose, lipids, haemoglobin A1c and insulin), dietary intake and nutritional status, quality of life, and physical function. There are currently few randomised clinical trials of nutrition

  6. Prelude to corneal tissue engineering – Gaining control of collagen organization

    PubMed Central

    Ruberti, Jeffrey W.; Zieske, James D.

    2012-01-01

    By most standard engineering practice principles, it is premature to credibly discuss the “engineering” of a human cornea. A professional design engineer would assert that we still do not know what a cornea is (and correctly so), therefore we cannot possibly build one. The proof resides in the fact that there are no clinically viable corneas based on classical tissue engineering methods available. This is possibly because tissue engineering in the classical sense (seeding a degradable scaffolding with a population synthetically active cells) does not produce conditions which support the generation of organized tissue. Alternative approaches to the problem are in their infancy and include the methods which attempt to recapitulate development or to produce corneal stromal analogs de novo which require minimal remodeling. Nonetheless, tissue engineering efforts, which have been focused on producing the fundamental functional component of a cornea (organized alternating arrays of collagen or “lamellae”) may have already provided valuable new insights and tools relevant to development, growth, remodeling and pathologies associated with connective tissue in general. This is because engineers ask a fundamentally different question (How can that be done?) than do biological scientists (How is that done?). The difference in inquiry has prompted us to closely examine (and to mimic) development as well as investigate collagen physicochemical behavior so that we may exert control over organization both in cell-culture (in vitro) and on the benchtop (de novo). Our initial results indicate that reproducing corneal stroma-like local and long-range organization of collagen may be simpler than we anticipated while controlling spacing and fibril morphology remains difficult, but perhaps not impossible in the (reasonably) near term. PMID:18775789

  7. How attention and contrast gain control interact to regulate lightness contrast and assimilation: a computational neural model.

    PubMed

    Rudd, Michael E

    2010-12-31

    Recent theories of lightness perception assume that lightness (perceived reflectance) is computed by a process that contrasts the target's luminance with that of one or more regions in its spatial surround. A challenge for any such theory is the phenomenon of lightness assimilation, which occurs when increasing the luminance of a surround region increases the target lightness: the opposite of contrast. Here contrast and assimilation are studied quantitatively in lightness matching experiments utilizing concentric disk-and-ring displays. Whether contrast or assimilation is seen depends on a number of factors including: the luminance relations of the target, surround, and background; surround size; and matching instructions. When assimilation occurs, it is always part of a larger pattern in which assimilation and contrast both occur over different ranges of surround luminance. These findings are quantitatively modeled by a theory that assumes lightness is computed from a weighted sum of responses of edge detector neurons in visual cortex. The magnitude of the neural response to an edge is regulated by a combination of contrast gain control acting between neighboring edge detectors and a top-down attentional gain control that selectively weights the response to stimulus edges according to their task relevance.

  8. A stable multimodel scheme control for the regulation of the transient behavior of a tunnel-diode trigger circuit.

    PubMed

    Bilbao-Guillerna, A; De la Sen, M; Alonso-Quesada, S; Ibeas, A

    2007-06-01

    A multimodel scheme is designed for a triggering tunnel-diode circuit. The scheme improves the transient behavior during the transition time period after switching from a stable system equilibrium point to another one which is known as a triggering process. Each model is obtained by a linearization of the circuit near an equilibrium point. Moreover, each of these models can be described as a combination of two other transfer functions describing the linearized plant behavior near two different equilibrium points. The scheme chooses online the model with the best tracking performance in order to generate the control law. Different reference transfer functions are proposed with the aim of generating the desired transient in the triggering process. Some simulations show the usefulness of this scheme.

  9. Gaining and sustaining schistosomiasis control: study protocol and baseline data prior to different treatment strategies in five African countries.

    PubMed

    Ezeamama, Amara E; He, Chun-La; Shen, Ye; Yin, Xiao-Ping; Binder, Sue C; Campbell, Carl H; Rathbun, Stephen; Whalen, Christopher C; N'Goran, Eliézer K; Utzinger, Jürg; Olsen, Annette; Magnussen, Pascal; Kinung'hi, Safari; Fenwick, Alan; Phillips, Anna; Ferro, Josefo; Karanja, Diana M S; Mwinzi, Pauline N M; Montgomery, Susan; Secor, W Evan; Hamidou, Amina; Garba, Amadou; King, Charles H; Colley, Daniel G

    2016-05-26

    The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was established in 2008 to answer strategic questions about schistosomiasis control. For programme managers, a high-priority question is: what are the most cost-effective strategies for delivering preventive chemotherapy (PCT) with praziquantel (PZQ)? This paper describes the process SCORE used to transform this question into a harmonized research protocol, the study design for answering this question, the village eligibility assessments and data resulting from the first year of the study. Beginning in 2009, SCORE held a series of meetings to specify empirical questions and design studies related to different schedules of PCT for schistosomiasis control in communities with high (gaining control studies) and moderate (sustaining control studies) prevalence of Schistosoma infection among school-aged children. Seven studies are currently being implemented in five African countries. During the first year, villages were screened for eligibility, and data were collected on prevalence and intensity of infection prior to randomisation and the implementation of different schemes of PZQ intervention strategies. These studies of different treatment schedules with PZQ will provide the most comprehensive data thus far on the optimal frequency and continuity of PCT for schistosomiasis infection and morbidity control. We expect that the study outcomes will provide data for decision-making for country programme managers and a rich resource of information to the schistosomiasis research community. The trials are registered at International Standard Randomised Controlled Trial registry (identifiers: ISRCTN99401114 , ISRCTN14849830 , ISRCTN16755535 , ISRCTN14117624 , ISRCTN95819193 and ISRCTN32045736 ).

  10. Fluid transients in pipes. Reduction and control of pressure surges in liquids

    NASA Astrophysics Data System (ADS)

    1984-11-01

    ESDU 84013 provides a simplified graphical method for predicting maximum pressure changes in liquid filled pipework systems that may be treated as one-line systems. The method applies to pressures induced by partial or total valve closure, covering all common valve types, or pump trips. Data are also given for the estimation of the size of air vessel, situated just downstream of a pump, to protect against excessive upsurge and downsurge pressure changes following pump trip. A computer program is included to analyze transients in one-line systems and does not use the simplifying assumptions necessary for the graphical data. Practical worked examples, illustrating the use of the methods, are included and guidance is given on the data required for a full fluid transients analysis going beyond the scope of ESDU 84013.

  11. Active flow control insight gained from a modified integral boundary layer equation

    NASA Astrophysics Data System (ADS)

    Seifert, Avraham

    2016-11-01

    Active Flow Control (AFC) can alter the development of boundary layers with applications (e.g., reducing drag by separation delay or separating the boundary layers and enhancing vortex shedding to increase drag). Historically, significant effects of steady AFC methods were observed. Unsteady actuation is significantly more efficient than steady. Full-scale AFC tests were conducted with varying levels of success. While clearly relevant to industry, AFC implementation relies on expert knowledge with proven intuition and or costly and lengthy computational efforts. This situation hinders the use of AFC while simple, quick and reliable design method is absent. An updated form of the unsteady integral boundary layer (UIBL) equations, that include AFC terms (unsteady wall transpiration and body forces) can be used to assist in AFC analysis and design. With these equations and given a family of suitable velocity profiles, the momentum thickness can be calculated and matched with an outer, potential flow solution in 2D and 3D manner to create an AFC design tool, parallel to proven tools for airfoil design. Limiting cases of the UIBL equation can be used to analyze candidate AFC concepts in terms of their capability to modify the boundary layers development and system performance.

  12. Forward masking as a mechanism of automatic gain control in odontocete biosonar: a psychophysical study.

    PubMed

    Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

    2008-07-01

    In a false killer whale Pseudorca crassidens, echo perception thresholds were measured using a go/no-go psychophysical paradigm and one-up-one-down staircase procedure. Computer controlled echoes were electronically synthesized pulses that were played back through a transducer and triggered by whale emitted biosonar pulses. The echo amplitudes were proportional to biosonar pulse amplitudes; echo levels were specified in terms of the attenuation of the echo sound pressure level near the animal's head relative to the source level of the biosonar pulses. With increasing echo delay, the thresholds (echo attenuation factor) decreased from -49.3 dB at 2 ms to -79.5 dB at 16 ms, with a regression slope of -9.5 dB per delay doubling (-31.5 dB per delay decade). At the longer delays, the threshold remained nearly constant around -80.4 dB. Levels of emitted pulses slightly increased with delay prolongation (threshold decrease), with a regression slope of 3.2 dB per delay doubling (10.7 dB per delay decade). The echo threshold dependence on delay is interpreted as a release from forward masking by the preceding emitted pulse. This release may compensate for the echo level decrease with distance, thus keeping the echo sensation level for the animal near constant within a certain distance range.

  13. Real-Time Feedback Control of Flow-Induced Cavity Tones. Part 1; Fixed-Gain Control

    NASA Technical Reports Server (NTRS)

    Kegerise, M. A.; Cabell, R. H.; Cattafesta, L. N., III

    2006-01-01

    A generalized predictive control (GPC) algorithm was formulated and applied to the cavity flow-tone problem. The control algorithm demonstrated multiple Rossiter-mode suppression at fixed Mach numbers ranging from 0.275 to 0.38. Controller performance was evaluated with a measure of output disturbance rejection and an input sensitivity transfer function. The results suggest that disturbances entering the cavity flow are collocated with the control input at the cavity leading edge. In that case, only tonal components of the cavity wall-pressure fluctuations can be suppressed and arbitrary broadband pressure reduction is not possible with the present sensor/actuator arrangement. In the control-algorithm development, the cavity dynamics were treated as linear and time invariant (LTI) for a fixed Mach number. The experimental results lend support to that treatment.

  14. Distributed cerebellar plasticity implements adaptable gain control in a manipulation task: a closed-loop robotic simulation

    PubMed Central

    Garrido, Jesús A.; Luque, Niceto R.; D'Angelo, Egidio; Ros, Eduardo

    2013-01-01

    Adaptable gain regulation is at the core of the forward controller operation performed by the cerebro-cerebellar loops and it allows the intensity of motor acts to be finely tuned in a predictive manner. In order to learn and store information about body-object dynamics and to generate an internal model of movement, the cerebellum is thought to employ long-term synaptic plasticity. LTD at the PF-PC synapse has classically been assumed to subserve this function (Marr, 1969). However, this plasticity alone cannot account for the broad dynamic ranges and time scales of cerebellar adaptation. We therefore tested the role of plasticity distributed over multiple synaptic sites (Hansel et al., 2001; Gao et al., 2012) by generating an analog cerebellar model embedded into a control loop connected to a robotic simulator. The robot used a three-joint arm and performed repetitive fast manipulations with different masses along an 8-shape trajectory. In accordance with biological evidence, the cerebellum model was endowed with both LTD and LTP at the PF-PC, MF-DCN and PC-DCN synapses. This resulted in a network scheme whose effectiveness was extended considerably compared to one including just PF-PC synaptic plasticity. Indeed, the system including distributed plasticity reliably self-adapted to manipulate different masses and to learn the arm-object dynamics over a time course that included fast learning and consolidation, along the lines of what has been observed in behavioral tests. In particular, PF-PC plasticity operated as a time correlator between the actual input state and the system error, while MF-DCN and PC-DCN plasticity played a key role in generating the gain controller. This model suggests that distributed synaptic plasticity allows generation of the complex learning properties of the cerebellum. The incorporation of further plasticity mechanisms and of spiking signal processing will allow this concept to be extended in a more realistic computational scenario

  15. Controlling the unruly maternal body: Losing and gaining control over the body during pregnancy and the postpartum period.

    PubMed

    Neiterman, Elena; Fox, Bonnie

    2017-02-01

    This paper examines the feeling of lost control of the body that so many women experience through pregnancy and the postpartum period - why they feel it and how they interpret that feeling - and women's responses to the sense of lost control. For the 63 Canadian women we interviewed, the sense of lost control was related to the degree they felt their bodies changed and the number of physical problems they experienced while pregnant. Many women's references to "luck" as the cause of body changes and problems experienced underscored how little control they felt they had when they were pregnant. At the same time, women felt responsible for the well-being of their babies, and thus experienced guilt about their unruly bodies. Careful attention to diet helped some women, but not others, regain some sense of control; women with past experience of pregnancy who "gave in" to body change were more sanguine. In the postpartum period, body work (especially exercise) functioned to increase women's sense of control, but a variety of motives led them to do this work.

  16. Control of periodontal infections: a randomized controlled trial I. The primary outcome attachment gain and pocket depth reduction at treated sites.

    PubMed

    Goodson, J Max; Haffajee, Anne D; Socransky, Sigmund S; Kent, Ralph; Teles, Ricardo; Hasturk, Hatice; Bogren, Anna; Van Dyke, Thomas; Wennstrom, Jan; Lindhe, Jan

    2012-06-01

    To compare the treatment outcome of scaling and root planing (SRP) in combination with systemic antibiotics, local antibiotic therapy and/or periodontal surgery. One hundred and eighty-seven patients were assigned to eight groups treated by SRP plus none, one, two or three adjunctive treatments and monitored for 24 months in a randomized controlled clinical trial using a 2 × 2 × 2 factorial design. Systemic amoxicillin + metronidazole (SMA), local tetracycline delivery (LTC) and periodontal surgery (SURG) were evaluated as adjuncts. Changes in clinical attachment level (CAL) and probing pocket depth (PPD) were statistically evaluated by ancova of main effects. Effects of adjunctive therapy to SRP were minimal at 3 months. Between 3 and 6 months PPD reduction occurred particularly in patients receiving periodontal surgery. After 6 months, both CAL gain and PPD reduction reached a plateau that was maintained at 24 months in all groups. The 24-month CAL gain was improved by SMA (0.50 mm) while PPD was reduced by SMA (0.51 mm) and SURG (0.36 mm). Smoking reduced CAL gain and PPD reduction. Patients receiving adjunctive therapies generally exhibited improved CAL gain and/or PPD reduction when compared with the outcome of SRP alone. Only additive, not synergistic effects of the various adjunctive therapies were observed. © 2012 John Wiley & Sons A/S.

  17. Rod lengthening with the magnetically controlled growing rod: factors influencing rod slippage and reduced gains during distractions.

    PubMed

    Cheung, Jason Pui Yin; Yiu, Karen Kar Lum; Samartzis, Dino; Kwan, Kenny; Tan, Boon-Beng; Cheung, Kenneth Man Chee

    2017-08-01

    Prospective study OBJECTIVE.: To identify the factors that are associated with rod slippage and to study the pattern of achieved length gain with a standard distraction methodology. Ability to achieve successful magnetically controlled growing rod (MCGR) distraction is crucial for gradual spine lengthening. Rod slippage has been described as a failure of internal magnet rotation leading to a slippage and an inability to distract the rod. However, its onset, significance and risk factors are currently unknown. In addition, how this phenomenon pertains to actual distracted lengths is unknown. A total of 22 patients with MCGR and at least 6 distraction episodes were prospectively studied. Patients with rod slippage occurring ≤6 distraction episodes were considered early rod slippage while those >6 or have yet not slipped were grouped as late rod slippage. The association of parameters including body habitus, maturity status, age of implantation, total number of distractions, months of distraction from initial implantation, initial and postoperative Cobb angle, T1-T12, T1-S1, T5-T12 kyphosis, curve flexibility, fusion block length, and distance between magnets in dual rods and between the magnets and apex of the curve with early or late onset of rod slippage was studied. Differences between expected and achieved distraction lengths were assessed with reference to rod slippage episodes and rod exchanges to determine any patterns of diminishing returns. Patients had mean age of 7.1 years at diagnosis with mean follow-up of 49.8 months. A mean 32.4 distractions were performed per patient. Early rod slippage occurred in 14 patients and late rod slippage occurred in 8 patients. Increased height, weight, body mass index, older age, increased T1-12 and T1-S1 lengths, and less distance between magnets were significantly associated with early rod slippage. Expected distraction lengths did not translate to achieved distraction lengths and reduced gains were only observed after

  18. Adaptive fuzzy output-feedback controller design for nonlinear systems via backstepping and small-gain approach.

    PubMed

    Liu, Zhi; Wang, Fang; Zhang, Yun; Chen, Xin; Chen, C L Philip

    2014-10-01

    This paper focuses on an input-to-state practical stability (ISpS) problem of nonlinear systems which possess unmodeled dynamics in the presence of unstructured uncertainties and dynamic disturbances. The dynamic disturbances depend on the states and the measured output of the system, and its assumption conditions are relaxed compared with the common restrictions. Based on an input-driven filter, fuzzy logic systems are directly used to approximate the unknown and desired control signals instead of the unknown nonlinear functions, and an integrated backstepping technique is used to design an adaptive output-feedback controller that ensures robustness with respect to unknown parameters and uncertain nonlinearities. This paper, by applying the ISpS theory and the generalized small-gain approach, shows that the proposed adaptive fuzzy controller guarantees the closed-loop system being semi-globally uniformly ultimately bounded. A main advantage of the proposed controller is that it contains only three adaptive parameters that need to be updated online, no matter how many states there are in the systems. Finally, the effectiveness of the proposed approach is illustrated by two simulation examples.

  19. Design of structure/control systems with transient response constraints exhibiting relative minima

    NASA Technical Reports Server (NTRS)

    Sepulveda, A. E.; Jin, I. M.

    1992-01-01

    Structural optimization problems involving dynamic behavior constraints often exhibit nonconvex design spaces. The direct application of a global optimization algorithm requires a large number of function evaluations which in term require a large number of dynamic structural analyses. This work presents a strategy aimed at finding the global optimum for problems with transient dynamic behavior constraints based on approximation concepts. The method consists of generating and solving a sequence of approximate problems using a global optimizer. The approximations are explicit and capture the inherent nonconvexity of the exact functions. A simple example problem is presented.

  20. Steady-state and transient-state analyses of TCP and TCP-friendly rate control mechanism using a control theoretic approach

    NASA Astrophysics Data System (ADS)

    Hisamatsu, Hiroyuki; Ohsaki, Hiroyuki; Murata, Masayuki

    2004-09-01

    In recent years, various real-time applications in the Internet have been emerging with rapid increase of the network bandwidth. A real-time application traditionally uses either UDP (User Datagram Protocol) or TCP (Transmission Control Protocol) as its transport layer protocol. However, using either UDP or TCP is insufficient for most real-time applications because of lacking a smooth rate control mechanism or suffering a significant transfer delay. In the literature, several transport-layer communication protocols for real-time applications have been proposed. In this paper, among these transport-layer communication protocols, we focus on TFRC (TCP-Friendly Rate Control). Steady state performances of TCP and TFRC connections such as throughput and fairness have been throughly investigated by many researchers using simulation experiments. However, transient state properties of TCP and TFRC connections such as stability and responsiveness have not been investigated. In this paper, we therefore analyze both steady state and transient state performances of TCP and TFRC connections using a control theoretic approach. We frist model TFRC and TCP connections with different propagation delays and the active queue management mechanism of RED (Random Early Detection) router as independent discrete-time systems. By combining these discrete-time systems, we analyze steady state performance of TCP and TFRC connections such as throughput, transfer delay, and packet loss probability. We also analyze transient state performance of TCP and TFRC connections using linearization of discrete-time systems around their equilibrium points.

  1. Gimbals Drive and Control Electronics Design, Development and Testing of the LRO High Gain Antenna and Solar Array Systems

    NASA Technical Reports Server (NTRS)

    Chernyakov, Boris; Thakore, Kamal

    2010-01-01

    Launched June 18, 2009 on an Atlas V rocket, NASA's Lunar Reconnaissance Orbiter (LRO) is the first step in NASA's Vision for Space Exploration program and for a human return to the Moon. The spacecraft (SC) carries a wide variety of scientific instruments and provides an extraordinary opportunity to study the lunar landscape at resolutions and over time scales never achieved before. The spacecraft systems are designed to enable achievement of LRO's mission requirements. To that end, LRO's mechanical system employed two two-axis gimbal assemblies used to drive the deployment and articulation of the Solar Array System (SAS) and the High Gain Antenna System (HGAS). This paper describes the design, development, integration, and testing of Gimbal Control Electronics (GCE) and Actuators for both the HGAS and SAS systems, as well as flight testing during the on-orbit commissioning phase and lessons learned.

  2. A gene-based information gain method for detecting gene-gene interactions in case-control studies.

    PubMed

    Li, Jin; Huang, Dongli; Guo, Maozu; Liu, Xiaoyan; Wang, Chunyu; Teng, Zhixia; Zhang, Ruijie; Jiang, Yongshuai; Lv, Hongchao; Wang, Limei

    2015-11-01

    Currently, most methods for detecting gene-gene interactions (GGIs) in genome-wide association studies are divided into SNP-based methods and gene-based methods. Generally, the gene-based methods can be more powerful than SNP-based methods. Some gene-based entropy methods can only capture the linear relationship between genes. We therefore proposed a nonparametric gene-based information gain method (GBIGM) that can capture both linear relationship and nonlinear correlation between genes. Through simulation with different odds ratio, sample size and prevalence rate, GBIGM was shown to be valid and more powerful than classic KCCU method and SNP-based entropy method. In the analysis of data from 17 genes on rheumatoid arthritis, GBIGM was more effective than the other two methods as it obtains fewer significant results, which was important for biological verification. Therefore, GBIGM is a suitable and powerful tool for detecting GGIs in case-control studies.

  3. Asthma Triggers: Gain Control

    MedlinePlus

    ... using the heater. Top of Page Outdoor Air Pollution About Outdoor Air Pollution and Asthma Actions You Can Take Additional Resources About Outdoor Air Pollution and Asthma Outdoor air pollution is caused by ...

  4. Determination of all feasible robust PID controllers for open-loop unstable plus time delay processes with gain margin and phase margin specifications.

    PubMed

    Wang, Yuan-Jay

    2014-03-01

    This paper proposes a novel alternative method to graphically compute all feasible gain and phase margin specifications-oriented robust PID controllers for open-loop unstable plus time delay (OLUPTD) processes. This method is applicable to general OLUPTD processes without constraint on system order. To retain robustness for OLUPTD processes subject to positive or negative gain variations, the downward gain margin (GM(down)), upward gain margin (GM(up)), and phase margin (PM) are considered. A virtual gain-phase margin tester compensator is incorporated to guarantee the concerned system satisfies certain robust safety margins. In addition, the stability equation method and the parameter plane method are exploited to portray the stability boundary and the constant gain margin (GM) boundary as well as the constant PM boundary. The overlapping region of these boundaries is graphically determined and denotes the GM and PM specifications-oriented region (GPMSOR). Alternatively, the GPMSOR characterizes all feasible robust PID controllers which achieve the pre-specified safety margins. In particular, to achieve optimal gain tuning, the controller gains are searched within the GPMSOR to minimize the integral of the absolute error (IAE) or the integral of the squared error (ISE) performance criterion. Thus, an optimal PID controller gain set is successfully found within the GPMSOR and guarantees the OLUPTD processes with a pre-specified GM and PM as well as a minimum IAE or ISE. Consequently, both robustness and performance can be simultaneously assured. Further, the design procedures are summarized as an algorithm to help rapidly locate the GPMSOR and search an optimal PID gain set. Finally, three highly cited examples are provided to illustrate the design process and to demonstrate the effectiveness of the proposed method.

  5. Synaptic inhibition controls transient oscillatory synchronization in a model of the insect olfactory system

    PubMed Central

    Assisi, Collins; Bazhenov, Maxim

    2011-01-01

    In a variety of neuronal systems it has been hypothesized that inhibitory interneurons corral principal neurons into synchronously firing groups that encode sensory information and sub-serve behavior (Buzsáki and Chrobak, 1995; Buzsáki, 2008). This mechanism is particularly relevant to the olfactory system where spatiotemporal patterns of projection neuron (PN) activity act as robust markers of odor attributes (Laurent et al., 1996; Wehr and Laurent, 1996). In the insect antennal lobe (AL), a network of local inhibitory interneurons arborizes extensively throughout the AL (Leitch and Laurent, 1996) providing inhibitory input to the cholinergic PNs. Our theoretical work has attempted to elaborate the exact role of inhibition in the generation of odor specific PN responses (Bazhenov et al., 2001a,b; Assisi et al., 2011). In large-scale AL network models we characterized the inhibitory sub-network by its coloring (Assisi et al., 2011) and showed that it can entrain excitatory PNs to the odor specific patterns of transient synchronization. In this focused review, we further examine the dynamics of entrainment in more detail by simulating simple model networks in various parameter regimes. Our simulations in conjunction with earlier studies point to the key role played by lateral (between inhibitory interneurons) and feedback (from inhibitory interneurons to principal cells) inhibition in the generation of experimentally observed patterns of transient synchrony. PMID:22529800

  6. CFORM- LINEAR CONTROL SYSTEM DESIGN AND ANALYSIS: CLOSED FORM SOLUTION AND TRANSIENT RESPONSE OF THE LINEAR DIFFERENTIAL EQUATION

    NASA Technical Reports Server (NTRS)

    Jamison, J. W.

    1994-01-01

    CFORM was developed by the Kennedy Space Center Robotics Lab to assist in linear control system design and analysis using closed form and transient response mechanisms. The program computes the closed form solution and transient response of a linear (constant coefficient) differential equation. CFORM allows a choice of three input functions: the Unit Step (a unit change in displacement); the Ramp function (step velocity); and the Parabolic function (step acceleration). It is only accurate in cases where the differential equation has distinct roots, and does not handle the case for roots at the origin (s=0). Initial conditions must be zero. Differential equations may be input to CFORM in two forms - polynomial and product of factors. In some linear control analyses, it may be more appropriate to use a related program, Linear Control System Design and Analysis (KSC-11376), which uses root locus and frequency response methods. CFORM was written in VAX FORTRAN for a VAX 11/780 under VAX VMS 4.7. It has a central memory requirement of 30K. CFORM was developed in 1987.

  7. Closed-Loop Control of Unsteady Transient Growth Disturbances in a Blasius Boundary Layer using DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Lavoie, Philippe; Hanson, Ronald; Bade, Kyle; Naguib, Ahmed; Belson, Brandt; Rowley, Clarence

    2012-11-01

    Plasma actuators have recently been shown to negate the effect of the transient growth instability occurring in a Blasius boundary layer for the purpose of delaying bypass transition. Specifically, during steady operation, the energy of a disturbance introduced via an array of static cylindrical roughness elements was reduced by up to 68%, as shown by Hanson et al. (Exp. Fluids, 2010). In the present work, the actuators used in the aforementioned study were integrated into a complete closed-loop control system capable of negating unsteady transient growth disturbances induced in a Blasius boundary layer established in a wind tunnel. Shear stress measurements from an array of hot-wires mounted just above the surface of the boundary-layer plate downstream of the actuators are used to provide feedback information about the state of the boundary layer. The effectiveness and robustness of the closed-loop controller are rigorously established based on both control-model simulations and experiments. NSERC and NSF grant number: CMMI 0932546.

  8. CFORM- LINEAR CONTROL SYSTEM DESIGN AND ANALYSIS: CLOSED FORM SOLUTION AND TRANSIENT RESPONSE OF THE LINEAR DIFFERENTIAL EQUATION

    NASA Technical Reports Server (NTRS)

    Jamison, J. W.

    1994-01-01

    CFORM was developed by the Kennedy Space Center Robotics Lab to assist in linear control system design and analysis using closed form and transient response mechanisms. The program computes the closed form solution and transient response of a linear (constant coefficient) differential equation. CFORM allows a choice of three input functions: the Unit Step (a unit change in displacement); the Ramp function (step velocity); and the Parabolic function (step acceleration). It is only accurate in cases where the differential equation has distinct roots, and does not handle the case for roots at the origin (s=0). Initial conditions must be zero. Differential equations may be input to CFORM in two forms - polynomial and product of factors. In some linear control analyses, it may be more appropriate to use a related program, Linear Control System Design and Analysis (KSC-11376), which uses root locus and frequency response methods. CFORM was written in VAX FORTRAN for a VAX 11/780 under VAX VMS 4.7. It has a central memory requirement of 30K. CFORM was developed in 1987.

  9. Vadose zone controls on damping of climate-induced transient recharge fluxes in U.S. agroecosystems

    NASA Astrophysics Data System (ADS)

    Gurdak, Jason

    2017-04-01

    Understanding the physical processes in the vadose zone that link climate variability with transient recharge fluxes has particular relevance for the sustainability of groundwater-supported irrigated agriculture and other groundwater-dependent ecosystems. Natural climate variability on interannual to multidecadal timescales has well-documented influence on precipitation, evapotranspiration, soil moisture, infiltration flux, and can augment or diminish human stresses on water resources. Here the behavior and damping depth of climate-induced transient water flux in the vadose zone is explored. The damping depth is the depth in the vadose zone that the flux variation damps to 5% of the land surface variation. Steady-state recharge occurs when the damping depth is above the water table, and transient recharge occurs when the damping depth is below the water table. Findings are presented from major agroecosystems of the United States (U.S.), including the High Plains, Central Valley, California Coastal Basin, and Mississippi Embayment aquifer systems. Singular spectrum analysis (SSA) is used to identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). SSA results indicate that nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. Results from HYDRUS-1D simulations indicate that transient water flux through the vadose zone are controlled by highly nonlinear interactions between mean infiltration flux and infiltration period related to the modes of climate

  10. Targeted prevention of excess weight gain and eating disorders in high-risk adolescent girls: a randomized controlled trial.

    PubMed

    Tanofsky-Kraff, Marian; Shomaker, Lauren B; Wilfley, Denise E; Young, Jami F; Sbrocco, Tracy; Stephens, Mark; Ranzenhofer, Lisa M; Elliott, Camden; Brady, Sheila; Radin, Rachel M; Vannucci, Anna; Bryant, Edny J; Osborn, Robyn; Berger, Sarah S; Olsen, Cara; Kozlosky, Merel; Reynolds, James C; Yanovski, Jack A

    2014-10-01

    The high prevalence and incidence of obesity and eating disorders in US adolescent girls are serious health problems. Because of the shared risk factors for obesity and eating disorders, a targeted prevention of both conditions is a priority. We determined whether an adapted interpersonal psychotherapy prevention program is more efficacious for reducing excess weight gain and worsening disordered eating than health education in adolescent girls at high risk of obesity and eating disorders. A parallel-group, randomized controlled trial was conducted between September 2008 and January 2013 in a university-based laboratory and a federal research hospital. The study included 113 adolescent (12-17-y-old) girls deemed at high risk of adult obesity and eating disorders because of a body mass index (BMI) between the 75th and 97th percentiles and reports of episodes of a loss of control over their eating. Girls were randomly assigned to participate in an adapted interpersonal psychotherapy or a health-education group program for 12 weekly 90-min group sessions. Follow-up assessments occurred immediately after group programs and at 6 and 12 mo. Participation in both conditions was associated with decreases in expected BMI gain, age-adjusted BMI metrics, the percentage of fat by using dual-energy X-ray absorptiometry, symptoms of depression and anxiety, and the frequency of loss-of-control eating over 12 mo of follow-up (Ps < 0.001) with no group difference. In follow-up analyses, interpersonal psychotherapy was more efficacious than health education at reducing objective binge eating at the 12-mo follow-up (P < 0.05). The intervention with adolescent girls with loss-of-control eating is associated with lower age-adjusted BMI and percentage of adiposity as well as improved mood symptoms over 1 y. Interpersonal psychotherapy further reduced objective binge eating. Additional research is needed to elucidate the mechanisms by which physical and psychological improvements were

  11. Targeted prevention of excess weight gain and eating disorders in high-risk adolescent girls: a randomized controlled trial12345

    PubMed Central

    Shomaker, Lauren B; Wilfley, Denise E; Young, Jami F; Sbrocco, Tracy; Stephens, Mark; Ranzenhofer, Lisa M; Elliott, Camden; Brady, Sheila; Radin, Rachel M; Vannucci, Anna; Bryant, Edny J; Osborn, Robyn; Berger, Sarah S; Olsen, Cara; Kozlosky, Merel; Reynolds, James C; Yanovski, Jack A

    2014-01-01

    Background: The high prevalence and incidence of obesity and eating disorders in US adolescent girls are serious health problems. Because of the shared risk factors for obesity and eating disorders, a targeted prevention of both conditions is a priority. Objective: We determined whether an adapted interpersonal psychotherapy prevention program is more efficacious for reducing excess weight gain and worsening disordered eating than health education in adolescent girls at high risk of obesity and eating disorders. Design: A parallel-group, randomized controlled trial was conducted between September 2008 and January 2013 in a university-based laboratory and a federal research hospital. The study included 113 adolescent (12–17-y-old) girls deemed at high risk of adult obesity and eating disorders because of a body mass index (BMI) between the 75th and 97th percentiles and reports of episodes of a loss of control over their eating. Girls were randomly assigned to participate in an adapted interpersonal psychotherapy or a health-education group program for 12 weekly 90-min group sessions. Follow-up assessments occurred immediately after group programs and at 6 and 12 mo. Results: Participation in both conditions was associated with decreases in expected BMI gain, age-adjusted BMI metrics, the percentage of fat by using dual-energy X-ray absorptiometry, symptoms of depression and anxiety, and the frequency of loss-of-control eating over 12 mo of follow-up (Ps < 0.001) with no group difference. In follow-up analyses, interpersonal psychotherapy was more efficacious than health education at reducing objective binge eating at the 12-mo follow-up (P < 0.05). Conclusions: The intervention with adolescent girls with loss-of-control eating is associated with lower age-adjusted BMI and percentage of adiposity as well as improved mood symptoms over 1 y. Interpersonal psychotherapy further reduced objective binge eating. Additional research is needed to elucidate the mechanisms

  12. The Azospirillum brasilense Che1 Chemotaxis Pathway Controls Swimming Velocity, Which Affects Transient Cell-to-Cell Clumping

    PubMed Central

    Bible, Amber; Russell, Matthew H.

    2012-01-01

    The Che1 chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Che1 to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Che1 affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a ΔaerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with che1 deleted show that Che1 directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Che1-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Che1 activity. Che1-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche. PMID:22522896

  13. Ultrafast Control of Magnetism in Ferromagnetic Semiconductors via Photoexcited Transient Carriers

    SciTech Connect

    Cotoros, Ingrid A.

    2008-12-01

    The field of spintronics offers perspectives for seamless integration of coupled and inter-tunable electrical and magnetic properties in a single device. For integration of the spin degree of freedom with current electronic technology, new semiconductors are needed that show electrically-tunable magnetic properties at room temperature and above. Dilute magnetic semiconductors derived from III-V compounds, like GaMnAs and InMnAs, show coupled and tunable magnetic, transport, and optical properties, due to the fact that their ferromagnetism is hole-mediated. These unconventional materials are ideal systems for manipulating the magnetic order by changing the carrier polarization, population density, and energy band distribution of the complementary subsystem of holes. This is the main theme we cover in this thesis. In particular, we develop a unique setup by use of ultraviolet pump, near-infrared probe femtosecond laser pulses, that allows for magneto-optical Kerr effect (MOKE) spectroscopy experiments. We photo-excite transient carriers in our samples, and measure the induced transient magnetization dynamics. One set of experiments performed allowed us to observe for the first time enhancement of the ferromagnetic order in GaMnAs, on an ultrafast time scale of hundreds of picoseconds. The corresponding transient increase of Curie temperature (Tc, the temperature above which a ferromagnetic material loses its permanent magnetism) of about 1 K for our experimental conditions is a very promising result for potential spintronics applications, especially since it is seconded by observation of an ultrafast ferromagnetic to paramagnetic phase transition above Tc. In a different set of experiments, we "write" the magnetization in a particular orientation in the sample plane. Using an ultrafast scheme, we alter the distribution of holes in the system and detect signatures of the particular memory state in the subsequent magnetization dynamics, with unprecedented hundreds of

  14. A Double-Blind Randomized Controlled Trial of Maternal Postpartum Deworming to Improve Infant Weight Gain in the Peruvian Amazon

    PubMed Central

    Casapía, Martín; Aguilar, Eder; Silva, Hermánn; Montresor, Antonio; Rahme, Elham; Fraser, William D.; Marquis, Grace S.; Vercruysse, Jozef; Allen, Lindsay H.; Blouin, Brittany; Razuri, Hugo; Pezo, Lidsky

    2017-01-01

    Background Nutritional interventions targeting the critical growth and development period before two years of age can have the greatest impact on health trajectories over the life course. Compelling evidence has demonstrated that interventions investing in maternal health in the first 1000 days of life are beneficial for both mothers and their children. One such potential intervention is deworming integrated into maternal postpartum care in areas where soil-transmitted helminth (STH) infections are endemic. Methodology/Principal Findings From February to August 2014, 1010 mother-infant pairs were recruited into a trial aimed at assessing the effectiveness of maternal postpartum deworming on infant and maternal health outcomes. Following delivery, mothers were randomly assigned to receive either single-dose 400 mg albendazole or placebo. Participants were followed-up at 1 and 6 months postpartum. There was no statistically significant difference in mean weight gain between infants in the experimental and control groups (mean difference: -0.02; 95% CI: -0.1, 0.08) at 6 months of age. Further, deworming had no effect on measured infant morbidity indicators. However, ad hoc analyses restricted to mothers who tested positive for STHs at baseline suggest that infants of mothers in the experimental group had greater mean length gain in cm (mean difference: 0.8; 95% CI: 0.1, 1.4) and length-for-age z-score (mean difference: 0.5; 95% CI: 0.2, 0.8) at 6 months of age. Conclusions/Significance In a study population composed of both STH-infected and uninfected mothers, maternal postpartum deworming was insufficient to impact infant growth and morbidity indicators up to 6 months postpartum. Among STH-infected mothers, however, important improvements in infant length gain and length-for-age were observed. The benefits of maternal postpartum deworming should be further investigated in study populations having higher overall prevalences and intensities of STH infections and, in

  15. A Double-Blind Randomized Controlled Trial of Maternal Postpartum Deworming to Improve Infant Weight Gain in the Peruvian Amazon.

    PubMed

    Mofid, Layla S; Casapía, Martín; Aguilar, Eder; Silva, Hermánn; Montresor, Antonio; Rahme, Elham; Fraser, William D; Marquis, Grace S; Vercruysse, Jozef; Allen, Lindsay H; Blouin, Brittany; Razuri, Hugo; Pezo, Lidsky; Gyorkos, Theresa W

    2017-01-01

    Nutritional interventions targeting the critical growth and development period before two years of age can have the greatest impact on health trajectories over the life course. Compelling evidence has demonstrated that interventions investing in maternal health in the first 1000 days of life are beneficial for both mothers and their children. One such potential intervention is deworming integrated into maternal postpartum care in areas where soil-transmitted helminth (STH) infections are endemic. From February to August 2014, 1010 mother-infant pairs were recruited into a trial aimed at assessing the effectiveness of maternal postpartum deworming on infant and maternal health outcomes. Following delivery, mothers were randomly assigned to receive either single-dose 400 mg albendazole or placebo. Participants were followed-up at 1 and 6 months postpartum. There was no statistically significant difference in mean weight gain between infants in the experimental and control groups (mean difference: -0.02; 95% CI: -0.1, 0.08) at 6 months of age. Further, deworming had no effect on measured infant morbidity indicators. However, ad hoc analyses restricted to mothers who tested positive for STHs at baseline suggest that infants of mothers in the experimental group had greater mean length gain in cm (mean difference: 0.8; 95% CI: 0.1, 1.4) and length-for-age z-score (mean difference: 0.5; 95% CI: 0.2, 0.8) at 6 months of age. In a study population composed of both STH-infected and uninfected mothers, maternal postpartum deworming was insufficient to impact infant growth and morbidity indicators up to 6 months postpartum. Among STH-infected mothers, however, important improvements in infant length gain and length-for-age were observed. The benefits of maternal postpartum deworming should be further investigated in study populations having higher overall prevalences and intensities of STH infections and, in particular, where whipworm and hookworm infections are of public

  16. Cell line specific control of polyethylenimine-mediated transient transfection optimized with "Design of experiments" methodology.

    PubMed

    Thompson, Ben C; Segarra, Camille R J; Mozley, Olivia L; Daramola, Olalekan; Field, Ray; Levison, Peter R; James, David C

    2012-01-01

    We describe a design of experiments (DoE) response surface modeling strategy to optimize the concentration of basal variables underpinning polyethylenimine (PEI) mediated transfection of different CHO-K1 derived parental cell populations in a chemically defined medium, specifically the relative concentration of linear 25 kD PEI, host CHO cells and plasmid DNA. Using recombinant secreted alkaline phosphatase (SEAP) reporter activity as the modeled response, a discrete simple maximum was predicted for each CHO host cell population. Differences between the modeled optima derived from host cell specific differences in PEI cytotoxicity, such that the PEI:cell interaction effectively limited PEI-DNA polyplex load at a relatively constant PEI:DNA ratio. However, across the three CHO host cell populations, SEAP reporter production was not proportional to plasmid DNA input at the host cell specific predicted basal variable optima. A 10-fold variation in SEAP reporter output per mass of plasmid DNA delivered was observed. To determine the cellular basis of this difference in transient productivity, host CHO cells were transfected with fluorescently labeled polyplexes followed by flow cytometric analysis. Each CHO host cell population exhibited a distinct functional phenotype, varying in the extent of PEI-DNA polyplex binding to the cell surface and degree of polyplex internalization. SEAP production was directly proportional to the level of polyplex internalization and heparan sulfate proteoglycan level. Taken together, these data show that choice of host CHO cell line is a critical parameter, which should rationally precede cell line specific transient production platform design using DoE methodology. Copyright © 2011 American Institute of Chemical Engineers (AIChE).

  17. Tumor control and therapeutic gain with different schedules of combined radiotherapy and local external hyperthermia in human cancer

    SciTech Connect

    Arcangeli, G.; Cividalli, A.; Nervi, C.; Creton, G.; Lovisolo, G.; Mauro, F.

    1983-08-01

    Tumor control and therapeutic gain have been evaluated in a series of studies on patients with multiple lesions employing different protocols of combined radiotherapy (RT) and local external hyperthermia (HT). Tumor response has been evaluated during a follow-up ranging 6 to 18 months. Local tumor control was constantly better in lesions treated with any combined modalities in comparison with RT alone. The use of high RT dose per fraction appeared to increase tumor control only in the combined modalities groups, the immediate (so called simultaneous) schedule (HT at 42.5/sup 0/C/45 min, applied immediately after each RT fraction, twice a week) being more effective than the delayed (so called sequential) treatment (HT at 42.5/sup 0/C/45 min, delivered 4 h after each RT fraction, twice a week). The combination of high RT dose per fraction with high temperature HT (45/sup 0/C for 30 min) achieved the best tumor control. Consequently, a good therapeutic enhancement factor (TEF) (1.58) was obtained when conventional RT doses per fraction were used in association with 42.5/sup 0/C HT. TEF values of 1.40 and 1.15 were observed when high RT doses per fraction were employed in association with the delayed and immediate 42.5/sup 0/C HT, respectively. HT at 45/sup 0/C can be safely employed only when tumors can be heated selectively or at least preferentially in comparison with normal tissue; in the lesions treated with such a schedule a TEF of 2.10 was obtained.

  18. Control of Transient Growth Induced Transition in a Zero--Pressure Gradient Boundary Layer Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald Edwin

    The level of the skin friction drag depends on the boundary layer state, either low, for the laminar case or high for the turbulent case. Flow control is sought to attenuate the streamwise velocity streaks preceding sub-critical bypass transition to turbulence. In addition, the targeted instability is ubiquitous to the self-sustaining wall-bounded turbulence cycle and at the root of the long-term goal of turbulence control. The longer spatial and temporal scales associated with the laminar case make a physical demonstration of a model-based boundary layer flow control more tractable. The effectiveness of control systems is inherently linked to the ability of the actuator to alter the flow to a desired state. Therefore, actuators are a critical enabling technology component in any active flow control system. Arguably, the most important missing technology in boundary layer flow control is effective and robust actuators, which can be readily integrated with an active flow control system. Plasma actuators fulfil these characteristics and are an ideal candidate for the control of the bypass transition instability. In this thesis, the receptivity of the boundary layer to forcing by arrays of plasma actuators capable of producing streamwise streaks was characterized. Following, the transient growth instability was targeted in an open-loop framework to identify the physics of the attenuation mechanism, which was shown to be a linear process. The control loop was then closed with feedback from simultaneous spanwise distributed shear stress sensors. A wavenumber specific control objective was used to demonstrate the effectiveness of feedback for steady disturbance attenuation as well as to provide robustness to off-model conditions. For all cases, the targeted disturbance was reduced by over 94% of its initial energy. The control effectiveness was also validated for quasi-steady forcing by varying the input disturbance level. Ultimately, control of transient growth due to

  19. Transient antiretroviral treatment during acute simian immunodeficiency virus infection facilitates long-term control of the virus.

    PubMed

    Wodarz, D; Arnaout, R A; Nowak, M A; Lifson, J D

    2000-08-29

    Experimental evidence and mathematical models indicate that CD4+ T-cell help is required to generate memory cytotoxicT-lymphocyte precursors (CTLp) that are capable of persisting without ongoing antigenic stimulation, and that such responses are necessary to clear an infection or to control it in the long term. Here we analyse mathematical models of simian immunodeficiency virus (SIV) replication in macaques, assuming that SIV impairs specific CD4+ T-cell responses. According to the models, fast viral replication during the initial stages of primary infection can result in failure to generate sufficient long-lived memory CTLp required to control the infection in the long term. Modelling of drug therapy during the acute phase of the infection indicates that transient treatment can minimize the amount of virus-induced immune impairment, allowing a more effective initial immune sensitization. The result is the development of high levels of memory CTLp that are capable of controlling SIV replication in the long term, in the absence of continuous treament. In the model, the success of treatment depends crucially on the timing and duration of antiretroviral therapy. Data on SIV-infected macaques receiving transient drug therapy during acute infection support these theoretical predictions. The data and modelling suggest that among subjects controlling SIV replication most efficiently after treatment, there is a positive correlation between cellular immune responses and virus load in the post-acute stage of infection. Among subjects showing less-efficient virus control, the correlation is negative. We discuss our findings in relation to previously published data on HIV infection.

  20. In-Flight Validation of a Pilot Rating Scale for Evaluating Failure Transients in Electronic Flight Control Systems

    NASA Technical Reports Server (NTRS)

    Kalinowski, Kevin F.; Tucker, George E.; Moralez, Ernesto, III

    2006-01-01

    Engineering development and qualification of a Research Flight Control System (RFCS) for the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) JUH-60A has motivated the development of a pilot rating scale for evaluating failure transients in fly-by-wire flight control systems. The RASCAL RFCS includes a highly-reliable, dual-channel Servo Control Unit (SCU) to command and monitor the performance of the fly-by-wire actuators and protect against the effects of erroneous commands from the flexible, but single-thread Flight Control Computer. During the design phase of the RFCS, two piloted simulations were conducted on the Ames Research Center Vertical Motion Simulator (VMS) to help define the required performance characteristics of the safety monitoring algorithms in the SCU. Simulated failures, including hard-over and slow-over commands, were injected into the command path, and the aircraft response and safety monitor performance were evaluated. A subjective Failure/Recovery Rating (F/RR) scale was developed as a means of quantifying the effects of the injected failures on the aircraft state and the degree of pilot effort required to safely recover the aircraft. A brief evaluation of the rating scale was also conducted on the Army/NASA CH-47B variable stability helicopter to confirm that the rating scale was likely to be equally applicable to in-flight evaluations. Following the initial research flight qualification of the RFCS in 2002, a flight test effort was begun to validate the performance of the safety monitors and to validate their design for the safe conduct of research flight testing. Simulated failures were injected into the SCU, and the F/RR scale was applied to assess the results. The results validate the performance of the monitors, and indicate that the Failure/Recovery Rating scale is a very useful tool for evaluating failure transients in fly-by-wire flight control systems.

  1. Application of Fuzzy-Logic Controller and Neural Networks Controller in Gas Turbine Speed Control and Overheating Control and Surge Control on Transient Performance

    NASA Astrophysics Data System (ADS)

    Torghabeh, A. A.; Tousi, A. M.

    2007-08-01

    This paper presents Fuzzy Logic and Neural Networks approach to Gas Turbine Fuel schedules. Modeling of non-linear system using feed forward artificial Neural Networks using data generated by a simulated gas turbine program is introduced. Two artificial Neural Networks are used , depicting the non-linear relationship between gas generator speed and fuel flow, and turbine inlet temperature and fuel flow respectively . Off-line fast simulations are used for engine controller design for turbojet engine based on repeated simulation. The Mamdani and Sugeno models are used to expression the Fuzzy system . The linguistic Fuzzy rules and membership functions are presents and a Fuzzy controller will be proposed to provide an Open-Loop control for the gas turbine engine during acceleration and deceleration . MATLAB Simulink was used to apply the Fuzzy Logic and Neural Networks analysis. Both systems were able to approximate functions characterizing the acceleration and deceleration schedules . Surge and Flame-out avoidance during acceleration and deceleration phases are then checked . Turbine Inlet Temperature also checked and controls by Neural Networks controller. This Fuzzy Logic and Neural Network Controllers output results are validated and evaluated by GSP software . The validation results are used to evaluate the generalization ability of these artificial Neural Networks and Fuzzy Logic controllers.

  2. The use of oxygen scavengers to prevent the transient discolouration of ground beef packaged under controlled, oxygen-depleted atmospheres.

    PubMed

    Gill, C O; McGinnis, J C

    1995-01-01

    Rates of O(2) absorption from air were determined for a type of commercial O(2) scavenger that is formulated for rapid O(2) absorption at chiller temperatures. Rates of O(2) absorption from N(2) atmospheres containing 600 ppm O(2) were determined for trays that each contained 350 g of ground beef. Packs with controlled atmospheres of N(2) that contained ground beef and O(2) scavengers were prepared, to determine the conditions under which the scavengers could prevent the transient discolouration of the meat which arises from its reaction with the residual O(2) initially present in pack atmospheres. The rates of O(2) absorption by individual scavengers varied from the average by ±50%. The rate of O(2) absorption declined with decreasing oxygen concentration, from an average value per scavenger of about 12 ml h(-1) when O(2) concentrations were between 20 and 10%. At O(2) concentrations <1% (10,000 ppm) the rate of O(2) absorption was directly proportioned to the O(2) concentration so that the O(2) concentration in an atmosphere in a gas-impermeable pouch declined exponentially with time. The absorption of O(2) by ground beef was similarly dependent on the O(2) concentration. At 2 °C, the transient discolouration of beef in atmospheres initially containing about 50 ppm O(2) was prevented by the presence of 17.5 scavengers per l of atmosphere. At -15 °C, discolouration was prevented by 5 scavengers per l. The findings indicate that the O(2) concentration in pack atmospheres has to be reduced below 10 ppm within 30 min at 2 °C, or 2 h at -1.5 °C if ground beef is not to transiently discolour. It is unlikely that the required rates of O(2) absorption could be obtained economically with currently available, commercial O(2) scavengers.

  3. Transient Load Following and Control Analysis of Advanced S-CO2 Power Conversion with Dry Air Cooling

    SciTech Connect

    Moisseytsev, Anton; Sienicki, James J.

    2016-01-01

    Supercritical carbon dioxide (S-CO2) Brayton cycles are under development as advanced energy converters for advanced nuclear reactors, especially the Sodium-Cooled Fast Reactor (SFR). The use of dry air cooling for direct heat rejection to the atmosphere ultimate heat sink is increasingly becoming a requirement in many regions due to restrictions on water use. The transient load following and control behavior of an SFR with an S-CO2 cycle power converter utilizing dry air cooling have been investigated. With extension and adjustment of the previously existing control strategy for direct water cooling, S-CO2 cycle power converters can also be used for load following operation in regions where dry air cooling is a requirement

  4. Limiting weight gain in overweight and obese women during pregnancy to improve health outcomes: the LIMIT randomised controlled trial

    PubMed Central

    2011-01-01

    Background Obesity is a significant global health problem, with the proportion of women entering pregnancy with a body mass index greater than or equal to 25 kg/m2 approaching 50%. Obesity during pregnancy is associated with a well-recognised increased risk of adverse health outcomes both for the woman and her infant, however there is more limited information available regarding effective interventions to improve health outcomes. The aims of this randomised controlled trial are to assess whether the implementation of a package of dietary and lifestyle advice to overweight and obese women during pregnancy to limit gestational weight gain is effective in improving maternal, fetal and infant health outcomes. Methods/Design Design: Multicentred randomised, controlled trial. Inclusion Criteria: Women with a singleton, live gestation between 10+0-20+0 weeks who are obese or overweight (defined as body mass index greater than or equal to 25 kg/m2), at the first antenatal visit. Trial Entry & Randomisation: Eligible, consenting women will be randomised between 10+0 and 20+0 weeks gestation using a central telephone randomisation service, and randomisation schedule prepared by non-clinical research staff with balanced variable blocks. Stratification will be according to maternal BMI at trial entry, parity, and centre where planned to give birth. Treatment Schedules: Women randomised to the Dietary and Lifestyle Advice Group will receive a series of inputs from research assistants and research dietician to limit gestational weight gain, and will include a combination of dietary, exercise and behavioural strategies. Women randomised to the Standard Care Group will continue to receive their pregnancy care according to local hospital guidelines, which does not currently include routine provision of dietary, lifestyle and behavioural advice. Outcome assessors will be blinded to the allocated treatment group. Primary Study Outcome: infant large for gestational age (defined as

  5. The transient accumulation of the signaling state of photoactive yellow protein is controlled by the external pH.

    PubMed

    Borucki, Berthold; Joshi, Chandra P; Otto, Harald; Cusanovich, Michael A; Heyn, Maarten P

    2006-10-15

    The signaling state of the photoreceptor photoactive yellow protein is the long-lived intermediate I(2)'. The pH dependence of the equilibrium between the transient photocycle intermediates I(2) and I(2)' was investigated. The formation of I(2)' from I(2) is accompanied by a major conformational change. The kinetics and intermediates of the photocycle and of the photoreversal were measured by transient absorption spectroscopy from pH 4.6 to 8.4. Singular value decomposition (SVD) analysis of the data at pH 7 showed the presence of three spectrally distinguishable species: I(1), I(2), and I(2)'. Their spectra were determined using the extrapolated difference method. I(2) and I(2)' have electronic absorption spectra, with maxima at 370 +/- 5 and 350 +/- 5 nm, respectively. Formation of the signaling state is thus associated with a change in the environment of the protonated chromophore. The time courses of the I(1), I(2), and I(2)' intermediates were determined from the wavelength-dependent transient absorbance changes at each pH, assuming that their spectra are pH-independent. After the formation of I(2)' ( approximately 2 ms), these three intermediates are in equilibrium and decay together to the initial dark state. The equilibrium between I(2) and I(2)' is pH dependent with a pK(a) of 6.4 and with I(2)' the main species above this pK(a). Measurements of the pH dependence of the photoreversal kinetics with a second flash of 355 nm at a delay of 20 ms confirm this pK(a) value. I(2) and I(2)' are photoreversed with reversal times of approximately 55 micros and several hundred microseconds, respectively. The corresponding signal amplitudes are pH dependent with a pK(a) of approximately 6.1. Photoreversal from I(2)' dominates above the pK(a). The transient accumulation of I(2)', the active state of photoactive yellow protein, is thus controlled by the proton concentration. The rate constant k(3) for the recovery to the initial dark state also has a pK(a) of

  6. Gaining control over responses to implicit attitude tests: Implementation intentions engender fast responses on attitude-incongruent trials.

    PubMed

    Webb, Thomas L; Sheeran, Paschal; Pepper, John

    2012-03-01

    The present research investigated whether forming implementation intentions could promote fast responses to attitude-incongruent associations (e.g., woman-manager) and thereby modify scores on popular implicit measures of attitude. Expt 1 used the Implicit Association Test (IAT) to measure associations between gender and science versus liberal arts. Planning to associate women with science engendered fast responses to this category-attribute pairing and rendered summary scores more neutral compared to standard IAT instructions. Expt 2 demonstrated that forming egalitarian goal intentions is not sufficient to produce these effects. Expt 3 extended these findings to a different measure of implicit attitude (the Go/No-Go Association Task) and a different stereotypical association (Muslims-terrorism). In Expt 4, managers who planned to associate women with superordinate positions showed more neutral IAT scores relative to non-planners and effects were maintained 3 weeks later. In sum, implementation intentions enable people to gain control over implicit attitude responses. © 2010 The British Psychological Society.

  7. Comparison of dual-time-constant and fast-acting automatic gain control (AGC) systems in cochlear implants.

    PubMed

    Boyle, Patrick J; Büchner, Andreas; Stone, Michael A; Lenarz, Thomas; Moore, Brian C J

    2009-04-01

    Cochlear implants usually employ an automatic gain control (AGC) system as a first stage of processing. AGC1 was a fast-acting (syllabic) compressor. AGC2 was a dual-time-constant system; it usually performed as a slow-acting compressor, but incorporated an additional fast-acting system to provide protection from sudden increases in sound level. Six experienced cochlear-implant users were tested in a counterbalanced order, receiving one-month of experience with a given AGC type before switching to the other type. Performance was evaluated shortly after provision of a given AGC type and after one-month of experience with that AGC type. Questionnaires, mainly relating to listening in quiet situations, did not reveal significant differences between the two AGC types. However, fixed-level and roving-level tests of sentence identification in noise both revealed significantly better performance for AGC2. It is suggested that the poorer performance for AGC1 occurred because AGC1 introduced cross-modulation between the target speech and background noise, which made perceptual separation of the target and background more difficult.

  8. Spectrum efficiency gains resulting from the implementation of adaptive transmit power control in fixed terrestrial links at 38 GHz

    NASA Astrophysics Data System (ADS)

    Callaghan, S. A.; Inglis, I.; Hansell, P.

    2009-06-01

    Adaptive transmit power control (ATPC) can be used to improve the spectrum efficiency of terrestrial point-to-point fixed links by limiting the transmit power to that required to maintain a constant bit error rate regardless of the propagation conditions. This results in a reduced transmit power being used during clear-sky conditions, lowering the interference resulting from the ATPC link. This improves the frequency reuse factor associated with a given band and geographic area, providing a spectrum efficiency gain. The project described in this paper found that implementing ATPC in the 38 GHz terrestrial fixed links band gives significant improvements in spectrum efficiency as measured by the increase in the number of links assigned to channel 1 (from ˜50% to ˜70%) and the decrease in the maximum bandwidth used (from ˜300 MHz to ˜180 MHz). However, a model plan exposed to an exceptionally intense frontal rain event showed a number of additional outages caused by ATPC, amounting to approximately 12% of the number of outages caused directly by rain. In comparison, when exposed to an annualized simulated rain database the number of extra outages in this case falls to 2.6%.

  9. Trial design: blood pressure control and weight gain prevention in prehypertensive and hypertensive smokers: the treatment and prevention study.

    PubMed

    Vander Weg, Mark W; Klesges, Robert C; Ebbert, Jon O; Lichty, Ellen J; DeBon, Margaret; North, Frederick; Schroeder, Darrell R; Dubbert, Patricia M

    2008-03-01

    Cigarette smokers with elevated blood pressure (BP) are at substantially higher risk for cardiovascular events compared to normotensive smokers. Although smoking cessation should be a primary treatment goal for these patients, increases in body weight accompanying smoking abstinence may further increase BP. Intervention strategies that facilitate smoking cessation and modify adverse changes in body weight and BP are needed. We describe an ongoing multi-site, two-phase, five-year randomized clinical trial. Participants are cigarette smokers with Prehypertension or Stage I Hypertension. In the first phase, participants receive a smoking cessation intervention combining behavioral counseling and nicotine replacement in an open-label fashion. In the second phase, participants who successfully quit smoking are randomly assigned to one of three lifestyle interventions: 1) weight gain prevention, 2) blood pressure control, or 3) usual lifestyle. Participants are followed for one year to assess changes in blood pressure, body weight, dietary intake, and physical activity. Results from the proposed study will provide important insights into the efficacy of various approaches to lifestyle modification in smokers at increased risk for cardiovascular events.

  10. Decentralized control of large transient in power systems: theory and application. Final report, January 1981-August 1983

    SciTech Connect

    DeCarlo, R.; Hawley, P.; Sebok, D.

    1983-08-01

    Chapter 1 describes a continuation algorithm to construct decentralized state feedback gains which place the natural frequencies (natural modes of vibration or eigenvalues) of a linearized power system at desired locations. Chapter 2 and 3 address the problem of designing a decentralized dither control for linearly interconnected synchronous machines, each of which is nonlinear. In Chapter 2, the theory finds application to the nonlinear third order model of a single machine infinite bus system where the primary control is via an ac-dc converter. Similarly Chapter 3 considers a two machine system with individual machine converters acting as the primary control. Computer simulations of the control action given various system perturbations are found in both Chapters 2 and 3.

  11. Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

    2011-01-01

    The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly done by cold biasing the reservoir and using electrical heaters to provide the required control power. With this method, the loop operating temperature can be controlled within 0.5K or better. However, because the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if the LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP was carried out to investigate the effects on the LHP operation when the control temperature sensor was placed on the heat source instead of the reservoir. In these tests, the LHP reservoir was cold-biased and was heated by a control heater. Test results show that it was feasible to use the heat source temperature for feedback control of the LHP operation. In particular, when a thermoelectric converter was used as the reservoir control heater, the heat source temperature could be maintained within a tight range using a proportional-integral-derivative or on/off control algorithm. Moreover, because the TEC could provide both heating and cooling to the reservoir, temperature oscillations during fast transients such as loop startup could be eliminated or substantially reduced when compared to using an electrical heater as the control heater.

  12. Detailed description of a prepregnancy care program and its impact on maternal glucose control, weight gain, and dropouts.

    PubMed

    Perea, Verónica; Orois, Aida; Amor, Antonio J; Jansà, Marga; Vidal, Merce; Gimenez, Marga; Conget, Ignacio; Vinagre, Irene

    2017-02-01

    The aim of this study was to analyze the clinical and metabolic changes observed during a prepregnancy care (PPC) program. We performed a retrospective, observational, cohort study of 104 women with type 1 diabetes initiating a PPC program from 2011 to 2014. The outcomes measured were changes in HbA1c levels, weight and hypoglycemic events during PPC. Risk factors associated with severe hypoglycemia events, achieving the HbA1c target and dropouts were evaluated. HbA1c decreased from 7.2 ± 0.8% (55.3 ± 8.8 mmol/mol) to 6.7 ± 0.9% (49.8 ± 10.3 mmol/mol) (P < .001) within a median of 14.2 months (interquartile interval 5.4-23.2); 71.2% obtained HbA1c  < 7% (53 mmol/mol). HbA1c at the end of PPC was associated with baseline HbA1c (β = .318, P = .001) and the number of previous pregnancies (β = .224, P = .038), PPC was accompanied by 1.4 ± 4.0 kg weight gain (P = .003) without changes in severe hypoglycemic events. The risk factors for severe hypoglycemia were severe hypoglycemic events during the 2 years before (odds ratio [OR] 11.99, confidence interval 95% 1.89-75.95) and PPC duration (OR 1.09, 1.03-1.16). A total of 33 patients (31.7%) dropped out from PPC during follow-up, with dropout being associated with age (OR 1.17, 1.04-1.36) and PPC duration (OR 1.06, 1.02-1.11). Our PPC program was associated with an improvement in glycemic control without a significant increase in severe hypoglycemic events, although with some weight gain. A considerable number of patients dropped out during follow-up, this being related to older age and a longer duration of the program. This information could be of help to design new and more effective PPC approaches. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Transient distraction and attentional control during a sustained selective attention task

    PubMed Central

    Demeter, Elise; Woldorff, Marty G.

    2016-01-01

    Distracting stimuli in the environment can pull our attention away from our goal-directed tasks. fMRI studies have implicated regions in right frontal cortex as being particularly important for processing distractors (e.g., Demeter, Hernandez-Garcia, Sarter, & Lustig, 2011; de Fockert & Theeuwes, 2012). Less is known, however, about the timing and sequence of how right frontal or other brain regions respond selectively to distractors and how distractors impinge upon the cascade of processes related to detecting and processing behaviorally-relevant target stimuli. Here we used electroencephalography (EEG) and event-related potentials (ERPs) to investigate the neural consequences of a perceptually salient but task-irrelevant distractor on the detection of rare target stimuli embedded in a rapid, serial visual presentation (RSVP) stream. We found that distractors that occur during the presentation of a target interfere behaviorally with detection of those targets, reflected by reduced detection rates, and that these missed targets show a reduced amplitude of the long-latency, detection-related P3 component. We also found distractors elicited a right-lateralized frontal negativity beginning at 100 ms, whose amplitude negatively correlated across subjects with their distraction-related behavioral impairment. Finally, we also quantified the instantaneous amplitude of the steady-state visual evoked potentials (SSVEPs) elicited by the RSVP stream and found that the occurrence of a distractor resulted in a transient amplitude decrement of the SSVEP, presumably reflecting the pull of attention away from the RSVP stream when distracting stimuli occur in the environment. PMID:26967946

  14. Transient Receptor Potential Canonical Type 3 Channels Control the Vascular Contractility of Mouse Mesenteric Arteries

    PubMed Central

    Yeon, Soo-In; Kim, Joo Young; Yeon, Dong-Soo; Abramowitz, Joel; Birnbaumer, Lutz; Muallem, Shmuel; Lee, Young-Ho

    2014-01-01

    Transient receptor potential canonical type 3 (TRPC3) channels are non-selective cation channels and regulate intracellular Ca2+ concentration. We examined the role of TRPC3 channels in agonist-, membrane depolarization (high K+)-, and mechanical (pressure)-induced vasoconstriction and vasorelaxation in mouse mesenteric arteries. Vasoconstriction and vasorelaxation of endothelial cells intact mesenteric arteries were measured in TRPC3 wild-type (WT) and knockout (KO) mice. Calcium concentration ([Ca2+]) was measured in isolated arteries from TRPC3 WT and KO mice as well as in the mouse endothelial cell line bEnd.3. Nitric oxide (NO) production and nitrate/nitrite concentrations were also measured in TRPC3 WT and KO mice. Phenylephrine-induced vasoconstriction was reduced in TRPC3 KO mice when compared to that of WT mice, but neither high K+- nor pressure-induced vasoconstriction was altered in TRPC3 KO mice. Acetylcholine-induced vasorelaxation was inhibited in TRPC3 KO mice and by the selective TRPC3 blocker pyrazole-3. Acetylcholine blocked the phenylephrine-induced increase in Ca2+ ratio and then relaxation in TRPC3 WT mice but had little effect on those outcomes in KO mice. Acetylcholine evoked a Ca2+ increase in endothelial cells, which was inhibited by pyrazole-3. Acetylcholine induced increased NO release in TRPC3 WT mice, but not in KO mice. Acetylcholine also increased the nitrate/nitrite concentration in TRPC3 WT mice, but not in KO mice. The present study directly demonstrated that the TRPC3 channel is involved in agonist-induced vasoconstriction and plays important role in NO-mediated vasorelaxation of intact mesenteric arteries. PMID:25310225

  15. Effect of lifestyle interventions of pregnant women on their dietary habits, lifestyle behaviors, and weight gain: a randomized controlled trial.

    PubMed

    Aşcı, Özlem; Rathfisch, Gülay

    2016-02-24

    Although it is known that lifestyle behaviors of pregnant women are closely related to maternal and fetal health, number of data concerning efficacy of intervention on lifestyle during pregnancy is limited. The purpose of this study is to determine the effect of lifestyle interventions on improving dietary habits and lifestyle behaviors, ensuring gestational weight gain (GWG) within recommended levels and limiting postpartum weight retention (PWR). The study was conducted as a randomized controlled trial in a family health center located in Istanbul, Turkey, between June 2011 and July 2012. The primary outcomes were GWG, and the proportion of pregnant women whose GWG was within the Institute of Medicine (IOM) guidelines. One hundred two pregnant women with gestation ≤12 weeks, age ≥18 years, gravidity ≤2, and who did not intend to lose weight in prepregnancy period were randomly included in this study as intervention (n = 51) and control (n = 51) groups. The study was completed with 45 women for each group. The control group received routine antenatal care. The intervention group was received an individualized lifestyle intervention focusing on healthy lifestyle, diet, exercise, and weight monitoring as four sessions at 12-15, 16-18, 20-24, and 37 weeks gestation. Lifestyle behaviors were evaluated with Health-Promoting Lifestyle Profile-II. Dietary habits were assessed by 3-day dietary recalls, and weight was followed from pregnancy until 6 weeks postpartum. The lifestyle interventions had a significant effect on improving lifestyle behaviors, protein intake, percentage of energy from protein, calcium, magnesium, iron, zinc, and vegetable intakes when adjusted for confounders (p < 0.05). The proportion of women who were within the IOM recommendations was higher in the intervention group (51.1 %) than in the control group (28.9 %) The odds ratio for GWG within IOM was statistically significant between the groups (OR = 0.59, 95 % CI, 0

  16. An Action Dependent Heuristic Dynamic Programming-controlled Superconducting Magnetic Energy Storage for Transient Stability Augmentation

    NASA Astrophysics Data System (ADS)

    Wang, Xinpu; Yang, Jun; Zhang, Xiaodong; Yu, Xiaopeng

    To enhance the stability of power system, the active power and reactive power can be absorbed from or released to Superconducting magnetic energy storage (SMES) unit according to system power requirements. This paper proposes a control strategy based on action dependent heuristic dynamic programing (ADHDP) which can control SMES to improve the stability of electric power system with on-line learning ability. Based on back propagation (BP) neural network, ADHDP approximates the optimal control solution of nonlinear system through iteration step by step. This on-line learning ability improves its performance by learning from its own mistakes through reinforcement signal from external environment, so that it can adjust the neural network weights according to the back propagation error to achieve optimal control performance. To investigate the effectiveness of the proposed control strategy, simulation tests are carried out in Matlab/Simulink. And a conventional Proportional-Integral (PI) controlled method is used to compare the performance of ADHDP. Simulation results show that the proposed controller demonstrates superior damping performance on power system oscillation caused by three-phase fault and wind power fluctuation over the PI controller.

  17. Imaging new transient nanostructures using a microfluidic chip integrated with a controlled environment vitrification system for cryogenic transmission electron microscopy.

    PubMed

    Lee, Jinkee; Jha, Ashish K; Bose, Arijit; Tripathi, Anubhav

    2008-11-18

    Nanostructures (vesicles, micelles, bilayers) are important in nanomedicine and biochemical processes. They are agents for encapsulation and eventual release of drugs, flavors, and fragrances. The structural transition from micelles to vesicles through disk-like intermediate states has been demonstrated previously. Here, we disclose a new route for the micelle-vesicle transition, where micelles aggregate to first form long tubules that become unstable, and break up into vesicles. A simple theory, based on energy principles, is presented to explain the tubule-vesicle transition. Observation of this new tubular intermediate state has been facilitated by the development of an integrated microfluidic chip/cryogenic transmission electron microscopy (cryo-TEM) unit. Although this transition has been observed in a specific amphiphilic system where micellar solutions of cetyltrimethylammonium bromide (CTAB) and dodecylbenzene sulfonic acid (HDBS) are mixed to form vesicles, this new tool can be applied broadly to study transient structures in nanoscale systems under the very controlled conditions provided by microfluidics.

  18. Transient controls on estuarine SPM fluxes: case study in the Dee Estuary, UK.

    NASA Astrophysics Data System (ADS)

    Amoudry, Laurent; Williams, Megan; Todd, David

    2017-04-01

    circulations in the estuary. Wavelet analysis provides clear evidence that such influx of sediment in the estuary is alternatively the result of periodic stratification at neap tides and of tidal asymmetry in suspended sediment concentration at spring tides. Such transient processes will be important to determine and predict estuarine responses to short-lived perturbations. Further analysis of other field campaigns will enable to determine the persistence of these processes over seasonal and annual timescales.

  19. The sympathetic nervous system is controlled by transient receptor potential vanilloid 1 in the regulation of body temperature

    PubMed Central

    Alawi, Khadija M.; Aubdool, Aisah A.; Liang, Lihuan; Wilde, Elena; Vepa, Abhinav; Psefteli, Maria-Paraskevi; Brain, Susan D.; Keeble, Julie E.

    2015-01-01

    Transient receptor potential vanilloid 1 (TRPV1) is involved in sensory nerve nociceptive signaling. Recently, it has been discovered that TRPV1 receptors also regulate basal body temperature in multiple species from mice to humans. In the present study, we investigated whether TRPV1 modulates basal sympathetic nervous system (SNS) activity. C57BL6/J wild-type (WT) mice and TRPV1 knockout (KO) mice were implanted with radiotelemetry probes for measurement of core body temperature. AMG9810 (50 mg/kg) or vehicle (2% DMSO/5% Tween 80/10 ml/kg saline) was injected intraperitoneally. Adrenoceptor antagonists or vehicle (5 ml/kg saline) was injected subcutaneously. In WT mice, the TRPV1 antagonist, AMG9810, caused significant hyperthermia, associated with increased noradrenaline concentrations in brown adipose tissue. The hyperthermia was significantly attenuated by the β-adrenoceptor antagonist propranolol, the mixed α-/β-adrenoceptor antagonist labetalol, and the α1-adrenoceptor antagonist prazosin. TRPV1 KO mice have a normal basal body temperature, indicative of developmental compensation. d-Amphetamine (potent sympathomimetic) caused hyperthermia in WT mice, which was reduced in TRPV1 KO mice, suggesting a decreased sympathetic drive in KOs. This study provides new evidence that TRPV1 controls thermoregulation upstream of the SNS, providing a potential therapeutic target for sympathetic hyperactivity thermoregulatory disorders.—Alawi, K. M., Aubdool, A. A., Liang, L., Wilde, E., Vepa, A., Psefteli, M.-P., Brain, S. D., Keeble, J. E. The sympathetic nervous system is controlled by transient receptor potential vanilloid 1 in the regulation of body temperature. PMID:26136480

  20. Transient Biocompatible Polymeric Platforms for Long-Term Controlled Release of Therapeutic Proteins and Vaccines

    PubMed Central

    Acar, Handan; Banerjee, Saikat; Shi, Heliang; Jamshidi, Reihaneh; Hashemi, Nastaran; Cho, Michael W.; Montazami, Reza

    2016-01-01

    Polymer-based interpenetrating networks (IPNs) with controllable and programmable degradation and release kinetics enable unique opportunities for physisorption and controlled release of therapeutic proteins or vaccines while their chemical and structural integrities are conserved. This paper presents materials, a simple preparation method, and release kinetics of a series of long-term programmable, biocompatible, and biodegradable polymer-based IPN controlled release platforms. Release kinetics of the gp41 protein was controlled over a 30-day period via tuning and altering the chemical structure of the IPN platforms. Post-release analysis confirmed structural conservation of the gp41 protein throughout the process. Cell viability assay confirmed biocompatibility and non-cytotoxicity of the IPNs. PMID:28546855

  1. Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques.

    PubMed

    Hayakawa, Tomohiko; Watanabe, Takanoshin; Senoo, Taku; Ishikawa, Masatoshi

    2017-04-04

    Galvanometer mirrors are used for optical applications such as target tracking, drawing, and scanning control because of their high speed and accuracy. However, the responsiveness of a galvanometer mirror is limited by its inertia; hence, the gain of a galvanometer mirror is reduced when the control path is steep. In this research, we propose a method to extend the corresponding frequency using a pre-emphasis technique to compensate for the gain reduction of galvanometer mirrors in sine-wave path tracking using proportional-integral-differential (PID) control. The pre-emphasis technique obtains an input value for a desired output value in advance. Applying this method to control the galvanometer mirror, the raw gain of a galvanometer mirror in each frequency and amplitude for sine-wave path tracking using a PID controller was calculated. Where PID control is not effective, maintaining a gain of 0 dB to improve the trajectory tracking accuracy, it is possible to expand the speed range in which a gain of 0 dB can be obtained without tuning the PID control parameters. However, if there is only one frequency, amplification is possible with a single pre-emphasis coefficient. Therefore, a sine wave is suitable for this technique, unlike triangular and sawtooth waves. Hence, we can adopt a pre-emphasis technique to configure the parameters in advance, and we need not prepare additional active control models and hardware. The parameters are updated immediately within the next cycle because of the open loop after the pre-emphasis coefficients are set. In other words, to regard the controller as a black box, we need to know only the input-to-output ratio, and detailed modeling is not required. This simplicity allows our system to be easily embedded in applications. Our method using the pre-emphasis technique for a motion-blur compensation system and the experiment conducted to evaluate the method are explained.

  2. Transient and steady state performance analysis of power flow control in a DFIG variable speed wind turbine

    NASA Astrophysics Data System (ADS)

    Nwosu, Cajethan M.; Oti, Stephen E.; Ogbuka, Cosmas U.

    2017-01-01

    This paper presents transient and steady state performance analysis of power flow control in a 5.0 kW Doubly-Fed Induction Generator (DFIG) Variable Speed Wind Turbine (VSWT) under sub synchronous speed, super synchronous speed and synchronous speed modes of operation. Stator flux orientation is used for the control of the rotor-side converter (RSC) and DFIG whereas the grid (or stator) voltage orientation is the preferred choice for the control of the grid-side converter (GSC). In each of the three speeds modes, power is always supplied to the grid through the stator of the DFIG. The magnitude of net power (stator power plus rotor power) is less than stator power during the sub synchronous speed mode; it is greater than stator power during the super synchronous speed mode while it is equal to the stator power during the synchronous speed mode. In synchronous speed mode, the rotor power is zero indicating that power is neither supplied to the grid from the rotor nor supplied to the rotor from the grid; here the magnitude of net power is equal to stator power. The simulation results thus obtained in a MATLAB/SIMULINK environment laid credence to the controllability of power flow reversal in a DFIG-VSWT through back-to-back power electronic converter.

  3. A 6-month randomized controlled trial to test the efficacy of a lifestyle intervention for weight gain management in schizophrenia

    PubMed Central

    2013-01-01

    Background Patients with schizophrenia have lower longevity than the general population as a consequence of a combination of risk factors connected to the disease, lifestyle and the use of medications, which are related to weight gain. Methods A multicentric, randomized, controlled-trial was conducted to test the efficacy of a 12-week group Lifestyle Wellness Program (LWP). The program consists of a one-hour weekly session to discuss topics like dietary choices, lifestyle, physical activity and self-esteem with patients and their relatives. Patients were randomized into two groups: standard care (SC) and standard care plus intervention (LWP). Primary outcome was defined as the weight and body mass index (BMI). Results 160 patients participated in the study (81 in the intervention group and 79 in the SC group). On an intent to treat analysis, after three months the patients in the intervention group presented a decrease of 0.48 kg (CI 95% -0.65 to 1.13) while the standard care group showed an increase of 0.48 kg (CI 95% 0.13 to 0.83; p=0.055). At six-month follow-up, there was a significant weight decrease of −1.15 kg, (CI 95% -2.11 to 0.19) in the intervention group compared to a weight increase in the standard care group (+0.5 kg, CI 95% -0.42–1.42, p=0.017). Conclusion In conclusion, this was a multicentric randomized clinical trial with a lifestyle intervention for individuals with schizophrenia, where the intervention group maintained weight and presented a tendency to decrease weight after 6 months. It is reasonable to suppose that lifestyle interventions may be important long-term strategies to avoid the tendency of these individuals to increase weight. Clinicaltrials.gov identifier NCT01368406 PMID:23418863

  4. A high current gain gate-controlled lateral bipolar junction transistor with 90 nm CMOS technology for future RF SoC applications

    NASA Astrophysics Data System (ADS)

    Chen, Shuo-Mao; Fang, Yean-Kuen; Yeh, Wen-Kuan; Lee, I. C.; Chiang, Yen-Ting

    2008-08-01

    A CMOS-compatible gate-controlled lateral BJT (GC-LBJT) was prepared with a conventional 90 nm CMOS technology for radio frequency system-on-chip (RF SoC) applications. The emitter injection efficiency and the doping profile in P-well were optimized by properly controlling source, drain, and well implants. Consequently, the GC-LBJT with a gate length of 0.15 μm can achieve a current gain over 2000 and 17/19 GHz for the fT/fmax, respectively, which are 1000%, 200%, and 60% improvements in current gain, fT and fmax, respectively as compared to the LBJT reported previously.

  5. Environmental factors controlling transient and seasonal changes of trace gases within shallow vadose zone

    NASA Astrophysics Data System (ADS)

    Pla, Concepcion; Galiana-Merino, Juan Jose; Cuezva, Soledad; Fernandez-Cortes, Angel; Garcia-Anton, Elena; Cuevas, Jaime; Cañaveras, Juan Carlos; Sanchez-Moral, Sergio; Benavente, David

    2014-05-01

    the soil produced CO2 (with a characteristic signal of -27‰ for C3 plants) in the cave atmosphere. The lowest levels of CO2 coincide with the highest of delta13C pointing to an input of exterior air during the degassing stage. Regarding the CH4 concentration inside the cave, higher values (0.3 ppm average concentration) are observed during outgassing stage than the isolation period (CH4 mean value of 0 ppm), confirming a major connection with the exterior atmosphere (average value of methane 1.8 ppm) during outgassing stage. By introducing wavelet analysis on obtained time series filtered signal of raw data show strong dependencies between trace gases and studied parameters. For instance, values of coherence between relative humidity and CO2 or 222Rn concentration are higher than 0.9. Results show that gas patterns dependence on relative humidity, atmospheric pressure and temperatures (indoor and outdoor) prevails throughout a year, determining the outgassing and isolation periods identified by statistical analyses. The measured of delta13C and CH4 concentration became a useful tool to understand processes affecting cave air and driving parameters variations inside the cave. Moreover, combining wavelet analysis, statistics and resemblance techniques, seasonal and transient behaviour of gases exchange can be highlighted in subterranean sites as Rull Cave.

  6. Regulation of Blood Glucose Concentration in Type 1 Diabetics Using Single Order Sliding Mode Control Combined with Fuzzy On-line Tunable Gain, a Simulation Study.

    PubMed

    Dinani, Soudabeh Taghian; Zekri, Maryam; Kamali, Marzieh

    2015-01-01

    Diabetes is considered as a global affecting disease with an increasing contribution to both mortality rate and cost damage in the society. Therefore, tight control of blood glucose levels has gained significant attention over the decades. This paper proposes a method for blood glucose level regulation in type 1 diabetics. The control strategy is based on combining the fuzzy logic theory and single order sliding mode control (SOSMC) to improve the properties of sliding mode control method and to alleviate its drawbacks. The aim of the proposed controller that is called SOSMC combined with fuzzy on-line tunable gain is to tune the gain of the controller adaptively. This merit causes a less amount of control effort, which is the rate of insulin delivered to the patient body. As a result, this method can decline the risk of hypoglycemia, a lethal phenomenon in regulating blood glucose level in diabetics caused by a low blood glucose level. Moreover, it attenuates the chattering observed in SOSMC significantly. It is worth noting that in this approach, a mathematical model called minimal model is applied instead of the intravenously infused insulin-blood glucose dynamics. The simulation results demonstrate a good performance of the proposed controller in meal disturbance rejection and robustness against parameter changes. In addition, this method is compared to fuzzy high-order sliding mode control (FHOSMC) and the superiority of the new method compared to FHOSMC is shown in the results.

  7. Regulation of Blood Glucose Concentration in Type 1 Diabetics Using Single Order Sliding Mode Control Combined with Fuzzy On-line Tunable Gain, a Simulation Study

    PubMed Central

    Dinani, Soudabeh Taghian; Zekri, Maryam; Kamali, Marzieh

    2015-01-01

    Diabetes is considered as a global affecting disease with an increasing contribution to both mortality rate and cost damage in the society. Therefore, tight control of blood glucose levels has gained significant attention over the decades. This paper proposes a method for blood glucose level regulation in type 1 diabetics. The control strategy is based on combining the fuzzy logic theory and single order sliding mode control (SOSMC) to improve the properties of sliding mode control method and to alleviate its drawbacks. The aim of the proposed controller that is called SOSMC combined with fuzzy on-line tunable gain is to tune the gain of the controller adaptively. This merit causes a less amount of control effort, which is the rate of insulin delivered to the patient body. As a result, this method can decline the risk of hypoglycemia, a lethal phenomenon in regulating blood glucose level in diabetics caused by a low blood glucose level. Moreover, it attenuates the chattering observed in SOSMC significantly. It is worth noting that in this approach, a mathematical model called minimal model is applied instead of the intravenously infused insulin–blood glucose dynamics. The simulation results demonstrate a good performance of the proposed controller in meal disturbance rejection and robustness against parameter changes. In addition, this method is compared to fuzzy high-order sliding mode control (FHOSMC) and the superiority of the new method compared to FHOSMC is shown in the results. PMID:26284169

  8. Melatonin agonist tasimelteon (VEC-162) for transient insomnia after sleep-time shift: two randomised controlled multicentre trials.

    PubMed

    Rajaratnam, Shantha Mw; Polymeropoulos, Mihael H; Fisher, Dennis M; Roth, Thomas; Scott, Christin; Birznieks, Gunther; Klerman, Elizabeth B

    2009-02-07

    Circadian rhythm sleep disorders are common causes of insomnia for millions of individuals. We did a phase II study to establish efficacy and physiological mechanism, and a phase III study to confirm efficacy of the melatonin agonist tasimelteon (VEC-162) for treatment of transient insomnia associated with shifted sleep and wake time. We undertook phase II and phase III randomised, double-blind, placebo-controlled, parallel-group studies. In a phase II study, 39 healthy individuals from two US sites were randomly assigned to tasimelteon (10 [n=9], 20 [n=8], 50 [n=7], or 100 mg [n=7]) or placebo (n=8). We monitored individuals for 7 nights: 3 at baseline, 3 after a 5-h advance of sleep-wake schedule with treatment before sleep, and 1 after treatment; we measured plasma melatonin concentration for circadian phase assessment. In a phase III study, 411 healthy individuals from 19 US sites, who had transient insomnia induced in a sleep clinic by a 5-h advance of the sleep-wake schedule and a first-night effect in a sleep clinic, were given tasimelteon (20 [n=100], 50 [n=102], or 100 mg [n=106]) or placebo (n=103) 30 min before bedtime. Prespecified primary efficacy outcomes were polysomnographic sleep efficiency (phase II study), latency to persistent sleep (phase III study), and circadian phase shifting (phase II study). Analysis was by intention to treat. Safety was assessed in both studies. These trials are registered with ClinicalTrials.gov, numbers NCT00490945 and NCT00291187. In the phase II study, tasimelteon reduced sleep latency and increased sleep efficiency compared with placebo. The shift in plasma melatonin rhythm to an earlier hour was dose dependent. In the phase III study, tasimelteon improved sleep latency, sleep efficiency, and wake after sleep onset (ie, sleep maintenance). The frequency of adverse events was similar between tasimelteon and placebo. After an abrupt advance in sleep time, tasimelteon improved sleep initiation and maintenance

  9. Relationship analysis between transient thermal control mode and image quality for an aerial camera.

    PubMed

    Liu, Weiyi; Xu, Yongsen; Yao, Yuan; Xu, Yulei; Shen, Honghai; Ding, Yalin

    2017-02-01

    Thermal control and temperature uniformity are important factors for aerial cameras. This paper describes the problems with existing systems and introduces modifications. The modifications have improved the temperature uniformity from 12.8°C to 4.5°C, and they enable images to be obtained at atmospheric and low pressures (35.4 KPa). First, thermal optical analysis of the camera is performed by using the finite element analysis method. This modeled the effect of temperature level and temperature gradient on imaging. Based on the results of the analysis, the corresponding improvements to the thermal control measures are implemented to improve the temperature uniformity. The relationship between the temperature control mode and temperature uniformity is analyzed. The improved temperature field corresponding to the thermal optical analysis is studied. Taking into account that the convection will be affected by the low pressure, the paper analyzes the thermal control effect, and imaging results are obtained in low pressure. The experimental results corroborate the analyses.

  10. Control of emboli in patients with recurrent or crescendo transient ischaemic attacks using preoperative transcranial Doppler-directed Dextran therapy.

    PubMed

    Lennard, N S; Vijayasekar, C; Tiivas, C; Chan, C W M; Higman, D J; Imray, C H E

    2003-02-01

    Transcranial Doppler (TCD)-directed Dextran 40 treatment after carotid endarterectomy reduces the rate of early postoperative thrombosis. This study assessed the efficacy of intravenous Dextran 40 at controlling symptoms and emboli before elective carotid endarterectomy in patients with recurrent or crescendo transient ischaemic attacks (TIAs). In a prospective study, patients with more than 70 per cent internal carotid artery stenosis who had two or more symptomatic episodes within 30 days and TCD-detected microemboli were studied. Dextran 40 was commenced at 20 ml/h and TCD was repeated to reassess the rate of embolization. The infusion was increased in 20-ml/h increments until symptoms and emboli were controlled. The patient then had carotid surgery on the next elective list. Nineteen patients with internal carotid stenosis greater than 70 per cent, recurrent symptoms and TCD-detected emboli were studied. All patients had symptoms and emboli controlled with Dextran 40. One patient with both unstable angina (awaiting urgent operation) and crescendo TIAs died from a myocardial infarct before undergoing operation. Of the 18 patients who had an operation, one suffered a non-disabling stroke on the third postoperative day. TCD-directed Dextran 40 offers a safe approach to high-risk patients before elective carotid endarterectomy, and warrants further study.

  11. Comparing Gain- and Loss-Framed Messages for Smoking Cessation With Sustained-Release Bupropion: A Randomized Controlled Trial

    PubMed Central

    Toll, Benjamin A.; O’Malley, Stephanie S.; Katulak, Nicole A.; Wu, Ran; Dubin, Joel A.; Latimer, Amy; Meandzija, Boris; George, Tony P.; Jatlow, Peter; Cooney, Judith L.; Salovey, Peter

    2008-01-01

    Prospect theory suggests that because smoking cessation is a prevention behavior with a fairly certain outcome, gain-framed messages will be more persuasive than loss-framed messages when attempting to encourage smoking cessation. To test this hypothesis, the authors randomly assigned participants (N = 258) in a clinical trial to either a gain- or loss-framed condition, in which they received factually equivalent video and printed messages encouraging smoking cessation that emphasized either the benefits of quitting (gains) or the costs of continuing to smoke (losses), respectively. All participants received open label sustained-release bupropion (300 mg/day) for 7 weeks. In the intent-to-treat analysis, the difference between the experimental groups by either point prevalence or continuous abstinence was not statistically significant. Among 170 treatment completers, however, a significantly higher proportion of participants were continuously abstinent in the gain-framed condition as compared with the loss-framed condition. These data suggest that gain-framed messages may be more persuasive than loss-framed messages in promoting early success in smoking cessation for participants who are engaged in treatment. PMID:18072836

  12. Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity

    NASA Astrophysics Data System (ADS)

    Asano, M.; Özdemir, Ş. K.; Chen, W.; Ikuta, R.; Yang, L.; Imoto, N.; Yamamoto, T.

    2016-05-01

    We report controllable manipulation of slow and fast light in a whispering-gallery-mode microtoroid resonator fabricated from Erbium (Er3+) doped silica. We observe continuous transition of the coupling between the fiber-taper waveguide and the microresonator from undercoupling to critical coupling and then to overcoupling regimes by increasing the pump power even though the spatial distance between the resonator and the waveguide was kept fixed. This, in turn, enables switching from fast to slow light and vice versa just by increasing the optical gain. An enhancement of delay of two-fold over the passive silica resonator (no optical gain) was observed in the slow light regime. Moreover, we show dynamic pulse splitting and its control in slow/fast light systems using optical gain.

  13. Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity

    SciTech Connect

    Asano, M.; Ikuta, R.; Imoto, N.; Yamamoto, T. E-mail: yamamoto@mp.es.osaka-u.ac.jp; Özdemir, Ş. K. E-mail: yamamoto@mp.es.osaka-u.ac.jp; Chen, W.; Yang, L.

    2016-05-02

    We report controllable manipulation of slow and fast light in a whispering-gallery-mode microtoroid resonator fabricated from Erbium (Er{sup 3+}) doped silica. We observe continuous transition of the coupling between the fiber-taper waveguide and the microresonator from undercoupling to critical coupling and then to overcoupling regimes by increasing the pump power even though the spatial distance between the resonator and the waveguide was kept fixed. This, in turn, enables switching from fast to slow light and vice versa just by increasing the optical gain. An enhancement of delay of two-fold over the passive silica resonator (no optical gain) was observed in the slow light regime. Moreover, we show dynamic pulse splitting and its control in slow/fast light systems using optical gain.

  14. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes.

    PubMed

    Zhang, Yong; Green, Christopher T; Tick, Geoffrey R

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number, Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease in Pe due to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes.

  15. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes

    USGS Publications Warehouse

    Zhang, Yong; Green, Christopher T.; Tick, Geoffrey R.

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number, Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease in Pe due to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer–aquitard complexes.

  16. Hierarchical Control Scheme for Improving Transient Voltage Recovery of a DFIG-Based WPP

    SciTech Connect

    Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

    2015-06-05

    Modern grid codes require that wind power plants (WPPs) inject reactive power according to the voltage dip at a point of interconnection (POI). This requirement helps to support a POI voltage during a fault. However, if a fault is cleared, the POI and wind turbine generator (WTG) voltages are likely to exceed acceptable levels unless the WPP reduces the injected reactive power quickly. This might deteriorate the stability of a grid by allowing the disconnection of WTGs to avoid any damage. This paper proposes a hierarchical control scheme of a doubly-fed induction generator (DFIG)-based WPP. The proposed scheme aims to improve the reactive power injecting capability during the fault and suppress the overvoltage after the fault clearance. To achieve the former, an adaptive reactive power-to-voltage scheme is implemented in each DFIG controller so that a DFIG with a larger reactive power capability will inject more reactive power. To achieve the latter, a washout filter is used to capture a high frequency component contained in the WPP voltage, which is used to remove the accumulated values in the proportional-integral controllers. Test results indicate that the scheme successfully supports the grid voltage during the fault, and recovers WPP voltages without exceeding the limit after the fault clearance.

  17. Loss and gain of Drosophila TDP-43 impair synaptic efficacy and motor control leading to age-related neurodegeneration by loss-of-function phenotypes.

    PubMed

    Diaper, Danielle C; Adachi, Yoshitsugu; Sutcliffe, Ben; Humphrey, Dickon M; Elliott, Christopher J H; Stepto, Alan; Ludlow, Zoe N; Vanden Broeck, Lies; Callaerts, Patrick; Dermaut, Bart; Al-Chalabi, Ammar; Shaw, Christopher E; Robinson, Iain M; Hirth, Frank

    2013-04-15

    Cytoplasmic accumulation and nuclear clearance of TDP-43 characterize familial and sporadic forms of amyotrophic lateral sclerosis and frontotemporal lobar degeneration, suggesting that either loss or gain of TDP-43 function, or both, cause disease formation. Here we have systematically compared loss- and gain-of-function of Drosophila TDP-43, TAR DNA Binding Protein Homolog (TBPH), in synaptic function and morphology, motor control, and age-related neuronal survival. Both loss and gain of TBPH severely affect development and result in premature lethality. TBPH dysfunction caused impaired synaptic transmission at the larval neuromuscular junction (NMJ) and in the adult. Tissue-specific knockdown together with electrophysiological recordings at the larval NMJ also revealed that alterations of TBPH function predominantly affect pre-synaptic efficacy, suggesting that impaired pre-synaptic transmission is one of the earliest events in TDP-43-related pathogenesis. Prolonged loss and gain of TBPH in adults resulted in synaptic defects and age-related, progressive degeneration of neurons involved in motor control. Toxic gain of TBPH did not downregulate or mislocalize its own expression, indicating that a dominant-negative effect leads to progressive neurodegeneration also seen with mutational inactivation of TBPH. Together these data suggest that dysfunction of Drosophila TDP-43 triggers a cascade of events leading to loss-of-function phenotypes whereby impaired synaptic transmission results in defective motor behavior and progressive deconstruction of neuronal connections, ultimately causing age-related neurodegeneration.

  18. Loss and gain of Drosophila TDP-43 impair synaptic efficacy and motor control leading to age-related neurodegeneration by loss-of-function phenotypes

    PubMed Central

    Diaper, Danielle C.; Adachi, Yoshitsugu; Sutcliffe, Ben; Humphrey, Dickon M.; Elliott, Christopher J.H.; Stepto, Alan; Ludlow, Zoe N.; Vanden Broeck, Lies; Callaerts, Patrick; Dermaut, Bart; Al-Chalabi, Ammar; Shaw, Christopher E.; Robinson, Iain M.; Hirth, Frank

    2013-01-01

    Cytoplasmic accumulation and nuclear clearance of TDP-43 characterize familial and sporadic forms of amyotrophic lateral sclerosis and frontotemporal lobar degeneration, suggesting that either loss or gain of TDP-43 function, or both, cause disease formation. Here we have systematically compared loss- and gain-of-function of Drosophila TDP-43, TAR DNA Binding Protein Homolog (TBPH), in synaptic function and morphology, motor control, and age-related neuronal survival. Both loss and gain of TBPH severely affect development and result in premature lethality. TBPH dysfunction caused impaired synaptic transmission at the larval neuromuscular junction (NMJ) and in the adult. Tissue-specific knockdown together with electrophysiological recordings at the larval NMJ also revealed that alterations of TBPH function predominantly affect pre-synaptic efficacy, suggesting that impaired pre-synaptic transmission is one of the earliest events in TDP-43-related pathogenesis. Prolonged loss and gain of TBPH in adults resulted in synaptic defects and age-related, progressive degeneration of neurons involved in motor control. Toxic gain of TBPH did not downregulate or mislocalize its own expression, indicating that a dominant-negative effect leads to progressive neurodegeneration also seen with mutational inactivation of TBPH. Together these data suggest that dysfunction of Drosophila TDP-43 triggers a cascade of events leading to loss-of-function phenotypes whereby impaired synaptic transmission results in defective motor behavior and progressive deconstruction of neuronal connections, ultimately causing age-related neurodegeneration. PMID:23307927

  19. Effect of Actuation Parameters on Opposition Control of Transient Growth in a Blasius Boundary Layer Using Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Hanson, Ronald; Lavoie, Philippe; Naguib, Ahmed

    2009-11-01

    This work is concerned with investigating an actuation scheme, using plasma actuators, designed to negate the effect of the transient growth instability occurring in a Blasius boundary layer and, by this means, delaying the bypass transition process. The actuators investigated consists of a spanwise array of symmetric plasma actuators, which are capable of generating spanwise periodic counter-rotating vortices. The effectiveness of the actuator array was tested on disturbances introduced via an array of cylindrical roughness elements. Early investigations have demonstrated a reduction of the total disturbance energy produced by the roughness elements by up to 68% depending on the actuator geometry. In the present study, the focus is on determining the effect that the excitation signal supplied to the actuator, such as waveform, frequency and amplitude, can have on the receptivity of the boundary layer to the plasma forcing. It is found that the excitation can change the modal content of the disturbance introduced inside the boundary layer by the actuator. The consequences of these results are discussed with respect to actuator modelling and issues related to eventual integration with a feedback control system for transition control.

  20. Differences in Causal Estimates from Longitudinal Analyses of Residualized versus Simple Gain Scores: Contrasting Controls for Selection and Regression Artifacts

    ERIC Educational Resources Information Center

    Larzelere, Robert E.; Ferrer, Emilio; Kuhn, Brett R.; Danelia, Ketevan

    2010-01-01

    This study estimates the causal effects of six corrective actions for children's problem behaviors, comparing four types of longitudinal analyses that correct for pre-existing differences in a cohort of 1,464 4- and 5-year-olds from Canadian National Longitudinal Survey of Children and Youth (NLSCY) data. Analyses of residualized gain scores found…

  1. Differences in Causal Estimates from Longitudinal Analyses of Residualized versus Simple Gain Scores: Contrasting Controls for Selection and Regression Artifacts

    ERIC Educational Resources Information Center

    Larzelere, Robert E.; Ferrer, Emilio; Kuhn, Brett R.; Danelia, Ketevan

    2010-01-01

    This study estimates the causal effects of six corrective actions for children's problem behaviors, comparing four types of longitudinal analyses that correct for pre-existing differences in a cohort of 1,464 4- and 5-year-olds from Canadian National Longitudinal Survey of Children and Youth (NLSCY) data. Analyses of residualized gain scores found…

  2. Adjustment of Adaptive Gain with Bounded Linear Stability Analysis to Improve Time-Delay Margin for Metrics-Driven Adaptive Control

    NASA Technical Reports Server (NTRS)

    Bakhtiari-Nejad, Maryam; Nguyen, Nhan T.; Krishnakumar, Kalmanje Srinvas

    2009-01-01

    This paper presents the application of Bounded Linear Stability Analysis (BLSA) method for metrics driven adaptive control. The bounded linear stability analysis method is used for analyzing stability of adaptive control models, without linearizing the adaptive laws. Metrics-driven adaptive control introduces a notion that adaptation should be driven by some stability metrics to achieve robustness. By the application of bounded linear stability analysis method the adaptive gain is adjusted during the adaptation in order to meet certain phase margin requirements. Analysis of metrics-driven adaptive control is evaluated for a linear damaged twin-engine generic transport model of aircraft. The analysis shows that the system with the adjusted adaptive gain becomes more robust to unmodeled dynamics or time delay.

  3. Intake of Sweets, Snacks and Soft Drinks Predicts Weight Gain in Obese Pregnant Women: Detailed Analysis of the Results of a Randomised Controlled Trial

    PubMed Central

    Renault, Kristina M.; Carlsen, Emma M.; Nørgaard, Kirsten; Nilas, Lisbeth; Pryds, Ole; Secher, Niels J.; Olsen, Sjurdur F.; Halldorsson, Thorhallur I.

    2015-01-01

    Background Lifestyle interventions targeting obese pregnant women often result in modest reduction in gestational weight gain, pregnancy complications and related risk factors. Examining adherence to the intervention can, however, provide valuable information on the importance of the different factors targeted. Objective To evaluate improvements and relevance of different dietary factors targeted with respect to gestational weight gain in a 3-arm Randomised Controlled Trial (n=342) among obese pregnant women with BMI≥30 kg/m2. Methods Randomisation 1:1:1 to either hypocaloric Mediterranean type of diet and physical activity intervention (D+PA); physical activity intervention alone (PA); or control (C). Diet was assessed at baseline (weeks 11–14) and endpoint (weeks 36–37) using a validated food frequency questionnaire. Results During the intervention women in the D+PA group significantly lowered their intakes of added sugars and saturated fat and increased their protein intake by ~1% of total energy compared to controls. Of these dietary variables only intakes of added sugar appeared to be related to GWG, while no association was observed for saturated fat or protein. Further analyses revealed that foods that contributed to intake of added sugars, including sweets, snacks, cakes, and soft drinks were strongly associated with weight gain, with women consuming sweets ≥2/day having 5.4 kg (95% CI 2.1-8.7) greater weight gain than those with a low (<1wk) intake. The results for soft drinks were more conflicting, as women with high weight gain tended to favour artificially sweetened soft drinks. Conclusion In our sample of obese pregnant women, craving for sweets, snacks, and soft drinks strongly predicts GWG. Emphasis on reducing intakes of these foods may be more relevant for limiting gestational weight gain than encouraging strict compliance to more specific diets. Trial Registration ClinicalTrials.gov NCT01345149 PMID:26192183

  4. Use of neural-network systems to control transient multimode lasing

    SciTech Connect

    Ledenev, V I

    2006-10-31

    A three-level neural network is considered which contains twenty five inputs, two hidden elements, and four outputs and is trained to recognise four situations at the input: the appearance of the fundamental mode of a Fabry-Perot resonator, the superposition of the fundamental and the first mode of the resonator with zero phases, the superposition of the fundamental and first mode of the resonator with phases 0 and {pi}, and the appearance of the second mode and the superposition of the fundamental and second modes. It is shown that the network can recognise correctly variations in the mode composition of the Fabry-Perot resonator over the modulus of the transverse distribution of the field during the development of two-mode lasing. The operation of the network is studied for the two response times: the time shorter than the resonator time and the time determined by the response time of a pyroelectric detector of laser radiation. (control of laser radiation parameters)

  5. Transient-Free Operations With Physics-Based Real-time Analysis and Control

    NASA Astrophysics Data System (ADS)

    Kolemen, Egemen; Burrell, Keith; Eggert, William; Eldon, David; Ferron, John; Glasser, Alex; Humphreys, David

    2016-10-01

    In order to understand and predict disruptions, the two most common methods currently employed in tokamak analysis are the time-consuming ``kinetic EFITs,'' which are done offline with significant human involvement, and the search for correlations with global precursors using various parameterization techniques. We are developing automated ``kinetic EFITs'' at DIII-D to enable calculation of the stability as the plasma evolves close to the disruption. This allows us to quantify the probabilistic nature of the stability calculations and provides a stability metric for all possible linear perturbations to the plasma. This study also provides insight into how the control system can avoid the unstable operating space, which is critical for high-performance operations close to stability thresholds at ITER. A novel, efficient ideal stability calculation method and new real-time CER acquisition system are being developed, and a new 77-core server has been installed on the DIII-D PCS to enable experimental use. Sponsored by US DOE under DE-SC0015878 and DE-FC02-04ER54698.

  6. Control of sarcomere length in skinned muscle fibres of Rana temporaria during mechanical transients.

    PubMed Central

    Goldman, Y E; Simmons, R M

    1984-01-01

    A new technique is described for high-speed measurement of striation spacing of single skinned muscle fibres. A galvanometer mirror directs helium-neon laser light on to the muscle fibre at a variable angle. Light diffracted by the cross-striations is collected by a position-sensitive photodetector. The incident angle necessary to centre the diffracted light beam on to the photodetector is related to sarcomere length. The instrument was tested by comparison with measurements obtained with a compound microscope. Discrepancies of several nanometers per half sarcomere were observed between these two methods. When the incident angle of the laser beam was varied sinusoidally about its mean position the magnitude of the discrepancy was reduced. During steady passive shortening of the muscle fibres the output of the diffraction instrument often displayed pauses and brief periods of rapid shortening. These irregularities were eliminated by averaging the sarcomere length output over a range of illumination angles by oscillating the incident angle of the laser beam. The results suggest that at the spatial resolution of several nanometers per half sarcomere, volume diffraction effects can cause the apparent sarcomere length measured from the angle of coherent light diffraction to differ from the mean striation spacing. With incident-angle oscillation the time and spatial resolution of the equipment were satisfactory for the sarcomere length signal to be fed back to a length controller for a 'sarcomere length clamp'. In active contractions, stiffness was closely related to steady developed tension at sub-saturating calcium concentrations. Skinned fibres are less stiff than intact fibres at a given level of developed tension. Images Fig. 7 PMID:6611404