Initial component control in disparity vergence: a model-basedstudy

The dual-mode theory for the control of disparity-vergence eye movements states that two components control the response to a step change in disparity. The initial component uses a motor preprogram to drive the eyes to an approximate final position. This initial component is followed by activation of a late component operating under visual feedback control that reduces residual disparity to within fusional limits. A quantitative model based on a pulse-step controller, similar to that postulated for saccadic eye movements, has been developed to represent the initial component. This model, an adaptation of one developed by D.S. Zee et al. (J. Neurophysiol., vol. 68, p. 1624-41, 1992), provides accurate simulations of Isolated initial component movements and is compatible with the known underlying neurophysiology and existing neurophysiological data. The model has been employed to investigate the difference in dynamics between convergent and divergent movements. Results indicate that the pulse-control component active in convergence is reduced or absent from the control signals of divergence movements. This suggests somewhat different control structures of convergence versus divergence, and is consistent with other directional asymmetries seen in horizontal vergence     

Components of disparity vergence eye movements: application of independent component analysis

The "dual mode" theory for the control of disparity vergence eye movements states that two control components, a preprogrammed "transient" component and a feedback-controlled "sustained" component, mediate the motor response. Although prior experimental work has isolated and studied the transient component, little is known of the sustained component's contribution to the dynamic vergence response. The timing between the two components and their relative magnitudes are of interest as they relate to the strategies used by the brain to coordinate and control the two components. Modeling studies provide an estimate of component magnitudes, but cannot uniquely identify component timing nor can the provide detailed information on component dynamics. Here, an eigenvector analysis is applied to a multivariate data set consisting of multiple responses to a step stimulus to confirm the presence of two major components in the vergence response. Next, a new application of independent component analysis is used to estimate the activation patterns of the two components. Results from five subjects show that the sustained component is activated concurrently with the transient component, dominates the later portion of the response, and maintains final position.     

Forming the fast Fourier transform of a step response in time-domain metrology

If the discrete Fourier transform of the step response of a network is taken, a large truncation error results, since only a finite number of samples is used. This error is usually removed by first differentiating the waveform, with consequent noise enhancement. The letter shows that the error may also be removed at discrete frequencies, simply by first subtracting a ramp from the step response.     

Long-term step response of a chain of a.c.-coupled amplifiers

In the long-distance transmission of television signals, the long-term step response of a chain of a.c.-coupled amplifiers is of interest. A solution is obtained for the asymptotic response, where the transfer functions are first-order, and some speculations are included about generalising the result to higher orders.     

Bulk lifetime determination of MOS structures by a voltage step response method

The time dependance of the current flowing through a MOS capacitor switched from an inversion state to a deeper inversion state is described by a simple model. A method is derived for determining the bulk lifetime from dynamic current measurements alone.     

An optimum bandlimited system with monotonic step response

That shape of passband response which causes a perfectly bandlimited low-pass system to have a monotonic step response with minimum rise time, is derived and compared with other systems.     

Transient response of microstrip step discontinuities on anisotropic substrate

In this paper, we present the numerical simulation of transient response of short pulse propagating through a microstrip step junction on anisotropic substrate having a tilted optical axis. In the simulation, the FD-TD method is extended to treat the cases having tilted optical axis expressed by a permittivity tensor with off-diagonal elements. The results show that the dispersion of transient signal caused by microstrip step discontinuities is quite significant and the dependence of transient characteristics of microstrip lines on the tilted angle of optical axis for anisotropic substrate can not be neglected.     

Speeding up the PLL frequency step response by two charge pulses

A simple method is presented for speeding up the frequency step response of a PLL-based synthesizer which uses an excess output frequency to quickly cancel the accumulated phase error. In this method, current pulses are delivered to the loop filter to overdrive the PLL and later to cancel the frequency error. Experiments confirm a good agreement between measurement results and theoretical expectations     

CPK-based grid authentication:a step forward

Effective grid authentication plays a critical role in grid security, which has been recognized as a key issue in the designing and extension of grid technologies. At present, public key infrastructure (PKI) has been widely applied for grid authentication, and this article proposes a novel grid authentication mechanism, which is based on combined public key (CPK) employing elliptic curve cryptography (ECC). The designing structure of the new grid authentication mechanism and its implementation procedure are described in details. Property analysis of the new mechanism is also made in comparison with that of the globus security infrastructure (GSI) authentication, which leads to the conclusion that CPK-based grid authentication, may be applied as an optimized approach towards efficient and effective grid authentication.     

Model-based analysis of dynamics in vergence adaptation

We previously proposed a model to study the dynamics of disparity vergence responses. This model was based on known physiology and consisted of pulse and step neural control processes feeding a linear second-order oculomotor plant. Here, we apply a slightly modified version of that model to analyze the influence of short-term adaptation on vergence dynamics. This analysis showed that, unlike normal vergence responses, adapted responses could not be accurately simulated without a delay between the step and pulse components. Through simulations of normal vergence and adapted vergence responses, we found a strong correlation between delay of the step signal and the size of the movement overshoot. This correlation suggests a strong interaction between neural process generating the pulse and step motor control signals.     

On minimum step response rise time of linear low-pass systems under the constraint of a given noise bandwidth

If the step-response rise time of a linear low-pass system is to be a minimum under the constraint of a given noise bandwidth, the systems parameters should be so tuned that the step response is strictly free from overshoot. This conclusion is also true when the system bandwidth is defined as its 3-dB bandwidth.     

Sensitivity analysis of relative accommodation and vergence

A sensitivity analysis was performed to determine the variation in response to changes in parameter values of a previously developed nonlinear static model of accommodation and vergence. To determine normal behavior, model simulation responses were computed using previously obtained parameter values in 4 subjects under 2 conditions. In the first, relative accommodation was evaluated by maintaining the vergence stimulus constant at 2.5 meter angles (MA) and varying the accommodative stimulus from -2.5 to 2.5 diopters (D) in 0.25-D steps. In the second, relative vergence was evaluated by maintaining the accommodative stimulus constant at 2.5 D and varying the vergence stimulus from 25 prism diopters (PD) base-in to 25 PD base-out in 5-PD steps. Sensitivity of the model parameters, consisting of controller gains for accommodation (ACG) and vergence (VCG), crosslink gains for accommodation-to-vergence (AC) and vergence-to-accommodation (CA), deadspace operators for accommodation (AE±AD) and vergence (VE±VD), and the tonic levels for accommodation (ABIAS) and vergence (VBIAS) were assessed by varying them at 50% and 150% of their normal values. It was found that the accommodation and vergence systems mere most sensitive to variation in crosslink gain, moderately sensitive to variation in controller gain and tonic level, and least sensitive to variation in size of the deadspace. These results may provide a quantitative basis for the occurrence of ocular dysfunctions associated with abnormal crosslink gains, such as strabismus, in clinical patients     

ACTS: The first step toward a switchboard in the sky

The Advanced Communications Technology Satellite (ACTS), now under development and scheduled for launch in May 1992, is presently the main focus of NASA's communications program. Key technologies for ACTS include electronically hopping spot beam antennas, on-board processing and circuit switching, and Ka-band transmission.     

Dynamics of autodyne response formation in microwave generators

The paper presents results of studying the dynamics of autodyne response formation when switching on a radio-pulse microwave generator which is subject to the influence of its own reflection radiation. Basic relations for a step-wise calculation of autodyne response as a function of time delay, autodyne response time constant, distortion parameter and intrinsic parameters of the self-oscillating system are obtained. Calculation and analysis of peculiarities of autodyne signal generation by radio-pulse oscillator are conducted for the cases of motionless and moving reflecting object under relatively low, medium and high inertia properties of the oscillator if compared to the propagation time of the reflected radiation. Experimental research results that confirm conclusions of theoretical analysis are obtained for a common hybrid-integrated autodyne TIGEL-08 module of the 8-mm frequency-range implemented on a planar two-meza Gunn diodes and the same module stabilized by the external high-Q resonator.     

CoolMOS CS服务器系列MOSFET:向理想开关迈进

前言 CoolMOS CS系列"超级结"MOSFET器件高压设备的成功是基于1998年英飞凌公司推出的CoolMOS技术.这些器件的优越性能实现了区域导通电阻的大幅度降低.     

Linear relation for vergence control of parallel stereo camera

The geometry between the horizontal and vertical shifts of a lens to the CCD plane is introduced for the automatic vergence control of a parallel stereo camera. Under conditions where the disparity of a stereo image remains constant, the horizontal shift of the camera lens which is causing the stereo disparity, and the vertical shift responsible for the focus, have linear geometry     

Breaking step: the return of asynchronous logic

Virtually all digital design is based on a synchronous approach. However, there are signs that it is beginning to hit some fundamental limitations. These limitations are described by the author. Asynchronous design as a means to overcome these limitations is then discussed. The way in which asynchronous circuits operate is discussed. The Amulet project at Manchester University, which adopted the micropipeline approach in investigating the application of asynchronous techniques to the reduction of high-performance microprocessors, is described. Future prospects for asynchronous design are briefly reviewed     

脚踏实地推进农村信息化

社会主义新农村建设被当作我国现代化进程中的重大历史任务写入了“十一五”规划建议中，作为社会主义新农村建设的有力手段，农村信息化工作也相应地受到了人们越来越多的关注。今年4月，信息产业部印发了《关于推进社会主义新农村建设工作的意见》，召开了推进社会主义新农村建设工作会议，对信息产业全面服务“三农”做出了具体部署。     

Modeling the transition region of a symmetric step junction

A junction of ideal spatial symmetry also possesses band-diagram symmetry. Exploiting both of these symmetries we have obtained solutions for the transition region of such junctions under low-level forward bias and at equilibrium with less redundancy than has existed in previous treatments. The quasiequilibrium approach to treating a forward-biased junction has been used previously by several workers, but we have carried it to the point of producing a family of curves that should prove useful in practical work. Futher, we offer two equilibrium interpretations of the curves that are closely related to the forward-biased case.     

Cylindrical geometry: a further step in active microwave tomography

A prototype imaging system for active microwave tomography using cylindrical geometry has been developed, making it possible to obtain images of the dielectric properties of biological targets at 2.45 GHz. This configuration allows a fast exploration of body slices placed along the array axis, in a way similar to that of present X-ray scanners. The electromagnetic compatibility (EMC) of this approach is critical because the strongly attenuated received fields are measured on the same array which is being used to emit a high-level illuminating signal. Therefore, carefully designed high-frequency architectures and detection techniques are necessary. The system requires no mechanical movements to illuminate the body from multiple directions (views) and measure the scattered fields. In this way, a complete data set consisting of 64 views is acquired in 3 s using low-power illumination. The system is described, and images obtained with biological phantoms and actual bodies are presented