Automated Extraction of Activity Features in Linear Envelopes of Locomotor Electromyographic Patterns

For the envelope of the electromyographic activity recorded during locomotion, a feature extraction scheme has been developed. It recognizes the time, duration, and amplitude of phases of activity. The method is based on the Tauberian approximation for modeling waveforms as a sum of identically shaped pulses with different time delays and amplitudes. Initial conditions on the pulse properties are set and an optimal solution is sought. Any multiple pulses that model one phase of activity are then combined into one equivalent pulse. The method is completely automated; thus, it operates without any user intervention.     

TOAD的开关特性研究

讨论了太赫兹光非对称解复用器 (TOAD)中半导体光放大器 (SOA)对具有不同能量和宽度的控制脉冲的动态增益响应 ,研究了控制脉冲能量、宽度、环时间非对称性、信号光脉冲相对于控制光脉冲的时延等因素对TOAD开关特性的影响 ,作了优化分析 ,并与实验结果进行了比较     

TOAD中半导体光放大器的动态增益响应及光脉冲研究

讨论了太赫兹光非对称解复用器中半导体放大器（ＳＯＡ）对具有不同能量和脉宽的控制脉冲的动态增益响应，研究了不同的逆时针信号脉冲和控制脉冲时延的民政部下通过ＳＯＡ后的地针信号脉冲的功率和相位变化。     

TOAD中半导体光放大器的动态增益响应及光脉冲传输特性研究

讨论了太赫兹光非对称解复用器中半导体光放大器 (SOA)对具有不同能量和脉宽的控制脉冲的动态增益响应 ,研究了不同的逆时针信号脉冲和控制脉冲时延的情况下通过 SOA后的逆时针信号脉冲的功率和相位变化。     

Internal Q-switching in semiconductor lasers: high intensity pulsesof the picosecond range and the spectral peculiarities

Optical pulses of ~100 ps duration, and ~10² W power were obtained from the industrial single heterostructure lasers with a standard pulse generation power of ~10 W in the internal Q-switching mode. Temporal and spectral analyses allow three components to be distinguished in the laser optical pulses: ordinary delayed pulses of large duration at energies considerably lower than the energy gap, short optical pulses caused by the gain-switching effect at higher energies, and short optical pulses at the end of the current pulse (Q-switching mode) at the highest energies. A model is proposed involving band tail states as a saturable absorber causing large delays     

Analysis of the Switching Characteristics of TOAD

The dynamic gain responses of the semiconductor optical amplifier (SOA) in a terahertz optical asymmetric demultiplexer (TOAD) to intense control pulses with different input energies and pulse widths are investigated. The influences on the switching characteristics of TOAD for different control pulse energies, widths, loop time asymmetry, and time delays between the signal pulse and control pulse are studied and analyzed in detail. The theoretical analysis coincides well with the experimental result.     

考虑多时钟周期瞬态脉冲叠加的锁存窗屏蔽模型

集成电路工艺水平的提升,使得由单粒子瞬态脉冲造成的芯片失效越发不容忽视．为了准确计算单粒子瞬态脉冲对锁存器造成的失效率,提出一种考虑多时钟周期瞬态脉冲叠加的锁存窗屏蔽模型．使用提出的考虑扇出重汇聚的敏化路径逼近搜索算法查找门节点到达锁存器的敏化路径,并记录路径延迟;在扇出重汇聚路径上,使用提出的脉冲叠加计算方法对脉冲进行叠加;对传播到达锁存器的脉冲使用提出的锁存窗屏蔽模型进行失效率的计算．文中的锁存窗屏蔽模型可以准确计算扇出重汇聚导致的脉冲叠加,并对多时钟周期情形具有很好的适用性．针对ISCAS’85基准电路的软错误率评估结果表明,与不考虑多时钟周期瞬态脉冲叠加的方法相比,文中方法使用不到2倍的时间开销,平均提高7．5％的软错误率评估准确度．     

多脉冲飞秒激光烧蚀铝靶动态特性研究

利用时间分辨阴影图研究了脉冲能量在200微焦的多脉冲飞 秒激光烧蚀铝靶的动态过程、并使用 扫描电镜研究了靶材表面烧蚀区域的形貌特征。时间分辨阴影图的记录结果表明,在不同时 间延迟条件 下,飞秒激光烧蚀铝靶形成的冲击波体积和喷射物的空间分布均随着脉冲个数的增加而发生 不同程度的变 化,尤其是单脉冲烧蚀情况下在1ns延时阴影图中观察到的近同心圆条纹会随着脉冲数目增 加逐渐变得模 糊乃至消失。烧蚀区的电子扫描显微镜图像清楚地揭示出烧蚀过程中伴随有液态铝的产生, 其溅射凝固后 在靶材表面形成小球和细丝状微纳结构。实验结果进一步证实了由前序脉冲烧蚀导致的铝靶 表面结构的改 变会对后继脉冲的烧蚀产生显著影响,从而使多脉冲烧蚀表现出明显不同于单脉冲烧蚀的特 性。这些结果 对飞秒激光脉冲沉积薄膜、直写生成表面微结构等应用的工艺参数优化具有很好的指导意义 。     

飞秒脉冲的破坏阈值研究

在Stuart等人理论模型的基础上,综合考虑Ming等人对电子密度衰减机制的研究,对飞秒激光的破坏机制进行了分析。通过计算模拟,分析了多光子电离、雪崩电离、电子衰减等机制与被辐照介质中自由电子密度之间的关系。分析表明脉冲宽度越窄,多光子电离过程提供的自由电子比例越小,其对激光破坏的作用也越小,此时雪崩电离过程将提供绝大部分电子,起到主导的作用;而随着脉宽增大,多光子电离提供的自由电子比例也将增大,其作用逐渐增强。当考虑衰减机制的影响后,电子密度在脉冲后沿不是维持在一个稳定的值,而是在达到极大值后呈下降趋势。在研究电子密度的基础上,利用计算飞秒脉冲破坏阈值的模型,分析了不同的衰减因子对破坏阈值的影响,研究表明,考虑电子衰减机制模拟得到的破坏阈值比不考虑时有所提高。     

短脉冲泵浦类锂铝离子X射线激光模拟

建立了适合描述短脉冲激光泵浦类Ｌｉ离子产生Ｘ射线激光的简化流体和原子动力学模型。短脉冲激光泵浦纤维靶产生等离子体的电子密度、电子温度、电离态分布等和驱动激光功率密度、脉宽及纤维靶半径相联系。研究了类Ｌｉ铝离子４ｆ－３ｄ跃迁激光增益系数随时间的演化过程，以及峰值增益和泵浦激光功率、脉宽及纤维靶半径之间的关系。     

Transferred Electron Logic Devices for Gigabit-Rate Signal Processing

A new approach for designing transferred electron logic devices (TELD's) is presented and experimental results described. Electrolytic thinning of GaAs wafers has been used to maintain uniform nd product across the wafers and minimize variations in the device characteristics. TELD's have been fabricated and their performance studied. The devices are evaluated as threshold Iogic elements. The parameters studied are 1) switching characteristics, 2) shortest pulses that can be processed, and 3) device delay and dissipation. Experimentally, pulses as small as 80 ps wide have been processed through transferred electron logic gates (TELG's) with device delays of the order of 50 ps and delay-dissipation product of 5-10 pJ, which make them suitable for gigabit-rate signal processing.     

Non-volatile programmable pulse computation cell

Analogue VLSI circuit elements for producing and processing pulses with programmable time delays are described. The elements can be interconnected to implement pulse computations or spiking neurons. As an example, the basic operation of a scale-invariant template matching system using coincidence detection is demonstrated     

Dynamic internal testing of CMOS circuits using hot luminescence

Subnanosecond pulses of hot electron luminescence are shown to be generated coincident with logic state switching of individual devices in CMOS circuits. These pulses are used to directly observe 90 ps gate delays in a ring oscillator as well as the logic switching and gate delays of a counter. By use of a detector with both space- and time-resolution, the dynamics of all the gates of the circuit are simultaneously measured. This noninvasive technique can be extended to smaller device size, as well as probing from the backside of the wafer. The optical emission may provide an alternative to electron beam testing for measuring the dynamics of high-speed CMOS circuits     

基于多速率滤波器组的UWB脉冲波束形成方法

在UWB脉冲信号的角度分集接收中,通常的空时处理中通道时延不易精确地控制。该文提出一种适合UWB脉冲信号的基于多速率滤波器组的波束形成方法,避开了时域处理中延迟控制的问题,同时实现了大带宽范围内的均匀一致的频率不变阵列响应。本文具体分析了进行多速率滤波的方式,其优点是滤波器设计简单,运算量与子带数目无关,同时UWB脉冲信号处理的不连续性使得其可以采用比较简单的时域插值算法。仿真实验结果证明了该文方法的可行性和有效性。     

Internal Q-switching in GaAs junction lasers

InternallyQ-switched light pulses have been obtained from junction lasers. It is believed that this is a completely new observation for semiconductor lasers. Using specially fabricated diodes, narrow bursts of light were detected immediately after the termination of the injection current pulse. The effect persists for a wide variation in the length of the current pulse, from less than 2 ns to several μs. The width of theQ-switched light pulse itself is less than 0.4 ns, this value being the resolution of our detection system. Its energy increases rapidly with the amplitude of the injection current. The occurrence of stimulated emission after the end of the injection pulse indicatesQ-switching due to a reduction of the internal absorption. This reduction allows those injected carriers that have not yet spontaneously recombined to produce the narrow burst of stimulated light. TheQ-switching is observed over a current amplitude range that is a very strong function of temperature. This range can be relatively large. One diode at 150°K showedQ-switching after current pulses from 1.2 to 5.0 amperes; for amplitudes greater than 5.0 amperes, normal stimulated emission occurred during the current pulse. As the temperature is increased, theQ-switched pulse is first observed near Tt, the so-called "transition temperature" where trapping effects first start to cause long delays between the application of the current pulse and the onset of stimulated emission. Therefore, it is believed that the same traps are involved in both the long delays and theQ-switching. The latter is observed only in diodes with low Ttvalues where the absorption due to traps accounts for a large proportion of the total losses of the laser. A model explaining these effects will be presented.     

Theoretical Analysis of the Rhombic Simulator Under Pulse Excitation

An analysis is given of the electromagnetic pulse generated in the space between the wires of a rhombic simulator by pulses of current traveling along the wires. After the mechanism of pulse excitation is clarified with the help of measured results, the electromangnetic pulse is investigated in terms of a current pulse with known shape that travels along the rhombic wires. The calculated pulse sequences agree very well with the measured ones. The "subpulse" radiated by each small segment of the wires as the current pulse traverses it is also studied. The time delays of the sequence of subpulses play an important role in the formation of the complete electromagnetic pulse. The amplitudes of the subpulses are relatively less important.     

Laser-induced plasma formation in water at nanosecond tofemtosecond time scales: calculation of thresholds, absorptioncoefficients, and energy density

The generation of plasmas in water by high-power laser pulses was investigated for pulse durations between 100 ns and 100 fs on the basis of a rate equation for the free electron density. The rate equation was numerically solved to calculate the evolution of the electron density during the laser pulse and to determine the absorption coefficient and energy density of the plasma. For nanosecond laser pulses, the generation of free electrons in distilled water is initiated by multiphoton ionization but then dominated by cascade ionization. For shorter laser pulses, multiphoton ionization gains ever more importance, and collision and recombination losses during breakdown diminish. The corresponding changes in the evolution of the free carrier density explain the reduction of the energy threshold for breakdown and of the plasma energy density observed with decreasing laser pulse duration. By solving the rate equation, we could also explain the complex pulse duration dependence of plasma transmission found in previous experiments. Good quantitative agreement was found between calculated and measured values for the breakdown threshold, plasma absorption coefficient, and plasma energy density     

Polarization mode dispersion and polarization dependent loss for apulse in single-mode fibers

Polarization mode dispersion (PMD) and polarization dependent loss (PDL) for a pulse in optical fibers are calculated with a model of two concatenated fibers. Each of the two fibers has both elliptical birefringence and PDL. The results show that the PMD and PDL for a short pulse can be very different from those for a narrow-band pulse in optical fibers. Two anomalous results are reported: (1) the effective PDL for a pulse can be smaller than the PDL difference of the two fibers and (2) the effective PMD for a pulse can be either larger than the sum of the differential group delays (DGDs) of the two fibers or less than the DGD difference of the two fibers, depending on the input pulsewidth. The pulse distortions when the pulses are launched into the two principal states of polarization (PSPs) are discussed     

Superradiant short-pulse propagation in the free-electron laseroscillator

A numerical study has been made of free-electron laser oscillators in which the electron pulse length is comparable to the slippage. It is shown that the saturated optical pulse exhibits superradiant spiking behavior in which the peak power is proportional to the square of the current and the efficiency grows in proportion to the square root of the current. The authors investigate the optimum cavity detuning length necessary to beat the lethargy in the small-signal regime and to obtain maximum overlap between the optical and the electron pulses during every bounce of the radiation within the optical cavity