光缆氢损探讨

本文针对曾困扰光缆领域的氢损问题，通过实验分析，阐明了检验光缆氢损的方法，探讨了产生氢损的主要根源，提出了避免光缆产生氢损的方法及氢损光缆的恢复办法。     

Influence of Hydrogen on Optical Fiber Loss in Submarine Cables

Characteristics of the loss increase in optical fibers due to hydrogen permeation are described, and it is shown that the loss increase due to OH formation in GeO2-doped single-mode fibers is thought to be small compared to the loss increase due to the vibration of hydrogen molecules even in 20 years. Furthermore, the hydrogen generation due to electrochemical reaction in the optical cables is described. Finally, the countermeasure against the problem is discussed.     

Cost-benefit analysis of one-server two-unit replacement system with imperfect switch

This paper deals with the cost-benefit analysis of a one-server two-unit system with imperfect switch where the unit, if available, is preferred to the standby. The repair time of an item (unit/standby/switch is arbitrarily distributed while failure rate of an item is constant. Initially, the unit is switched on (switch is working at t = 0). The repair of the switch is given preference after the current repair of the unit or standby is over. Explicit expressions for the expected up-time due to the unit, expected up-time due to the standby; expected busy period of the server due to the unit, due to the standby and that due to the switch are obtained to carry out the cost-benefit analysis.     

背景风场和温度梯度对重力波传播的影响

运用射线跟踪方法，计算了背景风场和温度梯度共同影响下大气重力波的传播射线，结果表明，在顺风传播情况下，较小波长的重力波在１００ｋｍ左右的高度上被捕获，较大波长时可穿透传播到热层，但射线在水平方向拉伸；在逆风传播情况下，较长波长的波在１２０ｋｍ之下的高度发生无环反射，较短波长的波在２００ｋｍ以上的高度发生有环反射，而介于两种反射波的波长之间的波则穿透传播到热层高度，射线变陡。分析表明，上述波的反射、     

Modulation Transfer Noise Effects from TDMA Carriers to FDM/FM Carriers in Memoryless Nonlinear Devices

This paper examines modulation transfer noise effects from TDMA carriers to FDM/FM carriers in a common memoryless nonlinear amplifier. The modulation transfer noise consists of discrete as well as continuous spectral components. Three types of discrete components are identified: those due to pulse filtering only, those due to on-off bursting only, and cross terms due to both mechanisms simultaneously. The continuous spectral component of the modulation transfer noise is due to pulse filtering only. A comparison of the relative intensities of all these noise components is also presented.     

Soliton position jitter caused by periodic amplification andself-frequency shift

The formula for soliton timing jitter due to self-frequency shift and pulse width fluctuations caused by spontaneous-emission noise has been deduced. Such timing jitter is compared with that caused by the carrier frequency shift due to spontaneous-emission noise. It is shown that the timing jitter due to the self-frequency shift can be as large as the timing jitter due to carrier frequency shift when the total transmission distance is 100 times longer than the soliton period     

Lifetime estimation for IGBT modules in wind turbine power converter system considering ambient temperature

Power semiconductors in the wind turbine power converter system suffer from two-scale thermal loadings, the fundamental frequency thermal cycling caused by the output frequency of converter and the low frequency thermal cycling due to the variation of long-term wind speed. These two-scale thermal loadings introduce different consumed lifetimes. Accurate lifetime estimation in the wind power application is desired for reliability prediction and health management. This paper adopts the Bayerer lifetime model to evaluate the consumed lifetime of power semiconductors in wind power converter systems based on a numerical junction temperature calculation method. Lifetime estimation can be improved by taking into account the ambient temperature. Studies show that fluctuations of the ambient temperature increase the consumed lifetime due to the low frequency thermal cycling, but have little effect on the consumed lifetime due to the fundamental frequency thermal cycling. Our results also show that the consumed lifetime due to fundamental frequency thermal cycling mainly falls on the high wind speed area, whereas the consumed lifetime due to low frequency thermal cycling is clustered in the area due to large low frequency junction temperature fluctuations. The resulting distribution characteristics can be used in the thermal management for reliability improvement.     

Hot-electron-induced punchthrough (HEIP) effect in submicrometer PMOSFET's

Degradation of device characterisitics due to hot-carrier injection in submicrometer PMOSFET has been investigated. We found that in submicrometer p-channel transistors the punchthrough voltage is seriously reduced due to hot-electon-induced punchthrough (HEIP). A worst case analysis of the experimental data shows substantially reduced lifetime due to HEIP.     

Simulation of system backend dielectric reliability

Backend dielectric breakdown degrades the reliability of circuits. A methodology to estimate chip lifetime due to backend dielectric breakdown is presented. It incorporates failures due to parallel tracks, the width effect, field enhancement due to line ends, and variation in activity and temperature. Different workloads are considered as well, in order to evaluate aging effects in microprocessors running real-world applications with realistic use conditions.     

Statistical variations in forward propagation rain depolarization due to drop size fluctuations

Observed electromagnetic wave depolarization in forward propagation due to precipitation tends to distribute statistically about some mean level of depolarization. This is due to random rain parameters that cause this depolarization. Using a drop-size modified depolarization model, we have analyzed the statistical scatter of the cross polarization ratio due to random distributions of drop population and size and found a standard deviation of approximately 2.5 dB about the mean, independent of frequency.     

Calculations Of Therapeutic Heat Generated by Ultrasound in Fat-Muscle-Bone Layers

An analytical approach to obtain the relative heating pattern due to the propagation of ultrasonic waves in a fat-muscle-bone layered tissue system is presented. The effects on the relative heating pattern due to the change of incident angle and the change of frequency are discussed in this paper. The contribution to heating due to mode conversion at the bone surface is also discussed.     

Loss increase for optical fibers exposed to hydrogen atmosphere

Loss spectrum changes for optical fibers exposed to a hydrogen atmosphere in the15-200degC temperature range are measured. Loss increase due to molecular hydrogen dissolved into fibers is investigated from the loss peak at 1.24 μm, and that due to hydroxyl group formation from the loss peak at 1.41 μm. The loss increase due to molecular hydrogen is fully explained by physical solubility theory and diffusion equation. The empirical formula for time, temperature, and hydrogen-pressure dependences of the loss increase due to hydroxyl group formation is evaluated from the experimental results. The loss increase at 1.3- and 1.5-μm wavelength band at room temperature are estimated.     

Effect of Human Error on The Availability of Periodically Inspected Redundant Systems

The engineered safeguards of nuclear power plants contain many redundant systems which are not operating under normal conditions but they are called upon to act when emergency conditions develop. To ensure their operability, the systems are periodically tested (usually once a month). In this paper, unavailability formulae for several common logic configurations are developed, taking into account the probability of failure of components due to human error in the simultaneous testing scheme. The probability of the component being down due to human error is assumed to depend on the number of components which have gone through the tests consecutively prior to the inspection of the component under consideration. The system unavailability is the sum of unavailability due to hardware failure alone and the unavailability contribution due to human error.     

Method of minimising the effect of disturbances on the estimate of the impulse response of a linear system

A method is proposed whereby the errors in the estimate of the impulse response, obtained from pseudorandom-binary-signal correlation experiments, due to low-frequency drift at the output of the system may be reduced. In particular, errors due to a constant, a linear, a quadratic and a cubic term in the power-series representation of the noise are eliminated. Moreover, the bias on the estimate of the impulse response, due to the nonzero value of the autocorrelation of the binary sequence for nonzero delays, is eliminated.     

Analysis of FM Systems with Co-Channel Interference Using a Click Model

Rice's click model for ideal FM detection is applied to systems with co-channel interference. Output noise terms consist of a high signal-to-noise ratio (SNR) term due to noise alone, a term due to the desired signal beating with the interferer, and a term due to the clicks. Click rates are determined with and without modulation and it is shown that in the computation of noise due to clicks the interferer can be treated as a simple sinusoid [i.e., an unmodulated carrier] Plots are given for detected SNR versus carrier-to-noise (CNR) with signal-to-interferer ratio (SIR) and modulation index as parameters. The effect of signal suppression is analyzed and for the range of parameters used in this paper it is found to be negligible.     

一体化二次变频微波收发信机电磁兼容研究

研究了一体化二次变频收发信机中各种组合频率干扰的产生原因:主要是由于混频器和放大器的非线性。详细描述几种组合频率干扰的形式:发信号与收高本振的组合干扰;收、发高中频频率相近造成的收发干扰;发通道高、低本振以及发中频之间频率组合干扰;收通道高、低本振频率组合干扰。分析其形成的原因、给系统造成的危害,并提出了相应的解决措施。最后给出了降低组合频率干扰电平的几种途径,对提高一体化二次变频收发信机的电磁兼容性进行了有益探讨。     

波分复用系统中四波混频引入光信噪比的恶化及其抑制

本文对陆上级联接掺铒光纤放大器（ＥＤＰＡ）波分复用光纤通信系统中国波混频所造成的各个光信道光信噪比的恶化提出了一套计算方法，并结合常规单模光纤及一种特殊设计的色散位移光纤进行了分析计算。结果表明：在四波混频所引入的光信噪比恶化中，因新生频率分量导致的噪声增加一般远大于光信号功率的减弱。不等信道间隔划分能有效地避免四波混频的影响，而光滤波器的带宽应在允许范围内尽量压窄。对采用色散补偿技术的级联ＥＤＦＡ波分复用系统，在同一光中继段内，使常规单模光纤置于特殊设计的色散位移光纤之前，能进一步减少四波混频带来的光信噪比的恶化。     

Monte Carlo simulation for electron transport in MESFETs includingrealistic band structure of GaAs

A full band Monte Carlo (FBMC) simulator was developed for electron transport in GaAs MESFETs. As a result of increased scattering rate due to the complicated band structure, the average velocity in the high field region was lower than the analytical band Monte Carlo (ABMC) result. Also, the simulated energy peak was higher than the ABMC result, due to electrons populating the upper bands. Not only due to a limited number of the first conduction band states capable of ionization, but also due to a small mass of the second conduction band, more than 95% of ionization events were shown to occur in the upper bands. The simulated ionization rate lies within the range of experimental results. To our knowledge, this is the first report on the full band two-dimensional (2-D) self-consistent GaAs MESFET simulation     

Si substrate structure for solid-state color imagers

Si substrate structure for a low-noise MOS-type color imager was proposed. Photodiodes fabricated in a p-well suppress noise due to spurious red and infrared sensitivity, blooming, and smear, Furthermore, defects are diminished by optimized three-step intrinsic gettering and a new plural ion implantation method. Defects include those due to the defect nuclei inherent in a Si substrate grown by the Czochralski method and those due to high-dose boron-ion implantation for a low-resistance well layer.     

Finite element analysis of gradient coil deformation and vibration in NMR microscopy

Resolution degradation due to gradient coil deformation and vibration in NMR microscopy is investigated using finite element analysis. From the analysis, deformations due to the Lorentz force can be as large as 1-10 mum depending on the gradient strength and coil frame material. Thus, these deformations can be one of the major resolution limiting factors in NMR microscopy. Coil vibration, which depends on the input current waveform and resolution degradation due to time-variant deformation and time-invariant deformation are investigated by numerical simulations.