接入IP

首先分析信息时代的接入特点,讨论了在ＩＰ网上承载不同业务的方法,研究了支持ＩＰ结构信号传送的方式,并说明适于ＩＰ接入的传输技术．最后介绍了ＩＴＵ－Ｔ对ＩＰ接入的研究要点。     

Optical bistability in an L-band dual-wavelength erbium-doped fiber laser with overlapping cavities

The authors investigate the optical bistability in an L-band dual-wavelength erbium-doped fiber (EDF) laser with overlapping cavities. The bistable input-output hysteresis behavior of the two lasing wavelengths evolves in antiphase. The bistable region is tens of milliwatts wide. The bistability is essentially due to the homogeneous saturable absorption of EDF. The cross-gain saturation causes the bistabilities of the two lasing lines to evolve in antiphase with respect to each other. The gain clamping effect helps to widen the bistable region, which may be controlled by the cavity loss and by the EDF length.     

Analysis of thermal instability in multi-finger power AlGaAs/GaAsHBT's

A new theory is developed in this paper to explain the collapse of current gain in multi-finger power AlGaAs/GaAs Heterojunction Bipolar Transistors (HBT's). The reasons behind this unwanted phenomenon are fully clarified using a simple model to investigate the thermo-electrical interaction between the fingers. The existence of multi-value equilibrium points in model's constitutive equations is shown to be the necessary condition for the collapse of current gain to appear. For a N-finger device, N different patterns of collapse exist. The criterion to select the global stable pattern is given. The method has been used to predict the collapse in AlGaAs/GaAs HBT's and the agreement is excellent. The method also predicts that the collapse can happen far earlier than is normally expected in multi-finger high-power devices. The influence of ballasting resistance and thermal resistance is also investigated     

数字滤波技术在气相紫外光电子能谱仪数据采集中的应用

为既能广泛用于稳定分子的研究又能用于瞬变物种研究的气相紫外光电子能谱仪设计了数据采集系统，应用Windows支持下的Visual C 6．0编程技术，编制了具有友好界面、操作简便的数据采集系统软件．数据采集系统利用Butterworth低通数字滤波器对采集到的数据进行处理，来消除高频的噪声提高信噪比．     

Modified Iterative Decoding Algorithm for Polar Code Using Maximum Likelihood Estimation

The key challenges in real time voice communication in long term evolution mobile are reduction in complexity and latency. Efficient encoding and decoding algorithms can cater to these. The implementation of such polar code based efficient algorithms is proposed in this paper. The overall latency of 3.8 ms is needed to process 8 bit block length. The novel sub-matrix near to identity matrix is presented. This resulted into minimization of loops among least reliable bits due to iterated parity check matrix. Look-up table based memory mapping is used in encoder to reduce latency while Euclidian decoding technique is used in decoder. The number of iterations is reduced by 50%. The experimentation is performed with additive white Gaussian noise and QPSK modulation. The proposed modified iterative decoding algorithm requires SNR of 5.5 dB and 192 computations for targeted bit error rate of 10^?4. The second proposed method needs 9 dB, 2 iterations for 384 computations. The penalty paid is quantization error of 0.63% due to restricting computations to fourth order series of hyperbolic function with same 8 bit block length.     

Process control system for VLSI fabrication

A modular framework for the implementation of process control in VLSI fabrication is described. The system integrates existing approaches to process control with new methodologies in order to achieve online optimization and control of unit processes with consideration of preceding and following process steps. The process control system is based on three core modules. The flexible recipe generator determines an initial operating point in response to a new product design. The run-by-run controller tunes the recipe between runs based on feedback from postprocess and in situ measurements. The real-time controller further modifies the equipment settings during a process step based on in situ measurements. The algorithmic bases of these modules are described. The flexible recipe generator was used to optimize the LPCVD (low-pressure chemical vapor deposition) of polysilicon. The run-by-run controller was used to locally optimize and control a simulation of the LPCVD of polysilicon     

TM scattering from a hollow slotted circular cylinder withthickness

TM scattering from a hollow, slotted, circular cylinder with thickness is investigated. The mode-matching technique (MMT) is used to express the scattered and guided fields in the angular spectral domain in terms of the radial waveguide mode. The boundary conditions are enforced on the conducting surface and the slot to obtain simultaneous equations. The simultaneous equations are solved to represent the fields in an analytic series form. The computed results are in very good agreement with other data. The numerical computations are performed to illustrate scattering behavior in terms of cylindrical geometry, incident angle, and frequency     

Linear antenna arrays with broad nulls with applications to adaptive arrays

The problem of designing a class of linear antenna arrays with broad nulls against interfering signals of variable direction of arrival is considered. The problem is formulated in an appropriate signal space selected for an efficient representation of array signals of specified angular occupancy. The array-weight vector is then chosen to be orthogonal to this space. The approach is seen to yield a min-max array in a sense to be defined in this paper. The application of such arrays to maintain the beamshape of an adaptive antenna array is also illustrated.     

Remote sensing of water vapor in the near IR from EOS/MODIS

The LOWTRAN-7 code was used to simulate remote sensing of water vapor over 20 different surface covers. The simulation was used to optimize the water vapor channel selection and to test the accuracy of the remote sensing method. The channel selection minimizes the uncertainty in the derived water vapor due to variations in the spectral dependence of the surface reflectance. The selection also minimizes the sensitivity of the selected channels to possible drift in the channel position. The use of additional MODIS channels reduces the errors due to the effect of haze, subpixel clouds and uncertainties in the temperature profile. Remote sensing of the variation of water vapor from day to day will be more accurate, because the surface reflectances vary slowly with time. The method was applied to Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data     

Nature Based Self-Learning Mechanism and Simulation of Automatic Control Smart Hybrid Antilock Braking System

The antilock braking system (ABS) is intended to augment braking effectiveness, maintains understeer and oversteer conditions. The braking system performance is degraded in the case of severe road conditions. The research paper presented the effectiveness of smart hybrid antilock braking system in automobiles. The concept of antilock braking system and manual braking system is anticipated to a single unit to overcome the problem facing in the braking system in vehicles. Lyapunov’s theoretical stability approach is used for the system stability. The concept of smart control development is used to solve system complexity and real time issues in different road conditions. Directional Control Valve (DCV) plays very important role in controlling the flow direction of brake oil. The Electronic Control Unit (ECU) is the slip controller for antilock braking system, which takes inputs from brake pedal, speed of all four wheels and various road conditions, processes the accumulated data to generate corresponding PWM signal for the DCVs. The ignition switch and ECU controls the activation and de-activation of directional control valve. The MATLAB/Simulink, 2015 version and experimental analysis using Automation Studio verified the model behavior in both ABS and manual braking mode. The system performance is analyzed during ignition ‘ON’ and ‘OFF’ conditions. The comparative study of the ABS mode and manual mode against wheel speed and vehicle speed is predicted in different time intervals. The smart hybrid ABS control provides better response in comparison to conventional braking. It is experimentally proved that the acclaimed antilock braking system reduces the stopping distance in comparison to the manual braking unit.

     

工程技术人员要在制造技术和产品创新上有所作为

概要地叙述了在PCB企业中工程技术人员的主要职责和任务。集成起来的工程技术人员才能形成战斗力,企业中工程技术人员的主体作为：（1）进行制造技术研究和产品创新与升级,使企业产品生产处于良性循环之中;（2）从技术上保证量化产品质量和稳定生产。因此,企业工程技术人员是解决企业中＂做什么＂和＂怎么做＂产品问题,并变为企业享受用的产品和财富。     

基于ICCP算法的地磁匹配定位方法

基于ICCP算法的地磁匹配定位可以用于限制惯导系统随时间增长的位置误差。给出ICCP算法的设计思想并进行推广,使算法能够在地磁测量数据存在误差的情况下,实现对惯导的误差校正。同时采用滑动窗口技术来快速寻找等值线上的最近点,在每一次收敛到局部最小的过程中都减少了寻找最近点的计算量,计算效率得以很大程度的提高。     

Force feedback control of robot manipulator by the accelerationtracing orientation method

The authors propose a novel approach to force and compliance control of multi-degree-of-freedom (DOF) robot manipulators. The acceleration tracing orientation method (ATOM) is applied to both controllers. The control law is described in the Cartesian space; however, the final command is the acceleration in the joint space. The interactive terms in each joint disturb and deteriorate the joint motion. The disturbance observer cancels out the total sum of these terms and enables each joint to trace the acceleration command. As a result, a robust control is possible in the force task. The testing of the proposed system in a three-DOF robot manipulator is discussed     

Thermal limitations of CW and pulsed silicon TRAPATT diodes

The power density distribution in the avalanche zone of a TRAPATT-diode is approximated by a rectangular pulse in order to consider it as a source function in the heat equation. Heat generation is considered to be periodic, and the dissipation is taken with a thermal time constant larger than the period. The increase in frequency needs a decrease in depletion width, improving the thermal conduction to the heat sink. The power density needed increases with frequency, thus raising the maximum temperature in the depletion region with frequency. The criteria for the best performance is that the two processes of heat generation and conduction to the heat sink are to be so adjusted as to lead to a mininum rise in temperature. The steady state temperature rise in CW operation comes out to beR_{TH} cdot P_{I} cdot W_{ASF}/v_{z} cdot f, while in the pulsed case this expression is related to the maximum temperature. The maximum temperature allowable in the depletion region should be lower than that required for any failure to occur. Using these criteria the thermal limitations for CW and pulsed operations of the TRAPATT diode have been analyzed.     

Antenna processing for surface target detection

An antenna processing system for target detection in receiver noise and heavy clutter is formulated by means of spacetime decision theory. The theory is applied to the case of a single target in clutter, with unknown target location and unknown amplitude and phase of the target return. The clutter background is assumed to be uniform in average power over the field of view. The target detection is accomplished by means of a generalized likelihood ratio test. A block diagram of the resulting decision-theoretic antenna processing system is shown. The decision-theoretic array does not form a beam in the ordinary sense, and consequently has equal gain in all directions in the forward hemisphere. However, the usual loss in gain occurring in conventional antennas which are omnidirectional does not occur in the decision-theoretic array. The decision-theoretic array is compared with conventional arrays to show the improvement possible by using the former. The quality criterion used to compare the systems is average risk, or the average probability of error in decision making. The array requires no scanning of any sort and is fixed relative to the vehicle that carries it.     

Time Domain Response of a Sphere in the Field of a Coil: Theory And Experiment

The time-harmonic solution for the anomalous vector potential due to a conducting permeable sphere in the field of a current-carrying loop is used to derive the corresponding step response. The step response is then used to obtain analytical expressions for the voltage induced in a second loop due to a chosen exciting current pulse train. The voltage induced in an actual system of coils is obtained by superposition. The effect of the measurement system is included in the analysis in order to experimentally verify the model. Measured responses of a number of aluminum and steel spheres at various distances from the coils are compared with theoretical predictions. The agreement between the two is generally good.     

Investigation of the fluid/structure interaction phenomenon in IC packaging

In the present study, experiment and simulation studies were conducted on the fluid/structure interaction (FSI) analysis of integrated circuit (IC) packaging. The visualisation of FSI phenomenon in the actual package is difficult due to limitations of package size, available equipment, and the high cost of the experimental setup. However, the experimental data are necessary to validate the simulation results in the FSI analysis of IC packaging. Scaled-up package size was fabricated to emulate the encapsulation of IC packaging and to study the effects of FSI phenomenon in the moulded package. The interaction between the fluid and the structure was observed. The deformation of the imitated chip was studied experimentally. The air-trap mechanism that occurred during the experiment is also presented in this paper. Simulation technique was utilised to validate the experimental result and to describe the physics of FSI. The predicted flow front was validated well by the experiment. Hence, the virtual modelling technique was proven to be excellent in handling this problem. The study also extends FSI modelling in actual-size packaging.     

Waste not, pollute not [animal waste recycling for powerproduction]

Recycling animal waste can keep water cleaner and generate electricity off the grid. The paper describes the use of animal waste in the form of biogas at AA Dairy to produce electricity. The gas is burned in a diesel engine converted to run on methane. 10-20% of the electricity produced in summer is sold to the grid, the figure rises to 35-40% in winter. The paper then discusses the wider picture of bioenergy conversion at farms in the USA. The chemical impact on groundwater and soil stewardship are also discussed     

A reduced order extended Kalman filter for sequential imagescontaining a moving object

The extended Kalman filter (EKF) is applied to the reduction of noise in sequential images containing a moving object and to the estimation of the object's velocity. A computationally tractable approximation of the EKF, called the parallel extended Kalman filter (PEKF), is generated. The PEKF consists of a parallel bank of third-order EKFs, operating on the Fourier coefficients of the image, followed by a finite impulse response filter. The PEKF is shown to converge to the optimal (in the mean square sense) algorithm in the limit as the velocity estimation errors approach zero. The performance of the PEKF is demonstrated for very low signal-to-noise ratio (SNR) images. The PEKF also provides a natural setting for tracking slow changes in the object (real or apparent) and its velocity, since these variations are included in the model. The relation of the PEKF to another frequency domain algorithm for velocity estimation is discussed. The algorithm is illustrated by application to an example and its performance is demonstrated in the presence of velocity estimation errors.     

基于粒子滤波的运动物体检测跟踪

提出了一种状态空间模型粒子滤波算法,并应用于运动目标的跟踪。该方法基于贝叶斯估计,利用粒子集来表示概率,通过递推的贝叶斯滤波来近似逼近最优化结果,在预设搜索区域用粒子群找到和目标模板最相似的中心位置,并以该位置作为观测值,进行跟踪。仿真实验结果和两种实际条件下效果比较表明该算法在跟踪低常速运动中精准性高,是一种有效的目标跟踪方法。