Modal correction for fiber-coupling efficiency in free-space optical communication systems through atmospheric turbulence

High-speed free-space optical communication systems have recently used fiber-optical components. The coupling efficiency with which the received laser beam can be coupled into a single-mode fiber is noticeably limited by atmospheric turbulence due to the degradation of its spatial coherence. Fortunately, adaptive optics (AO) can alleviate this limitation by partially correcting the turbulence-distorted wavefront. The coupling efficiency improvement provided by Zernike modal AO correction is numerically evaluated. It is found that the first 3-20 corrected polynomials can considerably improve the fiber-coupling efficiency. The improvement brought by AO is compared with that brought by a coherent fiber array. Finally, a hybrid technique that integrates AO and a coherent fiber array is proposed. Results show that the hybrid technique outperforms each of the two above-mentioned techniques. (C) 2009 Elsevier GmbH. All rights reserved.

Instabilities in a non-transferred direct current plasma torch operated at reduced pressure

Using an oscilloscope, a high-speed video camera and a double-electrostatic probe system, the periodicity and amplitude of the fluctuations in arc voltage, jet luminance and ion saturation current of a plasma jet were monitored to investigate various sources of instabilities and their effects in a non-transferred dc plasma torch operated at reduced pressure. The results show that besides a 300 Hz main fluctuation inherited from the power supply, arc voltage fluctuation of 3–4 kHz with an amplitude less than 5% of the mean voltage was mainly affected by the total gas flow rate. The arc voltage fluctuation can affect the energy distribution of the plasma jet which is detectable by electrostatic probes and a high-speed video camera. The steadiness of energy transfer is also affected by the laminar or turbulent flow state of the plasma.

Plasma and electrode emissions from a 1 kW hydrogen-nitrogen arcjet thruster

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

AD7690在高精度数字电源上的应用

This paper contains the performance , principles of AD7690 and application design based on TMS320F2808 MCU. AD7690 ’s characters of high speed and high precision satisfy the requirement s of accelerator digital power supply.中文摘要：介绍了 AD7690 的主要性能、 工作原理 ,给出了应用电路以及在 TMS320F2808 上的数字接口设计。AD7690 的高速、 高精度特点适合加速器高精度数字电源方案。

用VHDL实现的23位快速浮点数加减法器

With the development of LSI, FPGA/CPLD has been used more and more in the fields of digital signal processing and au-tocontrol and so on. And with the development of the techniques of digital processing, for fitting the system’s function, it should be a higher requirement to speed and used-resource to compute the floating point numbers. The author introduces a high speed adder-subtracter of the 23 bit’s floating point numbers, which is carried out with the parallel arithmetic and the computational speed cou...中文文摘：随着大规模集成电路的不断发展,FPGA/CPLD在数字信号处理、自动控制等方面得到了越来越多的应用。并且伴随着数字化处理技术的不断发展,为满足系统功能的要求,对浮点数运算的速度以及相应占用的资源也就提出了更高的要求。笔者即介绍了以VHDL语言为基础,采用并行算法且计算速度达到33MHz的,对23位标准浮点数实现的高速浮点加减法运算器,并以Cyclone II芯片EP2C20F484为硬件环境,最终进行时序模拟仿真,从而验证该浮点加减法器的正确性和快速特性。

Dynamic Measurement System for Dipoles of RCS for CS

A dynamic measurement system was developed by the Institute of Modern Physics (IMP) for the dipole prototype of Rapid Cycle Synchrotron (RCS) of China Spallation Neutron Source (CSNS). The repetition frequency of RCS is 25 Hz. The probe is a moving arc searching-coil, and the data acquisition system is based on the dynamic analysis modular of National Instrument. To get the error of high order harmonics of the field at basic frequency, the hardware integrator is replaced by a high speed ADC with software filter and integrator. A series of harmonic coefficients of field are used to express the varieties of dynamic fields in space and time simultaneously. The measurement system has been tested in Institute of High Energy Physics (IHEP), and the property of the dipole prototype of RCS has been measured. Some measurement results and the repeatability of system are illustrated in this paper.

高速多道脉冲分析系统研究

多道脉冲分析系统是射线分析仪器的核心部件，有着广泛用途。许多应用领域对其性能指标的要求日益提高。目前我国尚不能制造高性能指标的产品。我们的主要目标是在保证一定的脉冲分析精度的同时，提高脉冲分析速度，改进系统的控制，提高系统集成度。本文首先回顾近年来多道脉冲分析系统（MCA）的研究进展。然后，着重阐述新型高速多道脉冲分析系统各部分的原理与结构。其主要特点在于：（1）系统集成度大大提高，使用灵活；（2）改进了电容充放电回路，实现了恒流充放电，提高了脉冲峰值保持精度；（3）在合理分配系统各部分功能的基础上，独立提出了新的MCA状态机模型，实现了对整个系统的简单、灵活而全面的控制，使之成为一个基本自封的系统，并且使脉冲分析速度有较大提高；（4）给出一个新的数据传输总线和数据采集接口的初步方案。本文第三部分论述了作者对器件的选择和运用，电路的设计和布局等问题的考虑。本文侧重从硬件角度研究多道脉冲分析系统。设计的系统结构为后续的软件研制工作提供了便利。

多路信号处理与QDC门信号产生逻辑插件的研制

本论文描述了多路信号处理与QDC（电荷数字转换器）门信号产生逻辑插件的研制过程。该逻辑插件的逻辑电路和模拟电路都经过了精心的设计和调试。核物理研究沿着激发能、核自旋及核同位旋三个自由度深入开展，产生了核物理研究中许多新的前沿领域。随着入射能量的增加，开放的反应道增多，多重探测器投入使用，使核物理实验的数据参数已经从几十路上升到上千路，即需要电子学工作者研制和开发一些高速触发、高密度、高稳定性的电子学硬件系统。本论文描述的多路信号处理与QDC门信号产生逻辑插件，主要用于产生QDC的开门信号。该电路系统早十六路并行、独立的高速放大单元电路、高速比较单元电路、延迟和脉宽成形单元电路、逻辑信号扇出单元电路、触发指示单元电路及多路模拟信号求和单元电路构成。该逻辑插件可接收≥ 20mv的小辐度输入信号而产生32路标准ECL（高电平-0.8V，低电平-1.6V）互补输出逻辑信号。输出ECL逻辑信号用于产生QDC的门控信号。该插件的多路模拟信号求和单元电路对每路输入信号可产生幅度为50mv的输出信号。该输出信号可用于多重符衙事件的鉴别和产生trigger触发信号。总的来说，多路辐度信号处理与QDC门信号产生逻辑插件不仅适用于重离子核物理实验中产生QDC开门信号，也可用于其它核物理实验的多重符合事件的鉴别。该插件的研制成功为多参数获取系统提供了一个良发的前端硬件设备。

Phosphoproteome analysis of mouse liver using immobilized metal affinity purification and linear ion trap mass spectrometry

Since protein phosphorylation is a dominant mechanism of information transfer in cells, there is a great need for methods capable of accurately elucidating sites of phosphorylation. In recent years mass spectrometry has become an increasingly viable alternative to more traditional methods of phosphorylation analysis. The present study used immobilized metal affinity chromatography (IMAC coupled with a linear ion trap mass spectrometer to analyze phosphorylated proteins in mouse liver. A total of 26 peptide sequences defining 26 sites of phosphorylation were determined. Although this number of identified phosphoproteins is not large, the approach is still of interest because a series of conservative criteria were adopted in data analysis. We note that, although the binding of non-phosphorylated peptides to the IMAC column was apparent, the improvements in high-speed scanning and quality of MS/MS spectra provided by the linear ion trap contributed to the phosphoprotein identification. Further analysis demonstrated that MS/MS/MS analysis was necessary to exclude the false-positive matches resulting from the MS/MS experiments, especially for multiphosphorylated peptides. The use of the linear ion trap considerably enabled exploitation of nanoflow-HPLC/MS/MS, and in addition MS/MS/MS has great potential in phosphoproteome research of relatively complex samples. Copyright (C) 2004 John Wiley Sons, Ltd.

Capillary array electrophoresis with confocal fluorescence rotary scanner

A capillary array electrophoresis system with rotary corifocal fluorescence scanner was reported. High speed direct current rotary motor combined with a rotary encoder and the reflection mirror has been designed to direct exactly the excitation laser beam. to the array of capillaries, which are symmetrically distributed around the motor. The rotary encoder is introduced to accurately orient the position of each capillary and its output signal triggers the data acquiring system to record. the fluorescence signal corresponding to each capillary. Separations of several amino acids are demonstrated by eight-channel capillary array electrophoresis built by ourselves.

一种高速安全反向代理服务器的设计与实现

安全反向代理服务器架设在真实网页服务器与用户浏览器之间靠近真实服务器的一侧,通过传输层安全协议保障用户与真实服务器之间的通信.作为基于传输层安全协议的虚拟专用网服务器的一个最重要的组成部分,安全反向代理有着极大的商业价值和技术含量.在FreeBSD-6.3的基础上设计并实现了一个与传统TCP/IP并行的TCP/IP跳转表.基于TCP/IP跳转表设计并实现了一种多加速卡调度算法.设计并实现了直接从加速卡队列获取数据包的代理转发协议栈.设计并实现了基于后台真实服务器反馈的负载均衡算法.测试表明,由这些算法和协议栈组成的高速安全反向代理服务器新进连接数达到了国内领先水平.

实行三个基本转变促进黄土丘陵区农业和经济持续发展

依据黄土丘陵区几十年治理开发的正反两方面经验 ,认为该地区要真正抓住西部大开发大好机遇 ,迅速改变落后面貌 ,实现农业和经济的快速及可持续发展 ,必须在指导思想和农业生产上实现三个根本转变。即 :变以粮为主的广种薄收为高效的农林果牧综合发展 ;变自给自足的小农经济为以商品生产为主的集约经营 ;变生态经济相悖论为生态经济统一观

Wear mechanism map of uncoated HSS tools during drilling die-cast magnesium alloy

A wear mechanism map of uncoated high-speed steel (HSS) tools was constructed under the conditions of dry-drilling die-cast magnesium alloys. Three wear mechanisms appear in the map based on the microanalysis of drilled HSS tools by SEM, including adhesive wear, abrasive wear and diffusion wear. In the map, there exists a minor wear region which is called "safety zone". This wear mechanism map will be a good reference for choosing suitable drilling parameters when drilling die-cast magnesium alloys.

Characterization of the microstructure of biaxially oriented polypropylene using preparative temperature-rising elution fractionation

Two commercial biaxially oriented polypropylene (BOPP) resins, resin A and resin B, having different processing properties, were fractionated by preparative temperature-rising elution fractionation (TREF). The TREF fractions were further characterized by gel permeation chromatography (GPC), gel permeation chromatography coupled with light scattering (GPC-LS), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). GPC-LS did not find visible long-chain branching in either resin A or B. The results from TREF and DSC indicate that the fractional melting parameter f(T) may be used to predict the profile of the TREF cumulative weight distribution curve. GPC results show that the molecular weights of the fractions tend to increase with elution temperature. WAXD and DSC data show that the crystallinity of fractions does not increase monotonically with increase of elution temperature. There appears to be a maximum in the plot of crystallinity versus elution temperature. The high-speed BOPP resin A has a lower isotacticity but a homogeneous isotacticity distribution and a higher molecular weight but a broader molecular weight distribution than resin B.

S／T曲线速度规划在定点DSP上的实现

本文将S／T曲线速度规划的思想引入全数字伺服驱动系统中,通过提高速度的平滑性,特别是高速启、制动状态,来提高伺服系统的整体控制性能。基于定点数字信号处理器DSP芯片对提出的算法进行了实现。由于定点运算的限制,算法在实现中需要进行特殊的处理,本文对此进行了研究,并提出了一种余码补偿方案。实验研究表明,使用本文提出的方法可以提高系统运行的平稳性和控制的精确度。