Development of high field permanent magnet

Permanent magnets are believed to be applicable only to make small and weak magnets. It is possible, however, to make a magnet with much higher strength than those in the past by introducing a saturated iron pole. Cooling down the magnet further enhances the field strength to a great extent. We have demonstrated that a permanent dipole magnet exceeding a typical permanent magnet more than by factor 3 is possible. A new challenge is to conceive such magnet for an accelerator application where time dependent alternating field is often requested.     

螺线管结构参数对脉冲磁场的影响

研究了线圈间距、匝数、个数以及不锈钢套筒对脉冲磁体产生磁场的影响规律。在储能电容和电压不变的前提下,研究结果表明：增加线圈间距会导致磁感应强度降低,磁力线包络增大,但总电流达到峰值时刻减小;增加线圈匝数,峰值电流明显减小,会降低磁感应强度,但有利于抑制磁力线包络;增加并联线圈个数,有利于产生较长的均匀区,但是在供能一定的条件下,磁场强度有所降低,同时总电流达到峰值时刻减小。总体来看,在一定均匀区长度的设计要求下,减少单个线圈匝数,增加并联线圈个数,能够得到磁感应强度更大、均匀性更好的磁场,但要考虑线圈承载电流的能力。另外,不对称的阴阳极金属结构会导致磁场不对称分布,且磁感应强度达到峰值时刻要晚于总电流达到峰值的时刻。     

偏视场用三反系统消杂光设计及仿真

分析了偏视场用三反系统的杂散光特性,根据遮光罩设计的基本原则,介绍了利用计算机仿真技术进行消杂散光设计和评价的原理.系统为特殊的矩形视场,且在y方向视场偏轴,为此,设计了盒形外壁与锥形内壁相结合的外遮光罩结构,并在CAD中进行建模,采用内部挡光片为方形并且梯度排列的结构.在λ＝0.25μm,方位角为0°和90°时分别对...     

基于混频偏置合成的高速太赫兹无线通信系统

提出一种基于载波抑制混频与载波偏置功率合成的高速太赫兹无线通信方案。发射端利用载波抑制混频器和载波偏置功率合成在140 GHz载波上实现了开关键控(OOK)调制;接收端利用包络检波接收器进行检波接收。分别开展了不同混频本振功率及偏置功率下的检波响应实验、不同基带信号功率及偏置功率下的检波响应实验,以及不同输入功率下的检波响应实验。实验结果对OOK调制器设计,以及OOK类通信系统的优化均具有较好的指导意义。最后,利用优化的系统参数在70 cm距离上实现了140 GHz, 16 Gbps的无线通信,系统误码率(BER)优于10-5。     

New redundant logic design concept for high noise and low voltage scenarios

This paper presents a new redundant logic design concept named Turtle Logic (TL). It is a new probabilistic logic method based on port redundancy and complementary data, oriented toward emerging technologies beyond CMOS, where the thermal noise could be predominant and the reliability of the future circuits could be limited. The TL is a technology independent method, which aims to improve error tolerance when these errors are caused by noise within logic and functional units, sequential elements, and in general synchronous pipeline Finite State Machines. Turtle Logic operation is based on the consistency relation of redundant inputs. In the case of discrepancy, the output of the system keeps the previous value, therefore avoiding the propagation of incorrect inputs. A two's complement 8×8-bit pipelined Baugh–Wooley multiplier is implemented, on which several experiments reveal a perfect tolerance (0% errors) to single line discrepancies for both primary and internal nodes, with a cost of lost clock periods between 6% and 25%. The error ratio for the proposed Turtle Logic implementation with double discrepancies in both true and complementary lines are lower than 0.1% when the noise affects primary input nodes, and lower than 0.9% when the noise affects internal nodes.     

Quench analysis of a superconducting magnet with 98 coils connected in series

A novel insertion device for electron storage rings called the MAX-Wiggler has been constructed at MAX-lab. The MAX-Wiggler is a cold bore superconducting wiggler magnet with 47 3.5-T poles and a period length of 61 mm aimed for the production of X-rays at the 1.5-GeV electron storage ring MAX-II at MAX-lab. The MAX-Wiggler consists of 98 racetrack coils connected in series in the superconducting magnet and the total stored magnetic energy at the nominal maximum field strength of 3.5 T is 48 kJ. This paper describes the quench analysis of the magnet. Several protection schemes have been evaluated, such as an external dump resistor and safety switch or subdivision of the series of coils into sections with shunt resistors or silicon diodes in parallel to each group of coils in a section. It has been found that the most suitable protection scheme, in order to prevent the superconducting coils from getting overheated, is subdivision with a shunt path containing silicon diodes operating at liquid helium temperatures. The MAX-Wiggler has been commissioned and it has survived the quenches occurring during the initial training of the superconducting coils.     

窄带低频率高温超导滤波器的设计

高温超导滤波器具有带内插入损耗小、带边陡峭、带外抑制性好等优势,可以有效提高通信系统的抗干扰性能,节约频率资源。谐振器是实现高温超导滤波器的重要单元。本文给出了一款新型谐振器,该谐振器结构紧凑、调节方便,并且使用这种谐振器设计了一款十二阶的窄带低频高温超导滤波器。     

Development of a MAGLEV superconducting magnet for the Yamanashitest line in Japan: vibration characteristics and analysis for design

A high-performance and high-reliability magnetically levitated (MAGLEV) superconducting magnet (SCM) was developed. Its heat generation per unit time by the electromagnetic forces due to the spatially fifth ripple magnetic fields from levitation coils is under 2 W at the frequency range in which vehicles are levitated. The vibration mode of inner vessels that makes the largest contribution to heat generation in SCMs is clarified, the torsion mode. A modeling method to analyze SCM vibration, which considers the effect of the bogie frames of a vehicle, is examined, and heat generation in SCMs is calculated from the vibration of the inner vessel. Using the numerical analysis method, new SCMs combined with new bogie frames for the Yamanashi Test Line are designed. Good performance in vibration and heat generation of these SCMs is predicted by numerical analysis     

基于UC3906与单片机结合的光伏发电小系统设计

论文系统设计了包括太阳能电池板、充放电控制器控制蓄电池充放电、液晶显示电路、铅酸电池、逆变模块、直流电流逆变为交流电、负载供电的太阳能光伏发电小型系统。经性能指标测试,过压、过放、反接、短路等各种电路保护功能完好,能在液晶显示器上实时显示蓄电池的电压和放电电流值,逆变控制电路输出的正弦波交流电波形畸变小,电压、频率稳定。     

基于UC3906与单片机结合的光伏发电小系统设计

论文系统设计了包括太阳能电池板、充放电控制器控制蓄电池充放电、液晶显示电路、铅酸电池、逆变模块、直流电流逆变为交流电、负载供电的太阳能光伏发电小型系统。经性能指标测试,过压、过放、反接、短路等各种电路保护功能完好,能在液晶显示器上实时显示蓄电池的电压和放电电流值,逆变控制电路输出的正弦波交流电波形畸变小,电压、频率稳定。     

A novel dual-axis repulsive Maglev guiding system with permanent magnet: modeling and controller design

In this paper, we extend our previous result (1999, 2000) on designing a single-axis Maglev guiding system to a more involved task of designing a novel dual-axis positioning system. First, important issues related to construction of the mechanism of the dual-axis positioning system are addressed. Then, the dynamics of the dual-axis Maglev guiding system are analyzed. According to the derived analytic model, which is subject to unknown system parameters, an adaptive controller that can control the carrier at the desired target point of each axis with full alignment is presented. From the experiment results, a good performance in terms of regulation of the guiding-axis and tracking of the positioning-axis is achieved. This validates the design of the system hardware and demonstrates the feasibility of the developed controller.     

Estimating the bias field of MR images

The authors propose a modification of Wells et al. (ibid., vol. 15, no. 4, p. 429-42, 1996) technique for bias field estimation and segmentation of magnetic resonance (MR) images. They show that replacing the class other, which includes all tissue not modeled explicitly by Gaussians with small variance, by a uniform probability density, and amending the expectation-maximization (EM) algorithm appropriately, gives significantly better results. The authors next consider the estimation and filtering of high-frequency information in MR images, comprising noise, intertissue boundaries, and within tissue microstructures. The authors conclude that post-filtering is preferable to the prefiltering that has been proposed previously. The authors observe that the performance of any segmentation algorithm, in particular that of Wells et al. (and the authors' refinements of it) is affected substantially by the number and selection of the tissue classes that are modeled explicitly, the corresponding defining parameters and, critically, the spatial distribution of tissues in the image. The authors present an initial exploration to choose automatically the number of classes and the associated parameters that give the best output. This requires the authors to define what is meant by “best output” and for this they propose the application of minimum entropy. The methods developed have been implemented and are illustrated throughout on simulated and real data (brain and breast MR)     

Effects of high electric field and elevated-temperature bias stressing on radiation response in power VDMOSFETs

The effects of pre-irradiation high electric field and elevated-temperature bias stressing on radiation response of power VDMOSFETs have been investigated. Compared to unstressed devices, larger irradiation induced threshold voltage shift and mobility reduction in high electric field stressed devices have been observed, clearly demonstrating inapplicability of electrical stressing for radiation hardening of power MOSFETs. On the other hand, larger irradiation induced threshold voltage shift in elevated-temperature bias stressed, and more considerable mobility reduction in unstressed devices have been observed, confirming the necessity of performing the radiation qualification testing after the reliability screening of these devices. The underlying changes of gate oxide-trapped charge and interface trap densities have been calculated and analysed in terms of the mechanisms responsible for pre-irradiation stress effects.     

一种高压电晕检测系统的设计

在当今电晕放电现象检测研究领域中,多数检测方法对检测环境有严苛要求且检测过程中易产生较大误差。针对这一问题,设计了一种高压电晕检测系统,该系统通过对电晕放电产生的电磁波进行检测,由观测波形来判断电晕放电是否发生。重点设计了低噪声放大器和差分放大器等前端硬件部分,另外简单介绍了系统中信号采集和数字信号处理等后端部分,最后检测平台经现场测试具有误差小且能够实现200 m以内电晕放电检测的目标。     

Hysteresis of superconducting cylinder in transverse magnetic field

A piecewise continuous distribution of critical currents is used to predict the hysteresis of the superconducting cylinder in the transverse magnetic field slowly oscillating in time. The proposed hysteresis model takes into account that the magnetic field has the peripheral and radial components due to the screening effect of critical currents. The model is used to predict the hysteresis loss in a round superconducting wire. An analytical formula for the hysteresis loss is given     

偏视场光学系统中心遮光罩设计

对偏视场光学系统的遮光罩进行优化设计。偏视场在一个方向上非对称，设计主镜内遮光罩需要进行光线追迹，难度大。采用痕迹图方法获得光线在空间的位置坐标，确定系统有效视场大小及挡光部分位置，对内遮光罩的挡光部分进行开口处理，得到一个上短下长的特殊鸭嘴型遮光罩，降低设计难度。经过优化分析，最终的主镜内遮光罩沿Z轴方向的尺寸缩减为原来的一半，在Y轴方向上尺寸减小来降低非有效视场的大小。使用TracePro软件对设计好的遮光罩进行建模、仿真，得到PST在离轴角度为30时达到10-9量级，小于系统的5.5910-7指标要求。结果表明:使用痕迹图法对偏视场光学系统的主镜内遮光罩进行设计是可行的。     

基于高压脉冲电场技术的污水处理系统研究设计

针对污水处理厂剩余污泥含水率高,达到70%~80%,不利于进一步处理的问题,根据污水成分及其处理工艺特点,提出了一种基于高压脉冲电场技术的污水处理的方法。本文从理论上系统地阐述了高压脉冲电场处理装置的研制,设计了低成本高压脉冲电源,最高电压10 kV,最大电流50 A,并且能方便的调节电场参数。     

脉冲激光测距中高速精密时间间隔测量研究

在脉冲激光测距系统中,设计实现了基于FPGA和TDC-GP21的高速精密时间间隔测量系统。采用TDC-GP21的高精度测量模式,配置TDC-GP21完成了时间间隔测量,通过校准测量对测量结果进行补偿修正,提高了系统的测量精度;设计了多级嵌套状态机实现高速SPI通信,减小了系统单次测量周期;分析了影响测量精度的因素,比较分析了3种时刻鉴别方法的漂移误差,设计了高通阻容时刻鉴别模块,减小了系统的非线性误差。实验分别进行了基于FPGA脉冲信号的时间间隔测量和激光测距试验,对比验证了系统的测量误差,分析了系统在测量区间的线性度。实验结果表明,系统可以实现高速稳定测量,线性度良好,重复测量频率达1kHz,测量精度在±100ps内。     

4f光学系统制造理论高相似度无衍射光的参数研究

利用4f光学系统,可以产生多类型、高功率的无衍射光.然而,以前的研究主要集中在制造特定的无衍射光的光学应用中.首次综合分析了四类无衍射光在特定环宽的4f系统光强分布特性,利用傅里叶光学计算,首次分析四种类型无衍射光还原理论模型的优劣性,并发现所有的无衍射光的光强分布相似度会随着角谱采样的上升而下降的规律,用对应光学实验...