An Accelerated Simulation Method for ELDRS of Bipolar Operational Amplifiers Using a Dose-Rate Switching Experiment

Through different dose-rate switching evaluation methods,the radiation-response rules of operational amplifiers are studied when the irradiation dose rate is switched from high to low under different radiation temperatures and total doses. The experimental results indicate that the response characteristics could be affected by the switching total doses, irradiation temperatures,and dose rates individually or together. Accelerated evaluation on the ELDRS can be realized by adopting a proper dose-rate switching method. Meanwhile, the irradiation time can also be reduced. Finally, the mechanisms of the difference between various radiation responses are analyzed.

Switching variability index based multiple strategy CFAR detector

A switching variability index （SVl） constant false alarm rate （CFAR） detector is proposed for improving the detection performance of VI-CFAR detectors in multiple targets backgrounds. When the presence of non-homogeneity in CFAR reference windows is indicated by a VI-CFAR detector, a switching- CFAR detector is introduced to optimize the performance of the VI-CFAR detector in homogeneous, multiple targets and clutter edge backgrounds. The structure and parameters selection method of the SVI-CFAR detector is presented. Comparisons with classic CFAR detectors and recently proposed detectors are also given. Theoretical analysis and simulation results show that SVICFAR detector maintains the good performance of the VI-CFAR detector in homogeneous and clutter edge backgrounds, while greatly improving the capacity of anti-multi targets.

气体火花间隙开关通道电阻及热效应特性研究

针对一种应用于高功率重复频率Marx型脉冲功率源的两电极火花间隙气体开关,开展了火花通道电阻及其热效应特性研究,分析了火花间隙通道电阻热效应的影响因素,研究了重复频率连续工作条件下开关腔体内温度及气压变化。研究结果表明,开关腔体内气压和温度随着工作时间增长呈现先快速增加然后缓慢增长趋于稳定的趋势,脉冲电流幅值的增长对热量沉积的增加效果非常明显。研制的两电极火花间隙开关,在导通峰值电流14.7 kA、脉冲宽度160 ns的条件下连续运行9000个脉冲时,开关通道产生热量约36.6 kJ,在电流导通时间内,通过焦耳热效应计算得到开关导通时间内火花通道电阻平均值约0.12Ω。

蝴蝶优化算法对大青杨生长速率预测模型的改进

为提高大青杨生长速率的预测精度,提出了一种基于改进的蝴蝶优化算法(improved butterfly optimization algorithm, IBOA)与径向基函数(radial basis function, RBF)神经网络结合的预测木材材性方法。通过使用佳点集法对标准蝴蝶算法中的种群进行初始化,将自适应切换频率和Levy飞行相结合进一步优化人工蝴蝶算法。构建出了新的IBOA-RBF神经网络木材材性预测模型,将得到的结果与其他几种算法优化的RBF神经网络预测结果进行对比。结果表明:基于IBOA-RBF神经网络模型预测效果最好,收敛速度从37步降低到了23步,预测结果误差达到了5.72%,预测精度最高。可见,对蝴蝶算法的改进是可行的,且对相关人员定向培养大青杨起到较大的帮助。

左乙拉西坦品牌药转为非专利药后对癫痫患儿的临床疗效和不良反应分析

目的前瞻性观察左乙拉西坦(LEV)由品牌药转换为非专利药后对癫痫患儿的临床疗效和不良反应变化。方法以2019年4月至2020年12月在西安交通大学第二附属医院儿科就诊的196例癫痫患儿为研究对象,收集其从LEV品牌药转换为非专利药治疗前后的临床资料,并根据转换后疾病发作情况分为发作增加组、发作减少组及发作无变化组。分析转换前后各组LEV血药浓度、癫痫发作情况、不良反应及转换后发作增加患儿的临床特征。结果转换前LEV血药浓度为(8.09±2.42)μg/mL,转换后血药浓度为(8.28±2.17)μg/mL,经比较差异无统计学意义(t=0.521,P=0.831)。转换前LEV治疗剂量/血药浓度比值为(3.44±1.10)L/kg,转换后治疗剂量/血药浓度比值为(3.77±1.59)L/kg,经比较差异无统计学意义(t=0.723,P=0.762)。转换前LEV的治疗有效率为81.05%(154/190),转换为非专利药后有效率为75.79%(144/190),经比较差异无统计学意义(χ^(2)=1.555,P=0.212)。发病年龄小及联合治疗的患儿在转换后可能会出现发作增加,LEV品牌药转换为非专利药后,未见出现新的不良反应。结论LEV品牌药转为非专利药后对癫痫患儿治疗安全有效,对发病年龄小及联合治疗的患儿需要重点关注。

A Novel Dual-Rate Sampling Switched-Capacitor Configuration and Its Application

In order to realize accurate bilinear transformation from s- to z-domain,a novelswitched-capacitor configuration is proposed in the light of principles of dual-rate sampling and chargeconservation,which has also been used for building a 5th-order elliptic lowpass filter.The filter issimulated and measured in typical 0.34 μm/3.3 V Si CMOS process models,special full differentialoperational amplifiers and CMOS transfer gate switches,which achieves 80 MHz sampling rate,17.8MHz cutoff frequency,0.052 dB maximum passband ripple,42.1 dB minimum stopband attenuation and74 mW quiescent power dissipation.At the same time,the dual-rate sampling topology breaks thetraditional restrictions of filter introduced by unit-gain bandwidth and slew rate of operational amplifiersand also improves effectively their performances in high-frequency applications.It has been applied forthe design of an anti-alias filter in analog front-end of video decoder IC with 15 MHz signal frequencyyet.

高速铁路道岔的大修周期

基于高速道岔钢轨及弹性铁垫板的部件劣化规律,提出高速道岔大修周期建议。结果表明:高速道岔混凝土岔枕及无砟轨道设计使用寿命较长,大修应以成组更换道岔钢轨及联结零件为主;成组更换道岔曲外股钢轨应以辙叉翼轨侧面磨耗达到8 mm重伤限值为准,宜按照维修进行更换。成组更换道岔钢轨的周期为通过总质量450~900 Mt或服役时间19~45年,更换道岔弹性铁垫板的周期宜定为20年。建议高速道岔成组更换钢轨及联结零件的大修周期定为年通过总质量600 Mt或服役时间20年,且应根据道岔实际状态评估后决定是否列入大修计划。

LTD多间隙气体开关低概率自放电估计

开关触发前发生的低概率自击穿故障,是制约直线变压器驱动源(LTD)技术发展和工程应用的主要因素。针对多间隙气体开关的自放电概率展开研究,设计了简化结构的气体开关来测量更高气压下的自击穿电压;推导了考虑间隙分压不均的开关自击穿电压累积分布函数,计算LTD工作气压下的多间隙开关自击穿电压分布特性并进行实验验证;通过超越阈值方法对低工作系数下的小概率自放电事件进行威布尔分布拟合,得到自放电概率估计值;对气体开关开展了万发次考核实验,得到自放电概率测量值。结果表明:开关的自击穿电压分散性随着气压升高而增加,测量低气压下的自击穿电压无法外推得到实际工作高气压条件下的自放电概率;开关工作系数为65%和60%时,气体开关的自放电概率估计值为1:44×10^(-4)和3:01×10^(-5),与开关万发次考核的实验结果相近,验证了估计方法的可行性。

基于排序的自动剔除Switching-CFAR检测器

针对传统恒虚警(Constant False-Alarm Rate,CFAR)检测器在非均匀噪声环境下检测性能较差的问题,本文提出了一种基于排序的自动剔除Switching-CFAR(Automatic Censoring Switching-CFAR Detector Based on Sorting,ACS-CFAR)检测器.选择参考窗中间单元为测试单元,其余单元按照幅值升序排列,根据两个分界点位置参数,选择合适的参考单元集进行背景噪声功率估计以及结合参考单元数和目标恒虚警率计算相关系数,得到最优检测门限.经过仿真对比,ACS-CFAR检测器在均匀噪声环境下检测率为98.73%,接近于单元平均恒虚警(CA-CFAR)检测器;在非均匀噪声环境下检测率为98.16%,优于可变索引恒虚警(VI-CFAR)和自动删除平均恒虚警(ACCA-CFAR)检测器,虚警率误差均控制在0.10%以内.结果表明,本文提出的ACS-CFAR检测器在均匀噪声环境以及杂波和多目标干扰环境下均具有较好的检测性能.

四能级模型声光调Q CO_(2)激光器理论数值模拟

声光调Q CO_(2)激光器因其具有特定波长传输效率理想、光束聚焦性能好、连续功率高、输出脉冲大等特点,被广泛应用在激光测距、生产加工、空间通信、光谱学、环境探测、雷达成像领域中。文章考虑声光损耗情况下基于四能级模型给出了声光调Q CO_(2)激光器速率方程,在一定条件下通过离散迭代的方式对该速率方程组进行数值模拟,分析了声光调Q CO_(2)激光器的运行特性,以在生产研究中更好地使用、设计CO_(2)激光器。

浅谈PLC PID回路切换的稳定控制

PID控制器是工业自动化控制领域中应用最为广泛的一种算法控制器,在各种工业控制器上都集成有PID控制功能实现温度、压力等物理量的控制。主要讨论液压系统的流速和压力闭环控制和两种控制之间的切换,控制对象是液压伺服比例阀。工艺要求先流速控制再切换到压力控制,在项目后期调试过程中,两个PID回路的切换时刻,需要通过一种控制方法实现液压伺服比例阀的稳定控制。

Experimental Study of the Recovery Times of Spark Gap Switch with Different Gases

A two-pulse method is used to determine the insulation recovery time of the gas spark gap switch with different types of gas applied in a high power accelerator with a water dielectric pulse forming line. At the breakdown voltage of 450 kV, with the vacuum diode voltage of about 200 kV, and a current of 30 kA, recovery characteristics of H2, N2, SF6 were studied. The recovery percentages of the gas breakdown voltage and vacuum diode voltage were determined. The results show that hydrogen has the best recovery characteristics. At a pulse interval of 8.8 ms, the recovery percentages of both the gas breakdown voltage and vacuum diode voltage for hydrogen exceed 95%. For SF6 and N2 with an interval of 25 ms and 50 ms respectively, a 90% voltage recovery was obtained. The experiments also proved that the repetitive rate of the high power accelerator with a pulse forming line is mainly restricted by the gas switch repetitive rate; the recovery percentages of the vacuum diode voltage are limited by the recovery percentages of the gas switch breakdown voltage. The hydrogen switch can be employed for a high repetitive rate-high power accelerator with a pulse forming line.

基于QFSK调制的DC-DC变换器功率/数据复合传输方法

传统电力线通信方案的硬件设计较为复杂。DC-DC变换器具有发送数据的潜能,可进行功率/数据复合传输。文中提出一种基于四进制频移键控(QFSK)调制的电力电子开关调制方案,通过调制开关频率将数据信息嵌入原始脉宽调制(PWM)信号中,使得电压纹波携带数据的频率特征;再通过基于滑动离散傅里叶变换的解调方案实现数据接收,最终实现功率/数据的同步传输。首先,证明了PWM信号与电压纹波频率一致的关系;然后,给出数据调制与解调的方案;以负载突变工况为例,通过对Buck变换器建模,分析功率变换暂态过程对通信的干扰影响;最后,搭建由两个Buck变换器组成的实验平台,验证了所提方案可实现20 kbit/s的通信速率;并以光伏优化器为应用背景,验证了所提方案的有效性。

考虑移动储能的风雨灾害配电网弹性提升方法

以台风和暴雨为代表的极端自然灾害会导致配电网大规模故障。为减小故障损失,提出一种计及风雨联合灾害下考虑移动储能的配电网弹性提升方法。首先,量化台风和暴雨灾害对配电网造成的影响,构建风雨联合灾害下的配电网故障率模型并基于系统信息熵筛选典型故障场景;其次,以灾害期间切负荷经济损失最小为目标,建立混合整数二阶锥规划模型,提出计及弹性提升的移动储能运行调度方法;最后,通过仿真算例对所提方法的有效性进行验证。结果表明,本文所提方法能有效提升配电网弹性,减少停电带来的经济损失。

Modelling of passively Q-switched lasers with intracavity Raman conversion

We present a model of passively Q-switched Raman lasers by utilizing the rate equations. The intracavity fun-damental photon density, Raman photon density and the initial population-inversion density of the gain medium are assumed to be of Gaussian spatial distributions. These rate equations are normalized by introducing some synthetic parameters and solved numerically, and a group of general curves are generated. Prom these curves we can understand the dependence of the Raman laser pulse characteristics on the parameters about the pumping, the gain medium, the Raman medium and the resonator. An illustrative calculation for a passively Q-switched Nd^3＋：GdVO4 self-Raman laser is presented to demonstrate the usage of the curves and related formulas.

A theoretical and experimental investigation of an in-band pumped gain-switched thulium-doped fiber laser

In this paper, the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber （TDF） laser is investigated. The analytical formulations of pump energy threshold, peak power extraction efficiency, and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse. They are useful for understanding, designing, and optimizing the in-band pumped TDF lasers in a 1.9 μm-2.1 μm wavelength region. The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted, and our experimental results show good agreement with theoretical analysis.

Simulation of the Physical Performance of Optical Packet Switching Nodes

A graphical and visual simulation system for the study of optical packet switching (OPS) nodes is accomplished. With the simulation system, the effect on physical performance-bit error rate (BER) due to a variety of factors such as the crosstalk parameters of OPS nodes, number of cascaded OPS nodes, length of optical output buffer, traffic load and fluctuation of amplitude of optical signals are evaluated. Reliability of the simulation system is proved by the analytical results obtained in all the above cases.

A Network Calculus Approach for the Analysis of Packet-switching Networks

Network calculus is an evolving new methodology for backlog and delay analysis of packet-switching networks. With network calculus we are able to compute tight bounds on delays,backlogs,and effective bandwidths in a lossless setting applicable to packet-switching networks and better understand some physical properties of networks. In this paper,the basic network calculus concepts of arrival curves and service curves are introduced.Then we provide the approach for modeling leaky-bucket,generic cell rate algorithm(GCRA),constant bit rate(CBR)flow, variable bit rate(VBR) flow with arrival curve.It is shown that all rate-based packet schedulers can be by a simple rate latency service curve.And by applying these fundamental rules of network calculus,bounds on delay, buffer,effective bandwidth for leaky bucket,GCRA,CBR and VBR can be derived and some practical examples are given.Finally,we compare all the results obtained and conclude this paper.

100 kHz高功率高光束质量纳秒激光振荡器

高功率、高重复频率纳秒脉冲激光广泛应用于激光切割、激光焊接等领域。随着激光重复频率的提升,特别是高于50 kHz时,单个周期有限的时间内难以积累足够的上能级粒子,调Q脉冲的稳定性成为了激光器设计的难点。当前主要采用主振荡器的功率放大器(MOPA)方案,直接振荡获得兼具高功率、高重复频率及高光束质量的纳秒脉冲激光还比较困难。通过对激光动力学过程的仿真模拟,定量分析了高重复频率调Q过程中脉冲强度稳定性与泵浦速率的关系,并利用负透镜使振荡器工作在具有较大基模体积的热近非稳区,实现了Nd:YAG声光调Q激光振荡器在高重复频率、高功率、高光束质量三方面的均衡设计。首次利用侧泵模块实现了100 kHz高功率高光束质量纳秒脉冲激光的直接振荡产生,脉冲强度的离散系数仅为0.041,激光输出功率超过142 W,脉冲宽度为165 ns,光束质量因子M^(2)为1.5。

P2.5-PHPS发动机至混合驱动模式切换过程动态协调控制研究

搭载双离合变速器的P2.5插电式混合动力系统传动效率高,换挡和模式切换过程无动力中断,应用前景广阔,但其模式切换过程由于发动机与电机的扭矩响应特性存在差异,扭矩波动明显,影响驾乘体验。针对上述问题,提出一种发动机驱动至混合驱动模式切换的协调控制策略,以搭载双离合变速器的P2.5插电式混合动力系统为研究对象,对其发动机至混合驱动模式切换过程进行分析,依据分析结果将系统模式切换过程划分为4个阶段。在此基础上,基于PID反馈原理控制动力源的实际输出转矩并通过控制加速踏板开度变化率限制发动机的扭矩变化率,利用驱动电机扭矩快速响应的优势补偿发动机扭矩响应滞后来降低输出扭矩波动,制定模式切换过程多阶段双动力源扭矩协调控制策略。搭建基于P2.5插电式混合动力系统的发动机至混合驱动模式切换动态协调控制仿真模型。仿真结果表明,模式切换过程无动态协调控制策略的最大冲击度约7.1 m/s^(3),策略下最大冲击度约1.78 m/s^(3),减小74.9%,表明所提出的控制策略能有效减小模式切换过程冲击度,提高整车平顺性。