The nonlocal transport and switch effect in light-and electric-controlled silicene–superconductor hybrid structure

We theoretically investigate the influence of off-resonant circularly polarized light field and perpendicular electric field on the quantum transport in a monolayer silicene-based normal/superconducting/normal junction.Owing to the tunable band structure of silicene,a pure crossed Andreev reflection process can be realized under the optical and electrical coaction.Moreover,a switch effect among the exclusive crossed Andreev reflection,the exclusive elastic cotunneling and the exclusive Andreev reflection,where the former two are the nonlocal transports and the third one is the local transport,can be obtained in our system by the modulation of the electric and light fields.In addition,the influence of the relevant parameters on the nonlocal and local transports is calculated and analyzed as well.

Switching effects in superconductor/ferromagnet/superconductor graphene junctions

The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.

Improvement of switching characteristics by substrate bias in AlGaN/AlN/GaN heterostructure field effect transistors

A simple and effective approach to improve the switching characteristics of AlGaN/AlN/GaN heterostructure field effect transistors （HFETs） by applying a voltage bias on the substrate is presented. With the increase of the substrate bias, the OFF-state drain current is much reduced and the ON-state current keeps constant. Both the ON/OFF current ratio and the subthreshold swing are demonstrated to be greatly improved. With the thinned substrate, the improvement of the switching characteristics with the substrate bias is found to be even greater. The above improvements of the switching characteristics are attributed to the interaction between the substrate bias induced electrical field and the bulk traps in the GaN buffer layer, which reduces the conductivity of the GaN buffer layer.

Skin Effect of Reversely Switched Dynistor in Short Pulse Discharge Application

The skin effect in the reversely switched dynistor （RSD） devices is investigated in this paper. Based on the plasma bipolar drift model of the RSD, the current density distributions on the chip are simulated with considering the skin effect. The results indicate that the current density on the border can be several hundred to a thousand A/cm2 higher than that in the center of the chip. The skin effect becomes more prominent as the voltage increases and the inductance decreases in the main circuit. The phenomenon that most of a certain group of chips break over on the border has proved the existence of the skin effect.

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。

互联网使用对稻农收入的影响研究——基于生产环节信息获取的实证

增加农民收入是我国“三农”工作的核心任务。互联网在农业主体中的普及和应用已经逐步渗透到农业生产全过程,对农民收入增长产生重要影响。以湖北省1110个水稻种植户为实证研究对象,利用内生转换模型探究农户在生产环节使用互联网获取信息对其农业收入的影响。研究结果表明:使用互联网能够显著促进农户农业收入增长。在采用替换模型方法和不同被解释变量进行再估计后,结果依然稳健。机制分析显示,互联网使用通过提升农户生产技术效率、土地生产率和劳动生产率实现农业收入的增长。此外,互联网使用对人力资本水平高、家庭经营土地规模大、初始农业收入高的农户增收效果更为明显。因此,政府应通过以下措施助力农户利用互联网增收:继续加快数字乡村建设,完善农村互联网基础设施,推进互联网在涉农主体中的普及和应用;开展基础教育与技能培训;对低收入群体提供精准信息供给服务,推进信息资源下沉。

芪参补气活血养颜汤联合Q开关Nd∶YAG激光治疗女性黄褐斑的美学效果观察

目的:探讨芪参补气活血养颜汤联合Q开关Nd∶YAG激光治疗女性黄褐斑的美学效果。方法:选取笔者医院2019年1月-2022年1月收治的80例黄褐斑女性作为研究对象,按照随机数字表法分为观察组42例(采用芪参补气活血养颜汤联合Q开关Nd∶YAG 1064 nm激光治疗)和对照组38例(采用Q开关Nd∶YAG 1064 nm激光治疗)。观察两组的临床疗效,中医症状积分,皮肤状况,黄褐斑面积及颜色,不良反应发生率。结果:治疗后,观察组患者的总有效率为97.62%,高于对照组患者的84.21%(P<0.05)。治疗后,观察组患者情绪低落、胸胁胀痛、经行乳胀、口苦咽干等上述中医症状积分均低于对照组患者(P<0.05)。治疗后,观察组黑素指数、红斑指数及皱纹指数均低于对照组(P<0.05)。治疗后,观察组黄褐斑面积及颜色评分均低于对照组(P<0.05)。治疗后,观察组患者的总不良反应发生率与对照组患者比较差异无统计学意义(P>0.05)。结论:芪参补气活血养颜汤联合Q开关Nd∶YAG1064 nm激光能够提高黄褐斑治疗的临床疗效,改善患者临床症状,改善皮肤状况,减少黄褐斑面积及颜色,安全性较高,值得临床推广。

SiC MOSFET开关瞬态解析建模综述

在评估和优化半导体器件开关瞬态特性领域,解析模型因具有简单、直观、应用便捷等优点得到广泛研究。相较同等功率等级的硅基功率器件,碳化硅(silicon carbide,SiC)金属氧化物半导体场效应晶体管(metal-oxide-semiconductor field effect transistor,MOSFET)可以应用于更高开关速度,其开关瞬态特性更为复杂,开关瞬态解析建模也更加困难。该文总结现有的针对SiC MOSFET与二极管换流对的开关瞬态解析建模方法,在建模过程中依次引入各种简化假设,按照简化程度由低到高的顺序,梳理解析建模的逐步简化过程。通过对比,评估各模型的优缺点以及适用场合,对其中准确性、实用性都较强的分段线性模型进行详细介绍;之后,对开关瞬态建模中关键参数的建模方法进行总结与评价;最后,指出现有SiC MOSFET开关瞬态解析模型中存在的问题,并对其未来发展给出建议。

热开关装置及在电卡制冷原型器件中的研究进展

电卡效应制冷是一种新兴的绿色固态制冷技术,由于具有成本低、COP高及可微型化等优点被认为是取代传统压缩机制冷的选择之一。现今阻碍电卡制冷器件应用的主要问题是电卡材料单片温变不足,在器件设计中采用回热式或串联式结构可将材料温变放大至工程应用量级。介绍了串联式电卡制冷器件中热开关装置的概念、性能指标及目前国内外相关研究成果并结合电卡效应原理分析了不同种类热开关在电卡制冷器件中的适配性。介绍了回热式和串联式电卡制冷原型器件的研究成果,基于串联式电卡制冷器件进行模拟计算,分析热开关装置的性能对制冷器件性能的影响。串联式结构理论上更适配于电卡制冷器件,利用电场驱动流体介质的热开关装置响应速度快、断开热阻大的特点可以帮助串联式电卡制冷器件突破现今技术瓶颈,从而发挥电卡制冷技术在各制冷系统领域的技术潜力。

Switching effect on a two prey-one predator system with strong Allee effect incorporating prey refuge

In an environment,the food chains are balanced by the prey-predator interactions.When a predator species is provided with more than one prey population,it avails the option of prey switching between prey species according to their availability.So,prey switching of predators mainly helps to increase the overall growth rate of a predator species.In this work,we have proposed a two prey-one predator system where the predator population adopts switching behavior between two prey species at the time of consumption.Both the prey population exhibit a strong Allee effect and the predator population is considered to be a generalist one.The proposed system is biologically well-defined as the system variables are positive and do not increase abruptly with time.The local stability analysis reveals that all the predator-free equilibria are saddle points whereas the prey-free equilibrium is always stable.The intrinsic growth rates of prey,the strong Allee parameters,and the prey refuge parameters are chosen to be the controlling parameters here.The numerical simulation reveals that in absence of one prey,the other prey refuge parameter can change the system dynamics by forming a stable or unstable limit cycle.Moreover,a situation of bi-stability,tri-stability,or even multi-stability of equilibrium points occurs in this system.As in presence of the switching effect,the predator chooses prey according to their abundance,so,increasing refuge in one prey population decreases the count of the second prey population.It is also observed that the count of predator population reaches a comparatively higher value even if they get one prey population at its fullest quantity and only a portion of other prey species.So,in the scarcity of one prey species,switching to the other prey is beneficial for the growth of the predator population.

一种半桥LLC高压电源设计与实现

设计一种基于半桥LLC谐振变换器的高压电源,其基本结构包括逆变电路、谐振电路、倍压整流电路和反馈控制电路,可用于微波功率模块集成电源。为实现高压电源的高效率,详细分析了半桥LLC谐振电路中场效应管零电压开启的实现条件,并给出了实现该条件所需电路关键参数的计算方法。通过计算机仿真辅助优化电路参数,降低了场效应管和变压器的损耗。最后,研制了一台高压电源原理样机,其输出电压为-3000 V,满载输出功率为300 W,在245~300 V输入电压范围内效率大于96%,峰值效率为97.5%。

煤矿地面供电系统的优化改造及应用分析

针对煤矿地面供电系统存在稳定性、可靠性相对较低的不足,以监测矿用供电系统所用的10 kV开关柜运行情况为研究对象,基于该种开关柜的运行特点与监测需求,为10 kV开关柜设计了运行监测系统,介绍了该监测系统的总体结构,设计了该系统的硬件部分与软件部分,进行了工业性试验。试验结果表明,应用该监测系统来监测10 kV开关柜运行情况,可精准地记录断路器机械性能与动作情况,有助于进一步了解开关柜运行情况,提升矿井供电系统工作的稳定性、可靠性。

审计师变更的“新视角”效应——基于关键审计事项披露的文本证据

审计师变更能否给当期财务报表审计带来“新视角”进而改善审计质量一直是审计理论实证研究的难点。基于关键审计事项(CAM)披露的文本信息,本文实证考察了审计师变更的“新视角”效应。研究发现,审计师变更显著降低了公司本期CAM与上期的纵向文本相似度。相比重新上任,完全履新的审计师变更降低程度更大;“换师换所”和“换师不换所”均具有降低作用,但前者影响更大;相比只变更项目合伙人或经理,两者同时变更的降低作用最大;而且,降低作用主要集中于行业专长审计师。最后发现,变更公司CAM纵向相似度越低,审计投入越多、审计质量越高、信息有用性越强。研究拓展了审计师变更和CAM披露文献,为审计师轮换制度与新版审计报告准则实施提供了经验参考。

Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method

The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell＇s equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.

磁控开关的研究与应用

目前水位检测在产品上的多为干簧管类,应用成熟但需要有导线引入到开关上;磁控类开关通过磁场感应导线不与水接触,安全可靠性高,但产品应用不成熟,大多靠测试定义产品性能,由于磁控可有效利用距离小,容易出现问题。鉴于磁控开关在水位检测上突出的优势,本文根据磁控开关的工作原理,建立浮子永磁体模型,通过仿真得到永磁体磁场空间分布,结合霍尔电气性能,匹配合适的磁控开关有效控制距离;再通过磁控开关实际应用测试,定义开关的有效行程,从而实现磁控开关的有效应用。该研究为此类磁控开关的应用有指导意义。

农业生产者绿色生产要素投入行为的收入效应

以有机肥和生物农药两类绿色投入品为例,运用内生转换回归模型,实证分析农业生产者绿色生产要素投入行为的收入效应,并运用无条件分位数回归进行异质性分析。研究表明:(1)绿色生产要素投入行为受到内外部因素的影响,不同绿色生产要素的投入行为影响因素有所差异;(2)不同绿色生产要素投入决策条件下农业收入的影响因素有较大差异,新型农业经营类型能够显著提高农业收入;(3)绿色生产要素投入行为具有正向收入效应;(4)有机肥投入随着农业收入的提升,影响程度有逐渐递减趋势,生物农药投入对农业收入的影响程度呈现“倒U”型特征,不同主体类型和地理区域对不同农业收入水平的影响程度存在显著差异。

High-speed 2 × 2 silicon-based electro-optic switch with nanosecond switch time

A 2 × 2 electro-optic switch is experimentally demonstrated using the optical structure of a Mach-Zehnder interferometer （MZI） based on a submicron rib waveguide and the electrical structure of a PIN diode on silicon-on-insulator （SOI）. The switch behaviour is achieved through the plasma dispersion effect of silicon. The device has a modulation arm of 1 mm in length and cross-section of 400 nm×340 nm. The measurement results show that the switch has a VπLπ figure of merit of 0.145 V.cm and the extinction ratios of two output ports and cross talk are 40 dB, 28 dB and -28 dB, respectively. A 3 dB modulation bandwidth of 90 MHz and a switch time of 6.8 ns for the rise edge and 2.7 ns for the fall edge are also demonstrated.

Transport properties and anomalous fatigue effect of Ag/Bi_(0.9)La_(0.1)FeO_3/La_(0.7)Sr_(0.3)MnO_3 heterostructures

The transport properties and fatigue effect of Ag/Bi0.9La0.lFeO3/La0.7Sr0.3MnO3 heterostructures are described. By examining the I-V curves, an anomalous fatigue effect was found and its influences on resistive states were studied. I-V curves combined with C-f spectra were used to directly analyze the transport properties and fatigue effect. Compared to the first I-V cycle state, this structure shows more than one order increase of resistance after 100 cycles of ＂I-V curve training＂. The redistribution of oxygen vacancies in the depletion layer of Ag/Bi0.9La0.lFeO3 is believed to be responsible for the different resistance mechanisms and tenfold magnitude drop in resistance. The resistive switching is understood to be caused by electric field-induced carrier trapping and detrapping, which changes the depletion layer thickness at the Ag/Bi0.9La0.lFeO3 interface.

Three-dimension micro magnetic detector based on GMI effect

The giant magneto-impedance（GMI）effect of amorphous wire was analyzed theoretically.The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680kHz and18 mV.A pulse generator was designed to provide high frequency pulse to a magnetic impedance（MI）element.The induced voltage on the pickup coil wound on the amorphous wire was sampled and held with a detect circuit using analog switch.A stable magnetic sensor was constructed.A three-dimension micro magnetic field detector was designed with a central controller MSP430F449.High stability and sensitivity were obtained in the MI sensor with the detect circuit.Experiment results showed that the resolution of the detector was 1nT in the full scale of±2 Oe and the detector worked stably from the room temperature to about 80℃.A small ferromagnetic target was detected by the three-dimension detector in laboratory environment without magnetic shielding.The target moving direction was ascertained with the wave shape of axis parallel in that direction.

种群行为对疾病空间传播动态的影响

依据基于个体的空间模拟模型,文章构建了食饵感染疾病的一类捕食-食饵系统,并从特征调节的食饵偏好、寄生导致的宿主繁殖率下降以及捕食者对食饵资源的转换等方面研究种群行为的改变对疾病空间传播动态与生物控制的影响。其中,文章采用了无标度网络、小世界网络、随机网络以及规则格子等四种空间网络结构来明确网络异质性对疾病空间动态的影响。模拟结果显示,特征调节的捕食种群对食饵偏好的改变以及对食饵资源的转换行为显著影响了疾病的流行与捕食者的数量。不同网络结构下,疾病的流行与捕食者的数量之间均呈现显著的负相关性,这也说明捕食者对疾病的生物控制有不可忽视的作用;而寄生调节的宿主生长率对疾病的传播和捕食者数量产生较为微弱的影响。另外,空间网络拓扑结构的异质性对疾病的流行率也产生显著影响,网络结构异质性的增加将不利于局部感染作用的发生,从而抑制疾病的空间传播。最后,斑块发生率的模拟结果揭示,虽然网络节点的度越高越有利于局部相互作用的发生,但是已感染食饵为了权衡感染与捕食风险的正负作用,其斑块发生率呈现先增加后减弱的趋势。总之,种群的行为与网络空间结构的异质性均可作为控制疾病传播的有效策略,具有一定的研究意义。