Modeling Seasonal Fractionally Integrated Autoregressive Moving Average-Generalized Autoregressive Conditional Heteroscedasticity Model with Seasonal Level Shift Intervention

This paper introduces the class of seasonal fractionally integrated autoregressive moving average-generalized conditional heteroskedastisticty (SARFIMA- GARCH) models, with level shift type intervention that are capable of capturing simultaneously four key features of time series: seasonality, long range dependence, volatility and level shift. The main focus is on modeling seasonal level shift (SLS) in fractionally integrated and volatile processes. A natural extension of the seasonal level shift detection test of the mean for a realization of time series satisfying SLS-SARFIMA and SLS-GARCH models was derived. Test statistics that are useful to examine if seasonal level shift in an SARFIMA-GARCH model is statistically plausible were established. Estimation of SLS-SARFIMA and SLS-GARCH parameters was also considered.

Temperature dependence of the energy-level shift induced by the Bose-Einstein condensation of photons

We investigate the energy-level shift of a hydrogen atom in a two-dimensional optical microcavity, where there exists a Bose-Einstein condensation of photons. It is found that below the critical temperature Tc, the energy-level shift of the bound electron is dependent on temperature, and it is a monotonically increasing function of the absolute temperature T. Especially, at the absolute zero temperature, the energy-level shift entirely comes from the Lamb shift, and the atom can be treated approximately, that is, in vacuum.

Autoregressive Fractionally Integrated Moving Average-Generalized Autoregressive Conditional Heteroskedasticity Model with Level Shift Intervention

In this paper, we introduce the class of autoregressive fractionally integrated moving average-generalized autoregressive conditional heteroskedasticity?(ARFIMA-GARCH) models with level shift type intervention that are capable of capturing three key features of time series: long range dependence, volatility?and level shift. The main concern is on detection of mean and volatility level shift in a fractionally integrated time series with volatility. We will denote such a time series as level shift autoregressive fractionally integrated moving average (LS-ARFIMA) and level shift generalized autoregressive conditional heteroskedasticity (LS-GARCH). Test statistics that are useful to examine if mean and volatility level shifts are present in an autoregressive fractionally integrated moving average-generalized autoregressive conditional heteroskedasticity (ARFIMA-GARCH) model are derived. Quasi maximum likelihood estimation of the model is also considered.

A noise immunity improved level shift structure for a 600 V HVIC

A novel level shift circuit featuring with high dV/dt noise immunity and improved negative V_S capacity is proposed in this paper.Compared with the conventional structure,the proposed circuit adopting two cross-coupled PMOS transistors realizes the selective filtering ability by exploiting the path which filters out the noise introduced by the dV/dt.In addition,a differential noise cancellation circuit is proposed to enhance the noise immunity further.Meanwhile,the negative V_S capacity is improved by unifying the detected reference voltage and the logic block＇s threshold voltage.A high voltage half bridge gate drive IC adopting the presented structure is experimentally realized by using a usual 600 V BCD process and achieves the stable operation up to 65 V/ns of the dV/dt characteristics.

Shift Invariance Level Comparison of Several Contourlet Transforms and Their Texture Image Retrieval Systems

In this paper, we proposed a metric to measure the shift invariance of the three different contourlet transforms. And then, using the same structure texture image retrieval system which use subband coefficients energy, standard deviation and kurtosis features with Canberra distance, we gave a comparison of their texture description abilities. Experimental results show that contourlet-2.3 texture image retrieval system has almost retrieval rates with non-sub sampled contourlet system;the two systems have better retrieval results than the original contourlet retrieval system. On the other hand, for the relatively lower redundancy, we recommend using contourlet- 2.3 as texture description transform.

Tactics for Fiction Translation on Syntactical Level under Catford's Shifts Theory

In modern fiction translation, translators occasionally encounter multitudinous problems, which need to be solved by various translation tactics. The paper hereof aims to adopt John Catford's shifts theory to analyze the tactics used to solve the problems in fiction translation on syntactical level via translating Best Kept Secret.

一种交叉耦合型高CMTI电平移位电路设计

设计了一种新型交叉耦合结构高共模瞬态抗扰度(Common Mode Transient Immunity,CMTI)的电平移位电路。采用窄脉冲信号产生电路降低了的整体功耗;在电流控制型比较器的作用下,很大程度上降低了电平移位电路的传输延时;同时设计了辅助动态电流补偿结构提高电路的CMTI。基于高压0.18μm BCD工艺对电路进行设计与仿真实验,结果表明该电平移位电路的上升和下降延时均小于3.4 ns,CMTI为200 V/ns。

基于Quick Shift算法的高光谱影像分类

论述了面向对象分类方法处理高光谱高空间分辨率影像的优势与流程;分析了快速漂移(Quick Shift)算法的原理,该算法在进行模式搜索时具有可控制模态选择和平衡"过分割"与"欠分割"的特点。将该算法应用于高光谱影像分割,可得到面向对象分类所需的较理想的"同质"影像对象。为提高影像分割的效率,提出了一种基于灰度共生矩阵的自适应核带宽确定方法,能够兼顾影像空间特征和光谱特征。最后采用最小距离分类法、支持向量机分类法与提出的分类方法进行了对比试验,实验结果表明了该方法的有效性。

双有源桥直流变换器三电平扩展移相控制下电感电流有效值最优跟踪控制策略

多电平双有源桥直流变换器广泛应用于电压传输范围宽的场合,能够减小功率开关电压应力,并提供更多自由度,优化变换器性能。首先,该文提出基于三电平扩展移相控制的三电平双有源桥直流变换器最小电感电流有效值跟踪控制策略,建立三电平扩展移相控制策略下各工作模式下的数学模型,根据拉格朗日乘数法得到各可行域内部最优极值点处移相比之间的相互关系;然后,分析边界最优点,通过比较内部最优极值点和边界最优点处电感电流有效值,得到全局最优工作点;最后,根据传输功率与全局最优工作点处移相比的变化关系,得到全局最优工作点跟踪控制策略,克服寄生电阻和开关损耗对最优工作点的影响。将三电平扩展移相优化调制策略与两电平扩展移相控制、单移相控制以及峰值电流优化控制进行对比实验,实验结果验证了所提该优化策略能够有效减小电感电流有效值并提高变换效率。

基于改进的Mean Shift鲁棒跟踪算法

Mean Shift跟踪算法在目标尺度变化大和被遮挡时存在较大的缺陷。针对这一问题,提出了一种基于多级正方形匹配的自适应带宽选择和分块抗遮挡的目标跟踪算法。该算法采用目标中心点的离散程度和增量试探法计算出可能的变化尺度,然后采用多级正方形匹配法预测目标的运动趋势,将巴氏系数最大者的尺度作为Mean Shift核函数新的带宽。同时,对前景目标进行分块,根据子块的遮挡程度自适应改变子块权重并按一定准则融合有效子块的跟踪结果。实验结果表明,该算法具有很好的鲁棒性。

一种新型双端口三电平变换器

针对传统背靠背三电平变换器成本高、体积大、结构复杂等问题,文中提出一种新型双端口三电平变换器拓扑,通过器件复用方式减少开关器件数量,优化系统结构。首先,详细分析所提新型拓扑的工作原理,给出单相桥臂的6种有效开关状态、电流流通路径及对应双端口输出电平,并对各开关器件的电压应力进行分析。其次,研究并设计一种适用于该新型拓扑的载波层叠脉宽调制策略,加入直流偏移量以避免调制波重合产生的影响。然后,进一步分析该策略在同频与异频工作模式下的调制度范围、相角差约束等关键问题,给出各工作模式下直流偏移量选取原则及两端口调制度约束范围。最后,基于DSP-FPGA-Typhoon HIL 402实验平台对不同工作模式进行验证。实验结果表明,在实现所提新型拓扑双端口电压电流稳定输出的前提下,加入直流偏移量的载波层叠脉宽调制策略使得变换器输出的电能质量良好,谐波含量低。

三电平降压型DC/DC变换器的建模与控制

三电平非隔离DC/DC变换器具有高效率、高功率密度、低成本等优点,广泛应用于新能源储能领域。此处分析了三电平降压型DC/DC的工作原理,推导并建立了系统的小信号模型,采用载波移相控制。同时,针对高压侧电容中点电位不平衡问题,采用了一种电容电压平衡控制策略。最后,对所采用的变换器控制策略进行了仿真,并在一台60 kW样机上得到验证。

一种输出低电平可调的高边电平移位驱动电路

为满足宽输入范围DC/DC芯片的需求,本文设计了一种可调输出低电平电压的高边电平移位驱动电路。该电路无需使用二极管和双极型器件,通过MOS管配置高边驱动信号的低电平电压,并将其应用于高压DC/DC转换器芯片。芯片采用0.35μm BCD工艺流片,实验结果表明DC/DC转换器芯片工作正常,验证了本文设计的高边电平移位驱动电路。

A Novel Asymmetric Three-Phase Cascaded 21 Level Inverter Fed Induction Motor Using Multicarrier PWM with PI and Fuzzy Controller

Multilevel inverters are gaining popularity in high power applications. This paper proposes a new ladder type structure of cascaded three-phase multilevel inverter with reduced number of power semiconductor devices which is used to drive the induction motor. The ultimate aim of the paper is to produce multiple output levels with minimum number of semiconductor devices. This paper uses only 11 switches along with 3 diodes and 4 asymmetrical sources to produce an output voltage of 21 levels. The modulation technique plays a major role in commutation of the switches. Here we implement the multicarrier level shifting pulse width modulation technique to produce the commutation signals for the inverter. The proposed multilevel inverter is used to drive the three-phase induction motor. The mathematical modeling of three-phase induction motor is done using Simulink. Furthermore the PI and fuzzy logic controllers are also used to produce the reference waveform of the level shifting technique which in turn produces the commutation signals of the proposed multilevel converter. The controllers are used to control the speed of the induction motor. The effectiveness of the proposed system is proved with the help of simulation. The simulation is performed in MATLAB/Simulink. From the simulation results, it shows that the proposed multilevel inverter works properly to generate the multilevel output waveform with minimum number of semiconductor devices. The PI and fuzzy logic controller performances are evaluated using the results which indicate that with the help of controllers the harmonics has been reduced and the speed control of induction motor is achieved under different loading conditions.

基于灰度共生矩阵和Mean Shift的目标跟踪算法

针对运用单一颜色特征描述运动目标时抗干扰性较差的问题,提出一种融合灰度共生矩阵和颜色特征的Mean-Shift目标跟踪算法.采用灰度共生矩阵推导的6个纹理特征参数和颜色特征分别表征跟踪目标,引入马氏距离计算纹理特征的相似度,并结合Bhattacharyya系数计算颜色特征的相似度,同时利用Mean Shift算法进行目标定位.实验表明,改进算法能在复杂背景下,有效、准确地实现目标跟踪.

大数据政策治理企业“脱实向虚”——基于国家级大数据综合试验区的准自然实验

文章基于2007—2022年我国沪深两市A股上市公司数据,实证检验国家级大数据综合试验区政策对企业金融化的作用、机制和外部重要条件的影响。实证结果发现:国家级大数据综合试验区政策对企业金融化具有显著的治理作用;对非高科技企业、国有企业、东部地区企业的金融化具有较为突出的治理作用;能够有效改善企业信息不对称、提升企业发展质效以及平滑企业风险,从而能够有效治理企业金融化;进一步研究发现,在较强金融监管支撑下,国家级大数据综合试验区政策对企业金融化的治理效果更为明显。

护士自我调节疲劳现状及与医院磁性水平的关系研究

目的了解护士自我调节疲劳现状及感知医院磁性水平,探讨医院磁性水平对护士自我调节疲劳的影响,为制定干预措施提供参考。方法2023年5-8月,采用一般资料调查表、医院磁性要素量表、自我调节疲劳量表对西安市2所三级甲等医院的825名临床护士开展调查。结果护士自我调节疲劳总分(48.22±6.62)分,感知医院磁性水平总分(103.44±14.84)分。医院磁性水平与护士自我调节疲劳呈负相关;医院磁性水平、聘用类型、每月收入、夜班频次是护士自我调节疲劳的主要影响因素(均P<0.05),医院磁性水平可解释护士自我调节疲劳16.00%的总变异。结论护士自我调节疲劳及感知医院磁性水平均处于中等水平,医院磁性水平是护士自我调节疲劳的重要影响因素。管理者可以通过改善医院磁性水平以降低护士自我调节疲劳水平。

新型六开关两倍电压增益五电平逆变器

倍压多电平逆变拓扑具有自主升压和多电平输出的突出优点。提出了一种新型六开关两倍压增益五电平逆变拓扑,该拓扑由两个半桥单元和一个开关电容单元组成,通过载波层叠调制策略可以实现直流输入电源与电容器分时串并联运行,从而实现电路的自主升压和五电平输出电压波形。通过对比分析现有倍压多电平逆变拓扑,所提出的新型两倍压增益五电平逆变拓扑具有使用开关器件数量少、电压应力低、调制策略简单等优点。实验测试结果证明了所提五电平逆变拓扑在不同工况下的可行性与有效性。

抑制混合级联H桥逆变器电流倒灌的调制策略

传统调制策略下混合级联H桥变换器会出现因高低压单元输出电压极性不一致引起的电流倒灌问题。同时多个低压单元采用不同的脉冲宽度调制(pulse width modulation,PWM)方法会导致低压单元间出现输出功率不均衡问题。针对以上问题,结合不对称三单元混合级联H桥十一电平逆变器,提出了一种基于载波层叠的改进混合载波脉宽调制方法。该方法利用载波自由度和冗余开关状态,优化了低压单元的工作方式,使高低压单元在整个输出周期内保持输出电压极性一致,解决了逆变器在传统调制方法下出现的电流倒灌问题。同时,该方法中2个低压单元均工作在高频状态,使低压单元输出电压波形正负半周互补对称,实现了低压单元间输出功率自均衡。仿真和实验结果证明了调制策略的可行性及有效性。

采用定频移相控制的宽输出范围多电平LLC谐振变换器

针对电动汽车车载充电器的后级DC-DC环节,提出一种具备宽输出范围的多电平LLC谐振变换器。该变换器通过增加一组半桥和辅助变压器,构造出高于输入电压的多电平结构,结合定频移相脉宽调制控制,实现两倍电压增益拓展。该方案避免了变频控制下增益范围对谐振参数的制约,简化了参数设计过程。工作于串联谐振点使变换器在整个充电工作过程中均可实现功率管的零电压开关和整流管的零电流开关,有利于系统效率的提升。搭建一台输入380V、功率3.3kW的实验样机,验证所提拓扑与控制方案的可行性。经测试,变换器能为动力电池提供250~420V的充电电压,其峰值效率达到了97.1%。