双极性移相控制矩阵式高频链逆变器的研究

针对双向高频逆变器固有的电压冲击和开关损耗问题,采用一种双极性移相控制策略：前级H桥逆变器将直流电压调制成高频矩形波,然后由矩阵变换器解调成双极性SPWM波,经输出滤波后得到正弦波电压。在稳态下,用分析Buck变换器外特性的方法来分析单相矩阵式高频链逆变器的外部特性。通过软件仿真验证了此控制策略的正确性。     

Do balanced scales assess bipolar constructs? The case of the STAI scales.

Balanced scales, that is, scales based on items whose content is either negatively or positively polarized, are often used in the hope of measuring a bipolar construct. Research has shown that usually balanced scales do not yield 1-dimensional measurements. This threatens their construct validity. The authors show how to test bipolarity while accounting for method effects. This is demonstrated on a data set of state and trait anxiety measured with the State-Trait Anxiety Inventory (STAI; C. D. Spielberger, R. L. Gorsuch, R. Lushene, P. R. Vagg, & G. A. Jacobs, 1983) scales. Taking a test–retest perspective, assuming temporally stable method effects, the authors tested the bipolarity of the temporal change through suitable constraints specified in a structural equation model adapted from S. Vautier, R. Steyer, and A. Boomsma (2008). The model fit the data closely, χ2(13, N = 888) = 20.75, p = .07. Thus, the state and trait scales seem to measure bipolar constructs plus temporally stable method effects. Parameter estimates suggest reliable change scores for the state anxiety scale (ρ? = .90) and specific method effects for the state and trait scales of the STAI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coexistence of Grain‐Boundaries‐Assisted Bipolar and Threshold Resistive Switching in Multilayer Hexagonal Boron Nitride

The use of 2D materials to improve the capabilities of electronic devices is a promising strategy that has recently gained much interest in both academia and industry. However, while the research in 2D metallic and semiconducting materials is well established, detailed knowledge and applications of 2D insulators are still scarce. In this paper, the presence of resistive switching (RS) in multilayer hexagonal boron nitride (h‐BN) is studied using different electrode materials, and a family of h‐BN‐based resistive random access memories with tunable capabilities is engineered. The devices show the coexistence of forming free bipolar and threshold‐type RS with low operation voltages down to 0.4 V, high current on/off ratio up to 10⁶, and long retention times above 10 h, as well as low variability. The RS is driven by the grain boundaries (GBs) in the polycrystalline h‐BN stack, which allow the penetration of metallic ions from adjacent electrodes. This reaction can be boosted by the generation of B vacancies, which are more abundant at the GBs. To the best of our knowledge, h‐BN is the first 2D material showing the coexistence of bipolar and threshold RS, which may open the door to additional functionalities and applications.     

一种采用子波激发的超声测井发射电路

超声发射电路是超声测井仪器的关键电路。分析了常规的高压、单窄脉冲超声发射电路存在的问题,提出了子波激发的设计思想,设计并实现了基于CMOS集成开关的单、双极性电源供电的2种超声发射电路。采用周期性双极性子波激发,使发射信号的频谱与换能器的传输特性匹配,降低了发射电路的功耗。采用特定的子波激发,有效抑制了噪声干扰,实现有效信号的能量积累,提高了超声特征参数检测的准确性。电路结构简单,集成度高,功耗低,性能稳定。实际应用表明,该方案对超声测井具有重要的参考价值。     

Novel and Enhanced Optoelectronic Performances of Multilayer MoS2–WS2 Heterostructure Transistors

Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS₂–WS₂ heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS₂ or WS₂. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 10³. The planar device also exhibits high field‐effect ON/OFF ratio (>10⁵), high electron mobility of 65 cm²/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS₂ or WS₂ nanoflake transistors. The results suggest that formation of MoS₂–WS₂ heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications.     

光纤去偏器的理论和研制

用简明的方法讨论了Ｌｙｏｔ去偏器原理，用类矩形保偏光纤制作了多只去偏器，用两种方法测量了去偏器的参数，并将去偏器用于光纤陀螺。     

Computing a Pareto-optimal solution for multi-objective flexible linear programming in a bipolar framework

In this paper, we study the multi-objective flexible linear programming (MOFLP) problems (or fuzzy multi-objective linear programming problems) in the heterogeneous bipolar framework. Bipolarity allows us to distinguish between the negative and the positive preferences. Negative preferences denote what is unacceptable while positive preferences are less restrictive and express what is desirable. This viewpoint enables us to handle fuzzy sets representing constraints and objective functions separately and combine them in distinct ways. In this paper, a solution concept of Pareto-optimality for MOFLP problems is defined and an approach is proposed to single out such a solution for MOFLP with highest possible degree of feasibility.     

导盲系统中的道路斑马线识别方法

针对斑马线的特征,建立了基于图像的导盲辅助设备中道路斑马线的识别方法。引入表征灰度图像对比度的双极系数作为识别的理论基础,结合形态学方法消除双极系数图像中的噪声,筛选出具有强烈灰度对比度的道路斑马线区域,进而采用Radon变换进行特征提取后重建斑马线。通过对54幅道路图像的测试,该算法识别率达到96.2%。     

基于复合控制的LLC谐振变换器轻载纹波优化

为提高LLC谐振变换器输出电压稳定性,改善轻载工况下输出电压纹波,提出了一种复合控制策略以实现全桥LLC变换器全负载范围的稳定电压输出。此种控制策略混合了有限双极性PWM控制与PFM控制,轻载时采用有限双极性PWM控制模式,重载时采用PFM控制模式,以此实现零电压开关,有效提高了LLC谐振变换器的效率,使得输出纹波大大减小。最后,通过实验验证了分析的正确性以及所提复合控制策略的有效性。