Modeling and Dynamic Analysis of Fractional-Order Buck Converter in Continuous Conduction Mode

According to the fact that the actual inductor and actual capacitor are fractional, the mathematical and state-space averaging models of fractional order Buck converters in continuous conduction mode(CCM) are constructed by using fractional calculus theory. Firstly, the parameter conditions that ensure that the converter working in CCM is given and transfer functions are derived. Also, the inductor current and the output voltage are analyzed. Then the difference between the mathematical model and the circuit model are analyzed, and the effect of fractional order is studied by comparing the integer order with fractional order model. Finally, the dynamic behavior of the current-controlled Buck converter is investigated. Simulation experiments are achieved via the use of Matlab/Simulink. The experimental results verify the correctness of theoretical analysis, the order should be taken as a significant parameter. When the order is taken as a bifurcation parameter, the dynamic behavior of the converter will be affected and bifurcation points will be changed as order varies.

Indirect Output Voltage Control in Negative Output Elementary Super Lift Luo Converter Using PIC plus FLC in Discontinuous Conduction Mode

In this paper, the design of a proportional integral controller (PIC) plus fuzzy logic controller (FLC) for the negative output elementary super lift Luo converter (NOESLLC) operated in discontinuous conduction mode (DCM) is presented. In spite of the many benefits viz. the high voltage transfer gain, the high efficiency, and the reduced inductor current and the capacitor voltage ripples, it natured with non-minimum phase. This characteristic makes the control of NOESLLC cumbersome. Any attempt of direct controlling the output voltage may erupt to instability. To overcome this problem, indirect regulation of the output voltage based on the two-loop controller is devised. The savvy in the inductor current control improves the dynamic response of the output voltage. The FLC is designed for the outer (voltage) loop while the inner (current) loop is controlled by the PIC. For the developed ?19.6 V NOESLLC, the dynamic performances for different perturbations (line, load and component variations) are obtained for PIC plus FLC and compared with PIC plus PIC. The study of two cases is performed at various operating regions by developing the MATLAB/Simulink model.

Quantized Conductance of Majorana Zero Mode in the Vortex of the Topological Superconductor(Li_(0.84)Fe_(0.16))OHFeSe

The Major ana zero mode(MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-based superconductors as a zero-bias conductance peak in tunneling spectroscopy. In particular, a clean and robust MZM has been observed in the cores of free vortices in(Li_(0.84)Fe_(0.16))OHFeSe. Here using scanning tunneling spectroscopy, we demonstrate that Major ana-induced resonant Andreev reflection occurs between the STM tip and this zero-bias bound state,and consequently, the conductance at zero bias is quantized as 2e^2/h. Our results present a hallmark signature of the MZM in the vortex of an intrinsic topological superconductor, together with its intriguing behavior.

Hydraulic Conductivity Characteristics of Hot Dry Rocks under Different Fracture Modes

Enhanced geothermal system(EGS) is an effective method for developing and utilizing hot dry rock(HDR). The key to the effectiveness of EGS is the construction of an artificial fracture network. The permeability of fractures has severe effects on the heat transfer efficiency and sustainability of geothermal energy. However, the evolution characteristics of hydraulic conductivity under different failure modes have not been adequately studied for HDR. To clarify this, rocks with different failure modes were investigated by conducting thermal triaxial compression experiments, and the fluid seepage related to different rock failure modes was comprehensively investigated. The results showed that the characteristic stresses and crack surface roughness of the rock increased as the confining pressure increased. The permeability in the composited failure mode was the largest(11.4 μm;), followed by that in the Y-shaped shear failure mode(9.7 μm;), and that in the single-shear failure mode was the smallest(7.2 μm;). The confining pressures had an inhibitory effect on permeability. As the confining pressure increased from 5 to 30 MPa, the permeability decreased by 88.8%, 88.4%, and 89.9%, respectively. In contrast, the permeability was significantly enhanced by 128.3%, 94.6%, and 131% as the flow rate increased from 3 to 7 m L/min.

Investigation of AlGaN/GaN fluorine plasma treatment enhancement-mode high electronic mobility transistors by frequency-dependent capacitance and conductance analysis

This paper reports fluorine plasma treatment enhancement-mode HEMTs （high electronic mobility transistors） EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology. It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance-voltage measurement. Using capacitance-frequency measurement, it finds one type of trap in conventional DHEMTs with TT = （0.5 - 6） ms and DT ： （1 - 5）×10^13 cm^-2. eV^-1. Two types of trap are found in fluorine plasma treatment EHEMTs, fast with TW（f）= （0.2 - 2） μs and slow with TT（s） = （0.5 - 6） ms. The density of trap states evaluated on the EHEMTs is Dw（f） ： （1 - 3） × 10^12 cm^-2. eV^-1 and DT（s） =（2 - 6） × 10^12 cm-2. eV-1 for the fast and slow traps, respectively. The result shows that the fluorine plasma treatment reduces the slow trap density by about one order, but introduces a new type of fast trap. The slow trap is suggested to be a surface trap, related to the gate leakage current.

180°导通方式无刷直流电机换相转矩脉动研究

无刷直流电机(BLDCM)换相转矩脉动一直是业界关注的问题,但仅限于120°导通模式。文章研究了180°导通模式无刷直流电机在换相期间的转矩脉动变化,并与120°导通方式转矩脉动进行了比较。理论分析和仿真结果表明:电机在低速区域,120°导通模式比180°导通模式转矩脉动变化小,而在高速区域,180°导通模式比120°导通模式转矩脉动变化小。研究结果为无刷直流电机换相转矩脉动抑制提供了一种新的控制策略。

Bi-mode逆导门极换流晶闸管结构与特性研究

Bi-mode逆导门极换流晶闸管(BGCT)是为了改善传统逆导门极换流晶闸管(RC-GCT)电流均匀性和提高硅片有效面积利用率而提出的一种新结构。通过分析BGCT器件的版图布局结构,采用Sentaurus TCAD软件模拟并分析了BGCT、传统结构RC-GCT和IGCT传统功率器件的通态特性、正向阻断特性和关断特性,着重比较了RC-GCT与BGCT在400K温度下不同工作模式下特性差异。分析研究结果表明,BGCT器件能够改善RC-GCT器件的通态特性,提高硅片面积的利用率。

An Improved Modulation Strategy for Single-phase Three-level Neutral-point-clamped Converter in Critical Conduction Mode

Two-level totem-pole power factor correction(PFC)converters in critical conduction mode(CRM)suffer from the wide regulation range of switching frequency.Besides,in highfrequency applications,the number of switching times increases,resulting in significant switching losses.To solve these issues,this paper proposes an improved modulation strategy for the single-phase three-level neutral-point-clamped(NPC)converter in CRM with PFC.By optimizing the discharging strategy and switching state sequence,the switching frequency and its variation range have been efficiently reduced.The detailed performance analysis is also presented regarding the switching frequency,the average switching times,and the effect of voltage gain.A 2 k W prototype is built to verify the effectiveness of the proposed modulation strategy and analysis results.Compared with the totem-pole PFC converter,the switching frequency regulation range of the three-level PFC converter is reduced by 36.48%and the average switching times is reduced by 45.10%.The experimental result also shows a 1.2%higher efficiency for the three-level PFC converter in the full load range.

基于180°导通模式的无刷直流电动机控制系统研究

无刷直流电动机传统的120°导通模式,在每60°电角度需要进行开关切换使电流换相,在电流变化的过程中会产生较大的转矩脉动,从而影响无刷直流电动机的控制性能。针对无刷直流电动机开关切换时电流变化所产生的转矩脉动,分析了180°导通模式下的电流在不同转速范围内的变化过程,指出了在高速状态下,相比传统的120°导通模式,180°导通模式能抑制换相时间的增加,使相电流快速达到稳态,减小转矩脉动,但在低速状态则不利于缩短开关切换时间和抑制转矩脉动。采用TMS320F2812和电机内置的霍尔传感器以及相应的驱动模块,对电机两种导通模式进行了对比实验,验证了理论分析的正确性。

PA-44-180型飞机失速警告控制方式的改进研究

本文首先简介了PA-44-180型飞机的特点及失速状态。之后通过对中飞院PA-44-180型飞机失速警告系统控制方式的研究,掌握其工作特点。并针对系统的设计缺陷,提出对其控制线路进行改进的可行方案。按照该方案对中飞院执管的PA-44-180型飞机进行改进后明显提高了失速警告系统可靠性,方便了机务日常维护工作,进而对保障该型飞机机群的安全运行有较大意义。

站在巨人们的肩上攀登——《中国传统音乐180调谱例集》学习与研究

本文在肯定黄翔鹏先生著作的重大贡献前提下,谈谈对《中国传统音乐180调谱例集》的个人整理;也围绕180调数量和曲谱来源两大方面提出不同看法。

In-plane shear(ModeⅡ) crack sub-critical propagation of rock at high temperature

In-plane shear crack sub-critical propagation of rock at high temperature was studied by finite element method and shear-box(i.e.compression-shear) test with newly designed electrically conductive adhesive method.Numerical and experimental results show that the normalized shear(Mode Ⅱ) stress intensity factors,K ⅡT/KT0 is decreased as the temperature increases because high temperature can improve stress distribution at crack tip and reduce the Mode Ⅱ stress intensity factor.Microscopic features of fractured surface are of little pits and secondary micro-cracks in the vicinity(1.5-4.0 mm) of the crack tip.The chevron-shape secondary cracks gradually merge in the length of about 4-5 mm and disappear along the direction of crack propagation.Stable shear crack propagation time is increased with the increasing temperature while the stable shear crack propagation rate is decreased with the increasing temperature,since high temperature can increase the shear(Mode Ⅱ) fracture toughness and prevent the crack growth.It is necessary to ensure the ligament of specimen long enough to measure the maximum unstable crack propagation rate of rock.

Effect of holes on in-plane shear(Mode Ⅱ) crack sub-critical propagation of rock

Shear-box(i.e.compression-shear) test and newly designed electrically conductive adhesive method were used to measure shear crack sub-critical propagation time and rate of sandstone specimen.Different cubic specimens with and without holes were tested to study the effect of holes on the shear crack sub-critical propagation.Numerical and experimental results show that three independent variables of hole,the interval distance S,the distance between the center of hole and the crack tip L,and hole radius R,have different contribution to the ratio of stress intensity factor of the specimen with holes to that of the specimen without hole,KⅡ/KⅡ0.Increasing S and decreasing L and R will result in the decrease of KⅡ/KⅡ0 and help crack arrest.The weight relation of the independent variables for KⅡ/KⅡ0 is S>L>R.The specimen DH3 with the largest value of S and the smallest values of L and R has the longest sub-critical crack propagation time and the smallest sub-critical crack propagation rate.Adding two suitable holes symmetrically to the original crack plane in rock specimen is considered to be a potential method for crack arrest of rock.

Optimization of Safety Production Supervision Mode of Coalmining Enterprises

In view of the fact that safety production supervision of coal mines in China features low efficacy, this paper applies principles of cybernetics to simulate the dynamic process of safety supervision, and proposes that institutional variables be controlled to support intermediate goals, which in turn contribute to the ultimate safety production objective. Rather than focusing all attention on safety issues of working faces, supervising departments of coalmines are advised to pay much more attention to institutional factors that may impact people’s attitude and behavior, which are responsible for most coalmine accidents. It is believed that such a shift of attention can effectively reduce coalmining production accidents and greatly enhance supervision efficacy.

Research on Chinese Agricultural Industrialization Based on SCP Mode

Taking the SCP mode of industrial organization theory as the starting point,the paper analyzes Chinese agricultural market structure,market conduct and conduct performance and draws lessons from foreign experiences in developing agriculture.In the process of agricultural industrialization,Chinese agricultural development exists the problems of low intensive degree,low degree of differential products,surplus labor forces,low agricultural profit rate and low industrial contribution rate and farmers’ difficultly in adapting to market competition.The paper puts forward suggestions for addressing the problems,which include underpinning the cooperation of operation main bodies and developing rural cooperative organizations;promoting land transfer and clarifying land property;accelerating rural surplus labors transfer and abating trade barriers;increasing technology input and improving the contribution rate of technologies;improving circulation channels and intensifying agricultural competitiveness.

Design and Comparison of Controller for the Reduction of Conducted Electromagnetic Interference in an Inverter

This paper presents the design of a controller for the measurement and reduction of conducted Electro Magnetic Interference (EMI) caused in the power electronic circuits. The conducted EMI is also separating the Common Mode (CM) and Differential Mode (DM) simultaneously using Line Impedance Stabilization Network (LISN). EMI is mitigated by the fuzzy controller. By comparing common mode voltage with the standard reference value, the generated error can be minimized by using fuzzy controller. Fuzzy controller is varying the PWM signal of the power electronic switching devices for reducing the electromagnetic interference. In this paper, comparison of PI and fuzzy controller of the open loop and closed loop models are implemented using MATLAB® SIMULINK for measurement and reduction of the EMI level;and also simulation results of the PI controller and fuzzy controller analysis are presented in this paper. The fuzzy controller is provided to achieve the EMI level of the inverter within the standard limit.

Low-Temperature Thermal Conductance in Superlattice Nanowire with Structural Defect

Using the scattering-matrix cascading method, we investigate the effect of structural defect on the acoustic phonon transmission and thermal conductance in the superlattice nanowire at low temperatures. In the present system, the phonon transmissions exhibit quite complex oscillatory behaviour. It is found that a lateral defect in an otherwise periodic structure significantly decrease the thermal conductance and completely washes away the transmission quantization. However, the appreciable transmission quantization survives in the presence of a longitudinal defect whereas a good quantization plateau of thermal conductance emerges below the universal level in a wide temperature range with the lateral defect.

Welding mode transition and process stability in high power laser welding

For high-power CO2 laser welding, besides two well known stable welding processes, i.e. stable deep penetration welding (DPW) and stable heat conduction welding (HCW), the authors have found the third welding process, i.e. unstable-mode welding (UMW) under the certain condition. UMW has its basic feature that the two welding modes (DPW and HCW) appear intermittently, with jumping of penetration depth and weld width between large and small levels. In this paper, effects of welding parameters (focal position, laser power and traveling speed) on laser welding mode and weld appearance have been comprehensively studied. Double-U curves of laser welding mode transition have been obtained, which indicate the ranges of the three mentioned welding processes. This work affords science foundation for selecting the welding process parameters correctly and obtaining stable laser welding.

Bound states in the continuum on perfect conducting reflection gratings

Bound states can be supported on the surface of a periodically corrugated perfect conductor known as spoof surface plasmon polaritons with their dispersion curves reside below the light line.Here we show that bound states in the continuum(BICs)can also be achieved in such systems.Two types of grating structures are proposed to suppress the radiation leakage and hence generate bound states.The first one is a simple grating with broad grooves in which multiple cavity modes are accommodated.Due to the symmetry incompatibility and the destructive interaction mainly from the TM_(0)and TM_(1)modes,BICs at theΓpoint and at off-Γpoints are both realized.The second one is a dimerized grating with two grooves in each unit cell.The destructive interaction between the modes in the two grooves can suppresses the radiation and BICs at theΓpoint are observed.The Q factors of the whole bands can be further tuned by the dimerization strength effectively.This work may offer new opportunity for the applications of metallic grating in the low frequency bands.

一款高效率宽输入电压边界导通模式反激变换器

本文提出了一款高效率、宽输入电压的边界导通模式反激变换器结构。为了防止负载切换过程中芯片过压和欠压,提出了一种由电流调节电路(CRC)与自适应频率控制电路(AFCC)组成的新型模式切换环路,实现了芯片在不同模式之间的平滑切换,提高了负载的瞬态响应和转换效率;通过在环路中引入电流调节控制技术,减小了低纹波突发模式(LRBM)下的原边充电电流和输出最小负载电流,从而减小轻负载下的开关频率,降低功耗。基于0.18μmBCD工艺,实现了电路设计和版图设计,芯片面积为1.48×2.5mm^(2)。仿真结果表明,变换器在输入电压为3~32V、输出电压为5V时,轻、重负载切换过程中的输出电压瞬态响应最大变化为6%,峰值转换效率为88.6%。