脉冲激光电源的实用IGBT驱动电路设计

分析了大功率脉冲激光电源中IGBT模块所需驱动电路的基本要求,设计了一种IGBT驱动电路,并采用反激变换器作为其供电电源的解决方案.讨论了不连续导电模式情形下具有缓冲电路的反激变压器储能转换率的计算,由此确定了反激变压器和缓冲电路的核心参数.以单片开关电源VIPer22ADIP为关键器件,设计了输出为18V/5W的稳压型反激变换器,从而为实现全开关化的脉冲激光电源提供了可能.     

Applications of modularized circuit designs in a new hyper-chaotic system circuit implementation

Modularized circuit designs for chaotic systems are introduced in this paper.Especially,a typical improved modularized design strategy is proposed and applied to a new hyper-chaotic system circuit implementation.In this paper,the detailed design procedures are described.Multisim simulations and physical experiments are conducted,and the simulation results are compared with Matlab simulation results for different system parameter pairs.These results are consistent with each other and they verify the existence of the hyper-chaotic attractor for this new hyper-chaotic system.     

Proximal point algorithm for nonlinear multivalued type mappings in Hadamard spaces

In this paper, we modify the proximal point algorithm for finding common fixed points in CAT(0) spaces for nonlinear multivalued mappings and a minimizer of a convex function and prove Δ‐convergence of the proposed algorithm. A numerical example is presented to illustrate the convergence result. Our results improve and extend the corresponding results in the literature.     

导弹特种车辆行驶操稳性测量系统设计

针对红外热像仪性能检测设备国产化的紧迫需求,设计了检测样机的电路系统。根据红外检测的设计指标要求,提出了测控系统的总体方案,详细介绍了检测系统的硬件电路设计,阐述了红外系统MRTD、NETD等关键指标的测试算法,给出了电路检测软件和维修指导软件的设计方法。实验测试表明,该检测系统电路达到了设计指标要求,已应用于某小型红外系统检测诊断设备中。     

基于RBF网络的断路器电流自适应保护研究

针对传统断路器电流保护方法存在受系统运行方式影响、整定困难、智能化低等问题,本文提出了基于RBF的断路器电流自适应保护算法,并给出了算法的模型。该算法融合了RBF神经网络的故障检测和电流自适应保护。首先通过RBF网络检测负载线路的电流故障,然后用电流自适应算法进行保护。在对神经网络进行训练时,利用PSO算法对RBF神经网络的参数进行优化以此来提高网络的泛化能力和学习能力;然后采用优化后的PSO-RBF神经网络对电流故障进行诊断。实验表明,该算法较大地提高了断路器智能化管理水平。     

Poly(ester imide)s possessing low coefficients of thermal expansion and low water absorption (IV): Effects of ester‐linked tetracarboxylic dianhydrides with longitudinally extended structures

A series of poly(ester imide)s (PEsIs) were prepared using longitudinally extended structures of ester‐linked tetracarboxylic dianhydrides with different numbers of aromatic rings (N_Ar = 4‐6). In the PEsIs obtained using p‐phenylenediamine (p‐PDA), a clear trend was observed: the water absorption (W_A) decreased with increasing N_Ar. In contrast, no clear decrease in the T_g with increasing N_Ar was observed for the PEsIs obtained using 4,4′‐oxydianiline (4,4′‐ODA). The PEsIs obtained using a methyl‐substituted tetracarboxylic dianhydride (N_Ar = 5) showed more suppressed W_A and higher elongation at break (ε_b) values than those of the nonsubstituted counterparts. The former result is probably closely related to the enhanced crystallinity. However, methyl substitution caused an appreciable reduction in the thermal stability. Thus, the methyl‐substituted PEsIs did not meet the V‐0 standard in the UL‐94V test, unlike the substituent‐free counterparts. The PEsI copolymer obtained using the substituent‐free tetracarboxylic dianhydride (N_Ar = 6) with p‐PDA (75 mol%) and 4,4′‐ODA (25 mol%) had excellent combined properties, ie, a very high T_g (361°C), an ultralow coefficient of thermal expansion (2.2 ppm K^?1), an extremely low coefficient of hygroscopic expansion (3.3 ppm/RH%), moderate film ductility (ε_b^max = 23%), a moderate dielectric constant (3.22), and a low tan δ (2.76 × 10^?3) at 10 GHz in 50% relative humidity. Thus, this PEsI is a promising novel dielectric substrate material for use in the next generation of high‐performance flexible printed circuit boards.     

Achieving Efficient Multichannel Conductance in Through‐Space Conjugated Single‐Molecule Parallel Circuits

Constructing single‐molecule parallel circuits with multiple conduction channels is an effective strategy to improve the conductance of a single molecular junction, but rarely reported. We present a novel through‐space conjugated single‐molecule parallel circuit (f‐4Ph‐4SMe) comprised of a pair of closely parallelly aligned p‐quaterphenyl chains tethered by a vinyl bridge and end‐capped with four SMe anchoring groups. Scanning‐tunneling‐microscopy‐based break junction (STM‐BJ) and transmission calculations demonstrate that f‐4Ph‐4SMe holds multiple conductance states owing to different contact configurations. When four SMe groups are in contact with two electrodes at the same time, the through‐bond and through‐space conduction channels work synergistically, resulting in a conductance much larger than those of analogous molecules with two SMe groups or the sum of two p‐quaterphenyl chains. The system is an ideal model for understanding electron transport through parallel π‐stacked molecular systems and may serve as a key component for integrated molecular circuits with controllable conductance.     

Raman study of a liquid crystalline gel consisting of photochromic 4‐methyl‐N‐(4‐n‐heptyloxysalicylidene)aniline and a gelling agent (R,R′)‐1,2‐bis(dodecanoylamino)cyclohexane

A liquid crystalline physical gel has been prepared from the mixture of a nematic liquid crystal and a low molecular mass gelling agent containing a hydrogen‐bonding moiety. The newly synthesized liquid crystalline compound exhibited photochromism in the crystalline solid phase. Although photochromism was not observed in the nematic gel state of the mixture, the lifetime of photochromism in the solid phase became longer, compared with that of a single liquid crystalline compound. Some Raman bands of the mixture showed a marked change in both intensity and frequency through the phase transitions. These bands have been assigned to the vibrational modes related to the core part of molecule.     

Edge disjoint cycles through specified vertices

We give a sufficient condition for a simple graph G to have k pairwise edge‐disjoint cycles, each of which contains a prescribed set W of vertices. The condition is that the induced subgraph G[W] be 2k‐connected, and that for any two vertices at distance two in G[W], at least one of the two has degree at least |V(G)|/2 + 2(k ? 1) in G. This is a common generalization of special cases previously obtained by Bollobás/Brightwell (where k = 1) and Li (where W = V(G)). A key lemma is of independent interest. Let G be the complement of a bipartite graph with partite sets X, Y. If G is 2k connected, then G contains k Hamilton cycles that are pairwise edge‐disjoint except for edges in G[Y]. © 2005 Wiley Periodicals, Inc. J Graph Theory