高频群脉冲电解加工控制系统研究

介绍了高频群脉冲电解加工的控制系统，其核心部件由PMAC运动控制器和PCL-818HD多功能数据采集板构成，主要功能包括控制工具阴极进给、极间加工间隙及短路保护等。实验表明，该控制系统能保证加工的高精度、稳定性及可靠性。     

Investigation of micro-EDM material removal characteristics using single RC-pulse discharges

Similar to EDM, in micro-EDM, intense heat is generated between the workpiece and tool electrode by the discharge through a dielectric medium to result in the formation of a microcrater that is much smaller in size. In this study, a single-spark generator has been developed to study the erosion characteristics from the microcrater size. Using a simple heat transfer model, the efficiency at different discharge condition is also deduced. It is found that at lower-energy (<50 μJ) discharges, the energy required to remove the unit volume of material, defined as the specific energy, is found to be much less than that at higher-energy discharges. Additionally, the ratio of the standard deviation to the measured microcrater size is found to be lower at lower discharge energy, indicating greater consistency in shape and size when the discharge occurs at lower energy. The fundamental erosion mechanism of material is discussed by considering melting and evaporation phenomena using theoretical modeling. The average efficiency of erosion, when estimated to be due primarily to melting or evaporation alone, is found to be up to an order of magnitude higher at lower-energy discharges than that at higher-energy discharges.     

基于GAP技术的地震信息网络系统改造方案

江苏省地震信息网络系统是全省区域地震数据传输、数据交换、数据存储及信息服务的统一平台。针对网络系统目前存在的问题,提出了改造方案,即通过使用隔离网闸将业务传输系统和互连网进行物理隔离,升级网络关键设备和链路带宽,增加网络安全设备等技术手段,使网络系统达到了安全、稳定运行的目标,既满足了地震信息数据传输、交换、存储及多元化应用等的需求,又符合信息系统三级安全管理要求,可以为地震行业信息网络系统优化建设提供有益参考。     

火炮发射精度优化问题分析

火炮发射精度由射击密集度和射击准确度组成,身管振动影响火炮射击密集度和准确度.但影响身管振动的因素很多,一直来很难建立符合实际的振动模型,对火炮的射击精度进行准确分析.目前火炮发射精度分析时模型较简单,考虑因素较单一,特别是缺少多因素同时作用时火炮发射时的精度问题研究.为解决上述问题,建立了起落部分的虚拟样机模型,利用ADAMS动力学仿真软件综合分析了弹丸质心偏移量、高低机齿轮啮合间隙和衬瓦身管配合间隙三种因素耦合对炮口振动的影响.分析表明多因素对炮口振动存在耦合影响,为炮口振动特性的综合分析以及对接触间隙的优化控制提供了依据.     

DFT studies on armchair (5, 5) SWCNT functionalization. Modification of selected structural and spectroscopic parameters upon two-atom molecule attachment

Density functional theory (DFT) studies on adsorption of several gaseous homo- and hetero-diatomic molecules (AB) including H₂, O₂, N₂, NO and CO on external surface of H-capped pristine armchair (5, 5) single-walled carbon nanotube (SWCNT) were conducted. Structures of C₇₀H₁₀ and the corresponding C₇₀H₁₀–AB adducts were fully optimized at the B3LYP/6-311G* level of theory. Calculated HOMO/LUMO energy gaps (E_g), ¹³C NMR chemical shifts and IR/Raman parameters were analyzed and critically compared with available experimental data. Significant changes of carbon NMR atom chemical shifts (up to −100 ppm) and shielding anisotropies (up to −180 ppm) at sites of addition were observed. Functionalized SWCNTs produced IR and Raman spectra different from the pristine nanotube model. The selective changes in vibrational spectra will help in assigning the topology of functionalization at the nanotube wall.     

Modeling of microstrip antennas using neural networks techniques: A review

Artificial neural networks modeling have recently acquired enormous importance in microwave community especially in analyzing and synthesizing of microstrip antennas (MSAs) due to their generalization and adaptability features. A trained neural model estimates response very fast, which is nearly equal to its measured and/or simulated counterpart. Thus, it completely bypasses the repetitive use of conventional models as these models need rediscretization for every minor changes in the geometry, which itself is a time‐consuming exercise. The purpose of this article is to review this emerging area comprehensively for both analyzing and synthesizing of the MSAs. During reviewing process, some untouched cases are also observed, which are essentially required to be resolved for antenna designers. Unique and efficient neural networks‐based solutions are suggested for these cases. The proposed neural approaches are validated by fabricating and characterizing of the prototypes too. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:747–757, 2015.     

Optimal job sequence determination and operation machine allocation in flexible manufacturing systems: an approach using adaptive hierarchical ant colony algorithm

In this paper, an Adaptive Hierarchical Ant Colony Optimization (AHACO) has been proposed to resolve the traditional machine loading problem in Flexible Manufacturing Systems (FMS). Machine loading is one of the most important issues that is interlinked with the efficiency and utilization of FMS. The machine loading problem is formulated in order to minimize the system unbalance and maximize the throughput, considering the job sequencing, optional machines and technological constraints. The performance of proposed AHACO has been tested over a number of benchmark problems taken from the literature. Computational results indicate that the proposed algorithm is more effective and produces promising results as compared to the existing solution methodologies in the literature. The evaluation and comparison of system efficiency and system utilization justifies the supremacy of the algorithm. Further, results obtained from the proposed algorithm have been compared with well known random search algorithm viz. genetic algorithm, simulated annealing, artificial Immune system, simple ant colony optimization, tabu search etc. In addition, the algorithm has been tested over a randomly generated problem set of varying complexities; the results validate the robustness and scalability of the algorithm utilizing the concepts of ‘heuristic gap’ and ANOVA analysis.     

光子晶体的研究与应用

光子晶体是一种具有光子能带及能隙的新型材料。其特有的性质,使光子晶体具有广阔的应用前景。本文基于固体物理学的基本原理,对光子晶体的理论基础进行了简单介绍,根据其特有结构,对光子晶体的特性做了一定分析,并结合现实需要,综述了光子晶体在光学等方面的应用。     

光子晶体的研究与应用

光子晶体是一种具有光子能带及能隙的新型材料。其特有的性质,使光子晶体具有广阔的应用前景。本文基于固体物理学的基本原理,对光子晶体的理论基础进行了简单介绍,根据其特有结构,对光子晶体的特性做了一定分析,并结合现实需要,综述了光子晶体在光学等方面的应用。     

A test for stability robustness of linear time‐varying systems utilizing the linear time‐invariant ν‐gap metric

A stability robustness test is developed for internally stable, nominal, linear time‐invariant (LTI) feedback systems subject to structured, linear time‐varying uncertainty. There exists (in the literature) a necessary and sufficient structured small gain condition that determines robust stability in such cases. In this paper, the structured small gain theorem is utilized to formulate a (sufficient) stability robustness condition in a scaled LTI ν‐gap metric framework. The scaled LTI ν‐gap metric stability condition is shown to be computable via linear matrix inequality techniques, similar to the structured small gain condition. Apart from a comparison with a generalized robust stability margin as the final part of the stability test, however, the solution algorithm implemented to test the scaled LTI ν‐gap metric stability robustness condition is shown to be independent of knowledge about the controller transfer function (as opposed to the LMI feasibility problem associated with the scaled small gain condition which is dependent on knowledge about the controller). Thus, given a nominal plant and a structured uncertainty set, the stability robustness condition presented in this paper provides a single constraint on a controller (in terms of a large enough generalized robust stability margin) that (sufficiently) guarantees to stabilize all plants in the uncertainty set. Copyright © 2008 John Wiley & Sons, Ltd.