声诱饵回波模拟器仿真研究

随着水声技术的发展，水下武器对抗也日趋复杂。能够模拟目标回波的主动式声诱饵的出现，为对抗主动自导鱼雷及主动声纳提供了非常重要的帮助。着重对声诱饵的回波模拟器的作用机理进行了分析，然后给出了脉冲宽度、多普勒频移、时延与展宽、目标强度：最大回波强度等回波特征参数的估计方法，并对可以同时对抗声自导鱼雷和主动声纳的某声诱饵回波模拟器进行了仿真研究，并给出了仿真结果，对水声对抗技术研究有着重要的参考价值。     

基于FPGA技术的DSC-UWB发射系统

超宽带(UWB)无线通信技术是一种利用极窄脉冲进行通信的新技术,因其具有低功耗,良好的抗干扰和抗多径的能力以及系统高容量的特点,特别适用于军事隐蔽通信和室内密集多径环境下的高速数据接入,已成为一种极具竞争力的短距离无线通信方式。     

红帮产生和发展的历史机缘

红帮,作为中国近现代服装史上成就和影响最大的一个服装流派,其产生、发展和历史地位的取得,是有深刻的历史机缘和历史依据的。这大致可以从4个方面进行考察:一、从社会历史方面看,宁波人多地少的矛盾是其驱动力;二、从文化思想方面看,宁波地区重商惠商思想、辛亥革命、五四运动和“西风东渐”是其冲击力;三、近代城市和工商业的发展,是其拉动力;四、海洋文化哺育了它的顽强生命力。     

商业广告排版问题研究

研究对象是报纸的商业广告排版问题。将部分或全部待排商业广告指派到广告区域中，目标是广告之间不相互叠压地填满整个广告区域。首先根据问题的特点建立数学模型；然后运用两级分支定界算法对模型进行求解。仿真实验结果表明，该算法能快速地找到解，适合于实际应用。     

数字正交调制器在目标杂波仿真中应用

文中介绍数字正交上变频调制器AD9857的工作原理及其使用方法，并给出它在目标杂波模拟中的应用。     

精炼钢与非精炼钢对冲击功的影响

针对精炼与非精炼船钢低温冲击值的差异，分析了两种钢的化学成分、夹杂物和显微组织等对冲击值的影响。结果表明，钢的精炼可以增加钢的耐冲击能力，使钢的冲击韧性大大提高，满足实际使用要求。     

The effect of some instrument operating conditions on the x-ray microanalysis of particles in the environmental scanning electron microscope

The objective of this investigation was to evaluate the practical effects of electron beam broadening in the environmental scanning electron microscope (ESEM) on particle x-ray microanalysis and to determine some of the optimum operating conditions for this type of analysis. Four sets of experiments were conducted using a Faraday cage and particles of copper, glass, cassiterite, andrutile. The accelerating voltage and chamber pressure varied from 20 to 10 kV and from 665–66 Pa (5.0 to 0.5 torr), respectively. The standard gaseous secondary electron detectors (GSED) and the long environmental secondary dectectors (ESD) for the ESEM were evaluated at different working distances. The effect of these parameters on the presence of artifact peaks was evaluated. The particles were mounted on carbon tape on an aluminum specimen mount and were analyzed individually and as a mixture. Substrate peaks were present in almost all of the spectra. The presence of neighboring particle peaks and the number of counts in these depended upon the operating conditions. In general, few of these peaks were observed with the long ESD detector at 19 mm working distance and at low chamber pressures. More peaks and counts were observed with a deviation from these conditions. The most neighboring peaks and counts were obtained with the GSED detector at 21.5 mm working distance, 10 kV accelerating voltage, and 665 Pa (5.0 torr) chamber pressure. The results of these experiments support the idea that the optimum instrumental operating conditions for EDS analysis in the ESEM occur by minimizing the gas path length and the chamber water vapor pressure, and by maximizing the accelerating voltage. The results suggest that the analyst can expect x-ray counts from the mounting materials. These tests strongly support the recommendation of the manufacturer to use the long ESD detector and a 19 mm working distance for EDS analysis. The results of these experiments indicate that neighboring particles millimeters from the target may contribute x-ray counts to the spectrum.     

Compton profiles of MoP and WP: Validation of second order generalized gradient approximation

Recently, Zhao and Truhlar (J. Chem. Phys. 128, 184109, 2008) have constructed second order generalized gradient approximation (SOGGA) within the density functional theory. The authors have successfully tested the performance of SOGGA by computing lattice constants, cohesive energies, bond distances and few energetic quantities of different solids and molecules. In this paper, to establish the usefulness of SOGGA in deducing the momentum densities, we have compared our experimental Compton profiles of MoP and WP with those computed using GGA and SOGGA within density functional theory. It is seen that SOGGAPBE based Compton profiles of both the samples are in better agreement with the corresponding experimental data than those derived from BPBE-GGA. In addition, energy bands, density of states and relative nature of bonding in both the phosphides is explained in terms of equal-valence-electron-density profiles and Mulliken’s population analysis.     

An updated version of BoltzWann: A code for the evaluation of thermoelectric and electronic transport properties with a maximally-localized Wannier functions basis

BoltzWann is a code to evaluate thermoelectric and electronic transport properties of extended systems with a maximally-localized Wannier function basis set. The semiclassical Boltzmann transport equations for the homogeneous infinite system are solved in the constant relaxation-time approximation and band energies and band derivatives are obtained via Wannier interpolations. Thanks to the exponential localization of the Wannier functions obtained, very high accuracy in the Brillouin zone integrals can be achieved with very moderate computational costs. Moreover, the analytical expression for the band derivatives in the Wannier basis resolves any issues that may occur when evaluating derivatives near band crossings. We present here an updated version of the BoltzWann code, which is now fully integrated within Wannier90 version 2.0, with minor bug fixes and the possibility to study also two-dimensional systems.     

Study of thiol capped CdSe quantum dots using SeO2 precursor for selenium source

CdSe quantum dots in aqueous medium using thioglycollic acid as capping agent have been synthesized. The reaction was carried out in an open atmosphere at pH of 12 and refluxed at 100 °C for 8 h. Selenium dioxide which is less expensive and less toxic has been used as a precursor for selenium source by replacing Se powder and sodium selenite. For characterization QD solutions was taken at different time intervals ranging from 15 min to 6 h. UV–Vis spectroscopy shows that there is a strong blue shift in the prepared quantum dots due to quantum confinement effect. Band gap calculated at different time intervals lies between 2.34 and 2.73 eV which is more than the bulk band gap 1.74 eV and with the increase in size of the QDs, bandgap also decreases. Photoluminescence study was carried out at excitation wavelength of 350 nm and results shows that with increase in time the peak position shift toward higher wavelength. FTIR spectroscopy shows peaks of thioglycollic acid. SEM micrographs of the prepared quantum dots show zero dimensional spherical particles in nm range. For electrical conductivity dc conductivity measurement has been done which shows that with increase of temperature conductivity increases, it confirms the semiconducting nature of the quantum dot. Conduction mechanism found to be mainly due to localized states.