Study of speech enhancement in the background of ship-radiated noise

Spectral subtraction is wildly used in speech enhancement. But it is not always available in the ship working environment because of the fact that it is hard to discriminate the speech duration with the ship noise. So, in this paper, we propose a new approach, which first computes the frequency spectrum similarity and then discriminates the signal segments into speech or noise roughly. And then by the frame shifting method, we achieve a high discrimination precision. Finally, the improved algorithm is benchmarked on a large measured data and experimental results show that the proposed method can be used in various ship-radiated noise environments. The discrimination accuracy is 98％ for ship-radiated noise and 96％ for speech.     

基于PERT仿真的导弹技术准备流程优化分析

为满足导弹快速保障需求,利用PERT仿真对某导弹技术准备流程进行优化分析,同时引入工作关键度和重要度2个指标来定量评价各项工作对技术准备流程进度计划按时完工的影响。通过仿真准确预测了优化的效果,得到了项目完工概率及各项工作的定量评价指标值。结果表明,优化后技术准备时间明显缩短,并能准确预测优化效果,为流程进度控制提供合理的方法和参考依据。     

基于RBF神经网络的Kalman滤波在惯导系统传递对准中的应用

针对模型存在误差时传统的Kalman滤波算法误差变大甚至发散的缺点,利用RBF神经网络较强的非线性逼近能力,提出用RBF神经网络辅助Kalman滤波的新算法,将其应用于舰载机惯导系统的传递对准中。仿真表明该算法优于传统Kalman滤波算法。     

单周期控制的航空高功率因数变流器仿真

分析单周期控制的高功率因数变流器的工作原理,给出基于单周期控制的航空高功率因数变流器主电路和控制电路各组成部分的设计及参数,并应用OrCAD对基于单周期控制的高功率因数变流器进行仿真研究。仿真结果表明,基于单周期控制技术的单相高功率因数整流器的输入电流能很好地跟踪输入电压,输入电流总谐波畸变率THD控制在5％以内,功率因数PF达到0．99以上,控制方法简单、可靠和通用。     

Incorporation of halloysite nanotubes into PVDF matrix: Nucleation of electroactive phase accompany with significant reinforcement and dimensional stability improvement

Poly(vinylidene fluoride)/halloysite nanotubes (PVDF/HNTs) nanocomposites were prepared via melt compounding. Electroactive β- and γ-phases of PVDF were nucleated by the HNTs due to electrical interaction between negatively charged surface of the HNTs and CH₂ groups of the PVDF. The ends and surface defects of the HNTs were also responsible for the formation of γ-phase, since long trans conformations with gauche defects were induced at the two regions via the formation of hydrogen bonding. In addition to nucleation of the electroactive phase, the HNTs were found to reinforce the PVDF matrix and improve its dimensional stability, as evidenced by the substantially increased tensile strength and Young’s modulus, and the remarkably decreased coefficient of thermal expansion (CTE). The improved tensile property and reduced CTE were attributed to the uniformly dispersed HNTs and good interfacial interaction between HNTs and PVDF matrix via hydrogen bonding.     

一种基于GA-BP 算法的PIDNN 控制策略

为改善常规PID控制器对非线性对象的控制性能,提出一种基于GA-BP算法的PID神经网络（PID NeuralNetwork,PIDNN）控制策略。将PID控制规律融入神经网络,构成一种PIDNN控制器,并利用GA-BP算法来对其进行参数优化。采用所设计的PIDNN控制器对一种非线性系统进行仿真研究,仿真结果表明：GA-BP算法收敛速度快,所设计的PIDNN控制器与常规PID控制器相比,其控制稳定性和快速性等性能都得到了很大改善。     

Acoustic,thermal and luminous comfort in classrooms

Environmental comfort embodies four different research areas: thermal, luminic, acoustic and ergonomic comfort. However, regarding the built environment, architects and civil engineers should primarily concentrate their efforts on the first three, considering that ergonomic comfort is more related to designers. The purpose of the present paper is to discuss the results of a series of investigations regarding the performance of classrooms, which took place in classrooms of the Federal Center of Technological Education of the State Paraná (Centro Federal de Educação Tecnológica do Paraná—CEFET-PR). Thus, it was possible to cover most of the research area of environmental comfort in an integrated manner.     

加速退化失效产品可靠性评估方法

为了解决具有可靠性高、寿命长等特点的退化失效产品的可靠性评估问题,结合退化失效型产品失效特性,提出了加速退化方程的概念,研究了BS模型的加速退化数据的统计推断方法,为验证方法的有效性,将该方法用于金属化膜脉冲电容器的可靠性评定中.结果表明:该型电容器可靠性模型中未知参数的估计值分别为9.0669×10-8和0.0221,将该值代入失效分布函数即可确定电容器的失效模型,由此模型求得该型电容器充放电20000次的可靠度为0.9724.使用这种分析方式对退化失效产品进行可靠性分析将更能节省试验时间和费用.     

Electromagnetic simulation of passive ICs

This paper describes the outline of a method for simulating the electromagnetic behaviour of ICs fabricated in the RF passive integration process. The theory is an extension of that used in the CAD package Fasterix. This is modified to take account of the losses and other aspects of the IC process. The new theory is then applied to the design of a power amplifier for a mobile phone handset, and the results presented demonstrate its accuracy, speed and flexibility. Further results demonstrate that use of this powerful new model can lead to improved electrical performance of real RF applications.     

Simulation of temperature-compensated voltage limit curves for aerospace NiCd batteries using a first principles' model

Temperature-compensated voltage limits (V/T limits) are routinely used in Low Earth Orbit (LEO) satellites to permit fast charging of the NiCd battery with minimum overcharge and without the problems of thermal runaway during overcharge. The voltage limits are experimentally determined from extensive testing of cells for a proper design of the charge control system to achieve the desired charge/discharge ratio in orbit. Here, we demonstrate the use of first-principles', mathematical models to construct the V/T curves theoretically. The predicted charge/discharge ratios under various orbit conditions such as different states of charge, in-rush currents and temperatures are compared with the experimental data.