Optimal design of acoustic performance for automotive air-cleaner

The research on optimal design of acoustic performance for air-cleaner was presented and evaluated in this paper using a numerical simulation method and experimental method. A modified measurement was proposed in the paper to solve the problem of air flow noise caused by the original measurement layout. The modified measurement was proved to produce good results. A new study on the acoustic effect of filter was also developed here and noise reduction (NR) of the air-cleaner was predicted based on the study using the numerical simulation method. Actual intake noise was then predicted using the simulation method. Side branch silencers were designed to improve the acoustic capacity of the air-cleaner. The result shows that the newly optimized air-cleaner has a much better performance of noise elimination when engine operating.     

A Simple Physical Approach to Study Spectrum of Baryons

The exact solution of Schrödinger equation corresponding to a baryonic system is the main interest in the present work. We take into account both quadratic and Coulomb terms in the potential relation. Next, after presenting an exact solution, we have calculated the spin and isospin effects in both ground and excited states. The results are comparable with experimental data.     

一种捕捉多向刚性爆轰波的激波定位随机投影方法

提出一种激波定位随机投影方法,利用当地随机投影,引入激波指示器并提出恰当的判定当地投影区域的规则,使爆轰波多向推进的问题得以解决。数值实验表明,激波定位随机投影方法不仅适用于爆轰波的多向推进,还能高效求解刚性反应方程,易于推广到三维情况。     

基于微机电系统红外光源的长光程气体检测

针对红外气体传感器对光源的要求,选用了一种宽波长、高调制频率、低功耗的小体积微机电系统(micro-electro-mechanic system, MEMS)红外光源作为辐射源,其各项性能均能很好的满足红外传感系统对于光源的要求。由于其面光源的朗伯辐射特性,整形之后的红外光数值孔径仍然很大,采用传统的长光程气室结构很难实现长光程从而提高系统的检测灵敏度。本文结合双波长单光路的差分检测方法,设计了一种基于积分球特性的吸收气室,有效地解决了MEMS红外光源在高灵敏度气体检测应用中难于实现长光程的问题;并运用光在传输过程中光通量守恒的原理,推导了此积分球吸收气室的等效光程,解决了积分球气室等效光程计算的难题;同时采用FPGA主控芯片对MEMS红外光源进行高频调制并处理探测器的输出信号,使得外围电路的设计更加简单、灵活。设计中,使用直径为5 cm的积分球吸收气室便可实现166.7 cm的等效光程,研究结果显示系统可测得的最小甲烷浓度达0.001×10-6,极大地提高了红外检测系统的灵敏度。     

基于光谱诊断的热源间距对激光-脉冲GMAW复合焊等离子体物理特性影响研究

激光电弧复合焊中,热源间距会影响到等离子体物理特性,进而影响到焊接过程的稳定性及焊接质量。 基于Boltzmann作图法和Stark展宽法研究了不同热源间距下的激光-脉冲GMAW复合焊峰值阶段的温度场和电子密度分布,并结合高速摄影手段分析了热源间距对温度和电子密度的影响规律。 光谱诊断结果表明,随着热源间距的增大,激光等离子体的温度和电子密度都没有明显的变化;电弧温度出现下降,电弧电子密度则呈现先增高后降低的趋势。     

近红外定性分析模型的稳健性与适应性分析

研究了近红外定性分析中模型的稳健性与适应性问题。讨论了单独建模延长建模周期对模型性能的影响,结果显示这种方法可以显著提高模型的稳健性,同时对模型的台间适应性也有所提升,但提升作用有限;研究了不同仪器联合建模的方法对模型性能的影响,该方法不仅可以显著提高模型的适应性,而且可以有效提高模型的稳健性。对比单独建模,可以缩短建模时间,减少模型建立的工作量;延长模型的适用期限,提高建模效率。结果表明,对模型适应性的测试,单独建模其正确识别率较低,不能满足应用的要求,而多台仪器联合建模可以达到90%以上,提升效果明显;对模型稳健性的测试,联合建模也能得到相比单独建模更好的模型识别效果,具有很好的应用价值。     

检测含任意项特殊逻辑函数的图形方法

线性函数、冗余特殊、自反函数、自双反函数等特殊逻辑函数在电路设计中具有独特的优点.从特殊逻辑函数的定义出发,提出了基于K图检测含任意项线性函数、冗余函数的方法及基于分解图检测含任意项自反函数、自双反函数的方法,并举例说明了具体检测过程.应用结果表明,该图形方法具有直观,便捷等特点.     

Acoustic beam splitting in a sonic crystal around a directional band gap

Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size,which facilitates circumvention of a directional band gap.Experiments reveal that two distinct beams emerge at crystal output,in agreement with the numerical results obtained through the finite-element method.Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space.Split beams propagate in equal amplitude,whereas beam splitting is destructed for oblique incidence above a critical incidence angle.     

State-space approach to two-temperature generalized thermoelasticity without energy dissipation of medium subjected to moving heat source

In this work,a model of two-temperature generalized thermoelasticity without energy dissipation for an elastic half-space with constant elastic parameters is constructed.The Laplace transform and state-space techniques are used to obtain the general solution for any set of boundary conditions.The general solutions are applied to a specific problem of a half-space subjected to a moving heat source with a constant velocity.The inverse Laplace transforms are computed numerically,and the comparisons are shown in figures to estimate the effects of the heat source velocity and the two-temperature parameter.     

Modified characteristic finite difference fractional step method for moving boundary value problem of nonlinear percolation system

A fractional step scheme with modified characteristic finite differences running in a parallel arithmetic is presented to simulate a nonlinear percolation system of multilayer dynamics of fluids in a porous medium with moving boundary values. With the help of theoretical techniques including the change of regions, piecewise threefold quadratic interpolation, calculus of variations, multiplicative commutation rule of difference operators, multiplicative commutation rule of difference operators, decomposition of high order difference operators, induction hypothesis, and prior estimates, an optimal order in l ² norm is displayed to complete the convergence analysis of the numerical algorithm. Some numerical results arising in the actual simulation of migration-accumulation of oil resources by this method are listed in the last section.