盒形塑件的几何构型与计算机充模流动模拟

基于Hele_Shaw流动数学模型 ,给出了构造3D塑件CAD模型并向CAE模型转换的方法和技术 ,通过对塑件进行有限元网格的剖分以及注射成型过程的数值模拟 ,得到了减少塑件充模流动成型缺陷 ,改进熔体充模效果及产品设计的技术方法     

几何约束下TIG焊焊枪姿态研究

火箭发动机关键部件自动TIG焊中，因一些焊缝周围有特殊结构，为避免相碰，只能使焊枪偏转一个角度进行焊接，且此焊枪姿态与表征电弧电压的弧长和钨极伸出长度等有一定的关系，为了易于离线编程，必须对焊枪姿态进行深入分析。以火箭发动机典型的几何约束焊缝为例，提出了通用的求解思路。实际应用表明，此方法结果正确，可应用到各种几何约束焊缝的焊枪姿态分析中。     

A novel arc welding inverter with unit power factor based on DSP control

A novel inverter power source is developed characterized with constant output current and unit power factor input. Digital signal processor （ DSP ） is used to realize power factor correction and control of back-stage inverter bridge of the arc welding inverter. The fore-stage adopts double closed loop proportion and integration （PI） rectifier technique and the back- stage adopts digital pulse width modulation （ PWM） technique. Simulated waves can be obtained in Matlab/Simulink and validated by experiments. Experiments of the prototype showed that the total harmonic distortion （THD） can be controlled within 10% and the power factor is approximate to 1.     

Adiabatic versus non-adiabatic approach to the inner sphere vibrational effects on electrochemical reduction rates

This work is a theoretical comparative study on the adiabatic and non-adiabatic mechanisms of electrochemical reductions. In our previous paper [A. Ignaczak, W. Schmickler, Electrochim. Acta 52 (2007) 5621] several aspects of the reaction kinetics were discussed for the adiabatic electron transfer from the electrode to the reactant, taking aquocomplexes as a testing case. In the present work the same reactions are studied in the non-adiabatic approach. First order perturbation theory is applied to analyze the rate dependence on quantum effects associated with inner sphere nuclear vibrations using the same model Hamiltonian. It describes independently the solvent reorganization and the intramolecular modification of the reactant. In case of complexes the ligand shell in the oxidized and reduced states is characterized by two different frequencies, ω₁ and ω₂, respectively, so the ratio θ = ω₂/ω₁ describes asymmetry of the potential energy surface. An influence of different θ values combined with high and low ligand frequencies on the rate enhancement due to the nuclear tunnelling is tested.The quantum correction, calculated as k_q/k_s (k_q, the non-adiabatic rate; k_s, the adiabatic rate), is found to depend strongly on θ and ω₁ parameters as well as on the overpotential applied. The rate enhancement is especially sensitive to the initial state frequency ω₁ for systems characterized by larger θ values. For overpotential η = 0 V, when ω₁ = 250 cm⁻¹ the ratio k_q/k_s is equal to 1.35 (θ = 2/3), 0.65 (θ = 1) and 0.38 (θ = 3/2), while for ω₁ = 1000 cm⁻¹ the corresponding values are 4.05, 3.94 and 4.77. These values increase significantly when the overpotential is applied, up to 14 for the largest values of ω₁ and θ. The transfer coefficient is also presented for the two reaction mechanisms as a function of all parameters tested. An effect of the reactant-electrode interaction and the friction parameter on the rate constants is also analyzed for all cases.     

非线性尺寸链卷积算法的计算偏差修正

在统计公差卷积算法中,非线性装配函数的线性化会使计算结果产生偏差,并影响公差分析的精度．为了减小非线性装配函数线性化所产生的计算偏差,提出了一种偏差修正方法,分析了修正偏差的原理．该方法可有效地提高公差分析的精度,并用实例说明了该方法的有效性．     

玻化微珠保温砂浆的吸放湿及导热性能

针对湿热地区潮湿气候作用下建筑保温砂浆受潮的规律,采用天平称重法对玻化微珠保温砂浆进行了自然状态吸放湿实验,并采用热湿气候风洞实验法对其质量平衡含湿率进行测定,进而采用平板法对其湿平衡状态下的导热系数进行了一系列测试分析。结果表明,在南方地区潮湿气候条件下玻化微珠保温砂浆质量平衡含湿率约为3．55％;湿平衡状态下玻化微珠保温砂浆导热系数修正系数在1．04～1．11之间,平均值为1．08,考虑受潮现象的复杂性,建议在实际建筑工程节能设计时,该修正系数宜取1．10。     

输电塔-线体系覆冰作用非线性分析

在重冰区,高柔大跨越输电塔-线体系在覆冰、风载等作用下具有强烈的耦合特性和非线性特征。推导了绝缘子、索以及边界条件的刚度表达式,以向家坝-上海±800kV特高压直流输电线路为例,建立了输电塔、导线、绝缘子以及边界条件的简化数值分析模型。对大跨越输电塔－线体系进行了7种工况下的静力非线性分析。分析表明,在导线均匀覆冰及风荷载作用下,铁塔构件的P-△效应较小;在不均匀覆冰工况下,导线不平衡荷载对铁塔产生扭转效应,铁塔受压支座节点和最大悬臂处单元的轴向压力和弯矩具有较明显的P-△效应,应考虑荷载非线性的不利影响。     

三相单级全桥PFC电压尖峰机理分析与抑制

介绍了一种基于全桥结构的三相单级功率因数校正(PFC)变换器,该变换器工作于电感电流断续模式(DCM),电感电流即输入电流的峰值自动跟踪输入电压,可实现功率因数校正.建立了桥臂开关对臂导通时变换器的简化模型,并分析了该阶段变压器原边电压尖峰的产生机理.分析结果表明,由于变压器漏感的存在,变压器原边于桥臂开关对臂导通期间将产生很大的电压尖峰,该电压尖峰大小由变压器原边的漏感、电流与并联电容三个参数决定.最后,结合电路的工作原理,提出了一种变压器原边无源缓冲电路来抑制该电压尖峰.实验结果表明,变压器原边的电压尖峰得到了有效抑制.     

随机环境下的幂变换门限ARMA-ARCH模型的极限行为

提出了随机环境下的幂变换门限自回归滑动平均自回归条件异方差模型,得出了其以几何速率收敛的充分条件．     

MiroSot机器人足球视觉系统图象畸变的几何校正

针对MiroSot足球机器人视觉系统中的图像畸变,采用了一种新的几何畸变数学模型几何校正方法.考虑摄像头不在场地中央正上方及摄像头偏转后的情形,对镜头几何畸变数学模型进行了修正.通过取场地特征点坐标构成方程组,解出模型中的待定系数.采用牛顿迭代法实现全场坐标的校正运算,并在VC6.0上实现了新的几何校正算法,结果表明场地图像畸变得到了有效的校正.