户外噪声相干预测模型及其工程应用

基于几何衍射理论、相干虚源法等理论方法,提出一种适合于工程算法的户外噪声相干预测模型.该相干预测模型不仅能计算声源在经过有限长声屏障或多重声屏障时,由于多条路径衍射声形成的相干声场,还可计算声源在屏障等界面之间经多次反射后,多个反射声形成的相干声场.应用该相干预测模型对某变电站电力变压器周围的相干声场进行预测,通过与ISO9613-2标准算法、边界元法与实测值进行对比,结果表明,该户外噪声相干预测模型能反映出声波在不同位置处的波动性,比原有的ISO9613模型更接近测试结果,证明了所提理论模型的有效性,可应用于大范围的户外噪声预测计算.

散货船三维时域波浪载荷计算研究

采用三维势流理论进行船舶运动和波浪载荷预报时,有2种Green函数可供选择:自由Green函数和Rankine源。混合源法,同时使用这2种Green函数,结合了两者的优点。本文对三维时域混合源法开展研究,为了验证该方法的可行性,本文对一艘散货船进行了时域上运动和波浪载荷的计算,并将计算结果转化到频域上以得到RAO。最终把有航速随浪和顶浪工况下该散货船垂向运动和载荷的RAO与WASIM计算结果以及模型试验结果进行比较。比较结果表明,混合源法计算结果与WASIM结果大体一致;在波长较短时,两者计算结果和试验值结果吻合较好,波长较长时两者计算结果都较试验值偏大。随浪海况下2种计算结果较顶浪更贴近试验值。

阀控式铅酸蓄电池在城市轨道交通中的应用

本文结合阀控式铅酸蓄电池在西安地铁二号线的实际应用情况,分析比较两类阀控式铅酸蓄电池的不同特点,总结阀控式铅酸蓄电池在城市轨道交通各子系统中的实际应用要求,同时,本文提供了两种运用较为广泛的UPS蓄电池容量计算方法及蓄电池的日常维护要点。

Transfer element method with application to acoustic design of aeroengine nacelle

In the present survey, various methods for the acoustic design of aeroengine nacelle are first briefly introduced along with the comments on their advantages and disadvantages for practi- cal application, and then detailed analysis and discussion focus on a kind of new method which is called ＂transfer element method＂ （TEM） with emphasis on its application in the following three problems： turbomachinery noise generations, sound transmission in ducts and radiation from the inlet and outlet of ducts, as well as the interaction between them. In the theoretical frame of the TEM, the solution of acoustic field in an infinite duct with stator sound source or liner is extended to that in a finite domain with all knows and unknowns on the interface plane, and the relevant acoustic field is solved by setting up matching equation. In addition, based on combining the TEM with the boundary element method （BEM） by establishing the pressure and its derivative con- tinuum conditions on the inlet and outlet surface, the sound radiation from the inlet and outlet of ducts can also be investigated. Finally, the effects of various interactions between the sound source and acoustic treatment have been discussed in this survey. The numerical examples indicate that it is quite important to consider the effect of such interactions on sound attenuation during the acoustic design of aeroengine nacelle.

基于附加源项法的钠冷快堆冷热池三维分析

选择计算流体动力学(CFD)为模拟手段,建立快堆一回路钠池的三维闭式一体化CFD模型,对一回路中主要部件进行模拟,其中中间热交换器、独立热交换器、堆芯、主泵采用附加源项法进行模拟,得到中国实验快堆(CEFR)额定功率稳态运行时整个流场的三维速度场与温度场。计算值同CEFR设计值进行比较,结果符合预期,证明了模型的合理性。计算结果表明,钠池较明显地分为温度较低的冷钠池和温度较高的热钠池2个部分,热钠池温差较大,冷热流体搅混现象明显;同时冷钠池、热钠池不同高度的平均温度都很接近,说明分隔冷热钠池的热屏蔽效果较好。

一种用于提高点源法MTF检测精度的去噪方法

使用点源法可以严密检测调制传递函数(MTF),能够有效检验各个方向的MTF值,可用于空间探测相机在轨性能的监测。但点源图像存在噪声,利用传统滤波方法对其进行去噪处理,会存在检测精度不足甚至出现MTF曲线阶跃近似为0的现象,从而影响其对成像质量的评判。因此,根据点源图像光强分布的特点,提出一种基于平缓区均值的点源图去噪方法,并将该方法与传统滤波方法进行定量比较。仿真和实验结果表明:该方法将MTF曲线的检测率提高到90.91%以上,相比于传统滤波方法中效果最好的中值滤波,MTF的检测精度能提高98.73%,同时提高图像的峰值信噪比和结构相似度。