机翼防冰过程中冰脊问题的数值分析

对机翼防冰过程中冰脊的形成特点及冰脊对机翼气动特性的影响进行了计算分析.基于经典的Messinger结冰模型开发了多步结冰程序,对不同条件下过冷水滴的撞击结冰进行了热质耦合计算,计算结果和文献试验结果吻合较好,表明该热质耦合算法的正确性.在此基础上对不同环境温度、飞行速度和不同加热功率等条件下冰脊的生长特点和机翼的气动特性进行了计算分析.结果表明:在非霜冰条件下,冰脊主要在热防护极限外并紧挨着热防护极限的位置处形成和发展,而在霜冰条件下,冰脊主要在机翼下表面形成,但是在热防护区域内有显著的结冰出现,该条件下的结冰对机翼的气动特性具有较大的破坏性.     

Single-phase grid-connected PV system using three-arm rectifier-inverter

A grid-connected photovoltaic (PV) power supply system with on-line voltage regulation capability is presented. It employs the three-arm rectifier-inverter topology with PV modules connected directly on the dc-link. The common-arm is with line-frequency switching and synchronous to the input voltage, aiming for a lower switching loss and decoupling the control of rectifier and inverter portions. As a result, the rectifier and inverter portions can be controlled independently with the rectifier-arm and inverter-arm, respectively. For maximum power point tracking (MPFF) of the PV modules and balancing the power among utility, PV, and the load, a variable dc-link voltage is adopted and controlled by the rectifier-arm based on the MPPT control algorithm. The inverter-arm then regulates the load voltage with good regulation and low distortion. Due to large variation of the dc-link voltage, a feedforward plus feedback control technique with variable gain is developed to keep constant bandwidth of the current loop at any operation condition. Therefore, the performance of the rectifier and inverter portions can be ensured. A system containing a 2 kVA converter and a 1.2 kW PV module is set up, and some experimental results are provided for demonstrating the effectiveness of the proposed method.     

An efficient algorithm for multisensor track fusion

An efficient algorithm for track-to-track fusion by incorporating cross-covariance between tracks created by dissimilar sensors is described. An analytical solution of this problem is complicated if cross-correlation between sensors tracking the same target is taken into account. An explicit solution of the cross-covariance matrix at steady state is derived in terms of an integral. It is shown that solution of this integral involves inversion of a matrix whose elements are functions of parameters of individual trackers. Structure of this matrix is analyzed. An efficient analytical solution for inversion of this matrix is obtained. For fusion of similar sensors, it is shown that this matrix is reduced to the Routh-Hurwitz matrix which arises in the study of steady state stability of linear systems. Numerical results showing the amount of reduction of fused track covariance by taking into account the effects of cross-correlation between candidate tracks for fusion is also presented     

进口圆度仪智能化改造

以Talyrond73型圆度仪为例，介绍了圆度仪智能化改造的基本原理，圆度测量软件的主要功能以及回度误差评定方法的优化，探讨了保证检测精度的若干措施，并给出了检定结果。     

燃烧室燃烧与排放特性试验与数值计算

为了探寻燃烧室进口空气温度、压力以及油气比对点熄火边界、温升、燃烧效率以及主要排放物摩尔分数的影响规律， 对航空发动机燃烧室在多工况下的点熄火特性、出口温度分布与主要排放物摩尔分数进行了试验测试。分别采用正癸烷的简化 反应机理与C 12 H 23 燃料的单步反应机理，对该燃烧室火焰筒内流场结构、温度场、中间组分与主要排放物摩尔分数分布特性进行了 数值计算，并与相应试验数据进行了对比分析。结果表明：随着燃烧室进口空气温度、压力以及油气比的提高，燃烧室燃烧效率、 温升、出口平均温度与NO X 摩尔分数逐渐提高，而UHC与CO摩尔分数逐渐降低；与采用C 12 H 23 燃料单步反应机理相比，采用正癸 烷的简化反应机理计算得到的火焰筒内流场与温度场分布更为合理，火焰筒出口温度场分布以及主要排放物摩尔分数与相应试 验数据更为接近，计算精度得到较大提高。     

基于等基因序列双重随机遗传算法的复合材料铺层优化

复合材料铺层优化中常用的各种遗传算法，较难同时综合考虑表面45°、分层比例、连续铺层数限制等复杂工程约束问题，基于此，提出一种针对复合材料层压板的等基因序列双重随机遗传算法，在交换和突变算子中引入双重随机算法以保证优化迭代中基因序列的严格相等，基于SABRE 软件实现该优化算法，并通过算例验证算法的正确性。结果表明：该算法可满足均衡性、对称性、表面45°、连续铺层数限制、铺层比例等复杂工程约束，有较高的可靠性与工程适用性。     

Collimator-based Fourier-transform imaging

In viewpoint of signal processing, we describe the principle of collimator-based Fourier-transform imaging, from verifying Fourier-transform function of collimator to presenting theoretical model of dirty image. This gives us a guideline in designing collimator imager, that is configuring the subcollimators properly to improve the quality of the dirty image. Here we optimize the arrangement of the subcollimators of YOHKOH Hard X-ray Telescope (HXT) to get the Point Spread Function of sidelobes as small as possible and simulate that with MATLAB.     

Crosslink slot assignment in LEO networks

The problem of crosslink time slot assignment in low Earth orbiting (LEO) satellite networks is addressed. A crosslink channel connects two neighboring satellites through half-duplexed directional antennas. Coordination among the crosslinks between a satellite and all its neighbors in a dynamic LEO network is a delicate problem and rarely addressed in the literature. The problem is solved here using bipartite graphs. Two versions of slot assignment algorithm are given: distributed and centralized.     

路孔:河水带来的遥远繁华

路孔．一个傍水而建．因水而兴的古镇。身处路孔．开始怀念河水带来的遥远的繁华．也默默感受着濑溪河对路孔的不离不弃。 距重庆荣昌县城13公里的路孔镇不大．只有24平方公里．却足以让人怀古思幽。在古镇上，人们最津津乐道的是古镇的名．因水而名的传说。相传明朝有位叫曾傲的和尚，云游到此，见河对岸带风景宜人．适于修身养性．决定在此建座寺庙。和尚发觉坡边有八个石孔．似与河中相通，     

等截面通道角形挤压对高纯铝微观组织及力学性能的影响

采用等截面通道角形挤压技术对高纯铝进行室温大塑性变形 ,通过不同角度模具沿路径 A组合挤压 ,实现了高纯铝的晶粒细化 ,晶粒尺寸可达 0 .6 μm以下 ,且硬度和屈服强度显著增加。微观组织分析表明 :不同角度模具组合挤压可以得到不同的剪切平面组合 ,使得相邻两次挤压剪切平面的夹角为 75°,从而使得高纯铝在相对较小的塑性变形情况下得到超细晶粒结构 ,证明等截面通道角形挤压方法中剪切平面对晶粒细化效果的影响是非常大的