S7—200PLC在遥控器自动检测中的应用

在分析PLC控制系统的基础上,介绍了PLC在遥控器自动检测中的应用。本文对硬件和软件设计做了较为详细的描述,并给出了具体的梯形图程序,实现了PLC对遥控器按键的自动控制。实践表明PLC控制系统具有可靠性强、抗干扰能力强等优点。     

Process simulation and modeling: Anaerobic digestion of complex organic matter

This work is focused on evaluating kinetic models of complex organic matters hydrolysis and volatile fatty acids degradation in anaerobic digestion process, simulated using SuperPro design software. Kinetic model evaluation was also carried for simulated integrated system of liquid anaerobic digestion (LAD) of dairy manure and solid state anaerobic digestion (SS-AD) of corn stover. Already developed hydrolysis and volatile fatty acid (VFA) degradation kinetic constants were used to simulate anaerobic digestion processes of dairy manure and corn stover separately and in the integrated process as well. Hydrolysis of complex soluble organic matters such as protein, carbohydrate and fat was modelled using first-order kinetics. Monod model was tested for the VFAs such as acetic, propionic and butyric acid degradation and biogas production. Comparative study has been done between the experimental data published already and results obtained from SuperPro simulated processes. The simulated results were well comparable with the experimental results.     

热轧卷取温度对HC340LAD+Z带钢力学性能的影响

为了研究热轧卷取温度对热镀锌HC340LAD+Z带钢力学性能的影响规律,对同一炉次、相同规格的3批次钢坯,分别采用580、620、660 ℃3个卷取温度,以及相同的冷轧、热镀锌、退火工艺进行了试验研究。结果表明,随着卷取温度的升高,成品带钢的屈服强度、抗拉强度降低,伸长率稍有增加,均满足EN10346标准对HC340LAD+Z带钢力学性能的要求。热轧卷取温度为620 ℃时,HC340LAD+Z带钢的屈服强度为389.2 MPa,抗拉强度为474.3 MPa,伸长率A80为26.5%,其综合力学性能对比标准指标,富裕量最佳。     

LAI based trees selection for mid latitude urban developments: A microclimatic study in Cairo, Egypt

To study the leaf area index, LAI, based thermal performance in distinguishing trees for Cairo's urban developments, ENVI-met plants database was used as platform for a foliage modeling parameter, the leaf area density, LAD. Two Egyptian trees; Ficus elastica, and Peltophorum pterocarpum were simulated in 2 urban sites with one having no trees, whilst the second is having Ficus nitida trees. Trees LAD values were calculated using flat leaves' trees LAI definition to produce maximum ground solid shadow at peak time. An empirical value of 1 for LAI is applied to numerically introduce LAD values for ENVI-met.Basically, different meteorological records showed improvements for pedestrian comfort and ambient microclimate of the building using F. elastica. About 40–50% interception of direct radiation, reductions in surfaces' fluxes around trees and in radiant temperature T_mrt in comparison to base cases gave preferability to F. elastica. The lack of soil water prevented evapotranspiration to take place effectively and the reduced wind speeds concluded negligible air temperature differences from both base cases except slightly appeared with the F. elastica. Results show that a flat leaves tree if does not validate LAI of 1, the ground shading would not fulfill about 50% direct radiation interception and this value can be used as a reference for urban trees selection.Further simulations were held to investigate LAI value of maximum direct radiation interception.Performing additional simulations, F. elastica of LAI of 3 intercepted almost 84% of direct radiation and revealed implications about urban trees in practice and its actual LAI.     

筛网LAD通道液氮动态出流性能研究

为了研究筛网LAD通道结构在低温推进剂中的气液分离及输送性能,设计、加工了覆盖筛网的圆管通道并通过可视化实验获得了液氮中LAD通道有效工作时的极限排放高度,并分析了流动损失的组成.结果 表明,325×2300 Dutch Twill型编织筛网在自增压过程中发生泡破时的液氮极限排放高度为280 mm,所产生的水力静压损失...     

基于点云数据的单木三维绿量估算方法

针对不同树种的树叶疏密及空间结构不同,提出基于激光点云数据,顾及冠层叶面积密度的树木三维绿量（Living Vegetation Volume, LVV）计算方法。该方法首先根据树木局部点云的主方向相似度和局部点云轴向分布密度分离枝干与树叶,剔除非光合作用成分,提取树叶点云;然后建立体元模型,引入Graham算法确定分层树冠边界,获取激光接触频率,从而基于体元冠层分析（Voxel-based Canopy Profiling, VCP）方法求出冠层叶面积密度（Leaf Area Density, LAD）;最后分层棱柱体积乘以叶面积密度,累加得到树木的三维绿量。利用Riegl VZ-400地面激光扫描仪获取13棵不同形状和树种的树木点云数据,利用该方法估算各树木三维绿量,并与传统的凸包法和台积法的结果对比。实验结果表明,台积法计算的三维绿量值最大,凸包法计算的三维绿量次之,顾及冠层叶面积密度的树木三维绿量方法计算的三维绿量值最小,为台积法的36.69%,为凸包法的47.80%。相比传统方法,顾及冠层叶面积密度的树木三维绿量计算方法侧重光合作用组分叶片点云的统计,并考虑了树冠内部树叶分布情况,更符合树木的实际情况,能充分利用三维点云数据特性,反映树冠内部三维绿量分布。     

Delamination fracture of prestressing steel: An engineering approach

This paper provides a composites engineering approach to explain the stress corrosion behaviour of high-strength prestressing steel wires. To this end, two eutectoid steels in the form of hot rolled bar and cold drawn wire were subjected to slow strain rate tests in aqueous environments in corrosive conditions corresponding to localized anodic dissolution and hydrogen assisted cracking. While a tensile crack in the hot rolled bar always propagates in mode I, in the cold drawn wire an initially mode I crack deviates significantly from its normal mode I growth plane and approaches the wire axis or cold drawing direction, thus producing a mixed mode propagation. In hydrogen assisted cracking the deviation happens just after the fatigue pre-crack, whereas in localized anodic dissolution the material is able to undergo mode I cracking before the deflection takes place. Therefore, a different behaviour is observed in both steels and even in the same steel under distinct environmental conditions. An explanation of such behaviour can be found in the pearlitic microstructure of the steels. This microstructural arrangement is randomly-oriented in the case of the hot rolled bar and markedly oriented under the wire axis direction in the case of the cold drawn wire. Thus both materials behave as composites at the microstructural level and their plated structure (oriented or not) would explain the different time-dependent behaviour in a corrosive environment.     

基于递归神经网络的永磁同步电机参数辨识研究

电机参数的变化会加大永磁同步电动机(PMSM)的控制难度,所以研究参数辨识对于闭环控制系统的稳定运行有着重大的意义。在采用变分理论实现最小绝对值偏差法(LAD)的基础上,研究了一种基于递归神经网络(RNN)的辨识方法。仿真结果表明,该方法具有很快的收敛速度,能准确地辨识PMSM的定子电阻、d,q轴电枢电感及转子磁链等参数,并且具有良好鲁棒性,在出现参数变化或异常值情况下仍能辨识到正确结果。     

Simulation on vertical wicking behaviors of liquid hydrogen within metallic weaves in terrestrial and microgravity environments

To predict the wicking performance of liquid hydrogen (LH₂) in porous screens, we introduced an evaporative wicking model which has been verified by experiments in liquid nitrogen (LN₂). The effects of the fluid properties, the gravity level, the superheated degree and the screen structure parameters on the vertical wicking of saturated LH₂ were systematically investigated. The wicking in LH₂ performs better than that in LN₂, presenting higher maximal wicking height and wicking velocity. At lower gravity, the wicking performance is better in whole but much more sensitive to the changes of superheated condition and structure parameters of the screen. The thermal effect of superheated gas region plays a decisive role in wicking behaviors, significantly reducing the wicking velocity and equilibrium height. The effects of permeability and thickness of the screen are obviously different at superheated condition compared to the isothermal cases.     

LAD回归在变量异常方面的应用

对LAD回归关于响应变量的异常影响较小,而对解释变量的异常较为敏感的问题,给出一种简单方法：把水平方向的偏差转换成垂直方向的偏差来处理。应用结果表明,该方法具有较高的稳健性。