Experimental study on the width of the turbulent area around bridge pier

At present, the method of calculating the turbulent flow width around the bridge pier is not given in the "Standard for Inland River Navigation" (GB50139-2004) in China, and the bridge designer usually increases the bridge span in order to ensure the navigation safety, which increases both of the structural design difficulty and the project investments. Therefore, it is extremely essential to give a research on the turbulent flow width around the bridge pier. Through the experiments of the fixed bed and the mobile bed, the factors influencing the turbulent flow width around the bridge pier have been analyzed, such as the approaching flow speed, the water depth, the angles between the bridge pier and the flow direction, the sizes of bridge pier, the shapes of the bridge pier, and the scouring around the bridge pier, etc. Through applying the dimension analytic method to the measured data, the formula of calculating the turbulent flow width around the bridge pier is then inferred.     

A second order volume of fluid （VOF） scheme for numerical simulation of 2-D breaking waves

Among all environmental forces acting on ocean structures and marine vessels, those resulting from wave impacts are likely to yield the highest loads. Being highly nonlinear, transient and complex, a theoretical analysis of their impact would be impossible without numerical simulations. In this paper, a pressure-split two-stage numerical algorithm is proposed based on Volume Of Fluid (VOF) methodology. The algorithm is characterized by introduction of two pressures at each half and full cycle time step, and thus it is a second-order accurate algorithm in time. A simplified second-order Godunov-type solver is used for the continuity equations. The method is applied to simulation of breaking waves in a 2-D water tank, and a qualitative comparison with experimental photo observations is made. Quite consistent results are observed between simulations and experiments. Commercially available software and Boundary Integral Method (BIM) have also been used to simulate the same problem. The results from present code and BIM are in good agreement with respect to breaking location and timing, while the results obtained from the commercial software which is only first-order accurate in time has clearly showed a temporal and spatial lag, verifying the need to use a higher order numerical scheme.     

Using a SVM to evaluate damage to vibration isolators in an elastic raft system

Predicting damage to vibration isolators in a raft experiencing heavy shock loadings from explosions is an important task when designing a raft system. It is also vital to be able to research the vulnerability of heavily shocked floating rafts unreliable, especially when the allowable values The conventional approach to prediction has been or ultimate values of vibration isolators of supposedly uniform standard in a raft actually have differing and uncertain values due to defective workmanship. A new model for predicting damage to vibration isolators in a shocked floating raft system is presented in this paper. It is based on a support vector machine（SVM）, which uses Artificial Intelligence to characterize complicated nonlinear mapping between the impacting environment and damage to the vibration isolators. The effectiveness of the new method for predicting damage was illustrated by numerical simulations, and shown to be effective when relevant parameters of the model were chosen reasonably. The effect determining parameters, including kernel function and penalty factors, has on prediction results is also discussed. It can be concluded that the SVM will probably become a valid tool to study damage or vulnerability in a shocked raft system.     

基于LM算法神经网络的PMSM转子位置估算

针对永磁同步电机控制中传统机械传感器容易故障或失效,常规无传感器转子位置估计方法实现复杂、计算量大、易受干扰等问题,提出了基于LM算法神经网络的永磁同步电机转子位置估算器.通过采集两相静止坐标系下电压、电流以及与转子位置相关联的数据集来创建估算器模型,针对标准BP神经网络算法收敛速度慢、效率低的问题,将采用LM算法对数...     

海洋真菌抗表皮葡萄球菌抗生素的初步研究

从海藻和海绵表面或组织内分离筛选出五株具有抑制表皮葡萄球菌活性的海洋真菌,分别鉴定为木霉属、光孢青霉、曲霉属、尖孢镰刀霉和交链格孢霉.经单剂量法测定其每毫升发酵液抑制表皮葡萄球菌的效价分别相当于氨苄青霉素0.8单位、1.1单位、22.5单位、7.9单位和6.2单位.高效液相色谱分析显示这五株真菌的代谢产物具有较显著差异,抗菌活性生物自显影表明这些菌株的抗表皮葡萄球菌抗生素成分也呈现较高的多样性.化学显色试验表明其中一株曲霉菌DLEP2008001的最强活性成分可能为含有仲胺及羧基基团的甾体或三萜类化合物,而次强活性成分可能为含有仲胺基团的化合物.研究结果表明,作为抗表皮葡萄球菌后备药物的潜在来源,海洋真菌值得深入研究.     

Timing sequence changes of landscape plants in Shanghai Area,China

Based on published reports and direct observation, the common resources of landscape plant species in the Shanghai area were identified and studied in terms of the landscape characteristics of timing sequence changes over a one year time period. The results showed that there were 199 common landscape plant species in Shanghai, distributed in 67 families and 129 genera. These plants were categorized by three ornamental characteristics: flowers, foliage and fruits. The species were thus further analyzed according to the time periods which these characteristics were present. The results showed that flower ornamental distributed throughout the year, particularly from April to June, and plant species with colorful foliage could be seen every month, and particularly in November and December. On the other hand, few plant species with fruit ornamentals were observed in Shanghai area. The diversity of landscape timing sequence changes of the 199 plant species under examination was then analyzed by using the Shannon-Weiner and Simpson index formulas. The results showed that the higher diversity was observed in January, February and from August to October, while the lowest diversity was recorded from March to July and during November and December. The diversity of landscape characteristics of these plants was ranked according to foliage, flowers and fruit. Using this method, one park and one plant community were selected to evaluate the advantages and disadvantages of their time-changing plant landscape, with the goal of assessing the validity of the chosen ranking method. These results in the present study would be helpful to evaluate the plant landscape in a specified space and further enrich the diversity of plant and landscape by a target-oriented way.     

城市道路交通事故特征分析——以乌鲁木齐市为例

中国正处于快速城镇化进程中,交通事故呈现频发的趋势,并时常伴随着重大恶性事故,因此,对事故的分析与研究十分迫切而有必要.以乌鲁木齐市为例,对该市2007～2010年的交通事故作了分析与研究,得到了时间、空间等方面的分布特征,将有助于减少并预防城市道路交通事故.     

大功率空冷自增湿PEMFC温度控制方法

为研究大功率空冷自增湿质子交换膜燃料电池(PEMFC)温度控制对电堆输出性能的影响,分别采用模糊控制、PID控制、模糊-PID切换控制、自适应模糊PID控制对电堆进行试验测试.实验结果表明,不同控制方法在负载变化时的动态响应特性存在较大差异:模糊控制对电堆输出性能影响较大,在大电流输出时会造成明显的浓差极化;模糊控制、PID控制、模糊-PID切换控制在负载变化时动态响应存在较大的超调量,调节时间长;模糊自适应PID控制超调量小,调节时间短.与PID温度控制相比,自适应模糊PID温度控制超调量降低了75%,调节时间加快了20%.综合考虑调节时间、超调量、稳态误差、电堆输出性能等因素,自适应模糊PID温度控制有利于提高大功率空冷自增湿PEMFC输出特性.      

Numerical Simulation of Float-Over Installation for Offshore Platform

In this paper, a numerical investigation of a float-over installation for an offshore platform is presented to verify the feasibility of the actual installation. The hydrodynamic performance of a T-barge is investigated in the frequency domain, and the coupled motions are analyzed in the time domain. We then compare with those of the model test and determine that the response amplitude operator and the time series agree quite well. The barge exhibits favorable hydrodynamic behavior in the considered sea state, and the equipment loads are allowable. The mooring system and sway fender forces are within the permissible range. Based on these results, we can verify that the actual installation of the offshore platform is feasible. We accurately simulated many important factors and effectively reduced the risk associated with the offshore installation, which is of great importance. As such, we demonstrate that the numerical simulation of the float-over installation for offshore platforms has practical engineering significance.