采砂坑纵剖面尺寸对卵石河道河床演变影响的数值试验 ——以石亭江双盛段为例（“研究生论坛”）

人类活动与河流的河床演变形态、河相关系息息相关,人类活动使得山区河流在河道形态、泥沙运动等方面会发生一系列的变化,近些年建筑用沙需求量剧增,人们大量采挖河沙,改变了河流原有的河床边界,对河流的演变产生了诸多影响。研究河道采砂对河床演变的影响具有重要的学术及实践意义。本文依托HEC-RAS泥沙计算模块,以石亭江双盛段为研究对象,结合野外调查实际情况,拟定数种采砂坑工况,研究采砂坑纵剖面尺寸对河道河床演变的影响。根据资料和野外调查情况,首先,拟定HEC-RAS河道模型断面及水流和泥沙边界条件,然后在采砂方量及采沙坑宽度相同的条件下,拟定5种不同纵剖面尺寸（深长比）的采砂坑,利用HEC-RAS泥沙计算模块进行数值模拟试验,对试验结果中河道主槽深泓点高程及断面沖淤量数据进行了统计和分析。结果表明：人工采砂对河床整体的下切起促进作用,长浅型采砂坑比短深型采砂坑更能促进河床下切;采砂坑上下游河床下切变化不同,随着采砂坑深长比的增大,上游河床下切深度减小,而下游下切深度呈现先减小后增大的趋势;采沙坑会改变河道局部坡度,采砂坑上游河道局部坡度增大,下游河道局部坡度减小。本次试验研究了不同纵剖面尺寸采砂坑存在时,河床演变的变化状况,结论可对涉河工程的防护与设计及流域采砂规划提供一定的参考。     

电力市场动态分析

电力市场是利用市场机制的手段来实现电力系统资源的优化配置,因而电力市场既具有商品经济的一般运动规律,也有自身的特点。电力市场动态分析是研究电力市场从一个状态过渡到另一个状态的运动规律。电力市场各成员都是独立的利益驱动型主体,由此可以得出电力市场成员的动态模型,并在此基础上形成电力市场的动态模型。电力市场的各个成员之间依靠电价与供求数量等信号进行相互协调,但由于电价更新周期较长,导致电力市场的动态过渡过程较长,将造成频率变动过大,因此电力市场的动态过程需要加速,该文提出了罚款／津贴的方法来实现加速。最后分析了电力市场环境下的调频与稳定性问题。     

堰塞坝泄流冲刷试验研究

考虑到堰塞坝不同内坡坡度和不同坝体级配对溃坝过程的影响,设计了11组溃坝试验进行研究,根据对溃坝过程的摄影记录,观测到溃坝过程的四个阶段,其中阶段Ⅲ的坝体侵蚀最为剧烈,阶段Ⅰ内坡被侵蚀,阶段Ⅱ溃口顶部被侵蚀,阶段Ⅲ外坡被侵蚀,阶段Ⅳ坝体形态达到稳定,库区水位逐渐达到恒定值;运用WYG-Ⅱ型水位测量系统,得到整个溃坝过程水库的实时水位数据,试验结果表明:内坡坡度越大,溃坝洪峰流量越大;不均匀系数越大,溃坝洪峰流量由于绕流掀沙现象的存在反而增大,而后随着粗沙越多,细沙隐蔽作用突出,溃坝洪峰流量减小.     

基于Ansys和MotorCAD对交流伺服电动机性能的研究

基于某型号导弹发射装置电机的设计指标要求,运用Ansys有限元分析软件及Motor-CAD热分析软件分别进行性能优化分析,得出合理的设计方案。通过实测数据的验证得出:方案设计的准确率可达到93.5%以上,电机表面温升最大为19.2 K,与仿真值接近,方案设计合理。     

Shear Bond Strength of Different Adhesive Systems in Amalgam Repair

Strength of Materials - The purpose was to evaluate the effect of different adhesive systems on shear-bond-strength between amalgam and resin composite. 48 amalgam specimens were condensed into...     

Designing Porous Antifouling Interfaces for High-Power Implantable Biofuel Cell

Biofuel cells that can convert the chemical energy of biomass such as glucose into electricity are expected to continuously obtain energy from living organisms and solve bottlenecks of energy supply for implanted electronics. However, the use of biofuel cells is limited mainly by the sharp drop in performance after implanting in living organisms caused by biofouling and electrode surface inactivation. Herein, a simple and effective strategy to overcome these problems by designing a porous antifouling interface on biofuel cells, is demonstrated. It resists the biofouling from body fluid while sustaining reactant penetration, and also enhances immobilization of enzymes. As a result, the biofuel cell can maintain almost 100% performance after implanting in living organisms, and a maximal output power of 76.6 mW cm^-3 is achieved in vivo, which is ≈ 96 times of the highest performance reported to date. This strategy is universal and can be extended to the other electronic devices such as electrochemical sensors, which presents a new avenue for developing high-performance implanted electronics.     

Dislocation densities in cold worked copper by electron and X-ray diffraction methods

Electron backscatter diffraction (EBSD) and X-ray diffraction line profile analysis (XLPA) methods are suitable to determine dislocation densities within crystalline structures. A software was developed to obtain dislocation density from misorientations measured between the adjacent points by EBSD. However, this EBSD-based method can estimate only the density of geometrically necessary dislocations (GND), while XLPA method can give the total dislocation (TD) density. In this paper, GND densities are determined and compared them to the TD densities in as-received and severe plastic deformed copper samples. Based on these results, estimations are tested to provide reliable GND densities and to appreciate the applicability of this calculation method. Furthermore, correlations are found between TD densities and yield strengths estimated by hardness tests.