Analytical and Experimental Research on Wave Scattering by an Open-Type Rectangular Breakwater with Horizontal Perforated Plates

This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves.The hydrodynamic characteristics of this breakwater are analyzed through analytical potential solutions and experimental tests.The quadratic pressure drop conditions are exerted on the horizontal perforated plates to facilitate assessing the effect of wave height on the dissipated wave energy of breakwater through the analytical solution.The hydrodynamic quantities of the breakwater,including the reflection,transmission,and energyloss coefficients,together with vertical and horizontal wave forces,are calculated using the velocity potential decomposition method as well as an iterative algorithm.Furthermore,the reflection and transmission coefficients of the breakwater are measured by conducting experimental tests at various wave periods,wave heights,and both porosities and widths of the horizontal perforated plates.The analytical predicted results demonstrate good agreement with the iterative boundary element method solution and measured data.The influences of variable incident waves and structure parameters on the hydrodynamic characteristics of the breakwater are investigated through further calculations based on analytical solutions.Results indicate that horizontal perforated plates placed on the water surface for both sides of the rectangular breakwater can enhance the wave dissipation ability of the breakwater while effectively decreasing the transmission and reflection coefficients.

Performance and Safety Improvement of Induction Motors based on Testing and Evaluation Standards

The induction motor,which converts electrical energy into mechanical energy,has been recognized as the cornerstone of industrialization.The rotor of an induction motor can be either a squirrel cage rotor or a wound-type rotor,both existing as magnetless topologies.Three-phase squirrel cage induction motors are frequently utilized in industrial drives because they are dependable,have high starting torque,are selfstarting and affordable.Single-phase induction motors,on the other hand,are commonly used for small loads such as domestic appliances in form of modest fans,pumps and electric power tools.In South Africa,there have been reports of fires and explosions resulting in live and property loss because of induction motors that have not been thoroughly tested or are incorrectly labelled in terms of ratings,electrical safety and performance.The goal of this study is targeted at preventing end-user injuries and failures caused by non-compliant induction motors,by evaluating locally manufactured/imported induction motors based on tests and evaluation from standards(IEC and SANS).The study is conducted using experimental procedures at the Explosion Prevention Technology and Rotating Machines(EPT and RM)laboratory,South African Bureau of Standards(SABS),South Africa.The main finding from the study shows differences in the nameplate characteristics of various induction motors which could have detrimental effects such as production and operational downtime in their end-use industries,at later stages.

Experimental test of a new neutron threshold detector and its application

The possibility of using 209Bi as a new threshold detector to measurc high-energy neutrons was investigated for the first time. At the same time the experiment measured successfully the emitted neutron fiuence rate, energy spectrum and dose equivalent rate distributions in the heavy ion target area using a detector complex including 209Bi, 115In, 27A1, 19F and 12C samples.

Experimental Tests of the Operating Conditions of a Micro Gas Turbine Device

The aim of this work is to analyze the performance of a commercial micro gas turbine, focusing on the analysis of the fuel consumption and the outlet compressor and turbine temperature at various rpm, and to evaluate and compare the efficiency of the device. A test bench has been assembled with the available equipment in the laboratory of the department of mechanical and aerospace engineering in Roma. By using the software supplied by the manufacturer, the evaluation of the operating performance of the device at different speeds has been performed, obtaining all the values of interest.

Study of Neutron Cross Talk Rejection Based on Testing Experiment and Simulation

Experimental data analysis and simulation calculations were performed in order to evaluate the cross-talk rejection performance of a typical neutron detection array. For very closely packed scintillation bars, the CT rejection may rely on the position relation between the two signals. The criteria ｜△x｜≤ 15 cm and ｜△y｜≤12 cm are currently proposed for a rejection rate higher than 90%. For signals coming from distanced bars, the energy conservation relationship can be applied to reject the CT events with a similar performance. In both cases the results of simulation agree very well with the experimental data, assuring their applicability to other detection systems and physics problems.

Experimental Tests on a Pre-Heated Combustion Chamber for Ultra Micro Gas Turbine Device: Air/Fuel Ratio Evaluation

Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.

锂离子电池铝塑膜建模研究

为了准确建立软包锂离子电池有限元模型,进行了开裂准则适用性研究。开发了铝塑膜单向拉伸、等双向拉伸、杯突实验专用夹具并对铝塑膜进行相应测试,采用弹塑性有限元模型模拟相应的实验,并分别应用韧性断裂准则、剪切断裂准则、Mus chenborn-Sonne成形极限图(MSFLD)准则模拟铝塑膜的开裂行为。由模拟结果知:三个断裂准则都能较好地模拟单向拉伸和等双向拉伸实验中铝塑膜的开裂行为,而只有韧性断裂准则能够较好地模拟杯突实验中铝塑膜的开裂行为。该研究结果可为建立软包锂离子电池模型提供参考。

激光雷迪尔级帆船水动力特性试验与数值计算研究

采用试验观测和数值计算的方法研究了六自由度激光雷迪尔级帆船的水动力特性.设计了一套帆船六元力试验测量方法,通过拖曳水池试验获得帆船的水动力特性.采用雷诺时均计算方法和重叠网格技术,通过对试验和仿真的六元力结果进行对比,验证了数值计算方法的准确性.对不同航行姿态下的帆船水动力性能进行了模拟,分析了船体航速、迎角、侧倾角、漂角四个因素对帆船六元水动力的影响规律.研究结果表明:对纵向力影响权重较高的因子是航速和迎角,纵向力与航速呈非线性关系;对横向力影响较大的因子是漂角且两者呈线性关系;侧倾力矩主要受侧倾角和漂角的影响,随侧倾角的增加先减小后增大,在侧倾角为15°附近出现拐点;俯仰力矩受航速和迎角影响较大,随迎角的增大呈线性增大关系;转首力矩对漂角变化响应最大,随漂角增大线性增大.文中获得的六元水动力特性和数据可为提高帆船的操纵性提供重要数据支撑.

夹带式散粮垂直提升实验测试平台设计

该文研发了一种用于测试夹带式散粮垂直提升机效率和性能的实验测试平台,平台包括喂料结构、夹带式垂直提升结构和调控结构等。该实验平台可根据不同物料种类调节喂料装置与垂直提升段的间距,并通过调节输入气流参数调整皮带对物料的夹持力,在水平运输段使用皮带秤实时监测物料量以计算垂直提升效率。此外,通过分析运输过程中不同输入条件下垂直提升段上特殊点的振动特性,可以探究夹持力与喂料工艺参数对运输质量的影响,帮助改进垂直提升装置的结构。该平台用振动信号的形式表达调节参数对输送质量的影响,可提高教学质量,为培养创新型人才提供支持。

管中管流体流动与管柱变形测量实验平台设计与测试

基于海上管中管结构承载特性设计了管中管流体流动与管柱变形测量实验平台。该实验平台可更换不同的内管尺寸,研究不同管柱组合的变形和海水流动响应,能够通过调节外管外流速度、内管内流速度、顶部张紧力大小及水深等模拟海上管中管流体流动和变形特性。该实验平台可帮助学生加深对海上管中管的结构、原理及其作用的理解,提高专业兴趣,还可以进行管中管结构动态响应创新性实验研究,培养创新意识,提高解决复杂工程问题的能力。

机载激光武器试验评估技术研究

由于毁伤机理和使用方法的不同,现有机载武器和传感器的试验方法不适用于机载激光武器。为研究其特殊的试验与评估技术,从国外典型机载激光武器的试验情况着手,分析了主要的试验阶段、试验内容、试验类别、管理特点等,对气动光学特性、出光特性、目标探测识别跟踪、光束控制和杀伤性试验等主要科目的内容、方法进行研究。研究表明,美国为了避免试验技术落后研制技术,采取了多计划安排一体推进、大力构建试验机、建设试验设施和循序渐进开展试验等管理措施促进相关的研究。建议加强试验技术的投入,适时建设体系化试验机,加强测试和靶标等领域的研究,以期为新质武器的成熟和应用提供帮助。

土动力学与岩土地震工程

社会发展需求的增长、工程建造能力的提升以及气候变化等环境因素的改变带来的新震害现象、技术手段和工程需求,为土动力学及岩土地震工程研究提出了新挑战并创造了新机遇。文章重点针对近年来土动力学与岩土地震工程领域的一些新现象、新手段和新挑战进行综述,聚焦于土的动力特性、砂土地震液化、土的动力测试和岩土地震工程试验、岩土地震工程数值模拟以及岩土工程抗震等方面,分析当前理论研究和工程实践所面临的新问题和新挑战,梳理近年来所取得的一些最新进展,并对今后的研究方向进行探讨。

电镜表征公共服务实验室的开放运行与实践

“材料测试分析中心”的电镜表征实验室是依托于“双一流”建设学科的校院两级共建具有公共服务性质的校级注册实验室。经过多年的实验室开放运行,逐渐形成了从测试分析服务、支撑实验教学到实验创新开发的高效化、标准化和规范化管理运作模式。一方面,实验室可提供优质的测试分析服务,保证高质量的实验数据,有力支撑高校科研团队实验研究并助力与校外单位的技术合作;另一方面,实验室承担高素质人才培养的工作,在实验技术与设备培训、实验教学建设与改革、实践技术指导与分析支持中发挥着举足轻重的作用。结合实验室开放服务的关键管理和技术问题,创新实验管理方法、标准化实验工艺流程以及仪器设备功能开发,提高了实验室运行的开放效率,提升了实验技术人员的服务能力。

非常规储层微纳米孔隙介质中流体相态研究进展

非常规油气储层具有岩石骨架颗粒小、比表面积大、微纳米孔隙发育的特点,流体与孔隙介质间存在着诸多复杂的界面效应问题,影响微纳米孔隙介质中流体的相态变化规律。对于受限域流体,经典油气相态理论方法忽略分子间相互作用及界面效应的影响,预测微纳米孔隙介质中流体相变特征存在偏差。为了更全面地揭示油气在受限空间中的相态特征及其微观作用机理,总结当前微纳米孔隙介质中流体相态研究技术现状,详细阐述微观实验测试、相态理论模型和分子模拟3种主流技术方法,指出3种技术各自的优缺点,并对未来流体相态研究技术提出展望。分析认为:微观实验测试方法可通过研究流体热力学参数的变化来确定流体相变点,由于实验误差、人为误差等原因,需与理论计算相结合;相态理论模型方法可通过改进临界参数场、考虑流体与孔壁界面作用、考虑相间毛管压力修正相平衡判据方程等方法建立纳米孔隙空间相态理论模型,但是由于没有综合考虑界面效应带来的影响且缺乏有力的实验数据支撑,难以推广应用;分子模拟方法能在分子尺度上揭示流体分子的相行为,但现有研究主要围绕小分子展开,并且与流体发生相变时的临界参数结合得较少。后续研究应以多界面效应耦合影响的微纳米孔隙介质中油气流体相变特征为研究对象,以微观实验、理论模型和分子模拟为技术手段,为描述微纳米孔隙介质中流体相态提供合理的实验测试手段和可靠的理论计算模型。

变速抽水蓄能电机在发电工况不同转速下磁场和损耗研究

本文对变速抽水蓄能发电电动机的电压方程、磁链方程、电磁转矩方程和运动方程进行了推导,并建立了10MW变速抽水蓄能发电电动机二维电磁场的数学方程和物理模型,对变速抽水蓄能发电电动机的电磁场数学方程进行了计算,得到了变速抽水蓄能电机在发电机工况下超同步速时定子电压和定子电流的波形,分析了变速抽水蓄能电机在发电机工况下不同转速时磁密的分布规律,研究了不同转速下定子铁芯损耗和转子铁芯损耗占总铁芯损耗比例的变化规律。搭建了10MW变速抽水蓄能发电电动机样机试验测试平台,通过试验测试得到的结果与计算结果较为接近。

双螺杆压缩机工作性能测试实验平台搭建及教学应用

为提升“过程流体机械”实验教学的高阶性、创新性、挑战度,设计开发了双螺杆压缩机工作性能测试实验平台。该平台可实现工作性能测试、示功(p-V)图绘制等常规实验,并支持开展变工况调节特性分析以及啮合副型面优化设计验证等研究性实验。平台硬件部分根据啮合副型面特征设计了传感器布置方案;软件部分基于LabVIEW软件完成在变载工况下绘制p-V图、计算指示功率及分析效率等数据处理功能。该平台应用于实验教学可为培养学生的工程实践创新能力提供保障。

CBL教学在临床免疫学检验技术实验教学中的应用初探

目的:探讨以案例为基础的教学法(CBL)在临床免疫学检验技术实验教学中的应用及教学效果。方法:随机选取医学检验技术专业2020级本科大三两个班学生为研究对象,试验组50人,对照组52人。其中对照组采用传统教学,试验组采用CBL教学。对比两组观察指标:实验报告成绩、实验考核成绩及学生满意度等指标。结果:试验组学生实验报告成绩、实验考核成绩及对教学的满意度评价均高于对照组(P<0.05)。结论:在临床免疫学检验技术实验教学中应用CBL教学法,可以明显提高学生的学习兴趣,并显著提升实验成绩以及对教学的满意度,值得推广。

铝合金材料缺陷检测的磁声电方法

不同的无损检测方法适用于不同的场景,为丰富现有的无损检测方法,本文提出了一种适用于非铁磁材料缺陷检测的磁声电检测新方法。通过COMSOL仿真软件及磁声电检测实验平台,对铝合金材料裂缝缺陷进行检测,对不同缺陷尺寸进行仿真及实验研究,并验证该方法的可行性。仿真结果表明,在缺陷的边界处获得了明显的磁声电缺陷信号。验证了缺陷宽度与缺陷信号的关系,当缺陷宽度L大于波长λ时,缺陷电信号峰值时间t及幅值U均相同,反之,缺陷左、右壁产生的电信号相互叠加。研究表明,实验与仿真结果具有一致性,说明本文提出的磁声电检测新方法能够实现缺陷的高精度检测。

改良红黏土的强度和崩解特性及其微观机理

为探究土体强度特性与崩解特性之间的关系,通过提高土体压实度和具有较好生态效益的高分子生物聚合物瓜尔胶(Guar Gum)掺量两种方法对红黏土进行改良。开展不同压实度与瓜尔胶掺量改良红黏土的直剪试验、崩解试验及扫描电镜试验,研究分析了压实度以及瓜尔胶掺量对红黏土崩解特性及其抗剪强度的影响,并揭示了其微观机理。结果表明:增大压实度与掺入瓜尔胶可以有效提高红黏土的力学性质以及抗崩解性。随着压实度增大,试样黏聚力呈线性增长,内摩擦角有小幅度升高;掺入瓜尔胶对土体的内摩擦角与黏聚力均有较大提升。经过瓜尔胶改良后的红黏土最终崩解率明显降低,当掺量为0.25%时,试样不再发生崩解;增大压实度与掺入瓜尔胶两种方法都能提高土体黏聚力,增大内摩擦角,使土体粒间吸引力变强,从而提升土体的强度与抗崩解性能;与提高土体压实度相比,红黏土中掺入瓜尔胶对提升红黏土的水稳性有更好的效果。