超声振动螺线磨削砂轮表面的功率谱密度分析

超声振动螺线磨削过程中,砂轮表面微观形貌的变化复杂.为准确表征其特征,采用功率谱密度分析方法,将砂轮表面的微观结构分解为不同频率、振幅和相位的谐波,对比分析不同磨削行程时普通磨削和超声振动螺线磨削砂轮表面的磨损行为.结果表明:砂轮表面功率谱密度曲线的斜率k随着磨削行程的增大而逐渐减小,即k越小砂轮表面磨损越严重.其中,...     

液压约束活塞发动机的流量脉动仿真分析

为研究间隙误差对液压约束活塞发动机流量脉动的影响,在ADAMS中建立其含有间隙误差的主运动系统动力学模型,将ADAMS中得到的模型数据导入AMESim中,建立液压系统模型。通过对比不同间隙误差模型的参数输出,分析间隙误差对系统流量脉动的影响。研究结果表明,在一定范围内,间隙误差对流量脉动有明显的影响,并随着间隙误差的增大而增加;而且,连杆大头和曲轴曲柄之间转动副径向间隙误差对系统流量脉动的影响最大。     

Numerical analysis of heat transfer in arbitrary plane domains using a novel Trefftz energy method

In this article, we first propose a novel Trefftz energy method (TEM) for the numerical analysis of heat transfer in arbitrary plane domains. The TEM introduces the Trefftz energy bases in the complete linear space to approximate the numerical solution of the mixed boundary value problem in the heat transfer over an arbitrary plane domain. The Trefftz energy bases not only satisfy the Laplace equation but also preserve the energy, whose performance is better than the original Trefftz bases. Three benchmark numerical examples are tested to demonstrate the efficiency and accuracy of the proposed TEM. Although the multiple-scale Trefftz method can treat these problems with high accuracy, the TEM can further raise the accuracy with one order. Therefore, the present scheme is a competitive alternative to existing methods for solving heat transfer problems in arbitrary plane domains.     

Effects of Rapid Cooling Rate on Microstructure Formation and Microhardness of Binary Ti-44Al Alloy

快速冷却速率对Ti-44Al合金组织和显微硬度的影响

陈晓宇^1,2,方虹泽¹,王琪¹,陈瑞润¹,丁宏升¹,苏彦庆¹,郭景杰¹

（1. 哈尔滨工业大学 材料科学与工程学院,哈尔滨 150001;

2. 青岛大学 机电工程学院,山东 青岛 266071）

中文说明：

为细化TiAl合金的显微组织与晶粒,提高其力学性能,采用甩带快速凝固方法在不同冷却速率条件下制备了Ti-44Al（at.%）合金,研究了铸态与快速凝固合金的显微组织和显微硬度。XRD测试结果表明,合金中α2相含量随着冷却速率增加而增加,这是由于高的凝冷却率导致α相直接转变为α2相。随着冷却速率的增加,晶粒形态首先由树枝晶转变为等轴晶和树枝晶混合的组织,而后转变为等轴晶。经快速凝固制备后,合金晶粒尺寸由铸态的200-600 μm降低到快速凝固的18 μm。片层厚度由铸态的4.5 μm降低到快速凝固的1.1 μm。随着冷却速率的增加,α2相含量逐渐增加,γ相含量逐渐减少,并且快速凝固可以降低基体中元素偏析。快速凝固的合金晶粒细化,片层厚度降低,并且α2相含量增加,这导致显微硬度由铸态的247 HV提高到快速凝固的556 HV。

关键词：Ti-44Al合金,显微组织,显微硬度,甩带快速凝固,凝固路径

     

Overview of research on thermal safety of lithium-ion batteries

随着锂离子电池在生活和工作中的普及,锂离子电池的安全事故逐年增加,锂离子电池的安全研究逐渐引起学术界的关注。研究锂离子电池的热安全性,可以有效分析锂离子电池发生起火和爆炸的内在原因,指导锂离子电池安全性研究的开展。本文介绍了锂离子电池工作过程中产热的来源和影响因素,以及锂离子电池热失控发生时的内部反应和反应对应的温度,并对电池热失控时的热特性参数进行了总结。     

RETRACTED ARTICLE: Multimodal interface interaction design model based on dynamic augmented reality

New channels, new carriers continue to produce new data types, how to deal with complex and volatile multi-source data under IoT big data environment has become an important issue. Information perception is the basic content of the development of things, but also an important means to achieve information perception. Information interaction is the basic condition for the realization of Internet of things, but also the basic technology of interconnection. The information sensing of the Internet of Things is mainly the source of information provided by it, which is also the application base of the Internet of Things itself. To effectively process the IoT data, this paper proposes the multimodal intelligent data analyzing paradigm for Internet of things systems. Our proposed multiple game theory based data analyzing paradigm will guarantee the optimal combination of the mentioned model to construct the effect and robust analyzing pattern. We construct the optimal combination of Bayesian model, Decision Tree, Random Forest, Logistic Regression, SVM, Adaboost, Markov and Neural Network under the multiple game framework. Several new ideas are proposed to enhance the traditional Nash Equilibrium. Performance of the proposed method is validated through the simulation compared with the other state-of-the-art algorithms.

     

基于田口法定子冲片优化研究

高速永磁同步电机的噪声、振动和发热问题不可忽视。为改善高速永磁同步电机的噪声和振动性能,采用田口法对电机定子冲片进行优化。以定子冲片的槽口宽度、槽口高度和定子槽高度参数作为优化过程中的变量,选出一组最优的定子冲片结构参数组合来降低电机的转矩脉动、齿槽转矩和定子铁耗。仿真结果表明,田口法可以有效优化定子冲片结构,降低转矩脉动、齿槽转矩、定子铁耗,大大缩短了优化所需的时间。     

Enhanced H2 evolution and the interfacial electron transfer mechanism of titanate nanotube sensitized with CdS quantum dots and graphene quantum dots

Synergistic the modulation of photon absorption capability and interfacial charge transfer of the photocatalyst are highly required for developing high-performance heterojunction photocatalysts. The ternary CdS-graphene quantum dots-titanate nanotubes (CdS-GQDs-TNTs) nanocomposite have been prepared by an in situ growth method. The physicochemical characterization reveals that the GQDs are firmly decorated on both inner and outer surface of TNT through the formation of Ti–O–C chemical bonding, and CdS QDs are loaded on the outer surface of TNTs through strong interfacial interaction. The intimate integrated CdS-GQDs-TNTs nanocomposite exhibits much superior photocatalytic performance toward H₂ production compared with binary GQDs-TNTs and pure TNTs photocatalyst, which can be attributed to the combined interaction of the stronger visible light harvesting, the longer lifetime of photogenerated electron−hole pairs, faster interfacial charge transfer rate, fast and long-distance electron transport pass. The interfacial charge transfer mechanism of CdS-GQDs-TNTs ternary composite are proposed based on photoelectrochemical measurements.     

柴油机可变喷嘴增压器控制逻辑设计与参数标定

为了满足排放法规、提高发动机的效率和加快动态充气的响应,针对配置可变喷嘴涡轮增压器（VNT）的轻型卡车柴油机,设计了增压压力控制逻辑。控制器根据发动机转速和喷油量查询增压压力脉谱（MAP）,确定目标增压压力。采用开环预控制和闭环PID控制相结合的控制结构对增压压力进行控制,并通过排放试验标定了增压压力基本MAP、预控制MAP和PID参数因子MAP。发动机试验台上的实际控制试验结果表明,发动机实际的增压压力能够有效跟踪设定值,控制误差不超过8％。     

基于功能本体与可拓理论的专利群规避设计

目的 突破现有专利壁垒,以专利群为对象,提供一种专利知识表达规范,以及具象直观的规避设计方法。方法 通过关键词与国际专利分类号IPC(International Patent Classification)进行检索并确认目标主题专利群;通过功能本体词汇构建各专利的功能结构,并分别对其进行功能整合,得到专利群的总功能结构,以确认需规避的功能;在规避功能变更过程中应用可拓理论,对其功能概念及实现方式两个方面进行可拓分析与可拓变换以获取规避方案;对所得方案进行专利侵权判定。结论 利用功能本体词汇可使由自然语言记载的专利信息转化为规范化的功能知识,可拓基元模型与可拓变换的应用使功能变更过程更加具象、直观,使规避设计方案更易获取。针对一酒类包装盒专利群,验证了该方法的可行性。