热声热机中的能量模拟与分析

文中主要对回热器中的能流及其能流分量进行了模拟 ,并在此基础上分析了能流及其分量对热声热机的影响 ,为更深地理解热声热机中所发生的能量转换现象 ,更好地设计热声热机提供有价值的依据和参考。     

行波型热声热机的研究进展

Ceperley首先提出了行波型热声热机的概念 ,此后许多研究者对此类型的热机进行了理论及实验研究。文中对行波型热声热机的发展历史、研究现状及应用前景进行了简要介绍     

热声热机热声核内传热与流动特性实验研究

本文通过搭建扬声器驱动的热声热机可视化实验台,利用粒子成像测速仪(PIV)和红外热像仪得到冷、热端换热器间速度及温度场分布,对有无声场两种情况下热声核中速度及温度场的变化进行了实验研究。实验结果表明,外加声场改变了热声核中热对流的基本模式,增强了冷热端换热器间的换热能力,对热声核中的温度分布有着显著的影响。揭示了热声核中的流动与换热规律。     

同轴型行波热声热机的实验研究

自行设计搭建了国际首台同轴型行波热声热机的实验装置 ,以氮气为工质 ,获得频率为1 3 7Hz的谐振声波。回热器热端温度达到 2 0 0℃左右时 ,热声热机开始起振 ,平均振幅 0 .1 4bar     

行波热声发动机的优化设计

对行波热声发动机进行了优化设计 ;对回热器内部的功的损失和回热器的热漏损失进行了分析 ;给出了行波热声热机回热器的优化结构 ;对于设计行波型热声发动机有非常重要的理论指导意义。     

基于场协同理论的热声回热器数值研究

热声回热器是热声热机的重要部件。基于Rayleigh准则,提出回热器内流固之间的对流换热强度是影响热声热机整体性能的重要因素。利用改进的数值模型,模拟了平行板叠内回热器的速度与温度分布特性,并分析了板叠内部对流换热及整机性能之间的对应关系。此外,基于强化对流传热的场协同理论,提出了4种新型结构的异型回热器,并分别对其换热性能与热声转换性能进行了对比分析研究:表明采用混合型回热器的热声热机具有更优越的工作性能,输出声功的压力振幅较普通结构回热器可提高2.8%。研究结果验证了热声回热器内部对流换热强度与热声热机性能呈正相关性,通过改良回热器结构可有效提高热声热机的热声转换性能。     

热声热机

热声热机(Thermoacoustic Engine)是一种把热能转换成声能或者说声波等形式的机械功的装置。像其他许多热机一样,它可以逆向运行而作为制冷机,即利用声能将热量从低温热库输向高温热库。热声热机的高运行频率减少了热传导并且无需任何气室。与许多其他热机不同,除了工作流体本身,热声热机没有任何活动部件。     

热声交变流动中浮力效应理论分析

热声交变流动是热声热机的工作基础,研究交变流动机理有助于人们认识热声热机的工作过程。鉴于前人的理论分析一般没有考虑浮力效应的影响,本文从流体热动力学的角度研究了浮力对流与热声交变流动的耦合规律。基于线性理论方法,给出了考虑浮力项和热对流Rayleigh数的热声线性理论模型,分析了浮力效应对平行交变流动的影响,发现热对流...     

容腔调相的单级行波热声发动机起振特性

将容腔结构引入单级环路行波热声发动机系统中进行相位调节,分析了不同容腔位置、容腔内径和容腔长度时系统的起振特性。基于线性热声理论,采用网格传输矩阵数值方法求解系统的起振频率和起振温差;此外,将计算结果与实验结果进行了对比,验证了计算方法的合理性。结果表明:容腔结构可以明显改善系统的起振特性,系统起振温差大幅下降;不同容腔位置处,热机起振特性差异明显;存在最优的容腔内径和容腔长度组合,使得起振温差最低,而容腔尺寸对热机起振频率的影响较小。      

近临界区CO_2对热声谐振管性能的影响分析

谐振管是热声热机的主要部件之一,减小声功在谐振管中的耗散对改善热声热机输出特性具有积极意义。由于近临界区流体的热物性具有特殊性,用其作为工质时将会对谐振管内的声功损耗产生重要影响。本文对声功在以近临界区CO_2为工质的谐振管中的损耗情况进行了计算和分析。结果显示,在本文的计算条件下,相较于压力较低的CO_2,采用近临界区CO_2作为工质可降低谐振管内的声功损耗,并在工作压力略低于临界压力时,谐振管内的声功损耗可达到最小值.此外,在保持谐振频率不变的情况下,采用近临界区CO_2作为工质可一定程度上缩短谐振管的长度。     

Radiation modal expansion: application to active structural acoustic control

This paper demonstrates active structural acoustic control using multiple input/output adaptive sensoriactuators combined with radiation filters and a feedback control paradigm. A new method of reduced order modeling/design of radiation filters termed radiation modal expansion (RME) is presented. For the experiments detailed in this paper, the RME technique reduced the modeling of the radiation matrix from 400 transfer functions to 6 transfer functions (multiplied by a constant transformation matrix). Experimental results demonstrate reductions of radiated sound power on the order of 5 dB over the bandwidth of 0-800 Hz.     

6×6 matrix formalism of optical elements for modeling and analyzing 3D optical systems

Although conventional 2×2 ray matrices, i.e. ABCD matrices, provide a convenient means of obtaining initial estimates of the performance of an optical system during the early stages of the design process, they are suitable only for optical systems with the axisymmetric property. Accordingly, this study utilizes the 6×6 matrix formalism, which was proposed by our group, for optical boundary surfaces to develop a new approach for modeling and analyzing 3D optical systems comprising multiple lenses and/or mirrors and clarifying many of the system’s basic properties, e.g. the effective focal length, primary aberration and cardinal points, and so forth. To reduce the complexity of the modeling process, general matrix formalisms of sub-systems in a 3D optical system are presented. The validity of the proposed approach is evaluated by modeling and analyzing a simple 3D optical system and comparing the results with those obtained from the skew ray-tracing computer program and commercial optical design software. The results confirm that the proposed methodology provides a convenient means of obtaining initial insights into a variety of 3D optical systems with non-coplanar axes.     

OPS网络中SOA交换矩阵的串扰研究

通过对光开关和节点流量进行建模，利用新颖的等效串扰系数法，研究了基于XGM效应的SOA开关矩阵在OPS网络中的串扰问题.分析了SOA的各种参量以及节点流量特性对开关隔离度、节点中由串扰造成的误码率以及节点级联能力的影响.提出了优化SOA交换矩阵的具体措施，包括提高SOA的载流子寿命、控制脉冲能量和节点中流量的单播特性，以及降低SOA的饱和能量和有源区长度等.     

基于0-1稀疏循环矩阵的测量矩阵分离研究

当前压缩感知中测量矩阵的优化是测量阶段和重构阶段采用同一矩阵的事前优化。采用了以行变换为主的测量矩阵优化算法和过渡矩阵将压缩感知的测量矩阵和重构矩阵相分离,在测量阶段采用单像素相机的0-1稀疏矩阵,在重构阶段采用近似矩阵,这是区别于传统思路的测量数据和测量矩阵的事后优化方法。理论分析和实验结果表明,优化矩阵的性能好于稀疏循环矩阵,近似矩阵和优化矩阵具有相近的性能。研究成果降低了测量矩阵工程设计和实现的难度。     

原子吸收光谱法测定高纯稀土氧化铽中钙的干扰效应和分析条件的优选

本文用正交试验设计对高纯稀土氧化铽中钙测定时，对基体和酸度的干扰进行了试验。结果表明，基体和酸度的干扰表现为与分析元素无关。此外，仪器工作条件的改变．可产生不同程度的干扰。     

Deep learning-driven MIMO: Data encoding and processing mechanism

Large-scale Multiple-Input Multiple Output (MIMO) is the key technology of 5G communication. However, dealing with physical channels is a complex process. Machine learning techniques have not been utilized commercially because of the limited learning capabilities of traditional machine learning algorithms. We design a deep learning hybrid precoding scheme based on the attention mechanism. The method mainly includes channel modeling and deep learning encoding two modules. The channel modeling module mainly describes the problem formally, which is convenient for the subsequent method design and processing. The model design module introduces the design framework, details, and main training process of the model. We utilize the attention layer to extract the eigenvalues of the interference between multiple users through the output attention distribution matrix. Then, according to the characteristics of inter-user interference, the loss minimization function is used to study the optimal precoder to achieve the maximum reachable rate of the system. Under the same condition, we compare our proposed method with the traditional unsupervised learning-based hybrid precoding algorithm, the TTD-based (True-Time-Delay, TTD) phase correction hybrid precoding algorithm, and the deep learning-based method. Additionally, we verify the role of attention mechanism in the model. Extensive simulation results demonstrate the effectiveness of the proposed method. The results of this research prove that deep learning technology can play a driving role in the encoding and processing of MIMO with its unique feature extraction and modeling capabilities. In addition, this research also provides a good reference for the application of deep learning in MIMO data processing problems.     

基于单片机和光电开关的通用计数器设计

At presrent, the photoelectric switch is more and more widely used in the industrial automation equipment.It can be finished counting industrial products by using the characteristic of the photoelectric switch which can detect the objects without touching them. This design uses the modular design method,including power-supply module, The photoelectric conversion module, optocoupler isolation circuit module, power off protection module, matrix keyboard module, counting module and The display module. It mainly uses 51 single-chip microcomputer to control the system,uses the keilC51 software to design program,uses the Proteus software to complete the simulation. Through the experiment, it proves the design is feasible.     

Matrix hodoscopes for the Oka (Protvino) and NA62 (SPS,CERN) experimental setups

The matrix hodoscope of the OKA experimental setup and a prototype of the hodoscope for the NA62 experiment are described. The design of both hodoscopes is presented. The requirements for the hodoscope prototype are listed, and the efficiency and the time resolution obtained on the basis of experimental data are quoted.     

基于Eclipse图形建模框架的图形化脉冲序列设计软件的实现

采用Eclipse图形建模框架(Graphical Modeling Framework,GMF)技术构建了一个图形化磁共振脉冲序列设计软件.软件具备所见即所得的特点,用户使用拖放方式所画出的脉冲序列与教科书和参考文献上的脉冲序列几乎一样.软件支持核磁共振(Nuclear Magnetic Resonance,NMR)波谱和磁共振成像(Magnetic Resonance Imaging,MRI)的脉冲序列设计,同时提供实验参数管理模块,实现脉冲序列基础上的NMR实验设计和执行预览.得益于GMF完善的模型-视图-控制器模式和强大的代码生成能力,软件开发周期大幅度缩短、扩展能力大幅度提高.     

A new type of parts feeder driven by bimorph piezo actuator

A novel meander-line structure implemented with bimorph piezoelectric actuators driven by two sets of alternating current power with phase difference is developed in this article. Via the generated traveling wave, this mechanism is able to transport parts. The dynamic modeling of the structure, the driving control circuitry design, the motion trajectory analysis and the optimal transport feed rate is studied, and also verified by the practical experiment.