不同水平的普通话学习者单字调声调感知研究

首先采用实验语音学的理论和方法进行比较分析,进一步了解普通话学习者声调学习的情况,通过定量研究的方法,对两种不同水平(高级水平和初级水平)学习者的声调感知进行声学分析并对学习普通话过程中的语调掌握状况展开探讨。考察了20名不同水平学习者对普通话声调学习的感知情况。按学习者对汉语9个单元音的4个声调感知和12个复合元音的4个声调的单字调辨认,以及阳平-上声的区分实验数据,统计学习者的辨认准确率、各调类的偏误率和反应时间,最后利用SPSS数据分析软件从统计的角度进行了辨认准确率和反应时间的相关性分析,分别对声调感知的准确率和反应时间的显著性差异进行检验。     

在华巴斯坦留学生单字调的声学实验和统计调查分析

本文从纵向和横向的角度考察学生在不同阶段对汉语拼音声调的学习情况,对在华学习汉语的8名巴基斯坦学生进行调查分析,利用声学实验和数据统计分析的方法来考察了他们的声调特征。从历时的角度考察留学生对声调的习得程度,并分析其声调偏误。实验分析得出巴基斯坦学生的上声调最标准,其次是阳平。阴平和去声偏误较大。     

基于声学黑洞的复合隔声结构声学特性研究及试验

声学黑洞(Acoustic Black Hole,ABH)能够实现声波的聚集,通过粘贴阻尼层将其聚集的能量耗散,可有效降低声学黑洞复合结构的振动和声波的传递。针对中低频段噪声,设计了声学黑洞复合隔声结构,建立了其隔声量计算模型。研究了声学黑洞复合隔声结构的黑洞数量、黏弹性阻尼层、声学黑洞半径等参数对隔声性能的影响。研究结果表明：在160~1 000 Hz频率范围内,ABH能明显增加复合隔声结构的隔声性能,其传递损失在1/3倍频程内增加了1.9 dB。文中的研究结果为复合隔声结构的设计提供了借鉴。     

国内外数字影厅声学测量方法差异性研究

本文从国外影院认证的声学技术指标和测量方法着手,阐述国内外影院声学技术认证如何进行B环电声响应、混响时间(RT₆₀)和背景噪声测量,其次通过对国内外相关影院声学技术规范的测量方法进行比较,总结相关测量方法,进一步提高相关影院声学技术指标的测量精度,希望对我国数字电影声学放映相关标准修制定提供有益参考。     

RTM成型复合材料T型接头工艺参数优化与力学性能实验研究

对树脂传递模塑(RTM)成型的复合材料T型接头进行了工艺参数优化、制备及力学性能实验研究。应用流动模拟软件,对RTM成型的复合材料T型接头进行了基体流动数值模拟,确定模具最佳注射方式和出胶口位置,并优化了影响树脂充模时间的工艺参数,显著提高了RTM接头的工艺性能。根据优化工艺参数结果,制备了RTM成型的复合材料T型接头试样,并进行了拉伸和压缩试验,分析了其破坏机制。根据拉伸和压缩试验现象和结果,发现RTM成型的复合材料T型接头拉伸破坏模式主要为富树脂三角区的树脂与纤维布界面分层,其拉伸破坏主要取决于树脂基体抗剥离分层的拉伸强度;压缩破坏模式为底板中央部位的弯曲分层与折断,其压缩破坏由接头底板中的纤维布抗拉强度决定;T型接头的压缩破坏强度高于拉伸破坏强度。     

钢板力学性能对FLD0影响的试验研究

对上海宝钢公司生产的15种冷轧冲压用钢进行了力学和FLD试验,探讨了σs/σb、δ、n值、r值对成形极限平面应变特征点(FLD0)的影响.研究表明:FLD0随σs/σb上升而下降,随着δ、n值、r值的上升而提高.在板材力学性能指标中,n值对FLD0的影响最为显著.     

复合材料单搭接头的剪切强度对比实验研究

在常温和湿热高温的环境下,分别进行了三种不同的成碰工艺(RTM、引入缝纫的RTM和胶接)制备的单搭接头的剪切强度实验,研究了成型工艺对单搭接头的剪切强度的影响,并根据实验现象分析了单搭接头的剪切破坏机理.实验结果表明:引入缝纫的RTM成型试样的剪切强度性能最高,而胶接成型试样的剪切强度最低;环境温度对RTM和引入缝纫RTM成型试样的剪切强度影响不大,而对胶接成型试样的剪切强度有较大影响.     

R1234ze(E)在多元醇脂油中溶解度的实验研究

R1234ze(E)(1,1,1,3-四氟丙烯)是当下具有较强替代潜能的环保制冷剂之一。本文搭建了溶解度测试实验系统,对R1234ze(E)在两种多元醇脂油中的溶解度进行测试,测试的温度范围为40～80℃,压力范围为0.123～0.360 MPa。采用PR状态方程和MHV2混合规则及NRTL活度系数模型对实验结果进行关联计算,得到不同温度下的交互系数及计算值与实验值的平均相对误差。结果表明:R1234ze(E)在两种多元醇脂油中的溶解度均随着温度的升高而降低,且R1234ze(E)在两种多元醇脂油中的平衡压力与溶解度之间存在立方函数关系。在两种多元醇酯油中,计算值与实验值的平均相对误差分别为1.68%和1.11%,可较好的描述R1234ze(E)在两种多元醇酯油中的相平衡行为。     

功率MOSFET单粒子烧毁测试技术研究

总结了2种单粒子烧毁测试方法.在非破坏性测试原理基础上,研制成功针对星用功率MOSFET的单粒子烧毁动态测试系统.系统在锎源单粒子效应实验装置调试通过.利用该系统,在HI-13串列加速器上初步完成了星用MOSFET单粒子烧毁验证实验.     

结构声学耦合随机性分析的等几何有限元-边界元法研究EI北大核心CSCD

采用有限元法(FEM)进行水下壳结构振动响应分析,边界元法(BEM)进行结构振动声学分析;组合有限元法与边界元法构成耦合FEM-BEM方法进行水下薄壳结构声振强耦合分析。为了克服传统拉格朗日函数近似几何模型与物理场插值计算时的不连续与低精度问题,采用Loop细分曲面等几何法构建几何模型,并采用相同的样条函数进行物理场高阶插值计算,实现水下声振强耦合系统的CAD/CAE的集成分析。随机性分析致力于研究系统输入的不确定造成的输出不确定。蒙特卡罗模拟(MCs)因简单直接被认为是解决复杂多维不确定性问题的通用工具,然而巨大的计算成本降低了其适用性。采用本征正交分解(POD)和径向基函数(RBF)可降低计算成本,提高计算效率,实现基于MCs的快速随机性分析。考虑结构材料属性参数以及结构形状参数的不确定性对计算结果的影响,采用MCs分析随机变量下的结构声学响应的统计特征。最后通过若干算例验证该算法的正确性与有效性。     

An experimental and numerical study of He II two-phase flow in the TESLA test facility

We report on measurements of the liquid level and temperature corresponding to different local heat loads at several sections of the He II two-phase flow channel in the TESLA (Tera-eV Energy Superconducting Linear Accelerator) Test Facility phase I (TTF1) during its operation. The measurements show that under normal operating conditions saturation between He II and its vapor can be maintained even in the transient process of heat transfer. A computer code for He II stratified two-phase flow analysis has been developed for the numerical simulation of the He II and vapor flow in the configuration of the cryogenic cooling channel in TTF1. Comparison with the measurement shows the prediction by the code agrees well with the experimental results. The code also predicts the maximum heat load under which the two-phase tube in TTF1 would locally dry out. In its application, the code is helpful to evaluate the impact on the flow behaviour resulting from changes to the TTF1 configuration.     

An experimental study on grinding of Zr-based bulk metallic glass

There are limited studies in the literature about machinability of bulk metallic glass(BMG).As a novel and promising structural material,BMG material machining characteristics need to be verified before its utilization.In this paper,the effects of cutting speed,feed rate,depth of cut,abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated.The experimental evaluations were carried out using cubic boron nitride(CBN) and Al_2O_3 cup wheel grinding tools.The parameters were evaluated along with the results of cutting force,temperature and surface roughness measurements,X-ray,scanning electron microscope(SEM)and surface roughness analyse.The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased.The effect of feed rate was opposite to the cutting speed effect,and increasing feed rate caused higher grinding forces and substantially lower specific energy.Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks.The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks.The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the range of 0.34-0.58 μm.This study also demonstrates that conventional Al_2O_3 wheel is not suitable for grinding of the BMG in dry conditions.     

应用声发射评定金属点蚀过程的研究进展

点蚀是金属腐蚀中最危险的腐蚀形态。文章介绍了目前应用声发射技术对金属点蚀进行评价的方法,认为应用声发射技术探测钢点蚀,无论是实验室条件下还是在实际工程上,都是一种有效的工具。但是关于声发射信号源的产生,学者们却持不同的观点。他们认同的一种观点是点蚀的扩展伴随声源活动性的增加,而且在点蚀速率和声源活动性之间存在一定的相关性。结果证明声发射技术的特殊性质正适合于对结构材料的监测。     

JackPot: A novel model to study the influence of current non-uniformity and cabling patterns in cable-in-conduit conductors

JackPot is a new model that is used to analyse how and to what extend current non-uniformity among strands in a cable-in-conduit conductor (CICC) affects its performance. The joints at the extremities of the CICCs in coils and short samples introduce a non-uniform current distribution among the strands. A detailed and quantitative study down to strand level is required to explain the involved phenomena, to understand their implications on short sample and coil tests and to provide adequate solutions for improvements. The model can be used to evaluate the influence of the joint design and to define its baseline requirements for short-sample qualification testing, and for optimum magnet performance of for example the ITER coils.JackPot is an electrical network model that simulates the interaction between the superconducting strands in the cable (following their precise trajectories), the interstrand contact resistances, the conduit, and the cable’s connection to the joints. The backbone of JackPot is its cable geometry model, from which all relevant properties are derived. All parameters are derived from well defined experimental measurements on conductor sections and joints, except the axial strain for Nb₃Sn strands, which is the only free parameter in the model.The simulations demonstrate that the current non-uniformity is the source for a number of observed phenomena. Another conclusion is that completely filling the bottom joints and upper terminations of a short sample with solder, opposed to only (partly) soldering the cable surface, improves short-sample testing significantly for qualifying the ITER type CICCs. This paper describes the model and gives a few examples of applications for its validation.     

An experimental study on the in situ strength of SiC fibre in unidirectional SiC/Al composites

In order to investigate the effect of strain rate and high temperature exposure on the mechanical properties of the fibre in the unidirectional fibre reinforced metal-matrix composite, in situ SiC fibre bundles are extracted from two kinds of SiC/Al composite wires, which are heat-treated at two different temperatures (exposed in the air at 400 and 600 °C for 40 min after composition). Tensile tests for these two fibre bundles are performed at different strain rates (quasi-static test: 0.001 s⁻¹, dynamic test: 200, 700, and 1200 s⁻¹) and the stress–strain curves are obtained. The experimental results show that their mechanical properties are rate-dependent, the modulus E, strength σ_b and unstable strain _b (the strain corresponding to σ_b) all increase with increasing strain rate. Compared with the mechanical properties of the original SiC fibre, those of the two in situ fibres degrade to some extent, the degradation of the in situ fibre extracted from the composite wire exposed at 600 °C (hereafter referred to as in situ fibre 2) is more serious than that of the in situ fibre extracted from the composite wire exposed at 400 °C (hereafter referred to as in situ fibre 1). The mechanism of the degradation is investigated. A bi-modal Weibull statistical constitutive equation is established to describe the stress–strain relationship of the two in situ fibre bundles. The simulated stress–strain curves agree well with the experimental results.     

对于实现零售系统社会一体化的探讨

探讨了POS－EOS－VAN系统在实现零售系统一体化中的应用，分析了POS－EOS－VAN系统3个组成层次的结构及其作用；介绍了采用POS－EOS－VAN系统订货的整个流程；并总结出该系统所具有的特点。最后分析了实施POS－EOS－VAN系统所能实现的经济效益和社会效益以及中国零售业应用的前景。     

An experimental and finite element study of the transverse bending behaviour of CFRP composite T-joints in vehicle structures

The behaviour of a woven fabric carbon/epoxy composite T-joint (representing a simplified version the T-joint located at the connection between the B-pillar and the longitudinal rocker in a car body structure) is investigated using experimental and numerical methods. Details of the manufacturing process and experimental design factors are considered to understand their influence on the performance of the T-joint structure. The experimental results reveal the influence of manufacturing process and experimental setup on the load-carrying capacity and failure mode of the T-joint. Numerical simulation accurately predicts the stress distribution and load-carrying capacity of the T-joint obtained from experimental tests. The FEM model, which includes the adhesive interface layers at the edges, convincingly represents the experimentally found stiffness: the error is less than 3%. According to Hashin matrix tension criteria, the first ply failure occurs at 3.746 kN when the Hashin failure index (R) becomes equal to 1. Whereas, in the case of experimental tests, the first ply failure occurs around 3.4 kN, at which force the first load drop is observed.     

Wet thermo-mechanical behavior of steel–CFRP joints – An experimental study

The long term durability of CFRP strengthened steel structures is a key parameter for their safe use and effective design. Strengthened members can be subjected to different environmental conditions and loading scenarios during their service life, the effect of which on the failure mechanism of the strengthened member requires fundamental investigations. This paper presents an experimental investigation into the effects of wet thermo-mechanical loading on the bond strength and the failure mode of steel–CFRP single lap joints. A total of thirty four steel–CFRP single lap shear specimens were prepared and exposed to different combinations of wet thermal cycle ranges and sustained loads. The results show that these conditions (wet thermal cycles and sustained loads) have little impact on the bond strength of steel–CFRP lap joint when applied separately. However, when applied simultaneously, the bond strength of the joint is significantly reduced with failure observed at less than 30% of the static strength under temperatures that are well below the glass transition temperature of the adhesive.     

Frequency domain analysis of acoustic wave propagation in heterogeneous media considering iterative coupling procedures between the method of fundamental solutions and Kansa's method

Acoustic wave propagation in heterogeneous media is a topic of significant interest in many areas of science and engineering, including aeroacoustics and sound propagation in oceans. In the present work, numerical frequency domain models based on the joint use of the method of fundamental solutions and of the radial basis function collocation method (also known as Kansa's method) are discussed. In this context, the method of fundamental solutions is used to model the homogeneous part of the propagation domain, while Kansa's method is employed to model the presence of heterogeneities. The coupling between the two parts of the propagation domain is performed iteratively, allowing independent spatial discretization between the different subdomains of the model (i.e. matching collocation points at common surfaces are not necessary). Additionally, an optimised algorithm, based on the use of a varying relaxation parameter, is employed to speed up and/or to ensure the convergence of the iterative coupling process. At the end of the paper, numerical results illustrate the applicability and potentialities of the proposed formulations. Copyright © 2011 John Wiley & Sons, Ltd.