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。     

Mobile IP切换的实验研究

首先简要介绍了Mobile IP及其切换原理,然后通过具体实验分析了Mobile IP切换对传输层协议（TCP和UDP）造成的影响。实验主要测试了切换对TCP造成的影响,并由此类推出对UDP的影响。最后讨论了可行的改进措施,重点讨论了如何减少Mobile IP切换时的分组丢失和时延。     

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.     

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。     

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.     

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.     

利用五度字调模型实现普通话到兰州方言的转换

方言语音的转换对于实现个性化的汉语语音合成系统具有重要的意义。为了实现普通话到兰州方言的转换,论文利用《方言调查字表》建立了兰州方言的文本语料库,录制了普通话和兰州方言平行的语音语料库。利用五度字调模型建立了普通话和兰州方言的基频模型,利用统计方法建立了时长转换模型和停顿时长转换模型。在转换时,通过利用STRAIGHT算法修改普通话语音实现普通话到兰州方言的转换。对转换结果的MOS评测表明,转换后的单字平均MOS得分4.17,双字平均MOS得分为4.22,语句的平均MOS得分为3.55。     

Cryogenic fatigue behavior of plain weave glass/epoxy composite laminates under tension-tension cycling

This paper focuses on understanding the tension-tension fatigue behavior of woven glass fiber reinforced polymer laminates at cryogenic temperatures. Tension-tension fatigue tests at frequencies of 4 and 10 Hz with a stress ratio of 0.1 were conducted at room temperature, 77 and 4 K. The fatigue stress versus cycles to failure (S-N) relationships and fatigue limits for 10⁶ cycles were obtained. Fractured specimens tested under fatigue tests were also examined with optical microscope.     

Tension-tension fatigue behavior of GFRP woven laminates at low temperatures

This paper describes an experimental study on the fatigue damage behavior of GFRP woven laminates in terms of stiffness degradation and residual strength under cyclic loading at low temperatures. Uniaxial, load-controlled, tension-tension fatigue tests were conducted at room and low temperatures. The applied stress versus cycles to failure (S-N) relationships and fatigue limits were obtained for the GFRP woven laminates and the microcrack evolution due to fatigue loading was characterized using optical microscopy. Temperatures were also measured using a thermocouple embedded in the center of the specimens.     

Acoustic emission and fracture behavior of GFRP woven laminates at cryogenic temperatures

This paper describes an experimental and analytical study on fracture and damage behavior of GFRP woven laminates at cryogenic temperatures. CT (compact tension) tests were carried out at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) to evaluate the critical values of the fracture mechanics parameters. During the CT tests, AE (acoustic emission) method was implemented. AE signals can identify the critical load at which gross failure occurs. A FEA (finite element analysis) was also applied to calculate the fracture mechanics parameters. The failure criteria (Hoffman criterion and maximum strain criterion) or the damage variable based on the continuum damage mechanics was incorporated into the model to interpret the experimental measurements and to study the damage distributions within the specimen. Several methods of calculating J-integral are discussed.     

Friction stir processing: An effective technique to refine grain structure and enhance ductility

Commercial 5083 Al rolled plates were subjected to friction stir processing (FSP) with a tool rotational speed of 430 rpm and a traverse feed rate of 90 mm/min. This treatment resulted in a fine grained microstructure of 1.6 μm and an average misorientation angle of 24°. Ductility was measured using tensile elongations at a temperature of 250 °C at three strain rates, and demonstrated that a decrease in grain size resulted in significantly enhanced ductility and lower forming loads. The ductility of the friction stir processed material was enhanced by a factor ranging from 2.6 to 5 compared to the ductility of the as received material, in the range of the strain rates tested. The strain rate sensitivity of the processed material is 0.33 while for the as received, it is 0.018. The deformation mechanism, in the fine-grained specimens is mainly controlled by solute drag creep, though the contribution of grain boundary sliding to the deformation process cannot be overlooked. Both mechanisms led to significant flow localization and simultaneous cavity formation.     

Thermal performance of multilayer insulation around a horizontal cylinder

Thermal performance of multiplayer insulation (MLI) is affected by contact pressure between adjacent layers. In order to evaluate the thermal performance of the MLI fabricated in the horizontal cryostats of superconducting magnets, it is important to investigate the contact pressure in the MLI. In case of a horizontal cryostat, the MLI is wound around horizontal cylindrical surface and is compressed at the upper part of the cylinder due to the MLI self-weight. At first, a single thin film wound around the horizontal cylinder was analyzed to evaluate the contact pressure acting on the cylinder. The analysis has been extended to the multiply wound film around horizontal cylinder, in order to investigate the distribution of contact pressure between adjacent layers. By using experimental data obtained with a flat panel calorimeter, the results of this analysis have been applied to evaluate the thermal performance of MLI around a horizontal cylinder. And the non-dimensional contact pressure parameter P^* has been introduced as a useful parameter to evaluate and compare the thermal performance among different kinds of MLI.     

Development and performance test of a cryoprobe with heat transfer enhancement configuration

In the present study, a cryoprobe with heat transfer enhancement configuration (HTEC) is developed and its freezing performance is evaluated experimentally. Two kinds of heat transfer enhancement configurations, i.e., coiled wire insert and helical mesh insert, are proposed and used in the cryoprobe. Furthermore, in order to ensure that vapor can be discharged freely and only liquid nitrogen reaches the cryogenic section of the cryoprobe, a vapor–liquid separator is employed upstream of the cryoprobe. It is found that the precooling time of the cryoprobe is significantly shortened with the vapor–liquid separator. The enhancement of the freezing capacity with the helical mesh insert is slightly superior to that with the coiled wire insert. With the helical mesh insert, the freezing capacity of the cryoprobe can be enhanced by 41%, and the wall temperature can reach 111.3 K in about 10 min. Significant temperature oscillations are observed in the precooling stage of the cryoprobe with HTEC, while only slight temperature oscillations can be found without HTEC.     

Development of No-Vent™ liquid hydrogen storage system for space applications

A number of technological advances required to store and maintain normal-boiling-point and densified cryogenic liquids, including liquid hydrogen, under zero boil-off conditions in-space, for long periods of time, have been developed. These technologies include (1) thermally optimized compact cryogen storage systems that reduce environmental heat leak to the lowest-temperature cryogen, which minimizes cryocooler size and input power, and (2) actively-cooled shields that surround the storage systems and intercept heat leak. The processes and tools used to develop these technologies are discussed. A zero boil-off liquid hydrogen storage system technology demonstrator for validating the actively-cooled shield technology is presented.