Fabrication of silk fibroin film with properties of thermal insulation and temperature monitoring

Silk fibroin exhibits excellent mechanical properties, good biocompatibility, and biodegradability combined with benign processing conditions, attracting considerable research interest for the application as biomedical materials. Among the diverse forms of sponges, hydrogels, films, and mats manufactured from silk fibroin, films are especially appealing due to the high water and oxygen permeability, good cell attachment, and low immunogenicity. Fabrication of silk fibroin films with novel properties has been successfully developed simply by incorporating various functional components into it. In the present study, the properties of thermal insulation and temperature monitoring for the silk fibroin film are demonstrated for the first time through the incorporation of thermochromic microcapsules within it. Moreover, the silk fibroin film is also endowed with improved mechanical properties in terms of tension strength and elongation at break because of the reinforcing effect of thermochromic microcapsules. The silk fibroin film fabricated with novel features in this study can be a good candidate for the application of wound dressings, tissue engineering scaffolds, and bio‐related devices in the future. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1846–1852     

Investigation of Chinese word recognition scores of children in primary school classroom with different speech sound pressure levels

Chinese word recognition (CWR) test was conducted by grades 3 and 5 children under the different conditions of reverberation time (RT), background noise level (BNL) and speech sound pressure level (SSPL) in three primary-school classrooms. The CWR scores and signal to noise ratios (SNRs) have been obtained at listening positions. Results show that the CWR score for grades 3 and 5 children increases with increase of SSPL, decrease of RT or increase of age, but it decreases with increase of BNL under the same conditions. For a mixed noise of 56 dBA (speech-spectrum-like noise and ambient noise), the CWR scores in the classroom for grades 3 and 5 children reach a peak at SNR of 15–20 dBA under the same RT and age of children condition. For the natural ambient noise, the CWR score for grades 3 and 5 children gradually increases with increase of the SNR. The high SSPL could not guarantee good CWR for children in classroom, which also depends on RT and BNL in classroom. When the classroom has long RT or high BNL, the increase of SSPL would not be necessarily to achieve better CWR. The novelty of the present study is to further evaluate and confirm the results under environments of real classrooms (not simulated room in laboratory).     

浅海单矢量传感器宽带声源三维定位仿真

针对水平不变的浅海波导中单矢量传感器对低频宽带声源的三维被动定位问题,首先利用平均声强器估计声源方位；其次,通过分离简正模的声压和水平振速分量联合处理获得运动声源相对速度,进一步基于垂直声能流中简正模相干项特征频率不变性以及长时间窗口中多快拍信号的统一处理,建立WARPING变换频谱作为代价函数的搜索处理器,估计该段信号的初始距离,进而获得各时刻声源距离,所提出的方法避免了对拷贝声场和引导声源的依赖；最后,利用多阶简正模相干项与非相干项能量模基处理方法,当声场中存在三阶以上简正模时,可对声源深度进行匹配估计。仿真分析表明,单个矢量传感器能够给出声源的方位、距离及深度估计结果。     

A theoretical study on the effect of a permeable membrane in the air cavity of a double-leaf microperforated panel space sound absorber

A double-leaf microperforated panel absorber (DLMPP) is composed of a two microperforated panel (MPP) with a air cavity in-between, and without any backing structure. It shows a Helmholtz-type resonance peak absorption and additional low frequency absorption, therefore it can be used as a wideband space sound absorber. In this study, a theoretical study is made to examine the effect of a permeable membrane inside the air-cavity. Permeable membranes are studied in our previous studies and proved to be effective to improve the sound absorption performance of various type MPP sound absorbers. We investigate the absorption characteristics of a DLMPP with a permeable membrane in the cavity through numerical examples, and also studied the effect of honeycomb in the cavity of the same sound absorption structure.     

Hybrid acoustic synthesis – Assessment of rear final drives in an early stage of development,on the basis of transfer path analyses and test bench measurements

In order to be able to assess the acoustic characteristics of new rear axles respectively rear final drives at an early stage of development, a hybrid evaluation procedure was developed: this makes it possible to compare various construction stages on the basis of vehicle and test bench measurements. Transfer path analyses are used to calculate what contribution of the sound pressure on the driver’s ear is made up of structure-borne sound from the rear final drive (based on operational acceleration measured on the test bench and the bodywork’s transmission characteristics measured on the vehicle), which is used to classify the various construction stages. To use the test bench measurements for forecasting, the test object must have vibration characteristics that are as close as possible to those of the vehicle. In view of the above, comprehensive comparative measurements were taken with the help of artificial excitation and operational excitation. The measurement positions identified in the process were used to validate the calculation method by operating the very same rear final drive on the test bench and in a vehicle. In both cases, the rear final drive’s contribution of the total vehicle interior noise level was calculated, in one case on the basis of excitation from the vehicle measurement and in the other case on the basis of excitation from the test bench measurement. The good correlation between the vehicle-based and test bench-based calculations confirmed the applicability of the method. The “virtual” installation of the rear final drive enables faster construction stage comparisons because there is no need for alteration work on the vehicle and the rear final drive that is to be compared can simply be integrated into the existing test bench environment.     

复材结构刚度与隔声量的计算及参数优化

论文旨在满足结构刚度指标的前提下最大程度地提高复合材料(以下简称“复材”)结构的隔声性能。首先针对复材结构进行刚度分析，在铺层数和铺层比例不变的前提下，分析不同铺层构型对结构刚度的影响。然后利用统计能量分析法，确定铺层角度对结构隔声性能的影响，并与试验结果进行对比验证模型的有效性。最后以铺设在复材壁板上的隔音棉厚度和密度为两个优化参数，分析不同厚度和密度的隔音棉的插入损失，并进行参数最优化分析，寻找最佳组合方式。得出结论：不同铺设角度顺序对复材整体结构的弯曲刚度和吻合效应频率有影响，在相同尺寸和边界条件下，构型1屈曲稳定性承载能力较强，隔声效果最好，铺层方式最优；隔音棉密度对插入损失影响较小，而隔音棉厚度对插入损失影响较大。论文选取的隔音棉密度和厚度已经使壁板、隔音棉及内饰板的组合结构隔声量达到了收敛状态，是最优化的组合设计。     

Structural–acoustic sensitivity analysis of radiated sound power using a finite element/ discontinuous fast multipole boundary element scheme

The complete interaction between the structural domain and the acoustic domain needs to be considered in many engineering problems, especially for the acoustic analysis concerning thin structures immersed in water. This study employs the finite element method to model the structural parts and the fast multipole boundary element method to model the exterior acoustic domain. Discontinuous higher‐order boundary elements are developed for the acoustic domain to achieve higher accuracy in the coupling analysis. Structural–acoustic design sensitivity analysis can provide insights into the effects of design variables on radiated acoustic performance and thus is important to the structural–acoustic design and optimization processes. This study is the first to formulate equations for sound power sensitivity on structural surfaces based on an adjoint operator approach and equations for sound power sensitivity on arbitrary closed surfaces around the radiator based on the direct differentiation approach. The design variables include fluid density, structural density, Poisson's ratio, Young's modulus, and structural shape/size. A numerical example is presented to demonstrate the accuracy and validity of the proposed algorithm. Different types of coupled continuous and discontinuous boundary elements with finite elements are used for the numerical solution, and the performances of the different types of finite element/continuous and discontinuous boundary element coupling are presented and compared in detail. Copyright © 2016 John Wiley & Sons, Ltd.     

Theoretical and experimental investigation of fluid rheology effects on modulated ultrasound propagation

A mathematical model is developed and presented to capture the effect of viscoelastic nature of a material on modulated ultrasound (US) pulses. The model is established by considering perturbation of material elements subject to modulated US pulses and by introducing the exponential relaxation of the perturbed fluid elements with a spectrum of time constants. Both the model and experimental findings revealed that consecutive perturbation of a material via the modulated US pulses enabled to probe the relaxation times of similar order of magnitudes to the frequency of the US modulation while filtering out the impact of other relaxation times on the US measurement. The US experimental results were verified by those of a conventional rheometer. Hence carrying out measurements at different US modulation frequencies in the Hz ranges seems to allow one to obtain the relaxation time spectrum of the investigated material in the time scales of milliseconds to seconds.     

瓦状阻尼橡胶块对高铁车轮减振降噪的影响分析

依据声学测试标准,为了评价某型高铁车轮在安装不同形式橡胶块装置后的减振降噪效果,在半消声室内基于B&K振动噪声测试分析系统,对裸轮和橡胶块车轮开展振动声辐射室内测试实验,并基于有限元方法对车轮模态进行了仿真分析。测试结果可知:相比裸轮,WA、WB车轮模态阻尼比显著增加,车轮的减振效果明显,其中WA车轮的减振效果略优于WB车轮。径向激励下,WA车轮声功率级降低了8 dB(A),WB车轮声功率级降低了5.5 dB(A);轴向激励下,WA车轮声功率级降低了8.2 dB(A),WB车轮声功率级降低了6.2 dB(A)。分析可知橡胶块装置能有效抑制车轮的滚动噪声和曲线啸叫,对车轮的减振降噪有积极作用。     

乌克兰强流加速器条带靶截面探测器研制

乌克兰哈尔科夫物理技术研究所(KIPT)在建的100 MeV电子直线加速器,束流功率高达100kW,给拦截式条带靶束流截面探测器的电极选材带来巨大的困难。通过ANSYS有限元分析程序对探头与束流的相互作用进行模拟,得到了探头材料在1.2kW束流功率条件下的真空温升和受力、变形结果;通过初步的束流实验,观测了T300碳纤维束在束流作用下的信号情况,最终锁定用T300碳纤维束作为电极材料。这是国际上首次采用碳纤维束作为靶面电极。