轮胎厂蒸汽的生产使用和管理

介绍了轮胎厂蒸汽的生产、使用及管理过程中应该注意的问题。就如何以最低的成本生产蒸汽、以最佳的效果使用蒸汽、以最科学的方法管理蒸汽提出了自己的见解。特别对锅炉的配置与运行、管道及附件的正确安装、管道保温层的临界厚度及冷凝水的回收等问题进行了探讨。     

声波清灰器在动力锅炉上的应用

介绍声波清灰技术的原理以及在电站锅炉上的应用效果,根据声波清灰器改造和投运后的情况得出结论,并提出建议.     

积层线路板用液态感光成像油墨的应用研究

研究了积层线路板油墨的组成配方、制备和应用工艺,分析了不同预烘时间对油墨分辨率的影响以及过显和显影不足问题的形成,并从生产和实际操作的角度,提出了解决的方案。利用聚苯醚改性的环氧树脂,应用于油墨的配方中,改善了油墨固化后绝缘材料的耐热性、介电性等主要性能。油墨中改性环氧树脂的质量分数为13.0%时,固化后绝缘材料的玻璃化温度可达184.22℃,介电常数为3.19,介质耗损因数为0.019,可以作高频积层线路板的绝缘层。     

Classification of cardiac sound signals using constrained tunable-Q wavelet transform

The features extracted from the cardiac sound signals are commonly used for detection and identification of heart valve disorders. In this paper, we present a new method for classification of cardiac sound signals using constrained tunable-Q wavelet transform (TQWT). The proposed method begins with a constrained TQWT based segmentation of cardiac sound signals into heart beat cycles. The features obtained from heart beat cycles of separately reconstructed heart sounds and murmur can better represent the various types of cardiac sound signals than that from containing both. Therefore, heart sounds and murmur have been separated using constrained TQWT. Then the proposed novel raw feature set has been created by the parameters that have been optimized while constraining the output of TQWT together with that of extracted by using time-domain representation and Fourier–Bessel (FB) expansion of separated heart sounds and murmur. However, the adaptively selected features have been used to obtain the final feature set for subsequent classification of cardiac sound signals using least squares support vector machine (LS-SVM) with various kernel functions. The performance of the proposed method has been validated with publicly available datasets and the results have been compared with the existing short-time Fourier transform (STFT) based method. The proposed method shows higher percentage classification accuracy of 94.01 as compared to 93.53 of STFT based method. In comparison with STFT based method, it is noteworthy that the proposed method uses well defined and lower dimensionality of feature vector that can reduce the computational complexity.     

平移不变小波在心音信号去噪中的应用

小波阈值去噪方法可以消除心音信号中的噪声,但其缺乏平移不变性,可能在信号的奇异点附近产生人为的振荡现象,即Pesudo-Gibbs现象,影响去噪效果。采用平移不变(Translation Invariance,TI)小波阈值去噪的方法对心音信号进行去噪,通过对信号序列平移来改变奇异点在整段信号的位置,以降低或消除振荡。对信号采用平移不变小波去噪之前,先通过消除趋势项来降低信号采集过程中引入的干扰。实验结果表明,该方法消除了人为振荡现象,在保留心音信号主要特征的前提下,信号的信噪比(Signal-to-Noise Ratio,SNR)和根均方误差(Root Mean Square Error,RMSE)均得到明显改善。     

基于LabVIEW的三传声器声速测量方法研究

提出了一种新的声速测量方法,通过测量管道壁面上3个固定位置的声压求解出声速。以LabVIEW软件为测量分析平台,建立声速测量系统,测得当前介质在不同频率处的声速。与理论的声速计算值比较,测量结果验证了测量方法的正确性。     

涂料原料和涂层厚度对反射隔热保温性能影响研究

通过研究涂料配方中所用乳液、颜料、常规填料和隔热填料在红外灯下的反射、隔热和保温性能，发现高折射率的二氧化钛和含有微孔的硅藻土具有最佳的反射和隔热保温效果，轻质碳酸钙和重质碳酸钙具有一定的隔热保温作用，而理论上具有隔热保温效果的填料海泡石等并没有预期的效果。涂层厚度对隔热保温效果具有一定影响，但是没有颜料和填料的影响大。隔热涂料使用的填料应含有硅藻土、二氧化钛以及一些常规的填料。     

降噪高分子材料及其应用

降噪材料按降噪机理可分为阻尼减振材料、吸声材料和隔声材料。降噪高分子材料可广泛应用于建筑、交通、化工和生活等各个领域。综述了降噪高分子材料的主要种类及其作用机理，并对高分子降噪材料的研究现状和应用情况作了简单的介绍。     

开放型电石炉绝缘问题浅见

介绍了开放型电石炉绝缘的结构特点，分析了绝缘材料的运行条件，讨论了绝缘系统的设计问题，提出了绝缘测试的三种方法。     

A song of ice and vessels: Seasonal trends in the soundscape of the western arm of Lake Superior

The soundscapes of marine systems have been studied for decades to determine spatial and temporal patterns of biological, geological, and anthropogenic activity. However, comparatively little is known about freshwater soundscapes. Lake Superior is the world’s largest freshwater lake by surface area and home to a variety of aquatic animals. The Twin Ports of Duluth and Superior, located in the western arm of Lake Superior, are annually closed because of ice cover, providing a unique opportunity to explore sound levels in the absence of vessel traffic. Passive acoustic monitoring was conducted over 15 months between November 2018 and March 2020 to investigate seasonal patterns. Sound pressure levels were significantly lower (8 dB) at low frequencies (<100 Hz) during the winter and spring months (when ice cover increased). Quieter ambient sound pressure levels may provide an acoustic refuge to soniferous animals, especially those that vocalise during winter spawning. During the ice-free months, commercial shipping introduces a near continuous source of sound, increasing sound levels by up to 25 dB (at frequencies < 1,000 Hz). Climate change is expected to further reduce ice cover and thickness allowing the shipping season into the Twin Ports to be extended, thus warranting concern about the effect of noise from vessel activity on aquatic life. This study provides a baseline of the soundscape in the western arm of Lake Superior, against which scientists and environmental managers can assess future changes to this important habitat.