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《低温学》2015
This paper puts forward the partial scaling method of the Oxford-type moving-coil linear compressor for pulse tube cryocoolers and analyzes the related principles. The systematic experimental investigations are further made to verify the analyses. One of the typical compressors developed in the authors’ laboratory is chosen to be scaled, and then coupled with the original pulse tube cold finger. At the typical operating temperature of 80 K for the pulse tube cold finger, the scaled compressor’s maximum input electric power increases from 236.7 W to 370.0 W, and the cooling power is enhanced from 10.0 W to 15.0 W. The motor efficiency decreases from 78% to 73%, but the average cooling efficiency slightly increases from 11% to 12% of Carnot efficiency due to a better match between scaled compressor and original cold finger. The rationality and feasibility of the partial scaling method have been verified by the theoretical analyses and experimental investigations. 相似文献
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Navid Azadi Abdolreza Ohadi 《International Journal of Adaptive Control and Signal Processing》2012,26(5):451-468
The performance of conventional linear algorithms in active noise control applications deteriorates facing nonlinearities in the system mainly because of loudspeakers. On the other hand, fuzzy logic and neural networks are good candidates to overcome this drawback. In this paper, the acoustic attenuation of noise in a rectangular enclosure with a flexible panel and five rigid walls is presented both theoretically and experimentally using filtered gradient fuzzy neural network (FGFNN) error back propagation algorithm in which the secondary path effect is implemented in derivation of updating rules. Considering this effect in updating rules leads to faster convergence and stability of the active noise control system. On the other hand, the primary path in the investigated system comprises an identified nonlinear model of loudspeaker inside the aforementioned box, parameters of which vary with the input current. The loudspeaker is identified using series‐parallel neural network model identification method. As a comparison, the performance of filtered‐x least mean squares and FGFNN algorithms are compared. It is observed that FGFNN controller exhibits far better results in the presence of loudspeakers with nonlinear behavior in primary path.Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Acoustic modifications of loudspeaker announcements were investigated in a simulated aircraft cabin to improve passengers’ speech intelligibility and quality of communication in this specific setting. Four experiments with 278 participants in total were conducted in an acoustic laboratory using a standardised speech test and subjective rating scales. In experiments 1 and 2 the sound pressure level (SPL) of the announcements was varied (ranging from 70 to 85 dB(A)). Experiments 3 and 4 focused on frequency modification (octave bands) of the announcements. All studies used a background noise with the same SPL (74 dB(A)), but recorded at different seat positions in the aircraft cabin (front, rear). The results quantify speech intelligibility improvements with increasing signal-to-noise ratio and amplification of particular octave bands, especially the 2 kHz and the 4 kHz band. Thus, loudspeaker power in an aircraft cabin can be reduced by using appropriate filter settings in the loudspeaker system. 相似文献
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在参量阵扬声器系统中,需采用若干个压电陶瓷超声换能器单元组成换能器发射阵,换能器单元的数目和排列位置会对发射阵的指向性产生影响。通过改变换能器数目及之间的相对距离,模拟了超声发射阵的空间指向性。与实测结果进行了比较,验证了在设计超声发射阵列时,此模拟方法的可靠性和实用性。 相似文献
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通过对微型扬声器的阻抗曲线测试分析,说明微型扬声器在测试电压加大的条件下微型扬声器所特有的现象.对此特有现象进行了初步分析。并对通常条件下微型扬声器阻抗曲线测试时的电压怎样选择和怎样测试作了说明。 相似文献
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介绍了目前市场上对PA纸盆的要求和发展趋势;阐述了研发PA纸盆的一些技术要求(要点)和思路、方法,重点说明了对PA纸盆音质起关键性影响的因素,对纸浆打浆工艺、纸浆纤维配比等作了较深入细致的探讨. 相似文献
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在提出转移矩阵的概念后,从系统元素的串联及并联的矩阵表示方法入手,使得任何复杂系统都可用搭积木的方法得出其转移矩阵。详细描述了扬声器转移矩阵的导出过程。由矩阵表达的方程可以采用诸如Manab之类的计算机软件快捷地求解。转移矩阵为既简单又不失精确的数学方法。 相似文献