共查询到19条相似文献,搜索用时 406 毫秒
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随着高频脉冲管制冷机性能的不断改善,特别是在红外和超导应用方面已进入实用化阶段,需要对蓄冷器和压缩机作进一步研究,探索高频脉冲管制冷机的工作机理,优化制冷机的整机设计.本文介绍了一台斯特林型高频单级脉冲管制冷机,经过优化设计,最低制冷温度达到了33 K,在40 K有420 mW的制冷量,当输入电功率为200 W时,在80K有4.5 W的制冷量.文中针对压缩机效率在40~80 K温区随工作频率变化的曲线关系,指出了制冷机和压缩机的耦合问题是研究脉冲管制冷机的重点与难点.并分析了制冷机内部各种阻力损失和热损失随压缩机运行频率变化的原因. 相似文献
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针对脉冲管制冷机内部交变流动及多孔介质蓄冷机的特点建立了数值计算模型,采用改进的数值模拟方法对脉冲管制冷机内部气流的交变流动、换热以及制冷过程进行了详尽的数值研究,得到了脉冲管制冷机内各参数的动态变化,分析了各动态参数变化对制冷机整机性能的影响,并从提高数值方程的计算精度和收敛性方面给出了改进的数值模拟方法。模拟分析与实验结果符合良好。该模拟方法的特点从基本流动换热微分方程出发,尽可能多的考虑实际制冷机工作过程中的各种不可逆因素,包括实际气体的物性变化,各部件的流动阻力和传热损失。 相似文献
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为模拟和动态显示工作在液氦温区的两级4K脉冲管制冷机内部工作过程和参数变化规律,发展了一种新的欧拉法-拉格朗日法数值计算模型。采用拉格朗日方法,直接跟踪脉冲管中气体微元随周期性压力波动的具体运行轨迹;采用欧拉法,直接模拟蓄冷器内部的动态参数变化。本文简单介绍该模型,并模拟了一典型两级4 K脉冲管制冷机各参数的变化情况,分析了多层磁性蓄冷材料对制冷机性能的影响情况。 相似文献
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Psychophysical tuning curves (PTCs) were obtained in simultaneous and forward masking for a 20-ms, 1000-Hz signal presented at 10 dB SL. The signal was presented at the beginning of, at the temporal center of, at the end of, or immediately following a 400-ms masker. The first experiment was done in quiet; the second experiment was done in the presence of two bands of noise on either side of 1000 Hz. The results were similar in quiet and in noise. In simultaneous masking, the PTCs were broadest for the signal at masker onset, and generally sharpest for the signal at temporal center; the differences were largest on the high-frequency side. In most cases, there was virtually no difference in Q10 between the forward-masking PTC and the simultaneous-masking PTC with the signal temporally centered, although the high-frequency slope was always steeper in forward masking. These results indicate that, at least for brief signals, frequency selectivity measured with simultaneous-masking PTCs and the degree of sharpening revealed in forward-masking PTCs depend upon the temporal position of the signal within the simultaneous masker. 相似文献
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B P Kimberley D A Nelson S P Bacon 《The Journal of the Acoustical Society of America》1989,85(4):1660-1665
Simultaneous-masked psychophysical tuning curves (PTCs) were obtained from normal-hearing and sensorineural hearing-impaired listeners. The 20-ms signal was presented at the onset or at the temporal center of the 400-ms masker. For the normal-hearing listeners, as shown previously [S. P. Bacon and B. C. J. Moore, J. Acoust. Soc. Am. 80, 1638-1645 (1986)], the PTCs were sharper on the high-frequency side for a signal in the temporal center of the masker. For the hearing-impaired listeners, however, the shape of the PTC was virtually independent of the temporal position of the signal. These data suggest that the mechanisms responsible for sharpening the PTC with time in normal-hearing listeners are ineffective in listeners with moderate-to-severe sensorineural hearing loss. 相似文献
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Sound source localization on the horizontal plane is primarily determined by interaural time differences (ITDs) for low-frequency stimuli and by interaural level differences (ILDs) for high-frequency stimuli, but ITDs in high-frequency complex stimuli can also be used for localization. Of interest here is the relationship between the processing of high-frequency ITDs and that of low-frequency ITDs and high-frequency ILDs. A few similarities in human performance with high- and low-frequency ITDs have been taken as evidence for similar ITD processing across frequency regions. However, such similarities, unless accompanied by differences between ITD and ILD performance on the same measure, could potentially reflect processing attributes common to both ITDs and ILDs rather than to ITDs only. In the present experiment, both learning and variability patterns in human discrimination of ITDs in high-frequency amplitude-modulated tones were examined and compared to previously obtained data with low-frequency ITDs and high-frequency ILDs. Both patterns for high-frequency ITDs were more similar to those for low-frequency ITDs than for high-frequency ILDs. These results thus add to the evidence supporting similar ITD processing across frequency regions, and further suggest that both high- and low-frequency ITD processing is less modifiable and more noisy than ILD processing. 相似文献
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根据Redebaugh相位分析理论,建立了双向进气对于G-M型脉冲管制冷机性能影响的数学模型,在此基础上提出了制冷机性能优化的若干措施。同时建立了单级G-M型脉冲管制冷机性能实验系统,通过改进小孔阀的开度,优化旋转阀的进气频率和双向进气的开度,使系统性能得到了明显的改善。 相似文献
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P G Stelmachowicz W Jesteadt M P Gorga J Mott 《The Journal of the Acoustical Society of America》1985,77(2):620-627
Performance-intensity functions for monosyllabic words were obtained as a function of signal-to-noise ratio for broadband and low-pass filtered noise. Subjects were 11 normal-hearing listeners and 13 hearing-impaired listeners with flat, moderate sensorineural hearing losses and good speech-discrimination ability (at least 86%) in quiet. In the broadband-noise condition, only small differences in speech perception were noted between the two groups. In low-pass noise, however, large differences in performance were observed. These findings were correlated with various aspects of psychophysical tuning curves (PTCs) obtained from the same individuals. Results of a multivariate analysis suggest that performance in broadband noise is correlated with filter bandwidth (Q10), while performance in low-pass noise is correlated with changes on the low-frequency side of the PTC. 相似文献
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在太赫兹波段,存在几种新的高频效应会限制混频二极管的高频特性.应用热电子发射理论和隧道理论,研究了外延层肖特基二极管的高频特性,并以截止频率为品质因数对二极管进行优化设计.研究表明,当二极管工作频率大于等离子频率时,二极管相当于一个电容,失去了混频性能;提高基底掺杂浓度可以减小基底等离子共振效应;外延层等离子频率非常重要并且在研究外延层等离子共振效应时必须考虑传输时间效应;减小阳极直径、减小外延层厚度、提高外延层掺杂浓度可以提高二极管的工作频率.这对太赫兹波段室温混频器件的研制具有重要的参考价值. 相似文献
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单级高频脉冲管制冷机研究 总被引:1,自引:1,他引:1
采用单级高频脉冲管制冷机获得低于30 K的制冷温度是脉冲管应用的一个新方向.本文介绍了一套获得了26 K最低制冷温度的单级高频脉冲管制冷机,这是无多路旁通的单级高频脉冲管制冷机获得的最低温度.实验表明,即使对于惯性管作为主要调相结构的高频情况,双向进气方案在进一步调相和降低温度方面仍有很大作用.该工作为单级高频脉冲管制冷机在30~40 K温区的应用奠定了基础.该实验结果和模拟分析结果基本相符.通过和二级制冷机的比较说明了单级制冷机的优势,即较大的制冷量斜率. 相似文献
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In this paper, an improved fusion algorithm for infrared and visible images based on multi-scale transform is proposed. First of all, Morphology-Hat transform is used for an infrared image and a visible image separately. Then two images were decomposed into high-frequency and low-frequency images by contourlet transform (CT). The fusion strategy of high-frequency images is based on mean gradient and the fusion strategy of low-frequency images is based on Principal Component Analysis (PCA). Finally, the final fused image is obtained by using the inverse contourlet transform (ICT). The experiments and results demonstrate that the proposed method can significantly improve image fusion performance, accomplish notable target information and high contrast and preserve rich details information at the same time. 相似文献