共查询到20条相似文献,搜索用时 250 毫秒
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针对大冷量氦气循环低温系统的研制进行了论述,该系统由氦气循环、低温换热和监测控制三个单元组成。氦气循环单元为氦气提供循环动力,以及压力和流量的调节,氦气循环单元中的氦气压缩机由螺杆制冷压缩机进行改造,同时对螺杆压缩机的冷却、后处理进行了优化。低温换热单元为循环氦气提供冷源,该单元使用的冷源介质为液氮和液氦,先使用液氮对系统进行预冷,然后采取液氦进行降温。监测控制单元对系统中的温度、压力和流量测量点进行监测,上位机软件自动绘制温度和压力曲线,并对数据进行存储。 相似文献
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超导同步调相机是一种用于电力系统的新型动态无功补偿设备, 具有高效、 快速响应等优点. 本文描述了10 Mvar 高温超导同步调相机的总体结构, 励磁绕组采用 YBCO 高温超导带材绕制而成, 通过循环的20 K 冷氦气进行冷却. 低温系统主要包含3 台制冷机、1 台氦气泵、 冷头换热器及其他辅助设备, 通过旋转密封装置与电机转子部分进行连接. 本文重点介绍了低温系统的设计方法, 包括转子、 绝热力矩管和电流引线等关键部位漏热和氦气管路流阻的计算方法, 并通过多次降温试验进行实验验证. 通过对带负载试验结果分析得出: 存在最优的氦气压力和氦气泵转速运行参数, 使得电机转子部分获的最佳冷却效果. 通过与300 kvar 高温超导同步调相机的耦合测试发现, 所研制的低温系统可将转子系统冷却至22.4 K, 满足调相机应用中对低温环境的要求. 相似文献
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为了对换热器在低温结霜工况下的动态运行特性进行研究,设计搭建了换热器结霜工况性能实验台,安装了各参数测量仪表和传感器。实验台由制冷循环和模拟低温工况的风道循环两部分组成,并采用C#编程技术,基于.NET开发了集环境模拟、数据采集、显示和数据处理、实时曲线和视频显示功能于一体的远程测控系统,该试验系统的研制为低温结霜工况下换热器运行特性研究提供了更多的实验参考和计算依据。 相似文献
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《工程热物理学报》2021,42(10):2544-2552
超临界二氧化碳(SCO_2)布雷顿循环发电系统与传统火力发电系统相比,具有系统尺寸小、循环效率高、工质易获取等优势。本文首先采用Aspen HYSYS与Aspen Plus软件分别建立了三种循环模型:简单循环、再压缩循环和分流再压缩循环;并使用三种物性方法对每种循环进行了模拟;对比实验室的数据,研究了不同物性方法的模拟精确度,数据表明Aspen Plus软件下的REFPROP物性计算方法精确度较高。然后在不同的工况参数下,使用该物性方法计算对比了三种循环在相同工况下的循环效率,结果证实:为获得高效率,回热尤为重要。最后,以再压缩循环模型为基础,在不同的回热条件下,研究了循环中五个主要参数对循环效率的影响。本文结论可为SCO_2的再压缩循环模型设计提供参考。 相似文献
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A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
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Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
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A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
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40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
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Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
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Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
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Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
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The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
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References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献