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1.
In this work, assembly pressure and flow channel size on proton exchange membrane fuel cell performance are optimized by means of a multi-model. Based on stress-strain data of the SGL-22BB GDL obtained from its initial compression experiments, Young's modulus with different ranges of assembly pressure fits well through modeling. A mechanical model is established to analyze influences of assembly pressure on various gas diffusion layer parameters. Moreover, a CFD calculation model with different assembly pressures, channel width, and channel depth are established to calculate PEMFC performances. Furthermore, a BP neural network model is utilized to explore optimal combination of assembly pressure, channel width and channel depth. Finally, the CFD model is used to validate effect of size optimization on PEMFC performance. Results indicate that gap change of GDL below bipolar ribs is more remarkable than that below channels under action of the assembly pressure, making liquid water easily transported under high porosity, which is conducive to liquid water to the channels, reduces the accumulation of liquid water under the ribs, and enhances water removal in the PEMFC. Affected by the assembly force, change of GDL porosity affects its diffusion rate, permeability and other parameters, which is not conducive to mass transfer in GDL. Optimizing the depth and different dimensions through width of the flow field can effectively compensate for this effect. Therefore, the PEMFC performance can be enhanced through the comprehensive optimization of the assembly force, flow channel width and flow channel depth. The optimal parameter is obtained when assembly pressure, channel width and channel depth are set as 0.6 MPa, 0.8 mm, and 0.8 mm, respectively. The parameter optimization enhances the mass transfer, impedance, and electrochemical characteristics of PEMFC. Besides, it effectively enhances the quality transfer efficiency inside GDL, prevents flooding, and reduces concentration loss and ohmic loss.  相似文献   
2.
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems.  相似文献   
3.
Coupled large eddy simulation and the discrete element method are applied to study turbulent particle–laden flows, including particle dispersion and agglomeration, in a channel. The particle–particle interaction model is based on the Hertz–Mindlin approach with Johnson–Kendall–Roberts cohesion to allow the simulation of van der Waals forces in a dry air flow. The influence of different particle surface energies, and the impact of fluid turbulence, on agglomeration behaviour are investigated. The agglomeration rate is found to be strongly influenced by the particle surface energy, with a positive relationship observed between the two. Particle agglomeration is found to be enhanced in two separate regions within the channel. First, in the near-wall region due to the high particle concentration there driven by turbophoresis, and secondly in the buffer region where the high turbulence intensity enhances particle–particle interactions.  相似文献   
4.
提高信道的数据传输效率是人们不断追求的目标之一,也是衡量网络性能的标准之一,从几方面分析总结了为此而采取的各种措施。  相似文献   
5.
等径弯角挤压工艺(ECAEP)研究现状   总被引:3,自引:0,他引:3  
等径弯角挤压是制备块状细晶材料的一种大塑性变形工艺,目前得到国内外高度重视.本文简要介绍了等径弯角挤压工艺的基本原理和变形特点,从理论上对其变形方式和机理进行了分析,并详细介绍了该工艺的应用领域。  相似文献   
6.
电信服务营销渠道转型的必要性   总被引:5,自引:0,他引:5  
王越  王俊陶 《世界电信》2004,17(5):16-18
分析了电信企业服务营销渠道的特点、旧有的服务营销渠道模式和存在的问题以及今后电信业和市场等方面发展的新需求,对电信服务营销渠道转型的必要性进行了探讨和研究,同时提供了一个可供参考的服务营销渠道价值评估体系架构,从量化服务营销渠道对电信企业贡献价值的角度论述了服务营销渠道转型的必要性。  相似文献   
7.
S Gracias  V U Reddy 《Sadhana》1996,21(1):75-89
Recently, considerable amount of attention is being given to the field of wavelets and wavelet packets. It has found numerous applications in signal representation, image compression and applied mathematics. In this paper, we present a channel equalization method based on wavelet packets. The proposed equalizer structure is based on the fact that for sufficiently narrowband sequences, a non-ideal channel can be modelled as an attenuation and delay. If the data sequence is used to modulate a set of narrowband wavelet packets, then no equalization is required at the receiver end. The equalization problem reduces to that of determining the delay introduced by the channel for each of the wavelet packets. A minimum square variance algorithm for adaptively choosing the delay has been proposed. This algorithm has been shown to perform as desired analytically in a simple delay channel case. Simulations have been used to study its performance in the non-ideal channel’s case and the results corroborate theoretical predictions.  相似文献   
8.
无阈下信道签名方案及其应用   总被引:4,自引:0,他引:4  
介绍了开展封闭阈下信道签名研究的意义,综述了它们新的研究成果和应用。最后提出了若干有待进一步研究的问题。  相似文献   
9.
分析了一种数字解码卫星电视接收机,该机能接收利用MPEG-2进行数据压缩,采用SCPC或MCPC方式上星的卫星电视信号,具有选单显示,断电现场保护等功能。并对该机进行了原理分析,对主要集成电路的基本原理也作了简介,并给出了软件的部分主要流程及功能分析。  相似文献   
10.
OFDM与数字HDTV的单频网广播   总被引:1,自引:0,他引:1  
介绍地面数字HDTV的单频网广播技术,并与单载波主发射机方案进行比较,提出OFDM系统中的一种信道估值新方案,它能显著地改善OFDM系统的频谱利用率。数字HDTV的单频网广播被长时延多径干扰所困扰,给出了克服长时延多径干扰的一种方法。  相似文献   
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