排序方式: 共有19条查询结果,搜索用时 15 毫秒
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N.M. Hariharan P. Sivashanmugam S. Kasthurirengan 《International Journal of Refrigeration》2013,36(8):2420-2425
The objective of this study is to analyse the performance of thermoacoustic refrigerator (TAR) measured in terms of hot end temperature and temperature difference across refrigerator stack with two different spacing namely 0.4 mm and 0.8 mm and stack used in refrigerating section was made of low thermal conductivity materials namely Mylar sheet and photographic film & the experiments were carried out at 1 MPa pressure using helium as working fluid. High powered acoustic wave with frequency of 460 Hz and pressure amplitude of 0.07 MPa was obtained from twin thermoacoustic prime mover (TAPM) and this acoustic wave produced temperature difference of 16 °C across the Mylar sheet stack made of 0.4 mm spacing in refrigerator section. From this study, it has been inferred that twin TAPM can act as efficient drive for TAR. 相似文献
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Constructive belief and rational representation 总被引:1,自引:0,他引:1
Jon Doyle 《Computational Intelligence》1989,5(1):1-11
It is commonplace in artificial intelligence to divide an agent's explicit beliefs into two parts: the beliefs explicitly represented or manifest in memory, and the implicitly represented or constructive beliefs that are repeatedly reconstructed when needed rather than memorized. Many theories of knowledge view the relation between manifest and constructive beliefs as a logical relation, with the manifest beliefs representing the constructive beliefs through a logic of belief. This view, however, limits the ability of a theory to treat incomplete or inconsistent sets of beliefs in useful ways. We argue that a more illuminating view is that belief is the result of rational representation. In this theory, the agent obtains its constructive beliefs by using its manifest beliefs and preferences to rationally (in the sense of decision theory) choose the most useful conclusions indicated by the manifest beliefs. 相似文献
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Learning and classification of monotonic ordinal concepts 总被引:3,自引:0,他引:3
Ordinal reasoning plays a major role in human cognition. This paper identifies an important class of classification problems of patterns taken from ordinal domains and presents efficient, incremental algorithms for learning the classification rules from examples. We show that by adopting a monotonicity assumption of the output with respect to the input, inconsistencies among examples can be easily detected and the number of possible classification rules substantially reduced. By adopting a conservative classification criterion, the required number of rules further decreases. The monotonicity and conservatism of the classification also enable the resolution of conflicts among inconsistent examples and the graceful handling of don't knows and don't cares during the learning and classification phases. Two typical examples in which the suggested classification model works well are given. The first example is taken from the financial domain and the second from machining. 相似文献
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The heat transfer in heat exchangers is commonly calculated using the concept of Logarithmic Mean Temperature Difference (LMTD). As is well known this approach is only valid for counter-current and co-current heat exchanger configurations. For other configurations, corrections for the deviation from pure counter-current are introduced. From any standard text book in heat transfer it may be found that the LMTD approach may also be used if condensation and evaporation occurs in the heat exchanger. The purpose of the present paper is to investigate if the LMTD approach can be used in a compact brazed plate evaporator. It will be shown through integration of the governing equations that the LMTD approach indeed may be used for practical cases, even though deviations occur at small logarithmic mean temperature differences. The article presents suggestions on the correction factor (F) needed under some simplified assumptions in a compact brazed plate heat exchanger operating as an evaporator for heat pump and refrigeration applications. 相似文献
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We performed a study on the effect of the discharge airflow rate of the ceiling type air-conditioner on ventilation performance in the lecture room with the mixing ventilation. The experiments and CFD were conducted for analyzing ventilation performance. The concepts of mean air age and indoor CO2 concentration were used for evaluating ventilation performance. We made the CO2 generation model in the simulation and calculated a lot of cases with respect to the airflow rate of air-conditioner and the mechanical ventilation rate. And the selected experimental measurements were performed in the lecture room of the same layout as the numerical one for verifying simulation results. Mean air age is gradually increased, but CO2 concentration is oppositely decreased in the occupied zone with the increment of the discharge airflow rate of the ceiling type air-conditioner. This result shows that both mean air age and residual life time must be considered for evaluating ventilation performance when the contaminants are generated indoors. And the increment of discharge airflow of the ceiling type air-conditioner can induce the piston effect and push the contaminants out of the occupied zone. From this result, it is found out that ventilation performance can be increased when the momentum source like an air-conditioner is used in the room with the mixing ventilation. 相似文献
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PLC宽带通信技术及电磁辐射研究 总被引:4,自引:3,他引:1
电力线通信PLC(Power Line Communication)是以电力线作为通信载体,加上PLC的局端和终端调制解调器,将电力网作为电力通信网络。PLC是以太网的一个分支,采用了基于CSMA/CA的广播共享方式的接入网络原理。由于PLC信道具有时变性、大衰减性及存在复杂多样的干扰噪声.PLC高速载波通信采用正交频分多路复用OFDM(Orthogonal Frequency Division Muhiplexing)技术.可提高网络传输质量。探讨了PLC电磁辐射机理、家电电磁辐射及PLC电磁辐射标准、电磁辐射的影响和防护措施(改善或利用PLC系统电力线的对称性、减小PLC信号的功率谱密度、合理选择OFDM的参数等)。理论和实践表明,PLC的干扰是轻微和可以控制的。 相似文献
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A model for reasoning about persistence and causation 总被引:10,自引:0,他引:10
Reasoning about change requires predicting how long a proposition, having become true, will continue to be so. Lacking perfect knowledge, an agent may be constrained to believe that a proposition persists indefinitely simply because there is no way for the agent to infer a contravening proposition with certainty. In this paper, we describe a model of causal reasoning that accounts for knowledge concerning cause-and-effect relationships and knowledge concerning the tendency for propositions to persist or not as a function of time passing. Our model has a natural encoding in the form of a network representation for probabilistic models. We consider the computational properties of our model by reviewing recent advances in computing the consequences of models encoded in this network representation. Finally, we discuss how our probabilistic model addresses certain classical problems in temporal reasoning (e. g., the frame and qualification problems). 相似文献