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101.
声制冷机是一种新型制冷机,具有无机械运动部件,可靠性高寿命长,采用惰性气体为工质无污染等优点.驻波型热声制冷机的声功泵热效应是不可逆过程,内部不可逆损失导致热声制冷机效率偏低,制约了热声制冷机的发展和应用.本文研究了线性范围内驻波型制冷机换热器和回热器内的可压缩振荡流动与传热过程的熵产,分析了板间距,振荡频率和温度梯度对熵产的影响。 相似文献
102.
为了提高微波等离子推力器性能,改善等离子体对电磁波能量的吸收状况,提高核心区温度,提出外加磁场的方案,并对热等离子体进行了数值模拟.假设局域热平衡条件,采用Navier-Stokes,Maxwell和Saha方程,利用压力修正的半隐格式和时域有限差分求解方法,建立了径向磁镜场下推力器内等离子体流场的数值计算模型.数值模拟结果表明:外加磁场后的磁感应强度小于0.5 T时,推力器内热等离子体核心区最高温度随磁感应强度的增加而迅速提高.外加磁场后的磁感应强度大于0.5 T时,核心区最高温度随磁感应强度的增加而缓慢提高.磁感应强度为0.5 T时,热等离子体核心区最高温度与不加磁场相比提高了24%.外加磁场对等离子体流场速度分布影响不大.
关键词:
等离子体模拟
等离子体相互作用
等离子体流动 相似文献
103.
LI Ke-Ping 《理论物理通讯》2006,46(8)
In this work, we propose a new model of evolution networks, which is based on the evolution of the traffic flow. In our method, the network growth does not take into account preferential attachment, and the attachment of new node is independent of the degree of nodes. Our aim is that employing the theory of evolution network, we give a further understanding about the dynamical evolution of the traffic flow. We investigate the probability distributions and scaling properties of the proposed model. The simulation results indicate that in the proposed model, the distribution of the output connections can be well described by scale-free distribution. Moreover, the distribution of the connections is largely related to the traffic flow states, such as the exponential distribution (i.e., the scale-free distribution) and random distribution etc. 相似文献
104.
本文使用详细的化学反应机理模拟了C2H6/O2/N2/AR层流对冲扩散火焰中多环芳烃的生成动力学过程。反应机理包括96种组分的502个基元反应。通过数值计算分析了层流对冲火焰的结构和主要反应物、中间物质和反应产物的浓度变化,并与相关文献的实验结果进行了比较。结果表明,数值模拟在燃烧过程和PAH生成规律上与实验结果是一致的,但在某些组分的定量预报上存在一定的差别。 相似文献
105.
Martin Skutella 《Mathematical Programming》2002,91(3):493-514
In the single source unsplittable min-cost flow problem, commodities must be routed simultaneously from a common source vertex
to certain destination vertices in a given graph with edge capacities and costs; the demand of each commodity must be routed
along a single path so that the total flow through any edge is at most its capacity. Moreover, the total cost must not exceed
a given budget. This problem has been introduced by Kleinberg [7] and generalizes several NP-complete problems from various
areas in combinatorial optimization such as packing, partitioning, scheduling, load balancing, and virtual-circuit routing.
Kolliopoulos and Stein [9] and Dinitz, Garg, and Goemans [4] developed algorithms improving the first approximation results
of Kleinberg for the problem of minimizing the violation of edge capacities and for other variants. However, known techniques
do not seem to be capable of providing solutions without also violating the cost constraint. We give the first approximation
results with hard cost constraints. Moreover, all our results dominate the best known bicriteria approximations. Finally,
we provide results on the hardness of approximation for several variants of the problem.
Received: August 23, 2000 / Accepted: April 20, 2001?Published online October 2, 2001 相似文献
106.
A control volume type numerical methodology for the analysis of steady three‐dimensional rotating flows with heat transfer, in both laminar and turbulent conditions, is implemented and experimentally tested. Non‐axisymmetric momentum and heat transfer phenomena are allowed for. Turbulent transport is alternatively represented through three existing versions of the k–ε model that were adjusted to take into account the turbulence anisotropy promoted by rotation, streamline curvature and thermal buoyancy. Their relative performance is evaluated by comparison of calculated local and global heat balances with those obtained through measurements in a laboratory device. A modified version of the Lam and Bremhorst, low Reynolds number model is seen to give the best results. A preliminary analysis focused on the flow structure and the transfer of heat is reported. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
107.
Online weighted flow time and deadline scheduling 总被引:1,自引:0,他引:1
Luca Becchetti Stefano Leonardi Alberto Marchetti-Spaccamela Kirk Pruhs 《Journal of Discrete Algorithms》2006,4(3):339
In this paper we study some aspects of weighted flow time. We first show that the online algorithm Highest Density First is an O(1)-speed O(1)-approximation algorithm for P|ri,pmtn|∑wiFi. We then consider a related Deadline Scheduling Problem that involves minimizing the weight of the jobs unfinished by some unknown deadline D on a uniprocessor. We show that any c-competitive online algorithm for weighted flow time must also be c-competitive for deadline scheduling. We then give an O(1)-competitive algorithm for deadline scheduling. 相似文献
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