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排序方式: 共有186条查询结果,搜索用时 31 毫秒
61.
提出了利用热管技术对大功率LED(Light Emitting Diode)进行散热的构想,设计了LED热管散热器的原理结构,并对其传热机理、传热路线和各传热阶段的热阻进行了定性分析和定量分析,建立了传热模型,导出了总传热系数的计算式,并给出了该热管散热器的设计计算实例。 相似文献
62.
63.
实验研究了环保替代制冷工质R410A和R22在冷凝温度40℃时在内螺纹强化管(外径为9.52mm)内的冷凝换热特性,对二者的冷凝换热性能进行了对比,并研究了测试管外冷却水流量对换热系数的影响。结果表明:在管外冷却水流量相同时,R22的总换热系数K普遍比R410a小,而管内传热系数hr比R410A大。R22与R410A的总传热系数K均随管外冷却水流量的增加而增加,当制冷剂流量Gm大于300kg.s-1.m-2时,管外冷却水流量对总传热系数K的影响变小。 相似文献
64.
紫外分光光度法测定中央空调制冷剂溴化锂水溶液中的铬酸根 ,方法检测灵敏度高 ,操作简便、快速 ,数据准确可靠。 相似文献
65.
Yanfang Shen Seksan Kiatsupaibul Zelda B. Zabinsky Robert L. Smith 《Journal of Global Optimization》2007,38(3):333-365
We present an analytically derived cooling schedule for a simulated annealing algorithm applicable to both continuous and
discrete global optimization problems. An adaptive search algorithm is used to model an idealized version of simulated annealing
which is viewed as consisting of a series of Boltzmann distributed sample points. Our choice of cooling schedule ensures linearity
in the expected number of sample points needed to become arbitrarily close to a global optimum. 相似文献
66.
冷却速率对液态金属Zn快速凝固过程中微观结构的影响 总被引:1,自引:0,他引:1
用分子动力学模拟方法研究了六种不同冷却速率对液态金属Zn凝固过程微观结构的影响. 采用双体分布函数g(r)曲线、平均原子总能量、Honeycutt-Andersen(HA)键型指数法和原子团类型指数法(CTIM-2)对凝固过程中微观结构的变化进行了分析. 结果表明, 冷却速率对微观结构的转变有决定性影响, 当冷却速率为1×1014、5×1013、2×1013、1×1013、5×1012 K·s-1时, 系统形成以1551、1541、1431键型为主体的非晶态结构; 当冷却速率为1×1012 K·s-1时, 系统形成以1421、1422键型为主或以密排六方(hcp)基本原子团(12 0 0 0 6 6)和面心立方(fcc)基本原子团(12 0 0 0 1 2 0)共存的部分晶态结构. 同时发现, 在形成非晶的五个系统中,玻璃化转变温度Tg随着冷速的降低而降低. 相似文献
67.
We consider a one-dimensional dynamical system driven by a vector field −U′, where U is a multi-well potential satisfying some regularity conditions. We perturb this dynamical system by a stable symmetric non-Gaussian Lévy process whose scale decreases as a power function of time. It turns out that the limiting behaviour of the perturbed dynamical system is different for slow and fast decrease rates of the noise intensity. As opposed to the well-studied Gaussian case, the support of the limiting law is not located in the set of global minima of U. 相似文献
68.
Batch pressure vessels commonly used for hydrothermal liquefaction have typical heating times in the range of 30 to 60 min.
Thermodynamically, the complex set of reactions are path dependent, so that the heating rate can possibly affect yields and
the composition of the resultant liquid products. It is postulated that the mode of heat transfer becomes an uncontrolled
variable in kinetic studies and can seriously impact scale-up. To confirm this hypothesis and minimize these heat-transfer-related
artifacts, we designed a batch pressure vessel equipped with an induction heating system, which allows the reduction of heat-up
times by about two orders of magnitude to several seconds, compared to tens of minutes with standard pressure reactors. This
system was used to study the direct liquefaction of corn stover and aspen wood with a pretreatment. The heating rate was found
to have no significant effect on the composition of the liquid products. However, the liquid yields are dependent on the heating
rate. Varying the cooling rate does not show obvious effects. The results confirm that the heating rate, as governed by the
mode of heat transfer, is an important factor that needs to be considered during scale-up. 相似文献
69.
ATHENA Collaboration M. Amoretti C. Amsler G. Bonomi A. Bouchta P. D. Bowe C. Carraro C. L. Cesar M. Charlton M. Doser V. Filippini A. Fontana M. C. Fujiwara R. Funakoshi P. Genova J. S. Hangst R. S. Hayano L. V. Jrgensen A. Kellerbauer V. Lagomarsino R. Landua D. Lindelof E. Lodi Rizzini M. Macrí N. Madsen G. Manuzio P. Montagna H. Pruys C. Regenfus A. Rotondi G. Testera A. Variola L. Venturelli D. P. van der Werf Y. Yamazaki 《Physics letters. [Part B]》2004,590(3-4):133-142
We demonstrate cooling of 104 antiprotons in a dense, cold plasma of 108 positrons, confined in a nested cylindrical Penning trap at about 15 K. The time evolution of the cooling process has been studied in detail, and several distinct types of behavior identified. We propose explanations for these observations and discuss the consequences for antihydrogen production. We contrast these results with observations of interactions between antiprotons and “hot” positrons at about 3000 K, where antihydrogen production is strongly suppressed. 相似文献
70.
Markov chain methods for Boltzmann sampling work in phases with decreasing temperatures. The number of transitions in each phase crucially affects terminal state distribution. We employ dynamic programming to allocate iterations to phases to improve guarantees on sample quality. Numerical experiments on the Ising model are presented. 相似文献