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1.
An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w... 相似文献
2.
红外辐射在水雾中衰减计算的修正方法研究 总被引:2,自引:0,他引:2
水雾系统对红外光谱有着强烈的衰减作用,因此在军事目标的各种制导对抗中被予以高度的关注。以Mie散射理论为基础,分析了粒子对红外光谱前向散射的聚集特性,定义了近前向散射比,并确定了在应用朗伯比尔定律时需修正的粒子尺度和散射半角的范围。通过大量计算发现,单独将粒子尺度和散射半角的乘积作为独立变量计算的视消光系数不够精确。在中远红外波段,前向散射附近的小角度内散射强度积分与粒子尺度和散射角都成正比,若红外波长为定值,则与粒子半径成正比。最后根据前向散射规律给出了两个不单独以x.θ为变量的经验计算公式,使得对水雾消光的修正计算更加简便精确。 相似文献
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Haifeng Yao Yueping Niu Yandong Peng Shangqing Gong 《Optics Communications》2011,284(16-17):4059-4063
We investigate the nonlinear propagation of few-cycle rectangular laser pulses on resonant intersubband transitions in semiconductor quantum wells using an iterative predictor–corrector finite-difference time-domain method. An initial 2π rectangular pulse will split into Sommerfeld–Brillouin precursors and a self-induced transparency soliton during the course of propagation. The duration of generated soliton depends on the carrier-envelope phase of the incident pulse. In our case, not only the near-resonant frequency components but also the low frequency components could contribute to the generation of the soliton pulse when the condition of multi-photon resonance is satisfied. The phase-sensitive property of the solitons results from the phase-dependent distribution of high and low frequency sidebands of few-cycle rectangular pulses. 相似文献
5.
This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle
with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept
with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy
input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side
heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating
load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with
those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure
ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness
of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side
heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working
fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic
efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on
reversed Brayton cycle. 相似文献
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The optimal performance of heat-driven binary separation processes with linear phenomenological heat transfer law(q∝△(T-1)) is analyzed by taking the processes as heat engines which work between high-and low-temperature reservoirs and produce enthalpy and energy flows out of the system,and the temperatures of the heat reservoirs are assumed to be time-and space-variables.A numerical method is employed to solve convex optimization problem and Lagrangian function is employed to solve the average optimal contr... 相似文献
10.
The characteristic-value analysis of plastic dynamic buckling is presented for columns under the action of elastoplastic compression wave caused by an axial-step load. Two critical conditions constituting a dynamic instability criterion are derived on the basis of transformation and conservation of energy. The governing equations, the boundary conditions and the continuity conditions derived by the use of the first critical condition are the same as those given by the adjacent-equilibrium criterion and are insufficient for determining two characteristic parameters involved in the governing equations. A supplementary restraint equation for buckling deformations at the plastic-wave front and the elastic-wave front is derived by the use of the second critical condition. Then, a couple of characteristic equations for two characteristic parameters are derived on the condition that the governing equations have non-trivial solutions satisfying the boundary conditions, the continuity conditions and the supplementary restraint equation. The critical-load parameters, dynamic characteristic parameter (exponent parameter of inertia term) and dynamic buckling modes are calculated from the solutions of the characteristic equations. 相似文献