共查询到20条相似文献,搜索用时 15 毫秒
1.
WANG JianHui HE JiZhou & MAO ZhiYuan Department of Physics Nanchang University Nanchang China 《中国科学G辑(英文版)》2007,50(2):163-176
A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are dis-cussed in brief. 相似文献
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H. Maury P. Jonnard K. Le Guen J. -M. André Z. Wang J. Zhu J. Dong Z. Zhang F. Bridou F. Delmotte C. Hecquet N. Mahne A. Giglia S. Nannarone 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):193-199
The interplay between optical performance and the thermally activated interface chemistry of periodic Mg/SiC multilayers designed for application at 30.4 nm are investigated by optical (hard X-ray, soft X-ray and ultraviolet ranges, i.e. from 0.154 to 30.4 nm) reflectivity and X-ray emission spectroscopy. The multilayers are prepared by magnetron sputtering and then annealed up to a temperature of 500 °C. Two clear changes take place in the multilayer upon annealing. At first, between 200 and 300 °C a strong decrease of the reflectivity is observed, due to the development of interfacial roughness following the crystallization of the Mg layers. No interfacial compound is detected. Then, between 350 and 400 °C there is formation of the Mg2Si magnesium silicide at the interfaces following the reaction between the Mg and SiC layers. This also leads to the almost total loss of reflectivity of the multilayer. Thus, this kind of multilayer is thermally stable only for application requiring no heating above 200 °C. 相似文献
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An entangled quantum refrigerator working with a three-qubit one-dimensional isotropic Heisenberg XX model in a constant external magnetic field is constructed in this paper. Based on the quantum first law of thermodynamics, the expressions for several basic thermodynamic quantities such as the heat transferred, the net work and the coefficient of performance are derived. Moreover, the influence of the thermal entanglement on the basic thermodynamic
quantities is investigated. Several interesting features of the variation of the basic thermodynamic quantities with the thermal entanglement in zero and nonzero magnetic field are obtained. 相似文献
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The usual notion of separability has to be reconsidered when applied to states describing identical particles. A definition of separability not related to any a priori Hilbert space tensor product structure is needed: this can be given in terms of commuting subalgebras of observables. Accordingly, the results concerning the use of the quantum Fisher information in quantum metrology are generalized and physically reinterpreted. 相似文献
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We study the steady state of a three-level system in contact with a non-equilibrium environment, which is composed of two independent heat baths at different temperatures. We derive a master equation to describe the non-equilibrium process of the system. For the three level systems with two dipole transitions, i.e., the Λ-type and V-type, we find that the interferences of two transitions in a non-equilibrium environment can give rise to non-vanishing steady quantum coherence, namely, there exist non-zero off-diagonal terms in the steady state density matrix (in the energy representation). Moreover, the non-vanishing off-diagonal terms increase with the temperature difference of the two heat baths. Such interferences of the transitions were usually omitted by secular approximation, for it was usually believed that they only take effect in short time behavior and do not affect the steady state. Here we show that, in non-equilibrium systems, such omission would lead to the neglect of the steady quantum coherence. 相似文献
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We propose a scheme for long-distance quantum communication where the elementary entanglement is generated through two-photon interference and quantum swapping is performed through one-photon interference. Local “polarization” maximally entangled states of atomic ensembles are generated by absorbing a single photon from on-demand single-photon sources. This scheme is robust against phase fluctuations in the quantum channels, moreover speeds up long-distance high-fidelity entanglement generation rate. 相似文献
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研究了一维晶格中费曼棘齿-棘爪热机模型. 用粒子的概率主方程来描述粒子在晶格中的动力学特性, 推导出热流、 功率和效率的表达式. 通过数值计算分析势垒高度、 外力和温比对热流以及热机功率和效率的影响. 研究表明: 在粒子稳态概率流为零时, 存在非零的热流从高温库流入低温库, 类似于经典不可逆卡诺模型中的热漏; 热漏的存在使得热机的效率远远小于卡诺效率, 功率与效率之间为闭合的关系曲线, 热机为不可逆热机; 对热机性能参数进行优化, 可以使热机工作在最优性能状态下. 相似文献
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We propose a new model of the three-terminal quantum dot hybrid thermoelectric heat engine in which the electrons transfer between two electronic terminals at different temperatures and chemical potentials through two coupled single-level quantum dots. Based on master equation we derive the expressions for the output power and the efficiency. The working region of the hybrid heat engine is determined according to the first and second law of thermodynamics. The performance characteristic curves are plotted and the optimal performance parameters are obtained. Finally, the influence of the non-radiative effect on the optimal performance parameters is discussed in detail. 相似文献
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Two nonequilibrium methods for simulating homogeneous periodic heat flow are applied to 108 three-dimensional soft spheres in both the fluid and face-centered cubic solid phases. Both nonequilibrium methods use irreversible thermodynamics to express heat conductivity in terms of the work required to generate heat flow. The Evans-Gillan method, derived from Green-Kubo theory, correctly reproduces Ashurst's heat conductivities. An approach based on Gauss' principle of least constraint, in which the heat flow is constrained to a fixed value, fails this test. Heat flow is an inhomogeneous, nonlinear function of particle velocities and coordinates. Thus, Gauss' principle cannot be relied upon for treating inhomogeneous nonlinear nonholonomic constraints.Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract #W-7405-Eng-48. Work performed at U.C. Davis-Livermore with the support of the Army Research Office and the Air Force Office of Scientific Research. 相似文献
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Based on a two-qubit isotropic Heisenberg XY model under a constant external magnetic field,we construct a four-level entangled quantum heat engine(QHE).The expressions for the heat transferred,the work,and the efficiency are derived.Moreover,the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically.Several interesting features of the variations of the heat transferred,the work,and the efficiency with the concurrences of the thermal entanglement of two different thermal equilibrium states in zero and nonzero magnetic fields are obtained. 相似文献
15.
M Ponmurugan 《理论物理通讯》2020,72(2):25601-95
We study the efficiency at the maximum power of non-adiabatic dissipative(internally dissipative friction in finite time adiabatic processes) Carnot-like heat engines operating in finite time under the power law dissipation regime. We find that the non-adiabatic dissipation does not influence the universal minimum and maximum bounds on the efficiency at the maximum power obtained in the generalized dissipative Carnot-like heat engines which does not take in to account the non-adiabatic dissipation. 相似文献
16.
Entanglement diversion and quantum teleportation of entangled coherent states 总被引:2,自引:0,他引:2 下载免费PDF全文
The proposals on entanglement diversion and quantum teleportation of
entangled coherent states are presented.In these proposals, the entanglement between two coherent states, $|\alpha\rangle$ and $|-\alpha\rangle$, with the same amplitude but a phase difference
of $\pi$ is utilized as a quantum channel. The processes of the entanglement diversion and the teleportation are achieved by using the 50/50 symmetric beam splitters, the phase shifters and the photodetectors with the help of classical information. 相似文献
17.
The efficiency at the maximum power (EMP) for finite-time Carnot engines established with the low-dissipation model, relies significantly on the assumption of the inverse proportion scaling of the irreversible entropy generation ΔS(ir) on the operation time τ, i.e. ΔS(ir) ∝ 1/τ. The optimal operation time of the finite-time isothermal process for EMP has to be within the valid regime of the inverse proportion scaling. Yet, such consistency was not tested due to the unknown coefficient of the 1/τ-scaling. In this paper, we reveal that the optimization of the finite-time two-level atomic Carnot engines with the low-dissipation model is consistent only in the regime of ηC < 2(1 − δ)/(1 + δ), where ηC is the Carnot efficiency, and δ is the compression ratio in energy level difference of the heat engine cycle. In the large-ηC regime, the operation time for EMP obtained with the low-dissipation model is not within the valid regime of the 1/τ-scaling, and the exact EMP of the engine is found to surpass the well-known bound η+ = ηC/(2 − ηC). 相似文献
18.
H. Zhao L. Yi F. Liu B. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):185-188
We study heat conduction in a one-dimensional disordered
anharmonic chain with arbitrary heat bath by using extended Ford,
Kac and Mazur (FKM) formulation, which satisfy the
fluctuation-dissipation theorem. A simple formal expression for
the heat conductivity κ is obtained, from which the
asymptotic system-size (N) dependence is extracted. It shows
κ∼Nα. As a special case we give the expression
that κ∼N1/2 for free boundaries, and κ∼
N-1/2 for fixed boundaries, from which we can get the
conclusion that the momentum conservation is a key factor of the
anomalous heat conduction. Comparing with different ∇T,
the heat conductivity shows large difference between the linear
system and the nonlinear system. 相似文献
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A novel quantum key distribution scheme based on the path-spin hybrid entanglement is proposed and analyzed. In this proposed scheme, the entanglement between the path and the spin degrees of freedom is confined locally with the single particle and transmitted in one-way direction. Two split pulses of a single spin-1/2 particle are not simultaneously transmitted through the public quantum channels for the security goal. The scheme is robust against any individual attack even in noisy environments. Moreover, it also has high-efficiency since one single particle can be used to generate one bit key on average. 相似文献