共查询到19条相似文献,搜索用时 109 毫秒
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S. V. Bobashev B. G. Zhukov R. A. Kurakin S. A. Ponyaev B. I. Reznikov S. I. Rozov 《Technical Physics》2010,55(12):1754-1759
The working current dependences of the thermodynamic and electrophysical parameters of a free plasma piston moving with a
near-maximal velocity in the channel of an electromagnetic rail launcher with graphite electrodes are obtained. The composition
and weight of the plasma depend on the degree of electrode erosion due to discharge current passage (i = 40–80 kA). It is shown that the mean temperature of the plasma piston only slightly depends on the plasma mean pressure
and plasma piston weight and increases with current by a near-power law. The measured values of the maximal velocity of the
plasma piston front are compared with the calculated value of the sound velocity inside the piston. With the working current
and cross-sectional area of the channel fixed, the initial gas density in the channel is found to influence the ratio of the
piston maximal velocity to the sound velocity in the plasma. If the initial gas density is low (lower than some critical value),
the maximal velocity of the plasma piston front exceeds the sound velocity in the plasma. 相似文献
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This paper reports the design of a semi-active particle-based damping system in which a dry magnetic particle bed is used to dissipate the energy of a vibrating piston. The system is magnetized by a magnetic field generated by an electromagnetic coil. Hysteresis-free, ferromagnetic materials are selected for both the piston and particles. The damping efficiency increases as the magnetization of the piston and particles increases up to saturation. Semi-active control is achieved by varying the electric current supplied to the coil, which changes the magnetization and allows for real-time tunability of the damping rate. During the process of magnetization and demagnetization, the damping is reversible and temperature-independent over a wide temperature range. This system can be useful in aerospace, automobile and structural engineering applications, particularly in harsh environments. 相似文献
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A theoretical model that describes the transformation of electromagnetic radiation by microcavities in the form of microspheres
with a semiconductor nanostructure shell is developed. It is established that the regime of bistable two-mode laser oscillation
due to morphology-dependent resonances with different quality factors and spatial distributions of the electromagnetic field
can be implemented in a two-layer microcavity with a semiconductor-nanostructure shell. The region of two-mode oscillation
and the relation between the intensities of oscillating modes depend on the indices of refraction and the sizes of the microparticle
core and shell. 相似文献
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We consider the Casimir force acting on a d-dimensional rectangular piston due to a massless scalar field with periodic, Dirichlet and Neumann boundary conditions and
an electromagnetic field with perfect electric-conductor and perfect magnetic-conductor boundary conditions. The Casimir energy
in a rectangular cavity is derived using the cut-off method. It is shown that the divergent part of the Casimir energy does
not contribute to the Casimir force acting on the piston, thus renders an unambiguously defined Casimir force acting on the
piston. At any temperature, it is found that the Casimir force acting on the piston increases from −∞ to 0 when the separation
a between the piston and the opposite wall increases from 0 to ∞. This implies that the Casimir force is always an attractive
force pulling the piston towards the closer wall, and the magnitude of the force gets larger as the separation a gets smaller. Explicit exact expressions for the Casimir force for small and large plate separations and for low and high
temperatures are computed. The limits of the Casimir force acting on the piston when some pairs of transversal plates are
large are also derived. An interesting result regarding the influence of temperature is that in contrast to the conventional
result that the leading term of the Casimir force acting on a wall of a rectangular cavity at high temperature is the Stefan–Boltzmann
(or black-body radiation) term which is of order T
d+1, it is found that the contributions of this term from the two regions separating the piston cancel with each other in the
case of piston. The high-temperature leading-order term of the Casimir force acting on the piston is of order T, which shows that the Casimir force has a nontrivial classical ℏ→0 limit. Explicit formulas for the classical limit are computed. 相似文献
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Jorge Berger 《International Journal of Theoretical Physics》1990,29(9):985-995
We show that piston fluctuations are of crucial importance in the analysis of a Szilard engine. Some engines which do not require information in order to perform a Szilard cycle actually do not work. We pinpoint the mechanism and stages which require work investment when a measuring instrument is reset. 相似文献
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Using covariant quantization of the electromagnetic field, the Casimir force per unit area experienced by a long conducting cylindrical shell, under both Dirichlet and Neumann boundary conditions, is calculated. The renormalization procedure is based on the plasma cut-off frequency for real conductors. The real case of a gold (silver) cylindrical shell is considered and the corresponding electromagnetic Casimir pressure is computed. It is discussed that the Dirichlet and Neumann problems should be considered separately without adding their corresponding results. 相似文献
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The microwave-absorbing performances of carbonyl iron powder / silver core–shell composite particles are studied on the basis of the electromagnetic scattering theory and the energy conservation law. In addition, a calculation method for reflection loss of the carbonyl iron powder / silver core–shell composite particles with microwave is proposed. The calculated reflection loss of the carbonyl iron powder / silver core–shell composite particles is compared with the experimental results. The findings show that the trend of reflection loss of the carbonyl iron powder / silver composite particles can be predicted which can subsequently provide a relevant reference for future experiment and calculation of the absorbing mechanism of electromagnetic wave-microscopic carbonyl iron powder / silver core–shell composite particles. 相似文献
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金属包裹纳米微粒的光学特性研究(英文) 总被引:2,自引:0,他引:2
金属包裹纳米粒子是一种纳米量级的介质球核外包裹薄金属层的纳米粒子.在本文中,Au包裹Au2S纳米粒子被抽象成微型电磁谐振腔,其谐振波长决定于Au2S介质球核的半径.运用经典电磁理论可以得到谐振波长和谐振能量.由于Au包层很薄(2nm),这种微型谐振腔的耦合方式是有别于传统方式的透射耦合,因此Au包层的厚度决定了谐振的能量以及谐振腔品质因子Q.此外,本文还讨论了吸收峰的线宽. 相似文献