Results 1 - 10 of 78097
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[en] We investigate the Dirichlet-scalar equivalent of Casimir-Polder forces between an atom and a surface with arbitrary uniaxial corrugations. The complexity of the problem can be reduced to a one-dimensional Green's function equation along the corrugation which can be solved numerically. Our technique is fully nonperturbative in the height profile of the corrugation. We present explicit results for experimentally relevant sinusoidal and sawtooth corrugations. Parameterizing the deviations from the planar limit in terms of an anomalous dimension which measures the power-law deviation from the planar case, we observe up to order-one anomalous dimensions at small and intermediate scales and a universal regime at larger distances. This large-distance universality can be understood from the fact that the relevant fluctuations average over corrugation structures smaller than the atom-wall distance.
[en] Noise formula describing the 1/f noise in InSb films is pointed out. The noise-intensity coefficient K is introduced as a variable depending on film-preparation methods. Experimentally, K2 changes by two orders of magnitude. However, existing noise calculations show that K2 should remain constant except for a dimension factor. Therefore, the experimental results cannot be explained by the existing theory
[en] Classification criteria for stresses in locally thinned regions of tubes are examined with respect to the intent of Section III of the ASME Code for Class 1 components. Depending on the size of the thinned region, the membrane stresses caused by pressure loading may be classified as general primary, primary local or secondary. The criteria for classification of membrane stresses were investigated for some simple geometry and load cases, where plastic instability is the governing mode of failure due to primary loads. (author)
[en] The Friedmann–Robertson–Walker (FRW) universe and Bianchi I, II universes are investigated in the framework of the generalized uncertainty principle (GUP) with a linear and a quadratic term in Planck length and momentum, which predicts the minimum measurable length as well as maximum measurable momentum. We obtain a dynamic cosmological bounce for the FRW universe. With the Bianchi universe, we found that the universe may still be isotropic by implementing GUP. Moreover, the wall velocity appears to be stationary with respect to the universe velocity, which means that when the momentum of the universe evolves into a maximum measurable energy, the bounce is enhanced against the wall, which means that no maximum limit angle is manifested anymore. (paper)
[en] In this study, focusing of ultrasonic Lamb wave by negative refraction with mode conversion from antisymmetric to symmetric mode was investigated. When a wave propagates backward by negative refraction, the energy flux is antiparallel to the phase velocity. Backward propagation of Lamb wave is quite well known, but the behavior of backward Lamb wave at an interface has rarely been investigated. A pin-type transducer is used to detect Lamb wave propagating on a steel plate with a step change in thickness. Conversion from forward to backward propagating mode leads to negative refraction and thus wave focusing. By comparing the amplitudes of received Lamb waves at a specific frequency measured at different distance between transmitter and interface, the focusing of Lamb wave due to negative refraction was confirmed.
[en] The guided wave propagation in inhomogeneous multi-layered structures is experimentally explored based on theoretical dispersion curves. It turns out that proper selection of incident angle and frequency is critical for guided wave generation in multi-layered structures. Theoretical dispersion curves greatly depend on adhesive zone thickness, layer thickness and material properties. It was possible to determine the adhesive zone thickness of an inhomogeneous multi-layered structure by monitoring experimentally the change of dispersion curves.
[en] A number of optimal maintenance policies have been proposed and studied based on several types of warranty policies. As the criteria for optimality, the expected cost rate per unit time during the life cycle of the system is quite often used by many authors. However, the expected cost rate may depend on the length of life cycle and so the definition of life cycle plays a significant role in optimizing the maintenance policy. This paper considers a system maintenance policy during the post-warranty period under the renewing warranty policy and the life cycle is defined from the user's perspective. The life cycle starts with the installment of a new system and ends when the system is replaced by a new one at the expense of the user. In many renewing warranty models, the life cycle is defined as the lifelength of the new system installed initially, which is quite different from our definition. The expected cost rate per unit time is evaluated based on the life cycle newly defined and is compared with the existing results.
[en] The design and implementation of a multi-functional levels adaptation circuit for fast logic signals will be described briefly in this paper. This circuit is mainly adopted to accomplish levels adaptation between several fast logic signals. As the circuit is designed based on a multiple-using structure, it can supply 6 types conversion mode between the NIM, TTL, ECL logic level signals. The circuit can supplies 8 input channels for each level in single-width-standard NIM module. TTL and NIM outputs are a pairs of complementary output signals, and ECL input/output are differential signals. (authors)
[en] The transformation of paraxial and nonparaxial Bessel beams in a crystal of Iceland spar is considered theoretically. Calculation formulae for matching the thickness of the crystal and the parameters of the incident beam required for complete conversion of a circularly polarized zero-order Bessel beam into a second-order vortex beam are obtained. An optical system was designed for investigating the intensity distribution after passage through the crystal. Experimental and theoretical results are in good agreement. (paper)
[en] A theoretical model for geometrically nonlinear vibration analysis of piezoelectrically actuated circular plates made of functionally grade material (FGM) is presented based on Kirchhoff's-Love hypothesis with von-Karman type geometrical large nonlinear deformations. To determine the initial stress state and pre-vibration deformations of the smart plate a nonlinear static problem is solved followed by adding an incremental dynamic state to the pre-vibration state. The derived governing equations of the structure are solved by exact series expansion method combined with perturbation approach. The material properties of the FGM core plate are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. Control of the FGM plate's nonlinear deflections and natural frequencies using high control voltages is studied and their nonlinear effects are evaluated. Numerical results for FG plates with various mixture of ceramic and metal are presented in dimensionless forms. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage as well as gradient index of FGM plate on vibration characteristics of the smart structure