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981.
A new version of the fast optically pumped magnetometer, an optically pumped balanced quantum magnetometer, built around a pair of symmetric transitions in the hyperfine structure of the 87Rb ground state is implemented for the first time. The noise-limited sensitivity of the prototype in terms of the variance is 6 pT for a measurement time of 0.1 s. The basic advantages of the new magnetometer are the absence of dead zones when it changes orientation relative to the magnetic field and an extremely low sensitivity to the drift of pumping parameters. 相似文献
982.
The propulsion methods of the aquatic lives are the results of optimization by evolution and are useful for the design of
swimming-robot, etc. Among them, loach has unique propulsion technique both bending its long body and shaking caudal fin.
Our purpose of the research is to clarify its swimming mechanism through flow field analysis. Two dimensional motion and flow
around it have been experimentally visualized by particle image velocimetry (PIV). Vortices around a loach and the interactions
between the loach body and surrounding water are analyzed. Generating and growing vortices by bending its body, it pushes
water backward to gain repulsing force, and it seems that moves through vortices reducing the resistance force at the same
time. When a vortex reaches to the caudal fin, it accelerates both sides of the vortex pushing water backward and seems gaining
propulsion utilizing the caudal fin. After moving forward, loach leaves a vortex street like reverse Karman vortices, which
means that loach gains propulsion. 相似文献
983.
We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures. 相似文献
984.
N.D. Tho N. Chau S.C. Yu H.B. Lee N.D. The L.A. Tuan 《Journal of magnetism and magnetic materials》2006
Effect of annealing on the soft magnetic properties of Fe73.5Si13.5B9Nb3Au1 amorphous ribbon has been investigated by means of structure examination, magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) spectra measured in the frequency range of 1–10 MHz at a fixed current of 10 mA X-ray diffraction analysis showed that the as-cast sample was amorphous and it became nanocrystalline under a proper heat treatment. When annealing amorphous alloy at 530 °C for 30, 60, 90 min, soft magnetic properties have been improved drastically. Among the samples investigated, the sample annealed at 530 °C for 90 min showed the softest magnetic behavior. The MIR and PR curves revealed the desirable changes in anisotropy field depending upon annealing. 相似文献
985.
J.J. Kolodziej B. Such M. Goryl F. Krok P. Piatkowski M. Szymonski 《Applied Surface Science》2006,252(21):7614-7623
Surfaces of several AIIIBV compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination. 相似文献
986.
We present theoretical results of the electron impact ionization rate in GaAs/AlGaAs multiquantum well structures as a function of applied electric field for various geometries, i.e., well and barrier widths. In addition, we present preliminary measurements of the current-voltage characteristics of MBE grown devices which demonstrate very low leakage current as well as sharp breakdwon behavior. It is found that the net ionization rate, determined by averaging over the constitutent GaAs and AlGaAs layers, approaches the weighted average of the constituent bulk rates at high electric field strengths; the potential discontinuity is relatively unimportant. The electron ionization rate within the well regions alone is still higher than that in bulk GaAs, but is insufficiently enhanced to compensate for the much lower rate in the AlGaAs layers. As the field is lowered to 250.0 kV/cm, the average ionization rate in the multiquantum well structure becomes larger than in the bulk. 相似文献
987.
Jian Ming ZHAN Bijan DAVVAZ K. P. SHUM 《数学学报(英文版)》2007,23(8):1345-1356
We describe the relationship between the fuzzy sets and the algebraic hyperstructures. In fact, this paper is a continuation of the ideas presented by Davvaz in (Fuzzy Sets Syst., 117: 477- 484, 2001) and Bhakat and Das in (Fuzzy Sets Syst., 80: 359-368, 1996). The concept of the quasicoincidence of a fuzzy interval value with an interval-valued fuzzy set is introduced and this is a natural generalization of the quasi-coincidence of a fuzzy point in fuzzy sets. By using this new idea, the concept of interval-valued (α,β)-fuzzy sub-hypermodules of a hypermodule is defined. This newly defined interval-valued (α,β)-fuzzy sub-hypermodule is a We shall study such fuzzy sub-hypermodules and sub-hypermodules of a hypermodule. generalization of the usual fuzzy sub-hypermodule. consider the implication-based interval-valued fuzzy 相似文献
988.
An upper bound is obtained for the positive eigenvalues of the p-Laplacian with decaying potential on [0,∞). The bound is expressed in terms of the potential and is shown to be the best possible of its kind. 相似文献
989.
We investigate separability questions for the mapping class group of a surface. While this group is not subgroup separable in general, we prove a large family of interesting subgroups are separable. This includes many classically studied subgroups such as solvable subgroups, Heegaard and Handlebody groups, geometric subgroups, and all the terms in the Johnson filtration. 相似文献
990.
Covering numbers of precompact symmetric convex subsets of Hilbert spaces are investigated. Lower bounds are derived for sets containing orthogonal subsets with norms of their elements converging to zero sufficiently slowly. When these sets are convex hulls of sets with power-type covering numbers, the bounds are tight. The arguments exploit properties of generalized Hadamard matrices. The results are illustrated by examples from machine learning, neurocomputing, and nonlinear approximation. 相似文献