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911.
In this paper a theory of modal analysis for the dynamic response of fluid-structure systems is presented. A pair of generalized eigenvalue equations with three real symmetric matrices and their relationships are derived from the finite element equations in the form of structural displacements and fluid velocity potential. Generalized orthogonality relations of modal vectors are then developed. The response of the system to external excitation is derived in closed form by modal expansion. Two examples of the solution are given for illustration. 相似文献
912.
When a focused Gaussian ultrasonic beam in soft tissue normally impinges on the boundary of a contiguous bone, reflection and transmission occur. Taking account of the reflection, the steady-state temperature elevation along the beam axis for this case was calculated. The effect of perfusion is also included. 相似文献
913.
914.
Jiang Jianyi Sun Yupin Zeng Fanchun Yin Huaqing Du Jiaju 《Zeitschrift für Physik B Condensed Matter》1989,77(2):193-195
The single 110 K phase Bi(Pb)–Sr–Ca–Cu–O superconductor was made by sintering in air. Its zero-resistance temperature is 106 K, and it is an orthorhombic cell witha=5.403 Å,b=5.412 Å andc=37.062 Å. It formed around the low-T
c
phase. The forming period of the 110 K phase can be shortened by multiple sintering and grinding. If PbO is mixed into the samples after the 85 K phase has formed, the forming rate of the 110 K phase can be increased significantly. EDAX analysis of grain composition confirms that the Pb atoms enter the unit cell, and probably Pb cations replace some Ca cations. 相似文献
915.
916.
917.
电镜样品的激光镀膜技术 总被引:1,自引:0,他引:1
汪霖 《浙江大学学报(理学版)》1998,25(2):54-57
非导电的样品用扫描电镜进行观测时需要对样品进行镀膜处理以获得清晰的图像, 本文介绍应用脉冲激光沉积(PLD)技术对非导电样品的表面进行镀膜处理的方法和实验装置及实验结果. 相似文献
918.
A novel method, based on the coupling of ionic liquid-based headspace single-drop microextraction (SDME) with gas chromatography (GC), is developed for the determination of chlorobenzene derivatives. For the SDME of five chlorobenzene derivatives, a 1.0 μL 1-octyl-3-methylimidazolium hexafluorophosphate microdrop is exposed for 20 min to the headspace of a 15 ml aqueous sample containing 20% (w/v) NaCl placed in 25 ml vial at 40 °C. Then, the extractant is directly injected into the injector block of the GC instrument. To avoid ionic liquid leaking into the chromatographic column, a small glass tube is placed in the injection block. Under optimized operation conditions, linear relation between peak areas and analyte concentrations up to 1.5 mg L?1 has been obtained The detection limits range from 0.1 to 0.5 μg L?1 for the various analytes. The relative standard deviations at 1.0 μg L?1 range from 7.7 to 12.4%, and the enrichment factors from 41 to 127. The method is simple and sensitive, and does not suffer from the influence of a solvent peak. Its applicability is demonstrated by the determination of chlorobenzenes in wastewater samples. 相似文献
919.
关于控制算子的若干注记 总被引:1,自引:0,他引:1
Let B(H) be the set of all bounded linear operators on a Hilbert space H. An operator T∈B(H) is called dominant if (T-λ)(T-λ)*≤Mλ2(T-λ)*(T-λ),?λ∈C.The numerical range of T is difined by W (T) = {(Tx, x): ‖x‖ = 1, x∈H}. In Section 1 some new characteristic of dominant operators are given. If C = AB - BA, we prove that O∈W(C)- then A is a dominart or φ-quasihy ponor-mal. In Section 2 we prove that O∈σe(△Aσ) if A is a dominant, where(?), we also prove that if A∈B(H) is a norm attaining Ф-quasihyponormal, then A has a non-trivial invariant subspace. In Section 3 we discuss the closeness of the range of bounded linear operator FAB:X→AX-XB, and prove that R(δA)∩{A}′∩{An}′=0, where δA:X→AX-XA. 相似文献
920.
Predicting the shape of a critical nucleus in solids has been a long-standing problem in solid-state phase transformations. We show that a diffuse-interface approach together with a minimax algorithm is able to predict the critical nucleus morphology in elastically anisotropic solids without a priori assumptions. We demonstrate the possibility of nonconvex surfaces for critical nuclei. It is found that strong elastic energy contributions may lead to critical nuclei whose point group symmetry is below the crystalline symmetries of both the new and the parent phases. 相似文献