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61.
This paper deals with a variational formulation for the sensitivity problem of beam systems in the context of deformable solids with cracks. Natural frequencies are defined as state variables involved in the energy functional of the system, while the cracks length and position are treated as system parameters. The hierarchical equation system is formed and solved for the first and second derivatives of the natural frequency functions with respect to the cracks length and position. An analytical procedure for calculations of the second-order sensitivities of natural frequencies is proposed for the non-symmetrical equation system operator. Numerical algorithms are worked out and implemented computationally. Analytical and numerical aspects of the problem are discussed in detail through a number of illustrative results.The support of this work by the State Committee for Scientific Research (KBN) under Grant No. 4-050-0148/17-98-00 is gratefully acknowledged. 相似文献
62.
Yu-Qing Fang 《European Polymer Journal》2010,46(5):1163-1167
A series of polyimides (PIs) were copolymerized from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA), 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA) and 4,4′-oxydi(phthalic anhydride) (ODPA) via one-step method. The PIs possessed excellent solubility in polar aprotic solvents and easily formed thin flexible films by solution casting. The glass-transition temperatures (Tgs) of the PIs were in the range of 219-242 °C and thermal decomposition temperatures in nitrogen occurred above 350 °C. The resultant PI films exhibited high transparency at wavelengths greater than 400 nm and induced excellent uniform vertical alignment of liquid crystal (LC). Even after the rubbing process, the pretilt angles of LC were still above 89°. The PI seems to be a prospective material for alignment layers in flexible displays. 相似文献
63.
64.
S. Shahab Naghavi Thomas Gruhn Gerhard H. Fecher Katerina Medjanik Sergej A. Nepijko Ralph Rieger Klaus Müllen 《Journal of Molecular Spectroscopy》2011,265(2):95-1319
Functionalized polycyclic aromatic hydrocarbons (PAHs) are an interesting class of molecules in which the electronic state of the graphene-like hydrocarbon part is tuned by the functional group. Searching for new types of donor and acceptor molecules, a set of new PAHs has recently been investigated experimentally using ultraviolet photoelectron spectroscopy (UPS). In this work, the electronic structure of the PAHs is studied theoretically with the help of B3LYP hybrid density functionals. Using the ΔSCF method, electron binding energies have been determined which affirm, specify and complement the UPS data. Symmetry properties of molecular orbitals are analyzed for a categorization and an estimate of the related signal strength. While σ-like orbitals are difficult to detect in UPS spectra of condensed film, calculation provides a detailed insight into the hidden parts of the electronic structure of donor and acceptor molecules. In addition, a diffuse basis set (6-311++G**) was used to calculate electron affinity and LUMO eigenvalues. The calculated electron affinity (EA) provides a classification of the donor/acceptor properties of the studied molecules. Coronene-hexaone shows a high EA, comparable to TCNQ, which is a well-known classical acceptor. Calculated HOMO-LUMO gaps using the related eigenvalues have a good agreement with the experimental lowest excitation energies. TD-DFT also accurately predicts the measured optical gap. 相似文献
65.
We investigate theoretically the dynamics of three low-order transverse modes in a small-area vertical cavity surface emitting laser. We demonstrate the spontaneous breaking of axial symmetry of the transverse field distribution in such a device. In particular, we show that if the linewidth enhancement factor is sufficiently large dynamical regimes with broken axial symmetry can exist up to very high diffusion coefficients ~ 10 μm2/ns. 相似文献
66.
介绍了卫星制导武器直接瞄准攻击方式在对地精确打击中占据的关键位置,阐述了卫星制导武器直接瞄准攻击方法的原理。由于卫星制导武器直接瞄准攻击对目标定位要求较高,采用常用定位手段已不能满足系统对目标定位的要求,分析了使用相对GPS制导成为卫星制导武器直接瞄准攻击的关键的原因。相对GPS制导误差主要包括采用载机和武器相对GPS定位误差以及传感器对目标的相对定位误差,分别对两者的定位精度进行了分析和推导。仿真结果表明:这两者的综合误差理论值小于7.5 m,满足卫星制导武器在直接瞄准攻击中对目标定位的需求。 相似文献
67.
68.
With the B3LYP calculation method of density functional theory(DFT)and the 6-31G* basis set,full optimization calculation was made for phenoxathiin10-oxide(PTO)and 135 polybromine phenoxathiin 10-oxides(PBPTOs)with the Gaussian 03 program and molar heat capacity in constant volume(CVθ)value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom(NPBS)was studied,and the results indicated good correlation(R2 = 1.000)between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure(Cp,m)of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature(T,T-1 and T-2)was obtained with the least-squares method,and the correlation coefficient of the correlation equation(R2)was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated. 相似文献
69.
A. Bergamin G. Cavagnero G. Mana G. Zosi 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(2):225-232
In order to reduce measurement uncertainty of the (220) lattice spacing of silicon to a few parts per 109, a combined X-ray and optical interferometer capable of millimeter scans is being tested. A new series of measurements confirmed
the value obtained with our previous set-up, and the bounds of measurement uncertainty were investigated. The article supplements
the analysis of the error budget and provides a safer footing for the monocrystalline silicon lattice parameter value.
Received 13 August 1998 相似文献
70.
Yan-zheng Bai Ze-bing Zhou Hai-bo Tu Shu-chao Wu Lin Cai Li Liu Jun Luo 《Frontiers of Physics in China》2009,4(2):205-208
Low noise position measurement is fundamental for space inertial sensors, and at present the capacitive position sensor is
widely employed for space inertial sensors. The design for the possible suppression of the front-end electric noises for a
capacitive sensor is presented. A prototype capacitive sensor with 2×10−6pF/Hz1/2 at frequency above 0.04 Hz is achieved and further improvements are discussed.
相似文献