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排序方式: 共有1769条查询结果,搜索用时 15 毫秒
91.
92.
C.A. Dimopoulos 《Journal of Constructional Steel Research》2008,64(10):1077-1085
Design of either pin-ended or fixed circular steel arches with hollow circular cross-sections subjected to a uniformly distributed vertical load along the horizontal projection of the entire arch with the aid of the EC3 provisions is discussed. Appropriate modification factors are proposed that should be included in EC3 interaction equations, to improve their accuracy for the design of such arches. 相似文献
93.
高质量莫尔条纹信号的提取 总被引:9,自引:6,他引:3
本文分析了影响光栅信号质量的主要因素,指出了获得高质量光栅信号的途径,提出了一般设计方法及各参数的选择。文中给出的实验测试结果成功地用于JC-1型精密测角仪中。 相似文献
94.
本文用一种新的思路来分析H(01)或E(01)波激励下圆形介质棒天线的反射特性。与常规的从场源关系出发来分析天线问题不同,本文的方法从求解介质波导结构的色散特性入手,从散射的角度将天线辐射问题转化为表面波和空间波的传输问题,从而使分析过程得到了很大的简化。 相似文献
95.
We present several Hermite-type interpolation methods for rational cubics. In case the input data come from a circular arc, the rational cubic will reproduce it. 相似文献
96.
Robert A. Goldbeck Eefei Chen David S. Kliger 《International journal of molecular sciences》2009,10(4):1476-1499
Kinetic studies of the early events in cytochrome c folding are reviewed with a focus on the evidence for folding intermediates on the submillisecond timescale. Evidence from time-resolved absorption, circular dichroism, magnetic circular dichroism, fluorescence energy and electron transfer, small-angle X-ray scattering and amide hydrogen exchange studies on the t ≤ 1 ms timescale reveals a picture of cytochrome c folding that starts with the ~ 1-μs conformational diffusion dynamics of the unfolded chains. A fractional population of the unfolded chains collapses on the 1 – 100 μs timescale to a compact intermediate IC containing some native-like secondary structure. Although the existence and nature of IC as a discrete folding intermediate remains controversial, there is extensive high time-resolution kinetic evidence for the rapid formation of IC as a true intermediate, i.e., a metastable state separated from the unfolded state by a discrete free energy barrier. Final folding to the native state takes place on millisecond and longer timescales, depending on the presence of kinetic traps such as heme misligation and proline mis-isomerization. The high folding rates observed in equilibrium molten globule models suggest that IC may be a productive folding intermediate. Whether it is an obligatory step on the pathway to the high free energy barrier associated with millisecond timescale folding to the native state, however, remains to be determined. 相似文献
97.
Francesco Ciardelli Osvaldo Pieroni Adriano Fissi Carlo Carlini Angelina Altomare 《Polymer International》1989,21(2):97-106
Photoresponsive macromolecules are of interest both as novel organic materials for applications in photodevices and as models for photomodulated biological processes. The presence in polymer chains of photosensitive groups and of chiral groups capable of inducing optical activity into the polymer is very useful for the analysis of photomodulated structural variations and allows storage of the light effect in the form of chiral information. Polypeptides bearing photochromic groups in the side chains are very convenient as the chiroptical properties of the peptide chromophore can be correlated to the backbone conformation. Thus polymers of L-aspartic acid, L-glutamic acid and L-lysine with azobenzene or stilbene groups attached covalently to the side chains are discussed in terms of photoinduced conformational changes and chiroptical information storage in the spectral region of the peptide and of the photoresponsive chromophore. Optically active photochromic macromolecules with hydrocarbon backbone, such as copolymers of (—)-menthyl acrylate with vinyl or acryloyl derivatives of azobenzene, stilbene and indolinospirobenzopyran, also show in some cases photodependence of chiroptical properties with evidence of at least local conformational changes as a consequence of light irradiation which can be used for chiral information. 相似文献
98.
Since the cylindrical and circular crested weirs are economical and easily made compared to some other weirs, they can be used to measure the flow velocity, the water discharge and flow surface control structures in the canals and reservoirs. In this paper, the hydraulic properties of the cylindrical and circular crested weirs, such as the discharge coefficient, the depth on the crest of the weir and the energy loss in 18 laboratory models categorized in 5 categories have been investigated. The results of the experiments indicated that in both the cylindrical and circular crested weirs by increasing the total partial head, the discharge coefficient increases and any changes in the upstream wall slope has no effect on the discharge coefficient. Also, the partial energy loss more occurs in the cylindrical weirs than the half shaped cylindrical weirs and by increasing the downstream inclination angle, the partial energy loss increases subsequently. The partial flow depth on the crest of both the cylindrical and half shaped cylindrical weirs is equal to 0.7 and by increasing of the upstream inclination angle, the partial flow depth on the crest in the values greater than 0.6, increases slightly and the downstream inclination angle changes of the partial flow depth has no effect on the crest. 相似文献
99.
Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical (H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit (ADE) scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in non-uniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourth-order finite difference (FD) approximation to the spatial derivatives of the axisymmetric fluid–diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps, giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua (FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%–50% that of FLAC's basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%–1.8%. 相似文献
100.
《Soils and Foundations》2022,62(3):101150
The circular helicoid pile (CH pile) is a new type of special-shaped pile that has been developed in Japan and South Korea in the past decade and has been widely used in the fields of construction, transportation, natural energy and agriculture due to its excellent compressive and pullout bearing performances. Consequently, this new type of pile has good engineering application prospects. However, as an innovative engineering structure, the CH pile is not widely known by geotechnical engineers worldwide. The geometric structure of the CH pile is similar to a circular helicoid in differential geometry. Therefore, the pile-soil interaction problem cannot be reduced to a plane strain problem or an axisymmetric problem in theoretical research. In view of this, dry silica sand was used as the model foundation in this study, and a model test device and method that can effectively reflect the installation process and loading-bearing service state of CH piles were developed. Under different installation methods, pile structures and foundation soil conditions, 90 model tests were carried out to evaluate the engineering performances of CH piles during the whole process of installation and bearing, including the installation performances during the installation process, the compressive bearing performances under axial compressive loading and the pullout bearing performances under axial pullout loading. Compared with steel sheet piles and steel pipe piles, CH piles have better engineering performance and more economic benefits from the aspects of installation, construction, recycling, timeliness of engineering application, and the relative relationship between bearing capacity and pile mass. 相似文献