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991.
Alexandr Gre
enko 《Journal of Terramechanics》2007,44(1):123-131
Dr. Bekker’s first book Theory of land locomotion offers in fact two different concepts of thrust generation on soft ground with respect to the slip: (a) as the push of grousers causing horizontal soil “distortion” and (b) as the shear force in the failure plane linked with the shear deformation. Bekker preferred the second concept and backed it up by the unique shear-ring measuring technique. To clear up the matter, the author decided to re-examine the thrust generation by a track plate experimentally in field conditions. The tests have shown that the initial stage of thrust generation in compressible ground is always horizontal soil compression by grousers, which divides the soil under a track into separate blocks initially at rest. This compression increases at least to the transition point, when a block is sheared off simultaneously at the bottom and in both lateral planes and starts sliding along the channel formed by the preceding grouser. The analysis of these measurements enabled to define the compressive displacement of the face of the soil block (travel of the grouser) appurtenant to the mentioned transition point, useful to define the thrust–slip curve. The case may also be described by the conventional shear stress–shear displacement relationship, imagined to take place in the bottom failure plane, however, namely the “shear displacement” is rather an unusual quantity. 相似文献
992.
An efficient and extensible format,library, and API for binary trajectory data from molecular simulations
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Magnus Lundborg Rossen Apostolov Daniel Spångberg Anders Gärdenäs David van der Spoel Erik Lindahl 《Journal of computational chemistry》2014,35(3):260-269
Molecular dynamics simulations is an important application in theoretical chemistry, and with the large high‐performance computing resources available today the programs also generate huge amounts of output data. In particular in life sciences, with complex biomolecules such as proteins, simulation projects regularly deal with several terabytes of data. Apart from the need for more cost‐efficient storage, it is increasingly important to be able to archive data, secure the integrity against disk or file transfer errors, to provide rapid access, and facilitate exchange of data through open interfaces. There is already a whole range of different formats used, but few if any of them (including our previous ones) fulfill all these goals. To address these shortcomings, we present “Trajectory Next Generation” (TNG)—a flexible but highly optimized and efficient file format designed with interoperability in mind. TNG both provides state‐of‐the‐art multiframe compression as well as a container framework that will make it possible to extend it with new compression algorithms without modifications in programs using it. TNG will be the new file format in the next major release of the GROMACS package, but it has been implemented as a separate library and API with liberal licensing to enable wide adoption both in academic and commercial codes. © 2013 Wiley Periodicals, Inc. 相似文献
993.
The influence of the effect of molecular librations on the interaction of high-power ultrashort counterpulses in Kerr liquids
with anisotropic molecules is investigated. Molecular librations are shown to substantially affect the shape of the output
pulses. A narrow peak with an intensity fourfold to fivefold higher than the input-pulse intensity develops on the leading
edge. This peak is followed by a series of narrow damped spikes, the duration of which correlates with the libration time.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 398–401, May–June, 2000. 相似文献
994.
F. Grosshans P. Grangier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):119-125
Homodyne detection can be used to perform measurements on various quantum states of the light, such as conditional single
photon states produced by parametric fluorescence processes. In the pulsed regime, the time and frequency overlap between
the single photon wave packet and the local oscillator field plays a crucial role. We show in this paper that this overlap
can be characterized by an effective quantum efficiency, which is explicitly calculated in various situations of experimental
interest.
Received 27 July 2000 and Received in final form 29 November 2000 相似文献
995.
A concept of diagnostic accuracy progression for embedded coding of medical images was presented. Implementation of JPEG2000
encoder with a modified PCRD optimization algorithm was realized and initially verified as a tool for accurate medical image
streaming. Mean square error as a distortion measure was replaced by other numerical measures to revise quality progression
according to diagnostic importance of successively encoded image information. A faster increment of image diagnostic importance
during reconstruction of initial packets of code stream was reached. Modified Jasper code was initially tested on a set of
mammograms containing clusters of microcalcifications and malignant masses, and other radiograms. Teleradiologic applications
were considered as the first area of interests. 相似文献
996.
John D. Hobby 《Computational Geometry》1999,13(4):197-214
The fundamental problem of finding all intersections among a set of line segments in the plane has numerous important applications. Reliable implementations need to cope with degenerate input and limited precision. Representing intersection points with fixed precision can introduce extraneous intersections. This paper presents simple solutions to these problems and shows that they impose only a very modest performance penalty. Test data came from a data compression problem involving a map database. 相似文献
997.
S. Yu. Gus’kov N. V. Zmitrenko Yu. E. Markushkin Yu. A. Merkul’ev 《Journal of Russian Laser Research》2007,28(2):148-162
The energetic characteristics of the compression and burning of targets with beryllium and beryllium deuteride shells are
compared. The characteristics considered include the hydrodynamic efficiency, the efficiency of energy transmission to the
thermonuclear fuel, and the gain factor found from numerical simulation using the ‘Diana’ one-dimensional mathematical code.
The calculations are carried out for direct-drive cryogenic laser targets with the ablator shells made of beryllium or beryllium
deuteride with parameters corresponding to the third harmonic of energy of the neodymium-laser radiation with a pulse energy
of 1–3 MJ. It is proved that the gain of beryllium hydride targets can be brought to the level of beryllium targets due to
variations in the geometrical parameters of BeD2 targets. It is shown that the fission of BeD2 or BeDT ablators in reactor-scale targets could significantly contribute to the final thermonuclear yield.
__________
Translated from Preprint No. 20 of the P. N. Lebedev Physical Institute, Moscow (2001). 相似文献
998.
从描述皮秒光脉冲在色散缓变光纤(FSDD)中所满足的非线性Schro¨dinger方程(NLS)出发,数值模拟了高阶皮秒脉冲在增益系数取值不同的色散缓变光纤中的孤子效应压缩,研究分析了增益系数所产生的影响。计算结果表明,对于孤子阶数确定的光脉冲,增益系数有一最佳取值范围,对应于孤子效应压缩的参量———脉冲压缩比有最佳值。讨论了初始啁啾的影响。 相似文献
999.
1000.
Antoine Saucier 《Applied and Computational Harmonic Analysis》2005,18(3):300-328
We show that orthonormal bases of functions with multiscale compact supports can be obtained from a generalization of principal component analysis. These functions, called multiscale principal components (MPCs), are eigenvectors of the correlation operator expressed in different vector subspaces. MPCs are data-adaptive functions that minimize their correlation with the reference signal. Using MPCs, we construct orthogonal bases which are similar to dyadic wavelet bases. We observe that MPCs are natural wavelets, i.e. their average is zero or nearly zero if the signal has a dominantly low-pass spectrum. We show that MPCs perform well in simple data compression experiments, in the presence or absence of singularities. We also introduce concentric MPCs, which are orthogonal basis functions having multiscale concentric supports. Use as kernels in convolution products with a signal, these functions allow to define a wavelet transform that has a striking capacity to emphasize atypical patterns. 相似文献