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951.
The shock structure problem is one of the classical problems of fluid mechanics and at least for non-reacting dilute gases it has been considered essentially solved. Here we present a few recent findings, to show that this is not the case. There are still new physical effects to be discovered provided that the numerical technique is general enough to not rule them out a priori. While the results have been obtained for dense fluids, some of the effects might also be observable for shocks in dilute gases. 相似文献
952.
It is shown that time-dependent temperatures in a transient, conductive system can be approximately modeled by a fractional-order
differential equation, the order of which depends on the Biot number. This approximation is particularly suitable for complex
shapes for which a first-principles approach is too difficult or computationally time-consuming. Analytical solutions of these
equations can be written in terms of the Mittag-Leffler function. The approximation is especially useful if a suitable fractional-order
controller is to be designed for the system. 相似文献
953.
The supersymmetric WKB approximation of ring-shaped oscillator potential in r and θ dimensions with spherical polar coordinates 下载免费PDF全文
According to calculation of the energy spectrum of ring-shape oscillator potential by using the supersymmetric WKB approximation, it is shown that the energy spectrum of some noncentral separable potentials can be exactly obtained in r and θ dimensions by above method. 相似文献
954.
Nadjib Bouzar 《Annals of the Institute of Statistical Mathematics》2004,56(3):497-510
The purpose of this paper is to introduce and study the concepts of discrete semi-stability and geometric semi-stability for
distributions with support inZ
+. We offer several properties, including characterizations, of discrete semi-stable distributions. We establish that these
distributions posses the property of infinite divisibility and that their probability generating functions admit canonical
representations that are analogous to those of their continuous counterparts. Properties of discrete geometric semi-stable
distributions are deduced from the results obtained for discrete semi-stability. Several limit theorems are established and
some examples are constructed. 相似文献
955.
以一种新型的醌类光敏剂—菌生素 (HMB)为模型化合物 ,利用量子化学从头算HF/ 6 31G和含时密度泛函TD B3LYP/ 6 31G方法计算研究了卤代作用对醌类光敏剂分子性质和光敏活性的影响 .结果发现 ,卤代作用降低了HMB母体的HOMO和LUMO能级 (EHOMO和ELUMO)及其差值△E ,随卤族元素从上到下 ,EHOMO和ELUMO呈增大趋势 ,而△E呈减小趋势 ,使得分子激发光谱有不同程度的红移 ,在增加PQP三重态量子产率的同时降低了分子最低三重激发态的能量 ,两种作用相互抵消 ,使得卤代物的 1O2 量子产率与母体相似 ;增加了分子的绝热电子亲合势 ,使分子产生O2 -的能力下降 ;卤原子的引入 ,降低了HMB母体分子内氢键的强度 ,同时使顺式构型的分子内质子传递势垒增大 ,而使反式构型势垒减小 . 相似文献
956.
For the first time, the fractional order disturbance observer (FO-DOB) is proposed for vibration suppression applications such as hard disk drive servo control. It has been discovered in a recently published US patent application (US20010036026) that there is a tradeoff between phase margin loss and strength of the low frequency vibration suppression. Given the required cutoff frequency of the low pass filter, also known as the Q-filter, it turns out that the relative degree of the Q-filter is the major tuning knob for this tradeoff. The solution in US20010036026 was based on an integer order Q-filter with a variable relative degree. This actually motivated the use of a fractional order Q-filter. The fractional order disturbance observer is based on the fractional order Q-filter. The implementation issue is also discussed. The nice point of this paper is that the traditional DOB is extended to the fractional order DOB with the advantage that the FO-DOB design is now no longer conservative nor aggressive, i.e., given the cutoff frequency and the desired phase margin, we can uniquely determine the fractional order of the low pass filter. 相似文献
957.
This paper presents the applications of digital image correlation technique to the mesoscopic damage and fracture study of
some granular based composite materials including steelfiber reinforced concrete, sandstone and crystal-polymer composite.
The deformation fields of the composite materials resulted from stress localization were obtained by the correlation computation
of the surface images with loading steps and thus the related damage prediction and fracture parameters were evaluated. The
correlation searching could be performed either directly based on the gray levels of the digital images or from the wavelet
transform (WT) coefficients of the transform spectrum. The latter was developed by the authors and showed higher resolution
and sensitivity to the singularity detection. Because the displacement components came from the rough surfaces of the composite
materials without any coats of gratings or fringes of optical interferometry, both surface profiles and the deformation fields
of the composites were visualized which was helpful to compare each other to analyze the damage of those heterogeneous materials.
The project supported by the National Natural Science Foundation of China (10125211 and 10072002), the Scientific Committee
of Yunnan Province for the Program of Steel Fiber Reinforced Concrete, and the Institute of Chemical Materials, CAEP at Mianyang 相似文献
958.
Ryohei Hanayama Kenichi Hibino Shin’ichi Warisawa Mamoru Mitsuishi 《Optical Review》2004,11(5):337-343
Wavelength scanned interferometry allows the simultaneous measurement of top surface shape and optical thickness variation of a transparent object consisting of several parallel surfaces. Interference signals from these surfaces can be separated in frequency space, and their phases are detected by discrete Fourier analysis. However, these signal frequencies are shifted from the detection frequency by the refractive index dispersion of the object and a nonlinearity of the wavelength scanning. The Fourier analysis is sensitive to the detuning of the signal frequency and suffers from the multiple-beam interference noise. Conventional error-compensating algorithms cannot be applied to an object consisting of more than three reflecting surfaces. We derive a new 2N-1 sample error-compensating algorithm, which allows the phase detection of any order of harmonic frequency among the interference signals. The new algorithm suppresses the effect of signal frequency detuning as well as the multiple-beam interference noise and can be applied to the measurement of complex objects consisting of more than three reflecting surfaces. 相似文献
959.
The interaction of two parallel plane jets of different velocities is studied by flow visualization and PIV measurement to
examine the influence of velocity ratio on the development ofjets in the initial region. It is found that the parallel plane
jets develop toward the high velocity side and the jet width is reduced with a decrease in the jet velocity ratio. Corresponding
to the variation of mean velocity field to the velocity ratio, the magnitudes of turbulence intensities, Reynolds stress and
static pressure are weakened in the merging region of the jets and their peak locations of the properties are shifted to the
high velocity side. These results indicate that the interaction of two parallel jets is weakened with a decrease in the velocity
ratio of the jets. 相似文献
960.
Winoto S. H. 《显形杂志》2004,7(3):257-262
The 7th Asian Symposium on Visualization (7ASV) was successfully held in Singapore from 3rd to 7th November 2003. This event was originally scheduled from 26th to 30th May 2003, but had to be postponed because of the outbreak of SARS (Severe Acute Respiratory Syndrome) in some parts of the
world. A total number of 122 participants attended the Symposium of which, 107 were foreign participants from 16 countries
(excluding Singapore) worldwide. There were 104 papers covering broad range of topics presented at the Symposium which were
delivered in 2×7 long sessions, and 9 keynote papers. 相似文献