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101.
The present study aims to derive an analytical model on bed-load layer thickness in an open channel turbulent flow carrying sediments. Determination of the thickness of the bed-load layer is of utmost importance in the study of bed-load transport as it is required to determine the bed-load transport rate, as well as in the study of suspended load transport as it acts as reference level for the particles in suspension. Apart from the several deterministic approaches available in the literature, the work adopts probabilistic approach based on entropy theory to determine the bed-load layer thickness. The concept of entropy theory developed by Shannon is used and the method of Lagrange multipliers is employed for the maximization of entropy function to find the least biased probability distribution. To calculate the Lagrange multipliers, present in the probabilistic model of dimensionless bed-load layer thickness, two different methodologies are presented. The model of bed-load layer thickness is a function of dimensionless shear stress and also depends on three other parameters which are found to be functions of specific gravity of sediment particle and dimensionless particle diameter from a non-linear regression analysis. The proposed model is validated with wide sets of experimental data available in literature and a good agreement is achieved. Apart from comparison with data, the model is also compared with existing deterministic model and computation of relative percentage error proves the better efficiency of the present model. 相似文献
102.
N. A. Skakun V. M. Shershnev M. V. Vaschenko 《The European Physical Journal A - Hadrons and Nuclei》2006,29(3):383-388
To investigate orientation effects, an approach based on the measurements of γ-ray yields following the excitation of “narrow"
isolated resonances in the reactions occurring on the nuclei of interstitial impurity atoms, that occupy certain positions
in a crystal, has been proposed. The carbon atoms were shown to be located in octahedral interstitial sites of the Re-0.4
at. % 13C monocrystalline solution. The proton flux distribution in the (0001) channel was investigated via the 1.7476 MeV resonance
of the 13C(p,γ)14N reaction. Some particular qualities of the reaction yield were found to be dependent upon the proton energy. The method
of measurement of the electronic stopping power of channeled particles has been deduced. The γ-ray yield of the resonance
reactions induced by the channeled protons was shown to be dependent on the amplitude of the thermal vibrations of carbon
atoms. 相似文献
103.
The cross sections of the fragments produced in the projectile fragmentation reactions of the even calcium isotopes from A=36 to A=52 are calculated using the statistical abrasion ablation model.The neutron skin thickness are studied by investigating the fragments isotopic cross section distributions.The neutron-skin thicknesses of the calcium isotopes have a good linear correlation to the peak positions of their fragment isotopic cross section distributions.The correlation between the neutron skin thickness and the neutron density distributions of 48 Ca is investigated by introducing a parameter to adjust the diffuseness parameter in the fermi-type density distribution. 相似文献
104.
105.
The relationships between the morphological characteristics and the vulnerability of atherosclerotic plaque were analyzed
theoretically and several suggestions were proposed to evaluate the plaque vulnerability. Validated by animal experiments
and clinical studies, the theoretical results were confirmed.
Supported by the National Natural Science Foundation of China (Grant Nos. 10302016 and 60402023), the National Basic Research
Program of China (973 Program)(Grant No. 2006CB503803), and the National Hi-Tech Research and Development Program of China
(863 Program) (Grant No. 2007AA02Z448) 相似文献
106.
Method of measuring one-dimensional photonic crystal period-structure-film thickness based on Bloch surface wave enhanced Goos-Hänchen shift 下载免费PDF全文
Yao-Pu Lang 《中国物理 B》2023,32(1):17802-017802
This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave (BSW) enhanced Goos-Hänchen (GH) shift in one-dimensional photonic crystal (1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization (PSO) algorithm. The relationship between the structure of a 1DPC film composed of TiO2 and SiO2 layers and the GH shift, is investigated. Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1×103 times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift. 相似文献
107.
Rui Hong Yi-Xin Jiang Jie Leng Ming-Jin Liu Kai-Zhi Shen Qiang Fu Jie Zhang 《高分子科学》2021,39(6):756-769
General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications. To achieve the reinforcement and broaden the application scope of high-density polyethylene(HDPE), multi-flow vibration injection molding(MFVIM) and ultrahigh molecular weight polyethylene(UHMWPE) are synergistically employed in this work. Herein, the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported.The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated.When 5 wt% UHMWPE is added, MFVIM process with six flow times thickens the shear layer to the whole thickness. The tensile strength and modulus increase to 2.14 and 1.39 times, respectively, compared to neat HDPE on the premise of remaining 70% impact strength. Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness, as well as related to the corresponding size distributions of undissolved UHMWPE particles. This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials. Besides, excessive UHMWPE may impair the synergistic enhancement effect, which is also reasonably explained. 相似文献
108.
宽板塑性弯曲成形过程中的板厚变化规律 总被引:7,自引:0,他引:7
根据宽板弯曲过程中的变形与应力分布特征,提出了一种计算弯曲过程中板料厚度随弯曲程度变化的新的近似解答方法.该方法基于塑性增量理论,应用塑性成形过程的体积不变假设和弯曲过程的平面假设.作为算例,得到了理想刚塑性材料的板料厚度、变薄系数以及应变中性层内移系数随板料弯曲内表面曲率半径变化的规律,并与实验数据进行了比较,两吻合良好. 相似文献
109.
纳米二氧化硅水溶胶成膜特性研究 总被引:1,自引:0,他引:1
研究了纳米SiO2水溶胶的固液二相流成膜特性.结果表明,水溶胶中的Si02固体颗粒的粒径及质量分数对粘度的影响较小,对成膜能力和承载能力的影响较大;在薄膜润滑阶段,固体颗粒的粒径和质量分数对润滑状态的稳定性具有一定的影响,随着速度的增加,液体膜厚度逐渐增大,固体颗粒对液体润滑膜稳定性及性能的影响逐渐减弱;在弹流润滑阶段,固体颗粒的影响很小。 相似文献
110.
A simple eddy viscosity model is applied to the governing equations to establish the behaviour of the mean velocity in the turbulent axisymmetric near wake. The near wake develops from a long slender cylinder which is kept parallel to the flow and is developing under zero streamwise pressure gradient. The upstream turbulent boundary layer on the body of revolution is fully developed. In the inner layer of the flow downstream of the trailing edge, the turbulent inner layer of the upstream boundary layer grows into the initial logarithmic layer, and as a consequence, the centreline velocity in the near wake is shown to increase logarithmically with streamwise distances for large streamwise distances. The analysis further leads to two regions of the near wake flow (the inner near wake and the outer near wake), similar to that of a fully developed turbulent boundary layer, for which the governing equations have been derived. The matching between these two regions leads to a logarithmic variation in the normal direction. Also shown is the variation of the square of the wake width which varies logarithmically with streamwise distance in the near wake. These features are validated by comparison with available experimental data. 相似文献