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101.
Results are reported of an unsteady Reynolds‐averaged Navier–Stokes (RANS) method for simulation of the boundary layer and wake and wave field for a surface ship advancing in regular head waves, but restrained from body motions. Second‐order finite differences are used for both spatial and temporal discretization and a Poisson equation projection method is used for velocity–pressure coupling. The exact kinematic free‐surface boundary condition is solved for the free‐surface elevation using a body‐fitted/free‐surface conforming grid updated in each time step. The simulations are for the model problem of a Wigley hull advancing in calm water and in regular head waves. Verification and validation procedures are followed, which include careful consideration of both simulation and experimental uncertainties. The steady flow results are comparable to other steady RANS methods in predicting resistance, boundary layer and wake, and free‐surface effects. The unsteady flow results cover a wide range of Froude number, wavelength, and amplitude for which first harmonic amplitude and phase force and moment experimental data are available for validation along with frequency domain, linear potential flow results for comparisons. The present results, which include the effects of turbulent flow and non‐linear interactions, are in good agreement with the data and overall show better capability than the potential flow results. The physics of the unsteady boundary layer and wake and wave field response are explained with regard to frequency of encounter and seakeeping theory. The results of the present study suggest applicability for additional complexities such as practical ship geometry, ship motion, and maneuvering in arbitrary ambient waves. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
102.
Ahn JH Jung SH Kim JA Song SB Kwon SJ Kim KR Rhee SD Park SD Lee JM Kim SS Cheon HG 《Chemical & pharmaceutical bulletin》2005,53(8):1048-1050
In the continuation of efforts to modify the structure of our novel DP-IV inhibitors, a series of pyrazolidine derivatives with heteroaryl urea was synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV (DP-IV). 相似文献
103.
We investigate noncollinear sum-frequency generation in a time-resolved fluorescence upconversion experiment to eliminate group-velocity mismatch (GVM), a major mechanism that deteriorates time resolution. The noncollinear geometry inherently causes phase-front mismatch (PFM) that also spoils time resolution. The effects of GVM and PFM on the time resolution are studied by numerical calculations and experiments. Based on the investigation, a fluorescence upconversion apparatus with time resolution better than 45 fs (FWHM) is demonstrated. 相似文献
104.
Attosecond-pulse extreme-ultraviolet (XUV) photoionization in a two-color laser field is investigated. Attosecond pulse trains with different numbers of pulses are examined, and their strong dependence on photoelectronic spectra is found. Single-color driving-laser-field-assisted attosecond XUV photoionization cannot determine the number of attosecond pulses from the photoelectronic energy spectrum that are detected orthogonally to the beam direction and the electric field vector of the linearly polarized laser field. A two-color-field-assisted XUV photoionization scheme is proposed for directly determining the number of attosecond pulses from a spectrum detected orthogonally. 相似文献
105.
The influence of phosphate glass electrode in the configuration of resistive plate chamber has been studied using GEANT3.21
Monte Carlo code. Bakelite electrodes were replaced by phosphate glass electrodes, as these glass materials have low bulk
resistivity, are portable and easy to handle. These types of RPCs in their compact form of all materials are suitable for
high rate background environment. We find that these new types of RPCs give little higher response to γ-rays and e+/e− particles, both for single-and double gap RPCs. The results of simulation are discussed.
相似文献
106.
Dendritic chiral auxiliaries on silica: a new heterogeneous catalyst for enantioselective addition of diethylzinc to benzaldehyde 总被引:1,自引:0,他引:1
This article reports the first work on the use of silica supported dendritic chiral auxiliaries for the enantioselective addition of diethylzinc to benzaldehyde: the control of dendrimer propagation on the silica surface is of prime importance to obtain enhanced conversion, selectivity, and enantioselectivity. 相似文献
107.
Y. -M. Yu S. Nam J. -K. Rhee Byungsung O K. -S. Lee Y. D. Choi 《Journal of Crystal Growth》2000,210(4):521-526
ZnS1−xTex epilayers were grown on GaAs(1 0 0) substrates by hot-wall epitaxy in a wide range of Te composition. The Te composition was determined by Rutherford backscattering spectrometry and the lattice constant was measured by double-crystal rocking curve. It was found that the lattice of the epilayer matches well with that of the substrate at x=0.37 as expected by Vegard's rule, and the energy gap was also determined as a function of Te composition by spectrophotometer. It showed that a quadratic relation with the composition: Eg(x)=3.71−5.27x+3.83x2. Photoluminescence characteristics were also studied. 相似文献
108.
109.
Hye Jin Heo Hyoung Kyu Kim Jae Boum Youm Sung Woo Cho In-Sung Song Sun Young Lee Tae Hee Ko Nari Kim Kyung Soo Ko Byoung Doo Rhee Jin Han 《Experimental & molecular medicine》2016,48(8):e254
Mitochondria are crucial for maintaining the properties of embryonic stem cells (ESCs) and for regulating their subsequent differentiation into diverse cell lineages, including cardiomyocytes. However, mitochondrial regulators that manage the rate of differentiation or cell fate have been rarely identified. This study aimed to determine the potential mitochondrial factor that controls the differentiation of ESCs into cardiac myocytes. We induced cardiomyocyte differentiation from mouse ESCs (mESCs) and performed microarray assays to assess messenger RNA (mRNA) expression changes at differentiation day 8 (D8) compared with undifferentiated mESCs (D0). Among the differentially expressed genes, Pdp1 expression was significantly decreased (27-fold) on D8 compared to D0, which was accompanied by suppressed mitochondrial indices, including ATP levels, membrane potential, ROS and mitochondrial Ca2+. Notably, Pdp1 overexpression significantly enhanced the mitochondrial indices and pyruvate dehydrogenase activity and reduced the expression of cardiac differentiation marker mRNA and the cardiac differentiation rate compared to a mock control. In confirmation of this, a knockdown of the Pdp1 gene promoted the expression of cardiac differentiation marker mRNA and the cardiac differentiation rate. In conclusion, our results suggest that mitochondrial PDP1 is a potential regulator that controls cardiac differentiation at an early differentiation stage in ESCs. 相似文献
110.
The effectiveness of a new photomechanical-numerical hybrid method for evaluating stress intensity factors (SIFs) in orthotropic
composites is demonstrated. Reliable results are obtained from few moiré-measured displacements and they originate well away
from the crak tip. The method is illustrated for the case of a uniaxially loaded orthotropic glass/epoxy composite containing
a central, transverse crack. 相似文献