100 resultados para Bombs Away
Resumo:
The controlled equations defined in a physical plane are changed into those in a computational plane with coordinate transformations suitable for different Mach number M(infinity). The computational area is limited in the body surface and in the vicinities of detached shock wave and sonic line. Thus the area can be greatly cut down when the shock wave moves away from the body surface as M(infinity) --> 1. Highly accurate, total variation diminishing (TVD) finite-difference schemes are used to calculate the low supersonic flowfield around a sphere. The stand-off distance, location of sonic line, etc. are well comparable with experimental data. The long pending problem concerning a flow passing a sphere at 1.3 greater-than-or-equal-to M(infinity) > 1 has been settled, and some new results on M(infinity) = 1.05 have been presented.
Resumo:
By means of the matched asymptotic expansion method with one-time scale analysis we have shown that the inviscid geostrophic vortex solution represents our leading solution away from the vortex. Near the vortex there is a viscous core structure, with the length scale O(a). In the core the viscous stresses (or turbulent stresses) are important, the variations of the velocity and the equivalent height are finite and dependent of time. It also has been shown that the leading inner solutions of the core structure are the same for two different time scales of S/(ghoo)1/2 and S/a (ghoo)1/2. Within the accuracy of O(a) the velocity of a geostrophic vortex center is equal to the velocity of the local background flow, where the vortex is located, in the absence of the vortex. Some numerical examples demonstrate the contributions of these results.
Resumo:
The magnetospheric structure of a pulsar is discussed for a non-force-free magnetic field. The local solution to the axisymmetric equations of the pulsar is obtained by the method of expanding in the polar angle. Particular attention is given to the solutions near the polar axis and the equator. Near the pulsar surface, the magnetic field energy density is found to be larger than the other energy components; the gravitational potential and the kinetic energy are relatively larger far away from the pulsar surface. It is shown that these relations influence the mass distribution in the pulsar magnetosphere. The results also show that the plasma rotation may be nonrigid and, hence, that a corotational region with a closed magnetic field may not exist.
Resumo:
Recent studies showed that vibration caused by blasting mainly reflects the property of geological structure itself neighboring the blasting center. Different vibration signals can be collected for different geological structures under blasting. Hence, vibration signal can be used to identify geological structure, especial for a slope with a weak layer. As the geological structure for a practical slope is usually complicated, the simulation of vibration caused by blasting should be carried out first. Generally, the material in a certain zone near the blasting center will undergo damage, so the physical model to simulate this region is the most concerned. In this paper, the damaged zone near blasting center is neglected, and the blasting load can be considered being applied on the interface between the damaged zone and undamaged zone. Regarding the relations between the weight of explosive, the size of damaged zone, and the dynamic loading to propagate out away, the vibration caused by blasting for a practical layered slope is simulated. Compared with the measured signal in site, it can be seen that the simulating result is in well agreement with that of practical testing. The results also indicate that the farther the testing point apart from the blasting center, the more accurate the simulation is.
Resumo:
The optimization of off-null ellipsometry is described with emphasis on the improvement of resolution for visualizing biomolecule layers. For optical biosensor with layer thickness below 6.5 nm, a numerical simulation for the dependence of resolution on the azimuth settings of polarizer and analyzer is presented first. For comparison, three different resolutions are given at three azimuth settings which are near null and far away from null condition, respectively. Furthermore, the square or linear approximation relationship between the intensity and the layer thickness are also given at these settings. The difference among their accuracy is up to 100 times or so. Experimental results of the biosensor sample verify the optimization.
Resumo:
Strong mechanical forces can, obviously, disrupt cell-cell and cell-matrix adhesions, e.g., cyclic uniaxial stretch induces instability of cell adhesion, which then causes the reorientation of cells away from the stretching direction. However, recent experiments also demonstrated the existence of force dependent adhesion growth (rather than dissociation). To provide a quantitative explanation for the two seemingly contradictory phenomena, a microscopic model that includes both integrin-integrin interaction and integrin-ligand interaction is developed at molecular level by treating the focal adhesion as an adhesion cluster. The integrin clustering dynamics and integrin-ligand binding dynamics are then simulated within one unified theoretical frame with Monte Carlo simulation. We find that the focal adhesion will grow when the traction force is higher than a relative small threshold value, and the growth is dominated by the reduction of local chemical potential energy by the traction force. In contrast, the focal adhesion will rupture when the traction force exceeds a second threshold value, and the rupture is dominated by the breaking of integrin-ligand bonds. Consistent with the experiments, these results suggest a force map for various responses of cell adhesion to different scales of mechanical force. PMID: 20542514
Resumo:
A new idea of drag reduction and thermal protection for hypersonic vehicles is proposed based on the combination of a physical spike and lateral jets for shock-reconstruction. The spike recasts the bow shock in front of a blunt body into a conical shock, and the lateral jets work to protect the spike tip from overheating and to push the conical shock away from the blunt body when a pitching angle exists during flight. Experiments are conducted in a hypersonic wind tunnel at a nominal Mach number of 6. It is demonstrated that the shock/shock interaction on the blunt body is avoided due to injection and the peak pressure at the reattachment point is reduced by 70% under a 4A degrees attack angle.
Resumo:
We have improved the ordinary total internal reflection fluorescence microscopy (TIRFM). Two improvements have been achieved, one is the interface between opaque material and solution can be observed, another is the interface far away (usually several ten micro meters) the objective lens can be observed. By this improved TIRFM, the adsorption of protein molecules at a crystal/solution interface had been successfully observed. We have obtained the results of relationship between the amount of adsorbed protein molecules on bunched steps and the height of bunched steps of a protein crystal.
Resumo:
The configuration of semisubmersibles consisting of pontoons and columns and their corresponding heave motion response in incident progressive waves are examined. The purpose of the present study is to provide a theoretical approach to estimating the effects of volumetric allocation on natural period and response amplitude operator (RAO) in heave motion. We conclude that the amplitude of heave motion response can be considerably suppressed by appropriately adjusting volumetric allocation so that the natural heave period keeps away from the range of wave energy. The theoretical formulae are found in good agreement with the corresponding computational results by WAMIT.
Resumo:
Conical emission (CE) has been investigated experimentally by laser pulses with different pulse durations and spectral bandwidths. The results show that the overall CE curve will shift as the varying of spectral bandwidth of pump laser pulse. But for pump laser pulses which have same spectral bandwidth but different pulse duration, the CE angles will be same at the spectral region close to the pump wavelength while will be different at the spectral region far away from the pump wavelength. We have also fitted the measured CE angles with X-wave model. The calculated curves and the measured CE curves match reasonably well. The best fits indicate that the group velocity of the filament pulse may be greatly controlled by controlling the spectral bandwidth of pump laser pulse. (C) 2008 Elsevier B.V. All rights reserved.
Resumo:
A two-mode adjustable superresolving filter based on a birefringent filter is proposed. This kind of filter has superresolution in two modes of adjustment. One is rotation of the binary pupil filter on the optical axis of the system and the other is the tilt of the filter away from the pupil plane on axis parallel or perpendicular to the optical axis of the crystal. The filters act as complex amplitude filters in the former mode, and as pure phase filters in the latter. By analyzing two superresolving parameters, we obtain the optimal design parameters that ensure a large field of view, a large superresolving range, and a high setting accuracy. This kind of filter can provide more flexibility in practical applications. (c) 2006 Optical Society of America.
Resumo:
在飞秒抽运一探测光谱技术中,空间分辨的探测光信号反映了在不同空间位置的材料的非线性效应。当抽运光强度增大时,探测光信号中会出现明显的高阶特别是五阶非线性效应。利用劈裂算子方法直接解决了一维非线性传播方程的问题。在数值模拟中,研究了在不同抽运强度和位置下的抽运一探测过程中的五阶非线性效应。在足够高的抽运场下,探测信号出现清晰的振荡,显示了三阶和五阶非线性效应之间的干涉。当空间位置离抽运场中心足够远时,五阶比三阶非线性效应的衰减快得多,对其物理机制和趋势进行了定性的讨论。
Resumo:
This paper presents an experimental demonstration of light-induced evaporative cooling in a magneto-optical trap. An additional laser is used to interact with atoms at the edge of the atomic cloud in the trap. These atoms get an additional force and evaporated away from the trap by both the magnetic field and laser fields. There remaining atoms have lower kinetic energy and thus are cooled. It reports the measurements on the temperature and atomic number after the evaporative cooling with different parameters including the distance between the laser and the centre of the atomic cloud, the detuning, the intensity. The results show that the light-induced evaporative cooling is a way to generate an ultra-cold atom source.
Resumo:
针对现有光弹调制器标定方法的不足,提出了一种精确标定光弹调制器的新方法。首先利用起偏器、波片、光弹调制器和检偏器构成标定光路.通过寻找探测信号基频分量的极大值进行粗略标定,使光弹调制器的峰值延迟量处在1.841rad附近。然后撤走波片形成光弹凋制器的精确标定光路.在检偏器旋转90°前后获得探测信号的直流分量和二次谐波分量。最后利用这两种探测信号的直流分量和二次谐波分量精确地计算出光弹调制器的峰值延迟量。实验验让了此光掸调制器标定方法,实验结果表明其标定误差仅为0.7%。在此光掸凋制器标定方法中.光弹调制器
Resumo:
基于棱镜的色散特性,提出一种楔形窗口与聚焦透镜组合的方式,解决了高功率激光装置三倍频谐波分离所存在的问题,即三倍频的高通量传输和靶面辐照。结合“神光Ⅱ”装置多功能高能激光系统有关参数进行系统设计,确定了楔形窗口参数,并对其所引起的B积分和间距误差进行了分析。通过实验测试,三倍频传输通量由0.7~1 J/cm2提高到2.8 J/cm2,同时靶面三倍频和二倍频分离间距达到2.85 mm,实现了高功率激光装置高通量传输的三倍频谐波分离。