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731.
科学的统一性与力学的范围地位和方向 总被引:3,自引:1,他引:2
综述科学的统一性和统一性所决定的科学发展的方向,并从科学统一性的观战简评力不的范围,它在科学上的地位,影响和今后发展的方向。. 相似文献
732.
733.
Numerical investigation of axisymmetric shock wave focusing over paraboloidal reflectors 总被引:2,自引:0,他引:2
The problem of a plane shock wave incident to a paraboloidal reflector is numerically investigated. The numerical solver
used is developed by an improved, implicit, upwind total variation diminishing scheme in a finite-volume approach. The real-gas
effect is taken into account if high temperature occurs. The solver is validated on four test problems. The complicated flow
fields of axisymmetric shock wave focusing for different-depth reflectors at various incident shock Mach numbers are studied.
An interesting result of a maximum pressure happening at the reflector center is found. This is due to the occurrence of an
implosion phenomenon. A maximum temperature might occur at the reflector center or at other locations, depending on the incident
shock Mach number and the reflector depth. Moreover, vortical flows induced by shock wave focusing and their formation mechanism
are explored. It was found that the vortices near the reflector are caused by a ring-shaped shock/slipline interaction. Owing
to the slipline on the symmetry axis, a jet flow is induced, resulting in the formation of vortices near the symmetry axis.
Received 13 January 1998 / Accepted 10 November 1998 相似文献
734.
Sierpinski Gasket格点图上的渗流模型 总被引:2,自引:0,他引:2
本文研究了Sierpinski gasket上的边渗流模型。首先证明了该模型没有临界现象,进一步给出了其一个指数衰减律,进而证明了临界值的唯一性。 相似文献
735.
湍流一般机理及其应用 总被引:2,自引:0,他引:2
本文综述了湍流机理发展中最重要的一些文章,包括:Brown-Roshko的混合剪切层中大尺度涡的发展;Perry和Chong的湍流边界层中A形涡结构的湍流机理;以及笔者提出的关于3维湍流场中涡结构的涡量脉动对流和扩散并存的一般机理。在一般机理基础上建立了判别流场的准则,列举了在固壁边界附近的猝发现象并展望它的未来应用。 相似文献
736.
Aaya Nassar Ibrahim M. Ibrahim Fatma G. Amin Merna Magdy Ahmed M. Elgharib Eman B. Azzam Filopateer Nasser Kirllos Yousry Israa M. Shamkh Samah M. Mahdy Abdo A. Elfiky 《Molecules (Basel, Switzerland)》2021,26(21)
A novel human coronavirus prompted considerable worry at the end of the year 2019. Now, it represents a significant global health and economic burden. The newly emerged coronavirus disease caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the primary reason for the COVID-19 global pandemic. According to recent global figures, COVID-19 has caused approximately 243.3 million illnesses and 4.9 million deaths. Several human cell receptors are involved in the virus identification of the host cells and entering them. Hence, understanding how the virus binds to host-cell receptors is crucial for developing antiviral treatments and vaccines. The current work aimed to determine the multiple host-cell receptors that bind with SARS-CoV-2 and other human coronaviruses for the purpose of cell entry. Extensive research is needed using neutralizing antibodies, natural chemicals, and therapeutic peptides to target those host-cell receptors in extremely susceptible individuals. More research is needed to map SARS-CoV-2 cell entry pathways in order to identify potential viral inhibitors. 相似文献
737.
Nitesh Kumawat Andrejs Tucs Soumen Bera Gennady N. Chuev Marat Valiev Marina V. Fedotova Sergey E. Kruchinin Koji Tsuda Adnan Sljoka Amit Chakraborty 《Molecules (Basel, Switzerland)》2022,27(3)
The entry of the SARS-CoV-2, a causative agent of COVID-19, into human host cells is mediated by the SARS-CoV-2 spike (S) glycoprotein, which critically depends on the formation of complexes involving the spike protein receptor-binding domain (RBD) and the human cellular membrane receptor angiotensin-converting enzyme 2 (hACE2). Using classical site density functional theory (SDFT) and structural bioinformatics methods, we investigate binding and conformational properties of these complexes and study the overlooked role of water-mediated interactions. Analysis of the three-dimensional reference interaction site model (3DRISM) of SDFT indicates that water mediated interactions in the form of additional water bridges strongly increases the binding between SARS-CoV-2 spike protein and hACE2 compared to SARS-CoV-1-hACE2 complex. By analyzing structures of SARS-CoV-2 and SARS-CoV-1, we find that the homotrimer SARS-CoV-2 S receptor-binding domain (RBD) has expanded in size, indicating large conformational change relative to SARS-CoV-1 S protein. Protomer with the up-conformational form of RBD, which binds with hACE2, exhibits stronger intermolecular interactions at the RBD-ACE2 interface, with differential distributions and the inclusion of specific H-bonds in the CoV-2 complex. Further interface analysis has shown that interfacial water promotes and stabilizes the formation of CoV-2/hACE2 complex. This interaction causes a significant structural rigidification of the spike protein, favoring proteolytic processing of the S protein for the fusion of the viral and cellular membrane. Moreover, conformational dynamics simulations of RBD motions in SARS-CoV-2 and SARS-CoV-1 point to the role in modification of the RBD dynamics and their impact on infectivity. 相似文献
738.
739.
精确捕捉接触波和剪切波的Godunov型数值方法,如流行的HLLC格式,在模拟高超声速流动问题时会出现激波异常现象。对HLLC格式进行稳定性分析发现,流体主流方向的扰动都能有效衰减,但是横向的密度与剪切速度的扰动不会衰减。具有特殊对称性的二维Sedov爆轰波问题证明了横向通量和不稳定现象之间的密切联系。利用压力比和马赫数来探测数值激波层亚声速区的横向网格界面,并且在该界面的数值通量上增加熵波粘性和剪切波粘性来构造一种激波稳定的HLLC格式。分析表明,在熵波粘性和剪切波粘性的作用下,横向的所有扰动都会衰减。一系列数值测试证明了新格式不仅可以成功地抑制各类激波异常现象,还保留了原HLLC格式低耗散性的优点。 相似文献
740.
We study the quantum dynamics of an impurity-doped Bose–Einstein condensate (BEC) system. We show how to generate the macroscopic quantum superposition states (MQSSs) of the BEC by the use of projective measurements on impurity atoms. It is found that the nonclassicality of MQSSs can be manipulated by changing the number of the impurities and their interaction with the BEC. It is shown that the BEC matter-wave field exhibits a collapse and revival phenomenon which reveals the quantum nature of the BEC matter-wave field. We investigate the micro-macro entanglement between the impurities and the BEC, and find enhancement of the micro-macro entanglement induced by the initial quantum coherence of the impurity atoms. 相似文献