Steady Lateral Growth of Three-Dimensional Particle Laden Density Currents     

M.R. Moossavi Hekmati  M. Najafi  N. Ashrafi khorasani 《中国海洋工程》2018,32(4):467-475

In this paper the steady lateral growth of three-dimensional turbulent inclined turbidity current is investigated. To simulate the current, an experimental setup is developed to analyze the turbidity current for different regimes in the particle laden density currents environment. The Buckingham's π theorem together with a dimensional analysis is implemented to derive the appropriate non-dimensional variables. The experimental results were normalized and plotted in the form of non-dimensional graphs from which a theoretical model is developed and analyzed. Based on the results obtained for the steady lateral growth, three different regimes, namely, inertia-viscous one as the first regime, buoyancy-viscous and gravity-viscous as the second and third regimes are distinguished within the current.In these regimes, the force balance is between the driving and resisting forces. Namely, in the first regime, the force balance is between the inertia and viscous forces, in the second regime, the buoyancy and viscous forces, and in the third regime, gravity and viscous forces are balanced. The experimental results indicate that the lateral growth rate in the first regime is smaller than that in the second and third regimes due to the magnitude and type of the forces involved in those regimes. According to the graphical results, the three different lateral growth rates appear when the normalized current length is smaller than about 3, between about 3 and 10, and larger than about 10. In those regions,the slopes of the data are different with respect to one another.  相似文献   

Projectile preservation during oblique hypervelocity impacts          下载免费PDF全文

Ronald T. Daly  Peter H. Schultz 《Meteoritics & planetary science》2018,53(7):1364-1390

Impact angle plays a significant role in determining the fate of the projectile. In this study, we use a suite of hypervelocity impact experiments to reveal how impact angle affects the preservation, distribution, and physical state of projectile residues in impact craters. Diverse types of projectiles, including amorphous silicates, crystalline silicates, and aluminum, in two sizes (6.35 and 12.7 mm), were launched into blocks of copper or 6061 aluminum at speeds between 1.9 and 5.7 km s⁻¹. Crater interiors preserve projectile residues in all cases, including conditions relevant to the asteroid belt. These residues consist of projectile fragments or projectile-rich glasses, depending on impact conditions. During oblique impacts at 30° and 45°, the uprange crater wall preserves crystalline fragments of the projectile. The fragments of water-rich projectiles such as antigorite remain hydrated. Several factors contribute to enhanced preservation on the uprange wall, including a weaker shock uprange, uprange acceleration as the shock reflects off the back of the projectile, and rapid quenching of melts along the projectile–target interface. These findings have two broader implications. First, the results suggest a new collection strategy for flyby sample return missions. Second, these results predict that the M-type asteroid Psyche should bear exogenic, impactor-derived debris.  相似文献   

Fully nonlinear heavy ion-acoustic solitary waves in astrophysical degenerate relativistic quantum plasmas     

S. Sultana  R. Schlickeiser 《Astrophysics and Space Science》2018,363(5):103

Fully nonlinear features of heavy ion-acoustic solitary waves (HIASWs) have been investigated in an astrophysical degenerate relativistic quantum plasma (ADRQP) containing relativistically degenerate electrons and non-relativistically degenerate light ion species, and non-degenerate heavy ion species. The pseudo-energy balance equation is derived from the fluid dynamical equations by adopting the well-known Sagdeev-potential approach, and the properties of arbitrary amplitude HIASWs are examined. The small amplitude limit for the propagation of HIASWs is also recovered. The basic features (width, amplitude, polarity, critical Mach number, speed, etc.) of HIASWs are found to be significantly modified by the relativistic effect of the electron species, and also by the variation of the number density of electron, light ion, and heavy ion species. The basic properties of HIASWs, that may propagated in some realistic astrophysical plasma systems (e.g., in white dwarfs), are briefly discussed.  相似文献   

Algorithm for the Atmospheric Correction of Shortwave Channels of the MSU-MR Radiometer of the Meteor-M No. 2 Satellite     

Kuchma  M. O.  Bloshchinskiy  V. D. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):909-915

Izvestiya, Atmospheric and Oceanic Physics - The problem of atmospheric correction for shortwave channels of a multispectral low-resolution scanning radiometer onboard the Meteor-M No. 2 satellite...  相似文献   

Estimating Model Parameters from Self-Potential Anomaly of 2D Inclined Sheet Using Whale Optimization Algorithm: Applications to Mineral Exploration and Tracing Shear Zones     

Gobashy  Mohamed  Abdelazeem  Maha  Abdrabou  Mohamed  Khalil  Mohamed H. 《Natural Resources Research》2020,29(1):499-519

The use of spontaneous potential (SP) anomalies is well known in the geophysical literatures because of its effectiveness and significance in solving many complex problems in mineral exploration. The inverse problem of self-potential data interpretation is generally ill-posed and nonlinear. Methods based on derivative analysis usually fail to reach the optimal solution (global minimum) and trapped in a local minimum. A new simple heuristic solution to SP anomalies due to 2D inclined sheet of infinite horizontal length is investigated in this study to solve these problems. This method is based on utilizing whale optimization algorithm (WOA) as an effective heuristic solution to the inverse problem of self-potential field due to a 2D inclined sheet. In this context, the WOA was applied first to synthetic example, where the effect of the random noise was examined and the method revealed good results using proper MATLAB code. The technique was then applied on several real field profiles from different localities aiming to determine the parameters of mineralized zones or the associated shear zones. The inversion parameters revealed that WOA detected accurately the unknown parameters and showed a good validation when compared with the published inversion methods.

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Evaluation of Interactions Between Oilfield Chemicals and Reservoir Rocks     

Wuyep  E. O.  Oluyemi  G. F.  Yates  K.  Akisanya  A. R. 《Natural Resources Research》2020,29(2):1239-1258

Natural Resources Research - Sand failure and production occurs when the formation stress exceeds the strength of the formation, which is derived majorly from the natural material that cements the...  相似文献   

Determination of the regional deformation rates of Shanghai and Kashima VLBI stations based on ITRF97     

Zhi-gen Yang  Wen-yao Zhu  C. K. Shum  Feng-chun Shu   《Chinese Astronomy and Astrophysics》2002,26(4):303-502

The vertical deformation rates (VDRs) and horizontal deformation rates (HDRs) of Shanghai VLBI station in China and Kashima and Kashima34 VLBI stations in Japan were re-analysed using the baseline length change rates from Shanghai to 13 global VLBI stations, and from Kashima to 27 stations and from Kashima34 to 12 stations, based on the NASA VLBI global solution glb1123 (Ma, 1999). The velocity vectors of the global VLBI stations were referred to the ITRF97 reference frame, and the Eulerian vectors of different models of plate motion were used for comparative solutions. The VDR of Shanghai station is estimated to be −1.91±0.56 mm/yr, and those of Kashima and Kashima34 stations, −3.72±0.74mm/yr and −8.81±0.84mm/yr, respectively. The difference between the last two was verified by further analysis. Similar estimates were also made for the Kokee, Kauai and MK_VLBA VLBI stations in mid-Pacific.  相似文献   

A spectroscopic study of the peculiar galaxy UGC 5600     

L. V. Shalyapina  A. V. Moiseev  V. A. Yakovleva 《Astronomy Letters》2002,28(7):443-453

We present our observations of the galaxy UGS 5600 with a long-slit spectrograph (UAGS) and a multipupil field spectrograph (MPFS) attached to the 6-m Special Astrophysical Observatory telescope. Radial-velocity fields of the stellar and gaseous components were constructed for the central region and inner ring of the galaxy. We proved the existence of two nearly orthogonal kinematic subsystems and conclude that UGC 5600 is a galaxy with an inner polar ring. In the circumnuclear region, we detected noncircular stellar motions and suspected the existence of a minibar. The emission lines are shown to originate in H II regions. We estimated the metallicity from the intensity ratio of the [N II]λ6583 and Hα lines to be nearly solar, which rules out the possibility that the polar ring was produced by the accretion of gas from a dwarf companion.  相似文献   

The mass ratio of Charon to Pluto from Hubble Space Telescope astrometry with the fine guidance sensors     

C.B Olkin  L.H Wasserman  O.G Franz 《Icarus》2003,164(1):254-259

The mass ratio of Charon to Pluto is a basic parameter describing the binary system and is necessary for determining the individual masses and densities of these two bodies. Previous measurements of the mass ratio have been made, but the solutions differ significantly (Null et al., 1993; Young et al., 1994; Null and Owen, 1996; Foust et al., 1997; Tholen and Buie, 1997). We present the first observations of Pluto and Charon with a well-calibrated astrometric instrument—the fine guidance sensors on the Hubble Space Telescope. We observed the motion of Pluto and Charon about the system barycenter over 4.4 days (69% of an orbital period) and determined the mass ratio to be 0.122±0.008 which implies a density of 1.8 to 2.1 g cm⁻³ for Pluto and 1.6 to 1.8 g cm⁻³ for Charon. The resulting rock-mass fractions for Pluto and Charon are higher than expected for bodies formed in the outer solar nebula, possibly indicating significant postaccretion loss of volatiles.  相似文献   

Warm gas kinematics in shell galaxies     

R. Rampazzo  H. Plana  M. Longhetti  P. Amram  J. Boulesteix  J.-L. Gach  O. Hernandez 《Monthly notices of the Royal Astronomical Society》2003,343(3):819-830

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