Some aspects of entropic gravity in the presence of a noncommutative Schwarzschild-deSitter black hole     

S. Hamid Mehdipour 《Astrophysics and Space Science》2013,345(2):339-344

We study some features of entropic force approach in the presence of a noncommutative Schwarzschild-deSitter black hole. In this setup, there exists a similarity between the small and large scales. There are two finite cut-off in very short and long distances wherein the force and energy graph stop abruptly at those scales. We find that the existence of a deSitter core around the origin, induced by noncommutativity, in addition to a standard deSitter background at large scale may lead to a violation of the equivalence principle. Finally in order to directly observe the finite cut-off at short-scale gravity, caused by noncommutativity quantum fluctuations, we derive an effective gravitational constant.  相似文献   

Effect of sulphates and curing period on stress–strain curves and failure modes of soil–lime–natural pozzolana mixtures     

Hamid Gadouri  Khelifa Harichane  Mohamed Ghrici 《Marine Georesources & Geotechnology》2013,31(9):1130-1148

Abstract

An experimental investigation was undertaken in order to assess the effect of sodium (Na₂SO₄) and calcium (CaSO₄·2H₂O) sulphates and curing period on stress–strain curves and failure modes of grey (GS) and red (RS) clayey soils stabilised by lime (L), natural pozzolana (NP) and their combinations (L–NP). Several soil–L–NP mixtures were studied to be used as subgrade soils for road pavements. Stress–strain curves were obtained from unconfined compressive strength (UCS) test made on several soil–L–NP specimens after curing for 7 and 120 days. Tests results showed that the use of L or L–NP without sulphates produced a significant increase in peaks stress of both clayey soils and then modified their stress–strain curves from nonlinear to linear behaviour almost up to 70% of peak stress after a longer curing period. However, the presence of 2% Na₂SO₄ or any CaSO₄·2H₂O content provided beneficial effects on peaks stress and stress–strain curves of both stabilised clayey soils and then improved their linearity almost up to 95% of peak stress after curing for 120 days. In contrast, the presence of 6% Na₂SO₄ caused undesirable effects. In addition, both sulphates greatly affected the failure modes of soil–L–NP specimens, particularly at a later stage.  相似文献   

Ion acoustic shock waves in weakly relativistic and dissipative plasmas with nonthermal electrons and thermal positrons     

Hamid Reza Pakzad  Kurosh Javidan 《Astrophysics and Space Science》2011,331(1):175-180

Propagation of ion acoustic waves in plasmas containing electrons, positrons and high relativistic ions is investigated. It is shown that the Korteweg-de Vries (KdV) equation describes the nonlinear waves in this media. The amplitude and energy of the KdV solitary waves are derived and the effects of relativistic ions on these quantities are discussed.  相似文献   

Ion acoustic solitons of KdV and modified KdV equations in weakly relativistic plasma containing nonthermal electron,positron and warm ion     

Hamid Reza Pakzad 《Astrophysics and Space Science》2011,332(2):269-277

In this paper, the ion-acoustic solitons in a weakly relativistic electron-positron-ion plasma have been investigated. Relativistic ions, Maxwell-Boltzmann distributed positrons and nonthermal electrons are considered in collisionless warm plasma. Using a reductive perturbation theory, a Korteweg-de Vries (KdV) equation is derived, and the relativistic effect on the solitons is studied. It is found that the amplitude of solitary waves of the KdV equation diverges at the critical values of plasma parameters. Finally, in this situation, the solitons of a modified KdV (mKdV) equation with finite amplitude is derived.  相似文献   

Effect of <Emphasis Type="Italic">q</Emphasis>-nonextensive distribution of electrons on electron acoustic solitons     

Hamid Reza Pakzad 《Astrophysics and Space Science》2011,333(1):247-255

Ion acoustic shock waves (IASWs) are studied in a plasma consisting of electrons, positrons and ions. Boltzmann distributed positrons and superthermal electrons are considered in the plasma. The dissipation is taken into account the kinematic viscosity among the plasma constituents. The Korteweg–de Vries–Burgers (KdV–Burgers) equation is derived by reductive perturbation method. Shock waves are solutions of KdV–Burgers equation. It is observed that an increasing positron concentration decreases the amplitude of the waves. Furthermore, in the existence of the kinematic viscosity among the plasma, the shock wave structure appears. The effects of ion kinematic viscosity (η ₀) and the superthermal parameter (k) on the ion acoustic waves are found.  相似文献   

Full-scale experimental investigations on the response of a flooded passenger vehicle under subcritical conditions     

Al-Qadami  Ebrahim Hamid Hussein  Mustaffa  Zahiraniza  Shah  Syed Muzzamil Hussain  Matínez-Gomariz  Eduardo  Yusof  Khamaruzaman Wan 《Natural Hazards》2022,110(1):325-348

Natural Hazards - Vehicles can be easily swept away by floodwaters once the flow velocity and depth reach certain critical limits, with probabilities toward fatality reported to be nearly 50%....  相似文献