Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
We present a Quantum Space Model (QSM) of cosmic evolution based on the theory that space consists of energy quanta from which our universe came about. We used the Friedmann equations to trace its history and predict its ultimate fate. Results provide further support to our recent proposal that the accelerating expansion of the universe is due to a scalar space field which has become known as Dark Energy. In our model, the universe started from high energy space quanta which were triggered by quantum fluctuations that caused the Big Bang. It then expanded and cooled undergoing phase transitions to radiation, fundamental particles, and matter. Matter agglomerated and grew into stars, galaxies, etc. and was eventually consolidated by gravity into Black Holes, which finally ended in a Big Crunch in a state of deep freeze inside the Black hole at 1.380 trillion years. Fluctuations, quantum tunneling, or some other mechanisms caused a new Bang to start another cycle in its life. Our results are in good agreement with the theoretical predictions of a cyclic universe by Steinhardt and his associates, and by Penrose. Space and energy are equivalent as embodied in the Planck energy equation. They give rise to the two principal long range forces in the universe: the gravitational force and the space force. The latter may be the fifth force in the universe. The two forces could provide the clockwork mechanism operating our cyclic universe. If the Law of Conservation of Energy is universal, then the cosmos is eternal....
The inaccurate calculation of the gas lost is the principal cause of inaccurate determinations of the coalbed methane content via air reverse circulation sampling (ARCS). The positive pressure environment has a significant impact on gas desorption during the sampling process. To obtain the gas desorption mechanism of coal particles under positive pressure, positive pressure desorption experiments were conducted on coal samples with different particle sizes under different adsorption equilibrium pressures using a self-designed positive pressure desorption experimental device. And a positive diffusion model for coal particles was established, in which the diffusion coefficient was calculated based on the results of the positive desorption experiments. The diffusion model was then used to simulate the diffusion capacity of coal particles and compared with the test data. The results show that the responses of the positive pressure desorption and atmospheric pressure desorption to the adsorption equilibrium pressure are similar. The gas desorption velocity increases as the adsorption equilibrium pressure increases. Positive pressure can effectively inhibit gas desorption. The initial gas desorption velocity decreases as the positive pressure and coal particle size increase. Concurrently, the entire sample desorption process during ARCS can be divided into three stages: a slow desorption stage, an accelerated desorption stage, and an atmospheric desorption stage. The relationship between the diffusion coefficient and the positive pressure exhibits an exponential distribution, and the positive pressure diffusion model can describe the gas diffusion from coal particles well. The results of this study could help to establish a gas loss compensation model for the ARCS process....
The tensile, creep, fatigue and creep-fatigue tests of the nickel-based superalloy GH4169 were carried out. According to the deformation characteristics of GH4169 alloy, the Ohno-Karim kinematic model (O-K model) can be used to describe the tensile behavior. The creep constitutive model presented in this paper can be used to predict the three-stage creep characteristics of the GH4169 alloy. The modified Ohno-Karim kinematic hardening model, combined with an isotropic hardening model, can well predict the cyclic softening behavior of the material under symmetric loads and the mean stress relaxation behavior under asymmetric loads. Based on the modified Ohno-Karim kinematic hardening model, isotropic hardening model and creep constitutive model, a non-unified constitutive model was established. The creep-fatigue behavior of the GH4169 alloy under symmetric and asymmetric loads is simulated by using the non-unified constitutive model. The simulation results are very close to the experimental results; however, the prediction results of the time-dependent relaxation load are relatively small....
The seepage characteristics of rocks under conditions of multi-field activity have always been important in the field of rock mechanics. This study used the MTS815 multi-functional electrohydraulic servo rock testing machine to conduct seepage tests on long-flame coal specimens under different confining pressures, water pressures, and temperatures. This paper presents and discusses the seepage characteristics of coal specimens under the action of thermal hydraulic mechanical multi-field combinations. Considering parameters such as volumetric strain, temperature, thermal expansion coefficient, and initial porosity, the relationships of each parameter with porosity were obtained. The test results revealed that the volumetric strain of coal specimens increased gradually with the increase of temperature. The dynamic viscosity of water decreased with the increase of temperature, which accelerated the movement and circulation of water molecules. The increase in temperature caused the volume of the coal specimen to expand, the pores in the coal specimen squeezed against each other, the pore volume decreased, and the size of the seepage channel slowly decreased, which inhibited the seepage process. Furthermore, permeability gradually decreased with the increase of temperature. This inhibited the occurrence of seepage, and the higher the confining pressure, the lower was the permeability. The porosity of coal specimens decreased with the increase in temperature, which had an inhibitory effect on the seepage behavior. The results of this study provide experimental and theoretical support for the safe mining of coal and rock in underground mines....
Unimodular gravity is a modified theory with respect to general relativity by an extra condition that the determinant of the metric is fixed. Especially, if the energy-momentum tensor is not imposed to be conserved separately, a new geometric structure will appear with potential observational signatures. In this paper, we study the tidal deformability of a compact star in unimodular gravity under the assumption of a non-conserved energy-momentum tensor. Both the electric-type and magnetic-type quadrupole tidal Love numbers are calculated for neutron stars using the polytrope model. It is found that the electric-type tidal Love numbers are monotonically increasing, but the magnetic-type ones are decreasing, with the increase in the non-conservation parameter. Compared with the observational data from the detected gravitational-wave events, a small negative non-conservation parameter is favored....
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