Papers by Keyword: Pressure

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Authors: Archana Singh, Mahendra Aynyas, S.P. Sanyal
Abstract: We report a first principles calculation of pressure-induced structural phase transition properties of uranium chalcogenides (UX; X=S, Se and Te). The total energies as a function of volume are obtained by means of self-consistent tight binding linear muffin orbital method (TB-LMTO) by performing spin and non-spin polarized calculations to determine the magnetic and structural stabilities. From the present study, we predict a magnetic phase transition from ferromagnetic (FM) to non-magnetic (NM) state around 67.7 and 10.2 GPa for US and USe, respectively. The pressure-induced magnetic transitions are found second-order in nature. We have also predicted structural phase transition from FM-NaCl-type (B1 phase) structure to NM-CsCl-type (B2 phase) structure at around 77.5, 23.5 for US and USe, respectively, while UTe undergoes from FM-B1 to FM-B2 phase around 12.0 GPa.
Authors: Qi Wang, Qing Ming Wang
Abstract: The purpose of this study is to investigate the effects of two kinds of total contact insoles (TCI). Traditional TCI reflects the shape of foot, while deformed total contact insole(DTCI) was established basing on the shape of footprints on clay prototypes. A female experimenter was asked to exert different loadings on clay prototypes to make footprints. Shapes of the footprints have been recorded by a reverse engineering method. Force distribution results in given preconditions were reflected and recorded for quantified comparison. shapes of two total contact insoles were rebuilt under different loadings. Having deformation of different magnitude over each area as a reference, effect and possibility of further improvement have been explored. Our findings showed that insoles based on larger deformation can be utilized to redistribute peak pressure effectively under normal loading. The results indicates that DTCI in this study can be used as a more important tool in adjusting functions or comfort ratings of shoes.
Authors: Gang Li, Hui Lan Huang, Hua Zhang, Jian Bin Liu, Xiang Chen
Abstract: The compressible transient model of solar chimney power plant system was proposed. It was added to the pressure equation and the ideal gas state equation basis on the heat balance equation for the solar collector model. The air flow station can be easily calculated with the improved model. The results of dynamic changes of the total pressure difference calculated in the model were in good agreement with the given actual measured values in references. The solar chimney model was considered the influence of fluid pressure on the density. The influence of the structural chimney on the chimney efficiency was analyzed with the established model. It was shown that the chimney efficiency changes significantly with the chimney height and its diameter. The chimney efficiency was decreased with a convergent chimney shape while increased with the divergent one. When the tilt angle of chimney reached a peak and then further increased, the chimney efficiency was the constant. These results will provide the important reference to improving the system efficiency.
Authors: Yao Hong Shi, Zhan Zhao, Zhen Fang, Dao Qu Geng, Yun Dong Xuan
Abstract: This topic takes the miniature Pt resistance strain pressure sensor made by Institute of Electronics, Chinese Academy of Sciences, as the core sensing element, and designs corresponding high-precision, low cost, low power amplifying circuit so as to realize accurate detection of atmospheric pressure in time. In this topic, a new design of amplifying circuit is taken, which first connects the digital potentiometer to the bridge circuit to adjust its balance, and then amplifies the output signal of the bridge circuit once to ideal value. This design not only meets the requirement of measurement, but also is feasible and reduces the cost. At the same time, in order to improve the precision of the potentiometer adjusting the bridge balancing, paralleled resistances are creatively used beside the digital potentiometer and its influence to the bridge balance adjustment and the accuracy of the bridge measurement is analyzed in detail.
Authors: Guang Chuan Liang, Lin Lin Tan, He Tian
Abstract: Steady sate flow of natural gas in buried pipeline is predicted with both the heat transfer between the flowing gas and the surrounding and the Joule-Thompson effect. The steady-state flow continuity, momentum and energy equations constitute the governing equations. As a constant gas mass flux (or gas mass flow rate) distribution along the pipeline is obtained from the steady-state continuity equation, the mathematical model describing steady-state gas flow in pipeline may be reduced to a second-order ODE system of first-order initial-value problem with gas pressure and temperature as the dependent variables. The forth-order Runge-Kutta method is used to solve this ODE system. Comparison between the predicted results and the observed field data are very good
Authors: Masakazu Yarimitsu, Masaru Aniya
Abstract: The pressure dependence of the diffusion coefficient in the superionic α- and β-phases of Ag3SI has been studied by using the method of molecular dynamics. It is shown that in the high temperature α-phase, the Ag diffusion coefficient decreases with pressure. On the hand, in the intermediate temperature β-phase, the Ag diffusion coefficient exhibits a maximum at around 2.8 GPa. The structural origin of this behavior is discussed through the pressure dependence of the pair distribution functions.
Authors: P.U. Ohirhian, I.N. Abu
Abstract: A new equation for the viscosity of Natural Gas under Reservoir conditions has been developed. The equation was obtained by the analysis of experimental Pressure, Volume and Temperature (PVT) Data of Gas associated with Nigerian Crude Oil. The PVT Data were those of renowned companies that operate in Nigeria. The pressure ranged from 144 psia to 4100 psia, and a temperature variation between 130oF and 220oF. Comparison of the equation formulated in this work with experimental PVT viscosity gave an average absolute error of 1.55%, a maximum absolute error of 4.878% and a standard deviation of 1.29. A comparison of viscosity obtained from the charts of Carr et al and the equation of Lee et al with Nigerian PVT Viscosity showed that the new equation gave more accurate result. Since some Correlations perform better when applied to data from which they were derived, a further comparison test was performed. In this test, the new equation was used to solve two problems for which solutions by the method of Carr et al were available. The first problem from the Handbook of Natural Gas Engineering by Katz et al gave a viscosity of 1.158cp while the new equation gave 1.157cp. The second problem from Ikoku’s book (Natural Gas Production Engineering) gave a viscosity of 1.178cp and the new equation also gave 1.178cp. This closeness of the viscosity of the new equation to the values from the Carr et al method proved the applicability of the new equation to any type of Natural Gas.
Authors: Duk Young Jung, Yu Bong Kang, Toshie Tsuchiya, Sadami Tsutsumi
Abstract: Accurate measurement of the mechanical properties of artificial or cultivated cartilage is a major factor for determining successive regeneration of defective soft tissues. In this study, we developed a novel method that enabled the bulk modulus (k-modulus) to be measured nondestructively using the relationship between volume and pressure of living soft tissues. In order to validate this method we estimated the bulk modulus of soft silicone rubbers using our new method and a conventional method. The results showed a 5 ~ 10% difference between the results obtained with the two methods. Our method was used subsequently to measure the mechanical properties of cultivated cartilage samples (collagen gel type), that had been incubated for four weeks in the presence or absence of human articular chondrocytes (HACs). Our experiments showed that cultivated cartilage tissues grown in the presence of HACs had a higher bulk modulus (120 ± 20 kPa) than samples grown without HACs (90 ± 15 kPa). The results indicated that our novel method offered an effective method for measurement of volume changes in minute living soft tissues, with the measurements having a high degree of accuracy and precision. Furthermore, this method has significant advantages over conventional approaches as it can be used to rapidly and accurately evaluate the strength of soft tissues during cultivation without causing damage to the specimen.
Authors: Mohammad Mahdi Doustdar, Mohammad Mojtahedpoor
Abstract: The size of fuel propulsive droplets is one of the effective parameter in improvement of the mixture of air and fuel as well as combustion. The effects of Pressure on the average diameter of fuel propulsive droplets sizing and effective mass fraction in a duct are numerically investigated in the present paper. We named the mass of fuel vapor inside the flammability limit as the efficient mass fraction. The inlet pressure of entrance airflow is varied as 1, 2, 3, 4 and 5 (atm) to examine its effects on the fuel droplets and fuel/air mixing phenomena. As well, by growing the entrance air flow velocity from 36 to 50 (m/s) we have repeated this test again, which provides worthwhile information for the combustor design work. To fulfill the calculations a modified version of KIVA-3V code which is a transient, three-dimensional, multiphase, multicomponent code for the analysis of chemically reacting flows with sprays, is used.
Authors: S.S.M. Nor, Mujibur M. Rahman, A. T. A. Rahman, F. Tarlochan, H. Y. Rahman
Abstract: The strength of a green compacts formed through warm powder compaction route is strongly dependent on the forming load and temperature. As the forming load increases, the powder particles move from its initial position by sliding among them and die wall. This movement results in new arrangement and packing order of the particles. However, due to this movement, pores among the particles are generated that affects the mechanical properties of the green compacts. Having pores in green compacts lead to strain intensification at ligaments between pores during sintering at later stage, hence serve as areas for crack initiation. Therefore, as the powder forming relates directly to the load and temperature, strength to porosity relationship has to be analyzed based on those parameters. This paper presents the effect of porosity to the strength of green compacts formed at different load and temperature (70 kN to 130 kN; 30°C to 200°C). The bending strengths of green compacts are measured while Scanning Electron Microscopy is used for porosity evaluation. It has been found from the results that porosity and strength are related to each other at all forming parameters. In addition, high forming load and temperature give better strength due to porosity reduction.
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