Shao, Yongliang; Zhang, Lei; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Tian, Yuan; Huo, Qin
2014-08-05
We report a method to obtain the stress of crystalline materials directly from lattice deformation by Hooke's law. The lattice deformation was calculated using the crystallographic orientations obtained from electron backscatter diffraction (EBSD) technology. The stress distribution over a large area was obtained efficiently and accurately using this method. Wurtzite structure gallium nitride (GaN) crystal was used as the example of a hexagonal crystal system. With this method, the stress distribution of a GaN crystal was obtained. Raman spectroscopy was used to verify the stress distribution. The cause of the stress distribution found in the GaN crystal was discussed from theoretical analysis and EBSD data. Other properties related to lattice deformation, such as piezoelectricity, can also be analyzed by this novel approach based on EBSD data.
Wetzler, N.; Kurzon, I.; Rosenthal, M.; Segev, A.; Rybakov, M.; Ben-Avraham, Z.; Lyakhovsky, V.
2015-12-01
We study the relationship between crustal structure, tectonic slip, and seismicity. A detailed 3-D layered crustal model is constructed including the geometry and mechanical properties of the main geological units of the study area, Northern Israel and its surrounding. Boundary condition of the 3-D model had been set according to the regional GPS measurements and including localized weak zones extrapolated from the mapped faults. The regional crustal model is converted to 1-D seismic velocity model that was applied in second order relocation software (hypoDD), to obtain more accurate earthquake location. We compare earthquake record of the past 30 years with areas of uplifted shear stress in the crustal model, and compare it with a reference 3-D model with flat layers and similar rock properties. Numerical simulation shows spatial distribution of the zones with increased shear stress associated with differential gravitational load, weak zones geometry, and tectonic load. The obtained zones with high stress are well correlated with earthquake locations. Our results and interpretation highlight the importance and advantages of utilizing detailed crustal structure for assessment of regional seismic hazards.
Equivalence of Stress and Energy Calculations of Mean Stress
Pedersen, Ole Bøcker; Brown, L. M.
1977-01-01
Calculations of the mean stress in a plastically deformed matrix containing randomly distributed elastic inclusions are considered. The mean stress for an elastically homogeneous material is calculated on the basis of an energy consideration which completely accounts for elastic interactions....... The result is shown to be identical to that obtained from a stress calculation. The possibility of including elastic interactions in the case of elastic inhomogeneity is discussed....
Calculation and analysis of stress in strata under gob pillars
杨敬轩; 刘长友; 于斌; 吴锋锋
2015-01-01
Aiming at the difficulty in stress analysis for strata under pillars with actual bearing conditions, an approach was proposed to apply multi-sectional linear approximation to the characteristic curves of pillar loads, and stress of strata was calculated under pillars with linear load by calculation method for uniform load. This approach leads to a rapid analyzing method for strata stress under pillars with any form of loads. Through theoretical analysis, strata stress expressions for pillars under linear bearing conditions are obtained. In addition, two concepts, stress increase factor and stress factor, are proposed for the approximate analysis of strata stress by uniform load approximation method. It is also found that the stress increase factor of strata is related to the strata stress factor and the ratio of the minimum load on the pillar’ two ends to the maximum one;and the distribution features of stress factors and the sizes of their influencing areas in strata influenced by overlying pillars are obtained. Combining with the gob pillar conditions of Jurassic coal seam in Tongxin Coal Mine, it is demonstrated that the results obtained by stress distribution analysis of the strata stress in non-influencing areas of pillars with linear bearing through uniform load approximation are in basic accordance with the results obtained for pillars under linear bearing condition. Therefore, it is feasible and accurate to calculate stress in non-influencing area in strata under pillars with linear bearing condition by uniform load calculation method.
Calculation Methods for Wallenius’ Noncentral Hypergeometric Distribution
Fog, Agner
2008-01-01
distribution are derived. Range of applicability, numerical problems, and efficiency are discussed for each method. Approximations to the mean and variance are also discussed. This distribution has important applications in models of biased sampling and in models of evolutionary systems....... is the conditional distribution of independent binomial variates given their sum. No reliable calculation method for Wallenius' noncentral hypergeometric distribution has hitherto been described in the literature. Several new methods for calculating probabilities from Wallenius' noncentral hypergeometric...
METHOD FOR CALCULATION OF STRESSED STATE SUBSTANTIATED BY DYNAMIC MICROTWIN
V. V. Vlashevich
2014-01-01
Full Text Available Method for calculation of the stressed state in a dynamic twin has been developed on the basis of a non-thin non-coherent micro-twin model with continuous distribution of twinning dislocations at twin boundaries. In this case there is no additional generation with the help of twinning dislocation source. The model takes into account that the twin has coherent and noncoherent boundary sections. The developed model has made it possible to take into consideration a form of non-coherent sections of twinning boundaries in calculations of stressed and deformed state at dynamic twins. It has been established that localized stresses are migrating together with non-coherent sections of the twin. Normal stresses σxx change their sign in relation to direction of the twin development. Shear stresses σxy are alternating in signs in relation to an axis which is perpendicular to the direction of the twin development and which is passing through a mid-point of non-coherent twin section. Distribution of stresses σyy и σyz has similar configuration. Stresses σzx in the second and fourth quarters of XOY plane are negative and the stresses in the first and third quarters are positive. Distribution of stresses σzz practically does not differ from distribution of stresses σyy according to configuration but numerical values of stress tensor component data are different.The results have been obtained without thin twin model that permits to consider only elastic stage of the twinning process. The executed stress calculations at dynamic twin are important for forecasting at the accumulation stage of damage origination which is caused by twinning destruction and permit to improve forecasting accuracy of technical system resources on the basis of twinning materials such as alloys based on iron, copper, zinc, aluminium, titanium.
A Lattice Calculation of Parton Distributions
Alexandrou, Constantia; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian
2016-01-01
We present results for the $x$ dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. Compared to a previous calculation by us, the errors are reduced by a factor of about 2.5. Moreover, we present our first results for the polarized sector of the proton, which indicate an asymmetry in the proton sea in favor of the $u$ antiquarks for the case of helicity distributions, and an asymmetry in favor of the $d$ antiquarks for the case of transversity distributions.
A lattice calculation of parton distributions
Alexandrou, Constantia [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Poznann Univ. (Poland). Faculty of Physics; Hadjiyiannakou, Kyriakos [George Washington Univ., Washington, DC (United States). Dept. of Physics; Jansen, Karl; Steffens, Fernanda; Wiese, Christian [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2016-09-15
We present results for the x dependence of the unpolarized, helicity, and transversity isovector quark distributions in the proton using lattice QCD, employing the method of quasi-distributions proposed by Ji in 2013. Compared to a previous calculation by us, the errors are reduced by a factor of about 2.5. Moreover, we present our first results for the polarized sector of the proton, which indicate an asymmetry in the proton sea in favor of the u antiquarks for the case of helicity distributions, and an asymmetry in favor of the d antiquarks for the case of transversity distributions.
Calculation of the fatigue life distribution of a composite laminate
Anderson, IA.A.; Limonov, V.A. (AN LSSR, Institut Mekhaniki Polimerov, Riga, Latvian (USSR))
1991-02-01
A method based on a probabilistic interpretation of the Hashin criterion is proposed for calculating the fatigue life distributions of a unidirectional composite under conditions of a plane stressed state from test results obtained for simple loading schemes. By using the linear damage accumulation law, an estimate is obtained of the scatter of the composite fatigue life related to the scatter of the material fatigue strength. A procedure is then presented for estimating the fatigue life distribution of a composite laminate in the plane stressed state based on layer-by-layer fracture analysis using the linear damage summation law and the determining layer concept. 26 refs.
Calculating Cumulative Binomial-Distribution Probabilities
Scheuer, Ernest M.; Bowerman, Paul N.
1989-01-01
Cumulative-binomial computer program, CUMBIN, one of set of three programs, calculates cumulative binomial probability distributions for arbitrary inputs. CUMBIN, NEWTONP (NPO-17556), and CROSSER (NPO-17557), used independently of one another. Reliabilities and availabilities of k-out-of-n systems analyzed. Used by statisticians and users of statistical procedures, test planners, designers, and numerical analysts. Used for calculations of reliability and availability. Program written in C.
Numerical calculation of impurity charge state distributions
Crume, E. C.; Arnurius, D. E.
1977-09-01
The numerical calculation of impurity charge state distributions using the computer program IMPDYN is discussed. The time-dependent corona atomic physics model used in the calculations is reviewed, and general and specific treatments of electron impact ionization and recombination are referenced. The complete program and two examples relating to tokamak plasmas are given on a microfiche so that a user may verify that his version of the program is working properly. In the discussion of the examples, the corona steady-state approximation is shown to have significant defects when the plasma environment, particularly the electron temperature, is changing rapidly.
A Lattice Calculation of Parton Distributions
Alexandrou, Constantia [Cyprus Univ. Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus); Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Drach, Vincent [Univ. of Southern Denmark, Odense (Denmark). CP3-Origins; Univ. of Southern Denmark, Odense (Denmark). Danish IAS; Garcia-Ramos, Elena [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Hadjiyiannakou, Kyriakos [Cyprus Univ. Nicosia (Cyprus). Dept. of Physics; Jansen, Karl; Steffens, Fernanda; Wiese, Christian [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2015-04-15
We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using N{sub f}=2+1+1 twisted mass fermions with a pion mass of about 370 MeV. The focus of this work is a detailed description of the computation, including the lattice calculation, the matching to an infinite momentum and the nucleon mass correction. In addition, we test the effect of gauge link smearing in the operator to estimate the influence of the Wilson line renormalization, which is yet to be done.
A Lattice Calculation of Parton Distributions
Alexandrou, Constantia; Drach, Vincent; Garcia-Ramos, Elena; Hadjiyiannakou, Kyriakos; Jansen, Karl; Steffens, Fernanda; Wiese, Christian
2015-01-01
We report on our exploratory study for the direct evaluation of the parton distribution functions from lattice QCD, based on a recently proposed new approach. We present encouraging results using Nf = 2 + 1 + 1 twisted mass fermions with a pion mass of about 370 MeV. The focus of this work is a detailed description of the computation, including the lattice calculation, the matching to an infinite momentum and the nucleon mass correction. In addition, we test the effect of gauge link smearing in the operator to estimate the influence of the Wilson line renormalization, which is yet to be done.
Calculation of dose distribution above contaminated soil
Kuroda, Junya; Tenzou, Hideki; Manabe, Seiya; Iwakura, Yukiko
2017-07-01
The purpose of this study was to assess the relationship between altitude and the distribution of the ambient dose rate in the air over soil decontamination area by using PHITS simulation code. The geometry configuration was 1000 m ×1000 m area and 1m in soil depth and 100m in altitude from the ground to simulate the area of residences or a school grounds. The contaminated region is supposed to be uniformly contaminated by Cs-137 γ radiation sources. The air dose distribution and space resolution was evaluated for flux of the gamma rays at each altitude, 1, 5, 10, and 20m. The effect of decontamination was calculated by defining sharpness S. S was the ratio of an average flux and a flux at the center of denomination area in each altitude. The suitable flight altitude of the drone is found to be less than 15m above a residence and 31m above a school grounds to confirm the decontamination effect. The calculation results can be a help to determine a flight planning of a drone to minimize the clash risk.
Distributed Function Calculation over Noisy Networks
Zhidun Zeng
2016-01-01
Full Text Available Considering any connected network with unknown initial states for all nodes, the nearest-neighbor rule is utilized for each node to update its own state at every discrete-time step. Distributed function calculation problem is defined for one node to compute some function of the initial values of all the nodes based on its own observations. In this paper, taking into account uncertainties in the network and observations, an algorithm is proposed to compute and explicitly characterize the value of the function in question when the number of successive observations is large enough. While the number of successive observations is not large enough, we provide an approach to obtain the tightest possible bounds on such function by using linear programing optimization techniques. Simulations are provided to demonstrate the theoretical results.
王衡; 陈廷国
2016-01-01
According to the elastic analysis of rectangular hole castellated beams by using the finite element software ANSYS, the stress distribution of castellated beams was studied, which mainly included normal stress and shearing stress distribution of pier cross section, normal stress distribution of pier longitudinal section and normal stress distribution of beam bridge. In addition, the factors affecting the normal stress and shearing stress distribution of the center of pier cross section were studied in detail, which contained span-depth ratio, width-depth ratio, length-depth ratio and space-depth ratio. The research could provide reference for engineer-ing design.%通过有限元软件ANSYS对矩形孔蜂窝梁进行弹性分析，研究蜂窝梁应力分布规律，主要包括桥墩横截面正应力和剪应力分布、桥墩纵截面正应力分布及梁桥横截面正应力分布。另外，详细研究了跨高比、孔高比、长高比和距高比等因素对墩心横截面正应力和剪应力分布的影响。
Core stress distribution of phase shifting multimode polymer optical fiber
Furukawa, Rei, E-mail: furukawa@ee.uec.ac.jp; Matsuura, Motoharu [Center for Frontier Science and Engineering, The University of Electro-Communications, Chofugaoka 1-5-1, Chofu, Tokyo 182-8585 (Japan); Nagata, Morio; Mishima, Kenji [Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo 153-8904 (Japan); Inoue, Azusa; Tagaya, Akihiro; Koike, Yasuhiro [Keio Photonics Research Institute, Keio University, Saiwaiku Shinkawasaki 7-1, Kawasaki, Kanagawa 212-0032 (Japan)
2013-11-18
Poly-(methyl methacrylate-co-benzyl methacrylate) polarization-maintaining optical fibers are known for their high response to normal stress. In this report, responses to higher stress levels up to 0.45 MPa were investigated. The stress amplitude and direction in the fiber cross section were calculated and analyzed with a coincident mode-field obtained from the near-field pattern. The stress amplitude varies significantly in the horizontal direction and is considered to create multiple phases, explaining the measurement results. To investigate possible permanent deformation, the core yield point profile was analyzed. Although it largely exceeds the average applied stress, the calculated stress distribution indicates that the core could partially experience stress that exceeds the yield point.
无
2000-01-01
The stress fields induced by a dislocation and its image dislocations around a narrow elliptic void are formulated. Based on the solution, the stress distribution and effective stress intensity factor of a blunt (elliptic) crack were calculated under mode I constant loading. The results show that a dislocation-free zone (DFZ) is formed after dislocation emission. There exists a second stress peak in the DFZ except a stress peak at the blunt crack tip. With an increase in the applied stress intensity factor KIa or the friction stress τf of the material, the DFZ size and the peak stress at the crack tip decrease, but the peak stress in the DFZ and the effective stress intensity factor KIf presiding at the crack tip increase. Because of dislocation shielding effects, shielding ratio KIa/KIf increases with increasing KIa}, but it decreases with increasing τf.
钱才富; 乔利杰; 褚武扬
2000-01-01
The stress fields induced by a dislocation and its image dislocations around a narrow elliptic void are formulated. Based on the solution, the stress distribution and effective stress intensity factor of a blunt (elliptic) crack were calculated under mode I constant loading. The results show that a dislocation-free zone (DFZ) is formed after dislocation emission. There exists a second stress peak in the DFZ except a stress peak at the blunt crack tip. With an increase in the applied stress intensity factor Kla or the friction stress T, of the material, the DFZ size and the peak stress at the crack tip decrease, but the peak stress in the DFZ and the effective stress intensity factor Klf presiding at the crack tip increase. Because of dislocation shielding effects, shielding ratio Kla/Klf increases with increasing Kla, but it decreases with increasing Tf.
Hernandez R, Alejandro; Garcia I, Rafael; Mazur C, Zdislaw [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)
2004-07-01
The analysis begins with the generation of a computational geometric model of the gas turbine nozzle using reverse engineering techniques. For the obtaining of the original geometry of the blade, a measurement machine by coordinates and computerized numerical control was used. Next, the computational model is converted into a three-dimensional mesh. In advance, a study of boundary conditions was made of the nozzle material as well as of the turbine operating conditions during non-operating cycles, start-ups and shut-downs. On the other hand, with the boundary conditions imposed to the model, the distributions of the temperature and pressures on the aerofoil profile of the nozzle blade were calculated. These results had to be manipulated to be exported to a finite element software (ANSYS); at this point, another nozzle model was elaborated to be able to import the temperature distribution. With the temperatures correctly imported, the simulations for the calculation of the thermal stresses were made in the nozzle. [Spanish] El analisis inicia con la generacion de un modelo geometrico computacional de la tobera de la turbina de gas utilizando tecnicas de ingenieria inversa. Para la obtencion de la geometria original del alabe, se utilizo una maquina de medicion por coordenadas y control numerico computarizado. A continuacion, el modelo computacional es convertido en una malla tridimensional. Con antelacion, se realizo un estudio de las condiciones de frontera, tanto del material de la tobera como de las condiciones de operacion de la turbina, durante ciclos de paro, arranque y disparo. Por otra parte, con las condiciones de frontera impuestas al modelo, se calcularon las distribuciones de las temperaturas y presiones sobre el perfil aerodinamico de la paleta de la tobera. Estos resultados tuvieron que ser manipulados para ser exportados a un software de elemento finito (ANSYS); en este punto, se elaboro otro modelo de la tobera para poder importar la distribucion de
Stress distribution around mine workings
Gaidachuk, V. V.; Koshel', V. I.; Lugovoi, P. Z.
2011-02-01
The finite-element method is used to determine the stress state around arched mine workings in a mineral bed. Both presence and dip of the mineral bed have a strong effect on the stress state around the mine working. Recommendations for design of mine-working support are formulated
Stress Analysis and Calculation of Flow Interruption Capability Test Loop
FENG; Bo; QI; Xiao-guang; CHENG; Dao-xi
2012-01-01
<正>A stress-analysis and calculation has been done for the flow interruption capability test loop (Fig. 1). In the design condition, the test loop is operated on 350 ℃ and 20MPa. By reasonably simplifying and modeling, a stress-analysis program named Triflex was used to analyze the piping stress and optimize the piping supports, which meet the compliance. The work will provide the necessary basis for the construction of the loop and operation security.
Numerical calculation of ion runaway distributions
Embréus, Ola; Stahl, Adam; Hirvijoki, Eero; Fülöp, Tünde
2015-01-01
Ions accelerated by electric fields (so-called runaway ions) in plasmas may explain observations in solar flares and fusion experiments, however limitations of previous analytic work have prevented definite conclusions. In this work we describe a numerical solver of the 2D non-relativistic linearized Fokker-Planck equation for ions. It solves the initial value problem in velocity space with a spectral-Eulerian discretization scheme, allowing arbitrary plasma composition and time-varying electric fields and background plasma parameters. The numerical ion distribution function is then used to consider the conditions for runaway ion acceleration in solar flares and tokamak plasmas. Typical time scales and electric fields required for ion acceleration are determined for various plasma compositions, ion species and temperatures, and the potential for excitation of toroidal Alfv\\'en eigenmodes during tokamak disruptions is considered.
王学滨
2004-01-01
A method for calculation of temperature distribution in adiabatic shear band is proposed in terms of gradient-dependent plasticity where the characteristic length describes the interactions and interplaying among microstructures. First, the increment of the plastic shear strain distribution in adiabatic shear band is obtained based on gradient-dependent plasticity. Then, the plastic work distribution is derived according to the current flow shear stress and the obtained increment of plastic shear strain distribution. In the light of the well-known assumption that 90% of plastic work is converted into the heat resulting in increase in temperature in adiabatic shear band, the increment of the temperature distribution is presented. Next, the average temperature increment in the shear band is calculated to compute the change in flow shear stress due to the thermal softening effect. After the actual flow shear stress considering the thermal softening effect is obtained according to the Johnson-Cook constitutive relation, the increment of the plastic shear strain distribution, the plastic work and the temperature in the next time step are recalculated until the total time is consumed. Summing the temperature distribution leads to rise in the total temperature distribution. The present calculated maximum temperature in adiabatic shear band in titanium agrees with the experimental observations. Moreover, the temperature profiles for different flow shear stresses are qualitatively consistent with experimental and numerical results. Effects of some related parameters on the temperature distribution are also predicted.
Stress distribution in unstable austenitic steel
Kubler, R.; Inal, K.; Berveiller, M. [LPMM, UMR CNRS, ENSAM, Metz (France)
2002-07-01
Tensile tests performed on unstable austenitic material lead to formation of martensite. Therefore, plasticity and transformation occur at the same time leading to inelastic strain and consequently internal stresses. The present work focuses on the stress distribution in each phase of a two-phase material with an evolving microstructure. Experimental results based on X-ray diffraction are presented to give a trend of the evolution of stress distribution inside austenite and martensite during a tensile test at -60 C. After unloading, first results show compression in martensite and tension in austenite. It is also noticed that mechanical anisotropy is enhanced in both phases. (orig.)
Distribution of apparent stress in western China
吴忠良; 黄静; 林碧苍
2002-01-01
Distribution of apparent stress in Chinese mainland and its surrounding regions was presented using the NEIC broadband radiated energy catalogue and the Harvard CMT catalogue from January 1987 to December 1998. Due to the limitation on the number of samples, reliable results are only for the western China. It is observed that the average apparent stress in Chinese mainland is 0.8 MPa; The maximum apparent stress to the east of the Tibetan plateau is 2.6 MPa; And the average apparent stress in the north-south seismic belt is more than one time higher than its adjacent regions. Distribution pattern of apparent stress seems to have a large-scale correlation with the cumulative energy release level in the 20th century.
Distribution of Inherent Strains and Residual Stresses in Medium Thickness Plate Weldment
无
2001-01-01
A fundamental theory for the analysis of residual weldingstresses and deformation based on the inherent strain distribution along the welded joint is introduced. Distribution of inherent strains and longitudinal residual stresses in medium thickness plate weldment is calculated and analyzed.A new method of calculating inherent strains and longitudinal residual stresses is proposed.
Blade Group Fatigue Life Calculation under Resonant Stresses
Zlatko Petreski
2017-02-01
Full Text Available The results of the simulations of the blade group resonant stresses in a FE environment and fatigue life calculation are presented in this paper. Numerical calculation for determination of natural frequencies, mode shapes and dynamic stresses, based on FEM and NISA package is used. Analyses are made on the blade group with three blades with rectangular cross section and typical turbine blades with taper, pretwist and asymmetric airfoil as well. The influence of the position of the lacing wire on the resonant stresses is analyzed. Three-dimensional finite element models of the blade group are made by using twenty node isoparametric solid elements. The number of degrees of freedom is different for each model (more than 30000 DOF. The fatigue life and consequent life prediction according the stress load history of the blades is made. The results of the investigation are given in tables and graphics.
Coefficient of variation calculated from the range for skewed distributions.
Rhiel, G Steven
2006-02-01
In this research a coefficient of variation (CVS(high.low)) is developed that is calculated from the highest and lowest values in a set of data for samples from skewed distributions. A correction factor is determined such that CVS(high-low) is a dose estimate of the population coefficient of variation when sampling from three skewed chi-squared distributions and three skewed empirical distributions. The empirical distributions are from "real-world" data sets in psychology and education.
The Calculation of the Electrostatic Potential of Infinite Charge Distributions
Redzic, Dragan V.
2012-01-01
We discuss some interesting aspects in the calculation of the electrostatic potential of charge distributions extending to infinity. The presentation is suitable for the advanced undergraduate level. (Contains 3 footnotes.)
Residual stress distribution in rabbit limb bones.
Yamada, Satoshi; Tadano, Shigeru; Fujisaki, Kazuhiro
2011-04-29
The presence of the residual stresses in bone tissue has been noted and the authors have reported that there are residual stresses in bone tissue. The aim of our study is to measure the residual stress distribution in the cortical bone of the extremities of vertebrates and to describe the relationships with the osteon population density. The study used the rabbit limb bones (femur, tibia/fibula, humerus, and radius/ulna) and measured the residual stresses in the bone axial direction at anterior and posterior positions on the cortical surface. The osteons at the sections at the measurement positions were observed by microscopy. As a result, the average stresses at the hindlimb bones and the forelimb bones were 210 and 149 MPa, respectively. In the femur, humerus, and radius/ulna, the residual stresses at the anterior position were larger than those at the posterior position, while in the tibia, the stress at the posterior position was larger than that at the anterior position. Further, in the femur and humerus, the osteon population densities in the anterior positions were larger than those in the posterior positions. In the tibia, the osteon population density in the posterior position was larger than that in the anterior position. Therefore, tensile residual stresses were observed at every measurement position in the rabbit limb bones and the value of residual stress correlated with the osteon population density (r=0.55, P<0.01).
Macro design effects on stress distribution around implants: A photoelastic stress analysis
Serhat Emre Ozkir
2012-01-01
Conclusion: As there were observable differences between the implant types, straight placed cylindrical implants showed better stress distribution characteristics, while inclined tapering implants had better stress distribution characteristics.
Analytical stress tensor and pressure calculations with the CRYSTAL code
Doll, K.
2010-02-01
The calculation of the stress tensor and related properties and its implementation in the CRYSTAL code are described. The stress tensor is obtained from the earlier implemented analytical gradients with respect to the cell parameters. Subsequently, the pressure and enthalpy are computed, and a test concerning the pressure-driven phase transition in KI is used as an illustration. Finally, the possibility of applying external pressure is implemented. The constant-pressure optimization offers an alternative optimization method in addition to the already implemented optimization at constant volume.
Practical methods of calculating the autoclaves’ thermal stresses at building industry
A. A. Kozhukhar
2015-06-01
Full Text Available The study is devoted to elaboration of a simplified method for calculation of stresses arising in the autoclaves’ casing in the case of nonlinear distribution of temperature field on its cross section height. The piece-nonlinear function is applied to the temperature field of autoclaves as maximally corresponding to experimental results. On the basis of flat sections hypothesis an expression for temperature stresses is obtained. The analysis of their distribution by the autoclave casing height is made. The control test confirmed a sufficient efficiency of the offered method for engineering needs.
Shan Yang
2016-01-01
Full Text Available Power flow calculation and short circuit calculation are the basis of theoretical research for distribution network with inverter based distributed generation. The similarity of equivalent model for inverter based distributed generation during normal and fault conditions of distribution network and the differences between power flow and short circuit calculation are analyzed in this paper. Then an integrated power flow and short circuit calculation method for distribution network with inverter based distributed generation is proposed. The proposed method let the inverter based distributed generation be equivalent to Iθ bus, which makes it suitable to calculate the power flow of distribution network with a current limited inverter based distributed generation. And the low voltage ride through capability of inverter based distributed generation can be considered as well in this paper. Finally, some tests of power flow and short circuit current calculation are performed on a 33-bus distribution network. The calculated results from the proposed method in this paper are contrasted with those by the traditional method and the simulation method, whose results have verified the effectiveness of the integrated method suggested in this paper.
Finite element calculation of residual stress in dental restorative material
Grassia, Luigi; D'Amore, Alberto
2012-07-01
A finite element methodology for residual stresses calculation in dental restorative materials is proposed. The material under concern is a multifunctional methacrylate-based composite for dental restorations, activated by visible light. Reaction kinetics, curing shrinkage, and viscoelastic relaxation functions were required as input data on a structural finite element solver. Post cure effects were considered in order to quantify the residual stresses coming out from natural contraction with respect to those debited to the chemical shrinkage. The analysis showed for a given test case that residual stresses frozen in the dental restoration at uniform temperature of 37°C are of the same order of magnitude of the strength of the dental composite material per se.
Use of unbound volumes of drug distribution in pharmacokinetic calculations.
Stepensky, David
2011-01-18
Volume of drug distribution is a primary pharmacokinetic parameter. This study assessed effects of drugs' plasma protein binding and tissue distribution on volume of drug distribution and identified the most appropriate ways for its calculation. Effects of the distribution factors on the unbound and total drug plasma concentrations and on the corresponding volumes of distribution were studied using pharmacokinetic modeling and simulation approach based on in vitro and in vivo concentration vs. time data of diazepam, a model drug with extensive plasma protein binding and tissue distribution. Pharmacokinetics of diazepam were appropriately described by three-compartment pharmacokinetic model that incorporated the processes of plasma protein binding and tissue permeation. According to this model, displacement of the drug from plasma proteins increases the unbound (but not the total) plasma concentrations and induces faster drug elimination from the body. The distribution pattern of the drug in the body and the time course of unbound (pharmacologically active) drug concentrations correlated with the unbound volumes of distribution, but not with the total volumes of distribution. In conclusion, unbound volumes of distribution appropriately describe the drug distribution pattern and the time course of unbound drug concentrations and are recommended for use as primary pharmacokinetic parameters in pharmaceutical research. Copyright © 2010 Elsevier B.V. All rights reserved.
Significance of stress transfer in time-dependent earthquake probability calculations
Parsons, T.
2005-01-01
A sudden change in stress is seen to modify earthquake rates, but should it also revise earthquake probability? Data used to derive input parameters permits an array of forecasts; so how large a static stress change is require to cause a statistically significant earthquake probability change? To answer that question, effects of parameter and philosophical choices are examined through all phases of sample calculations, Drawing at random from distributions of recurrence-aperiodicity pairs identifies many that recreate long paleoseismic and historic earthquake catalogs. Probability density funtions built from the recurrence-aperiodicity pairs give the range of possible earthquake forecasts under a point process renewal model. Consequences of choices made in stress transfer calculations, such as different slip models, fault rake, dip, and friction are, tracked. For interactions among large faults, calculated peak stress changes may be localized, with most of the receiving fault area changed less than the mean. Thus, to avoid overstating probability change on segments, stress change values should be drawn from a distribution reflecting the spatial pattern rather than using the segment mean. Disparity resulting from interaction probability methodology is also examined. For a fault with a well-understood earthquake history, a minimum stress change to stressing rate ratio of 10:1 to 20:1 is required to significantly skew probabilities with >80-85% confidence. That ratio must be closer to 50:1 to exceed 90-95% confidence levels. Thus revision to earthquake probability is achievable when a perturbing event is very close to the fault in question or the tectonic stressing rate is low.
Significance of stress transfer in time-dependent earthquake probability calculation
Parsons, T.
2004-12-01
A sudden change in stress is seen to modify earthquake rates, but should it also revise earthquake probability? Data used to derive input parameters permit an array of forecasts; so how large a static stress change is required to cause a statistically significant earthquake probability change? To answer that question, effects of parameter and philosophical choices are examined through all phases of sample calculations. Drawing at random from distributions of recurrence-aperiodicity pairs identifies many that recreate long paleoseismic and historic earthquake catalogs. Probability-density functions built from the recurrence-aperiodicity pairs give the range of possible earthquake forecasts under a point-process renewal model. Consequences of choices made in stress-transfer calculations, such as different slip models, fault rake, dip and friction are tracked. For interactions among large faults, calculated peak stress changes may be localized, with most of the receiving fault area changed less than the mean. Thus to avoid overstating probability change on segments, stress-change values should be drawn from a distribution reflecting the spatial pattern rather than using the segment mean. Disparity resulting from interaction probability methodology is also examined. For a fault with a well-understood earthquake history, a minimum stress-change to stressing-rate ratio of 10:1 to 20:1 is required to significantly skew probabilities with >80-85% confidence. That ratio must be closer to 50:1 to exceed 90-95% confidence levels. Thus revision to earthquake probability is achievable when a perturbing event is very close to the fault in question, or the tectonic stressing rate is low.
Calculating fusion neutron energy spectra from arbitrary reactant distributions
Eriksson, J.; Conroy, S.; Andersson Sundén, E.; Hellesen, C.
2016-02-01
The Directional Relativistic Spectrum Simulator (DRESS) code can perform Monte-Carlo calculations of reaction product spectra from arbitrary reactant distributions, using fully relativistic kinematics. The code is set up to calculate energy spectra from neutrons and alpha particles produced in the D(d, n)3He and T(d, n)4He fusion reactions, but any two-body reaction can be simulated by including the corresponding cross section. The code has been thoroughly tested. The kinematics calculations have been benchmarked against the kinematics module of the ROOT Data Analysis Framework. Calculated neutron energy spectra have been validated against tabulated fusion reactivities and against an exact analytical expression for the thermonuclear fusion neutron spectrum, with good agreement. The DRESS code will be used as the core of a detailed synthetic diagnostic framework for neutron measurements at the JET and MAST tokamaks.
How to calculate stress in above/below ground transition
Schnackenberg, P.J.
1976-11-01
Stresses and deflections occur in natural gas pipe lines at the transition from the below ground (fully restrained) to the above ground (unrestrained) condition. Analysis of the stresses and deflections in transition areas, resulting from internal pressure/temperature change, is necessary in determining anchor block requirements and design. Longitudinal deflections are used to determine whether an anchor block is required. Anchor block forces required to maintain the pipe in a fully constrained condition are then determined. A brief review of the analysis that resulted in more accurate solutions for deflection and anchor block forces is presented. Sample calculations are given for line sizes up to 41-cm OD, pressure to 193 bars, and temperatures to 72/sup 0/C. (JRD)
Wall shear stress distributions on stented patent ductus arteriosus
Kori, Mohamad Ikhwan; Jamalruhanordin, Fara Lyana; Taib, Ishkrizat; Mohammed, Akmal Nizam; Abdullah, Mohammad Kamil; Ariffin, Ahmad Mubarak Tajul; Osman, Kahar
2017-04-01
A formation of thrombosis due to hemodynamic conditions after the implantation of stent in patent ductus arteriosus (PDA) will derived the development of re-stenosis. The phenomenon of thrombosis formation is significantly related to the distribution of wall shear stress (WSS) on the arterial wall. Thus, the aims of this study is to investigate the distribution of WSS on the arterial wall after the insertion of stent. Three dimensional model of patent ductus arteriosus inserted with different types of commercial stent are modelled. Computational modelling is used to calculate the distributions of WSS on the arterial stented PDA. The hemodynamic parameters such as high WSS and WSSlow are considered in this study. The result shows that the stented PDA with Type III stent has better hemodynamic performance as compared to others stent. This model has the lowest distributions of WSSlow and also the WSS value more than 20 dyne/cm2. From the observed, the stented PDA with stent Type II showed the highest distributions area of WSS more than 20 dyne/cm2. This situation revealed that the high possibility of atherosclerosis to be developed. However, the highest distribution of WSSlow for stented PDA with stent Type II indicated that high possibility of thrombosis to be formed. In conclusion, the stented PDA model calculated with the lowest distributions of WSSlow and WSS value more than 20dyne/cm2 are considered to be performed well in stent hemodynamic performance as compared to other stents.
Parsons, T.
2002-01-01
The M = 7.8 1906 San Francisco earthquake cast a stress shadow across the San Andreas fault system, inhibiting other large earthquakes for at least 75 years. The duration of the stress shadow is a key question in San Francisco Bay area seismic hazard assessment. This study presents a three-dimensional (3-D) finite element simulation of post-1906 stress recovery. The model reproduces observed geologic slip rates on major strike-slip faults and produces surface velocity vectors comparable to geodetic measurements. Fault stressing rates calculated with the finite element model are evaluated against numbers calculated using deep dislocation slip. In the finite element model, tectonic stressing is distributed throughout the crust and upper mantle, whereas tectonic stressing calculated with dislocations is focused mostly on faults. In addition, the finite element model incorporates postseismic effects such as deep afterslip and viscoelastic relaxation in the upper mantle. More distributed stressing and postseismic effects in the finite element model lead to lower calculated tectonic stressing rates and longer stress shadow durations (17-74 years compared with 7-54 years). All models considered indicate that the 1906 stress shadow was completely erased by tectonic loading no later than 1980. However, the stress shadow still affects present-day earthquake probability. Use of stressing rate parameters calculated with the finite element model yields a 7-12% reduction in 30-year probability caused by the 1906 stress shadow as compared with calculations not incorporating interactions. The aggregate interaction-based probability on selected segments (not including the ruptured San Andreas fault) is 53-70% versus the noninteraction range of 65-77%.
The Two Defaults Scenario for Stressing Credit Portfolio Loss Distributions
Dirk Tasche
2015-12-01
Full Text Available The impact of a stress scenario of default events on the loss distribution of a credit portfolio can be assessed by determining the loss distribution conditional on these events. While it is conceptually easy to estimate loss distributions conditional on default events by means of Monte Carlo simulation, it becomes impractical for two or more simultaneous defaults as then the conditioning event is extremely rare. We provide an analytical approach to the calculation of the conditional loss distribution for the CreditRisk + portfolio model with independent random loss given default distributions. The analytical solution for this case can be used to check the accuracy of an approximation to the conditional loss distribution whereby the unconditional model is run with stressed input probabilities of default (PDs. It turns out that this approximation is unbiased. Numerical examples, however, suggest that the approximation may be seriously inaccurate but that the inaccuracy leads to overestimation of tail losses and, hence, the approach errs on the conservative side.
Calculation of residual stresses by means of a 3D numerical weld simulation
Nicak, Tomas; Huemmer, Matthias [AREVA NP GmbH, Postfach 1109 (Germany)
2008-07-01
The numerical weld simulation has developed very fast in recent years. The problem complexity has increased from simple 2D models to full 3D models, which can describe the entire welding process more realistically. As recent research projects indicate, a quantitative assessment of the residual stresses by means of a 3D analysis is possible. The structure integrity can be assessed based on the weld simulation results superimposed with the operating load. Moreover, to support the qualification of welded components parametric studies for optimization of the residual stress distribution in the weld region can be performed. In this paper a full 3D numerical weld simulation for a man-hole drainage nozzle in a steam generator will be presented. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical FE analysis. The paper will present a robust procedure allowing reasonable predictions of the residual stresses for complex structures in industrial practice. (authors)
Reynolds shear stress and heat flux calculations in a fully developed turbulent duct flow
Antonia, R. A.; Kim, J.
1991-01-01
The use of a modified form of the Van Driest mixing length for a fully developed turbulent channel flow leads to mean velocity and Reynolds stress distributions that are in close agreement with data obtained either from experiments or direct numerical simulations. The calculations are then extended to a nonisothermal flow by assuming a constant turbulent Prandtl number, the value of which depends on the molecular Prandtl number. Calculated distributions of mean temperature and lateral heat flux are in reasonable agreement with the simulations. The extension of the calculations to higher Reynolds numbers provides some idea of the Reynolds number required for scaling on wall variables to apply in the inner region of the flow.
Analytical model and application of stress distribution on mining coal floor
ZHU Shu-yun; JIAN Zhen-quan; HOU Hong-liang; XIAO Wei-guo; YAO Pu
2008-01-01
Given the analysis of underground pressure, a stress calculation model of coal floor stress has been established based on a theory of elasticity. The model presents the law of stress distribution on the relatively fixed position of the mining coal floor: the extent of stress variation in a fixed floor position decreases gradually along with depth, the decreasing rate of the vertical stress is clearly larger than that of the horizontal stress at a specific depth. The direction of the maximum principal stress changes gradually from a vertical direction to a horizontal direction with the advance of the working face. The deformation and permeability of the rock mass of the coal floor are obtained by contrasting the difference of the principal stress established from theoretical calculations with curves of stress-strain and permeability-strain from tests, which is an important mechanical basis for preventing water inrush from confined aquifers.
Parsons, T.
2009-12-01
After a large earthquake, our concern immediately moves to the likelihood that another large shock could be triggered, threatening an already weakened building stock. A key question is whether it is best to map out Coulomb stress change calculations shortly after mainshocks to potentially highlight the most likely aftershock locations, or whether it is more prudent to wait until the best information is available. It has been shown repeatedly that spatial aftershock patterns can be matched with Coulomb stress change calculations a year or more after mainshocks. However, with the onset of rapid source slip model determinations, the method has produced encouraging results like the M=8.7 earthquake that was forecast using stress change calculations from 2004 great Sumatra earthquake by McCloskey et al. [2005]. Here, I look back at two additional prospective calculations published shortly after the 2005 M=7.6 Kashmir and 2008 M=8.0 Wenchuan earthquakes. With the benefit of 1.5-4 years of additional seismicity, it is possible to assess the performance of rapid Coulomb stress change calculations. In the second part of the talk, within the context of the ongoing Working Group on California Earthquake Probabilities (WGCEP) assessments, uncertainties associated with time-dependent probability calculations are convolved with uncertainties inherent to Coulomb stress change calculations to assess the strength of signal necessary for a physics-based calculation to merit consideration into a formal earthquake forecast. Conclusions are as follows: (1) subsequent aftershock occurrence shows that prospective static stress change calculations both for Kashmir and Wenchuan examples failed to adequately predict the spatial post-mainshock earthquake distributions. (2) For a San Andreas fault example with relatively well-understood recurrence, a static stress change on the order of 30 to 40 times the annual stressing rate would be required to cause a significant (90%) perturbation to the
Calculation and Analysis of Temperature Distribution in Hot Rolling Strip
Kaixiang Peng
2013-07-01
Full Text Available Modern steel grades require constant and reproducible production conditions both in the hot strip mill and in the cooling section to achieve constant material properties along the entire strip length and from strip to strip. Calculation of the temperature in final rolling process always utilizes factors such as the work piece's inner organizational structure, plastic deformation, and it's variations of properties and so on, also as well as the physical parameters such as gauge, shape, etc. In this paper, a finite element model is constructed for the temperature field in a rolling process. The temperature field of strip steel is modeled with a 3-D finite element analysis (FEA structure, simultaneously considering the distribution of the work roll temperature. Then the distribution of field is simulated numerically. From the model, the temperature contours can be obtained by analysis of the temperature distribution of contact area. At the same time, the distribution of temperature in any position at any time can be acquired. These efforts provide the reliable parameters for the later finishing temperature and shape control.
张波; 李玉坤; 井荣娟
2015-01-01
The pressure reducing valve with complicated structure is prone to having the issues of uncoordinated deformation and severe stress concentration under working pressure conditions, leading to issues like valve body fail⁃ure, reduced service life and gas leaks�To address the issue, taking RMG530 valve as the study object, numerical simulations have been conducted on the valve body and the fluids in the valve based on the actual working condi⁃tions�The results show that, under adiabatic condition, thermal stress dominates the coupled stress�The maximum stress is located at the orifice of valve cage with the value of 180 MPa�The valve bush has the maximum stress of 126 MPa�Under heating condition, the internal pressure dominates the coupled stress�The maximum stress from the inlet tube to the corner of valve seat is 170 MPa�The valve cage has the maximum stress of 106 MPa, and the valve bush has the maximum stress of 73 MPa�Compared with the adiabatic condition, the coupled stresses at the valve cage and valve bush at heating condition have significantly been reduced, indicating that heating can reduce the stress of valve cage and valve bush, leading to improved valve bush life and extended operation life of pressure reducing valve.%减压阀结构复杂，在工况压力下变形不协调，应力集中严重，容易造成阀体的强度失效，缩短阀体的使用寿命，造成天然气泄漏等问题。为此，以RMG530减压阀为研究对象，依据实际工况进行了阀体及阀内流体数值仿真计算。计算结果表明，在绝热条件下，耦合应力中热应力占据主导地位，应力最大点位于阀笼节流孔处，为180 MPa，阀套处最大应力为126 MPa；在加热条件下，耦合应力中内压应力占据主导地位；进口管段到阀座拐角处最大应力为170 MPa，阀笼处最大应力为106 MPa，阀套处最大应力为73 MPa；在加热条件下阀笼和阀套处的耦合应力比在绝热条
METHOD FOR CALCULATION OF STRESS-STRAIN STATE DUE TO SINGLE TWIN IN GRAIN OF VARIOUS FORMS
T. V. Drabysheuskaya
2016-01-01
Full Text Available The paper investigates a stress-strain state in a polycrystalline grain due to presence in its body of a single micro- twin in case of various grain boundary forms. A methodology for calculation of displacement and stress fields for the specified stress-strain state of a polygon-shaped grain has been developed in the paper. Nodal points in a polycrystalline grain that have a maximum stresses contributing to initiation of destruction have been revealed in the paper. The aim of this work has been to study the stress-strain state due to a single micro-twin in the polycrystalline grain and form of grain boundaries. The paper describes polycrystalline grains having a regular polygon shape and containing a single wedge twin in their body. Polycrystalline grain boundaries are presented as walls with complete dislocation. The investigated grains are located far from the surface of twinning material. The developed methodology for calculation of displacement and stresses created by wedge twin is based on the principle of superposition. Calculations on stress tensor components have been carried out for iron (Fe. The presented results of calculations for stress fields have indicated to validity of the used dislocation model. Twin and grain boundaries being stress concentrators are clearly visible on the obtained distributions of stress fields. Maximum normal stresses are observed on the twin boundaries; σxy maximum shear stresses are located at nodal points of the twin; σzy and σxz shear stresses are maximum on the grain boundaries. The conducted investigations have resulted in study of the stress-strain state due to a single wedge-shaped micro-twin in the polycrystalline grain and form of the grain boundaries. Zones of stress concentration in the polycrystalline grain have been identified in the presence of residual mechanical wedge twin. A method for evaluation of the given state has been developed in the paper.
CALCULATION OF STRESS AND DEFORMATION IN FUEL ROD CLADDING DURING PELLET-CLADDING INTERACTION
Dávid Halabuk
2015-12-01
Full Text Available The elementary parts of every fuel assembly, and thus of the reactor core, are fuel rods. The main function of cladding is hermetic separation of nuclear fuel from coolant. The fuel rod works in very specific and difficult conditions, so there are high requirements on its reliability and safety. During irradiation of fuel rods, a state may occur when fuel pellet and cladding interact. This state is followed by changes of stress and deformations in the fuel cladding. The article is focused on stress and deformation analysis of fuel cladding, where two fuels are compared: a fresh one and a spent one, which is in contact with cladding. The calculations are done for 4 different shapes of fuel pellets. It is possible to evaluate which shape of fuel pellet is the most appropriate in consideration of stress and deformation forming in fuel cladding, axial dilatation of fuel, and radial temperature distribution in the fuel rod, based on the obtained results.
Distribution Characteristics of Weld Residual Stress on Butt Welded Dissimilar Metal Plate
Lee, Kyoung Soo; Park, Chi Yong [KEPCO Research Institute, Daejeon (Korea, Republic of); Kim, Maan Won [Korea Hydro and Nuclear Power Co., Seoul (Korea, Republic of); Park, Jai Hak [Chungbuk National University, Cheongju (Korea, Republic of)
2010-09-15
In this study, the weld residual stress distribution at a dissimilar-metal welded plate of low alloy carbon steel and stainless steel, which are widely used in nuclear power plants, was characterized. A plate mock-up with butt welding was fabricated using SA 508 low alloy steel and Type 304 stainless steel plates and the residual stresses were measured by the X-ray diffraction method after electrolytic polishing of the plate specimen. Finite element analysis was carried out in order to simulate the butt welding of dissimilar metal plate, and the calculated weld residual stress distribution was compared with that obtained from the measured data. The characteristics of the three-dimensional residual stress distribution in a butt weld of dissimilar metal plates were investigated by comparing the measured and calculated residual stress data.
Relativistic effects in model calculations of double parton distribution function
Rinaldi, Matteo
2016-01-01
In this paper we consider double parton distribution functions (dPDFs) which are the main non perturbative ingredients appearing in the double parton scattering cross section formula in hadronic collisions. By using recent calculation of dPDFs by means of constituent quark models within the so called Light-Front approach, we investigate the role of relativistic effects on dPDFs. We find, in particular, that the so called Melosh operators, which allow to properly convert the LF spin into the canonical one and incorporate a proper treatment of boosts, produce sizeable effects on dPDFs. We discuss specific partonic correlations induced by these operators in transverse plane which are relevant to the proton structure and study under which conditions these results are stable against variations in the choice of the proton wave function.
FIBER ORIENTATION DISTRIBUTION OF PAPER SURFACE CALCULATED BY IMAGE ANALYSIS
Toshiharu Enomae; Yoon-Hee Han; Akira Isogai
2004-01-01
Anisotropy of paper is an important parameter of paper structure. Image analysis technique was improved for accurate fiber orientation in paper surfaces. Image analysis using Fast Fourier Transform was demonstrated to be an effective means to determine fiber orientation angle and its intensity. Binarization process of micrograph images of paper surface and precise calculation for average Fourier coefficients as an angular distribution by interpolation developed were found to improve the accuracy. This analysis method was applied to digital optical micrographs and scanning electron micrographs of paper. A laboratory handsheet showed a large deviation in the average value of fiber orientation angle, but some kinds of machine-made paper showed about 90 degrees in the orientation angle with very small deviations as expected. Korea and Japanese paper made in the traditional ways showed its own characteristic depending on its hand making processes.
ZHAO Xiqing; ZANG Xinliang; WANG Qingfeng; Park Joongkeun; YANG Qingxiang
2008-01-01
The stress-strain curve of an a-β Ti-8Mn alloy was measured and then it was calculated with finite element method (FEM) based on the stress-strain curves of the single α and β phase alloys.By comparing the calculated stress-strain curve with the measured one,it can be seen that they fit each other very well.Thus,the FE model built in this work is effective.According to the above mentioned model,the distributions of stress and strain in the α and β phases were simulated.The results show that the stress gradients exist in both α and β phases,and the distributions of stress are inhomogeneons.The stress inside the phase is generally higher than that near the interface.Meanwhile,the stress in the α phase is lower than that in the β phase,whereas the strain in the a phase is higher than that in the β phase.
Research on magnetic testing method of stress distribution
李路明; 黄松岭; 汪来富; 杨海青; 施克仁
2002-01-01
For implementing nondestructive evaluation of stress distribution inside ferromagnetic material, a magnetic testing method was developed which does not need artificial magnetizing field. This method was implemented by testing the normal component of the magnetic flux leakage above the object being tested with a constant lift-off from 1 to 10*!mm. The distribution of the stress inside the specimen can be gotten from that of the normal component of the magnetic flux leakage. A stress concentration specimen, which is a 10*!mm thickness mild steel plate with a welding seam on it, was tested using this method. The stress distribution of the magnetic testing was identical with that of small hole stress testing method. It indicates that the stress distribution of ferromagnetic material can be known by the magnetic testing method.
An efficient method for calculating RMS von Mises stress in a random vibration environment
Segalman, D.J.; Fulcher, C.W.G.; Reese, G.M.; Field, R.V. Jr. [Sandia National Labs., Albuquerque, NM (United States). Structural Dynamics and Vibration Control Dept.
1998-02-01
An efficient method is presented for calculation of RMS von Mises stresses from stress component transfer functions and the Fourier representation of random input forces. An efficient implementation of the method calculates the RMS stresses directly from the linear stress and displacement modes. The key relation presented is one suggested in past literature, but does not appear to have been previously exploited in this manner.
An efficient method for calculating RMS von Mises stress in a random vibration environment
Segalman, D.J.; Fulcher, C.W.G.; Reese, G.M.; Field, R.V. Jr. [Sandia National Labs., Albuquerque, NM (United States). Structural Dynamics and Vibration Control Dept.
1997-12-01
An efficient method is presented for calculation of RMS von Mises stresses from stress component transfer functions and the Fourier representation of random input forces. An efficient implementation of the method calculates the RMS stresses directly from the linear stress and displacement modes. The key relation presented is one suggested in past literature, but does not appear to have been previously exploited in this manner.
Temperature Distribution in Solar Cells Calculated in Three Dimensional Approach
Hamdy K. Elminir
2000-01-01
Full Text Available Field-testing is costly, time consuming and depends heavily on prevailing weather conditions. Adequate security and weather protection must also provide at the test site. Delays can also be caused due to bad weather and system failures. To overcome these problems, a Photovoltaic (PV array simulation may be used. For system design purpose, the model must reflect the details of the physical process occurring in the cell, to get a closer insight into device operation as well as optimization of particular device parameters. PV cell temperature ratings have a great effect on the main cell performance. Hence, the need for an exact technique to calculate accurately and efficiently the temperature distribution of a PV cell arises, from which we can adjust safe and proper operation at maximum ratings. The Scope of this work is to describe the development of 3D-thermal models, which are used to update the operation temperature, to get a closer insight into the response behavior and to estimate the overall performance.
Stress Distribution of Holed Geotextile Cross-section in Civil Engineering
SHANG Xin-ping; CHU Cai-yuan
2005-01-01
Stress distribution of holed geotextile cross-section under uniaxial and double-axial tension is analyzed with the boundary element method (BEM). The calculation results indicate that stress distribution of holed geotextile crosssection is greatly related to the dimension of the specimen, the size of the hole, the shape of the hole and the tensile condition, and the stress concentration area of holed geotextile from the side of the hole to 3-4 times of the hole diameter should be strengthened in order to improve quality of the projects. These results could provide guidance for engineering application of geotextiles.
刘玉岚; 王彪; 王殿富
2003-01-01
Due to the mismatch in the coefficients of thermal expansion of slicon chip and the surrounding plastic encapsulation materials, the induced thermal stress is the main cause for die and encapsulant rupture. The corner geometry is simplified as the semi-infinite wedge. Then the two-dimensional thermal stress distribution around the corner was obtained explicitly. Based on the stress calculation, the strain energy density factor criterion is used to evaluate the strength of the structure, which can not only give the critical condition for the stresses, but also determine the direction of fracture initiation around the corner.
LIUYu-lan; WANGBiao; WANGDian-fu
2003-01-01
Due to the mismatch in the coefficients of thermal epansion of slicon chip and the surrounding plastic encapsulation materials,the induced thermal stress is the main cause for die and encapsulant rupture.The corner geometry is simplified as the semi-infinite wedge.The the two-dimensional thermal stress distribution around the coner was obtained explicitly.Based on the stress calculation,the strain energy density factor criterion is used to evaluate the strength of the structure,which can not only give the critical condition for the stresses,but also determine the direction of fracture iuntiation around the corner.
Residual stress distribution in injection molded parts
P. Postawa
2006-08-01
Full Text Available Purpose: The paper presents the results of the investigations of influence of the amorphous polystyrene (PSprocessing on the diversity of the internal stresses observed in the injection moulded piece.Design/methodology/approach: For the tests, the standardized mould piece designed for the investigations ofthe processing shrinkage of thermoplastics materials has been used. The samples have been prepared using theDesign of Experiment (DoE theory.The state of internal stresses has been analysed by means of photoelastic method (used stress viewer equipmenton the basis of the layout and size of the isochromatics (fields with the same colour, which determine the mouldpiece’s areas where the same value for the difference of main tensions. In the article the results of investigationsof influence of 5 chosen processing parameters such as injection temperature Tw, mould temperature Tf,clamping pressure pd, cooling time tch and the injection speed vw on the changes in isochromatics layout as adeterminant for diversity of internal stresses in injection moulded pieces have been presented.Findings: The performed investigations of the influence of injection conditions on the state of internal stressesreached for injection mould pieces were to determine the parameters of injection at which the achieved state ofthe stresses in the mould piece (described by the difference of main tensions will show the lowest values.Practical implications: Effects of examinations of influence of processing conditions on residual stress ininjection molded parts (presented in the article could find practical application in polymer industry, both smalland large enterprises.Originality/value: New approach to fast estimation of value of residual stresses were present in the paper.
Application of Entropy Concept for Shear Stress Distribution in Laminar Pipe Flow
Choo, Yeon Moon; Choo, Tai Ho; Jung, Donghwi; Seon, Yun Gwan; Kim, Joong Hoon
2016-04-01
In the river fluid mechanics, shear stress is calculated from frictional force caused by viscosity and fluctuating velocity. Traditional shear stress distribution equations have been widely used because of their simplicity. However, they have a critical limitation of requiring energy gradient which is generally difficult to estimate in practice. Especially, measuring velocity/velocity gradient on the boundary layer is difficult in practice. It requires point velocity throughout the entire cross section to calculate velocity gradient. This study proposes shear stress distribution equations for laminar flow based on entropy theory using mean velocity and entropy coefficient. The proposed equations are demonstrated and compared with measured shear stress distribution using Nikuradse's data. Results showed that the coefficient of determination is around 0.99 indicating that the proposed method well describes the true shear stress distribution. Therefore, it was proved that shear stress distribution can be easily and accurately estimated by using the proposed equations. (This research was supported by a gran(13AWMP-B066744-01) from Advanced Water Management Research Program funded by Ministry of Land, Infrastructure and Transport of Korean Government)
Rixrath, E; Wendling-Mansuy, S; Flecher, X; Chabrand, P; Argenson, J N
2008-01-01
We have developed a mathematical model to calculate the contact stress distribution in total hip arthroplasty (THA) prosthesis between the articulating surfaces. The model uses the clearance between bearing surfaces as well as the inclination and thickness of the Ultra High Molecular Weight Poly-Ethylene (UHMWPE) cup to achieve this. We have used this mathematical model to contrast the maximal force during normal gait and during jogging. This is based on the assumption that the contact stress is proportional to the radial deformation of the cup. The results show that the magnitude of the maximal contact stress remains constant for inclination values in the range of [0-35 degrees ] and increase significantly with the cup clearance and liner thickness for inclination values in the range of [35-65 degrees ]. A major use for this model would be the calculation of spatial contact stress distribution during normal gait or jogging for different couples of bearing surfaces.
Calculation of the stress-strain stiffness matrix for given strains in an inelastic material
Friedrich, C.M.
1978-01-01
In the implicit method of non-linear analysis of stiffness matrices of finite elements, deflection fields and hence strains are assumed known at one stage of the calculations. A procedure is developed to calculate the stress-strain stiffness matrix from the strains without iteration of the stress components when the material is inelastic.
Predicted tyre-soil interface area and vertical stress distribution based on loading characteristics
Schjønning, Per; Stettler, M.; Keller, Thomas
2015-01-01
The upper boundary condition for all models simulating stress patterns throughout the soil profile is the stress distribution at the tyre–soil interface. The so-called FRIDA model (Schjønning et al., 2008. Biosyst. Eng. 99, 119–133) treats the contact area as a superellipse and has been shown...... to accurately describe a range of observed vertical stress distributions. Previous research has indicated that such distributions may be predicted from tyre and loading characteristics. The objective of this study was to establish a stepwise calculation procedure enabling accurate predictions from readily...... available data. We used multiple regression to identify equations for predicting the FRIDA model parameters from measured loading characteristics including tyre carcass volume (VT), wheel load (FW), tyre deflection (L), and an expression of tyre inflation pressure (Kr) calculated as the natural logarithm...
Calculation of Wave Radiation Stress in Combination with Parabolic Mild Slope Equation
ZHENG Yonghong; SHEN Yongming; QIU Dahong
2000-01-01
A new method for the calculation of wave radiation stress is proposed by linking the expressions for wave radiation stress with the variables in the parabolic mild slope equation. The governing equations are solved numerically by the finite difference method. Numerical results show that the new method is accurate enough, can be efficiently solved with little programming effort, and can be applied to the calculation of wave radiation stress for large coastal areas.
Distribution of ground stress on Puhe Coal Mine
Guo Zhibiao; Jiang Yulin; Pang Jiewen; Liu Jiawei
2013-01-01
Puhe Coal Mine is a typical Tertiary coal in Shenbei mining area.With an increase in mining depth,tectonic stress field becomes more complex,leading to increased deformation and failure of the soft rock roadway.Stress becomes an important factor of mine safety and stability.This paper analyzes the distribution of the regional tectonic field,and determines the distribution of situ stress measurement through measuring the ground stress field in the main mining area level of Puhe Coal Mine using stress relief method.The acquired in situ stress data at different locations and depths provide a reference for the rational arrangement of the stop and mine roadway supporting design,which are of great significance for the efficient safety production of the mine.
3-D distribution of tensile stress in rock specimens for the Brazilian test
Yong Yu; Chunyan Meng
2005-01-01
It is claimed that the formula used for calculating the tensile strength of a disk-shaped rock specimen in the Brazilian test is not accurate, because the formula is based on the 2-dimensional elastic theory and only suitable for very long or very short cylinders. The Matlab software was used to obtain the 2-dimensional distribution of stress in the rock specimen for Brazilian test. Then the 2-dimensional stress distribution in Brazilian disk was analyzed by the Marc FEM software. It can be found that the results obtained by the two software packages can verify each other. Finally, the 3-dimensional elastic stress in the specimen was calculated. The results demonstrate that the distribution of stress on the cross section of the specimen is similar to that in 2-dimension. However, the value of the stress on the cross section varies along the thickness of the specimen and the stress is bigger when getting closer to the end of the specimen. For the specimen with a height-to-diameter ratio of 1 and a Poisson's ratio of 0.25, the tensile strength calculated with the classical 2-D formula is 23.3% smaller than the real strength. Therefore, the classical 2-D formula is too conservative.
The model of stress distribution in polymer electrolyte membrane
Atrazhev, Vadim V; Dmitriev, Dmitry V; Erikhman, Nikolay S; Sultanov, Vadim I; Patterson, Timothy; Burlatsky, Sergei F
2014-01-01
An analytical model of mechanical stress in a polymer electrolyte membrane (PEM) of a hydrogen/air fuel cell with porous Water Transfer Plates (WTP) is developed in this work. The model considers a mechanical stress in the membrane is a result of the cell load cycling under constant oxygen utilization. The load cycling causes the cycling of the inlet gas flow rate, which results in the membrane hydration/dehydration close to the gas inlet. Hydration/dehydration of the membrane leads to membrane swelling/shrinking, which causes mechanical stress in the constrained membrane. Mechanical stress results in through-plane crack formation. Thereby, the mechanical stress in the membrane causes mechanical failure of the membrane, limiting fuel cell lifetime. The model predicts the stress in the membrane as a function of the cell geometry, membrane material properties and operation conditions. The model was applied for stress calculation in GORE-SELECT.
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Ceramic design concepts based on stress distribution analysis.
Esquivel-Upshaw, J F; Anusavice, K J
2000-08-01
This article discusses general design concepts involved in fabricating ceramic and metal-ceramic restorations based on scientific stress distribution data. These include the effects of ceramic layer thickness, modulus of elasticity of supporting substrates, direction of applied loads, intraoral stress, and crown geometry on the susceptibility of certain restoration designs to fracture.
Gravitation Field Calculations on a Dynamic Lattice by Distributed Computing
Mähönen, Petri; Punkka, Veikko
A new method of calculating numerically time evolution of a gravitational field in General Relatity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.
Gravitational field calculations on a dynamic lattice by distributed computing.
Mähönen, P.; Punkka, V.
A new method of calculating numerically time evolution of a gravitational field in general relativity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.
Cao, Yang-Bing; Feng, Xia-Ting; Yan, E.-Chuan; Chen, Gang; Lü, Fei-fei; Ji, Hui-bin; Song, Kuang-Yin
2016-05-01
Knowledge of the fracture hydraulic aperture and its relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the qualitative relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.
STRESS DISTRIBUTION NEAR GRAIN BOUNDARY IN ANISOTROPIC BICRYSTALS AND TRICRYSTALS
万建松; 岳珠峰
2004-01-01
The rate dependent crystallographic finite element program was implemented in ABAQUS as a UMAT for the analysis of the stress distributions near grain boundary in anisotropic bicrystals and tricrystals, taking the different crystallographic orientations into consideration. The numerical results of bicrystals model with the different crystallographic orientations shows that there is a high stress gradient near the grain boundaries. The characteristics of stress structures are dependent on the crystallographic orientations of the two grains. The existing of triple junctions in the tricrystals may result in the stress concentrations, or may not, depending on the crystallographic orientations of the three grains. The conclusion shows that grain boundary with different crystallographic orientations can have different deformation, damage, and failure behaviors. So it is only on the detail study of the stress distribution can the metal fracture be understood deeply.
Vertical Distribution of Tidal Flow Reynolds Stress in Shallow Sea
SONG Zhi-yao; NI Zhi-hui; LU Guo-nian
2009-01-01
Based on the results of the tidal flow Reynolds stresses of the field observations,indoor experiments,and numerical models,the parabolic distribution of the tidal flow Reynolds stress is proposed and its coefficients are determined theoretically in this paper.Having been well verified with the field data and experimental data,the proposed distribution of Reynolds stress is also compared with numerical model results,and a good agreement is obtained,showing that this distribution can well reflect the basic features of Reynolds stress deviating from the linear distribution that is downward when the tidal flow is of acceleration,upward when the tidal flow is of deceleration.Its dynamics cause is also discussed preliminarily and the influence of the water depth is pointed out from the definition of Reynolds stress,turbulent generation,transmission,and so on.The established expression for the vertical distribution of the tidal flow Reynolds stress is not only simple and explicit,but can also well reflect the features of the tidal flow acceleration and deceleration for further study on the velocity profile of tidal flow.
Flow-Induced Stress Distribution in Porous Scaffolds
Papavassiliou, Dimitrios; Voronov, Roman; Vangordon, Samuel; Sikavitsas, Vassilios
2010-11-01
Flow-induced stresses help the differentiation and proliferation of mesenchymal cells cultured in porous scaffolds within perfusion bioreactors. The distribution of stresses in a scaffold is thus important for understanding the tissue growth process in such reactors. Computational results for flow through Poly-L-Lactic Acid porous scaffolds that have been produced with salt-leaching techniques, and for scaffolds that have been constructed with nonwoven fibers, indicate that the probability density function (pdf) of the wall stress, when normalized with the mean and the standard deviation of the pdf, appears to follow a single type of pdf. The scaffolds were imaged with micro-CT and the simulations were run with lattice Boltzmann methods. The parameters of the distribution can be obtained using Darcy's law and the Blake-Kozeny-Carman equation. Experimental results available in the literature appear to corroborate the computational findings, leading to the conclusion that stresses in high-porosity porous materials follow a single distribution.
Analytical Calculation of Current Distribution in Multistrand Superconducting Cables
Bottura, L; Fabbri, M G
2003-01-01
In recent years the problem of current distribution in multistrand superconducting cables has received increasing attention for large scale superconductivity applications due to its effect on the stability of fusion magnets and the field quality of accelerator magnets. A modelling approach based on distributed parameters has revealed to be very effective in dealing with long cables made of some tens or hundreds of strands. In this paper we present a fully analytical solution equation for a distributed parameters model in cables made of an arbitrary number of strands, whose validity is subjected to symmetry conditions generally satisfied in practical cables. We give in particular analytical formulae of practical use for the estimation of the maximum strand currents, time constants and redistribution lengths as a function of the cable properties and the external voltage source.
Segalman, D.; Reese, G.
1998-09-01
The von Mises stress is often used as the metric for evaluating design margins, particularly for structures made of ductile materials. For deterministic loads, both static and dynamic, the calculation of von Mises stress is straightforward, as is the resulting calculation of reliability. For loads modeled as random processes, the task is different; the response to such loads is itself a random process and its properties must be determined in terms of those of both the loads and the system. This has been done in the past by Monte Carlo sampling of numerical realizations that reproduce the second order statistics of the problem. Here, the authors present a method that provides analytic expressions for the probability distributions of von Mises stress which can be evaluated efficiently and with good precision numerically. Further, this new approach has the important advantage of providing the asymptotic properties of the probability distribution.
Constant-Step Stress Accelerated Life Test of VFD under Logarithmic Normal Distribution Case
无
2006-01-01
In order to solve the life problem of vacuum fluorescent display (VFD) within shorter time, and reduce the life prediction cost, a constant-step stress accelerated life test was performed with its cathode temperature increased. Statistical analysis was done by applying logarithmic normal distribution for describing the life, and least square method (LSM) for estimating logarithmic normal parameters. Self-designed special software was used to predict the VFD life. It is verified by numerical results that the VFD life follows logarithmic normal distribution,and that the life-stress relationship satisfies linear Arrhenius equation completely. The accurate calculation of the key parameters enables the rapid estimation of VFD life.
Constant-step stress accelerated life test of VFD under Weibull distribution case
ZHANG Jian-ping; GENG Xin-min
2005-01-01
Constant-step stress accelerated life test of Vacuum Fluorescent Display (VFD) was conducted with increased cathode temperature. Statistical analysis was done by applying Weibull distribution for describing the life, and Least Square Method (LSM)for estimating Weibull parameters. Self-designed special software was used to predict the VFD life. Numerical results showed that the average life of VFD is over 30000 h, that the VFD life follows Weibull distribution, and that the life-stress relationship satisfies linear Arrhenius equation completely. Accurate calculation of the key parameter enabled rapid estimation of VFD life.
SAMDIST: A Computer Code for Calculating Statistical Distributions for R-Matrix Resonance Parameters
Leal, L.C.
1995-01-01
The: SAMDIST computer code has been developed to calculate distribution of resonance parameters of the Reich-Moore R-matrix type. The program assumes the parameters are in the format compatible with that of the multilevel R-matrix code SAMMY. SAMDIST calculates the energy-level spacing distribution, the resonance width distribution, and the long-range correlation of the energy levels. Results of these calculations are presented in both graphic and tabular forms.
SAMDIST A Computer Code for Calculating Statistical Distributions for R-Matrix Resonance Parameters
Leal, L C
1995-01-01
The: SAMDIST computer code has been developed to calculate distribution of resonance parameters of the Reich-Moore R-matrix type. The program assumes the parameters are in the format compatible with that of the multilevel R-matrix code SAMMY. SAMDIST calculates the energy-level spacing distribution, the resonance width distribution, and the long-range correlation of the energy levels. Results of these calculations are presented in both graphic and tabular forms.
A NUMERICAL STUDY OF THE STRESS DISTRIBUTION IN HOPPER FLOW
Haiping Zhu; Aibing Yu
2003-01-01
The stress distributions of granular flow in a cylindrical hopper with flat bottom are investigated by means of a combined approach of discrete element method (DEM) and averaging method. The filling and discharge of the hopper flow are first simulated at a particle level by means of a modified DEM. The results are then used to determine the velocity and stress profiles of the hopper flow by means of an averaging method. The analysis is focused on a central section plane of the hopper due to the relatively perfect axial symmetry. The velocity profiles are illustrated to be consistent with those obtained by the previous experiments, confirming the validity of the proposed approach. The distributions of four components of the planar stress tensor at different heights are quantified. It is shown that the vertical normal stress increases with increasing the height near the central axis, the horizontal normal stress varies more slowly at a higher level and is almost constant when the height is equal to or greater than about 12 particle diameter, and the magnitudes of two shear stresses are equal at the central zone of the hopper but not so at the points near the walls. The dependence of stress distributions on the wall mechanical properties such as sliding resistance and rolling resistance is also discussed.
Rail Inductance Calculations for Some Simple Current Distributions,
1986-02-01
Kowalenko ABSTRACT In this study, an expression for the inductance per unit length of the rails for a railgun -type electromagnetic launcher (EML) is...this report is unlimited. ,EYWORDS Electric guns, Electromagnetic launchers Railgun accelerators Current distribution Equations of motion ’ :.A1M... capacitor bank of an electromagnetic launcher, F d separation of the rails, m dt differential vector length element E(O) total initial energy stored by
无
2001-01-01
The thermal residual stresses and the stress distributions of short fiber reinforced metal matrix composite under tensile and compressive loadings were studied using large strain axisymmetric elasto-plastic finite element method. It is demonstrated that the thermal residual stresses can result in asymmetrical stress distributions and matrix plasticity. The thermal residual stresses decrease the stress transfer in tension and enhance the stress transfer in compression. The fiber volume fraction has more important effects on the thermal residual stresses and the stress distributions under tensile and compressive loadings than the fiber aspect ratio and the fiber end distance.
Visual Method for Spectral Energy Distribution Calculation of Blazars
Y. Huang; J. H. Fan
2014-09-01
In this work, we propose to use `The Geometer’s Sketchpad’ to the fitting of a spectral energy distribution of blazar based on three effective spectral indices, RO, OX, and RX and the flux density in the radio band. It can make us to see the fitting in detail with both the peak frequency and peak luminosity given immediately. We used our method to those sources whose peak frequency and peak luminosity are given and found that our results are consistent with those given in the work of Sambruna et al. (1996).
Measurement of probability distributions for internal stresses in dislocated crystals
Wilkinson, Angus J.; Tarleton, Edmund; Vilalta-Clemente, Arantxa; Collins, David M. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Jiang, Jun; Britton, T. Benjamin [Department of Materials, Imperial College London, Royal School of Mines, Exhibition Road, London SW7 2AZ (United Kingdom)
2014-11-03
Here, we analyse residual stress distributions obtained from various crystal systems using high resolution electron backscatter diffraction (EBSD) measurements. Histograms showing stress probability distributions exhibit tails extending to very high stress levels. We demonstrate that these extreme stress values are consistent with the functional form that should be expected for dislocated crystals. Analysis initially developed by Groma and co-workers for X-ray line profile analysis and based on the so-called “restricted second moment of the probability distribution” can be used to estimate the total dislocation density. The generality of the results are illustrated by application to three quite different systems, namely, face centred cubic Cu deformed in uniaxial tension, a body centred cubic steel deformed to larger strain by cold rolling, and hexagonal InAlN layers grown on misfitting sapphire and silicon carbide substrates.
Stress distribution in composite flatwise tension test specimens
Scott, Curtis A.; Pereira, J. Michael
1993-01-01
A finite element analysis was conducted to determine the stress distribution in typical graphite/epoxy composite flat wise tension (FWT) specimens under normal loading conditions. The purpose of the analysis was to determine the relationship between the applied load and the stress in the sample to evaluate the validity of the test as a means of measuring the out-of-plane strength of a composite laminate. Three different test geometries and three different material lay ups were modeled. In all cases, the out-of-plane component of stress in the test section was found to be uniform, with no stress concentrations, and very close to the nominal applied stress. The stress in the sample was found to be three-dimensional, and the magnitude of in-plane normal and shear stresses varied with the anisotropy of the test specimen. However, in the cases considered here, these components of stress were much smaller than the out-of-plane normal stress. The geometry of the test specimen had little influence on the results. It was concluded that the flat wise tension test provides a good measure of the out-of-plane strength for the representative materials that were studied.
鞠明和; 李学华; 姚强岭; 李冬伟; 种照辉; 周健
2015-01-01
Numerical investigation was performed to examine the effect of rear barrier pillar on stress distribution around a longwall face. Salamon theoretical formula was used to calculate the parameters of the caving zone, which was later assigned to double yield constitutive model in FLAC3D. Numerical results demonstrate that high stress concentration zone exists above the region where the second open-off cut intersects with the rear barrier pillar due to stress transfer and plastic zone expansion. It is also found that the maximum vertical stresses with varied distance to the seam floor are all within the projective plane of the rear barrier pillar and their positions concentrate on the barrier pillar adjacent to the connection corner of the second open-off cut. In addition, position of the maximum vertical stresses abruptly transfer from the connection corner adjacent to former panel to that adjacent to current panel along the panel direction.
Sawicka, B.D. (AECL Research, Chalk River Labs., Ontario (Canada)); Murphy, J.G.; Taheri, F.; Kanary, L.E. (Advanced Materials Engineering Centre, Halifax, Nova Scotia (Canada))
1992-06-01
Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modeling qualitatively represents the sintering stresses.
Sawicka, B. D.; Murphy, J. G.; Taheri, F.; Kanary, L. E.
1992-06-01
Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modelling qualitatively represents the sintering stresses.
Equilibrium circulation and stress distribution in viscoelastic creeping flow
Biello, Joseph A
2015-01-01
An analytic, asymptotic approximation of the nonlinear steady-state equations for viscoelastic creeping flow, modeled by the Oldroyd-B equations with polymer stress diffusion, is derived. Near the extensional stagnation point the flow stretches and aligns polymers along the outgoing streamlines of the stagnation point resulting in a stress-island, or birefringent strand. The polymer stress diffusion coefficient is used, both, as an asymptotic parameter and a regularization parameter. The structure of the singular part of polymer stress tensor is a Gaussian aligned with the incoming streamline of the stagnation point; a smoothed $\\delta$-distribution whose width is proportional to the square-root of the diffusion coefficient. The amplitude of the stress island scales with the Wiessenberg number and, although singular in the limit of vanishing diffusion, it is integrable in the cross stream direction due to its vanishing width; this yields a convergent secondary flow. The leading order velocity response to this...
Imaging shear stress distribution and evaluating the stress concentration factor of the human eye
Joseph Antony, S.
2015-03-01
Healthy eyes are vital for a better quality of human life. Historically, for man-made materials, scientists and engineers use stress concentration factors to characterise the effects of structural non-homogeneities on their mechanical strength. However, such information is scarce for the human eye. Here we present the shear stress distribution profiles of a healthy human cornea surface in vivo using photo-stress analysis tomography, which is a non-intrusive and non-X-ray based method. The corneal birefringent retardation measured here is comparable to that of previous studies. Using this, we derive eye stress concentration factors and the directional alignment of major principal stress on the surface of the cornea. Similar to thermometers being used for monitoring the general health in humans, this report provides a foundation to characterise the shear stress carrying capacity of the cornea, and a potential bench mark for validating theoretical modelling of stresses in the human eye in future.
无
2006-01-01
In this paper, primary manufacturing and assembling errors of three-ring gear reducer (TRGR) are analyzed. TRGR is a new transmission type whose eccentric phase difference between middle ring plate and side ring plates is 120°. Its mass of middle ring plate is equal to that of side ring plate or 180°, and its mass of middle ring plate is twice of that of side ring plate, which affects load distribution between ring plates. The primary manufacturing and assembling errors include eccentric error of eccentric sheath Em, internal gear plate Er and output external gear Eic. A new theoretical method is presented in this paper, which converts load on ring plates into the dedendum bending stress of ring plate to calculate load distribution coefficient ( LDC ), by means of gap elenent method (GEM), one of finite element method (FEM). The theoretical calculation and experimental study, which measures ring plate dedendum bending stress by means of sticking strain gauges on the dedendum of middle ring plate internal gear and side ring plate internal gears, are presented. The theoretical calculation and comparison with experiment result of LDC are implemented on two kinds of three-ring gear reducers whose eccentric phase difference between eccentric sheaths is 120° and 180° respectively. The research indicates that the result of theoretical calculation is consistent with that of experimental study. That is to say, the theoretical calculation method is feasible.
Calculated distribution of radionuclides in soils and sediments
Puigdomenech, I.; Bergstroem, U. [Studsvik Eco and Safety AB, Nykoeping (Sweden)
1994-12-01
The description of the accumulation of radionuclides in some biospheric compartments is in general based on a sorption distribution coefficient K{sub d}. This value is very decisive for the concentration of long-lived radionuclides in reservoirs that are important from the dose point of view. Sorption is due to several processes such as ion-exchange and a variety of physical and chemical interactions which are difficult to interpret with the current K{sub d}-methodology. In addition, many of the K{sub d} values are obtained from laboratory or geospheric conditions not comparable to conditions prevailing in the biosphere. The main objective with this work is to deepen the knowledge about the theoretical background of K{sub d}-values. To achieve this purpose, available theoretical models for ion-exchange and surface complexation have been adapted for simulation under biospheric conditions. The elements treated are cesium, radium, neptunium, uranium and plutonium The results show that a triple layer surface complexation model may be used in estimating K{sub d}-values for actinides as a function of important chemical parameters such as pH and E{sub H}. It is concluded that by estimating some equilibrium constants and making some careful approximations, surface complexation models can be used for performance assessment of radioactive waste repositories. 72 refs, 7 figs.
Bauld, N. R., Jr.; Goree, J. G.; Tzeng, L.-S.
1985-01-01
It is pointed out that edge delamination is a serious failure mechanism for laminated composite materials. Various numerical methods have been utilized in attempts to calculate the interlaminar stress components which precede delamination in a laminate. There are, however, discrepancies regarding the results provided by different methods, taking into account a finite-difference procedure, a perturbation procedure, and finite element approaches. The present investigation has the objective to assess the capacity of a finite difference method to predict the character and magnitude of the interlaminar stress distributions near an interface corner. A second purpose of the investigation is to determine if predictions by finite element method in-plane, interlaminar stress components near an interface corner represent actual laminate behavior.
Optimization of contact stress distribution in interference fit
Pedersen, Niels Leergaard
2015-01-01
Assembly of shaft and hub by an interference fit is a classical connection with known advantages and disadvantages.The advantage being the level of possible torque transfer while the disadvantage is a possible fretting fatiguefailure at the points of stress concentration. The pressure distribution...... in the contact is the source responsible for the fatigue failure. The distribution can be improved by design modification done directly on the contacting surfaceswhich however requires a very high production precision. Alternatively it is shown, how shape optimization of thehub side can improve the pressure...... distribution significantly....
Sakamoto, Y
2002-01-01
In the prevention of nuclear disaster, there needs the information on the dose equivalent rate distribution inside and outside the site, and energy spectra. The three dimensional radiation transport calculation code is a useful tool for the site specific detailed analysis with the consideration of facility structures. It is important in the prediction of individual doses in the future countermeasure that the reliability of the evaluation methods of dose equivalent rate distribution and energy spectra by using of Monte Carlo radiation transport calculation code, and the factors which influence the dose equivalent rate distribution outside the site are confirmed. The reliability of radiation transport calculation code and the influence factors of dose equivalent rate distribution were examined through the analyses of critical accident at JCO's uranium processing plant occurred on September 30, 1999. The radiation transport calculations including the burn-up calculations were done by using of the structural info...
Effect of restoration technique on stress distribution in roots with flared canals: an FEA study.
Belli, Sema; Eraslan, Öznur; Eraslan, Oğuz; Eskitaşcıoğlu, Gürcan
2014-04-01
The aim of this finite element analysis (FEA) study was to test the effect of different restorative techniques on stress distribution in roots with flared canals. Five three-dimensional (3D) FEA models that simulated a maxillary incisor with excessive structure loss and flared root canals were created and restored with the following techniques/materials: 1) a prefabricated post: 2) one main and two accessory posts; 3) i-TFC post-core (Sun Medical); 4) the thickness of the root was increased by using composite resin and the root was then restored using a prefabricated post; 5) an anatomic post was created by using composite resin and a prefabricated glass-fiber post. Composite cores and ceramic crowns were created. A 300-N static load was applied at the center of the palatal surface of the tooth to calculate stress distributions. SolidWorks/Cosmosworks structural analysis programs were used for FEA analysis. The analysis of the von Mises and tensile stress values revealed that prefabricated post, accessory post, and i-TFC post systems showed similar stress distributions. They all showed high stress areas at the buccal side of the root (3.67 MPa) and in the cervical region of the root (> 3.67 MPa) as well as low stress accumulation within the post space (0 to 1 MPa). The anatomic post kept the stress within its body and directed less stress towards the remaining tooth structure. The creation of an anatomic post may save the remaining tooth structure in roots with flared canals by reducing the stress levels.
Stress Free Temperature Testing and Residual Stress Calculations on Out-of-Autoclave Composites
Cox, Sarah; Tate, LaNetra C.; Danley, Susan; Sampson, Jeff; Taylor, Brian; Miller, Sandi
2012-01-01
Future launch vehicles will require the incorporation large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7 /Bismalieimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the residual stress of the materials.
Wall Shear Stress Distribution in Patient Specific Coronary Artery Bifurcation
Vahab Dehlaghi
2010-01-01
Full Text Available Problem statement: Atherogenesis is affected by hemodynamic parameters, such as wall shear stress and wall shear stress spatial gradient. These parameters are largely dependent on the geometry of arterial tree. Arterial bifurcations contain significant flow disturbances. Approach: The effects of branch angle and vessel diameter ratio at the bifurcations on the wall shear stress distribution in the coronary arterial tree based on CT images were studied. CT images were digitally processed to extract geometrical contours representing the coronary vessel walls. The lumen of the coronary arteries of the patients was segmented using the open source software package (VMTK. The resulting lumens of coronary arteries were fed into a commercial mesh generator (GAMBIT, Fluent Inc. to generate a volume that was filled with tetrahedral elements. The FIDAP software (Fluent Corp. was used to carry out the simulation by solving Navier-Stokes equations. The FIELDVIEW software (Version 10.0, Intelligent Light, Lyndhurst, NJ was used for the visualization of flow patterns and the quantification of wall shear stress. Post processing was done with VMTK and MATLAB. A parabolic velocity profile was prescribed at the inlets and outlets, except for 1. Stress free outlet was assigned to the remaining outlet. Results: The results show that for angle lower than 90°, low shear stress regions are observed at the non-flow divider and the apex. For angle larger than 90°, low shear stress regions only at the non-flow divider. By increasing of diameter of side branch ratio, low shear stress regions in the side branch appear at the non-flow divider. Conclusion: It is concluded that not only angle and diameter are important, but also the overall 3D shape of the artery. More research is required to further quantify the effects angle and diameter on shear stress patterns in coronaries.
无
2006-01-01
A two-dimensional model was established in the rectangular co-ordinate to study the thermal stress in the sapphire single crystal grown by the improved Kyropoulos. In the simulation, the distribution, the maximum and minimum values of the thermal stress were calculated. In addition, the relationship between the thermal stress and the shouldering angles was obtained that for lower shouldering angles, the maximum of the thermal stress value is lower and the minimum value is higher. It indicates that the distribution of the thermal stress can be improved by decreasing the shouldering angles of the crystal during the growth process. To evaluate the model, the experiment was carried out and the results are in good agreement with the calculation.
Approximate Calculation of Voltage in Three-Phase Primary Distribution Feeder
Iioka, Daisuke; Iwata, Kubou; Kondo, Hisashi; Sakaguchi, Takuma; Shigetou, Takaya; Matsumura, Toshiro
An approximate method to calculate voltage in three-phase primary distribution feeder has been proposed. Generally, nonlinear simultaneous equations have been solved to calculate the voltage in power system since the dependence of electrical equipment on voltage is represented by exponential model such as constant power load, constant current load and constant impedance load. The nonlinear simultaneous equations were transformed to linear simultaneous equations by the proposed method. As a result, the proposed method can calculate the voltage without convergence calculations. It was found that the approximate value of voltage in the three-phase primary distribution feeder is in good agreement with the exact value.
Distribution of horizontal tectonic stresses in the Kovdor ore region
Savchenko S.N.
2015-06-01
Full Text Available The boundary-element method in 2D setting of task of elasticity theory has been used for research of stress state of rock mass in the Kovdor intrusion taking into consideration its hierarchically-block geological structure. Particularities of stresses distribution have been revealed in the region of apatite-magnetite deposit development by the "Zhelezny" mine, "Kovdorsky GOK" JSC. Zones of maximum tension deformations have been determined in the vicinity of the open-pit under the given boundary conditions and mechanical properties of rocks
Hong-yuan FANG; Xue-qiu ZHANG; Jian-guo WANG; Xue-song LIU; Shen QU
2009-01-01
In recent years, some researchers have put forward the new viewpoint that the weld is merely formed during the cooling process, not concerned with the heating process. According to this view, it can be concluded that it is not the compressive but the tensile plastic strain that may remain in the weld. To analyze the formation mechanism of the longitudinal residual stress and plastic strain, finite element method (FEM) is employed in this paper to model the welding longitudinal residual stress and plastic strain. The calculation results show that both the residual compressive plastic strain and the tensile stress in the longitudinal direction can be found in the weld.
CALCULATION OF RESIDUAL STRESSES RESULTING FROM BENDING OF COLD FORMED STEEL BARS
Gökmen ATLIHAN
2007-01-01
Full Text Available In this study, the residual stresses in the forming of the seed capsule which used in manifacturing the ferforje was carried out. These residual stresses were made up in the process which bars with 8 mm diameter were converted to 6 x 6 mm2 square profiles. This process was actually a Rolling process performed at three levels. Plastic constant and strain hardening parameter were calculated at each level . Then, elasto-plastic stress analysis of the bar subjected to bending was analzed by means of Newton Cotes formulation. The load value that cause residual stresses on the steel bar was assumed to be constant in elasto-plastic analysis. Elastic, plastic and residual stresses under the load value were determined in each level and results were presented in the graphical format.
Komemushi, Atsushi; Tanigawa, Noboru; Kariya, Shuji; Yagi, Rie; Nakatani, Miyuki; Suzuki, Satoshi; Sano, Akira; Ikeda, Koshi; Utsunomiya, Keita; Harima, Yoko; Sawada, Satoshi
2012-01-01
Purpose. To assess differences in dose distribution of a vertebral body injected with bone cement as calculated by radiation treatment planning system (RTPS) and actual dose distribution. Methods. We prepared two water-equivalent phantoms with cement, and the other two phantoms without cement. The bulk density of the bone cement was imported into RTPS to reduce error from high CT values. A dose distribution map for the phantoms with and without cement was calculated using RTPS with clinical setting and with the bulk density importing. Actual dose distribution was measured by the film density. Dose distribution as calculated by RTPS was compared to the dose distribution measured by the film dosimetry. Results. For the phantom with cement, dose distribution was distorted for the areas corresponding to inside the cement and on the ventral side of the cement. However, dose distribution based on film dosimetry was undistorted behind the cement and dose increases were seen inside cement and around the cement. With the equivalent phantom with bone cement, differences were seen between dose distribution calculated by RTPS and that measured by the film dosimetry. Conclusion. The dose distribution of an area containing bone cement calculated using RTPS differs from actual dose distribution.
Numerical simulation of stress distribution in Al2 O3-TiC/Q235 diffusion bonded joints
无
2008-01-01
The distributions of the axial stress and shear stress in Al2O3-TiC/Q235 diffusion bonded joints were studied using finite element method (FEM). The effect of interlayer thickness on the axial stress and shear stress was also investigated. The results indicate that the gradients of the axial stress and shear stress are great near the joint edge. The maximal shear stress produces at the interface of the Al2O3-TiC and Ti interlayer. With the increase of Cu interlayer thickness, the magnitudes of the axial stress and shear stress first decrease and then increase. The distribution of the axial stress changes greatly with a little change in the shear stress. The shear fracture initiates at the interface of the Al2O3-TiC/ Ti interlayer with high shear stress and then propagates to the Al2O3-TiC side, which is consistent with the stress FEM calculating results.
Analysis of the strain and stress distribution in the wall of the developing and mature rat aorta.
Rachev, A; Greenwald, S E; Kane, T P; Moore, J E; Meister, J J
1995-01-01
The variation of wall stress distribution with age in the thoracic and abdominal aortas of normotensive rats was studied. Dimensions of the zero-stress configurations were measured at the ages of 4, 8, 12, 20, and 52 weeks. Using data from previously published inflation tests, the circumferential stress-strain relationship was obtained in each age group. The calculated stress distribution showed that the average circumferential stress remained practically constant after the age of 20 weeks. The circumferential stress at the innermost part of the arterial wall was greater than the stress at the outermost part, but the difference was maintained at a moderate level with adjustments in the zero-stress configuration. It is speculated that, after the age of 20 weeks, changes in arterial geometry and rheological properties tend to maintain a constant stress distribution under varying conditions of loading. This distribution was achieved by enhanced growth at the inner part of the media in comparison with the growth at its outer margins and suggests that during development and maturity, the growth of the aorta is modulated by circumferential stress.
Distributed generation hosting capacity calculation of MV distribution feeders in Turkey
Altin, Müfit; Oguz, Emre Utku; Bizkevelci, Erdal
2014-01-01
Integration of distributed generation into distribution networks introduces new challenges to distribution system operators while the penetration level increases. One of the challenges is the voltage rise issue as a part of the steady-state analysis of DGs during planning and operational stages......-state voltage impacts introduced by DGs. Finally, a general flow chart of steady-state analysis is proposed for Turkish DSOs....
Stress-strength reliability for general bivariate distributions
Alaa H. Abdel-Hamid
2016-10-01
Full Text Available An expression for the stress-strength reliability R=P(X1
Compression or tension? The stress distribution in the proximal femur
Meakin JR
2006-02-01
Full Text Available Abstract Background Questions regarding the distribution of stress in the proximal human femur have never been adequately resolved. Traditionally, by considering the femur in isolation, it has been believed that the effect of body weight on the projecting neck and head places the superior aspect of the neck in tension. A minority view has proposed that this region is in compression because of muscular forces pulling the femur into the pelvis. Little has been done to study stress distributions in the proximal femur. We hypothesise that under physiological loading the majority of the proximal femur is in compression and that the internal trabecular structure functions as an arch, transferring compressive stresses to the femoral shaft. Methods To demonstrate the principle, we have developed a 2D finite element model of the femur in which body weight, a representation of the pelvis, and ligamentous forces were included. The regions of higher trabecular bone density in the proximal femur (the principal trabecular systems were assigned a higher modulus than the surrounding trabecular bone. Two-legged and one-legged stances, the latter including an abductor force, were investigated. Results The inclusion of ligamentous forces in two-legged stance generated compressive stresses in the proximal femur. The increased modulus in areas of greater structural density focuses the stresses through the arch-like internal structure. Including an abductor muscle force in simulated one-legged stance also produced compression, but with a different distribution. Conclusion This 2D model shows, in principle, that including ligamentous and muscular forces has the effect of generating compressive stresses across most of the proximal femur. The arch-like trabecular structure transmits the compressive loads to the shaft. The greater strength of bone in compression than in tension is then used to advantage. These results support the hypothesis presented. If correct, a
Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index
Gabriel C. Blain
2015-12-01
Full Text Available ABSTRACT The Standardized Precipitation Index was developed as a probability-based index able to monitor rainfall deficit in a standardized or normalized way. Thus, the performance of this drought index is affected by the use of a distribution that does not provide an appropriate fit for the rainfall data. The goal of this study was to evaluate the adjustment of the gamma distribution for the rainfall amounts summed over several time scales (Pelotas, Rio Grande do Sul, Brazil, to assess the goodness-of-fit of alternative distributions to these rainfall series and to evaluate the normality assumption of the Standardized Precipitation Index series calculated from several distributions. Based on the Lilliefors test and on a normality test, it is verified that the gamma distribution is not suitable for calculating this Index in several timescales. The generalized normal distribution presented the best performance among all analysed distributions. It was also concluded that the drought early warning systems and the academic studies should re-evaluate the use of the gamma distribution in the Standardized Precipitation Index calculation algorithm. A computational code that allows calculating this drought index based on the generalized normal distribution has also been provided.
Jackin, Boaz Jessie; Miyata, Hiroaki; Ohkawa, Takeshi; Ootsu, Kanemitsu; Yokota, Takashi; Hayasaki, Yoshio; Yatagai, Toyohiko; Baba, Takanobu
2014-12-15
A method has been proposed to reduce the communication overhead in computer-generated hologram (CGH) calculations on parallel and distributed computing devices. The method uses the shifting property of Fourier transform to decompose calculations, thereby avoiding data dependency and communication. This enables the full potential of parallel and distributed computing devices. The proposed method is verified by simulation and optical experiments and can achieve a 20 times speed improvement compared to conventional methods, while using large data sizes.
WU Bo; CHEN Gang; JIANG Zhengfeng; ZHENG Junyi
2006-01-01
Approximate calculation methods of prevention maintenance period under the random distribution are given, and three kinds of approximate calculation models of prevention maintenance period based on different security demands are come up with according to maintenance problems of machinery systems in modern enterprise and starting with different demands of systems. And then, how to make certain the best maintenance period by using the approximate calculation methods is illustrated by an example.
METHOD TO CALCULATE STRESS INTENSITY FACTOR OF V-NOTCH IN BI-MATERIALS
Youtang Li; Ming Song
2008-01-01
Based on Zak's stress function,the eigen-equation of stress singularity of bi-materials with a Ⅴ-notch was obtained.A new definition of stress intensity factor for a perpendicular inter facial Ⅴ-notch of bi-material was put forward.The effects of shear modulus and Poisson's ratio of the matrix material and attaching material on eigen-values were analyzed.A generalized ex pression for calculating KI of the perpendicular V-notch of bi-materials was obtained by means of stress extrapolation.Effects of notch depth,notch angle and Poisson's ratio of materials on the singular stress field near the tip of the Ⅴ-notch were analyzed systematically with numerical simulations.As an example,a finite plate with double edge notches under uniaxial uniform ten sion was calculated by the method presented and the influence of the notch angle and Poisson's ratio on the stress singularity near the tip of notch was obtained.
Cox, J.A.M.; Groot, S.R. de; Hartogh, Chr.D.
1953-01-01
In this note the theoretical results for the angular distribution of γ-radiation emitted by oriented radioactive nuclei are applied to the case of 58Co nuclei. The angular distribution function of the γ-radiation has been calculated for an arbitrary degree of nuclear orientation and in dependence of
Amadei, A; Apol, MEF; DiNola, A; Berendsen, HJC
1996-01-01
A new theory is presented for calculating the Helmholtz free energy based on the potential energy distribution function. The usual expressions of free energy, internal energy and entropy involving the partition function are rephrased in terms of the potential energy distribution function, which must
Amadei, A; Apol, MEF; DiNola, A; Berendsen, HJC
1996-01-01
A new theory is presented for calculating the Helmholtz free energy based on the potential energy distribution function. The usual expressions of free energy, internal energy and entropy involving the partition function are rephrased in terms of the potential energy distribution function, which must
覃文洁; 张儒华; 左正兴
2004-01-01
The adaptive FEM analysis of the temperature field of the piston in one diesel engine is given by using the ANSYS software. By making full use of the post results provided by the software, the posteriori error estimation and adaptive accuracy meshing algorithm is developed. So the blindness of the mesh design through experiences can be avoided, and the accuracy requirement is adapted to the relative temperature gradient distribution across the entire domain. Therefore the meshes and solutions can be obtained at the same time. Based on the temperature field analysis, the thermal stress and deformation fields are calculated as well. The results show that the stress concentrates on the edge of the piston pin boss and the inside surface of the first ring groove, and the deformation of the head of the piston is greatest. But the difference between the long and short axes of the bottom cross section is greatest.
Stress reduction of Cu-doped diamond-like carbon films from ab initio calculations
Xiaowei Li
2015-01-01
Full Text Available Structure and properties of Cu-doped diamond-like carbon films (DLC were investigated using ab initio calculations. The effect of Cu concentrations (1.56∼7.81 at.% on atomic bond structure was mainly analyzed to clarify the residual stress reduction mechanism. Results showed that with introducing Cu into DLC films, the residual compressive stress decreased firstly and then increased for each case with the obvious deterioration of mechanical properties, which was in agreement with the experimental results. Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths.
Stress reduction of Cu-doped diamond-like carbon films from ab initio calculations
Li, Xiaowei; Ke, Peiling; Wang, Aiying, E-mail: aywang@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)
2015-01-15
Structure and properties of Cu-doped diamond-like carbon films (DLC) were investigated using ab initio calculations. The effect of Cu concentrations (1.56∼7.81 at.%) on atomic bond structure was mainly analyzed to clarify the residual stress reduction mechanism. Results showed that with introducing Cu into DLC films, the residual compressive stress decreased firstly and then increased for each case with the obvious deterioration of mechanical properties, which was in agreement with the experimental results. Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths.
Influence of Hardening Model on Weld Residual Stress Distribution
Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))
2009-06-15
This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a
A Modified Method for Calculating Notch-Root Stresses and Strains under Multiaxial Loading
Liu Jianhui
2014-04-01
Full Text Available Based on the analysis of notch-root stresses and strains in bodies subjected to multiaxial loading, a quantitative relationship between Neuber rule and the equivalent strain energy density method is found. In the case of elastic range, both Neuber rule and the equivalent strain energy density method get the same estimation of the local stresses and strains. Whereas in the case of elastic-plastic range, Neuber rule generally overestimates the notch-root stresses and strains and the equivalent strain energy density method tends to underestimate the notch-root stresses and strains. A modified method is presented considering the material constants of elastic-plastic Poisson's ratio, elastic modulus, shear elastic modulus, and yield stress. The essence of the modified model is to add a modified coefficient to Neuber rule, which makes the calculated results tend to be more precise and reveals its energy meaning. This approach considers the elastic-plastic properties of the material itself and avoids the blindness of selecting coefficient values. Finally the calculation results using the modified model are validated with the experimental data.
STANDARDIZED PRECIPITATION INDEX (SPI CALCULATED WITH THE USE OF LOG-NORMAL DISTRIBUTION
Edward Gąsiorek
2014-10-01
Full Text Available The problem analyzed in this paper is the continuation of research conducted on data from Wrocław-Swojec agro- and hydrometeorology observatory in 1964–2009 period and published in “Infrastruktura i Ekologia Terenów Wiejskich” nr 3/III/2012, pp. 197–208. The paper concerns two methods of calculation of standardized precipitation index (SPI. The first one extracts SPI directly from gamma distribution, since monthly precipitation sums in the 1964–2009 period in Wrocław are gamma distributed. The second method is based on the transformations of data leading to normal distribution. The authors calculate SPI with the use of log-normal distribution and confront it with values obtained by gamma and normal distributions. The aim of this paper is to comparatively assess the SPI values obtained with those three different methods.
Density functional theory calculations of the stress of oxidised (110) silicon surfaces
Melis, C; Colombo, L; Mana, G
2016-01-01
The measurement of the lattice-parameter of silicon by x-ray interferometry assumes the use of strain-free crystals. This might not be the case because surface relaxation, reconstruction, and oxidation cause strains without the application of any external force. In a previous work, this intrinsic strain was estimated by a finite element analysis, where the surface stress was modeled by an elastic membrane having a 1 N/m tensile strength. The present paper quantities the surface stress by a density functional theory calculation. We found a value exceeding the nominal value used, which potentially affects the measurement accuracy.
Hong Tang; Xiaogang Sun; Guibin Yuan
2007-01-01
In total light scattering particle sizing technique, the relationship among Sauter mean diameter D32, mean extinction efficiency Q, and particle size distribution function is studied in order to inverse the mean diameter and particle size distribution simply. We propose a method which utilizes the mean extinction efficiency ratio at only two selected wavelengths to solve D32 and then to inverse the particle size distribution associated with (Q) and D32. Numerical simulation results show that the particle size distribution is inversed accurately with this method, and the number of wavelengths used is reduced to the greatest extent in the measurement range. The calculation method has the advantages of simplicity and rapidness.
Cattania, C.; Khalid, F.
2016-09-01
The estimation of space and time-dependent earthquake probabilities, including aftershock sequences, has received increased attention in recent years, and Operational Earthquake Forecasting systems are currently being implemented in various countries. Physics based earthquake forecasting models compute time dependent earthquake rates based on Coulomb stress changes, coupled with seismicity evolution laws derived from rate-state friction. While early implementations of such models typically performed poorly compared to statistical models, recent studies indicate that significant performance improvements can be achieved by considering the spatial heterogeneity of the stress field and secondary sources of stress. However, the major drawback of these methods is a rapid increase in computational costs. Here we present a code to calculate seismicity induced by time dependent stress changes. An important feature of the code is the possibility to include aleatoric uncertainties due to the existence of multiple receiver faults and to the finite grid size, as well as epistemic uncertainties due to the choice of input slip model. To compensate for the growth in computational requirements, we have parallelized the code for shared memory systems (using OpenMP) and distributed memory systems (using MPI). Performance tests indicate that these parallelization strategies lead to a significant speedup for problems with different degrees of complexity, ranging from those which can be solved on standard multicore desktop computers, to those requiring a small cluster, to a large simulation that can be run using up to 1500 cores.
Dzifcakova, Elena
2013-01-01
New data for calculation of the ionization and recombination rates have have been published in the past few years. Most of these are included in CHIANTI database. We used these data to calculate collisional ionization and recombination rates for the non-Maxwellian kappa-distributions with an enhanced number of particles in the high-energy tail, which have been detected in the solar transition region and the solar wind. Ionization equilibria for elements H to Zn are derived. The kappa-distributions significantly influence both the ionization and recombination rates and widen the ion abundance peaks. In comparison with Maxwellian distribution, the ion abundance peaks can also be shifted to lower or higher temperatures. The updated ionization equilibrium calculations result in large changes for several ions, notably Fe VIII--XIV. The results are supplied in electronic form compatible with the CHIANTI database.
Method of Images for the Fast Calculation of Temperature Distributions in Packaged VLSI Chips
Hériz, Virginia Martín; Kemper, T; Kang, S -M; Shakouri, A
2008-01-01
Thermal aware routing and placement algorithms are important in industry. Currently, there are reasonably fast Green's function based algorithms that calculate the temperature distribution in a chip made from a stack of different materials. However, the layers are all assumed to have the same size, thus neglecting the important fact that the thermal mounts which are placed underneath the chip can be significantly larger than the chip itself. In an earlier publication, we showed that the image blurring technique can be used to calculate quickly temperature distribution in realistic packages. For this method to be effective, temperature distribution for several point heat sources at the center and at the corner and edges of the chip should be calculated using finite element analysis (FEA) or measured. In addition, more accurate results require correction by a weighting function that will need several FEA simulations. In this paper, we introduce the method of images that take the symmetry of the thermal boundary...
Vallejo, Adriana; Muniesa, Ana; Ferreira, Chelo; de Blas, Ignacio
2013-10-01
Nowadays the formula to calculate the sample size for estimate a proportion (as prevalence) is based on the Normal distribution, however it would be based on a Binomial distribution which confidence interval was possible to be calculated using the Wilson Score method. By comparing the two formulae (Normal and Binomial distributions), the variation of the amplitude of the confidence intervals is relevant in the tails and the center of the curves. In order to calculate the needed sample size we have simulated an iterative sampling procedure, which shows an underestimation of the sample size for values of prevalence closed to 0 or 1, and also an overestimation for values closed to 0.5. Attending to these results we proposed an algorithm based on Wilson Score method that provides similar values for the sample size than empirically obtained by simulation.
An improved method for calculating force distributions in moment-stiff timber connections
Ormarsson, Sigurdur; Blond, Mette
2012-01-01
An improved method for calculating force distributions in moment-stiff metal dowel-type timber connections is presented, a method based on use of three-dimensional finite element simulations of timber connections subjected to moment action. The study that was carried out aimed at determining how...... the slip modulus varies with the angle between the direction of the dowel forces and the fibres in question, as well as how the orthotropic stiffness behaviour of the wood material affects the direction and the size of the forces. It was assumed that the force distribution generated by the moment action...... taking place strives to minimize the slip rotation between the separate members of a given timber connection. The results of modified hand calculations based on the finite element calculations carried out were found to differ appreciably from the results of conventional hand calculations....
Upgraded Algorithm for Calculating the Turbo-Expander of Gas Distribution Stations
Chekardovskiy Mikhail
2016-01-01
Full Text Available The article deals with the urgency of adapting computational turbo-expander unit parameters techniques to the conditions of their application at gas distribution stations. Existing computational methods based on the use of air as the working medium yield incorrect data to determine the actual design parameters for operating conditions where the working medium is natural gas. A modernized algorithm of thermogasdynamic calculation of turbo-expanders in order to form the correct initial data for design calculations has been proposed. The objective of calculating turbo-expanders is to identify thermogasdynamic parameters and dimensions of the flow channel, rotational speed, and shaft power. Procedure of thermogasdynamic calculations is shown on the example of a turbo-expander running on natural gas. The result will simplify the process of selecting or designing turbo-expander units for gas distribution stations.
Nakachi, Yoshiki; Fukae, Takayuki; Sugahara, Toshinori; Nakamura, Hayato; Koyama, Mitsuaki; Ueda, Fukashi
It is well known that the voltage drop due to the inrush current at energizing transformer, may at times, interrupt electrical equipment. Generally, the voltage drop is calculated by using the sophisticated tool such as EMTP, so the transformer saturation phenomenon has been properly represented. However, it is not practical for distribution system engineers to calculate the voltage drop with transformer inrush by using EMTP, because there are a lot of network access requests needing such calculations with many kinds of transformers. Therefore, in this paper, a simplified and easy-to-use calculation tool for voltage drop caused by transformer inrush in distribution system is developed. In order to grasp the voltage drop by inrush current during the planning stage, it is formulated by considering the transformer saturation/unsaturation periods in each winding type, the developed tool is based on the versatile spreadsheet software such as Microsoft Excel®. It can be used with accuracy almost similar to the EMTP.
Monte Carlo calculations of the depth-dose distribution in skin contaminated by hot particles
Patau, J.-P. (Toulouse-3 Univ., 31 (France))
1991-01-01
Accurate computer programs were developed in order to calculate the spatial distribution of absorbed radiation doses in the skin, near high activity particles (''hot particles''). With a view to ascertaining the reliability of the codes the transport of beta particles was simulated in a complex configuration used for dosimetric measurements: spherical {sup 60}Co sources of 10-1000 {mu}m fastened to an aluminium support with a tissue-equivalent adhesive overlaid with 10 {mu}m thick aluminium foil. Behind it an infinite polystyrene medium including an extrapolation chamber was assumed. The exact energy spectrum of beta emission was sampled. Production and transport of secondary knock-on electrons were also simulated. Energy depositions in polystyrene were calculated with a high spatial resolution. Finally, depth-dose distributions were calculated for hot particles placed on the skin. The calculations will be continued for other radionuclides and for a configuration suited to TLD measurements. (author).
A comparison of methods for calculating notch tip strains and stresses under multiaxial loading
M. Lutovinov
2016-10-01
Full Text Available Selected methods for calculating notch tip strains and stresses in elastic–plastic isotropic bodies subjected to multiaxial monotonic loading were compared. The methods use sets of equations where hypothetical notch tip elastic strains and stresses obtained from FEM calculations serve as an input. The comparison was performed within two separate groups of methods: the first group consists of the methods intended for cases of multiaxial proportional loading and the second group deals with multiaxial non-proportional loading. Originally, the precision of the methods was validated by comparison with results obtained from elastic–plastic FEM analyses. Since computer performance at the time was lower than nowadays, verification of the proposed methods on FEM models with a finer mesh was needed. Such verification was carried out and is presented in this paper. The effect of various formulations of material stress–strain curve was also evaluated
Spur Gears Static and Dynamic Meshing Simulation and Tooth Stress Calculation
Jammal Ali
2015-01-01
Full Text Available Gear meshing is a complicated process, and is subjected to the simulation process in the following paper. A flexible quasi-static and dynamic finite element analysis (FEA models were built, to calculate contact principal and shear stresses. Full sized 3D spur gears are simulated under different boundary conditions. The first model, was a quasi-static analysis, where torque was used as input; and the second model, which was transient dynamic analysis, where rotational speed was used as input. The static analysis showed high stress concentration at the tooth contact point and under the contacting surface. The dynamic analysis provided the highest stress value at the different stages of gear engagement points along the line of action. Analytical and simulation result were in agreement in general, and the use of the new simulation model was discussed.
Calculated power distribution of a thermionic, beryllium oxide reflected, fast-spectrum reactor
Mayo, W.; Lantz, E.
1973-01-01
A procedure is developed and used to calculate the detailed power distribution in the fuel elements next to a beryllium oxide reflector of a fast-spectrum, thermionic reactor. The results of the calculations show that, although the average power density in these outer fuel elements is not far from the core average, the power density at the very edge of the fuel closest to the beryllium oxide is about 1.8 times the core avearge.
Murata, Isao [Osaka Univ., Suita (Japan); Mori, Takamasa; Nakagawa, Masayuki; Itakura, Hirofumi
1996-03-01
The method to calculate neutronics parameters of a core composed of randomly distributed spherical fuels has been developed based on a statistical geometry model with a continuous energy Monte Carlo method. This method was implemented in a general purpose Monte Carlo code MCNP, and a new code MCNP-CFP had been developed. This paper describes the model and method how to use it and the validation results. In the Monte Carlo calculation, the location of a spherical fuel is sampled probabilistically along the particle flight path from the spatial probability distribution of spherical fuels, called nearest neighbor distribution (NND). This sampling method was validated through the following two comparisons: (1) Calculations of inventory of coated fuel particles (CFPs) in a fuel compact by both track length estimator and direct evaluation method, and (2) Criticality calculations for ordered packed geometries. This method was also confined by applying to an analysis of the critical assembly experiment at VHTRC. The method established in the present study is quite unique so as to a probabilistic model of the geometry with a great number of spherical fuels distributed randomly. Realizing the speed-up by vector or parallel computations in future, it is expected to be widely used in calculation of a nuclear reactor core, especially HTGR cores. (author).
Calculation of multiple-scattering angular distributions of electrons and positrons
Negreanu, C. [Paul Scherrer Institute, CH-5232 PSI Villigen (Switzerland); Swiss Federal Institute of Technology (EPFL), CH-1015 Laussane (Switzerland); Llovet, X. [Serveis Cientifico-Tecnics, Universitat de Barcelona, Societat Catalana de Fisica (IEC), Lluis Sole i Sabaris 1-3, ES-08028 Barcelona (Spain); Chawla, R. [Paul Scherrer Institute, CH-5232 PSI Villigen (Switzerland); Swiss Federal Institute of Technology (EPFL), CH-1015 Laussane (Switzerland); Salvat, F. [Facultat de Fisica (ECM), Universitat de Barcelona, Societat Catalana de Fisica (IEC), Diagonal 647, ES-08028 Barcelona (Spain)]. E-mail: cesc@ecm.ub.es
2005-12-15
A robust numerical algorithm for the calculation of multiple-scattering angular distributions of high-energy electrons and positrons is described. This algorithm implements the multiple-scattering theories of Goudsmit-Saunderson, which disregards energy losses, and of Lewis, which accounts for energy losses within the continuous slowing down approximation. We have used partial-wave elastic scattering differential cross sections, generated with a recently developed program ELSEPA, in the calculations. The contribution of inelastic collisions to multiple-scattering angular distributions is treated in detail using inelastic scattering angular differential cross sections obtained from the Sternheimer-Liljequist generalised oscillator strength model. The stopping powers adopted in the calculations are consistent with the values recommended in the ICRU 37 report. The coefficients in the Legendre expansion of the single-scattering distribution are calculated by using the N-point Gauss-Legendre integration formula, coded in such a way that it allows the generation of a large number of expansion coefficients simultaneously. A computer program has been written to calculate angular multiple-scattering distributions for given path lengths, which can be readily adopted for class I Monte Carlo simulations.
Axial power distribution calculation using a neural network in the nuclear reactor core
Kim, Y. H.; Cha, K. H.; Lee, S. H. [Korea Electric Power Research Institute, Taejon (Korea, Republic of)
1997-12-31
This paper is concerned with an algorithm based on neural networks to calculate the axial power distribution using excore detector signals in the nuclear reactor core. The fundamental basis of the algorithm is that the detector response can be fairly accurately estimated using computational codes. In other words, the training set, which represents relationship between detector signals and axial power distributions, for the neural network can be obtained through calculations instead of measurements. Application of the new method to the Yonggwang nuclear power plant unit 3 (YGN-3) shows that it is superior to the current algorithm in place. 7 refs., 4 figs. (Author)
Calculation of Radar Probability of Detection in K-Distributed Sea Clutter and Noise
2011-04-01
Expanded Swerling Target Models, IEEE Trans. AES 39 (2003) 1059-1069. 18. G. Arfken , Mathematical Methods for Physicists, Second Edition, Academic...form solution for the probability of detection in K-distributed clutter, so numerical methods are required. The K distribution is a compound model...the integration, with the nodes and weights calculated using matrix methods , so that a general purpose numerical integration routine is not required
Numerical modeling of regional stress distributions for geothermal exploration
Guillon, Theophile; Peter-Borie, Mariane; Gentier, Sylvie; Blaisonneau, Arnold
2017-04-01
Any high-enthalpy unconventional geothermal projectcan be jeopardized by the uncertainty on the presence of the geothermal resource at depth. Indeed, for the majority of such projects the geothermal resource is deeply seated and, with the drilling costs increasing accordingly, must be located as precisely as possible to increase the chance of their economic viability. In order to reduce the "geological risk", i.e., the chance to poorly locate the geothermal resource, a maximum amount of information must be gathered prior to any drilling of exploration and/or operational well. Cross-interpretation from multiple disciplines (e.g., geophysics, hydrology, geomechanics …) should improve locating the geothermal resource and so the position of exploration wells ; this is the objective of the European project IMAGE (grant agreement No. 608553), under which the work presented here was carried out. As far as geomechanics is concerned, in situ stresses can have a great impact on the presence of a geothermal resource since they condition both the regime within the rock mass, and the state of the major fault zones (and hence, the possible flow paths). In this work, we propose a geomechanical model to assess the stress distribution at the regional scale (characteristic length of 100 kilometers). Since they have a substantial impact on the stress distributions and on the possible creation of regional flow paths, the major fault zones are explicitly taken into account. The Distinct Element Method is used, where the medium is modeled as fully deformable blocks representing the rock mass interacting through mechanically active joints depicting the fault zones. The first step of the study is to build the model geometry based on geological and geophysical evidences. Geophysical and structural geology results help positioning the major fault zones in the first place. Then, outcrop observations, structural models and site-specific geological knowledge give information on the fault
An, Deuk Man [Pusan Nat’l Univ., Busan (Korea, Republic of)
2017-01-15
In this study, we develop the exact field of modeⅠin an infinitely deep crack in a half-plane. Using this field, we obtain the exact stress intensity factor KⅠ. From the tractions on the crack faces induced by exact field, we calculate the stress intensity factor of this field. We compare the results with the stress intensity factor calculated using Bueckner’s weight function formula and that calculated by using Tada’s formula listed in “The Stress Analysis of Cracks Handbook” It was found that Bueckner’s formula yields accurate results. However, the results obtained using Tada’s formula exhibit inaccurate behavior.
Liu, Yuan; Ning, Chuangang
2015-10-01
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li-, C-, O-, F-, CH-, OH-, NH2-, O2-, and S2- show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
Kim, Dong Hyun; Kim, Hak Sung [Hanyang University, Seoul (Korea, Republic of); Kim, Hyo Chan; Yang, Yong Sik; In, Wang kee [KAERI, Daejeon (Korea, Republic of)
2016-05-15
In this paper, an analytical method based on thick walled theory has been studied to calculate stress and strain of ATF cladding. In order to prescribe boundary conditions of the analytical method, two algorithms were employed which are called subroutine 'Cladf' and 'Couple' of FRACAS, respectively. To evaluate the developed method, equivalent model using finite element method was established and stress components of the method were compared with those of equivalent FE model. One of promising ATF concepts is the coated cladding, which take advantages such as high melting point, a high neutron economy, and low tritium permeation rate. To evaluate the mechanical behavior and performance of the coated cladding, we need to develop the specified model to simulate the ATF behaviors in the reactor. In particular, the model for simulation of stress and strain for the coated cladding should be developed because the previous model, which is 'FRACAS', is for one body model. The FRACAS module employs the analytical method based on thin walled theory. According to thin-walled theory, radial stress is defined as zero but this assumption is not suitable for ATF cladding because value of the radial stress is not negligible in the case of ATF cladding. Recently, a structural model for multi-layered ceramic cylinders based on thick-walled theory was developed. Also, FE-based numerical simulation such as BISON has been developed to evaluate fuel performance. An analytical method that calculates stress components of ATF cladding was developed in this study. Thick-walled theory was used to derive equations for calculating stress and strain. To solve for these equations, boundary and loading conditions were obtained by subroutine 'Cladf' and 'Couple' and applied to the analytical method. To evaluate the developed method, equivalent FE model was established and its results were compared to those of analytical model. Based on the
Graphene mechanics: II. Atomic stress distribution during indentation until rupture.
Costescu, Bogdan I; Gräter, Frauke
2014-06-28
Previous Atomic Force Microscopy (AFM) experiments found single layers of defect-free graphene to rupture at unexpectedly high loads in the micronewton range. Using molecular dynamics simulations, we modeled an AFM spherical tip pressing on a circular graphene sheet and studied the stress distribution during the indentation process until rupture. We found the graphene rupture force to have no dependency on the sheet size and a very weak dependency on the indenter velocity, allowing a direct comparison to experiment. The deformation showed a non-linear elastic behavior, with a two-dimensional elastic modulus in good agreement with previous experimental and computational studies. In line with theoretical predictions for linearly elastic sheets, rupture forces of non-linearly elastic graphene are proportional to the tip radius. However, as a deviation from the theory, the atomic stress concentrates under the indenter tip more strongly than predicted and causes a high probability of bond breaking only in this area. In turn, stress levels decrease rapidly towards the edge of the sheet, most of which thus only serves the role of mechanical support for the region under the indenter. As a consequence, the high ratio between graphene sheets and sphere radii, hitherto supposed to be necessary for reliable deformation and rupture studies, could be reduced to a factor of only 5-10 without affecting the outcome. Our study suggests time-resolved analysis of forces at the atomic level as a valuable tool to predict and interpret the nano-scale response of stressed materials beyond graphene.
LI Xu-Dong; WANG Wei-Bo; LI Yong-Sheng; WU Dong-Liu
2011-01-01
Feasibility of measuring stress distributions of orthotropic composite materials and structures in plane stress state by the lock-in infrared thermography technique is analyzed and stress distributions of a lap joint structure made of a kind of glass reinforced plastic composite lamination plates under tensile loadings are obtained by the lock-in infrared thermography technique. Feasibility and credibility of using this technique to measure stress distributions of orthotropic composite materials and structures in plane stress state are proved by comparing the results with the data given by the digital speckle correlation method.%@@ Feasibility of measuring stress distributions of orthotropic composite materials and structures in plane stress state by the lock-in infrared thermography technique is analyzed and stress distributions of a lap joint structure made of a kind of glass reinforced plastic composite lamination plates under tensile loadings axe obtained by the lock-in infrared thermography technique.Feasibility and credibility of using this technique to measure stress distributions of orthotropic composite materials and structures in plane stress state axe proved by comparing the results with the data given by the digital speckle correlation method.
Model inverse calculation of current distributions in the cross-section of a superconducting cable
Usak, P. [Institute of Electrical Engineering, Department of Electrodynamics of Superconductors, Slovak Academy of Sciences, Bratislava (Slovakia)]. E-mail: elekusak@savba.sk; Sastry, P.V.P.S.S. [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); Schwartz, J. [Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310 (United States); National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Department of Mechanical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310 (United States)
2006-02-01
The solution of an inverse problem for magnetic field mapping, and the related current distribution in the cross-section of a superconducting cable are generally not unique. Nevertheless, for many natural configurations of a transport current distribution in the cross-section of a superconducting cable, the resulting magnetic field can be used for the reconstruction of a current distribution even in the presence of noise to a degree. We show it using several examples. To perform the inverse calculation, the Tichonov method of regularization was successfully applied. The approach was applied for superconducting cables, but its application is general.
Ro Du Min
2004-01-01
Methods and results of the numerical calculation of temperature distribution in the spherical segmented small capsule filled with heat-generating substance are presented. Variable finite-difference method allowed one to evaluate a small drop of temperature near the boundary between the filling substance and the thermocouple installed inside the capsule, which originates from the difference in thermal conductivity.
V. Rusan
2012-01-01
Full Text Available The paper considers calculation methods for reliability of agricultural distribution power networks while using Boolean algebra functions and analytical method. Reliability of 10 kV overhead line circuits with automatic sectionalization points and automatic standby activation has been investigated in the paper.
vanVlimmeren, BAC; Fraaije, JGEM
1996-01-01
We present a simple method for the numerical calculation of the noise distribution in multicomponent functional Langevin models. The topic is of considerable importance, in view of the increased interest in the application of mesoscopic dynamics simulation models to phase separation of complex
A Simple Spreadsheet Program for the Calculation of Lattice-Site Distributions
McCaffrey, John G.
2009-01-01
A simple spreadsheet program is presented that can be used by undergraduate students to calculate the lattice-site distributions in solids. A major strength of the method is the natural way in which the correct number of ions or atoms are present, or absent, at specific lattice distances. The expanding-cube method utilized is straightforward to…
Dirac-Fock atomic electronic structure calculations using different nuclear charge distributions
Visscher, L; Dyall, KG
1997-01-01
Numerical Hartree-Fock calculations based on the Dirac-Coulomb Hamiltonian for the first 109 elements of the periodic table are presented. The results give the total electronic energy, as a function of the nuclear model that is used, for four different models of the nuclear charge distribution. The
Dirac-Fock atomic electronic structure calculations using different nuclear charge distributions
Visscher, L; Dyall, KG
1997-01-01
Numerical Hartree-Fock calculations based on the Dirac-Coulomb Hamiltonian for the first 109 elements of the periodic table are presented. The results give the total electronic energy, as a function of the nuclear model that is used, for four different models of the nuclear charge distribution. The
García-Garduño, O. A., E-mail: oagarciag@innn.edu.mx, E-mail: amanda.garcia.g@gmail.com [Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, México and Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Instituto Politécnico Nacional, Legaria 694, México City 11500, México (Mexico); Rodríguez-Ponce, M. [Departamento de Biofísica, Instituto Nacional de Cancerología, Mexico City 14080, México (Mexico); Gamboa-deBuen, I. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510 (Mexico); Rodríguez-Villafuerte, M. [Instituto de Física, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510 (Mexico); Galván de la Cruz, O. O. [Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Mexico City 14269, México (Mexico); and others
2014-09-15
Purpose: To assess the impact of the detector used to commission small photon beams on the calculated dose distribution in stereotactic radiosurgery (SRS). Methods: In this study, six types of detectors were used to characterize small photon beams: three diodes [a silicon stereotactic field diode SFD, a silicon diode SRS, and a silicon diode E], an ionization chamber CC01, and two types of radiochromic film models EBT and EBT2. These detectors were used to characterize circular collimated beams that were generated by a Novalis linear accelerator. This study was conducted in two parts. First, the following dosimetric data, which are of particular interest in SRS, were compared for the different detectors: the total scatter factor (TSF), the tissue phantom ratios (TPRs), and the off-axis ratios (OARs). Second, the commissioned data sets were incorporated into the treatment planning system (TPS) to compare the calculated dose distributions and the dose volume histograms (DVHs) that were obtained using the different detectors. Results: The TSFs data measured by all of the detectors were in good agreement with each other within the respective statistical uncertainties: two exceptions, where the data were systematically below those obtained for the other detectors, were the CC01 results for all of the circular collimators and the EBT2 film results for circular collimators with diameters below 10.0 mm. The OAR results obtained for all of the detectors were in excellent agreement for all of the circular collimators. This observation was supported by the gamma-index test. The largest difference in the TPR data was found for the 4.0 mm circular collimator, followed by the 10.0 and 20.0 mm circular collimators. The results for the calculated dose distributions showed that all of the detectors passed the gamma-index test at 100% for the 3 mm/3% criteria. The aforementioned observation was true regardless of the size of the calculation grid for all of the circular collimators
An improved method for calculating force distributions in moment-stiff timber connections
Ormarsson, Sigurdur; Blond, Mette
2012-01-01
An improved method for calculating force distributions in moment-stiff multi-dowel timber connections is presented, a method based on use of three-dimensional finite element simulations of timber connections subjected to moment action. The study that was carried out aimed at determining how...... the slip modulus varies with the angle between the direction of the dowel forces and the fibres in question, as well as how the orthotropic stiffness behaviour of the wood material affects the direction and the size of the forces. It was assumed that the force distribution generated by the moment action...... taking place strives to minimize the slip rotation between the separate members of a given timber connection. The results of modified hand calculations and of the corresponding finite element calculations that were performed were found to agree rather closely, and to differ remarkably from the results...
Blurton, Steven Paul; Kesselmeier, M.; Gondan, Matthias
2012-01-01
related work on the density of first-passage times [Navarro, D.J., Fuss, I.G. (2009). Fast and accurate calculations for first-passage times in Wiener diffusion models. Journal of Mathematical Psychology, 53, 222-230]. Two representations exist for the distribution, both including infinite series. We......We propose an improved method for calculating the cumulative first-passage time distribution in Wiener diffusion models with two absorbing barriers. This distribution function is frequently used to describe responses and error probabilities in choice reaction time tasks. The present work extends...... derive upper bounds for the approximation error resulting from finite truncation of the series, and we determine the number of iterations required to limit the error below a pre-specified tolerance. For a given set of parameters, the representation can then be chosen which requires the least...
Effect of Taper on Stress Distribution of All Ceramic Fixed Partial Dentures: a 3D-FEA Study
F. Gerami-Panah
2005-09-01
Full Text Available Statement of Problem: Mechanical failure of ceramic materials is controlled by brittle fracture, mostly occurred in tension. In 3-unit all-ceramic FPDs the connector area is considered to be at fracture risk because of tensile stress concentrations.Purpose: The aim of this FE analysis was to evaluate the effect of taper on stress distribution in all-ceramic FPDs.Materials and Methods: In this experimental study two 3-D finite element models of thee-unit IPS-Empress 2 FPDs replacing mandible second premolar were created by means of finite element software. The digital images were obtained from CT scan of human skull. Abutment was reduced with 12 and 22 degrees of taper. The cement layer,PDL, cancellous bone and cortical bone were also modeled. Frameworks of core material were fabricated. A static load of 100 N was applied at mid pontic area.Resolved stresses were calculated according to the Von Mises criterion and principal stresses.Results: In both models stresses were concentrated at the connectors. The maximum stresses were lower in the model with larger taper. The maximum Von Mises stress was recorded at the connector region of the premolar and the pontic. In model with larger taper the patterns of stresses were also more distributed and less concentrated.Conclusion: The highest Von Mises and principal stress were recorded at the connectors. Tensile stresses developed at the gingival connector of premolar and pontic was higher than molar. The stress level in model with 22-degree taper was lower compare to 12-degree and the stress pattern was more distributed, lowered the risk ofconcentrations.
Á. Vas
2013-06-01
Full Text Available The prediction of weather generally means the solution of differential equations on the base of the measured initial conditions where the data of close and distant neighboring points are used for the calculations. It requires the maintenance of expensive weather stations and supercomputers. However, if weather stations are not only capable of measuring but can also communicate with each other, then these smart sensors can also be applied to run forecasting calculations. This applies the highest possible level of parallelization without the collection of measured data into one place. Furthermore, if more nodes are involved, the result becomes more accurate, but the computing power required from one node does not increase. Our Distributed Sensor Network for meteorological sensing and numerical weather Prediction Calculations (DSN-PC can be applied in several different areas where sensing and numerical calculations, even the solution of differential equations, are needed.
Toyosada, M.; Niwa, T. [Kyushu Univ., Fukuoka (Japan)
1995-12-31
In this paper, Newman`s calculation model is modified to solve his neglected effect of the change of stress distribution ahead of a crack, and to leave elastic plastic materials along the crack surface because of the compatibility of Dugdale model. In addition to above treatment, the authors introduce plastic shrinkage at an immediate generation of new crack surfaces due to emancipation of internal force with the magnitude of yield stress level during unloading process in the model. Moreover, the model is expanded to arbitrary stress distribution field. By using the model, RPG load is simulated for a center notched specimen under constant amplitude loading with various stress ratios and decreased maximum load while keeping minimum load.
Shear strength and stress distribution in wet granular media
Richefeu, Vincent; Radjaï, Farhang; El Youssoufi, Moulay Saïd
2009-06-01
We investigate the shear strength and stress distribution properties of wet granular media in the pendular state where the liquid is mainly in the form of capillary bonds between particles. This work is based on a 3D discrete-element approach (molecular dynamics) with spherical particles enriched by a capillary force law. We show that the capillary force can be expressed as an explicit function of the gap and volume of the liquid bridge. The length scales involved in this expression are analyzed by comparing with direct integration of the Laplace-Young equation. In the simulations, we consider a maximum number density of liquid bonds in the bulk in agreement with equilibrium of each liquid bridge. This liquid bond number is a decisive parameter for the overall cohesion of wet granular materials. It is shown that the shear strength can be expressed as a function of liquid bond characteristics. The expression proposed initially by Rumpf is thus generalized to account for size polydispersity We show that this expression is in good agreement with our experimental data that will be briefly described. At low confining stress, the tensile action of capillary bonds induces a self-stressed particle network organized in a bi-percolating structure of positive and negative particle pressures. Various statistical descriptors of the microstructure and bond force network are used to characterize this partition. Two basic properties emerge: (i) The highest particle pressure is located in the bulk of each phase (positive and negative particle pressures); (ii) The lowest pressure level occurs at the interface between the two phases, involving also the largest connectivity of the particles via tensile and compressive bonds.
Development of an algebraic stress/two-layer model for calculating thrust chamber flow fields
Chen, C. P.; Shang, H. M.; Huang, J.
1993-01-01
Following the consensus of a workshop in Turbulence Modeling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data, to account for the non-isotropic turbulence effects.
Fatima Salman
2010-01-01
Full Text Available The design of components subjected to contact stress as local compressive stress is important in engineering application especially in ball and socket Joining. Two kinds of contact stress are introduced in the ball and socket joint, the first is from normal contact while the other is from sliding contact. Although joining two long links (drive shaft in steering cars will cause the effect of flexural and tensional buckling stress in hollow columns through the ball and socket ends on the failure condition of the joining mechanism. In this paper the consideration of the combined effect of buckling Load and contact stress on the ball and socket joints have been taken, epically on the stress distribution in the contact area. Different parameters have been taken in the design of joint. This is done by changing the angles for applied loads with the principle axis, the angle of contact between ball and socket and using different applied loads. The problem has been solved using analytical solution for computing the critical loads and using these loads for calculating the stress distribution with finite element method using ANSYS 10. The numerical results have been compared with the experimental method using photo elasticity pattern which shows good agreement between experimental and simulation results.
Calculation of gas content in coal seam influenced by in-situ stress grads and ground temperature
王宏图; 李时雨; 吴再生; 杨晓峰; 秦大亮; 杜云贵
2002-01-01
On the basis of the analysis of coal-bed gas pressure in deep mine, and the coal-bed permeability (k) and the characteristic of adsorption parameter (b) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in-situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal-bed gas pressure with the computing results of coal-bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.
DIST: a computer code system for calculation of distribution ratios of solutes in the purex system
Tachimori, Shoichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1996-05-01
Purex is a solvent extraction process for reprocessing the spent nuclear fuel using tri n-butylphosphate (TBP). A computer code system DIST has been developed to calculate distribution ratios for the major solutes in the Purex process. The DIST system is composed of database storing experimental distribution data of U(IV), U(VI), Pu(III), Pu(IV), Pu(VI), Np(IV), Np(VI), HNO{sub 3} and HNO{sub 2}: DISTEX and of Zr(IV), Tc(VII): DISTEXFP and calculation programs to calculate distribution ratios of U(IV), U(VI), Pu(III), Pu(IV), Pu(VI), Np(IV), Np(VI), HNO{sub 3} and HNO{sub 2}(DIST1), and Zr(IV), Tc(VII)(DITS2). The DIST1 and DIST2 determine, by the best-fit procedures, the most appropriate values of many parameters put on empirical equations by using the DISTEX data which fulfill the assigned conditions and are applied to calculate distribution ratios of the respective solutes. Approximately 5,000 data were stored in the DISTEX and DISTEXFP. In the present report, the following items are described, 1) specific features of DIST1 and DIST2 codes and the examples of calculation 2) explanation of databases, DISTEX, DISTEXFP and a program DISTIN, which manages the data in the DISTEX and DISTEXFP by functions as input, search, correction and delete. and at the annex, 3) programs of DIST1, DIST2, and figure-drawing programs DIST1G and DIST2G 4) user manual for DISTIN. 5) source programs of DIST1 and DIST2. 6) the experimental data stored in the DISTEX and DISTEXFP. (author). 122 refs.
The measurement of thermal stress distributions along the flow path in injection-molded flat plates
Hastenberg, C.H.V.; Wildervanck, P.C.; Leenen, A.J.H.; Schennink, G.G.J.
1992-01-01
Internal stresses in injection-molded parts are the result of thermal, flow, and pressure histories. Internal stresses can be roughly divided into thermal and flow-induced stresses. In this paper, a modified layer-removal method is presented to determine thermal stress distributions in injection-mol
An Analytical Benchmark for the Calculation of Current Distribution in Superconducting Cables
Bottura, L; Fabbri, M G
2002-01-01
The validation of numerical codes for the calculation of current distribution and AC loss in superconducting cables versus experimental results is essential, but could be affected by approximations in the electromagnetic model or incertitude in the evaluation of the model parameters. A preliminary validation of the codes by means of a comparison with analytical results can therefore be very useful, in order to distinguish among different error sources. We provide here a benchmark analytical solution for current distribution that applies to the case of a cable described using a distributed parameters electrical circuit model. The analytical solution of current distribution is valid for cables made of a generic number of strands, subjected to well defined symmetry and uniformity conditions in the electrical parameters. The closed form solution for the general case is rather complex to implement, and in this paper we give the analytical solutions for different simplified situations. In particular we examine the ...
Ferraro, Vittorio; Marinelli, Valerio; Mele, Marilena
2013-04-01
It is known that the best predictions of sky luminances are obtainable by the CIE 15 standard skies model, but the predictions by this model need knowledge of the measured luminance distributions themselves, since a criterion for selecting the type of sky starting from the irradiance values has not found until now. The authors propose a new simple method of applying the CIE model, based on the use of the sky index Si. A comparison between calculated luminance data and data measured in Arcavacata of Rende (Italy), Lyon (France) and Pamplona (Spain) show a good performance of this method in comparison with other methods of calculation of luminance existing in the literature.
Oliveira, C
2001-01-01
A systematic study of isodose distributions and dose uniformity in sample carriers of the Portuguese Gamma Irradiation Facility was carried out using the MCNP code. The absorbed dose rate, gamma flux per energy interval and average gamma energy were calculated. For comparison purposes, boxes filled with air and 'dummy' boxes loaded with layers of folded and crumpled newspapers to achieve a given value of density were used. The magnitude of various contributions to the total photon spectra, including source-dependent factors, irradiator structures, sample material and other origins were also calculated.
Bundesmann, C.; Feder, R.; Lautenschlaeger, T.; Neumann, H. [Leibniz-Institute of Surface Modification, Leipzig (Germany)
2015-12-15
Ion beam sputter deposition allows tailoring the properties of the film-forming, secondary particles (sputtered target particles and backscattered primary particles) and, hence, thin film properties by changing ion beam (ion energy, ion species) and geometrical parameters (ion incidence angle, polar emission angle). In particular, the energy distribution of secondary particles and their influence on the ion beam deposition process of Ag was studied in dependence on process parameters. Energy-selective mass spectrometry was used to measure the energy distribution of sputtered and backscattered ions. The energy distribution of the sputtered particles shows, in accordance with theory, a maximum at low energy and an E{sup -2} decay for energies above the maximum. If the sum of incidence angle and polar emission angle is larger than 90 , additional contributions due to direct sputtering events occur. The energy distribution of the backscattered primary particles can show contributions by scattering at target particles and at implanted primary particles. The occurrence of these contributions depends again strongly on the scattering geometry but also on the primary ion species. The energy of directly sputtered and backscattered particles was calculated using equations based on simple two-particle-interaction whereas the energy distribution was simulated using the well-known Monte Carlo code TRIM.SP. In principal, the calculation and simulation data agree well with the experimental findings. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Bulk stress distributions in the pore space of sphere-packed beds under Darcy flow conditions
Pham, Ngoc H.; Voronov, Roman S.; Tummala, Naga Rajesh; Papavassiliou, Dimitrios V.
2014-03-01
In this paper, bulk stress distributions in the pore space of columns packed with spheres are numerically computed with lattice Boltzmann simulations. Three different ideally packed and one randomly packed configuration of the columns are considered under Darcy flow conditions. The stress distributions change when the packing type changes. In the Darcy regime, the normalized stress distribution for a particular packing type is independent of the pressure difference that drives the flow and presents a common pattern. The three parameter (3P) log-normal distribution is found to describe the stress distributions in the randomly packed beds within statistical accuracy. In addition, the 3P log-normal distribution is still valid when highly porous scaffold geometries rather than sphere beds are examined. It is also shown that the 3P log-normal distribution can describe the bulk stress distribution in consolidated reservoir rocks like Berea sandstone.
Bulk stress distributions in the pore space of sphere-packed beds under Darcy flow conditions.
Pham, Ngoc H; Voronov, Roman S; Tummala, Naga Rajesh; Papavassiliou, Dimitrios V
2014-03-01
In this paper, bulk stress distributions in the pore space of columns packed with spheres are numerically computed with lattice Boltzmann simulations. Three different ideally packed and one randomly packed configuration of the columns are considered under Darcy flow conditions. The stress distributions change when the packing type changes. In the Darcy regime, the normalized stress distribution for a particular packing type is independent of the pressure difference that drives the flow and presents a common pattern. The three parameter (3P) log-normal distribution is found to describe the stress distributions in the randomly packed beds within statistical accuracy. In addition, the 3P log-normal distribution is still valid when highly porous scaffold geometries rather than sphere beds are examined. It is also shown that the 3P log-normal distribution can describe the bulk stress distribution in consolidated reservoir rocks like Berea sandstone.
N.Ghahramany; G.R.Boroun
2003-01-01
A calculation of the proton structure function F2(x,Q2) is reported with an approximation method that relates the reduced cross section derivative and the F2(x, Q2) scaling violation at low x by using quadratic form for the structure function. This quadratic form approximation method can be used to determine the structure function F2 (x, Q2) from the HERA reduced cross section data taken at low x. This new approach can determine the structure functions F2(x,Q2) with reasonable precision even for low x values which have not been investigated. We observe that the Q2 dependence is quadratic over the full kinematic covered range. To test the validity of our new determined structure functions, we find the gluon distribution function in the leading order approximation with our new calculation for the structure functions and compare them with the QCD parton distribution functions.
N. Ghahramany; G.R. Boroun
2003-01-01
A calculation of the proton structure function F2(x,Q2) is reported with an approximation method that relates the reduced cross section derivative and the F2(x, Q2) scaling violation at low x by using quadratic form for the structure function. This quadratic form approximation method can be used to determine the structure function F2 (x, Q2)from the HERA reduced cross section data taken at low x. This new approach can determine the structure functions F2(x,Q2) with reasonable precision even for low x values which have not been investigated. We observe that the Q2 dependence is quadratic over the full kinematic covered range. To test the validity of our new determined structure functions, wefind the gluon distribution function in the leading order approximation with our new calculation for the structure functions and compare them with the QCD parton distribution functions.
Shao, Wen-Yi; Xian, Hao
2016-11-01
When building an experimental platform for light propagation along an inhomogeneous turbulent path, it is very essential to set up the reasonable distribution of phase screen. Based on multi-layered model of phase screen, an iterative optimization algorithm of phase screen position is given in this paper. Thereafter, the optimal position of phase screens is calculated under the Hufnagel-Valley5/7 and Hefei-day turbulence profile. The results show that the positions of phase screen calculated by the iterative algorithm can fit well with the turbulence profile rather than mechanically placed phase screens at equal distance. Compared with the uniform distribution of phase screens position, the residual phase error of the iterative algorithm decreases very significantly. The similarity degree between them is minimal when number of layers is equal to two. Project supported by the National Natural Science Foundation of China (Grant No. 61308082).
Calculation of depth-dose distribution of intermediate energy heavy-ion beams
无
2002-01-01
Based on the characteristics of the interactions between intermediate energy heavy-ion beam and target matter, a method to calculate the depth-dose distribution of heavy-ion beams with intermediate energy (10 -100 MeV/u) is presented. By comparing high energy beams where projectile fragmentation is overwhelm ing with lowenergies where energy straggling is the sole factor instead, a crescent energy spread with increasing depth and a simple fragmentation assumption were included for the depth-dose calculation of the intermediate energy beam. Rel ative depth-dose curves of carbon and oxygen ion beams with intermediate energie s were computed according to the method here. Comparisons between the calculated relative doses and measurements are shown. The calculated Bragg curves, especially the upstream and downstream Bragg peaks, agree with the measured data. Differences between the two results appear only around the peak regions because of th e limitations of the calculation and experimental conditions, but the calculated curves generally reproduce the measured data within the experimental errors. Th e reasons for the divergences were analyzed carefully and the magnitudes of the deviations are given.
Madfa, A A; Kadir, M R Abdul; Kashani, J; Saidin, S; Sulaiman, E; Marhazlinda, J; Rahbari, R; Abdullah, B J J; Abdullah, H; Abu Kasim, N H
2014-07-01
Different dental post designs and materials affect the stability of restoration of a tooth. This study aimed to analyse and compare the stability of two shapes of dental posts (parallel-sided and tapered) made of five different materials (titanium, zirconia, carbon fibre and glass fibre) by investigating their stress transfer through the finite element (FE) method. Ten three-dimensional (3D) FE models of a maxillary central incisor restored with two different designs and five different materials were constructed. An oblique loading of 100 N was applied to each 3D model. Analyses along the centre of the post, the crown-cement/core and the post-cement/dentine interfaces were computed, and the means were calculated. One-way ANOVAs followed by post hoc tests were used to evaluate the effectiveness of the post materials and designs (p=0.05). For post designs, the tapered posts introduced significantly higher stress compared with the parallel-sided post (pmaterials, the highest level of stress was found for stainless steel, followed by zirconia, titanium, glass fibre and carbon fibre posts (p<0.05). The carbon and glass fibre posts reduced the stress distribution at the middle and apical part of the posts compared with the stainless steel, zirconia and titanium posts. The opposite results were observed at the crown-cement/core interface.
Fernandez-de-Cossio, Jorge
2010-03-01
Fine isotopic structure patterns resolvable by ultrahigh-resolution mass spectrometers are diagnostic of the elemental composition of moderately large compounds. Despite the proven performance of Fourier transforms algorithms to calculate accurate high resolution isotopic distribution, its application to finer ultrahigh resolving power exhibits limited performance. Fast Fourier transforms algorithm requires sampling the relevant range at equally spaced mass values, but ultrahigh resolution mass spectrum displays highly localized complex patterns (peaks) separated in between by relatively large unstructured intervals. Computational efforts consumed on those uninformative intervals are a waste of resources. A fast and memory efficient procedure is introduced in this paper to calculate the isotopic distribution of a single relatively high-mass molecule at ultrahigh resolution by Fourier transforms approaches. The whole isotopic distribution is packed closer to the monoisotopic peak without distorting the actual scale of the peak fine structure. This packing procedure reduced 8 to 32 times the computation resources in comparison to the same calculation performed without packing. The procedure can be readily implemented in existing software.
Doucet, R.; Olivares, M.; DeBlois, F.; Podgorsak, E. B.; Kawrakow, I.; Seuntjens, J.
2003-08-01
Calculations of dose distributions in heterogeneous phantoms in clinical electron beams, carried out using the fast voxel Monte Carlo (MC) system XVMC and the conventional MC code EGSnrc, were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from a Varian Clinac-18 accelerator with a 10 × 10 cm2 applicator and an SSD of 100 cm. Depth doses were measured with thermoluminescent dosimetry techniques (TLD 700) in phantoms consisting of slabs of Solid WaterTM (SW) and bone and slabs of SW and lung tissue-equivalent materials. Lateral profiles in water were measured using an electron diode at different depths behind one and two immersed aluminium rods. The accelerator was modelled using the EGS4/BEAM system and optimized phase-space files were used as input to the EGSnrc and the XVMC calculations. Also, for the XVMC, an experiment-based beam model was used. All measurements were corrected by the EGSnrc-calculated stopping power ratios. Overall, there is excellent agreement between the corrected experimental and the two MC dose distributions. Small remaining discrepancies may be due to the non-equivalence between physical and simulated tissue-equivalent materials and to detector fluence perturbation effect correction factors that were calculated for the 9 MeV beam at selected depths in the heterogeneous phantoms.
Doucet, R [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Olivares, M [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); DeBlois, F [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Podgorsak, E B [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada); Kawrakow, I [National Research Council Canada, Ionizing Radiation Standards Group, Ottawa K1A 0R6, Canada (Canada); Seuntjens, J [Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Ave Cedar, Montreal H3G 1A4 (Canada)
2003-08-07
Calculations of dose distributions in heterogeneous phantoms in clinical electron beams, carried out using the fast voxel Monte Carlo (MC) system XVMC and the conventional MC code EGSnrc, were compared with measurements. Irradiations were performed using the 9 MeV and 15 MeV beams from a Varian Clinac-18 accelerator with a 10 x 10 cm{sup 2} applicator and an SSD of 100 cm. Depth doses were measured with thermoluminescent dosimetry techniques (TLD 700) in phantoms consisting of slabs of Solid Water{sup TM} (SW) and bone and slabs of SW and lung tissue-equivalent materials. Lateral profiles in water were measured using an electron diode at different depths behind one and two immersed aluminium rods. The accelerator was modelled using the EGS4/BEAM system and optimized phase-space files were used as input to the EGSnrc and the XVMC calculations. Also, for the XVMC, an experiment-based beam model was used. All measurements were corrected by the EGSnrc-calculated stopping power ratios. Overall, there is excellent agreement between the corrected experimental and the two MC dose distributions. Small remaining discrepancies may be due to the non-equivalence between physical and simulated tissue-equivalent materials and to detector fluence perturbation effect correction factors that were calculated for the 9 MeV beam at selected depths in the heterogeneous phantoms.
Determination of Surface Stress Distributions in Steel Using Laser-Generated Surface Acoustic Waves
Shi; Yifei; Ni; Chenyin; Shen; Zhonghua; Ni; Xiaowu; Lu; Jian
2008-05-01
High frequency surface acoustic waves (SAWs) are excited by a pulsed laser and detected by a specially designed poly(vinylidene fluoride) (PVDF) transducer to investigate surface stress distribution. Two kinds of stressed surfaces are examined experimentally. One is a steel plate elastically deformed under simple bending forces, where the surface stress varies slowly. The other is a welded steel plate for which the surface stress varies very rapidly within a small area near the welding seam. Applying a new signal processing method developed from correlation technique, the velocity distribution of the SAWs, which reflects the stress distribution, is obtained in these two samples with high resolution.
Stress distribution in implant retained finger prosthesis: a finite element study.
Amornvit, Pokpong; Rokaya, Dinesh; Keawcharoen, Konrawee; Thongpulsawasdi, Nimit
2013-12-01
Finger amputation may result from congenital cause, trauma, infection and tumours. The finger amputation may be rehabilitated with dental implant-retained finger prosthesis. The success of implant-retained finger prosthesis is determined by the implant loading. The type of the force is a determining factor in implant loading. To evaluate stress distributions in finger bone when the loading force is applied along the long axis of the implant using finite element analysis. The finite element models were created. The finger bone model containing cortical bone and cancellous bone was constructed by using radiograph. Astra Tech Osseo Speed bone level implant of 4.5 mm diameter and 14 mm length was selected. The force was applied to the top of the abutment along the long axis of the implant. Finite element analysis indicated that the maximum stress was located at the head of abutment screw. The minimum stress was located in the apical third of the implant fixture. The weakest point was calculated by safety factor which is located in the spongy bone at apical third of the fixtures. Finally, 4.9 times yield stress of spongy bone was needed for the deformation of the spongy bone. Finite element study showed that when the force was applied along the long axis of the implant, the maximum stress was located around the neck of the implant and the cortex bone received more stress than cancellous bone. So, to achieve long term success, the designers of implant systems must confront biomaterial and biomechanical problems including in vivo forces on implants, load transmission to the interface and interfacial tissue response.
Tominaka, Toshiharu [Ministry of Education, Culture, Sports, Science and Technology (MEXT), 2-5-1, Marunouchi, Chiyoda-ku, Tokyo 100-8959 (Japan)
2006-10-15
The current distributions of untwisted infinitely long superconductors have been studied during the current sweep and under an external field, using the inductance matrix among superconducting finite elements which are generated from a superconductor. The self- and mutual inductances of general polygonal conductors with a uniform current density over each cross section are precisely calculated from the analytical expressions for the geometrical mean distances. The current distributions among each superconducting element are obtained by solving the circuit equation with the Bean model and a nonlinear E-J relation based on the power law. In addition, the magnetic field and vector potential distributions of an untwisted superconducting composite are also obtained, using the analytical expressions for the magnetic field and vector potential due to polygonal conductors.
Krantz, Timothy L.
2011-01-01
The purpose of this study was to assess some calculation methods for quantifying the relationships of bearing geometry, material properties, load, deflection, stiffness, and stress. The scope of the work was limited to two-dimensional modeling of straight cylindrical roller bearings. Preparations for studies of dynamic response of bearings with damaged surfaces motivated this work. Studies were selected to exercise and build confidence in the numerical tools. Three calculation methods were used in this work. Two of the methods were numerical solutions of the Hertz contact approach. The third method used was a combined finite element surface integral method. Example calculations were done for a single roller loaded between an inner and outer raceway for code verification. Next, a bearing with 13 rollers and all-steel construction was used as an example to do additional code verification, including an assessment of the leading order of accuracy of the finite element and surface integral method. Results from that study show that the method is at least first-order accurate. Those results also show that the contact grid refinement has a more significant influence on precision as compared to the finite element grid refinement. To explore the influence of material properties, the 13-roller bearing was modeled as made from Nitinol 60, a material with very different properties from steel and showing some potential for bearing applications. The codes were exercised to compare contact areas and stress levels for steel and Nitinol 60 bearings operating at equivalent power density. As a step toward modeling the dynamic response of bearings having surface damage, static analyses were completed to simulate a bearing with a spall or similar damage.
The spatial distribution of earthquake stress rotations following large subduction zone earthquakes
Hardebeck, Jeanne L.
2017-01-01
Rotations of the principal stress axes due to great subduction zone earthquakes have been used to infer low differential stress and near-complete stress drop. The spatial distribution of coseismic and postseismic stress rotation as a function of depth and along-strike distance is explored for three recent M ≥ 8.8 subduction megathrust earthquakes. In the down-dip direction, the largest coseismic stress rotations are found just above the Moho depth of the overriding plate. This zone has been identified as hosting large patches of large slip in great earthquakes, based on the lack of high-frequency radiated energy. The large continuous slip patches may facilitate near-complete stress drop. There is seismological evidence for high fluid pressures in the subducted slab around the Moho depth of the overriding plate, suggesting low differential stress levels in this zone due to high fluid pressure, also facilitating stress rotations. The coseismic stress rotations have similar along-strike extent as the mainshock rupture. Postseismic stress rotations tend to occur in the same locations as the coseismic stress rotations, probably due to the very low remaining differential stress following the near-complete coseismic stress drop. The spatial complexity of the observed stress changes suggests that an analytical solution for finding the differential stress from the coseismic stress rotation may be overly simplistic, and that modeling of the full spatial distribution of the mainshock static stress changes is necessary.
Liu, Yuan [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Ning, Chuangang, E-mail: ningcg@tsinghua.edu.cn [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
2015-10-14
Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.
Tian, Jiandong; Duan, Zhigang; Ren, Weihong; Han, Zhi; Tang, Yandong
2016-04-04
The spectral power distributions (SPD) of outdoor light sources are not constant over time and atmospheric conditions, which causes the appearance variation of a scene and common natural illumination phenomena, such as twilight, shadow, and haze/fog. Calculating the SPD of outdoor light sources at different time (or zenith angles) and under different atmospheric conditions is of interest to physically-based vision. In this paper, for computer vision and its applications, we propose a feasible, simple, and effective SPD calculating method based on analyzing the transmittance functions of absorption and scattering along the path of solar radiation through the atmosphere in the visible spectrum. Compared with previous SPD calculation methods, our model has less parameters and is accurate enough to be directly applied in computer vision. It can be applied in computer vision tasks including spectral inverse calculation, lighting conversion, and shadowed image processing. The experimental results of the applications demonstrate that our calculation methods have practical values in computer vision. It establishes a bridge between image and physical environmental information, e.g., time, location, and weather conditions.
The denoising of Monte Carlo dose distributions using convolution superposition calculations.
El Naqa, I; Cui, J; Lindsay, P; Olivera, G; Deasy, J O
2007-09-07
Monte Carlo (MC) dose calculations can be accurate but are also computationally intensive. In contrast, convolution superposition (CS) offers faster and smoother results but by making approximations. We investigated MC denoising techniques, which use available convolution superposition results and new noise filtering methods to guide and accelerate MC calculations. Two main approaches were developed to combine CS information with MC denoising. In the first approach, the denoising result is iteratively updated by adding the denoised residual difference between the result and the MC image. Multi-scale methods were used (wavelets or contourlets) for denoising the residual. The iterations are initialized by the CS data. In the second approach, we used a frequency splitting technique by quadrature filtering to combine low frequency components derived from MC simulations with high frequency components derived from CS components. The rationale is to take the scattering tails as well as dose levels in the high-dose region from the MC calculations, which presumably more accurately incorporates scatter; high-frequency details are taken from CS calculations. 3D Butterworth filters were used to design the quadrature filters. The methods were demonstrated using anonymized clinical lung and head and neck cases. The MC dose distributions were calculated by the open-source dose planning method MC code with varying noise levels. Our results indicate that the frequency-splitting technique for incorporating CS-guided MC denoising is promising in terms of computational efficiency and noise reduction.
The denoising of Monte Carlo dose distributions using convolution superposition calculations
El Naqa, I [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States); Cui, J [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States); Lindsay, P [MD Anderson, Houston, TX (United States); Olivera, G [Tomotherapy Inc., Madison, WI (United States); Deasy, J O [Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO (United States)
2007-09-07
Monte Carlo (MC) dose calculations can be accurate but are also computationally intensive. In contrast, convolution superposition (CS) offers faster and smoother results but by making approximations. We investigated MC denoising techniques, which use available convolution superposition results and new noise filtering methods to guide and accelerate MC calculations. Two main approaches were developed to combine CS information with MC denoising. In the first approach, the denoising result is iteratively updated by adding the denoised residual difference between the result and the MC image. Multi-scale methods were used (wavelets or contourlets) for denoising the residual. The iterations are initialized by the CS data. In the second approach, we used a frequency splitting technique by quadrature filtering to combine low frequency components derived from MC simulations with high frequency components derived from CS components. The rationale is to take the scattering tails as well as dose levels in the high-dose region from the MC calculations, which presumably more accurately incorporates scatter; high-frequency details are taken from CS calculations. 3D Butterworth filters were used to design the quadrature filters. The methods were demonstrated using anonymized clinical lung and head and neck cases. The MC dose distributions were calculated by the open-source dose planning method MC code with varying noise levels. Our results indicate that the frequency-splitting technique for incorporating CS-guided MC denoising is promising in terms of computational efficiency and noise reduction. (note)
NOTE: The denoising of Monte Carlo dose distributions using convolution superposition calculations
El Naqa, I.; Cui, J.; Lindsay, P.; Olivera, G.; Deasy, J. O.
2007-09-01
Monte Carlo (MC) dose calculations can be accurate but are also computationally intensive. In contrast, convolution superposition (CS) offers faster and smoother results but by making approximations. We investigated MC denoising techniques, which use available convolution superposition results and new noise filtering methods to guide and accelerate MC calculations. Two main approaches were developed to combine CS information with MC denoising. In the first approach, the denoising result is iteratively updated by adding the denoised residual difference between the result and the MC image. Multi-scale methods were used (wavelets or contourlets) for denoising the residual. The iterations are initialized by the CS data. In the second approach, we used a frequency splitting technique by quadrature filtering to combine low frequency components derived from MC simulations with high frequency components derived from CS components. The rationale is to take the scattering tails as well as dose levels in the high-dose region from the MC calculations, which presumably more accurately incorporates scatter; high-frequency details are taken from CS calculations. 3D Butterworth filters were used to design the quadrature filters. The methods were demonstrated using anonymized clinical lung and head and neck cases. The MC dose distributions were calculated by the open-source dose planning method MC code with varying noise levels. Our results indicate that the frequency-splitting technique for incorporating CS-guided MC denoising is promising in terms of computational efficiency and noise reduction.
Landslide Monitoring Based on High-Resolution Distributed Fiber Optic Stress Sensor
Zhi-Yong Dai; Yong Liu; Li-Xun Zhang; Zhong-Hua Ou; Ce Zhou; Yong-Zhi Liu
2008-01-01
A landslide monitoring application is presented by using a high-resolution distributed fiber optic stress sensor. The sensor is used to monitor the intra-stress distribution and variations in landslide bodies, and can be used for the early warning of the occurrence of the landslides. The principle of distributed fiber optic stress sensing and the intra-stress monitoring method for landslides are described in detail. By measuring the distributed polarization mode coupling in the polarization-maintaining fiber, the distributed fiber stress sensor with stress measuring range 0 to 15 Mpa, spatial resolution 10 em and measuring range 0.5 km, is designed. The warning system is also investigated experimentally in the field trial.
无
2000-01-01
Follow Chen and Duda's model of spectral fall-off of (3, the dependence of peak parameters of ground motion, peak displacement dm, peak velocity vm and peak acceleration am, upon the environment stress (0-values are studied using near source seismic digital recordings for the sequence of the Wuding, Yunnan, M = 6.5 earthquake, in which, as a new thought, the peak parameters are assumed to be related to the medium Q-value. Three formulae for estimating the environment stress (0-values by the peak parameters of three types of ground motions are derived. Using these formulae, the environment stress (0-values are calculated for the sequence of the Wuding earthquake. The result show that (0-values calculated by the three formulae are constant largely, the averages of (0 are in the range of 5.0～35 MPa for most earthquakes. It belongs to the high-stress earthquakes sequence: the high-stress values are restricted to the relatively small area closely near to the epicenter of the main shock. The fine distribution structure for the contours of the environment stress (0-values is related closely to the strong aftershocks. The analysis of spatial and temporal feature of (0-values suggests that the earthquakes sequence in a rupture process generated at the specific intersection zone of seismo-tectonics under high-stress background.
A novel stress distribution analytical model of O-ring seals under different properties of materials
Wu, Di; Wang, Shao Ping; Wang, Xing Jian [School of Automation Science and Electrical Engineering, Beihang University, Beijing (China)
2017-01-15
The elastomeric O-ring seals have been widely used as sealing elements in hydraulic systems. The sealing performance of O-ring seals is related to stress distribution. The stresses distribution depends on the squeeze rate and internal pressure, and would vary with properties of O-ring seals materials. Thus, in order to study the sealing performance of O-ring seals, it is necessary to describe the analytic relationship between stress distribution and properties of O-ring seals materials. For this purpose, a novel Stress distribution analytical model (SDAM) is proposed in this paper. The analytical model utilizes two stress complex functions to describe the stress distribution of O-ring seals. The proposed SDAM can express not only the analytical relationship between stress distribution and Young’s modulus, but also the one between stress distribution and Poisson’s ratio. Finally, compared results between finite element analysis and the SDAM validate that the proposed model can effectively reveal the stress distribution under different properties for O-ring materials.
Dose distribution calculation for in-vivo X-ray fluorescence scanning
Figueroa, R. G. [Universidad de la Frontera, Departamento de Ciencias Fisicas, Av. Francisco Salazar 1145, Temuco 4811230, Araucania (Chile); Lozano, E. [Instituto Nacional del Cancer, Unidad de Fisica Medica, Av. Profesor Zanartu 1010, Santiago (Chile); Valente, M., E-mail: figueror@ufro.cl [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Ravadavia 1917, C1033AAJ, Buenos Aires (Argentina)
2013-08-01
In-vivo X-ray fluorescence constitutes a useful and accurate technique, worldwide established for constituent elementary distribution assessment. Actually, concentration distributions of arbitrary user-selected elements can be achieved along sample surface with the aim of identifying and simultaneously quantifying every constituent element. The method is based on the use of a collimated X-ray beam reaching the sample. However, one common drawback for considering the application of this technique for routine clinical examinations was the lack of information about associated dose delivery. This work presents a complete study of the dose distribution resulting from an in-vivo X-ray fluorescence scanning for quantifying biohazard materials on human hands. Absorbed dose has been estimated by means of dosimetric models specifically developed to this aim. In addition, complete dose distributions have been obtained by means of full radiation transport calculations in based on stochastic Monte Carlo techniques. A dedicated subroutine has been developed using the Penelope 2008 main code also integrated with dedicated programs -Mat Lab supported- for 3 dimensional dose distribution visualization. The obtained results show very good agreement between approximate analytical models and full descriptions by means of Monte Carlo simulations. (Author)
Klüter, Sebastian, E-mail: sebastian.klueter@med.uni-heidelberg.de; Schubert, Kai; Lissner, Steffen; Sterzing, Florian; Oetzel, Dieter; Debus, Jürgen [Department of Radiation Oncology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany, and Heidelberg Institute for Radiation Oncology (HIRO), Im Neuenheimer Feld 400, 69120 Heidelberg, Germany, and German Consortium for Translational Cancer Research (DKTK), Im Neuenheimer Feld 400, 69120 Heidelberg (Germany); Schlegel, Wolfgang [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Oelfke, Uwe [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany and Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom); Nill, Simeon [Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom)
2014-08-15
Purpose: The dosimetric verification of treatment plans in helical tomotherapy usually is carried out via verification measurements. In this study, a method for independent dose calculation of tomotherapy treatment plans is presented, that uses a conventional treatment planning system with a pencil kernel dose calculation algorithm for generation of verification dose distributions based on patient CT data. Methods: A pencil beam algorithm that directly uses measured beam data was configured for dose calculation for a tomotherapy machine. Tomotherapy treatment plans were converted into a format readable by an in-house treatment planning system by assigning each projection to one static treatment field and shifting the calculation isocenter for each field in order to account for the couch movement. The modulation of the fluence for each projection is read out of the delivery sinogram, and with the kernel-based dose calculation, this information can directly be used for dose calculation without the need for decomposition of the sinogram. The sinogram values are only corrected for leaf output and leaf latency. Using the converted treatment plans, dose was recalculated with the independent treatment planning system. Multiple treatment plans ranging from simple static fields to real patient treatment plans were calculated using the new approach and either compared to actual measurements or the 3D dose distribution calculated by the tomotherapy treatment planning system. In addition, dose–volume histograms were calculated for the patient plans. Results: Except for minor deviations at the maximum field size, the pencil beam dose calculation for static beams agreed with measurements in a water tank within 2%/2 mm. A mean deviation to point dose measurements in the cheese phantom of 0.89% ± 0.81% was found for unmodulated helical plans. A mean voxel-based deviation of −0.67% ± 1.11% for all voxels in the respective high dose region (dose values >80%), and a mean local
Istrate, Nicolae; Lindner, John
2014-03-01
We design an Earth-like artificial gravity field using the Darmois-Israel junction conditions of general relativity to connect the flat spacetime outside an infinitesimally thin cylinder to the curved spacetime inside. In the calculation of extrinsic curvature, our construction exploits Earth's weak gravity, which implies similar inside and outside curvatures, to approximate the unit normal inside by the negative unit normal outside. The stress-energy distribution on the cylinder's sides includes negative energy density.
An improved mixed numerical-experimental method for stress field calculation
Lopes, H. M. R.; Guedes, R. M.; Vaz, M. A.
2007-07-01
In this work a numerical-experimental method is used to study the dynamic behavior of an aluminum plate subjected to a small mass impact. The out-of-plane displacements, due to transient bending wave propagation, were assessed for successive time instants, using double pulse TV-holography, also known as pulsed ESPI. The experimental setup and the image processing methods were improved to allow the calculation of the plate transient stress field. Integral transforms are used to obtain the strain fields from spatial derivatives of displacements noisy data. A numerical simulation of the plate transient response was carried out with FEM Ansys ®. For this purpose a PZT transducer was used to record the impact force history, which was inputted in the numerical model. Finally, the comparisons between numerical and experimental results are presented in order to validate the present methodology.
Z.J.YANG; A.J.DEEKS
2008-01-01
A frequency-domain approach based on the semi-analytical scaled boundary finite element method (SBFEM) was developed to calculate dynamic stress intensity factors (DSIFs) at bimaterial interface cracks subjected to transient loading. Be-cause the stress solutions of the SBFEM in the frequency domain are analytical in the radial direction, and the complex stress singularity at the bimaterial interface crack tip is explicitly represented in the stress solutions, the mixed-mode DSIFs were calculated directly by definition. The complex frequency-response functions of DSIFs were then used by the fast Fourier transform (FFT) and the inverse FFT to calculate time histories of DSIFs. A benchmark example was modelled. Good re-sults were obtained by modelling the example with a small number of degrees of freedom due to the semi-analytical nature of the SBFEM.
Kanematsu, Nobuyuki
2007-01-01
A simple and efficient variant of the pencil-beam algorithm for dose distribution calculation is proposed. Compared to the conventional pencil-beam algorithms, the new algorithm is intrinsically faster due to minimized computation within the convolution integral. Namely, computation for physical interaction is decoupled from the convolution integral and the convolution kernel is approximated by simple grid-to-grid correlation. Implementation to a treatment planning system for carbon-ion radiotherapy has enabled realistic beam blurring with marginal speed decrease from the broad-beam calculation. Evaluation of a modeled proton pencil beam exhibits inaccuracy within its spread at the Bragg peak when the beam incidence is angled to all the dose grid axes, which will be minimized in broad-beam formation and may be acceptable depending on its relative significance to the other sources of errors. The new algorithm will provide balanced accuracy and speed without technical difficulty for high-resolution dose distrib...
V. V. Ivashechkin
2010-01-01
Full Text Available The paper considers a mathematical model for process of pressure impulse distribution in a water well which appear as a result of underwater gas explosions in cylindrical and spherical explosive chambers with elastic shells and in a rigid cylindrical chamber which is open from the bottom. The proposed calculation methodology developed on the basis of the mathematical model makes it possible to determine pressure in the impulse on a filter wall and at any point of a water well pre-filter zone.
Xiaozhi Wu; Shaofeng Wang
2007-01-01
Applying the parametric derivation method, Peierls energy and Peierls stress are calculated with a non-sinusoidal force law in the lattice theory, while the results obtained by the power-series expansion according to sinusoidal law can be deduced as a limiting case of nonsinusoidal law. The simplified expressions of Peierls energy and Peierls stress are obtained for the limit of wide and narrow. Peierls energy and Peierls stress decrease monotonically with the factor of modification of force law. Present results can be used expediently for prediction of the correct order of magnitude of Peierls stress for materials.
Lin, Zhili; Li, Xiaoyan; Zhao, Kuixia; Chen, Xudong; Chen, Mingyu; Pu, Jixiong
2016-06-01
For an inertial confinement fusion (ICF) system, the light intensity distribution in the hohlraum is key to the initial plasma excitation and later laser-plasma interaction process. Based on the concept of coordinate transformation of spatial points and vector, we present a robust method with a detailed procedure that makes the calculation of the three dimensional (3D) light intensity distribution in hohlraum easily. The method is intuitive but powerful enough to solve the complex cases of random number of laser beams with arbitrary polarization states and incidence angles. Its application is exemplified in the Shenguang III Facility (SG-III) that verifies its effectiveness and it is useful for guiding the design of hohlraum structure parameter.
Comparison of Residual Stress Distributions of Similar and Dissimilar Thick Butt-Weld Plates
Suzuki, Hiroshi; Katsuyama, Jinya; Morii, Yukio
Residual stress distributions of 35 mm thick dissimilar metal butt-weld between A533B ferritic steel and Type 304 austenitic stainless steel (304SS) with Ni alloy welds and similar metal butt-weld of 304SS were measured using neutron diffraction. Effects of differences in thermal expansion coefficients (CTEs) and material strengths on the weld residual stress distributions were discussed by comparison of the residual stress distributions between the similar and dissimilar metal butt-welds. Residual stresses in the similar metal butt-weld exhibited typical distributions found in a thick butt-weld and they were distributed symmetrically on either side of the weld line. Meanwhile, asymmetric residual stress distributions were observed near the root of the dissimilar metal butt-weld, which was caused by differences in CTEs and yield strengths among both parent materials and weld metals. Transverse residual stress distribution of the dissimilar metal butt-weld was similar trend to that of the similar metal butt-weld, since effect of difference in CTEs were negligible, while magnitude of the transverse residual stress near the root depended on the yield strengths of each metal. In contrast, the normal and longitudinal residual stresses in the dissimilar metal butt-weld distributed asymmetrically on either side of weld line due to influence of differences in CTEs.
Free energy calculations, enhanced by a Gaussian ansatz, for the "chemical work" distribution.
Boulougouris, Georgios C
2014-05-15
The evaluation of the free energy is essential in molecular simulation because it is intimately related with the existence of multiphase equilibrium. Recently, it was demonstrated that it is possible to evaluate the Helmholtz free energy using a single statistical ensemble along an entire isotherm by accounting for the "chemical work" of transforming each molecule, from an interacting one, to an ideal gas. In this work, we show that it is possible to perform such a free energy perturbation over a liquid vapor phase transition. Furthermore, we investigate the link between a general free energy perturbation scheme and the novel nonequilibrium theories of Crook's and Jarzinsky. We find that for finite systems away from the thermodynamic limit the second law of thermodynamics will always be an inequality for isothermal free energy perturbations, resulting always to a dissipated work that may tend to zero only in the thermodynamic limit. The work, the heat, and the entropy produced during a thermodynamic free energy perturbation can be viewed in the context of the Crooks and Jarzinsky formalism, revealing that for a given value of the ensemble average of the "irreversible" work, the minimum entropy production corresponded to a Gaussian distribution for the histogram of the work. We propose the evaluation of the free energy difference in any free energy perturbation based scheme on the average irreversible "chemical work" minus the dissipated work that can be calculated from the variance of the distribution of the logarithm of the work histogram, within the Gaussian approximation. As a consequence, using the Gaussian ansatz for the distribution of the "chemical work," accurate estimates for the chemical potential and the free energy of the system can be performed using much shorter simulations and avoiding the necessity of sampling the computational costly tails of the "chemical work." For a more general free energy perturbation scheme that the Gaussian ansatz may not be
Probabilistic Harmonic Calculation in Distribution Networks with Electric Vehicle Charging Stations
Jianxue Wang
2014-01-01
Full Text Available Integrating EV charging station into power grid will bring impacts on power system, among which the most significant one is the harmonic pollution on distribution networks. Due to the uncertainty of the EV charging process, the harmonic currents brought by EV charging stations have a random nature. This paper proposed a mathematical simulation method for studying the working status of charging stations, which considers influencing factors including random leaving factor, electricity price, and waiting time. Based on the proposed simulation method, the probability distribution of the harmonic currents of EV charging stations is obtained and used in the calculation of the probability harmonic power flow. Then the impacts of EVs and EV charging stations on distribution networks can be analyzed. In the case study, the proposed simulation and analysis method is implemented on the IEEE-34 distribution network. The influences of EV arrival rates, the penetration rate, and the accessing location of EV charging station are also investigated. Results show that this research has good potential in guiding the planning and construction of charging station.
Herzog, J.
1974-01-01
A method of calculating stage parameters and flow distribution of axial turbines is described. The governing equations apply to space between the blade rows and are based on the assumption of rotationally symmetrical, compressible, adiabatic flow conditions. Results are presented for stage design and flow analysis calculations. Theoretical results from the calculation system are compared with experimental data from low pressure steam turbine tests.
Effect of four factors in the calculation of induced voltages on a tree-shaped distribution line
Torres, Horacio; Perez, Ernesto; Herrera, Javier; Younes, Camilo; Salgado, Milton; Quintana, Carlos; Rondon, Daniel; Gallego, Luis; Montana, Johny; Vargas, Mauricio [Universidad Nacional de Colombia, Bogota (Colombia). Research Program on Acquisition and Analysis of Signals - PAAS]. E-mail: paas@paas.unal.edu.co
2001-07-01
The main objective of this paper is to show a sensibility analysis of four different factors: current waveform, return stroke velocity, lightning current amplitude and network configuration in the calculation of induced voltages on a tree-shaped distribution line. In order to calculate distribution line. In order to calculate the induced voltages it was used the EMTP/ATP program with the inclusion of Rusck's Coupling Model into the MODELS routine. (author)
An Experimental Study on Distribution of Vertical Stress in a Silo with a Central Inner Downcomer
景山; 易江林; 王金福; 汪展文; 金涌
2002-01-01
The distribution of vertical stress for both active and passive state in the silo with a central innerdowncomer is reported in this paper. Experimental measurement of the axial distribution of vertical stress for bothactive and passive state in the silo are in good agreement with that predicted by theoretical analysis. The meanaxial stress is reduced due to the presence of the inner downcomer in the silo.
E. V. Shmatok
2015-01-01
Full Text Available Nowadays mathematical modeling of peculiar features of a stress-strain state is considered as a perspective direction of research. In this regard the aim of this paper has been to make calculations of the stress-strain state initiated by a system of parallel lenticular residual mechanical twins that occur due to local surface deformation of Ni2MnGa single crystal martensitic phase.The method is applied while using a superposition principle of fields and approximation of a continuous distribution of twinning dislocations on twin boundaries in a continuous elastic medium.The calculations have made it possible to obtain distribution graphs of displacement fields and stresses and point out the fact that a configuration of displacement component distribution uy is significantly different from the displacement of components ux and uz having a displacement distribution similar to each other. The highest value of displacement occurs in the component uy in twins peaks.The paper also presents results of calculations for six components of a stress field the tensor. The obtained results have revealed similarity in stress distribution character of the components sxz and szz, but they differ numerically from each other about in two times. The largest value of the stresses occurring in the lenticular twins has been observed in components sxx, sxz, syy, syz and it has been focused mainly at the borders and peaks of twins.A common feature of the obtained components of displacement and stresses in a lenticular twins system is symmetry with regard to OY. In addition, the stress distribution of all obtained tensor components has been mainly localized at the borders and at the tops of twins where the highest values of stresses capable of exerting a significant impact on dislocation and diffusion processes are generally concentrated.
Hamák I.
2010-06-01
Full Text Available Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.
Fernández-Fernández, Mario; Rodríguez-González, Pablo; García Alonso, J Ignacio
2016-10-01
We have developed a novel, rapid and easy calculation procedure for Mass Isotopomer Distribution Analysis based on multiple linear regression which allows the simultaneous calculation of the precursor pool enrichment and the fraction of newly synthesized labelled proteins (fractional synthesis) using linear algebra. To test this approach, we used the peptide RGGGLK as a model tryptic peptide containing three subunits of glycine. We selected glycine labelled in two (13) C atoms ((13) C2 -glycine) as labelled amino acid to demonstrate that spectral overlap is not a problem in the proposed methodology. The developed methodology was tested first in vitro by changing the precursor pool enrichment from 10 to 40% of (13) C2 -glycine. Secondly, a simulated in vivo synthesis of proteins was designed by combining the natural abundance RGGGLK peptide and 10 or 20% (13) C2 -glycine at 1 : 1, 1 : 3 and 3 : 1 ratios. Precursor pool enrichments and fractional synthesis values were calculated with satisfactory precision and accuracy using a simple spreadsheet. This novel approach can provide a relatively rapid and easy means to measure protein turnover based on stable isotope tracers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Calculation of momentum distribution function of a non-thermal fermionic dark matter
Biswas, Anirban; Gupta, Aritra
2017-03-01
The most widely studied scenario in dark matter phenomenology is the thermal WIMP scenario. Inspite of numerous efforts to detect WIMP, till now we have no direct evidence for it. A possible explanation for this non-observation of dark matter could be because of its very feeble interaction strength and hence, failing to thermalise with the rest of the cosmic soup. In other words, the dark matter might be of non-thermal origin where the relic density is obtained by the so-called freeze-in mechanism. Furthermore, if this non-thermal dark matter is itself produced substantially from the decay of another non-thermal mother particle, then their distribution functions may differ in both size and shape from the usual equilibrium distribution function. In this work, we have studied such a non-thermal (fermionic) dark matter scenario in the light of a new type of U(1)B‑L model. The U(1)B‑L model is interesting, since, besides being anomaly free, it can give rise to neutrino mass by Type II see-saw mechanism. Moreover, as we will show, it can accommodate a non-thermal fermionic dark matter as well. Starting from the collision terms, we have calculated the momentum distribution function for the dark matter by solving a coupled system of Boltzmann equations. We then used it to calculate the final relic abundance, as well as other relevant physical quantities. We have also compared our result with that obtained from solving the usual Boltzmann (or rate) equations directly in terms of comoving number density, Y. Our findings suggest that the latter approximation is valid only in cases where the system under study is close to equilibrium, and hence should be used with caution.
Three-Body Model Calculation of Spin Distribution in Two-Nucleon Transfer Reaction
Ogata, Kazuyuki; Chiba, Satoshi
2011-01-01
The differential cross sections of two-nucleon transfer reactions 238U(18O,16O)240U around 10 MeV per nucleon are calculated by one-step Born-approximation with a 16O+2n+238U three-body model. The three-body wave function in the initial channel is obtained with the continuum-discretized coupled-channels method, and that in the final channel is evaluated with adiabatic approximation. The resulting cross sections have a peak around the grazing angle, and the spin distribution, i.e., the cross section at the peak as a function of the transferred spin, is investigated. The shape of the spin distribution is found not sensitive to the incident energies, optical potentials, and treatment of the breakup channels both in the initial and final states, while it depends on the excitation energy of the residual nucleus 240U. The peak of the spin distribution moves to the large-spin direction as the excitation energy increases. To fulfill the condition that the peak position should not exceeds 10 hbar, which is necessary f...
Gerth, E.; Glagolevskij, Yu. V.
The observable magnetic field of a star is the result of integration over its visible hemisphere, related to the information transferring medium: the spectral line profile. The hitherto practised simple integration of the magnetic field strength neglects the spotty face of the star and is physically wrong. Because of the topographically distributed line-generating elements in the stellar atmosphere, the contribution of all parts of the surface to the integration is different. For an effective computation, both the magnetic field and the element distribution are transformed from globes to Mercator maps and arranged as right-angled matrices. The numerical evaluation is performed by a special computer program, which uses matrices and vector algebra. The theory is based on the mathematical derivation of convolution integrals for the rotation of the star and the line profiles formed in its atmosphere, whereby the radiation from all surface areas in direction to the observer is integrated, accounting for the geometrical and radiation transfer conditions of the disk-like visible hemisphere and the element distribution of chemically peculiar (CP) stars. The computation starts from a given magnetic field structure on the surface of a star and progresses straightforward over convolution integrals to the phase curves of the integral magnetic field strength. The calculation procedure is independent of a special generation model of the stellar magnetic field and possesses common validity. In consideration of other approaches to the problem of field structure analysis, also the inversion of the convolution is discussed.
Gouinaud, Laure; Katz, Ira; Martin, Andrew; Hazebroucq, Jean; Texereau, Joëlle; Caillibotte, Georges
2015-01-01
A numerical pressure loss model previously used for adult human airways has been modified to simulate the inhalation pressure distribution in a healthy 9-month-old infant lung morphology model. Pressure distributions are calculated for air as well as helium and xenon mixtures with oxygen to investigate the effects of gas density and viscosity variations for this age group. The results indicate that there are significant pressure losses in infant extrathoracic airways due to inertial effects leading to much higher pressures to drive nominal flows in the infant airway model than for an adult airway model. For example, the pressure drop through the nasopharynx model of the infant is much greater than that for the nasopharynx model of the adult; that is, for the adult-versus-child the pressure differences are 0.08 cm H2O versus 0.4 cm H2O, 0.16 cm H2O versus 1.9 cm H2O and 0.4 cm H2O versus 7.7 cm H2O, breathing helium-oxygen (78/22%), nitrogen-oxygen (78/22%) and xenon-oxygen (60/40%), respectively. Within the healthy lung, viscous losses are of the same order for the three gas mixtures, so the differences in pressure distribution are relatively small.
Radial dose distributions from protons of therapeutic energies calculated with Geant4-DNA
Wang, He; Vassiliev, Oleg N.
2014-07-01
Models based on the amorphous track structure approximation have been successful in predicting the biological effects of heavy charged particles. Development of such models remains an active area of research that includes applications to hadrontherapy. In such models, the radial distribution of the dose deposited by delta electrons and directly by the particle is the main characteristic of track structure. We calculated these distributions with Geant4-DNA Monte Carlo code for protons in the energy range from 10 to 100 MeV. These results were approximated by a simple formula that combines the well-known inverse square distance dependence with two factors that eliminate the divergence of the radial dose integral at both small and large distances. A clear physical interpretation is given to the asymptotic behaviour of the radial dose distribution resulting from these two factors. The proposed formula agrees with the Monte Carlo data within 10% for radial distances of up to 10 μm, which corresponds to a dose range covering over eight orders of magnitude. Differences between our results and those of previously published analytical models are discussed.
Yang Ping; Li Pei; Zhang Li-Qiang; Wang Xiao-Liang; Wang Huan; Song Xi-Fu; Xie Fang-Wei
2012-01-01
The lattice,the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by firstprinciples calculations.The results show that the lattice constants change linearly with stress.Band gaps are broadened linearly as the uniaxial compressive stress increases.The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction,and the reason for band gap of n-type ZnO changing with stress is also explained.The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy.However,when the energy is higher than 4.0 eV,the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears.There are two peaks in the absorption spectrum in an energy range of 4.0-13.0 eV.The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO,which supplies the theoretical reference value for the modulation of the band gap of doped ZnO.
Tatsuyuki NEZU
2006-01-01
The three-dimensional stress distributions in the area surrounding indentation pattern for three different materials,Al2O3,Si3N4 and SiC were analyzed by finite element method(FEM). Those theoretical results were also compared with the experimental ones by Rockwell hardness test. The effect of loading stress on the plastic deformation in specimens,surface was investigated on the assumption of shear strain energy theory by Huber-Mises when the materials were indented. The distributions of nomal stress,shear stress,and Mises stress were analysed with variations of loading conditions. It is clear that the analytical results for the stress distributions,the crack length and its density of probability are in good agreement with the experimental results.
Spatial distribution of residual stresses in glass-ZrO2 sphero-cylindrical bilayers.
Wendler, Michael; Belli, Renan; Petschelt, Anselm; Lohbauer, Ulrich
2016-07-01
Residual stresses arising from inhomogeneous cooling after sintering have shown to play a preponderant role in the higher incidence of chippings observed for glass-zirconia dental prostheses. Still, current descriptions of their nature and distribution have failed to reconcile with clinical findings. Therefore, an axisymmetric sphero-cylindrical bilayer model was used in this study to determine the effect of the cooling rate on the final spatial distribution of residual stresses. Zirconia frameworks with two different radii (1.6 and 3.2mm) were CAD/CAM fabricated. Subsequent glass overlays with two different thickness ratios (1:1 and 2:1) were generated and heat pressed onto the zirconia substrates. The obtained structures were submitted to a last firing process and fast- (45°C/s) or slow-cooled (0.5°C/s) to room temperature. Unbonded bilayers were produced by firing glass overlays onto boron nitride coated zirconia. Thin sagittal and transversal sections were obtained from the specimens to assess residual stress distribution by means of light birefringence. The applied cooling rates did not affect distribution or magnitude of radial residual stresses (sagittal sections), whereas increased hoop stress magnitudes were measured (transversal sections) in fast-cooled specimens. A distinct stress nature was observed for the hoop stress component of unbonded overlays after fast cooling. Interaction between stress components seems to govern the final stress distribution, highlighting the importance of a multiaxial assessment of this problem in three-dimensional structures.
Residual Stress Distribution in PVD-Coated Carbide Cutting Tools-Origin of Cohesive Damage
B. Breidenstein
2012-09-01
Full Text Available PVD-coatings for cutting tools mean a substantial progress for tool lifetime and cutting conditions. Such tools, however, hold the risk of cost intensive sudden process breaks as a result of cohesive damage. This damage mechanism does not consist of a coating adhesion problem, but it can be traced back to the residual stress distribution in coating and substrate. This paper shows how residual stresses develop during the process chain for the manufacturing of PVDcoated carbide cutting tools. By means of different methods for residual stress determination it is shown that the distribution of residual stresses within the tool finally is responsible for the risk of cohesive tool damage.
Світлана Михайлівна Талах
2017-01-01
Full Text Available The problem of improving the scientific basis to determine the stress-strain state of non-rigid pavements, renovated by cold recycling technology, is considered. The results of numerical calculation of stress-strain state of non-rigid pavements in the section of road Kyv-Kovel (297 + 700 km - 302 + 400 km are given using automated calculation software complex of thin-walled spatial structures (KARTPK. The real state of the road section through 8.5 years after the renovation is analyzed
Calculation of the Distribution Rule of Equivalent Strain Rate near Explosive Welding Interface
李晓杰; 闫鸿浩; 李瑞勇; 王金相
2004-01-01
The objectives of this study were to analyze the distribution of equivalent strain rate near the stagnation point and probe into the effects of colliding angle on strain rate. An ideal fluid model of symmetrically colliding was used to research them. Calculations showed the equivalent strain rate and the colliding half angle are closely related to each other with the material geometrical size and explosive velocity selected, the equivalent strain has large gradient within several jet thicknesses near the stagnation point, the maximal strain points are lined up along a beeline, but a curve near the stagnation point. With different colliding angles, they can be fitted by using exponential curve. That is, the exponential curve can be regarded as the token curve in explosive welding.
Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method
Chen Chaobin; Huang Qunying; Wu Yican
2005-01-01
A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient's anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.
Distributed Multipolar Expansion Approach to Calculation of Excitation Energy Transfer Couplings.
Błasiak, Bartosz; Maj, Michał; Cho, Minhaeng; Góra, Robert W
2015-07-14
We propose a new approach for estimating the electrostatic part of the excitation energy transfer (EET) coupling between electronically excited chromophores based on the transition density-derived cumulative atomic multipole moments (TrCAMM). In this approach, the transition potential of a chromophore is expressed in terms of truncated distributed multipolar expansion and analytical formulas for the TrCAMMs are derived. The accuracy and computational feasibility of the proposed approach is tested against the exact Coulombic couplings, and various multipole expansion truncation schemes are analyzed. The results of preliminary calculations show that the TrCAMM approach is capable of reproducing the exact Coulombic EET couplings accurately and efficiently and is superior to other widely used schemes: the transition charges from electrostatic potential (TrESP) and the transition density cube (TDC) method.
Lu, Xiaonan [Argonne National Lab. (ANL), Argonne, IL (United States); Singh, Ravindra [Argonne National Lab. (ANL), Argonne, IL (United States); Wang, Jianhui [Argonne National Lab. (ANL), Argonne, IL (United States); Reilly, James T. [Reilly Associates, Pittson, PA (United States)
2017-01-01
Distribution Management System (DMS) applications require a substantial commitment of technical and financial resources. In order to proceed beyond limited-scale demonstration projects, utilities must have a clear understanding of the business case for committing these resources that recognizes the total cost of ownership. Many of the benefits provided by investments in DMSs do not translate easily into monetary terms, making cost-benefit calculations difficult. For example, Fault Location Isolation and Service Restoration (FLISR) can significantly reduce customer outage duration and improve reliability. However, there is no well-established and universally-accepted procedure for converting these benefits into monetary terms that can be compared directly to investment costs. This report presents a methodology to analyze the benefits and costs of DMS applications as fundamental to the business case.
Preliminary Analysis on Distribution Calculation of Elevator%电梯配电计算初析
谢宁
2014-01-01
以电机采用蜗轮蜗杆传动方式的一般电梯为例，提出电梯配电设计的功率应以满载时电功率转换为机械功率的传动功率为依据。对配置一般起重用（绕线转子异步）电动机为动力的曳引机的电梯主回路供电，提出配电计算思路。同时论述电动机铭牌功率和按需要系数法得出的功率，都不能真实反映电梯电功率和机械功率的能量关系。%A common elevator characterized in that the motor adopts worm-gear transmission is taken as an example, based on that the power of the elevator distribution design shall be the transmission power for converting the electrical power into the mechanical power under full load, a distribution calculation idea is proposed for power supply to the main circuit of the elevator with a general crane motor (asynchronous wound-rotor) as dynamic tractor. Besides, the rated power and the power calculated by demand factor method are discussed, both of which are unable to truly reflect the energy relationship between the electrical power and the mechanical power of the elevator.
Development of sump model for containment hydrogen distribution calculations using CFD code
Ravva, Srinivasa Rao, E-mail: srini@aerb.gov.in [Indian Institute of Technology-Bombay, Mumbai (India); Nuclear Safety Analysis Division, Atomic Energy Regulatory Board, Mumbai (India); Iyer, Kannan N. [Indian Institute of Technology-Bombay, Mumbai (India); Gaikwad, A.J. [Nuclear Safety Analysis Division, Atomic Energy Regulatory Board, Mumbai (India)
2015-12-15
Highlights: • Sump evaporation model was implemented in FLUENT using three different approaches. • Validated the implemented sump evaporation models against TOSQAN facility. • It was found that predictions are in good agreement with the data. • Diffusion based model would be able to predict both condensation and evaporation. - Abstract: Computational Fluid Dynamics (CFD) simulations are necessary for obtaining accurate predictions and local behaviour for carrying out containment hydrogen distribution studies. However, commercially available CFD codes do not have all necessary models for carrying out hydrogen distribution analysis. One such model is sump or suppression pool evaporation model. The water in the sump may evaporate during the accident progression and affect the mixture concentrations in the containment. Hence, it is imperative to study the sump evaporation and its effect. Sump evaporation is modelled using three different approaches in the present work. The first approach deals with the calculation of evaporation flow rate and sump liquid temperature and supplying these quantities through user defined functions as boundary conditions. In this approach, the mean values of the domain are used. In the second approach, the mass, momentum, energy and species sources arise due to the sump evaporation are added to the domain through user defined functions. Cell values adjacent to the sump interface are used in this. Heat transfer between gas and liquid is calculated automatically by the code itself. However, in these two approaches, the evaporation rate was computed using an experimental correlation. In the third approach, the evaporation rate is directly estimated using diffusion approximation. The performance of these three models is compared with the sump behaviour experiment conducted in TOSQAN facility.Classification: K. Thermal hydraulics.
MSc. Jusuf Qarkaxhija
2013-12-01
Full Text Available According to daily reports, the income from internet services is getting lower each year. Landline phone services are running at a loss, whereas mobile phone services are getting too mainstream and the only bright spot holding together cable operators (ISP in positive balance is the income from broadband services (Fast internet, IPTV. Broadband technology is a term that defines multiple methods of information distribution through internet at great speed. Some of the broadband technologies are: optic fiber, coaxial cable, DSL, Wireless, mobile broadband, and satellite connection. The ultimate goal of any broadband service provider is being able to provide voice, data and the video through a single network, called triple play service. The Internet distribution remains an important issue in Kosovo and particularly in rural zones. Considering the immense development of the technologies and different alternatives that we can face, the goal of this paper is to emphasize the necessity of a forecasting of such investment and to give an experience in this aspect. Because of the fact that in this investment are involved many factors related to population, geographical factors, several technologies and the fact that these factors are in continuously change, the best way is, to store all the data in a database and to use this database for different results. This database helps us to substitute the previous manual calculations with an automatic procedure of calculations. This way of work will improve the work style, having now all the tools to take the right decision about an Internet investment considering all the aspects of this investment.
Mohammad Rezaei
2015-06-01
Full Text Available Generally, longwall mining-induced stress results from the stress relaxation due to destressed zone that occurs above the mined panel. Knowledge of induced stress is very important for accurate design of adjacent gateroads and intervening pillars which helps to raise the safety and productivity of longwall mining operations. This study presents a novel time-dependent analytical model for determination of the longwall mining-induced stress and investigates the coefficient of stress concentration over adjacent gates and pillars. The model is developed based on the strain energy balance in longwall mining incorporated to a rheological constitutive model of caved materials with time-varying parameters. The study site is the Tabas coal mine of Iran. In the proposed model, height of destressed zone above the mined panel, total longwall mining-induced stress, abutment angle, induced vertical stress, and coefficient of stress concentration over neighboring gates and intervening pillars are calculated. To evaluate the effect of proposed model parameters on the coefficient of stress concentration due to longwall mining, sensitivity analysis is performed based on the field data and experimental constants. Also, the results of the proposed model are compared with those of existing models. The comparative results confirm a good agreement between the proposed model and the in situ measurements. According to the obtained results, it is concluded that the proposed model can be successfully used to calculate the longwall mining-induced stress. Therefore, the optimum design of gate supports and pillar dimensions would be attainable which helps to increase the mining efficiency.
Mohammad Rezaei; Mohammad Farouq Hossaini; Abbas Majdi
2015-01-01
Generally, longwall mining-induced stress results from the stress relaxation due to destressed zone that occurs above the mined panel. Knowledge of induced stress is very important for accurate design of adjacent gateroads and intervening pillars which helps to raise the safety and productivity of longwall mining operations. This study presents a novel time-dependent analytical model for determination of the longwall mining-induced stress and investigates the coefficient of stress concentration over adjacent gates and pillars. The model is developed based on the strain energy balance in longwall mining incorporated to a rheological constitutive model of caved materials with time-varying parameters. The study site is the Tabas coal mine of Iran. In the proposed model, height of destressed zone above the mined panel, total longwall mining-induced stress, abutment angle, induced vertical stress, and coeffi-cient of stress concentration over neighboring gates and intervening pillars are calculated. To evaluate the effect of proposed model parameters on the coefficient of stress concentration due to longwall mining, sensitivity analysis is performed based on the field data and experimental constants. Also, the results of the proposed model are compared with those of existing models. The comparative results confirm a good agreement between the proposed model and the in situ measurements. According to the obtained results, it is concluded that the proposed model can be successfully used to calculate the longwall mining-induced stress. Therefore, the optimum design of gate supports and pillar dimensions would be attainable which helps to increase the mining efficiency.
Abbas, Ahmed A; Santiwong, Peerapong; Wonglamsam, Amornrat; Srithavaj, Theerathavaj; Chanthasopeephan, Teeranoot
The purpose of this study was to evaluate stress distribution around two craniofacial implants in an auricular prosthesis according to the removal forces. Three attachment combinations were used to evaluate the stress distribution under removal forces of 45 and 90 degrees. Three attachment designs were examined: (1) a Hader bar with three clips; (2) a Hader bar with one clip and two extracoronal resilient attachments (ERAs); and (3) a Hader bar with one clip and two Locators. The removal force was determined by means of an Instron universal testing machine with a crosshead speed of 10 mm/minute. All three designs were created in three dimensions using SolidWorks. The applied removal force and the models were then introduced to finite element software to analyze the stress distribution. The angle of removal force greatly affected the magnitude and direction of stress distribution on the implants. The magnitude of stress under the 45-degree removal force was higher than the stress at 90 degrees. The combination of the 1,000-g retention clip and 2,268-g retention Locator exhibited the highest stress on the implant flange when the removal force was applied at 45 degrees. The removal angle greatly influences the amount of force and stress on the implants. Prosthodontists are encouraged to inform patients to remove the prosthesis at 90 degrees and, if possible, use a low-retentive attachment to reduce stress.
Hinrichs, Nina Singhal; Pande, Vijay S
2007-06-28
Markovian state models (MSMs) are a convenient and efficient means to compactly describe the kinetics of a molecular system as well as a formalism for using many short simulations to predict long time scale behavior. Building a MSM consists of grouping the conformations into states and estimating the transition probabilities between these states. In a previous paper, we described an efficient method for calculating the uncertainty due to finite sampling in the mean first passage time between two states. In this paper, we extend the uncertainty analysis to derive similar closed-form solutions for the distributions of the eigenvalues and eigenvectors of the transition matrix, quantities that have numerous applications when using the model. We demonstrate the accuracy of the distributions on a six-state model of the terminally blocked alanine peptide. We also show how to significantly reduce the total number of simulations necessary to build a model with a given precision using these uncertainty estimates for the blocked alanine system and for a 2454-state MSM for the dynamics of the villin headpiece.
Calculation of photon pulse height distribution using deterministic and Monte Carlo methods
Akhavan, Azadeh; Vosoughi, Naser
2015-12-01
Radiation transport techniques which are used in radiation detection systems comprise one of two categories namely probabilistic and deterministic. However, probabilistic methods are typically used in pulse height distribution simulation by recreating the behavior of each individual particle, the deterministic approach, which approximates the macroscopic behavior of particles by solution of Boltzmann transport equation, is being developed because of its potential advantages in computational efficiency for complex radiation detection problems. In current work linear transport equation is solved using two methods including collided components of the scalar flux algorithm which is applied by iterating on the scattering source and ANISN deterministic computer code. This approach is presented in one dimension with anisotropic scattering orders up to P8 and angular quadrature orders up to S16. Also, multi-group gamma cross-section library required for this numerical transport simulation is generated in a discrete appropriate form. Finally, photon pulse height distributions are indirectly calculated by deterministic methods that approvingly compare with those from Monte Carlo based codes namely MCNPX and FLUKA.
MENG Xiang-rui; GAO Zhao-ning; WANG Xiang-qian
2012-01-01
By turning to the theory of elastic thin plates,a mechanical model of the main roof breaking for severely inclined seam under long wall working was esbalished,in which formulaes were deduced for the calculation of the stress distribution.When the main roof stress distribution was characterized,the failure form of the roof in the long wall coal seam under work was given with the failure criterion deduced.The deduced failure criterion was then applied to the No.3232(3) face of the Lizuizi Coal Mine; the first pressure for the working face was accurately predicted.Results of the field application show that the main roof of the severely inclined coal seam under long wall working breaks in the O-X pattern,which is basically in accordance with the reality.
蜂窝梁应力和挠度计算方法%Stress and deflection calculation methods of castellated beams
李鹏飞; 姚谦峰
2011-01-01
In order to study the stress and deflection calculation methods, the stress characteristics of castellated beams were obtained through overall and local stability analysis by ANSYS.Based on the stress distribution and the structural characteristics of castellated beams, the practical formulas for stress calculation were deduced on the hypothesis of open-web truss theory.The deflection formulas were derived according to the web openings characteristics of castellated beams and the unit force method.By comparing the formula calculation results with finite element analysis results, the correctness of open-web truss theory hypothesis and precision of the formulas for stress and deflection were verified.%为了研究蜂窝梁应力和挠度的计算方法,应用有限元软件ANSYS对蜂窝梁进行了整体和局部分析,得出蜂窝梁的受力特点.结合蜂窝梁应力分布特点和自身结构特征,以空腹桁架理论为基础,对蜂窝梁力学行为进行分析,推导均布荷载作用下蜂窝梁应力的计算公式.根据蜂窝梁腹板开孔的结构特点,以单位力法为基础,推导蜂窝梁挠度的计算公式.对不同蜂窝梁进行数值分析和理论计算,将应力和挠度的公式计算结果与有限元分析结果进行对比,验证了空腹桁架计算假定的正确性以及应力和挠度计算公式的准确性.
Tomographic Imaging of Water Content and Mine-Induced Stress Distribution in North Aurora, Illinois
Meulemans, A. J.; Fratta, D.; Wang, H. F.
2013-12-01
Located in North Aurora, Illinois, the Lafarge-Conco plant is a room-and-pillar mine that is in active production of aggregates, taken from the Galena-Platteville formations. To better understand how stresses are distributed among the pillars over periods of mining production, tomographic images of the interior of the pillar using seismic data collected in November 2012 and March 2013 were created. Seismic tomographic images showed changes in seismic velocity between the two surveys, which is interpreted as change in stress. The southeast corner pillar showed a significant stress increase, and could indicate a possible area of very high stresses within the pillar. While the ground-penetrating radar (GPR) tomographic image was used to assess a very uniform water content and porosity distribution within the pillar. Understanding how stress and moisture distribution changes within pillars during excavation is valuable to mine design and to the maintenance of mine safety.
The stress distribution in tempered glass due to a crack
Arin, K.
1976-01-01
A model describing the failure in tempered glass is proposed and a method of solution is presented. An infinite elastic strip is assumed to represent the glass and the loads vanish everywhere on the boundary as well as at infinity. The problem is solved using the integral equations technique where the input is the residual stresses in the glass.
Anatomical evaluation and stress distribution of intact canine femur.
Verim, Ozgur; Tasgetiren, Suleyman; Er, Mehmet S; Ozdemir, Vural; Yuran, Ahmet F
2013-03-01
In the biomedical field, three-dimensional (3D) modeling and analysis of bones and tissues has steadily gained in importance. The aim of this study was to produce more accurate 3D models of the canine femur derived from computed tomography (CT) data by using several modeling software programs and two different methods. The accuracy of the analysis depends on the modeling process and the right boundary conditions. Solidworks, Rapidform, Inventor, and 3DsMax software programs were used to create 3D models. Data derived from CT were converted into 3D models using two different methods: in the first, 3D models were generated using boundary lines, while in the second, 3D models were generated using point clouds. Stress analyses in the models were made by ANSYS v12, also considering any muscle forces acting on the canine femur. When stress values and statistical values were taken into consideration, more accurate models were obtained with the point cloud method. It was found that the maximum von Mises stress on the canine femur shaft was 34.8 MPa. Stress and accuracy values were obtained from the model formed using the Rapidform software. The values obtained were similar to those in other studies in the literature. Copyright © 2012 John Wiley & Sons, Ltd.
Mansi Manish Oswal
2016-01-01
Full Text Available Purpose: Clinical success of implant prosthodontics is dependent in part upon the type of implant thread design. The selection of implant thread design plays an important role in the outcome of the treatment. This study was undertaken to evaluate the pattern of stress distribution using a finite element analysis; hence, the area which would be bearing maximum load for a given design would be arrived. Materials and Methods: Three implants with different thread designs, namely V-thread, buttress, and reverse buttress thread designs were considered and dimensions were standardized. The site considered was the mandibular molar region with cortical and trabecular bone assuming to be isotropic and homogeneous. The implant modeling was done with the CATIA software. Vertical loads of 100N were applied. The stresses were calculated as Von Mises stress criterion. Results: Maximum stresses were seen at the cortical bone and were transferred to the implant. Minimum Von Mises stresses were seen with reverse buttress thread design at the cortical bone. The stresses were observed least at the cancellous bone and maximum at the implant. Conclusion: Hence, within the limitations of this study the results obtained can be applied clinically for appropriate selection of implant thread design for a predictable success of implant therapy.
Oswal, Mansi Manish; Amasi, Ulhas N; Oswal, Manish S; Bhagat, Ashish S
2016-01-01
Clinical success of implant prosthodontics is dependent in part upon the type of implant thread design. The selection of implant thread design plays an important role in the outcome of the treatment. This study was undertaken to evaluate the pattern of stress distribution using a finite element analysis; hence, the area which would be bearing maximum load for a given design would be arrived. Three implants with different thread designs, namely V-thread, buttress, and reverse buttress thread designs were considered and dimensions were standardized. The site considered was the mandibular molar region with cortical and trabecular bone assuming to be isotropic and homogeneous. The implant modeling was done with the CATIA software. Vertical loads of 100N were applied. The stresses were calculated as Von Mises stress criterion. Maximum stresses were seen at the cortical bone and were transferred to the implant. Minimum Von Mises stresses were seen with reverse buttress thread design at the cortical bone. The stresses were observed least at the cancellous bone and maximum at the implant. Hence, within the limitations of this study the results obtained can be applied clinically for appropriate selection of implant thread design for a predictable success of implant therapy.
Tchitchekova, Deyana S. [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Morthomas, Julien; Perez, Michel [Univ. Lyon, INSA Lyon, MATEIS, UMR CNRS 5510, Villeurbanne (France); Ribeiro, Fabienne [IRSN, PSN, SEMIA, LPTM, Saint-Paul-Lez-Durance (France); Ducher, Roland [IRSN, PSN, SAG, LETR, Saint-Paul-Lez-Durance (France)
2014-07-21
A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.
Tchitchekova, Deyana S.; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel
2014-07-01
A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ˜3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.
Tchitchekova, Deyana S; Morthomas, Julien; Ribeiro, Fabienne; Ducher, Roland; Perez, Michel
2014-07-21
A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.
Velders, G.J.M.; Feil, D.
1989-01-01
Quantum-chemical density-functional theory (DFT) calculations, using the local-density approximation (LDA), have been performed for hydrogen-bounded silicon clusters to determine the electron density distribution of the Si-Si bond. The density distribution in the bonding region is compared with calc
Stress relaxation of narrow molar mass distribution polystyrene following uniaxial extension
Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole
2008-01-01
The stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, has been measured for a narrow molar mass distribution polystyrene inelt with a molecular weight of 145 kg/mol. The experiments are conducted on a filament stretching rheometer, where a clos...... rates. (C) 2008 The Society of Rheology....
Xiaocong He
2014-01-01
Full Text Available An analytical model for predicting the stress distributions within single-lap adhesively bonded beams under tension is presented in this paper. By combining the governing equations of each adherend with the joint kinematics, the overall system of governing equations can be obtained. Both the adherends and the adhesive are assumed to be under plane strain condition. With suitable boundary conditions, the stress distribution of the adhesive in the longitudinal direction is determined.
Ichikawa, Tsubasa; Sakamoto, Yuji; Subagyo, Agus; Sueoka, Kazuhisa
2011-12-01
The research on reflectance distributions in computer-generated holograms (CGHs) is particularly sparse, and the textures of materials are not expressed. Thus, we propose a method for calculating reflectance distributions in CGHs that uses the finite-difference time-domain method. In this method, reflected light from an uneven surface made on a computer is analyzed by finite-difference time-domain simulation, and the reflected light distribution is applied to the CGH as an object light. We report the relations between the surface roughness of the objects and the reflectance distributions, and show that the reflectance distributions are given to CGHs by imaging simulation.
Yamada, Satoshi; Tadano, Shigeru
2013-09-03
Residual stress is defined as the stress that remains in bone tissue without any external forces. This study investigated the effects of growth on residual stress distributions from the surface to deeper regions of cortical cylinders obtained from less-than-one-month-old (Group Y) and two-year-old (Group M) bovine femurs. In these experiments, five diaphysis specimens from each group were used. Residual stress was measured using a high-energy synchrotron white X-ray beam to penetrate X-rays into the deeper region of the bone specimens. The measurements in the cortical cylinders from Groups Y and M were performed at 0.5- and 1-mm intervals, respectively, from the outer surface to the deeper region of the diaphysis specimens at four positions: anterior, posterior, lateral, and medial. The residual stress was calculated on the basis of variation in the interplanar spacing of hydroxyapatite crystals in the bone tissue. According to the results, the diaphysis specimens from Group Y were not subjected to large residual stresses (average -1.2 MPa and 2.4 MPa at the surface region and 1.5mm depth, respectively). In Group M, the surface region of the diaphysis specimens was subjected to tensile residual stresses (average 6.7 MPa) and the deeper region was subjected to compressive stresses (average -8.2 MPa at 3mm depth). There was a strong significant difference between both these regions. The value of residual stresses at the surface region of the diaphysis specimens in both the groups had a positive statistical correlation with the cortical thickness at the measured locations.
Quaresma, Sergio E T; Cury, Patricia R; Sendyk, Wilson R; Sendyk, Claudio
2008-01-01
This study evaluates the influence of 2 commercially available dental implant systems on stress distribution in the prosthesis, abutment, implant, and supporting alveolar bone under simulated occlusal forces, employing a finite element analysis. The implants and abutments evaluated consisted of a stepped cylinder implant connected to a screw-retained, internal, hexagonal abutment (system 1) and a conical implant connected to a solid, internal, conical abutment (system 2). A porcelain-covered, silver-palladium alloy was used as a crown. In each case, a simulated, 100-N vertical load was applied to the buccal cusp. A finite element model was created based on the physical properties of each component, and the values of the von Mises stresses generated in the prosthesis, abutment, implant, and supporting alveolar bone were calculated. In the prostheses, the maximum von Mises stresses were concentrated at the points of load application in both systems, and they were greater in system 1 (148 N/mm2) than in system 2 (55 N/mm2). Stress was greater on the abutment of system 2 than of system 1 on both the buccal (342 N/mm2 x 294 N/mm2) and lingual (294 N/mm2 x 148 N/ mm2) faces. Stress in the cortical, alveolar bone crest was greater in system 1 than in system 2 (buccal: 99.5 N/mm2 x 55 N/mm2, lingual: 55 N/mm2 x 24.5 N/mm2, respectively). Within the limits of this investigation, the stepped cylinder implant connected to a screw-retained, internal hexagonal abutment produces greater stresses on the alveolar bone and prosthesis and lower stresses on the abutment complex. In contrast, the conical implant connected to a solid, internal, conical abutment furnishes lower stresses on the alveolar bone and prosthesis and greater stresses on the abutment.
Influence of intrinsic and extrinsic forces on 3D stress distribution using CUDA programming
Räss, Ludovic; Omlin, Samuel; Podladchikov, Yuri
2013-04-01
In order to have a better understanding of the influence of buoyancy (intrinsic) and boundary (extrinsic) forces in a nonlinear rheology due to a power law fluid, some basics needs to be explored through 3D numerical calculation. As first approach, the already studied Stokes setup of a rising sphere will be used to calibrate the 3D model. Far field horizontal tectonic stress is applied to the sphere, which generates a vertical acceleration, buoyancy driven. This simple and known setup allows some benchmarking performed through systematic runs. The relative importance of intrinsic and extrinsic forces producing the wide variety of rates and styles of deformation, including absence of deformation and generating 3D stress patterns, will be determined. Relation between vertical motion and power law exponent will also be explored. The goal of these investigations will be to run models having topography and density structure from geophysical imaging as input, and 3D stress field as output. The stress distribution in Swiss Alps and Plateau and its implication for risk analysis is one of the perspective for this research. In fact, proximity of the stress to the failure is fundamental for risk assessment. Sensitivity of this to the accurate topography representation can then be evaluated. The developed 3D numerical codes, tuned for mid-sized cluster, need to be optimized, especially while running good resolution in full 3D. Therefor, two largely used computing platforms, MATLAB and FORTRAN 90 are explored. Starting with an easy adaptable and as short as possible MATLAB code, which is then upgraded in order to reach higher performance in simulation times and resolution. A significant speedup using the rising NVIDIA CUDA technology and resources is also possible. Programming in C-CUDA, creating some synchronization feature, and comparing the results with previous runs, helps us to investigate the new speedup possibilities allowed through GPU parallel computing. These codes
Evaluation of residual stress distribution in shot-peened steel by synchrotron radiation
Akiniwa, Y; Suzuki, K; Yanase, E; Nishio, K; Kusumi, Y; Okada, H; Arai, K
2003-01-01
The in-depth distribution of residual stresses in shot-peened steels was measured by using high energy X-rays from a synchrotron radiation source. The relation between the 2 theta and sin sup 2 psi was obtained with the side-inclination method (psi diffractometer). The distribution of residual stresses was first evaluated by the nonlinearity of the sin sup 2 psi diagram by a simplex method. The estimated stress agreed with the distribution determined through the sin sup 2 psi method by using Cr-K alpha radiation combined with the conventional surface removal method. A new method was proposed to estimate the stress value of the distributed residual stress. The new method was a combination of the side-inclination method and the iso-inclination method (omega diffractometer) to maintain the penetration depth constant. The sin sup 2 psi diagram could be approximated by the linear relationship. The evaluated stress distribution agreed well with the distribution obtained by the surface removal method. (author)
CONSIDERATION OF ANISOTROPY AND CONTACT OF CRACKS EDGE AT STRESS CALCULATIONS OF ROLLING BEARINGS
2014-01-01
Investigation of influence of anisotropy on stress-deformed state of base (roller bearings track) considering the appearance of cracks with contacting edges in it is done in the work. The boundary integral equation method is used to determine the stresses. Solution of the Integral equation is done numerically by the mechanical quadrature method. At the task solution it is considered that cracks can be located in the compressive stresses areas, wherefore the cracks edges can contact. The unkno...
Lyons, B. C.; Jardin, S. C.; Ramos, J. J.
2012-08-01
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f) in the conventional banana regime for both ions and electrons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h). We work in a 4D phase space in which ψ defines a flux surface, θ is the poloidal angle, v is the magnitude of the velocity referenced to the mean flow velocity, and λ is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and λ. The Rosenbluth potentials, Φ and Ψ, which define the integral part of the collision operator, are expanded in Legendre series in cosχ, where χ is the pitch angle, Fourier series in cosθ, and finite elements in v. At each ψ, we solve a block tridiagonal system for hi (independent of fe), then solve another block tridiagonal system for he (dependent on fi). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia et al., J. Comput. Phys. 37, 183-204 (1980)] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D -C1 [S. C. Jardin et al., Comput. Sci. Discovery 5, 014002 (2012)]).
Lyons, B. C. [Program in Plasma Physics, Princeton University, Princeton, New Jersey 08543-0451 (United States); Jardin, S. C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Ramos, J. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)
2012-08-15
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f) in the conventional banana regime for both ions and electrons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h). We work in a 4D phase space in which {psi} defines a flux surface, {theta} is the poloidal angle, v is the magnitude of the velocity referenced to the mean flow velocity, and {lambda} is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and {lambda}. The Rosenbluth potentials, {Phi} and {Psi}, which define the integral part of the collision operator, are expanded in Legendre series in cos{chi}, where {chi} is the pitch angle, Fourier series in cos{theta}, and finite elements in v. At each {psi}, we solve a block tridiagonal system for h{sub i} (independent of f{sub e}), then solve another block tridiagonal system for h{sub e} (dependent on f{sub i}). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia et al., J. Comput. Phys. 37, 183-204 (1980)] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D-C{sup 1}[S. C. Jardin et al., Comput. Sci. Discovery 5, 014002 (2012)]).
B.C. Lyons, S.C. Jardin, and J.J. Ramos
2012-06-28
A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f ) in the conventional banana regime for both ions and elec trons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on the DKEs determine the relevant non-adiabatic pieces of f (called h ). We work in a 4D phase space in which Ψ defines a flux surface, θ is the poloidal angle, v is the total velocity referenced to the mean flow velocity, and λ is the dimensionless magnetic moment parameter. We expand h in finite elements in both v and λ . The Rosenbluth potentials, φ and ψ, which define the integral part of the collision operator, are expanded in Legendre series in cos χ , where χ is the pitch angle, Fourier series in cos θ , and finite elements in v . At each ψ , we solve a block tridiagonal system for hi (independent of fe ), then solve another block tridiagonal system for he (dependent on fi ). We demonstrate that such a formulation can be accurately and efficiently solved. NIES is coupled to the MHD equilibrium code JSOLVER [J. DeLucia, et al., J. Comput. Phys. 37 , pp 183-204 (1980).] allowing us to work with realistic magnetic geometries. The bootstrap current is calculated as a simple moment of the distribution function. Results are benchmarked against the Sauter analytic formulas and can be used as a kinetic closure for an MHD code (e.g., M3D-C1 [S.C. Jardin, et al ., Computational Science & Discovery, 4 (2012).]).
Jafari K
2014-12-01
Full Text Available Statement of Problem: A general process in implant design is to determine the reason of possible problems and to find the relevant solutions. The success of the implant depends on the control technique of implant biomechanical conditions. Objectives: The goal of this study was to evaluate the influence of both abutment and framework materials on the stress of the bone around the implant by using threedimensional finite element analysis. Materials and Methods: A three-dimensional model of a patient’s premaxillary bone was fabricated using Cone Beam Computed Tomography (CBCT. Then, three types of abutment from gold, nickel-chromium and zirconia and also three types of crown frame from silver-palladium, nickel-chromium and zirconia were designed. Finally, a 178 N force at angles of zero, 30 and 45 degrees was exerted on the implant axis and the maximum stress and strain in the trabecular, cortical bones and cement was calculated. Results: With changes of the materials and mechanical properties of abutment and frame, little difference was observed in the level and distribution pattern of stress. The stress level was increased with the rise in the angle of pressure exertion. The highest stress concentration was related to the force at the angle of 45 degrees. The results of the cement analysis proved an inverse relationship between the rate of elastic modulus of the frame material and that of the maximum stress in the cement. Conclusions: The impact of the angle at which the force was applied was more significant in stress distribution than that of abutment and framework core materials.
The Effect of Corner Radii and Part Orientation on Stress Distribution of Cold Forging Die
Ahmad B. Abdullah
2008-01-01
Full Text Available One of the most critical problems in cold forging is the huge stresses generated from the deformation of metal leads to die failure. The distribution of stresses mainly depends on geometry of the die. An approach to optimal design in cold forging die geometry and orientation are presented in this paper. The impression cold forging dies of the Universal joint was generated using three-dimensional CAD modeling software, SolidWorks. This CAD modeling software coupled with FEA tools, COSMOSWorks. The paper emphasizes on effect of the corner radius and dies orientation on stress distribution.
Study of stress distribution on a circular disk by photostress analysis
Manjit, Yongyut; Sukprasong, Saksit; Limpichaipanit, Apichart; Ngamjarurojana, Athipong
2015-07-01
Photostress analysis system was used to study the stress distribution on a circular disk. A reflection polariscope was used to observe the surface strains from the recorded fringe patterns by digital camera. The shape of sample is a circular disk was pressed on the top and bottom and the polariscope produced fringe patterns from sample on the model being stressed. The results were analyzed, the fringe pattern looked different in various magnitude of force because the stress distribution in sample was changed with magnitude of force. Deformation can be determined from the fringe patterns.
Flow induced noise calculations for non-axially distributed hydrophones in towed arrays
WANG Bin; TANG Weilin; FAN Jun
2009-01-01
Two improvements are put forward on the analyses of flow induced noise in towed arrays. First, the differences between Corcos/Carpenter pressure fluctuation models have been discussed at length, as well as flow induced noise calculated with these two models. Second, flow induced noise received by the finite hydrophones distributed non-axially is discussed and the relevant power spectrum is deduced. The results show that there are some disparities between the wavenumber spectrums and the responses of flow induced noise of these two models. Flow induced noise is closely related with the tow speed, the tube radius and the off-axis distance. The numerical analyses with Carpenter model indicate that the power spectrum of flow induced noise will increase 24 dB approximately with the tow speed doubled, decrease with the radius of the tube, and increase with the off-axis distance. The tube radius and the off-axis distance have greater influence on the high-frequency components than on the low-frequency components.
Cermak, V. (Geophys. Inst., Prague)
1974-01-01
The first draft of the heat flow map of Central and Eastern Europe demonstrates the general heat flow pattern in the Carpathians. The Pannonian Basin, located between the Carpathians and Dinarides, is a zone of anomalous heat flow (greater than 2.0 HFU). The geothermal activity decreases rapidly to 1.3-1.5 HFU in the Carpathian arc. A preliminary map of crustal thickness, based on the results of gravity and seismic surveys, shows that the Mohorovicic discontinuity lies at a shallow depth below the Basin (24-26 km) and is deeper below the Carpathians (50 km). With some basic assumptions concerning the distribution of thermal conductivity and heat production applied, deep temperatures along a traverse crossing the Carpathian arc were calculated. The Moho temperature of 700/sup 0/C beneath the peri-Pieninian Lineament may increase to 800-1000/sup 0/C beneath the Pannonian Basin, and regional heat flow differences may reach 1.0 HFU. This type of variation in the energy input from the upper mantle is important in interpreting the tectonic evolution of the entire area.
Effects of Rock Bolting on Stress Distribution around Tunnel Using the Elastoplastic Model
无
2006-01-01
To ensure the stability of a tunnel during construction, rock bolts are usually installed, which affects the stress distribution around the tunnel.Therefore, it is necessary to study the effects of rock bolting on the stress distribution around the tunnel.In this article, the effects of rock bolting on the stress distribution around the tunnel, including the position and orientation of bolts, the overburden depths, and the bolt lengths, are simulated using the ANSYS software with an elastoplastic model.The effect of multiple bolts of 2 m and 1 m lengths on the stress distribution in the roof and on the lateral sides of a tunnel and at different overburden depths is considered.An important finding is that the tensile stress region that is very dangerous for rock in the bottom of the tunnel grows rapidly with increasing overburden depths when rock bolts are installed only in the roof or on the lateral sides of a tunnel.The determination of the length of the rock bolt used around a tunnel is dependent on the loads and the integrity of the rock mass around the tunnel.In addition, rock bolting around the tunnel can obviously reduce the coefficients and the size of the region of stress concentration, especially when installed in high-stress areas.This fact is very important and essential for the design of tunnels and ensures engineering safety in tunnel engineering.
Amaral, Camilla F; Gomes, Rafael S; Rodrigues Garcia, Renata C M; Del Bel Cury, Altair A
2017-09-28
Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture. The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture. Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone. In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone. A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the
Yao Qiangling
2015-01-01
Full Text Available The borehole stress-meter was employed in this study to investigate the distribution of the side abutment stress in roadway subjected to dynamic pressure. The results demonstrate that the side abutment stress of the mining roadway reaches a peak value when the distance to the gob is 8 m and the distribution curve of the side abutment stress can be divided into three zones: stress rising zone, stress stabilizing zone, and stress decreasing zone. Further numerical investigation was carried out to study the effect of the coal mass strength, coal seam depth, immediate roof strength, and thickness on the distribution of the side abutment stress. Based on the research results, we determined the reasonable position of the mining roadway and the optimal width of the barrier pillar. The engineering application demonstrates that the retention of the barrier pillar with a width of 5 m along the gob as the haulage roadway for the next panel is feasible, which delivers favorable technological and economic benefits.
Harsha Pujari
2013-01-01
Full Text Available Aim: To compare and evaluate the stress distribution of new generation of Twisted File in comparison with ProTaper under bending or torsional conditions using a finite - element analysis model. Materials and Methods: Two NiTi files, a ProTaper file and the latest generation nickel titanium file which is the Twisted File of similar tip diameter were scanned using White light scanning system. Through this a real size digitized models of the two brands of NiTi instruments were obtained. Then, the outline of the instrument was extracted from the stacks of 3D data in software. Finally a mesh of linear, eight-noded, hexahedral elements was overlaid onto the rendered 3D image. The behavior of the instrument under bending or torsional loads was then analyzed mathematically in the software (ABAQUS V6, 5-1 taking into consideration the non linear mechanical characteristic of NiTi material. The results were expressed as von Mises stresses and were calculated by the von Mises criteria. Results: Higher stress values were seen in Twisted Files than the ProTaper universal, however, the angular deflection was seen to be more in Twisted Files. Conclusion: As more angular deflection was seen in Twisted File it was more flexible than ProTaper Universal but did not have the uniform stress distribution like the ProTaper universal.
de la Cruz, Javier; Cano, Ulises; Romero, Tatiana
2016-10-01
A critical parameter for PEM fuel cell's electric contact is the nominal clamping pressure. Predicting the mechanical behavior of all components in a fuel cell stack is a very complex task due to the diversity of materials properties. Prior to the integration of a 3 kW PEMFC power plant, a numerical simulation was performed in order to obtain the mechanical stress distribution for two of the most pressure sensitive components of the stack: the membrane, and the graphite plates. The stress distribution of the above mentioned components was numerically simulated by finite element analysis and the stress magnitude for the membrane was confirmed using pressure films. Stress values were found within the elastic zone which guarantees mechanical integrity of fuel cell components. These low stress levels particularly for the membrane will allow prolonging the life and integrity of the fuel cell stack according to its design specifications.
J. Gogoi
2012-01-01
Full Text Available This paper deals with the stress vs. strength problem incorporating multi-componentsystems viz. standby redundancy. The models developed have been illustrated assuming that allthe components in the system for both stress and strength are independent and follow differentprobability distributions viz. Exponential, Gamma and Lindley. Four different conditions forstress and strength have been considered for this investigation. Under these assumptions thereliabilities of the system have been obtained with the help of the particular forms of densityfunctions of n-standby system when all stress-strengths are random variables. The expressions forthe marginal reliabilities R(1, R(2, R(3 etc. have been derived based on its stress- strengthmodels. Then the corresponding system reliabilities Rn have been computed numerically andpresented in tabular forms for different stress-strength distributions with different values of theirparameters. Here we consider n 3 for estimating the system reliability R3.
Thermodynamic method for generating random stress distributions on an earthquake fault
Barall, Michael; Harris, Ruth A.
2012-01-01
This report presents a new method for generating random stress distributions on an earthquake fault, suitable for use as initial conditions in a dynamic rupture simulation. The method employs concepts from thermodynamics and statistical mechanics. A pattern of fault slip is considered to be analogous to a micro-state of a thermodynamic system. The energy of the micro-state is taken to be the elastic energy stored in the surrounding medium. Then, the Boltzmann distribution gives the probability of a given pattern of fault slip and stress. We show how to decompose the system into independent degrees of freedom, which makes it computationally feasible to select a random state. However, due to the equipartition theorem, straightforward application of the Boltzmann distribution leads to a divergence which predicts infinite stress. To avoid equipartition, we show that the finite strength of the fault acts to restrict the possible states of the system. By analyzing a set of earthquake scaling relations, we derive a new formula for the expected power spectral density of the stress distribution, which allows us to construct a computer algorithm free of infinities. We then present a new technique for controlling the extent of the rupture by generating a random stress distribution thousands of times larger than the fault surface, and selecting a portion which, by chance, has a positive stress perturbation of the desired size. Finally, we present a new two-stage nucleation method that combines a small zone of forced rupture with a larger zone of reduced fracture energy.
The importance of geospatial data to calculate the optimal distribution of renewable energies
Díaz, Paula; Masó, Joan
2013-04-01
Specially during last three years, the renewable energies are revolutionizing the international trade while they are geographically diversifying markets. Renewables are experiencing a rapid growth in power generation. According to REN21 (2012), during last six years, the total renewables capacity installed grew at record rates. In 2011, the EU raised its share of global new renewables capacity till 44%. The BRICS nations (Brazil, Russia, India and China) accounted for about 26% of the total global. Moreover, almost twenty countries in the Middle East, North Africa, and sub-Saharan Africa have currently active markets in renewables. The energy return ratios are commonly used to calculate the efficiency of the traditional energy sources. The Energy Return On Investment (EROI) compares the energy returned for a certain source and the energy used to get it (explore, find, develop, produce, extract, transform, harvest, grow, process, etc.). These energy return ratios have demonstrated a general decrease of efficiency of the fossil fuels and gas. When considering the limitations of the quantity of energy produced by some sources, the energy invested to obtain them and the difficulties of finding optimal locations for the establishment of renewables farms (e.g. due to an ever increasing scarce of appropriate land) the EROI becomes relevant in renewables. A spatialized EROI, which uses variables with spatial distribution, enables the optimal position in terms of both energy production and associated costs. It is important to note that the spatialized EROI can be mathematically formalized and calculated the same way for different locations in a reproducible way. This means that having established a concrete EROI methodology it is possible to generate a continuous map that will highlight the best productive zones for renewable energies in terms of maximum energy return at minimum cost. Relevant variables to calculate the real energy invested are the grid connections between
Impact of peak electricity demand in distribution grids: a stress test
Hoogsteen, Gerwin; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria; Schuring, Friso; Kootstra, Ben
2015-01-01
The number of (hybrid) electric vehicles is growing, leading to a higher demand for electricity in distribution grids. To investigate the effects of the expected peak demand on distribution grids, a stress test with 15 electric vehicles in a single street is conducted and described in this paper.
Calculation of ruin probabilities for a dense class of heavy tailed distributions
Bladt, Mogens; Nielsen, Bo Friis; Samorodnitsky, Gennady
2015-01-01
In this paper, we propose a class of infinite-dimensional phase-type distributions with finitely many parameters as models for heavy tailed distributions. The class of finite-dimensional phase-type distributions is dense in the class of distributions on the positive reals and may hence approximat...
Nielsen, Tine B; Wieslander, Elinore; Fogliata, Antonella;
2011-01-01
To investigate differences in calculated doses and normal tissue complication probability (NTCP) values between different dose algorithms.......To investigate differences in calculated doses and normal tissue complication probability (NTCP) values between different dose algorithms....
Jiang, W; Bo, H; Yongchun, G; LongXing, Ni
2010-01-01
Previous research into the strength of endodontically treated or vital teeth restored with inlays or onlays has not determined which restoration method and material provide the most favorable stress distribution upon loading. The purpose of this study was to calculate the von Mises stresses in a mandibular first molar using a 3-dimensional (3-D) finite element model. Models compared endodontically treated and vital teeth, a variety of restorative materials, and the use of either inlays or onlays to restore teeth. Four 3-D models of mandibular first molars were created: (1) the IV group (inlay restored, vital pulp); (2) the OV group (onlay restored, vital pulp); (3) the IE group (inlay restored, endodontically treated); and (4) the OE group (onlay restored, endodontically treated). In each group, 3 types of restorative material were tested: (1) composite resin, (2) ceramic, and (3) gold alloy. The materials had elastic moduli of 19 GPa, 65 GPa, and 96.6 GPa, respectively. Each model was subjected to a force of 45 N directed to the occlusal surface, applied either vertically or laterally (45 degrees obliquely). The stresses occurring in dentin tissue were calculated. The stress distribution patterns and the maximum von Mises stresses were calculated and compared. The different restorative materials exhibited similar stress distribution patterns under identical loading conditions. In each group, the gold-restored tooth exhibited the highest von Mises stress, followed by ceramic and composite resin. The maximum von Mises stress in dentin was found in the IE group (16.73 MPa), which was 5 times higher than the highest value found in the OV group (2.96 MPa). The highest stresses, which occurred at the floor of the preparation and the cervical region in dentin, were in the IE group. The stress concentration area in the IE group was also larger. The results indicate that endodontic treatment caused higher stress concentration in dentin compared with vital teeth, but that
Nagasao, Tomohisa; Miyamoto, Junpei; Tamaki, Tamotsu; Ichihara, Kazuhiko; Jiang, Hua; Taguchi, Toshihiko; Yozu, Ryohei; Nakajima, Tatsuo
2007-12-01
In the Nuss procedure, in which the deformed thorax is forcibly corrected by insertion of correction bars, considerable stresses occur on the patient's thorax. We performed the present study to elucidate how stress patterns on the thorax after this procedure differ between child and adult patients. Eighteen patients with pectus excavatum, constituting a child group (n = 10) and an adult group (n = 8), were included in the study. After a 3-dimensional computer-assisted design model was produced with computed tomographic data from each patient, simulation of the Nuss procedure was performed on the model. Then the stresses occurring on each thorax were calculated using the finite element method. The stresses were compared between the child and adult groups in terms of intensity on each rib and the distribution patterns over the whole thorax. With all 12 ribs, significantly greater stress occurred in the adult group than stress in the child group. Although the stresses occurring on the thorax demonstrated concentrated patterns in the child group, widely distributed patterns were observed in the adult group. The stresses that occur on the thorax after the Nuss procedure take different patterns between children and adults in terms of intensity and distribution. The differences should be taken into consideration in managing postoperative pain after the Nuss procedure.
Osamura, Kozo; Kuratani, Fumiyasu; Koide, Toshio; Ogawa, Wataru; Taniguchi, Hiroyasu; Monju, Yoshiyuki; Mizuta, Taiji; Shobu, Takahisa
2016-12-01
The artistic sound of a cymbal is produced by employing a special copper alloy as well as incorporating complicated and heterogeneous residual stress/strain distributions. In order to establish a modern engineering process that achieves high-quality control for the cymbals, it is necessary to investigate the distribution of the residual stresses/strains in the cymbal and their quantitative relation with the frequency characteristics of the sound generated from the cymbal. In the present study, we have successfully used synchrotron radiation to measure the distribution of residual strain in two kinds of cymbals—after spinforming as well as after hammering. The microstructure and the mechanical properties of the cymbals were measured as well their acoustic response. Based on our experimental data, the inhomogeneous residual stress/strain distributions in the cymbals were deduced in detail and their influence on the frequency characteristics of the sound produced by the cymbals was identified.
First-principles calculation of stress tensor in the LSDA+U formalism
Park, Se Young; Choi, Hyoung Joon
2016-12-01
We derive the stress-tensor formula within the LSDA+U scheme by differentiating analytically the LSDA+U total-energy function with respect to the strain tensor. The rotationally invariant form of the LSDA+U functional is employed and the double-counting correction is considered in the fully localized limit and around mean field. The electronic wave functions are expanded with either pseudoatomic orbitals (PAOs) or plane waves. In the PAO-basis case, the orthogonality stress term is included. Our LSDA+U stress-tensor formula is numerically tested with antiferromagnetic NiO and reproduces successfully the stress values obtained from numerical derivatives of the total-energy values. As an application, we study elastic constants, bulk moduli, and sound velocities of NiO and MnO, obtaining results in good agreement with experimental data.
Asada, Kazuo (Mitsubishi Heavy Industries Ltd., Tokyo (Japan)); Fukuoka, Hidekazu
1992-11-01
Decreasing characteristics of both stress and stress gradient with propagation distance at a 2-dimensional linear viscoelasticity wavefront are derived by using our 3-dimensional theoretical equation for particle velocity discontinuities. By finite-element method code DYNA3D, stress at a noncurvature dilatation wavefront of linear viscoelasticity is shown to decrease exponentially. This result is in good accordance with our theory. By dynamic photoelasticity experiment, stress gradients of urethane rubber plates at 3 types of wavefronts are shown to decrease exponentially at a noncurvature wavefront and are shown to be a decreasing function of (1/[radical]R) exp ([alpha][sub 1][sup 2]/(2[alpha][sub 0][sup 3][xi])) at a curvature wavefront. These experiment results are in good accordance with our theory. (author).
Kwak, Dong Ryul; Yoshida, Sanichiro; Sasaki, Tomohiro; Todd, Judith A; Park, Ik Keun
2016-04-01
This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints.
On temporal and spatial distribution of seismic apparent stresses in Yunnan area
QIN Jia-zheng; QIAN Xiao-dong
2006-01-01
motion is applied to a detailed study on the temporal and spatial distribution of the seismic apparent stresses (σa)for the moderate and small earthquakes and two aftershock sequences in Yunnan area. The results show that there exists an obvious non-homogeneity for the seismic apparent stresses in the spatial distribution. The concentrated regions of the high apparent stresses are related to the active places of the moderate and small earthquakes. Before the Dayao M=6.2 earthquake, there was a period in which the apparent stresses were high and the value was 5times of the average value, 0.25 MPa. The relatively high values of apparent stresses distribute around the epicentral area of the major shock and nearby. It indicates that the variation characteristics of the apparent stresses can be taken as a new kind of criterion for the earthquake-risk forecast. Usually the ratio of the apparent stresses of the aftershock sequence σaA to the ones σaM of main shock is less than 1.0.
Belli, Sema; Eraslan, Oğuz; Eskitaşcıoğlu, Gürcan
The aim of this finite-element stress analysis (FEA) was to determine the effect of degradation due to water storage on stress distributions in root-filled premolar models restored with composite using either a self-etch (SE) or an etch-and-rinse (E&R) adhesive. Four premolar FEA models including root filling, MOD cavity, and composite restorations were created. The cavities were assumed to be treated by SE or E&R adhesives and stored in water for 18 months. The elastic properties of the adhesive-dentin interface after 24-h and 18-month water storage were obtained from the literature and applied to the FEA models. A 300-N load was applied on the functional cusps of the models. The SolidWorks/Cosmosworks structural analysis program was used and the results were presented considering the von Mises stresses. Stresses in the cervical region increased over time on the load-application side of the main tooth models (SE: 84.11 MPa to 87.51 MPa; E&R: 100.24 MPa to 120.8 MPa). When the adhesive interfaces (hybrid layer, adhesive layer) and dentin were evaluated separately, the stresses near the root canal orifices increased over time in both models; however, this change was more noticeable in the E&R models. Stresses at the cavity corners decreased in the E&R model (within the adhesive layer), while SE models showed the opposite (within the hybrid layer). Change in the elastic modulus of the adhesive layer, hybrid layer, and dentin due to water storage has an effect on stresses in root-filled premolar models. The location and the level of the stresses differed depending on the adhesive used.
Vreede, F. A.
1981-05-01
The manual of instructions for the user of the CSIR triaxial rock stress measuring equipment is critically examined. It is shown that the values of the rock stresses can be obtained from the strain gauge records by means of explicit formulae, which makes the manual's computer program obsolete. Furthermore statistical methods are proposed to check for faulty data and inhomogeneity in rock properties and virgin stress. The possibility of non-elastic behavior of the rock during the test is also checked. A new computer program based on the explicit functions and including the check calculations is presented. It is much more efficient than the one in the manual since it does not require computer sub-routines, allowing it to be used directly on any modern computer. The output of the new program is in a format suitable for direct inclusion in the report of an investigation using strain cell results.
Burchett, S.N.; Mitchell, R.T.; Nguyen, L.; Peterson, D.W.; Sweet, J.N.
1999-03-09
We report the first in situ measurements of thermomechanical stresses in a 1000 I/O 250 {micro}m pitch piezoresistive flip chip test chip assembled to a 755 I/O 1.0 mm pitch 35 mm Ball Grid Array (BGA). The BGA substrates employed build-up dielectric layers containing micro-vias over conventional fiberglass laminate cores. Experimental data, which include in situ stress and die bending measurements, were correlated to closed form and Finite Element Method (FEM) calculations. Cracking and delamination were observed in some of the experimental groups undergoing temperature cycling. Through use of bounding conditions in the FEM simulations, these failures were associated with debonding of the underfill fillet from the die edge that caused stresses to shift to weaker areas of the package.
Hayashi, Yoshihiro; Miura, Takahiro; Shimada, Takuya; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo
2013-10-01
Tablet characteristics of tensile strength and disintegration time were predicted using residual stress distribution, simulated by the finite element method (FEM). The Drucker-Prager Cap (DPC) model was selected as the method for modeling the mechanical behavior of pharmaceutical powders composed of lactose (LAC), cornstarch (CS), and microcrystalline cellulose (MCC). The DPC model was calibrated using a direct shear test and analysis of the hardening law of the powder. The constructed DPC model was fed into the analysis using the FEM, and the mechanical behavior of pharmaceutical powders during compaction was analyzed using the FEM. The results revealed that the residual stress distribution of the tablets was uniform when the compression force increased. In particular, the residual stress distribution of tablets composed of equal amounts of LAC, CS, and MCC was more uniform than the tablets composed of 67% LAC and 33% CS, with no MCC. The tensile strength and disintegration time were predicted accurately from the residual stress distribution of tablets using multiple linear regression analysis and partial least squares regression analysis. This suggests that the residual stress distribution of tablets is related closely to the tensile strength and disintegration time.
刘雷; 裴福兴; 宋跃明; 邹力; 张聪; 周宗科
2002-01-01
Objective: To compare the influence of normal and degenerative discs on stress distribution of the thoracolumbar vertebrae under destructive load, explore the biomechanical background and clinical meaning and provide theoretical basis for clinical diagnosis and treatment.Methods: A mechanical model of thoracolumbar motion segment of normal and degenerative discs was built with a three dimensional finite element method and three stresses of vertical compression, compressive flexion and distractive flexion were comparatively analyzed.Results: With vertical compression and compressive flexion loads, the thoracolumbar motion segment of the normal disc showed that the central part of the upper and lower end-plates of the vertebrae and the central part of the trabecular bone adjacent to the end-plate were loaded with the most intensive stresses, meanwhile, the postero-lateral part of the annulus fibrosus was concentrated with stresses. Degenerative disc showed that the stress distribution of the trabecular bone was relatively averaged, the stresses of the central part adjacent to the end-plate were low, while at the same time, the stresses of the peripheral part were elevated relatively. With distraction flexion load, the stresses of the cortex bone, trabecular bone, end-plate and annulus fibrosus of the thoracolumbar vertebrae of degenerative discs were low, meanwhile, the stresses of the posterior structure of the vertebral body were relatively elevated compared with that of normal discs.Conclusions: There is difference in influence between normal and degenerative discs on the stress distribution of the thoracolumbar vertebrae with destructive load. The transferring way of load is changed after disc degeneration.
刘雷; 裴福兴; 等
2002-01-01
Objectie:To compare the influence of normal and degenerative discs on stress distribution of the thoracolumbar vertebrae under destructive load,explore the biomechanical background and clinical meaning and provide theoretical basis for clinical diagnosis and treatment.Methods:A mechanical model of thoracolumbar motion segment of normal and degenerative discs was built with a three dimensional finite element method and three stresses of vertical compression,compressive flexion and distractive flexion were comparatively analyzed.Results:With vertical compression and compressive flexion loads,the thoracolumbar motion segment of the normal disc showed that the central part of the upper and lower end-plates of the vertebrae and the central part of the trabecular bone adjacent to the end-plate were lgaded with the most intensive stresses,meanwhile,the postero-lateral part of the annulus fibrosus was concentrated with stresses.Degeneratie disc showed that the stress distribution of the trabecular bone was relatively averaged,the stresses of the central part adjacent to the end-plate were low,while at the same time,the stresses of the peripheral part were elevated relatively.With distraction flexion load,the stresses of the cortex bone,trabecular bone,end-plate and annulus fibrosus of the thoracolumbar vertebrae of degenerative discs were low,neanwhile,the stresses of the posterior structure of the vertebral body were relatively elevated compared with that of normal discs.Conclusions:There is difference in influence between normal and degen erative discs on the stress distribution of the thoracolumbar vertebrae with destructive load.The transferring way of load is changed after disc degeneration.
KASARDOVA, A; Ocelik, Vaclav; CSACH, K; MISKUF, J
A method for calculating the activation energy spectrum from isothermal data using Fourier techniques is used for studying the deformation processes in amorphous metals. The influence of experimental error on the calculated spectrum is discussed. The activation energy spectrum derived from the
KASARDOVA, A; Ocelik, Vaclav; CSACH, K; MISKUF, J
1995-01-01
A method for calculating the activation energy spectrum from isothermal data using Fourier techniques is used for studying the deformation processes in amorphous metals. The influence of experimental error on the calculated spectrum is discussed. The activation energy spectrum derived from the anela
YAN Zuwe; YAN Shuwang; LI Sa
2006-01-01
Based on elastoplastic model, 2D and 3D finite element method (FEM) are used to calculate the stress and displacement distribution in the soft clay slope under gravity and uniform load at the slope top. Stability analyses indicate that 3D boundary effect varies with the stress level of the slope. When the slope is stable, end effect of 3D space is not remarkable. When the stability decreases, end effect occurs; when the slope is at limit state, end effect reaches maximum. The energy causing slope failure spreads preferentially along y-z section, and when the failure resistance capability reaches the limit state, the energy can extend along x-axis direction. The 3D effect of the slope under uniform load on the top is related to the ratio of load influence width to slope height, and the effect is remarkable with the decrease of the ratio.
STRESS DISTRIBUTION IN THE STRATIFIED MASS CONTAINING VERTICAL ALVEOLE
Bobileva Tatiana Nikolaevna
2017-08-01
Full Text Available Almost all subsurface rocks used as foundations for various types of structures are stratified. Such heterogeneity may cause specific behaviour of the materials under strain. Differential equations describing the behaviour of such materials contain rapidly fluctuating coefficients, in view of this, solution of such equations is more time-consuming when using today’s computers. The method of asymptotic averaging leads to getting homogeneous medium under study to averaged equations with fixed factors. The present article is concerned with stratified soil mass consisting of pair-wise alternative isotropic elastic layers. In the results of elastic modules averaging, the present soil mass with horizontal rock stratification is simulated by homogeneous transversal-isotropic half-space with isotropy plane perpendicular to the standing axis. Half-space is loosened by a vertical alveole of circular cross-section, and virgin ground is under its own weight. For horizontal parting planes of layers, the following two types of surface conditions are set: ideal contact and backlash without cleavage. For homogeneous transversal-isotropic half-space received with a vertical alveole, the analytical solution of S.G. Lekhnitsky, well known in scientific papers, is used. The author gives expressions for stress components and displacements in soil mass for different marginal conditions on the alveole surface. Such research problems arise when constructing and maintaining buildings and when composite materials are used.
2012-11-20
... Part 325 Policy Statement on the Principles for Development and Distribution of Annual Stress Test... and factors to be used by the FDIC in developing and distributing the stress test scenarios for the annual stress tests required by the Dodd- Frank Wall Street Reform and Consumer Protection Act of 2010...
Shuqing HAO; Hongwei HUANG; Kun YIN
2007-01-01
By simplifying the characters in the air reverse circulation bit interior fluid field, the authors used air dynamics and fluid mechanics to calculate the air distribution in the bit and obtained an equation of flow distribution with a unique resolution. This study will provide help for making certain the bit parameters of the bit structure effectively and study the air reverse circulation bit interior fluid field character deeply.
Shen Tian-Ming; Chen Chong-Yang; Wang Yan-Sen
2007-01-01
In this paper a systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of H-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependences of the calculated angular distribution and polarization on the reduced energy and nuclear charge are fitted by the corresponding empirical formulas respectively.
Kravchuk Aleksandr Stepanovich
2015-10-01
Full Text Available For the first time with the help of the theory of analytic functions and Kolosov-Muskhelishvili formulas the problem of the two-dimensional theory of elasticity for a thickwalled ring with the uneven pressures, acting on its borders, was solved. The pressure on the inner and outer boundaries is represented by Fourier series. The authors represent the two complex functions which solve boundary problem in the form of Laurent series. The logarithmic terms in these series are absent because the boundary problem has the self-balancing loads on each boundary of ring. The coefficients in the Laurent series are calculated by the boundary conditions. Firstly, the equations were obtained in the general form. But the hypothesis about even distributions of pressures at borders of ring was used for constructing an example. It leads to the fact that all coefficients of analytic functions represented in Laurent series have to be only real. As a solving example, the representation of pressures in equivalent hypotrochoids was used. The application of the computer algebra system Mathematica greatly simplifies the calculation of the distribution of stresses and displacements in ring. It does not require manual formal separation of real and imaginary parts in terms of Kolosov-Muskhelishvili to display the distribution of the physical parameters. It separates them only for calculated numbers with the help of built-in functions.
Influence of stress-path on pore size distribution in granular materials
Das Arghya
2017-01-01
Full Text Available Pore size distribution is an important feature of granular materials in the context of filtration and erosion in soil hydraulic structures. Present study focuses on the evolution characteristics of pore size distribution for numerically simulated granular assemblies while subjected to various compression boundary constrain, namely, conventional drained triaxial compression, one-dimensional or oedometric compression and isotropic compression. We consider the effects initial packing of the granular assembly, loose or dense state. A simplified algorithm based on Delaunay tessellation is used for the estimation of pore size distribution for the deforming granular assemblies at various stress states. The analyses show that, the evolution of pore size is predominantly governed by the current porosity of the granular assembly while the stress path or loading process has minimal influence. Further it has also been observed that pore volume distribution reaches towards a critical distribution at the critical porosity during shear enhanced loading process irrespective of the deformation mechanism either compaction or dilation.
Influence of stress-path on pore size distribution in granular materials
Das, Arghya; Kumar, Abhinav
2017-06-01
Pore size distribution is an important feature of granular materials in the context of filtration and erosion in soil hydraulic structures. Present study focuses on the evolution characteristics of pore size distribution for numerically simulated granular assemblies while subjected to various compression boundary constrain, namely, conventional drained triaxial compression, one-dimensional or oedometric compression and isotropic compression. We consider the effects initial packing of the granular assembly, loose or dense state. A simplified algorithm based on Delaunay tessellation is used for the estimation of pore size distribution for the deforming granular assemblies at various stress states. The analyses show that, the evolution of pore size is predominantly governed by the current porosity of the granular assembly while the stress path or loading process has minimal influence. Further it has also been observed that pore volume distribution reaches towards a critical distribution at the critical porosity during shear enhanced loading process irrespective of the deformation mechanism either compaction or dilation.
Barama, Louisa
Subduction of the Nazca plate beneath the South American plate drives frequent and sometimes large magnitude earthquakes. During the past 40 years, significant numbers of outer rise earthquakes have occurred in the offshore regions of Colombia and Chile. In this study, we investigate the distribution of stress due to lithospheric bending and the extent of faults within the subducting plate. To calculate more accurate epicenters and to constrain which earthquakes occurred within the outer rise, we use hypocentroidal decomposition to relocate earthquakes with Global Centroid Moment Tensor (GCMT) solutions occurring after 1976 offshore Colombia and Chile. We determine centroid depths of outer rise earthquakes by inverting teleseismic P-, SH-, and SV- waveforms for earthquakes occurring from 1993 to 2014 with Mw ≥ 5.5. In order to further constrain the results of the waveform inversion, we estimate depths by comparing earthquake duration, amplitude, and arrival times for select stations with waveforms with good signal to noise ratios. Our results indicate that tensional earthquakes occur at depths down to 13 km and 24 km depth beneath the surface in the Colombia and Chile regions, respectively. Since faulting within the outer rise can make the plate susceptible to hydration and mantle serpentinization, we therefore infer the extent of possible hydration of the Nazca plate to extend no deeper than the extent of tensional outer rise earthquakes.
Yang, Jerry Zhijian
2014-01-01
Irving and Kirkwood formulism (IK formulism) provides a way to compute continuum mechanics quantities at certain location in terms of molecular variables. To make the approach more practical in computer simulation, Hardy proposed to use a spacial kernel function that couples continuum quantities with atomistic information. To reduce irrational fluctuations, Murdoch proposed to use a temporal kernel function to smooth the physical quantities obtained in Hardy's approach. In this paper, we generalize the original IK formulism to systematically incorporate both spacial and temporal average. The Cauchy stress tensor is derived in this generalized IK formulism (g-IK formulism). Analysis is given to illuminate the connection and difference between g-IK formulism and traditional temporal post-process approach. The relationship between Cauchy stress and first Piola-Kirchhoff stress is restudied in the framework of g-IK formulism. Numerical experiments using molecular dynamics are conducted to examine the analysis res...
Kovacević, M S; Nikezić, D
2006-09-10
A means of calculating optical power distribution in bent multimode optical fibers is proposed. It employs the power-flow equation approximated by the Fokker-Planck equation that is solved by the explicit finite-difference method. Conceptually important steps of this procedure include (i) dividing the full length of the bent optical fiber into a finite number of short, straight segments; (ii) solving the power equation for each segment sequentially to find its output distribution; and (iii) expressing that output distribution in rotated coordinates of the subsequent segment along the curved fiber to determine the input distribution for that subsequent segment and thus enable the calculation of the power flow and output distribution for it. The segment length and bend-induced perturbation of output angles are determined by geometric optics. The resulting power distributions are given at different cross sections along the curved fiber axis. They vary with the radius of fiber curvature and launch conditions. Results are compared to those for straight fiber. Bending loss is calculated as well.
Stress Distribution on Blasting Gallery Barrier Pillar due to Goaf Formation During Extraction
Kumar Reddy, Sandi; Sastry, Vedala Rama
2016-10-01
Semi-mechanised blasting gallery mining is a sustainable option to achieve higher production and productivity from underground thick coal seams. Judicious design of underground blasting gallery panel requires understanding of stress distribution on barrier pillars during different stages of extraction. This paper presents a study of stress distribution in and around barrier pillar for the different stages of extraction in the blasting gallery panel. Finite difference analysis taken up for final excavation (depillaring) in the panel with different stages of extraction. Analysis revealed that the stress transferred on barrier pillar increased as progress of excavation increased. Maximum stress was observed at a distance of 10 and 12 m from the pillar edge for virgin and goaved out panel sideby respectively, which gradually decreased towards centre of the pillar.
Abeer Abd-Alla EL-Helbawy
2016-09-01
Full Text Available The accelerated life tests provide quick information on the life time distributions by testing materials or products at higher than basic conditional levels of stress such as pressure, high temperature, vibration, voltage or load to induce failures. In this paper, the acceleration model assumed is log linear model. Constant stress tests are discussed based on Type I and Type II censoring. The Kumaraswmay Weibull distribution is used. The estimators of the parameters, reliability, hazard rate functions and p-th percentile at normal condition, low stress, and high stress are obtained. In addition, credible intervals for parameters of the models are constructed. Optimum test plan are designed. Some numerical studies are used to solve the complicated integrals such as Laplace and Markov Chain Monte Carlo methods.
Stress Distribution on Blasting Gallery Barrier Pillar due to Goaf Formation During Extraction
Kumar Reddy, Sandi; Sastry, Vedala Rama
2015-09-01
Semi-mechanised blasting gallery mining is a sustainable option to achieve higher production and productivity from underground thick coal seams. Judicious design of underground blasting gallery panel requires understanding of stress distribution on barrier pillars during different stages of extraction. This paper presents a study of stress distribution in and around barrier pillar for the different stages of extraction in the blasting gallery panel. Finite difference analysis taken up for final excavation (depillaring) in the panel with different stages of extraction. Analysis revealed that the stress transferred on barrier pillar increased as progress of excavation increased. Maximum stress was observed at a distance of 10 and 12 m from the pillar edge for virgin and goaved out panel sideby respectively, which gradually decreased towards centre of the pillar.
Peixoto, Hugo Eduardo, E-mail: hugo.e.peixoto@hotmail.com [Implantology Team, Latin American Institute of Research and Education in Dentistry, Curitiba, Paraná (Brazil); Bordin, Dimorvan, E-mail: dimorvan_bordin@hotmail.com [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Del Bel Cury, Altair A., E-mail: altcury@fop.unicamp.br [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Silva, Wander José da, E-mail: wanderjose@fop.unicamp.br [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Faot, Fernanda, E-mail: fernanda.faot@gmail.com [Department of Restorative Dentistry, School of Dentistry, Federal University of Pelotas, Gonçalves Chaves, 457, 2nd floor, Pelotas, Rio Grande do Sul 96015-560 (Brazil)
2016-08-01
Purpose: Evaluate the influence of abutment's material and geometry on stress distribution in a single implant-supported prosthesis. Materials and Methods: Three-dimensional models were made based on tomographic slices of the upper middle incisor area, in which a morse taper implant was positioned and a titanium (Ti) or zirconia (ZrN) universal abutments was installed. The commercially available geometry of titanium (T) and zirconia (Z) abutments were used to draw two models, TM1 and ZM1 respectively, which served as control groups. These models were compared with 2 experimental groups were the mechanical properties of Z were applied to the titanium abutment (TM2) and vice versa for the zirconia abutment (ZM2). Subsequently, loading was simulated in two steps, starting with a preload phase, calculated with the respective friction coefficients of each materials, followed by a combined preload and chewing force. The maximum von Mises stress was described. Data were analyzed by two-way ANOVA that considered material composition, geometry and loading (p < 0.05). Results: Titanium and zirconia abutments showed similar von Mises stresses in the mechanical part of the four models. The area with the highest concentration of stress was the screw thread, following by the screw body. The highest stress levels occurred in screw thread was observed during the preloading phase in the ZM1 model (931 MPa); and during the combined loading in the TM1 model (965 MPa). Statistically significant differences were observed for loading, the material × loading interaction, and the loading × geometry interaction (p < 0.05). Preloading contributed for 77.89% of the stress (p < 0.05). There were no statistically significant differences to the other factors (p > 0.05). Conclusion: The screw was the piece most intensely affected, mainly through the preload force, independent of the abutment's material. - Highlights: • The abutment's screw was the most impaired piece of the
The Effect of Corner Radii and Part Orientation on Stress Distribution of Cold Forging Die
Ahmad B. Abdullah; Kam S. Ling; Zahurin Samad
2008-01-01
One of the most critical problems in cold forging is the huge stresses generated from the deformation of metal leads to die failure. The distribution of stresses mainly depends on geometry of the die. An approach to optimal design in cold forging die geometry and orientation are presented in this paper. The impression cold forging dies of the Universal joint was generated using three-dimensional CAD modeling software, SolidWorks. This CAD modeling software coupled with FEA tools, COSMOSWorks....
Evaluation of missing pellet surface geometry on cladding stress distribution and magnitude
Capps, Nathan [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Montgomery, Robert [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Sunderland, Dion [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); ANATECH Corp, San Diego, CA 92121 (United States); Pytel, Martin [Electric Power Research Institute, Palo Alto, CA 94304 (United States); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States)
2016-08-15
Highlights: • Stress concentrations are related to pellet defect geometries. • The presence of radial cracks cause increases in stress concentration. • Increasing the size of MPS causes an increase hoop stress concentrations. - Abstract: Missing pellet surface (MPS) defects are local geometric defects in nuclear fuel pellets that result from pellet mishandling or manufacturing. The presence of MPS defects can cause significant clad stress concentrations that can lead to through-wall cladding failure for certain combinations of fuel burnup, and reactor power level or power change. Consequently, the impact of MPS defects has limited the rate of power increase, or ramp rate, in both pressurized and boiling water reactors (PWRs and BWRs, respectively). Improved three-dimensional (3-D) fuel performance models of MPS defect geometry can provide better understanding of the probability for pellet clad mechanical interaction (PCMI), and correspondingly the available margin against cladding failure by stress corrosion cracking (SCC). The Consortium of Advanced Simulations of Light Water Reactors (CASL) has been developing the Bison-CASL fuel performance code to consider the inherently multi-physics and multi-dimensional mechanisms that control fuel behavior, including cladding stress concentrations resulting from MPS defects. This paper evaluates the cladding hoop stress distributions as a function of MPS defect geometry with discrete pellet radial cracks for a set of typical operating conditions in a PWR fuel rod. The results provide a first step toward a probabilistic approach to assess cladding failure during power maneuvers. This analysis provides insight into how varying pellet defect geometries affect the distribution of the cladding stress, as well as the temperature distributions within the fuel and clad; and are used to develop stress concentration factors for comparing 2-D and 3-D models.
SHA Yun-dong; GUO Xiao-peng; LIAO Lian-fang; XIE Li-juan
2011-01-01
As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings, an effective method for predicting the fatigue life of a structure under random loadings was studied. Firstly, the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied, analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution. The formula for calculating Weibull parameters were given. Based on the Miner linear theory, the method for predicting the random sonic fatigue life based on the stress probability density was developed, and the model for fatigue life prediction was constructed. As an example, an aero-engine combustor liner structure was considered. The power spectrum density (PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM (finite element method/boundary element method) model, the fatigue life was estimated by using the constructed model. And considering the influence of the wide frequency band, the calculated results were modified. Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend. The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.
DING De-Sheng; ZHANG Yu
2004-01-01
@@ We present a simple calculation approach for the fundamental and second-harmonic sound beams with an arbitrary distribution source in the quasilinear approximation. The analysis is based on the assumption that the source function with an arbitrary geometry and distribution is expanded into the sum of a set of two-dimensional Gaussian functions. The two- and five-dimensional integral solutions for the fundamental and second-harmonic fields are, respectively, reduced in terms of Gaussian functions and simple one-dimensional integrals. The numerical evaluation of field distributions is then greatly simplified.
Calculation of principal stresses and their directions in selected cutting planes in rock drilling
František Krepelka
2011-12-01
Full Text Available The paper is focused on the analysis of principal stress fields induced in the system of drilling tool-rock during the drilling process in immediate surroundings of their mutual contact. Various load conditions were analyzed, representing torque, loading only by axial thrust force and combined loading by concurrent action of torque and thrust force on the drilled rock.
Consequences of using the plane stress assumption for damage calculation in crash analyses
Walters, C.L.
2014-01-01
Simulation of failure in plate materials (represented as shell elements) is critical for the correct determination of crash performance of ships and offshore structures. This need has traditionally been filled with failure loci that give the failure strain in terms of stress triaxiality. In recent y
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2011-01-01
[Objective] The aim was to study the distribution characteristics of terrain reflected radiation in Fujian Province.[Method] Based on solar radiation data,digital elevation model (DEM) and surface meteorological observation data in Fujian Province,plus surface albedo obtained by using remote sensing inversion method,the distribution of terrain reflected radiation in Fujian Province from 1988 to 2007 was simulated,and then its temporal and spatial distribution characteristics was studied.[Result] The simulat...
Chen, Aijie; Feng, Xiaoli; Zhang, Yanli; Liu, Ruoyu; Shao, Longquan
2015-01-01
To investigate the stress distribution in a maxillary canine restored with each of four different post systems at different levels of alveolar bone loss. Two-dimensional finite element analysis (FEA) was performed by modeling a severely damaged canine with four different post systems: CAD/CAM zirconia, CAD/CAM glass fiber, cast titanium, and cast gold. A force of 100 N was applied to the crown, and the von Mises stresses were obtained. FEA revealed that the CAD/CAM zirconia post system produced the lowest maximum von Mises stress in the dentin layer at 115.8 MPa, while the CAD/CAM glass fiber post produced the highest stress in the dentin at 518.2 MPa. For a severely damaged anterior tooth, a zirconia post system is the best choice while a cast gold post ranks second. The CAD/CAM glass fiber post is least recommended in terms of stress level in the dentin.
Tongqiang Xiao; Bai Jianbiao; Xu Lei; Zhang Xuebin
2011-01-01
Given the difficulties encountered in roadway support under coal pillars, we studied the characteristics of stress distribution and their effect on roadway stability, using theoretical analysis and numerical simulation. The results show that, under a coal pillar, vertical stress in a floor stratum increases while horizontal stress decreases. We conclude that the increased difference between vertical and horizontal stress is an important reason for deformation of the surrounding rock and failures of roadways under coal pillars. Based on this, we propose control technologies of the surrounding rock of a roadway under a coal pillar, such as high strength and high pre-stressed bolt support, cable reinforcement support,single hydraulic prop with beam support and reinforcement by grouting of the surrounding rock, which have been successfully applied in a stability control project of a roadway under a coal pillar.
Effect of fiber distribution on residual thermal stress in titanium matrix composite
马志军; 杨延清; 朱艳; 陈彦
2004-01-01
Residual thermal stresses (RTS) of SCS-6 SiC/Ti-24Al-11Nb composite were analyzed by using finite element method (FEM). Three models of fiber array in the composite and the effect of fiber distance on the RTS were discussed. In all the three models compressive stress was found in the radial direction and tensile stress in the tangential direction. It is pointed out that, in real composite system, hexagonal fiber geometry is superior because the distribution and the magnitude of the residual stress are similar to those in single fiber model. In square fiber geometry, it is easier to make the matrix crack due to the larger residual tangential stress. RTS becomes very large and changes violently when the fiber distance is less than 15μm or so, therefore too high fiber volume is apt to result in matrix crack.
Calculation of a velocity distribution from particle trajectory end-points.
Rasmussen, Lowell A.
1983-01-01
The longitudinal component of the velocity of a particle at or near a glacier surface is considered, its position as a function of time being termed its trajectory. Functional relationships are derived for obtaining the trajectory from the spatial distribution of velocity and for obtaining the velocity distribution from the trajectory. It is established that the trajectory end-points impose only an integral condition on the velocity distribution and that no individual point on the velocity distribution can be determined if only the end-points are known.-from Author
Zhang, Xiaoxu; Liu, Xiao; Chen, Zhe
2015-01-01
This paper presents a rapid approach to compute the magnetic field distribution in a flux-modulated permanent-magnet brushless motor. Partial differential equations are used to describe the magnet field behavior in terms of magnetic vector potentials. The whole computational domain is divided int...... magnetic field with those calculated by finite element method....
Lee, Moon Ho; Dudin, Alexander; Shaban, Alexy; Pokhrel, Subash Shree; Ma, Wen Ping
Formulae required for accurate approximate calculation of transition probabilities of embedded Markov chain for single-server queues of the GI/M/1, GI/M/1/K, M/G/1, M/G/1/K type with heavy-tail lognormal distribution of inter-arrival or service time are given.
VELOCITY DISTRIBUTION IN TRAPEZOID-SECTION OPEN CHANNEL FLOW WITH A NEW REYNOLDS-STRESS EXPRESSION
Ma Zheng
2003-01-01
By considering that the coherent structure is the main cause of the Reynolds stress, a new Reynolds stress expression was given. On this basis the velocity distribution in the trapezoid-section open channel flow was worked out with the pseudo-spectral method. The results were compared with experimental data and the influence of the ratio of length to width of the cross-section and the lateral inclination on the velocity distribution was analyzed. This model can be used the large flux in rivers and open channes.
On the symmetric α-stable distribution with application to symbol error rate calculations
Soury, Hamza
2016-12-24
The probability density function (PDF) of the symmetric α-stable distribution is investigated using the inverse Fourier transform of its characteristic function. For general values of the stable parameter α, it is shown that the PDF and the cumulative distribution function of the symmetric stable distribution can be expressed in terms of the Fox H function as closed-form. As an application, the probability of error of single input single output communication systems using different modulation schemes with an α-stable perturbation is studied. In more details, a generic formula is derived for generalized fading distribution, such as the extended generalized-k distribution. Later, simpler expressions of these error rates are deduced for some selected special cases and compact approximations are derived using asymptotic expansions.
Wada, Daichi; Igawa, Hirotaka; Murayama, Hideaki; Kasai, Tokio
2014-03-24
A signal processing method based on group delay calculations is introduced for distributed measurements of long-length fiber Bragg gratings (FBGs) based on optical frequency domain reflectometry (OFDR). Bragg wavelength shifts in interfered signals of OFDR are regarded as group delay. By calculating group delay, the distribution of Bragg wavelength shifts is obtained with high computational efficiency. We introduce weighted averaging process for noise reduction. This method required only 3.5% of signal processing time which was necessary for conventional equivalent signal processing based on short-time Fourier transform. The method also showed high sensitivity to experimental signals where non-uniform strain distributions existed in a long-length FBG.
Benazzi, Stefano; Kullmer, Ottmar; Grosse, Ian R; Weber, Gerhard W
2011-09-01
Simulations based on finite element analysis (FEA) have attracted increasing interest in dentistry and dental anthropology for evaluating the stress and strain distribution in teeth under occlusal loading conditions. Nonetheless, FEA is usually applied without considering changes in contacts between antagonistic teeth during the occlusal power stroke. In this contribution we show how occlusal information can be used to investigate the stress distribution with 3D FEA in lower first molars (M(1)). The antagonistic crowns M(1) and P(2)-M(1) of two dried modern human skulls were scanned by μCT in maximum intercuspation (centric occlusion) contact. A virtual analysis of the occlusal power stroke between M(1) and P(2)-M(1) was carried out in the Occlusal Fingerprint Analyser (OFA) software, and the occlusal trajectory path was recorded, while contact areas per time-step were visualized and quantified. Stress distribution of the M(1) in selected occlusal stages were analyzed in strand7, considering occlusal information taken from OFA results for individual loading direction and loading area. Our FEA results show that the stress pattern changes considerably during the power stroke, suggesting that wear facets have a crucial influence on the distribution of stress on the whole tooth. Grooves and fissures on the occlusal surface are seen as critical locations, as tensile stresses are concentrated at these features. Properly accounting for the power stroke kinematics of occluding teeth results in quite different results (less tensile stresses in the crown) than usual loading scenarios based on parallel forces to the long axis of the tooth. This leads to the conclusion that functional studies considering kinematics of teeth are important to understand biomechanics and interpret morphological adaptation of teeth.
Chun, H-J; Park, D-N; Han, C-H; Heo, S-J; Heo, M-S; Koak, J-Y
2005-03-01
In this study, effects of different overdenture attachments on the stress distributions in the maxillary bone surrounding the overdenture implants are studied. Four different types of attachment are considered. They are rigid Dalbo Stud, movable Dalbo Stress Broken, movable Dalro, and movable O-ring attachments. Three-dimensional finite element analysis was conducted with commercial package to obtain the stress distributions in the maxillary bone. Varying the attachment types and angle of inclination of load, the stress distributions in the portions of compact bone and trabecular bone were monitored separately. The analysis was conducted by assuming two different boundary conditions at the interface between cap and overdenture abutment in order to evaluate influence of interface boundary condition on stress distribution in the maxillary bone. They were perfect bonding condition and contact with friction at the interfaces. However, it is preferable to assume perfect bond condition at the interface for rigid type attachment systems and contact with friction at the interface for movable type attachment systems. From the numerical results, it was found that the load transfer mechanism of the implant system is altered significantly by the types of the overdenture attachment and also special care must be taken to assign proper boundary conditions at the interface for the analysis. The movable type Dalro attachment generated the highest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for contact with friction. The rigid type Dalbo Stud attachment generated the smallest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for perfect bonding condition.
Le Page, Yvon; Saxe, Paul
2002-03-01
A symmetry-general approach for the least-squares, therefore precise, extraction of elastic coefficients for strained materials is reported. It analyzes stresses calculated ab initio for properly selected strains. The problem, its implementation, and its solution strategy all differ radically from a previous energy-strain approach that we published last year, but the normal equations turn out to be amenable to the same constrainment scheme that makes both approaches symmetry general. The symmetry considerations governing the automated selection of appropriately strained models and their Cartesian systems are detailed. The extension to materials under general stress is discussed and implemented. VASP was used for ab initio calculation of stresses. A comprehensive range of examples includes a triclinic material (kyanite) and simple materials with a range of symmetries at zero pressure, MgO under hydrostatic pressure, Ti4As3 under [001] uniaxial strain, and Si under [001] uniaxial stress. The MgO case agrees with recent experimental work including elastic coefficients as well as their first and second derivatives. The curves of elastic coefficients for Si show a gradual increase in the 33 compliance coefficient, leading to a collapse of the material at -11.7 GPa, compared with -12.0 GPa experimentally. Interpretation of results for Be using two approximations [local density (LDA), generalized gradient (GGA)], two approaches (stress strain and energy strain), two potential types (projector augmented wave and ultrasoft), and two quantum engines (VASP and ORESTES) expose the utmost importance of the cell data used for the elastic calculations and the lesser importance of the other factors. For stiffness at relaxed cell data, differences are shown to originate mostly in the considerable overestimation of the residual compressive stresses at x-ray cell data by LDA, resulting in a smaller relaxed cell, thus larger values for diagonal stiffness coefficients. The symmetry
Calculation of the shrinkage-induced residual stress in a viscoelastic dental restorative material
Grassia, Luigi; D'Amore, Alberto
2013-02-01
A procedure able to describe the curing process of a particulate composite material used in a dental restoration is developed in the ANSYS environment. The material under concern is a multifunctional methacrylate-based composite for dental restoration, activated by visible light. The model accounts for the dependence of the viscoelastic functions on temperature and degree of cure. Three geometries have been considered in the analysis that are representative of three different classes of dental restoration and mainly differ by the C (constrained)-factor, (i.e. the bounded to unbounded surface ratio). It was found that the temperature could give a necrosis in the vicinity of the tooth nerve and that the average stress at the interface between the composite and the tooth scales exponentially with the C-factor. The residual stress at the dental restoration interface is also compared with the uniaxial tensile strength of twelve commercially available composite materials: it clearly appears that the level of residual stress may overcome the strength of the composite, especially at high C-factors.
Model of horizontal stress in the Aigion10 well (Corinth) calculated from acoustic body waves
Rousseau, A
2006-01-01
In this paper we try to deduce the in situ stresses from the monopole acoustic waves of the well AIG10 between 689 and 1004 meters in depth (Corinth Golf). This borehole crosses competent sedimentary formations (mainly limestone), and the active Aigion fault between 769 and 780 meters in depth. This study is the application of two methods previously described by the author who shows the relationships between in situ horizontal stresses, and (i) the presence or absence of double body waves, (ii) the amplitude ratios between S and P waves (Rousseau, 2005a,b). The full waveforms of this well exhibit two distinct domains separated by the Aigion fault. Within the upper area the three typical waves (P, S and Stoneley) may appear, but the S waves are not numerous, and there is no double body wave, whereas within the lower area there are sometimes double P waves, but no S waves. From those observations, we conclude that the stress domain is isotropic above the Aigion fault, and anisotropic below, which is consistent ...
WenJun Zhang
2011-12-01
Full Text Available In present study a Java algorithm to calculate degree distribution and detect network type was presented. Some indices, e.g., aggregation index, coefficient of variation, skewness, etc., were first suggested for detecting network type. Network types of some food webs reported in Interaction Web Database were determined using the algorithm. The results showed that the degree of most food webs was power law or exponentially distributed and they were complex networks. Different from classical distribution patterns (bionomial distribution, Poisson distribution, and power law distribution, etc., both network type and network complexity can be calculated and compared using the indices above. We suggest that they should be used in the network analysis. In addition, we defined E, E=s2-u, where u and s2 is mean and variance of degree respectively, as the entropy of network. A more complex network has the larger entropy. If E is not greater than 0, the network is a random network and, it is a complex network if E is greater than 0.
Yoon, B; Engelhardt, M; Green, J; Gupta, R; Hägler, P; Musch, B; Negele, J; Pochinsky, A; Syritsyn, S
2016-01-01
We present a lattice QCD calculation of transverse momentum dependent parton distribution functions (TMDs) of protons using staple-shaped Wilson lines. For time-reversal odd observables, we calculate the generalized Sivers and Boer-Mulders transverse momentum shifts in SIDIS and DY cases, and for T-even observables we calculate the transversity related to the tensor charge and the generalized worm-gear shift. The calculation is done on two different n_f=2+1 ensembles: domain-wall fermion (DWF) with lattice spacing 0.084 fm and pion mass of 297 MeV, and clover fermion with lattice spacing 0.114 fm and pion mass of 317 MeV. The results from those two different discretizations are consistent with each other.
He, Qing-yuan; He, Dong-qi; Han, Hong-bin; Yuan, Lan; Yang, Xiao-hong; Peng, Yun; Ka, Wei-bo; Zhang, Hao; Zhang, Hai-long; Li, Ke-jia; Xu, Feng; Tian, Jin; Liu, Xiao-hua; Xue, Xiao-qi
2013-06-18
To build a mathematical model to simulate the drug distribution accompanying with diffusion, distribution and clearance in the brain extracellular space (ECS). Magnetic resonance imaging (MRI) technology was used to monitor changes in the signal-intensity-related tracer gadolinium-diethylene triamine pentaacetic acidm(Gd-DTPA), as an external drug which was injected into the rat brain, and then the mathematical model was built by using the data to establish the diffusion, distribution and clearance process of Gd-DTPA in the brain ECS. The model equation was resolved by Laplace transform. In the sphere coordinates, the linear regressive model was adopted to obtain the estimation method of diffusion coefficient, clearance rate of drugs distribution in the brain ECS. The diffusion coefficient D and the clearance rate k were obtained as (2.73±0.364)×10(-4) mm(2)/s and (1.40±0.206)×10(-5) /s, respectively. The proposed method can accurately reflect the isotropic drug distribution in the brain ECS, and can serve as the foundation to further solve problems about the orthotropic distribution in the brain ECS.
Emre Tokar
2017-01-01
Full Text Available Objective: Implant-supported-overdentures, instead of conventional complete dentures, are frequently recommended to rehabilitate patients having edentulous mandible. The aim of this study was to evaluate the stress distribution characteristics of mandibular implant-supported overdentures with four different bar attachment designs. Materials and Method: A photoelastic mandibular model with three implants (3.75 mm - 13 mm placed at the interforaminal region was generated from a cast of an edentulous mandible. Four mandibular bar overdenture designs were fabricated: bar-clip, bar-galvano, bar-locator, and bar-ceka. Axial vertical loads (135 N were applied to the central fossa of the right first molar area for each overdenture design. Stress concentrations were recorded photographically and analyzed visually. Results: The tested bar attachment designs revealed low and moderate stress levels. The lowest stress was observed with the bar-clip design, followed by bar-locator, bar-ceka, and bar-galvano designs. Conclusion: The loads were distributed to all of the implants. Studied designs experienced moderate stress levels around the loaded side implant. Bars with distally placed stud attachments and surface treatment with electroforming seems to increase stress levels around the implants.
FENG Yun-zhi; FENG Hai-lan; WU Han-jiang
2005-01-01
Objective To assess stresses produced by different obturator prostheses. Methods Three-dimensional finite clement models of unilateral maxillary defects rehabilitated with different obturators were constructed. The different stresses were analyzed by three-dimensional finite element method under different load angle. Results The Von Mises stress values obtained for the remaining tissues adjacent to defect cavity were higher when rehabilitated by inferior hollow obturator in comparison with by superior hollow obturator. The maximum of Von Mises were higher when rehabilitated by resilient hollow obturator than by rigid hollow obturator. It was also observed that in the rigid type stress distribution contours formed in the remaining tissues adjacent to defect cavity, while in resilient hollow obturator prostheses the stress distributed mainly in the prosthesis itself. The oblique load shows the most maximum of Von Mises among all types of obturator prostheses. Conclusions A high lateral wall of an obturator may be more better in preserving the remaining structures than a shorter prosthesis lateral wall. A soft liner may be incorporated to reduce the pain of the residual maxillary structures and mucosa. When load on defect, higher stress would be generated to the residual maxillary structures. The adjustment of occlusual relationship is very important.
Dos Santos, Mateus Bertolini Fernandes; Zen, Bruno Massucato; Bacchi, Atais
2016-10-01
Framework misfit is a common problem observed in overdentures, which might result in prosthetic and biological complications. The aim of this study was to evaluate the influence of vertical misfit and clip material on the stress distribution in an overdenture-retaining bar system under masticatory loading. A 3-D finite element model of a resorbed jaw was created, including two implants and a bar-clip retained overdenture. A pressure of 100 MPa was applied to the right mandibular first molar. Different vertical misfit levels (50, 100, and 200 µm) and clip materials (plastic or gold) were evaluated. Data were evaluated using von Mises stress and microstrain. Vertical misfit amplification caused an increase in the microstrain values in the peri-implant bone tissue next to the ill-fitted component and increased the stresses in the prosthetic screws. The clip material influenced the stress and microstrain distribution in the prosthetic components and bone tissue. The levels of vertical misfit seem to be closely linked with the stress values in the prosthetic screws, mainly to that of the ill-fitted component. The gold clip presented an increase in the stress compared to the plastic clip.
THE CALCULATION OF STRESS-STRAIN STATE OF THREE-LAYER BEAM TAKING INTO ACCOUNT EDGE EFFECTS
Kh. M. Muselemov
2015-01-01
Full Text Available The work is dedicated to the calculation of the stress-strain state (SSS of the three-layer beam (TLB subject to boundary effects.In this paper, a system of differential equations of equilibrium of the threelayer beam. To solve these equations, it is necessary to know the 12 boundary conditions, co-which depend on support conditions and loading of sandwich beams under study. This system of equations is solved by the application package of mathematical modeling "Maple 5.4." The solution of this system we obtain expressions for determining de-formations and stress all components (bearing layers and filler, a three-layer beam anywhere under specified conditions of fastening the ends of the beam and its loading.
Anita Gupta; Pushpa M Rao
2008-03-01
A quadrupole ion trap consisting of electrode structures symmetric about -axis is an important tool for conducting several precision experiments. In practice the field inside the trap does not remain purely quadrupolar, and can be calculated using numerical methods. We have used boundary element method to calculate the potential inside the truncated as well as symmetrically misaligned quadrupolar ion trap. The calculated potential values are fitted to multipole expansion and the weights of multipole moments have been evaluated by minimizing the least square deviation. The higher-order multi-pole contribution in the fabricated hyperbolic electrodes due to truncation and machining imperfections is discussed. Non-linear effects arising due to the superposition of octupole moment manifest as anharmonic oscillations of trapped ions in the non-ideal Paul trap. Theoretical simulations of non-linear effects have been carried out.
连续箱梁的日照温差应力计算研究%Study on Calculation of Sunshine Thermal Stress in Continuous Box-girders
陈权; 王丽娟; 张元海; 诸昌钤
2009-01-01
According to the harmonious condition of deformation and the assumption of plane section, the general formula for calculating sunshine thermal stress of continuous box girders was derived. Then based on the existing experimental results and the modes of sunshine thermal gradients in the present code for design of railway and highway bridges, the practical calculating formula of thermal stress was presented. The method and formula for calculating secondary thermal bending moment were provided tnnzekew continuous box girders based on the three-moment equation of skew continuous beam. The corresponding programmaing was fulfilled. The thermal stresses in figh and skew continuous box girders were calculated through engineering practice and good agreement was achieved compared with those of ANSYS calculation. The longitudinal distribution pattern of the thermal stress in continuous box girder bridges was ascertained. It is put forward that (1) much attention should be paid to the checking calculation for nonnal stress and crack resistance at midspan cross-section of central span in the design of prestrssed concrete continuous box girder bridges; (2) the checking calculation for crack resistance of inclined cross -section near gravity axis in internal support area should also be treated seriously.%根据变形协调条件及平截面假定,首先推导了连续箱梁日照温差总应力的一般公式,并针对试验观测资料及我国铁路桥梁和公路桥梁设计规范中的不同日照温差梯度模式,给出了温度应力的实用计算公式.为了能够进一步应用于斜交连续箱梁,以斜交连续梁的三力矩方程为基础,给出了温度次弯矩的计算方法及公式.编制了相应温度应力分析程序,结合工程实例分别对正交和斜交连续箱梁的温度应力进行了计算分析,并与ANSYS有限元计算结果进行对比.通过分析连续箱梁日照温差应力沿梁跨方向的分布规律,提出在设计预应力混凝
Kulinich O. A.
2008-10-01
Full Text Available The near-surface silicon layers in silicon – dioxide silicon systems with modern methods of research are investigated. It is shown that these layers have compound structure and their parameters depend on oxidation and initial silicon parameters. It is shown the influence of initial defects on mechanical stress and deformation distribution in oxidized silicon.
汤任基; 汤昕燕
2001-01-01
Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint-Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equations and its general solution was then obtained. Based on the obtained solution, a method to calculate the bending center and the stress intensity factors of the cracked cylinger whose cross-section is not thin-walled, but of small torsion rigidity is proposed. Some numerical examples are given.
Stress Distribution of CF/EP Laminated Composites under Supercritical Conditions
Haihong Huang
2015-01-01
Full Text Available Enormous amounts of wastes have been produced due to extensive use of carbon fiber/epoxy resin (CF/EP composites. The fact that the supercritical fluid can be used to recycle these composites efficiently has attracted widespread concerns. A three-dimensional model of CF/EP laminates considering the interfacial layers was established. The internal stress distribution of laminates was simulated based on a heat transfer model; and the change of shear stress with supercritical temperature and pressure was investigated. The results show that the shear stress concentration was located in the interfacial layers; the maximum shear stress can be expressed by a curve of convex parabola to the temperature; and the most serious damage occurred in interfacial layers when temperature approached the glass-transition temperature of resin.
Liu, Zhan; Qian, Yingli; Zhang, Yuanli; Fan, Yubo
2016-01-01
The aim of this study was to evaluate stress distributions in the temporomandibular joints (TMJs) with temporomandibular disorders (TMDs) for comparison with healthy TMJs. A model of mandible and normal TMJs was developed according to CT images. The interfaces between the discs and the articular cartilages were treated as contact elements. Nonlinear cable elements were used to simulate disc attachments. Based on this model, seven models of various TMDs were established. The maximum stresses of the discs with anterior, posterior, medial and lateral disc displacement (ADD, PDD, MDD and LDD) were 12.09, 9.33, 10.71 and 6.07 times magnitude of the identically normal disc, respectively. The maximum stresses of the posterior articular eminences in ADD, PDD, MDD, LDD, relaxation of posterior attachments and disc perforation models were 21, 59, 46, 21, 13 and 15 times greater than the normal model, respectively. TMDs could cause increased stresses in the discs and posterior articular eminences.
Stress distribution in the ankle-foot orthosis used to correct pathological gait.
Chu, T M; Reddy, N P
1995-11-01
Abnormal motion of the ankle-foot complex presents a major problem in the rehabilitation of stroke patients. These patients often develop drop foot, a problem involving excessive and uncontrolled plantar flexion. An ankle-foot orthosis (AFO) is prescribed to constrain and inhibit this abnormal motion. The purpose of this investigation was to simulate the drop foot problem to determine the stress distribution in the orthosis. A quasi-static 3-D finite element analysis of the AFO complex was conducted using ADINA. Results confirmed the hypotheses that the maximum peak stress occurs in the neck, heel, and side-arc region of the AFO. However, the neck region of the AFO experienced the largest amount of stress. High stress concentration in the neck region observed in the present analysis is consistent with the common clinical observation that AFOs break down in the neck region.
Elastic Plastic Stress Distributions in Weld-bonded Lap Joint under Axial Loading
Essam A. Al-Bahkali
2014-06-01
Full Text Available Weld-bonding process is increasingly used in many industries such like automobile and aerospace. It offers significant improvements of sheet metal joints in static, dynamic, corrosion, noise resistance, stiffness and impact toughness properties. A full understanding of this process, including the elastic-plastic stress distribution in the joint, is a must for joints design and automation of manufacturing. Also, the modelling and analysis of this process, though it is complex, proves to be of prime importance. Thus, in this study a systematic experimental and theoretical study employing Finite Element Analysis (FEA is conducted on the weld-bonded joint, fabricated from Austenitic Stainless steel (AISI 304 sheets of 1.00 mm thickness and Epoxy adhesive Araldite 2011, subjected to axial loading. Complete 3-D finite element models are developed to evaluate the normal, shear and triaxial Von Mises stresses distributions across the entire joint, in both the elastic and plastic regions. The, needed quantities and properties, for the FE modelling and analysis, of the base metals and the adhesive, such like the elastic-plastic properties, modulus of elasticity, fracture limit, the nugget and Heat Affected Zones (HAZ properties, etc., are obtained from the experiments. The stress distribution curves obtained are found to be consistent with those obtained from the FE models and in excellent agreement with the experimental and theoretical published data, particularly in the elastic region. Furthermore, the stress distribution curves obtained for the weld-bonded joint display the best uniform smooth distribution curves compared to those obtained for the spot and bonded joint cases. The stress concentration peaks at the edges of the weld-bonded region, are almost eliminated resulting in achieving the strongest joint.
无
2001-01-01
Applying 3-dimension finite difference method, the distribution characteristics of horizontal field transfer func-tions for rectangular conductor have been computed, and the law of distribution for Re-part and Im-part has been given. The influences of source field period, the conductivity, the buried depth and the length of the conductor on the transfer functions were studied. The extrema of transfer functions appear at the center, the four corners and around the edges of conductor, and move with the edges. This feature demonstrates that around the edges are best places for transfer functions￠ observation.
Efficient calculation of local dose distribution for response modelling in proton and ion beams
Greilich, S; Kiderlen, M; Andersen, C E; Bassler, N
2013-01-01
We present an algorithm for fast and accurate computation of the local dose distribution in MeV beams of protons, carbon ions or other heavy-charged particles. It uses compound Poisson-process modelling of track interaction and succesive convolutions for fast computation. It can handle mixed particle fields over a wide range of fluences. Since the local dose distribution is the essential part of several approaches to model detector efficiency or cellular response it has potential use in ion-beam dosimetry and radiotherapy.
Greilich, Steffen; Hahn, Ute; Kiderlen, Markus;
2014-01-01
We present an algorithm for fast and accurate computation of the local dose distribution in MeV beams of protons, carbon ions or other heavy charged particles. It uses compound Poisson modeling of track interaction and successive convolutions for fast computation. It can handle arbitrary complex ...... mixed particle fields over a wide range of fluences. Since the local dose distribution is the essential part of several approaches to model detector efficiency and cellular response it has potential use in ion-beam dosimetry, radiotherapy, and radiobiology....
Changes in internal stress distributions during yielding of square prismatic gold nano-specimens
Batra, R.C., E-mail: rbatra@vt.edu [Department of Engineering Science and Mechanics, M/C 0219, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Pacheco, A.A. [Universidad del Norte, Department of Mechanical Engineering, Barranquilla (Colombia)
2010-05-15
We use molecular statics simulations with the tight-binding potential to analyze stress evolution in nanosize square prismatic gold specimens of different aspect ratios (length/width) deformed in either simple tension/compression or tension/compression. In the former case atoms on end faces are displaced axially but are free to move laterally, and in the latter case atoms on end faces are restrained from moving laterally during their axial displacement. It is found that the stress distribution in the unloaded reference configuration is non-uniform, and it satisfies the local and the global equilibrium equations. Large values of the von Mises stress and the maximum shear stress occur on atoms located at the third layer beneath the traction free surfaces forming different patterns for specimens loaded in tension and compression. The specimen is assumed to yield when its total strain energy drops noticeably. Maximum values of the von Mises stress and the maximum shear stress at yielding are essentially independent of specimen's length for specimens deformed in tension. For specimens deformed in compression, wave-like patterns of stresses along the axial centroidal axis are observed when the specimen yields.
V. Shcherbich
2013-01-01
Full Text Available The paper presents information on elaboration of algorithms and programs for intra-station optimization of load distribution between power plants and calculation of equivalent energy characteristics the Berezovskaya GRES which is one of the components of the system for optimum load distribution between thermal power plants (TPP of the Belarusian power system. Description of the accepted technical concepts, algorithm and program structures, composition and methods for input-output data, organization of personnel work with programs of load optimization has been given in the paper.
Dimitroulis, Christos; Raptis, Theophanes; Raptis, Vasilios
2015-12-01
We present an application for the calculation of radial distribution functions for molecular centres of mass, based on trajectories generated by molecular simulation methods (Molecular Dynamics, Monte Carlo). When designing this application, the emphasis was placed on ease of use as well as ease of further development. In its current version, the program can read trajectories generated by the well-known DL_POLY package, but it can be easily extended to handle other formats. It is also very easy to 'hack' the program so it can compute intermolecular radial distribution functions for groups of interaction sites rather than whole molecules.
Jiang, Jun, E-mail: phyjiang@yeah.net [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Cheng, Yongjun, E-mail: cyj83mail@gmail.com [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Bromley, M.W.J., E-mail: brom@physics.uq.edu.au [School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4075 (Australia)
2015-01-15
Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.
Giordano, Vincenzo; Godoy-Santos, Alexandre Leme; Belangero, William Dias; Pires, Robinson Esteves Santos; Labronici, Pedro José; Koch, Hilton Augusto
2017-01-01
To evaluate the mechanical stress and elastic deformation exercised in the thread/shaft transition of Schanz screws in assemblies with different screw anchorage distances in the entrance to the bone cortex, through the distribution and location of tension in the samples. An analysis of 3D finite elements was performed to evaluate the distribution of the equivalent stress (triple stress state) in a Schanz screw fixed bicortically and orthogonally to a tubular bone, using two mounting patterns: (1) thread/shaft transition located 20 mm from the anchorage of the Schanz screws in the entrance to the bone cortex and (2) thread/shaft transition located 3 mm from the anchorage of the Schanz screws in entrance to the bone cortex. The simulations were performed maintaining the same direction of loading and the same distance from the force vector in relation to the center of the hypothetical bone. The load applied, its direction, and the distance to the center of the bone were constant during the simulations in order to maintain the moment of flexion equally constant. The present calculations demonstrated linear behavior during the experiment. It was found that the model with a distance of 20 mm between the Schanz screws anchorage in the entrance to the bone cortex and the thread/shaft transition reduces the risk of breakage or fatigue of the material during the application of constant static loads; in this model, the maximum forces observed were higher (350 MPa). The distance between the Schanz screws anchorage at the entrance to the bone cortex and the smooth thread/shaft transition of the screws used in a femoral distractor during acute distraction of a fracture must be farther from the entrance to the bone cortex, allowing greater degree of elastic deformation of the material, lower mechanical stress in the thread/shaft transition, and minimized breakage or fatigue. The suggested distance is 20 mm.
Mongrain Rosaire
2009-04-01
Full Text Available Abstract Background In-stent restenosis rates have been closely linked to the wall shear stress distribution within a stented arterial segment, which in turn is a function of stent design. Unfortunately, evaluation of hemodynamic performance can only be evaluated with long term clinical trials. In this work we introduce a set of metrics, based on statistical moments, that can be used to evaluate the hemodynamic performance of a stent in a standardized way. They are presented in the context of a 2D flow study, which analyzes the impact of different strut profiles on the wall shear stress distribution for stented coronary arteries. Results It was shown that the proposed metrics have the ability to evaluate hemodynamic performance quantitatively and compare it to a common standard. In the context of the simulations presented here, they show that stent's strut profile significantly affect the shear stress distribution along the arterial wall. They also demonstrates that more streamlined profiles exhibit better hemodynamic performance than the standard square and circular profiles. The proposed metrics can be used to compare results from different research groups, and provide an improved method of quantifying hemodynamic performance in comparison to traditional techniques. Conclusion The strut shape found in the latest generations of stents are commonly dictated by manufacturing limitations. This research shows, however, that strut design can play a fundamental role in the improvement of the hemodynamic performance of stents. Present results show that up to 96% of the area between struts is exposed to wall shear stress levels above the critical value for the onset of restenosis when a tear-drop strut profile is used, while the analogous value for a square profile is 19.4%. The conclusions drawn from the non-dimensional metrics introduced in this work show good agreement with an ordinary analysis of the wall shear stress distribution based on the
On the calculation of x-ray scattering signals from pairwise radial distribution functions
Dohn, Asmus Ougaard; Biasin, Elisa; Haldrup, Kristoffer;
2015-01-01
We derive a formulation for evaluating (time-resolved) x-ray scattering signals of solvated chemical systems, based on pairwise radial distribution functions, with the aim of this formulation to accompany molecular dynamics simulations. The derivation is described in detail to eliminate any possi...
Greilich, Steffen; Hahn, Ute; Kiderlen, Markus
2014-01-01
We present an algorithm for fast and accurate computation of the local dose distribution in MeV beams of protons, carbon ions or other heavy charged particles. It uses compound Poisson modeling of track interaction and successive convolutions for fast computation. It can handle arbitrary complex ...
da Silveira, Pedro Rodrigo Castro
2014-01-01
This thesis describes the development and deployment of a cyberinfrastructure for distributed high-throughput computations of materials properties at high pressures and/or temperatures--the Virtual Laboratory for Earth and Planetary Materials--VLab. VLab was developed to leverage the aggregated computational power of grid systems to solve…
Zha, Xianjie; Dai, Zhiyang
2017-01-01
The 2015 Mw 7.8 Nepal earthquake occurred on the segment of the main Himalayan thrust fault between the Indian and Eurasian plates, and caused serious casualties. This earthquake may produce a profound impact on the evolution of the Tibetan Plateau and have brought a stress loading to faults within the plateau. In this paper, a high-resolution slip distribution of the 2015 Nepal earthquake is inverted from the InSAR and GPS data in the near field, and is used to compute the evolution of the cumulative Coulomb stress changes on faults in the earthquake-prone zone in the Tibetan Plateau. In the given reasonable parameters, the calculated co- and post-seismic stress changes on faults do not exceed 1.0 kPa at the north of latitude 32° in the Tibetan Plateau. The largest positive stress changes occur on the South Tibet Detachment fault, and the magnitudes are much less than 100 kPa. The estimated seismicity rate change on the segment of the South Tibet Detachment fault can be up to a level of two hundred thousandths. This indicates that there is a high hazard of earthquake triggering in the South Tibet Detachment fault and its adjacent regions. In the northern and eastern Tibetan Plateau, the estimated seismicity rate changes are lower than a level of one thousandth. However, some faults with a relative high background seismicity rate, such as the Xianshuihe and Longmenshan faults, may have a high hazard of earthquake triggering in the future.
Analytical Method to Calculate the DC Link Current Stress in Voltage Source Converters
Gohil, Ghanshyamsinh Vijaysinh; Bede, Lorand; Teodorescu, Remus;
2014-01-01
The dc-link capacitor is one of the critical components, which influences the lifetime of the whole voltage source converter unit. For reliable design, the operating temperature of the dc-link capacitor should be known, which is primarily determined by the ambient temperature and the rms value...... of the current flowing through the dc-link capacitor. A simple analytical method to calculate the rms value of the dc-link capacitor current is presented in this paper. The effect of the line current ripple on the rms value of the dc-link capacitor current is considered. This yields accurate results, especially...
Lawrenz, Morgan; Baron, Riccardo; Wang, Yi; McCammon, J Andrew
2012-01-01
The Independent-Trajectory Thermodynamic Integration (IT-TI) approach for free energy calculation with distributed computing is described. IT-TI utilizes diverse conformational sampling obtained from multiple, independent simulations to obtain more reliable free energy estimates compared to single TI predictions. The latter may significantly under- or over-estimate the binding free energy due to finite sampling. We exemplify the advantages of the IT-TI approach using two distinct cases of protein-ligand binding. In both cases, IT-TI yields distributions of absolute binding free energy estimates that are remarkably centered on the target experimental values. Alternative protocols for the practical and general application of IT-TI calculations are investigated. We highlight a protocol that maximizes predictive power and computational efficiency.
Noguchi, Yoshifumi [Department of Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan); Computational Materials Science Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)], E-mail: NOGUCHI.Yoshifumi@nims.go.jp; Ishii, Soh; Ohno, Kaoru [Department of Physics, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)
2007-05-15
Short-range electron correlation plays a very important role in small systems and significantly affects the double ionization energy (DIE) spectra and the two-electron distribution functions of a CO molecule, for example. In our calculations, the local density approximation (LDA) of the density functional theory is chosen as a starting point, the GW approximation (GWA) is performed in a next step, and finally the Bethe-Salpeter equation for the T-matrix, describing the particle-particle ladder diagrams up to the infinite order, is solved via the eigenvalue problem. The calculated DIE spectra, which are directly given by the eigenvalues, reflect the short-range electron correlation and are in good agreement with the experiment. We confirm that the Coulomb hole appears in the two-electron distribution function constructed from the eigenfunction.
Calculating Kolmogorov complexity from the output frequency distributions of small Turing machines.
Soler-Toscano, Fernando; Zenil, Hector; Delahaye, Jean-Paul; Gauvrit, Nicolas
2014-01-01
Drawing on various notions from theoretical computer science, we present a novel numerical approach, motivated by the notion of algorithmic probability, to the problem of approximating the Kolmogorov-Chaitin complexity of short strings. The method is an alternative to the traditional lossless compression algorithms, which it may complement, the two being serviceable for different string lengths. We provide a thorough analysis for all Σ(n=1)(11) 2(n) binary strings of length nalgorithms, this work promises to deliver a range of applications, and to provide insight into the question of complexity calculation of finite (and short) strings. Additional material can be found at the Algorithmic Nature Group website at http://www.algorithmicnature.org. An Online Algorithmic Complexity Calculator implementing this technique and making the data available to the research community is accessible at http://www.complexitycalculator.com.
WANGXiufeng; CHENXinzhao; LIUZhao
2003-01-01
The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.
Ivanenko, I. P.; Kanevsky, B. L.; Roganova, T. M.; Sizov, V. V.; Triphonova, S. V.
1985-01-01
Analytical and numerical methods of calculation of the energy and three dimensional EPS characteristics are reported. The angular and lateral functions of electrons in EPS have been obtained by the Landau and small angle approximations A and B and compared with earlier data. A numerical method of solution of cascade equations for the EPS distribution function moments has been constructed. Considering the equilibrium rms angle as an example, errors appearing when approximating the elementary process cross sections by their asymptotic expressions are analyzed.
CALCULATION STUDIES OF SPATIAL DISTRIBUTION OF THE ABSORBED DOSE RATE FOR VARIOUS SEEDS
N. A. Nerozin
2015-01-01
Full Text Available Purpose. Conducting computational studies of dosimetric characteristics of microsources with the radionuclide I‑125, pilot production of which is established in the research and production complex of isotope and radiopharmaceuticals, JSC “State Scientific Centre of the Russian Federation — Institute for Physics and Power Engineering named after A. I. Leypunsky” (SSC RF IPPE. Sources of production IPPE are similar to the model 6711 of the company Nicomed Amersham, dosimetric characteristics of which are standardized in accordance with the TG43 AAPM formalism.Materials and methods. Microsourse «SEED No. 6711» (model of the company Nicomed Amersham is hermetically sealed in a titanium capsule silver rod covered with a thin layer of radioactive I‑125. The half-life of iodine‑125 is 59,43 days. In the process of decay of I‑125 is converted into the Te‑125.Calculation of parameters of microsources and their comparison with the standard model 6711 is carried out with use of the computer code MCNP.Results. The method of calculation of the basic dosimetric characteristics of the microsourse SSC RF-IPPE in accordance with the TG43 formalism is developed. A comparative analysis of experimental data and calculated results by MCNP code, which allowed to identify possible reasons for differences, is performed. The estimated dose characteristics and recommended standard data for dose characteristics of micro «SEED No. 6711» are compared.Conclusions. There are two possible reasons for the differences between experimental and calculated results. The first one may be the roughness of the surface of a silver rod or diffusion of radioactive iodine in silver. The second reason might be the difference of the cross sections of the characteristic radiation of silver used in MCNP code. In the comparison of calculated dose characteristics and recommended standard the role of the application activity is very important. In compliance with the standard
Wang, Y. B.; Xu, Y.; Zhang, Y.; Song, G. F.; Chen, L. H.
2012-12-01
We calculated the coupling coefficient of different types of laterally coupled distributed feedback (LC-DFB) structures with coupled-wave theory and the two-dimensional semivectorial finite difference method. Effects neglected in previous studies such as other partial waves, the ohmic contact and metal contact layers are taken into account in this calculation. The LC-DFB structure with metal gratings is especially studied due to its advantage over index-coupled structures. The dependence of coupling coefficient on structure parameters is theoretically calculated such as grating order, ridge width, thickness of the residual cladding layer, grating depth and lateral proximity of gratings to the ridge waveguide. A complex-coupled GaSb-based 2 µm LC-DFB structure is optimized to achieve a high coupling coefficient of 14.5 cm-1.
Ashvin Thambyah
2015-01-01
Full Text Available The compressive response of articular cartilage has been extensively investigated and most studies have focussed largely on the directly loaded matrix. However, especially in relation to the tissue microstructure, less is known about load distribution mechanisms operating outside the directly loaded region. We have addressed this issue by using channel indentation and DIC microscopy techniques that provide visualisation of the matrix microstructural response across the regions of both direct and nondirect loading. We hypothesise that, by comparing the microstructural response following stress relaxation and creep compression, new insights can be revealed concerning the complex mechanisms of load bearing. Our results indicate that, with stress relaxation, the initial mode of stress decay appears to primarily involve relaxation of the surface layer. In the creep loading protocol, the main mode of stress release is a lateral distribution of load via the mid matrix. While these two modes of stress redistribution have a complex relationship with the zonally differentiated tissue microstructure and the depth of strain, four mechanostructural mechanisms are proposed to describe succinctly the load responses observed.
Mohammad Derikvand; Ghanbar Ebrahimi
2014-01-01
We studied the effect of loose tenon dimensions on stress and strain distributions in T-shaped mortise and loose tenon (M<) furni-ture joints under uniaxial bending loads, and determined the effects of loose tenon length (30, 45, 60, and 90 mm) and loose tenon thickness (6 and 8 mm) on bending moment capacity of M< joints constructed with polyvinyl acetate (PVAc) adhesive. Stress and strain distributions in joint elements were then estimated for each joint using ANSYS finite element (FE) software. The bending moment capacity of joints increased significantly with thickness and length of the tenon. Based on the FE analysis results, under uniaxial bending, the highest shear stress values were obtained in the middle parts of the tenon, while the highest shear elastic strain values were estimated in glue lines between the tenon sur-faces and walls of the mortise. Shear stress and shear elastic strain values in joint elements generally increased with tenon dimensions and corre-sponding bending moment capacities. There was consistency between predicted maximum shear stress values and failure modes of the joints.
A. Hassan Ahangari
2008-09-01
Full Text Available Objective: The main goal of this study was to evaluate stress distribution of endodonti-cally treated maxillary central incisors restored with glass fiber posts, composite resin cores, and crowns with different ferrule designs.Materials and Methods: Four three-dimensional models of a maxillary central incisor were modeled in SolidWorks 2006. Tooth with no ferrule, tooth with a 2 mm circumferen-tial ferrule, tooth with a 2 mm beveled ferrule and tooth with a 0.5 mm circumferential ferrule. The teeth were restored with glass fiber posts, composite resin cores, and full ce-ramics crowns. Each model was loaded (1 N on the palatal side at an angle of 45 degrees to tooth long axis. Von Mises stress findings along the inner surface of the root canals were assessed and compared.Results: The Von Mises Stress at CEJ was the highest in the model without a ferrule when compared to the other models (without ferrule 0.0696, short ferrule 0.0492, cylindrical fer-rule 0.0248, and beveled ferrule 0.0387 MPa.Conclusion: Endodontically treated maxillary central incisors with a ferrule length vary-ing between 0.5 mm and 2.0 mm exhibit lower stress distribution compared to those with-out a ferrule. Keeping a long ferrule is suggested to decrease the stress at the cervical area of restored teeth.
Liu, H H; McCullough, E C; Mackie, T R
1998-01-01
A convolution/superposition based method was developed to calculate dose distributions and wedge factors in photon treatment fields generated by dynamic wedges. This algorithm used a dual source photon beam model that accounted for both primary photons from the target and secondary photons scattered from the machine head. The segmented treatment tables (STT) were used to calculate realistic photon fluence distributions in the wedged fields. The inclusion of the extra-focal photons resulted in more accurate dose calculation in high dose gradient regions, particularly in the beam penumbra. The wedge factors calculated using the convolution method were also compared to the measured data and showed good agreement within 0.5%. The wedge factor varied significantly with the field width along the moving jaw direction, but not along the static jaw or the depth direction. This variation was found to be determined by the ending position of the moving jaw, or the STT of the dynamic wedge. In conclusion, the convolution method proposed in this work can be used to accurately compute dose for a dynamic or an intensity modulated treatment based on the fluence modulation in the treatment field.
On the calculation of x-ray scattering signals from pairwise radial distribution functions
Dohn, Asmus Ougaard; Biasin, Elisa; Haldrup, Kristoffer;
2015-01-01
We derive a formulation for evaluating (time-resolved) x-ray scattering signals of solvated chemical systems, based on pairwise radial distribution functions, with the aim of this formulation to accompany molecular dynamics simulations. The derivation is described in detail to eliminate any possi...... possible ambiguities, and the result includes a modification to the atom-type formulation which to our knowledge is previously unaccounted for. The formulation is numerically implemented and validated.......We derive a formulation for evaluating (time-resolved) x-ray scattering signals of solvated chemical systems, based on pairwise radial distribution functions, with the aim of this formulation to accompany molecular dynamics simulations. The derivation is described in detail to eliminate any...
Durda, Daniel D.; Kring, David A.; Pierazzo, Elisabetta; Melosh, H. J.
1997-03-01
The origin of the K/T boundary sequence of impact ejecta of the Chicxulub impact crater has been reexamined by constructing a computer simulation of the launch and deposition of both low- and high-energy ejecta. The distribution of low- and high-energy ejecta following a vertical impact is illustrated based on 20,000 tracer particles. The distribution is also shown for a 25 deg oblique impact from the southeast. Most of the high-energy ejecta stays within 50,000 km of Earth, with several percent reaching 100,000 km or more before reentering the atmosphere. About 25 percent of the material reaccretes within 2 hrs, about 50 percent within 8 hrs, and about 75 percent within about 72 hrs. At least 20-30 percent of the ejected material escapes the Earth. The implications of these findings for the postimpact environment are considered.
2012-11-15
... of Annual Stress Test Scenarios AGENCY: Office of the Comptroller of the Currency (OCC), Treasury... general processes and factors to be used by the OCC in development and distributing the stress test scenarios for the annual stress test required by the Dodd- Frank Wall Street Reform and Consumer...
Pore size distribution calculation from 1H NMR signal and N2 adsorption-desorption techniques
Hassan, Jamal
2012-09-01
The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N2 adsorption-desorption and 1H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121-134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs-Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.
Tudor DRUGAN
2003-08-01
Full Text Available The aim of the paper was to present the usefulness of the binomial distribution in studying of the contingency tables and the problems of approximation to normality of binomial distribution (the limits, advantages, and disadvantages. The classification of the medical keys parameters reported in medical literature and expressing them using the contingency table units based on their mathematical expressions restrict the discussion of the confidence intervals from 34 parameters to 9 mathematical expressions. The problem of obtaining different information starting with the computed confidence interval for a specified method, information like confidence intervals boundaries, percentages of the experimental errors, the standard deviation of the experimental errors and the deviation relative to significance level was solves through implementation in PHP programming language of original algorithms. The cases of expression, which contain two binomial variables, were separately treated. An original method of computing the confidence interval for the case of two-variable expression was proposed and implemented. The graphical representation of the expression of two binomial variables for which the variation domain of one of the variable depend on the other variable was a real problem because the most of the software used interpolation in graphical representation and the surface maps were quadratic instead of triangular. Based on an original algorithm, a module was implements in PHP in order to represent graphically the triangular surface plots. All the implementation described above was uses in computing the confidence intervals and estimating their performance for binomial distributions sample sizes and variable.
Bae, Hong Yeol; Song, Tae Kwang; Chun, Yun Bae; Oh, Chang Young; Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of); Lee, Kyoung Soo; Park, Chi Yong [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)
2008-07-01
Weld overlay is one of the residual stress mitigation method which arrest crack. An overlay weld sued in this manner is termed a Preemptive Weld OverLay(PWOL). PWOL was good for distribution of residual stress of Dissimilar Metal Weld(DMW) by previous research. Because range of overlay welding is wide relatively, residual stress distribution on PWR is affected by welding sequence. In order to examine the effect of welding sequence, PWOL was applied to a specific DMW of KORI nuclear power plant by finite element analysis method. As a result, the welding direction that from nozzle to pipe is better good for residual stress distribution on PWR.
Temperature and Thermal Stress Distribution for Metal Mold in Squeeze Casting Process
K.H.Chang; G.C.Jang; C.H.Lee; S.H.Lee
2008-01-01
In the squeeze casting process, loaded high pressure (over approximately 100 MPa) and high temperature influence the thermo-mechanical behavior and performance of the used metal mold. Therefore, to safely maintain the metal molds, the thermo-mechanical characteristics (temperature and thermal stress) of metal mold in the squeeze casting must be investigated. In this paper, temperature and thermal stress distribution of steel mold in squeeze casting process were investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis considering temperature-dependent thermo- physical and mechanical properties of the steel mold.
Wang, Li, E-mail: l.wang@griffith.edu.au [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Iacopi, Alan; Dimitrijev, Sima; Walker, Glenn [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Fernandes, Alanna [Bluglass Ltd., 74 Asquith Street, Silverwater, NSW 2128 (Australia); Hold, Leonie; Chai, Jessica [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia)
2014-08-01
The advantages and disadvantages of using off-axis substrates for heteroepitaxial growth of 3C-SiC on Si(111) substrates are investigated in this paper. 3C-SiC is deposited on on-axis and 4° off-axis 150 mm Si(111) substrates using low pressure chemical vapour deposition. The dependence of surface morphology, roughness, crystallinity, alignment between the epilayer and the substrate, and film stress are evaluated using atomic force microscopy, X-ray diffraction, and wafer curvature measurement. Highly parallel steps are observed on both on-axis and off-axis Si substrates after surface preparation, yet step density is doubled and step height is much larger (> 21 times of single step height) for 4° off-cut Si compared to on-axis Si. X-ray diffraction results indicate that SiC grown on on-axis Si substrates are well-aligned with the Si substrates, while the SiC grown on off-axis substrates are tilted positively by as large angle as 1.66°. The well-aligned SiC grown on on-axis Si substrate exhibits lower and uniform residual stress compared to the film grown on off-axis Si substrates, which exhibits a nonuniform distribution of higher stress. The stress distribution is found to be dependent on Si surface step direction and height. These misorientation dependent tilting and stress distribution mechanisms are expected to be applicable to other hetero-epitaxial growth systems with similar mismatch magnitude. - Highlights: • SiC grown on on-axis Si substrates are well-aligned with the Si substrates. • The well-aligned SiC grown on on-axis Si exhibits lower and uniform stress. • SiC grown on off-axis substrate has a positive tilting of 1.66°. • SiC grown on off-axis Si exhibits a nonuniform distribution of higher stress. • The stress and tilting are dependent on Si surface step direction and height.
Morel, Kenneth R; Shepherd, Bryan E
2008-12-01
The past decade has witnessed a significant increase in research on the detection of malingered Posttraumatic Stress Disorder (PTSD) in civil litigation, other disability pension contexts, and in forensic cases. This article reviews the basic principles and statistical procedures that can be used to design and develop a Symptom Validity Test (SVT) for PTSD. We demonstrate how the practical application of the binomial distribution can detect response bias in specific psychiatric disorders such as PTSD and can provide empirically grounded probabilistic evidence of malingering. We cite the Morel Emotional Numbing Test for Posttraumatic Stress Disorder (MENT) as an example.
Sougaijam Vijay Singh
2015-01-01
Full Text Available Aims: Adequate bone support is an essential factor to avoid undue stress to the tooth. This is important when the tooth is endodontically treated and requires a post. The purpose of the present finite element (FE analysis study was to evaluate the stress distribution of post on endodontically treated tooth with reduced alveolar bone height support and after bone augmentation. The null hypothesis was that there is no difference between the stress distribution of post on endodontically treated teeth with reduced alveolar bone height support and after alveolar bone height augmented using bone graft substitute. Materials and Methods: The three-dimensional model was fabricated using ANSYS Workbench version 13.0 software to represent an endodontically treated mandibular second premolar restored with a full ceramic crown restoration and was analyzed using FE analysis. A load of 300N at an angle of 60° to the vertical was applied to the triangular ridge of the buccal cusp in a buccolingual plane. The stresses on the tooth with normal alveolar bone height, reduced alveolar bone height, and after bone augmentation because of reduced bone height were calculated using von misses stresses. Results: A maximum stress value of 136.04 MPa was observed in dentin with an alveolar bone height of 4 mm from the cemento-enamel junction (CEJ. However, after 2 mm of alveolar bone augmentation, the stress value was 104.32 MPa, which was comparable to the stress value of 105.56 observed with the normal bone height of 2 mm from the CEJ. Conclusion: Similar values of stresses were observed in teeth with normal and augmented bone height. Increased stresses were observed with alveolar bone loss of 4 mm from the CEJ.
Hwang, Won Shik; Lee, Hwee Seung; Huh, Nam Su [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of)
2013-10-15
In the present work, the welding residual stress due to repair welding and the stress redistribution behavior due to primary pressure are investigated via 2-dimensional non-linear finite element analyses. In particular, the effect of repair welding width on stress distribution is emphasized. Although, large tensile residual stresses are produced at the PWSCC sensitive region due to repair welding, these stresses are highly reduced due to stress redistribution caused by primary load. Based on the present finite element results, it has been revealed that the effect of width of repair welding on stress distribution is not significant. In the past few years, many numerical and experimental works have been made to assess a structural integrity of cracked components subjected to primary water stress corrosion cracking in dissimilar metal weld (DMW) using Alloys 82/182 in nuclear industries worldwide. These works include a prediction of weld residual stresses in dissimilar metal weld by either numerical or experimental works since an accurate estimation of residual stress distribution in dissimilar metal weld is the most important element for integrity assessment of components subjected to primary water stress corrosion cracking. During an actual welding process, in general, a repair welding is often performed when a defect indication is detected during post-welding inspection. It has been revealed that such a repair welding could lead to higher tensile residual stress in dissimilar metal weld, which is detrimental to the crack growth due to primary water stress corrosion cracking. Thus, the prediction of residual stress considering a repair welding is needed, and then many efforts were made on this issue. In the present work, the effect of width of repair welding on stress distribution of dissimilar metal butt weld of nuclear piping is evaluated based on the detailed 2-dimensional non-linear finite element analyses. For this purpose, the welding residual stress due to
Anami, Lilian Costa; da Costa Lima, Júlia Magalhães; Takahashi, Fernando Eidi; Neisser, Maximiliano Piero; Noritomi, Pedro Yoshito; Bottino, Marco Antonio
2015-04-01
The goal of this study was to evaluate the distribution of stresses generated around implants with different internal-cone abutments by photoelastic (PA) and finite element analysis (FEA). For FEA, implant and abutments with different internal-cone connections (H- hexagonal and S- solid) were scanned, 3D meshes were modeled and objects were loaded with computer software. Trabecular and cortical bones and photoelastic resin blocks were simulated. The PA was performed with photoelastic resin blocks where implants were included and different abutments were bolted. Specimens were observed in the circular polariscope with the application device attached, where loads were applied on same conditions as FEA. FEA images showed very similar stress distribution between two models with different abutments. Differences were observed between stress distribution in bone and resin blocks; PA images resembled those obtained on resin block FEA. PA images were also quantitatively analyzed by comparing the values assigned to fringes. It was observed that S abutment distributes loads more evenly to bone adjacent to an implant when compared to H abutment, for both analysis methods used. It was observed that the PA has generated very similar results to those obtained in FEA with the resin block.
Domènech, Guillem; Mavrouli, Olga; Corominas, Jordi; Abellán, Antonio
2014-05-01
Magnitude-frequency relations are a key issue when evaluating the rockfall hazard. It is a common practice to calculate them using databases of past events. However, in some cases, they are not available or complete. Alternatively, the analysis of the scar volume distribution on the wall face provides useful information on the slope's rockfall activity. The Montsec range, located in the Eastern Pyrenees, Spain, is a limestone cliff from upper cretaceous. In some parts, clear evidences of rockfall activities are present: Large recent rockfall scars are distinguished by their orange colour in comparison with grey non active surfaces on the slope face. To identify the scars and analyse their volume distribution, a methodology has been carried out (Santana et al. 2011) which is based on the elaboration of data from a high resolution Digital Elevation Model (DEM) obtained with Terrestrial Laser Scanner (TLS). This methodology requires a point cloud of the slope and it includes the following steps: a) identification of discontinuity sets b) generation of discontinuity surfaces c) calculation of areas of the exposed discontinuity surfaces and rockfall scar heights, and d) calculation of the rockfall scar volume distribution. Three discontinuity sets were identified on the point cloud. To generate the discontinuity surfaces, SEFL software was used. The input data for accepting that two neighbouring points of the point cloud belong to the same surface, was a minimum spacing of 0.4m. The resulting planes were visually checked. Assuming that the discontinuities of set 1 preserve the basal shape of the rockfall scars and the altitude is parallel to the discontinuities of set 2, the volume can be calculated as the product of the area of surfaces of set 1 with the length of the surfaces of set 2 using the afore mentioned SEFL software. Areas were found to follow a Lognormal distribution and lengths a Pearson6 one. The volume calculation was then made probabilistically by means
Li Jianwei; Liu Changyou; Zhao Tong
2016-01-01
This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain. This approach combines numerical simulations and field tests based on the conditions of gully terrain in the Chuancao Gedan Mine. The effects of gully ter-rain on the in situ stress field of coal beds can be identified by the ratio of self-weight stress to vertical stress (g) at the location corresponding to the maximum vertical stress. Based on the function g=f(h), the effect of gully terrain on the stress field of overlying strata of the entire field can be characterized as a significantly affected area, moderately affected area, or non-affected area. Working face 6106 in the Chuancao Gedan Mine had a coal bed depth<80 m and was located in what was identified as a signifi-cantly affected area. Hence, mining may cause sliding of the gully slope and increased loading (including significant dynamic loading) on the roof strata. Field tests suggest that significant dynamic pressures were observed at the body and foot of the gully slope, and that dynamic loadings were observed upslope of the working face expansion, provided that the expanding direction of the working face is parallel to the gully.
Effect of thermoplastic appliance thickness on initial stress distribution in periodontal ligament
De-Shin Liu
2015-04-01
Full Text Available A numerical investigation into the initial stress distribution induced within the periodontal ligament by thermoplastic appliances with different thicknesses is performed. Based on the plaster model of a 25-year-old male patient, a finite element model of the maxillary lateral incisors and their supporting structures is constructed. In addition, four finite element models of thermoplastic appliances with different thicknesses in the range of 0.5–1.25 mm are also constructed based on the same plaster model. Finite element analysis simulations are performed to examine the effects of the force delivered by the thermoplastic appliances on the stress response of the periodontal ligament during the elastic recovery process. The results show that the stress induced in the periodontal ligament increases with an increasing appliance thickness. For example, the stress triples from 0.0012 to 0.0038 MPa as the appliance thickness is increased from 0.75 to 1.25 mm. The results presented in this study provide a useful insight into as a result of the compressive and tensile stresses induced by thermoplastic appliances of different thicknesses. Moreover, the results enable the periodontal ligament stress levels produced by thermoplastic appliances of different thicknesses to be reliably estimated.
Calculating Kolmogorov complexity from the output frequency distributions of small Turing machines.
Fernando Soler-Toscano
Full Text Available Drawing on various notions from theoretical computer science, we present a novel numerical approach, motivated by the notion of algorithmic probability, to the problem of approximating the Kolmogorov-Chaitin complexity of short strings. The method is an alternative to the traditional lossless compression algorithms, which it may complement, the two being serviceable for different string lengths. We provide a thorough analysis for all Σ(n=1(11 2(n binary strings of length n<12 and for most strings of length 12≤n≤16 by running all ~2.5 x 10(13 Turing machines with 5 states and 2 symbols (8 x 22(9 with reduction techniques using the most standard formalism of Turing machines, used in for example the Busy Beaver problem. We address the question of stability and error estimation, the sensitivity of the continued application of the method for wider coverage and better accuracy, and provide statistical evidence suggesting robustness. As with compression algorithms, this work promises to deliver a range of applications, and to provide insight into the question of complexity calculation of finite (and short strings. Additional material can be found at the Algorithmic Nature Group website at http://www.algorithmicnature.org. An Online Algorithmic Complexity Calculator implementing this technique and making the data available to the research community is accessible at http://www.complexitycalculator.com.
Calculations of lightning-induced voltages in medium voltage distribution lines
Munhoz Rojas, Patricio E. [Instituto de Tecnologia para o Desenvolvimento (LACTEC/UFPR), Curitiba, PR (Brazil)], E-mail: patricio@lactec.org.br; Pinto, Cleverson Luiz da Silva [Companhia Paranaense de Energia (COPEL), Curitiba, PR (Brazil)], E-mail: cleverson@copel.com
2007-07-01
The objective of this paper is to show the results of a new computer program, written in Mat Lab environment, that is intended to calculate the lightning induced voltages in multi-conductor non-homogeneous lines, in order to be able to evaluate the impact of the usual protective measures implemented against lightning-induced disturbances. The main new features of this program are: a coupling model in terms of the scalar potentials referred to a remote ground was adopted; the coupling to the vertical conductors was considered in a manner similar to rest of the line; the describing equations were converted into a system of coupled ordinary differential equations, by a discretization only in space, which was subsequently solved using the powerful ODE solvers existing in Mat Lab. The validation of the new program has been performed by comparing its predicted results with other theoretical and computational results available in the literature and also with other experimental results published in the literature. It is shown that the agreement with other well established theoretical results is very good and, also, that the agreement between the newly calculated results and some published experimental results is better than previously obtained results. (author)
Stress Distribution on Sandwich Structure with Triangular Grid Cores Suffered from Bending Load
Cui Xu
2015-01-01
Full Text Available Triangular grid reinforced by carbon fiber/epoxy (CF/EP was designed and manufactured. The sandwich structure was prepared by gluing the core and composite skins. The mechanical properties of the sandwich structure were investigated by the finite element analysis (FEA and three-point bending methods. The calculated bending stiffness and core shear stress were compared to the characteristics of a honeycomb sandwich structure. The results indicated that the triangular core ultimately failed under a bending load of 11000 N; the principal stress concentration was located at the loading region; and the cracks occurred on the interface top skin and triangular core. In addition, the ultimate stress bearing of the sandwich structure was 8828 N. The experimental results showed that the carbon fiber reinforced triangular grid was much stiffer and stronger than the honeycomb structure.
Callisti, M., E-mail: mc3a09@soton.ac.uk; Polcar, T.
2015-01-15
Highlights: • The stress-induced martensitic transformation is affected by the grain size. • Grain boundaries stop the growth of martensitic bands between adjacent grains. • Larger shear deformation is accommodated by interlayer with larger grain size. • The Ni–Ti(–Cu) interlayer controls wear on the functional top layer. - Abstract: The stress-induced martensitic transformation occurring in sputter-deposited Ni{sub 48.1}Ti{sub 51.9} and Ni{sub 43.4}Ti{sub 49.6}Cu{sub 7} interlayers, integrated in a W-S-C/Ni–Ti(–Cu) bilayer design, was investigated by transmission electron microscopy, after these bilayers were subjected to different sliding conditions. Martensitic bands across the interlayers were formed depending on the sliding direction with their shape and distribution a function primarily of both applied normal load and grain size. The Ni{sub 48.1}Ti{sub 51.9} interlayer (lateral grain size of ∼3 μm) showed well oriented and ordered martensitic bands extended through the interlayer thickness under low load (5 N). At a higher load (18 N) the growth of these bands was limited by the stabilised martensite formed as a consequence of the high compressive stress, at the interface with the substrate. The Ni{sub 43.4}Ti{sub 49.6}Cu{sub 7} interlayer (lateral grain size of ∼650 nm) exhibited no significant evidence of stabilised martensite under different loading conditions. The martensitic transformation was limited by the smaller grain size and most of the stress was relaxed by elastic and, to some extent, pseudo-elastic deformation of the austenitic phase. Grain boundaries were found to stop the growth of martensitic bands, thus limiting the activation of the martensitic transformation into the neighbouring grains during sliding. The grain refinement caused a change in the capability of the interlayer to relax shear and compressive stresses. Such a change was found to affect the formation of the WS{sub 2}-rich tribolayer on the W-S-C sliding
Guasp, J.; Pastor, I.; Álvarez-Estrada, R. F.; Castejón, F.
2015-02-01
Analytical results obtained recently of the ab-initio classical incoherent Thomson Scattering (TS) spectrum from a single-electron (Alvarez-Estrada et al 2012 Phys. Plasmas 19 062302) have been numerically implemented in a paralelized code to efficiently compute the TS emission from a given electron distribution function, irrespective of its characteristics and/or the intensity of the incoming radiation. These analytical results display certain differences, when compared with other authors, in the general case of incoming linearly and circularly polarized radiation and electrons with arbitrary initial directions. We regard such discrepancies and the ubiquitous interest in TS as motivations for this work. Here, we implement some analytical advances (like generalized Bessel functions for incoming linearly polarized radiation) in TS. The bulk of this work reports on the efficient computation of TS spectra (based upon our analytical approach), for an electron population having an essentially arbitrary distribution function and for both incoming linearly and circularly polarized radiation. A detailed comparison between the present approach and a previous Monte Carlo one (Pastor et al 2011 Nuclear Fusion 51 043011), dealing with the ab-initio computation of TS spectra, is reported. Both approaches are shown to fully agree with each other. As key computational improvements, the analytical technique yields a × 30 to × 100 gain in computation time and is a very flexible tool to compute the scattered spectrum and eventually the scattered electromagnetic fields in the time domain. The latter are computed explicitly here for the first time, as far as we know. Scaling laws for the power integrated over frequency versus initial kinetic energy are studied for the case of isotropic and monoenergetic electron distribution functions and their potential application as diagnostic tools for high-energy populations is briefly discussed. Finally, we discuss the application of these
Aydarous, A Sh; Charles, M W; Darley, P J
2008-01-01
This study is a part of a programme of research to provide validated dose measurement and calculation techniques for beta emitting hot particles by the construction of well-defined model hot particle sources. This enables parallel measurements and calculations to be critically compared. This particular study concentrates on the high-energy beta emitter, (106)Ru/(106)Rh (Emax = 3.54 MeV). This source is a common constituent of failed nuclear fuel, particularly in accident situations. The depth dose distributions were measured using radiochromic dye film (RDF); an imaging photon detector coupled to an LiF thermoluminescent dosemeter (LiF-IPD) and an extrapolation ionisation chamber (ECH). Dose calculations were performed using the Monte Carlo radiation transport code MCNP4C. Doses were measured and calculated as average values over various areas and depths. Of particular interest are the doses at depths of 7 and 30-50 mg cm(-2), and averaged over an area of 1 cm2, as recommended by the International Commission on Radiological Protection for use in routine and accidental over-exposures of the skin. In this case, the average ratios (MCNP/measurement) for RDF, ECH and LiF-IPD were 1.07 +/- 0.02, 1.02 +/- 0.01 and 0.83 +/- 0.16, respectively. There are significantly greater discrepancies between the ECH and LiF-IPD measurement techniques and calculations-particularly for shallow depths and small averaging areas.
Research on Stress Calculation of the Boiler Steam Pipe%对锅炉汽水管道应力的计算研究
廉平; 冯婷婷
2015-01-01
文章对锅炉汽水管道的应力进行分析，对锅炉汽水管道的应力计算进行了研究。%This paper analyzes the stress of the boiler and steam pipe, the stress calculation of the boiler and steam pipe is studied.
Santos-Martins, Diogo; Fernandes, Pedro Alexandrino; Ramos, Maria João
2016-11-01
In the context of SAMPL5, we submitted blind predictions of the cyclohexane/water distribution coefficient (D) for a series of 53 drug-like molecules. Our method is purely empirical and based on the additive contribution of each solute atom to the free energy of solvation in water and in cyclohexane. The contribution of each atom depends on the atom type and on the exposed surface area. Comparatively to similar methods in the literature, we used a very small set of atomic parameters: only 10 for solvation in water and 1 for solvation in cyclohexane. As a result, the method is protected from overfitting and the error in the blind predictions could be reasonably estimated. Moreover, this approach is fast: it takes only 0.5 s to predict the distribution coefficient for all 53 SAMPL5 compounds, allowing its application in virtual screening campaigns. The performance of our approach (submission 49) is modest but satisfactory in view of its efficiency: the root mean square error (RMSE) was 3.3 log D units for the 53 compounds, while the RMSE of the best performing method (using COSMO-RS) was 2.1 (submission 16). Our method is implemented as a Python script available at https://github.com/diogomart/SAMPL5-DC-surface-empirical.
Danza, Matteo; Palmieri, Annalisa; Farinella, Francesca; Brunelli, Giorgio; Carinci, Francesco; Girardi, Ambra; Spinelli, Giuseppe
2009-01-01
The aim of research was to study spiral family implant by finite element analysis (FEA) inserted in different bone qualities connected with abutments of different angulations. The biomechanical behaviour of 4.2 × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutments subjected to static loads, in contact with high and poor bone qualities was evaluated by FEA. The lowest stress value was found in the system composed by implants and straight abut-ments loaded with a vertical force, while the highest stress value was found in implants with 15° angulated abutment loaded with an angulated force. In addition, we found the lower the bone quality, the higher the distribution of the stress within the bone. Spiral family implants can be used successfully in low bone quality but applying a straight force is recommended.
LIU Yao-wei; GAO An-tai; SHI Jin; SU He-jun
2007-01-01
The heat flow in crust and the thermal stress generated by the flow play a very important role in earthquake occurrence. Different crustal structure has different effect on heat distribution and associated thermal stress. In all of typical seismogenic crustal structure models, including the bulge of Moho surface, the deep-large fault in the mid-lower crust, low-velocity and high-conductive layer in the middle crust, and the typical crustal structure in mid-upper crust, the thermal stress produced by deep heat disturbance may move up to the mid-upper crust. This leads to upper brittle part of crust break and hence, strong earthquakes. This result is constructive in enhancing our understanding of the role of deep heat flow in curst in development of earthquake and its generation, as well as the generation mechanism of the shallow flowing fluid.
Stress distribution and mechanical properties of free and assembled Ni3Al nanoclusters
Zhurkin, E. E.; Hautier, G.; Hou, M.
2006-03-01
Classical molecular dynamics with a semiempirical N -body potential is used to study the distribution of local stress in bimetallic Ni3Al nanoparticles and in cluster-assembled materials. The materials considered are synthesized with these particles by low-energy deposition at 0.5eV per atom and by compaction with an external pressure of 2GPa , thus featuring different nanostructures. Both are nanoporous, the lowest density being obtained by deposition. Their mechanical response to a uniaxial external load is then studied and deformation mechanisms are identified and are found to be similar in both nanostructures. In the core of isolated clusters, the partial pressures on the nickel and aluminium subsystems are found to differ by several GPa and, as a balance to surface tension, the hydrostatic core pressure is positive and depends on the cluster size. The surface stress is tensile and, because of structural disorder, the partial pressures distributions on Ni and Al at the surface are scattered. When nanostructured systems are formed, strong and highly inhomogeneous shear stress appears, the cluster cores may become tensile, and the interfacial areas remain mainly tensile as well. The partial pressure difference between Ni and Al is somewhat reduced. It is shown that the effect of temperature is to reduce this difference still further and to homogenize the spatial stress distribution. When subjected to a uniaxial stress, both materials display an elastic and a plastic regime. The elastic limit is the lowest for the most porous material and decreases with increasing temperature. Plastic deformation is dominated by both grain boundary sliding and by the enlargement of the open volumes, without evidence for the nucleation of cracks. These open volumes are found to facilitate dislocation activity which is evidenced in grains with sizes as small as two nanometers. This dislocation activity is found to result in the production of stacking faults as well as to the
Ojedokun, Olalekan Yinka
2012-01-01
The concurrent foundation failure of telecommunication masts in Nigeria and all over the world which endanger the lives and properties of residents situated within the fall distance of the telecommunication mast are a thing of great concern. In this study, a GSM mast that underwent foundation failure at Ibadan, Oyo State, Nigeria was critically examined with a view to providing engineering solution. The soil investigation at the global system for mobile communications (GSM) telecommunication tower comprised of laboratory tests: sieve analysis, Atterberg limits and moisture content tests were carried out on the soil samples obtained while Dutch cone penetrometer test was performed on the site to a depth of refusal to determine the allowable bearing pressure at various depths of the soil. The application of Boussineq's and Westergard's formulae for point loads using Java programme to simulate and compute the stress distribution at various predetermined depths showed the stress distribution pattern beneath the f...
Calculation of force distribution for a periodically supported beam subjected to moving loads
Hoang, T.; Duhamel, D.; Foret, G.; Yin, H. P.; Joyez, P.; Caby, R.
2017-02-01
In this study, a novel model for a periodically supported beam subjected to moving loads was developed using a periodicity condition on reaction forces. This condition, together with Fourier transforms and Dirac combs, forms a relation between the beam displacement and support reaction forces. This relation explains the force distribution at the supports, and holds for any type of support and foundation behaviors. Based on this relation, a system equivalence for a periodically supported beam is presented in this paper. An application to non-ballasted viscoelastic supports is presented as an example and the results clearly match the existing model. Next, an approximation of real-time responses was developed for the moving loads as periodic series. The comparison shows that this approximation can be used for a limited number of loads if the distances between loads are sufficiently large. The system equivalence for a periodically supported beam is efficient for supports with linear behavior, and could be extended to other behaviors.
On the Calculation of Optimum Mass Distribution of a Multi-Stage Rocket Vehicle
V. B. Tawakley
1967-04-01
Full Text Available The effect of gravity on the optimum distribution of total required mass among the various stages of a multiple stage rocket arranged series has been considered by making the payload ratio minimum so as to obtain a specified mission velocity at the end of powered flight. The special case when the physical parameters for all the step rockets are each equal, has been discussed in detail. It has also been shown that if the mission requirement is to achieve a given all burnt height, then even at the expense of more total initial mass no more total a given all burnt velocity. Finally it is proved that in order to achieve a given all burnt velocity by arranging the stages in parallel results in an increase in the total initial mass compared to the case when they are arranged in series and the magnitude of this increase depends upon the number of stages.
Rajkiran Chitumalla
2012-01-01
Full Text Available Aims: The aim of the study was to evaluate the stress distribution patterns in teeth and supporting structures of fixed prosthesis and design modifications in a fixed prosthesis with either normal or reduced bone support of an additional abutment. Study was also undertaken to disprove Ante′s law. Materials and Methods: Main models and variations of main models (modification 1, 2, 3, 4, 5, 6, 7, 8 were subjected to 200 N at angulations of 90° and 15° on functional cusps. Results for each loading were obtained as stress distribution color images and numerical values were recorded. A three-dimensional finite element analysis study of variations of normal models was performed using two finite element softwares, namely PRO-Engineer wildfire version 1.0 manufacturer: Parametric technology corporation, Needham, MA 02494 U.S.A. Results: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Eventhough the pericemental area of compromised abutments with an additional abutment (canine was more than the combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante′s law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments. Conclusions: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Even though the pericemental area of compromised abutments with an additional abutment (canine was more than combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante′s law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments.
Characteristics of stress distribution in trapezoid-shaped CSG dam during earthquake
Kondo, M.; Kawasaki, H. [Ministry of Land, Infrastructure and Transport (Japan). Water Management and Dam Division; Sasaki, T. [Public Works Research Institute, Tsukuba (Japan). Hydraulic Engineering Research Group
2004-07-01
There is currently a shortage of dam sites with optimal conditions in Japan. Dam design and construction technologies must also respond to a growing demand for cost reductions and environmental concerns. Cemented Sand and Gravel (CSG) is a new dam construction material that reduces the costs of material production. However, it is not as strong as concrete. The trapezoid shape was proposed to resolve this problem, as a trapezoidal cross section can minimize stress inside the dam body and reduce fluctuations during earthquakes. This paper examines the effects of dam size and the deformability of the foundation ground on the dynamic behavior of a trapezoid-shaped CSG dam during an earthquake, as well as examining the differences between the dynamic behaviors of trapezoid-shaped CSG dams and conventional concrete gravity dams. Finite element models of both dams were used to conduct the comparison. Analysis results included stress distribution during usual loading conditions. It was concluded that stress generated inside the dam body of trapezoid-shaped CSG during earthquakes is considerably lower than concrete gravity dams with a conventional triangle shape. In addition, stress distribution inside the dam body is affected largely by the relative deformability of the foundation to CSG. 4 refs., 2 tabs.,12 figs.
Goiato, Marcelo Coelho; Shibayama, Ricardo; Gennari Filho, Humberto; de Medeiros, Rodrigo Antonio; Pesqueira, Aldiéris Alves; dos Santos, Daniela Micheline; de Araújo, Cleudmar Amaral
2016-01-01
Photoelastic analysis was used to evaluate the biomechanical behaviour of implant-supported, double-screwed crowns with different connection systems and cantilever lengths. Three models were made in PL-2 photoelastic resin and divided into six groups, on the basis of the implant connection system (external hexagon [EH] or Morse taper [MT]), type of abutment (Mini Pilar [Neodent, Curitiba, Paraná, Brazil] or "UCLA") and number of crowns in the cantilever (one or two). The implant-prosthesis unit was placed in a circular polariscope. Occlusal surfaces of the crowns were subjected to 100-N loads in the axial and oblique (45°) directions in a universal testing machine (EMIC). Generated stresses were recorded and analysed qualitatively in a graphics program (Adobe Photoshop). Under axial loading, all of the groups had similar numbers of fringes, which were increased when the crowns were subjected to oblique loading. The highest number of fringes was found during oblique loading in the EH + Mini Pilar group. In conclusion, although the type of implant connection system did not have a direct influence on the stress distribution for axial loading, the cantilever length did have a direct influence on stress distribution. Models with two crowns in the cantilever showed more stress, with a greater concentration of force on the cervical part of the implant.
Physiological stress in koala populations near the arid edge of their distribution.
Nicole Ashley Davies
Full Text Available Recent research has shown that the ecology of stress has hitherto been neglected, but it is in fact an important influence on the distribution and numbers of wild vertebrates. Environmental changes have the potential to cause physiological stress that can affect population dynamics. Detailed information on the influence of environmental variables on glucocorticoid levels (a measure of stress at the trailing edge of a species' distribution can highlight stressors that potentially threaten species and thereby help explain how environmental challenges, such as climate change, will affect the survival of these populations. Rainfall determines leaf moisture and/or nutritional content, which in turn impacts on cortisol concentrations. We show that higher faecal cortisol metabolite (FCM levels in koala populations at the trailing arid edge of their range in southwestern Queensland are associated with lower rainfall levels (especially rainfall from the previous two months, indicating an increase in physiological stress when moisture levels are low. These results show that koalas at the semi-arid, inland edge of their geographic range, will fail to cope with increasing aridity from climate change. The results demonstrate the importance of integrating physiological assessments into ecological studies to identify stressors that have the potential to compromise the long-term survival of threatened species. This finding points to the need for research to link these stressors to demographic decline to ensure a more comprehensive understanding of species' responses to climate change.
无
2002-01-01
Based on simplified axisymmetrical forming model, a elasto-plastic FEM simulation system of multi-pass conventional spinning is developed. Taking the typical draw-spinning as the study object, and establishing reasonable mechanics model, research on the first pass of spinning process is carried out with FEM system developed. The distributions of the stress and strain are obtained by three types of roller-trace curves: straight line, involute curves and quadratic curves. The results are as follows: (1) The v...
The double-end-pumped cubic Nd:YVO4 laser: Temperature distribution and thermal stress
P Elahi; S Morshedi
2010-01-01
Thermal effects of a double-end-pumped cubic Nd:YVO4 laser crystal are investigated in this paper. A detailed analysis of temperature distribution and thermal stress in cubic crystal with circular shape pumping is discussed. It has been shown that by considering the total input powers as constant, the double-end-pumped configurations with equal pump power can be considered as having a minimum thermal effect with respect to the other end-pumped configuration.
Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G., E-mail: tiagorusin@ime.eb.b, E-mail: rebello@ime.eb.b, E-mail: vellozo@cbpf.b, E-mail: renatoguedes@ime.eb.b [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Nuclear; Vital, Helio C., E-mail: vital@ctex.eb.b [Centro Tecnologico do Exercito (CTEx), Rio de Janeiro, RJ (Brazil); Silva, Ademir X., E-mail: ademir@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear
2011-07-01
A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)
Improving accuracy of the calculation of in-core power distributions for light water reactors
Tsuiki, M.; Beere, W.H. (Institute for energy technology, OECD Halden Reactor Project (Norway))
2009-10-15
Comparisons have been made of VNEM prototype system to the measured data obtained from Ringhals unit 3 NPP at its beginning of life, hot-stand-by state. Three cases with difference control rod bank positions and Boron concentrations have been compared: Case 1: nearly all rod banks withdrawn, Boron = 1315 ppm Case 2: bank C = nearly half-inserted, bank D = fully inserted, Boron = 1131 ppm Case 3: banks C and D = fully inserted, Boron = 1060 ppm The results can be summarized as: error: maximum detector reading (%) error: keff (%) Case 1 -2.1 -0.175 Case 2 1.5 -0.022 Case 3 -0.5 -0.044 Excellent agreement was observed in the comparison of the neutron detector readings and the core eigenvalues. The method of core modelling and parameters used in calculation of VNEM is completely the same as the 'PWR standard option' determined from similar comparisons of VNEM and other PWRs. No empirical, or any sort of adjustment was done. (author)
The optimized calculation of driving points distribution in large segmented mirrors
Hui, Mei; Dong, Li-Quan; Zou, Yu-di; Yu, Fei; Zhao, Yue-jin
2009-11-01
The cophase calibration system is applied for adaptive optical phasing with a large segmented telescope mirror, which commonly uses 3-DOF micro-position device with three micro-displacement actuators to drive segments in parallel, making the entire segmented mirror in phase at one time and obtaining the desired sensor readings accordingly. In order to run the active control system to make the segments cophase, it is necessary to calculate the coordinates of the three driving points correctly for segmented mirrors specially limited in geometric parameters, especially for the stability and sensitivity of the micro-positioning device. The mirrors will be supported on a massively parallel system of electrostatically controlled, interconnected microactuators that can be coordinated to achieve precise actuation Adjusting posture of each segment independently so as to obtain the co-phasing errors and to control them at a nanometer level. Several generations of individual actuators as well as parallel arrays of actuators with segmented mirrors have been designed. A mechanical model of the system has been constructed and simulated numerically to obtain the actual position of three actuators using the RPY angle describing means. A three-channel parallel control scheme has been developed and implemented on a segmented mirror array. A universal evaluating method for optimization is prompted and will be a good guide to the design optimization of micro-positioning device for each segmented mirror when the mirrors are groundbased horizontally.
L. Boeckli
2012-07-01
Full Text Available The objective of this study is the production of an Alpine Permafrost Index Map (APIM covering the entire European Alps. A unified statistical model that is based on Alpine-wide permafrost observations is used for debris and bedrock surfaces across the entire Alps. The explanatory variables of the model are mean annual air temperatures, potential incoming solar radiation and precipitation. Offset terms were applied to make model predictions for topographic and geomorphic conditions that differ from the terrain features used for model fitting. These offsets are based on literature review and involve some degree of subjective choice during model building. The assessment of the APIM is challenging because limited independent test data are available for comparison and these observations represent point information in a spatially highly variable topography. The APIM provides an index that describes the spatial distribution of permafrost and comes together with an interpretation key that helps to assess map uncertainties and to relate map contents to their actual expression in the terrain. The map can be used as a first resource to estimate permafrost conditions at any given location in the European Alps in a variety of contexts such as research and spatial planning.
Results show that Switzerland likely is the country with the largest permafrost area in the Alps, followed by Italy, Austria, France and Germany. Slovenia and Liechtenstein may have marginal permafrost areas. In all countries the permafrost area is expected to be larger than the glacier-covered area.
Ashley S Hammond
Full Text Available Human mothers wean their children from breast milk at an earlier developmental stage than do ape mothers, resulting in human children chewing solid and semi-solid foods using the deciduous dentition. Mechanical forces generated by chewing solid foods during the post-weaning period travel through not only the deciduous teeth, but also the enamel caps of the developing permanent teeth within the maxilla and mandible, which are not present in the adult face. The effects of mechanical stress propagating through these very stiff structures have yet to be examined. Based on a heuristic model, we predicted that the enamel of the embedded developing teeth would act to reduce stresses in the surrounding bony elements of the juvenile face. We tested this hypothesis by simulating occlusal loading in a finite element (FE model of a child's cranium with a complete set of deciduous teeth and the first permanent molars embedded in the bony crypt in the maxilla. We modeled bone and enamel with appropriate material properties and assessed the effect of embedding high-stiffness enamel structures on stress distribution in the juvenile face. Against expectation, the presence of unerupted enamel caps does not affect the magnitude or location of stresses in the juvenile face. Our results do not support the hypothesis that the unerupted secondary teeth act to moderate stresses in the juvenile face.
Effect of phytohormones on absorption and distribution of ions in salt-stressed bean plants
Zofia Starck
2014-02-01
Full Text Available Bean plant seedlings grown in water culture were treated for 5 days either with NaCl or with 7-times concentrated nutrient solution (diminished water potential by 3-103 hPa in both cases. Control and stressed plants were treated for 24 hrs with zeatin and GA,. NaCl-stress reduced distinctly ion absorption rate (K, Ca and P. Zeatin and GA3 promoted potassium uptake, but only in NaCI-treated plants. These hormones diminished Na accumulation in metabolically active organs but increased P- and Ca-content. In plants grown under both kind of stresses zeatin and GA3 partially reestablished the ratio of the main mono- to divalent cations, which increased in the leaves and apical part of the stressed plants. ABA introduced into the nutrient solution caused inhibition of the ion uptake (K, Ca, Mg and P. similar to that caused by NaCl-stress. The above reported results seem to confirm the supposition, that hormones act as an important factor contributing to regulation of both uptake and distribution of ions. In this way growth substances may also participate in the regulation of transport of various substances (among others - assimilates in the whole plant.
Lavagnino, Michael; Arnoczky, S P Steven P; Frank, Katherine; Tian, Tao
2005-01-01
The purpose of this study was to determine if an association exists between the tensile properties and the collagen fibril diameter distribution in in vitro stress-deprived rat tail tendons. Rat tail tendons were paired into two groups of 21 day stress-deprived and 0 time controls and compared using transmission electron microscopy (n = 6) to measure collagen fibril diameter distribution and density, and mechanical testing (n =6) to determine ultimate stress and tensile modulus. There was a statistically significant decrease in both ultimate tensile strength (control: 17.95+/-3.99 MPa, stress-deprived: 6.79+/-3.91 MPa) and tensile modulus (control: 312.8+/-89.5 MPa, stress-deprived: 176.0+/-52.7 MPa) in the in vitro stress-deprived tendons compared to controls. However, there was no significant difference between control and stress-deprived tendons in the number of fibrils per tendon counted, mean fibril diameter, mean fibril density, or fibril size distribution. The results of this study demonstrate that the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons is not correlated with the collagen fibril diameter distribution and, therefore, the collagen fibril diameter distribution does not, by itself, dictate the decrease in mechanical properties observed in in vitro stress-deprived rat tail tendons.
Harrison, R. J.; Feinberg, J. M.
2007-12-01
First-order reversal curves (FORCs) are a powerful method for characterizing the magnetic hysteresis properties of natural and synthetic materials, and are rapidly becoming a standard tool in rock magnetic and paleomagnetic investigations. Here we describe a modification to existing algorithms for the calculation of FORC diagrams using locally-weighted regression smoothing (often referred to as loess smoothing). Like conventional algorithms, the FORC distribution is calculated by fitting a second degree polynomial to a region of FORC space defined by a smoothing factor, N. Our method differs from conventional algorithms in two ways. Firstly, rather than a square of side (2N+1) centered on the point of interest, the region of FORC space used for fitting is defined as a span of arbitrary shape encompassing the (2N+1)2 data points closest to the point of interest. Secondly, data inside the span are given a weight that depends on their distance from the point being evaluated: data closer to the point being evaluated have higher weights and have a greater effect on the fit. Loess smoothing offers two advantages over current methods. Firstly, it allows the FORC distribution to be calculated using a constant smoothing factor all the way to the Hc = 0 axis. This eliminates possible distortions to the FORC distribution associated with reducing the smoothing factor close to the Hc = 0 axis, and does not require use of the extended FORC formalism and the reversible ridge, which swamps the low-coercivity signal. Secondly, it allows finer control over the degree of smoothing applied to the data, enabling automated selection of the optimum smoothing factor for a given FORC measurement, based on an analysis of the standard deviation of the fit residuals. The new algorithm forms the basis for FORCinel, a new suite of FORC analysis tools for Igor Pro (www.wavemetrics.com), freely available on request from the authors.
Egor M. Mikhailovsky
2015-06-01
Full Text Available We proposed a method for numerically solving the problem of flow distribution in hydraulic circuits with lumped parameters for the case of random closing relations. The conventional and unconventional types of relations for the laws of isothermal steady fluid flow through the individual hydraulic circuit components are studied. The unconventional relations are presented by those given implicitly by the flow rate and dependent on the pressure of the working fluid. In addition to the unconventional relations, the formal conditions of applicability were introduced. These conditions provide a unique solution to the flow distribution problem. A new modified nodal pressure method is suggested. The method is more versatile in terms of the closing relation form as compared to the unmodified one, and has lower computational costs as compared to the known technique of double-loop iteration. The paper presents an analysis of the new method and its algorithm, gives a calculated example of a gas transportation network, and its results.
Liu, Feng; Crozier, Stuart
2004-08-01
This paper evaluates a new, low-frequency finite-difference time-domain method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretization of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modelling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multi-layered spherical phantom model and a complete body model.
Wiktor, Julia; Jomard, Gérald; Torrent, Marc; Bertolus, Marjorie
2017-01-01
We performed first-principles calculations of the momentum distributions of annihilating electron-positron pairs in vacancies in uranium dioxide. Full atomic relaxation effects (due to both electronic and positronic forces) were taken into account and self-consistent two-component density functional theory schemes were used. We present one-dimensional momentum distributions (Doppler-broadened annihilation radiation line shapes) along with line-shape parameters S and W. We studied the effect of the charge state of the defect on the Doppler spectra. The effect of krypton incorporation in the vacancy was also considered and it was shown that it should be possible to observe the fission gas incorporation in defects in UO2 using positron annihilation spectroscopy. We suggest that the Doppler broadening measurements can be especially useful for studying impurities and dopants in UO2 and of mixed actinide oxides.
Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Rahim Hematiyan, Mohammad; Koontz, Craig; Meigooni, Ali S.
2015-12-01
Compression is a technique to immobilize the target or improve the dose distribution within the treatment volume during different irradiation techniques such as AccuBoost® brachytherapy. However, there is no systematic method for determination of dose distribution for uncompressed tissue after irradiation under compression. In this study, the mechanical behavior of breast tissue between compressed and uncompressed states was investigated. With that, a novel method was developed to determine the dose distribution in uncompressed tissue after irradiation of compressed breast tissue. Dosimetry was performed using two different methods, namely, Monte Carlo simulations using the MCNP5 code and measurements using thermoluminescent dosimeters (TLD). The displacement of the breast elements was simulated using a finite element model and calculated using ABAQUS software. From these results, the 3D dose distribution in uncompressed tissue was determined. The geometry of the model was constructed from magnetic resonance images of six different women volunteers. The mechanical properties were modeled by using the Mooney-Rivlin hyperelastic material model. Experimental dosimetry was performed by placing the TLD chips into the polyvinyl alcohol breast equivalent phantom. The results determined that the nodal displacements, due to the gravitational force and the 60 Newton compression forces (with 43% contraction in the loading direction and 37% expansion in the orthogonal direction) were determined. Finally, a comparison of the experimental data and the simulated data showed agreement within 11.5% ± 5.9%.
Influence of bank vegetation and gravel bed on velocity and Reynolds stress distributions
Hossein AFZALIMEHR; Subhasish DEY
2009-01-01
This paper presents the results of a laboratory flume experimental study on the interaction of bank vegetation and gravel bed on the flow velocity (primarily on the location of the maximum velocity, Umax) and the Reynolds stress distributions. The results reveal that the dip of the maximum velocity below the water surface is up to 35% of flow depth and the difference between Umax and the velocity at the water surface is considerable in the presence of vegetation on the walls. The zone of the log-law varies from y/h=2 up to 15 percent of flow depth and it does not depend on distance from the wall. Deviation of the velocity profile in the outer layer over a gravel bed with vegetation cover on the walls is much larger than the case of flow over a gravel bed without vegetation cover on the walls. The presence of vegetation on the walls changes uniform flow to non-uniform flow. This fact can be explained by considering the nonlinear Reynolds stress distribution and location of maximum velocity in each profile at different distances across the flume. The Reynolds stress distributions at the distance 0.02 m from the wall have negative values and away from the wall, they change the sign taking positive values with specific convex form with apex in higher location. Average of von Karman constant κ for this study is equal to 0.16. Based on κ=0.16, the methods of Clauser and the Reynolds stress are compatible for determination of shear velocity.
Dussaillant, Francisca; Apablaza, Mauricio
2017-08-01
After a major earthquake, the assignment of scarce mental health emergency personnel to different geographic areas is crucial to the effective management of the crisis. The scarce information that is available in the aftermath of a disaster may be valuable in helping predict where are the populations that are in most need. The objectives of this study were to derive algorithms to predict posttraumatic stress (PTS) symptom prevalence and local distribution after an earthquake and to test whether there are algorithms that require few input data and are still reasonably predictive. A rich database of PTS symptoms, informed after Chile's 2010 earthquake and tsunami, was used. Several model specifications for the mean and centiles of the distribution of PTS symptoms, together with posttraumatic stress disorder (PTSD) prevalence, were estimated via linear and quantile regressions. The models varied in the set of covariates included. Adjusted R2 for the most liberal specifications (in terms of numbers of covariates included) ranged from 0.62 to 0.74, depending on the outcome. When only including peak ground acceleration (PGA), poverty rate, and household damage in linear and quadratic form, predictive capacity was still good (adjusted R2 from 0.59 to 0.67 were obtained). Information about local poverty, household damage, and PGA can be used as an aid to predict PTS symptom prevalence and local distribution after an earthquake. This can be of help to improve the assignment of mental health personnel to the affected localities. Dussaillant F , Apablaza M . Predicting posttraumatic stress symptom prevalence and local distribution after an earthquake with scarce data. Prehosp Disaster Med. 2017;32(4):357-367.
Otoguro, Saori; Hayashi, Yoshihiro; Miura, Takahiro; Uehara, Naoto; Utsumi, Shunichi; Onuki, Yoshinori; Obata, Yasuko; Takayama, Kozo
2015-01-01
The stress distribution of tablets after compression was simulated using a finite element method, where the powder was defined by the Drucker-Prager cap model. The effect of tablet shape, identified by the surface curvature, on the residual stress distribution was investigated. In flat-faced tablets, weak positive shear stress remained from the top and bottom die walls toward the center of the tablet. In the case of the convexly curved tablet, strong positive shear stress remained on the upper side and in the intermediate part between the die wall and the center of the tablet. In the case of x-axial stress, negative values were observed for all tablets, suggesting that the x-axial force always acts from the die wall toward the center of the tablet. In the flat tablet, negative x-axial stress remained from the upper edge to the center bottom. The x-axial stress distribution differed between the flat and convexly curved tablets. Weak stress remained in the y-axial direction of the flat tablet, whereas an upward force remained at the center of the convexly curved tablet. By employing multiple linear regression analysis, the mechanical properties of the tablets were predicted accurately as functions of their residual stress distribution. However, the multiple linear regression prediction of the dissolution parameters of acetaminophen, used here as a model drug, was limited, suggesting that the dissolution of active ingredients is not a simple process; further investigation is needed to enable accurate predictions of dissolution parameters.
Wing Kam Fung
2010-02-01
Full Text Available The case-control study is an important design for testing association between genetic markers and a disease. The Cochran-Armitage trend test (CATT is one of the most commonly used statistics for the analysis of case-control genetic association studies. The asymptotically optimal CATT can be used when the underlying genetic model (mode of inheritance is known. However, for most complex diseases, the underlying genetic models are unknown. Thus, tests robust to genetic model misspecification are preferable to the model-dependant CATT. Two robust tests, MAX3 and the genetic model selection (GMS, were recently proposed. Their asymptotic null distributions are often obtained by Monte-Carlo simulations, because they either have not been fully studied or involve multiple integrations. In this article, we study how components of each robust statistic are correlated, and find a linear dependence among the components. Using this new finding, we propose simple algorithms to calculate asymptotic null distributions for MAX3 and GMS, which greatly reduce the computing intensity. Furthermore, we have developed the R package Rassoc implementing the proposed algorithms to calculate the empirical and asymptotic p values for MAX3 and GMS as well as other commonly used tests in case-control association studies. For illustration, Rassoc is applied to the analysis of case-control data of 17 most significant SNPs reported in four genome-wide association studies.
ABA pretreatment can alter the distribution of polysomes in salt-stressed barley sprouts
Szypulska Ewa
2016-12-01
Full Text Available The study analyzed caryopses of barley (Hordeum vulgare cv. Stratus. Caryopses were germinated in darkness at 20°C in three experimental setups: (a in distilled water for 24 hours, followed by 100 mM NaCl for another 24 hours (salinity stress, SS, (b in 100 μM of abscisic acid for the first 24 hours, followed by rinsing with distilled water to remove residual ABA, and in 100 mM NaCl for another 24 hours (ABA pretreatment + salinity stress, ABAS, (c in distilled water only (control, C. Changes in the content of free polysomes (FP, membrane-bound polysomes (MBP, cytoskeleton-bound polysomes (CBP and cytomatrix-bound polysomes (CMBP were examined in barley sprouts germinated in SS and ABAS treatments for 48 hours. In salt-stressed barley sprouts, the concentrations of membrane-bound and cytoskeleton-bound polysomes (MBP, CBP and CMBP decreased significantly, whereas an increase was noted only in the free polysome (FP fraction. ABA pretreatment altered the distribution of polysomes in stressed plants. The content of cytoskeletonbound polysomes (CBP and CMBP increased, FP levels decreased, whereas no changes in MBP content were observed in response to ABA treatment. Our results suggest that plants respond to salt stress by increasing the concentrations of free polysomes that are probably released from damaged cell structures, mainly membranes. Our present and previous findings indicate that ABA could inhibit the release of FP in stressed plants by enhancing polysome binding to the cytoskeleton.
Teixeira, V. [Univ. of Minho, IMAT, Materials Inst., Physics Dept., Braga (Portugal)
2002-07-01
The major problem in thermal barrier coatings (TBC) applied to gas turbine components is the spallation of ceramic coating under thermal cycling processes. In order to prevent spallation and improve the thermo-mechanical behaviour of the TBC, graded ceramic coatings can be fabricated. Therefore, a detailed study of the optimization of the gradient profile is necessary in respect to thermal stress relief. In this paper a numerical model of elastic thermal stress distribution within a multilayered system which consists of a functionally gradient material (FGM), is presented. The structure of the graded coating system is made of a ceramic layer and a metallic layer, where between them there is an interlayer which is a graded composite made of the metal (NiCr-alloy) and the ceramic (ZrO{sub 2}Y{sub 2}O{sub 3}). The effects of elastic modulus of the alloy substrate, the graded interlayer thickness and ceramic layer porosity on residual stress distribution were studied for the case of a graded TBC using a linear compositional profile for the FGM. (orig.)
WANG Xuelei; LI Qingmin; LI Chengrong; YANG Rui; GAO Shuguo
2013-01-01
Before diagnosed by DGA (dissolved gas analysis) methods,gas caution values,which index the level of gas formation,must be used to evaluate the possibility of incipient faults to reduce the misdiagnosis in the normal state.However,the calculation of these values is now only based on cumulative percentile method without taking into account operating conditions.To overcome this disadvantage,a new approach to calculate the transformer caution values is presented.This approach is based on statistical distribution and correlation analysis,and it takes the individual variation and fluctuation caused by intemal and external factors into consideration.Then 6550 transformer DGA data collected from North China Power Grid are analyzed in this paper.The results show that the volume fraction of TH (total hydrocarbon)approximately obeys normal distribution when the 3-sigma rule is used to calculate its caution value.The volume fraction of CO has a strong positive correlation with oil temperature.For H2,the negative correlation with oil temperature is significant when the volume fraction is not very low.The caution value curves for CO and H2 are obtained by regression analyses.Thus,the gas caution values/curves obtained using the new method are not always constant,but vary with oil temperature,which is an advantage of the proposed method compared with cumulative percentile method.The variation of gas caution values/curves also reflects the influence of the external factors,for instance,varying with monitoring time ensures that the gas caution values are always consistent with operating status.
Evaluation of Missing Pellet Surface Geometry on Cladding Stress Distribution and Magnitude
Capps, Nathan A.; Montgomery, Robert O.; Sunderland, Dion J.; Spencer, Ben; Pytel, Martin; Wirth, Brian D.
2014-10-01
Missing pellet surface (MPS) defects are local geometric defects that periodically occur in nuclear fuel pellets, usually as a result of the mishandling during the manufacturing process. The presences of these defects can lead to clad stress concentrations that are substantial enough to cause a through wall failure for certain conditions of power level, burnup, and power increase. Consequently, the impact of potential MPS defects has limited the rate of power increase or ramp rates in both PWR and BWR systems. Improved 3D MPS models that consider the effect of the MPS geometry can provide better understanding of the margins against PCMI clad failure. The Peregrine fuel performance code has been developed as a part the Consortium of Advanced Simulations of Light Water Reactors (CASL) to consider the inherently multi-physics and multi-dimensional mechanisms that control fuel behavior, including cladding failure by the presence of MPS defects. This paper presents an evaluation of the cladding stress concentrations as a function of MPS defect geometry. The results are the first step in a probabilistic approach to assess cladding failure during power maneuvers. This analysis provides insight into how varying pellet defect geometries affect the distribution of the cladding stress and fuel and cladding temperature and will be used to develop stress concentration factors for 2D and 3D models.
Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling
Turner, R. H.
1983-01-01
Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.
Temperature-time distribution and thermal stresses on the RTG fins and shell during water cooling
Turner, R. H.
1983-01-01
Radioisotope thermoelectric generator (RTG) packages designed for space missions generally do not require active cooling. However, the heat they generate cannot remain inside of the launch vehicle bay and requires active removal. Therefore, before the Shuttle bay door is closed, the RTG coolant tubes attached to the heat rejection fins must be filled with water, which will circulate and remove most of the heat from the cargo bay. There is concern that charging a system at initial temperature around 200 C with water at 24 C can cause unacceptable thermal stresses in the RTG shell and fins. A computer model is developed to estimate the transient temperature distribution resulting from such charging. The thermal stresses resulting from the temperature gradients do not exceed the elastic deformation limit for the material. Since the simplified mathematical model for thermal stresses tends to overestimate stresses, it is concluded that the RTG can be cooled by introducing water at 24 C to the initially hot fin coolant tubes while the RTG is in the Shuttle cargo bay.
On the spatial distribution of seismicity and the 3D tectonic stress field in western Greece
Kassaras, Ioannis; Kapetanidis, Vasilis; Karakonstantis, Andreas
2016-10-01
We analyzed a large number of focal mechanisms and relocated earthquake hypocenters to investigate the geodynamics of western Greece, the most seismically active part of the Aegean plate-boundary zone. This region was seismically activated multiple times during the last decade, providing a large amount of enhanced quality new information that was obtained by the Hellenic Unified Seismological Network (HUSN). Relocated seismicity using a double-difference method appears to be concentrated above ∼35 km depth, exhibiting spatial continuity along the convergence boundary and being clustered elsewhere. Earthquakes are confined within the accreted sediments escarpment of the down-going African plate against the un-deformed Eurasian hinterland. The data arrangement shows that Pindos constitutes a seismic boundary along which large stress heterogeneities occur. In Cephalonia no seismicity is found to be related with the offshore Cephalonia Transform Fault (CTF). Onshore, Nsbnd S crustal extension dominates, while in central and south Peloponnesus the stress field appears rotated by 90°. Shearing-stress obliquity by 30° is indicated along the major strike-slip faults, consistent with clockwise crustal rotation. Within the lower crust, the stress field appears affected by plate kinematics and distributed deformation of the lower crust and upper mantle, which guide the regional geodynamics.
Comparative cephalopod shell strength and the role of septum morphology on stress distribution
Robert Lemanis
2016-09-01
Full Text Available The evolution of complexly folded septa in ammonoids has long been a controversial topic. Explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. The complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. However, the power of modern finite element analysis now permits direct testing of mechanical hypothesis on complete, empirical models of the shells taken from computed tomographic data. Here we compare, for the first time using empirical models, the capability of the shells of extant Nautilus pompilius, Spirula spirula, and the extinct ammonite Cadoceras sp. to withstand hydrostatic pressure and point loads. Results show hydrostatic pressure imparts highest stress on the final septum with the rest of the shell showing minimal compression. S. spirula shows the lowest stress under hydrostatic pressure while N. pompilius shows the highest stress. Cadoceras sp. shows the development of high stress along the attachment of the septal saddles with the shell wall. Stress due to point loads decreases when the point force is directed along the suture as opposed to the unsupported chamber wall. Cadoceras sp. shows the greatest decrease in stress between the point loads compared to all other models. Greater amplitude of septal flutes corresponds with greater stress due to hydrostatic pressure; however, greater amplitude decreases the stress magnitude of point loads directed along the suture. In our models, sutural complexity does not predict greater resistance to hydrostatic pressure but it does seem to increase resistance to point loads, such as would be from predators. This result permits discussion of palaeoecological reconstructions on the basis of septal morphology. We further
Comparative cephalopod shell strength and the role of septum morphology on stress distribution.
Lemanis, Robert; Zachow, Stefan; Hoffmann, René
2016-01-01
The evolution of complexly folded septa in ammonoids has long been a controversial topic. Explanations of the function of these folded septa can be divided into physiological and mechanical hypotheses with the mechanical functions tending to find widespread support. The complexity of the cephalopod shell has made it difficult to directly test the mechanical properties of these structures without oversimplification of the septal morphology or extraction of a small sub-domain. However, the power of modern finite element analysis now permits direct testing of mechanical hypothesis on complete, empirical models of the shells taken from computed tomographic data. Here we compare, for the first time using empirical models, the capability of the shells of extant Nautilus pompilius, Spirula spirula, and the extinct ammonite Cadoceras sp. to withstand hydrostatic pressure and point loads. Results show hydrostatic pressure imparts highest stress on the final septum with the rest of the shell showing minimal compression. S. spirula shows the lowest stress under hydrostatic pressure while N. pompilius shows the highest stress. Cadoceras sp. shows the development of high stress along the attachment of the septal saddles with the shell wall. Stress due to point loads decreases when the point force is directed along the suture as opposed to the unsupported chamber wall. Cadoceras sp. shows the greatest decrease in stress between the point loads compared to all other models. Greater amplitude of septal flutes corresponds with greater stress due to hydrostatic pressure; however, greater amplitude decreases the stress magnitude of point loads directed along the suture. In our models, sutural complexity does not predict greater resistance to hydrostatic pressure but it does seem to increase resistance to point loads, such as would be from predators. This result permits discussion of palaeoecological reconstructions on the basis of septal morphology. We further suggest that the ratio
Welding sequence effects on residual stress distribution in offshore wind monopile structures
Ali Mehmanparast
2016-01-01
Full Text Available Residual stresses are often inevitably introduced into the material during the fabrication processes, such as welding, and are known to have significant effects on the subsequent fatigue crack growth behavior of welded structures. In this paper, the importance of welding sequence on residual stress distribution in engineering components has been reviewed. In addition, the findings available in the literature have been used to provide an accurate interpretation of the fatigue crack growth data on specimens extracted from the welded plates employed in offshore wind monopile structures. The results have been discussed in terms of the role of welding sequence in damage inspection and structural integrity assessment of offshore renewable energy structures.
Stress/strain distributions for weld metal solidification crack in stainless steels
无
2000-01-01
This paper has simulated the driving force of solidification crack of stainless steels, that is, stress/strain field in the trail of molten pool. Firstly, the effect of the deformation in the molten pool was eliminated after the element rebirth method was adopted. Secondly, the influence of solidification shrinkage was taken into account by increasing thermal expansion coefficients of the steels at elevated temperatures. Finally, the stress/strain distributions of different conditions have been computed and analyzed. Furthermore, the driving force curves of the solidification crack of the steels have been obtained by converting strain-time curves into strain-temperature curves, which founds a basis for predicting welding solidification crack.
WANGShu-hong; ZUODun-wen; WANGMin; WANGZong-rong
2004-01-01
The integrated structure parts are widely used in aircraft. The distortion caused by residual stresses in thick pre-stretched aluminum plates during machining integrated parts is a common and serious problem. To predict and control the machining distortion, the residual stress distribution in the thick plate must be measured firstly. The modified removal method for measuring residual stress in thick pre-stretched aluminum plates is proposed and the stress-strain relation matrix is deduced by elasticity theory. The residual stress distribution in specimen of 7050T7451 plate is measured by using the method, and measurement results are analyzed and compared with data obtained by other methods. The method is effective to measure the residual stress.
Çelik Köycü, Berrak; Imirzalioğlu, Pervin; Özden, Utku Ahmet
2016-01-01
Functional occlusal loads and intraoral temperature changes create stress in teeth. The purpose of this study was to evaluate the impact of simultaneous thermomechanical loads on stress distribution related to inlay restored teeth by three-dimensional finite element analysis. A mandibular first molar was constructed with tooth structures, surrounding bone and inlays of Type II gold alloy, ceramic, and composite resin. Stress patterns on the restorative materials, adhesive resin, enamel and dentin were analyzed after simulated temperature changes from 36°C to 4 or 60°C for 2 s with 200-N oblique loading. The results showed that the three types of inlays had similar stress distribution in the tooth structures and restorative materials. Concerning the adhesive resin, the composite resin inlay model exhibited lower stresses than ceramic and gold alloy inlays. Simultaneous thermomechanical loads caused high stress patterns in inlay-restored teeth. Composite resin inlays may be the better choice to avoid adhesive failure.
Mohammed Ibrahim, M; Thulasingam, C; Nasser, K S. G. A; Balaji, V; Rajakumar, M; Rupkumar, P
2011-01-01
...).The objectives of the study was to compare the influence of stress distribution in the implants of screw-vent tapered and parallel design by varying the implant diameter with a standard implant length...
明洞局部应力计算浅析%Local Stress Calculation Analysis Of Visible Hole
赵春菲
2012-01-01
坝陵河大桥是沪瑞国道主干线贵州省镇宁至胜境关高速公路主跨1088m的单跨吊悬索桥。西锚碇为隧道锚,该隧道锚为目前国内最大的隧道式锚碇。由于锚碇上端的明洞一侧有汽车荷载的作用,而另外一侧只有土压力的作用,为了验算结构的受力状况,建立三维模型,进行三维有限元分析。本次分析根据结构的空间尺寸建立计算模型,考虑明洞在最不利荷载工况组合作用下承受的最大内力,进行结构应力分析,并据此进行结构强度分析。%Balinghe bridge is a single span self-anchored suspension bridge at the Hurui national road in Guizhou province with main span of 1088m.The west anchorage is tunnel anchor,which is the biggest tunnel anchor in our country.One side of the visible hole on the upper end of anchorage is of the function of vehicle load,and the other side is of the function of soil stress.The 3D model was established to perform 3D finite-element analysis to test the structure loading condition.The calculation model was developed according to the structure's space size and the maximum bearing internal force of visible hole under the combination function of disadvantage load was considered for structure stress and strength analysis.
Curran, J. C.; Tan, L.
2011-12-01
In gravel bed rivers, low flows generate shear stresses less than what is needed to entrain the largest particles but large enough to transport the fines. During sustained low flows, fine sediment winnows from the bed surface and an armored surface layer forms. As the surface armor forms, a surface structure develops that increases bed roughness and flow resistance and can be characterized by the presence of clusters. Individual clusters are known to exert a significant influence over the spatial and temporal flow processes acting in the vicinity of the bed. A series of flume experiments investigated the turbulent structures formed around clusters naturally developed during bed armoring. The series of experiments created armored beds using four different flow rates and four different bulk grain size distributions which progressively increased in the percent sand in the bed sediment. Following an initial run segment that established equilibrium sediment transport and full bed mobility, the flow rate in the flume was reduced and the bed surface fully armored. Once armored, clusters were identified using a combination of bed DEM, vertical profile, and visual analysis. Instantaneous three-dimensional flow velocities were measured around the clusters using an Acoustic Doppler Velocimeter, and these values were used to calculate Reynolds shear stresses, turbulence intensities, and turbulent kinetic energy in the flow field. Results show a significant change in the flow profiles over a cluster when compared to an open area of the armored bed. Reynolds shear stresses doubled over the cluster and turbulence intensity reached a peak value right above the single cluster. The results also suggest the effects of the single cluster on the surrounding flow dynamics are quite localized and limited to 30cm in lateral orientation. Quadrant analysis showing large ejection and sweep events around clusters indicates vortex formation at the cluster crest. The magnitude of the coherent
Costa, Akf; Xavier, Ta; Noritomi, Py; Saavedra, G; Borges, Als
2014-01-01
SUMMARY The purpose of this study was to evaluate the influence the width of the occlusal isthmus and inlay material had on the stress distribution, displacement, and fracture resistance of upper human premolars. For this in vitro test, 35 intact upper premolars (UPM) were selected and five were kept intact for the control group (group I). The remaining 30 were divided into two experimental groups (n=15) according to the width of isthmus: conservative (CP) and extensive preparation (EP), one third and more than two thirds of cuspal distance, respectively. Five teeth from each experimental group were left without restoration for negative controls (CPnc and EPnc), and the remaining 10 in each group were subdivided according to the inlay material (resin or ceramic): group CPr, CP + indirect resin; group CPc, CP + ceramic; group EPr, EP + indirect resin; and group EPc, EP + ceramic. The cemented inlays were loaded in a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. The fractured specimens were analyzed with stereomicroscopy, and the values of the fracture resistance evaluated by analysis of variance and Tukey test. For the finite element analyses, an average UPM for each group was modeled in Rhinoceros CAD software and imported to Ansys 13.0. An average of 320,000 tetrahedral elements and 540,000 nodes for the seven models were performed using the same experimental simulation setup for each. The models were constrained on the base, and a displacement of 0.02 mm was applied to keep a linear behavior for the analysis. A von Mises stress and total displacement fields were used for the coherence test and the maximum principal stress fields were used for mechanical behavior comparisons. Group I (161.73 ± 22.94) showed a significantly higher mean value than the other experimental groups (EPc: 103.55 ± 15.84; CPc: 94.38 ± 12.35; CPr: 90.31 ± 6.10; EPr: 65.42 ± 10.15; CPnc: 65.46 ± 5.37; EPnc: 58.08 ± 9.62). The stress distribution was
Hasan Çallioğlu
2011-02-01
An analytical thermoelasticity solution for a disc made of functionally graded materials (FGMs) is presented. Infinitesimal deformation theory of elasticity and power law distribution for functional gradation are used in the solution procedure. Some relative results for the stress and displacement components along the radius are presented due to internal pressure, external pressure, centrifugal force and steady state temperature. From the results, it is found that the grading indexes play an important role in determining the thermomechanical responses of FG disc and in optimal design of these structures.
Bahman Tarvirdizade
2014-01-01
Full Text Available We consider the estimation of stress-strength reliability based on lower record values when X and Y are independently but not identically inverse Rayleigh distributed random variables. The maximum likelihood, Bayes, and empirical Bayes estimators of R are obtained and their properties are studied. Confidence intervals, exact and approximate, as well as the Bayesian credible sets for R are obtained. A real example is presented in order to illustrate the inferences discussed in the previous sections. A simulation study is conducted to investigate and compare the performance of the intervals presented in this paper and some bootstrap intervals.
Parallel glide: flow of dislocations with internal stress source/sink distribution
Karlo T Raić
2008-01-01
Full Text Available The unexpected glide of dislocations on a plane parallel to the film/substrate interface in ultrathin copper films, which has been called parallel glide (Balk et al 2003 Acta Metall. 51 447, is described using an analytical model. The phenomenon is observed as a problem involving inlet/outlet flow from different positions of a grain boundary into the grain channel. In this sense, parallel glide is presented as the flow of dislocations with an internal stress source/sink distribution.
A.G. KHAN
1995-01-01
Full Text Available The vesicular - arbuscular (VA mycorrhizal fungi are geographically ubiquitous soil inhabitants and form universal symbiotic relationship with plants from every phylum. These fungi link host plants with host soils and their biota in the mycorrhizosphere and play an important role in plant health, productivity and soil structure. Although VA mycorrhizal fungi do not show any host specificity, there is increasing evidence that various climatic and edaphic environmental factors such as land use and management practices, physical, chemical and biological properties of host soils and host plant characteristics influence their occurrence, taxonomic distribution and effectiveness. The interaction of these factors with vesicular-arbuscular mycorrhizae (VAM is poorly understood except in a few cases. It is now very clear that VA mycorrhizal associations are ecologically significant factors that require more attention than previously accorded. This paper discusses the occurrence, distribution and significance of VAM in environmentally stressed soil conditions that limit plant growth such as drought, waterlogging and salinity.
Andresen, Markus; Ma, Ke; Liserre, Marco
2015-01-01
A Smart Transformer (ST) can cover an important managing role in the future electrical distribution grid. For the moment, the reliability and cost are not competitive with traditional transformers and create a barrier for its application. This work conduct detail designs and analysis for a promis......A Smart Transformer (ST) can cover an important managing role in the future electrical distribution grid. For the moment, the reliability and cost are not competitive with traditional transformers and create a barrier for its application. This work conduct detail designs and analysis...... for a promising modular ST solution, which is composed of Modular Multi-level converter, Quad Active Bridge DC-DC converters, and two-level voltage source converters. The focus is put on the loading conditions and thermal stress of power semiconductor devices in order to discover critical parts of the whole...
Hamid R. Nikraz
2007-01-01
Full Text Available Fracture mechanics is a branch of mechanics, which deals with the cracked body. Every construction material that currently in use inevitably is not flawless. The pre-existing crack may grow to cause structure failure due to low stress, which acts to a structure. Stress intensity factor (K is a single parameter in fracture mechanics, which can be used to examine if a crack, would propagate in a cracked structure under particular loading condition. Finite element method is used to analyze the cracked body to provide the displacements data around the crack tip (at quarter point elements due to load prescribed, for stress intensity factor determination. Two methods of stress intensity factor calculation, Quarter Point Displacement Technique (QPDT and Displacement Correlation Technique (DCT, were evaluated. A series of standard fracture testing were undertaken to provide the fracture load data (Pf, which coupled with the stress intensity factor analytical formula to calculate fracture toughness. The results showed that under a particular mesh arrangement, the result of finite element analysis could deviate from the analytical formula calculation result. The QPDT method is suitable for compact tension specimen but DCT seemed to be not. For cracked beam analysis, the QPDT and DCT calculations were in good agreement with the analytical formula as long as coupled with the appropriate mesh arrangement around the crack tip.
Kozier, K. S. [Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ont. K0J 1J0 (Canada)
2006-07-01
This paper examines the sensitivity of MCNP5 k{sub eff} results to various deuterium data files for a simple benchmark problem consisting of an 8.4-cm radius sphere of uranium surrounded by an annulus of deuterium at the nuclide number density corresponding to heavy water. This study was performed to help clarify why {Delta}k{sub eff} values of about 10 mk are obtained when different ENDF/B deuterium data files are used in simulations of critical experiments involving solutions of high-enrichment uranyl fluoride in heavy water, while simulations of low-leakage, heterogeneous critical lattices of natural-uranium fuel rods in heavy water show differences of <1 mk. The benchmark calculations were performed as a function of deuterium reflector thickness for several uranium compositions using deuterium ACE files derived from ENDF/B-VII.b1 (release beta 1), ENDF/B-VI.4 and JENDL-3.3, which differ primarily in the energy/angle distributions for elastic scattering <3.2 MeV. Calculations were also performed using modified ACE files having equiprobable cosine bin values in the centre-of-mass reference frame in a progressive manner with increasing energy. It was found that the {Delta}k{sub eff} values increased with deuterium reflector thickness and uranium enrichment. The studies using modified ACE files indicate that most of the reactivity differences arise at energies <1 MeV; hence, this energy range should be given priority if new scattering distribution measurements are undertaken. (authors)
Kauweloa, Kevin I; Gutierrez, Alonso N; Stathakis, Sotirios; Papanikolaou, Niko; Mavroidis, Panayiotis
2016-07-01
A toolkit has been developed for calculating the 3-dimensional biological effective dose (BED) distributions in multi-phase, external beam radiotherapy treatments such as those applied in liver stereotactic body radiation therapy (SBRT) and in multi-prescription treatments. This toolkit also provides a wide range of statistical results related to dose and BED distributions. MATLAB 2010a, version 7.10 was used to create this GUI toolkit. The input data consist of the dose distribution matrices, organ contour coordinates, and treatment planning parameters from the treatment planning system (TPS). The toolkit has the capability of calculating the multi-phase BED distributions using different formulas (denoted as true and approximate). Following the calculations of the BED distributions, the dose and BED distributions can be viewed in different projections (e.g. coronal, sagittal and transverse). The different elements of this toolkit are presented and the important steps for the execution of its calculations are illustrated. The toolkit is applied on brain, head & neck and prostate cancer patients, who received primary and boost phases in order to demonstrate its capability in calculating BED distributions, as well as measuring the inaccuracy and imprecision of the approximate BED distributions. Finally, the clinical situations in which the use of the present toolkit would have a significant clinical impact are indicated.
König, Gerhard; Miller, Benjamin T; Boresch, Stefan; Wu, Xiongwu; Brooks, Bernard R
2012-10-09
One of the key requirements for the accurate calculation of free energy differences is proper sampling of conformational space. Especially in biological applications, molecular dynamics simulations are often confronted with rugged energy surfaces and high energy barriers, leading to insufficient sampling and, in turn, poor convergence of the free energy results. In this work, we address this problem by employing enhanced sampling methods. We explore the possibility of using self-guided Langevin dynamics (SGLD) to speed up the exploration process in free energy simulations. To obtain improved free energy differences from such simulations, it is necessary to account for the effects of the bias due to the guiding forces. We demonstrate how this can be accomplished for the Bennett's acceptance ratio (BAR) and the enveloping distribution sampling (EDS) methods. While BAR is considered among the most efficient methods available for free energy calculations, the EDS method developed by Christ and van Gunsteren is a promising development that reduces the computational costs of free energy calculations by simulating a single reference state. To evaluate the accuracy of both approaches in connection with enhanced sampling, EDS was implemented in CHARMM. For testing, we employ benchmark systems with analytical reference results and the mutation of alanine to serine. We find that SGLD with reweighting can provide accurate results for BAR and EDS where conventional molecular dynamics simulations fail. In addition, we compare the performance of EDS with other free energy methods. We briefly discuss the implications of our results and provide practical guidelines for conducting free energy simulations with SGLD.
Effect of Water Stress on Root Distribution and Extension of Different Triticale Genotypes
H.R. Khazaei
2014-12-01
Full Text Available Root depth and distribution have an important role in drought resistance and optimization of moisture content of soil. This research was carried out in order to consider of root response of triticale genotypes to water stress and recognition of root trait that can effective in resistance of water stress. This experiment was in a factorial experiment based on completely random design on the year 2009. The genotypes of triticale was included (i ET-82-15 (ii ET-82-8 (iii ET-82-17 and commercial triticale genotype Juanillo-92. Two irrigation regimes included 100 and 50 % of field capacity, respectively. The result showed that water stress result in increased 9% of root depth in each plant. Differences between minimum root depth was observed in ET-82-15 rather than maximum root depth in Juanillo-92 was approximately 8.2 centimeters. Late irrigation caused to diminish 25% of root length. Differences between maximum root length in ET-82-15 and minimum root length in ET-82-17 was not significant (p
Zechmann, Bernd; Liou, Liang-Chun; Koffler, Barbara E; Horvat, Lucija; Tomašić, Ana; Fulgosi, Hrvoje; Zhang, Zhaojie
2011-01-01
Glutathione is an important antioxidant in most prokaryotes and eukaryotes. It detoxifies reactive oxygen species and is also involved in the modulation of gene expression, in redox signaling, and in the regulation of enzymatic activities. In this study, the subcellular distribution of glutathione was studied in Saccharomyces cerevisiae by quantitative immunoelectron microscopy. Highest glutathione contents were detected in mitochondria and subsequently in the cytosol, nuclei, cell walls, and vacuoles. The induction of oxidative stress by hydrogen peroxide (H2O2) led to changes in glutathione-specific labeling. Three cell types were identified. Cell types I and II contained more glutathione than control cells. Cell type II differed from cell type I in showing a decrease in glutathione-specific labeling solely in mitochondria. Cell type III contained much less glutathione contents than the control and showed the strongest decrease in mitochondria, suggesting that high and stable levels of glutathione in mitochondria are important for the protection and survival of the cells during oxidative stress. Additionally, large amounts of glutathione were relocated and stored in vacuoles in cell type III, suggesting the importance of the sequestration of glutathione in vacuoles under oxidative stress. PMID:22093747
An Analytical Study on Distribution of Statically Determinate Stresses in Particulate Half Space
Wu Bingkun
1996-01-01
General solution of stresses solved from the two-dimensiona I system of equilibrium equations in Cartesian coordinates is characterized by the presence of two families of characteristic lines along which initial stresses and discontinuities in them are transmitted intact far down to infinity. This is against our intuition and not verifiable by experimental findings.For the fundamental case of infinite uniform pressure on the upper surface, a comparison between solutions from equilibrium equations in Cartesian coordinates and from those in polar coordinates is carried out in details. The semi-infinite characteristic lines in the former are bent up to exponential spirals with both ends on the upper surface in the latter. Thus,the transmission pattern from solution in polar coordinates comes closer to actual situation. However, in polar reference frame, the solution for distribution of stresses in particulate half space under surface strip pressure or so can then only be obtained from boundary value problem of second order partial differential equation.
Distribution of Selenium and Oxidative Stress in Breast Tumor-Bearing Mice
Pei-Chung Chen
2013-02-01
Full Text Available The present study investigated the effects of breast tumors on the blood and tissue distribution of essential trace mineral selenium (Se, and oxidative stress status of mice. Female 10-week-old BALB/cByJNarl mice were randomly assigned into control (CNL and breast tumor-bearing (TB groups. TB mice were injected subcutaneously into the right hind thigh with 5 × 106 EMT6 mouse mammary tumor cells. After 22 days, we measured Se concentrations, Se-dependent glutathione peroxidase (GPx activities, and malondialdehyde (MDA products (indicator of oxidative stress in plasma, various tissues, and plasma vascular endothelial growth factor (VEGF concentrations. There were no significant differences in body weights and daily intake between both groups. Compared with the CNL group, TB mice have decreases in plasma Se concentrations and GPx activities, as well as higher plasma VEGF and MDA concentrations. Plasma Se concentrations were also negatively correlated with plasma MDA and VEGF concentrations. Furthermore, tissue Se concentrations and GPx activities in TB animals were lower; whereas the MDA concentrations higher in various tissues including liver, kidney, brain, lung, spleen, and thymic tissues. In conclusion, disruption of Se homeostasis critically reflects oxidative stress in target tissues, thus may increase the risk for progression of breast cancer and metastasis.
Impact of weightlessness on cardiac shape and left ventricular stress/strain distributions.
Iskovitz, Ilana; Kassemi, Mohammad; Thomas, James D
2013-12-01
In this paper, a finite element model of the heart is developed to investigate the impact of different gravitational loadings of Earth, Mars, Moon, and microgravity on the cardiac shape and strain/stress distributions in the left ventricle. The finite element model is based on realistic 3D heart geometry, detailed fiber/sheet micro-architecture, and a validated orthotropic cardiac tissue model and constitutive relationship that capture the passive behavior of the heart at end-diastole. The model predicts the trend and magnitude of cardiac shape change at different gravitational levels with great fidelity in comparison to recent cardiac sphericity measurements performed during simulated reduced-gravity parabolic flight experiments. Moreover, the numerical predictions indicate that although the left ventricular strain distributions remain relatively unaltered across the gravitational fields and the strain extrema values occur at the same relative locations, their values change noticeably with decreasing gravity. As for the stress, however, both the magnitude and location of the extrema change with a decrease in the gravitational field. Consequently, tension regions of the heart on Earth can change into compression regions in space.
Miniaturization of Micro-Solder Bumps and Effect of IMC on Stress Distribution
Choudhury, Soud Farhan; Ladani, Leila
2016-07-01
As the joints become smaller in more advanced packages and devices, intermetallic (IMCs) volume ratio increases, which significantly impacts the overall mechanical behavior of joints. The existence of only a few grains of Sn (Tin) and IMC materials results in anisotropic elastic and plastic behavior which is not detectable using conventional finite element (FE) simulation with average properties for polycrystalline material. In this study, crystal plasticity finite element (CPFE) simulation is used to model the whole joint including copper, Sn solder and Cu6Sn5 IMC material. Experimental lap-shear test results for solder joints from the literature were used to validate the models. A comparative analysis between traditional FE, CPFE and experiments was conducted. The CPFE model was able to correlate the experiments more closely compared to traditional FE analysis because of its ability to capture micro-mechanical anisotropic behavior. Further analysis was conducted to evaluate the effect of IMC thickness on stress distribution in micro-bumps using a systematic numerical experiment with IMC thickness ranging from 0% to 80%. The analysis was conducted on micro-bumps with single crystal Sn and bicrystal Sn. The overall stress distribution and shear deformation changes as the IMC thickness increases. The model with higher IMC thickness shows a stiffer shear response, and provides a higher shear yield strength.
Yazicioglu, Duygu; Bayram, Burak; Oguz, Yener; Cinar, Duygu; Uckan, Sina
2016-02-01
The aim of this study was to evaluate the stress distribution of the short dental implants and bone-to-implant contact ratios in the posterior maxilla using 3-dimensional (3D) finite element models. Two different 3D maxillary posterior bone segments were modeled. Group 1 was composed of a bone segment consisting of cortical bone and type IV cancellous bone with 100% bone-to-implant contact. Group 2 was composed of a bone segment consisting of cortical bone and type IV cancellous bone including spherical bone design and homogenous tubular hollow spaced structures with 30% spherical porosities and 70% bone-to-implant contact ratio. Four-millimeter-diameter and 5-mm-height dental implants were assumed to be osseointegrated and placed at the center of the segments. Lateral occlusal bite force (300 N) was applied at a 25° inclination to the implants long axis. The maximum von Mises stresses in cortical and cancellous bones and implant-abutment complex were calculated. The von Mises stress values on the implants and the cancellous bone around the implants of the 70% bone-to-implant contact group were almost 3 times higher compared with the values of the 100% bone-to-implant contact group. For clinical reality, use of the 70% model for finite element analysis simulation of the posterior maxilla region better represents real alveolar bone and the increased stress and strain distributions evaluated on the cortical and cancellous bone around the dental implants.
Vasile Cojocaru
2016-12-01
Full Text Available Several methods can be used in the FEM studies to apply the loads on a plain bearing. The paper presents a comparative analysis of maximum stress obtained for three loading scenarios: resultant force applied on the shaft – bearing assembly, variable pressure with sinusoidal distribution applied on the bearing surface, variable pressure with parabolic distribution applied on the bearing surface.
Yang, Xue; Rong, Qi-guo; Yang, Ya-dong
2015-02-18
To compare influences of different retention attachments on stress among supporting structures. By 3-dimensional laser scanner and reverse engineering computer aided design (CAD) software, a basic partially edentulous digital model with mandibular premolar and molar missing was established. Implant attachment and removable partial dentures (RPD) were added into the basic model to build three kinds of models: RPD only, RPD + implant + Locator attachment, and RPD + implant + Magfit attachment. Vertical and inclined loads were put on artificial teeth unilaterally. By means of 3-dimensional finite element analysis, the stress distribution and displacement of the main supportive structures were compared. A complete 3-dimensional finite element model was established, which contained tooth structure, and periodontal structures. The displacement of the denture was smaller in Locator (9.38 μm vertically, 45.48 μm obliquely) and Magfit models (9.54 μm vertically, 39.45 μm obliquely) compared with non-implant RPD model (95.27 μm vertically, 155.70 μm obliquely). Compared with the two different attachments, cortical bone stress value was higher in Locator model (Locator model 10.850 MPa vertically, 43.760 MPa obliquely; Magfit model 7.100 MPa vertically, 19.260 MPa obliquely).The stress value of abutment periodontal ligamentin Magfit model (0.420 MPa vertically) was lower than that in Locator model (0.520 MPa vertically). The existence of implant could reduce maximum von Mises value of each supportive structure when Kennedy I partially edentulous mandible was restored. Comparing the structure of Magfit and Locator attachment, the contact of Magfit attachment was rigid, while Locator was resilient. Locator attachment could improve stability of the denture dramatically. Locator had stronger effect on defending horizontal movement of the denture.
Meng-meng LU; Kang-he XIE; Chuan-xun LI; Kun WANG
2011-01-01
In actual engineering practice, the stress increment within a composite foundation caused by external loads may varysimultaneously with depth and time. In addition, column installation always leads to a decay of soil permeability towards the column. However, almost none of the consolidation theories for composite foundation comprehensively consider these factors until now. For this reason, a stress increment due to external loads changing simultaneously with time and depth was incorporated into the analysis, and three possible variation patterns of soil's horizontal permeability coefficient were considered to account for the detrimental influence of column installation. These three patterns included a constant distribution pattern (Pattern Ⅰ), a linear distribution pattern (Pattern Ⅱ), and a parabolic distribution pattern (Pattern Ⅲ). Solutions were obtained for the average excess pore water pressures and the average degree of consolidation respectively. Then several special cases were discussed in detail based on the general solution obtained. Finally, comparisons were made, and the results show that the present solution is the most general rigorous solution in the literature, and it can be broken down into a number of previous solutions. The consolidation rate is accelerated with the increase in the value of the top to the bottom stress ratio. The consolidation rate calculated by the solution for Pattern Ⅰ is less than that for Pattern Ⅱ, which in rurn is less than that for Pattern Ⅲ.
弯矩作用下筒仓孔口应力集中的计算%Stress concentration calculation of silo wall opening subjected to out-plane moment
马瑞挺
2012-01-01
为了了解筒仓洞口在弯矩作用下的应力分布，利用平板理论结合复变函数和保角映射技术，研究了筒仓开孔的孔口应力集中问题，通过将仓壁孔口的应力计算简化成平面问题，求出了孔口的应力，得出在平面外弯矩作用下，弯曲应力集中主要发生在和弯矩作用方向垂直的边．%In order to understand stress distribution of silo wall opening under moment, using plate theory, complex variable function and conformal mapping technique, the problem of orifice stress concentration in silo opening is studied through silo wall opening is simplified as plane problem in stress calculation, and then, the stress concentration of opening is obtained. Moreover, when it is subjected to out-plane moment, bending stress concentration mainly exists in perpendicular side of bending direction.
Yu-Ching Shih
2014-04-01
Full Text Available Micro-cantilever sensors are widely used to detect biomolecules, chemical gases, and ionic species. However, the theoretical descriptions and predictive modeling of these devices are not well developed, and lag behind advances in fabrication and applications. In this paper, we present a novel multiscale simulation framework for nanomechanical sensors. This framework, combining density functional theory (DFT calculations and finite element method (FEM analysis, is capable of analyzing molecular adsorption-induced deformation and stress fields in the sensors from the molecular scale to the device scale. Adsorption of alkanethiolate self-assembled monolayer (SAM on the Au(111 surface of the micro-cantilever sensor is studied in detail to demonstrate the applicability of this framework. DFT calculations are employed to investigate the molecular adsorption-induced surface stress upon the gold surface. The 3D shell elements with initial stresses obtained from the DFT calculations serve as SAM domains in the adsorption layer, while FEM is employed to analyze the deformation and stress of the sensor devices. We find that the micro-cantilever tip deflection has a linear relationship with the coverage of the SAM domains. With full coverage, the tip deflection decreases as the molecular chain length increases. The multiscale simulation framework provides a quantitative analysis of the displacement and stress fields, and can be used to predict the response of nanomechanical sensors subjected to complex molecular adsorption.
Spas, W. [Deutsche Montan Technologie GmbH, Bochum (Germany). Car Synergies Division
2001-07-01
There are sufficient Woehler curves for hoisting systems which describe the life of hoisting cables as a function of the operating conditions. They are based on calculable and measurable stress fractions. The upper limit for the maximum number of hoisting cycles is set by the Woehler curves from tensile swelling tests on single wires. The difference between the scatter of these two types of stress/load cycle curves is the sum of all stress components calculable by non-conventional methods. The current project attempted a quantification of these unknown stress components. If all stress fractions are known, accurate service life calculations will be possible. [German] Wie bereits zuvor beschrieben liegen Woehlerkurven fuer Foerderanlagen, auf denen die Foerderseile ihre Ablegereife aufgrund von Ermuedungsdrahtbruechen erreichen, in ausreichender Zahl vor. Diese Woehlerkurven, die die Lebensdauer von Foerderseilen als Funktion der Betriebsbedingungen der Anlagen darstellen, basieren auf zur Zeit berechen- und messbaren Spannungsanteilen. Eine Obergrenze fuer die maximal erreichbaren Foerderzyklen eines Seiles bilden jedoch die Woehlerkurven aus Zugschwellversuchen an Einzeldraehten. Die Differenz zwischen den Streubereichen dieser beiden Typen von Spannungs-Lastzyklen-Kurven stellt die Summe aller nicht mit konventionellen Methoden berechenbarer Spannungsanteile dar. Ziel dieses Untersuchungsvorhabens ist es, diese unbekannten Spannungsanteile zu quantifizieren. Bei Kenntnis aller Spannungsanteile, die waehrend eines Treibvorganges in einem Foerderseil auftreten koennen, ist es moeglich, eine Lebensdauerberechnung von Foerderseilen durchzufuehren, die alle real auftretenden Betriebsbeanspruchungen beruecksichtigt und somit eine Berechnung der erreichbaren Zyklenzahlen bzw. Betriebszeit von Seilen im Voraus ermoeglicht. (orig.)
M. Cibiş (Merih); W.V. Potters (Wouter); F.J.H. Gijsen (Frank); H. Marquering (Henk); E. VanBavel (Ed); A.F.W. van der Steen (Ton); A.J. Nederveen (Aart); J.J. Wentzel (Jolanda)
2014-01-01
textabstractWall shear stress (WSS) is involved in many pathophysiological processes related to cardiovascular diseases, and knowledge of WSS may provide vital information on disease progression. WSS is generally quantified with computational fluid dynamics (CFD), but can also be calculated using
Stress distribution at diffusion-bonded interface of Fe3Al with Cr18-Ni8 steel
Wang Juan; Li Yajiang; Xia Chunzhi
2008-01-01
Fe3Al and Cr18-Ni8 steel were bonded in vacuum and an interface was formed between Fe3Al and Crl8-Ni8 steel. Stress distribution at the diffusion-bonded interface was researched by numerical simulation and finite element method (FEM).The results indicated that the peak stress appeared at the interface near Crl8-Ni8 steel side. This is the key factor to induce crack at this position. With the enhancement of heating temperature, the peak stress at the bonded interface increases. When the temperature is 1 100 ℃ ,the peak stress is up to 65.9 Mpa, which is bigger than that at 1 000℃ by 9.4%.In addition, the peak stress becomes bigger with the increase of the thickness of base metal from 1 mm to 8 ram. While the thickness is more than 8 mm, the peak stress varies slightly with the change of the thickness.
Gerard, B.; Ulm, F. [Service Ensembles de Production, Departement Surveillance Diagnostic Maintenance, Direction des Etudes et Recherches, Electricite de France (EDF), 92 - Clamart (France)
1997-11-01
This document presents an analysis of the different calculation methods for pre-stressed concrete structure which can be performed by using finite element methods. Two methods of calculating the pre-stressing of concrete structures with finite elements have been determined. The equivalent method which consists of replacing the action of pre-stressing the concrete by equivalent forces. These method is well suited to dimensioning and studying the overall stability of a structure. It is not an easy matter to take into account the coupled or time-varying phenomena. This approach ignores the evolution of the interaction between the pre-stressing and the concrete. The explicit method which consists of including the mechanical resolution of the pre-stressed cables in that of a concrete structure. Not only does this allow a local study of the pre-stressed to be made, it also allows the coupling which developed over time to be determined, e.g. slip, deferred deformation and coupling between the steel and concrete behaviours. This method enables non-linear phenomena with varying degrees of complexity, such as fracture or yielding of the steels, drying out of the concrete, creep, etc to be described. The two methods are complementary. This document presents the mathematical and computer developments relating to each of this method. In the case of the explicit method, certain of the Code-Aster functions already make it possible to meet several EDF application requirements. Several couplings can be taken into account, such as thermomechanical, shrinkage in drying, creep, relaxation and injection of the cables. Three immediate developments of Code-Aster are proposed for the following applications: - a procedure for calculating the pre-stress losses along the pre-stressing cables; - a command to allocate these forces in the form of an initial force field in the bar elements associated with the cables; - a procedure for linking elements whose nodes do not coincide with each other
Georgia eBalsevich
2015-01-01
Full Text Available Major depression is one of the most common psychiatric disorders, severely affecting the quality of life of millions of people worldwide. Despite the availability of several classes of antidepressants, treatment efficacy is still very variable and many patients do not respond to the treatment. Clomipramine (CMI, a classical and widely used antidepressant, shows widespread interindividual variability of efficacy, while the environmental factors contributing to such variability remain unclear. We investigated whether chronic stress modulates the bio-distribution of CMI, and as a result the behavioral response to CMI treatment in a mouse model of chronic social defeat stress. Our results show that stress exposure increased anxiety-like and depressive-like behaviors and altered the stress response. Chronic defeat stress furthermore significantly altered CMI bio-distribution. Interestingly, CMI bio-distribution highly correlated with anxiety-like and depressive-like behaviors only under basal conditions. Taken together, we provide first evidence demonstrating that chronic stress exposure modulates CMI bio-distribution and behavioral responses. This may contribute to CMI’s broad interindividual variability, and is especially relevant in clinical practice.
Mohammad Javad Moghaddas
2013-01-01
Full Text Available Introduction: The aim of this study was to evaluate the effect of proximal contour of class II composite restorations placed with straight or contoured matrix band using composite resins with different modulus of elasticity on stress distribution by finite element method. Methods: In order to evaluate the stress distribution of class II composite restorations using finite element method, upper right first molar and second premolar were modeled. Proximal boxes were designed and restored with universal Z250 and packable P60 composite resins (3M ESPE using two matrix systems: flat Tofflemire matrix and precurved sectional matrix. Finally models were evaluated under loads of 200 and 400 Newton at 90 degrees angle and the results were graphically illustrated in the form of Von Misses stresses. Results: In general the stress obtained under 400 Newton load was significantly greater than the stress of models under 200 Newton load. Von Misses stress distribution pattern of two different Z250 and P60 composites were very similar in all modes of loading and proximal contour. In all analyzed models there was a significant difference between models restored with Tofflemire matrix with flat contour and models restored with sectional matrix with curved contour. This difference was greater in first molar than second premolar. Conclusion: Use of a contoured matrix band results in less stress in class II composite resin restorations.
Hossein Abachizadeh
2012-09-01
Full Text Available Introduction: The aim of this study was to evaluate the effect of proximal contour of class II composite restorations placed with straight or contoured matrix band using composite resins with different modulus of elasticity on stress distribution by finite element method. Methods: In order to evaluate the stress distribution of class II composite restorations using finite element method, upper right first molar and second premolar were modeled. Proximal boxes were designed and restored with universal Z250 and packable P60 composite resins (3M ESPE using two matrix systems: flat Tofflemire matrix and precurved sectional matrix. Finally models were evaluated under loads of 200 and 400 Newton at 90 degrees angle and the results were graphically illustrated in the form of Von Misses stresses. Results: In general the stress obtained under 400 Newton load was significantly greater than the stress of models under 200 Newton load. Von Misses stress distribution pattern of two different Z250 and P60 composites were very similar in all modes of loading and proximal contour. In all analyzed models there was a significant difference between models restored with Tofflemire matrix with flat contour and models restored with sectional matrix with curved contour. This difference was greater in first molar than second premolar. Conclusion: Use of a contoured matrix band results in less stress in class II composite resin restorations.
WANG En-yuan; LIU Xiao-fei; ZHAO En-lai; LIU Zhen-tang
2008-01-01
The incidence of dynamic coal or rock disasters is closely related to the distribution of stress in the surrounding rock. Our experiments show that electromagnetic radiation (EMR) signals are related to the state of stress of a coal body. The higher the stress, the more intense the deformation and fractures of a coal body and the stronger the EMR signals. EMR signals reflect the degrees of concentrated stress of a coal body and danger of a rock burst. We selected EMR intensity as the test index of the No.237 gob-surrounded coal face in the Nanshan coal mine. We tested the EMR characteristics of the stress distribution on the strike, on the incline and in the interior of the coal body. The EMR rule of rock bursts, caused by sudden changes in stress, is analyzed. Our re-search shows that EMR technology can be not only used to test qualitatively the stress distribution of the surrounding rock, but also to predict a possible occurrence of rock burst. Based on this, effective distress measures are used to eliminate or at least weaken the incidence of rock bursts. We hope that safety in coalmines will be enhanced.
Parsons, T.; Ji, C.; Kirby, E.
2008-12-01
On the 12th of May, 2008 a devastating Ms=8.0 earthquake struck the eastern edge of the Tibetan Plateau, collapsing buildings and killing thousands in major cities aligned along the western Sichuan basin in China. After a high-magnitude earthquake like the 12 May event, rearrangement of stresses in the crust commonly causes subsequent damaging earthquakes. The Sichuan basin and surroundings are crossed by major active strike-slip and thrust faults. By 72 hours after the earthquake, coseismic stress changes were calculated on models of those faults, with many showing significant stress increases. Rapid mapping of stress changes was intended to locate fault sections with relatively higher odds of producing the largest aftershocks and to enable prospective testing of the static-stress triggering hypothesis. A recent prospective test of the method was conducted by McCloskey et al. [2005] after the great 2004 Sumatra earthquake, and was validated by a M=8.7 shock that struck three months later in a region calculated to have been stressed by the mainshock. Our test begins at the time peer review was completed, 38 days after the mainshock on 19 June, 2008. Thus aftershocks occurring between that time and the present can be used for prospective testing. As of this writing, in our test region magnitude greater than 4.0 aftershocks have been largely confined to the mainshock rupture zone, with virtually no activity on Sichuan basin faults with calculated stress increases. Examination of magnitude-frequency behavior of the aftershocks suggests either a corner magnitude at about magnitude 6, or a deficiency in the magnitude greater than 6 range. This experiment is ongoing, and time will tell if the Coulomb model is confirmed in the Sichuan region; our conclusion at present is that there has been no validation, and that use of a generalized aftershock forecast model would have been sufficient.
Guo, Xiaoya; Zhu, Jian; Maehara, Akiko; Monoly, David; Samady, Habib; Wang, Liang; Billiar, Kristen L; Zheng, Jie; Yang, Chun; Mintz, Gary S; Giddens, Don P; Tang, Dalin
2017-02-01
Computational models have been used to calculate plaque stress and strain for plaque progression and rupture investigations. An intravascular ultrasound (IVUS)-based modeling approach is proposed to quantify in vivo vessel material properties for more accurate stress/strain calculations. In vivo Cine IVUS and VH-IVUS coronary plaque data were acquired from one patient with informed consent obtained. Cine IVUS data and 3D thin-slice models with axial stretch were used to determine patient-specific vessel material properties. Twenty full 3D fluid-structure interaction models with ex vivo and in vivo material properties and various axial and circumferential shrink combinations were constructed to investigate the material stiffness impact on stress/strain calculations. The approximate circumferential Young's modulus over stretch ratio interval [1.0, 1.1] for an ex vivo human plaque sample and two slices (S6 and S18) from our IVUS data were 1631, 641, and 346 kPa, respectively. Average lumen stress/strain values from models using ex vivo, S6 and S18 materials with 5 % axial shrink and proper circumferential shrink were 72.76, 81.37, 101.84 kPa and 0.0668, 0.1046, and 0.1489, respectively. The average cap strain values from S18 material models were 150-180 % higher than those from the ex vivo material models. The corresponding percentages for the average cap stress values were 50-75 %. Dropping axial and circumferential shrink consideration led to stress and strain over-estimations. In vivo vessel material properties may be considerably softer than those from ex vivo data. Material stiffness variations may cause 50-75 % stress and 150-180 % strain variations.
Reda Sonia M.
2006-01-01
Full Text Available Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both.
Precision irrigation management in wine grape production is hindered by the lack of a reliable method to easily quantify and monitor vine water status. Mild to moderate water stress is desirable in wine grape for controlling vine vigor and optimizing fruit yield and quality. A crop water stress ind...
Guyot, Y; Luyten, F P; Schrooten, J; Papantoniou, I; Geris, L
2015-12-01
Bone tissue engineering strategies use flow through perfusion bioreactors to apply mechanical stimuli to cells seeded on porous scaffolds. Cells grow on the scaffold surface but also by bridging the scaffold pores leading a fully filled scaffold following the scaffold's geometric characteristics. Current computational fluid dynamic approaches for tissue engineering bioreactor systems have been mostly carried out for empty scaffolds. The effect of 3D cell growth and extracellular matrix formation (termed in this study as neotissue growth), on its surrounding fluid flow field is a challenge yet to be tackled. In this work a combined approach was followed linking curvature driven cell growth to fluid dynamics modeling. The level-set method (LSM) was employed to capture neotissue growth driven by curvature, while the Stokes and Darcy equations, combined in the Brinkman equation, provided information regarding the distribution of the shear stress profile at the neotissue/medium interface and within the neotissue itself during growth. The neotissue was assumed to be micro-porous allowing flow through its structure while at the same time allowing the simulation of complete scaffold filling without numerical convergence issues. The results show a significant difference in the amplitude of shear stress for cells located within the micro-porous neo-tissue or at the neotissue/medium interface, demonstrating the importance of taking along the neotissue in the calculation of the mechanical stimulation of cells during culture.The presented computational framework is used on different scaffold pore geometries demonstrating its potential to be used a design as tool for scaffold architecture taking into account the growing neotissue. Biotechnol. Bioeng. 2015;112: 2591-2600. © 2015 Wiley Periodicals, Inc.
X-ray diffraction residual stress calculation on textured La 2/3Sr 1/3MnO 3 thin film
Meda, Lamartine; Dahmen, Klaus H.; Hayek, Saleh; Garmestani, Hamid
2004-03-01
Residual stresses and texture in La2/3Sr1/3MnO3 (LSMO) thin films have been investigated. The films were deposited on (1 0 0) LaAlO3 (LAO) and (1 0 0) MgO single crystals by liquid delivery-metal organic chemical vapor deposition (LD-MOCVD). X-ray diffraction (XRD) pole figures showed (0 0 1)LSMO//(0 0 1)LAO and (0 0 1)LSMO//(0 0 1)MgO preferred orientation. Residual stresses were calculated using a modified sin2 ψ method, crystallite group method (CGM), assuming a biaxial stress state. Compressive stresses on the order of 224 and 1150 MPa were obtained for LSMO films deposited on LAO (LSMO/LAO) and MgO (LSMO/MgO), respectively.
Przybycin, Anna M.; Scheck-Wenderoth, Magdalena; Schneider, Michael
2014-05-01
The North Alpine Foreland Basin is situated in the northern front of the European Alps and extends over parts of France, Switzerland, Germany and Austria. It formed as a wedge shaped depression since the Tertiary in consequence of the Euro - Adriatic continental collision and the Alpine orogeny. The basin is filled with clastic sediments, the Molasse, originating from erosional processes of the Alps and underlain by Mesozoic sedimentary successions and a Paleozoic crystalline crust. For our study we have focused on the German part of the basin. To investigate the deep structure, the isostatic state and the load distribution of this region we have constructed a 3D structural model of the basin and the Alpine area using available depth and thickness maps, regional scale 3D structural models as well as seismic and well data for the sedimentary part. The crust (from the top Paleozoic down to the Moho (Grad et al. 2008)) has been considered as two-parted with a lighter upper crust and a denser lower crust; the partition has been calculated following the approach of isostatic equilibrium of Pratt (1855). By implementing a seismic Lithosphere-Asthenosphere-Boundary (LAB) (Tesauro 2009) the crustal scale model has been extended to the lithospheric-scale. The layer geometry and the assigned bulk densities of this starting model have been constrained by means of 3D gravity modelling (BGI, 2012). Afterwards the 3D load distribution has been calculated using a 3D finite element method. Our results show that the North Alpine Foreland Basin is not isostatically balanced and that the configuration of the crystalline crust strongly controls the gravity field in this area. Furthermore, our results show that the basin area is influenced by varying lateral load differences down to a depth of more than 150 km what allows a first order statement of the required compensating horizontal stress needed to prevent gravitational collapse of the system. BGI (2012). The International
On Shear Stress Distributions for Flow in Smooth or Partially Rough Annuli
Kjellstroem, B.; Hedberg, S.
1966-08-15
It is commonly assumed that for turbulent flow in annuli the radii of zero shear and maximum velocity are coincident. By inspection of the differential equations for such flow and by an integral analysis it is shown that this is not necessarily true. To check whether important differences could occur, experiments were made in which velocity and shear stress distributions were measured in one smooth and two partially rough annuli. The results show no difference in the radii for the smooth annulus, but for the partially rough annuli there was a small but significant difference. This difference explains the breakdown of Hall's transformation theory reported by other investigators. The error introduced by use of Hall's theory is however small, of the order of 10 % or less.
Centrella, Stephen; Vrijmoed, Johannes C.; Putnis, Andrew; Austrheim, Håkon
2017-04-01
The importance of heterogeneous stress and pressure distribution within a rock has been established over the last decades (see review in Tajčmanová et al., 2015). During a hydration reaction, depending on whether the system is open to mass transfer, the volume changes of the reaction may be accommodated by removing material into the fluid phase that leaves the system (Centrella et al., 2015; Centrella et al., 2016). The magnitudes and the spatial distribution of stress and pressure that evolve during such processes is largely unknown. We present here a natural example where a granulite is hydrated at amphibolite facies conditions from the Bergen Arcs in Norway. Granulitic garnet is associated with kyanite and quartz on one side, and amphibole-biotite on the other side. The first couple replaces the plagioclase of the granulite matrix whereas the second replaces the garnet. We use electron probe microanalysis (EPMA) and X-ray mapping to investigate the spatial and possible temporal relationships between these two parageneses. Gresens' analysis has been used to determine the mass balance and the local volume changes associated with the two reactions. The reaction to kyanite+quartz induces a loss in volume compared to the original plagioclase whereas the second reaction amphibole+biotite gains volume compared to the original garnet. The specific mass evolution associated with both reactions suggests a local mass balance probably associated with a single hydration event. Using the methodology of Vrijmoed & Podladchikov (2015) we test whether the microstructure may be partly related to the local stress heterogeneity around the garnet inclusion. We evaluate the phase assemblage and distribution at chemical equilibrium under a given input pressure field that can be computed with the Thermolab software. By varying the input pressure field using the Finite Element Method and comparing the resulting equilibrium assemblage to the real data an estimate of the local stress
3D finite element analysis to detect stress distribution: spiral family implants.
Danza, Matteo; Zollino, Ilaria; Paracchini, Luigi; Riccardo, Guidi; Fanali, Stefano; Carinci, Francesco
2009-12-01
Spiral family implants are a root-form fixtures with increasing thickness of tread. This characteristic gives a self-tapping and self-condensing bone properties to implants. To study spiral family implant inserted in different bone quality and connected with abutments of different angulations a Finite Element Analysis (FEA) was performed. Once drawn the systems that were object of the study by CAD (Computer Aided Design), the FEA discretized solids composing the system in many infinitesimal little elementary solids defined finite elements. This lead to a mesh formation where the single finite elements were connected among them by nodes. For the 3 units bone-implant-abutments several thousand of tetrahedral elements having 10 parabolic nodes were employed. The biomechanical behaviour of 4.2 mm × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutment subjected to static loads, in contact with high and poor bone quality was evaluated by FEA. A double system was analyzed: a) FY strength acting along Y axis and having 200 N intensity; b) FY and FZ couple of strengths applied along Y and Z directions and having respectively 200N and 140N intensity. The materials were considered as homogeneous, linear and isotropic. Then the FEA simulation was performed hypothesizing a linearity between loads and deformations. The lowest stress value was found in the system composed by implants and straight abutments loaded with a vertical strength, while the highest stress value were found in implants and 15° angulated abutment loaded with a angulated strength. In addition, the lower is the bone quality (i.e. D4) the higher is the distribution of the stress within the bone. Spiral family implants can be used successfully in low bone quality but a straight force is recommended.
无
2011-01-01
High geo-stress and its engineering problems have severely affected the development of civil infrastructures in western China. The problems include high rock slope instabilities,rock burst,gas explosion and large-scale soft rock deformation in deep tunnels.This paper investigates the distribution of the high geo-stresses and the models of the stress concentration areas in the eastern margin of Qinghai-Tibet plateau so that a solid foundation can be formed to address the problems.The investigation is based on a comprehensive analysis of the previous research data of the eastern margin and uses remote sensing techniques,geophysics,geochemistry,and large scale geological surveying methods.The investigation has found that some special tectonic zones have high geo-stresses.The high geo-stresses are located at(1) the convergent boundary areas between two fault blocks with large strength differences,(2) the tectonic necks in front of active fault blocks,and(3) the intersection and/or termination areas of faults within the fault blocks.An example for(1) is the north Qilian high geo-stress area.Another example for(2) is the Minshan high geo-stress area in the northwest Sichuan.Furthermore,the investigation has summarized six basic models to characterize the high geo-stress concentration areas.The first one is the convergent stress concentration model at the boundary of two fault blocks.The other five stress concentration modes are oblique fissures or intersecting areas,areas without lower velocity layer in the crust,areas of compression induced tensile cracking,tectonic wedge areas,and tectonic neck areas,respectively.
Hansen, Lars; Wallis, David; Kempton, Imogen; Lebensohn, Ricardo; Wilkinson, Angus
2017-04-01
During high-temperature deformation of rocks, stresses are predicted to be distributed heterogeneously throughout the constituent grains. After unloading, much of this stress is potentially retained in the aggregate as residual stress, a phenomenon that may have large-scale geodynamic implications. After large stress changes in the solid Earth (e.g., glacial unloading or post-seismic relaxation), residual stresses can affect the immediate mechanical response of the rocks. Furthermore, examination of residual stresses in naturally deformed rocks additionally presents an opportunity to learn about ancient deformation events. These residual stresses arise from the anisotropic nature of the mechanical properties of minerals and from the heterogeneous substructures that form within grains (e.g., dislocation arrays and subgrain boundaries). This heterogeneity is therefore related to mechanical interactions on short (e.g., between individual dislocations), intermediate (e.g., between groups of dislocations), and long (e.g., between grains of differing orientation) spatial scales. We examine residual stresses in upper mantle analogues with three different methods. First, stress-dip tests were conducted on olivine single crystals at temperatures greater than 1250°C in a new uniaxial deformation apparatus with a piezoelectric actuator. These experiments reveal that the average residual stresses stored in deformed single crystals can be on the order of 50% of the applied differential stress. However, the magnitude of residual stress is likely a function of crystal orientation during deformation. Second, high angular-resolution electron backscatter diffraction (HR-EBSD) allows the residual stresses in deformed single crystals and polycrystals to be mapped with <1 micron spatial resolution. HR-EBSD mapping reveals stress heterogeneities on the order of differential stresses applied during deformation. Stresses averaged over each map are in reasonable agreement with the outcome
Changes of DHN1 expression and subcellular distribution in A. delicisoa cells under osmotic stress
QIU; Quansheng; (邱全胜); WANG; Zezhou(王泽宙); CAI; Qigui(蔡起贵); JIANG; Rongxi(姜荣锡)
2002-01-01
The changes of DHN1 expression and subcellular distribution in A. delicisoa cells under osmotic stress were studied by using GFP as a reporter molecule. Through creating the Xba I and BamH I restriction sites at the ends of dhn1 by PCR, the expression vector for the fusion protein DHN1-mGFP4 was constructed by cloning dhn1 into plasmid pBIN-35SmGFP4. Then the DHN1-mGFP4 expression vector was transformed into A. delicisoa suspension cells by microprojectile bombardment method. Bright green fluorescence of GFP which shows the high-level expression of DHN1-mGFP4 was visualized after culture for 10 h. However, the green fluorescence was only located within the nucleus. By increasing the culture medium osmotic potential, the green fluorescence was visualized in the cytoplasm (mainly around the plasma membranes). The generation of GFP fluorescence in the cytoplasm was also promoted by increasing the medium osmotic potential. Moreover, GFP green fluorescence was abolished by protein synthesis inhibitor dicyclohexylcarbodiimid, indicating that the cytoplasmic DHN1 was newly synthesized under osmotic stress. Furthermore, ABA promoted the presence of green fluorescence in the cytoplasm, and the GFP fluorescence was visualized within a shorter time under a higher osmotic potential.
Closed form stress distribution in 2D elasticity for all boundary conditions
无
2007-01-01
This paper applies a Hamiltonian method to study analytically the stress distributions of orthotropic two-dimensional elasticity in (x, z) plane for arbitrary boundary conditions without beam assumptions. It is a method of separable variables for partial differential equations using displacements and their conjugate stresses as unknowns. Since coordinates (x, z) can not be easily separated, an alternative symplectic expansion is used.Similar to the Hamiltonian formulation in classical dynamics, we treat the x coordinate as time variable so that z becomes the only independent coordinate in the Hamiltonian matrix differential operator. The exponential of the Hamiltonian matrix is symplectic. There are homogenous solutions with constants to be determined by the boundary conditions and particular integrals satisfying the loading conditions. The homogenous solutions consist of the eigen-solutions of the derogatory zero eigenvalues (zero eigen-solutions)and that of the well-behaved nonzero eigenvalues (nonzero eigen-solutions). The Jordan chains at zero eigenvalues give the classical Saint-Venant solutions associated with averaged global behaviors such as rigid-body translation, rigid-body rotation or bending. On the other hand, the nonzero eigen-solutions describe the exponentially decaying localized solutions usually ignored by Saint-Venant's principle. Completed numerical examples are newly given to compare with established results.
Distributed stress and temperature sensing based on Rayleigh scattering of low-coherence light
Gorshkov, B. G.; Taranov, M. A.; E Alekseev, A.
2017-08-01
A novel arrangement for fiber optic distributed stress and temperature sensing based on the Rayleigh scattering spectra correlation method is proposed. The principal feature of the arrangement is usage of low-coherence light in probe pulses, which ensures a wide dynamic range for measurements at moderate sensitivity. Such a characteristic corresponds to performance specifications for infrastructure monitoring systems. A theory of optical time domain reflectometry for arbitrary coherence light is developed describing the contrast in reflectograms and Rayleigh scattering spectra properties. The experimental setup uses a wideband source of light pulses and an electronically controlled micro-electro-mechanical system optical filter for wavelength tuning. Temperature change experiments show root mean square (RMS) noise levels of 0.13 °C, 0.24 °C and 0.3 °C for fiber lengths of 2 km, 8 km and 25 km, respectively, at a spatial resolution of about 1 m (for 10 min data collection). As much as 2000 µstrain dynamic range is demonstrated in the stress measurement experiment while the noise level (RMS error) is estimated to be 2 µstrain. Our experimental results are compared with the theory and a satisfactory match is demonstrated.
Uptake and Distribution of Aluminum in Root Apices of Two Rice Varieties under Aluminum Stress
MIFTAHUDIN
2007-09-01
Full Text Available Aluminum (Al toxicity is the major limiting factor of plant growth and production in acid soils. The target of Al toxicity is the root tip, which affects mainly on root growth inhibition. The aim of this research was to study the uptake and distribution of Al in root apices of two rice varieties IR64 (Al-sensitive and Krowal (Al-tolerant, which were grown on nutrient solution containing 0, 15, 30, 45, and 60 ppm of Al. The root growth was significantly inhibited in both rice varieties at as low as 15 ppm Al concentration. The adventive roots of both varieties showed stunted growth in respons to Al stress. There was no difference in root growth inhibition between both rice varieties as well as among Al concentrations. Al uptake on root apices was qualitatively and quantitatively analyzed. Histochemical staining of roots using hematoxylin showed dark purple color on 1 mm region of Al-treated root apices. Rice var. IR 64 tended to take up more Al in root tip than Krowal did. However, there was no statistically significant difference (p = 0.176 in root Al content of both varieties in response to different concentration and period of Al treatments. Al distribution in root apices was found in the epidermal and subepidermal region in both rice varieties. Based on those results, rice var. Krowal that was previously grouped as Al-tolerant variety has similar root growth and physiological response to Al stress as compared to Al-sensitive variety IR64.
Effect of impurities and stress on the damage distributions of rapidly grown KDP crystals
Runkel, M.; Tan, M.; De Yoreo, J.; Zaitseva, N.
1997-12-20
Development of high damage threshold, 50 cm, rapidly grown KF*P frequency triplers for operation of the National Ignition Facility (NIF) in the 14 J/cm2, 351 nm, 3 ns regime requires a thorough understanding of how the crystal growth parameters and technologies affect laser induced damage. Of particular importance is determining the effect of ionic impurities (e.g. Cr3+, Fe3+, Al3+) which may be introduced in widely varying concentrations via starting salts. In addition, organic particulates can contaminate the solution as leachants from growth platforms or via mechanical ablation. Mechanical stresses in the crystals may also play a strong role in the laser-induced damage distribution (LIDD), particularly in the cases of large boules where hydrodynamic forces in the growth tank may be quite high. WE have developed a dedicated, automated damage test system with diagnostic capabilities specifically designed for measured time resolved bulk damage onset and evolution. The data obtained make it possible to construct characteristic damage threshold distributions for each sample. Test results obtained for a variety of KDP samples grown from high purity starting salts and individually doped with Lucite and Teflon, iron, chromium, and aluminium show that the LIDD drops with increasing contamination content. The results also show that solution filtration leads to increased damage performance for undoped crystals but is not solely responsibility for producing the high LIDDs required by the NIF. The highest LIDD measured on a rapidly grown sample indicate that it is possible to produce high damage threshold material using ultrahigh purity, recrystallized starting salts, continuous filtration and a platform designed to minimize internal stress during growth.
Sofronov, I.D.; Voronin, B.L.; Butnev, O.I. [VNIIEF (Russian Federation)] [and others
1997-12-31
The aim of the work performed is to develop a 3D parallel program for numerical calculation of gas dynamics problem with heat conductivity on distributed memory computational systems (CS), satisfying the condition of numerical result independence from the number of processors involved. Two basically different approaches to the structure of massive parallel computations have been developed. The first approach uses the 3D data matrix decomposition reconstructed at temporal cycle and is a development of parallelization algorithms for multiprocessor CS with shareable memory. The second approach is based on using a 3D data matrix decomposition not reconstructed during a temporal cycle. The program was developed on 8-processor CS MP-3 made in VNIIEF and was adapted to a massive parallel CS Meiko-2 in LLNL by joint efforts of VNIIEF and LLNL staffs. A large number of numerical experiments has been carried out with different number of processors up to 256 and the efficiency of parallelization has been evaluated in dependence on processor number and their parameters.
Emamieh M. Emamieh S
2003-07-01
Full Text Available Since three decade ago, the application of the concept of finite element analysis (EEA have received a keen interest among dental investigators. In practice the FEA provides detailed stress information regarding to a non-homogenious body such as craniofocal skeletal growth, tooth post ceramo-metal crowns and etc. The aim of this study was the determination of the influence of stress distribution at the cement interface of metal ceramic restoration-dentin."nMaterials and Methods: An idealized metal-ceramic crown model was developed. The model was divided into very small segments. Various loading conditions was applied to the model. A super sap software was used for analyzing the stress distribution."nResults & Conclusion: The results of this study suggest that the higher shear stress was developed in the cervical region by two dimensional methods."n"n"n"n"n
Straka, A. M.; Schijf, J.
2010-12-01
For proper calculation of distribution coefficients in metal sorption studies it is essential to fully separate dissolved from particulate metal. This is typically done via membrane filtration whereby the cutoff between dissolved and particulate fractions is somewhat arbitrarily set at 0.22 μm, dictated by available pore sizes. However, the pH-dependent formation of colloid-bound metal, able to bypass this procedure, can lead to analytical artifacts by adding an unknown and variable amount of particulate metal to the mechanically defined ‘dissolved’ pool, especially for organic substrates. We investigated this phenomenon in the context of yttrium and rare earth element (YREE) sorption on the marine macroalga Ulva lactuca (sea lettuce). U. lactuca is a suitable model for marine organic matter as it has a simple morphology, is ubiquitous throughout the world’s oceans, and readily sorbs a great variety of trace metals. Solutions containing all YREEs were equilibrated for 6-12 hours with dehydrated, powdered U. lactuca tissue over a wide pH range (3.0-8.5) at three ionic strengths (0.05, 0.5 and 5.0 M NaCl), after which aliquots were filtered through 0.22 μm membranes. The resulting filtrates were further separated into >30 kDa and >3 kDa colloidal fractions by sequential centrifugation in Amicon® ultrafiltration tubes. In all three experiments, YREEs are truly dissolved (30 kDa) at high pH with a sharp transition in between, suggesting pH-dependent YREE complexation with large organic ligands released by the algal cells. The fraction of small colloids (3-30 kDa) is generally negligible. The same sorption edge emerged for fresh algal tissue, implying that the release of organic ligands is not caused by pervasive cell rupture. In 0.5 and 5.0 M NaCl solutions the sorption edge is centered around pH 6-8, but in 0.05 M NaCl it occurs around pH 4-6 whence more than 80% of dissolved YREEs is actually bound to colloids at pH 6. On the other hand, the amount of
Cicero, R., E-mail: ciceror@unican.e [INESCO INGENIEROS S.L., Santander (Spain); Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain); Cicero, S. [Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain); Gorrochategui, I. [Centro Tecnologico de Componentes, Santander (Spain); Lacalle, R. [INESCO INGENIEROS S.L., Santander (Spain); Departamento de Ciencia e Ingenieria del Terreno y los Materiales, Universidad de Cantabria, Santander (Spain)
2010-01-15
Nuclear power plants are generally designed and inspected according to the ASME Code. This code indicates stress intensity (S{sub INT}) as the parameter to be used in the stress analysis of components. One of the particularities of S{sub INT} is that it always takes positive values, independently of the nature of the stress (tensile or compressive). This circumstance is relevant in the Fatigue Monitoring Systems used in nuclear power plants, due to the manner in which the different variable stresses are combined in order to obtain the final total stress range. This paper describes some situations derived from the application of the ASME Code, shows different ways of dealing with them and illustrates their influence on the evaluation of the fatigue usage factor through a case study.
Schumaker, Merit G.; Kennedy, Gregory; Thadhani, Naresh; Hankin, Markos; Stewart, Sarah T.; Borg, John P.
2017-01-01
Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, the researcher cannot easily observe particle interactions during a planar shock experiment. By using mesoscale simulations, we can unravel granular particle interactions. Unlike homogenous materials, the averaged Hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. From planar shock experiments for dry and water-saturated Oklahoma sand, we constructed simulations using Sandia National Laboratory code known as CTH and then compared these simulated results to the experimental results. This document compares and presents stress and temperature distributions from simulations, with a discussion on the difference between Hugoniot measurements and distribution peaks for dry and water-saturated sand.
Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel
Frih, Intissar; Montay, Guillaume; Adragna, Pierre-Antoine
2017-01-01
This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.
Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel
Frih, Intissar; Montay, Guillaume; Adragna, Pierre-Antoine
2017-03-01
This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.
吁新华; 谈至明
2012-01-01
The flexural stresses and tensile strains in asphalt pavement layers were studied. The hood face coefficient was proposed to characterize the influences of vertical compression stresses and shear stresses on the flexural stresses and tensile strains; the neutral axis moving coefficient was introduced to describe the differences between smooth contact and full friction contact in layers; the flexure torque distribution coefficient was put forward to show the influences of different bend curvature on asphalt layer and base. As to asphalt pavement with nonuniform modulus, the surface equivalent modulus was deduced by bending rigidity equivalent principle, and then the errors of the approximate calculation methods for the tensile strains at the bottom of surface and the flexural stresses at the bottom of base in asphalt pavement whit nonuniform modulus were discussed. Usually, the approximate calculation errors are less than 5%.%研究了各种条件下沥青路面结构弯拉应力和应变规律,引入曲面系数修正竖向压应力和剪应力的影响,引入面层弯曲中性轴下移量参数修正层间光滑与连续之间的差异,引入面层与基层弯矩分配系数反映面层、基层弯曲曲率不同的影响；对于模量不均匀面层,提出了弯曲刚度等效原则换算式；最后,讨论了各种条件下的沥青面层层底弯拉应变、半刚性或刚性基层层底弯拉应力的计算精度,其误差均不超过5％.
Modelling effects of tyre inflation pressure on the stress distribution near the soil-tyre interface
Schjønning, Per; Lamandé, Mathieu; Tøgersen, Frede A
2008-01-01
Several investigations have shown that the distribution of vertical stress in soil just below a loaded tyre is not uniform. The stress distribution and the size and form of the tyre-soil interface are decisive for the stress propagation in the soil profile. We measured the distribution of vertical...... stress in the contact area for two radial-ply agricultural trailer tyres (650/65R30.5 and 800/50R34) loaded with 60 kN. The study took place on a sandy soil at a water content slightly less than field capacity. We tested the effect of three different inflation pressures (50, 100 and 240 k......Pa) in a randomised block design with three replicates. The vertical stress was measured with load cells located in 0.1 m soil depth. The vertical stress data were used also for identifying the soil area in contact with the tyre, i.e. the tyre footprint. A model (named FRIDA) is proposed that describes the tyre...
Paillet, Frederick L.; Kim, Kunsoo
1987-06-01
The character and distribution of borehole breakouts in deeply buried basalts at the Hanford Site in south central Washington State are examined in light of stress indicator data and hydraulic-fracturing stress data by means of acoustic televiewer and acoustic waveform logging systems. A series of boreholes penetrating the Grande Ronde Basalt of the Columbia River Basalt Group were logged to examine the extent of breakouts at depths near 1000 m. Breakouts occur discontinuously throughout the interiors of most flows. In some boreholes the distribution of borehole wall breakouts closely correlates with the incidence of core disking. Differences in the distribution of breakouts and disking are attributed to differences in failure mechanisms. A thin interval of breakout-free basalt occurs near the upper and lower limits of flow interiors, with many intervals of breakouts terminating at the intersection of oblique fractures with the borehole. Hydraulic-fracturing stress measurement results obtained from four deep boreholes indicate anisotropic horizontal principal stresses, with maximum principal stress along an approximate north trending axis, consistent with the east trending orientation of breakouts. Acoustic waveform logs indicate that there is no measurable difference between the seismic properties of breakout-free flow tops and flow interiors. The highly coherent waveforms obtained in almost all flow interiors indicate that damage to the borehole wall associated with breakout formation remains confined to the thin annulus of stress concentration.
Saravana Kumar, Gurunathan; George, Subin Philip
2017-02-01
This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress-strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.
Measurement and study of the distributing law of in-situ stresses in rock mass at great depth
无
2006-01-01
To solve the technical cruxes of the conventional system in deep rock mass, an automatic testing system for hydraulic fracturing that includes a single tube for hydraulic loop, a pressure-relief valve, central-tubeless packers, and a multichannel real-time data acquisition system was used for in-situ stresses measurement at great depths (over 1000 m) in a coalfield in Juye of Northern China.The values and orientations of horizontal principal stresses were determined by the new system. The virgin stress field and its distributing law were decided by the linear regression from the logged 37 points in seven boreholes. Besides, the typical boreholes arranged in both the adjacent zone and far away zone of the faults were analyzed, respectively. The results show that a stress concentration phenomenon and a deflection in the orientation of the maximal horizontal stress exist in the adjacent zone of the faults, which further provides theoretical basis for design and optimization of mining.
Rezwanul Haque
2017-01-01
Full Text Available Neutron diffraction was used to describe the residual stress distributions in self-piercing riveted (SPR joints. The sheet material displayed a compressive residual stress near the joint, and the stress gradually became tensile in the sheet material far away from the joint. The stress in the rivet leg was lower in the thick joint of the softer steel sheet than in the thin joint of the harder steel sheet. This lower magnitude was attributed to the lower force gradient during the rivet flaring stage of the SPR process curve. This study shows how the residual stress results may be related to the physical occurrences that happened during joining, using the characteristics curve. The study also shows that neutron diffraction technique enabled a crack in the rivet tip to be detected which was not apparent from a cross-section.
Toda, Shinji
2008-10-01
The well-recorded aftershocks and well-determined source model of the Noto Hanto earthquake provide an excellent opportunity to examine earthquake triggering associated with a blind thrust event. The aftershock zone rapidly expanded into a `butterfly pattern' predicted by static Coulomb stress transfer associated with thrust faulting. We found that abundant aftershocks occurred where the static Coulomb stress increased by more than 0.5 bars, while few shocks occurred in the stress shadow calculated to extend northwest and southeast of the Noto Hanto rupture. To explore the three-dimensional distribution of the observed aftershocks and the calculated stress imparted by the mainshock, we further resolved Coulomb stress changes on the nodal planes of all aftershocks for which focal mechanisms are available. About 75% of the possible faults associated with the moderate-sized aftershocks were calculated to have been brought closer to failure by the mainshock, with the correlation best for low apparent fault friction. Our interpretation is that most of the aftershocks struck on the steeply dipping source fault and on a conjugate northwest-dipping reverse fault contiguous with the source fault. Since we found that the Coulomb hypothesis works well for the Noto Hanto sequence, we subsequently computed stress changes on the nearby active faults. Although the calculated stress changes were found to be negligible on the major faults south of the Noto Peninsula, several short active faults near the epicentral area were calculated to have been brought several bars closer to failure. Thus, the probability of strong shaking in and around the epicentral area may still be high due to the transfer of stress to the adjacent faults by a short blind thrust fault.
Liu, Dong'an; Peng, Linfa; Lai, Xinmin
In practice, the assembly error of the bipolar plate (BPP) in a PEM fuel cell stack is unavoidable based on the current assembly process. However its effect on the performance of the PEM fuel cell stack is not reported yet. In this study, a methodology based on FEA model, "least squares-support vector machine (LS-SVM)" simulation and statistical analysis is developed to investigate the effect of the assembly error of the BPP on the pressure distribution and stress failure of membrane electrode assembly (MEA). At first, a parameterized FEA model of a metallic BPP/MEA assembly is established. Then, the LS-SVM simulation process is conducted based on the FEA model, and datasets for the pressure distribution and Von Mises stress of MEA are obtained, respectively for each assembly error. At last, the effect of the assembly error is obtained by applying the statistical analysis to the LS-SVM results. A regression equation between the stress failure and the assembly error is also built, and the allowed maximum assembly error is calculated based on the equation. The methodology in this study is beneficial to understand the mechanism of the assembly error and can be applied to guide the assembly process for the PEM fuel cell stack.
Calculation of Growth Stress in SiO2 Scales Formed by Oxidation of SiC Fibers (PREPRINT)
2012-07-01
Kinetics of High - Purity Silicon Carbide from 800 to 1100 C. J. Am. Ceram. Soc. 79, 2897-2911 (1996). 45 Ogbuji, U. J. T. & Opila, E. J. A Comparison...to SiO2 generates very large growth stresses. Microstructural evidence for these stresses exists for crystalline scales on SiC fibers. High ...dislocation densities in crystalline SiO2 near the SiC -SiO2 interface suggest high shear stresses exist during growth of new crystalline scale.1 Axial cracks
Xiaojun JIN; Lixing HUO; Yufeng ZHANG; Bingren BAI; Xiaowei LI; Jun CAO
2004-01-01
On the basis of the thermal-elastic-plastic theory, a three-dimensional finite element numerical simulation is performed on the girth welded residual stresses of the duplex stainless steel pipe with ANSYS nonlinear finite element program for the first time. Three-dimensional FEM using mobile heat source for analysis transient temperature field and welding stress field in circumferential joint of pipes is founded. Distributions of axial and hoop residual stresses of the joint are investigated. The axial and the hoop residual stresses at the weld and weld vicinity on inner surface of pipes are tensile, and they are gradually transferred into compressive with the increase of the departure from the weld. The axial residual stresses at the weld and weld vicinity on outer surface of pipes is compressive while the hoop one is tensile. The distributions of residual stresses compared positive-circle with negative-circle show distinct symmetry. These results provide theoretical knowledge for the optimization of process and the control of welding residual stresses.
Bulaqi, Haddad Arabi; Mousavi Mashhadi, Mahmoud; Safari, Hamed; Samandari, Mohammad Mahdi; Geramipanah, Farideh
2015-06-01
Implants in posterior regions of the jaw require short dental implants with long crown heights, leading to increased crown-to-implant ratios and mechanical stress. This can lead to fracture and screw loosening. The purpose of this study was to investigate the dynamic nature and behavior of prosthetic components and preimplant bone and evaluate the effect of increased crown height space (CHS) and crown-to-implant ratio on stress concentrations under external oblique forces. The severely resorbed bone of a posterior mandible site was modeled with Mimics and Catia software. A second mandibular premolar tooth was modeled with CHS values of 8.8, 11.2, 13.6, and 16 mm. A Straumann implant (4.1×8 mm), a directly attached crown, and an abutment screw were modeled with geometric data and designed by using SolidWorks software. Abaqus software was used for the dynamic simulation of screw tightening and the application of an external load to the buccal cusp at a 75.8-degree angle with the occlusal plane. The distribution of screw load and member load at each step was compared, and the stress values were calculated within the dental implant complex and surrounding bone. During tightening, the magnitude and distribution of the preload and clamp load were uniform and equal at the cross section of all CHSs. Under an external load, the screw load decreased and member load increased. An increase in the CHS caused the corresponding distribution to become more nonuniform and increased the maximum compressive and tensile stresses in the preimplant bone. Additionally, the von Mises stress decreased at the abutment screw and increased at the abutment and fixture. Under nonaxial forces, increased CHS does not influence the decrease in screw load or increase in member load. However, it contributes to screw loosening and fatigue fracture by skewing the stress distribution to the transverse section of the implant. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry
Kostal, M.; Juricek, V.; Rypar, V.; Svadlenkova, M. [Research Center Rez Ltd., 250 68 Husinec-Rez 130 (Czech Republic); Cvachovec, F. [Univ. of Defence, Kounicova 65, 662 10 Brno (Czech Republic)
2011-07-01
The power density distribution in a reactor has significant influence on core structures and pressure vessel mechanical resistance, as well as on the physical characteristics of nuclear fuel. This quantity also has an effect on the leakage neutron and photon field. This issue has become of increasing importance, as it touches on actual questions of the VVER nuclear power plant life time extension. This paper shows the comparison of calculated and experimentally determined pin by pin power distributions. The calculation has been performed with deterministic and Monte Carlo approaches. This quantity is accompanied by the neutron and photon flux density calculation and measurements at different points of the light water zero-power (LR-0) research reactor mock-up core, reactor built-in component (core barrel), and reactor pressure vessel and model. The effect of the different data libraries used for calculation is discussed. (authors)