Effective stress coefficient for uniaxial strain condition
Alam, Mohammad Monzurul; Fabricius, Ida Lykke
2012-01-01
the reason for change in effective stress coefficient under stress. Our model suggests that change in effective stress coefficient will be higher at uniaxial stress condition than at hydrostatic condition. We derived equations from the original definition of Biot to estimate effective stress coefficient from...... one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...
Effective stress coefficient for uniaxial strain condition
Alam, M.M.; Fabricius, I.L.
2012-01-01
one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....
Effective stress coefficient for uniaxial strain condition
Alam, Mohammad Monzurul; Fabricius, Ida Lykke
2012-01-01
one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...
Effective stress coefficient for uniaxial strain condition
Alam, M.M.; Fabricius, I.L.
2012-01-01
The effective stress coefficient, introduced by Biot, is used for predicting effective stress or pore pressure in the subsurface. It is not a constant value. It is different for different types of sediment and it is stress dependent. We used a model, based on contact between the grains to describ...
Influence of effective stress coefficient on mechanical failure of chalk
Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Hjuler, M.L.
2012-01-01
and vice versa. However, as the effective stress working on the rock decreases with increased effective stress coefficient, the reduction of elastic region will have less effect on pore collapse strength if we consider the change in the effective stress coefficient. This finding will help estimate a more...
Influence of effective stress coefficient on mechanical failure of chalk
Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Hjuler, M.L.
2012-01-01
The Effective stress coefficient is a measure of how chalk grains are connected with each other. The stiffness of chalk may decrease if the amount of contact cements between the grains decreases, which may lead to an increase of the effective stress coefficient. We performed CO2 injection in chal...
Static and dynamic effective stress coefficient of chalk
Alam, M. Monzurul; Fabricius, Ida Lykke; Christensen, Helle Foged
2012-01-01
Deformation of a hydrocarbon reservoir can ideally be used to estimate the effective stress acting on it. The effective stress in the subsurface is the difference between the stress due to the weight of the sediment and a fraction (effective stress coefficient) of the pore pressure. The effective...... elastic deformation caused by pore pressure buildup, for example, during waterflooding. By contrast, during the increase in differential stress, as in the case of pore pressure depletion due to production, n increases with stress while α decreases.......Deformation of a hydrocarbon reservoir can ideally be used to estimate the effective stress acting on it. The effective stress in the subsurface is the difference between the stress due to the weight of the sediment and a fraction (effective stress coefficient) of the pore pressure. The effective...... stress coefficient is thus relevant for studying reservoir deformation and for evaluating 4D seismic for the correct pore pressure prediction. The static effective stress coefficient n is estimated from mechanical tests and is highly relevant for effective stress prediction because it is directly related...
Regel, Jeppe Bendix; Orozova-Bekkevold, Ivanka; Andreassen, Katrine Alling
2017-01-01
, is significantly different from 1. The log-derived Biot's coefficient is above 0.8 in the Shetland Chalk Group and in the Tyne Group, and 0.6-0.8 in the Heno Sandstone Formation. We show that the effective vertical and horizontal stresses obtained using the log-derived Biot's coefficient result in a drilling...
Change in Biot's effective stress coefficient of chalk during pore collapse
Alam, M. Monzurul; Fabricius, Ida Lykke
2013-01-01
the grains could also change during elastic deformation of the grains in a rock mechanics test. Diagenetic change in grain contact cement of chalk can be compared with stress-induced change in the laboratory. The change in porosity is studied with reference to the change in effective stress on grain contacts......Biot's effective stress coefficient (α) is a measure of how well grains in the rocks are connected with each other. The amount of contact cements between the grains determines the stiffness of rocks. Change in grain contact occurs during natural diagenesis of sedimentary rock. Contact between...... and porosity reduces at a slower rate. We noticed that presence of non carbonates and hydrocarbon could increase σ'm. During rock mechanics test in the lab, with increased applied stress, σ'm increases, Biot's effective stress coefficient shows a decreasing trend, while a minor porosity reduction was observed...
THEORETICAL MODEL OF EFFECTIVE STRESS COEFFICIENT FOR ROCK/SOIL-LIKE POROUS MATERIALS
Kai Zhang; Hui Zhou; Dawei Hu; Yang Zhao; Xiating Feng
2009-01-01
Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous ma-terial and the property of liquid, denotes the connectivity of pores in Representative Element Area (REA). If the conductivity of the porous material is anisotropic, the equivalent connec-tivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coeffi-cient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.
Kubilay ASLANTAŞ
2003-02-01
Full Text Available The coated tools are regularly used in today's metal cutting industry. Because, it is well known that thin and hard coatings can reduce tool wear, improve tool life and productivity. Such coatings have significantly contributed to the improvements cutting economies and cutting tool performance through lower tool wear and reduced cutting forces. TiN coatings have especially high strength and low friction coefficients. During the cutting process, low friction coefficient reduce damage in cutting tool. In addition, maximum stress values between coating and substrate also decrease as the friction coefficient decreases. In the present study, stress analysis is carried out for HSS (High Speed Steel cutting tool coated with TiN. The effect of the friction coefficient between tool and chip on the stresses developed at the cutting tool surface and interface of coating and HSS is investigated. Damage zones during cutting process was also attempted to determine. Finite elements method is used for the solution of the problem and FRANC2D finite element program is selected for numerical solutions.
Shao, Y. F.; Song, F.; Jiang, C. P.; Xu, X. H.; Wei, J. C.; Zhou, Z. L.
2016-02-01
We study the difference in the maximum stress on a cylinder surface σmax using the measured surface heat transfer coefficient hm instead of its average value ha during quenching. In the quenching temperatures of 200, 300, 400, 500, 600 and 800°C, the maximum surface stress σmmax calculated by hm is always smaller than σamax calculated by ha, except in the case of 800°C; while the time to reach σmax calculated by hm (fmmax) is always earlier than that by ha (famax). It is inconsistent with the traditional view that σmax increases with increasing Biot number and the time to reach σmax decreases with increasing Biot number. Other temperature-dependent properties also have a small effect on the trend of their mutual ratios with quenching temperatures. Such a difference between the two maximum surface stresses is caused by the dramatic variation of hm with temperature, which needs to be considered in engineering analysis.
The Influence of Biot’s Coefficient on the Estimation of Effective Stress on Deep Sea Sediments
Awadalkarim, Ahmed; Fabricius, Ida Lykke
and P-wave velocity data with the calculated effective stresses to show how different calculated vertical effective stress influences shale compaction trends. This may provide a basis to understand how physical properties vary with effective stress and shale mineralogy. Our results may be relevant...
Effective Viscosity Coefficient of Nanosuspensions
Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.
2008-12-01
Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.
Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation
2016-05-01
it can be used as an additional glass characterization method . If the SOC of a glass sample is known, the stress state of a glass specimen can be...evaluated through photoelastic methods both qualitatively and quantitatively. Approved for public release; distribution is unlimited. 11 8...ARL-TN-0756 ● MAY 2016 US Army Research Laboratory Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation
Wobble friction coefficient in post-stressed concrete
Diego Ernesto Dueñas Puentes
2010-04-01
Full Text Available This work was aimed at establishing a wobble friction coefficient (K from records regarding some post-stressed bridges built in Colombia. Such records were arranged and analysed together with stress diagrams resulting from the corres-ponding plans, calculations and reports. Suitable records were produced from this review to make the analysis. Once the records had been selected, the probable wobble friction coefficient (K was then calculated for each case and this coefficient was related to the length of the cable and the total area of the strands composing the cable. These records and their results were subsequently grouped according to the type of bridge to produce a wobble friction coefficient (K for each specific structure. The study indicated that the wobble friction coefficient was lower than that indicated by the Colombian Seismic Bridge Design Code, Instituto Nacional De Vías, 1995]. The influence of tensioning equipment, materials and labour suggested a format for recording tensioning to reduce inaccuracy when readings are being taken. A reduction in the costs of tensioning would arise from taking the forgoing into account.
Coefficient of thermal expansion of stressed thin films
WANG Zheng-dao; JIANG Shao-qing
2006-01-01
A new technique was proposed to determine the coefficient of thermal expansion (CTE) of thin films at low temperature. Different pre-stress could be applied and the elastic modulus of materials at different temperatures was measured with CTE simultaneously to eliminate the influence of mechanical deformation caused by the pre-stress. By using this technique,the CTEs of polyimide/silica nanocomposite films with different silica doping levels were experimentally studied at temperature from 77 K to 287 K,and some characteristics related to this new technique were discussed.
Linjun, Xie, E-mail: linjunx@zjut.edu.cn [College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Guohong, Xue; Ming, Zhang [Shanghai Nuclear Engineering Research & Design Institute, Shanghai 200233 (China)
2016-08-01
Graphical abstract: HDS stress coefficient test apparatus. - Highlights: • This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. • The mathematical relation between the load and the strain is obtained about the HDS, and the mathematical model of the stress coefficient and the friction coefficient is established. So, a set of test apparatuses for obtaining the stress coefficient is designed according to the model scaling criterion and the friction coefficient of the K1000 HDS is calculated to be 0.336 through the obtained stress coefficient. • The relation curve between the theoretical load and the friction coefficient is obtained through analysis and indicates that the change of the friction coefficient f would influence the pretightening load under the condition of designed stress. The necessary pretightening load in the design process is calculated to be 5469 kN according to the obtained friction coefficient. Therefore, the friction coefficient and the pretightening load under the design conditions can provide accurate pretightening data for the analysis and design of the reactor HDS according to the operations. - Abstract: This paper performs mathematic deduction to the physical model of Hold Down Spring (HDS), establishes a mathematic model of axial load P and stress, stress coefficient and friction coefficient and designs a set of test apparatuses for simulating the pretightening process of the HDS for the first time according to a model similarity criterion. By carrying out tests and researches through a stress testing technique, P–σ curves in loading and unloading processes of the HDS are obtained and the stress coefficient k{sub f} of the HDS is obtained. So, the
Variability on Raman Shift to Stress Coefficient of Porous Silicon
LEI Zhen-Kun; KANG Yi-Lan; CEN Hao; HU Ming
2006-01-01
Porous silicon film is a capillary-like medium, which is able to reveal different meso-elastic modulus with porosity. During the preparation of porous silicon samples, the capillary force is a non-classic force related to the liquid evaporation which directly influences the evolution of residual stress. In this study, a non-linear relation of Raman shift to stress coefficient and the porosity is obtained from the elastic modulus measured with nano-indentation by Bellet et al. fJ. Appl. Phys. 60 (1996) 3772] Dynamic capillarity during the drying process of porous silicon is investigated using micro-Raman spectroscopy, and the results reveal that the residual stress resulted from the capillarity increased rapidly. Indeed, the dynamic capillarity has a close relationship with a great deal of micro-pore structures of the porous silicon.
Effective Diffusion Coefficients in Coal Chars
Johnsson, Jan Erik; Jensen, Anker
2001-01-01
Knowledge of effective diffusion coefficients in char particles is important when interpreting experimental reactivity measurements and modeling char combustion or NO and N2O reduction. In this work, NO and N2O reaction with a bituminous coal char was studied in a fixed-bed quartz glass reactor....... The experimental results were compared with theoretical values calculated from the mean pore radius and the cross-linked pore model. The method of mean pore radius underestimated the effective diffusion coefficient more than an order of magnitude. Using the cross-linked pore model, the bimodal pore size...
DENG Zengan; ZHAO Dongliang; WU Kejian; YU Ting; SHI Jian
2008-01-01
By taking into consideration the effects of ocean surface wave-induced Stokes drift velocity U,w and current velocityU,c on the drag coefficient,the spatial distributions of drag coefficient and wind stress in 2004 are computed over the tropical andnorthern Pacific using an empirical drag coefficient parameterization formula based on wave steepness and wind speed.The globalocean current field is generated from the Hybrid Coordinate Ocean Model (HYCOM) and the wave data are generated from Wave-watch Ⅲ (WW3).The spatial variability of the drag coefficient and wind stress is analyzed.Preliminary results indicate that theocean surface Stokes drift velocity and current velocity exert an important influence on the wind stress.The results also show thatconsideration of the effects of the ocean surface Stokes drift velocity and current velocity on the wind stress can significantly im-prove the modeling of ocean circulation and air-sea interaction processes.
Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled
2017-02-01
We investigated the feasibility of residual stress assessment based on Hall coefficient measurements in precipitation hardened IN718 nickel-base superalloy. As a first step, we studied the influence of microstructural variations on the galvanomagnetic properties of IN718 nickel-base superalloy. We found that the Hall coefficient of IN718 increases from ≈ 8.0×10-11 m3/C in its fully annealed state of 15 HRC Rockwell hardness to ≈ 9.4×10-11 m3/C in its fully hardened state of 45 HRC. We also studied the influence of cold work, i.e., plastic deformation, at room temperature and found that cold work had negligible effect on the Hall coefficient of fully annealed IN718, but significantly reduced it in hardened states of the material. For example, measurements conducted on fully hardened IN718 specimens showed that the Hall coefficient decreased more or less linearly with cold work from its peak value of ≈ 9.4×10-11 m3/C in its intact state to ≈ 9.0×10-11 m3/C in its most deformed state of 22% plastic strain. We also studied the influence of applied stress and found that elastic strain significantly increases the Hall coefficient of IN718 regardless of the state of hardening. The relative sensitivity of the Hall coefficient to elastic strain was measured as a unitless gauge factor K that is defined as the ratio of the relative change of the Hall coefficient ΔRH/RH divided by the axial strain ɛ = σ/E, where σ is the applied uniaxial stress and E is the Young's modulus of the material. We determined that the galvanomagnetic gauge factor of IN718 is κ ≈ 2.6 - 2.9 depending on the hardness level. Besides the fairly high value of the gauge factor, it is important that it is positive, which means that compressive stress in surface-treated components decreases the Hall coefficient in a similar way as plastic deformation does, therefore the unfortunate cancellation that occurs in fully hardened IN718 in the case of electric conductivity measurements will not
TO DETERMINATION OF DAMPING COEFFICIENT OF VERTICAL DEAD STRESS OF EARTH DAMS ON A DEPTH
NESTEROVA E. V.
2015-12-01
Full Text Available Raising of problem. At the problem solving about determination of deflected mode (DM of build constructions by the finite element method (FEM on accuracy of solving substantial influence is rendered by the sizes of effective area of foundation. It is suggested to develop the criteria of determining the size of effective area. Presently at the calculation of vertical fallouts of earth dams with the trapeziform section (fig. 1, is assumed that the epure of contact pressures has a rectangular form [2, 6]. Thus actual epure of contact pressures on the sole of dam has form of trapezoid (fig. 1. Thus, there is a disparity between actual and accepted in the normative documents in the contact pressures on the sole of earth dams. Purpose. At writing of this article we were pursue a purpose to calculate the value of damping coefficient of vertical dead stress on the depth of foundation, trapeziform loading determined and to foundation attached. About it has been already written not a bit in scientific literature [2; 5; 6; 7; 13]. In our view, for determination of vertical fallouts of foundation of earth dams it is necessary to use the formula of D-1 DBN [7], corrected in it the damping coefficient of vertical stress on a depth, conditioned of dam weight, that is to calculate a trapezoidal form of environmental stress (fig. 1. Conclusion. The damping coefficients of vertical stress calculated by us on a depth (tablas. 1 allow more exactly to determine their values, than coefficients, presented in normative documents [7]. This is caused by more complete, than it takes a place in normative documents, in the light of configuration of the environmental stress.
José Gabriel Vieira Neto
2016-04-01
Full Text Available ABSTRACT Widely disseminated in both national and international scenarios, greenhouses are agribusiness solutions which are designed to allow for greater efficiency and control of the cultivation of plants. Bearing this in mind, the construction of greenhouses should take into consideration the incidence of wind, and other such aspects of comfort and safety, and ensure they are factored into the design of structural elements. In this study, we evaluated the effects of pressure coefficients established by the European standard EN 13031-1 (2001 and the Brazilian standard ABNT (1988, which are applicable to the structures of greenhouses with flat roofs, taking into account the following variables: roof slope, external and internal pressure coefficients and height-span ratio of the structure. Using the ANSYSTM computer program, zones of columns and roof were discretized by the Beam44 finite element to identify the maximum and minimum stress portions connected to the aerodynamic coefficients. With this analysis, we found that, in the smallest roof slope (a equal to 20°, the frame stress was quite similar for standards adopted. On the other hand, for the greatest inclination (a equal to 26°, the stress was consistently lower under the Brazilian standard. In view of this, we came to the conclusion that the differences between stresses when applying both standards were more significant at the higher degrees of height-span ratio and roof slope.
Hadronic Transport Coefficients from Effective Field Theories
Torres-Rincon, Juan M
2012-01-01
This dissertation focuses on the calculation of transport coefficients in the matter created in a relativistic heavy-ion collision after the chemical freeze-out. This matter can be well approximated by a pion gas out of equilibrium. We describe the theoretical framework to obtain the shear and bulk viscosities, the thermal and electrical conductivities and the flavor diffusion coefficients of a meson gas at low temperatures. To describe the interactions of the degrees of freedom, we use effective field theories with chiral and heavy quark symmetries. We introduce the unitarization methods in order to obtain a scattering amplitude that satisfies the unitarity condition exactly. We perform the calculation of the transport properties of the low temperature phase of quantum chromodynamics -the hadronic medium- that can be used in the hydrodynamic simulations of a relativistic heavy-ion collision and its subsequent evolution. We show that the shear viscosity over entropy density exhibits a minimum in a phase trans...
Ageing effect of chloride diffusion coefficient
Polder, R.B.
2006-01-01
Most of the currently used models to predict chloride ingress a constant diffusion coefficient over time. However, a reduction of the diffusion coefficient over time, is ob-served at specimens that are exposed to chlorides. This reduction of the diffusion coefficient is expressed with the ageing coe
Retrieval of ocean surface wind stress and drag coefficient from spaceborne SAR
杨劲松; 黄韦艮; 周长宝
2001-01-01
A model for retrieval of wind stress and drag coefficient on the sea surface with the data measured by spacebome synthetic aperture radar (SAR) has been developed based on the SAR imaging mechanisms of ocean surface capillary waves and short gravity waves. This model consists of radiometric calibration, wind speed retrieval and wind stress and drag coefficient calculation. A Radarsat SAR image has been used to calculate wind stress and drag coeffi cient. Good results have been achieved.
Araya, A.; Stroosnijder, L.; Girmay, G.; Keesstra, S.D.
2011-01-01
In the semi-arid region of Tigray, Northen Ethiopia a two season experiment was conducted to measure evapotranspiration, estimate yield response to water stress and derive the crop coefficient of teff using the single crop coefficient approach with simple, locally made lysimeters and field plots. Du
Effective Electrocardiogram Steganography Based on Coefficient Alignment.
Yang, Ching-Yu; Wang, Wen-Fong
2016-03-01
This study presents two types of data hiding methods based on coefficient alignment for electrocardiogram (ECG) signals, namely, lossy and reversible ECG steganographys. The lossy method is divided into high-quality and high-capacity ECG steganography, both of which are capable of hiding confidential patient data in ECG signals. The reversible data hiding method can not only hide secret messages but also completely restore the original ECG signal after bit extraction. Simulations confirmed that the perceived quality generated by the lossy ECG steganography methods was good, while hiding capacity was acceptable. In addition, these methods have a certain degree of robustness, which is rare in conventional ECG stegangraphy schemes. Moreover, the proposed reversible ECG steganography method can not only successfully extract hidden messages but also completely recover the original ECG data.
DEFINITION STRESS INTENSITY COEFFICIENT TWO-DIMENSIONAL BODIES UNDER THERMAL LOAD
Shkril’ А.
2014-12-01
Full Text Available On the basis of the finite element scheme of the moment method (FEM implemented method of determining the coefficients of stress intensity (K in two-dimensional bodies under the action of temperature load. Results of test problems showed that the methods for determining the energy of K are more effeciency compared with the.
Hwang, Seulgi; Kim, Youngman
2011-08-01
Thin films are used in wide range of applications in industry, such as solar cells and LEDs. When thin films are deposited on substrates, various stresses are generated due to the mechanical difference between the film and substrate. These stresses can cause defects, such as cracking and buckling. Therefore, knowledge of the mechanical properties is important for improving their reliability and stability. In this study, the thermal expansion coefficient of FCC metallic thin films, such as Ag and Cu, which have different grain sizes and thicknesses, were calculated using the thermal cycling method. As a result, thermal expansion coefficient increased with increasing grain size. However, the film thickness had no remarkable effect.
Effects of lubricant's friction coefficient on warm compaction powder metallurgy
LI Yuan-yuan; NGAI Tungwai Leo; WANG Shng-lin; ZHU Min; CHEN Wei-ping
2005-01-01
The correct use of lubricant is the key of warm compaction powder metallurgy.Different lubricants produce different lubrication effects and their optimal application temperature will be different.Three different lubricants were used to study the effects of friction coefficient on warm compaction process.Friction coefficients of these lubricants were measured at temperatures ranging from ambient temperature to 200 ℃.Iron-base samples were prepared using different processing temperatures and their green compact densities were studied.
Crop and soil-water stress coefficients of tomato in the glass-greenhouse conditions
Z. Razmi
2011-12-01
Full Text Available In order to determine the actual evapotranspiration of tomato in the greenhouse, crop and soil-water stress coefficients were surveyed. To compare the actual evapotranspiration at different irrigation intervals (1, 2, 4, 6 and 8-day, a completely randomized blocks design with four replications was performed. The present study was carried out in a greenhouse covered by 4 mm thick glass. Maximum and minimum temperatures and solar radiation were measured inside the greenhouse once in 24 h. Relative humidity was measured in the greenhouse once in 2 h. Microclimate data were measured in a metrological station, 100 m from the greenhouse, simultaneously, at outside the greenhouse. Reference crop evapotranspiration was calculated by FAO Penman-Monteith method for inside and outside of the greenhouse. Results indicated that the reference evapotranspiration in the inside of the greenhouse was 73% of outside the greenhouse. The actual evapotranspiration of tomato for inside of the greenhouse was determined by using the water balance method. By using the pergeometer and albidometer data, the crop coefficient for inside the greenhouse at three different stages (development, mid, and end of growth was determined as 0.85, 1.0 and 0.77, respectively. Soil-water stress coefficient, with readily available coefficient of 0.7, was determined to be in the range of 0.53 to 0.98 for all the treatments. This coefficient was 0.88 for water-stressed 4-day treatment, and reduced to 0.72 for 8-day treatment.
Memory Effects and Transport Coefficients for Non-Newtonian Fluids
Kodama, T
2008-01-01
We discuss the roles of viscosity in relativistic fluid dynamics from the point of view of memory effects. Depending on the type of quantity to which the memory effect is applied, different terms appear in higher order corrections. We show that when the memory effect applies on the extensive quantities, the hydrodynamic equations of motion become non-singular. We further discuss the question of memory effect in the derivation of transport coefficients from a microscopic theory. We generalize the application of the Green-Kubo-Nakano (GKN) to calculate transport coefficients in the framework of projection operator formalism, and derive the general formula when the fluid is non-Newtonian.
Hwang, Seulgi; Kim, Youngman
2011-02-01
Cu thin films underwent thermal cycling to determine their coefficient of thermal expansion (CTE). The thermal stress of the Cu thin films with various microstructures (different grain size and film thickness) was measured using a curvature measurement system. The thermal expansion coefficients of the films were obtained from the slope of the stress-temperature curve with the knowledge of the Young's modulus and Poisson's ratio. The change in thermal stress with temperature of the Cu thin films tended to decrease with increasing grain size, resulting in an increase in the CTE. The thickness of Cu thin film had little effect on the thermal stress or the CTE.
Determination of effective thermal expansion coefficients of unidirectional fibrous nanocomposites
Dai, Ming; Schiavone, Peter; Gao, Cun-Fa
2016-10-01
We present an efficient numerical scheme (based on complex variable techniques) to calculate the effective thermal expansion coefficients of a composite containing unidirectional periodic fibers. Moreover, the mechanical behavior of the fibers incorporates interface effects allowing the ensuing analytical model of the composite to accommodate deformations at the nanoscale. The resulting `nanocomposite' is subjected to a uniform temperature variation which leads to periodic deformations within the plane perpendicular to the fibers and uniform deformations along the direction of the fibers. These deformation fields are determined by analyzing a representative unit cell of the composite subsequently leading to the corresponding effective thermal expansion coefficients. Numerical results are illustrated via several physical examples. We find that the influence of interface effects on the effective thermal expansion coefficients (in particular that corresponding to the transverse direction in the plane perpendicular to the fibers) decays rapidly as the fibers become harder. In addition, by comparing the results obtained here with those from effective medium theories, we show that the latter may induce significant errors in the determination of the effective transverse thermal expansion coefficient when the fibers are much softer than the matrix and the fiber volume fraction is relatively high.
Liu, An-Nuo; Wang, Lu-Lu; Li, Hui-Ping; Gong, Juan; Liu, Xiao-Hong
2016-11-22
The literature on posttraumatic growth (PTG) is burgeoning, with the inconsistencies in the literature of the relationship between PTG and posttraumatic stress disorder (PTSD) symptoms becoming a focal point of attention. Thus, this meta-analysis aims to explore the relationship between PTG and PTSD symptoms through the Pearson correlation coefficient. A systematic search of the literature from January 1996 to November 2015 was completed. We retrieved reports on 63 studies that involved 26,951 patients. The weighted correlation coefficient revealed an effect size of 0.22 with a 95% confidence interval of 0.18 to 0.25. Meta-analysis provides evidence that PTG may be positively correlated with PTSD symptoms and that this correlation may be modified by age, trauma type, and time since trauma. Accordingly, people with high levels of PTG should not be ignored, but rather, they should continue to receive help to alleviate their PTSD symptoms.
Effect of Rare Earths on Diffusion Coefficient and Transfer Coefficient of Carbon during Carburizing
无
2001-01-01
The diffusion coefficient of carbon in surface layer of steel-20 rare earth carburized at 880 ℃ and 900 ℃ for 8 h was calculated by substituting the measured layer depths into the diffusion equation. The mathematical model of the transfer coefficient of carbon was deduced based on the kinetics of weight gain during gas carburizing. The calculated results show that the main reason why the gas carburizing process is accelerated is due to the obvious increase in the diffusion coefficient and transfer coefficient of carbon resulted from the addition of RE.
Enhancement of Seebeck Coefficients by Resonant Tunneling Effect
Daqiq, Reza
2017-10-01
The Seebeck coefficients in an MgO-based double-barrier magnetic tunnel junction (DBMTJ) with a semiconductor (e.g., Ge) spacer are studied using non-equilibrium Green's function formalism in the linear response regime. The DBMTJ results show a magnitude enhancement compared with a single-barrier MTJ (SBMTJ) at the specific thicknesses of the semiconductor spacer due to the resonant tunneling effect through the DBMTJ structure. With an increase of the average temperature of the junctions, the Seebeck coefficients also increase and they are at a maximum in the anti-parallel configuration of the magnetizations. Therefore, it is possible to achieve large Seebeck coefficients using a DBMTJ compared with a conventional SBMTJ structure.
HUO Kaicheng; SHUI Zhonghe; LI Yue
2006-01-01
By using the uptodate temperatuer-stress testing machine, the thermal expansion coefficient of concrete at early ages was studied and indicative conclusions were achieved: temperature rising due to hydration heat is not directly correlated with cracking, but the temperature and stress evolution process should be taken into consideration in the same time. Proper chemical admixtures and mineral compositions can improve the mechanical properties of concrete such as thermal expansion coefficient, which is very indicative in practice.
Surface Roughness Effects on Discharge Coefficient of Broad Crested Weir
Shaker A. Jalil
2014-06-01
Full Text Available The aim of this study is to investigate the effects of surface roughness sizes on the discharge coefficient for a broad crested weirs. For this purpose, three models having different lengths of broad crested weirs were tested in a horizontal flume. In each model, the surface was roughed four times. Experimental results of all models showed that the logical negative effect of roughness increased on the discharge (Q for different values of length. The performance of broad crested weir improved with decrease ratio of roughness to the weir height (Ks/P and with the increase of the total Head to the Length (H/L. An empirical equation was obtained to estimate the variation of discharge coefficient Cd in terms total head to length ratio, with total head to roughness ratio.
Investigation of CNTFET Performance with Gate Control Coefficient Effect
S.A. Khan
2014-06-01
Full Text Available For the first time, a deep study of gate control coefficient (αG effect on CNTFET performance has done in this research. A new, analytical CNTFET simulation along with multiple parameter approach has executed with 3D output in MATLAB and that used it to examine device performance. It is found that, drain current and transconductance increases with high gate control coefficient. On the other hand, total capacitance decreases with high αG value resulting improved charging energy. Likewise, drain induced barrier lowering (DIBL decreases with αG that provides less deviation from ideal device performance. Finally, subthreshold swing comes very close to the theoretical limit at high αG which is desired for low threshold voltage and low-power operation for FETs scaled down to small sizes.
Maria Isabel Ferreira
2017-06-01
Full Text Available There are several causes for the failure of empirical models to estimate soil water depletion and to calculate irrigation depths, and the problem is particularly critical in tall, uneven, deficit irrigated (DI crops in Mediterranean climates. Locally measured indicators that quantify water status are useful for addressing those causes and providing feed-back information for improving the adequacy of simple models. Because of their high aerodynamic resistance, the canopy conductance of woody crops is an important factor in determining evapotranspiration (ET, and accurate stress coefficient (Ks values are needed to quantify the impact of stomatal closure on ET. A brief overview of basic general principles for irrigation scheduling is presented with emphasis on DI applications that require Ks modelling. The limitations of existing technology related to scheduling of woody crops are discussed, including the shortcomings of plant-based approaches. In relation to soil water deficit and/or predawn leaf water potential, several woody crop Ks functions are presented in a secondary analysis. Whenever the total and readily available water data were available, a simple Ks model was tested. The ultimate aim of this discussion is to illustrate the central concept: that a combination of simple ET models and water stress indicators is required for scheduling irrigation of deep-rooted woody crops.
Effect of stacking sequence on the coefficients of mutual influence of composite laminates
Dupir (Hudișteanu, I.; Țăranu, N.; Axinte, A.
2016-11-01
Fiber reinforced polymeric (FRP) composites are nowadays widely used in engineering applications due to their outstanding features, such as high specific strength and specific stiffness as well as good corrosion resistance. A major advantage of fibrous polymeric composites is that their anisotropy can be controlled through suitable choice of the influencing parameters. The unidirectional fiber reinforced composites provide much higher longitudinal mechanical properties compared to the transverse ones. Therefore, composite laminates are formed by stacking two or more laminas, with different fiber orientations, as to respond to complex states of stresses. These laminates experience the effect of axial-shear coupling, which is caused by applying normal or shear stresses, implying shear or normal strains, respectively. The normal-shear coupling is expressed by the coefficients of mutual influence. They are engineering constants of primary interest for composite laminates, since the mismatch of the material properties between adjacent layers can produce interlaminar stresses and/or plies delamination. The paper presents the variation of the in-plane and flexural coefficients of mutual influence for three types of multi-layered composites, with different stacking sequences. The results are obtained using the Classical Lamination Theory (CLT) and are illustrated graphically in terms of fiber orientations, for asymmetric, antisymmetric and symmetric laminates. Conclusions are formulated on the variation of these coefficients, caused by the stacking sequence.
COMPRESSIBILITY EFFECTS ON DISTRIBUTIONS OF PRESSURE AND LIFT COEFFICIENTS
AZZEDINE NAHOUI
2015-06-01
Full Text Available Reduce energy consumption of airplanes, or enhance the aerodynamic performance of compressors and turbines by reducing drag, or increasing lift is a major challenge for many institutions specializing in aerodynamics [1, 2]. One way to achievethis, isconsidered the study of compressible potential flow compared to incompressible potential flow [3], Outside the boundary layer, to study the effects of compressibility and the control parameters. And the pressure coefficient and lift distributions around the NACA 0012 profile, NACA 0015 and NACA 0018 were studied and presented in terms of the Mach number, angle of attack and the relative thickness of the profiles.
Effect of electrostatic field on dynamic friction coefficient of pistachio
M. H Aghkhani
2016-04-01
Full Text Available Introduction: Separation and grading of agricultural products from the production to supply, has notable importance. The separation can be done based on physical, electrical, magnetic, optical properties and etc. It is necessary for any development of new systems to study enough on the properties and behavior of agricultural products. Some characteristics for separation are size (length, width and thickness, hardness, shape, density, surface roughness, color, speed limit, aerodynamic properties, electrical conductivity, elasticity and coefficient of static friction point. So far, the friction properties of agricultural products used in the separating process, but the effect of electrostatic charging on static and dynamic coefficients of friction for separation had little attention. The aim of this study was to find out the interactions between electrostatic and friction properties to find a way to separate products that separation is not possible with conventional methods or not sufficiently accurate. In this paper, the separation of close and smiley pistachios by electrostatic charging was investigated. Materials and Methods: Kallehghoochi pistachio cultivar has the top rank in production in Iran. Therefore, it was used as a sample. The experimental design that used in this study, had moisture content at three levels (24.2, 14.5 and 8.1 percent, electric field intensity at three levels (zero, 4000 and 7000 V, speed of movement on the surface at three levels (1300, 2500 and 3300 mm per minute, friction surface (galvanized sheet iron, aluminum and flat rubber and pistachio type at two levels (filled splits and closed that was measured and analyzed in completely randomized factorial design. A friction measuring device (built in Ferdowsi University of Mashhad used to measure the friction force. It has a removable table that can move in two directions with adjustable speed. The test sample put into the vessel with internal dimensions of 300 × 150
Chidambaram, Nachiappan; Mazzalai, Andrea; Muralt, Paul
2012-08-01
Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) thin films play an increasingly important role for two reasons: first, such a configuration generates higher voltages than parallel plate capacitor-type electrode (PPE) structures, and second, the application of an electric field leads to a compressive stress component in addition to the overall stress state, unlike a PPE structure, which results in tensile stress component. Because ceramics tend to crack at relatively moderate tensile stresses, this means that IDEs have a lower risk of cracking than PPEs. For these reasons, IDE systems are ideal for energy harvesting of vibration energy, and for actuators. Systematic investigations of PZT films with IDE systems have not yet been undertaken. In this work, we present results on the evaluation of the in-plane piezoelectric coefficients with IDE systems. Additionally, we also propose a simple and measurable figure of merit (FOM) to analyze and evaluate the relevant piezoelectric parameter for harvesting efficiency without the need to fabricate the energy harvesting device. Idealized effective coefficients e(IDE) and h(IDE) are derived, showing its composite nature with about one-third contribution of the transverse effect, and about two-thirds contribution of the longitudinal effect in the case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric field along one of the Si directions. Randomly oriented 1-μm-thick PZT 53/47 film deposited by a sol-gel technique, was evaluated and yielded an effective coefficient e(IDE) of 15 C·m(-2). Our FOM is the product between effective e and h coefficient representing twice the electrical energy density stored in the piezoelectric film per unit strain deformation (both for IDE and PPE systems). Assuming homogeneous fields between the fingers, and neglecting the contribution from below the electrode fingers, the FOM for IDE structures with larger electrode gap is derived to be
Nonscaling calculation of the effective diffusion coefficient in periodic channels
Kalinay, Pavol
2017-01-01
An algorithm calculating the effective diffusion coefficient D(x) in 2D and 3D channels with periodically varying cross section along the longitudinal coordinate x is presented. Unlike other methods, it is not based on scaling of the transverse coordinates, or the smallness of the width of the channel. The result is expressed as an integral of specific contributions to D(x) coming from the positions neighboring to x. The method avoids the hierarchy of derivatives of the channel shaping function h(x), so it is also suitable for the channels with cusps or jumps of their width. The method describes correctly D(x) in wide channels, giving the expected behavior in the limit of infinite width (no confinement).
Kwaśniewki, Janusz; Dominik, Ireneusz; Lalik, Krzysztof; Holewa, Karolina
2016-10-01
This paper presents the Self-excited Acoustical System (SAS) in elastic construction stress change measurement. The system is based on the acoustical autoresonance phenomena and enables an indirect measurement of the construction effort level. The essence of the SAS system is to use a piezoelectric vibration emitter and a piezoelectric vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which are operating in a closed loop with a positive feedback. This causes the excitation of the system. The change of the velocity of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the stress change in the examined material. A variable, which determines the change of the acoustic wave velocity, is called an acoustoelastic coefficient β. Such a coefficient allows to determine the absolute stress value in the tested material.
EFFECTIVE DIFFUSION AND EFFECTIVE DRAG COEFFICIENT OF A BROWNIAN PARTICLE IN A PERIODIC POTENTIAL
Hongyun Wang
2011-01-01
We study the stochastic motion of a Brownian particle driven by a constant force over a static periodic potential.We show that both the effective diffusion and the effective drag coefficient are mathematically well-defined and we derive analytic expressions for these two quantities.We then investigate the asymptotic behaviors of the effective diffusion and the effective drag coefficient,respectively,for small driving force and for large driving force.In the case of small driving force,the effective diffusion is reduced from its Brownian value by a factor that increases exponentially with the amplitude of the potential.The effective drag coefficient is increased by approximately the same factor.As a result,the Einstein relation between the diffusion coefficient and the drag coefficient is approximately valid when the driving force is small.For moderately large driving force,both the effective diffusion and the effective drag coefficient are increased from their Brownian values,and the Einstein relation breaks down. In the limit of very large driving force,both the effective diffusion and the effective drag coefficient converge to their Brownian values and the Einstein relation is once again valid.
Stefan Karlsson
2017-04-01
Full Text Available Monovalent cations enable efficient ion-exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical, or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda-lime-silicates (SLS such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+, and Cs+ by drawing relations to physicochemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion-exchange rate.
Karlsson, Stefan; Wondraczek, Lothar; Ali, Sharafat; Jonson, Bo
2017-04-01
Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.
The effect of academic stress and attachment stress on stress-eaters and stress-undereaters.
Emond, Michael; Ten Eycke, Kayla; Kosmerly, Stacey; Robinson, Adele Lafrance; Stillar, Amanda; Van Blyderveen, Sherry
2016-05-01
It is well established that stress is related to changes in eating patterns. Some individuals are more likely to increase their overall food intake under conditions of stress, whereas others are more likely to consume less food when stressed. Attachment style has been linked to disordered eating and eating disorders; however, comparisons of eating behaviors under attachment versus other types of stress have yet to be explored. The present laboratory study examined the eating patterns in self-identified stress-undereaters and stress-eaters under various types of stress. More specifically, the study examined the effects of academic and attachment stress on calorie, carbohydrate and sugar consumption within these two groups. Under the guise of critiquing student films, university students viewed either one of two stress-inducing videos (academic stress or attachment stress, both designed to be emotionally arousing) or a control video (designed to be emotionally neutral), and their food intake was recorded. Results demonstrated that the video manipulations were effective in inducing stress. Differential patterns of eating were noted based on group and stress condition. Specifically, stress-undereaters ate fewer calories, carbohydrates and sugars than stress-eaters in the academic stress condition, but not in the attachment stress or control condition. Findings suggest that specific types of stressors may influence eating behaviors differently.
Hosoda, Hideki; Mishima, Yoshinao [Tokyo Inst. of Tech., Yokohama (Japan). Precision and Intelligence Lab.; Suzuki, Tomoo [Tokyo Inst. of Tech. (Japan)
1997-12-31
Yield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49mol.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77 K, air at room temperature (R.T.) and in an argon atmosphere between 473 K and 873 K. Only at 77 K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be between 2 and 11GPa in all the test temperature range. The values are extremely high compared with Young`s modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650 K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.
Jebaraj Johnley Muthuraj, Josiah
Cathodic protection is widely used for corrosion prevention. However, this process generates hydrogen at the protected metal surface, and diffusion of hydrogen through the metal may cause hydrogen embrittlement or hydrogen induced stress corrosion cracking. Thus the choice of a metal for use as fasteners depends upon its hydrogen uptake, permeation, diffusivity and trapping. The diffusivity of hydrogen through four high strength alloys (AISI 4340, alloy 718, alloy 686, and alloy 59) was analyzed by an electrochemical method developed by Devanathan and Stachurski. The effect of plasma nitriding and microstructure on hydrogen permeation through AISI 4340 was studied on six different specimens: as-received (AR) AISI 4340, nitrided samples with and without compound layer, samples quenched and tempered (Q&T) at 320° and 520°C, and nitrided samples Q&T 520°C. Studies on various nitrided specimens demonstrate that both the gamma'-Fe 4N rich compound surface layer and the deeper N diffusion layer that forms during plasma nitriding reduce the effective hydrogen diffusion coefficient, although the gamma'-Fe4N rich compound layer has a larger effect. Multiple permeation transients yield evidence for the presence of only reversible trap sites in as-received, Q&T 320 and 520 AISI 4340 specimens, and the presence of both reversible and irreversible trap sites in nitrided specimens. Moreover, the changes in microstructure during the quenching and tempering process result in a significant decrease in the diffusion coefficient of hydrogen compared to as-received specimens. In addition, density functional theory-based molecular dynamics simulations yield hydrogen diffusion coefficients through gamma'- Fe4N one order of magnitude lower than through α-Fe, which supports the experimental measurements of hydrogen permeation. The effect of microstructure and trapping was also studied in cold rolled, solutionized, and precipitation hardened Inconel 718 foils. The effective hydrogen
Xin-Fu Bai; Jian-Jun Zhu; Ping Zhang; Yan-Hua Wang; Li-Qun Yang; Lei Zhang
2007-01-01
The response of halophyte arrowleaf saltbush (Atriplex triangularis Willd) plants to a gradient of salt stress were investigated with hydroponically cultured seedlings. Under salt stress, both the Na+ uptake into root xylem and negative pressures in xylem vessels increased with the elevation of salinity (up to 500 mol/m3) in the root environment. However, the increment in negative pressures in root xylem far from matches the decrease in the osmotic potential of the root bathing solutions, even when the osmotic potential of xylem sap is taken into consideration. The total water potential of xylem sap in arrowleaf saltbush roots was close to the osmotic potential of root bathing solutions when the salt stress was low, but a progressively increased gap between the water potential of xylem sap and the osmotic potential of root bathing solutions was observed when the salinity in the root environment was enhanced. The maximum gap was 1.4 MPa at a salinity level of 500 mol/m3 without apparent dehydration of the tested plants. This discrepancy could not be explained with the current theories in plant physiology. The radial reflection coefficient of root in arrowleaf saltbush decreased with the enhanced salt stress was and accompanied by an increase in the Na+ uptake into xylem sap. However, the relative Na+ in xylem exudates based on the corresponding NaCl concentration in the root bathing solutions showed a tendency of decrease. The results showed that the reduction in the radial reflection coefficient of roots in the arrowleaf saltbush did not lead to a mass influx of NaCl into xylem when the radial reflection coefficient of the root was considerably small; and that arrowleaf saltbush could use small xylem pressures to counterbalance the salt stresses, either with the uptake of large amounts of salt, or with the development of xylem pressures dangerously negative. This strategy could be one of the mechanisms behind the high resistance of arrowleaf saltbush plants to salt
Redox Couples with Unequal Diffusion Coefficients: Effect on Redox Cycling
Mampallil Augustine, Dileep; Mathwig, Klaus; Kang, Shuo; Lemay, Serge G.
2013-01-01
Redox cycling between two electrodes separated by a narrow gap allows dramatic amplification of the faradaic current. Unlike conventional electrochemistry at a single electrode, however, the mass-transport-limited current is controlled by the diffusion coefficient of both the reduced and oxidized fo
Biaxial stress effects on magnetization perpendicular to the stress plane
Sablik, M.J.; Kwun, H.; Burkhardt, G.L. [Southwest Research Inst., San Antonio, TX (United States); Langman, R.A. [Univ. of Tasmania, Hobart, Tasmania (Australia)
1995-11-01
Effects of biaxial stress in steel on magnetization in a direction normal to the stress plane were investigated both theoretically and experimentally. The two results, which agreed qualitatively, showed that the magnetization in the normal direction generally decreased with the absolute value of the sum of the two principal stresses. The implication to nondestructive measurements of biaxial stress is discussed.
Xu, Peng; Mao, Xinyan; Jiang, Wensheng
2017-05-01
Three independent methods, the dynamical balance (DB) method, the turbulence parameter (TP) method, and the log-layer fit (LF) method, are commonly employed to estimate the bottom stress and bottom drag coefficient in strong tidal systems. However, their results usually differ from each other and the differences are attributed to form drag. Alternatively, some researchers argued that the differences are caused by overestimates in some methods. Aiming to measure the performances of the three independent methods, they were simultaneously constructed in a bay with highly asymmetric tides. The results of the DB and TP methods are consistent with each other in not only the magnitude but also time variation patterns. The consistency of results of the two methods indicates that skin friction is dominant in the bay. The results of the DB and TP methods reveal obvious flood-dominant asymmetry caused by tidal straining. This flood-dominant asymmetry is enhanced during the transition period from spring to neap tide. When the original log-layer fit is employed, the results are much larger than those of the DB and TP methods, and these differences cannot be attributed to form drag since skin friction is dominant in the bay. Moreover, the results of the original log-layer fit reveal an obvious ebb-dominant asymmetry, which is contradictory to the results of the DB and TP methods. Therefore, the results of the original fit are just overestimates and lack physical meaning. By considering the effect of stratification on the mixing length, the modified log-layer fit achieves results with magnitudes that are close to those of the DB and TP methods, indicating that the modified log-layer fit is more representative of the bottom stress than the original log-layer fit in terms of physical meaning. However, the results of the modified log-layer fit still exhibit an ebb-dominant asymmetry in contrast to that of the DB and TP methods, implying that the empirical formula of the mixing
Effect of mulching on melon (cv. Campero) crop coefficient
Cerekovic, Natasa; Todorovic, Mladen; Snyder, Richard L.
2011-01-01
and development parameters which can contribute in difference of Kc values for this climatic region. Since the crop is mostly bare soil during initial growth, the Kc ini is mainly determined by the wetting frequency through irrigation and precipitation, the fraction of soil wetted by irrigation, and the ETo rate....... The Kc mid values determined with equations are average adjustments for the mid-season period for the melon crop in Policoro, taking in consideration relevant weather data for wind speed and relative humidity as averages for these period. High Kc values were related to irrigation events. Kc end values...... that improvments in genetics and crossbreeding techniques, crop management, climatic conditions changes (temperature, relative humidity, wind speed) and irrigation technique have a significant impact on the crop development and crop coefficient value....
Zhiwen LIU; Zhengqing CHEN; Gao LIU; Xinpeng SHAO
2009-01-01
The aerodynamic interference effects on aero-static coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test.The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly com-pared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.
Arregui-Mena, José David; Margetts, Lee; Griffiths, D. V.; Lever, Louise; Hall, Graham; Mummery, Paul M.
2015-10-01
In this paper, the authors test the hypothesis that tiny spatial variations in material properties may lead to significant pre-service stresses in virgin graphite bricks. To do this, they have customised ParaFEM, an open source parallel finite element package, adding support for stochastic thermo-mechanical analysis using the Monte Carlo Simulation method. For an Advanced Gas-cooled Reactor brick, three heating cases have been examined: a uniform temperature change; a uniform temperature gradient applied through the thickness of the brick and a simulated temperature profile from an operating reactor. Results are compared for mean and stochastic properties. These show that, for the proof-of-concept analyses carried out, the pre-service von Mises stress is around twenty times higher when spatial variability of material properties is introduced. The paper demonstrates that thermal gradients coupled with material incompatibilities may be important in the generation of stress in nuclear graphite reactor bricks. Tiny spatial variations in coefficient of thermal expansion (CTE) and Young's modulus can lead to the presence of thermal stresses in bricks that are free to expand.
M. Ghorbanian Kerdabadi
2017-02-01
Full Text Available Introduction: Crop coefficient varies in different environmental conditions, such as deficit irrigation, salinity and intercropping. The effect of soil fertility and texture of crop coefficient and evapotranspiration of maize was investigated in this study. Low soil fertility and food shortages as a stressful environment for plants that makes it different evapotranspiration rates of evapotranspiration calculation is based on the FAO publication 56. Razzaghi et al. (2012 investigate the effect of soil type and soil-drying during the seed-filling phase on N-uptake, yield and water use, a Danish-bred cultivar (CV. Titicaca was grown in field lysimeters with sand, sandy loam and sandy clay loam soil. Zhang et al (2014 were investigated the Effect of adding different amounts of nitrogen during three years (from 2010 to 2012 on water use efficiency and crop evapotranspiration two varieties of winter wheat. The results of their study showed. The results indicated the following: (1 in this dry land farming system, increased N fertilization could raise wheat yield, and the drought-tolerant Changhan No. 58 showed a yield advantage in drought environments with high N fertilizer rates; (2 N application affected water consumption in different soil layers, and promoted wheat absorbing deeper soil water and so increased utilization of soil water; and (3 comprehensive consideration of yield and WUE of wheat indicated that the N rate of 270 kg/ha for Changhan No. 58 was better to avoid the risk of reduced production reduction due to lack of precipitation; however, under conditions of better soil moisture, the N rate of 180 kg/ha was more economic. Materials and Methods: The study was a factorial experiment in a completely randomized design with three soil texture treatment, including silty clay loam, loam and sandy-loam soil and three fertility treatment, including without fertilizer, one and two percent fertilizer( It was conducted at the experimental farm in
Hirpara, Darshna G; Gajera, H P; Hirapara, Jaydeep G; Golakiya, B A
2017-08-31
Trichoderma is one of the most exploited biocontrol agent for the management of plant diseases. Twenty strains of Trichoderma (six of T. harzianum, four of T. viride, three of T. virens, three of T. koningii, each one of T. hamatum, T. reesei, T. parceramosum and Trichoderma spp.) subjected to in vitro antagonism up to 12days after inoculation against Sclerotium rolfsii Sacc. causing stem rot in groundnut. A new concept was developed to determine inhibition coefficient representing pathogen biology and biocontrol related biophysical variables. Results explained differential inhibition coefficient of test pathogen by Trichoderma antagonists. The inhibition coefficient of test pathogen was examined highest (91.13%) by T. virens NBAII Tvs12 followed by T. virens MTCC 794 (89.33%) and T. koningii MTCC 796 (62.39%). Microscopic study confirmed biocontrol mechanism as mycoparasitism for Tvs12 and antibiosis for T. koningii MTCC 796. The sclerotial biogenesis of test pathogen was elevated during weak antagonism and diminished in interactions with strong antagonists. The inhibition coefficient of S. rolfsii was significantly negatively correlated with sclerotia formation and lipid peroxidation during the antagonism. Trichoderma strains were screened for fungicides (carbendazim and tebuconazole, thiram and mancozeb) and abiotic stress (drought and salt) tolerance. Results indicated that T. koningii MTCC 796 efficiently grew better than the other strains with maximum radial growth under adverse conditions. The genetic variability among the Trichoderma was determined using 34 gene specific markers which amplified 146 alleles. The SSR similarities explained substantial diversity (15 to 87%) across Trichoderma strains and pathogen S. rolfsii. Principal coordinates analysis (PCA) were comparable to the cluster analysis and first three most informative PC components explained 64.45% of the total variation. In PCA, potent antagonists appear to be distinct from other strains. Five
Dehghan
2016-06-01
Full Text Available Background Job satisfaction, job performance, job stress and heat stress affect the productivity of workers. Objectives This research aimed to study the relationship between heat stress indices with job satisfaction, job performance and job stress in casting workers. Patients and Methods This descriptive-analytical cross sectional survey was performed during summer 2013 on one hundred casting workers. Data were collected by questionnaires of occupational stress, job satisfaction and job performance. Heat stress was measured by the Wet Bulb Globe Temperature (WBGT and Heat Strain Score Index (HSSI questionnaire. The data were analyzed using correlation coefficient by the SPSS16 software. Results The results showed that job satisfaction had a negative correlation with WBGT index (R = -0.42, P < 0.001 and HSSI (R = -0.49, P < 0.001. Also, there was no statistical correlation among occupational stress and job performance with heat stress indices. Conclusions The present study showed that heat stress had a negative effect on job satisfaction; also there were no significant effects on job stress and job performance.
Characterizing urban vulnerability to heat stress using a spatially varying coefficient model.
Heaton, Matthew J; Sain, Stephan R; Greasby, Tamara A; Uejio, Christopher K; Hayden, Mary H; Monaghan, Andrew J; Boehnert, Jennifer; Sampson, Kevin; Banerjee, Deborah; Nepal, Vishnu; Wilhelmi, Olga V
2014-04-01
Identifying and characterizing urban vulnerability to heat is a key step in designing intervention strategies to combat negative consequences of extreme heat on human health. This study combines excess non-accidental mortality counts, numerical weather simulations, US Census and parcel data into an assessment of vulnerability to heat in Houston, Texas. Specifically, a hierarchical model with spatially varying coefficients is used to account for differences in vulnerability among census block groups. Socio-economic and demographic variables from census and parcel data are selected via a forward selection algorithm where at each step the remaining variables are orthogonalized with respect to the chosen variables to account for collinearity. Daily minimum temperatures and composite heat indices (e.g. discomfort index) provide a better model fit than other ambient temperature measurements (e.g. maximum temperature, relative humidity). Positive interactions between elderly populations and heat exposure were found suggesting these populations are more responsive to increases in heat. Copyright © 2014 Elsevier Ltd. All rights reserved.
Effective stress law for the permeability of a limestone
Ghabezloo, Siavash; Guédon, Sylvine; Martineau, François
2008-01-01
The effective stress law for the permeability of a limestone is studied experimentally by performing constant head permeability tests in a triaxial cell with different conditions of confining pressure and pore pressure. Test results have shown that a pore pressure increase and a confining pressure decrease both result in an increase of the permeability, and that the effect of the pore pressure change on the variation of the permeability is more important than the effect of a change of the confining pressure. A power law is proposed for the variation of the permeability with the effective stress. The permeability effective stress coefficient increases linearly with the differential pressure and is greater than one as soon the differential pressure exceeds few bars. The test results are well reproduced using the proposed permeability-effective stress law. A conceptual pore-shell model based on a detailed observation of the microstructure of the studied limestone is proposed. This model is able to explain the ex...
On the micropolar flow in a circular pipe: the effects of the viscosity coefficients
无
2011-01-01
This paper considers the stationary flow of incompressible micropolar fluid through a thin cylindrical pipe governed by the pressure drop between pipe's ends. Its goal is to investigate the influence of the viscosity coefficients on the effective flow. Depending on the magnitude of viscosity coefficients with respect to the pipe's thickness, it derives different asymptotic models and discusses their properties.
Fractal scaling of effective diffusion coefficient of solute in porous media
无
2001-01-01
Fractal approach is used to derive a power law relation betweeneffective diffusion coefficient of solute in porous media and the geometry parameter characterizing the media. The results are consistent with the empirical equations analogous to Archie'slaw and are expected to be applied to prediction of effective diffusion coefficient.
Determination of effective heat transport coefficients for wall-cooled packed beds
Borkink, J.G.H.; Borkink, J.G.H.; Westerterp, K.R.
1992-01-01
The influence is studied of several assumptions, often made in literature, on the values for the effective radial heat conductivity, wall heat transfer coefficient and overall heat transfer coefficient, as obtained from experiments in wall-cooled packed beds without a chemical reaction. Especially t
Lee, Youho; Lee, Jeong Ik; Cheon, Hee [KAIST, Daejeon (Korea, Republic of)
2015-05-15
Accurate modeling of thermal shock induced stresses has become ever most important to emerging accident-tolerant ceramic cladding concepts, such as silicon carbide (SiC) and SiC coated zircaloy. Since fractures of ceramic (entirely ceramic or coated) occur by excessive tensile stresses with linear elasticity, modeling transient stress distribution in the material provides a direct indication of the structural integrity. Indeed, even for the current zircaloy cladding material, the oxide layer formed on the surface - where cracks starts to develop upon water quenching - essentially behaves as a brittle ceramic. Hence, enhanced understanding of thermal shock fracture of a brittle material would fundamentally contribute to safety of nuclear reactors for both the current fuel design and that of the coming future. Understanding thermal shock fracture of a brittle material requires heat transfer rate between the solid and the fluid for transient temperature fields of the solid, and structural response of the solid under the obtained transient temperature fields. In water quenching, a solid experiences dynamic time-varying heat transfer rates with phase changes of the fluid over a short quenching period. Yet, such a dynamic change of heat transfer rates during the water quenching transience has been overlooked in assessments of mechanisms, predictability, and uncertainties for thermal shock fracture. Rather, a time-constant heat transfer coefficient, named 'effective heat transfer coefficient' has become a conventional input to thermal shock fracture analysis. No single constant heat transfer could suffice to depict the actual stress evolution subject to dynamic heat transfer coefficient changes with fluid phase changes. Use of the surface temperature dependent heat transfer coefficient will remarkably increase predictability of thermal shock fracture of brittle materials and complete the picture of stress evolution in the quenched solid. The presented result
Yamashita, Osamu [Research and Development, Materials Science Co. Ltd., 5-5-44, Minamikasugaoka, Ibaraki, Osaka 567-0046 (Japan)
2009-09-15
The resultant Seebeck coefficient {alpha}{sub R}(T{sub z}) of a thermoelectric (TE) element was derived analytically from the temperature dependence of the intrinsic Seebeck coefficient {alpha}{sub I}(T{sub z}) by taking into account the Thomson effect, where T{sub z} is a temperature at z along a TE element. The analysis was performed by expanding {alpha}{sub I}(T{sub z}) in a power series in (T{sub z}-T), where T is a mean temperature. As a result, when {alpha}{sub I}(T{sub z}) has a convex curve exhibiting a local maximum at T{sub z}=T, {alpha}{sub R}(T{sub z}) is increased at the interfaces of a TE element, while when it has a concave curve giving a local minimum at T{sub z}=T, {alpha}{sub R}(T{sub z}) deteriorates there. If the p-type (Bi{sub 0.4}Sb{sub 0.6}){sub 2}Te{sub 3} with a local maximum of {alpha}{sub I}(T{sub z}) at T=390 K is employed for a TE element, {alpha}{sub R}(T{sub z})/{alpha}{sub I}(T) at both interfaces is increased up to 1.53 under the condition of T = 390 K and {delta}T=200 K. A similar enhancement in {alpha}{sub R}(T{sub z})/{alpha}{sub I}(T) appeared even in the n-type (Zr-Hf)NiSn half-Heusler. When {alpha}{sub I}(T{sub z}) varies nonlinearly with changes in T{sub z}, therefore, the TE figure of merit Z{sub R}(T{sub z})T{sub z} is found to be affected dramatically at the interfaces. The average resultants Z{sub AR}(T) estimated for the p-type Bi-Te and n-type half-Heusler compound reach great values of 1.46 and 1.26 times as large as their intrinsic Z(T), respectively. The experimental method to confirm such a phenomenon is also proposed here. The performance of a TE element is thus expected to be enhanced significantly not only by improving the intrinsic Z(T{sub z})T{sub z} but also by optimizing the T{sub z}-dependence of {alpha}{sub I}(T{sub z}). (author)
Effective diffusion coefficient of biological liquids in porous calcium phosphate coatings
Nazarenko, N. N.; Knyazeva, A. G.
2016-11-01
The study offers a method to estimate effective diffusion coefficients for transfer of biological liquids in porous materials. The method is based on the analysis of areas occupied by pores and solid materials on slice images. The possibility is shown for ascertaining a correlation between the effective coefficient and technological conditions because different structure and porosity are observed experimentally. The correlations of effective diffusion coefficients with the production voltage for different coating-base compositions, on which the coating was grown, have been built.
Mazumder, Surasree; Alam, Jan-e
2014-01-01
The effects of gluon radiation by charm quarks on the transport coefficients {\\it e.g.} drag, longitudinal and transverse diffusion and shear viscosity have been studied within the ambit of perturbative quantum chromodynamics (pQCD) and kinetic theory. We found that while the soft gluon radiation has substantial effects on the transport coefficients of the charm quarks in the quark gluon plasma its effects on the equilibrium distribution function is insignificant.
Acoustoelastic effect in stressed heterostructures.
Osetrov, Alexander Vladimirovich; Fröhlich, Heinz-Jürgen; Koch, Reinhold; Chilla, Eduard
2002-01-01
Mechanical stresses influence the phase velocity of acoustic waves, known as the AE (acoustoelastic) effect. In order to calculate the AE effect of biaxially stressed layered systems, we extended the transfer matrix method for acoustic wave propagation by considering the change of the density, the influence of residual stress, and the modification of the elastic stiffness tensor by residual strain and by third-order constants. The generalized method is applied to the calculation of the angular dispersion of the AE effect for transverse bulk modes and surface acoustic waves on Ge(001). Our calculations reveal that the AE effect significantly depends on the propagation direction and can even change sign. The maximal velocity change occurs for transversally polarized waves propagating parallel to the [110] direction. For the layered Ge/Si(001) system, the AE effect is investigated for Love modes propagating in the [100] and [110] directions. The AE effect increases rapidly with increasing layer thickness and almost reaches its maximal value when the wave still penetrates into the unstressed substrate.
剪切系数对Timoshenko梁模型影响研究%Effects of Shear Coefficients on Timoshenko Beam
王乐; 冷德新
2015-01-01
Timoshenko首次在梁理论中引入剪切系数用于表征梁的剪应力沿截面的变化，剪切系数对于Timoshenko梁建模至关重要，研究剪切系数对Timoshenko梁模型固有特性的影响。首先采用有限元法建立了动力学模型，给出等截面梁和变截面梁刚度矩阵计算方法，然后研究不同剪切系数对梁频率和振型的影响。结果表明，剪切系数会对模型的频率计算结果带来一定影响，但对振型影响很小，采用第二种剪切系数的模型计算精度更高。%Abstact:Timoshenko was the first tointroduce a shear coefficient to account for the variation of the shear stress along the cross-section, the shear coefficient was important to Timoshenko Beam. The effects of shear coefficients on the inherent characteristics of Timoshenko beam were studied. First, the dynamic model was established using FEM, the calculation methods of stiffness matrices were proposed for uniform beam and non-uniform beam, and then the influence of different coefficients on the frequency and mode shape of beam was discussed. The results show that shear coefficients bring about some influence on frequencies, but have little effect on mode shape; the precision of the model using the second shear coefficient is higher.
N.B. Naduvinamani
2017-05-01
Full Text Available The effect of couple stresses on static and dynamic characteristics of exponential slider bearing in the presence of magnetic field considering squeeze action is theoretically analyzed in this paper. The modified magnetohydrodynamic couple stress Reynolds type equation is derived on the basis of Stokes couple stress model and closed form expressions are obtained for static and dynamic character coefficients. Comparing with bearing lubricated with non-conducting Newtonian lubricants, the magnetohydrodynamic couple stress lubrication provides the higher steady load carrying capacity, dynamic stiffness and damping coefficient. The exponential bearing shows higher efficiency for small film thickness at higher value of couple stress parameter and Hartmann number.
Kustova, Elena V.; Kremer, Gilberto M.
2015-09-01
Shear viscosity coefficient is calculated for both equilibrium and strongly non-equilibrium state-to-state vibrational distributions taking into account increasing diameters of vibrationally excited molecules. Under conditions of local thermal equilibrium, the effect of vibrational excitation on the shear viscosity coefficient is found to be negligible for temperatures below 5000 K. For T > 10 000 K, the contribution of excited states becomes important. Under non-equilibrium conditions characteristic for shock heated and supersonic expanding flows vibrational level populations deviate strongly from the Boltzmann distribution. Nevertheless, estimated coupled effect of molecular size and non-Boltzmann distributions on the shear viscosity coefficient is negligible.
Effect of coefficient changes on stability of linear retarded systems with constant time delays
Barker, L. K.
1977-01-01
A method is developed to determine the effect of coefficient changes on the stability of a retarded system with constant time delays. The method, which uses the tau-decomposition method of stability analysis, is demonstrated by an example.
Weibull Effective Area for Hertzian Ring Crack Initiation Stress
Jadaan, Osama M. [University of Wisconsin, Platteville; Wereszczak, Andrew A [ORNL; Johanns, Kurt E [ORNL
2011-01-01
Spherical or Hertzian indentation is used to characterize and guide the development of engineered ceramics under consideration for diverse applications involving contact, wear, rolling fatigue, and impact. Ring crack initiation can be one important damage mechanism of Hertzian indentation. It is caused by sufficiently-high, surface-located, radial tensile stresses in an annular ring located adjacent to and outside of the Hertzian contact circle. While the maximum radial tensile stress is known to be dependent on the elastic properties of the sphere and target, the diameter of the sphere, the applied compressive force, and the coefficient of friction, the Weibull effective area too will be affected by those parameters. However, the estimations of a maximum radial tensile stress and Weibull effective area are difficult to obtain because the coefficient of friction during Hertzian indentation is complex, likely intractable, and not known a priori. Circumventing this, the Weibull effective area expressions are derived here for the two extremes that bracket all coefficients of friction; namely, (1) the classical, frictionless, Hertzian case where only complete slip occurs, and (2) the case where no slip occurs or where the coefficient of friction is infinite.
RANS SIMULATION OF HYDROFOIL EFFECTS ON HYDRODYNAMIC COEFFICIENTS OF A PLANING CATAMARAN
Amin Najafi
2016-03-01
Full Text Available Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using RANS method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly, and requires meticulous laboratory equipment; therefore, utilizing numerical methods and developing a virtual laboratory seems highly efficient. In the present study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s (1992 experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency independent especially at high frequencies.
Effective dose conversion coefficients for radionuclides exponentially distributed in the ground
Saito, Kimiaki [Japan Atomic Energy Agency, Tokyo (Japan); Ishigure, Nobuhito [Nagoya University, Graduate School of Medicine, Nagoya City (Japan); Petoussi-Henss, Nina; Schlattl, Helmut [Helmholtz Zentrum Muenchen-German Research Center for Environmental Health, Department of Radiation Physics and Diagnostics, Neuherberg (Germany)
2012-11-15
In order to provide fundamental data required for dose evaluation due to environmental exposures, effective dose conversion coefficients, that is, the effective dose rate per unit activity per unit area, were calculated for a number of potentially important radionuclides, assuming an exponential distribution in ground, over a wide range of relaxation depths. The conversion coefficients were calculated for adults and a new-born baby on the basis of dosimetric methods that the authors and related researchers have previously developed, using Monte Carlo simulations and anthropomorphic computational phantoms. The differences in effective dose conversion coefficients due to body size between the adult and baby phantoms were found to lie within 50 %, for most cases; however, for some low energies, differences could amount to a factor of 3. The effective dose per unit source intensity per area was found to decrease by a factor of 2-5, for increasing relaxation depths from 0 to 5 g/cm{sup 2}, above a source energy of 50 keV. It is also shown that implementation of the calculated coefficients into the computation of the tissue weighting factors and the adult reference computational phantoms of ICRP Publication 103 does not significantly influence the effective dose conversion coefficients of the environment. Consequently, the coefficients shown in this paper could be applied for the evaluation of effective doses, as defined according to both recommendations of ICRP Publications 103 and 60. (orig.)
Tool for Studying the Effects of Range Restriction in Correlation Coefficient Estimation
1990-07-01
AFHRL-TP-90-6 AIR FORCE TOOL FOR STUDYING THE EFFECTS OF RANGE RESTRICTION IN CORRELATION COEFFICIENT ESTIMATION H U Douglas E. JacksonM Eastern New...the Lftects of kange Restriction in Correlation Coefficient Estimation PE - 62703F PR - 7719 4. AUTHOR(S) TA - 18 Douglas E. Jackson WU - 46 Malcolm J...that one must try to estimate the correlation coefficient between two random variables X and Y in some population P using data taken f-om a
Effect of residual stress on peak cap stress in arteries.
Vandiver, Rebecca
2014-10-01
Vulnerable plaques are a subset of atherosclerotic plaques that are prone to rupture when high stresses occur in the cap. The roles of residual stress, plaque morphology, and cap stiffness on the cap stress are not completely understood. Here, arteries are modeled within the framework of nonlinear elasticity as incompressible cylindrical structures that are residually stressed through differential growth. These structures are assumed to have a nonlinear, anisotropic, hyperelastic response to stresses in the media and adventitia layers and an isotropic response in the intima and necrotic layers. The effect of differential growth on the peak stress is explored in a simple, concentric geometry and it is shown that axial differential growth decreases the peak stress in the inner layer. Furthermore, morphological risk factors are explored. The peak stress in residually stressed cylinders is not greatly affected by changing the thickness of the intima. The thickness of the necrotic layer is shown to be the most important morphological feature that affects the peak stress in a residually stressed vessel.
S. Gholizadeh
2016-06-01
Full Text Available This study was carried out to study the inbreeding coefficient and its effect on reproductive performance of dairy cows (age at first calving, calving interval and open days in Isfahan province. Records of 31,977 (primiparous cows, 36,982 and 51,423 (multiparous cows for age at first calving, calving interval and open days were used, respectively. The inbreeding coefficients of animals were calculated using pedigree information of 78,425 females and 8,056 males, which were born from 1963 to 2009. The overall mean and maximum inbreeding coefficients in Holstein cows were 2.33% and 31.30%, respectively. The results showed that 57,234 animals were inbred with 3.57% inbreeding coefficient. Regression coefficients on inbreeding coefficient for age at first calving, calving interval and open days were 0.589±0.21, 1.08±0.15 and 0.27±12, respectively. Estimated inbreeding indicated significantly negative effect on the reproductive traits in different parturition periods. The results revealed that the average inbreeding trend was increased in the dairy herds. The increased inbreeding was due to close mating systems between the candidates, and it showed negative effects on the reproductive traits in Isfahan dairy herds.
Sadooghi, N.; Tabatabaee, S. M. A.
2017-05-01
The effects of finite magnetization and electric polarization on dissipative and non-dissipative (anomalous) transport coefficients of a chiral fluid are studied. First, using the second law of thermodynamics as well as Onsager’s time-reversal symmetry principle, the complete set of dissipative transport coefficients of this medium is derived. It is shown that the properties of the resulting shear and bulk viscosities are mainly affected by the anisotropy induced by external electric and magnetic fields. Then, using the fact that the anomaly induced currents do not contribute to entropy production, the corresponding algebro-differential equations to non-dissipative anomalous transport coefficients are derived in a certain derivative expansion. The solutions of these equations show that, within this approximation, anomalous transport coefficients are, in particular, given in terms of the electric susceptibility of the medium.
Coefficient of restitution dependence of intruder rise time in two-dimensional Brazil-nut effect
Kesuma, T.; Aji, D. P. Purwa; Viridi, S.; Suprijadi
2016-04-01
Brazil-Nut Effect (BNE) is a granular material phenomenon, where larger grains (usually known as intruder) rise to the top when the granular system vibrated. We observe a single intruder rise time of BNE phenomenon in a two-dimensional molecular dynamics simulation of hard spheres collision scheme. Some experiments have shown that some granular properties, such as size and density ratio, play an important role to determine the rise time. However, other property, such as coefficients of restitution, is considered not to have a measurable impact. We explore the intruder inelasticity dependence of the rise time by varying its coefficient of restitution. We found that the intruder rise time tends to be flat for relatively high coefficient of restitution and increases exponentially below a certain deflecting point for low coefficient of restitution. This holds for specific mass ratio.
Effect of perfectly matched layer reflection coefficient on modal analysis of leaky waveguide modes.
Lai, Chih-Hsien; Chang, Hung-chun
2011-01-17
The reflection coefficient is one important parameter of the perfectly matched layer (PML). Here we investigate its effect on the modal analysis of leaky waveguide modes by examining three different leaky waveguide structures, i.e., the holey fiber, the air-core terahertz pipe waveguide, and the gain-guided and index-antiguided slab waveguide. Numerical results reveal that the typical values 10(-8) ~10(-12) are inadequate for obtaining the imaginary part of the complex propagation constant, and the suggested reflection coefficient would be much smaller, for example, 10(-50) or 10(-100). With such a small coefficient, both the computational window size and the PML thickness can be significantly reduced without loss of stability. Moreover, in some cases, the modal field profiles can only be accurately obtained with such a small coefficient.
EFFECTIVE STRESS AND STRAIN IN FINITE DEFORMATION
周喆; 秦伶俐; 黄文彬; 王红卫
2004-01-01
Whether the concept of effective stress and strain in elastic-plastic theory is still valid under the condition of finite deformation was mainly discussed. The uni-axial compression experiments in plane stress and plane strain states were chosen for study. In the two kinds of stress states, the stress- strain curve described by logarithm strain and rotated Kirchhoff stress matches the experiments data better than the curves defined by other stressstrain description.
Adjustment of minimum seismic shear coefficient considering site effects for long-period structures
Guan, Minsheng; Du, Hongbiao; Cui, Jie; Zeng, Qingli; Jiang, Haibo
2016-06-01
Minimum seismic base shear is a key factor employed in the seismic design of long-period structures, which is specified in some of the major national seismic building codes viz. ASCE7-10, NZS1170.5 and GB50011-2010. In current Chinese seismic design code GB50011-2010, however, effects of soil types on the minimum seismic shear coefficient are not considered, which causes problems for long-period structures sited in hard or rock soil to meet the minimum base shear requirement. This paper aims to modify the current minimum seismic shear coefficient by taking into account site effects. For this purpose, effective peak acceleration (EPA) is used as a representation for the ordinate value of the design response spectrum at the plateau. A large amount of earthquake records, for which EPAs are calculated, are examined through the statistical analysis by considering soil conditions as well as the seismic fortification intensities. The study indicates that soil types have a significant effect on the spectral ordinates at the plateau as well as the minimum seismic shear coefficient. Modified factors related to the current minimum seismic shear coefficient are preliminarily suggested for each site class. It is shown that the modified seismic shear coefficients are more effective to the determination of minimum seismic base shear of long-period structures.
Cortinez, J. M.; Valocchi, A. J.; Herrera, P. A.
2013-12-01
Because of the finite size of numerical grids, it is very difficult to correctly account for processes that occur at different spatial scales to accurately simulate the migration of conservative and reactive compounds dissolved in groundwater. In one hand, transport processes in heterogeneous porous media are controlled by local-scale dispersion associated to transport processes at the pore-scale. On the other hand, variations of velocity at the continuum- or Darcy-scale produce spreading of the contaminant plume, which is referred to as macro-dispersion. Furthermore, under some conditions both effects interact, so that spreading may enhance the action of local-scale dispersion resulting in higher mixing, dilution and reaction rates. Traditionally, transport processes at different spatial scales have been included in numerical simulations by using a single dispersion coefficient. This approach implicitly assumes that the separate effects of local-dispersion and macro-dispersion can be added and represented by a unique effective dispersion coefficient. Moreover, the selection of the effective dispersion coefficient for numerical simulations usually do not consider the filtering effect of the grid size over the small-scale flow features. We have developed a multi-scale Lagragian numerical method that allows using two different dispersion coefficients to represent local- and macro-scale dispersion. This technique considers fluid particles that carry solute mass and whose locations evolve according to a deterministic component given by the grid-scale velocity and a stochastic component that corresponds to a block-effective macro-dispersion coefficient. Mass transfer between particles due to local-scale dispersion is approximated by a meshless method. We use our model to test under which transport conditions the combined effect of local- and macro-dispersion are additive and can be represented by a single effective dispersion coefficient. We also demonstrate that for
Min Zhang
2015-10-01
Full Text Available In order to study the effects of uneven adhesion coefficient and crosswind on alignment design indexes, a six-axle semi-trailer is selected as the typical vehicle model to investigate the effects of uneven adhesion coefficient caused by superelevation under the condition of rainfall on the truck's lateral stability, quantifying the crosswind using TruckSim. Based on the basic theory of vehicle dynamics, vehicle safety driving model is established. Also, the minimum radius is calculated with the consideration of uneven adhesion coefficient and crosswind. The results show that the effects of uneven adhesion coefficient and crosswind on the truck's lateral stability increase with the increasing of the truck's speed. Truck's lateral slide instability begins to appear when crosswind grade grows up to 9 or above. According to sensitive analysis, speed, rainfall, crosswind, and the interaction of the speed and rainfall have significant influences on the truck's lateral stability. The results quantify the effects of uneven adhesion coefficient and crosswind on truck's lateral stability. The advised index for horizontal curve design control is proposed, which provides a good reference for road safety design and safety protective measures. It can also provide theoretical basis and guidelines for highway safe operation in the windy and rainy areas.
EFFECTS OF ROCK BEHAVIOR AND STRESS CONDITIONON FIELD STRESS DETERMINATION
D.H.（Steve）Zou
1995-01-01
Non-consistency of stress results is often observed during field measurements. In some cases, even the measurements are made at the same location in a massive rockmass, the results can vary widely. In order to solve the problem, extensive research has been carried out to study the major factors which may affect stress determination. They include the rock behaviour and the stress state. For rocks showing non-isotropic behaviour, the values of Young's modulus and Poisson ratio vary with the orientation of loading and measurement. Stress condition in the rock affects the rock behaviour. Furthermore, the loading condition on rock samples during laboratory tests is different from in the field and therefore the determined elastic constants may not represent the field condition. In general, the Young's modulus may depend on the orientation, the loading path, the stress magnitude and the stress ratio. This paper examines in detail the effects of those factors, especially for rocks showing transversely isotropic behaviour. It is found that the discrepancy of stress results from fieldts in this type of rock is mainly due to over simplification of the rock behavior and inadequate use of elastic constants of the rock during stress calculation. A case study is given, which indicates the significance of these factors and demonstrates the proper procedure for stress calculation from
Random effects coefficient of determination for mixed and meta-analysis models.
Demidenko, Eugene; Sargent, James; Onega, Tracy
2012-01-01
The key feature of a mixed model is the presence of random effects. We have developed a coefficient, called the random effects coefficient of determination, [Formula: see text], that estimates the proportion of the conditional variance of the dependent variable explained by random effects. This coefficient takes values from 0 to 1 and indicates how strong the random effects are. The difference from the earlier suggested fixed effects coefficient of determination is emphasized. If [Formula: see text] is close to 0, there is weak support for random effects in the model because the reduction of the variance of the dependent variable due to random effects is small; consequently, random effects may be ignored and the model simplifies to standard linear regression. The value of [Formula: see text] apart from 0 indicates the evidence of the variance reduction in support of the mixed model. If random effects coefficient of determination is close to 1 the variance of random effects is very large and random effects turn into free fixed effects-the model can be estimated using the dummy variable approach. We derive explicit formulas for [Formula: see text] in three special cases: the random intercept model, the growth curve model, and meta-analysis model. Theoretical results are illustrated with three mixed model examples: (1) travel time to the nearest cancer center for women with breast cancer in the U.S., (2) cumulative time watching alcohol related scenes in movies among young U.S. teens, as a risk factor for early drinking onset, and (3) the classic example of the meta-analysis model for combination of 13 studies on tuberculosis vaccine.
Leung, Juliana Y; Srinivasan, Sanjay
2016-09-01
Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It
Leung, Juliana Y.; Srinivasan, Sanjay
2016-09-01
Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It
Surplus thermal energy model of greenhouses and coefficient analysis for effective utilization
Seung-Hwan Yang
2016-03-01
Full Text Available If a greenhouse in the temperate and subtropical regions is maintained in a closed condition, the indoor temperature commonly exceeds that required for optimal plant growth, even in the cold season. This study considered this excess energy as surplus thermal energy (STE, which can be recovered, stored and used when heating is necessary. To use the STE economically and effectively, the amount of STE must be estimated before designing a utilization system. Therefore, this study proposed an STE model using energy balance equations for the three steps of the STE generation process. The coefficients in the model were determined by the results of previous research and experiments using the test greenhouse. The proposed STE model produced monthly errors of 17.9%, 10.4% and 7.4% for December, January and February, respectively. Furthermore, the effects of the coefficients on the model accuracy were revealed by the estimation error assessment and linear regression analysis through fixing dynamic coefficients. A sensitivity analysis of the model coefficients indicated that the coefficients have to be determined carefully. This study also provides effective ways to increase the amount of STE.
Surplus thermal energy model of greenhouses and coefficient analysis for effective utilization
Yang, S.H.; Son, J.E.; Lee, S.D.; Cho, S.I.; Ashtiani-Araghi, A.; Rhee, J.Y.
2016-11-01
If a greenhouse in the temperate and subtropical regions is maintained in a closed condition, the indoor temperature commonly exceeds that required for optimal plant growth, even in the cold season. This study considered this excess energy as surplus thermal energy (STE), which can be recovered, stored and used when heating is necessary. To use the STE economically and effectively, the amount of STE must be estimated before designing a utilization system. Therefore, this study proposed an STE model using energy balance equations for the three steps of the STE generation process. The coefficients in the model were determined by the results of previous research and experiments using the test greenhouse. The proposed STE model produced monthly errors of 17.9%, 10.4% and 7.4% for December, January and February, respectively. Furthermore, the effects of the coefficients on the model accuracy were revealed by the estimation error assessment and linear regression analysis through fixing dynamic coefficients. A sensitivity analysis of the model coefficients indicated that the coefficients have to be determined carefully. This study also provides effective ways to increase the amount of STE. (Author)
The effect of structural coefficient on stiffness and deformation of hydrostatic guideway
Lai, Zhifeng; Qiao, Zheng; Zhang, Peng; Wang, Bo; Wu, Yangong
2016-10-01
Hydrostatic guideway has been widely used for ultra-precision machine tools due to its high stiffness and motion accuracy. In order to optimize the stiffness and motion accuracy of hydrostatic guideway, the effect of different diameters orifice restrictors on the stiffness and deformation of hydrostatic guideway is investigated in detail in this paper. The theoretically optimal structural coefficient is verified through the experiments. Hydrostatic guideway can obtain the maximum stiffness when the value of optimal structural coefficient is 0.707. And changing the diameter of orifice restrictors is an effective method to adjusting the structural coefficient. Due to the error caused by manufacture and assembly of hydrostatic guideway, the optimal structural coefficient is hard to be obtained accurately. Based on this condition, a larger structural coefficient is adopted to reduce the oil pressure in the pocket of hydrostatic guideway effectively, so that the deformation of guideway can be reduced. And finally, the stiffness loss caused by the deformation decreased. In addition, the experimental results show that the maximum deformation of hydrostatic guideway can be reduced from 2.06μm to 1.82μm and the stiffness arise from 1453N/μm to 1855N/μm when orifice restrictors with 0.15mm diameter are used rather than 0.2mm diameter.
A stress "deafness" effect in European Portuguese.
Correia, Susana; Butler, Joseph; Vigário, Marina; Frota, Sónia
2015-03-01
Research on the perception of word stress suggests that speakers of languages with non-predictable or variable stress (e.g., English and Spanish) are more efficient than speakers of languages with fixed stress (e.g., French and Finnish) at distinguishing nonsense words contrasting in stress location. In addition, segmental and suprasegmental cues to word stress may also impact on the ability of speakers to perceive stress. European Portuguese (EP) is a language with variable stress and vowel reduction. Previous studies on EP have identified duration as the main cue for stress. In the present study, we investigated the perception of word stress in EP, both in nuclear (NP) and post-nuclear (PN) positions, by means of three experiments. Experiment I was an ABX discrimination task with stress and phoneme contrasts, without vowel reduction. Experiments 2 and 3 were sequence recall tasks with stress and phoneme contrasts, vowel reduction being added to the stress contrast only in experiment 3. Results showed significantly higher error rates in the stress contrast condition than in the phoneme contrast condition, when duration alone (PN), or duration and pitch accents (NP), are present in the stimuli (experiments I and 2). When vowel reduction is added, EP speakers are able to perceive stress contrasts (experiment 3). The results show that vowel reduction appears to be the most robust cue for stress in EP. In the absence of vowel quality cues, a stress "deafness" effect may emerge in a language with non-predictable stress that combines both suprasegmental and segmental information to signal word stress. These findings have implications for claims of a prosodic-based cross-linguistic perception of word stress in the absence of vowel quality, and for stress "deafness" as a consequence of a predictable stress grammar.
CAO Hai-Xia; WU Yin-Zhong; LI Zhen-Ya
2005-01-01
In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It is exhibited that the dielectric gradient has a nontrivial influence on the effective pyroelectric coefficient, but has a little influence on the polarization offset; and the polarization gradient plays an important role in the abnormal hysteresis loop phenomenon of the co.mpositionally step-like graded ferroelectric structures. Moreover, the origin of the polarization offset is explored,which can be attributed to the polarization gradient in the compositionally step-like graded structure.
Long-Range Effects on the Pyroelectric Coefficient of Ferroelectric Superlattice
DONG Wen; YAO Dong-Lai; WU Yin-Zhong; LI Zhen-Ya
2002-01-01
Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two differentferroelectric materials are investigated based on the transverse Ising model. The effects of the interfacial coupling andthe thickness of one period on the pyroelectric coefficient of the ferroelectric superlattice are studied by taking intoaccount the long-range interaction. It is found that with the increase of the strength of the long-range interaction, thepyroelectric coefficient decreases when the temperature is lower than the phase transition temperature; the number ofthe pyroelectric peaks decreases gradually and the phase transition temperature increases. It is also found that with thedecrease of the interfacial coupling and the thickness of one period, the phase transition temperature and the number ofthe pyroelectric peaks decrease.
Long—Range Effects on the Pyroelectric Coefficient of Ferroelectric Superlattice
DONGWen; WUYin－Zhong; 等
2002-01-01
Long-range effects on the pyroelectric coefficient of a ferroelectric superlattice consisting of two different ferroelectric materials are investigated based on the transverse Ising model.The effects of the interfacial coupling and the thickness of one period on the pyroelectric coefficient of the ferroelectric superlattics are studied by taking into account the long-range interaction.It is found that with the increase of the strength of the long-range interaction,the pyroelectric coefficient decreases when the temperature is lower than the phase transition temperature;the mumber of the pyroelectric peaks decreases gradually and the phase transition temperature increases,It is also found that with the decrease of the interfacial coupling and the thickness of one period.the phase transition temperature and the number of the pyroelectric peaks decrease.
Investigation of La3+ Doping Effect on Piezoelectric Coefficients of BLT Ceramics
Wodecka-Dus B.
2017-06-01
Full Text Available Effects of La3+ admixture in barium lanthanum titanate (BLT ceramics system with colossal permittivity on performance of prospective piezoelectric cold plasma application were studied. Usage of cold atmospheric pressure plasma appears promising in terms of industrial and healthcare applications. Performed investigation provide consistent evaluation of doping lanthanum amount on piezoelectric coefficients values with simultaneous capability of charge accumulation for effective plasma generation. Modification of ferroelectric materials with heterovalent ions, however with the lower radii than the original atoms, significantly affects their domain mobility and consequently electromechanical properties. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented, and values of piezoelectric and dielectric parameters were recorded. Finally the results indicated that addition of 0.4 mol.% of La3+ ions to the ceramic structure maximally increased the values of piezoelectric coefficient to d33 = 20 pC/N and to huge dielectric constant to ε33T = 29277.
Stress Effects on Multiple Memory System Interactions.
Ness, Deborah; Calabrese, Pasquale
2016-01-01
Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory systems, we review recent animal and human studies exploring the effects of stress on multiple memory systems. Apart from discussing the interaction between distinct memory systems in stressful situations, we will also outline the fundamental role of the amygdala in mediating such stress effects. Additionally, based on the methods applied in the herein discussed studies, we will discuss how memory translates into behaviour.
Stress Effects on Multiple Memory System Interactions
Deborah Ness
2016-01-01
Full Text Available Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory systems, we review recent animal and human studies exploring the effects of stress on multiple memory systems. Apart from discussing the interaction between distinct memory systems in stressful situations, we will also outline the fundamental role of the amygdala in mediating such stress effects. Additionally, based on the methods applied in the herein discussed studies, we will discuss how memory translates into behaviour.
The influence of reactor core parameters on effective breeding coefficient Keff
Liu Li-Po; Liu Yi-Bao; Wang Juan; Yang Bo; Zhang Tao
2008-01-01
The values of effective breeding coefficient Keff in a reactor core of nuclear power plant are calculated for different values of parameters (core structure, fuel assembly component) by using the Monte Carlo method. The obtained values of Keff are compared and analysed, which can provide theoretical basis for reactor design.
Estimation of the Nonlinear Random Coefficient Model when Some Random Effects Are Separable
du Toit, Stephen H. C.; Cudeck, Robert
2009-01-01
A method is presented for marginal maximum likelihood estimation of the nonlinear random coefficient model when the response function has some linear parameters. This is done by writing the marginal distribution of the repeated measures as a conditional distribution of the response given the nonlinear random effects. The resulting distribution…
THE EFFECT OF THE ALUMINIUM ALLOY SURFACE ROUGHNESS ON THE RESTITUTION COEFFICIENT
Stanisław Bławucki
2015-08-01
Full Text Available The paper presents the results of research on the effect of the surface roughness of aluminum alloy on its coefficient of restitution. It describes the current method of finishing the workpiece surface layer after cutting and innovative measuring device which was used in the research. The material used in the research was aluminium alloy EN AW 7075. The paper also presents a relationship between the coefficient of restitution and surface roughness of the milled samples as well as impressions left by bead in function of velocity and a sample surface roughness.
Effect of Ionic Liquids on Organic Reactions Based on Activity Coefficients at Infinite Dilution
马征; 董晓霞; 胡玉峰; 张柏松; 徐长英; 刘艳升
2013-01-01
It is important to know how ILs (ionic liquids) influence organic reaction. In this paper, activity coeffi-cients at infinite dilution of more than 80 organic compounds in ILs are collected and analyzed systematically. Through the study on typical organic reactions happened in ILs, such as Diels-Alder, esterification and Friedel-Crafts reaction, the ratio of activity coefficients at infinite dilution of products and reactants is employed to estimate different effects of different structural ILs on the rate and selectivity of reactions.
Pharoah, J. G.; Karan, K.; Sun, W.
This paper reviews the approach taken in the literature to model the effective transport coefficients - mass diffusivity, electrical conductivity, thermal conductivity and hydraulic permeability - of carbon-fibre based porous electrode of polymer electrolyte membrane fuel cells (PEMFCs). It is concluded that current PEMFC model do not account for the inherent anisotropic microstructure of the fibrous electrodes. Simulations using a 2-D PEMFC cathode model show that neglecting the anisotropic nature and associated transport coefficients of the porous electrodes significantly influences both the nature and the magnitude of the model predictions. This emphasizes the need to appropriately characterize the relevant anisotropic properties of the fibrous electrode.
On the effect of shear coefficients in free vibration analysis of curved beams
Kim, Jin Gon; Lee, Jae Kon; Yoon, Hyun Joong [Catholic University of Daegu, Daegu (Korea, Republic of)
2014-08-15
We did a comparative study of shear coefficients in free vibration analysis of curved beams having circular and rectangular cross sections. Until recently, the shear coefficient k in Timoshenko beam theory has been studied by many researchers to include transverse shear deformation effect. To obtain more reliable numerical results, a higher-order hybrid-mixed curved beam element is formulated and programmed in MATLAB. The present numerical experiments show that k = 6(1+v){sup 2}/(7+12v+4v{sup 2}) is the best expression both for circular and rectangular cross-sections in the flexural vibration of curved beams.
Usang, M. D.; Ivanyuk, F. A.; Ishizuka, C.; Chiba, S.
2016-10-01
Nuclear fission is treated by using the Langevin dynamical description with macroscopic and microscopic transport coefficients (mass and friction tensors), and it is elucidated how the microscopic (shell and pairing) effects in the transport coefficients, especially their dependence on temperature, affects various fission observables. We found that the microscopic transport coefficients, calculated by linear response theory, change drastically as a function of temperature: in general, the friction increases with growing temperature while the mass tensor decreases. This temperature dependence brings a noticeable change in the mass distribution and kinetic energies of fission fragments from nuclei around 236U at an excitation energy of 20 MeV. The prescission kinetic energy decreases from 25 MeV at low temperature to about 2.5 MeV at high temperature. In contrast, the Coulomb kinetic energy increases as the temperature increases. Interpolating the microscopic transport coefficients among the various temperatures enabled our Langevin equation to use the microscopic transport coefficients at a deformation-dependent local temperature of the dynamical evolution. This allowed us to compare directly the fission observables of both macroscopic and microscopic calculations, and we found almost identical results under the conditions considered in this work.
Effect of Opening the Sash of a Centre-Pivot Roof Window on Wind Pressure Coefficients
Iqbal, Ahsan; Wigö, Hans; Heiselberg, Per
2014-01-01
This paper describes the effect of outward opening the sash of a window on local and overall wind pressures. Wind tunnel experiments were used for the purpose of evaluation. A centre-pivot roof window on a pitched roof in a modelled scaled building was used in the analysis of wind pressures. The ...... pressure distribution nearby the window. The use of wind pressure coefficients from the analysis of sealed plain surface may lead to erroneous estimation of airflow rate.......This paper describes the effect of outward opening the sash of a window on local and overall wind pressures. Wind tunnel experiments were used for the purpose of evaluation. A centre-pivot roof window on a pitched roof in a modelled scaled building was used in the analysis of wind pressures....... The wind pressures were defined in terms of wind pressure coefficients. Traditionally wind pressure coefficients are extracted from the analysis of sealed plain surface. These wind pressure coefficients are used to estimate the natural ventilation rate through windows/openings due to wind effect. Surface...
Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey
Zhou, Quanlin; Liu, Hui Hai; Molz, Fred J.; Zhang, Yingqi; Bodvarsson, Gudmundur S.
2005-03-28
Matrix diffusion is an important mechanism for solutetransport in fractured rock. We recently conducted a literature survey onthe effective matrix diffusion coefficient, Dem, a key parameter fordescribing matrix diffusion processes at the field scale. Forty fieldtracer tests at 15 fractured geologic sites were surveyed and selectedfor study, based on data availability and quality. Field-scale Dem valueswere calculated, either directly using data reported in the literature orby reanalyzing the corresponding field tracer tests. Surveyed dataindicate that the effective-matrix-diffusion-coefficient factor FD(defined as the ratio of Dem to the lab-scale matrix diffusioncoefficient [Dem]of the same tracer) is generally larger than one,indicating that the effective matrix diffusion coefficient in the fieldis comparatively larger than the matrix diffusion coefficient at therock-core scale. This larger value could be attributed to the manymass-transfer processes at different scales in naturally heterogeneous,fractured rock systems. Furthermore, we observed a moderate trend towardsystematic increase in the emDFmDDF value with observation scale,indicating that the effective matrix diffusion coefficient is likely tobe statistically scale dependent. The FD value ranges from 1 to 10,000for observation scales from 5 to 2,000 m. At a given scale, the FD valuevaries by two orders of magnitude, reflecting the influence of differingdegrees of fractured rock heterogeneity at different sites. In addition,the surveyed data indicate that field-scale longitudinal dispersivitygenerally increases with observation scale, which is consistent withprevious studies. The scale-dependent field-scale matrix diffusioncoefficient (and dispersivity) may have significant implications forassessing long-term, large-scale radionuclide and contaminant transportevents in fractured rock, both for nuclear waste disposal and contaminantremediation.
Effective stress law for anisotropic double porous media
ZHAO Ying; CHEN Mian; ZHANG Guangqing
2004-01-01
An effective stress law is derived analytically to describe the effect of pore (fracture pore and matrix-block pore) fluid pressure on the linearly elastic response of anisotropic saturated dual-porous rocks, which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic simply multiplied by Biot coefficient. The effective stress law involves four constants for transversely isotropic response; these constants can be expressed in terms of the moduli of the single porous material, double porous material and of the solid material. These expressions are simplified considerably when the anisotropy is structural rather than intrinsic, i.e. in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves grain bulk modulus, four moduli and two compliances of the porous material for transverse isotropy. The law reduces, in the case of isotropic response, to that suggested by Li Shuiquan (2001). And reduction to the single-porosity (derived analytically by Carroll (1979)) is presented to demonstrate the conceptual consistency of the proposed law.
FIELD-SCALE EFFECTIVE MATRIX DIFFUSION COEFFICIENT FOR FRACTURED ROCK:RESULTS FROM LITERATURE SURVEY
Q. Zhou; Hui-Hai Liu; F.J. Molz; Y. Zhang; G.S. Bodvarsson
2005-04-08
Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D{sub m}{sup e}, a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D{sub m}{sup e} values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor F{sub D} (defined as the ratio of D{sub m}{sup e} to the lab-scale matrix diffusion coefficient [D{sub m}] of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the F{sub D} value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The F{sub D} value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F{sub D} value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal
Gritsch, M.; Saumweber, C.; Schulz, A.; Wittig, S.; Sharp, E.
2000-01-01
Discharge coefficients of three film-cooling hole geometries are presented over a wide range of engine like conditions. The hole geometries comprise a cylindrical hole and two holes with a diffuser-shaped exit portion (a fanshaped and a laidback fanshaped hole). For all three hole geometries the hole axis was inclined 30 deg with respect to the direction of the external (hot gas) flow. The flow conditions considered were the hot gas crossflow Mach number (up to 0.6), the coolant crossflow Mach number (up to 0.6) and the pressure ratio across the hole (up to 2). The effect of internal crossflow approach direction, perpendicular or parallel to the main flow direction, is particularly addressed in the present study. Comparison is made of the results for a parallel and perpendicular orientation, showing that the coolant crossflow orientation has a strong impact on the discharge behavior of the different hole geometries. The discharge coefficients were found to strongly depend on both hole geometry and crossflow conditions. Furthermore, the effects of internal and external crossflow on the discharge coefficients were described by means of correlations used to derive a predicting scheme for discharge coefficients. A comparison between predictions and measurements reveals the capability of the method proposed.
Mijajlović Miroslav M.
2016-01-01
Full Text Available The friction coefficient in many friction stir welding researches is generally used as an effective, constant value without concern on the adaptable and changeable nature of the friction during welding sequence. This is understandable because the main problem in analyzing friction in friction stir welding are complex nature of the friction processes, case-dependent and time dependent contact between the bodies, influence of the temperature, sliding velocity, etc. This paper is presenting a complex experimental-numerical-analytical model for estimating the effective friction coefficient on contact of the bobbin tool and welding plates during welding, considering the temperature at the contact as the most influencing parameter on friction. The estimation criterion is the correspondence of the experimental temperature and temperature from the numerical model. The estimation procedure is iterative and parametric - the heat transport parameters and friction coefficient are adapted during the estimation procedure in a realistic manner to achieve relative difference between experimental and model’s temperature lower than 3%. The results show that friction coefficient varies from 0.01 to 0.21 for steel-aluminium alloy contact and temperature range from 406°C to 22°C.
Effect of stress on structural brain asymmetry.
Zach, Petr; Vales, Karel; Stuchlik, Ales; Cermakova, Pavla; Mrzilkova, Jana; Koutela, Antonella; Kutova, Martina
2016-09-01
There is a growing body of evidence that stressful events may affect the brain not only as a whole, but also in multiple laterality aspects. The present review is aimed at discussing the effect of stress and stress hormones on structural brain asymmetry. Differences and crossroads of functional and structural asymmetry are briefly mentioned throughout the document. The first part of this review summarizes major findings in the field of structural brain asymmetries in animals and humans from the evolutionary perspective. Additionally, effect of stress on animals is discussed generally. The second part then explores asymmetrical effects of stress on structural changes of principal brain areas - amygdala, hippocampus, neocortex, diencephalon, basal forebrain and basal ganglia from the point of normal lateralization, steroids, trauma and genetic factors. At the end we present hypothesis why stress appears to have asymmetrical effects on lateralized brain structures.
Ping'en Li; Youquan Yin; Xianyue Su
2006-01-01
Based on the nonlinear theory of acoustoelasticity,considering the triaxial terrestrial stress,the fluid static pressure in the borehole and the fluid nonlinear effect jointly,the dispersion curves of the monopole Stoneley wave and dipole flexural wave propagating along the borehole axis in a homogeneous isotropic formation are investigated by using the perturbation method.The relation of the sensitivity coefficient and the velocity-stress coefficient to frequency are also analyzed.The results show that variations of the phase velocity dispersion curve are mainly affected by three sensitivity coefficients related to third-order elastic constant.The borehole stress concentration causes a split of the flexural waves and an intersection of the dispersion curves of the flexural waves polarized in directions parallel and normal to the uniaxial horizontal stress direction.The stress-induced formation anisotropy is only dependent on the horizontal deviatoric terrestrial stress and independent of the horizontal mean terrestrial stress,the superimposed stress and the fluid static pressure.The horizontal terrestrial stress ratio ranging from 0 to 1 reduces the stress-induced formation anisotropy.This makes the intersection of flexural wave dispersion curves not distinguishable.The effect of the fluid nonlinearity on the dispersion curve of the mode wave is small and can be ignored.
Bretscher, M.M.
1984-01-01
Simple diffusion theory cannot be used to evaluate control rod worths in thermal neutron reactors because of the strongly absorbing character of the control material. However, reliable control rod worths can be obtained within the framework of diffusion theory if the control material is characterized by a set of mesh-dependent effective diffusion parameters. For thin slab absorbers the effective diffusion parameters can be expressed as functions of a suitably-defined pair of blackness coefficients. Methods for calculating these blackness coefficients in the P/sub 1/, P/sub 3/, and P/sub 5/ approximations, with and without scattering, are presented. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method, based on reaction rate ratios, is discussed.
Cooper pair breaking and isotope effect coefficient variation in high-T{sub c} superconductors
Singh, S.P.; Pandey, R.K.; Singh, P. [G.B. Pant Univ. Pantanagar, Nainital (India)
1996-06-01
The effect of pair breaking on the isotope effect coefficient a = {minus}d ln T{sub c}/d ln M in La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and Pr-, Ca-, and Zn-doped YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} and EuBa{sub 2}Cu{sub 3}O{sub 7{minus}x} is studied using the generalized Abrikosov-Gorkov theory recently employed by Singh and Kishore for superconductivity. It is argued that the isotope effect coefficient a can be further enhanced, in agreement with experimental observation, by considering the dependence of the characteristic scattering time {tau}{sub s} for Cooper pairs on the concentration n of impurities (both magnetic and nonmagnetic) and the disorder ignored by them.
Piasecka Magdalena
2016-01-01
Full Text Available The aim of the paper is to estimate effect of the heating surface enhancement on FC-72 flow boiling heat transfer for a vertical minichannel 1.7 mm deep, 24 mm wide and 360 mm long. Two types of enhanced heating surfaces were used: one with minicavities distributed unevenly, and the other with capillary metal fibrous structure. It was to measure temperature field on the plain side of the heating surface by means of the infrared thermography and to observe the two-phase flow patterns on the enhanced foil side. The paper analyses mainly the impact of the microstructured heating surface on the heat transfer coefficient. The results are presented as heat transfer coefficient dependences on the distance along the minichannel length. The data obtained using two types of enhanced heating surfaces in experiments was compared with the data when smooth foil as the heating surface was used. The highest local values of heat transfer coefficient were obtained using enhanced foil with minicavities - in comparison to other cases. Local values of heat transfer coefficient received for capillary fibrous structure were the lowest, even compared with data obtained for smooth foil. Probably this porous structure caused local flow disturbances.
Sambaer, Wannes; Zatloukal, Martin; Kimmer, Dusan
2013-04-01
Realistic SEM image based 3D filter model considering transition/free molecular flow regime, Brownian diffusion, aerodynamic slip, particle-fiber and particle-particle interactions together with a novel Euclidian distance map based methodology for the pressure drop calculation has been utilized for a polyurethane nanofiber based filter prepared via electrospinning process in order to more deeply understand the effect of particle-fiber friction coefficient on filter clogging and basic filter characteristics. Based on the performed theoretical analysis, it has been revealed that the increase in the fiber-particle friction coefficient causes, firstly, more weaker particle penetration in the filter, creation of dense top layers and generation of higher pressure drop (surface filtration) in comparison with lower particle-fiber friction coefficient filter for which deeper particle penetration takes place (depth filtration), secondly, higher filtration efficiency, thirdly, higher quality factor and finally, higher quality factor sensitivity to the increased collected particle mass. Moreover, it has been revealed that even if the particle-fiber friction coefficient is different, the cake morphology is very similar.
Effect of graphene nanoplatelets on coefficient of thermal expansion of polyetherimide composite
Wu, Huang, E-mail: huang.wu.84@gmail.com [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States); Drzal, Lawrence T. [Composite Materials and Structures Center, Michigan State University, East Lansing, MI 48864 (United States); Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48864 (United States)
2014-07-01
Thermal expansion is one of the major concerns for polymer composites. In this research, graphene nanoplatelets (GNPs) were added to polyetherimide (PEId) thermoplastic polymer in order to reduce the coefficient of thermal expansion (CTE) of the injection molded composite. First, the coefficient of linear thermal expansion (LTE) was measured in three directions in the anisotropic coupon: 0°, 90° and the out of plane Z direction. It is found that the GNP particles are very effective in terms of reducing the LTE in 0° direction due to high degree of alignment. After annealing above glass transition temperature, significant increase of 0° LTE and decrease of Z° LTE were observed. The bulk CTE was calculated by adding up the LTEs in all three directions and is found to be independent of annealing. Second, several models were applied to predict both CTE and LTE. It is found that Schapery's lower limit model fits the experimental CTE very well. Chow's model was applied for LTEs in three directions. The behavior of GNP-5/PEId composites is explained by the combination of Chow's model and morphology obtained by scanning electron microscope (SEM). - Highlights: • Coefficient of thermal expansion (CTE) of polymer composite is characterized. • Reduction of linear thermal expansion depends on filler orientation. • Filler orientation is characterized based on the location of the specimen. • Filler orientation is changed by annealing, causing subsequent change in CTE. • CTE and linear thermal expansion coefficient are modeled.
Du, Shan; Shehata, Mohamed; Badawy, Wael; Rahman, Choudhury A.
2013-03-01
In this paper, we proposed a discrete cosine transform (DCT)-based attnuation and accentuation method to remove lighting effects on face images for faciliating face recognition task under varying lighting conditions. In the proposed method, logorithm transform is first used to convert a face image into logarithm domain. Then discrete cosine transform is applied to obtain DCT coefficients. The low-frequency DCT coefficients are attenuated since illumination variations mainly concentrate on the low-frequency band. The high-frequency coefficients are accentuated since when under poor illuminations, the high-frequency features become more important in recognition. The reconstructed log image by inverse DCT of the modified coefficients is used for the final recognition. Experiments are conducted on the Yale B database, the combination of Yale B and Extended Yale B databases and the CMU-PIE database. The proposed method does not require modeling and model fitting steps. It can be directly applied to single face image, without any prior information of 3D shape or light sources.
Adiabatic Effectiveness and Heat Transfer Coefficient on a Film-Cooled Rotating Blade
Garg, Vijay K.
1997-01-01
three-dimensional Navier-Stokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotating film-cooled turbine blade. The blade chosen is the United Technologies Research Center(UTRC) rotor with five film-cooling rows containing 83 holes, including three rows on the shower head with 49 holes, covering about 86% of the blade span. The mainstream is akin to that under real engine conditions with stagnation temperature 1900 K and stagnation pressure 3 MPa. The blade speed is taken to be 5200 rpm. The adiabatic effectiveness is higher for a rotating blade as compared to that for a stationary blade. Also, the direction of coolant injection from the shower-head holes considerably affects the effectiveness and heat transfer coefficient values on both the pressure and suction surfaces. In all cases the heat transfer coefficient and adiabatic effectiveness are highly three-dimensional in the vicinity of holes but tend to become two-dimensional far downstream.
Dmitry M. Yershov
2012-12-01
Full Text Available This paper proposes the method to obtain values of the coefficients of cause-effect relationships between strategic objectives in the form of intervals and use them in solving the problem of the optimal allocation of organization’s resources. We suggest taking advantage of the interval analytical hierarchy process for obtaining the ntervals. The quantitative model of strategic performance developed by M. Hell, S. Vidučić and Ž. Garača is employed for finding the optimal resource allocation. The uncertainty originated in the optimization problem as a result of interval character of the cause-effect relationship coefficients is eliminated through the application of maximax and maximin criteria. It is shown that the problem of finding the optimal maximin, maximax, and compromise resource allocation can be represented as a mixed 0-1 linear programming problem. Finally, numerical example and directions for further research are given.
Effect of current density on distribution coefficient of solute at solid-liquid interface
常国威; 王自东; 吴春京; 胡汉起
2003-01-01
When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interfaceenergy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between thedistribution of solute at solid-liquid interface and current density was established, and the effect of current on thedistribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and theradius of curvature at the dendritic tip was discussed. The results show that as the current density increases, thedistribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm2 , thelatter varies significantly.
Effect of Lubricant Viscosity and Surface Roughness on Coefficient of Friction in Rolling Contact
S.G. Ghalme
2013-12-01
Full Text Available The main objective of this paper is to investigate the effect of surface roughness and lubricant viscosity on coefficient of friction in silicon nitride- steel rolling contact. Two samples of silicon nitride with two different values of surface roughness were tested against steel counter face. The test was performed on four ball tester in presence of lubricant with two different values of viscosity. Taguchi technique a methodology in design of experiment implemented to plan the experimentation and same is utilized to evaluate the interacting effect of surface roughness and lubricant viscosity. Analysis of experimental results presents a strong interaction between surface roughness and lubricant viscosity on coefficient of friction in rolling contact.
Zhu, Z.; Toksoz, M. N.
2014-12-01
Theoretical calculation of seismoelectric conversion coefficients is difficult because it requires a large number of parameters that are hard to obtain. Much laboratory data are needed to validate the theoretical results. The most critical issue is determining independently the effect of porosity and permeability on seismoelectric coefficients. In general, when the rock porosity increases, the permeability increases too, and vice versa. In this study, we make measurements on both synthetic sandstone and two Berea (500 and 100) samples. We built a man-made "sandstone" sample with round cracks which are distributed in a horizontal plane. Thus the small cube (1.7 cm^3 ) only has one value of porosity and different permeabilities in the three directions. It is a sample with anisotropy in permeability. Laboratory experiments in a water tank show that the seismoelectric conversion coefficient is related to permeabilities in the three directions. The seismoelectric coefficient is highest in the direction of maximum permeability and lowest in the direction of minimum permeability. The measurements with the isotropic Berea samples show that seismoelectric coefficient increases with both porosity and permeability. Application of the result to borehole logging measurements requires analysis of the data from P, S, and Stoneley waves. P and Stoneley waves give large seismoelectric signals in the presence of fractures or high permeability zones. Shear waves, that do not induce fluid flow, provide very small seismoelectric signals. If the fracture strike in the formation is along the borehole axis, the P-wave induces stronger seismoelectric signal. Seismoelectric well logging might prove help for exploring the fractures or micro fractures in a borehole wall.
Cost-Effective Stress Management Training.
Shea, Gordon F.
1980-01-01
Stress management training can be a cost effective way to improve productivity and job performance. Among many relaxation techniques, the most effective in terms of teachability, participant motivation, and profitability are self-hypnosis, progressive relaxation, and transcendental meditation. (SK)
Effect of stress on energy flux deviation of ultrasonic waves in GR/EP composites
Prosser, William H.; Kriz, R. D.; Fitting, Dale W.
1990-01-01
Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis (fiber axis) and the x1 for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers a new nondestructive technique of evaluating stress in composites.
Coefficient of Variation Can Identify the Most Important Effects of Experimental Treatments
José Carlos LORENZO
2015-04-01
Full Text Available Most agricultural experiments involve evaluation of multiple variables and at times it can be difficult to identify the biologically relevant effects of the experimental treatments after performing the traditional ANOVA, Tukey and t-tests. The coefficient of variation formula could be an important tool to focus ‘Result and Discussion’ sections only on the most important changes produced by the experimental treatments. This short report is intended to exemplify the use of the coefficient of variation in three plant physiology experiments. The first one dealt with the effects of common bean plantlet exposure to high temperature under controlled conditions (levels: 28 and 40 °C. The second experiment was related to common bean seed exposure to liquid nitrogen during five different periods of time (levels: 0, 7, 14, 21 and 28 days. The third experiment was bi-factorial: factor 1 was the ‘type of plant material’ (levels: pineapple plants genetically transformed and the untransformed control; and factor 2 was the ‘time of in vitro-plantlet hardening’ (levels: 0, 15 and 30 days. Contents of phenolics, aldehydes, chlorophylls and proteins were determined. Percentage of seed germination, electrolyte leakage, peroxidase activity, plant height and weight were also measured. Experiments were monofactorial with two levels, monofactorial with five levels and bifactorial, respectively, with randomized design. The coefficient of variation showed that the most remarkable effects of high temperature were recorded in free phenolics and chlorophylls (a, b, total. Electrolyte leakage and chlorophyll b concentration were the most modified indicators as a result of seed exposure to liquid nitrogen. In the third experiment, modification in the levels of malondialdehyde and other aldehydes were the most relevant changes resulting from factors interactions. A similar procedure has not been published, except for our previous publications, not focused
Examination of effective stress in clay rock
Chun-Liang Zhang
2017-06-01
Full Text Available This paper examines the effective stress in indurated clay rock theoretically and experimentally. A stress concept is derived from the analysis of the microstructure and of the pore water in the highly-indurated Callovo-Oxfordian and Opalinus clay rocks, and subsequently validated by various experiments performed on these claystones. The concept suggests that the interparticle or effective stress in a dense clay–water system is transferred through both the adsorbed interparticle pore water in narrow pores and the solid–solid contact between non-clay mineral grains. The experiments show that the adsorbed pore water in the claystones is capable of bearing deviatoric effective stresses up to the failure strength. The applied stresses are for the most part or even totally transferred by the bound pore water, i.e. the swelling pressure in the interparticle bound pore water is almost equivalent to the effective stress. This stress concept provides a reasonable view to the nature of the effective stress in argillaceous rock and forms the fundamental basis for studies of the hydro-mechanical properties and processes in clay formations.
Shivalinge Gowda; S Krishnaveni; T Yashoda; T K Umesh; Ramakrishna Gowda
2004-09-01
Photon mass attenuation coefficients of some thermoluminescent dosimetric (TLD) compounds, such as LiF, CaCO3, CaSO4, CaSO4·2H2O, SrSO4, CdSO4, BaSO4, C4H6BaO4 and 3CdSO4·8H2O were determined at 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The attenuation coefficient data were then used to compute the effective atomic number and the electron density of TLD compounds. The interpolation of total attenuation cross-sections of photons of energy in elements of atomic number was performed using the logarithmic regression analysis of the data measured by the authors and reported earlier. The best-fit coefficients so obtained in the photon energy range of 279.2 to 320.07 keV, 514.0 to 661.6 keV and 1115.5 to 1332.5 keV by a piece-wise interpolation method were then used to find the effective atomic number and electron density of the compounds. These values are found to be in agreement with other available published values.
Spatially varying cross-correlation coefficients in the presence of nugget effects
Kleiber, William
2012-11-29
We derive sufficient conditions for the cross-correlation coefficient of a multivariate spatial process to vary with location when the spatial model is augmented with nugget effects. The derived class is valid for any choice of covariance functions, and yields substantial flexibility between multiple processes. The key is to identify the cross-correlation coefficient matrix with a contraction matrix, which can be either diagonal, implying a parsimonious formulation, or a fully general contraction matrix, yielding greater flexibility but added model complexity. We illustrate the approach with a bivariate minimum and maximum temperature dataset in Colorado, allowing the two variables to be positively correlated at low elevations and nearly independent at high elevations, while still yielding a positive definite covariance matrix. © 2012 Biometrika Trust.
Effect of Heat Transfer Coefficient on the Temperature Gradient for Hollow Fiber
王华平; 余晓蔚; 杨崇倡; 胡学超; 庄毅
2001-01-01
The heat transfer coefficient h caused by blowing affects the heat transfer of fiber greatly. Especially,unsymmetrical blowing forms the unsymmetrical temperature gradient on the fiber cross.section. Based on the results of spinning simulation by computer, the changes of heat transfer coefficient on the cross-section along the spinning line and the effects on distributions of temperature gradients were discussedl It is showed that for the spinning simulation of hollow fiber under strong blowing condition, the heat transfer coetticient should bemodified as: h=0.437×10-4[ G/Vρ ( R2/ R2-n2 ) ] -o.333(V2+ 64( VYsin (θ))2)0.167
Effect of heat treatment on the thermal expansion coefficient of austempered ductile iron
Tadayon saidi, M. [Dept. Metallurgy-Karaj Azad Univ.-Karaj (Iran); Baghersaie, N. [Tehran Center, Control Dept., Eng. Research Inst., Ministry of Jihad Agriculture (Iran); Varahram, N. [RAZI Metallurgical Research Inst.-Tehran (Iran)
2005-07-01
Austempered ductile iron provide a unique combination of strength and toughness coupled with excellent design flexibility for automotive application as compared to forged or cast steels. Some material properties such as thermal expansion coefficient and its influence in final machining tolerance is a matter of discussion in the automotive industry. In this study the effect of heart treatment cycle on the microstructure and thermal expansion of ADI was investigated. Samples were austempered at 275 C and 375 C for one hour and then dilatometric test carried out in the temperature range of 50 C to 350 C, then the result was compared with the thermal expansion coefficient of forged steel. Microstructure and mechanical investigations were used to the assurance of these results. The results indicate that replacing of forged steel with ADI due to lower cost production and reduction in weight is possible if the correct tolerance were selected. (orig.)
Effect of normal stresses on the results of thermoplastic mold filling simulation
Bakharev Alexander
2016-01-01
Full Text Available The paper deals with the effect of the normal stresses on the predicted flow front during the filling stage of thermoplastic injection molding. The normal stresses are predicted using the non-linear Criminale-Ericksen-Filbey model (a variant of the second-order fluid rheological model with viscosity, first and second normal stress coefficients dependent upon magnitude of shear rate incorporated into a comprehensive 3D simulation software for mold-filling analysis. The additional stress term allows the prediction of the so called ear-flow effect (melt racing on the edges of the cavity.
Optical coefficients in a semiconductor quantum ring: Electric field and donor impurity effects
Duque, C. M.; Acosta, Ruben E.; Morales, A. L.; Mora-Ramos, M. E.; Restrepo, R. L.; Ojeda, J. H.; Kasapoglu, E.; Duque, C. A.
2016-10-01
The electron states in a two-dimensional quantum dot ring are calculated in the presence of a donor impurity atom under the effective mass and parabolic band approximations. The effect of an externally applied electric field is also taken into account. The wavefunctions are obtained via the exact diagonalization of the problem Hamiltonian using a 2D expansion within the adiabatic approximation. The impurity-related optical response is analyzed via the optical absorption, relative refractive index change and the second harmonics generation. The dependencies of the electron states and these optical coefficients with the changes in the configuration of the quantum ring system are discussed in detail.
Adverse effects of stress on microbiota
The complex communities of microorganisms that colonize the gastrointestinal tract impact the health status of an animal. The health of an animal as well as production traits are also affected by exposure to stress. The aim of present study was to evaluate the effects of dehorning stress on the gut ...
Estimation of Inbreeding Coefficient and Its Effects on Lamb Survival in Sheep
mohammad almasi
2016-04-01
Full Text Available Introduction The mating of related individuals produces an inbred offspring and leads to an increased homozygosity in the progeny, genetic variance decrease within families and increase between families. The ration of homozygosity for individuals was calculated by inbreeding coefficient. Inbred individuals may carry two alleles at a locus that are replicated from one gene in the previous generations, called identical by descent. The inbreeding coefficient should be monitored in a breeding program, since it plays an important role at decreasing of homeostasis, performance, reproduction and viability. The trend of inbreeding is an indicator for determining of inbreeding level in the herd. Inbreeding affects both phenotypic means of traits and genetic variances within population, thus it is an important factor for delimitations of genetic progress in a population. Reports showed an inbreeding increase led to decrease of phenotypic value in some of the productive and reproductive traits. Materials and Methods In the current study, the pedigree data of 14030 and 6215 records of Baluchi and Iranblack lambs that collected from 1984 to 2011 at the Abbasabad Sheep Breeding Station in Mashhad, Iran, 3588 records of Makoei lambs that collected from 1994 to 2011 at the Makoei sheep breeding station and 6140, records of Zandi lambs that collected from 1991 to 2011 at the Khejir Sheep Breeding Station in Tehran, Iran were used to estimating the inbreeding coefficient and its effects on lamb survival in these breeds. Lamb survival trait was scored as 1 and 0 for lamb surviving and not surviving at weaning weight, respectively. Inbreeding coefficient was estimated by relationship matrix algorithm (A=TDT' methodology using the CFC software program. Effects of inbreeding coefficient on lamb survival were estimated by restricted maximum likelihood (REML method under 12 different animal models using ASReml 3.0 computer programme. Coefficient of inbreeding for each
Predicting the synergy of multiple stress effects
Liess, Matthias; Foit, Kaarina; Knillmann, Saskia; Schäfer, Ralf B.; Liess, Hans-Dieter
2016-09-01
Toxicants and other, non-chemical environmental stressors contribute to the global biodiversity crisis. Examples include the loss of bees and the reduction of aquatic biodiversity. Although non-compliance with regulations might be contributing, the widespread existence of these impacts suggests that for example the current approach of pesticide risk assessment fails to protect biodiversity when multiple stressors concurrently affect organisms. To quantify such multiple stress effects, we analysed all applicable aquatic studies and found that the presence of environmental stressors increases individual sensitivity to toxicants (pesticides, trace metals) by a factor of up to 100. To predict this dependence, we developed the “Stress Addition Model” (SAM). With the SAM, we assume that each individual has a general stress capacity towards all types of specific stress that should not be exhausted. Experimental stress levels are transferred into general stress levels of the SAM using the stress-related mortality as a common link. These general stress levels of independent stressors are additive, with the sum determining the total stress exerted on a population. With this approach, we provide a tool that quantitatively predicts the highly synergistic direct effects of independent stressor combinations.
Zhang, Tao; Guo, Zhansheng
2014-03-01
The effects of electrode properties and fabricated pressure on Li ion diffusion and diffusion-induced stress in a cylindrical Li-ion battery are studied. It is found that hydrostatic pressure or elastic modulus variation in the active layer have little effect on the distribution of Li ions for a higher diffusivity coefficient, but both can facilitate Li ion diffusion for a lower diffusivity coefficient. The elastic modulus variation has a significant effect on the distribution of stress and hydrostatic pressure can reduce the surface stress for the lower diffusivity coefficient. A higher charging rate causes a more transient response in the stress history, but a linear charging history is observed for slow charging rates. A higher charging rate would not inflict extra damage on the electrode for the higher diffusivity coefficient and the stress history becomes highly transient and charging rate dependent for the lower diffusivity coefficient. The effect of fabricated pressure can be neglected.
Effective assessment of tyre-road friction coefficient using a hybrid estimator
Ren, Hongbin; Chen, Sizhong; Shim, Taehyun; Wu, Zhicheng
2014-08-01
Vehicle stability and active safety control depend heavily on tyre forces available on each wheel of a vehicle. Since tyre forces are strongly affected by the tyre-road friction coefficient, it is crucial to optimise the use of the adhesion limits of the tyres. This study presents a hybrid method to identify the road friction limitation; it contributes significantly to active vehicle safety. A hybrid estimator is developed based on the three degrees-of-freedom vehicle model, which considers longitudinal, lateral and yaw motions. The proposed hybrid estimator includes two sub-estimators: one is the vehicle state information estimator using the unscented Kalman filter and another is the integrated road friction estimator. By connecting two sub-estimators simultaneously, the proposed algorithm can effectively estimate the road friction coefficient. The performance of the proposed estimation algorithm is validated in CarSim/Matlab co-simulation environment under three different road conditions (high-μ, low-μ and mixed-μ). Simulation results show that the proposed estimator can assess vehicle states and road friction coefficient with good accuracy.
Effective anomalous Hall coefficient in an ultrathin Co layer sandwiched by Pt layers
Zhang, Peng; Wu, Di; Jiang, Zhengsheng; Sang, Hai, E-mail: weiwei.lin@u-psud.fr, E-mail: haisang@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Lin, Weiwei, E-mail: weiwei.lin@u-psud.fr, E-mail: haisang@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Institut d' Electronique Fondamentale, Université Paris-Sud, Orsay 91405 (France)
2014-02-14
Anomalous Hall effect in Co/Pt multilayer is important to study the effect of interface with strong spin-orbit coupling. However, the shunting effect of the layers in such system and the circuit in the plane perpendicular to the injected current were overlooked in most works and thus, anomalous Hall coefficient in Co/Pt multilayer has not been determined accurately. Considering the shunting effect and the equivalent circuit, we show that the effective anomalous Hall coefficient of a 0.5 nm thick Co layer sandwiched by Pt layers R{sub S} is 0.29 ± 0.01 μΩ cm/T at the zero temperature limit and increases to about 0.73 μΩ cm/T at the temperature of 300 K. R{sub S} is one order larger than that in bulk Co film, indicating the large contribution of the Co/Pt interface. R{sub S} increases with the resistivity of Co as well as a resistivity independent contribution of −0.23 ± 0.01 μΩ cm/T. The equivalent anomalous Hall current in the Co layer has a maximum of 1.1% of the injected transverse current in the Co layer around the temperature of 80 K.
Hirata, Kenji; Hattori, Naoya; Katoh, Chietsugu; Shiga, Tohru; KURODA, Satoshi; Kubo, Naoki; Usui, Reiko; Kuge, Yuji; Tamaki, Nagara
2011-01-01
Objective: Cerebral blood flow (CBF) estimation with C15O2 PET usually assumes a single tissue compartment model and a fixed brain-blood partition coefficient of water. However, the partition coefficient may change in pathological conditions. The purpose of this study was to investigate the changes of partition coefficient of water in pathological regions and its effect on regional CBF assessment. Methods: Study protocol included 22 patients with occlusive cerebrovascular disease to compare p...
Effective diffusion coefficients of gas mixture in heavy oil under constant-pressure conditions
Li, Huazhou Andy; Sun, Huijuan; Yang, Daoyong
2016-09-01
We develop a method to determine the effective diffusion coefficient for each individual component of a gas mixture in a non-volatile liquid (e.g., heavy oil) at high pressures with compositional analysis. Theoretically, a multi-component one-way diffusion model is coupled with the volume-translated Peng-Robinson equation of state to quantify the mass transfer between gas and liquid (e.g., heavy oil). Experimentally, the diffusion tests have been conducted with a PVT setup for one pure CO2-heavy oil system and one C3H8-CO2-heavy oil system under constant temperature and pressure, respectively. Both the gas-phase volume and liquid-phase swelling effect are simultaneously recorded during the measurement. As for the C3H8-CO2-heavy oil system, the gas chromatography method is employed to measure compositions of the gas phase at the beginning and end of the diffusion measurement, respectively. The effective diffusion coefficients are then determined by minimizing the discrepancy between the measured and calculated gas-phase composition at the end of diffusion measurement. The newly developed technique can quantify the contributions of each component of mixture to the bulk mass transfer from gas into liquid. The effective diffusion coefficient of C3H8 in the C3H8-CO2 mixture at 3945 ± 20 kPa and 293.85 K, i.e., 18.19 × 10^{ - 10} m^{ 2} / s, is found to be much higher than CO2 at 3950 ± 18 kPa and 293.85 K, i.e., 8.68 × 10^{ - 10} m^{ 2} / s. In comparison with pure CO2, the presence of C3H8 in the C3H8-CO2 mixture contributes to a faster diffusion of CO2 from the gas phase into heavy oil and consequently a larger swelling factor of heavy oil.
Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons.
Veinot, K G; Eckerman, K F; Hertel, N E
2016-02-01
With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above ∼30 MeV the cranial and caudal values are greater.
Organ and Effective Dose Coefficients for Cranial and Caudal Irradiation Geometries: Neutrons
Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.; Hiller, M. M.
2017-09-01
With the introduction of new recommendations by ICRP Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors, and the introduction of reference sex-specific computational phantoms (ICRP Publication 110). Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision of ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT), and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for neutron irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue absorbed doses for caudal and cranial exposures to neutrons ranging in energy from 10-9 MeV to 10 GeV have been performed using the MCNP6 radiation transport code and the adult reference voxel phantoms of ICRP Publication 110. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above about 30 MeV the cranial and caudal values are greater.
Garberoglio, Giovanni, E-mail: garberoglio@fbk.eu [Interdisciplinary Laboratory for Computational Science (LISC), FBK-CMM and University of Trento, via Sommarive 18, I-38123 Povo (Italy); Jankowski, Piotr [Department of Quantum Chemistry, Faculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, PL-87-100 Toruń (Poland); Szalewicz, Krzysztof [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Harvey, Allan H. [Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305-3337 (United States)
2014-07-28
We present a path-integral Monte Carlo procedure for the fully quantum calculation of the second molecular virial coefficient accounting for intramolecular flexibility. This method is applied to molecular hydrogen (H{sub 2}) and deuterium (D{sub 2}) in the temperature range 15–2000 K, showing that the effect of molecular flexibility is not negligible. Our results are in good agreement with experimental data, as well as with virials given by recent empirical equations of state, although some discrepancies are observed for H{sub 2} between 100 and 200 K.
Effective dose conversion coefficients for X-ray radiographs of the chest and the abdomen
Lima, F.R.A. [Centro regional de Ciencias Nucleares, CRCN/CNEN, Rua Conego Barata, 999, Tamarineira, Recife, PE (Brazil); Kramer, R.; Vieira, J.W.; Khoury, H.J. [Departamento de Energia Nuclear, DEN/UFPE, Cidade Universitaria, Recife, PE (Brazil)]. E-mail: falima@cnen.gov.br
2004-07-01
The recently developed MAX (Male Adult voXel) and the FAXht (Female Adult voXel) head and trunk phantoms have been used to calculate organ and tissue equivalent dose conversion coefficients for X-ray radiographs of the chest and the abdomen as a function of source and field parameters, like voltage, filtration, field size, focus-to-skin distance, etc. Based on the equivalent doses to twenty three organs and tissues at risk, the effective dose has been determined and compared with corresponding data for others phantoms. The influence of different radiation transport codes, different tissue compositions and different human anatomies have been investigated separately. (Author)
Effective dose conversion coefficients for X-ray radiographs of the chest and the abdomen
Lima, F.R.A. [Centro regional de Ciencias Nucleares, CRCN/CNEN, Rua Conego Barata, 999, Tamarineira, Recife, PE (Brazil); Kramer, R.; Vieira, J.W.; Khoury, H.J. [Departamento de Energia Nuclear, DEN/UFPE, Cidade Universitaria, Recife, PE (Brazil)]. E-mail: falima@cnen.gov.br
2004-07-01
The recently developed MAX (Male Adult voXel) and the FAXht (Female Adult voXel) head and trunk phantoms have been used to calculate organ and tissue equivalent dose conversion coefficients for X-ray radiographs of the chest and the abdomen as a function of source and field parameters, like voltage, filtration, field size, focus-to-skin distance, etc. Based on the equivalent doses to twenty three organs and tissues at risk, the effective dose has been determined and compared with corresponding data for others phantoms. The influence of different radiation transport codes, different tissue compositions and different human anatomies have been investigated separately. (Author)
Measurement on Effective Shear Viscosity Coefficient of Iron under Shock Compression at 100 GPa
LI Yi-Lei; LIU Fu-Sheng; ZHANG Ming-Jian; MA Xiao-Juan; LI Ying-Lei; ZHANG Ji-Chun
2009-01-01
The oscillatory damping curve of a shock front propagating in iron shocked to 103 GPa is measured by use of two-stage light-gas gun and electric pin techniques. The corresponding effective shear viscosity coefficient is deduced to be about 2000 Pa.s from Miller and Ahrens' formula.The result is consistent with that of Mineev's data at 31GPa,while it is higher by five orders than the predictions based on the static measurements at about 5 GPa and 2000K and molecular dynamic simulation up to 135-375 GPa and 4300-6000 K,and the discussions are presented.
Pentti Nieminen
2013-09-01
Full Text Available Background: a major problem in evaluating and reviewing the published findings of studies on the association between a quantitative explanatory variable and a quantitative dependent variable is that the results are analysed and reported in many different ways. To achieve an effective review of different studies, a consistent presentation of the results is necessary. This paper aims to exemplify the main topics related to summarising and pooling research findings from multivariable models with a quantitative response variable.Methods: we outline the complexities involved in synthesising associations. We describe a method by which it is possible to transform the findings into a common effect size index which is based on standardised regression coefficients. To describe the approach we searched original research articles published before January 2012 for findings of the relationship between polychlorinated biphenyls (PCBs and birth weight of new-borns. Studies with maternal PCB measurements and birth weight as a continuous variable were included.Results: the evaluation of 24 included articles reveled that there was variation in variable measurement methods, transformations, descriptive statistics and inference methods. Research syntheses were performed summarizing regression coefficients to estimate the effect of PCBs on birth weight. A birth weight decline related to increase in PCB level was found.Conclusions: the proposed method can be useful in quantitatively reviewing published studies when different exposure measurement methods are used or differential control of potential confounding factors is not an issue.
Mbah, C J
2007-01-01
Sunscreen products are widely used to protect the skin from sun-related deleterious effects. The objective of the study was to investigate the potential effect of glycerol, propylene glycol and polyethylene glycol 400 on dermal absorption of oxybenzone by studying their effects on its partition coefficient. The partition coefficient was evaluated in a chloroform-water system at room temperature. It was found that glycerol and propylene glycol decreased the partition coefficient of oxybenzone, while an increase in partition coefficient was observed with polyethylene glycol 400. The findings suggest that polyethylene glycol 400 in contrast to glycerol and propylene glycol has the potential of increasing the vehicle-skin partition coefficient of oxybenzone when cosmetic products containing such an UV absorber are topically applied to the skin.
Yoshinaga, Tomokazu; Akashi, Haruaki
2015-09-01
A Monte Carlo simulation (MCS) is applied to investigate the secondary electron emission in Argon Townsend discharges. The influxes of ions, photons and metastable species onto the cathode surface are estimated simply from the number of inelastic collisions. The effect of photons becomes significant especially under higher pd conditions since the photon influx increases. This suggests the possibility of the estimation of the secondary electron emission coefficient of photons by examining breakdown voltage characteristics (Paschen curves). The effect of metastable species is much smaller than those of ions and photons and is negligible. The Paschen curves evaluated with MCS agrees well with the results of one-dimensional fluid model simulation when the photon effect is neglected, showing the necessity of further improvement. Supported by JSPS KAKENHI Grant Number 26820108.
... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health
Jahromi, Mahdi Karimyar; Minaei, Shahnaz; Abdollahifard, Sareh; Maddahfar, Majid
2016-01-01
Introduction: Occupational stress is one of the major problems of health care staff, substantially affecting their professional and personal performance. This research has been conducted with the aim of determining the effect of stress management on occupational stress and satisfaction among the Midwives in Obstetrics and Gynecology Hospital wards at Motahari Hospital in Jahrom, Iran 2013-2014. Methods: This is a Quasi-experimental study of the pre- and post-clinical trials type. The study population included midwives employed in the Obstetrics and Gynecology Hospital wards selected trough census. The samples were categorized into two groups randomly. The intervention group participated in the short-term training workshop of stress management. The studied samples were measured in terms of occupational stress and satisfaction before, right after, and one month after the workshop. Occupational stress measurement was measured by Toft-Anderson occupational stress questionnaire (1981). Similarly, the occupational satisfaction was measured by JDI checklist developed by Stephen Robins (1994). In order to analyze the information, SPSS 16 together with descriptive statistics tests (frequency, percentile, mean, and standard deviation), independent sample t-tests, iterative measurement and Spearman correlation coefficient were used. Results: A total of 70 people (two 35-person groups) of midwives participated in this study. The findings revealed that there was a significant difference between the mean of scores of occupational stress between the two groups before and after the workshop (p=0.001). There was, however, no significant difference between the scores of satisfactions across the two groups. Discussion: Training of skills of coping with stress including stress management can be effective in diminishing level of occupational stress. Mitigation of stress without catering for professional, occupational, organizational, and environmental factors would not lead to
The effect of core configuration on temperature coefficient of reactivity in IRR-1
Bettan, M.; Silverman, I.; Shapira, M.; Nagler, A. [Soreq Nuclear Research Center, Yavne (Israel)
1997-08-01
Experiments designed to measure the effect of coolant moderator temperature on core reactivity in an HEU swimming pool type reactor were performed. The moderator temperature coefficient of reactivity ({alpha}{sub {omega}}) was obtained and found to be different in two core loadings. The measured {alpha}{sub {omega}} of one core loading was {minus}13 pcm/{degrees}C at the temperature range of 23-30{degrees}C. This value of {alpha}{sub {omega}} is comparable to the data published by the IAEA. The {alpha}{sub {omega}} measured in the second core loading was found to be {minus}8 pcm/{degrees}C at the same temperature range. Another phenomenon considered in this study is core behavior during reactivity insertion transient. The results were compared to a core simulation using the Dynamic Simulator for Nuclear Power Plants. It was found that in the second core loading factors other than the moderator temperature influence the core reactivity more than expected. These effects proved to be extremely dependent on core configuration and may in certain core loadings render the reactor`s reactivity coefficient undesirable.
无
2001-01-01
The Metzner and Otto correlation is the single practical method for incorporating non-Newtonian effects in the mixing process. In this article, the Metzner and Otto' s idea, the role of viscoelasticity on the Metzner and Otto coefficient, ks, effects of flow regime on ks and the determination of ks for Rushton turbine impeller have been studied using the direct method of the laser Doppler anemometry (LDA) velocity meusurement for the case of viscoelastic liquids. The normalized mean tangential velocity profiles are independent of Rushton turbine impeller speeds. Contrary to literature findings, it is shown that the variation of local shear rate against the impeller speed is better correlated by the power equation, i.e. γ = ks＇ * Nb＇, in the transition region, i.e. ～ 30 ＜ Re <～ 2000.Also, a correlation between improved coefficient, ks＇, and the elasticity number of viscoelastic liquids is given which is very helpful in designing of the mixing of both viscoelastic and inelastic non-Newtonian fluids through relating rheological properties to kinematical and dynamical parameters of the mixing process.
Mongrain, Rosaire; Faik, Isam; Leask, Richard L; Rodés-Cabau, Josep; Larose, Eric; Bertrand, Olivier F
2007-10-01
In the context of drug eluting stent, we present two-dimensional numerical models of mass transport of the drug in the wall and in the lumen to study the effect of the drug diffusion coefficients in the three principal media (blood, vascular wall, and polymer coating treated as a three-compartment problem) and the impact of different strut apposition configurations (fully embedded, half embedded, and not embedded). The different conditions were analyzed in terms of their consequence on the drug concentration distribution in the arterial wall. We apply the concept of the therapeutic window to the targeted vascular wall region and derive simple metrics to assess the efficiency of the various stent configurations. Although most of the drug is dispersed in the lumen, variations in the blood flow rate within the physiological range of coronary blood flow and the diffusivity of the drug molecule in the blood were shown to have a negligible effect on the amount of drug in the wall. Our results reveal that the amount of drug cumulated in the wall depends essentially on the relative values of the diffusion coefficients in the polymer coating and in the wall. Concerning the strut apposition, it is shown that the fully embedded strut configuration would provide a better concentration distribution.
The Effect of Unbalanced Coefficient of Magnetron on the Structure and Properties of CNx Coatings
WEN Xiaobin; LI Xian; WANG Tao; JIANG Bailing
2011-01-01
The effect of unbalanced coefficient of magnetron (UCM) on the structure and tribological properties of CrNx hard coatings was studied. The CrNx coatings were deposited on both Si wafer and hardened tool steel substrates using a closed-field unbalanced magnetron sputtering ion plating technique in a gas mixture of Ar+N2 under different unbalanced magnetron conditions. The coatings were characterized by means of XRD, XPS, SEM, microhardness tester and pin-on-disc tribometer to study respectively their structure, chemical bonding state, microstructure, hardness and tribological properties. The experimental results show that the UCM has a profound effect on the structure, hardness and tribological properties of the CrNx coatings. With increasing the values of UCM, the dominant phases in the deposited coatings evolved from Cr+Cr2N to Cr2N+CrN, the microstructure became denser and the hardness increased; in addition, reduced coefficient of friction and improved wear resistance of CrNx coatings were also observed under a larger UCM.
Influence of the stress on magnetoelectric effect in magnetostrictive-PZT bilayers
DING Jian-ming; ZHONG Chong-gui; JIANG Qing
2007-01-01
In this letter,we investigate the influence of the stress on magnetoelectric(ME)effect in a magnetostrictivePZT bilayer.ME voltage coefficient α*E=δE/δH,where δE is the induced electric field for an applied alternating current (ac)magnetic field δH,is obtained by solving the stressrelated piezoelectric constitutive equation and the conventional magnetostrictive equation with appropriate boundary condition.Based on the free-energy density function of the PZT film in stress state,we get the stress-related piezoelectric charge coefficient Pd*31 and dielectric permittivity Pε*33.After taking the cobalt ferrite(CFO)as magnetostrictive phase,it is found that α*E increases with decreasing 2-d compressive stress for CFO-PZT,which not only is qualitatively consistent with previous experimental measurements,but also provides a possible route to improve the ME effect.
Motional Effect on Wall Shear Stresses
Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won
Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....
Oxidative stress effects of thinner inhalation
2011-01-01
Thinners are chemical mixtures used as industrial solvents. Humans can come into contact with thinner by occupational exposure or by intentional inhalation abuse. Thinner sniffing causes damage to the brain, kidney, liver, lung, and reproductive system. We discuss some proposed mechanism by which thinner induces damage. Recently, the induction of oxidative stress has been suggested as a possible mechanism of damage. This paper reviews the current evidence for oxidative stress effects induced ...
Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients
Dan Wendt; Greg Mines
2011-10-01
Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients Dan Wendt, Greg Mines Idaho National Laboratory The use of mixed working fluids in binary power plants can provide significant increases in plant performance, provided the heat exchangers are designed to take advantage of these fluids non-isothermal phase changes. In the 1980's testing was conducted at DOE's Heat Cycle Research Facility (HCRF) where mixtures of different compositions were vaporized at supercritical pressures and then condensed. This testing had focused on using the data collected to verify that Heat Transfer Research Incorporated (HTRI) codes were suitable for the design of heat exchangers that could be used with mixtures. The HCRF data includes mixture compositions varying from 0% to 40% isopentane and condenser tube orientations of 15{sup o}, 60{sup o}, and 90{sup o} from horizontal. Testing was performed over a range of working fluid and cooling fluid conditions. Though the condenser used in this testing was water cooled, the working fluid condensation occurred on the tube-side of the heat exchanger. This tube-side condensation is analogous to that in an air-cooled condenser. Tube-side condensing heat transfer coefficient information gleaned from the HCRF testing is used in this study to assess the suitability of air-cooled condenser designs for use with mixtures. Results of an air-cooled binary plant process model performed with Aspen Plus indicate that that the optimal mixture composition (producing the maximum net power for the scenario considered) is within the range of compositions for which data exist. The HCRF data is used to assess the impact of composition, tube orientation, and process parameters on the condensing heat transfer coefficients. The sensitivity of the condensing coefficients to these factors is evaluated and the suitability of air-cooled condenser designs with mixtures is assessed. This paper summarizes the evaluation
vanEck, M; Berkhof, H; Nicolson, N; Sulon, J
1996-01-01
This study examined the effects of perceived stress and related individual characteristics, mood states, and stressful daily events on salivary cortisol levels. Forty-one ''high stress'' and 46 ''low stress'' subjects were selected on the basis of Perceived Stress Scale scores from a sample of male,
Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient.
Lal, Shankar; Pant, K K
2016-08-01
Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday's law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.
Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient
Lal, Shankar; Pant, K. K.
2016-08-01
Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday's law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.
Yamashita, Osamu; Odahara, Hirotaka; Ochi, Takahiro; Satou, Kouji
2009-01-01
The resultant local Seebeck coefficient α R (= α S- α T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric efficiency, where α S is the local Seebeck coefficient and α T is the one caused by the Thomson effect. It is shown in this paper that α S, α T, and α R of the p- and n-type Cu/Bi Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of the composite on which the temperature difference Δ T is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position from the local experimental data of R,Δ I,Δ T, and V generated by applying an additional current of ± I to the composite, where R is the electrical resistance and Δ I is a current generated by the composite. As a result, it was found that the absolute values of α S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite, respectively, while those of α T are less than 8% of α S all over the composite and are so small that the relation α R≈ α S can be held. We thus succeeded in measuring α R at the interfaces of the composite.
Litjens, G.J.S.; Hambrock, T.; Hulsbergen- van de Kaa, C.A.; Barentsz, J.O.; Huisman, H.J.
2012-01-01
Purpose: To determine the interpatient variability of prostate peripheral zone (PZ) apparent diffusion coefficient (ADC) and its effect on the assessment of prostate cancer aggressiveness. Materials and Methods: The requirement for institutional review board approval was waived. Intra- and
A fiber-bridging model with stress gradient effects
Yi, Sun; Tao, Li
2000-05-01
A fiber-bridging model with stress gradient effects is proposed for unidirectional fiber-reinforced composites. The stress gradient terms are introduced by solving a micromechanical model under a non-uniform stress loading. It is shown that the stress gradient effect is significant on both the fiber-bridging stress distribution and the value of the critical load of fiber failure.
F Samadiyan
2016-07-01
amount of a third off chemical fertilizer of urea, 46 % Nitrogen was given to the plant and two third by the end of clawing the plot. In the period of growing in order to control brushes 2, 4, D herbicide and Fenitrothion insecticidal was used for countering the louse pest and other insects. In the laboratory, leaf area was measured using scanner and 4.Image 0.2 software program. To determine changes of growth indices, regression relations were used. Total dry matter, leaf area index, net assimilation rate, crop growth rate, light interception extinction were measured. Results and Discussion The results showed that the effects of N fertilizilation were significant on the maximum leaf area index, total dry matter and light interception percent were related to Pishtaz cultivar and 150 kg N ha-1 fertilizer treatment significantly resulted Maximum light interception percent, net assimilation rate, with other treatments. Effects of cultivar were significant on maximum light absorption. The Maximum absorption of light, crop growth rate, total dry matter was related to Pishtaz. The interaction between nitrogen and the harvest index was significant at the five percent level. The evidence showed that higher light interception in plants, is associated with the higher performance of plant. The increase of light interception promote the biological and economic performance. Conclusions The results showed that application of 150 kg nitrogen per hectare, with the highest level of leaf area index and higher light absorption caused higher extinction coefficient of light in the canopy. Nitrogen fertilizer consumption increased light absorption by leaves, therefore the light extinction coefficient consuming more nitrogen in the plant community. The Maximum absorption of light, crop growth rate, total dry matter was related to pishtaz. Scale of light extinction coefficient for fertilizer treatment control, 50, 100, 150 kg ha-1, was 0.4675, 0.4794, 0.4858 and 0.495, respectively and for
Strain rate effects in stress corrosion cracking
Parkins, R.N. (Newcastle upon Tyne Univ. (UK). Dept. of Metallurgy and Engineering Materials)
1990-03-01
Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.
Noise and stress effects on preschool personnel
Fredrik Sjödin
2012-01-01
Full Text Available The aim of the study was to analyze the presence of stress-related health problems among preschool employees and the way in which these reactions are related to noise and other work parameters. The investigation included 101 employees at 17 preschools in Umeå County, located in northern Sweden. Individual noise recordings and recordings in dining rooms and play halls were made at two departments from each preschool. The adverse effects on the employees were analyzed by use of different validated questionnaires and by saliva cortisol samples. Stress and energy output were pronounced among the employees, and about 30% of the staff experienced strong burnout syndromes. Mental recovery after work was low, indicated by remaining high levels of stress after work. The burnout symptoms were associated with reduced sleep quality and morning sleepiness. Cortisol levels supported the conclusion about pronounced daily stress levels of the preschool employees.
Mei-Yu LEE
2014-11-01
Full Text Available This paper investigates the effect of the nonzero autocorrelation coefficients on the sampling distributions of the Durbin-Watson test estimator in three time-series models that have different variance-covariance matrix assumption, separately. We show that the expected values and variances of the Durbin-Watson test estimator are slightly different, but the skewed and kurtosis coefficients are considerably different among three models. The shapes of four coefficients are similar between the Durbin-Watson model and our benchmark model, but are not the same with the autoregressive model cut by one-lagged period. Second, the large sample case shows that the three models have the same expected values, however, the autoregressive model cut by one-lagged period explores different shapes of variance, skewed and kurtosis coefficients from the other two models. This implies that the large samples lead to the same expected values, 2(1 – ρ0, whatever the variance-covariance matrix of the errors is assumed. Finally, comparing with the two sample cases, the shape of each coefficient is almost the same, moreover, the autocorrelation coefficients are negatively related with expected values, are inverted-U related with variances, are cubic related with skewed coefficients, and are U related with kurtosis coefficients.
EFFECT OF THE FLOW FIELD DEFORMATION IN THE WIND TUNNEL ON THE AERODYNAMIC COEFFICIENTS
Dušan Maturkanič
2015-06-01
Full Text Available The flow field quality has a principal signification at wind tunnel measurement. The creation of the flow field of air by fan leads to the rotation of entire flow field which is, moreover, deformed at the bends of the wind tunnel with close circulation. Despite the wind tunnels are equipped with the devices which eliminate these non-uniformities, in the most of cases, the air flow field has not ideal parameters in the test section. For the evaluation of the measured results of the model in the wind tunnel, the character of flow field deformation is necessary. The following text describes the possible general forms of the flow field nonuniformity and their effect on the aerodynamic coefficients calculation.
K. Gerrit Held
2016-06-01
Full Text Available Spectral optoacoustic (OA imaging enables spatially-resolved measurement of blood oxygenation levels, based on the distinct optical absorption spectra of oxygenated and de-oxygenated blood. Wavelength-dependent optical attenuation in the bulk tissue, however, distorts the acquired OA spectrum and thus makes quantitative oxygenation measurements challenging. We demonstrate a correction for this spectral distortion without requiring a priori knowledge of the tissue optical properties, using the concept of multiple irradiation sensing: recording the OA signal amplitude of an absorbing structure (e.g. blood vessel, which serves as an intrinsic fluence detector, as function of irradiation position. This permits the reconstruction of the bulk effective optical attenuation coefficient μeff,λ. If performed at various irradiation wavelengths, a correction for the wavelength-dependent fluence attenuation is achieved, revealing accurate spectral information on the absorbing structures. Phantom studies were performed to show the potential of this technique for handheld clinical combined OA and ultrasound imaging.
Effect of partition coefficient on microsegregation during solidification of aluminium alloys
MH Avazkonandeh-Gharavol; M Haddad-Sabzevar; H Fredriksson
2014-01-01
In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The sam-ples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidifica-tion. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experi-mental profiles, compared to those calculated using the equilibrium partition coefficients.
Zhou, Hao-Miao; Li, Meng-Han; Liu, Hui; Cui, Xiao-Le
2015-12-01
For the converse magnetoelectric coupling effect of the piezoelectric/magnetostrictive/piezoelectric tri-layer symmetric magnetoelectric laminates, based on the nonlinear thermo-magneto-mechanical constitutive equations of the giant magnetostrictive materials and the thermo-electro-mechanical constitutive equations of the piezoelectric materials, according to Newton's second law and the magnetic circuit theorem, an equivalent circuit is established. Then an expression of the converse magnetoelectric coefficient describing nonlinear thermo-magneto-electro-mechanical coupling is established. The curve of the nonlinear converse magnetoelectric coefficient versus the bias magnetic field, is predicted effectively by the expression, and the predictions are in good agreement with the experimental result both qualitatively and quantitatively. Furthermore, the model can predict the complex influences of the bias magnetic field, the stress and the ambient temperature on the converse magnetoelectric coefficient. It can be found from these predictions that the converse magnetoelectric coefficient decreases with the increasing temperature and increases with the increasing tensile stress. Under the common effect of the ambient temperature and the stress, it is also found that the converse magnetoelectric coefficient changes sharply with the ambient temperature when the tensile stress is applied on the laminates, but it has a good stability of temperature when a large compressive stress is applied. Therefore, this work contributes to the researches on the giant converse magnetoelectric coefficient and the designs of magnetoelectric devices based on the converse magnetoelectric coupling.
Minghai Hong
2017-03-01
Full Text Available Crop coefficients (Kc are important for the development of irrigation schedules, but few studies on Kc focus on saline soils. To propose the growth-stage-specific Kc values for sunflowers in saline soils, a two-year micro-plot experiment was conducted in Yichang Experimental Station, Hetao Irrigation District. Four salinity levels including non-salinized (ECe = 3.4–4.1 dS·m–1, low (ECe = 5.5–8.2 dS·m–1, moderate (ECe = 12.1–14.5 dS·m–1, and high (ECe = 18.3–18.5 dS·m–1 levels were arranged in 12 micro-plots. Based on the soil moisture observations, Vensim software was used to establish and develop a physically-based water flow in the soil-plant system (WFSP model. Observations in 2012 were used to calibrate the WFSP model and acceptable accuracy was obtained, especially for soil moisture simulation below 5 cm (R2 > 0.6. The locally-based Kc values (LKc of sunflowers in saline soils were presented according to the WFSP calibration results. To be specific, LKc for initial stages (Kc1 could be expressed as a function of soil salinity (R2 = 0.86, while R2 of LKc for rapid growth (Kc2, middle (Kc3, and mature (Kc4 stages were 0.659, 1.156, and 0.324, respectively. The proposed LKc values were also evaluated by observations in 2013 and the R2 for initial, rapid growth, middle, and mature stages were 0.66, 0.68, 0.56 and 0.58, respectively. It is expected that the LKc would be of great value in irrigation management and provide precise water application values for salt-affected regions.
On the use of age-specific effective dose coefficients in radiation protection of the public
Kocher, D.C.; Eckerman, K.F.
1998-11-01
Current radiation protection standards for the public include a limit on effective dose in any year for individuals in critical groups. This paper considers the question of how the annual dose limit should be applied in controlling routine exposures of populations consisting of individuals of all ages. The authors assume that the fundamental objective of radiation protection is limitation of lifetime risk and, therefore, that standards for controlling routine exposures of the public should provide a reasonable correspondence with lifetime risk, taking into account the age dependence of intakes and doses and the variety of radionuclides and exposure pathways of concern. Using new calculations of the per capita (population-averaged) risk of cancer mortality per unit activity inhaled or ingested in the US Environmental Protection Agency`s Federal Guidance Report No. 13, the authors show that applying a limit on annual effective dose only to adults, which was the usual practice in radiation protection of the public before the development of age-specific effective dose coefficients, provides a considerably better correspondence with lifetime risk than applying the annual dose limit to the critical group of any age.
Cao, Guangxi; He, Cuiting; Xu, Wei
2016-03-01
This study investigates the correlation between weather and agricultural futures markets on the basis of detrended cross-correlation analysis (DCCA) cross-correlation coefficients and q-dependent cross-correlation coefficients. In addition, detrended fluctuation analysis (DFA) is used to measure extreme weather and thus analyze further the effect of this condition on agricultural futures markets. Cross-correlation exists between weather and agricultural futures markets on certain time scales. There are some correlations between temperature and soybean return associated with medium amplitudes. Under extreme weather conditions, weather exerts different influences on different agricultural products; for instance, soybean return is greatly influenced by temperature, and weather variables exhibit no effect on corn return. Based on the detrending moving-average cross-correlation analysis (DMCA) coefficient and DFA regression results are similar to that of DCCA coefficient.
CAO Zheng-rui; HONG Yan-ji; WEN Ming
2009-01-01
A dimensionless factor was introduced to deduce the analytic expression of impulse coupling coefficient for conical nozzles in the case of spherical symmetry, and a high precision impact pendulum system was used to measure impulse coupling coefficients of 15 conical nozzles with different cone angles and lengths. The expression was corrected according to experi-mental values. The results indicate that: 1) impulse coupling coefficient increases firstly and then decreases with augment of dimensionless length when cone angle is fixed;2) impulse coupling coefficient decreases monotonously with augment of cone angle when dimensionless length is fixed;3) it is of great importance for improving impulse coupling coefficient to increase the rate of laser energy deposition.
Wei Zhang
Full Text Available Repeated stress can trigger a range of psychiatric disorders, including anxiety. The propensity to develop abnormal behaviors after repeated stress is related to the severity, frequency and number of stressors. However, the pattern of stress exposure may contribute to the impact of stress. In addition, the anxiogenic nature of repeated stress exposure can be moderated by the degree of coping that occurs, and can be reflected in homotypic habituation to the repeated stress. However, expectations are not clear when a pattern of stress presentation is utilized that diminishes habituation. The purpose of these experiments is to test whether interrupted stress exposure decreases homotypic habituation and leads to greater effects on anxiety-like behavior in adult male rats. We found that repeated interrupted restraint stress resulted in less overall homotypic habituation compared to repeated daily restraint stress. This was demonstrated by greater production of fecal boli and greater corticosterone response to restraint. Furthermore, interrupted restraint stress resulted in a lower body weight and greater adrenal gland weight than daily restraint stress, and greater anxiety-like behavior in the elevated plus maze. Control experiments demonstrated that these effects of the interrupted pattern could not be explained by differences in the total number of stress exposures, differences in the total number of days that the stress periods encompased, nor could it be explained as a result of only the stress exposures after an interruption from stress. These experiments demonstrate that the pattern of stress exposure is a significant determinant of the effects of repeated stress, and that interrupted stress exposure that decreases habituation can have larger effects than a greater number of daily stress exposures. Differences in the pattern of stress exposure are therefore an important factor to consider when predicting the severity of the effects of repeated
A test for interfacial effects and stress transfer in ceramic matrix composites
Bascom, Willard D.; Lee, Ilzoo
1988-01-01
The efforts to fabricate single embedded filament specimens of carbon and SiC fibers were unsuccessful largely due to the thermal stresses resulting from differences in thermal coefficient of expansion. Other factors appear to have been involved including embrittlement of the metal substrate by the H2 gas in the chemical vapor deposition flow stream and reaction layers formed between the silicon carbide and the metal substrate. The carbon fiber may have been attacked by the CVD reactant. It is concluded that these differential stresses are so large as to make the embedded fiber test impractical for the study of interphase effects and stress transfer in fiber ceramic matrix systems.
Extending the Universal One-Loop Effective Action: heavy-light coefficients
Ellis, Sebastian A. R.; Quevillon, Jérémie; You, Tevong; Zhang, Zhengkang
2017-08-01
The Universal One-Loop Effective Action (UOLEA) is a general expression for the effective action obtained by evaluating in a model-independent way the one-loop expansion of a functional path integral. It can be used to match UV theories to their low-energy EFTs more efficiently by avoiding redundant steps in the application of functional methods, simplifying the process of obtaining Wilson coefficients of operators up to dimension six. In addition to loops involving only heavy fields, matching may require the inclusion of loops containing both heavy and light particles. Here we use the recently-developed covariant diagram technique to extend the UOLEA to include heavy-light terms which retain the same universal structure as the previously-derived heavy-only terms. As an example of its application, we integrate out a heavy singlet scalar with a linear coupling to a light doublet Higgs. The extension presented here is a first step towards completing the UOLEA to incorporate all possible structures encountered in a covariant derivative expansion of the one-loop path integral.
The effect of elastic modulus and friction coefficient on rubber tube sealing performance
Li, Zhimiao; Xu, Siyuan; Ren, Fushen; Liu, Jubao
2015-03-01
The packer is the key element in separating geosphere layers of water injection, water plugging and fracturing operations in the oilfield. The sealing ability of the packer is depending on the contact pressure between rubber tube and the casing. The circumferential strain of casing wall was tested by the strain gauge to get the contact pressure distribution along axial direction of the tube. The friction force between the casing and the rubber tube was taken by the pressure sensor in compression process. Under the 20,60 and 100 degrees Celsius conditions, the friction forces and the contact pressure distribution were taken in work condition of single rubber tube, double rubber tubes and combination rubber tubes after oil immersion .The result shows that elastic modulus of rubber tube has little effect on the friction force and contact pressure. With elastic modulus decreasing, the friction forces has gradually decreasing trend; The friction coefficient has much impact on friction force: the friction forces under the condition of dry friction and wet friction are respectively equivalent to 48.27% and 5.38% axial compression forces. At wet friction condition, the contact pressure distribution is more uniform and the sealing effect is better.
L.I. Gladka
2012-10-01
Full Text Available The analysis of basic and combined models for calculation of effective kinetic coefficients required to describe diffusion processes in two-phase heterogeneous environments is conducted. For a transition zone that grows between two interacting diffusion phases was built a new model of effective medium. In this model the effective kinetic coefficient depends on the kinetic coefficients in each of the phases, volumetric particle phases and additional free parameter, which generally characterizes the type of structure of a bi-phase zone. It is shown that the combined model is constructed to describe the percolation behavior of effective medium. The phenomenological approach describes the formation and development of bi-phase zones in ternary systems which including streams through both phases and the analysis of the impact of the model on the resulting effective medium diffusion zone.
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.
Zamani, N., E-mail: n.zamani@sutech.ac.ir [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Keshavarz, A., E-mail: keshavarz@sutech.ac.ir [Department of Physics, Shiraz University of Technology, Shiraz 71555-313 (Iran, Islamic Republic of); Nadgaran, H., E-mail: nadgaran@susc.ac.ir [Department of Physics, College of Science, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)
2016-06-01
In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge–Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.
Zamani, N.; Keshavarz, A.; Nadgaran, H.
2016-06-01
In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.
Effect of atmospheric environment on the attenuation coefficient of light in water
Liu, Juan; Tang, Yijun; Zhu, Kaixing; Ge, Yuan; Chen, Xuegang; He, Xingdao; Liu, Dahe
2014-01-01
The attenuation coefficient of 532 nm light in water under different atmospheric conditions was investigated. Measurements were made over a two-year period at the same location and show that the attenuation coefficient is significantly influenced by the atmospheric environment. It is lowest when the atmospheric pressure is high and temperature is low, and is highest when the atmospheric pressure is low and temperature is high. The maximum attenuation coefficient of pure water in these studies was about three times the minimum value. The mechanism of the phenomena is discussed. These results are also important in underwater acoustics.
Wu, Yan; Duan, Guosheng; Zhao, Xiang
2015-03-01
Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.
V. Allocca
2013-08-01
Full Text Available To assess the mean annual groundwater recharge of the karst aquifers in southern Apennines (Italy, the estimation of the mean annual effective infiltration coefficient (AEIC was conducted by means of an integrated approach based on hydrogeological, hydrological, geomorphological, land use and soil cover analyses. We studied a large part of the southern Apennines that is covered by a meteorological network and containing 40 principal karst aquifers. Using precipitation and air temperature time series gathered through monitoring stations operating in the period 1926–2012, the annual effective precipitation (AEP was estimated, and its distribution was modelled, by considering the orographic barrier and rain shadow effects of the Apennines chain, as well as the altitudinal control. Four sample karst aquifers with available long spring discharge time series were identified for estimating the AEIC by means of the hydrological budget equation. The resulting AEIC values were correlated with other parameters that control groundwater recharge, such as the extension of outcropping karst-rock, morphological settings, land use and covering soil type. A simple correlation relationship between AEIC, lithology and the summit flat and endorheic areas was found. This empirical model has been used to estimate AEIC and mean annual groundwater recharge in other regional karst aquifers. The estimated AEIC values ranged between 48% and 78%, thus matching intervals estimated for other karst aquifers in European and Mediterranean countries. These results represent a deeper understanding of an aspect of groundwater hydrology in karst aquifers which is fundamental for the formulation of appropriate management models of groundwater resources, also taking into account mitigation strategies for climate change impacts. Finally, the proposed hydrological characterisations are also perceived as useful for the assessment of mean annual runoff over carbonate mountains, which is
Effect of Tension on Friction Coefficient Between Lining and Wire Rope with Low Speed Sliding
PENG Yu-xing; ZHU Zhen-cai; CHEN Guo-an; CAO Guo-hua
2007-01-01
In order to obtain the exact friction coefficient between lining and wire rope, the tension of wire rope is studied as a factor which affects this coefficient. A mechanical model of a wire rope subjected to axial load was established to determine the torque of the wire rope. The contact motion between lining and wire rope was regarded as a screw rotation and the axial force of the lining resulting from the torque of the wire rope was analyzed. Theoretical formulas relating tension of the wire rope and the friction coefficient was obtained. Experiments between lining and wire rope with low sliding speed were carried out with friction tester made by us. Experimental results show that increment of the friction coefficient is proportional to that of the tension of the wire rope with a low sliding speed. The experimental results agree with the theoretical calculation; the errors are less than 6%, which proves the validity of the theoretical model.
THE EFFECT OF THICKNESS OF PILLAR IN THE CHANNEL BEND TO CHANGES THE COEFFICIENT OF SUPERELEVATION
ISHAK M. GALIB
2016-05-01
Full Text Available The present study discusses phenomena occurred in a natural channel where a bridge is built in a river bend. The present study aims at determining the effect of pillars thickness on water surface slope in transverse direction on channel bend which is defined in superelevation coefficient (Cs. Physical modelling applies 180o channel bend, 0.75 m radius, and 0.5 m width. It was applied in both with pillar and without pillar flows in subcritical-turbulent flow. For the flows with pillar there were pillar interval of 30o and 60o. The results show that the highest value of Cs (7.826 is found in the flows with pillar of the 30o interval in 30o river bend. In the interval of 60 where the pillar thickness is 3cm, the Cs value is greater than when the pillar thickness is 2 cm, on the other hand in the interval of 30o the Cs value is smaller. It is recommended for the next research to apply hydraulic condition with average velocity divided by the critical velocity must be greater than one.
Blackness coefficients, effective diffusion parameters, and control rod worths for thermal reactors
Bretscher, M.M.
1984-09-01
Simple diffusion theory cannot be used to evaluate control rod worths in thermal reactors because of the strongly absorbing character of the control material. However, good results can be obtained from a diffusion calculation by representing the absorber slab by means of a suitable pair of internal boundary conditions, ..cap alpha.. and ..beta.., which are ratios of neutron flux to neutron current. Methods for calculating ..cap alpha.. and ..beta.. in the P/sub 1/, P/sub 3/, and P/sub 5/ approximations, with and without scattering, are presented. By appropriately weighting the fine-group blackness coefficients, broad group values, <..cap alpha..> and <..beta..>, are obtained. The technique is applied to the calculation of control rod worths of Cd, Ag-In-Cd, and Hf control elements. Results are found to compare very favorably with detailed Monte Carlo calculations. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method is briefly discussed and applied to the calculation of control rod worths in the Ford Nuclear Reactor at the University of Michigan. Calculated and measured worths are found to be in good agreement.
Landau level-superfluid modified factor and effective X/$\\gamma$-ray coefficient of a magnetar
Gao, Z F; Wang, N; Chou, C K; Huo, W S
2013-01-01
As soon as the energy of electrons near the Fermi surface are higher than $Q$, the threshold energy of inverse $\\beta-$ decay, the electron capture process will dominate. The resulting high-energy neutrons will destroy anisotropic ${}^3P_2$ neutron superfluid Cooper pairs. By colliding with the neutrons produced in the process $n+ (n\\uparrow n\\downarrow)\\longrightarrow n+ n+ n$, the kinetic energy of the outgoing neutrons will be transformed into thermal energy. The transformed thermal energy would transported from the star interior to the star surface by conduction, then would be transformed into radiation energy as soft X-rays and gamma-rays. After a highly efficient modulation within the pulsar magnetosphere, the surface thermal emission (mainly soft X/$\\gamma$-ray emission) has been shaped into a spectrum with the observed characteristics of magnetars. By introducing two important parameters: Landau level-superfluid modified factor and effective X/$\\gamma$-ray coefficient, we numerically simulate the proc...
Effect of region of interest on interobserver variance in apparent diffusion coefficient measures.
Bilgili, Yasemin; Unal, Birsen
2004-01-01
Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MR imaging are useful measurements for assessment of cellular alterations in pathologic conditions of the brain. In this study, two radiologists independently quantitated ADCs and region-of interest sizes in prespecified locations of human brain to test interobserver ADC variance and the effect of varying ROI sizes on ADC differences. Twenty-seven patients with normal MR findings underwent diffusion-weighted imaging (b value = 1000 s/mm(2)) on a 1.5-T system. Two radiologists independently placed two ROI areas of 22 +/- 5 mm(2) and 62 +/- 6 mm(2) (former area inside the latter area) at different sites of the brain (centrum semiovale, frontal white matter, nucleus caudatus, putamen, thalamus, substantia nigra, red nucleus, and pons) from trace images. Differences in ADC measurement obtained from each region of the brain for each radiologist and the size of each ROI were compared statistically. Mean ADC of prespecified areas of brain ranged between 0.673 and 0.818 mm(2)/s x10(-3). Interobserver variance was significant in some of the specified areas (centrum semiovale, frontal white matter, pons, substantia nigra, and red nucleus). Varying ROI sizes at the pons, substantia nigra, and red nucleus yielded statistically different ADC values. ADC values are found to be unreliable for use in assessing brain disease in some specified areas of the brain owing to interobserver variance and different ROI sizes.
Gaikwad, Dhammajyot Kundlik; Pawar, Pravina P.; Selvam, T. Palani
2017-09-01
The mass attenuation coefficients (μ/ρ) for some enzymes, proteins, amino acids and fatty acids were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies, by performing transmission experiments using 57Co, 133Ba, 137Cs, 60Co and 22Na sources collimated to produce 0.52 cm diameter beams. A NaI (Tl) scintillation detector with energy resolution 8.2% at 663 keV was used for detection. The experimental values of (μ/ρ) were then used to determine the atomic cross section (σa), electronic cross section (σe), effective atomic number (Zeff) and electron density (Neff). It was observed that (μ/ρ), σa and σe decrease initially and then tends to be almost constant at higher energies. Values of Zeff and Neff were observed roughly constant with energy. The deviations in experimental results of radiological parameters were believed to be affected by physical and chemical environments. Experimental results of radiological parameters were observed in good agreement with WinXCom values.
Stress Matters: Effects of Anticipated Lexical Stress on Silent Reading
Breen, Mara; Clifton, Charles, Jr.
2011-01-01
This paper presents findings from two eye-tracking studies designed to investigate the role of metrical prosody in silent reading. In Experiment 1, participants read stress-alternating noun-verb or noun-adjective homographs (e.g. "PREsent", "preSENT") embedded in limericks, such that the lexical stress of the homograph, as determined by context,…
M Ramezanizadeh
2013-01-01
Full Text Available In this paper the effects of ice accretion on the pressure distribution and the aerodynamic coefficients in a cascade of stator blades were experimentally investigated. Experiments were conducted on stage 67A type stator Controlled-Diffusion blades, which represent the mid-span of the first stage of the stator for a high-bypass turbofan engine. The measurements were carried out over a range of cascade angle of attack from 20° to 45° at Reynolds number of 500000. Experimental blade surface pressure coefficient distribution, lift and drag force coefficients, and momentum coefficients for clean blades were compared with those of the iced blades and the effects of ice accretion on these parameters were discussed. It is observed that the ice accretion on the blades causes the formation of flow bubble on the pressure side, downstream of the leading edge. By increasing the angle of attack from 20° to 35° , the bubble length decreases and the pressure coefficient increases inside the bubble region, constantly. In addition, for the iced blades the diffusion points at the suction side come closer to the trailing edge. In addition, it is found that by increasing the angle of attack up to 35° , the ice accretion has no significant effect on the lift coefficient but the drag coefficient increases comparing with the clean blades. More over at 40° and 45° , by increasing the flow interference effects between the blades, the iced blades experience higher lift and lower drag in comparison with the clean ones.
Stress effects in twisted highly birefringent fibers
Wolinski, Tomasz R.
1994-03-01
Hydrostatic pressure and uniaxial longitudinal strain effects in twisted highly birefringent optical fibers have been investigated from the point of the Marcuse mode-coupling theory. The problem is analyzed in terms of local normal modes of the ideal fiber and in the limit of weak twist, where large linear birefringence dominates over twist effect, and therefore twist coupling between local modes is not effective. The authors present the results of birefringence measurements in highly birefringent bow-tie fibers influenced simultaneously by hydrostatic pressure up to 100 MPa and twisting the result for highly birefringent elliptical-core fibers influenced by uniaxial longitudinal strain up to 4000 (mu) (epsilon) and twisting effect. The birefringence measurement method is based on twist-induced effects and has been successfully applied in a stress environment. The experiment was conducted with a specially designed stress generating device that makes it possible to simultaneously generate various mechanical perturbations such as hydrostatic and radial pressure, axial strain and twist, allowing study of their influence on mode propagation in optical fibers. A comparison with theoretical results as well as with pervious experimental data on stress influence on the beat length parameter in highly birefringent fibers is also provided.
Effective tunneling coefficient of a coupled double-well system modulated
Tsukada,Noriaki; Yoshida, H.; Suzuki, T.
2008-01-01
We numerically study coherent tunneling oscillations of the particles between two levels in a double-well potential in the presence of anharmonic periodic potentials. Extremely short driving pulses modify the tunneling coefficient to ef f= cos A, where is the bare tunneling coefficient without the driving field and A is the pulse area of the driving wave form. The modulation amplitude of the ef f gradually decreases as the driving wave form becomes broad and is given by ef f...
Effects of work and life stress on semen quality.
Janevic, Teresa; Kahn, Linda G; Landsbergis, Paul; Cirillo, Piera M; Cohn, Barbara A; Liu, Xinhua; Factor-Litvak, Pam
2014-08-01
To evaluate associations between work-related stress, stressful life events, and perceived stress and semen quality. Cross-sectional analysis. Northern California. 193 men from the Child Health and Development Studies evaluated between 2005-2008. None. Measures of stress including job strain, perceived stress, and stressful life events; outcome measures of sperm concentration, percentage of motile sperm, and percentage of morphologically normal sperm. We found an inverse association between perceived stress score and sperm concentration (estimated coefficient b=-0.09×10(3)/mL; 95% confidence interval [CI]=-0.18, -0.01), motility (b=-0.39; 95% CI=-0.79, 0.01), and morphology (b=-0.14; 95% CI, -0.25, -0.04) in covariate-adjusted linear regression analyses. Men who experienced two or more stressful life events in the past year compared with no stressful events had a lower percentage of motile sperm (b=-8.22; 95% CI, -14.31, -2.13) and a lower percentage of morphologically normal sperm (b=-1.66; 95% CI, -3.35, 0.03) but a similar sperm concentration. Job strain was not associated with semen parameters. In this first study to examine all three domains of stress, perceived stress and stressful life events but not work-related stress were associated with semen quality. Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.
Studies on effect of stress preconditioning in restrain stress-induced behavioral alterations.
Kaur, Rajneet; Jaggi, Amteshwar Singh; Singh, Nirmal
2010-02-01
Stress preconditioning has been documented to confer on gastroprotective effects on stress-induced gastric ulcerations. However, the effects of prior exposure of stress preconditioning episodes on stress-induced behavioral changes have not been explored yet. Therefore the present study was designed to investigate the ameliorative effects of stress preconditioning in immobilization stress-induced behavioral alterations in rats. The rats were subjected to restrain stress by placing in restrainer (5.5 cm in diameter and 18 cm in length) for 3.5 h. Stress preconditioning was induced by subjecting the rats to two cycles of restraint and restrain-free periods of 15 min each. Furthermore, a similar type of stress preconditioning was induced using different time cycles of 30 and 45 min. The extent and severity of the stress-induced behavioral alterations were assessed using different behavioral tests such as hole-board test, social interaction test, open field test, and actophotometer. Restrain stress resulted in decrease in locomotor activity, frequency of head dips and rearing in hole board, line crossing and rearing in open field, and decreased following and increased avoidance in social interaction test. Stress preconditioning with two cycles of 15, 30 or 45 min respectively, did not attenuate stress-induced behavioral changes to any extent. It may be concluded that stress preconditioning does not seem to confer any protective effect in modulating restrain stress-induced behavioral alterations.
Effect of Inlet Geometry on the Turbine Blade Tip Region Heat Transfer Coefficient and Effectiveness
2007-11-02
weight loss can rapidly occur, thus increasing leakage flow loss. A typical clearance gap flow is illustrated in Fig. 1, where the arrows represent the... gap flow . The effect of shroud motion was confined to a thin layer adja- cent to the shroud in both cases. The cavity region flow patterns, 2 mean...1988) showed that gap flow was essentially loss-free up to the separation bubble and then under- went sudden expansion causing significant diffusion
İsmail Hakkı ERTEN
2008-10-01
Full Text Available This study aims to compare the appropriateness of two statistical procedures for measuring the effectiveness of vocabulary learning strategies: percentages and correlation coefficients. To do this a group of 20 learners of English were asked to study 12 words in a written list, with their pronunciations, dictionary definitions, and example sentences. Data was collected through introspection where students were asked to verbalize their mental processes as they studied the target words. A pre-test and post-test were given to measure the task achievement. The qualitative data was transcribed verbatim and content-analysed for tokens of strategy use as well as by noting whether each use of strategies led to successful recall of the words on which they were used. To calculate the strategy effectiveness, both simple percentage calculation and correlation coefficients were employed for comparison. The findings indicated that percentage calculation can give a more realistic picture of strategy effectiveness than correlation coefficients.
Yankovskii, A. P.
2016-07-01
We propose two refined structural models of the thermal behavior of a rib-reinforced composite medium at general anisotropy of the materials of compound components. For the criterion of equivalence of the rib-reinforced composite to the fictitious homogeneous anisotropic material, equality of the specific heat dissipation in them was used, which permits determining the upper and lower bounds of the effective heat conductivity coefficients of the composite material. The design values of the effective heat conductivity coefficients of a honeycomb structure with cavities filled and not filled with foam plastic have been determined. It has been shown that the refinement of certain thermal characteristics of 12%, and the refined "fork" of values of these quantities, does not exceed 2.5%. Indirect comparison has been made between the calculated and experimental values of the effective heat conductivity coefficients of such compounds, which has shown that the results obtained in the work are qualitatively reliable.
Prosser, William H.; Kriz, R. D.; Fitting, Dale W.
1990-01-01
Ultrasonic waves suffer energy flux deviation in graphite/epoxy because of the large anisotropy. The angle of deviation is a function of the elastic coefficients. For nonlinear solids, these coefficients and thus the angle of deviation is a function of stress. Acoustoelastic theory was used to model the effect of stress on flux deviation for unidirectional T300/5208 using previously measured elastic coefficients. Computations were made for uniaxial stress along the x3 axis fiber axis) and the x1 axis for waves propagating in the x1x3 plane. These results predict a shift as large as three degrees for the quasi-transverse wave. The shift in energy flux offers new nondestructive technique of evaluating stress in composites.
Togrul, Inci Turk; Ispir, Ayse [Firat University, Engineering Faculty, Department of Chemical Engineering, 23279 Elazig (Turkey)
2007-10-15
This article represents the results of the variation in density and shrinkage of apricots during its osmotic dehydration. Shrinkage was investigated by means of dimensionless volume, diameter and length. Various osmotic agents such as sucrose, glucose, fructose, maltodextrin and sorbitol were used. It was found that the shrinkage of apricots could be well correlated with the moisture content of the sample during osmotic dehydration. The relationship between dimensionless parameters and moisture content was investigated by using eight non-linear models for each osmotic agent. It was find that the following proposed model can be confidently use for explaining the effect of shrinkage during osmotic dehydration of apricots.V/V{sub 0},D/D{sub 0},L/L{sub 0},{rho}/{rho}{sub 0}=a+b. exp (cX)+d. exp (e.X{sup f})In addition, the osmotic dehydration kinetics of apricots with and without shrinkage was studied. The effective diffusivities calculated from the diffusional model with and without shrinkage varied from 10.342 x 10{sup -9} m{sup 2}/s to 5.139 x 10{sup -9} and from 1.755 x 10{sup -10} and 0.767 x 10{sup -10} m{sup 2}/s, respectively. (author)
Effective stress analysis method of seismic response for high tailings dam
LIU Hou-xiang; LI Ning; LIAO Xue; WU Cong-shi; PAN Xu-dong
2007-01-01
Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diflusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam's acceleration, seismic dynamic stress and pore water pressure were obtained.The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly.The interior stress is compressive stress.the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.O. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method.The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams'stability during earthquake is secondary reason.
Alles, J; Mudde, R F
2007-07-01
Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one-to-one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one-to-one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x-rays traveling through water.
HU Chun-bo; ZENG Zhuo-xiong
2006-01-01
A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The proposed model is used to simulate gas-particle downer reactor flows. The computationsl results of both particle volume fraction and mean velocity are in agreement with the experimental results. After analyzing effects of empirical coefficient on prediction results, we can come to a conclusion that, inside the limit range of empirical coefficient, the predictions do not reveal a large sensitivity to the empirical coefficient in the downer reactor, but a relatively great change of the constants has important effect on the prediction.
Effect of spreading coefficient on three-phase relative permeability of nonaqueous phase liquids
Keller, Arturo A.; Chen, Mingjie
2003-10-01
Three-phase flow conditions are encountered regularly, for example, during migration of released NAPL through the vadose zone, certain stages of soil vapor extraction, bioslurping, or generation of gases by microbes. To model three-phase flow, a common approach is to construct three-phase relative permeabilities based on a combination of two-phase relative permeabilities. Although this circumvents a lack of experimental data, it can lead to serious underprediction or overprediction of residual NAPL saturation. This can mislead decision makers that need to predict whether a particular spill will reach the water table or predict the speed of a NAPL front or conduct an assessment of the performance of remediation actions. Experimental data to estimate three-phase relative permeabilities is sparse. A study by [2000a] generated significant experimental information. Their analysis focused on the high NAPL saturation region, given their emphasis on oil reservoir engineering. For environmental applications the low saturation region is of more interest. Using this data set, we derived a set of empirical relations that relate NAPL three-phase relative permeability krn to NAPL saturation Sn and spreading coefficient Cs for Sn less than about 0.1, such that krn = ? where A1 = 0.012 exp (-1.3Cs) and A2 = 2.1 - 0.60Cs + 0.036Cs2. At higher Sn, krn ≈ Sn4, independent of Cs. We present a pore-scale conceptual model that provides a phenomenological basis for the use of Cs as a predictor of krn at low Sn. We then present a number of simulated case studies that highlight the effect of these three-phase relative permeabilities on risk assessment or remediation design.
Rizzolo, Denise; Zipp, Genevieve Pinto; Stiskal, Doreen; Simpkins, Susan
2009-01-01
Background: Health science programs can be demanding and difficult for many students, leading to high levels of stress. High levels of stress can have a negative effect on students and subsequently the practicing clinician. Research suggests that yoga, humor, and reading are simple, effective methods to help reduce stress. To date no research…
Matteoni, G.; Georgakis, C.T.
2012-01-01
Theoretical and experimental investigations to date have assumed that bridge cables can be modeled as ideal circular cylinders and the associated aerodynamic coefficients are invariant with the wind angle-of-attack. On the other hand, bridge cables are normally characterized by local alterations...... of their inherent surface roughness and shape, which might present a significant disturbance for the surrounding wind flow. The present study focuses on the experimental determination, based on static wind tunnel tests, of the aerodynamic coefficients of full-scale bridge cable section models both perpendicular...... and inclined to the flow, for varying wind angles-of-attack. The wind tunnel test results demonstrate that the aerodynamic coefficients of bridge cables can be significantly affected by the wind angle-of-attack....
EFFECT OF HYDROPLANE PROFILE ON HYDRODYNAMIC COEFFICIENTS OF AN AUTONOMOUS UNDERWATER VEHICLE
Ahmad Hajivand
2016-03-01
Full Text Available AUVs are the most suitable tool for conduction survey concerning with global environmental problems. AUVs maneuverability should be carefully checked so as to improve energy efficiency of the vehicle and avoid unexpected motion. Oblique towing test (OTT is simulated virtually in a computational fluid dynamic (CFD environment to obtain hydrodynamic damping coefficients of a full-scale autonomous underwater vehicle. Simulations are performed for bare hull and hull equipped with four different hydroplanes. The hydrodynamic forces and moment are obtained to calculate hydrodynamic coefficients. Nonlinear damping coefficients are also obtained by using suitable curve fitting. Experiments of resistance and OTT are carried out in specific condition, for validation purpose. Following the extracting numerical results a mathematical model is developed to calculate hydrodynamic force for different sail type in order to predict autonomous underwater vehicle (AUV maneuverability. The results shows good agreement between theory and experiment.
Effect of Low Diffusion Coefficient on Eutectic Instability of Al-25 wt%Sm Alloy
WANG Nan
2008-01-01
Diffusion coefficient decides the solute diffusion length and is a critical parameter in the selection of microstructure scales and in governing microstructure transitions. Al-25 wt% Sm alloy is selected to reveal the impact of low diffusion coefficient on the eutectic instability, and the results are compared with those of Al-Cu alloys.Laser remelting experiments are performed and the transition growth velocity from eutectic to α-Al dendrite is examined. Compared with Al-Cu alloys, the eutectic instability takes place at a velocity more than one order of magnitude smaller. The theoretical calculation by the Trivedi-Magnin- Kurz (TMK) model also predicts that the eutectic will become instable at smaller growth velocity for Al-Sm alloy than Al-Cu alloy, which is ascribed to the low diffusion coefficient.
A FIBER-BRIDGING MODEL WITH STRESS GRADIENT EFFECTS
孙毅; 李涛
2000-01-01
Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China)ABSTRACT: A fiber-bridging model with stress gradient effects is proposed for unidirectional fiber-reinforced composites. The stress gradient terms are introduced by solving a micromechanical model under a non-uniform stress loading. It is shown that the stress gradient effect is significant on both the fiber-bridging stress distribution and the value of the critical load of fiber failure.
Stress Symptoms: Effects on Your Body and Behavior
... heart disease, obesity and diabetes. Common effects of stress on your body Headache Muscle tension or pain ... drive Stomach upset Sleep problems Common effects of stress on your mood Anxiety Restlessness Lack of motivation ...
Osmotic and Heat Stress Effects on Segmentation
Weiss, Julian
2016-01-01
During vertebrate embryonic development, early skin, muscle, and bone progenitor populations organize into segments known as somites. Defects in this conserved process of segmentation lead to skeletal and muscular deformities, such as congenital scoliosis, a curvature of the spine caused by vertebral defects. Environmental stresses such as hypoxia or heat shock produce segmentation defects, and significantly increase the penetrance and severity of vertebral defects in genetically susceptible individuals. Here we show that a brief exposure to a high osmolarity solution causes reproducible segmentation defects in developing zebrafish (Danio rerio) embryos. Both osmotic shock and heat shock produce border defects in a dose-dependent manner, with an increase in both frequency and severity of defects. We also show that osmotic treatment has a delayed effect on somite development, similar to that observed in heat shocked embryos. Our results establish osmotic shock as an alternate experimental model for stress, affecting segmentation in a manner comparable to other known environmental stressors. The similar effects of these two distinct environmental stressors support a model in which a variety of cellular stresses act through a related response pathway that leads to disturbances in the segmentation process. PMID:28006008
Petersen, Helena; Kecklund, Göran; D'Onofrio, Paolo; Nilsson, Jens; Åkerstedt, Torbjörn
2013-02-01
The purpose of this study was to investigate if and how sleep physiology is affected by naturally occurring high work stress and identify individual differences in the response of sleep to stress. Probable upcoming stress levels were estimated through weekly web questionnaire ratings. Based on the modified FIRST-scale (Ford insomnia response to stress) participants were grouped into high (n = 9) or low (n = 19) sensitivity to stress related sleep disturbances (Drake et al., 2004). Sleep was recorded in 28 teachers with polysomnography, sleep diaries and actigraphs during one high stress and one low stress condition in the participants home. EEG showed a decrease in sleep efficiency during the high stress condition. Significant interactions between group and condition were seen for REM sleep, arousals and stage transitions. The sensitive group had an increase in arousals and stage transitions during the high stress condition and a decrease in REM, whereas the opposite was seen in the resilient group. Diary ratings during the high stress condition showed higher bedtime stress and lower ratings on the awakening index (insufficient sleep and difficulties awakening). Ratings also showed lower cognitive function and preoccupation with work thoughts in the evening. KSS ratings of sleepiness increased during stress for the sensitive group. Saliva samples of cortisol showed no effect of stress. It was concluded that moderate daily stress is associated with a moderate negative effect on sleep sleep efficiency and fragmentation. A slightly stronger effect was seen in the sensitive group. © 2012 European Sleep Research Society.
Lyu, Juncheng; Shi, Hong; Wang, Suzhen; Zhang, Jie
2016-02-01
This research aimed to estimate the effect of perceived social factors in the community stress and problems on the residents' psychopathology such as depression and suicidal behaviors. Subjects of this study were the informants (N=1618) in a psychological autopsy (PA) study with a case-control design. We interviewed two informants (a family member and a close friend) for 392 suicides and 416 living controls, which came from 16 rural counties randomly selected from three provinces of China. Community stress and problems were measured by the WHO SUPRE-MISS scale. Depression was measured by CES-D scale, and suicidal behavior was assessed by NCS-R scale. Multivariable liner and logistic regression models and the Structural Equation Modeling (SEM) were applied to probe the correlation of the depression and the suicidal behaviors with some major demographic variables as covariates. It was found that community stress and problems were directly associated with rural Chinese residents' depression (Path coefficient=0.127, Pstress and problem and suicidal behaviors, but community stress and problem can affect suicidal behaviors indirectly through depression. The path coefficient between depression and suicidal behaviors was 0.975. The current study predicts a new research viewpoint, that is, the depression is the intermediate between community stress and problem and suicidal behaviors. It might be an effective route to prevent depression directly and suicidal behaviors indirectly by reducing the community stress and problems.
Rong, Li; Nielsen, Peter V; Zhang, Guoqiang
2010-04-01
This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 x 10(4) to 5.43 x 10(4) (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.
Tunnel design considering stress release effect
Van-hung DAO
2009-01-01
In tunnel design,the determination of installation time and the stiffness of supporting structures is very important to the tunnel stability.This study used the convergence-confinement method to determine the stress and displacement of the tunnel while considering the counter-pressure curve of the ground base,the stress release effect,and the interaction between the tunnel lining and the rock surrounding the tunnel chamber.The results allowed for the determination of the installation time,distribution and strength of supporting structures.This method was applied to the intake tunnel in the Ban Ve Hydroelectric Power Plant,in Nghe An Province,Vietnam.The results show that when a suitable displacement u0 ranging from 0.0865 m to 0.0919 m occurrs,we can install supporting structures that satisfy the stability and economical requirements.
Kim, Eun-Young; Choi, Shi-Hoon [Sunchon National University, Suncheon (Korea, Republic of); Kim, Sung Il [POSCO Technical Research Laboratories, Gwangyang (Korea, Republic of)
2016-11-15
The effect of the strength coefficient (K{sub B}) of bainite on micromechanical deformation and failure behaviors of a hot-rolled 590MPa steel (590FB) during uniaxial tension was simulated using the elasto-plastic finite element method (FEM). The spatial distribution of the constituent phases was obtained using a phase identification technique based on optical microstructure. Empirical equations which depend on chemical composition were used to determine the stress-strain relationship of the constituent phases of the 590FB steel. The stress-strain partitioning and failure behavior were analyzed by increasing the K{sub B} of bainite. The elasto-plastic FEM results revealed that effective strain in the ferrite-bainite boundaries, and maximum principal stress in fibrous bainite, were enhanced as the K{sub B} increased. The elasto-plastic FEM results also demonstrated that the K{sub B} significantly affects the micromechanical deformation and failure behaviors of the hot-rolled 590FB steel during uniaxial tension.
Ansari, Rafat R.; Suh, Kwang I.; Sebag, J.
2006-02-01
PURPOSE: Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery. Ultimately, the development of drugs to liquefy and detach vitreous from retina should prevent disease by mitigating the contribution of vitreous to retinopathy and eliminate the need for surgery. However, the mechanism of action of pharmacologic vitreolysis remains unclear. The technique of Dynamic light scattering (DLS) was used to evaluate the effects of microplasmin by following the diffusion coefficients of spherical polystyrene nano-particles injected with microplasmin into the vitreous. METHODS: Diffusion coefficients in dissected (n=9) porcine eyes were measured in vitro. DLS was performed on all specimens at 37°C as often as every 10 minutes for up to 6 hours following injections of human recombinant microplasmin at doses ranging from 0.125 mg to 0.8 mg, with 20 nm diameter tracer nanospheres. RESULTS: DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous, demonstrating a fast (early) component, resulting from the flexible hyaluronan molecules, and a slow (late) component, resulting form the stiff collagen molecules. Microplasmin increased porcine vitreous diffusion coefficients. A new approach was developed to use DLS measurements of vitreous diffusion coefficients to evaluate the effects of microplasmin in intact eyes. CONCLUSIONS: Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies indicate that this new approach using DLS to measure vitreous diffusion coefficients can be used to study the effects of pharmacologic vitreolysis using microplasmin and other agents in intact eyes and ultimately in vivo.
Alles, J.; Mudde, R.F.
2007-01-01
Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fl
Nurul Amalina Mohd Zain
2014-02-01
Full Text Available The use of periodical water stress and potassium fertilization may enhance rice tolerance to drought stress and improve the crop’s instantaneous water use efficiency without much yield reduction. This study was conducted to assess the effects of different periodical water stress combined with potassium fertilization regimes on growth, yield, leaf gas exchanges and biochemical changes in rice grown in pots and compare them with standard local rice grower practices. Five treatments including (1 standard local grower’s practice (control, 80CF = 80 kg K2O/ha + control flooding; (2 120PW15 = 120 kg K2O/ha + periodical water stress for 15 days; (3 120DS15V = 120 kg K2O/ha + drought stress for 15 days during the vegetative stage; (4 120DS25V = 120 kg K2O/ha + drought stress for 25 days and (5 120DS15R = 120 kg K2O/ha + drought stress for 15 days during the reproductive stage, were evaluated in this experiment. Control and 120PW15 treatments were stopped at 100 DAS, and continuously saturated conditions were applied until harvest. It was found that rice under 120PW15 treatment showed tolerance to drought stress evidenced by increased water use efficiency, peroxidase (POX, catalase (CAT and proline levels, maximum efficiency of photosystem II (fv/fm and lower minimal fluorescence (fo, compared to other treatments. Path coefficient analysis revealed that most of parameters contribute directly rather than indirectly to rice yield. In this experiment, there were four factors that are directly involved with rice yield: grain soluble sugar, photosynthesis, water use efficiency and total chlorophyll content. The residual factors affecting rice yield are observed to be quite low in the experiment (0.350, confirming that rice yield was mostly influenced by the parameters measured during the study.
Stress effects on memory : An update and integration
Schwabe, Lars; Joëls, Marian; Roozendaal, Benno; Wolf, Oliver T.; Oitzl, Melly S.
2012-01-01
It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in
Stress effects on memory: an update and integration
Schwabe, L.; Joels, M.; Roozendaal, B.; Wolf, O.T.; Oitzl, M.S.
2012-01-01
It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in
Stress effects on memory : An update and integration
Schwabe, Lars; Joëls, Marian; Roozendaal, Benno; Wolf, Oliver T.; Oitzl, Melly S.
2012-01-01
It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in
Rong, Li; Nielsen, Peter V.; Zhang, Guoqiang
2010-01-01
This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass...... to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 × 104 to 5.43 × 104 (based on wind tunnel length). The surface concentration increases as velocity decreases and varies...... greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation...
Faria, Marco Tulio C.
This paper presents a finite element procedure specially devised to analyze the misalignment effects on the behavior of spiral groove gas face seals operating at high speeds. In this study, the seal stationary face is slightly misaligned and the flexibly mounted face is perfectly aligned. Predictions of some steady-state and dynamic performance characteristics versus misalignment angle are presented for spirally grooved gas seals operating under stringent conditions. Curves of dynamic force coefficients versus the static misalignment angle of the seal face indicate that the seal misalignment affects considerably the dynamic response of gas lubricated face seals. At high speeds, the static seal misalignment not only results in increased stiffness coefficients but also leads to negative damping coefficients, which may be a sign of the seal susceptibility to excessive angular motions.
Acute stress does not affect the impairing effect of chronic stress on memory retrieval
Jamile Ozbaki
2016-07-01
Full Text Available Objective(s: Due to the prevalence and pervasiveness of stress in modern life and exposure to both chronic and acute stresses, it is not clear whether prior exposure to chronic stress can influence the impairing effects of acute stress on memory retrieval. This issue was tested in this study. Materials and Methods: Adult male Wistar rats were randomly assigned to the following groups: control, acute, chronic, and chronic + acute stress groups. The rats were trained with six trials per day for 6 consecutive days in the water maze. Following training, the rats were either kept in control conditions or exposed to chronic stress in a restrainer 6 hr/day for 21 days. On day 22, a probe test was done to measure memory retention. Time spent in target and opposite areas, platform location latency, and proximity were used as indices of memory retention. To induce acute stress, 30 min before the probe test, animals received a mild footshock. Results: Stressed animals spent significantly less time in the target quadrant and more time in the opposite quadrant than control animals. Moreover, the stressed animals showed significantly increased platform location latency and proximity as compared with control animals. No significant differences were found in these measures among stress exposure groups. Finally, both chronic and acute stress significantly increased corticosterone levels. Conclusion: Our results indicate that both chronic and acute stress impair memory retrieval similarly. Additionally, the impairing effects of chronic stress on memory retrieval were not influenced by acute stress.
Acute stress does not affect the impairing effect of chronic stress on memory retrieval
Ozbaki, Jamile; Goudarzi, Iran; Salmani, Mahmoud Elahdadi; Rashidy-Pour, Ali
2016-01-01
Objective(s): Due to the prevalence and pervasiveness of stress in modern life and exposure to both chronic and acute stresses, it is not clear whether prior exposure to chronic stress can influence the impairing effects of acute stress on memory retrieval. This issue was tested in this study. Materials and Methods: Adult male Wistar rats were randomly assigned to the following groups: control, acute, chronic, and chronic + acute stress groups. The rats were trained with six trials per day for 6 consecutive days in the water maze. Following training, the rats were either kept in control conditions or exposed to chronic stress in a restrainer 6 hr/day for 21 days. On day 22, a probe test was done to measure memory retention. Time spent in target and opposite areas, platform location latency, and proximity were used as indices of memory retention. To induce acute stress, 30 min before the probe test, animals received a mild footshock. Results: Stressed animals spent significantly less time in the target quadrant and more time in the opposite quadrant than control animals. Moreover, the stressed animals showed significantly increased platform location latency and proximity as compared with control animals. No significant differences were found in these measures among stress exposure groups. Finally, both chronic and acute stress significantly increased corticosterone levels. Conclusion: Our results indicate that both chronic and acute stress impair memory retrieval similarly. Additionally, the impairing effects of chronic stress on memory retrieval were not influenced by acute stress. PMID:27635201
Effect and mechanism of stresses on rock permeability at different scales
YIN; Shangxian; WANG; Shangxu
2006-01-01
The effect of geo-stress fields on macroscopic hydro-geological conditions or microcosmic permeability of water-bearing media should follow some laws or principles. Cases study and tests show that: (1) At macro-geologic large scale, deformed and crashed rocks which were induced by geo-stress fields changing provided space for groundwater storage and flow. Groundwater adjusts water-bearing space and dilatants fractures by flowing and press transferring. Coupling of liquid and solid can be implemented for rocks and groundwater. Although tectonic fields witness several times of change and build-up in geological time, stress fields forming regional tectonic framework are coherent with seepage fields, orientation of the maximum horizontal stress demonstrates main seepage directions. (2) At macro-geologic middle scale, zones of stresses changing sharply, quite low stresses,stress or shear concentration can be used to show locations and types of main fractures, zones of geo-stresses changing equably can be acted as normal base media zones of tri-porosity media. (3) At micro-geologic small scale, tri-porosity media include fractured rocks, porous rocks and capillary rocks. Investigations indicate that porosity or permeability is functions of effective stresses, and porosity or permeability changing rules of porous rocks with variation of effective stresses can be described as the index model, the model of power exponent functions is suitable for those of fractured rocks, the model of the second power parabola for capillary rocks. The porosity and permeability loss in fractured rocks, which are greater than that in porous rocks, are shown by calculation of effective compressive coefficient and closing pressure in cracks. The calculations can also explain themechanism why porosity changes are always larger than permeability changes. It is proved by the thick wall cylinder theory that the second power parabola relation between porosity or permeability loss and effective
Pishnamazi, A; Renema, R A; Paul, D C; Wenger, I I; Zuidhof, M J
2015-10-01
With increasing disparity between broiler breeder target weights and broiler growth potential, maintenance energy requirements have become a larger proportion of total broiler breeder energy intake. Because energy is partitioned to growth and egg production at a lower priority than maintenance, accurate prediction of maintenance energy requirements is important for practical broiler breeder feed allocation decisions. Environmental temperature affects the maintenance energy requirement by changing rate of heat loss to the environment. In the ME system, heat production (energy lost) is part of the maintenance requirement (ME). In the current study, a nonlinear mixed model was derived to predict ME partitioning of broiler breeder hens under varied temperature conditions. At 21 wk of age, 192 Ross 708 hens were individually caged within 6 controlled environmental chambers. From 25 to 41 wk, 4 temperature treatments (15°C, 19°C, 23°C, and 27°C) were randomly assigned to the chambers for 2-week periods. Half of the birds in each chamber were fed a high-energy (HE; 2,912 kcal/kg) diet, and half were fed a low-energy (LE; 2,790 kcal/kg) diet. The nonlinear mixed regression model included a normally distributed random term representing individual hen maintenance, a quadratic response to environmental temperature, and linear ADG and egg mass (EM) coefficients. The model assumed that energy requirements for BW gain and egg production were not influenced by environmental temperature because hens were homeothermic, and the cellular processes for associated biochemical processes occurred within a controlled narrow core body temperature range. Residual feed intake (RFI) and residual ME (RME) were used to estimate efficiency. A quadratic effect of environmental temperature on broiler breeder MEm was predicted ( Birds fed the HE diet were more efficient, with a lower RME than birds on the LE diet (-0.63 vs. 0.63 kcal/kg), translating to ME of 135.2 and 136.5 kcal
Effective Stress-Porosity Relationship above and Within the Oil Window in the North Sea Basin
Kenneth S. Okiongbo
2011-01-01
Full Text Available This study investigates the effective stress - porosity relationship above and within the oil window in the Kimmeridge Clay Formation (KCF in the North Sea Basin (UK using effective stress and porosity determined from wireline logs and pore pressure data. Porosity was determined from an empirical porosity - sonic transit - time transform, calibrated using shale and mudstone core porosity measurements from Jurassic shales in the North Sea. Effective stress was determined from the total overburden stress and pore pressure. The total overburden stress was calculated by integration of the density log. The results show that porosity range between ~11-20% in the pre-generation zone but decreased to <5% within the oil window. Compaction coefficient ($ values above the oil window vary from ~0.08-0.09 M/Pa, but vary from ~0.05-0.06 M/Pa within the oil window implying that deeper burial and a high degree of chemical precipitation and cementation has created a stiff matrix giving rise to low $ values. The effective stress-porosity relationship above and within the oil window reflects a possible decrease in effective stress occasioned by increase in porosity in the pregeneration zone.
The effects of stress on glutamatergic transmission in the brain.
Yuan, Ti-Fei; Hou, Gonglin
2015-01-01
Stress leads to detrimental effects on brain functions and results in various diseases. Recent studies highlight the involvement of glutamatergic transmission in pathogenesis of depressive behaviors and fears. Acute stress generates different impacts on the excitatory transmission compared to chronic stress. Different neuromodulators and epigenetic factors also participate in the alteration of synaptic transmission and the regulation of synaptic plasticity. Restoration of the glutamatergic transmission in stress-affected brain areas therefore provides novel directions of therapeutic interventions against stress.
Effect of plasma actuator and splitter plate on drag coefficient of a circular cylinder
Akbıyık Hürrem
2016-01-01
Full Text Available In this paper, an experimental study on flow control around a circular cylinder with splitter plate and plasma actuator is investigated. The study is performed in wind tunnel for Reynolds numbers at 4000 and 8000. The wake region of circular cylinder with a splitter plate is analyzed at different angles between 0 and 180 degrees. In this the study, not only plasma actuators are activated but also splitter plate is placed behind the cylinder. A couple electrodes are mounted on circular cylinder at ±90 degrees. Also, flow visualization is achieved by using smoke wire method. Drag coefficient of the circular cylinder with splitter plate and the plasma actuator are obtained for different angles and compared with the plain circular cylinder. While attack angle is 0 degree, drag coefficient is decreased about 20% by using the splitter plate behind the circular cylinder. However, when the plasma actuators are activated, the improvement of the drag reduction is measured to be 50%.
Butenko V. K.
2009-10-01
Full Text Available The installation for measuring of specific coefficient of candle-power light of returning surfaces on the accordance of ДСТУ 4100-2002 is developed. The construction of installation provides more wide in comparison with analogues range of measuring — from 10–1 to 104 kd/(lk·m2. Limit of the basic assumed relative error of measuring is no more then ±15%.
Fully Coupled Simulation of the Plasma Liquid Interface and Interfacial Coefficient Effects
Lindsay, Alexander; Shannon, Steven
2016-01-01
There is a growing interest in the study of coupled plasma-liquid systems because of their applications to biomedicine, biological and chemical disinfection, agriculture, and other areas. Without an understanding of the near-surface gas dynamics, modellers are left to make assumptions about the interfacial conditions. For instance it is commonly assumed that the surface loss or sticking coefficient of gas-phase electrons at the interface is equal to 1. In this work we explore the consequences of this assumption and introduce a couple of ways to think about the electron interfacial condition. In one set of simulations we impose a kinetic condition with varying surface loss coefficient on the gas phase interfacial electrons. In a second set of simulations we introduce a Henry's law like condition at the interface in which the gas-phase electron concentration is assumed to be in thermodynamic equilibrium with the liquid-phase electron concentration. It is shown that for a range of electron Henry coefficients spa...
A HAMMADI
2002-12-01
Full Text Available Viscosity B‑coefficients in glycerol obtained at 25 °C for many salts by a rearrangement in the Jones‑Dole expression are compared with those calculated applying existing theories, based on the model of hard‑charged spheres moving in a solvent continuum. Specific agreement between theory and experiment was not generally good. While the results show that Einstein’s relation can be applied to large aqueous ions, provided that the true volume‑fraction of the ions in solution can be ascertained; this expression does not lead to accurate B‑values in glycerol. For the ion‑size dependence of the B‑coefficient in aqueous solutions, Clark’s theoretical predictions agree with experiments qualitatively, in the case of glycerol, however, the model shows limitations even for small ions, for which the dielectric friction theory is expected to be applicable. Finally, all the above theories give a positive B‑coefficient, while experimental evidences showed that B could be negative.
Qiang Zhang
2015-01-01
Full Text Available An analytical model on electromechanical coupling coefficient and the length optimization of a bending piezoelectric ultrasonic transducer are proposed. The piezoelectric transducer consists of 8 PZT elements sandwiched between four thin electrodes, and the PZT elements are clamped by a screwed connection between fore beam and back beam. Firstly, bending vibration model of the piezoelectric transducer is built based on the Timoshenko beam theory. Secondly, the analytical model of effective electromechanical coupling coefficient is built based on the bending vibration model. Energy method and electromechanical equivalent circuit method are involved in the modelling process. To validate the analytical model, sandwich type piezoelectric transducer example in second order bending vibration mode is analysed. Effective electromechanical coupling coefficient of the transducer is optimized with simplex reflection technique, and the optimized ratio of length of the transducers is obtained. Finally, experimental prototypes of the sandwich type piezoelectric transducers are fabricated. Bending vibration mode and impedance of the experimental prototypes are tested, and electromechanical coupling coefficient is obtained according to the testing results. Results show that the analytical model is in good agreement with the experimental model.
Modeling the Effects of Stress: An Approach to Training
Cuper, Taryn
2010-01-01
Stress is an integral element of the operational conditions experienced by combat medics. The effects of stress can compromise the performance of combat medics who must reach and treat their comrades under often threatening circumstances. Examples of these effects include tunnel vision, loss of motor control, and diminished hearing, which can result in an inability to perceive further danger, satisfactorily treat the casualty, and communicate with others. While many training programs strive to recreate this stress to aid in the experiential learning process, stress inducement may not always be feasible or desired. In addition, live simulations are not always a practical, convenient, and repeatable method of training. Instead, presenting situational training on a personal computer is proposed as an effective training platform in which the effects of stress can be addressed in a different way. We explore the cognitive and motor effects of stress, as well as the benefits of training for mitigating these effects in real life. While many training applications focus on inducing stress in order to "condition" the stress response, the author explores the possibilities of modeling stress to produce a similar effect. Can presenting modeled effects of stress help prepare or inoculate soldiers for stressful situations in which they must perform at a high level? This paper investigates feasibility of modeling stress and describes the preliminary design considerations of a combat medic training system that utilizes this method of battlefield preparation.
Study on the effect of process conditions on the thermo-optic coefficient of amorphous silicon films
Zhou, Xiang; Liu, Shuang; Tang, Haihua; Zhong, Zhiyong; Liu, Yong
2016-05-01
A thermo-optical coefficient (TOC) test platform based on FILMeasure-20 was designed and the thermal coefficient of hydrogenated amorphous silicon (a-Si:H) thin films material at 1330 nm was tested. a-Si:H were deposited on the quartz glass using a plasma-enhanced chemical vapor deposition (PECVD) system. Fourier transform infrared spectrometer (FTIR) was used to characterize the infrared spectral feature of films. The hydrogen content of films was influenced by different radio frequency (RF) power and deposition pressure conditions according to the FTIR spectra and theoretical analysis, and the thermo-optic effect of a-Si:H varied with temperature characteristics. Experimental results indicated that selecting the appropriate process conditions to prepare a-Si:H films can effectively increase or avoid the impact of thermo-optical effect on the optical devices.
Effect of Thermal Stresses on the Failure Criteria of Fiber Composites
Leong, Martin Klitgaard; Sankar, Bhavani V.
2010-01-01
When composite laminates are operated at cryogenic temperatures, thermal stresses arise. This is due to the difference in coefficients of thermal expansion of different plies and also between the fiber and matrix. While the former is taken into account in the composite structural analysis......, the latter, called micro-thermal stresses, has not been given much attention. In this paper the Direct Micromechanics Method is used to investigate the effects of micro-thermal stresses on the failure envelope of composites. Using FEA the unit-cell of the composite is analyzed. Assuming the failure criteria...... for the fiber and matrix are known, the exact failure envelope is developed. Using the micromechanics results, the Tsai-Wu failure envelope is modified to account for the micro-thermal stresses. The approach is demonstrated using two example structures at cryogenic temperature....
Thermal Stresses in a Cylinder Block Casting Due to Coupled Thermal and Mechanical Effects
XU Yan; KANG Jinwu; HUANG Tianyou; HU Yongyi
2008-01-01
Thermal stress in castings results from nonuniform cooling. The thermal stress and the deforma-tion can change the casting and mold contact conditions which then alter the heat transfer between the cast-ing and the mold. The contact element method was used to study the interaction between a sand mold and a casting. The contact status was then fed back to the heat transfer analysis between the sand mold and the casting to re-evaluate the heat transfer coefficient based on the gap size or pressure between surfaces. The thermal and mechanical phenomena are then coupled in two directions. The method was applied to analyze stress in a stress frame specimen casting and a cylinder block. The results are more accurate than without consideration of the contact effects on the heat transfer.
Effect of Rotor Diameter on the Thermal Stresses of a Turbine Rotor Model
Dávalos, J. O.; García, J. C.; Urquiza, G.; Castro-Gómez, L. L.; Rodríguez, J. A.; De Santiago, O.
2016-04-01
Thermal stresses in a simplified steam turbine rotor model during a cold startup are analyzed using finite element analysis (FEA). In order to validate the numerical model, an experimental array is developed in which a hollow cylinder is heated with hot air in the external surface. At the thick wall of the cylinder, temperature distribution is measured in real time, while at the same time an algorithm computes thermal stresses. Additional computational fluid dynamics (CFD) calculations are made to obtain magnitudes of velocity and pressure in order to compute convective heat transfer coefficient. The experimental results show good agreement with the FEA computations. To evaluate the effect of rotor diameter size, FEA computations with variation in external and internal diameters are performed. Results show that thermal stresses are proportional to rotor diameter size. Also, zones of higher stress concentration are found in the external and internal surfaces of the rotor.
The effect of protein dielectric coefficient on the ionic selectivity of a calcium channel.
Boda, Dezso; Valiskó, Mónika; Eisenberg, Bob; Nonner, Wolfgang; Henderson, Douglas; Gillespie, Dirk
2006-07-21
Calcium-selective ion channels are known to have carboxylate-rich selectivity filters, a common motif that is primarily responsible for their high Ca(2+) affinity. Different Ca(2+) affinities ranging from micromolar (the L-type Ca channel) to millimolar (the ryanodine receptor channel) are closely related to the different physiological functions of these channels. To understand the physical mechanism for this range of affinities given similar amino acids in their selectivity filters, we use grand canonical Monte Carlo simulations to assess the binding of monovalent and divalent ions in the selectivity filter of a model Ca channel. We use a reduced model where the electolyte is modeled by hard-sphere ions embedded in a continuum dielectric solvent, while the interior of protein surrounding the channel is allowed to have a dielectric coefficient different from that of the electrolyte. The induced charges that appear on the protein/lumen interface are calculated by the induced charge computation method [Boda et al., Phys. Rev. E 69, 046702 (2004)]. It is shown that decreasing the dielectric coefficient of the protein attracts more cations into the pore because the protein's carboxyl groups induce negative charges on the dielectric boundary. As the density of the hard-sphere ions increases in the filter, Ca(2+) is absorbed into the filter with higher probability than Na(+) because Ca(2+) provides twice the charge to neutralize the negative charge of the pore (both structural carboxylate oxygens and induced charges) than Na(+) while occupying about the same space (the charge/space competition mechanism). As a result, Ca(2+) affinity is improved an order of magnitude by decreasing the protein dielectric coefficient from 80 to 5. Our results indicate that adjusting the dielectric properties of the protein surrounding the permeation pathway is a possible way for evolution to regulate the Ca(2+) affinity of the common four-carboxylate motif.
Han, Eun Young; Ha, Wi-Ho; Jin, Young-Woo; Bolch, Wesley E; Lee, Choonsik
2015-03-01
After an incident of radiological dispersal devices (RDD), health care providers will be exposed to the contaminated patients in the extended medical treatments. Assessment of potential radiation dose to the health care providers will be crucial to minimize their health risk. In this study, we compiled a set of conversion coefficients (mSv MBq(-1) s(-1)) to readily estimate the effective dose from the time-integrated activity for the health care providers while they deal with internally contaminated patients at different ages. We selected Co-60, Ir-192, Am-241, Cs-137, and I-131 as the major radionuclides that may be used for RDD. We obtained the age-specific organ burdens after the inhalation of those radionuclides from the Dose and Risk Calculation Software (DCAL) program. A series of hybrid computational phantoms (1-, 5-, 10-, and 15 year-old, and adult males) were implemented in a general purpose Monte Carlo (MC) transport code, MCNPX v 2.7, to simulate an adult male health care provider exposed to contaminated patients at different ages. Two exposure scenarios were taken into account: a health care provider (a) standing at the side of patients lying in bed and (b) sitting face to face with patients. The conversion coefficients overall depended on radionuclides, the age of the patients, and the orientation of the patients. The conversion coefficient was greatest for Co-60 and smallest for Am-241. The dose from the 1 year-old patient phantom was up to three times greater than that from the adult patient phantom. The conversion coefficients were less dependent on the age of the patients in the scenario of a health care provider sitting face to face with patients. The dose conversion coefficients established in this study will be useful to readily estimate the effective dose to the health care providers in RDD events.
M. Stewart
2015-02-01
Full Text Available The determination of the piezoelectric coefficient of thin films using interferometry is hindered by bending contributions. Using finite element analysis (FEA simulations, we show that the Lefki and Dormans approximations using either single or double-beam measurements cannot be used with finite top electrode sizes. We introduce a novel method for characterising piezoelectric thin films which uses a differential measurement over the discontinuity at the electrode edge as an internal reference, thereby eliminating bending contributions. This step height is shown to be electrode size and boundary condition independent. An analytical expression is derived which gives good agreement with FEA predictions of the step height.
Fully coupled simulation of the plasma liquid interface and interfacial coefficient effects
Lindsay, Alexander D.; Graves, David B.; Shannon, Steven C.
2016-06-01
There is a growing interest in the study of coupled plasma-liquid systems because of their applications to biomedicine, biological and chemical disinfection, agriculture, and other areas. Optimizing these applications requires a fundamental understanding of the coupling between phases. Though much progress has been made in this regard, there is still more to be done. One area that requires more research is the transport of electrons across the plasma-liquid interface. Some pioneering works (Rumbach et al 2015 Nat. Commun. 6, Rumbach et al 2015 J. Phys. D: Appl. Phys. 48 424001) have begun revealing the near-surface liquid characteristics of electrons. However, there has been little work to determine the near-surface gas phase electron characteristics. Without an understanding of the near-surface gas dynamics, modellers are left to make assumptions about the interfacial conditions. For instance it is commonly assumed that the surface loss or sticking coefficient of gas-phase electrons at the interface is equal to 1. In this work we explore the consequences of this assumption and introduce a couple of ways to think about the electron interfacial condition. In one set of simulations we impose a kinetic condition with varying surface loss coefficient on the gas phase interfacial electrons. In a second set of simulations we introduce a Henry’s law like condition at the interface in which the gas-phase electron concentration is assumed to be in thermodynamic equilibrium with the liquid-phase electron concentration. It is shown that for a range of electron Henry coefficients spanning a range of known hydrophilic specie Henry coefficients, the gas phase electron density in the anode can vary by orders of magnitude. Varying reflection of electrons by the interface also has consequences for the electron energy profile; increasing reflection may lead to increasing thermalization of electrons depending on choices about the electron energy boundary condition. This variation
Assessing reproducibility by the within-subject coefficient of variation with random effects models.
Quan, H; Shih, W J
1996-12-01
In this paper we consider the use of within-subject coefficient of variation (WCV) for assessing the reproducibility or reliability of a measurement. Application to assessing reproducibility of biochemical markers for measuring bone turnover is described and the comparison with intraclass correlation is discussed. Both maximum likelihood and moment confidence intervals of WCV are obtained through their corresponding asymptotic distributions. Normal and log-normal cases are considered. In general, WCV is preferred when the measurement scale bears intrinsic meaning and is not subject to arbitrary shifting. The intraclass correlation may be preferred when a fixed population of subjects can be well identified.
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.
Effects of work stress and home stress on autonomic nervous function in Japanese male workers.
Maeda, Eri; Iwata, Toyoto; Murata, Katsuyuki
2015-01-01
Autonomic imbalance is one of the important pathways through which psychological stress contributes to cardiovascular diseases/sudden death. Although previous studies have focused mainly on stress at work (work stress), the association between autonomic function and stress at home (home stress) is still poorly understood. The purpose was to clarify the effect of work/home stress on autonomic function in 1,809 Japanese male workers. We measured corrected QT (QTc) interval and QT index on the electrocardiogram along with blood pressure and heart rate. Participants provided self-reported information about the presence/absence of work/home stress and the possible confounders affecting QT indicators. Home stress was related positively to QT index (p=0.040) after adjusting for the possible confounders, though work stress did not show a significant relation to QTc interval or QT index. The odds ratio of home stress to elevated QT index (≥105) was 2.677 (95% CI, 1.050 to 6.822). Work/home stress showed no significant relation to blood pressure or heart rate. These findings suggest that autonomic imbalance, readily assessed by QT indicators, can be induced by home stress in Japanese workers. Additional research is needed to identify different types of home stress that are strongly associated with autonomic imbalance.
Perceived stress and self-esteem mediate the effects of work-related stress on depression.
Lee, Jong-Sun; Joo, Eun-Jeong; Choi, Kyeong-Sook
2013-02-01
The aim of the present study was to investigate the impact of perceived stress and self-esteem on work-related stress and depression. Two hundred and eighty-four Korean nurses participated in the study. The participants completed four questionnaires, including the Korean short version of the occupational stress scale, the perceived stress scale, the Rosenberg self-esteem scale and the Beck depression inventory. Structural equation modelling was used to determine the relationships among work-related stress, perceived stress, self-esteem, and depression. Work-related stress was positively associated with depression. Perceived stress was inversely related to self-esteem and positively associated with work-related stress and depression, respectively. Self-esteem was negatively associated with work-related stress and depression. Structural equation modelling revealed that self-esteem and perceived stress fully mediate the relationship between work-related stress and depression. Future studies should further investigate the effect of psychological characteristics on work-related stress and symptoms of depression.
Failure Probability Model considering the Effect of Intermediate Principal Stress on Rock Strength
Yonglai Zheng
2015-01-01
Full Text Available A failure probability model is developed to describe the effect of the intermediate principal stress on rock strength. Each shear plane in rock samples is considered as a micro-unit. The strengths of these micro-units are assumed to match Weibull distribution. The macro strength of rock sample is a synthetic consideration of all directions’ probabilities. New model reproduces the typical phenomenon of intermediate principal stress effect that occurs in some true triaxial experiments. Based on the new model, a strength criterion is proposed and it can be regarded as a modified Mohr-Coulomb criterion with a uniformity coefficient. New strength criterion can quantitatively reflect the intermediate principal stress effect on rock strength and matches previously published experimental results better than common strength criteria.
Zhou, Rong; Yu, Xiaqing; Ottosen, Carl-Otto; Rosenqvist, Eva; Zhao, Liping; Wang, Yinlei; Yu, Wengui; Zhao, Tongmin; Wu, Zhen
2017-01-25
with combined stress tolerance might not be correlated with the single stress tolerance. In this study, drought stress had a predominant effect on tomato over heat stress, which explained why simultaneous application of heat and drought revealed similar physiological responses to the drought stress. These results will uncover the difference and linkage between the physiological response of tomatoes to drought, heat and combined stress and be important for the selection and breeding of tolerant tomato cultivars under single and combine stress.
SUN Guowen; SUN Wei; ZHANG Yunsheng; LIU Zhiyong
2012-01-01
N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone (ITZ) between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself.For the convenience of applications,the mortar and concrete were considered as a four-phase spherical model,consisting of cement continuous phase,dispersed aggregates phase,interface transition zone and their homogenized effective medium phase.A general effective medium equation was estabhshed to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure.During calculation,the tortuosity (n) and eonstrictivity factors (Ds/D0) of pore in the hardened pastes are n≈3.2,Ds/D0=1.0× 10-4 respectively from the test data.The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results; The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.
Irina Chamine
2015-01-01
Full Text Available Objective. Stress-reducing therapies help maintain cognitive performance during stress. Aromatherapy is popular for stress reduction, but its effectiveness and mechanism are unclear. This study examined stress-reducing effects of aromatherapy on cognitive function using the go/no-go (GNG task performance and event related potentials (ERP components sensitive to stress. The study also assessed the importance of expectancy in aromatherapy actions. Methods. 81 adults were randomized to 3 aroma groups (active experimental, detectable, and undetectable placebo and 2 prime subgroups (prime suggesting stress-reducing aroma effects or no-prime. GNG performance, ERPs, subjective expected aroma effects, and stress ratings were assessed at baseline and poststress. Results. No specific aroma effects on stress or cognition were observed. However, regardless of experienced aroma, people receiving a prime displayed faster poststress median reaction times than those receiving no prime. A significant interaction for N200 amplitude indicated divergent ERP patterns between baseline and poststress for go and no-go stimuli depending on the prime subgroup. Furthermore, trends for beneficial prime effects were shown on poststress no-go N200/P300 latencies and N200 amplitude. Conclusion. While there were no aroma-specific effects on stress or cognition, these results highlight the role of expectancy for poststress response inhibition and attention.
Amirataee, Babak; Montaseri, Majid; Sanikhani, Hadi
2016-10-01
Reference evapotranspiration (ET0) is considered a key parameter for evaluating the climatic changes as well as spatial and temporal patterns of parameters influencing the eco-hydrological processes. The analysis of trend variations of this index can be used to determine appropriate strategies in planning and management of water resources. In this paper, the trend variations of monthly and annual ET0 in Urmia Lake basin, located in the northwest of Iran, have been analyzed using data from 14 synoptic stations in the study area. Regarding the significant effect of autocorrelation coefficients with different lags on trend variations of ET0, this paper has resorted to modified Mann-Kendall test via eliminating the significance effect of autocorrelation coefficients with different lags to analyze the trend variations. Furthermore, Theil-Sen estimator has been used to determine the slope of trend line of ET0. The results indicated an increasing trend in ET0 values at all the studied stations. Having used the modified Mann-Kendall test, the values of significant increasing (positive) trend, which were estimated using common Mann-Kendall test, dramatically decreased. As such, the values of only 7 stations have been significant at 95 % level. The results confirmed the need for eliminating the significance effect of autocorrelation coefficients with different lags to determine and evaluate the trend of hydrological variables.
Coefficient of Performance Optimization of Single-Effect Lithium-Bromide Absorption Cycle Heat Pumps
Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard
2015-01-01
In this paper, we investigate the coefficient of performance (COP) of a LiBr absorption cycle heat pump under different operating conditions. The investigation is carried out using a dynamical model fitted against data recorded from an actual heat pump used for district heating in S......⊘nderborg, Denmark. Since the model is too complex to study analytically, we vary different input variables within the permissible operating range of the heat pump and evaluate COP at the resulting steady-state operating points. It is found that the best set-point for each individual input is located at an extreme......-state operation of the heat pump, while avoiding crystallization issues....
Hintz, C. J.; Shaw, T. J.; Chandler, G. T.; McCorkle, D. C.; Bernhard, J. M.; Blanks, J. K.
2006-12-01
Field studies have suggested that calcite saturation states (Ømega) near and below saturation alter trace element distribution coefficients in benthic foraminifera. Recent benthic foraminiferal culture experiments at the University of South Carolina investigated the response of trace element signatures to three different calcite saturation seawater environments by manipulating total alkalinity (TA). Starting with near-surface Gulf Stream water (Ømega = 3, TA=2380 μeq kg-1), two seawater reservoirs were titrated with HCl to lower their calcite saturation states (Ømega = 2, TA = 1910 μeq kg-1; Ømega = 1.1, TA = 1320 μeq kg-1). Mixed-species foraminiferal assemblages, with the calcite-specific fluorescent label calcein, were inoculated into 13 total culture chambers evenly distributed among the control and 2 treatment seawater reservoirs. These cultures were maintained at 7.2 ± 0.1 °C temperature and 36.6 ± 0.4 ‰ salinity for 8 months. Total alkalinity and dissolved inorganic carbon, measured biweekly, characterized the carbonate system and verified that the calcite saturation state remained stable over the culture duration. Trace element concentrations were also measured biweekly. Foraminiferal reproduction ( Bulimina marginata) was observed in each seawater chemistry. These individuals were utilized for trace element and stable isotope (data not presented here) analysis. Additionally, terminal chambers precipitated in alkalinity-adjusted cultures were identified by the absence of the pre-culture calcein label used on all inoculated foraminifera. These cultured chambers were separated by laser microdissection and analyzed for trace element content by isotope dilution inductively-coupled plasma mass spectrometry. We present the initial results of these trace element distribution coefficients measured in cultured benthic foraminifera from three different Ømega. This research was funded by National Science Foundation grants OCE-0351029 and OCE-0437366.
Is Terzaghi’s effective stress a stress variable under seepage conditions?
雷国辉; 赵仲辉; 吴宏伟
2015-01-01
From the continuum mechanics perspective, an attempt was made to clarify the role of Terzaghi’s effective stress in the theoretical analysis of saturated soil subjected to seepage. The necessity of performing a coupled hydromechanical analysis to solve the seepage−deformation interaction problem was illustrated by examining the equations of static equilibrium among the effective stress, seepage force, pore-water pressure and total stress. The conceptual definition of stress variable that satisfies the principles of continuum mechanics is applied in the coupled hydromechanical analysis. It is shown that Terzaghi’s effective stress is in fact not a stress variable under seepage conditions, and the seepage force acting on the soil skeleton cannot be viewed as a body force. This offers a clue to the underlying cause of a paradox between the real Pascal’s hydrostatic state and the hydrostatic state predicted by a class of continuum hydromechanical theories.
Effects of Humor on Teacher Stress, Affect, and Job Satisfaction
Shirley, Jacqueline Dena
2013-01-01
Teachers are at high risk for stress, negative emotion, and job dissatisfaction, which has been linked with health problems and early attrition. Humor has been found to relieve various forms of stress. However, there is a gap in the literature regarding humor effects on teacher stress and its related consequences. The purpose of this quantitative,…
Effects of Humor on Teacher Stress, Affect, and Job Satisfaction
Shirley, Jacqueline Dena
2013-01-01
Teachers are at high risk for stress, negative emotion, and job dissatisfaction, which has been linked with health problems and early attrition. Humor has been found to relieve various forms of stress. However, there is a gap in the literature regarding humor effects on teacher stress and its related consequences. The purpose of this quantitative,…
Effects of Hospital Workers' Friendship Networks on Job Stress.
Shin, Sung Yae; Lee, Sang Gyu
2016-01-01
This study attempted to identify the sources of job stress according to job position and investigate how friendship networks affect job stress. Questionnaires based on The Health Professions Stress Inventory (HPSI) developed by Wolfgang experienced by healthcare providers were collected from 420 nurses, doctors and radiological technologists in two general hospitals in Korea by a multistage cluster sampling method. Multiple regression analysis was used to examine the effects of friendship networks on job stress after controlling for other factors. The severity of job stress differed according to level of job demands (p = .006); radiologic technologists experienced the least stress (45.4), nurses experienced moderate stress (52.4), and doctors experienced the most stress (53.6). Those with long-term friendships characterized by strong connections reported lower levels of stress than did those with weak ties to friends among nurses (1.3, p stress experienced by nurses (8.2, p stress (9.2, p stress. The strength and density of such friendship networks were related to job stress. Life information support from their friendship network was the primary positive contributor to control of job stress.
Eldridge, Sandra M; Ashby, Deborah; Kerry, Sally
2006-10-01
Cluster randomized trials are increasingly popular. In many of these trials, cluster sizes are unequal. This can affect trial power, but standard sample size formulae for these trials ignore this. Previous studies addressing this issue have mostly focused on continuous outcomes or methods that are sometimes difficult to use in practice. We show how a simple formula can be used to judge the possible effect of unequal cluster sizes for various types of analyses and both continuous and binary outcomes. We explore the practical estimation of the coefficient of variation of cluster size required in this formula and demonstrate the formula's performance for a hypothetical but typical trial randomizing UK general practices. The simple formula provides a good estimate of sample size requirements for trials analysed using cluster-level analyses weighting by cluster size and a conservative estimate for other types of analyses. For trials randomizing UK general practices the coefficient of variation of cluster size depends on variation in practice list size, variation in incidence or prevalence of the medical condition under examination, and practice and patient recruitment strategies, and for many trials is expected to be approximately 0.65. Individual-level analyses can be noticeably more efficient than some cluster-level analyses in this context. When the coefficient of variation is <0.23, the effect of adjustment for variable cluster size on sample size is negligible. Most trials randomizing UK general practices and many other cluster randomized trials should account for variable cluster size in their sample size calculations.
Na Liu
2015-10-01
Full Text Available Hadron production in semi-inclusive deep-inelastic scattering of leptons from nuclei is an ideal tool to determine and constrain the transport coefficient in cold nuclear matter. The leading-order computations for hadron multiplicity ratios are performed by means of the SW quenching weights and the analytic parameterizations of quenching weights based on BDMPS formalism. The theoretical results are compared to the HERMES positively charged pions production data with the quarks hadronization occurring outside the nucleus. With considering the nuclear geometry effect on hadron production, our predictions are in good agreement with the experimental measurements. The extracted transport parameter from the global fit is shown to be qˆ=0.74±0.03 GeV2/fm for the SW quenching weight without the finite energy corrections. As for the analytic parameterization of BDMPS quenching weight without the quark energy E dependence, the computed transport coefficient is qˆ=0.20±0.02 GeV2/fm. It is found that the nuclear geometry effect has a significant impact on the transport coefficient in cold nuclear matter. It is necessary to consider the detailed nuclear geometry in studying the semi-inclusive hadron production in deep inelastic scattering on nuclear targets.
Khalid Hameed Hussein
2013-01-01
Full Text Available In the current research, the work concentrated on studying the effect of curvature of solar parabolic trough solar collector on wind loading coefficients and dynamic response of solar collector. The response of collector to the aerodynamic loading was estimated numerically and experimentally. The curvature of most public parabolic trough solar collectors was investigated and compared. The dynamic response of solar collector due to wind loading was investigated by using numerical solution of fluid-structure interaction concept. The experimental work was done to verify the numerical results and shows good agreement with numerical results. The numerical results were obtained by using finite element software package (ANSYS 14. It was found that the change in collector curvature (focal length lead to remarkable changes in wind loading coefficients (drag, lift, and moment, dynamic response (displacement and natural frequencies but does not affect the first mode shape.
Moghanizadeh, Abbas; Farzi, Abolfazl [Islamic Azad Univ., Esfarayen (Iran, Islamic Republic of). Dept. of Civil Engineering
2016-07-01
The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.
Influence of effective stress on swelling pressure of expansive soils
Baille Wiebke
2016-01-01
Full Text Available The volume change and shear strength behaviour of soils are controlled by the effective stress. Recent advances in unsaturated soil mechanics have shown that the effective stress as applicable to unsaturated soils is equal to the difference between the externally applied stress and the suction stress. The latter can be established based on the soil-water characteristic curve (SWCC of the soil. In the present study, the evolution of swelling pressure in compacted bentonite-sand mixtures was investigated. Comparisons were made between magnitudes of applied suction, suction stress, and swelling pressure.
Giles, Grace E; Mahoney, Caroline R; Brunyé, Tad T; Taylor, Holly A; Kanarek, Robin B
2014-01-01
Extensive experimental psychology research has attempted to parse the complex relationship between psychosocial stress, mood, cognitive performance, and physiological changes. To do so, it is necessary to have effective, validated methods to experimentally induce psychosocial stress. The Trier Social Stress Test (TSST) is the most commonly used method of experimentally inducing psychosocial stress, but it is resource intensive. Less resource intense psychosocial stress tasks include the Socially Evaluative Cold Pressor Task (SECPT) and a computerized mental arithmetic task (MAT). These tasks effectively produce a physiological and psychological stress response and have the benefits of requiring fewer experimenters and affording data collection from multiple participants simultaneously. The objective of this study was to compare the magnitude and duration of these three experimental psychosocial stress induction paradigms. On each of four separate days, participants completed either a control non-stressful task or one of the three experimental stressors: the TSST, SECPT, or MAT. We measured mood, working memory performance, salivary cortisol and alpha-amylase (AA), and heart rate. The TSST and SECPT exerted the most robust effects on mood and physiological measures. TSST effects were generally evident immediately post-stress as well as 10- and 20-minutes after stress cessation, whereas SECPT effects were generally limited to the duration of the stressor. The stress duration is a key determinant when planning a study that utilizes an experimental stressor, as researchers may be interested in collecting dependent measures prior to stress cessation. In this way, the TSST would allow the investigator a longer window to administer tasks of interest.
Grace E Giles
Full Text Available Extensive experimental psychology research has attempted to parse the complex relationship between psychosocial stress, mood, cognitive performance, and physiological changes. To do so, it is necessary to have effective, validated methods to experimentally induce psychosocial stress. The Trier Social Stress Test (TSST is the most commonly used method of experimentally inducing psychosocial stress, but it is resource intensive. Less resource intense psychosocial stress tasks include the Socially Evaluative Cold Pressor Task (SECPT and a computerized mental arithmetic task (MAT. These tasks effectively produce a physiological and psychological stress response and have the benefits of requiring fewer experimenters and affording data collection from multiple participants simultaneously. The objective of this study was to compare the magnitude and duration of these three experimental psychosocial stress induction paradigms. On each of four separate days, participants completed either a control non-stressful task or one of the three experimental stressors: the TSST, SECPT, or MAT. We measured mood, working memory performance, salivary cortisol and alpha-amylase (AA, and heart rate. The TSST and SECPT exerted the most robust effects on mood and physiological measures. TSST effects were generally evident immediately post-stress as well as 10- and 20-minutes after stress cessation, whereas SECPT effects were generally limited to the duration of the stressor. The stress duration is a key determinant when planning a study that utilizes an experimental stressor, as researchers may be interested in collecting dependent measures prior to stress cessation. In this way, the TSST would allow the investigator a longer window to administer tasks of interest.
Bioinjection treatment: effects of post-injection residual stress on left ventricular wall stress.
Lee, Lik Chuan; Wall, Samuel T; Genet, Martin; Hinson, Andy; Guccione, Julius M
2014-09-22
Injection of biomaterials into diseased myocardium has been associated with decreased myofiber stress, restored left ventricular (LV) geometry and improved LV function. However, its exact mechanism(s) of action remained unclear. In this work, we present the first patient-specific computational model of biomaterial injection that accounts for the possibility of residual strain and stress introduced by this treatment. We show that the presence of residual stress can create more heterogeneous regional myofiber stress and strain fields. Our simulation results show that the treatment generates low stress and stretch areas between injection sites, and high stress and stretch areas between the injections and both the endocardium and epicardium. Globally, these local changes are translated into an increase in average myofiber stress and its standard deviation (from 6.9 ± 4.6 to 11.2 ± 48.8 kPa and 30 ± 15 to 35.1 ± 50.9 kPa at end-diastole and end-systole, respectively). We also show that the myofiber stress field is sensitive to the void-to-size ratio. For a constant void size, the myofiber stress field became less heterogeneous with decreasing injection volume. These results suggest that the residual stress and strain possibly generated by biomaterial injection treatment can have large effects on the regional myocardial stress and strain fields, which may be important in the remodeling process.
Jaworske, D. A.; Maciag, C.
1987-01-01
To examine the effect of bromination of carbon fibers on the coefficient of thermal expansion (CTE) of carbon fiber epoxy composites, several pristine and brominated carbon fiber-epoxy composite samples were subjected to thermomechanical analysis. The CTE's of these samples were measured in the uniaxial and transverse directions. The CTE was dominated by the fibers in the uniaxial direction, while it was dominated by the matrix in the transverse directions. Bromination had no effect on the CTE of any of the composites. In addition, the CTE of fiber tow was measured in the absence of a polymer matrix, using an extension probe. The results from this technique were inconclusive.
Roselinde Kaiser Henderson
2012-06-01
Full Text Available The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing to clinical therapy. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding tasks. In addition, research suggests that the impact of stress on cognitive functioning depends on an individual’s response to stressors: moderate responses to stress can lead to improved performance while extreme (high or low responses can lead to impaired performance. The present studies tested the hypothesis that 1 learning to behaviorally control stressors leads to improved performance on a test of general executive functioning, the color-word Stroop, and that 2 this improvement emerges specifically for people who report moderate (subjective responses to stress. Experiment 1: Stroop performance, measured before and after a stress manipulation, was compared across groups of undergraduate participants (n=109. People who learned to control a noise stressor and received accurate performance feedback demonstrated reduced Stroop interference compared with people exposed to uncontrollable noise stress and feedback indicating an exaggerated rate of failure. In the group who learned behavioral control, those who reported moderate levels of stress showed the greatest reduction in Stroop interference. In contrast, in the group exposed to uncontrollable events, self-reported stress failed to predict performance. Experiment 2: In a second sample (n=90, we specifically investigated the role of controllability by keeping the rate of failure feedback constant across groups. In the group who learned behavioral control, those who reported moderate levels of stress
Effect of stress on field dependence.
Sarris, V; Heineken, E; Peters, H
1976-08-01
60 subjects were tested in the rod-and-frame test under flicker conditions (stress). As compared to scores in a control situation (no flicker), the rod-and-frame scores were large under stress and increased monotonically during the session. Futhermore, both intra- and interindividual variability of rod-and-frame performance changed under stress conditions in a consistent manner. The general results, which clearly point to a reliable influence of stress on field dependency, are discussed within the methodological framework of Witkin's theory of perception and personality.
EFFECT OF WORKPLACE STRESS ON JOB PERFORMANCE
Azman Ismail
2015-05-01
Full Text Available The study examines the relationship between workplace stress and job performance. A survey method was employed to gather self-administered questionnaires from executive and non-executive employees of a leading private investment bank in Peninsular Malaysia. The outcomes of SmartPLS path model analysis of the data showed two important findings: firstly, physiological stress was positively and significantly correlated with job performance. Secondly, psychological stress was positively and significantly correlated with job performance. This finding reveals that physiological and psychological stresses act as important predictors of job performance in the studied organization. The paper provides discussion, implications and conclusion.
Biofilm effects on size gradation, drag coefficient and settling velocity of sediment particles
Qian-qian SHANG; Hong-wei FANG; Hui-ming ZHAO; Guo-jian HE; Zheng-hui CUI
2014-01-01
Sediment particles are often colonized by biofilm in a natural aquatic ecological system, especially in eutrophic water body. A series of laboratory experiments on particle size gradation, drag coefficient and settling velocity were conducted after natural sediment was colonized by biofilm for 5, 10, 15 and 20 days. Particle image acquisition, particle tracking techniques of Particle Image Velocimetry and Particle Tracking Velocimetry were utilized to analyze the changes of these properties. The experimental results indicate that the size gradation, the drag force exerted on bio-particles, and the settling velocity of bio-particles underwent significant change due to the growth of biofilm onto the sediment surface. The study proposes a characteristic particle size formula and a bio-particle settling velocity formula based on the regression of experiment results, that the settling velocity is only 50% to 60%as the single particle which has the same diameter and density. However, biofilm growth causes large particle which the settling velocities are approximately 10 times larger than that of primary particles. These results may be specifically used in the low energy reservoir or lake environment.
The effect of impermeable boundaries of arbitrary geometry on the apparent diffusion coefficient.
Frøhlich, Astrid F; Jespersen, Sune N; Ostergaard, Leif; Kiselev, Valerij G
2008-09-01
The apparent diffusion coefficient (ADC) obtained from NMR measurements is modelled for diffusion in a compartment restricted by an impermeable boundary. For a given pulse sequence, the ADC can be determined from the connected velocity autocorrelation function (the second-order velocity cumulant), which we show can be expressed as a double surface integral over the boundary, involving the probability for molecules to diffuse from one boundary point to another. There is no restriction on the geometry of the boundary. This result allows a fast calculation of the ADC for an arbitrary time course of the diffusion-sensitizing gradient. Explicit examples are given for diffusion within three basic geometries for different pulse sequences. The ADCs measured with the Stejskal-Tanner pulse sequence and a more realistic pulse sequence with slice selection gradient and eddy current compensation are found to yield almost identical results. The application of the results are discussed in relation to determination of the microscopic structure of brain white matter.
Sazhin, Sergei S.
2013-01-01
The previously developed kinetic model for droplet heating and evaporation into a high pressure air is generalised to take into account the combined effects of inelastic collisions between molecules in the kinetic region, a non-unity evaporation coefficient and temperature gradient inside droplets. It is pointed out that for the parameters typical for Diesel engine-like conditions, the heat flux in the kinetic region is a linear function of the vapour temperature at the outer boundary of this region, but practically does not depend on vapour density at this boundary for all models, including and not including the effects of inelastic collisions, and including and not including the effects of a non-unity evaporation coefficient. For any given temperature at the outer boundary of the kinetic region the values of the heat flux are shown to decrease with increasing numbers of internal degrees of freedom of the molecules. The rate of this decrease is strong for small numbers of these degrees of freedom but negligible when the number of these degrees exceeds 20. This allows us to restrict the analysis to the first 20 arbitrarily chosen degrees of freedom of n-dodecane molecules when considering the effects of inelastic collisions. The mass flux at this boundary decreases almost linearly with increasing vapour density at the same location for all above-mentioned models. For any given vapour density at the outer boundary of the kinetic region the values of the mass flux are smaller for the model, taking into account the contribution of internal degrees of freedom, than for the model ignoring these degrees of freedom. It is shown that the effects of inelastic collisions lead to stronger increase in the predicted droplet evaporation time in Diesel engine-like conditions relative to the hydrodynamic model, compared with the similar increase predicted by the kinetic model considering only elastic collisions. The effects of a non-unity evaporation coefficient are shown to be
Kassemi, Mohammad; Kartuzova, Olga
2016-03-01
Pressurization and pressure control in cryogenic storage tanks are to a large extent affected by heat and mass transport across the liquid-vapor interface. These mechanisms are, in turn, controlled by the kinetics of the phase change process and the dynamics of the turbulent recirculating flows in the liquid and vapor phases. In this paper, the effects of accommodation coefficient and interfacial turbulence on tank pressurization and pressure control simulations are examined. Comparison between numerical predictions and ground-based measurements in two large liquid hydrogen tank experiments, performed in the K-site facility at NASA Glenn Research Center (GRC) and the Multi-purpose Hydrogen Test Bed (MHTB) facility at NASA Marshall Space Flight Center (MSFC), are used to show the impact of accommodation coefficient and interfacial and vapor phase turbulence on evolution of pressure and temperatures in the cryogenic storage tanks. In particular, the self-pressurization comparisons indicate that: (1) numerical predictions are essentially independent of the magnitude of the accommodation coefficient; and (2) surprisingly, laminar models sometimes provide results that are in better agreement with experimental self-pressurization rates, even in parametric ranges where the bulk flow is deemed fully turbulent. In this light, shortcomings of the present CFD models, especially, numerical treatments of interfacial mass transfer and turbulence, as coupled to the Volume-of-Fluid (VOF) interface capturing scheme, are underscored and discussed.
Valiskó, Mónika; Boda, Dezső, E-mail: boda@almos.vein.hu [Department of Physical Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém (Hungary)
2014-06-21
Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.
Valiskó, Mónika; Boda, Dezső
2014-06-21
Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, "The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations," J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of "solvated ionic radius" assumed by earlier studies.
Levin, E. M.
2016-06-01
Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S , depends on the free (mobile) carrier concentration, n , and effective mass, m*, as S ˜m*/n2 /3 . The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spin-lattice relaxation measurements. The NMR spin-lattice relaxation rate, 1 /T1 , depends on both n and m* as 1 /T1˜(m*)3/2n (within classical Maxwell-Boltzmann statistics) or as 1 /T1˜(m*)2n2 /3 (within quantum Fermi-Dirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficient and 125Te NMR spin-lattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study A gxS bxG e50-2xT e50 , well-known GeTe-based high-efficiency tellurium-antimony-germanium-silver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.
Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake
Jouni J. Heiskanen
2014-05-01
Full Text Available Lakes and other inland waters contribute significantly to regional and global carbon budgets. Emissions from lakes are often computed as the product of a gas transfer coefficient, k 600 , and the difference in concentration across the diffusive boundary layer at the air–water interface. Eddy covariance (EC techniques are increasingly being used in lacustrine gas flux studies and tend to report higher values for derived k 600 than other approaches. Using results from an EC study of a small, boreal lake, we modelled k 600 using a boundary-layer approach that included wind shear and cooling. During stratification, fluxes estimated by EC occasionally were higher than those obtained by our models. The high fluxes co-occurred with winds strong enough to induce deflections of the thermocline. We attribute the higher measured fluxes to upwelling-induced spatial variability in surface concentrations of CO2 within the EC footprint. We modelled the increased gas concentrations due to the upwelling and corrected our k 600 values using these higher CO2 concentrations. This approach led to greater congruence between measured and modelled k values during the stratified period. k 600 has a well-resolved and ~cubic relationship with wind speed when the water column is unstratified and the dissolved gases well mixed. During stratification and using the corrected k 600 , the same pattern is evident at higher winds, but k 600 has a median value of ~7 cm h−1 when winds are less than 6 m s−1, similar to observations in recent oceanographic studies. Our models for k 600 provide estimates of gas evasion at least 200% higher than earlier wind-based models. Our improved k 600 estimates emphasize the need for integrating within lake physics into models of greenhouse gas evasion.
Discussion and prediction on decreasing flow stress scale effect
无
2006-01-01
Based on crystal plasticity theory and surface layer model, relation of flow stress to billet dimension and grain size was built,and rationality of derived relation was verified with tensile tests of different size billets. With derived expressions, relation of decreasing flow stress scale effect to billet dimension, grain size as well as billet shape was discussed and predicted. The results show that flow stress is proportional to billet size; with decrease of grain size, flow stress is less influenced by billet dimension. When both cross section area and grain size are same, flow stress decrease of rectangular section billet or sheet is larger than that of circular section billet.
Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa
2016-01-01
A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.
Houghton, Jeffery D.; Wu, Jinpei; Godwin, Jeffrey L.; Neck, Christopher P.; Manz, Charles C.
2012-01-01
This article develops and presents a model of the relationships among emotional intelligence, self-leadership, and stress coping among management students. In short, the authors' model suggests that effective emotion regulation and self-leadership, as mediated through positive affect and self-efficacy, has the potential to facilitate stress coping…
Houghton, Jeffery D.; Wu, Jinpei; Godwin, Jeffrey L.; Neck, Christopher P.; Manz, Charles C.
2012-01-01
This article develops and presents a model of the relationships among emotional intelligence, self-leadership, and stress coping among management students. In short, the authors' model suggests that effective emotion regulation and self-leadership, as mediated through positive affect and self-efficacy, has the potential to facilitate stress coping…
Low-stress and high-stress singing have contrasting effects on glucocorticoid response
Daisy eFancourt
2015-09-01
Full Text Available Performing music in public is widely recognised as a potentially stress-inducing activity. However, despite the interest in music performance as an acute psychosocial stressor, there has been relatively little research on the effects of public performance on the endocrine system. This study examined the impact of singing in a low-stress performance situation and a high-stress live concert on levels of glucocorticoids (cortisol and cortisone in 15 professional singers. The results showed a significant decrease in both cortisol and cortisone across the low-stress condition, suggesting that singing in itself is a stress-reducing (and possibly health-promoting activity, but significant increases across the high-stress condition. This is the first study to demonstrate that singing affects glucocorticoid responses and that these responses are modulated by the conditions of performance.
Effect of drought and salinity stresses on germination indices of vetch (Vicia villosa L.
Sh Ghaderi
2016-05-01
Full Text Available One of the important issues in the arid and semi-arid regions is the water deficit and soil salinity. Therefore, selecting tolerant species to salinity and drought especially in seed germination and emergence stage is important. In the present study the effects of drought and salt stress on seed germination of vetch (Vicia villosa L. which is palatable forage was investigated. The germination percentage, germination rate, plumule and radicle, seed vigor and alometric coefficient under both stresses were recorded. A completely randomised design was carried out using six salinity treatments (control distilled water, 50, 100, 150, 200 and 300 mM NaCl and six drought treatments (control, 0.2, 0.4, 0.6, 0.8 and 1 MPa polyethylene glycol 6000. For each treatment 15 seeds in Petri dish were placed as replicate and put in Gerrminator for two weeks. Results showed that both stresses significantly (P
Effects of orthostasis on endocrine responses to psychosocial stress.
Nater, Urs M; Ditzen, Beate; Strahler, Jana; Ehlert, Ulrike
2013-12-01
Standardized psychological procedures have been designed to induce physiological stress responses. However, the impact of standing (orthostasis) on the physiological reaction after psychological stress remains unclear. The purpose of the current analysis was to examine and quantify the relative contribution of orthostasis to the physiological stress response by comparing a "standing with stress" to a "standing without stress" condition. We investigated the effect of standing with and without stress on responses of the sympathetic-adrenomedullary (SAM) system and the hypothalamic-pituitary-adrenal (HPA) axis using a standardized psychosocial stress protocol (Trier Social Stress Test) and a non-stress condition in a repeated measures design. Subjects (N=30) were exposed to both conditions in randomized order and had to maintain a standing, upright position for 10minutes. In the "standing with stress" condition, significant increases in repeatedly assessed plasma norepinephrine (NE) and epinephrine (EP), as well as in saliva cortisol were found, while in the "standing without stress" condition, no significant changes in plasma epinephrine and saliva cortisol were observed. Calculations of the relative contribution of orthostasis to physiological stress responses revealed that 25.61% of the NE increase, 82.94% of the EP increase, and 68.91% of the cortisol increase, could be attributed to psychosocial stress adjusted for the effects of orthostasis and basal endocrine output. Although these results are indicative for a marked endocrine reaction that is caused by psychosocial stress alone, our findings show that the contribution of orthostasis must be taken into account when interpreting endocrine data collected in a psychosocial stress test.
Yazdani, Mohsen; Rezaei, Sara; Pahlavanzadeh, Saeid
2010-01-01
BACKGROUND: Stress has been defined as a barrier to concentration, problem solving, decision making, and other necessary abilities for students’ learning; it also has some symptoms and illnesses in the students such as depression and anxiety. In reviewing stress and its consequences, the methods of coping with stress in the method of response to it would be more important than the nature of stress itself. Therefore, this study aimed to determine the effectiveness of stress management training program on depression, anxiety and stress rate of the nursing students. METHODS: This parallel group randomized quasi-experimental trial, was done on 68 Bs nursing students of Nursing and Midwifery School in Isfahan University of Medical Sciences from 2010 to 2011. The questionnaires of this study consisted of individual characteristics and Depression, Anxiety and Stress Scale (DASS-42). In a random fashion, The intervention group was trained with stress management training program in 8 two hours sessions, twice a week. The questionnaires were completed by both groups before, after and one month after the study. RESULTS: The results of the study indicated that there was no significant difference before the intervention in depression, anxiety and stress mean scores in the two groups. After the intervention, the mean scores of anxiety and stress in the intervention group was 5.09 (4.87) and 8.93 (6.01) and in the control group was 10 (6.45) and 13.17 (7.20), that reduction in depression mean score was significantly greater in the intervention group in the control group (p = 0.040). Furthermore, the mean scores of anxiety and stress showed a significant difference between the two groups (Anxiety p = 0.001; Stress p = 0.011); this reduction also had been remained after a month. CONCLUSIONS: According to the results of the present study, holding stress management training program workshops in different courses of the mental health department can improve mental health of the
The Importance of Structure Coefficients in Interpreting Regression Research.
Heidgerken, Amanda D.
The paper stresses the importance of consulting beta weights and structure coefficients in the interpretation of regression results. The effects of multilinearity and suppressors and their effects on interpretation of beta weights are discussed. It is concluded that interpretations based on beta weights only can lead the unwary researcher to…
Rose, Jørgen; Svendsen, Svend
2005-01-01
be quite tedious, and therefore a method to generate and optimize solutions has been developed and implemented in a program that also takes into account the effects of different types of thermal bridges, i.e. roof windows, insulation fasteners, roof/wall joints etc. This paper describes a new method...... for design of flat roofs and a pc-program that can be used for calculating the total heat loss coefficient of externally insulated roofs with insulation in tapered layers, taking into account thermal bridges in the roof construction....
Kumar, Sandeep; Singh, Sukhpal
2016-05-01
Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi2O3 + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μm) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Zeff) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.
The third virial coefficient of a two-component unitary Fermi gas across an Efimov-effect threshold
Gao, Chao; Endo, Shimpei; Castin, Yvan
2015-01-01
We consider a mixture of two single-spin-state fermions with an interaction of negligible range and infinite s-wave scattering length. By varying the mass ratio α across α_c≃ 13.6069 one can switch on and off the Efimov effect. We determine analytically the third cluster coefficient of the gas. We show that it is a smooth function of α across αc since, unexpectedly, the three-body parameter characterizing the interaction is relevant even on the non-Efimovian side α<αc .
Zero temperature coefficient of resistivity induced by photovoltaic effect in Y Ba2Cu3O6.96 ceramics
Feng Yang
2015-01-01
Full Text Available I-V characteristics of YBCO-Ag system under blue laser (λ = 450 nm illumination were studied from 100 to 300 K and obvious photovoltaic effects were observed. All the I-V curves in the temperature range intersect at a point in the first quadrant while the laser points to the cathode electrode, indicating a zero temperature coefficient of resistivity. This implies that the outputting voltage keeps constant in a broad temperature range when a critical bias current is assigned. The intersection points of different laser intensities fall in a straight line, the slope of which (Rc is independent of temperature and laser intensity.
Riedel, D.; Castex, M. C.
First measurements of effective absorption coefficient and penetration depth are given here from the ablation of poly-methylmethacrylate (PMMA) and poly-tetrafluoroethylene (PTFE) samples at 125 nm ( 10 eV). The coherent VUV source used which provides smooth, efficient and clean etched areas, is briefly described. Experimental curves of etch depth as a function of the number of laser shots and etch rate as a function of energy density are obtained and compared with previous works performed at 157 nm (F2 laser) and 193 nm (ArF laser). Experimental results are described with a Beer-Lambert absorption law and discussed.
Kicken, P.J.H.; Zankl, M.; Kemerink, G.J
1999-07-01
X ray projection data (see Part I) and GSF phantoms ADAM and EVA were used as input for the GSF Monte Carlo transport code to calculate hitherto unavailable dose conversion coefficients (DCCs) for common projections in arteriography of the lower limbs. These DCCs served to estimate organ equivalent doses and effective dose in a study of 455 patients. The effective dose caused by percutaneous needle puncture arteriography of one leg was on average 1 mSv, by Seldinger catherisation for arteriography of both legs 4 mSv, and by intravenous digital subtraction arteriography (DSA) 5 mSv. For needle puncture and Seldinger arteriography the effective dose attributable to fluoroscopy was about 50% for male and 60% for female patients. The contribution of DSA was between 15 and 35%, that of cut films between 17 to 28%, depending on gender and procedure. The effective dose in intravenous arteriography was mainly due to DSA (91-93%). (author)
Righter, K.; Pando, K.; Danielson, L. R.; Humayun, M.
2017-01-01
Earth's core contains approximately 10% of a light element that is likely a combination of S, C, Si, and O, with Si possibly being the most abundant light element. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE) in Fe liquids, and thus the partitioning behavior of those elements between core and mantle. The effect of Si can be small such as for Ni and Co, or large such as for Mo, Ge, Sb, As. The effect of Si on many siderophile elements is unknown yet could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of Pt (with Re and Ru in progress or planned) between metal and silicate melt. The results will be applied to Earth, for which we have excellent constraints on the mantle Pt concentrations.
Effects of controllable vs. uncontrollable stress on circadian temperature rhythms.
Kant, G J; Bauman, R A; Pastel, R H; Myatt, C A; Closser-Gomez, E; D'Angelo, C P
1991-03-01
The effects of sustained stress on body temperature were investigated in rats implanted with mini-transmitters that permitted remote measurement of body temperature. Temperature was first monitored during control conditions. Following the control period, rats were either shaped to avoid/escape signalled around-the-clock intermittent footshock (controllable stress) or yoked to the controlling rats such that the controlling rat and the yoked rat received shock of the same duration, but only the controlling rat could terminate shock by pulling a ceiling chain. Under control conditions, rats demonstrated regular rhythms in body temperature which averaged 1 degree higher during the 12-h dark cycle than the light cycle. Stress disrupted the rhythm and markedly decreased the night-day difference in temperature, especially in the yoked rats in which almost no difference between light and dark cycle temperature was seen. The disruption was most marked for the first days of stress. A regular temperature rhythm was reestablished following about 5 days of stress although the stress condition continued. Leverpressing for food was also affected by the stress conditions with both stress groups leverpressing less than controls and the uncontrollable stress group pressing less than the controllable stress group. These data offer additional evidence of the increased pathophysiological effects of uncontrollable as compared to controllable stress.
Standardized Regression Coefficients as Indices of Effect Sizes in Meta-Analysis
Kim, Rae Seon
2011-01-01
When conducting a meta-analysis, it is common to find many collected studies that report regression analyses, because multiple regression analysis is widely used in many fields. Meta-analysis uses effect sizes drawn from individual studies as a means of synthesizing a collection of results. However, indices of effect size from regression analyses…
Effective Admittivity of Biological Tissues as a Coefficient of Elliptic PDE
Jin Keun Seo
2013-01-01
can be computed from pointwise admittivity by solving Maxwell equations. We compute the effective admittivity of simple models as a function of frequency to obtain Maxwell-Wagner interface effects and Debye relaxation starting from mathematical formulations. Finally, layer potentials are used to obtain the Maxwell-Wagner-Fricke expression for a dilute suspension of ellipses and membrane-covered spheres.
Overcoming the effects of stress on reactor operator performance
He Xuhong; Wei Li; Zhao Bingquan [Tsinghua Univ., Nuclear Power Plant Simulation Training Center, Beijing (China)
2003-03-01
Reactor operators may be exposed to significant levels of stress during plant emergencies and their performance may be affected by the stress. This paper first identified the potential sources of stress in the nuclear power plant, then discussed the ways in which stress is likely to affect the reactor operators, and finally identified several training approaches for reducing or eliminating stress effects. The challenges for effective stress reducing training may seem daunting, yet the challenges are real and must be addressed. This paper reviewed researches in training design, knowledge and skill acquisition, and training transfer point to a number of strategies that can be used to address these challenges and lead to more effective training and development. (author)
Constraining friction, dilatancy and effective stress with earthquake rates in the deep crust
Beeler, N. M.; Thomas, A.; Burgmann, R.; Shelly, D. R.
2015-12-01
Similar to their behavior on the deep extent of some subduction zones, families of recurring low-frequency earthquakes (LFE) within zones of non-volcanic tremor on the San Andreas fault in central California show strong sensitivity to stresses induced by the tides. Taking all of the LFE families collectively, LFEs occur at all levels of the daily tidal stress, and are in phase with the very small, ~200 Pa, shear stress amplitudes while being uncorrelated with the ~2 kPa tidal normal stresses. Following previous work we assume LFE sources are small, persistent regions that repeatedly fail during shear within a much larger scale, otherwise aseismically creeping fault zone and that the correlation of LFE occurrence reflects modulation of the fault creep rate by the tidal stresses. We examine the predictions of laboratory-observed rate-dependent dilatancy associated with frictional slip. The effect of dilatancy hardening is to damp the slip rate, so high dilatancy under undrained pore pressure reduces modulation of slip rate by the tides. The undrained end-member model produces: 1) no sensitivity to the tidal normal stress, as first suggested in this context by Hawthorne and Rubin [2010], and 2) fault creep rate in phase with the tidal shear stress. Room temperature laboratory-observed values of the dilatancy and friction coefficients for talc, an extremely weak and weakly dilatant material, under-predict the observed San Andreas modulation at least by an order of magnitude owing to too much dilatancy. This may reflect a temperature dependence of the dilatancy and friction coefficients, both of which are expected to be zero at the brittle-ductile transition. The observed tidal modulation constrains the product of the friction and dilatancy coefficients to be at most 5 x 10-7 in the LFE source region, an order of magnitude smaller than observed at room temperature for talc. Alternatively, considering the predictions of a purely rate-dependent talc friction would
Paul, Reginald; Paddison, Stephen J
2005-12-08
Proton transport in perfluorosulfonic acid (PFSA) membranes is investigated through a statistical mechanical model that includes the effects of the interaction of the tethered sulfonate groups with both the water and solvated protons. We first derive a potential that describes the electrostatic field due to the dissociated sulfonic acid groups by extending the work of Gronbech-Jensen et al. [ Mol. Phys. 92, 941 (1997)] to a finite array of point charges. A highly convergent series is obtained which includes the effects of screening due to the protons. We then investigate the effects of both dielectric saturation and two distinct formulations of ionic screening on the proton self-diffusion coefficient in Nafion membranes over a range of water contents. Our computations show that the two phenomena (i.e., dielectric saturation and ionic screening) under constant temperature conditions result in canceling affects. Our calculations provide a radial dependence of the proton mobility suggesting that the dominant self-diffusion occurs in the central region of the pores, well separated from the sulfonate groups. Through comparison of our calculated diffusion coefficients with the experimental values we derived a slightly smaller average separation distance of the hydronium ion from the sulfonate ions than suggested by either electronic structure calculations or multistate empirical valence bond molecular-dynamics simulations.
Contrast-induced nephrotoxicity: possible synergistic effect of stress hyperglycemia.
O'Donnell, David H
2010-07-01
Oxidative stress on the renal tubules has been implicated as a mechanism of injury in both stress hyperglycemia and contrast-induced nephrotoxicity. The purpose of this study was to determine whether the combination of these effects has a synergistic effect on accentuating renal tubular apoptosis and therefore increasing the risk of contrast-induced nephrotoxicity.
Effects of shear stress on the microalgae Chaetoceros muelleri
Michels, M.H.A.; Goot, van der A.J.; Norsker, N.H.; Wijffels, R.H.
2010-01-01
The effect of shear stress on the viability of Chaetoceros muelleri was studied using a combination of a rheometer and dedicated shearing devices. Different levels of shear stress were applied by varying the shear rates and the medium viscosities. It was possible to quantify the effect of shear
Kristensen, Gustav
2013-01-01
Cohorts are the aggregate of individuals who experience the same event within the same time interval. Cohorts can be based on people born in a given year, for example in 1940 or within a span of years, e.g. born in 1940-1944. The year of birth is here the defining event for cohorts. The health di...... differs between cohorts. This article focuses on the protective and detrimental cohort effect in relation to the risk of death from apoplexy. A dummy variable method is recommended to describe the changing cohort effect over a century....
Wang, Longfei; Liu, Shuhai; Wang, Zheng; Zhou, Yongli; Qin, Yong; Wang, Zhong Lin
2016-02-23
Effective piezoelectric semiconductor based hybrid photocatalysts are successfully developed by assembling TiO2 nanoparticles on ZnO monocrystalline nanoplatelets. The piezopotential can be introduced and tuned by thermal stress on the piezoelectric material of ZnO monocrystalline nanoplatelets through cooling hybrid photocatalysts from high temperature to room temperature with different rates based on the mismatched thermal expansion coefficient of the two materials, which can be used to engineer the heterojunction band structure and significantly enhance the photocatalytic performance in a wide range by improving charge separation. It is proposed that the piezotronic effect enhanced photocatalyst will provide a strategy for high-performance photocatalysis applications.
Effect of laser light on the sticking coefficient in ZnS thin-film growth
Arnone, C.; Daneu, V.; Riva-Sanseverino, S.
1980-12-01
Some preliminary results are presented concerning an effect of laser light (λ=4880 Å) on the growth of an evaporated ZnS film. We observe an increase in thickness in the region of the film illuminated by laser light. The spatial resolution is high and the observed phenomenon is not thermal in origin. A simple and unique method for investigating the dynamics of the effect during its evolution is described.
Effect of Thermal Stress on Cardiac Function
Wilson, Thad E.; Crandall, Craig G.
2011-01-01
Whole-body heating decreases pulmonary capillary wedge pressure and cerebral vascular conductance, and causes an inotropic shift in the Frank-Starling curve. Whole-body cooling increases pulmonary capillary wedge pressure and cerebral vascular conductance without changing systolic function. These and other data indicate factors affecting cardiac function may mechanistically contribute to syncope during heat stress and improvements in orthostatic tolerance during cold stress.
Fu-qiang Gao; Hong-pu Kang [Central Coal Research Institute, Beijing (China). Mining and Designing Branch
2008-12-15
The importance of the pre-tensioned force of rock bolts has been recognized by more and more researchers. To investigate the effect of pre-tensioned rock bolts on stress redistribution around roadways, a numerical analysis was carried out on a level drift at Chengzhuang coal mine using FLAC3D and a special post-process methodology, using surfer, is proposed to process the numerical simulation results. The results indicate that pre-tensioned rock bolts have a significant effect on stress redistribution around a roadway. In the roof, pre-tensioned rock bolts greatly increase vertical stress; as a result, the strength of the rock mass increased significantly which results in a greater capacity of bearing a large horizontal stress. The horizontal stress decreases in the upper section of the roof, indicating that pre-tensioned rock bolts significantly reduce the coefficient and the size of the region concentration of horizontal stress. At the lateral side, pre-tensioned rock bolts greatly increase the horizontal stress; therefore, the rock mass strength significantly increases which results also in a greater capacity of bearing a large vertical stress. The greater the size of pre-tensioned force, the larger the region of stress redistribution around a roadway is affected and the higher the size of the stress on the roadway surface the more the rock mass strength increases. 10 refs., 6 figs., 1 tab.
GAO Fu-qiang; KANG Hong-pu
2008-01-01
The importance of the pre-tensioned force of rock bolts has been recognized by more and more researchers. To investigate the effect of pre-tensioned rock bolts on stress redistribution around roadways, a numerical analysis was carded out using FLAC3D and a special post-process methodology, using surfer, is proposed to process the numerical simulation results. The results indicate that pre-tensioned rock bolts have a significant effect on stress redistribution around a roadway. In the roof, pre-tensioned rock bolts greatly increase vertical stress; as a result, the strength of the rock mass increased significantly which results in a greater capacity of bearing a large horizontal stress. The horizontal stress decreases in the upper section of the roof, indicating that pre-tensioned rock bolts significantly reduce the coefficient and the size of the region concentration of horizontal stress. At the lateral side, pre-tensioned rock bolts greatly increase the horizontal stress; therefore, the rock mass strength significantly increases which results also in a greater capacity of bearing a large vertical stress. The greater the size of pre-tensioned force, the larger the region of stress redistribution around a roadway is affected and the higher the size of the stress on the roadway surface the more the rock mass strength increases.
Chen, Sheng-Hui; Wang, Hsuan-Wen; Chang, Ting-Wei
2012-03-12
Considering the Mott-Davis density of state model and Rayleigh scattering effect, we present an approach to model the absorption profile of microcrystalline silicon thin films in this paper. Maxwell-Garnett effective medium theory was applied to analyze the absorption curves. To validate the model, several experimental profiles have been established and compared with those results from the model. With the assistance of the genetic algorithm, our results show that the absorption curves from the model are in good agreement with the experiments. Our findings also indicate that, as the crystal volume fraction increases, not only do the defects in amorphous silicon reduce, but the bulk scattering effect is gradually enhanced as well.
Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer’s and diabetes. A neurohormonal stress response (referred here as a systemic response produced by activ...
Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer’s and diabetes. A neurohormonal stress response (referred here as a systemic response produced by activ...
Stress and Memory: Behavioral Effects and Neurobiological Mechanisms
Carmen Sandi
2007-01-01
Full Text Available Stress is a potent modulator of learning and memory processes. Although there have been a few attempts in the literature to explain the diversity of effects (including facilitating, impairing, and lack of effects described for the impact of stress on memory function according to single classification criterion, they have proved insufficient to explain the whole complexity of effects. Here, we review the literature in the field of stress and memory interactions according to five selected classifying factors (source of stress, stressor duration, stressor intensity, stressor timing with regard to memory phase, and learning type in an attempt to develop an integrative model to understand how stress affects memory function. Summarizing on those conditions in which there was enough information, we conclude that high stress levels, whether intrinsic (triggered by the cognitive challenge or extrinsic (induced by conditions completely unrelated to the cognitive task, tend to facilitate Pavlovian conditioning (in a linear-asymptotic manner, while being deleterious for spatial/explicit information processing (which with regard to intrinsic stress levels follows an inverted U-shape effect. Moreover, after reviewing the literature, we conclude that all selected factors are essential to develop an integrative model that defines the outcome of stress effects in memory processes. In parallel, we provide a brief review of the main neurobiological mechanisms proposed to account for the different effects of stress in memory function. Glucocorticoids were found as a common mediating mechanism for both the facilitating and impairing actions of stress in different memory processes and phases. Among the brain regions implicated, the hippocampus, amygdala, and prefrontal cortex were highlighted as critical for the mediation of stress effects.
Almeida J, A. T. [FUNDACENTRO, Centro Regional de Minas Gerais, Brazilian Institute for Safety and Health at Work, Belo Horizonte, 30180-100 Minas Gerais (Brazil); Nogueira, M. S. [Center of Development of Nuclear Technology / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Santos, M. A. P., E-mail: mnogue@cdtn.br [Regional Center for Nuclear Science / CNEN, 50.740-540 Recife, Pernambuco (Brazil)
2015-10-15
Full text: In this paper, the interaction of X-rays with some shielding materials has been studied for materials containing different amounts of barite and aggregates. The total mass attenuation coefficient (μ{sub t}) for three shielding materials has been calculated by using WinXCOM program in the energy range from RQR qualities (RQR-4, RQR-6, RQR-9, and RQR-10). They were: cream barite (density 2.99 g/cm{sup 3} collected in the State of Sao Paulo), purple barite (density 2.95 g/cm{sup 3} collected in the State of Bahia) and white barite (density 3.10 g/cm{sup 3} collected in the State of Paraiba). The chemical analysis was carried out by an X-ray fluorescence spectrometer model EDX-720, through dispersive energy. The six elements of the higher concentration found in the sample and analyzed by Spectrophotometry of Energy Dispersive X-ray for the samples were Ba(60.9% - white barite), Ca(17,92% - cream barite), Ce(3,60% - white barite), Fe(17,16% - purple barite), S(12,11% - white barite) and Si(29,61% - purple barite). Also, the effective atomic number (Z{sub eff}) and the effective electron density (N{sub eff}) were calculated using the values of the total mass attenuation coefficient. The dependence of these parameters on the incident photon energy and the chemical composition has been examined. (Author)
[STRESS AND INFARCT LIMITING EFFECTS OF EARLY HYPOXIC PRECONDITIONING].
Lishmanov, Yu B; Maslov, L N; Sementsov, A S; Naryzhnaya, N V; Tsibulnikov, S Yu
2015-09-01
It was established that early hypoxic preconditioning is an adaptive state different from eustress and distress. Hypoxic preconditioning has the cross effects, increasing the tolerance of the heart to ischemia-reperfusion and providing antiulcerogenic effect during immobilization stress.
Effect of Opening the Sash of a Centre-Pivot Roof Window on Wind Pressure Coefficients
Iqbal, Ahsan; Wigö, Hans; Heiselberg, Per
2014-01-01
This paper describes the effect of outward opening the sash of a window on local and overall wind pressures. Wind tunnel experiments were used for the purpose of evaluation. A centre-pivot roof window on a pitched roof in a modelled scaled building was used in the analysis of wind pressures...
Mechanical fatigue of polysilicon: Effects of mean stress and stress amplitude
Kahn, H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)]. E-mail: harold.kahn@case.edu; Chen, L. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Ballarini, R. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)
2006-02-15
Polycrystalline silicon (polysilicon) fatigue specimens with micrometer-sized dimensions were fabricated and subjected to cyclic loading using an integrated electrostatic actuator. The fatigue effects were determined by comparing the single edge-notched beam monotonic bend strength measured after cyclic loading to the monotonic strength of 'virgin' specimens that had received no cycling. Both strengthening and weakening were observed, depending on the levels of mean stress and fatigue stress amplitude during the cyclic loading. Monotonic loading with similar sub-critical stress levels had no effect. The physical mechanisms responsible for this behavior are discussed, and a model based on grain boundary plasticity is presented for the strengthening behavior.
Morphologic effects of the stress response in fish.
Harper, Claudia; Wolf, Jeffrey C
2009-01-01
Fish and other aquatic animals are subject to a broad variety of stressors because their homeostatic mechanisms are highly dependent on prevailing conditions in their immediate surroundings. Yet few studies have addressed stress as a potential confounding factor for bioassays that use fish as test subjects. Common stressors encountered by captive fish include physical and mental trauma associated with capture, transport, handling, and crowding; malnutrition; variations in water temperature, oxygen, and salinity; and peripheral effects of contaminant exposure or infectious disease. Some stress responses are detectable through gross or microscopic examination of various organs or tissues; as reported in the literature, stress responses are most consistently observed in the gills, liver, skin, and components of the urogenital tract. In addition to presenting examples of various stressors and corresponding morphologic effects, this review highlights certain challenges of evaluating stress in fish: (1) stress is an amorphous term that does not have a consistently applied definition; (2) procedures used to determine or measure stress can be inherently stressful; (3) interactions between stressors and stress responses are highly complex; and (4) morphologically, stress responses are often difficult to distinguish from tissue damage or compensatory adaptations induced specifically by the stressor. Further investigations are necessary to more precisely define the role of stress in the interpretation of fish research results.
Rajneesh Kumar
2014-01-01
Full Text Available The reflection of plane waves at the free surface of thermally conducting micropolar elastic medium with two temperatures is studied. The theory of thermoelasticity with and without energy dissipation is used to investigate the problem. The expressions for amplitudes ratios of reflected waves at different angles of incident wave are obtained. Dissipation of energy and two-temperature effects on these amplitude ratios with angle of incidence are depicted graphically. Some special and particular cases are also deduced.
Mumaw, R.J.
1994-08-01
Operational personnel may be exposed to significant levels of stress during unexpected changes in plant state an plant emergencies. The decision making that identifies operational actions, which is strongly determined by procedures, may be affected by stress, and performance may be impaired. ER report analyzes potential effects of stress in nuclear power plant (NPP) settings, especially in the context of severe accident management (SAM). First, potential sources of stress in the NPP setting are identified. This analysis is followed by a review of the ways in which stress is likely to affect performance, with an emphasis on performance of cognitive skills that are linked to operational decision making. Finally, potential training approaches for reducing or eliminating stress effects are identified. Several training approaches have the potential to eliminate or mitigate stress effects on cognitive skill performance. First, the use of simulated events for training can reduce the novelty and uncertainty that can lead to stress and performance impairments. Second, training to make cognitive processing more efficient and less reliant on attention and memory resources can offset the reductions in these resources that occur under stressful conditions. Third, training that targets crew communications skills can reduce the likelihood that communications will fail under stress.
Effect of low segregation coefficient on Ga-doped multicrystalline silicon solar cell performance
Dhamrin, Marwan; Kamisako, Koichi; Saitoh, Tadashi [Tokyo University of Agriculture and Technology, Tokyo (Japan); Eguchi, Takeshi; Hirasawa, Teruhiko; Yamaga, Isao [Dai-ichi Kiden Co., Tokyo (Japan)
2005-11-15
High-quality Ga-doped ingots are grown in different casting furnaces at optimized growth parameters; 3.5 kg ingots exhibit normal distribution of diffusion lengths along their height with very high diffusion lengths at the center of the ingot. Effective lifetimes as high as 1.1 ms are realized in 10 {omega} cm Ga-doped wafers after proper P-diffusion and hydrogen passivation. Average effective lifetimes above 400 {mu}s are also realized after P-diffusion and hydrogen passivation for Ga-doped wafers cut from 75 kg ingot where the response to P-diffusion and hydrogen passivation is pronounced. High effective lifetimes are realized over the whole ingot with minimum values of 20 {mu}s at the top of the ingot, indicating the possible use of about 85% of the ingot for solar cell production. Conversion efficiencies above 15.5% were realized in utilizing more than 80% of the ingot. High efficiencies of about 16% were realized in wafers with resistivities higher than 5 {omega} cm p-type multicrystalline silicon wafers. (Author)
Effect of Surface Topography on Stress Concentration Factor
CHENG Zhengkun; LIAO Ridong
2015-01-01
Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.
Effects of Hospital Workers' Friendship Networks on Job Stress.
Sung Yae Shin
Full Text Available This study attempted to identify the sources of job stress according to job position and investigate how friendship networks affect job stress.Questionnaires based on The Health Professions Stress Inventory (HPSI developed by Wolfgang experienced by healthcare providers were collected from 420 nurses, doctors and radiological technologists in two general hospitals in Korea by a multistage cluster sampling method. Multiple regression analysis was used to examine the effects of friendship networks on job stress after controlling for other factors.The severity of job stress differed according to level of job demands (p = .006; radiologic technologists experienced the least stress (45.4, nurses experienced moderate stress (52.4, and doctors experienced the most stress (53.6. Those with long-term friendships characterized by strong connections reported lower levels of stress than did those with weak ties to friends among nurses (1.3, p < .05 and radiological technologists (11.4, p < .01. The degree of cohesion among friends had a positive impact on the level of job stress experienced by nurses (8.2, p < .001 and radiological technologists (14.6, p < .1. Doctors who participated in workplace alumni meetings scored higher than those who did not. However, those who participated in alumni meetings outside the workplace showed the opposite tendency, scoring 9.4 (p < .05 lower than those who did not. The resources from their friendship network include both information and instrumental support. As most radiological technologists were male, their instrumental support positively affected their job stress (9.2, p < .05. Life information support was the primary positive contributor to control of nurses' (4.1, p < .05, radiological technologists' (8.0, p < .05 job stress.The strength and density of such friendship networks were related to job stress. Life information support from their friendship network was the primary positive contributor to control of job
Qing-Ming Li; Bin-Bin Liu; Yang Wu; Zhi-Rong Zou
2008-01-01
To reveal and quantify the interactive effects of drought stresses and elevated CO2 concentration [CO2] on photochemistry efficiency of cucumber seedlings, the portable chlorophyll meter was used to measure the chlorophyll content, and the Imaging-PAM was used to image the chlorophyll fluorescence parameters and rapid light response curves (RLC) of leaves in two adjacent greenhouses. The results showed that chlorophyll content of leaves was reduced significantly with drought stress aggravated. Minimal fluorescence (Fo) was increased while maximal quantum yield of PSII (Fv/Fm) decreased significantly by severe drought stress. The significant decrease of effective quantum yield of PSll (Y(Ⅱ)) accompanied by the significant increase of quantum yield of regulated energy dissipation (Y(NPQ)) was observed under severe drought stress condition, but there was no change of quantum yield of nonregulated energy dissipation (Y(NO)). We detected that the coefficient of photochemical quenching (Qp) decreased, and non-photochemical quenching (NPQ) increased significantly under severe drought stress. Furthermore, we found that maximum apparent electron transport rate (ETRmax) and saturating photosynthetically active radiation (PPFDsat) decreased significantly with drought stress aggravated. However, elevated [CO2] significantly increased FvlFm, Qp and PPFDsat, and decreased NPQ under all water conditions, although there were no significant effects on chlorophyll content, Fo, Y(Ⅱ), Y(NPQ), Y(NO) and ETRmax. Therefore, it is concluded that CO2-fertilized greenhouses or elevated atmospheric [CO2] in the future could be favorable for cucumber growth and development, and beneficial to alleviate the negative effects of drought stresses to a certain extent.
Gopinath, Ashok
1996-01-01
Analytical and numerical studies are to be carried out to examine time-averaged thermal effects which are induced by the interaction of strong acoustic fields with a rigid boundary (thermoacoustic streaming). Also of interest is the significance of a second-order thermal expansion coefficient that emerges from this analysis. The model problem to be considered is that of a sphere that is acoustically levitated such that it is effectively isolated in a high-intensity standing acoustic field. The solution technique involves matched asymptotic analysis along with numerical solution of the boundary layer equations. The objective of this study is to predict the thermoacoustic streaming behavior and fully understand the role of the associated second-order thermodynamic modulus.
Drikis, Ivars; Plate, Matiss; Sennikovs, Juris; Virbulis, Janis
2017-09-01
Simulations of 3D anisotropic stress are carried out in and oriented Si crystals grown by FZ and CZ processes for different diameters, growth rates and process stages. Temperature dependent elastic constants and thermal expansion coefficients are used in the FE simulations. The von Mises stress at the triple point line is 5-11% higher in crystals compared to crystals. The process parameters have a larger effect on the von Mises stress than the crystal orientation. Generally, the crystal has a higher azimuthal variation of stress along the triple point line ( 8%) than the crystal ( 2%). The presence of a crystal ridge increases the stress beside the ridge and decreases it on the ridge compared with the round crystal.
Porras, Simo P; Sarmini, Karim; Fanali, Salvatore; Kenndler, Ernst
2003-04-01
Association constants, Kc, were derived from the electrophoretic mobilities of the anionic solutes (seven benzoates with hydroxy or chloro substituents) by capillary zone electrophoresis in different solvent systems, consisting of binary mixtures of water with up to 20% (v/v) methanol or acetonitrile, respectively. The association constants expectedly are found to decrease with increasing organic solvent concentration. The effect of organic solvents on the Kc of the benzoates with beta-cyclodextrin was analyzed applying the concept of the transfer activity coefficient (or the medium effect). This concept enables the evaluation of the significance of the contributions of the individual species involved in the complexation equilibrium in the different solvents: the benzoate ion, beta-cyclodextrin, and the anionic benzoate-beta-cyclodextrin complex. The medium effect on benzoate was calculated from the change in acidity constant of benzoic acid in the different mixed solvents and the corresponding transfer activity coefficients of the proton and the molecular acid. The transfer activity coefficients for beta-cyclodextrin results from its solubility at saturation in the different solvents. In this way, an estimation of the standard free energy of transfer, deltaG(t)0, of each species involved in the complexation equilibrium was possible for the transfer from water into the respective mixed solvent. It was found that the organic solvents do not significantly affect deltaG(t)0 for the benzoate anion. However, the organic solvents play a different role concerning the stabilization of beta-cyclodextrin and the complex anion: whereas the addition of acetonitrile has nearly no influence on deltaG(t)0 of the anionic complex, the reduction in Kc is caused by the enhanced stabilization of beta-cyclodextrin (reflected by its better solubility). Addition of methanol, on the other hand, lowers the solubility of beta-cyclodextrin, thus giving positive values for deltaG(t)0. Thus
Banquet, F. [Electricite de France, Villeurbanne (France)
1996-08-01
The HEI code, 8th edition, addendum n{degrees}1, which was used for condenser design, makes no distinction between grade 2 titanium characteristics and those of 304L and 316L stainless steels. In 1993 the Electric Power Research Institute (EPRI) published the results of a study on a test condenser: these suggest that the overall heat transfer coefficient of a titanium bundle is substantially higher than that of the same bundle made from stainless steel. The EPRI study inspired the 9th edition of the HEI Standards. To form its own opinion, EDF conducted a study to compare these various design methods and, in particular, to evaluate the effect of the thermal conductivity of materials on the overall heat transfer coefficient; a two-dimensional thermohydraulic code was used, considering different condensers from EDF nuclear power plants. During the study EDF observed that the thermal conductivity values of materials varied greatly depending on the sources, mainly grade 2 titanium and, to a lesser extent, 304L and 316L. It had the thermal conductivity of these materials measured using a highly accurate method in a manufacturer-independent laboratory. In conclusion, EDF considers: The EPRI correction method is wholly acceptable, The HEI 9 code is acceptable on condition that the material correction factors are slightly modified. 5 refs., 11 tabs.
Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki
2016-09-01
The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.
WUQI－TANG; J.L.MOREL; 等
1994-01-01
The supply of cadmium from soil to plant roots mainly depends on the diffusion prooess.This work was conducted to study the effects of some soil properties on cadmium diffusion coefficient (D) in soil. Measurements were made using the Shofield and Graham-Bryce's isotopic labelling method.Cadmium diffusion coefficients varied from 10-7to 10-9 cms2-1.Higher values were observed in acid sandy soils and lower values in calcareous clay soils.Liming an acid soil resulted in a substantial decrease of D.Addition of cadmium as nitrate salt generally increased D,while addition of sewage sludge and organic matter resulted in a significant decrease of cadmium diffusion.The rhizospheric activity also induced a moderate reduction in D.The relationships between D(10-9cms2-1)on the on hand and soil pH.moisture(Mc,g kg-1) ,organic matter(OM,g kg-1),clay(Cy,gkg-1)and cadmium content(Cd,mgkg-1) on the other were obtained by the multiple regression:D=182.1-29.91pH+0.210Mc-0.303OM+0.011Cy+1.64Cd(R2=0.859,n=22).
Saâdi, Zakaria
2014-05-01
The radon exhalation rate at the earth's surface from soil or rock with radium as its source is the main mechanism behind the radon activity concentrations observed in both indoor and outdoor environments. During the last two decades, many subsurface radon transport models have used Rogers and Nielson's formula for modeling the unsaturated soil bulk radon diffusion coefficient. This formula uses an "air-filled effective porosity" to account for radon adsorption and radon dissolution in the groundwater. This formula is reviewed here, and its hypotheses are examined for accuracy in dealing with subsurface radon transport problems. The author shows its limitations by comparing one dimensional steady-state analytical solutions of the two-phase (air/water) transport equation (Fick's law) with Rogers and Nielson's formula. For radon diffusion-dominated transport, the calculated Rogers and Nielson's radon exhalation rate is shown to be unrealistic as it is independent of the values of the radon adsorption and groundwater dissolution coefficients. For convective and diffusive transport, radon exhalation rates calculated using Fick's law and this formula agree only for high values of gas-phase velocity and groundwater saturation. However, these conditions are not usually met in most shallow subsurface environments where radon migration takes place under low gas phase velocities and low water saturation.
Fulwood, Ethan L; Kramer, Andrew
2013-09-01
This study examines the effect of a measurement size bias in coefficients of variation on the evaluation of intraspecific skeletal variability in a sample of eight prosimian species (Eulemur fulvus, Hapalemur griseus, Lemur catta, Varecia variegata, Galago senegalensis, Otolemur crassicaudatus, Nycticebus coucang, and Tarsius syrichta). Measurements with smaller means were expected to have higher coefficients of variation (CVs) due to the impact of instrumental precision on the ability to assess variability. This was evaluated by testing for a negative correlation between CVs and means in the total sample, within each species, and within each measurement, and by testing for the leveraging impact of small measurements on the significance of comparisons of variability between regions of the prosimian skeleton. Three comparisons were made: cranial versus postcranial variability, epiphysis versus diaphysis variability, and forelimb versus hindlimb variability. CVs were significantly negatively correlated with means within the total sample (r(2) = 0.208, P < 0.0001) and within each species. CVs and means were significantly correlated within only three of the measurements, which may reflect the relatively low body size range of the species studied. As predicted by the higher variability of smaller measurements, removing the smallest measurements from comparisons of variable classes containing measurements of different mean magnitudes pushed the comparisons below significance. These results indicate caution should be exercised when using CVs to assess variability across sets of measurements with different means.
Timing matters: temporal dynamics of stress effects on memory retrieval.
Schwabe, Lars; Wolf, Oliver T
2014-09-01
Stress may impair memory retrieval. This retrieval impairment has been attributed to the action of the stress hormone cortisol, which is released with a delay of several minutes after a stressful encounter. Hence, most studies tested memory retrieval 20-30 min after stress, when the stress-induced cortisol increase peaks. In the present experiment, we investigated whether retrieval impairments can also be found at later intervals after stress. To this end, participants learned a list of words on day 1. Twenty-four hours later, they were first exposed to a stressor or a nonstressful control manipulation and completed a recognition test for the words either immediately thereafter, 25 min later, or 90 min later. Our findings showed that stress did not impair memory retrieval when memory was tested immediately after the stressor, before cortisol levels were elevated. However, retrieval performance was impaired 25 min after stress, when cortisol levels peaked, as well as 90 min after the stressor, when cortisol levels had already returned to baseline. The retrieval impairment 90 min after stress appeared to be even stronger than the one after 25 min. These findings suggest that the detrimental effects of stress on retrieval performance may last longer than is usually assumed.
Prenatal stress and its effect on infant development
Huizink, A.C.
2000-01-01
In this dissertation the effect of prenatal maternal stress on infant development and behavior is discussed. In a prospective longitudinal study of 170 nulliparous women, data was gatheren on the maternal stress level three times during pregnancy by means of questionnaires and endocrinologic
Effect of Huzikang-duannaibao on piglets' ablactation stress
Zhou Shenglin; Jiang Zhengyun
2003-01-01
Piglets' alactation-stress with diarrhea as a main symptom is a serious problem in pig farming. The experiment indicates that the complex premix additive Huzikang-duannaibao can be used to control ablactation-stress syndromes and its effects are better than that of the common antibiotic ligomycin.
Effect of Friction Model and Tire Maneuvering on Tire-Pavement Contact Stress
Haichao Zhou
2015-01-01
Full Text Available This paper aims to simulate the effects of different friction models on tire braking. A truck radial tire (295/80R22.5 was modeled and the model was validated with tire deflection. An exponential decay friction model that considers the effect of sliding velocity on friction coefficients was adopted for analyzing braking performance. The result shows that the exponential decay friction model used for evaluating braking ability meets design requirements of antilock braking system (ABS. The tire-pavement contact stress characteristics at various driving conditions (static, free rolling, braking, camber, and cornering were analyzed. It is found that the change of driving conditions has direct influence on tire-pavement contact stress distribution. The results provide the guidance for tire braking performance evaluation.
Rodionova, V.; Baraban, I.; Chichay, K.; Litvinova, A.; Perov, N.
2017-01-01
For glass-coated amorphous ferromagnetic Fe-based microwires both joint and separate effect of metallic nucleus diameter, d, and the ratio of metallic nucleus diameter to the total diameter of microwire in glass shell, d/D, on magnetic properties is investigated. Thereby the contribution of both shell-induced stresses, associated with the ratio of diameters, and internal nucleus stresses (residual, quenching), associated with the diameter of the nucleus are estimated. A strong and non-monotonic effect of the metallic nucleus diameter and metallic nucleus diameter/total microwire diameter ratio on magnetostatic and magnetostrictive properties was established. For analysis, we considered magnetically bi-stable microwires of "classic" Fe77.5Si7.5B15 alloy with positive magnetostriction coefficient.
No effects of psychosocial stress on intertemporal choice.
Johannes Haushofer
Full Text Available Intertemporal choices - involving decisions which trade off instant and delayed outcomes - are often made under stress. It remains unknown, however, whether and how stress affects intertemporal choice. We subjected 142 healthy male subjects to a laboratory stress or control protocol, and asked them to make a series of intertemporal choices either directly after stress, or 20 minutes later (resulting in four experimental groups. Based on theory and evidence from behavioral economics and cellular neuroscience, we predicted a bidirectional effect of stress on intertemporal choice, with increases in impatience or present bias immediately after stress, but decreases in present bias or impatience when subjects are tested 20 minutes later. However, our results show no effects of stress on intertemporal choice at either time point, and individual differences in stress reactivity (changes in stress hormone levels over time are not related to individual differences in intertemporal choice. Together, we did not find support for the hypothesis that psychosocial laboratory stressors affect intertemporal choice.
Effects of Stress and MDMA on Hippocampal Gene Expression
Georg F. Weber
2014-01-01
Full Text Available MDMA (3,4-methylenedioxymethamphetamine is a substituted amphetamine and popular drug of abuse. Its mood-enhancing short-term effects may prompt its consumption under stress. Clinical studies indicate that MDMA treatment may mitigate the symptoms of stress disorders such as posttraumatic stress syndrome (PTSD. On the other hand, repeated administration of MDMA results in persistent deficits in markers of serotonergic (5-HT nerve terminals that have been viewed as indicative of 5-HT neurotoxicity. Exposure to chronic stress has been shown to augment MDMA-induced 5-HT neurotoxicity. Here, we examine the transcriptional responses in the hippocampus to MDMA treatment of control rats and rats exposed to chronic stress. MDMA altered the expression of genes that regulate unfolded protein binding, protein folding, calmodulin-dependent protein kinase activity, and neuropeptide signaling. In stressed rats, the gene expression profile in response to MDMA was altered to affect sensory processing and responses to tissue damage in nerve sheaths. Subsequent treatment with MDMA also markedly altered the genetic responses to stress such that the stress-induced downregulation of genes related to the circadian rhythm was reversed. The data support the view that MDMA-induced transcriptional responses accompany the persistent effects of this drug on neuronal structure/function. In addition, MDMA treatment alters the stress-induced transcriptional signature.
Małgorzata, W; Merecz, Dorota; Drabek, Marcin
2010-01-01
This is the second part of the publication on approaches to occupational stress prevention and a state of the art in different European countries. In this part, stress prevention within an organization is described and discussed. Although there is no one way of tackling stress at work, some recommendations can be formulated to increase the effectiveness of such interventions. The effective stress reducing programs should be aimed both at changes in the organization itself and empowerment of employees' coping with stress resources. It is also important to take the advantage of wide spectrum of methods and techniques (e.g., work redesign, participation, team work, cognitive behavioral methods, relaxation, etc.) remembering that one size does not fit all. The intervention should be carefully planned and adopted to the various branches, an individual organization or department and should be preceded by the identification of stress risks and risk groups. To have the stress prevention program successfully introduced one should also consider factors which may influence (positively or negatively) the process of program implementation.
NEGATIVE EFFECT OF METALLOID STRESS ON WHEAT
Marína Maglovski
2015-02-01
Full Text Available Arsenic (As belongs to heavy metals and its accumulation in plants, besides damaging the organism itself, represents a potential health risk to animal and human consumers. Therefore, contamination of soils and waters with this compound is a serious environmental problem. In this work we focused on investigating a negative impact of As on selected parameters of growth of wheat plants (Triticum aestivum L. cv. Genoveva grown in hydropony. In the stage of first assimilation leaves we applied a solution of heavy metal (1 mg.kg-1 As3+ on wheat plants. For plants grown under hydropony conditions we observed different plant parameters such as length, weight, amount of fresh and dry biomass. Further we analyzed accumulation of hydrogen peroxide and products membrane lipid peroxidation as indicators of oxidative stress. In addition to these we also measured the content of photosynthetic pigments, maximal quantum yield and proline in plant tissue. Our data indicate reduction of the biomass of shoots forthcoming as a result of exposure of stressed plants to As. Decline of biomass accumulation was accompanied by increase of hydrogen peroxide in plant tissue. In contrast, level of lipid peroxidation was suppressed in stressed shoots. Contents of photosynthetic pigments soundly decreased. Interestingly, fluorescence (Fp=Fm in stressed wheat shoots increased. Similarly in tested shoots the content of proline was increased. The results indicate that the applied dose of As has a negative impact on the growth and photosynthetic performance of stressed plants. A better understanding of the mechanisms responsible for As resistance and toxicity in plants requires further investigation.
Chatterjee, Sulagna; Chattopadhyay, Sanatan
2017-01-01
In the current work, an analytical model has been developed to estimate the amount of induced stress in nanowires which are horizontally embedded with different fractions within an Insulator-on-Silicon substrate. For estimating such stress, different crystallographic orientations of substrates and embedded nanowires have been considered. The induced stress for both the difference in thermo-elastic constants and lattice-mismatch is included and accuracy of the analytical model has been verified with the similar results obtained from ANSYS Multiphysics. Induced stress is observed to be insensitive of the nanowire size, however, depends significantly on the fractional insertion of the nanowires. A tensile stress of 1.95 GPa and a compressive stress of -1.0719 GPa have been obtained for the oriented Si-nanowires. Hole mobility of 850 cm2/Vs can be achieved for the 3/4th insertion of the nanowires which is comparable to electron mobility and therefore can be utilized for the design of symmetric nano-electronic devices.
Hui Zhang
2014-05-01
Full Text Available In this paper, we have investigated the dependence of both the electromechanical effect and the electrostriction on the compressive stress in PMN-30%PT single crystal on the basis of single domain polarization rotation model. In the model, the electroelastic energy induced by the compressive stress is taken into account. The results have demonstrated that the compressive stress can lead to a significant change in the initial polarization state in the crystal. The reason lies in the stress induced anisotropy which is the coupling between the compressive stress and the electrostrictive coefficients. Thus, the initial polarization state in single crystal is determined by the combination of both electrocrystalline anisotropy and the stress induced anisotropy. The compressive stress along the [100] axis can make the polarization in the crystal be perpendicular to the stress direction, and make it difficult to be polarized to the saturation. This model is useful for better understanding both the polarization rotation and electromechanical effect in ferroelectric crystals with the compressive stress present.
Bhuiyan, A. S.; Biswas, M. R.
2011-11-01
The effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical flat plate have been investigated. The results are obtained numerically by transforming the governing system of boundary layer equations into a system of non-dimensional equations. Numerical results for different values of pressure stress work parameter, viscous dissipation parameter, and Prandtl number have been obtained. The velocity profiles, temperature distributions, skin friction coefficient, and the rate of heat transfer have been presented graphically for the effects of the aforementioned parameters. Results are compared with previous investigation.
Cellular effects of swim stress in the dorsal raphe nucleus.
Kirby, Lynn G; Pan, Yu-Zhen; Freeman-Daniels, Emily; Rani, Shobha; Nunan, John D; Akanwa, Adaure; Beck, Sheryl G
2007-07-01
Swim stress regulates forebrain 5-hydroxytryptamine (5-HT) release in a complex manner and its effects are initiated in the serotonergic dorsal raphe nucleus (DRN). The purpose of this study was to examine the effects of swim stress on the physiology of DRN neurons in conjunction with 5-HT immunohistochemistry. Basic membrane properties, 5-HT(1A) and 5-HT(1B) receptor-mediated responses and glutamatergic excitatory postsynaptic currents (EPSCs) were measured using whole-cell patch clamp techniques. Rats were forced to swim for 15min and 24h later DRN brain slices were prepared for electrophysiology. Swim stress altered the resting membrane potential, input resistance and action potential duration of DRN neurons in a neurochemical-specific manner. Swim stress selectively elevated glutamate EPSC frequency in 5-HT DRN neurons. Swim stress non-selectively reduced EPSC amplitude in all DRN cells. Swim stress elevated the 5-HT(1B) receptor-mediated inhibition of glutamatergic synaptic activity that selectively targeted 5-HT cells. Non-5-HT DRN neurons appeared to be particularly responsive to the effects of a milder handling stress. Handling elevated EPSC frequency, reduced EPSC decay time and enhanced a 5-HT(1B) receptor-mediated inhibition of mEPSC frequency selectively in non-5-HT DRN cells. These results indicate that swim stress has both direct, i.e., changes in membrane characteristics, and indirect effects, i.e., via glutamatergic afferents, on DRN neurons. These results also indicate that there are distinct local glutamatergic afferents to neurochemically specific populations of DRN neurons, and furthermore that these distinct afferents are differentially regulated by swim stress. These cellular changes may contribute to the complex effects of swim stress on 5-HT neurotransmission and/or the behavioral changes underlying the forced swimming test model of depression.
何柏林; 魏康
2015-01-01
Objective To analyze the stress concentration coefficient of SMA490BW steel butt joint for bogie, which has an im-portant significance for improving VHCF properties of bogie welded structure and ensuring the safe, reliable operation of high-speed train. Methods Finite element model of very high cycle fatigue sample of SMA490BW steel butt joint for bogie was built. The in-fluences of joint geometric parameters ( weld edge transition arc radius r,weld toe inclination angleθ) on stress concentration coeffi-cient Kt of weld toe were studied based on the finite element software ABAQUS, and the relationship between the stress concentra-tion coefficient and the geometric parameters was analyzed and established based on regression analysis of Origin software. Results When the weld edge transition arc radius r was 0. 2 mm, the stress concentration coefficient Kt was 1. 391, 1. 747, 1. 976, 2. 263, 2. 425, 2. 525 respectively at weld toe inclination angle θ of 10°, 20°, 30°, 40°, 50°, 60°;when the weld toe inclination angleθwas 30°, the stress concentration coefficient Kt was 1. 976, 1. 763, 1. 535, 1. 419, 1. 345, 1. 306, 1. 257, 1. 201 respectively at weld edge transition arc radius r of 0. 2, 0. 5, 1, 1. 5, 2, 2. 5, 3, 4 mm. Conclusion Stress concentration at weld toe of butt welded joint was relatively large, and weld edge transition arc radius r and weld toe inclination angle θ played important roles in stress concentration coefficient Kt . For the same weld edge transition arc radius r, the stress concentration coefficient Kt at weld toe increased with increasing inclination angle θ. While in the case of the same weld toe inclination angle θ, the stress concentration coefficient Kt at weld toe decreased with increasing transition arc radius r. The stress concentration coefficient equation has a gui-ding significance to the improvement of stress concentration at weld toe and the design of ultrasonic fatigue sample of butt joint for bogie.%
Nina, A. [Institute of Physics, University of Belgrade, P.O. Box 57, Belgrade (Serbia); Cadez, V. [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia); Sulic, D., E-mail: dsulic@ipb.ac.rs [Faculty of Ecology and Environmental Protection, Union - Nikola Tesla University, Cara Dusana 62, 11000 Belgrade (Serbia); Sreckovic, V. [Institute of Physics, University of Belgrade, P.O. Box 57, Belgrade (Serbia); Zigman, V. [University of Nova Gorica, Vipavska 13, Rona Dolina, SI-5000 Nova Gorica (Slovenia)
2012-05-15
In this paper, we present a model for determination of a weakly time dependent effective recombination coefficient for the perturbed terrestrial ionospheric D-region plasma. We study consequences of a class M1.0 X-ray solar flare, recorded by GOES-15 satellite on February 18, 2011 between 14:00 and 14:15 UT, by analyzing the amplitude and phase real time variations of very low frequency (VLF) radio waves emitted by transmitter DHO (located in Germany) at frequency 23.4 kHz and recorded by the AWESOME receiver in Belgrade (Serbia). Our analysis is limited to ionospheric perturbations localized at altitudes around 70 km where the dominant electron gain and electron loss processes are the photo-ionization and recombination, respectively.
Yuan, Du-Qi; Wang, Can-Jun
2010-04-01
Based on the form of the n-dimensional generic power-law potential, the state equation and the heat capacity, the analytical expressions of the Joule-Thomson coefficient (JTC) for an ideal Bose gas are derived in n-dimensional potential. The effect of the spatial dimension and the external potential on the JTC are discussed, respectively. These results show that: (i) For the free ideal Bose gas, when n/s Constant, T is the thermodynamic temperature, varpii is the external field's energy), is obtained. The potential makes the JTC increase when Δ > 0, on the contrary, it makes the JTC decrease when Δ < 0. (iii) In the homogenous strong external potential, the JTC gets the maximum on the condition of kT/varpii < 1.
Garland, Gregory Ellis
The temperature dependence of transport properties of a moderately dense square well gas is studied in order to understand the effects of attractive forces (particularly bound states). The quantum cluster expansions of the Green -Kubo time correlation functions for the thermal conductivity, shear viscosity, and self-diffusion coefficients are given, and exact expressions to zeroth (Boltzmann level) and first order in the density are obtained. Specializing to Boltzmann statistics and the classical square well potential allows calculations of the kinetic potential parts of the first density correction; the important contributions to the remaining triple collision parts are discussed. Good agreement with molecular dynamics results is found; quantitative difference from real fluids are observed, however. Possible reasons for the discrepancies are discussed. A brief description of the ultility and limitations of the hard sphere model is given for comparison. The dynamics structure factor is calculated for a dense fluid of hard spheres and compared with recent neutron scattering data for Krypton.
Wu, Chuandong; Liu, Jiemin; Yan, Luchun; Chen, Haiying; Shao, Huiqi; Meng, Tian
2015-02-01
Odor activity value (OAV) has been widely used for the assessment of odor pollution from various sources. However, little attention has been paid to the extreme OAV variation and potential inaccuracies of odor contribution assessment caused by odor interaction effects. The objective of this study is to assess the odor interaction effect for precise assessment of odor contribution. In this paper, samples were collected from a food waste disposal plant, and analyzed by instrumental and olfactory method to conclude odorants' occurrence and OAV. Then odor activity value coefficient (γ) was first proposed to evaluate the type and the level of binary interaction effects based on determination of OAV variation. By multiplying OAV and γ, odor activity factor (OAF) was used to reflect the real OAV. Correlation between the sum of OAF and odor concentration reached 80.0 ± 5.7%, which was 10 times higher than the sum of OAV used before. Results showed that hydrogen sulfide contributed most (annual average 66.4 ± 15.8%) to odor pollution in the waste disposal plant. However, as odor intensity of samples in summer rising, odor contribution of trimethylamine increased to 48.3 ± 3.7% by the strong synergistic interaction effect, while odor contribution of phenol decreased to 0.1 ± 0.02% for the increasing antagonistic interaction effect.
Effects of heat stress on day-old broiler chicks.
Ernst, R A; Weathers, W W; Smith, J
1984-09-01
Short-term heat stress can occur when chicks are transported from the hatchery to growing facilities. Two experiments were conducted to determine the possible effects of short-term heat stress on growth and feed conversion of broiler (Hubbard X Hubbard) chicks. The heat stress was accomplished by placing chicks in Jamesway 252 incubators at dry bulb temperatures ranging from 40 to 45 C for variable times. Growth, feed consumption, and mortality were measured for 16 days following the heat stress. Short sublethal heat stress significantly reduced growth rate to 16 days in these experiments without any effect on feed conversion ratio. The results indicate that the hatchery industry should avoid overheating chicks even for periods as short as 1 hr.
Residual stresses and their effects in composite laminates
Hahn, H. T.; Hwang, D. G.
1983-01-01
Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.
Differential effects of stress and glucocorticoids on adult neurogenesis.
Schoenfeld, Timothy J; Gould, Elizabeth
2013-01-01
Stress is known to inhibit neuronal growth in the hippocampus. In addition to reducing the size and complexity of the dendritic tree, stress and elevated glucocorticoid levels are known to inhibit adult neurogenesis. Despite the negative effects of stress hormones on progenitor cell proliferation in the hippocampus, some experiences which produce robust increases in glucocorticoid levels actually promote neuronal growth. These experiences, including running, mating, enriched environment living, and intracranial self-stimulation, all share in common a strong hedonic component. Taken together, the findings suggest that rewarding experiences buffer progenitor cells in the dentate gyrus from the negative effects of elevated stress hormones. This chapter considers the evidence that stress and glucocorticoids inhibit neuronal growth along with the paradoxical findings of enhanced neuronal growth under rewarding conditions with a view toward understanding the underlying biological mechanisms.
无
2007-01-01
The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method (FEM). The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone (HAZ), and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen would diffuse and accumulate in the higher stress region.
Effects of stress on human mating preferences: stressed individuals prefer dissimilar mates
Lass-Hennemann, Johanna; Deuter, Christian E.; Kuehl, Linn K.; Schulz, André; Blumenthal, Terry D.; Schachinger, Hartmut
2010-01-01
Although humans usually prefer mates that resemble themselves, mating preferences can vary with context. Stress has been shown to alter mating preferences in animals, but the effects of stress on human mating preferences are unknown. Here, we investigated whether stress alters men's preference for self-resembling mates. Participants first underwent a cold-pressor test (stress induction) or a control procedure. Then, participants viewed either neutral pictures or pictures of erotic female nudes whose facial characteristics were computer-modified to resemble either the participant or another participant, or were not modified, while startle eyeblink responses were elicited by noise probes. Erotic pictures were rated as being pleasant, and reduced startle magnitude compared with neutral pictures. In the control group, startle magnitude was smaller during foreground presentation of photographs of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to self-resembling mates. In the stress group, startle magnitude was larger during foreground presentation of self-resembling female nudes compared with other-resembling female nudes and non-manipulated female nudes, indicating a higher approach motivation to dissimilar mates. Our findings show that stress affects human mating preferences: unstressed individuals showed the expected preference for similar mates, but stressed individuals seem to prefer dissimilar mates. PMID:20219732
Resistance to early-life stress in mice: effects of genetic background and stress duration
Helene M. Savignac
2011-04-01
Full Text Available Early-life stress can induce marked behavioural and physiological impairments in adulthood including cognitive deficits, depression, anxiety and gastrointestinal dysfunction. Although robust rat models of early-life stress exist there are few established effective paradigms in the mouse. Genetic background and protocol parameters used are two critical variables in such model development.Thus we investigated the impact of two different early-life stress protocols in two commonly used inbred mouse strains. C57BL/6 and innately anxious BALB/c male mice were maternally deprived 3 hrs daily, either from postnatal day 1 to 14 (Protocol 1 or 6 to 10 (Protocol 2. Animals were assessed in adulthood for cognitive performance (spontaneous alternation behaviour test, anxiety (open field, light/dark box and elevated plus maze tests and depression-related behaviours (forced swim test in addition to stress-sensitive physiological changes. Overall, the results showed that early-life stressed mice from both strains displayed good cognitive ability and no elevations in anxiety. However, paradoxical changes occurred in C57BL/6 mice as the longer protocol (protocol 1 decreased anxiety in the light-dark box and increased exploration in the elevated plus maze. In BALB/c mice there were also limited effects of maternal separation with both separation protocols inducing reductions in stress-induced defecation and protocol 1 reducing the colon length. These data suggest that, independent of stress duration, mice from both strains were on the whole resilient to the maladaptive effects of early-life stress. Thus maternal-separation models of brain-gut axis dysfunction should rely on either different stressor protocols or other strains of mice.
Perceived effectiveness of critical incident stress debriefing by Australian nurses
O'Connor, J; Jeavons, S
2003-01-01
This paper examines the perceived effectiveness of stress debriefing by a sample of 129 Australian hospital nurses and the relationship of their perceptions to demographic variables such as qualifications and work area...
Effect of drought stress induced by polyethylene glycol (PEG) on ...
Effect of drought stress induced by polyethylene glycol (PEG) on germination indices in corn ( Zea mays L.) hybrids. ... African Journal of Biotechnology ... and success in this stage is dependent on moisture content of soil at time of planting.
Parain, D; Delapierre, G
1991-01-01
We assessed the influence of increasing stimulus intensity from motor threshold to pain threshold on short latency somatosensory evoked potentials recorded over the parietal and frontal scalp in 14 subjects during median nerve stimulation at the wrist. We used the curvature polynomial coefficient to evaluate alterations of the main components. The N20 and P27 curvature coefficients are not modified. The change of the N30 curvature coefficient is the result of shortened P45 latency. The increase of N60 curvature coefficient shows a great interindividual variability, probably due to a central amplification and synchronization or to involvement of nerve fibres with different excitability.
Wang, Hao; Chen, Jiajun
2012-01-01
Foam flushing is an in situ soil remediation technology based on the traditional surfactant flushing method. The contribution of mobility control to contaminant removal by foam is helpful for improving this technology. Foam flushing of polychlorinated biphenyl (PCB)-contaminated unconsolidated media was performed to evaluate the effect of the partition coefficient (PC) and sweep efficiency (SE) on PCB removal. Column flushing with surfactant solution and foam with different types and concentrations of surfactant was carried out for PCB removal. Two types of quartz sand were investigated to evaluate the Jamin effect on the SE value of the washing agent. The results demonstrate that a small PC value and large SE value are necessary to achieve high PCB removal for foam flushing. Compared with solution flushing, the introduction of foam can effectively control the mobility of the washing agent. Similar to solution flushing, solubilization is a key factor which dominates the removal of PCBs in foam flushing. In addition, the SE value and PCB removal by foam flushing is less affected by particle size. Therefore, foam flushing was proved to be more effective in porous media with low hydraulic conductivity and high porosity. An integrated flushing with water, surfactant solution and foam was performed and the results prove that this technology successfully combines the advantages of solution solubilization and mobility control by foam, and thus further increases the remediation efficiency of PCBs to 94.7% for coarse sand.
Hao Wang; Jiajun Chen
2012-01-01
Foam flushing is an in situ soil remediation technology based on the traditional surfactant flushing method.The contribution of mobility control to contaminant removal by foam is helpful for improving this technology.Foam flushing of polychlorinated biphenyl (PCB)-contaminated unconsolidated media was performed to evaluate the effect of the partition coefficient (PC) and sweep efficiency (SE) on PCB removal.Column flushing with surfactant solution and foam with different types and concentrations of surfactant was carried out for PCB removal.Two types of quartz sand were investigated to evaluate the Jamin effect on the SE value of the washing agent.The results demonstrate that a small PC value and large SE value are necessary to achieve high PCB removal for foam flushing.Compared with solution flushing,the introduction of foam can effectively control the mobility of the washing agent.Similar to solution flushing,solubilization is a key factor which dominates the removal of PCBs in foam flushing.In addition,the SE value and PCB removal by foam flushing is less affected by particle size.Therefore,foam flushing was proved to be more effective in porous media with low hydraulic conductivity and high porosity.An integrated flushing with water,surfactant solution and foam was performed and the results prove that this technology successfully combines the advantages of solution solubilization and mobility control by foam,and thus further increases the remediation efficiency of PCBs to 94.7％ for coarse sand.
Kodavanti, Urmila P
2016-12-01
Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer's and diabetes. A neurohormonal stress response (referred to here as a systemic response produced by activation of the sympathetic nervous system and hypothalamus-pituitary-adrenal (HPA)-axis) has been implicated in a variety of psychological and physical stresses, which involves immune and metabolic homeostatic mechanisms affecting all organs in the body. In this review, we provide new evidence for the involvement of this well-characterized neurohormonal stress response in mediating systemic and pulmonary effects of a prototypic air pollutant - ozone. A plethora of systemic metabolic and immune effects are induced in animals exposed to inhaled pollutants, which could result from increased circulating stress hormones. The release of adrenal-derived stress hormones in response to ozone exposure not only mediates systemic immune and metabolic responses, but by doing so, also modulates pulmonary injury and inflammation. With recurring pollutant exposures, these effects can contribute to multi-organ chronic conditions associated with air pollution. This review will cover, 1) the potential mechanisms by which air pollutants can initiate the relay of signals from respiratory tract to brain through trigeminal and vagus nerves, and activate stress responsive regions including hypothalamus; and 2) the contribution of sympathetic and HPA-axis activation in mediating systemic homeostatic metabolic and immune effects of ozone in various organs. The potential contribution of chronic environmental stress in cardiovascular, neurological, reproductive and metabolic diseases, and the knowledge gaps are also discussed. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.
Effects of heat stress on baroreflex function in humans
Crandall, Craig G.; Cui, Jian; Wilson, Thad E.
2003-01-01
INTRODUCTION: Heat stress significantly reduces orthostatic tolerance in humans. The mechanism(s) causing this response remain unknown. The purpose of this review article is to present data pertaining to the hypothesis that reduced orthostatic tolerance in heat stressed individuals is a result of heat stress induced alterations in baroflex function. METHODS: In both normothermic and heat stressed conditions baroreflex responsiveness was assessed via pharmacological and non-pharmacological methods. In addition, the effects of heat stress on post-synaptic vasoconstrictor responsiveness were assessed. RESULTS: Generally, whole body heating did not alter baroreflex sensitivity defined as the gain of the linear portion of the baroreflex curve around the operating point. However, whole body heating shifted the baroreflex curve to the prevailing (i.e. elevated) heart rate and muscle sympathetic nerve activity. Finally, the heat stress impaired vasoconstrictor responses to exogenous administration of adrenergic agonists. CONCLUSION: Current data do not support the hypothesis that reduced orthostatic tolerance associated with heat stress in humans is due to impaired baroreflex responsiveness. This phenomenon may be partially due to the effects of heat stress on reducing vasoconstrictor responsiveness.
Effects of Cadmium Stress on the Quality of Rice Seeds
Juan; CHEN; Hui; FANG; Ying; ZHANG; Yuanyuan; FAN
2013-01-01
Germination and hydroponic experiments are performed on rice seeds growing in soils treated with Cd stress,with rice seeds of the same variety that is not treated with Cd stress as a control,to study the effects of Cd stress on quality of rice seeds.The results have shown that:(1)Cd stress reduces the thousand grain weight of rice seeds,and higher Cd content means lower thousand grain weight;(2)The germination vigor and germination percentage of rice seeds under Cd stress as well as theirα-amylase activity andβ-amylase activity are all lower than those of the control.They decreases as the Cd stress increases;(3)For rice seeds under Cd stress,the height,fresh and dry weight of seedlings,as well as the chlorophyll content,photosynthetic rate and content of soluble protein of their leaves are all lower than those of the control.This indicates that Cd stress has certain effects on the germination and growth of the rice seeds.
TANG Wen-xue
2017-03-01
Full Text Available Wide usage of mulching technology has increased crop yields, but the large amounts of mulching film residue resulting from widespread use of plastic film in China has brought about a series of pollution hazards. Based on a 4-year (2011-2014 long-term experiment, the effects of different kinds of collecting mothod (zero plastic film residues, conventional plastic film residues, whole plastic film residues remainded on plastic film residues, residual coefficient and maize yield were explored. Plastic film residues mainly remained in 0~10 cm, 10~20 cm soil layers. In 0~30 cm soil layers, the two types of mulch residues (>25 cm2, 4~25 cm2 under zero plastic film residues treatment were much less than conventional plastic film residues and whole plastic film residues remainded treatments, no significant differences were observed in the mulch residues (2 among 3 treatments. After maize harvest, the amount of plastic film residues under zero plastic film residues, conventional plastic film residues and whole plastic film residues remainded treatments were 52.71, 80.85 kg·hm-2 and 152.65 kg·hm-2, respectively, the residual coefficient for zero plastic film residues, conventional plastic film residues and whole plastic film residues remainded treatments were -9.45%, 8.53% and 54.42%, respectively. The stem diameter, ear length, ear width, ear row number, grain number per row and 100-grain weight of maize decreased with the increase of residual film amount. Compared with the conventional plastic film residues, the mean grain yield of whole plastic film residues remainded treatment decreased by 15.08%, whereas the zero plastic film residues treatment increased by 4.70%. The plastic film residues, residual coefficient and maize yield were comprehensively analyzed, the conventional plastic film residues practice should be adopted currently without appropriate plastic film residues collector. But from the long-term development, we should speed up the
Effects of Consolidation Stress State on Normally Consolidated Clay
Lade, Poul V.
2000-01-01
and on isotropically consolidated, cubical specimens, both tested in triaxial compression and extension, clearly showed the influence of the undisturbed fabric as well as the effect of the initial consolidation stress states. While the K0-consolidated specimens appeared to retain their original fabric and exhibit......The effect of consolidation stress state on the stress-strain and strength characteristics has been studied from experiments on undisturbed block samples of a natural, normally consolidated clay known as San Francisco Bay Mud. The results of experiments on K0-consolidated, hollow cylinder specimens...
Cohesive stresses and size effect in quasi-brittle materials
V E Saouma; D Natekar
2002-08-01
A novel approach to the derivation of Ba$\\breve{z}$ant’s size effect law is presented. Contrarily to the original Lagrangian derivation which hinged on energetic consideration, a Newtonian approach based on local stress intensity factors is presented. Through this approach, it is shown that Ba$\\breve{z}$ant’s size effect law is the ﬁrst (and dominant) term in a series expansion for the nominal stress. Furthermore, analytical expressions for are derived for selected specimen geometries.
Effects of mechanical-bending and process-induced stresses on metal effective work function
Yang, Xiaodong; Chu, Min; Huang, Anping; Thompson, Scott
2013-01-01
Effective work function (EWF) change is investigated under both externally-applied mechanical stresses and process-induced stresses. Four-point wafer bending and ring bending techniques are used to generate uniaxial and biaxial mechanical stresses, respectively. For the process-induced stresses, bowing technique and charge pumping method are used for stress characterization and interface state measurement. It was found that higher stress presents in devices with thinner metal gate, regardless the thermal treatment cycle. EWF decreases under both tensile and compressive stress was observed due to the increase of defect activation energy lowering induced donor-like interface states.
Pinheiro Cleber
2008-07-01
Full Text Available Abstract Background One of the current shortcomings of radiofrequency (RF tumor ablation is its limited performance in regions close to large blood vessels, resulting in high recurrence rates at these locations. Computer models have been used to determine tissue temperatures during tumor ablation procedures. To simulate large vessels, either constant wall temperature or constant convective heat transfer coefficient (h have been assumed at the vessel surface to simulate convection. However, the actual distribution of the temperature on the vessel wall is non-uniform and time-varying, and this feature makes the convective coefficient variable. Methods This paper presents a realistic time-varying model in which h is a function of the temperature distribution at the vessel wall. The finite-element method (FEM was employed in order to model RF hepatic ablation. Two geometrical configurations were investigated. The RF electrode was placed at distances of 1 and 5 mm from a large vessel (10 mm diameter. Results When the ablation procedure takes longer than 1–2 min, the attained coagulation zone obtained with both time-varying h and constant h does not differ significantly. However, for short duration ablation (5–10 s and when the electrode is 1 mm away from the vessel, the use of constant h can lead to errors as high as 20% in the estimation of the coagulation zone. Conclusion For tumor ablation procedures typically lasting at least 5 min, this study shows that modeling the heat sink effect of large vessels by applying constant h as a boundary condition will yield precise results while reducing computational complexity. However, for other thermal therapies with shorter treatment using a time-varying h may be necessary.
Alireza Vejdani-Noghreiyan
2016-06-01
Full Text Available Introduction International Commission on Radiological Protection (ICRP has provided a comprehensive discussion on threshold dose for radiation-induced cataract in ICRP publication 116. Accordingly, various parts of the eye lens have different radio-sensitivities. Recently, some studies have been performed to develop a realistic eye model with the aim of providing accurate estimation of fluence-to-dose conversion coefficients for different parts of the eye. However, the effect of accommodation, which changes the lens shape and pupil size, on dose conversion coefficients has not been considered yet. In this study, we purport to develop an accommodation-dependent eye model and to study the effects of accommodation on the electron and proton fluence-to-dose conversion coefficients. Materials and Methods Herein, a modified eye model was developed by considering the effects of accommodation on the lens shape and pupil size. In addition, MCNPX 2.6 Monte Carlo transport code was used to calculate the effects of eye lens accommodation on electron and proton fluence-to-dose conversion coefficients. Results Calculation of dose conversion coefficients demonstrated that the accommodation causes up to 40% discrepancy for fluence-to-dose conversion coefficients of electrons in the range of 600 to 800 keV, which is due to the change of eye lens shape during the accommodation of the eye. Conclusion Since the accommodation of the eye change the lens shape and pupil size, it has considerable effect on fluence-to-dose conversion coefficients of electrons at some ranges of incident particle energies that should be considered in simulation. However, the fluctuation of dose conversion coefficients of protons is negligible.
Zhang, Yongcun; Shang, Shipeng; Liu, Shutian
2017-01-01
Asymptotic homogenization (AH) is a general method for predicting the effective coefficient of thermal expansion (CTE) of periodic composites. It has a rigorous mathematical foundation and can give an accurate solution if the macrostructure is large enough to comprise an infinite number of unit cells. In this paper, a novel implementation algorithm of asymptotic homogenization (NIAH) is developed to calculate the effective CTE of periodic composite materials. Compared with the previous implementation of AH, there are two obvious advantages. One is its implementation as simple as representative volume element (RVE). The new algorithm can be executed easily using commercial finite element analysis (FEA) software as a black box. The detailed process of the new implementation of AH has been provided. The other is that NIAH can simultaneously use more than one element type to discretize a unit cell, which can save much computational cost in predicting the CTE of a complex structure. Several examples are carried out to demonstrate the effectiveness of the new implementation. This work is expected to greatly promote the widespread use of AH in predicting the CTE of periodic composite materials.
Effect of hydrogen on stress corrosion cracking of copper
Li-jie QIAO
2008-01-01
The effects of hydrogen on electrochemical behavior and susceptibility of stress corrosion cracking (SCC) of pure copper were studied. SCC susceptibility of pure copper in a 1 M NaNO2 solution was increased by pre-charged hydrogen. The effect of hydrogen on the sus-ceptibility is more obvious in the low stress region due to the longer fracture time, which resulted in a longer time for more hydrogen to diffuse toward the crack tip. Synergistic effects of hydrogen and stress on corrosion and SCC pro-cesses were discussed. The results showed that an inter-action between stress and hydrogen at the crack tip could increase the anodic dissolution rate remarkably.
Zhou, Hong; Muellerleile, Paige; Ingram, Debra; Wong, Seok P.
2011-01-01
Intraclass correlation coefficients (ICCs) are commonly used in behavioral measurement and psychometrics when a researcher is interested in the relationship among variables of a common class. The formulas for deriving ICCs, or generalizability coefficients, vary depending on which models are specified. This article gives the equations for…
Zhou, Hong; Muellerleile, Paige; Ingram, Debra; Wong, Seok P.
2011-01-01
Intraclass correlation coefficients (ICCs) are commonly used in behavioral measurement and psychometrics when a researcher is interested in the relationship among variables of a common class. The formulas for deriving ICCs, or generalizability coefficients, vary depending on which models are specified. This article gives the equations for…
Sivaraja Subramania Pillai
2013-01-01
Full Text Available This study investigates the effect of flow velocity and building surface temperature effects on Convective Heat Transfer Coefficient (CHTC from urban building surfaces by numerical simulation. The thermal effects produced by geometrical and physical properties of urban areas generate a relatively differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI phenomena. The urban thermal comfort is directly related to the CHTC from the urban canopy surfaces. This CHTC from urban canopy surfaces expected to depend upon the wind velocity flowing over the urban canopy surfaces, urban canopy configurations, building surface temperature etc. But the most influential parameter on CHTC has not been clarified yet. Urban canopy type experiments in thermally stratified wind tunnel have normally been used to study the heat transfer issues. But, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary on individual canyon surfaces such as building roof, walls and ground. Numerical simulation validated by wind tunnel experiments can be an alternative for the prediction of CHTC from building surfaces in an urban area. In our study, wind tunnel experiments were conducted to validate the low-Reynolds-number k- ε model which was used for the evaluation of CHTC from surfaces. The calculated CFD results showed good agreement with experimental results. After this validation, the effects of flow velocity and building surface temperature effects on CHTC from urban building surfaces were investigated. It has been found that the change in velocity remarkably affects the CHTC from urban canopy surfaces and change in surface temperature has almost no effect over the CHTC from urban canopy surfaces.
Sivaraja Subramania Pillai
2013-06-01
Full Text Available This study investigates the effect of flow velocity and building surface temperature effects on Convective Heat Transfer Coefficient (CHTC from urban building surfaces by numerical simulation. The thermal effects produced by geometrical and physical properties of urban areas generate a relatively differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI phenomena. The urban thermal comfort is directly related to the CHTC from the urban canopy surfaces. This CHTC from urban canopy surfaces expected to depend upon the wind velocity flowing over the urban canopy surfaces, urban canopy configurations, building surface temperature etc. But the most influential parameter on CHTC has not been clarified yet. Urban canopy type experiments in thermally stratified wind tunnel have normally been used to study the heat transfer issues. But, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary on individual canyon surfaces such as building roof, walls and ground. Numerical simulation validated by wind tunnel experiments can be an alternative for the prediction of CHTC from building surfaces in an urban area. In our study, wind tunnel experiments were conducted to validate the low-Reynolds-number k-ε model which was used for the evaluation of CHTC from surfaces. The calculated CFD results showed good agreement with experimental results. After this validation, the effects of flow velocity and building surface temperature effects on CHTC from urban building surfaces were investigated. It has been found that the change in velocity remarkably affects the CHTC from urban canopy surfaces and change in surface temperature has almost no effect over the CHTC from urban canopy surfaces.
Zerr, R. Joseph; Azmy, Yousry [The Pennsylvania State University, University Park, PA (United States); Ouisloumen, Mohamed [Westinghouse Electric Company, LLC, Monroeville, PA (United States)
2008-07-01
Studies have been performed to test for significant gains in core design computational accuracy with the added implementation of direction-dependent diffusion coefficients. The DRAGON code was employed to produce two-group homogeneous B{sub 1} diffusion coefficients and direction-dependent diffusion coefficients with the TIBERE module. A three-dimensional diffusion model of a mini-core was analyzed with the resulting cross section data sets to determine if the multiplication factor or node power was noticeably altered with the more accurate representation of neutronic behaviour in a high-void configuration. Results indicate that using direction-dependent diffusion coefficients homogenized over an entire assembly do not produce significant differences in the results compared to the B{sub 1} counterparts and are much more computationally expensive. Direction-dependent diffusion coefficients that are specific to smaller micro-regions may provide more noteworthy gains in the accuracy of core design computations. (authors)
Effect of initial stress on reflection at the free surface of anisotropic elastic medium
M D Sharma
2007-12-01
The propagation of plane waves is considered in a general anisotropic elastic medium in the presence of initial stress. The Christoffel equations are solved into a polynomial of degree six. The roots of this polynomial represent the vertical slowness values for the six quasi-waves resulting from the presence of a discontinuity in the medium. Three of these six values are identified with the three quasi-waves traveling in the medium but away from its boundary. Reflection at the free plane surface is studied for partition of energy among the three reflected waves. For post-critical incidence, the reflected waves are inhomogeneous (evanescent) waves. Numerical examples are considered to exhibit the effects of initial stress on the phase direction, attenuation and reflection coefficients of the reflected waves. The phase velocities and energy shares of the reflected waves change significantly with initial stress as well as anisotropic symmetry. The presence of initial stress, however, has a negligible effect on the phase directions of reflected waves.
Stress profile in a two-dimensional silo: Effects induced by friction mobilization
Vivanco, Francisco; Mercado, José; Santibáñez, Francisco; Melo, Francisco
2016-08-01
The effects of friction mobilization on the stress profile within a two-dimensional silo are investigated via simulations of discrete elements. Friction mobilization is driven by cyclic vertical displacement of the sidewalls. Two regimes have been observed for small filling height, with stress profiles identified as saturated (Janssen's profile) and exponentially growing. The transition between these regimes is denoted by an almost linear stress profile, similar to that of a hydrostatic system, with a significantly greater characteristic height compared to the height of the column of grains. For tall columns, the process of friction inversion is more complex. A partial inversion of friction mobilization is observed when the motion is reversed from upward to downward, which results in two coexisting zones of opposite mobilization. These zones are separated by a wide compaction front with a gradual upward progression sustained by the displacement of the walls. Conversely, if the motion is reversed, the two opposing friction mobilization zones retract, the transition zone becomes smooth, and the system rapidly transforms from two coexisting mobilization states to a Janssen-like regime. In both regimes, the general characteristics from the resulting stress profiles are depicted by generalizing Janssen's equation to include partial mobilization through the varying effective friction coefficient along the silo walls.
Stress profile in a two-dimensional silo: Effects induced by friction mobilization.
Vivanco, Francisco; Mercado, José; Santibáñez, Francisco; Melo, Francisco
2016-08-01
The effects of friction mobilization on the stress profile within a two-dimensional silo are investigated via simulations of discrete elements. Friction mobilization is driven by cyclic vertical displacement of the sidewalls. Two regimes have been observed for small filling height, with stress profiles identified as saturated (Janssen's profile) and exponentially growing. The transition between these regimes is denoted by an almost linear stress profile, similar to that of a hydrostatic system, with a significantly greater characteristic height compared to the height of the column of grains. For tall columns, the process of friction inversion is more complex. A partial inversion of friction mobilization is observed when the motion is reversed from upward to downward, which results in two coexisting zones of opposite mobilization. These zones are separated by a wide compaction front with a gradual upward progression sustained by the displacement of the walls. Conversely, if the motion is reversed, the two opposing friction mobilization zones retract, the transition zone becomes smooth, and the system rapidly transforms from two coexisting mobilization states to a Janssen-like regime. In both regimes, the general characteristics from the resulting stress profiles are depicted by generalizing Janssen's equation to include partial mobilization through the varying effective friction coefficient along the silo walls.
Effect of yoga on academic performance in relation to stress
Kauts Amit
2009-01-01
Full Text Available Background: Academic performance is concerned with the quantity and quality of learning attained in a subject or group of subjects after a long period of instruction. Excessive stress hampers students′ performance. Improvement in academic performance and alertness has been reported in several yogic studies. Aims and Objectives: The main objective of the study was to assess the effect of yoga on academic performance in relation to stress. Materials and Methods: The study started with 800 adolescent students; 159 high-stress students and 142 low-stress students were selected on the basis of scores obtained through Stress Battery. Experimental group and control group were given pre test in three subjects, i.e., Mathematics, Science, and Social Studies. A yoga module consisting of yoga asanas, pranayama, meditation, and a value orientation program was administered on experimental group for 7 weeks. The experimental and control groups were post-tested for their performance on the three subjects mentioned above. Results: The results show that the students, who practiced yoga performed better in academics. The study further shows that low-stress students performed better than high-stress students, meaning thereby that stress affects the students′ performance.
The effects of yoga on anxiety and stress.
Li, Amber W; Goldsmith, Carroll-Ann W
2012-03-01
Stress and anxiety have been implicated as contributors to many chronic diseases and to decreased quality of life, even with pharmacologic treatment. Efforts are underway to find non-pharmacologic therapies to relieve stress and anxiety, and yoga is one option for which results are promising. The focus of this review is on the results of human trials assessing the role of yoga in improving the signs and symptoms of stress and anxiety. Of 35 trials addressing the effects of yoga on anxiety and stress, 25 noted a significant decrease in stress and/or anxiety symptoms when a yoga regimen was implemented; however, many of the studies were also hindered by limitations, such as small study populations, lack of randomization, and lack of a control group. Fourteen of the 35 studies reported biochemical and physiological markers of stress and anxiety, but yielded inconsistent support of yoga for relief of stress and anxiety. Evaluation of the current primary literature is suggestive of benefits of yoga in relieving stress and anxiety, but further investigation into this relationship using large, well-defined populations, adequate controls, randomization and long duration should be explored before recommending yoga as a treatment option.
Inoue, Gen; Kawase, Motoaki
2016-09-01
It is important to reduce the oxygen diffusion resistance through PEFC porous electrode, because it is the key to reduce the PEFC cost. However, the gas diffusion coefficient of CL is lower than MPL in spite of framework consisted of same carbon blacks. In this study, in order to understand the reasons of the lower gas diffusion performance of CL, the relationship between a carbon black agglomerate structure and ionomer adhesion condition is evaluated by a numerical analysis with an actual reconstructed structure and a simulated structure. As a result, the gas diffusion property of CL strongly depends on the ionomer adhesion shape. In the case of adhesion shape with the same curvature of ionomer interface, each pore can not be connected enough. So the pore tortuosity increases. Moreover, in the case of existence of inefficient large pores formed by carbon black agglomerate and ununiformly coated ionomer, the gas diffusion performance decrease rapidly. As the measurement values in actual CL are almost equal to that with model structure with inefficient large pores. These characteristics can be confirmed by actual cross-section image obtained by FIB-SEM.
The effect of music on the human stress response.
Myriam V Thoma
Full Text Available BACKGROUND: Music listening has been suggested to beneficially impact health via stress-reducing effects. However, the existing literature presents itself with a limited number of investigations and with discrepancies in reported findings that may result from methodological shortcomings (e.g. small sample size, no valid stressor. It was the aim of the current study to address this gap in knowledge and overcome previous shortcomings by thoroughly examining music effects across endocrine, autonomic, cognitive, and emotional domains of the human stress response. METHODS: Sixty healthy female volunteers (mean age = 25 years were exposed to a standardized psychosocial stress test after having been randomly assigned to one of three different conditions prior to the stress test: 1 relaxing music ('Miserere', Allegri (RM, 2 sound of rippling water (SW, and 3 rest without acoustic stimulation (R. Salivary cortisol and salivary alpha-amylase (sAA, heart rate (HR, respiratory sinus arrhythmia (RSA, subjective stress perception and anxiety were repeatedly assessed in all subjects. We hypothesized that listening to RM prior to the stress test, compared to SW or R would result in a decreased stress response across all measured parameters. RESULTS: The three conditions significantly differed regarding cortisol response (p = 0.025 to the stressor, with highest concentrations in the RM and lowest in the SW condition. After the stressor, sAA (p=0.026 baseline values were reached considerably faster in the RM group than in the R group. HR and psychological measures did not significantly differ between groups. CONCLUSION: Our findings indicate that music listening impacted the psychobiological stress system. Listening to music prior to a standardized stressor predominantly affected the autonomic nervous system (in terms of a faster recovery, and to a lesser degree the endocrine and psychological stress response. These findings may help better understanding the
The Effect of Music on the Human Stress Response
Thoma, Myriam V.; La Marca, Roberto; Brönnimann, Rebecca; Finkel, Linda; Ehlert, Ulrike; Nater, Urs M.
2013-01-01
Background Music listening has been suggested to beneficially impact health via stress-reducing effects. However, the existing literature presents itself with a limited number of investigations and with discrepancies in reported findings that may result from methodological shortcomings (e.g. small sample size, no valid stressor). It was the aim of the current study to address this gap in knowledge and overcome previous shortcomings by thoroughly examining music effects across endocrine, autonomic, cognitive, and emotional domains of the human stress response. Methods Sixty healthy female volunteers (mean age = 25 years) were exposed to a standardized psychosocial stress test after having been randomly assigned to one of three different conditions prior to the stress test: 1) relaxing music (‘Miserere’, Allegri) (RM), 2) sound of rippling water (SW), and 3) rest without acoustic stimulation (R). Salivary cortisol and salivary alpha-amylase (sAA), heart rate (HR), respiratory sinus arrhythmia (RSA), subjective stress perception and anxiety were repeatedly assessed in all subjects. We hypothesized that listening to RM prior to the stress test, compared to SW or R would result in a decreased stress response across all measured parameters. Results The three conditions significantly differed regarding cortisol response (p = 0.025) to the stressor, with highest concentrations in the RM and lowest in the SW condition. After the stressor, sAA (p=0.026) baseline values were reached considerably faster in the RM group than in the R group. HR and psychological measures did not significantly differ between groups. Conclusion Our findings indicate that music listening impacted the psychobiological stress system. Listening to music prior to a standardized stressor predominantly affected the autonomic nervous system (in terms of a faster recovery), and to a lesser degree the endocrine and psychological stress response. These findings may help better understanding the
The effect of music on the human stress response.
Thoma, Myriam V; La Marca, Roberto; Brönnimann, Rebecca; Finkel, Linda; Ehlert, Ulrike; Nater, Urs M
2013-01-01
Music listening has been suggested to beneficially impact health via stress-reducing effects. However, the existing literature presents itself with a limited number of investigations and with discrepancies in reported findings that may result from methodological shortcomings (e.g. small sample size, no valid stressor). It was the aim of the current study to address this gap in knowledge and overcome previous shortcomings by thoroughly examining music effects across endocrine, autonomic, cognitive, and emotional domains of the human stress response. Sixty healthy female volunteers (mean age = 25 years) were exposed to a standardized psychosocial stress test after having been randomly assigned to one of three different conditions prior to the stress test: 1) relaxing music ('Miserere', Allegri) (RM), 2) sound of rippling water (SW), and 3) rest without acoustic stimulation (R). Salivary cortisol and salivary alpha-amylase (sAA), heart rate (HR), respiratory sinus arrhythmia (RSA), subjective stress perception and anxiety were repeatedly assessed in all subjects. We hypothesized that listening to RM prior to the stress test, compared to SW or R would result in a decreased stress response across all measured parameters. The three conditions significantly differed regarding cortisol response (p = 0.025) to the stressor, with highest concentrations in the RM and lowest in the SW condition. After the stressor, sAA (p=0.026) baseline values were reached considerably faster in the RM group than in the R group. HR and psychological measures did not significantly differ between groups. Our findings indicate that music listening impacted the psychobiological stress system. Listening to music prior to a standardized stressor predominantly affected the autonomic nervous system (in terms of a faster recovery), and to a lesser degree the endocrine and psychological stress response. These findings may help better understanding the beneficial effects of music on the human body.
Rozin Kleiner, Ana Francisca; Galli, Manuela; Araujo do Carmo, Aline; Barros, Ricardo M L
2015-09-01
The aim of this study was to investigate the effect of flooring on barefoot gait according to age and gender. Two groups of healthy subjects were analyzed: the elderly adult group (EA; 10 healthy subjects) and the middle-aged group (MA; 10 healthy subjects). Each participant was asked to walk at his or her preferred speed over two force plates on the following surfaces: 1) homogeneous vinyl (HOV), 2) carpet, 3) heterogeneous vinyl (HTV) and 4) mixed (in which the first half of the pathway was covered by HOV and the second by HTV). Two force plates (Kistler 9286BA) embedded in the data collection room floor measured the ground reaction forces and friction. The required coefficient of friction (RCOF) was analyzed. For the statistical analysis, a linear mixed-effects model for repeated measures was performed. During barefoot gait, there were differences in the RCOF among the flooring types during the heel contact and toe-off phases. Due to better plantar proprioception during barefoot gait, the EA and MA subjects were able to distinguish differences among the flooring types. Moreover, when the EA were compared with the MA subjects, differences could be observed in the RCOF during the toe-off phase, and gender differences in the RCOF could also be observed during the heel contact phase in barefoot gait.
Bleakley, Bronwyn H; Brodie, Edmund D
2009-07-01
How and why cooperation evolves, particularly among nonrelatives, remains a major paradox for evolutionary biologists and behavioral ecologists. Although much attention has focused on fitness consequences associated with cooperating, relatively little is known about the second component of evolutionary change, the inheritance of cooperation or reciprocity. The genetics of behaviors that can only be expressed in the context of interactions are particularly difficult to describe because the relevant genes reside in multiple social partners. Indirect genetic effects (IGEs) describe the influence of genes carried in social partners on the phenotype of a focal individual and thus provide a novel approach to quantifying the genetics underlying interactions such as reciprocal cooperation. We used inbred lines of guppies and a novel application of IGE theory to describe the dual genetic control of predator inspection and social behavior, both classic models of reciprocity. We identified effects of focal strain, social group strain, and interactions between focal and group strains on variation in focal behavior. We measured psi, the coefficient of the interaction, which describes the degree to which an individual's phenotype is influenced by the phenotype of its social partners. The genetic identity of social partners substantially influences inspection behavior, measures of threat assessment, and schooling and does so in positively reinforcing manner. We therefore demonstrate strong IGEs for antipredator behavior that represent the genetic variation necessary for the evolution of reciprocity.
Kotzamanidis, S. T.; Lithourgidis, A. S.; Roupakias, D. G.
2009-07-01
The effect of plant density on the coefficient of variation (CV) for individual plant yield was studied in barley (Hordeum vulgare L.). An F2 population originating from the cross Niki x Carina was planted in three densities: high (51.32 plants m{sup -}2), intermediate (4.61 plants m{sup -}2), and low (1.15 plants m-2) using the honeycomb design. In each of the experiments, the most promising 15 plants were selected based on the individual plant yield. Progeny (F3) of the 30 plants selected from the intermediate and the low plant density were grown the following year in two experiments under an intermediate and low density. It was observed that in the F2 population the CV was reduced from 71 to 55% when the density reduced from 51.32 to 4.61 plants m{sup -}2, whereas the CV value was increased when the density was further reduced to 1.15 plants m{sup -}2. Similarly, the following year the CV was increased from 39 to 56% when the density was decreased from 4.61 to 1.15 plants m{sup -}2 in the F3 generation, and from 22 to 58% in the control. It was concluded that for barley an optimum plant density might exist under which the CV for individual plant yield is minimized and therefore the effectiveness of selection might be optimized. (Author)18 refs.
Effect of ground stress on hydraulic fracturing of methane well
DU Chun-zhi; MAO Xian-biao; MIAO Xie-xing; WANG Peng
2008-01-01
Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the permeability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) otherwise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with increasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.
Baert, Jan M; Janssen, Colin R; Sabbe, Koen; De Laender, Frederik
2016-08-18
Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity-ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity-productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity-productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions.
Effect of Stress on Transformer Insulation
Kapil Gandhi
2012-06-01
Full Text Available Power transformers use Kraft paper as insulation in the electrical windings present in the core, which is immersed in oil. In service, the temperature of the windings of core will go to 750C to 850C. If the transformer is over loaded, then the temperature can exceed upto 100°C causing the cellulose chains in the paper to cleave at an accelerated rate, which results in the degradation of mechanical strength and performance of the insulation. The Degree of Polymerization (DP will also decrease. If proper action will not take, this can lead to failure of the transformer and disruption to electricity supply and large economic losses to the operating utility. Transformer condition should be maintained because of its importance to electricity network. The life of transformer depends on the life of the oil impregnated paper insulation system to greater extent. Degradation of the cellulose insulation is an irreversible process. After thermal degradation of the paper winding, Furfuraldehyde (FFA is the chemical compound, which is released into the oil from paper. The concentration of FFA has been directly related to the condition of the paper insulation. In the present paper an experimental investigation has been made to evaluate the degradation of transformer oil contaminated by nano-particles of pine wood under accelerated thermal and electrical stress and results are correlated with breakdown strength, density & interfacial tension of the pure oil. The contaminated oil samples are tested at electric stress of 2.0 kV, 3.0 kV, 4.0 kV & 5.0 kV for 24, 48, 72 & 96 hours simultaneously.
Effect of stress on semen quality in semen donors.
Poland, M L; Giblin, P T; Ager, J W; Moghissi, K S
1986-01-01
Fifty-three donors with good semen quality were studied monthly for sperm count and motility over 9 to 22 months. Medical students (n = 31) in freshman and sophomore years subjected to the stress of twice-yearly examinations were compared with nonstudents (n = 22) not exposed to common stressful periods. Sperm count and quality (count X motility) for the student group were significantly elevated during examination months versus nonexamination months. Controls demonstrated no differences over these months. Differences between individuals, donor selection factors, and the effects of variable degrees of stress on sperm transport may have contributed to this finding.
M. A. Habib
2013-01-01
Full Text Available Boiler swing rate, which is the rate at which the boiler load is changed, has significant influence on the parameters of the boiler operating conditions such as drum water pressure and level, steam quality in the riser tubes, wall temperatures of riser tubes, and the associated thermal stresses. In this paper, the thermal stresses developed in boiler tubes due to elevated rates of heat transfer and friction are presented versus thermal stresses developed in tubes operated under normal conditions. The differential equations comprising the nonlinear model and governing the flow inside the boiler tubes were formulated to study different operational scenarios in terms of resulting dynamic response of critical variables. The experimental results and field data were obtained to validate the present nonlinear dynamic model. The calculations of the heat flux and the allowable steam quality were used to determine the maximum boiler swing rates at different conditions of riser tube of friction factor and heat flux. Diagrams for the influence of friction factor of the boiler tubes and the heat flux, that the tube is subjected to, on the maximum swing rate were examined.
Litjens, Geert J S; Hambrock, Thomas; Hulsbergen-van de Kaa, Christina; Barentsz, Jelle O; Huisman, Henkjan J
2012-10-01
To determine the interpatient variability of prostate peripheral zone (PZ) apparent diffusion coefficient (ADC) and its effect on the assessment of prostate cancer aggressiveness. The requirement for institutional review board approval was waived. Intra- and interpatient variation of PZ ADCs was determined by means of repeated measurements of normal ADCs at three magnetic resonance (MR) examinations in a retrospective cohort of 10 consecutive patients who had high prostate-specific antigen levels and negative findings at transrectal ultrasonographically-guided biopsy. In these patients, no signs of PZ cancer were found at all three MR imaging sessions. The effect of interpatient variation on the assessment of prostate cancer aggressiveness was examined in a second retrospective cohort of 51 patients with PZ prostate cancer. Whole-mount step-section pathologic evaluation served as reference standard for placement of regions of interest on tumors and normal PZ. Repeated-measures analysis of variance was used to determine the significance of the interpatient variations in ADCs. Linear logistic regression was used to assess whether incorporating normal PZ ADCs improves the prediction of cancer aggressiveness. Analysis of variance revealed that interpatient variability (1.2-2.0×10(-3) mm2/sec) was significantly larger than measurement variability (0.068×10(-3) mm2/sec±0.027 [standard deviation]) (P=.0058). Stand-alone tumor ADCs showed an area under the receiver operating characteristic curve (AUC) of 0.91 for discriminating low-grade versus high-grade tumors. Incorporating normal PZ ADC significantly improved the AUC to 0.96 (P=.0401). PZ ADCs show significant interpatient variation, which has a substantial effect on the prediction of prostate cancer aggressiveness. Correcting this effect results in a significant increase in diagnostic accuracy. © RSNA, 2012.
HU Guixian; SONG Mingshi
1991-01-01
In this paper a new relation between the second virial coefficients A2, Mw and (dVes/dC)c→0=Ks was derived from proposed model theory of concentration effects in GPC for mono- and poly-dispersed polymers. Based on this relation a new method for determination of second virial coefficients from the combination of (dVes/dC)c→ 0=Ks ,Mw and KH measurements was proposed.The values of A2 for mono-and poly-dispersed polystyrenes with molecular weight range from 104 to 106 in good and theta solvents were determined by proposed method. Results show that their values of A2 are in agreement with those obtained by light scattering.
Effect of yoga on academic performance in relation to stress
Kauts Amit; Sharma Neelam
2009-01-01
Background: Academic performance is concerned with the quantity and quality of learning attained in a subject or group of subjects after a long period of instruction. Excessive stress hampers students′ performance. Improvement in academic performance and alertness has been reported in several yogic studies. Aims and Objectives: The main objective of the study was to assess the effect of yoga on academic performance in relation to stress. Materials and Methods: The study started ...
Effects of external stress on defect complexes in semiconductors
Tessema, Genene [Department of Physics, Addis Ababa University, PO Box 1176, Addis Ababa (Ethiopia); Helmholtz-Institut fuer Strahlen und Kernphysik, Nussalle 14-16, 53115 Bonn (Germany)
2007-07-04
Crystal field gradients that exist at lattice sites in solids depend on the symmetry of charge distribution around atomic sites. The charge symmetry could be broken either by the presence of impurity complexes in the host matrix or by external stress on the samples, which leads to an observable magnitude of electric field gradients (EFGs). The perturbed {gamma}-{gamma} angular correlation (PAC) method is employed here to investigate the effect of uniaxial stress on {sup 111}Cd sites in crystalline doped semiconductors.
... diabetes. Shopdiabetes.org: Your Stress-Free System for Family Dinners! - 2017-03-book-oclock-scramble.html Shopdiabetes.org Your Stress-Free System for Family Dinners! A year of delicious meals to help prevent ...
Pawlak, M., E-mail: mpawlak@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5/7, Toruń (Poland); Maliński, M. [Department of Electronics and Computer Science, Koszalin University of Technology, 2 Śniadeckich St., Koszalin 75-453 (Poland)
2015-01-10
Highlights: • The new method of determination of the effective infrared absorption coefficient is presented. • The method can be used for transparent samples for the excitation radiation. • The effect of aluminum foil on the PTR signal in a transmission configuration is discussed. - Abstract: In this paper we propose a new procedure of simultaneous estimation of the effective infrared optical absorption coefficient and the thermal diffusivity of solid state samples using the photothermal infrared radiometry method in the transmission configuration. The proposed procedure relies on the analysis of the frequency dependent signal obtained from the samples covered with thin aluminum foil. This method can be applied for both optically opaque and transparent samples. The proposed method is illustrated with the results of the thermal diffusivity and the effective IR absorption coefficient obtained for several Cd{sub 1−x}Mg{sub x}Se crystals.
The Effects of Stress on Physical Activity and Exercise
Stults-Kolehmainen, Matthew A.; Sinha, Rajita
2013-01-01
Background Psychological stress and physical activity (PA) are believed to be reciprocally related; however, most research examining the relationship between these constructs is devoted to the study of exercise and/or PA as an instrument to mitigate distress. Objective The aim of this paper was to review the literature investigating the influence of stress on indicators of PA and exercise. Methods A systematic search of Web of Science, Pub-Med, and SPORTDiscus was employed to find all relevant studies focusing on human participants. Search terms included “stress”, “exercise”, and “physical activity”. A rating scale (0–9) modified for this study was utilized to assess the quality of all studies with multiple time points. Results The literature search found 168 studies that examined the influence of stress on PA. Studies varied widely in their theoretical orientation and included perceived stress, distress, life events, job strain, role strain, and work–family conflict but not lifetime cumulative adversity. To more clearly address the question, prospective studies (n = 55) were considered for further review, the majority of which indicated that psychological stress predicts less PA (behavioral inhibition) and/or exercise or more sedentary behavior (76.4 %). Both objective (i.e., life events) and subjective (i.e., distress) measures of stress related to reduced PA. Prospective studies investigating the effects of objective markers of stress nearly all agreed (six of seven studies) that stress has a negative effect on PA. This was true for research examining (a) PA at periods of objectively varying levels of stress (i.e., final examinations vs. a control time point) and (b) chronically stressed populations (e.g., caregivers, parents of children with a cancer diagnosis) that were less likely to be active than controls over time. Studies examining older adults (>50 years), cohorts with both men and women, and larger sample sizes (n > 100) were more likely
The effects of stress on singing voice accuracy.
Larrouy-Maestri, Pauline; Morsomme, Dominique
2014-01-01
The quality of a music performance can be lessened or enhanced if the performer experiences stressful conditions. In addition, the quality of a sung performance requires control of the fundamental frequency of the voice, which is particularly sensitive to stress. The present study aimed to clarify the effects of stress on singing voice accuracy. Thirty-one music students were recorded in a stressful condition (ie, a music examination) and a nonstressful condition. Two groups were defined according to the challenge level of the music examination (first and second music levels). Measurements were made by self-reported state anxiety (CSAI-2R questionnaire) and by observing heart rate activity (electrocardiogram) during each performance. In addition, the vocal accuracy of the sung performances was objectively analyzed. As expected, state anxiety and heart rate were significantly higher on the day of the music examination than in the nonstressful condition for all the music students. However, the effect of stress was positive for the first-year students but negative for the second-year students, for whom the music examination was particularly challenging. In addition, highly significant correlations were found between the intensity of cognitive symptoms and the vocal accuracy criteria. This study highlights the contrasting effects of stress on singing voice accuracy but also the need to consider the challenge level and perception of the symptoms in experimental and pedagogical settings. Copyright © 2014 The Voice Foundation. Published by Mosby, Inc. All rights reserved.
Stress effects on memory: an update and integration.
Schwabe, Lars; Joëls, Marian; Roozendaal, Benno; Wolf, Oliver T; Oitzl, Melly S
2012-08-01
It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in particular catecholamine and glucocorticoid, actions are taken into account. Integrating two popular models, we argue here that rapid catecholamine and non-genomic glucocorticoid actions interact in the basolateral amygdala to shift the organism into a 'memory formation mode' that facilitates the consolidation of stressful experiences into long-term memory. The undisturbed consolidation of these experiences is then promoted by genomic glucocorticoid actions that induce a 'memory storage mode', which suppresses competing cognitive processes and thus reduces interference by unrelated material. Highlighting some current trends in the field, we further argue that stress affects learning and memory processes beyond the basolateral amygdala and hippocampus and that stress may pre-program subsequent memory performance when it is experienced during critical periods of brain development.
Effects of Simulation on Nursing Student Stress: An Integrative Review.
Cantrell, Melody L; Meyer, Susan L; Mosack, Victoria
2017-03-01
The effects of stress on nursing students' health and learning is important to educators. The purpose of this review was to critically integrate the literature related to the stress that nursing students experience regarding high-fidelity simulation (HFS). Literature from multiple search engines and databases was systematically searched. Keywords and Boolean combinations included nursing students, simulation, stress, anxiety, and self-efficacy. Qualitative or quantitative studies published in English between 2010 and 2015 and studies including the effects of simulation on nursing student anxiety and stress were included. Seventeen studies were chosen. Overall, students reported either moderate or high stress associated with simulation, but they rated the HFS experience as a valuable learning tool. This review demonstrated student acceptance of simulation as a learning strategy. However, more high-quality studies are needed to investigate techniques that can be implemented to decrease the negative effects of simulation stress on nursing students. [J Nurs Educ. 2017;56(3):139-144.]. Copyright 2017, SLACK Incorporated.
Mechanical behavior and stress effects in hard superconductors: a review
Koch, C. C.; Easton, D. S.
1977-11-01
The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys niobium-titanium and niobium-zirconium exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2/sup 0/K revealed serrated stress-strain curves, nonlinear elastic effects and reduced ductility. The nonlinear behavior is probably due to twinning and detwinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb/sub 3/Sn and V/sub 3/Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are generally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapor deposited on high strength carbon fibers are presented. Hysteretic stress-strain behavior in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in the performance of high field magnets. Measurements of the critical current density, J/sub c/, under stress in a magnetic field are reported. Modest stress-reversible degradation in J/sub c/ was observed in niobium-titanium composites, while more serious degradation was found in Nb/sub 3/Sn samples. The importance of mechanical behavior to device performance is discussed.
Morales-Acevedo, Arturo [CINVESTAV del IPN, Electrical Engineering Department, Avenida IPN No. 2508, 07360 Mexico, D. F. (Mexico)
2009-01-15
A simple model for the generation of carriers by photons incident on a (linearly) decreasing band-gap material, such as has been described in recent CIGS solar cells, is developed. The model can be generalized for different cases such as increasing band-gap grading or for having a more complex band-gap profile. The model developed for direct band semiconductors such as CIGS or AlGaAs allows us to define an effective absorption coefficient, so that the ideal photocurrent density can be calculated in a similar manner as for solar cells with non-graded band-gap materials. We show that this model gives completely different results as those expected from intuitive approaches for calculating this ideal photocurrent density. We also show that grading of the band-gap of the absorbing material in solar cells makes the photocurrent less sensitive to the total band-gap change, in such a way that the design of the band-gap variation can be more flexible in order to have other advantages such as higher built-in voltage or higher back surface field in the device structure. (author)
Musammil, N M; Porsezian, K; Subha, P A; Nithyanandan, K
2017-02-01
We investigate the dynamics of vector dark solitons propagation using variable coefficient coupled nonlinear Schrödinger (Vc-CNLS) equation. The dark soliton propagation and evolution dynamics in the inhomogeneous system are studied analytically by employing the Hirota bilinear method. It is apparent from our asymptotic analysis that the collision between the dark solitons is elastic in nature. The various inhomogeneous effects on the evolution and interaction between dark solitons are explored, with a particular emphasis on nonlinear tunneling. It is found that the tunneling of the soliton depends on a condition related to the height of the barrier and the amplitude of the soliton. The intensity of the tunneling soliton either forms a peak or a valley, thus retaining its shape after tunneling. For the case of exponential background, the soliton tends to compress after tunneling through the barrier/well. Thus, a comprehensive study of dark soliton pulse evolution and propagation dynamics in Vc-CNLS equation is presented in the paper.
Spelling-stress regularity effects are intact in developmental dyslexia.
Mundy, Ian R; Carroll, Julia M
2013-01-01
The current experiment investigated conflicting predictions regarding the effects of spelling-stress regularity on the lexical decision performance of skilled adult readers and adults with developmental dyslexia. In both reading groups, lexical decision responses were significantly faster and significantly more accurate when the orthographic structure of a word ending was a reliable as opposed to an unreliable predictor of lexical stress assignment. Furthermore, the magnitude of this spelling-stress regularity effect was found to be equivalent across reading groups. These findings are consistent with intact phoneme-level regularity effects also observed in dyslexia. The paper discusses how findings of intact spelling-sound regularity effects at both prosodic and phonemic levels, as well as other similar results, can be reconciled with the obvious difficulties that people with dyslexia experience in other domains of phonological processing.
Effects of chronic stress on sleep in rats.
Kant, G J; Pastel, R H; Bauman, R A; Meininger, G R; Maughan, K R; Robinson, T N; Wright, W L; Covington, P S
1995-02-01
The present study was conducted to determine the effects of chronic stress on sleep using a rodent paradigm of around-the-clock signalled intermittent foot shock in which some rats can pull a chain to avoid/escape shock while another group of rats is yoked to the first group. We measured sleep using telemetry; four-channel EEG was collected 24 h/day in rats during 2 prestress days; days 1, 2, 3, 7, and 14 during chronic stress; and 3 poststress days. States of REM sleep, non-REM (NREM) sleep, and waking were scored for each 15-s period of the EEG recordings. During the prestress period, rats slept (REM plus NREM) 55% of available time during the light hours and 34% of the dark hours with the remainder represented by waking. On the first day of stress, total sleep and, especially REM sleep, decreased markedly. By the second day of stress, only REM sleep in the controllable stress group (but not the uncontrollable stress group) was still significantly decreased compared to prestress levels, and REM sleep returned to baseline levels by day 7 of stress. The recovery of sleep quantity was accomplished by increased sleep during the dark hours, resulting in a long-lasting disruption of normal circadian sleep patterning.
Straka, A. M.; Schijf, J.
2010-12-01
organic ligand released, as monitored by DOC concentrations, is nearly identical in each case. All sorption edges were satisfactorily modeled with an appropriate pH-dependent complexation model. At 0.05 M ionic strength, distribution coefficients calculated from the 0.22 μm filtrates show an unexpected inversion around pH 5 to decreasing sorption with increasing pH, most prominently for the MREEs, clearly reflecting the erroneous omission of YREE colloids from the particulate fraction. This feature could be completely reversed by using the modeled colloidal contributions to correct the measurements. A similar correction of the 0.5 and 5.0 M data revealed a more insidious effect on both absolute and relative distribution coefficients that was not otherwise apparent from their pH-dependent behavior. Failure to account for colloid-bound metals can ostensibly lead to a substantial misinterpretation of experimental results, an issue that is not sufficiently acknowledged or addressed in many metal sorption studies.
Asymmetric effect of mechanical stress on the forward and reverse reaction catalyzed by an enzyme.
Collin Joseph
Full Text Available The concept of modulating enzymatic activity by exerting a mechanical stress on the enzyme has been established in previous work. Mechanical perturbation is also a tool for probing conformational motion accompanying the enzymatic cycle. Here we report measurements of the forward and reverse kinetics of the enzyme Guanylate Kinase from yeast (Saccharomyces cerevisiae. The enzyme is held in a state of stress using the DNA spring method. The observation that mechanical stress has different effects on the forward and reverse reaction kinetics suggests that forward and reverse reactions follow different paths, on average, in the enzyme's conformational space. Comparing the kinetics of the stressed and unstressed enzyme we also show that the maximum speed of the enzyme is comparable to the predictions of the relaxation model of enzyme action, where we use the independently determined dissipation coefficient [Formula: see text] for the enzyme's conformational motion. The present experiments provide a mean to explore enzyme kinetics beyond the static energy landscape picture of transition state theory.
The impact of stress on tumor growth: peripheral CRF mediates tumor-promoting effects of stress
Stathopoulos Efstathios N
2010-09-01
effect. Moreover, antalarmin suppressed neoangiogenesis in 4T1 tumors in vivo. Conclusion This is the first report demonstrating that peripheral CRF, at least in part, mediates the tumor-promoting effects of stress and implicates CRF in SMAD2 and β-catenin expression.
Stress and Incongruity Theory: Effects of Crowding,
1981-01-01
Nogami, G. Y. Crowding: Effects of group size, room size or density. Journal of Applied Social Psychology , 1976, 6, 105-125. Osgood, C. E. and...perceived control and behavioral effects. Journal of Applied Social Psychology , 1974, 4, 171-186. -43- Sommer, R. Personal space: The behavioral
Antidepressant and anti-stress effects of curcumin inmice
YingXU; Bao-shanKU; Hai-yanYAO; Yong-heZHANG; Xue-junLI
2004-01-01
Curcumin (diferuloylmethane), a yellow colouring agent contained in the rhizome of Curcuma Longa (turmeric), has a wide array of pharmacological and biological activities, such as antioxidant, anti-inflammatory, immunomodulating and anticarcinogenic effects. In this study, curcumin was examined for the antidepressant and anti-stress effects in forced swimming,
Protracted effects of chronic stress on serotonin dependent thermoregulation
Natarajan, Reka; Northrop, Nicole A.; Yamamoto, Bryan K.
2016-01-01
Chronic stress is known to affect serotonin (5HT) neurotransmission in the brain and to alter body temperature. Body temperature is controlled in part, by the medial preoptic area of the hypothalamus (mPOA). To investigate the effect of chronic stress on 5HT and how it affects body temperature regulation, we examined whether exposure to a chronic unpredictable stress paradigm (CUS) produces long-term alterations in thermoregulatory function of the mPOA through decreased 5HT neurotransmission. Adult male Sprague-Dawley rats underwent 21 days of CUS. Four days after last stress exposure, basal body temperature in the home cage and body temperature in a cold room maintained at 10°C were recorded. CUS rats had significantly higher subcutaneous basal body temperature at 13:00 h compared to unstressed (NoStress) rats. Whereas the NoStress rats were able to significantly elevate body temperature from basal levels at 30 and 60 min of exposure to the cold room, the CUS rats showed a hypothermic response to the cold. Treatment during CUS with metyrapone, a corticosterone synthesis inhibitor, blocked stress-induced decrease in body temperature in response to the cold challenge. CUS also decreased 5HT transporter protein immunoreactivity in the mPOA and 5HT2A/C agonist injection into the mPOA after CUS exposure caused stressed rats to exhibit a sensitized hyperthermic response to cold. These results indicate that CUS induced changes to the 5HTergic system alters mPOA function in thermoregulation. These findings help explain mechanisms underlying chronic stress induced disorders such as chronic fatigue syndrome wherein long lasting thermoregulatory deficits are observed. PMID:26414686
Protracted effects of chronic stress on serotonin-dependent thermoregulation.
Natarajan, Reka; Northrop, Nicole A; Yamamoto, Bryan K
2015-01-01
Chronic stress is known to affect serotonin (5HT) neurotransmission in the brain and to alter body temperature. The body temperature is controlled in part, by the medial preoptic area (mPOA) of the hypothalamus. To investigate the effect of chronic stress on 5HT and how it affects body temperature regulation, we examined whether exposure to a chronic unpredictable stress (CUS) paradigm produces long-term alterations in thermoregulatory function of the mPOA through decreased 5HT neurotransmission. Adult male Sprague-Dawley rats underwent 21 d of CUS. Four days after the last stress exposure, basal body temperature in the home cage and body temperature in a cold room maintained at 10 °C were recorded. The CUS rats had significantly higher subcutaneous basal body temperature at 13:00 h compared to unstressed (NoStress) rats. Whereas the NoStress rats were able to significantly elevate body temperature from basal levels at 30 and 60 min of exposure to the cold room, the CUS rats showed a hypothermic response to the cold. Treatment during CUS with metyrapone, a corticosterone synthesis inhibitor, blocked stress-induced decrease in body temperature in response to the cold challenge. CUS also decreased 5HT transporter protein immunoreactivity in the mPOA and 5HT2A/C agonist injection into the mPOA after CUS exposure caused stressed rats to exhibit a sensitized hyperthermic response to cold. These results indicate that the CUS induced changes to the 5HTergic system alter mPOA function in thermoregulation. These findings help us to explain the mechanisms underlying chronic stress-induced disorders such as chronic fatigue syndrome wherein long lasting thermoregulatory deficits are observed.
Heat Stress on Poultry: Metabolism, Effects and Efforts to Overcome
Mohammad Hasil Tamzil
2014-06-01
Full Text Available Poultry industries in the tropics are challenged by high ambient temperatures and humidities which cause poultry suffer from heat stress. Heat stress contributes to the instability of certain compounds, such as enzymes. Consequently the enzymes function reduces. Affecting the physiological and hormonal conditions of the poultry. In such condition, the body will attempt to restore homeostasis to the state before it happened. When physiological failed to meet the condition, the body will use the genetic pathway by activating Heat Shock Protein (HSP genes to protect proteins which are sensitive to high temperatures. Heat stress in poultry triggers the emergence of various diseases and affects the growth of poultry and egg production. These negative effects on poultry can be minimized by selecting the type of chickens which are tolerant to high ambient temperature, modifying microclimates of cages and adding anti-stress compounds through feed and or drink.
dos Reis, Ralpho Rinaldo; Sampaio, Silvio César; de Melo, Eduardo Borges
2013-10-01
Collecting data on the effects of pesticides on the environment is a slow and costly process. Therefore, significant efforts have been focused on the development of models that predict physical, chemical or biological properties of environmental interest. The soil sorption coefficient normalized to the organic carbon content (Koc) is a key parameter that is used in environmental risk assessments. Thus, several log Koc prediction models that use the hydrophobic parameter log P as a descriptor have been reported in the literature. Often, algorithms are used to calculate the value of log P due to the lack of experimental values for this property. Despite the availability of various algorithms, previous studies fail to describe the procedure used to select the appropriate algorithm. In this study, models that correlate log Koc with log P were developed for a heterogeneous group of nonionic pesticides using different freeware algorithms. The statistical qualities and predictive power of all of the models were evaluated. Thus, this study was conducted to assess the effect of the log P algorithm choice on log Koc modeling. The results clearly demonstrate that the lack of a selection criterion may result in inappropriate prediction models. Seven algorithms were tested, of which only two (ALOGPS and KOWWIN) produced good results. A sensible choice may result in simple models with statistical qualities and predictive power values that are comparable to those of more complex models. Therefore, the selection of the appropriate log P algorithm for modeling log Koc cannot be arbitrary but must be based on the chemical structure of compounds and the characteristics of the available algorithms.
Schmedes, Sarah; Marshall, Pamela; King, Jonathan L; Budowle, Bruce
2013-07-01
Various types of biological samples present challenges for extraction of DNA suitable for subsequent molecular analyses. Commonly used extraction methods, such as silica membrane columns and phenol-chloroform, while highly successful may still fail to provide a sufficiently pure DNA extract with some samples. Synchronous coefficient of drag alteration (SCODA), implemented in Boreal Genomics' Aurora Nucleic Acid Extraction System (Boreal Genomics, Vancouver, BC), is a new technology that offers the potential to remove inhibitors effectively while simultaneously concentrating DNA. In this initial study, SCODA was tested for its ability to remove various concentrations of forensically and medically relevant polymerase chain reaction (PCR) inhibitors naturally found in tissue, hair, blood, plant, and soil samples. SCODA was used to purify and concentrate DNA from intentionally contaminated DNA samples containing known concentrations of hematin, humic acid, melanin, and tannic acid. The internal positive control (IPC) provided in the Quantifiler™ Human DNA Quantification Kit (Life Technologies, Foster City, CA) and short tandem repeat (STR) profiling (AmpFℓSTR® Identifiler® Plus PCR Amplification Kit; Life Technologies, Foster City, CA) were used to measure inhibition effects and hence purification. SCODA methodology yielded overall higher efficiency of purification of highly contaminated samples compared with the QIAquick® PCR Purification Kit (Qiagen, Valencia, CA). SCODA-purified DNA yielded no cycle shift of the IPC for each sample and yielded greater allele percentage recovery and relative fluorescence unit values compared with the QIAquick® purification method. The Aurora provided an automated, minimal-step approach to successfully remove inhibitors and concentrate DNA from challenged samples.
Stress effects on coarticulation in English and Greek
Koenig, Laura; Okalidou, Areti
2003-04-01
The effects of stress on production variability and V-to-V coarticulation were compared in American English and Greek, two languages which differ in vowel inventory size and in the magnitude of V-to-V coarticulation (Okalidou and Koenig, 1999). Six speakers, one male and two females from each language, were recorded producing nonsense VCV utterances in a carrier phrase, with randomly alternating stress. The Greek stimuli included all five vowels of the language; the English stimuli included the closest counterparts of the Greek vowels. The medial plosive consonants alternated between the bilabial and alveolar place of articulation, yielding different degrees of coarticulatory resistance (Recasens, 1985, 1989). Plosives were chosen to have similar VOT values across languages in order to minimize duration effects. A comparison of stressed versus unstressed vowel areas reveals significant differences across languages. Specific vowel effects and language effects are also noted with respect to changes in production variability under the stressed versus unstressed conditions. The magnitude of V-to-V influences as a function of stress and position is discussed in terms of the above crosslinguistic comparison in order to obtain further insight on the coarticulatory behavior of languages which differ in the size of vowel inventory (Manuel and Krakow, 1984).
Stress Effects on Stop Bursts in Five Languages
Marija Tabain
2016-11-01
Full Text Available This study examines the effects of stress on the stop burst in five languages differing in number of places of articulation, as reflected in burst duration, spectral centre of gravity, and spectral standard deviation. The languages studied are English (three places of articulation /p t k/, the Indonesian language Makasar (four places /p t c k/, and the Central Australian languages Pitjantjatjara, Warlpiri (both five places /p t ʈ c k/, and Arrernte (six places /p t̪ t ʈ c k/. We find that languages differ in how they manifest stress on the consonant, with Makasar not showing any effect of stress at all, and Warlpiri showing an effect on burst duration, but not on the spectral measures. For the other languages, the velar /k/ has a “darker” quality (i.e., lower spectral centre of gravity, and/or a less diffuse spectrum (i.e., lower standard deviation under stress; while the alveolar /t/ has a “lighter” quality under stress. In addition, the dental /t̪/ has a more diffuse spectrum under stress. We suggest that this involves enhancement of the features [grave] and [diffuse] under stress, with velars being [+grave] and [–diffuse], alveolars being [–grave], and dentals being [+diffuse]. We discuss the various possible spectral effects of enhancement of these features. Finally, in the languages with five or six places of articulation, the stop burst is longer only for the palatal /c/ and the velar /k/, which have intrinsically long burst durations, and not for the anterior coronals /t̪ t ʈ/, which have intrinsically short burst durations. We suggest that in these systems, [burst duration] is a feature that separates these two groups of consonants.
Bai, Gang; Xie, Qiyun; Liu, Zhiguo; Wu, Dongmei
2015-08-01
A nonlinear thermodynamic formalism has been proposed to calculate the physical properties of the epitaxial SrTiO3 films containing vertical nano-pillar array on Si-substrate. The out-of-plane stress induced by the mismatch between film and nano-pillars provides an effective way to tune the physical properties of ferroelectric SrTiO3 films. Tensile out-of-plane stress raises the phase transition temperature and increases the out-of-plane polarization, but decreases the out-of-plane dielectric constant below Curie temperature, pyroelectric coefficient, and piezoelectric coefficient. These results showed that by properly controlling the out-of-plane stress, the out-of-plane stress induced paraelectric-ferroelectric phase transformation will appear near room temperature. Excellent dielectric, pyroelectric, piezoelectric properties of these SrTiO3 films similar to PZT and other lead-based ferroelectrics can be expected.
Effectiveness of stress management training on stress reduction in pregnant women
Mahboobeh Shirazi
2016-10-01
.1 for moderated level stress (P= 0.001 and 40.1 to 16.6 for high level of stress (P= 0.0001 respectively. Conclusion: First trimester of pregnancy is a crucial stage of fetal growth and development. Based on our findings, stress management training in this period has beneficial effects on stress reduction and enhances maternal health status.
Siavash TABATABAEIAN; Masoud MIRZAEI; Asghar SADIGHZADEH; Vahid DAMIDEH; Abdollah SHADARAM
2012-01-01
In this paper,the effects of the existence of plasma actuator electrodes and also various configurations of the actuator for controlling the flow field around a circular cylinder are experimentally investigated.The cylinder is made of PVC (Polyvinyl Chloride) and considered as a dielectric barrier.Two electrodes are flush-mounted on the surface of the cylinder and are connected to a DC high voltage power supply for generation of electrical discharge.Pressure distribution results show that the existence of the electrodes and also the plasma are able to change the pressure distribution around the cylinder and consequently the lift and drag coefficients.It is found that the effect of the existence of the electrodes is comparable with the effect of plasma actuator in controlling the flow field around the cylinder and this effect is not reported by other researchers.Eventually it is concluded that the existence of the electrodes or any extra objects on the cylinder and also the existence of the plasma are capable of changing the flow field structure around the cylinder so that the behavior of the lift and drag coefficients of the cylinder will be changed significantly.
Drabik, Dominik; Przybyło, Magda; Sikorski, Aleksander; Langner, Marek
2016-03-01
Fluorescence Correlation Spectroscopy (FCS) is a technique, which allows determination of the diffusion coefficient and concentration of fluorescent objects suspended in the solution. The measured parameter is the fluctuation of the fluorescence signal emitted by diffusing molecules. When 100 nm DOPC vesicles labeled with various fluorescent dyes (Fluorescein-PE, NBD-PE, Atto488 DOPE or βBodipy FL) were measured, different values of diffusion coefficients have been obtained. These diffusion coefficients were different from the expected values measured using the dynamic light scattering method (DLS). The FCS was initially developed for solutions containing small fluorescent molecules therefore the observed inconsistency may result from the nature of vesicle suspension itself. The duration of the fluorescence signal may depend on the following factors: the exposure time of the labeled object to the excitation beam, the photo-physical properties (e.g., stability) of a fluorophore, the theoretical model used for the calculations of the diffusion coefficient and optical properties of the vesicle suspension. The diffusion coefficients determined for differently labeled liposomes show that its dependence on vesicle size and quantity of fluorescent probed used for labeling was significant demonstrating that the fluorescence properties of the fluorophore itself (bleaching and/or blinking) were critical factors for a correct outcome of FCS experiment. The new, based on combined FCS and DLS measurements, method for the determination of the focal volume prove itself to be useful for the evaluation of a fluorescence dye with respect to its applicability for FCS experiment.
Nasresfahani, Mohammad Reza; Niroumand, Behzad; Kermanpur, Ahmad; Raeissi, Mehdi
2016-09-01
Modification of solidification structures by applying electric current has been the subject of interest in recent years. However, the exact relationships between the dendrite growth parameters and the current density are not yet clear. The dendrite tip geometry is an important growth parameter which can be characterized using the dendrite tip radius and the universal amplitude coefficient. In this paper, the dendrite tip shape was investigated in the absence and presence of an electric field using a transparent model material, i.e. the succinonitrile-acetone alloy. The results showed that both dendrite tip radius and universal amplitude coefficient increased by increasing the applied current density. The increase in the tip radius was attributed to the Joule heat produced at the solid-liquid interface which reduced the interface undercooling. The increase in the universal amplitude coefficient was postulated to be due to the changes in the distribution coefficient of the alloy system which would result in higher solute concentration in front of the solid-liquid interface. Owing to the increased universal amplitude coefficient, more prominent dendritic fins were observed at dendrites tips under electric current.
Shahram Hashemnia
2014-09-01
Full Text Available This paper presents an empirical investigation on the effects of occupational stress, psychological stress as well as job burnout on women’s employee performance in city of Karaj, Iran. The proposed study designs a questionnaire in Likert scale and distributes it among all female employees who worked for Bank Maskan in this city. In our survey, employee performance consists of three parts of interpersonal performance, job performance as well as organizational performance. Cronbach alpha has been used to verify the overall questionnaire, all components were within acceptable levels, and the implementation of Kolmogorov-Smirnov test has indicated that the data were not normally distributed. Using Spearman correlation ratio as well as regression techniques, the study has determined that while psychological stress influenced significantly on all three components of employee performance including interpersonal performance, job performance as well as organizational performance, the effect on job performance was greater than the other components. In addition, occupational stress only influences on organizational as well as interpersonal performance. Finally, employee burnout has no impact on any components of employee performance.
Sikandaner, Hu Erxidan; Park, So Young; Kim, Min Jung; Park, Shi Nae; Yang, Dong Won
2017-02-15
Noise exposure has been well characterized as an environmental stressor, and is known to have auditory and non-auditory effects. Phosphodiesterase 5 (PDE5) inhibitors affect memory and hippocampus plasticity through various signaling cascades which are regulated by cGMP. In this study, we investigated the effects of sildenafil on memory deficiency, neuroprotection and oxidative stress in mice caused by chronic noise exposure. Mice were exposed to noise for 4h every day up to 14days at 110dB SPL of noise level. Sildenafil (15mg/kg) was orally administered 30min before noise exposure for 14days. Behavioral assessments were performed using novel object recognition (NOR) test and radial arm maze (RAM) test. Higher levels of memory dysfunction and oxidative stress were observed in noise alone-induced mice compared to control group. Interestingly, sildenafil administration increased memory performance, decreased oxidative stress, and increased neuroprotection in the hippocampus region of noise alone-induced mice likely through affecting memory related pathways such as cGMP/PKG/CREB and p25/CDK5, and induction of free radical scavengers such as SOD1, SOD2, SOD3, Prdx5, and catalase in the brain of stressed mice.
Antioxidant Effects of Some Drugs on Immobilization Stress Combined with Cold Restraint Stress
Svetlana Trivic
2009-11-01
Full Text Available The aim of this work was to investigate the effect on antioxidant potential of some commonly used drugs (morphine, tramadol, bromocriptine, haloperidol and azithromycin on immobilization stress (IS combined with cold restraint stress (CRS in the rat. After the drug treatment the animals were kept immobilized in the cold chamber at 4±0.3ºC for 3 hours and then decapitaed and the livers were extracted. The following parameters were determined in the liver homogenate: content of reduced glutathione, activities of catalase, xanthine oxidase, glutathione reductase, glutathione peroxidase, peroxidase, and lipid peroxidation intensity. A battery of biochemical assays was used and the resulting data were statistically analyzed. Combined stress exhibited a prooxidative action (increased catalase activity, lowered content of reduced glutathione. Significantly enhanced catalase activity that was observed in all groups compared to the control indicates that the primary reactive oxygen species (ROS metabolite is hydrogen peroxide, which decomposes very rapidly (very high catalase activity, thus hindering formation of OH radicals as the most toxic ROS. None of the tested drugs showed a protective effect on combined IS and CRS. The intensity of lipid peroxidation did not change either in the combined stress or under additional influence of the drugs. Probably, under our experimental conditions, the time was not sufficiently long to observe damage of lipid membrane by ROS.
Investigation of temperature effect on stress of flexspline
项青; 尹征南
2014-01-01
The effect of temperature loading on the stress of a flexspline is investigated. Based on the geometric and mechanical characteristics of the harmonic gear flexspline, a circular thin shell model is presented in this paper. The theoretical solution for the flexspline under different displacement loads and different temperature fields is derived. Meanwhile, an impact factor formula, which reflects the effect of the temperatures of the inner and outer surfaces of the flexspline on the stress of the flexspline, is presented. Finally, numerical calculations by the finite element method (FEM) are adopted to verify the corresponding conclusions.
Effect of mindfulness-based stress reduction on sleep quality
Andersen, Signe; Würtzen, Hanne; Steding-Jessen, Marianne;
2013-01-01
The prevalence of sleep disturbance is high among cancer patients, and the sleep problems tend to last for years after the end of treatment. As part of a large randomized controlled clinical trial (the MICA trial, NCT00990977) of the effect of mindfulness-based stress reduction (MBSR) on psycholo......The prevalence of sleep disturbance is high among cancer patients, and the sleep problems tend to last for years after the end of treatment. As part of a large randomized controlled clinical trial (the MICA trial, NCT00990977) of the effect of mindfulness-based stress reduction (MBSR...
Toussaint, Loren; Shields, Grant S; Dorn, Gabriel; Slavich, George M
2016-06-01
To examine risk and resilience factors that affect health, lifetime stress exposure histories, dispositional forgiveness levels, and mental and physical health were assessed in 148 young adults. Greater lifetime stress severity and lower levels of forgiveness each uniquely predicted worse mental and physical health. Analyses also revealed a graded Stress × Forgiveness interaction effect, wherein associations between stress and mental health were weaker for persons exhibiting more forgiveness. These data are the first to elucidate the interactive effects of cumulative stress severity and forgiveness on health, and suggest that developing a more forgiving coping style may help minimize stress-related disorders.
Stress memory effect in viscoelastic stagnant lid convection
Patočka, V.; Čadek, O.; Tackley, P. J.; Čížková, H.
2017-06-01
Present thermochemical convection models of planetary evolution often assume a purely viscous or viscoplastic rheology. Ignoring elasticity in the cold, outer boundary layer is, however, questionable since elastic effects may play an important role there and affect surface topography as well as the stress distribution within the stiff cold lithosphere. Here we present a modelling study focused on the combined effects of Maxwell viscoelastic rheology and a free surface in the stagnant lid planetary convection. We implemented viscoelastic rheology in the StagYY code using a tracer-based stress advection scheme that suppresses subgrid oscillations. We apply this code to perform thermal convection models of the cooling planetary mantles and we demonstrate that while the global characteristics of the mantle flow do not change significantly when including viscoelasticity, the stress state of the cold lithosphere may be substantially different. Transient cooling of an initially thin upper thermal boundary layer results in a complex layered stress structure due to the memory effects of viscoelastic rheology. The stress state of the lid may thus contain a record of the planetary thermal evolution.
Effect of Particle Size on Shear Stress of Magnetorheological Fluids
Chiranjit Sarkar
2015-05-01
Full Text Available Magnetorheological fluids (MRF, known for their variable shear stress contain magnetisable micrometer-sized particles (few micrometer to 200 micrometers in a nonmagnetic carrier liquid. To avoid settling of particles, smaller sized (3-10 micrometers particles are preferred, while larger sized particles can be used in MR brakes, MR clutches, etc. as mechanical stirring action in those mechanisms does not allow particles to settle down. Ideally larger sized particles provide higher shear stress compared to smaller sized particles. However there is need to explore the effect of particle sizes on the shear stress. In the current paper, a comparison of different particle sizes on MR effect has been presented. Particle size distributions of iron particles were measured using HORIBA Laser Scattering Particle Size Distribution Analyser. The particle size distribution, mean sizes and standard deviations have been presented. The nature of particle shapes has been observed using scanning electron microscopy. To explore the effect of particle sizes, nine MR fluids containing small, large and mixed sized carbonyl iron particles have been synthesized. Three concentrations (9%, 18% and 36% by volume for each size of particles have been used. The shear stresses of those MRF samples have been measured using ANTON PAAR MCR-102 Rheometer. With increase in volume fraction of iron particles, the MR fluids synthesized using “mixed sized particles” show better shear stress compared to the MR fluids containing “smaller sized spherical shaped particles” and “larger sized flaked shaped particles” at higher shear rate.
Baste, Vrushali S; Gadkari, Jayashree V
2014-01-01
Medical students are exposed to many stressors and if stress is perceived negatively or becomes excessive can affect academic performance and health adversely. The objective of this study was to assess stress, predominant stressor and effect of music on perceived stress. 90 undergraduate students were selected randomly. A written questionnaire about personal information, stressful factors, ways to cope up stress, Rosenberg self-esteem scale (Rosenberg, 1965) and 'Quick Inventory of Depressive Symptomatology' self-rated 16 (QIDS-SR-16) was given.45.6% Students had mild stress, 7.7% students had moderate stress and 1.1% students had severe stress. Academic factors were the predominant cause of stress in most students, followed by physical, social and emotional. On Rosenberg self-esteem scale (Rosenberg, 1965) 85.6% students had high self-esteem and on QIDS-SR16 50% students had depression. Effect of music on perceived stress was statistically significant. Medical curriculum is associated with increased stress in students. Music can be used as simple, inexpensive and effective therapy for stress.
Ma, Li; Gao, Pei-yi; Hu, Qing-mao; Lin, Yan; Jing, Li-na; Xue, Jing; Chen, Zhi-jun; Wang, Yong-jun; Liu, Mei-li; Cai, Ye-feng
2011-06-01
We explored the relationship between predicted infarct core, predicted ischemic penumbras and predicted final infarct volumes obtained though apparent diffusion coefficient (ADC)-based method, as well as other clinical variables, and functional outcome. Patients with acute cerebral ischemic stroke were retrospectively recruited. The National Institutes of Health Stroke Scale score was evaluated at baseline and the modified Rankin Scale (mRS) at day 90. Favorable outcome was defined as an mRS score of 0 to 2, and unfavorable outcome as 3 to 6. Multimodal stroke magnetic resonance imaging was carried out at presentation. The volumes of diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) were measured using the regions of interest (ROI) method. The volumes of predicted infarct core, predicted ischemic penumbra and predicted final infarct were obtained by an automated image analysis system based on baseline ADC maps. The association between baseline magnetic resonance imaging volumes, baseline clinical variables, and functional outcome was statistically analyzed. The study included 30 males and 20 females (mean±SD age, 56±10 years). Baseline DWI, PWI and PWI-DWI mismatch volumes were not correlated with day-90 mRS (P>0.05). Predicted infarct core, predicted ischemic penumbra and predicted final infarct through ADC-based method were all correlated with day-90 mRS (PStroke Scale and recanalization also demonstrated a trend toward a favorable outcome. Receiver operating characteristic analysis showed that the area under the curve of predicted final infarct volume and recanalization were higher with statistical significance (PStroke Scale and recanalization may have effect on functional outcome in acute ischemic stroke.
M Wahab Amjad
Full Text Available Biomolecules have been widely investigated as potential therapeutics for various diseases. However their use is limited due to rapid degradation and poor cellular uptake in vitro and in vivo. To address this issue, we synthesized a new nano-carrier system comprising of cholic acid-polyethylenimine (CA-PEI copolymer micelles, via carbodiimide-mediated coupling for the efficient delivery of small interfering ribonucleic acid (siRNA and bovine serum albumin (BSA as model protein. The mean particle size of siRNA- or BSA-loaded CA-PEI micelles ranged from 100-150 nm, with zeta potentials of +3-+11 mV, respectively. Atomic force, transmission electron and field emission scanning electron microscopy demonstrated that the micelles exhibited excellent spherical morphology. No significant morphology or size changes were observed in the CA-PEI micelles after siRNA and BSA loading. CA-PEI micelles exhibited sustained release profile, the effective diffusion coefficients were successfully estimated using a mathematically-derived cylindrical diffusion model and the release data of siRNA and BSA closely fitted into this model. High siRNA and BSA binding and loading efficiencies (95% and 70%, respectively were observed for CA-PEI micelles. Stability studies demonstrated that siRNA and BSA integrity was maintained after loading and release. The CA-PEI micelles were non cytotoxic to V79 and DLD-1 cells, as shown by alamarBlue and LIVE/DEAD cell viability assays. RT-PCR study revealed that siRNA-loaded CA-PEI micelles suppressed the mRNA for ABCB1 gene. These results revealed the promising potential of CA-PEI micelles as a stable, safe, and versatile nano-carrier for siRNA and the model protein delivery.
Rajesh, S.; Murali, K. P.; Jantunen, H.; Ratheesh, R.
2011-11-01
High permittivity and low-loss ceramic fillers have been prepared by means of the solid state ceramic route. Ceramic-filled composites were prepared by the Sigma Mixing, Extrusion, Calendering, which was followed by the Hot pressing (SMECH) process. The microwave dielectric properties of the composites were studied using X-band waveguide cavity perturbation technique. The temperature coefficient of the relative permittivity of the composites was investigated in the 0-100 °C temperature range using a hot and cold chamber coupled with an impedance analyzer. The temperature coefficient of the relative permittivity of the composites showed strong dependence on the temperature coefficient of the relative permittivity of the filler material. In the present study, a high-permittivity polymer/ceramic composite, having τεr ∼63 ppm/K, has been realized. This composite is suitable for outdoor wireless applications.
Dr.I.Neethi Manickam,
2011-04-01
Full Text Available Coir pith can be used as fuel in loose form or in briquettes. Bulk density, coefficient of friction, porosity and particle density affects densification and combustion of coir pith. The moisture content and particle size ranges were 10.1 to 60.2%w.b. and 0.098 to 0.925mm respectively. Porosity was varied from 0.623 to 0.862 and the particle density was varied from 0.939 to 0.605 gm/cc for the above ranges of moisture content and particle size. Bulk density was in the range of 0.097 to 0.341gm/cc. The coefficient of friction against mild steel was in the range of 0.5043 to 0.6332. Models were developed to find out bulk density, porosity, particle density and coefficient of friction for different moisture content and particle size.
Effects of progressive muscle relaxation on postmenopausal stress
Arunima Chaudhuri
2015-01-01
Full Text Available Background: Menopause increases stress level among females and this may be a contributing factor in developing metabolic syndrome. Objectives: The objective of this study is to study the effects of progressive muscle relaxation on cardiorespiratory efficiency and autonomic functions in over weight and obese working stressed postmenopausal females. Materials and Methods: A total of 30 postmenopausal overweight or obese (body mass index [BMI]: 24.97 ± 1.28 females belonging to the age group 50-55 years were included. Stress level in the subjects was assessed according to the presumptive life event stress scale. The perceived stress scale (PSS of Sheldon Cohen was used for measuring the perception of stress. Fasting blood samples were collected to exclude diabetic subjects and analyze lipid profile. BMI and waist/hip ratio were calculated. Resting pulse rate and blood pressure, respiratory rate were measured. VO 2 max, physical fitness index, breath holding time and 40 mm endurance test time were calculated for estimation of cardiopulmonary efficiency. Autonomic function tests were carried. Subjects were given progressive muscle relaxation training for 3 months and all parameters were reevaluated. Data was analyzed using SPSS version 16 (SPSS Inc., Chicago, USA. Results: PSS in pre-training session was 26.16 ± 1.7 and in post-training session was 14.33 ± 2.01 and the difference was statistically significant. There was a significant decrease in pulse rate, blood pressure, BMI, waist/hip ratio, cholesterol, low-density lipoprotein following preventive medicine residency training. Results of autonomic function tests and cardiopulmonary efficiency test improved significantly following relaxation training. Conclusions: Increased stress levels may increase BMI and waist/hip ratio, dyslipidemia and lead to autonomic dysfunctions and increase incidence of cardiovascular disease in postmenopausal females. Lifestyle modification with relaxation exercises
Chen, Li-Hao; Liu, Zong-Pei; Pan, Yung-Ning
2016-08-01
In this paper, the effect of homogenization heat treatment on α value [coefficient of thermal expansion (10-6 K-1)] of low thermal expansion cast irons was studied. In addition, constrained thermal cyclic tests were conducted to evaluate the dimensional stability of the low thermal expansion cast irons with various heat treatment conditions. The results indicate that when the alloys were homogenized at a relatively low temperature, e.g., 1023 K (750 °C), the elimination of Ni segregation was not very effective, but the C concentration in the matrix was moderately reduced. On the other hand, if the alloys were homogenized at a relatively high temperature, e.g., 1473 K (1200 °C), opposite results were obtained. Consequently, not much improvement (reduction) in α value was achieved in both cases. Therefore, a compound homogenization heat treatment procedure was designed, namely 1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ, in which a relatively high homogenization temperature of 1473 K (1200 °C) can effectively eliminate the Ni segregation, and a subsequent holding stage at 1023.15 K (750 °C) can reduce the C content in the matrix. As a result, very low α values of around (1 to 2) × 10-6 K-1 were obtained. Regarding the constrained thermal cyclic testing in 303 K to 473 K (30 °C to 200 °C), the results indicate that regardless of heat treatment condition, low thermal expansion cast irons exhibit exceedingly higher dimensional stability than either the regular ductile cast iron or the 304 stainless steel. Furthermore, positive correlation exists between the α 303.15 K to 473.15 K value and the amount of shape change after the thermal cyclic testing. Among the alloys investigated, Heat I-T3B (1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ) exhibits the lowest α 303 K to 473 K value (1.72 × 10-6 K-1), and hence has the least shape change (7.41 μm) or the best dimensional stability.
Stress and its effects on horses reproduction
Amal M. AboEl-Maaty
2011-01-01
A total of 90 mares and horses were subjected to blood sampling for determining the effect of management (farm), reproductive condition, sex, age, breed and month of the year during breeding on circulating levels of cortisol and sex hormones. Blood samples were collected from December to the following June from four farms. Blood sera underwent testosterone, estradiol, progesterone and cortisol assaying using ELISA kits. Cortisol levels were significantly low in lactating mares during their fo...
Hayasi, Ryoei; Masuda, Yoshiharu; Hashimoto, Shozo; Kuriyama, Shinhou
2008-06-01
Experimental studies have been conducted using the dynamic photoelastic technique combined with a strain gauge to investigate geometric effects on stress wave propagation in axially impacted epoxy resins of plate-like structure. Dynamic photoelasticity provides a means of visualizing the stress wave field inside a solid. A device that triggers the generation of stress waves by direct projectile impact is used to conduct high-speed photoelasticity and strain gauge measurements. This triggering is achieved by an electrical connection between projectile and sample. The geometric effects of the width-to-wavelength ratio on the propagation speed and attenuation coefficient of stress waves were analyzed for isotropic rectangular rods of different width-to-thickness ratios, the thickness being the same in each case. The experimental results for stress wave speed as a function of width-to-wavelength ratio are in reasonable agreement with theoretical predictions based on a modified Love's equation involving the geometric effects due to lateral inertia.
Effect of meditation on neurophysiological changes in stress mediated depression.
Kasala, Eshvendar Reddy; Bodduluru, Lakshmi Narendra; Maneti, Yogeshwar; Thipparaboina, Rajesh
2014-02-01
Meditation is a complex mental practice involving changes in sensory perception, cognition, hormonal and autonomic activity. It is widely used in psychological and medical practices for stress management as well as stress mediated mental disorders like depression. A growing body of literature has shown that meditation has profound effects on numerous physiological systems that are involved in the pathophysiology of major depressive disorder (MDD). Although meditation-based interventions have been associated with improvement in depressive symptoms and prevention of relapse, the physiological mechanisms underlying the therapeutic effects of meditation are not clearly defined and even paradoxical. This paper reviews many of the physiological abnormalities found in cytokine & stress mediated depression and the reversal of these anomalies by different meditation techniques.
The effect of oxidative stress during exercise in the horse.
Williams, C A
2016-10-01
Oxidative stress is an imbalance of the oxidant-to-antioxidant ratio in the body. Increases in oxidative stress and changes in antioxidant status have been shown during endurance and intense exercise and eventing competition in horses. Antioxidants include vitamins, minerals, enzymes, and proteins that must be synthesized in the body or obtained from the diet. Therefore, exercise level and diet are both factors that play a role in influencing the oxidative stress and antioxidant status of the equine athlete. Along with exercise intensity and duration, diet, age, and training program can also affect oxidative stress in the horse. Several studies using exogenous supplementation of vitamin E, vitamin C, and alpha-lipoic acid have shown positive results in decreasing the effects of exercise (endurance and intense exercise)-induced oxidative stress and increasing the antioxidant status based on the markers and antioxidants measured, whereas other studies using superoxide dismutase showed little effects on the exercise horse. The "free radical theory of aging" states that long-term effects of the degenerative changes associated with aging may induce oxidative stress. However, in old horses (22 ± 2 yr), lipid peroxidation levels and blood antioxidant concentrations were similar to those found in younger but mature (12 ± 2 yr) horses both at rest and during exercise. Other studies found that yearlings (18 ± 2.4 mo) that are novel to forced exercise had less lipid peroxidation and greater antioxidant status than mature mares (13 ± 2.1 yr) prior to exercise training. Exercise training reduced oxidative stress markers and improved antioxidant status in mares, whereas few effects were seen in yearlings. This indicates that youth provided more defense against oxidative stress due to exercise than the exercise training program. Other studies during competition (endurance, jumping, eventing, and racing) have investigated the influence on oxidative stress with varying results
Shembel, E.M.; Ksenzhek, O.S.; Lituinova, V.I.; Lobach, G.A.
1986-09-01
The authors measured the diffusion coefficients of SO/sub 2/ in electrolytes based on propylene carbonate, acetonitrile, dimethylformamide and dimethylsulfoxide in order to estimate possible diffusion limitations with respect to SO/sub 2/ and to establish the influence exerted by the solvent type on the process. The diffusion coefficients were calculated from the limiting diffusion currents of steady-state polarization curves for sulfur dioxide reduction recorded at a gold microdisk electrode which had a diameter of 2 x 10/sup -3/ cm. In lithium salt solutions the potentiodynamic curves recorded at the microelectrode do not exhibit a limiting current but are characterized by a current maximum.
Effects of hemin and thermal stress exposure on JWA expression
ZHAO Ming; CHEN Rui; LI Aiping; ZHOU Jianwei
2007-01-01
To investigate the expression of JWA after hemin and (or) thermal stress exposure,we treated K562 (chronic myelogenous leukemia cells) cells with different doses of hemin and thermal stress using different exposure times.The expression of JWA protein was determined by Western blot analysis.Reverse transcription-polymerase chain reaction was carried out to determine JWA mRNA expression.JWA promoter transcription activity analysis was performed by chloramphenicol acetyl transferase-enzyme linked immunosorbent assay (CAT-ELISA).The expression of JWA protein was significantly increased by up to (3.23 +0.57) folds compared to the control in K562 cells after hemin treatment (50 μM for one week),and a similar pattern was observed in the cells after treatment with thermal stress (42℃) for 2 hours [increased by (8.00+ 1.73) folds].The expression of JWA mRNA was also significantly elevated by up to (1.37 + 0.06)folds in K562 cells treated with hemin (30 μM for 48 hours),and a similar regulatory pattern [increased by (1.87±0.13)folds] was observed with thermal stress exposure (42℃) for 30 minutes.However,a combined antagonistic effect was observed in the treatment of K562 cells with hemin (30 μM,48 h) followed by thermal stress (42℃,30 min).CAT-ELISA further confirmed that either hemin or thermal stress treatment could up-regulate JWA transcription activity,however,the effects could be counteracted partly by treatment with a combination of both.Hemin and thermal stress might regulate JWA expression via distinct intracellular signal transduction pathways.
Liu, Jenny J. W.
2017-01-01
Background The consequences of stress are typically regarded from a deficit-oriented approach, conceptualizing stress to be entirely negative in its outcomes. This approach is unbalanced, and may further hinder individuals from engaging in adaptive coping. In the current study, we explored whether negative views and beliefs regarding stress interacted with a stress framing manipulation (positive, neutral and negative) on measures of stress reactivity for both psychosocial and physiological stressors. Method Ninety participants were randomized into one of three framing conditions that conceptualized the experience of stress in balanced, unbalanced-negative or unbalanced-positive ways. After watching a video on stress, participants underwent a psychosocial (Trier Social Stress Test), or a physiological (CO2 challenge) method of stress-induction. Subjective and objective markers of stress were assessed. Results Most of the sampled population regarded stress as negative prior to framing. Further, subjective and objective reactivity were greater to the TSST compared to the CO2 challenge. Additionally, significant cubic trends were observed in the interactions of stress framing and stress-induction methodologies on heart rate and blood pressure. Balanced framing conditions in the TSST group had a significantly larger decrease in heart rate and diastolic blood pressure following stress compared to the positive and negative framing conditions. Conclusion Findings confirmed a deficit-orientation of stress within the sampled population. In addition, results highlighted the relative efficacy of the TSST compared to CO2 as a method of stress provocation. Finally, individuals in framing conditions that posited stress outcomes in unbalanced manners responded to stressors less efficiently. This suggests that unbalanced framing of stress may have set forth unrealistic expectations regarding stress that later hindered individuals from adaptive responses to stress. Potential
Effect of Yb doping on the refractive index and thermo-optic coefficient of YVO4 single crystals.
Soharab, M; Bhaumik, Indranil; Bhatt, R; Saxena, A; Karnal, A K; Gupta, P K
2017-02-20
Single crystals of YVO4 with different doping concentrations of Yb (1.5, 3.0, 8.0, and 15.0 at. %) and with good crystalline quality (FWHM ∼43-55 arc sec of rocking curve) were grown by the optical floating zone technique. Refractive index measurements were carried out at four wavelengths as a function of temperature. The measurements show that as the doping concentration of Yb is increased, the refractive index varies marginally for ne whereas there is a significant change in the value of no. The thermo-optic coefficient (dn/dT) was found to be positive with a value ∼10-5/°C, which is 1 order higher than that for the undoped YVO4 crystal. The thermo-optic coefficient is higher for ne compared to that of no. Also, a set of relations describing the wavelength dependence of the thermo-optic coefficient were established that are useful for calculating the thermo-optic coefficient at any temperature in the range 30°C-150°C and at any wavelength in the range 532-1551 nm.
Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy
Fardi Ilkhchy, A.; Jabbari, Masoud; Davami, P.
2012-01-01
The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat...
Adams, Elaine
1996-01-01
Job stress is a multidimensional phenomenon. The researcher sought to examine variables that cause vocational teachers to experience stress in their teaching occupations and to evaluate the effects of these related stressors. This research evaluated the relationships between school systems and vocational teacher stress, teacher internal characteristics and vocational teacher stress, and students and vocational teacher stress. It also analyzed vocational teacher stre...
Effect of road transport stress on Erthrocyte Osmotic Fragility (EOF ...
olayemitoyin
was conducted with the aim of investigating the effect of two and half hours of road ... concentration, glucose concentration and erythrocyte osmotic fragility using standard methods. ... that road transportation was stressful to the subjects and measurement of erythrocyte ... The study was conducted in the laboratory of Human.
Grover, Kelly E; Green, Kelly L; Pettit, Jeremy W; Monteith, Lindsey L; Garza, Monica J; Venta, Amanda
2009-12-01
The present study examined the unique and interactive effects of stress and problem-solving skills on suicidal behaviors among 102 inpatient adolescents. As expected, life event stress and chronic stress each significantly predicted suicidal ideation and suicide attempt. Problem solving significantly predicted suicidal ideation, but not suicide attempt. Problem solving moderated the associations between life event stress and suicidal behaviors, as well as between chronic stress and suicidal ideation, but not chronic stress and suicide attempt. At high levels of stress, adolescents with poor problem-solving skills experienced elevated suicidal ideation and were at greater risk of making a nonfatal suicide attempt. The interactive effects decreased to non-significance after controlling for depressive symptoms and hopelessness. Clinical implications are discussed.
Shields, Grant S; Moons, Wesley G; Slavich, George M
2017-01-01
Executive function is a neuropsychological construct that enables controlled cognitive processing, which has been hypothesized to enhance individuals' resilience to stress. However, little empirical work has directly examined how executive function under different conditions mitigates the negative effects of stress exposure on health. To address this issue, we recruited 110 healthy young adults and assessed their recent life stress exposure, executive function in either a stressful or non-stressful context, and current health complaints. Based on existing research, we hypothesized that individuals exhibiting better executive function following a laboratory-based stressor (but not a control task) would demonstrate weaker associations between recent stress exposure and health because they perceived recent life stressors as being less severe. Consistent with this hypothesis, better executive function during acute stress, but not in the absence of stress, was associated with an attenuated link between participants' recent life stress exposure and their current health complaints. Moreover, this attenuating effect was mediated by lesser perceptions of stressor severity. Based on these data, we conclude that better executive function under stress is associated with fewer health complaints and that these effects may occur by reducing individuals' perceptions of stressor severity. The data thus suggest the possibility of reducing stress-related health problems by enhancing executive function.
Shields, Grant S.; Moons, Wesley G.; Slavich, George M.
2017-01-01
Executive function is a neuropsychological construct that enables controlled cognitive processing, which has been hypothesized to enhance individuals’ resilience to stress. However, little empirical work has directly examined how executive function under different conditions mitigates the negative effects of stress exposure on health. To address this issue, we recruited 110 healthy young adults and assessed their recent life stress exposure, executive function in either a stressful or non-stressful context, and current health complaints. Based on existing research, we hypothesized that individuals exhibiting better executive function following a laboratory-based stressor (but not a control task) would demonstrate weaker associations between recent stress exposure and health because they perceived recent life stressors as being less severe. Consistent with this hypothesis, better executive function during acute stress, but not in the absence of stress, was associated with an attenuated link between participants’ recent life stress exposure and their current health complaints. Moreover, this attenuating effect was mediated by lesser perceptions of stressor severity. Based on these data, we conclude that better executive function under stress is associated with fewer health complaints and that these effects may occur by reducing individuals’ perceptions of stressor severity. The data thus suggest the possibility of reducing stress-related health problems by enhancing executive function. PMID:28114849
Effect of intermediate principal stress on strength of soft rock under complex stress states
马宗源; 廖红建; 党发宁
2014-01-01
A series of numerical simulations of conventional and true triaxial tests for soft rock materials using the three-dimensional finite difference code FLAC3D were presented. A hexahedral element and a strain hardening/softening constitutive model based on the unified strength theory (UST) were used to simulate both the consolidated-undrained (CU) triaxial and the consolidated-drained (CD) true triaxial tests. Based on the results of the true triaxial tests simulation, the effect of the intermediate principal stress on the strength of soft rock was investigated. Finally, an example of an axial compression test for a hard rock pillar with a soft rock interlayer was analyzed using the two-dimensional finite difference code FLAC. The CD true triaxial test simulations for diatomaceous soft rock suggest the peak and residual strengths increase by 30%when the effect of the intermediate principal stress is taken into account. The axial compression for a rock pillar indicated the peak and residual strengths increase six-fold when the soft rock interlayer approached the vertical and the effect of the intermediate principal stress is taken into account.
Tchakui, Murielle Vanessa; Woafo, Paul
2016-11-01
This work deals with the dynamics of three unidirectionally coupled Duffing oscillators and that of three coupled piezoelectric actuators, considering the special case of inchworm motors. Two configurations of the network are studied: ring configuration and chain configuration. The effects of the coupling coefficient and the time delay are analyzed through different bifurcation diagrams and phase difference variation. It is shown that varying the coupling coefficient and the time delay leads to the appearance of different dynamical behaviors: steady states, periodic and quasiperiodic oscillations, chaos, and phase synchronization.
Food stress causes sex-specific maternal effects in mites.
Walzer, Andreas; Schausberger, Peter
2015-08-01
Life history theory predicts that females should produce few large eggs under food stress and many small eggs when food is abundant. We tested this prediction in three female-biased size-dimorphic predatory mites feeding on herbivorous spider mite prey: Phytoseiulus persimilis, a specialized spider mite predator; Neoseiulus californicus, a generalist preferring spider mites; Amblyseius andersoni, a broad diet generalist. Irrespective of predator species and offspring sex, most females laid only one small egg under severe food stress. Irrespective of predator species, the number of female but not male eggs decreased with increasing maternal food stress. This sex-specific effect was probably due to the higher production costs of large female than small male eggs. The complexity of the response to the varying availability of spider mite prey correlated with the predators' degree of adaptation to this prey. Most A. andersoni females did not oviposit under severe food stress, whereas N. californicus and P. persimilis did oviposit. Under moderate food stress, only P. persimilis increased its investment per offspring, at the expense of egg number, and produced few large female eggs. When prey was abundant, P. persimilis decreased the female egg sizes at the expense of increased egg numbers, resulting in a sex-specific egg size/number trade-off. Maternal effects manifested only in N. californicus and P. persimilis. Small egg size correlated with the body size of daughters but not sons. Overall, our study provides a key example of sex-specific maternal effects, i.e. food stress during egg production more strongly affects the sex of the large than the small offspring.
Stress and its effects on horses reproduction
Amal M. AboEl-Maaty
2011-11-01
Full Text Available A total of 90 mares and horses were subjected to blood sampling for determining the effect of management (farm, reproductive condition, sex, age, breed and month of the year during breeding on circulating levels of cortisol and sex hormones. Blood samples were collected from December to the following June from four farms. Blood sera underwent testosterone, estradiol, progesterone and cortisol assaying using ELISA kits. Cortisol levels were significantly low in lactating mares during their foal heat but significantly high levels were recorded in both repeat breeder mares and horses used for racing. High and significant testosterone and estradiol levels were recorded in both stallions used for breeding especially after semen collection and early pregnant mares. Similar testosterone levels were recorded in both early pregnant mares and racing horses but high levels were recorded in stallions. Estradiol was high in both early pregnant and mares with endometritis but the highest levels were observed in stallions. Horses held in private farms had high cortisol levels compared to those of governmental farms. In contrast to mares, horses had low cortisol and high estradiol levels. Cortisol levels were high from April to June (Spring and early summer compared to its levels from December to March (Winter. Arab horses had low cortisol compared to native and imported foreign breeds. In conclusion, environmental condition, exercise, breed, management and the purpose of raising horses all are affecting its cortisol levels.
Stress in Irish dentists: developing effective coping strategies.
Rogers, Cathryn
2012-02-01
Recent research has highlighted the need to recognise occupation-specific risk factors contributing to stress and burnout. As health professionals, it is important for dentists to recognise the symptoms and the effects of stress on physical, psychological and professional well being. This article reviews the relevant scientific evidence, and provides practical cognitive psychological measures to guide improved well-being for dentists. Any stigma-related factors need to be acknowledged and addressed for the wellbeing of dentists and their patients, and the dental profession is well placed to provide leadership on this issue. Peer support is central to meeting this challenge.
Effect of Upper Mantle Heterogeneities on Lithosphere Stresses and Topography
Osei Tutu, A.; Steinberger, B.; Rogozhina, I.; Sobolev, S. V.
2016-12-01
The orientation and magnitude of lithosphere stresses give us knowledge about most of the processes within the Earth that are not easy to observe. It has been established (Steinberger, Schmeling, and Marquart 2001) that large contribution of the forces producing lithosphere stresses have their source origination from the buoyancies of both the upper and lower mantle acting beneath the lithosphere. The contribution of the crustal thickness to the stresses has been estimated to be less than 10% (Steinberger et al. 2001) in most region and increases in areas with high gravitational potential energy like the Himalayas. In most of these studies, the effect of the crust was determined separately by computing the gravitational potential energy from the crust (Ghosh et al. 2013) and applied as correction. (Artyushkov 1973) showed that the inhomogeneous nature of the crust contribute to the stresses observed as against using constant lithosphere thickness in most studies, due to the complexities for implementing a variable lithosphere. We seek extend the approach of Ghosh et al. (2013) by coupling the Crust 1.0 (Laske et al. 2013) to a varaible lithosphere thickness in our numerical method. Using a 3D global lithosphere-asthenosphere model (Popov and Sobolev 2008) with visco-elasto-plastic rheology, coupled at 300 km depth to a mantle modeled with a spectral technique (Hager and O'Connell, 1981), we compute lithosphere stresses and topography. we compare our model with observations; the World Stress Map, Global Strain Rate Map and the observed topgraphy. We use S40RTS seismic tomography below 300 km depth, with radial viscosity distribution (Steinberger et al 2006). To account for all the heterogeneities in the upper mantle (300 km) we used different 3D temperatures models setups. The first model is the thermal lithosphere model (Artemieva and Mooney, 2001) in continental regions and assumes half-space cooling of sea floor with age (Müller et al. 2008) for oceans. For the
The Effect of De-Stress Training Program on the Stress of Mothers With Slow Paced Children
Charmforoush Jalali
2016-05-01
Full Text Available Background Handicap is a critical factor with significant effects on family. Stress is the main result of such effects on parents. As a classical procedure, mothers have the major caregiving role to the child; therefore, they experience more stress than other members. Then, development program for stress management is essential. Objectives The current study aimed to develop and assess a de-stress training program on decreasing the stress of mothers with mentally retarded children. Materials and Methods The current study was a semi-experimental research with Follow-up. Study subjects included 20 mothers with slow paced children connected to a non-governmental organization (NGO of show paced children in Tehran, Iran. Mothers were randomly divided into experimental and control groups (10 cases in each group. All mothers responded to the parental stress scale used to measure mothers’ stress. Experimental group received de-stress training program for 13 sessions. Post-test was administered in session fourteenth and after one month the results were followed-up. Data were analyzed by univariate analysis of covariance (P < 0.01. Results Data presented a significant difference between the control and experiment groups. Also, results did not show a significant difference between the post-test and follow up. It means that the effect of training was persistent. Conclusions De-stress training program significantly decreased the stress of mothers with show paced children, and the training effect was persistent.
[Effects of organic manure on wheat growth under lead stress].
Qiao, Sha-sha; Zhang, Yong-qing; Yang, Li-wen; Pei, Hong-bin; Sun, Hong-shuai
2011-04-01
A pot experiment was conducted to study the effects of organic manure on the wheat growth under different levels of lead stress. With increasing lead stress level, whether fertilization or not, the plant height, shoot dry mass, adventitious root number, root total length, root dry mass, root activity, root total and active absorbing area, and root SOD and POD activities decreased, and root MDA content presented an increasing trend. The decrement of the above-mentioned parameters differed with fertilization treatments. Applying organic manure mitigated the impact of lead stress on wheat growth to some extent, delayed the senescence of wheat roots, and promoted root development and growth, ultimately leading to the increase of wheat yield and the decrease of lead content in grain.
The effect of acute and chronic stress on growth.
Sävendahl, Lars
2012-10-23
Impaired bone growth is observed in many children exposed to stress, but whether the underlying cause is psychological or secondary to a variety of chronic disorders is unclear. The growth plate is specifically targeted by stress through many different mechanisms, including increased serum concentrations of proinflammatory cytokines and cortisol, as well as impaired actions of the growth hormone (GH)-insulin-like growth factor-1 (IGF-1) axis. Both glucocorticoids, such as cortisol, and proinflammatory cytokines adversely affect several aspects of chondrogenesis in the growth plate, and these effects can be ameliorated by raising local IGF-1 concentrations. However, this intervention does not completely normalize growth. In children with stress related to chronic inflammation, the cornerstone of improving stress-impaired growth remains the judicious use of glucocorticoids while ensuring effective control of the disease process. Specific immunomodulatory therapy that targets the actions of tumor necrosis factor-α (TNFα) is at least partially effective at rescuing linear growth in many children with juvenile idiopathic arthritis (JIA). Patients who do not respond to anti-TNF treatment may be candidates for therapeutic agents that target other proinflammatory cytokines and for GH intervention. Although GH treatment rescues linear growth in some patients with JIA, it is unknown whether GH can rescue growth in those patients who do not respond to anticytokine therapy. Further experimental and clinical studies are needed to explore these and other new potential treatment strategies that could improve bone growth in patients who do not respond to conventional therapy.
The Effect of Oxidative Stress and Antioxidants on Men Fertility
Abolfazl Akbari
2013-07-01
Full Text Available Background: Various factors affects men fertility and oxidative stress as an important factor which affects fertility has recently got great concern. Oxidative stress refers to conditions of imbalance between productions of reactive oxygen species (ROS and antioxidant defense mechanism. Reactive species of oxygen, free radicals and peroxide are produced in the cell when metabolism of oxygen is incomplete in the mitochondrial respiratory chain.Materials and Methods: In this review we will consider effect of oxidative stress on male fertility and the principal antioxidant defences.Results: Factors such as hypoxia, cytokines, growth factors, chemotherapy, radio frequency waves and UV radiation can increase ROS production. Oxidative stress as one of the strongest physiological factors can lead to damage of sperm and reduction of seminal plasma quality and thereby cause infertility in men. Enzymatic and non-enzymatic defences inhibit oxidant attack. The enzymatic defense include: superoxide dismutases, glutathione peroxidases, and catalase. The non-enzymatic defences include ascorbate (vitamin C and a-tocopherol (vitamin E, beta carotene, and albumin, which neutralize free radicals. Conclusion: Oxidative stress affects male fertility through induction of lipid peroxidation, inactivation of proteins, impair of sperm motility and DNA damage.
Effect of thermal stresses on the mechanism of tooth pain.
Oskui, Iman Z; Ashtiani, Mohammed N; Hashemi, Ata; Jafarzadeh, Hamid
2014-11-01
Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism. Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation. Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings. The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.
Investigating The Effect Of Job Stress On Performance Of Employees
Oyungerel Altangerel
2015-02-01
Full Text Available Abstract This study is conducted to investigate the effect of job stress on job performance. A random sampling technique is used to collect primary data of 120 employees of four telecommunication companies of Mongolia i.e. Mobicom Unitel Skytel and G-mobile. A well-structured questionnaire is utilized to collect relevant data descriptive and logistic analysis is used to estimate and describe the findings of results. It is found that work overload is major reason of stress among employees and majority of employees reduce their productivity and loss of interest in job due to stress. As for concern health issue eyes strain dizziness and disorder in sleep are due to job stress. According to results of logit model parameters of education experience and salary per month are statistically significant and have positive impact on employees performance but age family size no relaxation time giving to employees during working hours and work overload are statistically significant and have negative impact on employees job performance. For suggestions companies should increase salaries of employees and give reward to employees those have work overload. Workload of employees should reduce by proper work redesign and efficient management by proper allocation of job. It is also found that stress also becomes reason of several illnesses and majority of employees dont have medical facilities first aid at working place therefore it is suggested that companies should also provide medical facilities first aid for employees at work place.
STABILITY ANALYSIS OF THREE LOBE HYDRODYNAMIC JOURNAL BEARING: COUPLE STRESS FLUID EFFECTS
N.P.Mehta
2010-10-01
Full Text Available The effects of couple stress fluid, when added to a Newtonian base, are studied by deriving a generalized form of the Reynolds equation. A couple stress parameter ‘l’ has been used to indicate the length of the long chain molecule being added. Finite element method has been used to solve the generalized Reynolds equation for each lobe to obtain the respective pressure distributions. Stable equilibrium conditions in terms of eccentricity ratios and the attitude angles have been obtained for the vertical load condition. The journal has been perturbed from this equilibrium condition to give the stiffness and the damping coefficients. It has been observed that slight variation of the coupe stress parameter ‘l’ has great influence on the dynamic characteristics, i.e. the stiffness and the dampingcoefficients. The threshold speed and the critical mass of the journal, obtained as a solution to the linearized equations of motion, are used to demonstrate the increased stability of the journal bearing system.
The Effects of Weather Sensitivity on Stressed Personnel
1981-06-01
AD P002928 THE EFFECTS OF WEATHER SENSITIVITY ON STRESSED PERSONNEL DR, CHARLES WALLACH Decisions and Designs, Inc. 8400 Westpark Drive McLean, VA...meteorologist on his staff. But weather effects are transitory and seldom comform to the order of battle, although it might be useful to keep them in mind...is only one of many in- stances--in the Spring of 1978 I was invited to make ion mpasurements in the Defense Nuclear Agency office suite occupied by
CROSS-EFFECTS OF ADAPTATION TO STRESS SITUATIONS
Alexey Viktorovich MESHCHERYAKOV
2015-01-01
Full Text Available To counteract the stress it is necessary to study its effect on the internal condition of the body. The level of achievements in various sports and employments is determined by the exhaust motor programs that are improved in the process of trainings, ensuring the achievement of high results and reducing the mental and energy losses. Adaptation to short-term impacts of the stressor naturally leads to increased physiological capacity of the sympathetic-adrenal regulation. The recruitment of this regulatory system is an essential and absolute link of adaptation to the effects of environmental factors. It can be affirmed that adaptation to extreme situations increases the resistance not only to separate factors but to all factors affecting the body. Thus, adaptation has a positive cross-effect. We believe it is important to assess the possible impacts of the elaborated methodology on the development of the vestibular apparatus that includes cross-effects of adaptation to stress situations on the readiness of athletes. The article presents conclusions about the possibilities to improve the coordination abilities of athletes through targeted effect on their special preparedness by the original methods which intensify the effects of adaptation to stress situations. The changes were assessed based on the data obtained using a stabilometric platform.
Oei, Nicole Yü Lan
2010-01-01
The present thesis contains five experimental studies into the effects of stress on memory I healthy males. Hydrocortisone (and propranolol) administration or the induction of social stress are used to heighten cortisol levels, and consequently to study its effects on working memory performance and
Oei, Nicole Yü Lan
2010-01-01
The present thesis contains five experimental studies into the effects of stress on memory I healthy males. Hydrocortisone (and propranolol) administration or the induction of social stress are used to heighten cortisol levels, and consequently to study its effects on working memory performance and
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Rose, Jørgen; Svendsen, Svend
2005-01-01
and insulation has to be fulfilled. Based on a given design of the tapered insulation the total heat loss coefficient of the roof can be calculated using formulae in EN ISO 6946 for typical segments of the tapered insulation. Performing design and calculations for large roofs with numerous different segments can...... for design of flat roofs and a pc-program that can be used for calculating the total heat loss coefficient of externally insulated roofs with insulation in tapered layers, taking into account thermal bridges in the roof construction.......In order to achieve durability of flat roofs with external insulation, it is necessary to secure proper drainage of the roof, i.e. to avoid water leaking into the insulation. The design of the tapered insulation of the roof is quite difficult as requirements with respect to both drainage...
O. Mahran
2014-04-01
Full Text Available The small signal gain coefficient and the gain of Erbium-Doped Fiber Amplifier (EDFA in the wavelength range (1400-1700 nm for different erbium concentrations and different amplifier lengths are calculated and studied. A core graded-index and erbium-doped concentration, are optimized for an EDFA in simplified two-level model. There is evidence to show that, the gain increases with the erbium concentration and the amplifier length. Where the relation between the gain and the amplifier length at different wavelengths is linear with the maximum gain at &lambda = 1530 nm. Also the temperature dependence of the small signal gain coefficient and the gain at the peak wavelength of EDFA was studied which shows, slightly increase in the values of both with temperature. The value of the signal wavelength was chosen in the gain window of EDFA at 1530 nm.
Fan, Yan; Pestke, Karin; Feeser, Melanie; Aust, Sabine; Pruessner, Jens C; Böker, Heinz; Bajbouj, Malek; Grimm, Simone
2015-11-01
Previous evidence shows that acute stress changes both amygdala activity and its connectivity with a distributed brain network. Early life stress (ELS), especially emotional abuse (EA), is associated with altered reactivity to psychosocial stress in adulthood and moderates or even reverses the stress-attenuating effect of oxytocin (OXT). The neural underpinnings of the interaction between ELS and OXT remain unclear, though. Therefore, we here investigate the joint effect of ELS and OXT on transient changes in amygdala-centered functional connectivity induced by acute psychosocial stress, using a double-blind, randomized, placebo-controlled, within-subject crossover design. Psychophysiological interaction analysis in the placebo session revealed stress-induced increases in functional connectivity between amygdala and medial prefrontal cortex, posterior cingulate cortex, putamen, caudate and thalamus. Regression analysis showed that EA was positively associated with stress-induced changes in connectivity between amygdala and hippocampus. Moreover, hierarchical linear regression showed that this positive association between EA and stress-induced amygdala-hippocampal connectivity was moderated after the administration of intranasal OXT. Amygdala-hippocampal connectivity in the OXT session correlated negatively with cortisol stress responses. Our findings suggest that altered amygdala-hippocampal functional connectivity during psychosocial stress may have a crucial role in the altered sensitivity to OXT effects in individuals who have experienced EA in their childhood.
Hao, Jing-Hong; Yi, Yang; Shang, Qing-Mao; Dong, Chun-Juan; Zhang, Zhi-Gang
2012-03-01
To approach the related mechanisms of exogenous salicylic acid (SA) in improving plant drought-resistance, this paper studied the effects of applying exogenous SA to the rhizosphere on the plant growth, membrane lipid peroxidation, proline accumulation, water use efficiency, net photosynthetic rate (Pn), and chlorophyll fluorescence parameters of cucumber (Cucumis sativus) seedlings under drought stresses (60% and 50% of saturated water capacity). Applying SA relieved the inhibitory effects of drought stress on plant growth, Pn, and water use efficiency, decreased membrane lipid peroxidation, and promoted proline accumulation. Meanwhile, the SA decreased the decrements of the maximum photochemical efficiency of PS II, actual photochemical efficiency of PS II, potential activity of PS II, effective photochemical efficiency of PS II, and photochemical quenching coefficient under drought stress significantly, and limited the increase of non-photochemical quenching coefficient. All the results suggested that applying exogenous SA could alleviate the oxidation damage of cell membrane resulted from the drought-caused membrane lipid peroxidation, improve the Pn by increasing PS II activity to benefit water utilization, enhance the regulation capability of osmosis to decrease water loss and increase water use efficiency, and thereby, improve the plant drought-resistance.
Titos, G.; Cazorla, A.; Zieger, P.; Andrews, E.; Lyamani, H.; Granados-Muñoz, M. J.; Olmo, F. J.; Alados-Arboledas, L.
2016-09-01
Knowledge of the scattering enhancement factor, f(RH), is important for an accurate description of direct aerosol radiative forcing. This factor is defined as the ratio between the scattering coefficient at enhanced relative humidity, RH, to a reference (dry) scattering coefficient. Here, we review the different experimental designs used to measure the scattering coefficient at dry and humidified conditions as well as the procedures followed to analyze the measurements. Several empirical parameterizations for the relationship between f(RH) and RH have been proposed in the literature. These parameterizations have been reviewed and tested using experimental data representative of different hygroscopic growth behavior and a new parameterization is presented. The potential sources of error in f(RH) are discussed. A Monte Carlo method is used to investigate the overall measurement uncertainty, which is found to be around 20-40% for moderately hygroscopic aerosols. The main factors contributing to this uncertainty are the uncertainty in RH measurement, the dry reference state and the nephelometer uncertainty. A literature survey of nephelometry-based f(RH) measurements is presented as a function of aerosol type. In general, the highest f(RH) values were measured in clean marine environments, with pollution having a major influence on f(RH). Dust aerosol tended to have the lowest reported hygroscopicity of any of the aerosol types studied. Major open questions and suggestions for future research priorities are outlined.
N. S.M. El-Tayeb
2005-01-01
Full Text Available Nowadays, there is an increase interest in polymeric composite materials for high-performance in many industrial applications. In other words, the tribo-studies on polymeric materials are growing fast to enhance the polymeric products such as bearings, seals, ring and bushes. The current work presents an attempt to study the correlation between the type of counterface material and frictional heating at the interface surfaces for different, normal loads (23N, 49N and 72N, sliding velocities (0.18, 1.3 and 5.2 m sË1 and interval time (0-720 sec. Sliding friction experiments are performed on a pin-on-ring (POR tribometer under dry contact condition. Interface temperature and friction force were measured simultaneously during sliding of glass fiber reinforced epoxy (GFRE composite against three different counter face materials, hardened steel (HS, cast iron (CI and Aluminum alloy (Al. Experimental results showed that the type of counterface material greatly influences both interface temperature and friction coefficient. Higher temperature and friction coefficient were evident when sliding took place against HS surface, compared to sliding against CI and Al under same condition. When sliding took place against HS, the friction coefficient of GFRE composite was about an order of magnitude higher than sliding the GFRE composite against the other counter face materials. Based on the optical microscope graphs, the friction and induced temperature results of GFRE composite are analyzed and discussed.
Vasil'eva, N N; Bryndina, I G
2012-07-01
The aim of the present study was to investigate the effect of chronic exposure to immobilization and psychosocial stress on surface activity, biochemical composition of pulmonary surfactant and lung fluid balance of rats with different stress-resistance. It is shown that both types of stress lead to elevation of lysophospholipids level and decrease of surface-active properties of pulmonary surfactant, more prominent in stress-vulnerable rats. Blood supply was decreased and extravascular fluid was increased under the psychosocial stress only in stress-vulnerable animals, in all rest cases the blood supply was increased and the content of extravascular fluid was not changed. Surfactant alteration was coupled on the level of 11-OCS in the blood and amount of fluid in the lungs. The obtained results indicate that different degree of impairment in the pulmonary surfactant system during immobilization and psychosocial conflicts depends on different resistance to emotional stress.
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.
The effect of stress state on zirconium hydride reorientation
Cinbiz, Mahmut Nedim
Prior to storage in a dry-cask facility, spent nuclear fuel must undergo a vacuum drying cycle during which the spent fuel rods are heated up to elevated temperatures of ≤ 400°C to remove moisture the canisters within the cask. As temperature increases during heating, some of the hydride particles within the cladding dissolve while the internal gas pressure in fuel rods increases generating multi-axial hoop and axial stresses in the closed-end thin-walled cladding tubes. As cool-down starts, the hydrogen in solid solution precipitates as hydride platelets, and if the multiaxial stresses are sufficiently large, the precipitating hydrides reorient from their initial circumferential orientation to radial orientation. Radial hydrides can severely embrittle the spent nuclear fuel cladding at low temperature in response to hoop stress loading. Because the cladding can experience a range of stress states during the thermo-mechanical treatment induced during vacuum drying, this study has investigated the effect of stress state on the process of hydride reorientation during controlled thermo-mechanical treatments utilizing the combination of in situ X-ray diffraction and novel mechanical testing analyzed by the combination of metallography and finite element analysis. The study used cold worked and stress relieved Zircaloy-4 sheet containing approx. 180 wt. ppm hydrogen as its material basis. The failure behavior of this material containing radial hydrides was also studied over a range of temperatures. Finally, samples from reactor-irradiated cladding tubes were examined by X-ray diffraction using synchrotron radiation. To reveal the stress state effect on hydride reorientation, the critical threshold stress to reorient hydrides was determined by designing novel mechanical test samples which produce a range of stress states from uniaxial to "near-equibiaxial" tension when a load is applied. The threshold stress was determined after thermo-mechanical treatments by
Particle shape effects on the stress response of granular packings.
Athanassiadis, Athanasios G; Miskin, Marc Z; Kaplan, Paul; Rodenberg, Nicholas; Lee, Seung Hwan; Merritt, Jason; Brown, Eric; Amend, John; Lipson, Hod; Jaeger, Heinrich M
2014-01-01
We present measurements of the stress response of packings formed from a wide range of particle shapes. Besides spheres these include convex shapes such as the Platonic solids, truncated tetrahedra, and triangular bipyramids, as well as more complex, non-convex geometries such as hexapods with various arm lengths, dolos, and tetrahedral frames. All particles were 3D-printed in hard resin. Well-defined initial packing states were established through preconditioning by cyclic loading under given confinement pressure. Starting from such initial states, stress-strain relationships for axial compression were obtained at four different confining pressures for each particle type. While confining pressure has the largest overall effect on the mechanical response, we find that particle shape controls the details of the stress-strain curves and can be used to tune packing stiffness and yielding. By correlating the experimentally measured values for the effective Young's modulus under compression, yield stress and energy loss during cyclic loading, we identify trends among the various shapes that allow for designing a packing's aggregate behavior.