Badler, N. I.; Lee, P.; Wong, S.
1985-01-01
Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements.
Modeling of Sylgard Adhesive Strength
Stevens, Ralph Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-02-03
Sylgard is the name of a silicone elastomeric potting material manufactured by Dow Corning Corporation.1 Although the manufacturer cites its low adhesive strength as a feature of this product, thin layers of Sylgard do in fact have a non-negligible strength, which has been measured in recent tensile and shear debonding tests. The adhesive strength of thin layers of Sylgard potting material can be important in applications in which components having signi cantly di erent thermal expansion properties are potted together, and the potted assembly is subjected to temperature changes. The tensile and shear tractions developed on the potted surfaces of the components can cause signi cant internal stresses, particularly for components made of low-strength materials with a high area-to-volume ratio. This report is organized as follows: recent Sylgard debonding tests are rst brie y summarized, with particular attention to the adhesion between Sylgard and PBX 9501, and also between Sylgard and aluminum. Next, the type of numerical model that will be used to simulate the debonding behavior exhibited in these tests is described. Then the calibration of the debonding model will be illustrated. Finally, the method by which the model parameters are adjusted (scaled) to be applicable to other, non- tested bond thicknesses is summarized, and all parameters of the model (scaled and unscaled) are presented so that other investigators can reproduce all of the simulations described in this report as well as simulations of the application of interest.
The Mean Remaining Strength Of Systems In A Stress-Strength Model
Gürler, Selma
2014-01-01
In this paper, we study the mean remaining strength of a component inthe stress-strength setup. We present the models for the mean remaining strength for systems consisting of n independent components underthe k-out-of-n:F , parallel and series configurations. We assume thatthe strengths of the components are nonidentically distributed randomvariables and components are designed under the common stress.
Photophoretic Strength on Chondrules 1: Modeling
Loesche, Christoph; Teiser, Jens; Friedrich, Jon M; Bischoff, Addi
2013-01-01
Photophoresis is a physical process that transports particles in optical thin parts of protoplanetary disks, especially at the inner edge and at the optically surface. To model the transport and resulting effects in detail, it is necessary to quantify the strength of photophoresis for different particle classes as a fundamental input. Here, we explore photophoresis for a set of chondrules. The composition and surface morphology of these chondrules was measured by X-ray tomography. Based on the three-dimensional models, heat transfer through illuminated chondrules was calculated. The resulting surface temperature map was then used to calculate the photophoretic strength. We found that irregularities in particle shape and variations in composition induce variations in the photophoretic force. These depend on the orientation of a particle with respect to the light source. The variations of the absolute value of the photophoretic force on average over all chondrules is $4.17\\%$. The deviation between the directio...
Yarn Strength Modelling Using Fuzzy Expert System
Abhijit Majumdar, Ph.D.
2008-12-01
Full Text Available Yarn strength modelling and prediction has remained as the cynosure of research for the textile engineers although the investigation in this domain was first reported around one century ago. Several mathematical, statistical and empirical models have been developed in the past only to yield limited success in terms of prediction accuracy and general applicability. In recent years, soft computing tools like artificial neural networks and neural-fuzzy models have been developed, which have shown remarkable prediction accuracy. However, artificial neural network and neural-fuzzy models are trained using enormous amount of noise free input-output data, which are difficult to collect from the spinning industries. In contrast, fuzzy logic based models could be developed by using the experience of the spinner only and it gives good understanding about the roles played by various inputs on the outputs. This paper deals with the modelling of ring spun cotton yarn strength using a simple fuzzy expert system. The prediction accuracy of the model was found to be very encouraging.
ZERODUR strength modeling with Weibull statistical distributions
Hartmann, Peter
2016-07-01
The decisive influence on breakage strength of brittle materials such as the low expansion glass ceramic ZERODUR is the surface condition. For polished or etched surfaces it is essential if micro cracks are present and how deep they are. Ground surfaces have many micro cracks caused by the generation process. Here only the depths of the micro cracks are relevant. In any case presence and depths of micro cracks are statistical by nature. The Weibull distribution is the model used traditionally for the representation of such data sets. It is based on the weakest link ansatz. The use of the two or three parameter Weibull distribution for data representation and reliability prediction depends on the underlying crack generation mechanisms. Before choosing the model for a specific evaluation, some checks should be done. Is there only one mechanism present or is it to be expected that an additional mechanism might contribute deviating results? For ground surfaces the main mechanism is the diamond grains' action on the surface. However, grains breaking from their bonding might be moved by the tool across the surface introducing a slightly deeper crack. It is not to be expected that these scratches follow the same statistical distribution as the grinding process. Hence, their description with the same distribution parameters is not adequate. Before including them a dedicated discussion should be performed. If there is additional information available influencing the selection of the model, for example the existence of a maximum crack depth, this should be taken into account also. Micro cracks introduced by small diamond grains on tools working with limited forces cannot be arbitrarily deep. For data obtained with such surfaces the existence of a threshold breakage stress should be part of the hypothesis. This leads to the use of the three parameter Weibull distribution. A differentiation based on the data set alone without preexisting information is possible but requires a
Strength Modeling of High-Strength Concrete with Hybrid Fibre Reinforcement
A. Ravichandran
2009-01-01
Full Text Available The low tensile strength and limited ductility, the unavoidable deficiency, of concrete can be overcome by the addition of fibres. High strength concrete (HSC of 60 MPa containing hybrid fibres, combination of steel and polyolefin fibres, at different volume fraction of 0.5, 1.0, 1.5 and 2.0% were compared in terms of compressive, splitting tensile strength and flexural properties with HSC containing no fibres. Test results showed that the fibres when used in hybrid form could result in enhanced flexural toughness compared to steel fibre reinforced concrete [HSFRC]. The compressive strength of the fibre-reinforced concrete reached maximum at 1.5% volume fractions and the splitting tensile strength and modulus of rupture improved with increasing volume fraction. Strength models were established to predict the compressive and splitting tensile strength and modulus of rupture of the fibre-reinforced concrete. The models give prediction matching the measurements.
Photophoretic strength on chondrules. 1. Modeling
Loesche, Christoph; Wurm, Gerhard; Teiser, Jens [Faculty of Physics, University of Duisburg-Essen, Lotharstr. 1, D-47057 Duisburg (Germany); Friedrich, Jon M. [Department of Chemistry, Fordham University, Bronx, NY 10458 (United States); Bischoff, Addi, E-mail: christoph.loesche@uni-due.de [Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster (Germany)
2013-12-01
Photophoresis is a physical process that transports particles in optically thin parts of protoplanetary disks, especially at the inner edge and at the optical surface. To model the transport and resulting effects in detail, it is necessary to quantify the strength of photophoresis for different particle classes as a fundamental input. Here, we explore photophoresis for a set of chondrules. The composition and surface morphology of these chondrules were measured by X-ray tomography. Based on the three-dimensional models, heat transfer through illuminated chondrules was calculated. The resulting surface temperature map was then used to calculate the photophoretic strength. We found that irregularities in particle shape and variations in composition induce variations in the photophoretic force. These depend on the orientation of a particle with respect to the light source. The variation of the absolute value of the photophoretic force on average over all chondrules is 4.17%. The deviation between the direction of the photophoretic force and illumination is 3.°0 ± 1.°5. The average photophoretic force can be well approximated and calculated analytically assuming a homogeneous sphere with a volume equivalent mean radius and an effective thermal conductivity. We found an analytic expression for the effective thermal conductivity. The expression depends on the two main phases of a chondrule and decreases with the amount of fine-grained devitrified, plagioclase-normative mesostasis up to factor of three. For the chondrule sample studied (Bjurböle chondrite), we found a dependence of the photophoretic force on chondrule size.
models for predicting compressive strength and water absorption of ...
user
combine laterite and quarry dust in sandcrete blocks or concrete are few. One of ... model for optimization of compressive strength of sand- laterite blocks using ..... compressive strength of Pulverise fuel Ash-Cement concrete''. IOSR Journal of ...
Interaction Strength and a Generalized Bak-Sneppen Evolution Model
李炜; 蔡勖
2002-01-01
The Bak-Sneppen evolution model is generalized in terms of a new concept and quantity: interaction strength.Based on a quantitative definition, the interaction strength describes the strength of the interaction between thenearest-neighbour individuals in the model Self-organized criticality is observed for the generalized model withten different values of interaction strength. The gap equation governing the self-organization is derived. It is alsofound that the self-organized threshold depends on the value of the interaction strength.
A probability model for the strength of carbon nanotubes
X. Frank Xu
2014-07-01
Full Text Available A longstanding controversy exists on the form of the probability distribution for the strength of carbon nanotubes: is it Weibull, lognormal, or something else? We present a theory for CNT strength through integration of weakest link scaling, flaw statistics, and brittle fracture. The probability distribution that arises exhibits multiple regimes, each of which takes the form of a Weibull distribution. Our model not only gives a possible resolution to the debate but provides a way to attain reliable estimates of CNT strength for materials design from practical-sized (non-asymptotic data sets of CNT strength. Last, the model offers an explanation for the severe underestimation of CNT strength from strength tests of CNT bundles.
Statistical Model of the 3-D Braided Composites Strength
XIAO Laiyuan; ZUO Weiwei; CAI Ganwei; LIAO Daoxun
2007-01-01
Based on the statistical model for the tensile statistical strength of unidirectional composite materials and the stress analysis of 3-D braided composites, a new method is proposed to calculate the tensile statistical strength of the 3-D braided composites. With this method, the strength of 3-D braided composites can be calculated with very large accuracy, and the statistical parameters of 3-D braided composites can be determined. The numerical result shows that the tensile statistical strength of 3-D braided composites can be predicted using this method.
A Strength Model and Service Envelope for PBX 9501
Stevens, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2014-02-05
An analytical method is proposed for making an assessment of the severity of the response of PBX 9501 in structural response simulations. The approach is based on the coherent use of a strength model and a failure criterion. The strength model is based on a creep rupture function and an associated cumulative damage model. The material's residual strength at any time during a simulation of structural response is determined by taking into account both the actual stress history up to that time, and a hypothetical continuation of the applied stresses that are assumed to grow until material failure results. The residual strength is used by the failure criterion to define the region of safe (non-failed) material response. The Mohr-Coulomb failure criterion is chosen for its general applicability to materials with both cohesive and frictional strength. The combined use of the residual strength model and the failure criterion provides a quantitative method of assessing the severity of the response of PBX 9501 material in structural simulations: the proximity of any evolving, general state of stress to the failure surface (which shrinks due to the cumulative damage caused by the past stress history) can be calculated and used as a measure of margin to failure. The strength model has been calibrated to a broad range of uniaxial tension and compression tests, and a small set of creep tests, and is applicable to a broad range of loading conditions.
Yarn Strength Modelling Using Genetic Fuzzy Expert System
Banerjee, Debamalya; Ghosh, Anindya; Das, Subhasis
2013-05-01
This paper deals with the modelling of cotton yarn strength using genetic fuzzy expert system. Primarily a fuzzy expert system has been developed to model the cotton yarn strength from the constituent fibre parameters such as fibre strength, upper half mean length, fibre fineness and short fibre content. A binary coded genetic algorithm has been used to improve the prediction performance of the fuzzy expert system. The experimental validation confirms that the genetic fuzzy expert system has significantly better prediction accuracy and consistency than that of the fuzzy expert system.
Echo structures and Target Strength modelling for a synthetic submarine
Schippers, P.; Beerens, S.P.
2007-01-01
Since the early nineties, performance modelling of active sonars has been developed at TNO in the ALMOST model, including propagation and sonar processing, based on point targets of given Target Strength. Recently, the modelling was extended with a computation module for target echo structure, resul
Micromechanical modelling of mechanical behaviour and strength of wood
Mishnaevsky, Leon; Qing, Hai
2008-01-01
An overview of the micromechanical theoretical and numerical models of wood is presented. Different methods of analysis of the effects of wood microstructures at different scale levels on the mechanical behaviour, deformation and strength of wood are discussed and compared. Micromechanical models...
Modelling the effect of shear strength on isentropic compression experiments
Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary
2017-01-01
Isentropic compression experiments (ICE) are a way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 - 102 GPa, while the yield strength of the material can be as low as 10-2 GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength compared with a model based purely on hydrodynamics.
A Report on the Validation of Beryllium Strength Models
Armstrong, Derek Elswick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-02-05
This report discusses work on validating beryllium strength models with flyer plate and Taylor rod experimental data. Strength models are calibrated with Hopkinson bar and quasi-static data. The Hopkinson bar data for beryllium provides strain rates up to about 4000 per second. A limitation of the Hopkinson bar data for beryllium is that it only provides information on strain up to about 0.15. The lack of high strain data at high strain rates makes it difficult to distinguish between various strength model settings. The PTW model has been calibrated many different times over the last 12 years. The lack of high strain data for high strain rates has resulted in these calibrated PTW models for beryllium exhibiting significantly different behavior when extrapolated to high strain. For beryllium, the α parameter of PTW has recently been calibrated to high precision shear modulus data. In the past the α value for beryllium was set based on expert judgment. The new α value for beryllium was used in a calibration of the beryllium PTW model by Sky Sjue. The calibration by Sjue used EOS table information to model the temperature dependence of the heat capacity. Also, the calibration by Sjue used EOS table information to model the density changes of the beryllium sample during the Hopkinson bar and quasi-static experiments. In this paper, the calibrated PTW model by Sjue is compared against experimental data and other strength models. The other strength models being considered are a PTW model calibrated by Shuh- Rong Chen and a Steinberg-Guinan type model by John Pedicini. The three strength models are used in a comparison against flyer plate and Taylor rod data. The results show that the Chen PTW model provides better agreement to this data. The Chen PTW model settings have been previously adjusted to provide a better fit to flyer plate data, whereas the Sjue PTW model has not been changed based on flyer plate data. However, the Sjue model provides a reasonable fit to
Forecast Jointed Rock Mass Compressive Strength Using a Numerical Model
Protosenya Anatoliy
2016-01-01
Full Text Available The method of forecasting the strength of the jointed rock mass by numerical modeling of finite element method in ABAQUS was described. The paper presents advantages of this method to solve the problem of determining the mechanical characteristics of jointed rock mass and the basic steps of creating a numerical geomechanical model of jointed rock mass and numerical experiment. Numerical simulation was carried out with jointed rock mass in order to obtain the ratio of strain and stress while loading the numerical model, determining parameters of quantitative assessment of the impact of the discontinuities orientation on the value of the compressive strength, compressive strength anisotropy. The results of the numerical experiment are compared with the data of experimental studies investigations. Innovative materials and structures are analyzed in this paper. The results that were obtained by calculation show qualitative agreement with the results of laboratory experiments of jointed rock mass.
Modeling and experimental analysis of magnetostriction in high strength steels
Della Torre E.
2013-01-01
Full Text Available Previous studies on the magnetostriction in high strength steels have ignored the internal anisotropies due to previous material handling. Cold-rolling an iron alloy will stretch and distort the magnetic domains in the direction of rolling. These altered domain shapes impact the magnetic characteristics of the alloy; adding an additional preferred direction of magnetization to the easy or hard axes within the crystalline structure. This paper presents data taken on rods of a high strength steel that have been machined parallel to the rolling direction; as well as simulated results using a Preisach-type magnetostriction model. The model, whose formulation is based on the DOK magnetization-based model, aims specifically to simulate the Villari reversal phenomenon observed in the magnetostriction measurements of high strength steels and some Terfenol-D alloys.
A multifluid mix model with material strength effects
Chang, C. H. [Los Alamos National Laboratory; Scannapieco, A. J. [Los Alamos National Laboratory
2012-04-23
We present a new multifluid mix model. Its features include material strength effects and pressure and temperature nonequilibrium between mixing materials. It is applicable to both interpenetration and demixing of immiscible fluids and diffusion of miscible fluids. The presented model exhibits the appropriate smooth transition in mathematical form as the mixture evolves from multiphase to molecular mixing, extending its applicability to the intermediate stages in which both types of mixing are present. Virtual mass force and momentum exchange have been generalized for heterogeneous multimaterial mixtures. The compression work has been extended so that the resulting species energy equations are consistent with the pressure force and material strength.
A Variable Flow Modelling Approach To Military End Strength Planning
2016-12-01
System Dynamics (SD) model is ideal for strategic analysis as it encompasses all the behaviours of a system and how the behaviours are influenced by...Markov Chain Models Wang describes Markov chain theory as a mathematical tool used to investigate dynamic behaviours of a system in a discrete-time... MODELLING APPROACH TO MILITARY END STRENGTH PLANNING by Benjamin K. Grossi December 2016 Thesis Advisor: Kenneth Doerr Second Reader
Transition Strength Sums and Quantum Chaos in Shell Model States
Kota, V K B; Kar, K; Gómez, J M G; Retamosa, J
2000-01-01
For the embedded Gaussian orthogonal ensemble (EGOE) of random matrices, the strength sums generated by a transition operator acting on an eigenstate vary with the excitation energy as the ratio of two Gaussians. This general result is compared to exact shell model calculations, with realistic interactions, of spherical orbit occupancies and Gamow-Teller strength sums in some $(ds)$ and $(fp)$ shell examples. In order to confirm that EGOE operates in the chaotic domain of the shell model spectrum, calculations are carried out using two different interpolating hamiltonians generating order-chaos transitions. Good agreement is obtained in the chaotic domain of the spectrum, and strong deviations are observed as nuclear motion approaches a regular regime (transition strength sums appear to follow the Dyson's $\\Delta_3$ statistic). More importantly, they shed new light on the newly emerging understanding that in the chaotic domain of isolated finite interacting many particle systems smoothed densities (they inclu...
S. Chowdhury
2015-11-01
Full Text Available In this study, Wood Ash (WA prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45 and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20% including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM, strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper.
Chowdhury, S; Maniar, A; Suganya, O M
2015-11-01
In this study, Wood Ash (WA) prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength) of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45) and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20%) including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM), strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper.
RECEIVED SIGNAL STRENGTH INDICATION MODELING IN INDOOR WIRELESS SENSOR NETWORKS
Edson Taira Procopio
2013-01-01
Full Text Available This study aims to identify mathematical models that represent the relation between Received Signal Strength Indication (RSSI and objects in an indoor Wireless Sensor Network (WSN. Using the Least Squares Method, four linear models have been identified: The first one relates uplink RSSI and objects; the second one relates downlink RSSI and objects; the third one relates uplink RSSI and obstacles and the fourth one relates downlink RSSI and obstacles. The obtained results, characterized by small residual values, attest the validation of all four models.
Survival model construction guided by fit and predictive strength.
Chauvel, Cécile; O'Quigley, John
2016-10-05
Survival model construction can be guided by goodness-of-fit techniques as well as measures of predictive strength. Here, we aim to bring together these distinct techniques within the context of a single framework. The goal is how to best characterize and code the effects of the variables, in particular time dependencies, when taken either singly or in combination with other related covariates. Simple graphical techniques can provide an immediate visual indication as to the goodness-of-fit but, in cases of departure from model assumptions, will point in the direction of a more involved and richer alternative model. These techniques appear to be intuitive. This intuition is backed up by formal theorems that underlie the process of building richer models from simpler ones. Measures of predictive strength are used in conjunction with these goodness-of-fit techniques and, again, formal theorems show that these measures can be used to help identify models closest to the unknown non-proportional hazards mechanism that we can suppose generates the observations. Illustrations from studies in breast cancer show how these tools can be of help in guiding the practical problem of efficient model construction for survival data.
Modeling of elastic-strength properties of elastomers
O. V. Karmanova
2016-01-01
Full Text Available Model "structure-property", which takes into account the structural heterogeneity of polymer compositions has been developed. Experimental compositions based on styrene-butadiene rubber SCS 30ARK and crosslinked, high viscosity polymer (high-molecular filler - VMN in different proportions, as well as softeners (industrial oil I-12A, oil PN-6, low-molecular polybutadiene PBN were investigated. Samples that differ significantly in viscosity were obtained. The rubber blends and vulcanizates, based on the experimental of polymer compositions, were prepared. Physico-mechanical properties - tensile strength, elongation at break, Shore A. A hardness were determined. For describe the physical and mechanical properties of polymers logarithmic additivity rule was used. The properties of the polymer composition (PС were determined by a single dominant component (resin composition consisting of a high rubber and a filler and further components (softeners. Identification algorithm consists of four steps. The implementation of this algorithm is carried out using experimental design techniques. Estimation of the unknown parameters in the equation was carried out using the method of least squares. Quality evaluation of the model was conducted with the criteria Fisher, turning points, the Durbin-Watson, R / S-criterion. It is found that the model adequately describes the change of physicomechanical properties depending on the composition of polymer compositions. 3d graphics of the physical-mechanical properties of the polymer compositions were built. This allowed us to estimate the contribution of the dominant component and optional components (including combinations thereof to change the parameters. It has been established that the introduction of rubber in total more than 50% of the components (BMH and softeners reduced conventional tensile strength and dramatically increases the relative error of model calculations. (BMH and softeners
Allometric functional response model: body masses constrain interaction strengths.
Vucic-Pestic, Olivera; Rall, Björn C; Kalinkat, Gregor; Brose, Ulrich
2010-01-01
1. Functional responses quantify the per capita consumption rates of predators depending on prey density. The parameters of these nonlinear interaction strength models were recently used as successful proxies for predicting population dynamics, food-web topology and stability. 2. This study addressed systematic effects of predator and prey body masses on the functional response parameters handling time, instantaneous search coefficient (attack coefficient) and a scaling exponent converting type II into type III functional responses. To fully explore the possible combinations of predator and prey body masses, we studied the functional responses of 13 predator species (ground beetles and wolf spiders) on one small and one large prey resulting in 26 functional responses. 3. We found (i) a power-law decrease of handling time with predator mass with an exponent of -0.94; (ii) an increase of handling time with prey mass (power-law with an exponent of 0.83, but only three prey sizes were included); (iii) a hump-shaped relationship between instantaneous search coefficients and predator-prey body-mass ratios; and (iv) low scaling exponents for low predator-prey body mass ratios in contrast to high scaling exponents for high predator-prey body-mass ratios. 4. These scaling relationships suggest that nonlinear interaction strengths can be predicted by knowledge of predator and prey body masses. Our results imply that predators of intermediate size impose stronger per capita top-down interaction strengths on a prey than smaller or larger predators. Moreover, the stability of population and food-web dynamics should increase with increasing body-mass ratios in consequence of increases in the scaling exponents. 5. Integrating these scaling relationships into population models will allow predicting energy fluxes, food-web structures and the distribution of interaction strengths across food web links based on knowledge of the species' body masses.
Tantalum strength model incorporating temperature, strain rate and pressure
Lim, Hojun; Battaile, Corbett; Brown, Justin; Lane, Matt
Tantalum is a body-centered-cubic (BCC) refractory metal that is widely used in many applications in high temperature, strain rate and pressure environments. In this work, we propose a physically-based strength model for tantalum that incorporates effects of temperature, strain rate and pressure. A constitutive model for single crystal tantalum is developed based on dislocation kink-pair theory, and calibrated to measurements on single crystal specimens. The model is then used to predict deformations of single- and polycrystalline tantalum. In addition, the proposed strength model is implemented into Sandia's ALEGRA solid dynamics code to predict plastic deformations of tantalum in engineering-scale applications at extreme conditions, e.g. Taylor impact tests and Z machine's high pressure ramp compression tests, and the results are compared with available experimental data. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Tow collapse model for compression strength of textile composites
Emehel, T.C.; Shivakumar, K.N. [North Carolina A and T State Univ., Greensboro, NC (United States)
1995-12-31
The unidirectional composite compression strength model based on microbuckling of fibers embedded in a rigid-plastic matrix was extended to multiaxial laminates and textile composites. The resulting expression is a function of matrix yield strength under the fiber constraint, fiber misalignment angle, fiber volume fraction, and the area fractions of various sets of inclined tows. The analysis was verified by experimentation. Compression tests were conducted on laminated, three-dimensional triaxially braided and orthogonally woven composites using the IITRI test specimen. The laminate specimens were made up of AS4/3501-6 graphite/epoxy composite with (0){sub 24}, (0/30/0/{minus}30){sub 3S}, and ((0/90)6/0){sub S} stacking sequence. Textile composites were made of BASF G30-500 graphite fiber tows (tow size is 6K) and Dow Chemicals Tactix 123 matrix. Fiber preform architecture of braided and woven composites before resin consolidation was 0/{+-}17 and 0/90, respectively and after consolidation it was about (7/{+-}20) and (5/90/90), respectively. The analysis agreed reasonably well with the test data for all cases considered. The axial fiber/tow misalignment angle for laminated, braided, and woven composites were about 4, 7, and 5 degrees, respectively. The compression strength was found to be strongly dependent on the percentage of axial tows and its misalignment angle. A small variation in the off-axis fiber/tow orientation had marginal effect on the compression strength. Hence, the off axis tow misalignment angle can be assumed to be same as the initial laminate or the two orientation angle.
Holographic superconductor models with the Maxwell field strength corrections
Pan, Qiyuan; Wang, Bin
2011-01-01
We study the effect of the quadratic field strength correction to the usual Maxwell field on the holographic dual models in the backgrounds of AdS black hole and AdS soliton. We find that in the black hole background, the higher correction to the Maxwell field makes the condensation harder to form and changes the expected relation in the gap frequency. This effect is similar to that caused by the curvature correction. However, in the soliton background we find that different from the curvature effect, the correction to the Maxwell field does not influence the holographic superconductor and insulator phase transition.
Stochastic Models for Strength of Wind Turbine Blades using Tests
Toft, Henrik Stensgaard; Sørensen, John Dalsgaard
2008-01-01
The structural cost of wind turbine blades is dependent on the values of the partial safety factors which reflect the uncertainties in the design values, including statistical uncertainty from a limited number of tests. This paper presents a probabilistic model for ultimate and fatigue strength...... of wind turbine blades especially considering the influence of prior knowledge and test results and how partial safety factors can be updated when additional full-scale tests are performed. This updating is performed by adopting a probabilistic design basis based on Bayesian statistical methods....
Henry de Frahan, M. T., E-mail: marchdf@umich.edu; Johnsen, E. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Belof, J. L.; Cavallo, R. M.; Ancheta, D. S.; El-dasher, B. S.; Florando, J. N.; Gallegos, G. F.; LeBlanc, M. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808 (United States); Raevsky, V. A.; Ignatova, O. N.; Lebedev, A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188 (Russian Federation)
2015-06-14
We present a set of high explosive driven Rayleigh-Taylor strength experiments for beryllium to produce data to distinguish predictions by various strength models. Design simulations using existing strength model parameterizations from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, suggests growth consistent with little material strength. We focus mostly on efforts to simulate the data using published strength models as well as the more recent RING relaxation model developed at VNIIEF. The results of the strength experiments indicate weak influence of strength in mitigating the growth with the RING model coming closest to predicting the material behavior. Finally, we present shock and ramp-loading recovery experiments.
Modelling of tension stiffening for normal and high strength concrete
Christiansen, Morten Bo; Nielsen, Mogens Peter
1998-01-01
Accurate calculations of the stiffness of concrete members are rare. Only in the uncracked state and the fully cracked state, where the reinforcement is near yielding, the stiffness calculations are relatively easy. The difficulties are due to the fact that concrete between cracks may give...... a substantial contribution to the stiffness, a phenomenon which is generally referred to as tension stiffening. The present paper describes a new theory of tension stiffening. It is based on a simple physical model for pure tension, which works with three different stages of crack generation. In a simplified...... form the model is extended to apply to biaxial stress fields as well. To determine the biaxial stress field, the theorem of minimum complementary elastic energy is used. The theory has been compared with tests on rods, disks, and beams of both normal and high strength concrete, and very good results...
Cervine tibia morphology and mechanical strength: a suitable tibia model?
Throop, Alexander D W; Landauer, Alexander K; Clark, Alexander Martin; Kuxhaus, Laurel
2015-03-01
Animal models for orthopaedic implant testing are well-established but morphologically dissimilar to human tibiae; notably, most are shorter. The purpose of this study was to quantitatively evaluate the morphology and mechanical properties of the cervine tibia, particularly with regard to its suitability for testing orthopaedic implants. Two endosteal and eleven periosteal measurements were made on 15 cervine tibiae. The mechanical strength in axial compression and torsion was measured using 11 tibiae. The cervine tibia is morphologically similar to the human tibia and more closely matches the length of the human tibia than current tibia models (ovine, porcine, and caprine). The distal epiphysis dimensions are notably different, but no more so than the current tibia models. The torsional stiffness of the cervine tibia is within the range of previously reported values for human tibiae. Furthermore, in many regions, cervine tibiae are abundant and locally available at a low cost. Given these mechanical and morphological data, coupled with potential cost savings if regionally available, the cervine tibia may be an appropriate model for orthopaedic implant testing.
Investigating Lithosphere Strength With Thin-Shell Tectonic Modeling
Moder, C.; Carena, S.
2007-12-01
The behavior of many major faults on Earth can only be explained if they are assumed to be much weaker than expected from Byerlee's Law alone. However, there is no agreement over what is a realistic range of friction parameters for faults, or its possible dependency on fault network geometry. Both can be studied with numerical forward modeling, but this requires knowledge of the detailed 3-D geometry of the faults. The latter is now available for most of California, thanks to the SCEC Community Fault Model (southern California) and to the USGS program "3-D Geologic Maps and Visualization" (San Francisco Bay and surrounding region). We model the behavior of the California fault network with the finite-element code SHELLS. We use as input a coarse global grid, with local high-resolution representation of actual faults based on the existing 3-D fault maps. By comparing the simulation results with data on fault-slip rates, we can determine how the faults in this network interact, the role of small faults, and we can quantify the typical fault strength in a continental transform plate boundary setting.
A dependent stress-strength interference model based on mixed copula function
Gao, Jian Xiong; An, Zong Wen; Liu, Bo [School of Mechatronics Engineering, Lanzhou University of Technology, Lanzhou (China)
2016-10-15
In the traditional Stress-strength interference (SSI) model, stress and strength must satisfy the basic assumption of mutual independence. However, a complex dependence between stress and strength exists in practical engineering. To evaluate structural reliability under the case that stress and strength are dependent, a mixed copula function is introduced to a new dependent SSI model. This model can fully characterize the dependence between stress and strength. The residual square sum method and genetic algorithm are also used to estimate the unknown parameters of the model. Finally, the validity of the proposed model is demonstrated via a practical case. Results show that traditional SSI model ignoring the dependence between stress and strength more easily overestimates product reliability than the new dependent SSI model.
Endanus Harijanto
2005-09-01
Full Text Available Tooth crown restoration was made in a complex system consisting of several elements, namely tensile strength and shear strength bond between copper alloy and acrylic resin after tin plating. The aim of this exemination was to find a model representing connection between tensile strength and shear strength in between copper alloy with acrylic resin in statistic method. In conclusion, this exemination utilizing a strength model = 0.645 + 1.237 × tensile strength resulted shear strength exemination. On the other hand, the utilization of a strength = –0.506 + 0.808 × shear strength resulted tensile strength exemination.
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.
Strength evolution law of cracked rock based on localized progressive damage model
ZHANG Ping; LI Xi-bing; LI Ning
2008-01-01
In the light of the localized progressive damage model, the evolution law of cohesive and frictional strength with irreversible strains was determined. Then, the location and the extent of the excavation disturbed zone in one deep rock engineering were predicted by using the strength evolution law. The theoretical result is close to the result of in-situ test. The strength evolution law excels the elastic-perfectly plastic model and elasto-brittte plastic model in which the cohesive and frictional strength are mobilized simultaneously. The results obtained indicate that the essential failure mechanism of the cracked rock can be described by the cohesion weakening and friction strengthening evolution law.
Functional and Muscular Adaptations in an Experimental Model for Isometric Strength Training in Mice
Karsten Krüger; Gessner, Denise K; Michael Seimetz; Jasmin Banisch; Robert Ringseis; Klaus Eder; Norbert Weissmann; Mooren, Frank C.
2013-01-01
Exercise training induces muscular adaptations that are highly specific to the type of exercise. For a systematic study of the differentiated exercise adaptations on a molecular level mouse models have been used successfully. The aim of the current study was to develop a suitable mouse model of isometric strength exercise training characterized by specific adaptations known from strength training. C57BL/6 mice performed an isometric strength training (ST) for 10 weeks 5 days/week. Additionall...
Development and Validation of a Rule-Based Strength Scaling Method for Musculoskeletal Modelling
Oomen, Pieter; Annegarn, Janneke; Rasmussen, John
2015-01-01
Rule based strength scaling is an easy, cheap and relatively accurate technique to personalize musculoskeletal (MS) models. This paper presents a new strength scaling approach for MS models and validates it by maximal voluntary contractions (MVC). A heterogeneous group of 63 healthy subjects...
A constitutive model for the anelastic behavior of Advanced High Strength Steels
Torkabadi, A.; Liempt, van P.; Meinders, V.T.; Boogaard, van den A.H.
2015-01-01
In this work a physically based model describing the anelastic behaviour and nonlinear unloading in Advanced High Strength Steels (AHSS) is proposed. The model is fitted to the experimental data obtained from uni-axial tests on a dual-phase high strength steel grade (HCT780). The results show a good
Non-linear critical taper model and determination of accretionary wedge strength
Yang, Che-Ming; Dong, Jia-Jyun; Hsieh, Yuan-Lung; Liu, Hsueh-Hua; Liu, Cheng-Lung
2016-12-01
The critical taper model has been widely used to evaluate the strength contrast between the wedge and the basal detachment of fold-and-thrust belts and accretionary wedges. However, determination of the strength parameters using the traditional critical taper model, which adopts the Mohr-Coulomb failure criterion, is difficult, if not impossible. In this study, we propose a modified critical taper model that incorporates the non-linear Hoek-Brown failure criterion. The parameters in the proposed critical Hoek-Brown wedge CHBW model can be directly evaluated via field investigations and laboratory tests. Meanwhile, the wedge strength is a function of the wedge thickness, which is oriented from stress non-linearity. The fold-and-thrust belt in western central Taiwan was used as an example to validate the proposed model. The determined wedge strength was 0.86 using a representative wedge thickness of 5.3 km; this was close to the inferred value of 0.6 from the critical taper. Interestingly, a concave topographic relief is predicted as a result of the wedge thickness dependency of the wedge strength, even if the wedge is composed of homogeneous materials and if the strength of the detachment is uniform. This study demonstrates that the influence of wedge strength on the critical taper angle can be quantified by the spatial distribution of strength variables and by the consideration of the wedge thickness dependency of wedge strength.
Zhou, Annan; Sheng, Daichao
2009-01-01
The model recently presented by Sheng, Fredlund, and Gens, known as the SFG model, provides a consistent explanation of yield stress, shear strength, and volume change behaviour of unsaturated soils...
Asif Ali
2016-10-01
Full Text Available Reinforced Concrete is composed of concrete and steel, where compressive strength of concrete and tensile strength of steel are utilized to achieve the required member strength. The high tensile property of steel is thus used to confine and increase compressive strength and ductility of RC columns. Confined concrete is defined as concrete that is restrained laterally by any internal or external means i.e. reinforcement consisting of steel stirrups or spirals, Fiber Reinforced Polymer (FRP, Circular Concrete Filled Steel Tube, RC shell jacketing etc. An appropriate amount of confinement increases the strength, ductility and energy dissipation capacity of RC members. This paper focuses on finding out strength and ductility enhancement of low strength RC columns by reinforcement using existing confinement models. Confinement models are stress-strain curves developed for concrete compression member under uniaxial or dynamic loading, confined with transverse reinforcement. Different models along with their experimental validations are discussed in this paper to get state of the art knowledge of confinement studies possible for low strength concrete. The models recommended from this study are used to evaluate existing structures made with low strength concrete
Using a strengths model to build an on-line nursing education program.
Wieck, K Lynn; Alfred, Danita; Haas, Barbara K; Yarbrough, Susan
2014-01-01
The on-line environment is the new frontier for academia struggling to define its place in the evolving economy. A concern is how to engage students who maximize their on-line experience and graduate in a timely manner. A strengths model was used as the basis for development of an on-line doctoral nursing program. Upon entering the program, students were given a strengths assessment that focused both students and faculty on the positive attributes students were bringing to their doctoral studies. A positive feedback methodology using on-line discussions in each course was used to support the identified strengths. The optimal picture of a successful entering doctoral student appears to be a person whose top five strengths are learner, achiever, input, connectedness and responsibility. A strengths model promotes a positive learning environment and supports a teacher-learner dynamic where faculty members are encouraged to focus on the students' strengths rather than their challenges.
Doh, Hyeonjin; Salk, Sung-Ho Suck
1996-01-01
Using the Hubbard model Hamiltonian in a mean field level, we examine the variation of antiferromagnetic strength with applied magnetic field. It is demonstrated that minima in the antiferromagnetic strength exist at the the even integer denominator values of rational number for magnetic flux per plaquette. The undulatory behavior of antiferromagnetic strength with the external magnetic field is found. It is seen to be related to the undulatory net statistical phase owing to the influence of ...
Henry de Frahan, M. T. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; Belof, J. L. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Cavallo, R. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Raevsky, V. A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ignatova, O. N. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Lebedev, A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ancheta, D. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; El-dasher, B. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Florando, J. N. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Gallegos, G. F. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Johnsen, E. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; LeBlanc, M. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA
2015-06-14
A recent collaboration between LLNL and VNIIEF has produced a set of high explosive driven Rayleigh-Taylor strength data for beryllium. Design simulations using legacy strength models from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, shows close to classical growth. We characterize the material properties of the beryllium tested in the experiments. We also discuss recent efforts to simulate the data using the legacy strength models as well as the more recent RING relaxation model developed at VNIIEF. Finally, we present shock and ramp-loading recovery experiments conducted as part of the collaboration.
Use of glazed ceramic waste as additive in mortar and the mathematical modelling of its strength.
Altin, Zehra Gulten; Erturan, Seyfettin; Tepecik, Abdulkadir
2008-04-01
This study investigated the reusability of waste material from the tile manufacturing industry as an alternative material to natural pozzolan trass. Yield strength values of mortar made from Portland cement (CEM 142.5), were measured by adding glazed ceramic waste and trass at various weight ratios (5 to 40%). The test results proved that the strength values at 2, 7, and 28 days gave good results for concentrations of waste materials less than 5-10% in the cement. A decrease in strength was observed at higher concentrations. Mathematical modelling results showed a logarithmic correlation between the mortar strength and weight fraction of cement.
Theoretical Strength of Face-Centred-Cubic Single Crystal Copper Based on a Continuum Model
LIU Xiao-Ming; LIU Zhan-Li; YOU Xiao-Chuan; NIE Jun-Feng; ZHUANG Zhuo
2009-01-01
The constitutive relation of single crystal copper based on atomistic potential is implemented to capture the nonlinear inter-atomic interactions. Uniaxial loading tests of single crystal copper with inter-atomic potential finite-element model are carried out to determine the corresponding ideal strength using the modified Born stability criteria. Dependence of the ideal strength on the crystallographic orientation is studied, and tension-compression asymmetry in ideal strength is also investigated. The results suggest that asymmetry for yielding strength of nano-materials may result from anisotropic character of crystal instability. Moreover, the results also reveal that the critical resolved shear stress in the direction of slip is not an accurate criterion for the ideal strength since it could not capture the dependence on the loading conditions and hydrostatic stress components for the ideal strength.
A.Suresh Babu; V.Jayabalan
2009-01-01
In recent times, conventional materials are replaced by metal matrix composites (MMCs) due to their high specific strength and modulus.Strength reliability, one of the key factors restricting wider use of composite materials in various applications, is commonly characterized by Weibull strength distribution function.In the present work, statistical analysis of the strength data of 15% volume alumina particle (mean size 15 μm)reinforced in aluminum alloy (1101 grade alloy) fabricated by stir casting method was carried out using Weibull probability model.Twelve tension tests were performed according to ASTM B577 standards and the test data, the corresponding Weibull distribution was obtained.Finally the reliability of the composite behavior in terms of its fracture strength was presented to ensure the reliability of composites for suitable applications.An important implication of the present study is that the Weibull distribution describes the experimentally measured strength data more appropriately.
J. E. Winandy; P. K. Lebow
2001-01-01
In this study, we develop models for predicting loss in bending strength of clear, straight-grained pine from changes in chemical composition. Although significant work needs to be done before truly universal predictive models are developed, a quantitative fundamental relationship between changes in chemical composition and strength loss for pine was demonstrated. In...
Norman, Sumner L; Lobo-Prat, Joan; Reinkensmeyer, David J
2017-07-01
Robotic devices can train strength, coordination, or a combination of both. If a robotic device focuses on coordination, what happens to strength recovery, and vice versa? Understanding this interaction could help optimize robotic training. We developed a computational neurorehabilitation model to gain insight into the interaction between strength and coordination recovery after stroke. In the model, the motor system recovers by optimizing the activity of residual corticospinal cells (focally connected, excitatory and inhibitory) and reticulospinal cells (diffusely connected and excitatory) to achieve a motor task. To do this, the model employs a reinforcement learning algorithm that uses stochastic search based on a reward signal produced by task execution. We simulated two tasks that require strength and coordination: a finger movement task and a bilateral wheelchair propulsion task. We varied the reward signal to value strength versus coordination, determined by a weighting factor. The model predicted a nonlinear relationship between strength and coordination recovery consistent with clinical data obtained for each task. The model also predicted that stroke can cause a competition between strength and coordination recovery, due to a scarcity of focal and inhibitory cells. These results provide a rationale for implementing robotic movement therapy that can adaptively alter the combination of force and coordination training to target desired components of motor recovery.
Ichoku, C.; Chin, M.; Diehl, T.; Wooster, M.; Roberts, G.; Giglio, L.
2007-05-01
Chemical transport models currently derive their smoke emission sources from counts of fire hot spots detected from satellites, usually with single daily overpasses. However, fires vary in size and strength, with a significant diurnal trend, making the use of pixel counts measured at the same time of day very unreliable for estimating smoke sources. Fortunately, the Moderate-resolution Imaging Spectro-radiometer (MODIS) twin sensors onboard the Terra and Aqua satellites, not only detect fires everywhere at four strategic times of day, but also measure their strength in the form of fire radiative power (FRP) or rate of release of fire radiative energy (FRE). FRP is now also being derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) sensor onboard the geostationary Meteosat-8 platform, which observes Africa and Europe virtually every 15 mins. The SEVIRI measurements show that MODIS 4-times-a-day measurements capture the essence of the fire diurnal cycle. Therefore, MODIS is currently the only satellite data source ideal for estimating daily smoke emissions globally. In a number of recent studies, FRP has been found to be directly proportional to both the rate of biomass consumption and the rate of smoke aerosol emission. Indeed, (1) a combustion factor (Fc), which relates FRE to burned biomass was established, and (2) a FRE-based emission coefficient (Ce), which is a simple coefficient to convert FRP (or FRE) to smoke aerosol emissions was derived for different parts of the world. The results obtained from satellite have been reproduced in the laboratory, and the ingestion of FRP in models is now being tested using the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. Although MODIS has been in operation since the last 6 years, regrettably, this rare but formidable data resource it provides (FRP) has been left largely unutilized. In this presentation, we will show the preliminary results of using FRP to improve the
The strength model of self-control in sport and exercise psychology
Chris eEnglert
2016-03-01
Full Text Available The strength model of self-control assumes that all acts of self-control (e.g., emotion regulation, persistence are empowered by a single global metaphorical strength that has limited capacity. This strength can become temporarily depleted after a primary self-control act, which, in turn, can impair performance in subsequent acts of self-control. Recently, the assumptions of the strength model of self-control also have been adopted and tested in the field of sport and exercise psychology. The present review paper aims to give an overview of recent developments in self-control research based on the strength model of self-control. Furthermore, recent research on interventions on how to improve and revitalize self-control strength will be presented. Finally, the strength model of self-control has been criticized lately, as well as expanded in scope, so the present paper will also discuss alternative explanations of why previous acts of self-control can lead to impaired performance in sport and exercise.
Target echo strength modelling at FOI, including results from the BeTSSi II workshop
Östberg, Martin
2016-01-01
An overview of the target echo strength (TS) modelling capacity at the Swedish Defense Research Agency (FOI) is presented. The modelling methods described range from approximate ones, such as raytracing and Kirchhoff approximation codes, to high accuracy full field codes including boundary integral equation methods and finite elements methods. Illustrations of the applicability of the codes are given for a few simple cases tackled during the BeTTSi II (Benchmark Target Echo Strength Simulation) workshop held in Kiel 2014.
Micromechanical modeling of strength and damage of fiber reinforced composites
Mishnaevsky, L. Jr.; Broendsted, P.
2007-03-15
The report for the first year of the EU UpWind project includes three parts: overview of concepts and methods of modelling of mechanical behavior, deformation and damage of unidirectional fiber reinforced composites, development of computational tools for the automatic generation of 3D micromechanical models of fiber reinforced composites, and micromechanical modelling of damage in FRC, and phenomenological analysis of the effect of frequency of cyclic loading on the lifetime and damage evolution in materials. (au)
Novel Predictive Model of the Debonding Strength for Masonry Members Retrofitted with FRP
Iman Mansouri
2016-11-01
Full Text Available Strengthening of masonry members using externally bonded (EB fiber-reinforced polymer (FRP composites has become a famous structural strengthening method over the past decade due to the popular advantages of FRP composites, including their high strength-to-weight ratio and excellent corrosion resistance. In this study, gene expression programming (GEP, as a novel tool, has been used to predict the debonding strength of retrofitted masonry members. The predictions of the new debonding resistance model, as well as several other models, are evaluated by comparing their estimates with experimental results of a large test database. The results indicate that the new model has the best efficiency among the models examined and represents an improvement to other models. The root mean square errors (RMSE of the best empirical Kashyap model in training and test data were, respectively, reduced by 51.7% and 41.3% using the GEP model in estimating debonding strength.
The prediction of brick wall strengths with artificial neural networks model
Demir, Ali; Kumanlioglu, Ahmet Ali
2017-01-01
The aim of this study is to predict with Artificial Neural Networks (ANN) shear strength of brick masonry walls. Shear strength of the walls is determined with diagonal shear tests. It is very difficult to determine strengths of brick masonry walls with experimental procedures. Therefore, an Artificial Neural Networks model is developed with data obtained by investigating many papers from literature and experiments carried out by the authors. Finally, a good degree of coherency is obtained between the experimental and predicted data. The model that is developed makes it possible to easily predict shear strength of the masonry walls. Additionally, this model can be continuously trained with new data and its applicability range can easily be expanded.
Integrating attentional control theory and the strength model of self-control.
Englert, Chris; Bertrams, Alex
2015-01-01
In the present article, we argue that it may be fruitful to incorporate the ideas of the strength model of self-control into the core assumptions of the well-established attentional control theory (ACT). In ACT, it is assumed that anxiety automatically leads to attention disruption and increased distractibility, which may impair subsequent cognitive or perceptual-motor performance, but only if individuals do not have the ability to counteract this attention disruption. However, ACT does not clarify which process determines whether one can volitionally regulate attention despite experiencing high levels of anxiety. In terms of the strength model of self-control, attention regulation can be viewed as a self-control act depending on the momentary availability of self-control strength. We review literature that has revealed that self-control strength moderates the anxiety-performance relationship, discuss how to integrate these two theoretical models, and offer practical recommendations of how to counteract negative anxiety effects.
Weiguo Li
2012-01-01
Full Text Available A thermodamage strength theoretical model taking into account the effect of residual stress was established and applied to each temperature phase based on the study of effects of various physical mechanisms on the fracture strength of ultrahigh-temperature ceramics. The effects of SiC particle size, crack size, and SiC particle volume fraction on strength corresponding to different temperatures were studied in detail. This study showed that when flaw size is not large, the bigger SiC particle size results in the greater effect of tensile residual stress in the matrix grains on strength reduction, and this prediction coincides with experimental results; and the residual stress and the combined effort of particle size and crack size play important roles in controlling material strength.
BEAM 1.7: development for modelling fuel element and bundle buckling strength
Cheng, G.; Xu, S.; Xu, Z.; Paul, U.K. [Atomic Energy of Canada, Mississauga, Ontario (Canada)
2010-07-01
This paper describes BEAM, an AECL developed computer program, used to assess mechanical integrity of CANDU fuel bundles. The BEAM code has been developed to satisfy the need for buckling strength analysis of fuel bundles. Buckling refers to the phenomenon where a compressive axial load is large enough that a small lateral load can cause large lateral deflections. The buckling strength refers to the critical compressive axial load at which lateral instability is reached. The buckling strength analysis has practical significance for the design of fuel bundles, where the buckling strength of a fuel element/bundle is assessed so that the conditions leading to bundle jamming in the pressure tube are excluded. This paper presents the development and qualification of the BEAM code, with emphasis on the theoretical background and code implementation of the newly developed fuel element/bundle buckling strength model. (author)
An efficient numerical target strength prediction model: Validation against analysis solutions
Fillinger, L.; Nijhof, M.J.J.; Jong, C.A.F. de
2014-01-01
A decade ago, TNO developed RASP (Rapid Acoustic Signature Prediction), a numerical model for the prediction of the target strength of immersed underwater objects. The model is based on Kirchhoff diffraction theory. It is currently being improved to model refraction, angle dependent reflection and t
Youngs-Type Material Strength Model in the Besnard-Harlow-Rauenzahn Turbulence Equations
Denissen, Nicholas Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Plohr, Bradley J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-08-17
Youngs [AWE Report Number 96/96, 1992] has augmented a two-phase turbulence model to account for material strength. Here we adapt the model of Youngs to the turbulence model for the mixture developed by Besnard, Harlow, and Rauenzahn [LANL Report LA-10911, 1987].
Strength Analysis Modelling of Flexible Umbilical Members for Marine Structures
S. Sævik
2012-01-01
Full Text Available This paper presents a 3-dimensional finite element formulation for predicting the behaviour of complex umbilical cross-sections exposed to loading from tension, torque, internal and external pressure including bending. Helically wound armours and tubes are treated as thin and slender beams formulated within the framework of small strains but large displacements, applying the principle of virtual displacements to obtain finite element equations. Interaction between structural elements is handled by 2- and 3-noded contact elements based on a penalty parameter formulation. The model takes into account a number of features, such as material nonlinearity, gap and friction between individual bodies, and contact with external structures and with a full 3-dimensional description. Numerical studies are presented to validate the model against another model as well as test data.
Micromechanical modeling of unidirectional composites with uneven interfacial strengths
Ashouri Vajari, Danial; Legarth, Brian Nyvang; Niordson, Christian Frithiof
2013-01-01
Composite materials under loads normal to the fiber orientation often fail due to debonding between fibers and matrix. In this paper a micromechanical model is developed to study the interfacial and geometrical effects in fiber-reinforced composites using generalized plane strain by means......, a trapezoidal cohesive zone model is used. A parametric study is carried out to evaluate the influence of the interfacial properties, fiber position and fiber volume fraction on the overall stressestrain response as well as the end-crack opening displacement and the opening crack angle. All the results...
A Model for Determining Strength for Embedded Elliptical Crack in Ultra-high-temperature Ceramics
Ruzhuan Wang
2015-08-01
Full Text Available A fracture strength model applied at room temperature for embedded elliptical crack in brittle solid was obtained. With further research on the effects of various physical mechanisms on material strength, a thermo-damage strength model for ultra-high-temperature ceramics was applied to each temperature phase. Fracture strength of TiC and the changing trends with elliptical crack shape variations under different temperatures were studied. The study showed that under low temperature, the strength is sensitive to the crack shape variation; as the temperature increases, the sensitivities become smaller. The size of ellipse’s minor axes has great effect on the material strength when the ratio of ellipse’s minor and major axes is lower than 0.5, even under relatively high temperatures. The effect of the minor axes of added particle on material properties thus should be considered under this condition. As the crack area is set, the fracture strength decreases firstly and then increases with the increase of ratio of ellipse’s minor and major axes, and the turning point is 0.5. It suggests that for the added particles the ratio of ellipse’s minor and major axes should not be 0.5. All conclusions significantly coincided with the results obtained by using the finite element software ABAQUS.
EFFECT OF NANOPOWDER ADDITION ON THE FLEXURAL STRENGTH OF ALUMINA CERAMIC - A WEIBULL MODEL ANALYSIS
Daidong Guo
2016-05-01
Full Text Available Alumina ceramics were prepared either with micrometer-sized alumina powder (MAP or with the addition of nanometer-sized alumina powder (NAP. The density, crystalline phase, flexural strength and the fracture surface of the two ceramics were measured and compared. Emphasis has been put on the influence of nanopowder addition on the flexural strength of Al₂O₃ ceramic. The analysis based on the Weibull distribution model suggests the distribution of the flexural strength of the NAP ceramic is more concentrated than that of the MAP ceramic. Therefore, the NAP ceramics will be more stable and reliable in real applications.
Strength Reliability Analysis of Turbine Blade Using Surrogate Models
Wei Duan
2014-05-01
Full Text Available There are many stochastic parameters that have an effect on the reliability of steam turbine blades performance in practical operation. In order to improve the reliability of blade design, it is necessary to take these stochastic parameters into account. In this study, a variable cross-section twisted blade is investigated and geometrical parameters, material parameters and load parameters are considered as random variables. A reliability analysis method as a combination of a Finite Element Method (FEM, a surrogate model and Monte Carlo Simulation (MCS, is applied to solve the blade reliability analysis. Based on the blade finite element parametrical model and the experimental design, two kinds of surrogate models, Polynomial Response Surface (PRS and Artificial Neural Network (ANN, are applied to construct the approximation analytical expressions between the blade responses (including maximum stress and deflection and random input variables, which act as a surrogate of finite element solver to drastically reduce the number of simulations required. Then the surrogate is used for most of the samples needed in the Monte Carlo method and the statistical parameters and cumulative distribution functions of the maximum stress and deflection are obtained by Monte Carlo simulation. Finally, the probabilistic sensitivities analysis, which combines the magnitude of the gradient and the width of the scatter range of the random input variables, is applied to evaluate how much the maximum stress and deflection of the blade are influenced by the random nature of input parameters.
J BU; Z TIAN
2016-03-01
Properties of concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the pore structure-compressive strength relationship in concrete. Several concrete mixtures with different pore structures are proportioned and subjected to static compressive tests. The pore structure features such as porosity, pore size distribution are extracted using mercury intrusion porosimetry technique. A statistical model is developed to relate thecompressive strength to relevant pore structure features.
Brittleness Generation Mechanism and Failure Model of High Strength Lightweight Aggregate Concrete
无
2006-01-01
The brittleness generation mechanism of high strength lightweight aggregate concrete(HSLWAC) was presented, and it was indicated that lightweight aggregate was the vulnerable spot,initiating brittleness. Based on the analysis of the brittleness failure by the load-deflection curve, the brittleness presented by HSLWAC was more prominent compared with ordinary lightweight aggregate concrete of the same strength grade. The model of brittleness failure was also established.
Mechanical Response of Polycarbonate with Strength Model Fits
2012-02-01
is used as free -parameter to improve the quality of the fit. ̇ is the strain rate and ?̇? is the reference strain rate for which 1/s was used...experimental data. Table 3. ZA model parameters. Bo= 0.006715948 1/K B1= 0.00009503 1/K Bpa = 550 MPa Bopa= 48 MPa ωa= -8 ▬ ωb= -0.01 ▬ β= 0.5...Hybrid Hard/Ductile All-Plastic-and Glass-Plastic-Based Composites ; ARL-TR-3155; U.S. Army Research Laboratory: Aberdeen Proving Ground, MD, February
Genetic regulation of bone strength: a review of animal model studies.
Adams, Douglas J; Ackert-Bicknell, Cheryl L
2015-01-01
Population- and family-based studies have established that fragility fracture risk is heritable; yet, the genome-wide association studies published to date have only accounted for a small fraction of the known variation for fracture risk of either the femur or the lumbar spine. Much work has been carried out using animal models toward finding genetic loci that are associated with bone strength. Studies using animal models overcome some of the issues associated with using patient data, but caution is needed when interpreting the results. In this review, we examine the types of tests that have been used for forward genetics mapping in animal models to identify loci and/or genes that regulate bone strength and discuss the limitations of these test methods. In addition, we present a summary of the quantitative trait loci that have been mapped for bone strength in mice, rats and chickens. The majority of these loci co-map with loci for bone size and/or geometry and thus likely dictate strength via modulating bone size. Differences in bone matrix composition have been demonstrated when comparing inbred strains of mice, and these matrix differences may be associated with differences in bone strength. However, additional work is needed to identify loci that act on bone strength at the materials level.
Unit-Sphere Multiaxial Stochastic-Strength Model Applied to Anisotropic and Composite Materials
Nemeth, Noel, N.
2013-01-01
Models that predict the failure probability of brittle materials under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This methodology has been extended to predict the multiaxial strength response of transversely isotropic brittle materials, including polymer matrix composites (PMCs), by considering (1) flaw-orientation anisotropy, whereby a preexisting microcrack has a higher likelihood of being oriented in one direction over another direction, and (2) critical strength, or K (sub Ic) orientation anisotropy, whereby the level of critical strength or fracture toughness for mode I crack propagation, K (sub Ic), changes with regard to the orientation of the microstructure. In this report, results from finite element analysis of a fiber-reinforced-matrix unit cell were used with the unit-sphere model to predict the biaxial strength response of a unidirectional PMC previously reported from the World-Wide Failure Exercise. Results for nuclear-grade graphite materials under biaxial loading are also shown for comparison. This effort was successful in predicting the multiaxial strength response for the chosen problems. Findings regarding stress-state interactions and failure modes also are provided.
Models of bending strength for Gilsocarbon graphites irradiated in inert and oxidising environments
Eason, Ernest D., E-mail: eeason@ix.netcom.com [Modeling and Computing Services, PO Box 18583, Boulder, CO 80308 (United States); Hall, Graham N., E-mail: graham.n.hall@manchester.ac.uk [Nuclear Graphite Research Group, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Marsden, Barry J., E-mail: barry.j.marsden@manchester.ac.uk [Nuclear Graphite Research Group, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Heys, Graham B., E-mail: Graham.Heys@hse.gsi.gov.uk [Office for Nuclear Regulation, An Agency of the Health and Safety Executive, Building 3, Redgrave Court, Merton Road, Bootle, Merseyside L20 7HS (United Kingdom)
2013-05-15
This paper presents the development and validation of an empirical model of fast neutron damage and radiolytic oxidation effects on bending strength for the moulded Gilsocarbon graphites used in Advanced Gas-cooled Reactors (AGRs). The inert environment model is based on evidence of essentially constant strength as fast neutron dose increases in inert environment. The model of combined irradiation and oxidation calibrates that constant along with an exponential function representing the degree of radiolytic oxidation as measured by weight loss. The change in strength with exposure was found to vary from one AGR station to another. The model was calibrated to data on material trepanned from AGR moderator bricks after varying operating times.
Investigation of stress–strain models for conﬁned high strength concrete
Metin Husem; Selim Pul
2007-06-01
The effects of conﬁnement reinforcement on the behaviour of high strength concrete columns are investigated for which prismatic experimental specimens were prepared. In the experiment specimens, four longitude reinforcement and conﬁnement reinforcement were used. For each experiment, stress–strain relationship of concrete was obtained and compared with models proposed earlier. The results show that conﬁnement reinforcement improved the ductility of high strength concrete. The ascending branch of stress–strain curves depended on the ratio of conﬁnement reinforcement was similar to the modiﬁed Kent–Park model and the descending branch similar to the Nagashima model.
A Microstructure Based Strength Model for Slag Blended Concrete with Various Curing Temperatures
Li-Na Zhang
2016-01-01
Full Text Available Ground granulated blast furnace slag, which is a byproduct obtained during steel manufacture, has been widely used for concrete structures in order to reduce carbon dioxide emissions and improve durability. This paper presents a numerical model to evaluate compressive strength development of slag blended concrete at isothermal curing temperatures and time varying curing temperatures. First, the numerical model starts with a cement-slag blended hydration model which simulates both cement hydration and slag reaction. The accelerations of cement hydration and slag reaction at elevated temperatures are modeled by Arrhenius law. Second, the gel-space ratios of hardening concrete are calculated using reaction degrees of cement and slag. Using a modified Powers’ gel-space ratio strength theory, the strength of slag blended concrete is evaluated considering both strengthening factors and weakening factors involved in strength development process. The proposed model is verified using experimental results of strength development of slag blended concrete with different slag contents and different curing temperatures.
Wu Fuqiang; Yao Weixing
2008-01-01
The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article.It is concluded that the inner original defects,which derived from the manufacturing process of composite laminates,are the common and major reason of causing the random distributions of the static strength and the fatigue life.And there is a correlative relation between the two distributions.With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material,the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained.And then the model which is used to describe the distributions of fatigue life of composites,based on their distributions of static strength,is set up.This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates.The experimental data of three kinds of composite laminates are employed to verify this model,and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.
A 3D multilevel model of damage and strength of wood: Analysis of microstructural effects
Qing, Hai; Mishnaevsky, Leon
2011-01-01
A 3D hierarchical computational model of damage and strength of wood is developed. The model takes into account the four scale microstructures of wood, including the microfibril reinforced structure at nanoscale, multilayered cell walls at microscale, hexagon-shape-tube cellular structure at meso...
The Strength-Based Counseling Model: A Paradigm Shift in Psychology
Smith, Elsie J.
2006-01-01
Sometimes, it is difficult for a profession to move forward because its members interpret emerging conceptual models from the perspective of old frameworks. Each of the five reactants in this issue of "The Counseling Psychologist" interpreted the strength-based counseling model within their own self-adopted framework--Adlerian psychology, role…
Implementation of strength and burn models for plastic-bonded explosives and propellants
Reaugh, J E
2009-05-07
We have implemented the burn model in LS-DYNA. At present, the damage (porosity and specific surface area) is specified as initial conditions. However, history variables that are used by the strength model are reserved as placeholders for the next major revision, which will be a completely interactive model. We have implemented an improved strength model for explosives based on a model for concrete. The model exhibits peak strength and subsequent strain softening in uniaxial compression. The peak strength increases with increasing strain rate and/or reduced ambient temperature. Under triaxial compression compression, the strength continues to increase (or at least not decrease) with increasing strain. This behaviour is common to both concrete and polymer-bonded explosives (PBX) because the microstructure of these composites is similar. Both have aggregate material with a broad particle size distribution, although the length scale for concrete aggregate is two orders of magnitude larger than for PBX. The (cement or polymer) binder adheres to the aggregate, and is both pressure and rate sensitive. There is a larger bind binder content in concrete, compared to the explosive, and the aggregates have different hardness. As a result we expect the parameter values to differ, but the functional forms to be applicable to both. The models have been fit to data from tests on an AWE explosive that is HMX based. The decision to implement the models in LS-DYNA was based on three factors: LS-DYNA is used routinely by the AWE engineering analysis group and has a broad base of experienced users; models implemented in LS-DYNA can be transferred easily to LLNL's ALE 3D using a material model wrapper developed by Rich Becker; and LS-DYNA could accommodate the model requirements for a significant number of additional history variables without the significant time delay associated with code modification.
Bansal, Manik; Singh, I. V.; Mishra, B. K.; Sharma, Kamal; Khan, I. A.
2017-04-01
A stochastic XFEM model based on microstructural observations has been developed to evaluate the tensile strength of NBG-18 nuclear graphite. The nuclear graphite consists of pitch matrix, filler particles, pores and micro-cracks. The numerical simulations are performed at two length scales due to large difference in average size of filler particles and pores. Both deterministic and stochastic approaches have been implemented. The study intends to illustrate the variation in tensile strength due to heterogeneities modeled stochastically. The properties of pitch matrix and filler particles are assumed to be known at the constituent level. The material models for both pitch and fillers are assumed to be linear elastic. The stochastic size and spatial distribution of the pores and filler particles has been modeled during the micro and macro analysis respectively. The strength of equivalent porous pitch matrix evaluated at micro level has been distributed stochastically in the elemental domain along with filler particles for macro analysis. The effect of micro-cracks has been incorporated indirectly by considering fracture plane in each filler particle. Tensile strength of nuclear graphite is obtained by performing the simulations at macro-level. Statistical parameters evaluated using numerical tensile strength data agree well with experimentally obtained statistical parameters available in the literature.
Krüger, Karsten; Gessner, Denise K; Seimetz, Michael; Banisch, Jasmin; Ringseis, Robert; Eder, Klaus; Weissmann, Norbert; Mooren, Frank C
2013-01-01
Exercise training induces muscular adaptations that are highly specific to the type of exercise. For a systematic study of the differentiated exercise adaptations on a molecular level mouse models have been used successfully. The aim of the current study was to develop a suitable mouse model of isometric strength exercise training characterized by specific adaptations known from strength training. C57BL/6 mice performed an isometric strength training (ST) for 10 weeks 5 days/week. Additionally, either a sedentary control group (CT) or a regular endurance training group (ET) groups were used as controls. Performance capacity was determined by maximum holding time (MHT) and treadmill spirometry, respectively. Furthermore, muscle fiber types and diameter, muscular concentration of phosphofructokinase 1 (PFK), succinate dehydrogenase (SDHa), and glucose transporter type 4 (GLUT4) were determined. In a further approach, the effect of ST on glucose intolerance was tested in diabetic mice. In mice of the ST group we observed an increase of MHT in isometric strength tests, a type II fiber hypertrophy, and an increased GLUT4 protein content in the membrane fraction. In contrast, in mice of the ET group an increase of VO(2max), a shift to oxidative muscle fiber type and an increase of oxidative enzyme content was measured. Furthermore strength training was effective in reducing glucose intolerance in mice fed a high fat diet. An effective murine strength training model was developed and evaluated, which revealed marked differences in adaptations known from endurance training. This approach seems also suitable to test for therapeutical effects of strength training.
Karsten Krüger
Full Text Available Exercise training induces muscular adaptations that are highly specific to the type of exercise. For a systematic study of the differentiated exercise adaptations on a molecular level mouse models have been used successfully. The aim of the current study was to develop a suitable mouse model of isometric strength exercise training characterized by specific adaptations known from strength training. C57BL/6 mice performed an isometric strength training (ST for 10 weeks 5 days/week. Additionally, either a sedentary control group (CT or a regular endurance training group (ET groups were used as controls. Performance capacity was determined by maximum holding time (MHT and treadmill spirometry, respectively. Furthermore, muscle fiber types and diameter, muscular concentration of phosphofructokinase 1 (PFK, succinate dehydrogenase (SDHa, and glucose transporter type 4 (GLUT4 were determined. In a further approach, the effect of ST on glucose intolerance was tested in diabetic mice. In mice of the ST group we observed an increase of MHT in isometric strength tests, a type II fiber hypertrophy, and an increased GLUT4 protein content in the membrane fraction. In contrast, in mice of the ET group an increase of VO(2max, a shift to oxidative muscle fiber type and an increase of oxidative enzyme content was measured. Furthermore strength training was effective in reducing glucose intolerance in mice fed a high fat diet. An effective murine strength training model was developed and evaluated, which revealed marked differences in adaptations known from endurance training. This approach seems also suitable to test for therapeutical effects of strength training.
Fritsch, Andreas; Dormieux, Luc; Hellmich, Christian; Sanahuja, Julien
2009-01-01
Hydroxyapatite (HA) biomaterials production has been a major field in biomaterials science and biomechanical engineering. As concerns prediction of their stiffness and strength, we propose to go beyond statistical correlations with porosity or empirical structure-property relationships, as to resolve the material-immanent microstructures governing the overall mechanical behavior. The macroscopic mechanical properties are estimated from the microstructures of the materials and their composition, in a homogenization process based on continuum micromechanics. Thereby, biomaterials are envisioned as porous polycrystals consisting of HA needles and spherical pores. Validation of respective micromechanical models relies on two independent experimental sets: biomaterial-specific macroscopic (homogenized) stiffness and uniaxial (tensile and compressive) strength predicted from biomaterial-specific porosities, on the basis of biomaterial-independent ("universal") elastic and strength properties of HA, are compared with corresponding biomaterial-specific experimentally determined (acoustic and mechanical) stiffness and strength values. The good agreement between model predictions and the corresponding experiments underlines the potential of micromechanical modeling in improving biomaterial design, through optimization of key parameters such as porosities or geometries of microstructures, in order to reach the desired values for biomaterial stiffness or strength.
Fillenwarth, Brian Albert
As large countries such as China begin to industrialize and concerns about global warming continue to grow, there is an increasing need for more environmentally friendly building materials. One promising material known as a geopolymer can be used as a portland cement replacement and in this capacity emits around 67% less carbon dioxide. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products such as fly ash. Although the benefits of geopolymers are substantial, there are a few difficulties with designing geopolymer mixes which have hindered widespread commercialization of the material. One such difficulty is the high variability of the materials used for their synthesis. In addition to this, interrelationships between mix design variables and how these interrelationships impact the set behavior and compressive strength are not well understood. A third complicating factor with designing geopolymer mixes is that the role of calcium in these systems is not well understood. In order to overcome these barriers, this study developed predictive optimization models through the use of genetic programming with experimentally collected set times and compressive strengths of several geopolymer paste mixes. The developed set behavior models were shown to predict the correct set behavior from the mix design over 85% of the time. The strength optimization model was shown to be capable of predicting compressive strengths of geopolymer pastes from their mix design to within about 1 ksi of their actual strength. In addition to this the optimization models give valuable insight into the key factors influencing strength development as well as the key factors responsible for flash set and long set behaviors in geopolymer pastes. A method for designing geopolymer paste mixes was developed from the generated optimization models. This design method provides an invaluable tool for use in future geopolymer research as well as
Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion
Solon, Kimberly; Flores Alsina, Xavier; Mbamba, Christian Kazadi
2015-01-01
) and ion pairing on modelling of anaerobic digestion processes in such plant-wide models of wastewater treatment. Using the BSM2 as a case study with a number of model variants and cationic load scenarios, this paper presents the effects of an improved physico-chemical description on model predictions....... The paper describes: 1) how the anaerobic digester performance is affected by physico-chemical corrections; 2) the effect on pH and the anaerobic digestion products (CO2, CH4 and H2); and, 3) how these variations are propagated from the sludge treatment to the water line. Results at high ionic strength......Plant-wide models of wastewater treatment (such as the Benchmark Simulation Model No. 2 or BSM2) are gaining popularity for use in holistic virtual studies of treatment plant control and operations. The objective of this study is to show the influence of ionic strength (as activity corrections...
Modeling the Residual Strength of a Fibrous Composite Using the Residual Daniels Function
Paramonov, Yu.; Cimanis, V.; Varickis, S.; Kleinhofs, M.
2016-09-01
The concept of a residual Daniels function (RDF) is introduced. Together with the concept of Daniels sequence, the RDF is used for estimating the residual (after some preliminary fatigue loading) static strength of a unidirectional fibrous composite (UFC) and its S-N curve on the bases of test data. Usually, the residual strength is analyzed on the basis of a known S-N curve. In our work, an inverse approach is used: the S-N curve is derived from an analysis of the residual strength. This approach gives a good qualitive description of the process of decreasing residual strength and explanes the existence of the fatigue limit. The estimates of parameters of the corresponding regression model can be interpreted as estimates of parameters of the local strength of components of the UFC. In order to approach the quantitative experimental estimates of the fatigue life, some ideas based on the mathematics of the semiMarkovian process are employed. Satisfactory results in processing experimental data on the fatigue life and residual strength of glass/epoxy laminates are obtained.
Modeling Cable and Guide Channel Interaction in a High-Strength Cable-Driven Continuum Manipulator
Moses, Matthew S.; Murphy, Ryan J.; Kutzer, Michael D. M.; Armand, Mehran
2015-01-01
This paper presents several mechanical models of a high-strength cable-driven dexterous manipulator designed for surgical procedures. A stiffness model is presented that distinguishes between contributions from the cables and the backbone. A physics-based model incorporating cable friction is developed and its predictions are compared with experimental data. The data show that under high tension and high curvature, the shape of the manipulator deviates significantly from a circular arc. Howev...
Wang, Xiao-Yong
2017-01-26
Limestone is widely used in the construction industry to produce Portland limestone cement (PLC) concrete. Systematic evaluations of hydration kinetics, compressive strength development, and carbonation resistance are crucial for the rational use of limestone. This study presents a hydration-based model for evaluating the influences of limestone on the strength and carbonation of concrete. First, the hydration model analyzes the dilution effect and the nucleation effect of limestone during the hydration of cement. The degree of cement hydration is calculated by considering concrete mixing proportions, binder properties, and curing conditions. Second, by using the gel-space ratio, the compressive strength of PLC concrete is evaluated. The interactions among water-to-binder ratio, limestone replacement ratio, and strength development are highlighted. Third, the carbonate material contents and porosity are calculated from the hydration model and are used as input parameters for the carbonation model. By considering concrete microstructures and environmental conditions, the carbon dioxide diffusivity and carbonation depth of PLC concrete are evaluated. The proposed model has been determined to be valid for concrete with various water-to-binder ratios, limestone contents, and curing periods.
Xiao-Yong Wang
2017-01-01
Full Text Available Limestone is widely used in the construction industry to produce Portland limestone cement (PLC concrete. Systematic evaluations of hydration kinetics, compressive strength development, and carbonation resistance are crucial for the rational use of limestone. This study presents a hydration-based model for evaluating the influences of limestone on the strength and carbonation of concrete. First, the hydration model analyzes the dilution effect and the nucleation effect of limestone during the hydration of cement. The degree of cement hydration is calculated by considering concrete mixing proportions, binder properties, and curing conditions. Second, by using the gel–space ratio, the compressive strength of PLC concrete is evaluated. The interactions among water-to-binder ratio, limestone replacement ratio, and strength development are highlighted. Third, the carbonate material contents and porosity are calculated from the hydration model and are used as input parameters for the carbonation model. By considering concrete microstructures and environmental conditions, the carbon dioxide diffusivity and carbonation depth of PLC concrete are evaluated. The proposed model has been determined to be valid for concrete with various water-to-binder ratios, limestone contents, and curing periods.
Ricks, Trenton M.; Lacy, Thomas E., Jr.; Bednarcyk, Brett A.; Arnold, Steven M.; Hutchins, John W.
2014-01-01
A multiscale modeling methodology was developed for continuous fiber composites that incorporates a statistical distribution of fiber strengths into coupled multiscale micromechanics/finite element (FE) analyses. A modified two-parameter Weibull cumulative distribution function, which accounts for the effect of fiber length on the probability of failure, was used to characterize the statistical distribution of fiber strengths. A parametric study using the NASA Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) was performed to assess the effect of variable fiber strengths on local composite failure within a repeating unit cell (RUC) and subsequent global failure. The NASA code FEAMAC and the ABAQUS finite element solver were used to analyze the progressive failure of a unidirectional SCS-6/TIMETAL 21S metal matrix composite tensile dogbone specimen at 650 degC. Multiscale progressive failure analyses were performed to quantify the effect of spatially varying fiber strengths on the RUC-averaged and global stress-strain responses and failure. The ultimate composite strengths and distribution of failure locations (predominately within the gage section) reasonably matched the experimentally observed failure behavior. The predicted composite failure behavior suggests that use of macroscale models that exploit global geometric symmetries are inappropriate for cases where the actual distribution of local fiber strengths displays no such symmetries. This issue has not received much attention in the literature. Moreover, the model discretization at a specific length scale can have a profound effect on the computational costs associated with multiscale simulations.models that yield accurate yet tractable results.
Fatigue reliability based on residual strength model with hybrid uncertain parameters
Jun Wang; Zhi-Ping Qiu
2012-01-01
The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model.By solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness,the fatigue reliability with hybrid parameters can be obtained.The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters.A comparison among the presented hybrid model,non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples.The results show that the presented hybrid model,which can ensure structural security,is effective and practical.
Strength Modeling of Reinforced Concrete Beam with Externally Bonded FRP Reinforcement
N. Pannirselvam
2008-01-01
Full Text Available This research study presents the evaluation of the structural behaviour of reinforced concrete beams with externally bonded Fibre Reinforced Polymer (FRP reinforcements. Three different steel ratios with two different Glass Fibre Reinforced Polymer (GFRP types and two different thicknesses in each type of GFRP were used. Totally fifteen rectangular beams of 3 m length were cast. Three rectangular beams were used as reference beam (Control Beams and the remaining were fixed with GFRP laminates on the soffit of the rectangular beam. The variables considered for the study includes longitudinal steel ratio, type of GFRP laminates, thickness of GFRP laminates and composite ratios. Flexural test, using simple beam with third-point loading was adopted to study the performance of FRP plated beams interms flexural strength, deflection, ductility and was compared with the unplated beams. The test results show that the beams strengthened with GFRP laminates exhibit better performance. The flexural strength and ductility increase with increase in thickness of GFRP plate. The increase in first crack loads was up to 88.89% for 3 mm thick WRGFRP plates and 100.00% for 5 mm WRGFRP plated beams and increase in ductility interms of energy and deflection was found to be 56.01 and 64.69% respectively with 5 mm thick GFRP plated beam. Strength models were developed for predicting the flexural strength (ultimate load, service load and ductility of FRP beams. The strength model developed give prediction matching the measurements.
Starck Ta PTW strength model recommendation for use with SESAME 93524 EoS
Sjue, Sky K. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Prime, Michael Bruce [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-02-27
The purpose of this document is to provide a calibration of the Preston-Tonks- Wallace (PTW) strength model for use with the new SESAME equation of state (EoS) 93524. The calibration data included in this t spans temperatures from 198 K to 673 K and strain rates from 0.001/s to 3200/s.
Ego Depletion and the Strength Model of Self-Control: A Meta-Analysis
Hagger, Martin S.; Wood, Chantelle; Stiff, Chris; Chatzisarantis, Nikos L. D.
2010-01-01
According to the strength model, self-control is a finite resource that determines capacity for effortful control over dominant responses and, once expended, leads to impaired self-control task performance, known as "ego depletion". A meta-analysis of 83 studies tested the effect of ego depletion on task performance and related outcomes,…
Ego Depletion and the Strength Model of Self-Control: A Meta-Analysis
Hagger, Martin S.; Wood, Chantelle; Stiff, Chris; Chatzisarantis, Nikos L. D.
2010-01-01
According to the strength model, self-control is a finite resource that determines capacity for effortful control over dominant responses and, once expended, leads to impaired self-control task performance, known as "ego depletion". A meta-analysis of 83 studies tested the effect of ego depletion on task performance and related outcomes,…
Multimedia-Based Therapy Model for Non-Pharmacological Stroke with Decrease Impaired Muscle Strength
Hajar Puji Sejati, Rr; Muhimmah, Izzati; Mahtarami, Affan
2016-01-01
Stroke patients who experience a decrease in muscle strength need to do exercises so that they can increase their muscle strength. In order to enable the patient does exercise independently the multimedia-based stroke therapy model is needed. These exercises can be done independently, with supervision of the family member at home. So, we develop prototype of the multimedia-based therapy for the family member so that they can assist patients performing exercises without attending therapy session in hospital. This model was built according to the advices from physiotherapist and a medical rehabilitation doctor. This model has been evaluated through focused group discussion by physiotherapists. And they gave positive responses to this proposed model.
Effects of ion strength and ion pairing on (plant-wide) modelling of anaerobic digestion processes
Flores-Alsina, Xavier; Mbamba, Christian Kazadi; Solon, Kimberly;
2014-01-01
The objective of this study is to show the influence of ionic strength (as activity corrections) andion pairing on (plant-wide) modelling of anaerobic digestion processes in wastewater treatment plants(WWTPs). Using the Benchmark Simulation Model No. 2 (BSM2) as a case study, this paper presents...... the effects that an improved physico-chemical description will have on the predicted effluent quality (EQI) and operational cost (OCI) indices. The acid-base equilibria implemented in the Anaerobic Digestion Model No.1 (ADM1) are modified to account for non-ideal aqueous-phase chemistry. The model corrects...... processes. Results at high ionic strength demonstrate that corrections to account for non-ideal conditions lead to significant differences in predicted process performance. In addition, the paper describes: 1) how the anaerobic digester performance is affected; 2) the effect on pH and the anaerobic...
Theoretical Calculation Model of Single Rip Tearing Strength for the Nonwoven Composites
QIAN Cheng
2005-01-01
The nonwoven composites have sandwich structure, with the first and third layers being nonwovens and the middle layer of woven fabric. On the basis of tests of the single rip tearing strength and drawing out resistances of both the nonwoven composites and the woven fabric, the single rip tearing failure mechanism of the composites were analyzed.Then theoretical calculation model for the single rip tearing strength was established, which indicates that the breaking strength of warp and weft yarns in the nonwoven composites, the density of warp and weft yarns and drawing out resistances are the main influencing factors. In the end,experimental verification was made, which shows that theoretical values conform to the measured values well.
Duncan, Bryan
2012-01-01
There is now a wealth of satellite data products available with which to evaluate a model fs simulation of tropospheric composition and other model processes. All of these data products have their strengths and limitations that need to be considered for this purpose. For example, uncertainties are introduced into a data product when 1) converting a slant column to a vertical column and 2) estimating the amount of a total column of a trace gas (e.g., ozone, nitrogen dioxide) that resides in the troposphere. Oftentimes, these uncertainties are not well quantified and the satellite data products are not well evaluated against in situ observations. However, these limitations do not preclude us from using these data products to evaluate our model processes if we understand these strengths and limitations when developing diagnostics. I will show several examples of how satellite data products are being used to evaluate particular model processes with a focus on the strengths and limitations of these data products. In addition, I will introduce the goals of a newly formed team to address issues on the topic of "satellite data for improved model evaluation and process studies" that is established in support of the IGAC/SPARC Global Chemistry ]Climate Modeling and Evaluation Workshop.
Chung, Yi-Shih
2015-09-01
An increasing amount of evidence suggests that aberrant driving behaviors are not entirely rational. On the basis of the dual-process theory, this study postulates that drivers may learn to perform irrational aberrant driving behaviors, and these behaviors could be derived either from a deliberate or an intuitive decision-making approach. Accordingly, a seemingly irrational driving behavior model is proposed; in this model, the theory of planned behavior (TPB) was adopted to represent the deliberate decision-making mechanism, and habit strength was incorporated to reflect the intuitive decision process. A multiple trivariate mediation structure was designed to reflect the process through which driving behaviors are learned. Anticipated affective reactions (AARs) were further included to examine the effect of affect on aberrant driving behaviors. Considering the example of speeding behaviors, this study developed scales and conducted a two-wave survey of students in two departments at a university in Northern Taiwan. The analysis results show that habit strength consists of multiple aspects, and frequency of past behavior cannot be a complete repository for accumulating habit strength. Habit strength appeared to be a crucial mediator between intention antecedents (e.g., attitude) and the intention itself. Including habit strength in the TPB model enhanced the explained variance of speeding intention by 26.7%. In addition, AARs were different from attitudes; particularly, young drivers tended to perform speeding behaviors to reduce negative feelings such as regret. The proposed model provides an effective alternative approach for investigating aberrant driving behaviors; corresponding countermeasures are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.
The Inclusion of Arbitrary Load Histories in the Strength Decay Model for Stress Rupture
Reeder, James R.
2014-01-01
Stress rupture is a failure mechanism where failures can occur after a period of time, even though the material has seen no increase in load. Carbon/epoxy composite materials have demonstrated the stress rupture failure mechanism. In a previous work, a model was proposed for stress rupture of composite overwrap pressure vessels (COPVs) and similar composite structures based on strength degradation. However, the original model was limited to constant load periods (holds) at constant load. The model was expanded in this paper to address arbitrary loading histories and specifically the inclusions of ramp loadings up to holds and back down. The broadening of the model allows for failures on loading to be treated as any other failure that may occur during testing instead of having to be treated as a special case. The inclusion of ramps can also influence the length of the "safe period" following proof loading that was previously predicted by the model. No stress rupture failures are predicted in a safe period because time is required for strength to decay from above the proof level to the lower level of loading. Although the model can predict failures during the ramp periods, no closed-form solution for the failure times could be derived. Therefore, two suggested solution techniques were proposed. Finally, the model was used to design an experiment that could detect the difference between the strength decay model and a commonly used model for stress rupture. Although these types of models are necessary to help guide experiments for stress rupture, only experimental evidence will determine how well the model may predict actual material response. If the model can be shown to be accurate, current proof loading requirements may result in predicted safe periods as long as 10(13) years. COPVs design requirements for stress rupture may then be relaxed, allowing more efficient designs, while still maintaining an acceptable level of safety.
Made-to-measure galaxy modelling utilising absorption line strength data
Long, Richard
2016-01-01
We enhance the Syer & Tremaine made-to-measure (M2M) particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data thus creating a `chemo-M2M' modelling scheme. We apply the enhanced method to four galaxies (NGC 1248, NGC 3838, NGC 4452, NGC 4551) observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean chi^2 per bin values of ~1 with >95\\% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these distributions are plausible representations of real galaxies requires further consideration. Overall we consider the modelling exercise to be a promising first step in developing a `chemo-M2M' modelling system and in understanding some of the issues to be addressed. Whilst the made-to-measure techniques developed have been ...
Three Dimensional Computation Model of Field Strength and Coverage of DVB-T Network
JIANGHao; CHENXIAOGUANG
2005-01-01
As one of the three digital television standards globally, DVB has more than 300 members till now. Among the three main standards, satellite (DVB-S), cable (DVB-C) and terrestrial (DVB-T), DVB-T, as the most complex transmission standard in DVB system, enjoys more advantages than ISDB-T and ATSC. DVB-T is a multl-carrier system adopting COFDM modulation mode. The calculation of network planning and optimization is needed in practice, which is the problem to be solved urgently in broadcasting and communication engineering. Traditional equation for field strength calculation cannot be generalized in some specific area. Hence, a new versatile equation should be advanced as the basis of DVB-T network planning. Based on the 3D direction of transmitter antenna and concerning ground reflection and different topographic loss, this paper advances a new mathematical model for the calculation of 3D field strength distribution of DVB-T network with the fundamental wave transmission equation. Then according to the characteristics of chosen DVB-T system and parameters of receiver, field strength threshold value for different coverage is given and network coverage is obtained. For the need of practical engineering, a program is designed here using Matlab based on the new model of DVB-T network field strength planning and optimization. Simple and succinct, this program has perspicuous interface and extensive application.
Yingwu Zhou
2015-01-01
Full Text Available Sulfate corrosion is one of the most important factors responsible for the performance degradation of concrete materials. In this paper, an accelerated corrosion by a sulfate solution in a dry-wet cycle was introduced to simulate the external sulfate corrosion environment. The deterioration trend of concrete strength and development law of sulfate-induced concrete corrosion depth under sulfate attacks were experimentally studied. The damaged concrete section is simply but reasonably divided into uncorroded and corroded layers and the two layers can be demarcated by the sulfate corrosion depth of concrete. The accelerated corrosion test results indicated that the strength degradation of concrete by sulfate attack had a significant relation with the corrosion depth. Consequently, this paper aims to reveal such relation and thus model the strength degradation law. A large amount of experimental data has finally verified the validity and applicability of the models, and a theoretical basis is thus provided for the strength degradation prediction and the residual life assessment of in-service concrete structures under sulfate attacks.
DeSmitt, Holly J; Domire, Zachary J
2016-12-01
Biomechanical models are sensitive to the choice of model parameters. Therefore, determination of accurate subject specific model parameters is important. One approach to generate these parameters is to optimize the values such that the model output will match experimentally measured strength curves. This approach is attractive as it is inexpensive and should provide an excellent match to experimentally measured strength. However, given the problem of muscle redundancy, it is not clear that this approach generates accurate individual muscle forces. The purpose of this investigation is to evaluate this approach using simulated data to enable a direct comparison. It is hypothesized that the optimization approach will be able to recreate accurate muscle model parameters when information from measurable parameters is given. A model of isometric knee extension was developed to simulate a strength curve across a range of knee angles. In order to realistically recreate experimentally measured strength, random noise was added to the modeled strength. Parameters were solved for using a genetic search algorithm. When noise was added to the measurements the strength curve was reasonably recreated. However, the individual muscle model parameters and force curves were far less accurate. Based upon this examination, it is clear that very different sets of model parameters can recreate similar strength curves. Therefore, experimental variation in strength measurements has a significant influence on the results. Given the difficulty in accurately recreating individual muscle parameters, it may be more appropriate to perform simulations with lumped actuators representing similar muscles.
Global Models of Ridge-Push Force, Geoid, and Lithospheric Strength of Oceanic plates
Mahatsente, Rezene
2017-08-01
An understanding of the transmission of ridge-push related stresses in the interior of oceanic plates is important because ridge-push force is one of the principal forces driving plate motion. Here, I assess the transmission of ridge-push related stresses in oceanic plates by comparing the magnitude of the ridge-push force to the integrated strength of oceanic plates. The strength is determined based on plate cooling and rheological models. The strength analysis includes low-temperature plasticity (LTP) in the upper mantle and assumes a range of possible tectonic conditions and rheology in the plates. The ridge-push force has been derived from the thermal state of oceanic lithosphere, seafloor depth and crustal age data. The results of modeling show that the transmission of ridge-push related stresses in oceanic plates mainly depends on rheology and predominant tectonic conditions. If a lithosphere has dry rheology, the estimated strength is higher than the ridge-push force at all ages for compressional tectonics and at old ages (>75 Ma) for extension. Therefore, under such conditions, oceanic plates may not respond to ridge-push force by intraplate deformation. Instead, the plates may transmit the ridge-push related stress in their interior. For a wet rheology, however, the strength of young lithosphere (tectonics. In this case, the ridge-push related stress may dissipate in the interior of oceanic plates and diffuses by intraplate deformation. The state of stress within a plate depends on the balance of far-field and intraplate forces.
Wun Wong
2003-01-01
Full Text Available The assessment of medical outcomes is important in the effort to contain costs, streamline patient management, and codify medical practices. As such, it is necessary to develop predictive models that will make accurate predictions of these outcomes. The neural network methodology has often been shown to perform as well, if not better, than the logistic regression methodology in terms of sample predictive performance. However, the logistic regression method is capable of providing an explanation regarding the relationship(s between variables. This explanation is often crucial to understanding the clinical underpinnings of the disease process. Given the respective strengths of the methodologies in question, the combined use of a statistical (i.e., logistic regression and machine learning (i.e., neural network technology in the classification of medical outcomes is warranted under appropriate conditions. The study discusses these conditions and describes an approach for combining the strengths of the models.
A predictive model of the tensile strength of twisted carbon nanotube yarns
Jeon, Seung-Yeol; Jang, Jinhyeok; Koo, Bon-Woong; Kim, Young-Woon; Yu, Woong-Ryeol
2017-01-01
Due to the outstanding mechanical properties of individual carbon nanotubes (CNTs) at the nanoscale, CNT yarns are expected to demonstrate high strength at the macroscale. In this study, a predictable model was developed to predict the tensile strength of twisted CNT yarns. First, the failure mechanism of twisted CNT yarns was investigated using in situ tensile tests and ex situ observations. It was revealed that CNT bundles, which are groups of CNTs that are tightly bound together, formed during tensile loading, leaving some voids around the bundles. Failure of the CNT yarns occurred as the CNT bundles were pulled out of the yarns. Two stresses that determined the tensile strength of the CNT yarns were identified: interfacial shear and frictional stresses originating from van der Waals interactions, and the lateral pressure generated by the twisted yarn structure. Molecular dynamics and yarn mechanics were used to calculate these two stresses. Finally, the tensile strength of CNT yarns was predicted and compared with experimental data, showing reasonable agreement.
2016-11-01
Full Text Available The paper presents the report of an investigation into the model development and optimization of the compressive strength of 55/45 to 70/30 cement/Rice Husk Ash (RHA in hollow sandcrete block. The low cost and local availability potential of RHA, a pozzolanic material gasps for exploitation. The study applies the Scheffe\\'s optimization approach to obtain a mathematical model of the form f(xi1 ,xi2 ,xi3 xi4 , where x are proportions of the concrete components, viz: cement, RHA, sand and water. Scheffe\\'s i experimental design techniques are followed to mould various hollow block samples measuring 450mm x 225mm x 150mm and tested for 28 days strength. The task involved experimentation and design, applying the second order polynomial characterization process of the simplex lattice method. The model adequacy is checked using the control factors. Finally, a software is prepared to handle the design computation process to take the desired property of the mix, and generate the optimal mix ratios. Reversibly, any mix ratios can be desired and the attainable strength obtained.
Experimental analysis and constitutive modelling of steel of A-IIIN strength class
Kruszka, Leopold; Janiszewski, Jacek
2015-09-01
Fundamentally important is the better understanding of behaviour of new building steels under impact loadings, including plastic deformations. Results of the experimental analysis in wide range of strain rates in compression at room temperature, as well as constitutive modelling for and B500SP structural steels of new A-IIIN Polish strength class, examined dynamically by split Hopkinson pressure bar technique at high strain rates, are presented in table and graphic forms. Dynamic mechanical characteristics of compressive strength for tested building structural steel are determined as well as dynamic mechanical properties of this material are compared with 18G2-b steel of A-II strength class, including effects of the shape of tested specimens, i.e. their slenderness. The paper focuses the attention on those experimental tests, their interpretation, and constitutive semi-empirical modelling of the behaviour of tested steels based on Johnson-Cook's model. Obtained results of analyses presented here are used for designing and numerical simulations of reinforced concrete protective structures.
THE AVALANCHE DYNAMICS IN RANDOM NEAREST NEIGHBOR MODELS OF EVOLUTION WITH INTERACTION STRENGTH
无
2006-01-01
A generalized Bak-Sneppen model (BS model) of biological evolution with interaction strength θ is introduced in d-dimensional space, where the "nearest neighbors"are chosen among the 2d neighbors of the extremal site, with the probabilities related to the sizes of the fitnesses. Simulations of one- and two-dimensional models are given.For given θ＞ 0, the model can self-organize to a critical state, and the critical threshold fc(θ) decreases as θ increases. The exact gap equation depending on θ is presented, which reduces to the gap equation of BS model as θ tends to infinity. An exact equation for the critical exponent γ(θ) is also obtained. Scaling relations are established among the six critical exponents of the avalanches of the model.
Parent Ratings of the Strengths and Difficulties Questionnaire: What Is the Optimum Factor Model?
Gomez, Rapson; Stavropoulos, Vasilis
2017-07-01
To date, at least 12 different models have been suggested for the Strengths and Difficulties Questionnaire (SDQ). The current study used confirmatory factor analysis to examine the relative support for these models. In all, 1,407 Malaysian parents completed SDQ ratings of their children (age range = 5-13 years). Although the findings showed some degree of support for all 12 models, there was most support for an oblique six-factor model that included the five SDQ domains (emotional problems, conduct problems, hyperactivity, peer problems, and low prosocial behavior) and a positive construal factor comprising all the 10 SDQ positive worded items. The original proposed five-factor oblique model also showed good fit. The implications of the findings for understanding the results of past studies of the structural models of the parent version of the SDQ, and for clinical and research practice involving the SDQ are discussed.
Ams, David A [Los Alamos National Laboratory
2012-06-11
Rationale for experimental design: Np(V) -- important as analog for Pu(V) and for HLW scenarios; High ionic strength -- relevant to salt-based repositories such as the WIPP; Halophilic microorganisms -- representative of high ionic strength environments. For the first time showed: Significant adsorbant to halophilic microorganisms over entire pH range under high ionic strength conditions; Strong influence of ionic strength with increasing adsorption with increasing ionic strength (in contrast to trends of previous low ionic strength studies); Effect of aqueous Np(V) and bacterial surface site speciation on adsorption; and Developed thermodynamic models that can be incorporated into geochemical speciation models to aid in the prediction of the fate and transport of Np(V) in more complex systems.
Neela Deshpande
2014-12-01
Full Text Available In the recent past Artificial Neural Networks (ANN have emerged out as a promising technique for predicting compressive strength of concrete. In the present study back propagation was used to predict the 28 day compressive strength of recycled aggregate concrete (RAC along with two other data driven techniques namely Model Tree (MT and Non-linear Regression (NLR. Recycled aggregate is the current need of the hour owing to its environmental friendly aspect of re-use of the construction waste. The study observed that, prediction of 28 day compressive strength of RAC was done better by ANN than NLR and MT. The input parameters were cubic meter proportions of Cement, Natural fine aggregate, Natural coarse Aggregates, recycled aggregates, Admixture and Water (also called as raw data. The study also concluded that ANN performs better when non-dimensional parameters like Sand–Aggregate ratio, Water–total materials ratio, Aggregate–Cement ratio, Water–Cement ratio and Replacement ratio of natural aggregates by recycled aggregates, were used as additional input parameters. Study of each network developed using raw data and each non dimensional parameter facilitated in studying the impact of each parameter on the performance of the models developed using ANN, MT and NLR as well as performance of the ANN models developed with limited number of inputs. The results indicate that ANN learn from the examples and grasp the fundamental domain rules governing strength of concrete.
Ductile failure analysis of high strength steel in hot forming based on micromechanical damage model
YingLiang
2016-01-01
Full Text Available The damage evolution of high strength steel at elevated temperature is investigated by using the Gurson-Tvergaard-Needleman (GTN model. A hybrid method integrated thermal tensile test and numerical technique is employed to identify the damage parameters. The analysis results show that the damage parameters are different at different temperature as the variation of tested material microstructure. Furthermore, the calibrated damage parameters are implemented to simulate a bugling forming at elevated temperature. The experimental results show the availability of GTN damage model in analyzing sheet formability in hot forming.
F. A. Mirza
2015-08-01
Full Text Available Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs. This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al2O3, Y2O3, and carbon nanotubes. The predicted results were observed to be in good agreement with the experimental data reported in the literature.
Correlation between band excitation energies and strength parameters in the pseudo-SU(3) model
Thalluri, S. (Koneru Lakshmaiah Coll. of Engineering, Green Fields, Guntur (India). Dept. of Physics; Andhra Christian Coll., Guntur (India). Dept. of Physics)
1982-11-01
Low-lying energy spectra of some odd-A isotopes of Lu and Ta are predicted using the quadrupole-quadrupole interaction as the effective residual interaction together with the usual spin-orbit and extrapolation terms in the Hamiltonian. It is suggested that the Coriolis antipairing force might generate the correct doublet structure of the 1/2/sup +/ bands, especially in highly deformed regions. It is shown that the pseudo-SU(3) model satisfies the general requirement that it is capable of describing the spectral behaviour of different nuclei with only minor variations in the strength parameters. Correlations between the band excitation energies and the strength parameters are also given in a first approximation. The ratios of interband M1 transition probabilities are also presented.
Reliability Stress-Strength Models for Dependent Observations with Applications in Clinical Trials
Kushary, Debashis; Kulkarni, Pandurang M.
1995-01-01
We consider the applications of stress-strength models in studies involving clinical trials. When studying the effects and side effects of certain procedures (treatments), it is often the case that observations are correlated due to subject effect, repeated measurements and observing many characteristics simultaneously. We develop maximum likelihood estimator (MLE) and uniform minimum variance unbiased estimator (UMVUE) of the reliability which in clinical trial studies could be considered as the chances of increased side effects due to a particular procedure compared to another. The results developed apply to both univariate and multivariate situations. Also, for the univariate situations we develop simple to use lower confidence bounds for the reliability. Further, we consider the cases when both stress and strength constitute time dependent processes. We define the future reliability and obtain methods of constructing lower confidence bounds for this reliability. Finally, we conduct simulation studies to evaluate all the procedures developed and also to compare the MLE and the UMVUE.
Esteves, L.P.
2012-01-01
-based materials. Beyond the discussion of whether or not the introduction of superabsorbent polymers leads to a strength reduction, this paper uses both experimental and theoretical background to separate the effect of SAP in both pore structure and internal relative humidity and the effect from the active......Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...
Modeling Cable and Guide Channel Interaction in a High-Strength Cable-Driven Continuum Manipulator
Moses, Matthew S.; Murphy, Ryan J.; Kutzer, Michael D. M.; Armand, Mehran
2016-01-01
This paper presents several mechanical models of a high-strength cable-driven dexterous manipulator designed for surgical procedures. A stiffness model is presented that distinguishes between contributions from the cables and the backbone. A physics-based model incorporating cable friction is developed and its predictions are compared with experimental data. The data show that under high tension and high curvature, the shape of the manipulator deviates significantly from a circular arc. However, simple parametric models can fit the shape with good accuracy. The motivating application for this study is to develop a model so that shape can be predicted using easily measured quantities such as tension, so that real-time navigation may be performed, especially in minimally-invasive surgical procedures, while reducing the need for hazardous imaging methods such as fluoroscopy.
Modeling Cable and Guide Channel Interaction in a High-Strength Cable-Driven Continuum Manipulator.
Moses, Matthew S; Murphy, Ryan J; Kutzer, Michael D M; Armand, Mehran
2015-12-01
This paper presents several mechanical models of a high-strength cable-driven dexterous manipulator designed for surgical procedures. A stiffness model is presented that distinguishes between contributions from the cables and the backbone. A physics-based model incorporating cable friction is developed and its predictions are compared with experimental data. The data show that under high tension and high curvature, the shape of the manipulator deviates significantly from a circular arc. However, simple parametric models can fit the shape with good accuracy. The motivating application for this study is to develop a model so that shape can be predicted using easily measured quantities such as tension, so that real-time navigation may be performed, especially in minimally-invasive surgical procedures, while reducing the need for hazardous imaging methods such as fluoroscopy.
Finite Element Modeling of the Inertia Friction Welding of Dissimilar High-Strength Steels
Bennett, C. J.; Attallah, M. M.; Preuss, M.; Shipway, P. H.; Hyde, T. H.; Bray, S.
2013-11-01
Finite element (FE) process modeling of inertia friction welding between dissimilar high-strength steels, AerMet® 100 and SCMV, has been carried out using the DEFORM™-2D (v10.0) software. This model was validated against experimental data collected for a test weld performed between the materials; this included process data such as upset and rotational velocities as well as thermal data collected during the process using embedded thermocouples. The as-welded hoop residual stress from the FE model was also compared with experimental measurements taken on the welded component using synchrotron X-ray and neutron diffraction techniques. The modeling work considered the solid-state phase transformations which occur in the steels, and the trends in the residual stress data were well replicated by the model.
MODELS TO ESTIMATE BRAZILIAN INDIRECT TENSILE STRENGTH OF LIMESTONE IN SATURATED STATE
Zlatko Briševac
2016-06-01
Full Text Available There are a number of methods of estimating physical and mechanical characteristics. Principally, the most widely used is the regression, but recently the more sophisticated methods such as neural networks has frequently been applied, as well. This paper presents the models of a simple and a multiple regression and the neural networks – types Radial Basis Function and Multiple Layer Perceptron, which can be used for the estimate of the Brazilian indirect tensile strength in saturated conditions. The paper includes the issues of collecting the data for the analysis and modelling and the overview of the performed analysis of the efficacy assessment of the estimate of each model. After the assessment, the model which provides the best estimate was selected, including the model which could have the most wide-spread application in the engineering practice.
Stuparu, Dana; Bachmann, Daniel; Bogaard, Tom; Twigt, Daniel; Verkade, Jan; de Bruijn, Karin; de Leeuw, Annemargreet
2017-04-01
Flood forecasts, warning and emergency response are important components in flood risk management. Most flood forecasting systems use models to translate weather predictions to forecasted discharges or water levels. However, this information is often not sufficient for real time decisions. A sound understanding of the reliability of embankments and flood dynamics is needed to react timely and reduce the negative effects of the flood. Where are the weak points in the dike system? When, how much and where the water will flow? When and where is the greatest impact expected? Model-based flood impact forecasting tries to answer these questions by adding new dimensions to the existing forecasting systems by providing forecasted information about: (a) the dike strength during the event (reliability), (b) the flood extent in case of an overflow or a dike failure (flood spread) and (c) the assets at risk (impacts). This work presents three study-cases in which such a set-up is applied. Special features are highlighted. Forecasting of dike strength. The first study-case focusses on the forecast of dike strength in the Netherlands for the river Rhine branches Waal, Nederrijn and IJssel. A so-called reliability transformation is used to translate the predicted water levels at selected dike sections into failure probabilities during a flood event. The reliability of a dike section is defined by fragility curves - a summary of the dike strength conditional to the water level. The reliability information enhances the emergency management and inspections of embankments. Ensemble forecasting. The second study-case shows the setup of a flood impact forecasting system in Dumfries, Scotland. The existing forecasting system is extended with a 2D flood spreading model in combination with the Delft-FIAT impact model. Ensemble forecasts are used to make use of the uncertainty in the precipitation forecasts, which is useful to quantify the certainty of a forecasted flood event. From global
Mechanical model for yield strength of nanocrystalline materials under high strain rate loading
朱荣涛; 周剑秋; 马璐; 张振忠
2008-01-01
To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed.As a first step of the research,the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification.Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase,and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed,then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials.The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data.Further discussion was presented for calculation results and relative experimental observations.
Application of ANFIS for analytical modeling of tensile strength of functionally graded steels
Ali Nazari
2012-06-01
Full Text Available In the present study, the tensile strength of ferritic and austenitic functionally graded steels produced by electroslag remelting has been modeled. To produce functionally graded steels, two slices of plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of ferrite and austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with adaptive network-based fuzzy inference systems (ANFIS. To build the model for graded ferritic and austenitic steels, training, testing and validation using respectively 174 and 120 experimental data were conducted. According to the input parameters, in the ANFIS model, the Vickers microhardness of each layer was predicted. A good fit equation which correlates the Vickers microhardness of each layer to its corresponding chemical composition was achieved by the optimized network for both ferritic and austenitic graded steels. Afterwards; the Vickers microhardness of each layer in functionally graded steels was related to the yield stress of the corresponding layer and by assuming Holloman relation for stress-strain curve of each layer, they were acquired. Finally, by applying the rule of mixtures, tensile strength of functionally graded steels configuration was found through a numerical method. The obtained results from the proposed model are in good agreement with those acquired from the experiments.
Scale-up model describing the impact of lubrication on tablet tensile strength.
Kushner, Joseph; Moore, Francis
2010-10-31
Lubrication of 2:1 and 1:1 blends of microcrystalline cellulose and spray-dried lactose or dibasic calcium phosphate (DCP) with 0.33% or 1% magnesium stearate, as model free-flowing pharmaceutical formulations, was performed in rotary drum blenders. Blender process parameters examined in this study included type (Bin, V, and Turbula), volume (0.75-Quart to 200-L), fraction of headspace in the blender after the blend is loaded (30-70%), speed (6-202 rpm), and time (up to 225 min). Based on analysis of the experimental data, the following model for the impact of the lubrication process on tablet tensile strength at 0.85 solid fraction, TS(SF=0.85), was obtained, TS(SF=0.85)=TS(SF=0.85,0) [βexp(-γ×V(1/3)×F(headspace)×r)+(1-β)], where V is blender volume, F(headspace) is the headspace fraction, r is the number of revolutions (i.e. speed × time), TS(SF=0.85,0) is the initial tensile strength of the blend, β is the sensitivity of the blend to lubrication, and γ is the lubrication rate constant of the formulation. This model can be used to maintain tensile strength during scale-up, by ensuring that (V(1/3)F(headspace)r)(1)=(V(1/3)F(headspace)r)(2). The model also suggests that formulations with DCP are less sensitive to lubrication and more slowly lubricated than formulations with spray-dried lactose (i.e. smaller β and γ values).
Shafieyzadeh, M.
2015-12-01
In the flexural test, the theoretical maximum tensile stress at the bottom fiber of a test beam is known as the modulus of rupture or flexural strength. This work deals with the effects of Silica Fume and Styrene-Butadiene Latex (SBR) on flexural strength of concrete. An extensive experimentation was carried out to determine the effects of silica fume and SBR on flexural strength of concrete. Two water-binder ratios and several percentages of silica fume and SBR were considered. Abrams' Law, which was originally formulated for conventional concrete containing cement as the only cementations material, is used for prediction of flexural strength of these concretes. The aim of this work is to construct an empirical model to predict the flexural strength of silica fume-SBR concretes using concrete ingredients and time of curing in water. Also, the obtained results for flexural strength tests have been compared with predicted results.
A COMPARISON OF THE TENSILE STRENGTH OF PLASTIC PARTS PRODUCED BY A FUSED DEPOSITION MODELING DEVICE
Juraj Beniak
2015-12-01
Full Text Available Rapid Prototyping systems are nowadays increasingly used in many areas of industry, not only for producing design models but also for producing parts for final use. We need to know the properties of these parts. When we talk about the Fused Deposition Modeling (FDM technique and FDM devices, there are many possible settings for devices and models which could influence the properties of a final part. In addition, devices based on the same principle may use different operational software for calculating the tool path, and this may have a major impact. The aim of this paper is to show the tensile strength value for parts produced from different materials on the Fused Deposition Modeling device when the horizontal orientation of the specimens is changed.
Reliability analysis of diesel engine crankshaft based on 2D stress strength interference model
无
2006-01-01
A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put forward. The principle, geometric schematic and limit state equation of this model are presented. Reliability evaluation for a kind of diesel engine crankshaft was made based on this theory, in which multi-axial loading fatigue criteria was employed. Because more important factors, i.e.stress asymmetric ratio and its variability, are considered, it theoretically can make more accurate evaluation for structural component reliability than the traditional interference model. Correspondingly, a Monte-Carlo Method simulation solution is also given. The computation suggests that this model can yield satisfactory reliability evaluation.
Model-free analysis for large proteins at high magnetic field strengths.
Chang, Shou-Lin; Hinck, Andrew P; Ishima, Rieko
2007-08-01
Protein backbone dynamics is often characterized using model-free analysis of three sets of (15)N relaxation data: longitudinal relaxation rate (R1), transverse relaxation rate (R2), and (15)N-{H} NOE values. Since the experimental data is limited, a simplified model-free spectral density function is often used that contains one Lorentzian describing overall rotational correlation but not one describing internal motion. The simplified spectral density function may be also used in estimating the overall rotational correlation time, by making the R2/R1 largely insensitive to internal motions, as well as used as one of the choices in the model selection protocol. However, such approximation may not be valid for analysis of relaxation data of large proteins recorded at high magnetic field strengths since the contribution to longitudinal relaxation from the Lorentzian describing the overall rotational diffusion of the molecule is comparably small relative to that describing internal motion. Here, we quantitatively estimate the errors introduced by the use of the simplified spectral density in model-free analysis for large proteins at high magnetic field strength.
Modeling and Simulation to Muscle Strength Training of Lower Limbs Rehabilitation Robots
Ke-Yi Wang
2015-01-01
Full Text Available Considering the issues of lower limb rehabilitation robots with single control strategies and poor training types, a training method for improving muscle strength was put forward in this paper. Patients’ muscle strength could be achieved by targeted exercises at the end of rehabilitation. This approach could be realized through programming wires’ force. On the one hand, each wires force was measured by tension sensor and force closed loop control was established to control the value of wires’ force which was acted on trainees. On the other hand, the direction of output force was changed by detecting the trainees’ state of motion and the way of putting load to patient was achieved. Finally, the target of enhancing patients’ muscle strength was realized. Dynamic model was built by means of mechanism and training types of robots. Force closed loop control strategy was established based on training pattern. In view of the characteristics of the redundance and economy of wire control, the process for simple wire's load changes was discussed. In order to confirm the characteristics of robot control system, the controller was simulated in Matlab/Simulink. It was verified that command signal could be traced by control system availably and the load during muscle training would be provided effectively.
Lee, Won Hee; Lisanby, Sarah H; Laine, Andrew F; Peterchev, Angel V
2014-01-01
This study examines the characteristics of the electric field (E-field) induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). The electric field induced by five ECT electrode configurations (bilateral, bifrontal, right unilateral, focal electrically administered seizure therapy, and frontomedial) as well as an MST coil configuration (circular) was computed in an anatomically realistic finite element model of the human head. We computed the maps of the electric field strength relative to an estimated neural activation threshold, and used them to evaluate the stimulation strength and focality of the various ECT and MST paradigms. The results show that the median ECT stimulation strength in the brain is 3-11 times higher than that for MST, and that the stimulated brain volume is substantially higher with ECT (47-100%) than with MST (21%). Our study provides insight into the observed reduction of cognitive side effects in MST compared to ECT, and supports arguments for lowering ECT current amplitude as a means of curbing its side effects.
Sudan Acharya, Madhu
2010-05-01
The crib retaining structures made of wooden/bamboo logs with live plants inside are called vegetative crib walls which are now becoming popular due to their advantages over conventional civil engineering walls. Conventionally, wooden crib walls were dimensioned based on past experiences. At present, there are several guidelines and design standards for machine finished wooden crib walls, but only few guidelines for the design and construction of vegetative log crib walls are available which are generally not sufficient for an economic engineering design of such walls. Analytical methods are generally used to determine the strength of vegetated crib retaining walls. The crib construction is analysed statically by satisfying the condition of static equilibrium with acceptable level of safety. The crib wall system is checked for internal and external stability using conventional monolithic and silo theories. Due to limitations of available theories, the exact calculation of the strength of vegetated wooden/bamboo crib wall cannot be made in static calculation. Therefore, experimental measurements are generally done to verify the static analysis. In this work, a model crib construction (1:20) made of bamboo elements is tested in the centrifuge machine to determine the strength behaviour of the slope supported by vegetated crib retaining wall. A geotechnical centrifuge is used to conduct model tests to study geotechnical problems such as the strength, stiffness and bearing capacity of different structures, settlement of embankments, stability of slopes, earth retaining structures etc. Centrifuge model testing is particularly well suited to modelling geotechnical events because the increase in gravitational force creates stresses in the model that are equivalent to the much larger prototype and hence ensures that the mechanisms of ground movements observed in the tests are realistic. Centrifuge model testing provides data to improve our understanding of basic mechanisms
TIG-dressing of High Strength Butt Welded Connection. Part 2: Physical Testing and Modelling
Van Es, S.H.J.; Kolstein, M.H.; Pijpers, R.J.M.; Bijlaard, F.S.K.
2014-01-01
Weld improvement techniques are aimed at reducing the notch effects of welds and generally focus on two aspects: a change of geometry of the weld toe and a change of the weld residual stresses. In this paper, fatigue tests are discussed, performed on butt welded specimens in steel grades ranging from S460 to S1100 in the TIG-dressed condition. The test results are compared with modelled fatigue strength according to the notch stress theory and similar specimens in the as-welded condition. The...
Esteves, L.P.
2012-01-01
Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...
Schlittmeier, Sabine J; Weissgerber, Tobias; Kerber, Stefan; Fastl, Hugo; Hellbrück, Jürgen
2012-01-01
Background sounds, such as narration, music with prominent staccato passages, and office noise impair verbal short-term memory even when these sounds are irrelevant. This irrelevant sound effect (ISE) is evoked by so-called changing-state sounds that are characterized by a distinct temporal structure with varying successive auditory-perceptive tokens. However, because of the absence of an appropriate psychoacoustically based instrumental measure, the disturbing impact of a given speech or nonspeech sound could not be predicted until now, but necessitated behavioral testing. Our database for parametric modeling of the ISE included approximately 40 background sounds (e.g., speech, music, tone sequences, office noise, traffic noise) and corresponding performance data that was collected from 70 behavioral measurements of verbal short-term memory. The hearing sensation fluctuation strength was chosen to model the ISE and describes the percept of fluctuations when listening to slowly modulated sounds (f(mod) sounds, the algorithm estimated behavioral performance data in 63 of 70 cases within the interquartile ranges. In particular, all real-world sounds were modeled adequately, whereas the algorithm overestimated the (non-)disturbance impact of synthetic steady-state sounds that were constituted by a repeated vowel or tone. Implications of the algorithm's strengths and prediction errors are discussed.
Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal
2017-01-01
Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 103 to 104 s-1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.
Vector interaction strength in Polyakov-Nambu-Jona-Lasinio models from hadron-quark phase diagrams
Lourenço, O; Frederico, T; Delfino, A; Malheiro, M
2012-01-01
We estimate the vector interaction strength of the Polyakov-Nambu-Jona-Lasinio (PNJL) parametrizations, assuming that its transition curves should be as close as possible of the recently studied RMF-PNJL hadron-quark phase diagrams. Such diagrams are obtained matching relativistic mean-field hadronic models, and the PNJL quark ones. By using this method we found for the magnitude of the vector interaction, often treated as a free parameter, a range of 7.66 GeV$^{-2}\\lesssim G_V \\lesssim 16.13$ GeV$^{-2}$, or equivalently, $1.52 \\lesssim G_V/G_s \\lesssim 3.2$, with $G_s$ being the scalar coupling constant of the model. These values are compatible but restricts the range of 4 GeV$^{-2}\\lesssim G_V \\lesssim 19$ GeV$^{-2}$, recently obtained from lattice QCD data through a different mean-field model approach.
Investigation of a bifactor model of the Strengths and Difficulties Questionnaire.
Caci, Hervé; Morin, Alexandre J S; Tran, Antoine
2015-10-01
The Strengths and Difficulties Questionnaire (SDQ) is used to measure psychopathological symptoms in children and adolescents from 4 to 17 years old, but its underlying structure is still a matter of debate. Indeed, on the basis of a systematic review of English and non-English articles conducted using multiple databases, 54 studies reporting on the factor structure of the SDQ were located. The original 5 first-order factor structure is generally supported by exploratory procedures, but support based on confirmatory factor analyses is not clear. We analysed data from 889 youths from the general French population, rated on the SDQ by their teachers. We tested the original model, hierarchical models and bifactor models. The best-fitting model is a bifactor model with the five a priori factors grouped in two global factors (Externalizing Disorders-Hyperactivity and Conduct-and Internalizing Disorders-Peer relationships and Emotions) and one Strength/Prosocial factor. However, we show that the Conduct-Specific factor should not be used in practice in its current state, that the Hyperactivity-Specific factor mainly covers hyperactivity rather than inattention, and that the Peer Problems-Specific factor mainly reflects a preference for solitude. Nevertheless, the measurement model proved to be fully invariant across gender and school levels (kindergarten, primary and secondary schools), with statistically significant differences in latent means between genders only. Beyond computing the five a priori scores when using the teacher ratings of the SDQ, our results prove the usefulness of computing Externalizing Disorders and Internalizing Disorders global scores.
Bray, Steven R; Martin Ginis, Kathleen A; Woodgate, Jennifer
2011-07-01
Self-regulation consumes a form of strength or energy. The authors investigated aftereffects of self-regulation depletion on muscle-endurance performance in older adults. Participants (N = 61, mean age = 71) were randomized to a self-regulation-depletion or control group and completed 2 muscle-endurance performance tasks involving isometric handgrip squeezing that were separated by a cognitive-depletion task. The depletion group showed greater deterioration of muscle-endurance performance than controls, F(1, 59) = 7.31, p = .009. Results are comparable to those of younger adults in a similar study and support Baumeister et al.'s limited-strength model. Self-regulation may contribute to central-nervous-system fatigue; however, biological processes may allow aging muscle to offset depletion of self-regulatory resources affecting muscle-endurance performance.
Bast, Callie Corinne Scheidt
1994-01-01
This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.
Proteolysis process in fermented sausage model systems as studied by NMR relaxometry.
García García, Ana Belén; Larsen, Lotte Bach; Cambero Rodríguez, María Isabel; Cruz Díaz, Karen Paola; Bertram, Hanne Christine
2015-03-25
Proton NMR relaxation analyses were performed in sausage model systems (SMS) at different manufacturing times (0, 1, 3, 5, 7, and 9 days) to evaluate changes in water distribution and mobility. Three different water populations were identified, T2b (5-10 ms), T21 (30-70 ms), and T22 (100-300 ms), and the progress of ripening could be followed as a shift toward shorter relaxation times. In addition, the combined effect of adding commercial proteases (Pronase E and aspartyl proteinase) on protein breakdown and structural integrity of sausage models (SMS+P) was investigated, resulting in the formation of a more fluid and less organized meat matrix that led to changes in water populations T2b2 and T22 compared with SMS. A very different protein degradation pattern between SMS and SMS+P was observed by means of SDS-PAGE and fluorescamine assay, supporting that some degree of protein aggregation is needed for the presence of the T22 population in fermented sausages.
3D phase-field modelling of dislocation loop sink strengths
Thuinet, L.; Rouchette, H.; Legris, A.
2017-01-01
This work presents a 3D phase-field model to correctly evaluate dislocation loop sink strength. This method is applied to a wide range of microstructures (dislocation loops of various types with isotropic or anisotropic elasticity, like in Zr, cohabitation of different types of loop in the same calculation domain), which allows to exhibit several original results. Among them, in the case of isotropic elasticity, our model shows that the sink strength of vacancy loops is higher than that of interstitial ones for low loop radii. In the case of Zr, the effect on sink biases of the shape anisotropy of self-interstitial atoms, already exhibited in the case of straight dislocations, is enhanced for loops and stabilizes basal vacancy and prism-plane interstitial ones. Moreover, isotropic elastic interactions promote the coexistence of parallel vacancy and interstitial loops. This result is still valid in the case of prism-plane loops in Zr, which could provide explanations to several experimental facts.
Mechanical strength of 17,134 model proteins and cysteine slipknots.
Mateusz Sikora
2009-10-01
Full Text Available A new theoretical survey of proteins' resistance to constant speed stretching is performed for a set of 17,134 proteins as described by a structure-based model. The proteins selected have no gaps in their structure determination and consist of no more than 250 amino acids. Our previous studies have dealt with 7510 proteins of no more than 150 amino acids. The proteins are ranked according to the strength of the resistance. Most of the predicted top-strength proteins have not yet been studied experimentally. Architectures and folds which are likely to yield large forces are identified. New types of potent force clamps are discovered. They involve disulphide bridges and, in particular, cysteine slipknots. An effective energy parameter of the model is estimated by comparing the theoretical data on characteristic forces to the corresponding experimental values combined with an extrapolation of the theoretical data to the experimental pulling speeds. These studies provide guidance for future experiments on single molecule manipulation and should lead to selection of proteins for applications. A new class of proteins, involving cysteine slipknots, is identified as one that is expected to lead to the strongest force clamps known. This class is characterized through molecular dynamics simulations.
Spyridon Liakas
2017-08-01
Full Text Available The particulate discrete element method (DEM can be employed to capture the response of rock, provided that appropriate bonding models are used to cement the particles to each other. Simulations of laboratory tests are important to establish the extent to which those models can capture realistic rock behaviors. Hitherto the focus in such comparison studies has either been on homogeneous specimens or use of two-dimensional (2D models. In situ rock formations are often heterogeneous, thus exploring the ability of this type of models to capture heterogeneous material behavior is important to facilitate their use in design analysis. In situ stress states are basically three-dimensional (3D, and therefore it is important to develop 3D models for this purpose. This paper revisits an earlier experimental study on heterogeneous specimens, of which the relative proportions of weaker material (siltstone and stronger, harder material (sandstone were varied in a controlled manner. Using a 3D DEM model with the parallel bond model, virtual heterogeneous specimens were created. The overall responses in terms of variations in strength and stiffness with different percentages of weaker material (siltstone were shown to agree with the experimental observations. There was also a good qualitative agreement in the failure patterns observed in the experiments and the simulations, suggesting that the DEM data enabled analysis of the initiation of localizations and micro fractures in the specimens.
Modeling the dependence of strength on grain sizes in nanocrystalline materials.
He, Wei; Bhole, Sanjeev D; Chen, DaoLun
2008-01-01
A model was developed to describe the grain size dependence of hardness (or strength) in nanocrystalline materials by combining the Hall-Petch relationship for larger grains with a coherent polycrystal model for nanoscale grains and introducing a log-normal distribution of grain sizes. The transition from the Hall-Petch relationship to the coherent polycrystal mechanism was shown to be a gradual process. The hardness in the nanoscale regime was observed to increase with decreasing grain boundary affected zone (or effective grain boundary thickness, Δ) in the form of Δ(-1/2). The critical grain size increased linearly with increasing Δ. The variation of the calculated hardness value with the grain size was observed to be in agreement with the experimental data reported in the literature.
Krueger, O.; Ebinghaus, R.; Kock, H.H.; Richter-Politz, I.; Geilhufe, C.
1998-12-31
Anthropogenic emission sources of gaseous mercury at the contaminated industrial site BSL Werk Schkopau have been determined by measurements and numerical modelling applying a local dispersion model. The investigations are based on measurements from several field campaigns in the period of time between December 1993 and June 1994. The estimation of the source strengths was performed by inverse modelling using measurements as constraints for the dispersion model. Model experiments confirmed the applicability of the inverse modelling procedure for the source strength estimation at BSL Werk Schkopau. At the factory premises investigated, the source strengths of four source areas, among them three closed chlor-alkali productions, one partly removed acetaldehyde factory and additionaly one still producing chlor-alkali factory have been identified with an approximate total gaseous mercury emission of lower than 2.5 kg/day. (orig.)
artificial neural network model for low strength rc beam shear capacity
User
predicting the shear strength of 26 low strength RC beams. Even though ... research activity over the last 20 years. The ... 2012 Kwame Nkrumah University of Science and Technology (KNUST) ... art approach to computation procedures is the.
Berg, J. van den; Wal, R.S.W. van de; Oerlemans, J.
2006-01-01
A vertically integrated two-dimensional ice flow model was coupled to an elastic lithosphere-Earth model to study the effects of lateral variations in lithospheric strength on local bedrock adjustment. We used a synthetic bedrock profile and a synthetic climate to model a characteristic ice sheet
van de Berg, W.J.; van de Wal, R.S.W.; Oerlemans, J.
2006-01-01
A vertically integrated two-dimensional ice flow model was coupled to an elastic lithosphere-Earth model to study the effects of lateral variations in lithospheric strength on local bedrock adjustment. We used a synthetic bedrock profile and a synthetic climate to model a characteristic ice sheet
VARIANCE ANALYSIS OF WOOL WOVEN FABRICS TENSILE STRENGTH USING ANCOVA MODEL
VÎLCU Adrian
2014-05-01
Full Text Available The paper has conducted a study on the variation of tensile strength for four woven fabrics made from wool type yarns depending on fiber composition, warp and weft yarns tensile strength and technological density using ANCOVA regression model. In instances where surveyed groups may have a known history of responding to questions differently, rather than using the traditional sharing method to address those differences, analysis of covariance (ANCOVA can be employed. ANCOVA shows the correlation between a dependent variable and the covariate independent variables and removes the variability from the dependent variable that can be accounted by the covariates. The independent and dependent variable structures for Multiple Regression, factorial ANOVA and ANCOVA tests are similar. ANCOVA is differentiated from the other two in that it is used when the researcher wants to neutralize the effect of a continuous independent variable in the experiment. The researcher may simply not be interested in the effect of a given independent variable when performing a study. Another situation where ANCOVA should be applied is when an independent variable has a strong correlation with the dependent variable, but does not interact with other independent variables in predicting the dependent variable’s value. ANCOVA is used to neutralize the effect of the more powerful, non-interacting variable. Without this intervention measure, the effects of interacting independent variables can be clouded
Zhang, Zengmeng; Hou, Jiaoyi; Ning, Dayong; Gong, Xiaofeng; Gong, Yongjun
2017-05-01
Fluidic artificial muscles are popular in robotics and function as biomimetic actuators. Their pneumatic version has been widely investigated. A novel water hydraulic artificial muscle (WHAM) with high strength is developed in this study. WHAMs can be applied to underwater manipulators widely used in ocean development because of their environment-friendly characteristics, high force-to-weight ratio, and good bio-imitability. Therefore, the strength of WHAMs has been improved to fit the requirements of underwater environments and the work pressure of water hydraulic components. However, understanding the mechanical behaviors of WHAMs is necessary because WHAMs use work media and pressure control that are different from those used by pneumatic artificial muscles. This paper presents the static and dynamic characteristics of the WHAM system, including the water hydraulic pressure control circuit. A test system is designed and built to analyze the drive characteristics of the developed WHAM. The theoretical relationships among the amount of contraction, pressure, and output drawing force of the WHAM are tested and verified. A linearized transfer function is proposed, and the dynamic characteristics of the WHAM are investigated through simulation and inertia load experiments. Simulation results agree with the experimental results and show that the proposed model can be applied to the control of WHAM actuators.
Abrosimov, N. A.; Novosel'tseva, N. A.
2017-05-01
A technique for numerically analyzing the dynamic strength of two-layer metal-plastic cylindrical shells under an axisymmetric internal explosive loading is developed. The kinematic deformation model of the layered package is based on a nonclassical theory of shells. The geometric relations are constructed using relations of the simplest quadratic version of the nonlinear elasticity theory. The stress and strain tensors in the composite macrolayer are related by Hooke's law for an orthotropic body with account of degradation of the stiffness characteristics of the multilayer package due to local failure of some its elementary layers. The physical relations in the metal layer are formulated in terms of a differential theory of plasticity. An energy-correlated resolving system of dynamic equations for the metal-plastic cylindrical shells is derived by minimizing the functional of total energy of the shells as three-dimensional bodies. The numerical method for solving the initial boundary-value problem formulated is based on an explicit variational-difference scheme. The reliability of the technique considered is verified by comparing numerical results with experimental data. An analysis of the ultimate strains and strength of one-layer basalt-and glass-fiber-reinforced plastic and two-layer metalplastic cylindrical shells is carried out.
Fiber-Level Modeling of Dynamic Strength of Kevlar® KM2 Ballistic Fabric
Grujicic, M.; Hariharan, A.; Pandurangan, B.; Yen, C.-F.; Cheeseman, B. A.; Wang, Y.; Miao, Y.; Zheng, J. Q.
2012-07-01
In recent years, modeling of the high-performance ballistic fabric has gradually shifted from the continuum and yarn length scales to the sub-yarn length scale which enabled establishment of the relationships between the fabric penetration resistance and various fiber-level phenomena such as fiber-fiber friction, fiber twist, transverse properties of the fibers, and the stochastic nature of fiber strength. In general, these sub-yarn modeling schemes involve special numerical techniques (e.g., digital-element method) and customized computational codes. This status of the sub-yarn fabric-modeling methods and tools makes them not readily available to wider academic and industrial research communities. In the present work, an attempt is made to use conventional finite-element methods and tools in order to carry out sub-yarn numerical analysis of the penetration resistance of Kevlar® KM2 ballistic fabric. The goal was to demonstrate that results could be obtained which are comparable to their digital-element method = based counterparts. Specifically, a series of transient nonlinear dynamics finite-element analyses was carried out in order to investigate the role of the following two important sub-yarn phenomena on the penetration resistance of Kevlar® KM2 fabric: (a) fiber transverse properties including nonlinear elastic and plastic response and (b) fiber-fiber friction within the context of stochastically distributed fiber axial strength. It is generally found that the results obtained are consistent with their digital-element method-based counterparts.
Cannabis social clubs in Belgium: organizational strengths and weaknesses, and threats to the model.
Decorte, Tom
2015-02-01
Cannabis Social Clubs (CSCs) are private organizations or clubs of users that produce cannabis for non-profit distribution to adult members to meet their personal needs without having to turn to the black market. CSCs can be found in many countries, but the term often covers very different empirical realities. Inspired by the Spanish CSCs and similarly taking advantage of a grey area in the Belgian cannabis legislation, Belgian cannabis activists set up the first Belgian CSC in 2006, and there are now at least 5 Belgian CSCs. The paper's main objective is to analyse the (internal) strengths and weaknesses and the (external) opportunities and threats of the model, as it exists today. The paper draws on a review of international literature and qualitative data on the Belgian cannabis social clubs. Field visits and interviews were conducted with each club. We analysed membership application forms, cultivation protocols and contracts with growers, cannabis ownership certificates of members, information leaflets, the clubs' websites, and all media articles and documentaries on the clubs in the Belgian media. The paper describes the membership criteria and house rules, the members' profile, the organization and protocols for cannabis production, the distribution of cannabis through 'exchange fairs', the administrative features of the clubs and their contacts with other CSCs and with local authorities, the drug sector and the media. Belgian CSCs seem not profit-driven, and operate as a system in which cannabis is not too easily available. The clubs have fairly direct control over the quality and the potency of the cannabis they distribute. The model offers important potential opportunities, in terms of economic advantages and monitoring consumption patterns. The main threats to Belgian CSCs consist of attempts to criminalize the model, the emergence of profit-driven clubs and systemic violence from criminal entrepreneurs. Weaknesses of the model relate to the unstable or
Predicting bond strength from a single Hartree-Fock ground state using the localized pair model.
Hennessey, Dylan C; Sheppard, Brendan J H; Mackenzie, Dalton E C K; Pearson, Jason K
2014-12-14
We present an application of the recently introduced Localized Pair Model (LPM) [Z. A. Zielinksi and J. K. Pearson, Comput. Theor. Chem., 2013, 1003, 7990] to characterize and quantify properties of the chemical bond in a series of substituted benzoic acid molecules. By computing interelectronic distribution functions for doubly-occupied Edmiston-Ruedenberg localized molecular orbitals (LMOs), we show that chemically intuitive electron pairs may be uniquely classified and bond strength may be predicted with remarkable accuracy. Specifically, the HF/u6-311G(d,p) level (where u denotes a complete uncontraction of the basis set) is used to generate the relevant LMOs and their respective interelectronic distribution functions can be linearly correlated to the well-known Hammett σp or σm parameters with near-unity correlation coefficients.
A review of shear strength models for rock joints subjected to constant normal stiffness
Sivanathan Thirukumaran
2016-06-01
Full Text Available The typical shear behaviour of rough joints has been studied under constant normal load/stress (CNL boundary conditions, but recent studies have shown that this boundary condition may not replicate true practical situations. Constant normal stiffness (CNS is more appropriate to describe the stress–strain response of field joints since the CNS boundary condition is more realistic than CNL. The practical implications of CNS are movements of unstable blocks in the roof or walls of an underground excavation, reinforced rock wedges sliding in a rock slope or foundation, and the vertical movement of rock-socketed concrete piles. In this paper, the highlights and limitations of the existing models used to predict the shear strength/behaviour of joints under CNS conditions are discussed in depth.
Finite Element Modelling Full Vehicle Side Impact with Ultrahigh Strength Hot Stamped Steels
Taylor, T.; Fourlaris, G.; Cafolla, J.
2016-10-01
"Hot stamped boron steel" 22MnB5 has been imperative in meeting the automotive industry's demand for materials exhibiting higher tensile strength in the final component. In this paper, the crash performance of three experimental grades developed for automotive hot stamping technologies, exhibiting wider tensile property ranges than 22MnB5, was validated by finite element modelling full vehicle side impact with the experimental material data applied to the B-pillar reinforcement. The superior anti-intrusive crash performance of grade 38MnB5 was demonstrated, with 11 mm less intrusion of the B-pillar reinforcement compared to 22MnB5. Moreover, the superior "impact-energy absorptive" crash performance of grade 15MnCr5 was demonstrated, with 0.15 kJ greater impact-energy absorption by the B-pillar reinforcement compared to 22MnB5.
Analytic EoS and PTW strength model recommendation for Starck Ta
Sjue, Sky K. [Los Alamos National Laboratory; Prime, Michael Bruce [Los Alamos National Laboratory
2016-09-01
The purpose of this document is to provide an analytic EoS and PTW strength model for Starck Ta that can be consistently used between different platforms and simulations at three labs. This should provide a consistent basis for comparison of the results of calculations, but not the best implementation for matching a wide variety of experimental data. Another version using SESAME tables should follow, which will provide a better physical representation over a broader range of conditions. The data sets available at the time only include one Hopkinson bar at a strain rate of 1800/s; a broader range of high-rate calibration data would be preferred. The resulting fit gives the PTW parameter p = 0. To avoid numerical issues, p = 0:001 has been used in FLAG. The PTW parameters that apply above the maximum strain rate in the data use the values from the original publication.
Uthman Baroudi
2015-01-01
Full Text Available Wireless sensor networks can provide effective means for monitoring and controlling a wide range of applications. Recently, tremendous effort was directed towards devising sensors powered from ambient sources such as heat, wind, and vibration. Wireless energy transfer is another source that has attractive features that make it a promising candidate for supplying power to wireless sensor nodes. This paper is concerned with characterizing and modeling the charging time and received signal strength indicator for wireless energy transfer system. These parameters play a vital role in deciding the geometry of sensor network and the routing protocols to be deployed. The development of communication protocols for wireless-powered wireless sensor networks is also improved with the knowledge of such models. These two quantities were computed from data acquired at various coordinates of the harvester relative to a fixed position of RF energy source. Data was acquired for indoor and outdoor scenarios using the commercially available PowerCast energy harvester and evaluation board. Mathematical models for both indoor and outdoor environments were developed and analyzed. A few guidelines on how to use these models were suggested. Finally, the possibility of harvesting the energy from the ambient RF power to energize wireless sensor nodes was also investigated.
A mass-length scaling law for modeling muscle strength in the lower limb.
Correa, Tomas A; Pandy, Marcus G
2011-11-10
Musculoskeletal computer models are often used to study muscle function in children with and without impaired mobility. Calculations of muscle forces depend in part on the assumed strength of each muscle, represented by the peak isometric force parameter, which is usually based on measurements obtained from cadavers of adult donors. The aim of the present study was twofold: first, to develop a method for scaling lower-limb peak isometric muscle forces in typically-developing children; and second, to determine the effect of this scaling method on model calculations of muscle forces obtained for normal gait. Muscle volumes were determined from magnetic resonance (MR) images obtained from ten children aged from 7 to 13yr. A new mass-length scaling law was developed based on the assumption that muscle volume and body mass are linearly related, which was confirmed by the obtained volume and body mass data. Two musculoskeletal models were developed for each subject: one in which peak isometric muscle forces were estimated using the mass-length scaling law; and another in which these parameters were determined directly from the MR-derived muscle volumes. Musculoskeletal modeling and quantitative gait analysis were then used to calculate lower-limb muscle forces in normal walking. The patterns of muscle forces predicted by the model with scaled peak isometric force values were similar to those predicted by the MR-based model, implying that assessments of muscle function obtained from these two methods are practically equivalent. These results support the use of mass-length scaling in the development of subject-specific musculoskeletal models of children.
A cohesive zone model to simulate the hydrogen embrittlement effect on a high-strength steel
G. Gobbi
2016-01-01
Full Text Available The present work aims to model the fracture mechanical behavior of a high-strength low carbon steel, AISI 4130 operating in hydrogen contaminated environment. The study deals with the development of 2D finite element cohesive zone model (CZM reproducing a toughness test. Along the symmetry plane over the crack path of a C(T specimen a zero thickness layer of cohesive elements are implemented in order to simulate the crack propagation. The main feature of this kind of model is the definition of a traction-separation law (TSL that reproduces the constitutive response of the material inside to the cohesive elements. Starting from a TSL calibrated on hydrogen non-contaminated material, the embrittlement effect is simulated by reducing the cohesive energy according to the total hydrogen content including the lattice sites (NILS and the trapped amount. In this perspective, the proposed model consists of three steps of simulations. First step evaluates the hydrostatic pressure. It drives the initial hydrogen concentration assigned in the second step, a mass diffusion analysis, defining in this way the contribution of hydrogen moving across the interstitial lattice sites. The final stress analysis, allows getting the total hydrogen content, including the trapped amount, and evaluating the new crack initiation and propagation due to the hydrogen presence. The model is implemented in both plane strain and plane stress configurations; results are compared in the discussion. From the analyses, it resulted that hydrogen is located only into lattice sites and not in traps, and that the considered steel experiences a high hydrogen susceptibility. By the proposed procedure, the developed numerical model seems a reliable and quick tool able to estimate the mechanical behavior of steels in presence of hydrogen.
Rajbhandari, Mani Man Singh
2011-01-01
Public-Private Partnership (PPP) model in education is being importantly valuable in developing countries in enriching the strength pf public schools that government appears to be heavy and slow. PPP model however, initiate developmental program that encourage teachers motivation to teach. This further allows private and local community group…
Composition design of superhigh strength maraging stainless steels using a cluster model
Zhen Li
2014-02-01
Full Text Available The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe12]Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni with surplus Ni was then determined to ensure the second phase (Ni3M precipitation, based on which new multi-component alloys [(Ni,Cu16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V16 were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1 alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67Nb0.32Al0.19V0.36Cu1.78 wt% has higher tensile strengths with YS=1456 MPa and UTS=1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.
Composition design of superhigh strength maraging stainless steels using a cluster model
Zhen Li; Ruiqian Zhang; Qianfeng Zha; Yingmin Wang; Jianbing Qiang; Chuang Dong
2014-01-01
The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe-Ni-Cr corresponds to the cluster formula [NiFe12] Cr3, where NiFe12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe12](Cr2Ni) with surplus Ni was then determined to ensure the second phase (Ni3M) precipitation, based on which new multi-component alloys [(Ni,Cu)16Fe192](Cr32(Ni,Mo,Ti,Nb,Al,V)16) were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni3M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu4Ni12)Fe192](Cr32(Ni8.5Mo2Ti2Nb0.5Al1V1)) alloy (Fe74.91Ni8.82Cr11.62Mo1.34Ti0.67N-b0.32Al0.19V0.36Cu1.78 wt%) has higher tensile strengths with YS ¼ 1456 MPa and UTS ¼ 1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.
Development of an Atlas of Strengths and Establishment of an Appropriate Model Structure
1981-11-01
30. Edwards, R. H. T. and Hyde, S. Methods of measuring muscle strength and fatigue. Physiotherapy ; 1977, 63(2), 51-55. 31. Falkel, J. Planter flexor...34 and in rare instances "heart attacks," or "cardiac arrest," strokes , or pulmonary embolism. If this research project causes any physical injury to you...and Hyde, S. Methods of measuring muscle strength and fatigue. Physiotherapy ; 1977, 63(2), 51-55. KEYWORDS: Muscle strength tests, male and female
Juan Manuel Lizarazo Marriaga
2010-04-01
Full Text Available The present study was conducted for predicting the compressive strength of concrete based on unit weight ultrasonic and pulse velocity (UPV for 41 different concrete mixtures. This research emerged from the need for a rapid test for predicting concrete’s compressive strength. The research was also conducted for predicting concrete’s electrical resistivity based on unit weight ultrasonic, pulse velocity (UPV and compressive strength with the same mixes. The prediction was made using simple regression analysis and artificial neural networks. The results revealed that artificial neural networks can be used for effectively predicting compressive strength and electrical resistivity.
Bradshaw, James F.; Sandefur, Paul G., Jr.; Young, Clarence P., Jr.
1991-01-01
A comprehensive study of braze alloy selection process and strength characterization with application to wind tunnel models is presented. The applications for this study include the installation of stainless steel pressure tubing in model airfoil sections make of 18 Ni 200 grade maraging steel and the joining of wing structural components by brazing. Acceptable braze alloys for these applications are identified along with process, thermal braze cycle data, and thermal management procedures. Shear specimens are used to evaluate comparative shear strength properties for the various alloys at both room and cryogenic (-300 F) temperatures and include the effects of electroless nickel plating. Nickel plating was found to significantly enhance both the wetability and strength properties for the various braze alloys studied. The data are provided for use in selecting braze alloys for use with 18 Ni grade 200 steel in the design of wind tunnel models to be tested in an ambient or cryogenic environment.
Jorgensen, Bradley S; Martin, John F; Pearce, Meryl; Willis, Eileen
2013-01-30
Research employing household water consumption data has sought to test models of water demand and conservation using variables from attitude theory. A significant, albeit unrecognised, challenge has been that attitude models describe individual-level motivations while consumption data is recorded at the household level thereby creating inconsistency between units of theory and measurement. This study employs structural equation modelling and moderated regression techniques to addresses the level of analysis problem, and tests hypotheses by isolating effects on water conservation in single-person households. Furthermore, the results question the explanatory utility of habit strength, perceived behavioural control, and intentions for understanding metered water conservation in single-person households. For example, evidence that intentions predict water conservation or that they interact with habit strength in single-person households was contrary to theoretical expectations. On the other hand, habit strength, self-reports of past water conservation, and perceived behavioural control were good predictors of intentions to conserve water.
A viscoplastic micromechanical model for the yield strength of nanocrystalline materials
Lebensohn, R; Bringa, E; Caro, A
2006-03-14
In this paper we present a micromechanical approach based on Fast Fourier Transforms to study the role played by dislocation glide and grain boundary (GB) accommodation in the determination of the plastic behavior of nanostructured materials. For this, we construct unit cells representing self-similar polycrystals with different grain sizes in the nanometer range and use local constitutive equations for slip and GB accommodation. We study the effect of grain size, strain rate and pressure on the local and effective behavior of nanostructured fcc materials with parameters obtained from experiments and atomistic simulations. Predictions of a previous qualitative pressure-sensitive model for the effective yield strength behind a shock front are substantially improved by considering strain partition between slip and GB activity. Under quasiestatic conditions, assuming diffusion-controlled mechanisms at GB, the model predicts a strain-rate sensitivity increase in nanocrystalline samples with respect to the same coarse-grained material of the same order as in recently published experiments.
Using coronal seismology to estimate the magnetic field strength in a realistic coronal model
Chen, Feng
2015-01-01
Coronal seismology is extensively used to estimate properties of the corona, e.g. the coronal magnetic field strength are derived from oscillations observed in coronal loops. We present a three-dimensional coronal simulation including a realistic energy balance in which we observe oscillations of a loop in synthesised coronal emission. We use these results to test the inversions based on coronal seismology. From the simulation of the corona above an active region we synthesise extreme ultraviolet (EUV) emission from the model corona. From this we derive maps of line intensity and Doppler shift providing synthetic data in the same format as obtained from observations. We fit the (Doppler) oscillation of the loop in the same fashion as done for observations to derive the oscillation period and damping time. The loop oscillation seen in our model is similar to imaging and spectroscopic observations of the Sun. The velocity disturbance of the kink oscillation shows an oscillation period of 52.5s and a damping tim...
Multi-scale Model of Residual Strength of 2D Plain Weave C/SiC Composites in Oxidation Atmosphere
Chen, Xihui; Sun, Zhigang; Sun, Jianfen; Song, Yingdong
2016-06-01
Multi-scale models play an important role in capturing the nonlinear response of woven carbon fiber reinforced ceramic matrix composites. In plain weave carbon fiber/silicon carbon (C/SiC) composites, the carbon fibers and interphases will be oxidized at elevated temperature and the strength of the composite will be degraded when oxygen enters micro-cracks formed in the as-produced parts due to the mismatch in thermal properties between constituents. As a result of the oxidation on fiber surface, fiber shows a notch-like morphology. In this paper, the change rule of fiber notch depth is fitted by circular function. And a multi-scale model based upon the change rule of fiber notch depth is developed to simulate the residual strength and post-oxidation stress-strain curves of the composite. The multi-scale model is able to accurately predict the residual strength and post-oxidation stress-strain curves of the composite. Besides, the simulated residual strength and post-oxidation stress-strain curves of 2D plain weave C/SiC composites in oxidation atmosphere show good agreements with experimental results. Furthermore, the oxidation time and temperature of the composite are investigated to show their influences upon the residual strength and post-oxidation stress-strain curves of plain weave C/SiC composites.
Probing recent star formation with absorption-line strengths in hierarchical models and observations
Trager, S. C.; Somerville, R. S.
2009-01-01
Stellar population parameters (e. g. age, metallicity and stellar abundance ratios) derived from spectral line strengths provide a powerful probe of galaxy properties and formation histories. We implement the machinery for extracting line strengths and 'single-stellar-population-equivalent' (SSP-equ
Kortschot, R. J.; Lyklema, J.; Philipse, A. P.; Erné, B. H.
2014-01-01
Electroacoustics and laser Doppler electrophoresis were employed to measure the mobility of surface-modified silica colloids in ethanol as a function of the ionic strength. Sufficiently low volume fractions were chosen to exclude effects of interparticle interactions. At high ionic strength, the ele
Bast, Callie C.; Jurena, Mark T.; Godines, Cody R.; Chamis, Christos C. (Technical Monitor)
2001-01-01
This project included both research and education objectives. The goal of this project was to advance innovative research and education objectives in theoretical and computational probabilistic structural analysis, reliability, and life prediction for improved reliability and safety of structural components of aerospace and aircraft propulsion systems. Research and education partners included Glenn Research Center (GRC) and Southwest Research Institute (SwRI) along with the University of Texas at San Antonio (UTSA). SwRI enhanced the NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) code and provided consulting support for NESSUS-related activities at UTSA. NASA funding supported three undergraduate students, two graduate students, a summer course instructor and the Principal Investigator. Matching funds from UTSA provided for the purchase of additional equipment for the enhancement of the Advanced Interactive Computational SGI Lab established during the first year of this Partnership Award to conduct the probabilistic finite element summer courses. The research portion of this report presents the cumulation of work performed through the use of the probabilistic finite element program, NESSUS, Numerical Evaluation and Structures Under Stress, and an embedded Material Strength Degradation (MSD) model. Probabilistic structural analysis provided for quantification of uncertainties associated with the design, thus enabling increased system performance and reliability. The structure examined was a Space Shuttle Main Engine (SSME) fuel turbopump blade. The blade material analyzed was Inconel 718, since the MSD model was previously calibrated for this material. Reliability analysis encompassing the effects of high temperature and high cycle fatigue, yielded a reliability value of 0.99978 using a fully correlated random field for the blade thickness. The reliability did not change significantly for a change in distribution type except for a change in
Bilgehan, Mahmut
2011-03-01
In this paper, adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) model have been successfully used for the evaluation of relationships between concrete compressive strength and ultrasonic pulse velocity (UPV) values using the experimental data obtained from many cores taken from different reinforced concrete structures having different ages and unknown ratios of concrete mixtures. A comparative study is made using the neural nets and neuro-fuzzy (NF) techniques. Statistic measures were used to evaluate the performance of the models. Comparing of the results, it is found that the proposed ANFIS architecture with Gaussian membership function is found to perform better than the multilayer feed-forward ANN learning by backpropagation algorithm. The final results show that especially the ANFIS modelling may constitute an efficient tool for prediction of the concrete compressive strength. Architectures of the ANFIS and neural network established in the current study perform sufficiently in the estimation of concrete compressive strength, and particularly ANFIS model estimates closely follow the desired values. Both ANFIS and ANN techniques can be used in conditions where too many structures are to be examined in a restricted time. The presented approaches enable to practically find concrete strengths in the existing reinforced concrete structures, whose records of concrete mixture ratios are not available or present. Thus, researchers can easily evaluate the compressive strength of concrete specimens using UPV and density values. These methods also contribute to a remarkable reduction in the computational time without any significant loss of accuracy. A comparison of the results clearly shows that particularly the NF approach can be used effectively to predict the compressive strength of concrete using UPV and density values. In addition, these model architectures can be used as a nondestructive procedure for health monitoring of
Target Strength of Southern Resident Killer Whales (Orcinus orca): Measurement and Modeling
Xu, Jinshan; Deng, Zhiqun; Carlson, Thomas J.; Moore, Brian
2012-04-04
A major criterion for tidal power licensing in Washington’s Puget Sound is the management of the risk of injury to killer whales due to collision with moving turbine blades. An active monitoring system is being proposed for killer whale detection, tracking, and alerting that links to and triggers temporary turbine shutdown when there is risk of collision. Target strength (TS) modeling of the killer whale is critical to the design and application of any active monitoring system. A 1996 study performed a high-resolution measurement of acoustic reflectivity as a function of frequency of a female bottlenose dolphin (2.2 m length) at broadside aspect and TS as a function of incident angle at 67 kHz frequency. Assuming that killer whales share similar morphology structure with the bottlenose dolphin, we extrapolated the TS of an adult killer whale 7.5 m in length at 67 kHz frequency with -8 dB at broadside aspect and -28 dB at tail side. The backscattering data from three Southern Resident killer whales were analyzed to obtain the TS measurement. These data were collected at Lime Kiln State Park using a split-beam system deployed from a boat. The TS of the killer whale at higher frequency (200 kHz) was estimated based on a three-layer model for plane wave reflection from the lung of the whale. The TS data of killer whales were in good agreement with our model. In this paper, we also discuss and explain possible causes for measurement estimation error.
Probing recent star formation with absorption-line strengths in hierarchical models and observations
Trager, S C
2009-01-01
Stellar population parameters derived from spectral line-strengths provide a powerful probe of galaxy properties and formation histories. We implement the machinery for extracting single-stellar-population-equivalent stellar population parameters from synthetic spectra generated by a hierarchical galaxy formation model. We find that the SSP-equivalent age is related to the light-weighted age in a complicated fashion that reflects the influence of recently-formed stars and is poorly correlated with the mass-weighted age. The tendency for SSP-equivalent ages to be biased young means that archaeological downsizing overstates the mass-weighted downsizing in age with mass. We find that the SSP-equivalent metallicity closely tracks the mass- and light-weighted metallicities, so that observed mass--metallicity relations for old galaxies closely reflect the underlying trends. We construct mock catalogues of early-type galaxies in a Coma cluster-sized halo and compare them directly to observations of early-type galaxi...
Quasi-static and dynamic responses of advanced high strength steels: Experiments and modeling
Khan, Akhtar; Baig, Muneer; Choi, Shi Hoon; Yang, Hoe Seok; Sun, Xin
2012-03-01
Measured responses of advanced high strength steels (AHSS) and their tailor welded blanks (TWBs), over a wide range of strain-rates (10*4 to 103 s*1) are presented. The steels investigated include transformation induced plasticity (TRIP), dual phase (DP), and drawing quality (DQ) steels. The TWBs include DQ-DQ and DP-DP laser welds. A tensile split Hopkinson pressure bar (SHPB) was used for the dynamic experiments. AHSS and their TWB's were found to exhibit positive strain-rate sensitivity. The Khan-Huang-Liang (KHL) constitutive model is shown to correlate and predict the observed responses reasonably well. Micro-texture characterization of DQ steels, DQ-DQ and DP-DP laser welds were performed to investigate the effect of strain-rate on texture evolution of these materials. Electron backscatter diffraction (EBSD) technique was used to analyze the micro-texture evolution and kernel average misorientation (KAM) map. Measurement of micro-hardness profile across the cross section of tensile samples was conducted to understand the effect of initial microstructure on ductility of laser weld samples.
Paramonov, Yu.; Cimanis, V.; Varickis, S.; Kleinhofs, M.
2013-11-01
A review of the previous works of the authors dedicated to the use of Daniels' sequence (DS) for analyzing the relation between the distribution of the static strength of components of a unidirectional fibrous composite (UFC) and the distribution of its fatigue life is presented. A generalization of the DS which can be used to analyze the association of distribution of the static strength of composite components with distribution of the static strength of the UFC itself is given. In analyzing the fatigue life of a UFC, unlike in Daniels' model, the loading rate and randomness of the number of still workable components in the weak microvolume in which the destruction process takes place are taken into account. By analyzing the fatigue life, it is possible to explain the existence of the random fatigue strength and to calculate the maximum load at which the probability of absence of fatigue failure is great enough when the number of cycles of fatigue loading tends to infinity. Numerical examples of processing of experimental data are presented, and estimates for parameters of the corresponding nonlinear regression model, which can be interpreted as the strength parameters of UFC, are obtained.
Shi, Ming F.; Zhang, Li; Zhu, Xinhai
2016-08-01
The Yoshida nonlinear isotropic/kinematic hardening material model is often selected in forming simulations where an accurate springback prediction is required. Many successful application cases in the industrial scale automotive components using advanced high strength steels (AHSS) have been reported to give better springback predictions. Several issues have been raised recently in the use of the model for higher strength AHSS including the use of two C vs. one C material parameters in the Armstrong and Frederick model (AF model), the original Yoshida model vs. Original Yoshida model with modified hardening law, and constant Young's Modulus vs. decayed Young's Modulus as a function of plastic strain. In this paper, an industrial scale automotive component using 980 MPa strength materials is selected to study the effect of two C and one C material parameters in the AF model on both forming and springback prediction using the Yoshida model with and without the modified hardening law. The effect of decayed Young's Modulus on the springback prediction for AHSS is also evaluated. In addition, the limitations of the material parameters determined from tension and compression tests without multiple cycle tests are also discussed for components undergoing several bending and unbending deformations.
Gao, R.; Halsema, van F.E.D.; Temminghoff, E.J.M.; Leeuwen, van H.P.; Valenberg, van H.J.F.; Eisner, M.D.; Boekel, van M.A.J.S.
2010-01-01
This study aims to determine whether the dynamic ion speciation (DIS) model, as introduced in part I, can predict the ion composition in freshly prepared simulated milk ultrafiltrate (SMUF) under various conditions, e.g. pH, ionic strength and presence of various polyphosphates. Experiments were
Prentice, Leon H; Tyas, Martin J; Burrow, Michael F
2007-01-01
The release of ions from a glass-ionomer glass, which in the polyacid matrix effects the cross-linking and setting of a cement, can be modelled and initiated by acid-treatment in a dilute acid. This study examined the effect of time of acetic acid leaching on the working time, setting time, and strength of a model GIC. A reactive fluoride glass was immersed in hot acetic acid for 0 (control), 5, 15, 35, 65, 95 and 125 min, filtered and dried. The glass was mixed with an experimental GI liquid in a capsule system and the mixed pastes assessed for working and initial setting time. Compressive strength testing was undertaken according to ISO9917:2003. Immersion time had a significant effect on both working and setting time of the resultant pastes only up to 65 min of immersion, and corresponded with a thin-film ion diffusion model. Compressive strength did not vary significantly with immersion time. The glass-ionomer setting reaction can be conveniently retarded by immersion of the powder in acetic acid, without affecting strength. A reactivity model was developed, whereby the effects of various changes to the leaching process may be usefully examined.
Fedosov, Sergey; Belousova, Lubov; Plesner, Igor
1993-01-01
The quantitative aspects of mitochondrial creatinekinase (mitCK) binding to mitochondrial membranes were investigated. A simple adsorption and binding model was used for data fitting, taking into account the influence of protein concentration, pH, ionic strength and substrate concentration on the...
Bellini, Scott; McConnell, Luke L.
2010-01-01
Video-self modeling (VSM) is an effective but underused instructional strategy for youth on the autism spectrum. The authors present VSM in the context of strength-based educational programming for youth on the autism spectrum. The authors summarize research studies investigating VSM with youth on the autism spectrum in school settings and discuss…
Dike Strength Analysis on a Regional Scale Based On a Stochastic Subsoil Model
Koelewijn, A. R.; Vastenburg, E. W.
2013-12-01
[Knoeff et al. 2011] J.G. Knoeff, E.W. Vastenburg, G.A. van den Ham & J. Lopez de la Cruz, Automated levee flood risk management, 5th Int. Conf. on Flood Management, Tokyo, 2011 [Koelewijn et al. 2011] A.R. Koelewijn, G.A.M. Kruse & J. Pruiksma, Stochastic subsoil modelling - first set-up of the model and reliability analyses, report 12042000-002-HYE-0001, Deltares, Delft, 2011 [In Dutch] [Lam et al. 2013] K.S. Lam, P.W. Gill & L.W.A. Zwang, Implementation of new levee strength modules for continuous safety assessments, Comprehensive Flood Risk Managment, Taylor & Francis, London, 2013, 317-326. Dike sections with stochastic subsoil profiles.
无
2002-01-01
In the present study, a modified Hall-Petch correlation on the basis of dislocation pile-up model was used to estimate the yield strength of SiCp/Al composites. The experimental results show that the modified Hall-Petch correlation expressed as σcy=244+371λ-1/2 fits very well with the experimental data, which indicated that the strength increase of SiCp/Al composites might be due to the direct blocking of dislocation motion by the particulate-matrix interface,namely, the dislocation pile-up is the most possible strengthening mechanism for SiCp/Al composites.
Harries, Simon K; Lubans, David R; Callister, Robin
2016-02-01
To determine changes in maximal strength between two different resistance training progression models, linear (LP) and daily undulating (DUP), over a 12-week resistance training programme in sub-elite adolescent rugby union players. The study used a quasi-experimental study design. Following baseline assessments, participants from Squad 1 were randomised to either LP or DUP; participants from Squad 2 formed a non-randomised comparison group (CON). Participants were 26 sub-elite adolescent rugby union players who were assessed at baseline and after 12 weeks. Outcomes included 5 repetition maximum (RM) box squat and bench press, height, body weight, skeletal muscle mass, percentage body fat and maturation status. Participants in both the LP and DUP groups significantly increased their squat and bench press strength from baseline to 12 weeks. There were no significant differences between groups for squat and bench press increases after 12 weeks (p>0.05). No significant increases in squat or bench press strength were observed after 12 weeks in the CON group. Increases in lower body strength were large in the LP group (ES: 1.64) and very large in the DUP group (ES: 2.33). Upper body strength changes were small in both groups (LP, ES: 0.57; DUP, ES: 0.31). Twelve weeks of LP or DUP resistance training are both effective at increasing maximal lower and upper body strength in adolescent rugby athletes. Additionally, twice weekly frequency of resistance training in adolescent rugby athletes with greater than 6-months resistance training experience is sufficient to elicit substantial increases in maximal strength. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Dinh Dang, N.; Ciemala, M.; Kmiecik, M.; Maj, A.
2013-05-01
The line shapes of giant dipole resonance (GDR) in the decay of the compound nucleus 88Mo, which is formed after the fusion-evaporation reaction 48Ti + 40Ca at various excitation energies E* from 58 to 308 MeV, are generated by averaging the GDR strength functions predicted within the phonon damping model (PDM) using the empirical probabilities for temperature and angular momentum. The average strength functions are compared with the PDM strength functions calculated at the mean temperature and mean angular momentum, which are obtained by averaging the values of temperature and angular momentum using the same temperature and angular momentum probability distributions, respectively. It is seen that these two ways of generating the GDR linear line shape yield very similar results. It is also shown that the GDR width approaches a saturation at angular momentum J≥ 50 ℏ at T=4 MeV and at J≥ 70 ℏ at any T.
Dang, N Dinh; Kmiecik, M; Maj, A
2013-01-01
The line shapes of giant dipole resonance (GDR) in the decay of the compound nucleus $^{88}$Mo, which is formed after the fusion-evaporation reaction $^{48}$Ti + $^{40}$Ca at various excitation energies $E^{*}$ from 58 to 308 MeV, are generated by averaging the GDR strength functions predicted within the phonon damping model (PDM) using the empirical probabilities for temperature and angular momentum. The average strength functions are compared with the PDM strength functions calculated at the mean temperature and mean angular momentum, which are obtained by averaging the values of temperature and angular momentum using the same temperature and angular-momentum probability distributions, respectively. It is seen that these two ways of generating the GDR linear line shape yield very similar results. It is also shown that the GDR width approaches a saturation at angular momentum $J\\geq$ 50$\\hbar$ at $T=$ 4 MeV and at $J\\geq$ 70$\\hbar$ at any $T$.
Modelling and assessment of the electric field strength caused by mobile phone to the human head
Buckus Raimondas
2016-01-01
Full Text Available Background/Aim. Electromagnetic field exposure is the one of the most important physical agents that actively affects live organisms and environment. Active use of mobile phones influences the increase of electromagnetic field radiation. The aim of the study was to measure and assess the electric field strength caused by mobile phones to the human head. Methods. In this paper the software “COMSOL Multiphysics” was used to establish the electric field strength created by mobile phones around the head. Results. The second generation (2G Global System for Mobile (GSM phones that operate in the frequency band of 900 MHz and reach the power of 2 W have a stronger electric field than (2G GSM mobile phones that operate in the higher frequency band of 1,800 MHz and reach the power up to 1 W during conversation. The third generation of (3G UMTS smart phones that effectively use high (2,100 MHz radio frequency band emit the smallest electric field strength values during conversation. The highest electric field strength created by mobile phones is around the ear, i.e. the mobile phone location. The strength of mobile phone electric field on the phantom head decreases exponentially while moving sidewards from the center of the effect zone (the ear, and constitutes 1-12% of the artificial head’s surface. Conclusion. The highest electric field strength values of mobile phones are associated with their higher power, bigger specific energy absorption rate (SAR and lower frequency of mobile phone. The stronger electric field emitted by the more powerful mobile phones takes a higher percentage of the head surface. The highest electric field strength created by mobile phones is distributed over the user ear.
Rodkin, M. V.
Earthquake shear zones are known to consist of rigid asperities and weak zones [Das and Kostrov, 1983; et al], i.e. rupture zones can be described as random systems con- sisting of subzones with very different strength values. It seems probably, that the distribution of strength values of elements of geophysical media can be described by the Cauchy law [Kagan, 1994; Rodkin, 2001; et al.]. Below, geophysical media was modeled as a system consisting of elements with strength values obeying the Cauchy law. A simple algorithm was used to model a process of generation of rupture zones in a such media. Catalog of artificial quakes was obtained in result of numerical model- ing. Individual rupture zone is described here by its length and initial strength. Set of rupture zones obtained is characterized by the used stress value and the model b-value. The distributions of length values of rupture zones obtained this way obey the law sim- ilar to power-law taking place in case of real earthquakes. A number of correlations between model stress value, number of quakes and b-value characteristic of this model was exposed. Some of the model regularities agree with well known properties of seis- mic regime. Some others were not revealed before, but were shown to agree with the world Harvard catalog data. Only one result (a positive correlation between the stress value and a number of quakes) seems to contradict with real seismic regime. Actually, a negative correlation was obtained between density of earthquakes and characteristic apparent stress values. This result testifies for an importance of effect of weakening of geophysical media in the process of earthquake generation.
Frostberg, Erik; Ström, Petter; Gerke, Oke;
2014-01-01
and conclusions. The purpose of this study was to investigate whether a single dose infliximab has an adverse effect on the anastomotic healing process, observed as reduced anastomotic breaking strength and histopathologically verified lower grade of inflammatory response, in the small intestine of a rabbit....... METHODS: Thirty New Zealand rabbits (median weight 2.5 kg) were allocated to treatment with an intravenous bolus of either 10 mg/kg infliximab (n = 15) or placebo (n = 15). One week later all rabbits underwent two separate end-to-end anastomoses in the jejunum under general anesthesia. At postoperative...... day three, the anastomotic breaking strength was determined and histopathological changes were examined. RESULTS: The mean value of anastomotic breaking strength in the placebo group was 1.89 +/- 0.36 N and the corresponding value was 1.81 +/- 0.33 N in the infliximab treated rabbits...
Optimal Model for Velocity Strength Training Methods for Boy Sprinters Base on Fuzzy Matrix
Juntao Sun
2013-04-01
Full Text Available With literature consultation, Delphi method, fuzzy mathematics, experimental method and mathematical statistics method, from multi viewpoints, this study analyzes the velocity strength quality of boy two-level sprinters in quality and quantity. The result shows, with fuzzy mathematics, we can judge the relative degree between velocity strength and various methods, with quantitative disposal to analyze quantitatively, which has certain theoretic significance; according to analysis of fuzzy relation and corresponding relation, build the classification figure for velocity strength training method for boy sprinters; relative data proof, the optimal organization of different training methods can outstand the training specialization and save time and energy, so as to supplement the special training theories, to provide theoretic references and practical instructions for most coaches’ training processes, to improve the efficiency.
Huang-bin Lin
2016-01-01
Full Text Available In the dynamic time-history analysis of structural elastoplasticity, it is important to develop a universal mathematical model that can describe the force-displacement characteristics for restoring force. By defining three control parameters (stiffness degradation, slip closure γ, energy degradation β, the Park restoring force mathematical model can simulate various components. In this study, the Park restoring force has been improved by adding two control parameters (energy-based strength degradation βe and ductility-based strength degradation βd. Based on the testing data, the constitutive model is input and 55 numerical models are developed to analyze the effects of various parameters on structural behavior. Conclusion. (1 β has determinative effect on structural behavior; the effect of βe is basically consistent with that of β; α has significant effect on shear forces and bending moments; γ has significant effect on displacements and accelerations; βd has significant effect on shearing forces, acceleration, and total energy consumptions. (2 Based on the classification of four types of damage level, the recommended values for α, γ, β, βe, and βd are presented. (3 Based on the testing data of high-strength columns, the recommended values for the five control parameters of the improved Park restoring force model are presented.
Florian Schellenberg
2015-01-01
Full Text Available Background. Knowledge of the musculoskeletal loading conditions during strength training is essential for performance monitoring, injury prevention, rehabilitation, and training design. However, measuring muscle forces during exercise performance as a primary determinant of training efficacy and safety has remained challenging. Methods. In this paper we review existing computational techniques to determine muscle forces in the lower limbs during strength exercises in vivo and discuss their potential for uptake into sports training and rehabilitation. Results. Muscle forces during exercise performance have almost exclusively been analysed using so-called forward dynamics simulations, inverse dynamics techniques, or alternative methods. Musculoskeletal models based on forward dynamics analyses have led to considerable new insights into muscular coordination, strength, and power during dynamic ballistic movement activities, resulting in, for example, improved techniques for optimal performance of the squat jump, while quasi-static inverse dynamics optimisation and EMG-driven modelling have helped to provide an understanding of low-speed exercises. Conclusion. The present review introduces the different computational techniques and outlines their advantages and disadvantages for the informed usage by nonexperts. With sufficient validation and widespread application, muscle force calculations during strength exercises in vivo are expected to provide biomechanically based evidence for clinicians and therapists to evaluate and improve training guidelines.
Nemeth, Noel
2013-01-01
Models that predict the failure probability of monolithic glass and ceramic components under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" failure models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This report develops a formulation to describe the probability density distribution of the orientation of critical strength-controlling flaws that results from an applied load. This distribution is a function of the multiaxial stress state, the shear sensitivity of the flaws, the Weibull modulus, and the strength anisotropy. Examples are provided showing the predicted response on the unit sphere for various stress states for isotropic and transversely isotropic (anisotropic) materials--including the most probable orientation of critical flaws for offset uniaxial loads with strength anisotropy. The author anticipates that this information could be used to determine anisotropic stiffness degradation or anisotropic damage evolution for individual brittle (or quasi-brittle) composite material constituents within finite element or micromechanics-based software
Tang, Bingtao; Wang, Qiaoling; Wei, Zhaohui; Meng, Xianju; Yuan, Zhengjun
2016-05-01
Ultra-high-strength in sheet metal parts can be achieved with hot stamping process. To improve the crash performance and save vehicle weight, it is necessary to produce components with tailored properties. The use of tailor-welded high-strength steel is a relatively new hot stamping process for saving weight and obtaining desired local stiffness and crash performance. The simulation of hot stamping boron steel, especially tailor-welded blanks (TWBs) stamping, is more complex and challenging. Information about thermal/mechanical properties of tools and sheet materials, heat transfer, and friction between the deforming material and the tools is required in detail. In this study, the boron-manganese steel B1500HS and high-strength low-alloy steel B340LA are tailor welded and hot stamped. In order to precisely simulate the hot stamping process, modeling and simulation of hot stamping tailor-welded high-strength steels, including phase transformation modeling, thermal modeling, and thermal-mechanical modeling, is investigated. Meanwhile, the welding zone of tailor-welded blanks should be sufficiently accurate to describe thermal, mechanical, and metallurgical parameters. FE simulation model using TWBs with the thickness combination of 1.6 mm boron steel and 1.2 mm low-alloy steel is established. In order to evaluate the mechanical properties of the hot stamped automotive component (mini b-pillar), hardness and microstructure at each region are investigated. The comparisons between simulated results and experimental observations show the reliability of thermo-mechanical and metallurgical modeling strategies of TWBs hot stamping process.
Ravindranadh BOBBILI; V. MADHU; A.K. GOGIA
2014-01-01
An artificial neural network (ANN) constitutive model is developed for high strength armor steel tempered at 500 ?C, 600 ?C and 650 ?C based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook (JeC) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500e650 ?C), strains (0.05e0.2) and strain rates (1000e5500/s) are employed to formulate JeC model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the JeC model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.
Strayer, L.; Suppe, J.
2012-12-01
It is increasingly clear that many major faults are weak relative to quasistatic friction because of dynamical effects involving the microprocesses of high-velocity friction and the energetics of large-scale fault rupture. Even at the toes of accretionary wedges where velocity strengthening is expected, large displacements can occur dynamically. We seek to better understand the relationship between the large-scale strength of such faults and of the crust containing them over a timescale much greater than seismic cycles. Critical-taper theory provides straightforward quantitative relationships between accretionary wedge geometry and absolute basal fault and wedge strengths with minimal assumptions. Wedge tapers constrain the far-field stresses under which detachments slip and wedges grow during wedge-growing events, whether they are dynamical or quasistatic. To date most applications of wedge mechanics to accretionary wedges involve analog and numerical modeling with largely conceptual insight, for example illuminating the role of geological heterogeneity. Here we demonstrate that recent theoretical advances that are successful in extracting absolute wedge and detachment strengths from the geometry of active wedges can also be applied to extract large-scale strengths in distinct element numerical models in both mechanically homogeneous and heterogeneous wedges. The distinct element method (DEM) is an ideal tool for the study and modeling of critical taper wedges: model wedges can be initially cohesive (bonded) or cohesionless. Faults and folds form naturally as the result of progressive bond breakage during shortening and wedge growth. Heterogeneity can be introduced by creating layered groups of particles of differing mechanical properties. The DEM suffers to some extent in that macro material properties cannot be directly prescribed but rather must be defined by a modest number of micro-properties and the process in necessarily iterative and developing a wide
Thakur, Punam; Xiong, Yongliang; Borkowski, Marian; Choppin, Gregory R.
2014-05-01
The dissociation constants of ethylenediaminetetraacetic acid (H4EDTA), and the stability constants of Am3+, Cm3+and Eu3+ with EDTA4- have been determined at 25 °C, over a range of concentration varying from 0.1 to 6.60 m NaClO4 using potentiometric titration and an extraction technique, respectively. The formation of only 1:1 complex, M(EDTA)-, where (M = Am3+, Cm3+ and Eu3+), was observed under the experimental conditions. The observed ionic strength dependencies of the dissociation constants and the stability constants have been described successfully over the entire ionic strength range using the Pitzer model. The thermodynamic stability constant: logβ1010=20.55±0.18 for Am3+, logβ1010=20.43±0.20 for Cm3+ and logβ1010=20.65±0.19 for Eu3+ were calculated by extrapolation of data to zero ionic strength in an NaClO4 medium. In addition, logβ1010 of 20.05 ± 0.40 for Am3+ was obtained by simultaneously modeling data both in NaCl and NaClO4 media. For all stability constants, the Pitzer model gives an excellent representation of the data using interaction parameters β(0), β(1), and Cϕ determined in this work. The improved model presented in this work would enable researchers to model accurately the potential mobility of actinides (III) and light rare earth elements to ionic strength of 6.60 m in low temperature environments in the presence of EDTA.
Adel T. Abbas
2017-01-01
Full Text Available The Grade-H high strength steel is used in the manufacturing of many civilian and military products. The procedures of manufacturing these parts have several turning operations. The key factors for the manufacturing of these parts are the accuracy, surface roughness (Ra, and material removal rate (MRR. The production line of these parts contains many CNC turning machines to get good accuracy and repeatability. The manufacturing engineer should fulfill the required surface roughness value according to the design drawing from first trail (otherwise these parts will be rejected as well as keeping his eye on maximum metal removal rate. The rejection of these parts at any processing stage will represent huge problems to any factory because the processing and raw material of these parts are very expensive. In this paper the artificial neural network was used for predicting the surface roughness for different cutting parameters in CNC turning operations. These parameters were investigated to get the minimum surface roughness. In addition, a mathematical model for surface roughness was obtained from the experimental data using a regression analysis method. The experimental data are then compared with both the regression analysis results and ANFIS (Adaptive Network-based Fuzzy Inference System estimations.
Shell model description of Gamow-Teller strengths for $^{42}$Ti, $^{46}$Cr, $^{50}$Fe and $^{54}$Ni
Kumar, Vikas; Hirsch, Jorge G
2015-01-01
A systematic shell model description of the experimental Gamow-Teller transition strength distributions in $^{42}$Ti, $^{46}$Cr, $^{50}$Fe and $^{54}$Ni is presented. These transitions have been recently measured via $\\beta$ decay of these $T_z$=-1 nuclei, produced in fragmentation reactions at GSI and also with ($^3${He},$t$) charge-exchange (CE) reactions corresponding to $T_z = + 1$ to $T_z = 0$ carried out at RCNP-Osaka. The calculations are performed in the $pf$ model space, using the GXPF1a and KB3G effective interactions. Qualitative agreement is obtained for the individual transitions, while the calculated summed transition strengths closely reproduce the observed ones.
Self-control, self-regulation, and doping in sport: a test of the strength-energy model.
Chan, Derwin K; Lentillon-Kaestner, Vanessa; Dimmock, James A; Donovan, Robert J; Keatley, David A; Hardcastle, Sarah J; Hagger, Martin S
2015-04-01
We applied the strength-energy model of self-control to understand the relationship between self-control and young athletes' behavioral responses to taking illegal performance-enhancing substances, or "doping." Measures of trait self-control, attitude and intention toward doping, intention toward, and adherence to, doping-avoidant behaviors, and the prevention of unintended doping behaviors were administered to 410 young Australian athletes. Participants also completed a "lollipop" decision-making protocol that simulated avoidance of unintended doping. Hierarchical linear multiple regression analyses revealed that self-control was negatively associated with doping attitude and intention, and positively associated with the intention and adherence to doping-avoidant behaviors, and refusal to take or eat the unfamiliar candy offered in the "lollipop" protocol. Consistent with the strength-energy model, athletes with low self-control were more likely to have heightened attitude and intention toward doping, and reduced intention, behavioral adherence, and awareness of doping avoidance.
Zhiqiang Chen
2016-03-01
Full Text Available The hydro-mechanical coupling transport process of sand production is numerically investigated with special attention paid to the bonding effect between sand grains. By coupling the lattice Boltzmann method (LBM and the discrete element method (DEM, we are able to capture particles movements and fluid flows simultaneously. In order to account for the bonding effects on sand production, a contact bond model is introduced into the LBM-DEM framework. Our simulations first examine the experimental observation of “initial sand production is evoked by localized failure” and then show that the bonding or cement plays an important role in sand production. Lower bonding strength will lead to more sand production than higher bonding strength. It is also found that the influence of flow rate on sand production depends on the bonding strength in cemented granular media, and for low bonding strength sample, the higher the flow rate is, the more severe the erosion found in localized failure zone becomes.
Panatchai Chetchotisak
2015-09-01
Full Text Available Because of nonlinear strain distributions caused either by abrupt changes in geometry or in loading in deep beam, the approach for conventional beams is not applicable. Consequently, strut-and-tie model (STM has been applied as the most rational and simple method for strength prediction and design of reinforced concrete deep beams. A deep beam is idealized by the STM as a truss-like structure consisting of diagonal concrete struts and tension ties. There have been numerous works proposing the STMs for deep beams. However, uncertainty and complexity in shear strength computations of deep beams can be found in some STMs. Therefore, improvement of methods for predicting the shear strengths of deep beams are still needed. By means of a large experimental database of 406 deep beam test results covering a wide range of influencing parameters, several shapes and geometry of STM and six state-of-the-art formulation of the efficiency factors found in the design codes and literature, the new STMs for predicting the shear strength of simply supported reinforced concrete deep beams using multiple linear regression analysis is proposed in this paper. Furthermore, the regression diagnostics and the validation process are included in this study. Finally, two numerical examples are also provided for illustration.
Pistoia, W; van Rietbergen, B; Lochmüller, E-M; Lill, C A; Eckstein, F; Rüegsegger, P
2004-01-01
Although osteoporosis is characterized by quantitative (mass) and qualitative (structural) changes, standard clinical techniques (dual-energy X-ray absorptiometry, DXA) only measure the former. Three-dimensional micro-finite-element (micro-FE) models based on high-resolution images can account for structural aspects as well, and it has recently been shown that an improved prediction of distal radius strength is possible with micro-FE analysis. A clinical application of this technique, however, is limited by its high imaging and computational demands. The objective of this study is to investigate if an improved prediction of bone strength can be obtained as well when only a small part of the radius is used for micro-FE modeling. Images of a 1-cm region of the metaphysis of the distal radius of 54 cadaver arms (mean age: 82 +/- 9 SD) made with a three-dimensional peripheral quantitative computed tomography (pQCT) device at 165- micro m resolution formed the basis for micro-FE models that were used to predict the bone failure load. Following imaging, specimens were experimentally compressed to failure to produce a Colles'-type fracture. Failure loads predicted from micro-FE analyses agreed well with those measured experimentally (R2 = 0.66, p radius strength.
Bertollo, Nicky; Da Assuncao, Ruy; Hancock, Nicholas J; Lau, Abe; Walsh, William R
2012-09-01
Arthroplasty has evolved with the application of electron beam melting (EBM) in the manufacture of porous mediums for uncemented fixation. Osseointegration of EBM and plasma-sprayed titanium (Ti PS) implant dowels in adult sheep was assessed in graduated cancellous defects and under line-to-line fit in cortical bone. Shear strength and bony ingrowth (EBM) and ongrowth (Ti PS) were assessed after 4 and 12 weeks. Shear strength of EBM exceeded that for Ti PS at 12 weeks (P = .030). Ongrowth achieved by Ti PS in graduated cancellous defects followed a distinctive pattern that correlated to progressively decreasing radial distances between defect and implant, whereas cancellous ingrowth values at 12 weeks for the EBM were not different. Osteoconductive porous structures manufactured using EBM present a viable alternative to traditional surface treatments. Copyright © 2012 Elsevier Inc. All rights reserved.
A dynamic warm-up model increases quadriceps strength and hamstring flexibility.
Aguilar, Alain J; DiStefano, Lindsay J; Brown, Cathleen N; Herman, Daniel C; Guskiewicz, Kevin M; Padua, Darin A
2012-04-01
Research suggests that static stretching can negatively influence muscle strength and power and may result in decreased functional performance. The dynamic warm-up (DWU) is a common alternative to static stretching before physical activity, but there is limited research investigating the effects of a DWU. The purpose of this study was to compare the acute effects of a DWU and static stretching warm-up (SWU) on muscle flexibility, strength, and vertical jump using a randomized controlled trial design. Forty-five volunteers were randomly assigned into a control (CON), SWU, or DWU group. All participants rode a stationary bicycle for 5 minutes and completed a 10-minute warm-up protocol. During this protocol, the DWU group performed dynamic stretching and running, the SWU group performed static stretching, and the CON group rested. Dependent variables were measured immediately before and after the warm-up protocol. A digital inclinometer measured flexibility (degrees) for the hamstrings, quadriceps, and hip flexor muscles. An isokinetic dynamometer measured concentric and eccentric peak torque (N·m/kg) for the hamstrings and quadriceps. A force plate was used to measure vertical jump height (meters) and power (watts). In the DWU group, there was a significant increase in hamstring flexibility (pretest: 26.4 ± 13.5°, posttest: 16.9 ± 9.4°; p 0.05). The DWU significantly improved eccentric quadriceps strength and hamstrings flexibility, whereas the SWU did not facilitate any positive or negative changes in muscle flexibility, strength, power, or vertical jump. Therefore, the DWU may be a better preactivity warm-up choice than an SWU.
Longbiao, Li
2017-04-01
In this paper, the strength degradation of non-oxide and oxide/oxide fiber-reinforced ceramic-matrix composites (CMCs) subjected to cyclic loading at elevated temperatures in oxidative environments has been investigated. Considering damage mechanisms of matrix cracking, interface debonding, interface wear, interface oxidation and fibers fracture, the composite residual strength model has been established by combining the micro stress field of the damaged composites, the damage models, and the fracture criterion. The relationships between the composite residual strength, fatigue peak stress, interface debonding, fibers failure and cycle number have been established. The effects of peak stress level, initial and steady-state interface shear stress, fiber Weibull modulus and fiber strength, and testing temperature on the degradation of composite strength and fibers failure have been investigated. The evolution of residual strength versus cycle number curves of non-oxide and oxide/oxide CMCs under cyclic loading at elevated temperatures in oxidative environments have been predicted.
Effects of Micro-structure and Micro-parameters on Brazilian Tensile Strength Using Flat-Joint Model
Xu, Xueliang; Wu, Shunchuan; Gao, Yongtao; Xu, Miaofei
2016-09-01
It has been widely accepted that tensile strength plays a dominant role in the failure mechanism of rock or rock-like material. Tensile strength is determined mainly via two methods: the direct tension test and Brazilian test. Due to the strictness of preparing the specimen and difficulty of conducting the direct tension test, Brazilian test has been widely applied to determine the tensile strength of geo-materials. However, there is no exact standard for Brazilian test specimen. Moreover, Brazilian tensile strength (BTS) is affected by many factors, such as loading rate, loading platen width, model size. So far, most parametric studies of geo-materials have involved compression tests, but few studies have systematically focused on Brazilian test. The continuum methods have difficulty reproducing the failure process of Brazilian test, and 2D discrete element methods can not reflect the real mechanical behavior of a 3D cylindrical disk specimen. Moreover, the standard bonded-particle model has intrinsic problems in simulating geo-materials. This paper, using a 3D flat-joint model (FJM3D), investigates the effects of micro-structure and micro-parameters on BTS. The micro-structure consists of model size, model resolution, and degree of heterogeneity. The micro-parameters include the average coordination number, crack density, and bond strength. The effects on BTS are summarized, and this summary will be useful for guiding future Brazilian tests. Finally, FJM3D is used to calibrate Brisbane tuff by Brazilian test and the uniaxial compression test. The simulation results are in good agreement with those measured from experiments, and the failure process of Brazilian test is analyzed in detail at the microscale. Because of the heterogeneity of rock, cracks initiate near the loading platen instead of the center of the specimen. Even so, BTS can be an useful tensile index for geo-materials in a triaxial stress state, which is similar to the physical situations, and
Levine, Paul A.; Randerson, James T.; Swenson, Sean C.; Lawrence, David M.
2016-12-01
The relationship between terrestrial water storage (TWS) and atmospheric processes has important implications for predictability of climatic extremes and projection of future climate change. In places where moisture availability limits evapotranspiration (ET), variability in TWS has the potential to influence surface energy fluxes and atmospheric conditions. Where atmospheric conditions, in turn, influence moisture availability, a full feedback loop exists. Here we developed a novel approach for measuring the strength of both components of this feedback loop, i.e., the forcing of the atmosphere by variability in TWS and the response of TWS to atmospheric variability, using satellite observations of TWS, precipitation, solar radiation, and vapor pressure deficit during 2002-2014. Our approach defines metrics to quantify the relationship between TWS anomalies and climate globally on a seasonal to interannual timescale. Metrics derived from the satellite data were used to evaluate the strength of the feedback loop in 38 members of the Community Earth System Model (CESM) Large Ensemble (LENS) and in six models that contributed simulations to phase 5 of the Coupled Model Intercomparison Project (CMIP5). We found that both forcing and response limbs of the feedback loop in LENS were stronger than in the satellite observations in tropical and temperate regions. Feedbacks in the selected CMIP5 models were not as strong as those found in LENS, but were still generally stronger than those estimated from the satellite measurements. Consistent with previous studies conducted across different spatial and temporal scales, our analysis suggests that models may overestimate the strength of the feedbacks between the land surface and the atmosphere. We describe several possible mechanisms that may contribute to this bias, and discuss pathways through which models may overestimate ET or overestimate the sensitivity of ET to TWS.
Single-Particle Spin-Orbit Strengths of the Nucleon and Hyperons by $SU_{6}$ Quark-Model
Fujiwara, Y; Fujita, T; Nakamoto, C; Suzuki, Y
2000-01-01
The quark-model hyperon-nucleon interaction suggests an importantantisymmetric spin-orbit component. It is generated from a color analogue ofthe Fermi-Breit interaction dominating in the one-gluon exchange processbetween quarks. We discuss the strength S_B of the single-particle spin-orbitpotential, following the Scheerbaum's prescription. Using the SU6 quark-modelbaryon-baryon interaction which was recently developed by the Kyoto-Niigatagroup, we calculate NN, Lambda N and Sigma N G-matrices in symmetric nuclearmatter and apply them to estimate the strength S_B. The ratio of S_B to thenucleon strength S_N =~ -40 MeV*fm^5 is (S_Lambda)/(S_N) =~ 1/5 and(S_Sigma)/(S_N) =~ 1/2 in the Born approximation. The G-matrix calculation ofthe model FSS modifies S_Lambda to (S_Lambda)/(S_N) =~ 1/12. For S_N andS_Sigma, the effect of the short-range correlation is comparatively weakagainst meson-exchange potentials with a short-range repulsive core. Thesignificant reduction of the Lambda single-particle potential arises fr...
İnce, İsmail; Fener, Mustafa
2016-08-01
Either directly or indirectly, building stone is exposed to diverse atmospheric interactions depending on the seasonal conditions. Due to those interactions, objects of historic and cultural heritage, as well as modern buildings, partially or completely deteriorate. Among processes involved in rock deterioration, the freeze-thaw (F-T) cycle is one of the most important. Even though pyroclastic rocks have been used as building stone worldwide due to their easy workability, they are the building stone most affected by the F-T cycle. A historical region in Central Anatolia, Turkey, Cappadoia encompasses exceptional natural wonders characterized by fairy chimneys and unique historical and cultural heritage. Human-created caves, places of worship and houses have been dug into the pyroclastic rocks, which have in turn been used in architectural construction as building stone. Using 10 pyroclastic rock samples collected from Cappadocia, we determined the rock's index-mechanical properties to develop a statistical model for estimating percentage loss of uniaxial compressive strength a critical parameter of F-T cycle's important value. We used dry density (ρd), ultrasonic velocity (Vp), point load strengths (IS(50)), and slake-durability test indexes (Id4) values of unweathered rocks in our model, which is highly reliable (R2 = 0.84) for predetermination of percentage loss of uniaxial compressive strengths of pyroclastic rocks without requiring any F-T tests.
Martin Ginis, Kathleen A; Bray, Steven R
2010-12-01
The limited strength model posits that self-regulatory strength is a finite, renewable resource that is drained when people attempt to regulate their emotions, thoughts or behaviours. The purpose of this study was to determine whether self-regulatory depletion can explain lapses in exercise effort, planning and adherence. In a lab-based experiment, participants exposed to a self-regulatory depletion manipulation generated lower levels of work during a 10 min bicycling task, and planned to exert less effort during an upcoming exercise bout, compared with control participants. The magnitude of reduction in planned exercise effort predicted exercise adherence over a subsequent 8-week period. Together, these results suggest that self-regulatory depletion can influence exercise effort, planning and decision-making and that the depletion of self-regulatory resources can explain episodes of exercise non-adherence both in the lab and in everyday life.
Wetherington, Jeffrey D; Pfister, Marc; Banfield, Christopher; Stone, Julie A; Krishna, Rajesh; Allerheiligen, Sandy; Grasela, Dennis M
2010-09-01
Systematic implementation of model-based drug development (MBDD) to drug discovery and development has the potential to significantly increase the rate of medical breakthroughs and make available new and better treatments to patients. An analysis of the strengths, weaknesses, opportunities, and threats (ie, SWOT) was conducted through focus group discussions that included 24 members representing 8 pharmaceutical companies to systematically assess the challenges to implementing MBDD into the drug development decision-making process. The application of the SWOT analysis to the successful implementation of MBDD yielded 19 strengths, 27 weaknesses, 34 opportunities, and 22 threats, which support the following conclusions. The shift from empirical drug development to MBDD requires a question-based mentality; early, proactive planning; dynamic access to multisource data; quantitative knowledge integration; multidisciplinary collaboration; effective communication and leadership skills; and innovative, impactful application of pharmacometrics focused on enhancing quantitative decision making. The ultimate goal of MBDD is to streamline discovery and development of innovative medicines to benefit patients.
Leadenham, Stephen; Erturk, Alper
2014-04-01
There has been growing interest in enabling wireless health and usage monitoring for rotorcraft applications, such as helicopter rotor systems. Large dynamic loads and acceleration fluctuations available in these environments make the implementation of vibration-based piezoelectric energy harvesters a very promising choice. However, such extreme loads transmitted to the harvester can also be detrimental to piezoelectric laminates and overall system reliability. Particularly flexible resonant cantilever configurations tuned to match the dominant excitation frequency can be subject to very large deformations and failure of brittle piezoelectric laminates due to excessive bending stresses at the root of the harvester. Design of resonant piezoelectric energy harvesters for use in these environments require nonlinear electroelastic dynamic modeling and strength-based analysis to maximize the power output while ensuring that the harvester is still functional. This paper presents a mathematical framework to design and analyze the dynamics of nonlinear flexible piezoelectric energy harvesters under large base acceleration levels. A strength-based limit is imposed to design the piezoelectric energy harvester with a proof mass while accounting for material, geometric, and dissipative nonlinearities, with a focus on two demonstrative case studies having the same linear fundamental resonance frequency but different overhang length and proof mass values. Experiments are conducted at different excitation levels for validation of the nonlinear design approach proposed in this work. The case studies in this work reveal that harvesters exhibiting similar behavior and power generation performance at low excitation levels (e.g. less than 0.1g) can have totally different strength-imposed performance limitations under high excitations (e.g. above 1g). Nonlinear modeling and strength-based design is necessary for such excitation levels especially when using resonant cantilevers with no
Stephano Zerlottini Isaac
2013-09-01
Full Text Available OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS to dentin of two different restorative systems: silorane-based (P90, and methacrylate-based (P60, using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5 were prepared in 20 teeth, which were divided into two groups (n=10 restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2 and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10. The teeth were sectioned into samples with area between 0.85 and 1.25 mm2 that were submitted to µTBS testing, using a universal testing machine (EMIC at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests. RESULTS: For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p0.05, or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05. Regarding fracture pattern, there was no statistical difference among groups (p=0.0713 and 56.3% of the fractures were adhesive. CONCLUSION: It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.
Saifutdinov, A. I.; Timerkaev, B. A.
2012-09-01
A drift model of a glow discharge is proposed, which takes account of the nonlocal dependence of the ionization source on the electric field strength. The problem is reduced to solving a nonlinear differential equation of second order for the strength squared using the Newton-Kantorovich quasilinearization method.
Investigations to Model and Analyse the OHC Strength of Hybrid Composites
B. Siddeswarappa
2009-01-01
Full Text Available In recent years, the utilization of hybrid polymer matrix composite materials in many engineering fields has increasedtremendously. The present investigation is devoted on fabric-reinforced hybrid composite laminates with different volumefractions of the constituent materials; epoxy resin, plain-woven glass fabric, and textile satin fabric. Fracture toughness ofa material has immense importance in the determination of the resistance of the material to crack propagation. Hence thisarticle explores the findings of the experimentation on the compressive strength and fracture toughness of fabric-reinforcedlaminates with 0/90O & ± 45O orientation with five notch configurations. The fracture toughness has been found to increasecontinuously with increased volumes of glass fabric and it is less dependent on notch size upto certain limit. Data collectedduring experimentations are validated using analysis of variance (ANOVA technique. Percentage contribution of each parameterwas evaluated using ANOVA technique with fiber content, orientation and notch size as input parameters, while theoutput parameter being the OHC strength of the laminate
Ng, Vincent; Cao, Mengyang; Marsh, Herbert W; Tay, Louis; Seligman, Martin E P
2016-10-13
The factor structure of the Values in Action Inventory of Strengths (VIA-IS; Peterson & Seligman, 2004) has not been well established as a result of methodological challenges primarily attributable to a global positivity factor, item cross-loading across character strengths, and questions concerning the unidimensionality of the scales assessing character strengths. We sought to overcome these methodological challenges by applying exploratory structural equation modeling (ESEM) at the item level using a bifactor analytic approach to a large sample of 447,573 participants who completed the VIA-IS with all 240 character strengths items and a reduced set of 107 unidimensional character strength items. It was found that a 6-factor bifactor structure generally held for the reduced set of unidimensional character strength items; these dimensions were justice, temperance, courage, wisdom, transcendence, humanity, and an overarching general factor that is best described as dispositional positivity. (PsycINFO Database Record
A Modified Johnson-Cook Model for Advanced High-Strength Steels Over a Wide Range of Temperatures
Qingdong, Zhang; Qiang, Cao; Xiaofeng, Zhang
2014-12-01
Advanced high-strength steel (AHSS) is widely used in automotive industry. In order to investigate the mechanical behaviors of AHSS over a wide range of temperatures, quasi-static tensile experiments were conducted at the temperatures from 298 to 1073 K on a Gleeble-3500 thermo-simulation machine. The results show that flow behaviors are affected by testing temperature significantly. In order to describe the flow features of AHSS, the Johnson-Cook (JC) model is employed. By introducing polynomial functions to consider the effects of temperature on hardening behavior, the JC model is modified and used to predict flow behavior of AHSS at different experimental conditions. The accuracy of the modified JC model is verified and the predicted flow stress is in good agreement with experimental results, which confirms that the modified JC model can give an accurate and precise estimate over a wide range of temperatures.
Ishii, Ken; Imaizumi, Tomohito; Abe, Koki; Takao, Yoshimi; Tamura, Shuko
This paper details a network-controlled measurement system for use in fisheries engineering. The target strength (TS) of fish is important in order to convert acoustic integration values obtained during acoustic surveys into estimates of fish abundance. The target strength pattern is measured with the combination of the rotation system for the aspect of the sample and the echo data acquisition system using the underwater supersonic wave. The user interface of the network architecture is designed for collaborative use with researchers in other organizations. The flexible network architecture is based on the web direct-access model for the rotation mechanism. The user interface is available for monitoring and controlling via a web browser that is installed in any terminal PC (personal computer). Previously the combination of two applications was performed not by a web browser but by the exclusive interface program. So a connection model is proposed between two applications by indirect communication via the DCOM (Distributed Component Object Model) server and added in the web direct-access model. A prompt report system in the TS measurement system and a positioning and measurement system using an electric flatcar via a web browser are developed. By a secure network architecture, DCOM communications via both Intranet and LAN are successfully certificated.
Singh, Savita; Singh, Alok; Sharma, Sudhir Kumar
2016-06-01
In this paper, an analytical modeling and prediction of tensile and flexural strength of three dimensional micro-scaled novel coconut shell powder (CSP) reinforced epoxy polymer composites have been reported. The novel CSP has a specific mixing ratio of different coconut shell particle size. A comparison is made between obtained experimental strength and modified Guth model. The result shows a strong evidence for non-validation of modified Guth model for strength prediction. Consequently, a constitutive modeled equation named Singh model has been developed to predict the tensile and flexural strength of this novel CSP reinforced epoxy composite. Moreover, high resolution Raman spectrum shows that 40 % CSP reinforced epoxy composite has high dielectric constant to become an alternative material for capacitance whereas fractured surface morphology revealed that a strong bonding between novel CSP and epoxy polymer for the application as light weight composite materials in engineering.
Basavaraj, C. K.; Vishwas, M.
2016-09-01
This paper discusses the process parameters for fused deposition modelling (FDM). Layer thickness, Orientation angle and shell thickness are the process variables considered for studies. Ultimate tensile strength, dimensional accuracy and manufacturing time are the response parameters. For number of experimental runs the taguchi's L9 orthogonal array is used. Taguchis S/N ratio was used to identify a set of process parameters which give good results for respective response characteristics. Effectiveness of each parameter is investigated by using analysis of variance. The material used for the studies of process parameter is Nylon.
Mourad, Hashem M.; Bronkhorst, Curt A.; Addessio, Francis L.; Cady, Carl M.; Brown, Donald W.; Chen, Shuh Rong; Gray, George T.
2014-05-01
The present paper focuses on the development of a fully implicit, incrementally objective integration algorithm for a hypoelastic formulation of -viscoplasticity, which employs the mechanical threshold strength model to compute the material's flow stress, taking into account its dependence on strain rate and temperature. Heat generation due to high-rate viscoplastic deformation is accounted for, assuming adiabatic conditions. The implementation of the algorithm is discussed, and its performance is assessed in the contexts of implicit and explicit dynamic finite element analysis, with the aid of example problems involving a wide range of loading rates. Computational results are compared to experimental data, showing very good agreement.
Ozturk, H.; Altinpinar, M.
2017-07-01
The point load (PL) test is generally used for estimation of uniaxial compressive strength (UCS) of rocks because of its economic advantages and simplicity in testing. If the PL index of a specimen is known, the UCS can be estimated using conversion factors. Several conversion factors have been proposed by various researchers and they are dependent upon the rock type. In the literature, conversion factors on different sedimentary, igneous and metamorphic rocks can be found, but no study exists on trona. In this study, laboratory UCS and field PL tests were carried out on trona and interbeds of volcano-sedimentary rocks. Based on these tests, PL to UCS conversion factors of trona and interbeds are proposed. The tests were modeled numerically using a distinct element method (DEM) software, particle flow code (PFC), in an attempt to guide researchers having various types of modeling problems (excavation, cavern design, hydraulic fracturing, etc.) of the abovementioned rock types. Average PFC parallel bond contact model micro properties for the trona and interbeds were determined within this study so that future researchers can use them to avoid the rigorous PFC calibration procedure. It was observed that PFC overestimates the tensile strength of the rocks by a factor that ranges from 22 to 106.
Ma, Ning; Park, Taejoon; Kim, Dongun; Kim, Chongmin; Chung, Kwansoo
2010-06-01
The impact performance in a Charpy impact test was experimentally and numerically studied for the advanced high-strength steel sheets (AHSS) TWIP940 and TRIP590 as well as the high-strength grade known as 340R. To characterize the mechanical properties, uni-axial simple tension tests were conducted to determine the anisotropic properties and strain rate sensitivities of these materials. In particular, the high-speed strain-rate sensitivity of TRIP590 and 340R (rate sensitive) was also characterized to account for the high strain rates involved in the Charpy impact test. To evaluate fracture behavior in the Charpy impact test, a new damage model including a triaxiality-dependent fracture criterion and hardening behavior with stiffness deterioration was introduced. The model was calibrated via numerical simulations and experiments involving simple tension and V-notch tests. The new damage model along with the anisotropic yield function Hill 1948 was incorporated into the ABAQUS/Explicit FEM code, which performed reasonably well to predict the impact energy absorbed during the Charpy impact test.
Askari, Hesam; Zbib, Hussein M.; Sun, Xin
2013-06-01
In this study, the strengthening effect of inclusions and precipitates in metals is investigated within a multiscale approach that utilizes models at various length scales, namely, Molecular Mechanics (MM), discrete Dislocation Dynamics (DD), and an Eigenstrain Inclusion Method (EIM). Particularly, precipitates are modeled as hardsoft particles whose stress fields interact with dislocations. The stress field resulting from the elastic mismatch between the particles and the matrix is accounted for through the EIM. While the MM method is employed for the purpose of developing rules for DD for short range interaction between a single dislocation and an inclusion, the DD method is used to predict the strength of the composite resulting from the interaction between ensembles of dislocations and particles. As an application to this method, the mechanical behavior of Advanced High Strength Steel (AHSS) is investigated and the results are then compared to the experimental data. The results show that the finely dispersive precipitates can strengthen the material by pinning the dislocations up to a certain shear stress and retarding the recovery, as well as annihilation of dislocations. The DD results show that strengthening due to nano sized particles is a function of the density and size of the precipitates. This size effect is then explained using a mechanistic model developed based on dislocation-particle interaction.
Vrugt, J.A.; Diks, C.G.H.; Gupta, H.V.; Bouten, W.; Verstraten, J.M.
2005-01-01
Hydrologic models use relatively simple mathematical equations to conceptualize and aggregate the complex, spatially distributed, and highly interrelated water, energy, and vegetation processes in a watershed. A consequence of process aggregation is that the model parameters often do not represent
Sippel, Judith; Meeßen, Christian; Cacace, Mauro; Mechie, James; Fishwick, Stewart; Heine, Christian; Scheck-Wenderoth, Magdalena; Strecker, Manfred R.
2017-01-01
We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume-lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.
Bast, Callie C.; Boyce, Lola
1995-01-01
The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.
G Appa Rao; R Sundaresan
2012-02-01
This paper reports on development of size-dependent shear strength expression for reinforced concrete deep beams using reﬁned strut-and-tie model. The generic form of the size effect law has been retained considering the merits of Siao’s model and modiﬁed Bazant’s size effect law using the large experimental data base reported in the literature. The proposed equation for predicting the shear strength of deep beams incorporates the compressive strength of concrete, ratios of the longitudinal and the web reinforcement, shear span-to-depth ratio and the effective depth.
Plastic and damage behaviour of a high strength X100 pipeline steel: Experiments and modelling
Tanguy, B. [Centre des Materiaux, Mines Paris, Paristech, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France); Luu, T.T. [Centre des Materiaux, Mines Paris, Paristech, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France); Applied Mechanics Division, IFP, 92852 Rueil-Malmaison (France); Perrin, G. [Applied Mechanics Division, IFP, 92852 Rueil-Malmaison (France); Pineau, A. [Centre des Materiaux, Mines Paris, Paristech, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France); Besson, J. [Centre des Materiaux, Mines Paris, Paristech, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France)], E-mail: jacques.besson@ensmp.fr
2008-05-15
The purpose of this work is to develop a constitutive model integrating anisotropic behaviour and ductile damage for a X100 pipeline steel. The model is based on a set of experiments on various smooth, notched and cracked specimens and on a careful fractographic examination of the damage mechanisms. The model is based on an extension of the Gurson-Tvergaard-Needleman model which includes plastic anisotropy. Provided brittle delamination is not triggered, the developed model can accurately describe the plastic and damage behaviour of the material. The model is then used as a numerical tool to investigate the effect of plastic anisotropy and delamination on ductile crack extension. It is shown in particular that it is not possible to obtain a unified description of rupture properties for notched and cracked specimens tested along different directions without accounting for plastic anisotropy.
European column buckling curves and finite element modelling including high strength steels
Jönsson, Jeppe; Stan, Tudor-Cristian
2017-01-01
Eurocode allows for finite element modelling of plated steel structures, however the information in the code on how to perform the analysis or what assumptions to make is quite sparse. The present paper investigates the deterministic modelling of flexural column buckling using plane shell element...
2013-03-01
36 Jeffrey K. Sapp , “A Calculator Adaptation of the Markov Chain Model for Manpower Analysis,” 12. 37 R. Gillard, “Steps...of the Royal Statistical Society 20, no. 1 (March 1971): 85–110. Sapp , Jeffrey K. “A Calculator Adaptation of the Markov Chain Model for Manpower
De Bruijn, E.; Van der Helm, F.C.T.; Happee, R.
2015-01-01
Background: Musculoskeletal models served to analyze head–neck motion and injury during automotive impact. Although muscle activation is known to affect the kinematic response, a model with properly validated muscle contributions does not exist to date. The goal of this study was to enhance a muscul
Schippers, P.; Volker, A.W.F.; Golliard, J.; Jong, C. de
2006-01-01
Propagation and sonar performance are modelled by TNO’s ALMOST program, already being developed since the Eighties. It models propagation between sonar and target based on ray theory, including effects of sediment bottoms, reverberation and ambient noise. Moreover, antenna directivity (beam forming)
De Bruijn, E.; Van der Helm, F.C.T.; Happee, R.
2015-01-01
Background: Musculoskeletal models served to analyze head–neck motion and injury during automotive impact. Although muscle activation is known to affect the kinematic response, a model with properly validated muscle contributions does not exist to date. The goal of this study was to enhance a muscul
The importance of spatial models for estimating the strength of density dependence
Thorson, James T.; Skaug, Hans J.; Kristensen, Kasper;
2014-01-01
Identifying the existence and magnitude of density dependence is one of the oldest concerns in ecology. Ecologists have aimed to estimate density dependence in population and community data by fitting a simple autoregressive (Gompertz) model for density dependence to time series of abundance...... for an entire population. However, it is increasingly recognized that spatial heterogeneity in population densities has implications for population and community dynamics. We therefore adapt the Gompertz model to approximate local densities over continuous space instead of population-wide abundance......, and to allow productivity to vary spatially. Using simulated data generated from a spatial model, we show that the conventional (nonspatial) Gompertz model will result in biased estimates of density dependence, e.g., identifying oscillatory dynamics when not present. By contrast, the spatial Gompertz model...
Increased consumer density reduces the strength of neighborhood effects in a model system.
Merwin, Andrew C; Underwood, Nora; Inouye, Brian D
2017-09-04
An individual's susceptibility to attack can be influenced by conspecific and heterospecifics neighbors. Predicting how these neighborhood effects contribute to population-level processes such as competition and evolution requires an understanding of how the strength of neighborhood effects is modified by changes in the abundances of both consumers and neighboring resource species. We show for the first time that consumer density can interact with the density and frequency of neighboring organisms to determine the magnitude of neighborhood effects. We used the bean beetle, Callosobruchus maculatus, and two of its host beans, Vigna unguiculata and V. radiata, to perform a response-surface experiment with a range of resource densities and three consumer densities. At low beetle density, damage to beans was reduced with increasing conspecific density (i.e. resource dilution) and damage to the less preferred host, V. unguiculata, was reduced with increasing V. radiata frequency (i.e. frequency-dependent associational resistance). As beetle density increased, however, neighborhood effects were reduced; at the highest beetle densities neither focal nor neighboring resource density nor frequency influenced damage. These findings illustrate the importance of consumer density in mediating indirect effects among resources, and suggest that accounting for consumer density may improve our ability to predict population-level outcomes of neighborhood effects and to use them in applications such as mixed-crop pest management. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Computer models of steam pipeline components in the evaluation of their local strength
J. Okrajni; W. Essler
2010-01-01
Purpose: The paper discusses the issue of modelling the heating and cooling processes of T-pipes in a power plant pipeline in the start-up conditions of a boiler. The main purpose of this work is the description of the mechanical behaviour of power plant components working under mechanical and thermal loading and validation of the computer modelling methods.Design/methodology/approach: The FEM modelling has been used to describe the local stress-strain behaviour of the chosen component.Findin...
The strength of the tropical inversion and its response to climate change in 18 CMIP5 models
Qu, Xin; Hall, Alex; Klein, Stephen A.; Caldwell, Peter M.
2015-07-01
We examine the tropical inversion strength, measured by the estimated inversion strength (EIS), and its response to climate change in 18 models associated with phase 5 of the coupled model intercomparison project (CMIP5). While CMIP5 models generally capture the geographic distribution of observed EIS, they systematically underestimate it off the west coasts of continents, due to a warm bias in sea surface temperature. The negative EIS bias may contribute to the low bias in tropical low-cloud cover in the same models. Idealized perturbation experiments reveal that anthropogenic forcing leads directly to EIS increases, independent of "temperature-mediated" EIS increases associated with long-term oceanic warming. This fast EIS response to anthropogenic forcing is strongly impacted by nearly instantaneous continental warming. The temperature-mediated EIS change has contributions from both uniform and non-uniform oceanic warming. The substantial EIS increases in uniform oceanic warming simulations are due to warming with height exceeding the moist adiabatic lapse rate in tropical warm pools. EIS also increases in fully-coupled ocean-atmosphere simulations where concentration is instantaneously quadrupled, due to both fast and temperature-mediated changes. The temperature-mediated EIS change varies with tropical warming in a nonlinear fashion: The EIS change per degree tropical warming is much larger in the early stage of the simulations than in the late stage, due to delayed warming in the eastern parts of the subtropical oceans. Given the importance of EIS in regulating tropical low-cloud cover, this suggests that the tropical low-cloud feedback may also be nonlinear.
On the modelling of strength differential and anisotropy exhibited by titanium
Manopulo, Niko; Raemy, Christian; Hora, Pavel
2016-08-01
Modelling the response of titanium alloys under plastic deformation is challenging. In addition to strong anisotropy, these materials exhibit tension-compression asymmetry as well as anisotropic hardening even under monotonous loading conditions. The present contribution aims to propose a new modelling approach for titanium materials, by a homogeneous introduction of asymmetry into existing symmetric yield functions. Furthermore, anisotropic hardening effects are tracked describing the strain dependant yield surface evolution. The results are validated using the earing profile of deep drawn cups.
Cressie, Noel; Calder, Catherine A; Clark, James S; Ver Hoef, Jay M; Wikle, Christopher K
2009-04-01
Analyses of ecological data should account for the uncertainty in the process(es) that generated the data. However, accounting for these uncertainties is a difficult task, since ecology is known for its complexity. Measurement and/or process errors are often the only sources of uncertainty modeled when addressing complex ecological problems, yet analyses should also account for uncertainty in sampling design, in model specification, in parameters governing the specified model, and in initial and boundary conditions. Only then can we be confident in the scientific inferences and forecasts made from an analysis. Probability and statistics provide a framework that accounts for multiple sources of uncertainty. Given the complexities of ecological studies, the hierarchical statistical model is an invaluable tool. This approach is not new in ecology, and there are many examples (both Bayesian and non-Bayesian) in the literature illustrating the benefits of this approach. In this article, we provide a baseline for concepts, notation, and methods, from which discussion on hierarchical statistical modeling in ecology can proceed. We have also planted some seeds for discussion and tried to show where the practical difficulties lie. Our thesis is that hierarchical statistical modeling is a powerful way of approaching ecological analysis in the presence of inevitable but quantifiable uncertainties, even if practical issues sometimes require pragmatic compromises.
A micromechanics model of the stiffness and strength of laminates with fiber waviness
Harris, Charles E.; Lee, Jong-Won
1988-01-01
A mathematical model based on the Euler-Bernoulli beam theory is proposed for predicting the effective Young's moduli of piecewise isotropic composite laminates with local ply curvatures in the main load-carrying layers. Strains in corrugated layers, In-Phase layers, Out-of-Phase layers are predicted for various geometries and material configurations by assuming matrix layers as elastic foundations of different spring constants. The effective Young's moduli measured from corrugated aluminum specimens and aluminum/epoxy specimens with In-Phase and Out-of-Phase wavy patterns coincide very well with the model predictions. Moire fringe analysis of an In-Phase specimen and an Out-of-Phase specimen are also presented confirming the main assumption of the model related to the elastic constraint due to the matrix layers. The present model is also compared with the experimental results and other models, including the micro-buckling models, published in the literature. The results of the present study show that even a very small scale local ply curvature produces a noticeable effect on the mechanical constitutive behavior of a laminated composite.
Reid, Allecia E; Aiken, Leona S
2011-11-01
The purpose of this research was to select from the health belief model (HBM), theories of reasoned action (TRA) and planned behaviour (TPB), information-motivation-behavioural skills model (IMB) and social cognitive theory (SCT) the strongest longitudinal predictors of women's condom use and to combine these constructs into a single integrated model of condom use. The integrated model was evaluated for prediction of condom use among young women who had steady versus casual partners. At Time 1, all constructs of the five models and condom use were assessed in an initial and a replication sample (n = 193, n = 161). Condom use reassessed 8 weeks later (Time 2) served as the main outcome. Information from IMB, perceived susceptibility, benefits, and barriers from HBM, self-efficacy and self-evaluative expectancies from SCT, and partner norm and attitudes from TPB served as indirect or direct predictors of condom use. All paths replicated across samples. Direct predictors of behaviour varied with relationship status: self-efficacy significantly predicted condom use for women with casual partners, while attitude and partner norm predicted for those with steady partners. Integrated psychosocial models, rich in constructs and relationships drawn from multiple theories of behaviour, may provide a more complete characterisation of health protective behaviour.
Modeling cation diffusion in compacted water-saturatedNa-bentonite at low ionic strength
Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.
2007-08-28
Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm{sup -3} (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.2 kg dm{sup -3}.
Fluid stiction modeling for quickly separating plates considering the liquid tensile strength
Roemer, Daniel Beck; Johansen, Per; Pedersen, Henrik C.;
2015-01-01
separation speed and low plate distance are present. In the case of small initial plate separation, fluid tension is known to develop and the stiction force may exceed the maximum stiction force calculated by assuming strictly positive pressures in the fluid film. In this paper, a model for simulating......Fluid stiction may significantly influence the dynamic behavior when attempting to quickly separate two plates in close contact. The liquid fluid film, filling the gap between the plates, experiences a pressure drop resulting from an increasing distance, and cavitation may appear if sufficient...... the need for finite element/volume methods. The considered geometry is two long parallel plates submerged in liquid, as present in many valve applications. The model is compared to experimental measurements, and it is found that the model is able to predict the stiction effect with reasonable accuracy...
Modelling of ultrasonic impact treatment (UIT of welded joints and its effect on fatigue strength
K.L. Yuan
2015-10-01
Full Text Available Ultrasonic impact treatment (UIT is a remarkable post-weld technique applying mechanical impacts in combination with ultrasound into the welded joints. In the present work, a 3D simulation method including welding simulation, numerical modelling of UIT-process and an evaluation of fatigue crack growth has been developed. In the FE model, the actual treatment conditions and local mechanical characteristics due to acoustic softening are set as input parameters. The plastic deformation and compressive stress layer are found to be more pronounced when acoustic softening takes place. The predicted internal residual stress distributions of welded joint before and after UIT are compared with experimental results, showing a fairly good agreement with each other. Finally, simulated results of fatigue crack growth in various residual stress fields are well compared with test results, so that the proposed model may provide an effective tool to simulate UIT-process in engineering structures.
Tanoto, Yopi Y.; Anggono, Juliana; Siahaan, Ian H.; Budiman, Wesley
2017-01-01
There are several parameters that must be set before manufacturing a product using 3D printing. These parameters include the orientation deposition of that product, type of material, form fill, fill density, and other parameters. The finished product of 3D printing has some responses that can be observed, measured, and tested. Some of those responses are the processing time, the dimensions of the end product, its surface roughness and the mechanical properties, i.e. its yield strength, ultimate tensile strength, and impact resistance. This research was conducted to study the relationship between process parameters of 3D printing machine using a technology of fused deposition modeling (FDM) and the generated responses. The material used was ABS plastic that was commonly used in the industry. Understanding the relationship between the parameters and the responses thus the resulting product can be manufactured to meet the user needs. Three different orientations in depositing the ABS polymer named XY(first orientation), YX (second orientation), and ZX (third orientation) were studied. Processing time, dimensional accuracy, and the product strength were the responses that were measured and tested. The study reports that the printing process with third orientation was the fastest printing process with the processing time 2432 seconds followed by orientation 1 and 2 with a processing time of 2688 and 2780 seconds respectively. Dimension accuracy was also measured from the width and the length of gauge area of tensile test specimens printed in comparison with the dimensions required by ASTM 638-02. It was found that the smallest difference was in thickness dimension, i.e. 0.1 mm thicker in printed sample using second orientation than as required by the standard. The smallest thickness deviation from the standard was measured in width dimension of a sample printed using first orientation (0.13 mm). As with the length dimension, the closest dimension to the standard was
... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...
... en español Entrenamiento de la fuerza muscular Strength training is a vital part of a balanced exercise routine that includes aerobic activity and flexibility exercises. Regular aerobic exercise, such as running or ...
Kim, Kwang Yeom; Zhuang, Li; Yang, Hwayoung; Kim, Hanna; Min, Ki-Bok
2016-04-01
Berea sandstone in northern Ohio is a transversely isotropic rock. X-ray CT investigations showed that its internal structure is composed of cross-bedded loose layers and relatively thin tightly packed layers called bedding. Uniaxial compression tests were performed on different Berea sandstone specimens. The uniaxial compressive strength (UCS) decreases with increasing porosity, and also decreases with increasing inclination of the bedding plane relative to horizontal line. Two-dimensional discrete modeling was applied to investigate the micromechanical behavior of Berea sandstone. Different microparameters were assigned to loose and tight layers. The UCS simulation results agree well with the experimental results. At the peak stress, cracks almost always develop in loose layers regardless of the bedding plane orientation. In addition, both normal and shear cracks occur earlier for specimens with a higher inclination angle. No correlations were found between the inclination angle of failure planes and the orientation of bedding planes. The bedding planes of Berea sandstone are not weak planes. The strength anisotropy of Berea sandstone is not significant compared with other rocks such as shale, gneiss, and schist.
Chadha, K.; Shahriari, D.; Tremblay, R.; Bhattacharjee, P. P.; Jahazi, M.
2017-07-01
Constitutive modeling of the ingot breakdown process of large size ingots of high strength steel was carried out through comprehensive thermomechanical processing using Gleeble 3800® thermomechanical simulator, finite element modeling (FEM), optical and electron back scatter diffraction (EBSD). For this purpose, hot compression tests in the range of 1473 K to 1323 K (1200 °C to 1050 °C) and strain rates of 0.25 to 2 s-1 were carried out. The stress-strain curves describing the deformation behavior of the dendritic microstructure of the cast ingot were analyzed in terms of the Arrhenius and Hansel-Spittel models which were implemented in Forge NxT 1.0® FEM software. The results indicated that the Arrhenius model was more reliable in predicting microstructure evolution of the as-cast structure during ingot breakdown, particularly the occurrence of dynamic recrystallization (DRX) process which was a vital parameter in estimating the optimum loads for forming of large size components. The accuracy and reliability of both models were compared in terms of correlation coefficient (R) and the average absolute relative error (ARRE).
Chadha, K.; Shahriari, D.; Tremblay, R.; Bhattacharjee, P. P.; Jahazi, M.
2017-09-01
Constitutive modeling of the ingot breakdown process of large size ingots of high strength steel was carried out through comprehensive thermomechanical processing using Gleeble 3800® thermomechanical simulator, finite element modeling (FEM), optical and electron back scatter diffraction (EBSD). For this purpose, hot compression tests in the range of 1473 K to 1323 K (1200 °C to 1050 °C) and strain rates of 0.25 to 2 s-1 were carried out. The stress-strain curves describing the deformation behavior of the dendritic microstructure of the cast ingot were analyzed in terms of the Arrhenius and Hansel-Spittel models which were implemented in Forge NxT 1.0® FEM software. The results indicated that the Arrhenius model was more reliable in predicting microstructure evolution of the as-cast structure during ingot breakdown, particularly the occurrence of dynamic recrystallization (DRX) process which was a vital parameter in estimating the optimum loads for forming of large size components. The accuracy and reliability of both models were compared in terms of correlation coefficient (R) and the average absolute relative error (ARRE).
Kwon, Anthony J; Hunter, William D; Moldavsky, Mark; Salloum, Kanaan; Bucklen, Brandon
2016-05-01
OBJECTIVE The lateral transpsoas approach to the lumbar spine is a well-defined procedure for the management of discogenic spinal pathology necessitating surgical intervention. Intervertebral device subsidence is a postoperative clinical risk that can lead to recurrence of symptomatic pathology and the need for surgical reintervention. The current study was designed to investigate static versus expandable lateral intervertebral spacers in indirect decompression for preserving vertebral body endplate strength. METHODS Using a cadaveric biomechanical study and a foam-block vertebral body model, researchers compared vertebral body endplate strength and distraction potential. Fourteen lumbar motion segments (7 L2-3 and 7 L4-5 specimens) were distributed evenly between static and expandable spacer groups. In each specimen discectomy was followed by trialing and spacer impaction. Motion segments were axially sectioned through the disc, and a metal stamp was used to apply a compressive load to superior and inferior vertebral bodies to quantify endplate strength. A paired, 2-sample for means t-test was performed to determine statistically significant differences between groups (p ≤ 0.05). A foam-block endplate model was used to control simulated disc tension when a spacer with 2- and 3-mm desired distraction was inserted. One-way ANOVA and a post hoc Student Newman-Keuls test were performed (p ≤ 0.05) to determine differences in distraction. RESULTS Both static and expandable spacers restored intact neural foramen and disc heights after device implantation (p > 0.05). Maximum peak loads at endplate failure for static and expandable spacers were 1764 N (± 966 N) and 2284 N (± 949 N), respectively (p ≤ 0.05). The expandable spacer consistently produced greater desired distraction than was created by the static spacer in the foam-block model (p ≤ 0.05). Distraction created by fully expanding the spacer was significantly greater than the predetermined goals of 2 mm
Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice
Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert Jan; Sterk, H.A.M.
2016-01-01
Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic
Select strengths and biases of models in representing the Arctic winter boundary layer over sea ice
Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert Jan; Sterk, H.A.M.
2016-01-01
Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic
A Test of the Need Hierarchy Concept by a Markov Model of Change in Need Strength.
Rauschenberger, John; And Others
1980-01-01
In this study of 547 high school graduates, Alderfer's and Maslow's need hierarchy theories were expressed in Markov chain form and were subjected to empirical test. Both models were disconfirmed. Corroborative multiwave correlational analysis also failed to support the need hierarchy concept. (Author/IRT)
A Test of the Need Hierarchy Concept by a Markov Model of Change in Need Strength.
Rauschenberger, John; And Others
1980-01-01
In this study of 547 high school graduates, Alderfer's and Maslow's need hierarchy theories were expressed in Markov chain form and were subjected to empirical test. Both models were disconfirmed. Corroborative multiwave correlational analysis also failed to support the need hierarchy concept. (Author/IRT)
郑长民; 薛雁; 陈蕾
2010-01-01
To investigate the effects of substance P in globus pallidus on haloperidol-induced Parkinson's disease model rat.Methods In behavioral experiments,guide cannulae constructed from stainless steel were implanted into the globus pallidus.After five days recovery,0.5 μl drugs(normal saline,SMSP,SR140333B,SR140333B + SMSP)were bilaterally microinjected into the globus pallidus in awake rats with haloperidol administration intraperitoneally.The catalepsy was then observed within 60 min.In electrophysiological study,an in vivo extracellular recording was performed to observe the effects of substance P on the firing rate of pallidal neurons.Resuits Haloperidol induced catalepsy in rats with intrapallidal saline microinjection.The maximum average latency was(259.8±34.8)s at the time point of 30th min.The minimum average latency was(145.2±54.8)s at 50th min.Bilateral microinjection of SMSP into globus pallidus significantly attenuated haloperidol-induced catalepsy (The average latency was(10.4±3.4)s at lOth rain and(58.4±38.8)s at 60th min,P＜0.01).This anticataleptic effect was completely counteracted by selective NK-1 receptors antagonist SR140333B(The average latency was(176.4±64.4)s at 10th min and(139.2±59.7)s at 60th rain,P＜0.01).Furthermore,micropressure ejection of SMSP significantly increased the firing rate of pallidal neurons(Basal:(13.4±4.2)Hz,SMSP:(17.5±5.6)Hz).The average increase was(29.4±8.6)%(P＜0.05,n=13).SR140333 B completely blocked SMSPinduced increase in firing rate(SR140333B:(10.3±2.5)Hz,SR140333 B + SMSP:(11.3±3.0)Hz,P＞0.05,n=8).Conclusion Based on the action of substance P in globus pallidus of parkinsonian rats,it is we hypothesized that activation of substance P receptor in globus pallidus may play a role in the treatment of Parkinson's disease.%目的 观察苍白球P物质对氟哌啶醇帕金森病僵直模型大鼠的影响.方法 行为学实验采用大鼠腹腔注射氟哌啶醇诱发帕金森病僵直模犁,苍白球分
A systems perspective of waste and energy - Strengths and weaknesses of the ORWARE model
Eriksson, Ola
2000-11-01
Waste management of today in Sweden is a complex phenomenon that demands for a scientific and systematic approach. The complexity is a result of a wide variety of actors, technologies, and impact on the environment, health, and the economy. Waste management also has a high relevance with respect to energy. There are direct connections as e.g. energy recovery from waste, but also indirect as the systems complexity and the environmental and economical impacts. Helpful tools in the planning of waste management are different types of models of which ORWARE is one. Based on principles from Life Cycle Analysis (LCA) and complemented with a simple Cost Benefit Analysis (CBA) ORWARE can provide some help in finding environmentally sound solutions for waste management systems. The model does not answer all questions raised by practitioners but can still be used for advisory purposes. The model does not include sociological or political aspects but it covers the area of physical flows with impacts on environment, society and economy. Other impacts have to be considered with other methods. The experiences from using ORWARE in Swedish municipalities during more than a half decade clearly shows the advantages and disadvantages of the tool. The model is very flexible when it comes to the possibility of site-specific adjustments of input data and process functions. With help of the model the complexity of the studied system can be illustrated by e.g. a map of the number of connections between different types of information. In this way ORWARE supports dialogue between different stakeholders and collects knowledge in a unique way. On the other hand, modelling such an extensive and complex system often leads to errors that takes time to find and correct. The model can not be considered as user friendly and does not cover all aspects wanted by the society. There are also educational problems with different time frames and space boundaries in the analysis that make the results hard
The Public Health Innovation Model: Merging Private Sector Processes with Public Health Strengths.
Lister, Cameron; Payne, Hannah; Hanson, Carl L; Barnes, Michael D; Davis, Siena F; Manwaring, Todd
2017-01-01
Public health enjoyed a number of successes over the twentieth century. However, public health agencies have arguably been ill equipped to sustain these successes and address the complex threats we face today, including morbidity and mortality associated with persistent chronic diseases and emerging infectious diseases, in the context of flat funding and new and changing health care legislation. Transformational leaders, who are not afraid of taking risks to develop innovative approaches to combat present-day threats, are needed within public health agencies. We propose the Public Health Innovation Model (PHIM) as a tool for public health leaders who wish to integrate innovation into public health practice. This model merges traditional public health program planning models with innovation principles adapted from the private sector, including design thinking, seeking funding from private sector entities, and more strongly emphasizing program outcomes. We also discuss principles that leaders should consider adopting when transitioning to the PHIM, including cross-collaboration, community buy-in, human-centered assessment, autonomy and creativity, rapid experimentation and prototyping, and accountability to outcomes.
Alessandro Barbiero
2014-01-01
Full Text Available In many statistical applications, it is often necessary to obtain an interval estimate for an unknown proportion or probability or, more generally, for a parameter whose natural space is the unit interval. The customary approximate two-sided confidence interval for such a parameter, based on some version of the central limit theorem, is known to be unsatisfactory when its true value is close to zero or one or when the sample size is small. A possible way to tackle this issue is the transformation of the data through a proper function that is able to make the approximation to the normal distribution less coarse. In this paper, we study the application of several of these transformations to the context of the estimation of the reliability parameter for stress-strength models, with a special focus on Poisson distribution. From this work, some practical hints emerge on which transformation may more efficiently improve standard confidence intervals in which scenarios.
Li, Yan; Chen, Jianjun; Liu, Jipeng; Zhang, Lei; Wang, Weiguo; Zhang, Shaofeng
2013-09-01
The reliability of all-ceramic crowns is of concern to both patients and doctors. This study introduces a new methodology for quantifying the reliability of all-ceramic crowns based on the stress-strength interference theory and finite element models. The variables selected for the reliability analysis include the magnitude of the occlusal contact area, the occlusal load and the residual thermal stress. The calculated reliabilities of crowns under different loading conditions showed that too small occlusal contact areas or too great a difference of the thermal coefficient between veneer and core layer led to high failure possibilities. There results were consistent with many previous reports. Therefore, the methodology is shown to be a valuable method for analyzing the reliabilities of the restorations in the complicated oral environment.
Omerspahic, E.; Mattiasson, K.
2003-09-01
Within the scope of thermodynamics with internal variables, constitutive and evolution equations (representing ductile deformation of sheets made of high strength steel alloys) with mixed hardening and damage have been derived. As a result of the derivation, the rate-dependent elastoplastic constitutive model is identified. The material is assumed to be oriented in the principal damage directions, indicating orthotropic damage. Owing to postulates within continuum damage mechanics, a general expression for degradation of elastic properties in materials has been obtained. A numerical algorithm for the integration of the constitutive equations has been developed as well, based on an elastic predictor plastic/damage corrector procedure. The plastic/damage corrector is based on a fully implicit backward Euler scheme. In order to consider viscoplastic material properties, the overstress (in the definition of the plastic multiplier) is a function of the plastic yield function.
Carter, Evan C; McCullough, Michael E
2014-01-01
Few models of self-control have generated as much scientific interest as has the limited strength model. One of the entailments of this model, the depletion effect, is the expectation that acts of self-control will be less effective when they follow prior acts of self-control. Results from a previous meta-analysis concluded that the depletion effect is robust and medium in magnitude (d = 0.62). However, when we applied methods for estimating and correcting for small-study effects (such as publication bias) to the data from this previous meta-analysis effort, we found very strong signals of publication bias, along with an indication that the depletion effect is actually no different from zero. We conclude that until greater certainty about the size of the depletion effect can be established, circumspection about the existence of this phenomenon is warranted, and that rather than elaborating on the model, research efforts should focus on establishing whether the basic effect exists. We argue that the evidence for the depletion effect is a useful case study for illustrating the dangers of small-study effects as well as some of the possible tools for mitigating their influence in psychological science.
Li Qiang
2013-07-01
Full Text Available BP neural network was used in this study to model the porosity and the compressive strength of a gradient Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The influences of the load applied on the epispastic polystyrene template (F, the centrifugal acceleration (v and sintering temperature (T on the porosity (P and compressive strength (σ of the sintered products were studied by using the registered three-layer BP model. The accuracy of the model was verified by comparing the BP model predicted results with the experimental ones. Results show that the model prediction agrees with the experimental data within a reasonable experimental error, indicating that the three-layer BP network based modeling is effective in predicting both the properties and processing parameters in designing the gradient Al2O3-ZrO2 ceramic foam filter. The prediction results show that the porosity percentage increases and compressive strength decreases with an increase in the applied load on epispastic polystyrene template. As for the influence of sintering temperature, the porosity percentage decreases monotonically with an increase in sintering temperature, yet the compressive strength first increases and then decreases slightly in a given temperature range. Furthermore, the porosity percentage changes little but the compressive strength first increases and then decreases when the centrifugal acceleration increases.
Barber, Amelia E; Norton, J Paul; Wiles, Travis J; Mulvey, Matthew A
2016-06-01
Urinary tract infections (UTIs) are some of the most common bacterial infections worldwide and are a source of substantial morbidity among otherwise healthy women. UTIs can be caused by a variety of microbes, but the predominant etiologic agent of these infections is uropathogenic Escherichia coli (UPEC). An especially troubling feature of UPEC-associated UTIs is their high rate of recurrence. This problem is compounded by the drastic increase in the global incidence of antibiotic-resistant UPEC strains over the past 15 years. The need for more-effective treatments for UTIs is driving research aimed at bettering our understanding of the virulence mechanisms and host-pathogen interactions that occur during the course of these infections. Surrogate models of human infection, including cell culture systems and the use of murine, porcine, avian, teleost (zebrafish), and nematode hosts, are being employed to define host and bacterial factors that modulate the pathogenesis of UTIs. These model systems are revealing how UPEC strains can avoid or overcome host defenses and acquire scarce nutrients while also providing insight into the virulence mechanisms used by UPEC within compromised individuals, such as catheterized patients. Here, we summarize our current understanding of UTI pathogenesis while also giving an overview of the model systems used to study the initiation, persistence, and recurrence of UTIs and life-threatening sequelae like urosepsis. Although we focus on UPEC, the experimental systems described here can also provide valuable insight into the disease processes associated with other bacterial pathogens both within the urinary tract and elsewhere within the host.
CTH Implementation of a Two-Phase Material Model With Strength: Application to Porous Materials
2012-07-01
The idea of fitting constants τ0 and D0 in [13] is based on an approximation of the stationary solution of the viscoelastic model equations [17]. It...limit is Y = σ11 and 11 xu . Therefore, the stationary point of (16) after index summation can be found from .2 YG The last...concentration c (CMS variable); iii) scalar volume concentration θ ( TET variable); iv) scalar entropy disequilibrium χ (XI variable); v) symmetric strain
Modeling the effects of pH and ionic strength on swelling of anionic polyelectrolyte gels
Drozdov, A. D.; deClaville Christiansen, J.
2015-07-01
A constitutive model is developed for the elastic response of an anionic polyelectrolyte gel under swelling in water with an arbitrary pH and an arbitrary molar fraction of dissolved monovalent salt. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solute (mobile ions). Transport of solvent and solute is thought of as their diffusion through the polymer network accelerated by an electric field formed by mobile and fixed ions and accompanied by chemical reactions (dissociation of functional groups attached to polymer chains and formation of ion pairs between bound charges and mobile counter-ions). Constitutive equations are derived by means of the free energy imbalance inequality for an arbitrary three-dimensional deformation with finite strains. These relations are applied to analyze equilibrium swelling diagrams on poly(acrylic acid) gel, poly(methacrylic acid) gel, and three composite hydrogels under water uptake in a bath (i) with a fixed molar fraction of salt and varied pH, and (ii) with a fixed pH and varied molar fraction of salt. To validate the ability of the model to predict observations quantitatively, material constants are found by matching swelling curves under one type of experimental conditions and results of simulation are compared with experimental data in the other type of tests.
Apparent strength conceals instability in a model for the collapse of historical states.
Daniel John Lawson
Full Text Available An explanation for the political processes leading to the sudden collapse of empires and states would be useful for understanding both historical and contemporary political events. We examine political disintegration across eras, cultures and geographical scale to form a simple hypothesis that can be expressed verbally yet formulated mathematically. Factions within a state make choices described by game-theory about whether to accept the political status quo, or to attempt to better their circumstances through costly rebellion. In lieu of precise data we verify our model using sensitivity analysis. We find that a small amount of dissatisfaction is typically harmless to the state, but can trigger sudden collapse when there is a sufficient buildup of political inequality. Contrary to intuition, a state is predicted to be least stable when its leadership is at the height of its political power and thus most able to exert its influence through external warfare, lavish expense or autocratic decree.
Apparent strength conceals instability in a model for the collapse of historical states
Lawson, Daniel John
2013-01-01
An explanation for the political processes leading to the sudden collapse of empires and states would be useful for understanding both historical and contemporary political events. We seek a general description of state collapse spanning eras and cultures, from small kingdoms to continental empires, drawing on a suitably diverse range of historical sources. Our aim is to provide an accessible verbal hypothesis that bridges the gap between mathematical and social methodology. We use game-theory to determine whether factions within a state will accept the political status quo, or wish to better their circumstances through costly rebellion. In lieu of precise data we verify our model using sensitivity analysis. We find that a small amount of dissatisfaction is typically harmless, but can trigger sudden collapse when there is a sufficient buildup of political inequality. Contrary to intuition, a state is predicted to be least stable when its leadership is at the height of its political power and thus most able to...
Apparent strength conceals instability in a model for the collapse of historical states.
Lawson, Daniel John; Oak, Neeraj
2014-01-01
An explanation for the political processes leading to the sudden collapse of empires and states would be useful for understanding both historical and contemporary political events. We examine political disintegration across eras, cultures and geographical scale to form a simple hypothesis that can be expressed verbally yet formulated mathematically. Factions within a state make choices described by game-theory about whether to accept the political status quo, or to attempt to better their circumstances through costly rebellion. In lieu of precise data we verify our model using sensitivity analysis. We find that a small amount of dissatisfaction is typically harmless to the state, but can trigger sudden collapse when there is a sufficient buildup of political inequality. Contrary to intuition, a state is predicted to be least stable when its leadership is at the height of its political power and thus most able to exert its influence through external warfare, lavish expense or autocratic decree.
Industrial-Strength Model-Based Testing - State of the Art and Current Challenges
Jan Peleska
2013-03-01
Full Text Available As of today, model-based testing (MBT is considered as leading-edge technology in industry. We sketch the different MBT variants that - according to our experience - are currently applied in practice, with special emphasis on the avionic, railway and automotive domains. The key factors for successful industrial-scale application of MBT are described, both from a scientific and a managerial point of view. With respect to the former view, we describe the techniques for automated test case, test data and test procedure generation for concurrent reactive real-time systems which are considered as the most important enablers for MBT in practice. With respect to the latter view, our experience with introducing MBT approaches in testing teams are sketched. Finally, the most challenging open scientific problems whose solutions are bound to improve the acceptance and effectiveness of MBT in industry are discussed.
Park, Taejoon; Seok, Dong-Yoon; Lee, Chul-Hwan; Noma, Nobuyasu; Kuwabara, Toshihiko; Stoughton, Thomas B.; Chung, Kwansoo
2011-08-01
A two-surface isotropic-kinematic hardening law was developed based on a two-surface plasticity model previously proposed by Lee et al., (2007, Int. J. Plast. 23, 1189-1212). In order to properly represent the Bauschinger and transient behaviors as well as permanent softening during reverse loading with various pre-strains, both the inner yield surface and the outer bounding surface expand (isotropic hardening) and translate (kinematic hardening) in this two-surface model. As for the permanent softening, both the isotropic hardening and the kinematic hardening evolution of the outer bounding surface were modified by introducing softening parameters. The numerical formulation was also developed based on the incremental plasticity theory and the developed constitutive law was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. In this work, a dual phase (DP) steel was considered as an advanced high strength steel sheet and uni-axial tension tests and uni-axial tension-compression-tension tests were performed for the characterization of the material property. For a validation purpose, the developed two-surface plasticity model was applied to the 2-D draw bending test proposed as a benchmark problem of the NUMISHEET 2011 conference and successfully validated with experiments.
Michel Audiffren
2015-03-01
Full Text Available Since the 1960's, hundreds of articles have been published on the effects of exercise on cognition and more recently on executive functions. A large variety of effects have been observed: acute or long-lasting, facilitating or debilitating. Several theoretical frameworks have been proposed to explain these effects with plausible mechanisms. However, as yet none of these models has succeeded in unifying all the observations in a single framework that subsumes all effects. The aim of the present review is to revisit the strength model of self-control initiated by Baumeister and his colleagues in the 1990's in order to extend its assumptions to exercise psychology. This model provides a heuristic framework that can explain and predict the effects of acute and chronic exercise on effortful tasks tapping self-regulation or executive functions. A reconsideration of exercise as a self-control task results from this perspective. A new avenue for future research is delineated besides more traditional approaches.
Sleep deprivation, low self-control, and delinquency: a test of the strength model of self-control.
Meldrum, Ryan C; Barnes, J C; Hay, Carter
2015-02-01
Recent work provides evidence that sleep deprivation is positively related to delinquency. In this study, we draw on Baumeister and colleagues' strength model of self-control to propose an explanation for this association. Specifically, we argue that low self-control is the construct that bridges the relationship between sleep deprivation and delinquency. To test the proposed model, we examine survey data drawn from a longitudinal multi-city cohort study of adolescents who were followed from birth through age 15 (N = 825; 50% female; 82% non-Hispanic white, 59% two-parent nuclear family). The results from regression models using latent factors indicate: sleep deprivation is positively related to low self-control; low self-control is positively related to delinquency; and the relationship between sleep deprivation and delinquency is indirect and operates through low self-control. Impressively, these relationships emerged when accounting for potential background sources of spuriousness, including neighborhood context, depressive symptoms, parenting practices, unstructured socializing with peers, and prior delinquency. Implications and directions for future research are discussed.
Anoop K. Sood
2012-01-01
Full Text Available Fused deposition modelling (FDM is gaining distinct advantage in manufacturing industries because of its ability to manufacture parts with complex shapes without any tooling requirement and human interface. The properties of FDM built parts exhibit high dependence on process parameters and can be improved by setting parameters at suitable levels. Anisotropic and brittle nature of build part makes it important to study the effect of process parameters to the resistance to compressive loading for enhancing service life of functional parts. Hence, the present work focuses on extensive study to understand the effect of five important parameters such as layer thickness, part build orientation, raster angle, raster width and air gap on the compressive stress of test specimen. The study not only provides insight into complex dependency of compressive stress on process parameters but also develops a statistically validated predictive equation. The equation is used to find optimal parameter setting through quantum-behaved particle swarm optimization (QPSO. As FDM process is a highly complex one and process parameters influence the responses in a non linear manner, compressive stress is predicted using artificial neural network (ANN and is compared with predictive equation.
Conor L Evans
2015-03-01
Full Text Available Three dimensional, in vitro spheroid cultures offer considerable utility for the development and testing of anticancer photodynamic therapy regimens. More complex than monolayer cultures, three-dimensional spheroid systems replicate many of the important cell-cell and cell-matrix interactions that modulate treatment response in vivo. Simple enough to be grown by the thousands and small enough to be optically interrogated, spheroid cultures lend themselves to high-content and high-throughput imaging approaches. These advantages have enabled studies investigating photosensitizer uptake, spatiotemporal patterns of therapeutic response, alterations in oxygen diffusion and consumption during therapy, and the exploration of mechanisms that underlie therapeutic synergy. The use of quantitative imaging methods, in particular, has accelerated the pace of three-dimensional in vitro photodynamic therapy studies, enabling the rapid compilation of multiple treatment response parameters in a single experiment. Improvements in model cultures, the creation of new molecular probes of cell state and function, and innovations in imaging toolkits will be important for the advancement of spheroid culture systems for future photodynamic therapy studies.
Li Jian
2015-09-01
Full Text Available The dynamic strength and accumulated plastic strain are two important parameters for evaluating the dynamic response of soil. As a special clay, the remolded red clay is often used as the high speed railway subgrade filling, but studies on its dynamic characteristics are few. For a thorough analysis of the suitability of the remolded red clay as the subgrade filling, a series of long-term cyclic load triaxial test under different load histories are carried out. Considering the influence of compactness, confining pressure, consolidation ratio, vibration frequency and dynamic load to the remolded red clay dynamic property, the tests obtain the development curves of the dynamic strength and accumulated plastic strain under different test conditions. Then, through curve fitting method, two different hyperbolic models respectively for the dynamic strength and accumulated plastic strain are built, which can match the test datum well. By applying the dynamic strength model, the critical dynamic strength of the remolded red clay are gained. Meanwhile, for providing basic datum and reference for relevant projects, all key parameters for the dynamic strength and accumulated plastic strain of the remolded red clay are given in the paper.
Rebič, Matúš; Laaksonen, Aatto; Šponer, Jiří; Uličný, Jozef; Mocci, Francesca
2016-08-04
Most molecular dynamics (MD) simulations of DNA quadruplexes have been performed under minimal salt conditions using the Åqvist potential parameters for the cation with the TIP3P water model. Recently, this combination of parameters has been reported to be problematic for the stability of quadruplex DNA, especially caused by the ion interactions inside or near the quadruplex channel. Here, we verify how the choice of ion parameters and water model can affect the quadruplex structural stability and the interactions with the ions outside the channel. We have performed a series of MD simulations of the human full-parallel telomeric quadruplex by neutralizing its negative charge with K(+) ions. Three combinations of different cation potential parameters and water models have been used: (a) Åqvist ion parameters, TIP3P water model; (b) Joung and Cheatham ion parameters, TIP3P water model; and (c) Joung and Cheatham ion parameters, TIP4Pew water model. For the combinations (b) and (c), the effect of the ionic strength has been evaluated by adding increasing amounts of KCl salt (50, 100, and 200 mM). Two independent simulations using the Åqvist parameters with the TIP3P model show that this combination is clearly less suited for the studied quadruplex with K(+) as counterions. In both simulations, one ion escapes from the channel, followed by significant deformation of the structure, leading to deviating conformation compared to that in the reference crystallographic data. For the other combinations of ion and water potentials, no tendency is observed for the channel ions to escape from the quadruplex channel. In addition, the internal mobility of the three loops, torsion angles, and counterion affinity have been investigated at varied salt concentrations. In summary, the selection of ion and water models is crucial as it can affect both the structure and dynamics as well as the interactions of the quadruplex with its counterions. The results obtained with the TIP4Pew
Nabi, Jameel-Un; Ishfaq, Mavra
2016-07-01
We calculate Gamow-Teller strength distributions for β β-decay nuclei ^{76}Ge and ^{82}Se using the deformed pn-QRPA model. We use a deformed Nilsson basis and consider pairing correlations within the deformed BCS theory. Ground state correlations and two-particle and two-hole mixing states were included in our pn-QRPA model. Our calculated strength distributions were compared with experimental data and previous calculation. The total Gamow-Teller strength and centroid placement calculated in our model compares well with the measured value. We calculate β-decay and positron capture rates on ^{76}Ge and ^{82}Se in supernovae environments and compare them to those obtained from experimental data and previous calculation. Our study shows that positron capture rates command the total weak rates at high stellar temperatures. We also calculate energy rates of β-delayed neutrons and their emission probabilities.
Hamed Pishdast
2009-01-01
Full Text Available This paper presents a new naïve approach for simulating bone remodeling process. It is based on the uniform strength theory of optimization and employs a truss-like model for bone. The truss was subjected to external loads including 5 point loads simulating the hip joint contact forces and 3 muscular forces at the attachment sites of the muscles to the bone and the rest are reactions of ligaments. The strain in the links was calculated and the links with high strains were identified. The initial truss is modified by introducing new links wherever the strain exceeds a prescribed or critical value. The critical value was assumed to be equal to an average of the absolute value of strains in the initial model. Each link which undergoes a high strain is replaced by several new links by adding new nodes around it using Delaunay method. Introducing the new links to the truss, which is conducted according to a weighted arithmetic mean formula, will strengthen the structure and reduce the strain within the respective zone. This procedure was repeated for several times. Convergence was achieved when there were no critical links remaining. This method was used to study the 2D shape of proximal femur in the frontal plane and provided results which are in a fairly good agreement with CT image of the human proximal femur.
Fatih Yapıcı
2016-01-01
Full Text Available In this study, the compressive strength of heat treated Scotch Pine was modeled using artificial neural network. The compressive strength (CS value parallel to grain was determined after exposing the wood to heat treatment at temperature of 130, 145, 160, 175, 190 and 205ºC for 3, 6, 9, 12 hours. The experimental data was evaluated by using multiple variance analysis. Secondly, the effect of heat treatment on the CS of samples was modeled by using artificial neural network (ANN.
Shen, Yih-Jiun
2007-01-01
This study compared the effectiveness of short-term developmental group counseling applying Gestalt-play versus cognitive-verbal approaches with Taiwanese adolescents. On a measure of behavioral and emotional strengths, teachers reported significant changes in students' overall behavioral and emotional strengths measured via total scores. Specific…
Shen, Yih-Jiun
2007-01-01
This study compared the effectiveness of short-term developmental group counseling applying Gestalt-play versus cognitive-verbal approaches with Taiwanese adolescents. On a measure of behavioral and emotional strengths, teachers reported significant changes in students' overall behavioral and emotional strengths measured via total scores. Specific…
Gardner, Benjamin; Lally, Phillippa
2013-10-01
Habit formation is thought to aid maintenance of physical activity, but little research is available into determinants of habit strength aside from repeated performance. Previous work has shown that intrinsically motivated physical activity, underpinned by inherent satisfaction derived from activity, is more likely to be sustained. We explored whether this might reflect a tendency for self-determined activity to become more strongly habitual. A sample of 192 adults aged 18-30 completed measures of motivational regulation, intention, behaviour, and habit strength. Results showed that self-determined regulation interacted with past behaviour in predicting habit strength: prior action was more predictive of habit strength among more autonomously motivated participants. There was an unexpected direct effect of self-determined regulation on habit strength, independently of past behaviour. Findings offer possible directions for future habit formation work.
Nash, Charles A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hamm, L. Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, Frank G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); McCabe, Daniel J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2014-12-19
The primary treatment of the tank waste at the DOE Hanford site will be done in the Waste Treatment and Immobilization Plant (WTP) that is currently under construction. The baseline plan for this facility is to treat the waste, splitting it into High Level Waste (HLW) and Low Activity Waste (LAW). Both waste streams are then separately vitrified as glass and poured into canisters for disposition. The LAW glass will be disposed onsite in the Integrated Disposal Facility (IDF). There are currently no plans to treat the waste to remove technetium, so its disposition path is the LAW glass. Due to the water solubility properties of pertechnetate and long half-life of ^{99}Tc, effective management of ^{99}Tc is important to the overall success of the Hanford River Protection Project mission. To achieve the full target WTP throughput, additional LAW immobilization capacity is needed, and options are being explored to immobilize the supplemental LAW portion of the tank waste. Removal of ^{99}Tc, followed by off-site disposal, would eliminate a key risk contributor for the IDF Performance Assessment (PA) for supplemental waste forms, and has potential to reduce treatment and disposal costs. Washington River Protection Solutions (WRPS) is developing some conceptual flow sheets for supplemental LAW treatment and disposal that could benefit from technetium removal. One of these flowsheets will specifically examine removing ^{99}Tc from the LAW feed stream to supplemental immobilization. To enable an informed decision regarding the viability of technetium removal, further maturation of available technologies is being performed. This report contains results of experimental ion exchange distribution coefficient testing and computer modeling using the resin SuperLig^{®} 639^{a} to selectively remove perrhenate from high ionic strength simulated LAW. It is advantageous to operate at higher concentration in order to treat the waste
Sinder, Benjamin P; Salemi, Joseph D; Ominsky, Michael S; Caird, Michelle S; Marini, Joan C; Kozloff, Kenneth M
2015-02-01
Osteogenesis imperfecta (OI) is a heritable collagen-related bone dysplasia, characterized by brittle bones with increased fracture risk that presents most severely in children. Anti-resorptive bisphosphonates are frequently used to treat pediatric OI and controlled clinical trials have shown that bisphosphonate therapy improves vertebral outcomes but has little benefit on long bone fracture rate. New treatments which increase bone mass throughout the pediatric OI skeleton would be beneficial. Sclerostin antibody (Scl-Ab) is a potential candidate anabolic therapy for pediatric OI and functions by stimulating osteoblastic bone formation via the canonical Wnt signaling pathway. To explore the effect of Scl-Ab on the rapidly growing OI skeleton, we treated rapidly growing 3week old Brtl/+ mice, harboring a typical heterozygous OI-causing Gly→Cys substitution on col1a1, for 5weeks with Scl-Ab. Scl-Ab had anabolic effects in Brtl/+ and led to new cortical bone formation and increased cortical bone mass. This anabolic action resulted in improved mechanical strength to WT Veh levels without altering the underlying brittle nature of the material. While Scl-Ab was anabolic in trabecular bone of the distal femur in both genotypes, the effect was less strong in these rapidly growing Brtl/+ mice compared to WT. In conclusion, Scl-Ab was able to stimulate bone formation in a rapidly growing Brtl/+ murine model of OI, and represents a potential new therapy to improve bone mass and reduce fracture risk in pediatric OI.
Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee
2015-11-01
Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength. Copyright
Kaj Frick
2013-01-01
were as demonstrated by other research on municipalities’ limited development capacity. Hälsosam’s narrow focus was also supported by the limited priorities of the national municipal employers. This gave a narrow perspective in the central social partners’ consultants to Leksand and other municipalities. Hälsosam thereby demonstrates both the strengths and the weaknesses of the Nordic work environment model. On the one hand, the local dialogue was even further improved. On the other, local and central trade union cooperation with the employers did not enable them to much raise the organizational problems of work overload and poor work environment management. Leksand’s municipal employees remained squeezed between limited taxes and unlimited service demands and had to “solve” this by too hard work.
In vivo monitoring of bone-implant bond strength by microCT and finite element modelling.
Stadelmann, Vincent A; Conway, Carl M; Boyd, Steven K
2013-01-01
Immediately after implantation, a dynamic process of bone formation and resorption takes place around an orthopaedic implant, influencing its mechanical fixation. The delay until complete fixation depends on local bone architecture and metabolism. Despite its importance, the temporal pattern of implant fixation is still unknown. The optimal duration of post-operative care is therefore difficult to establish for an individual situation, and a method to evaluate non-invasively the evolution of the mechanical stability would be a significant asset in a clinical environment. The aim of this study was to evaluate the potential of micro-finite element modelling based on in vivo micro-computed tomography to monitor longitudinally the contact between bone and implant and the implant strength in vivo. The model was first validated for screw pull-out in synthetic bone surrogate. Correlation coefficients of R(2) = 0.94 and 0.85 (p < 0.01) were measured between experimental and numerical results for stiffness and failure loads, respectively. Then, the mechanical integration of screws in the proximal tibia of 12 rats was monitored at seven time points over a period of 1 month. We observed significant increases (p < 0.05) of bone-screw contact (+28%), stiffness (+93%) and failure load (+71%) over the course of the experiment, and more than 75% of these changes occurred during the first 2 weeks. Limitations, such as image artefacts and radiation, still compromise the immediate clinical application of this method, but it has a promising potential in preclinical animal studies, as it provides very valuable data about the dynamic aspect of implant integration with considerably reduced animal resources.
Li, Xiaodong; Ominsky, Michael S; Warmington, Kelly S; Morony, Sean; Gong, Jianhua; Cao, Jin; Gao, Yongming; Shalhoub, Victoria; Tipton, Barbara; Haldankar, Raj; Chen, Qing; Winters, Aaron; Boone, Tom; Geng, Zhaopo; Niu, Qing-Tian; Ke, Hua Zhu; Kostenuik, Paul J; Simonet, W Scott; Lacey, David L; Paszty, Chris
2009-04-01
The development of bone-rebuilding anabolic agents for potential use in the treatment of bone loss conditions, such as osteoporosis, has been a long-standing goal. Genetic studies in humans and mice have shown that the secreted protein sclerostin is a key negative regulator of bone formation, although the magnitude and extent of sclerostin's role in the control of bone formation in the aging skeleton is still unclear. To study this unexplored area of sclerostin biology and to assess the pharmacologic effects of sclerostin inhibition, we used a cell culture model of bone formation to identify a sclerostin neutralizing monoclonal antibody (Scl-AbII) for testing in an aged ovariectomized rat model of postmenopausal osteoporosis. Six-month-old female rats were ovariectomized and left untreated for 1 yr to allow for significant estrogen deficiency-induced bone loss, at which point Scl-AbII was administered for 5 wk. Scl-AbII treatment in these animals had robust anabolic effects, with marked increases in bone formation on trabecular, periosteal, endocortical, and intracortical surfaces. This not only resulted in complete reversal, at several skeletal sites, of the 1 yr of estrogen deficiency-induced bone loss, but also further increased bone mass and bone strength to levels greater than those found in non-ovariectomized control rats. Taken together, these preclinical results establish sclerostin's role as a pivotal negative regulator of bone formation in the aging skeleton and, furthermore, suggest that antibody-mediated inhibition of sclerostin represents a promising new therapeutic approach for the anabolic treatment of bone-related disorders, such as postmenopausal osteoporosis.
Mejía, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U”, Ciudad Universitaria, 58066 Morelia, Michoacán (Mexico); Altamirano, G.; Bedolla-Jacuinde, A. [Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U”, Ciudad Universitaria, 58066 Morelia, Michoacán (Mexico); Cabrera, J.M. [Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB – Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic, Av. de las Bases de Manresa, 1, 08240 Manresa (Spain)
2014-07-29
In this research work, modeling of the hot flow behavior was carried out in a low carbon advanced ultra-high strength steels (A-UHSS) microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm). For this purpose, experimental stress–strain data of uniaxial hot-compression tests over a wide range of temperatures (1223, 1273, 1323 and 1373 K (950, 1000, 1050 and 1100 °C)) and strain rates (10{sup −3}, 10{sup −2} and 10{sup −1} s{sup −1}) were used. The stress–strain relationships as a function of temperature and strain rate were successfully described on the basis of the approach proposed by Estrin, Mecking, and Bergström, together with the classical Avrami equation and the conventional hyperbolic sine function. The analysis of the modeling parameters of the hot flow curves shows that boron additions to A-UHSS play a major role in softening mechanisms rather than on hardening. The peak stress (σ{sub p}) and steady-state stress (σ{sub ss}) values show a decreasing trend with increasing boron content, which indicates that boron additions promote a solid solution softening effect additional to that produced by DRX. The time for 50% recrystallization (t{sub 50%}) tends to increase with boron additions, revealing that boron additions cause a delay of the DRX kinetics during hot deformation. Similarly, the presence of boron in the steel decreases the apparent activation energy for recrystallization (Q{sub t}), indicating that boron additions accelerate the onset of DRX. The constitutive equations developed in this way provided an excellent description of the experimental hot flow curves.
Sinder, B P; White, L E; Salemi, J D; Ominsky, M S; Caird, M S; Marini, J C; Kozloff, K M
2014-08-01
Treatments to reduce fracture rates in adults with osteogenesis imperfecta are limited. Sclerostin antibody, developed for treating osteoporosis, has not been explored in adults with OI. This study demonstrates that treatment of adult OI mice respond favorably to sclerostin antibody therapy despite retention of the OI-causing defect. Osteogenesis imperfecta (OI) is a heritable collagen-related bone dysplasia, characterized by brittle bones with increased fracture risk. Although OI fracture risk is greatest before puberty, adults with OI remain at risk of fracture. Antiresorptive bisphosphonates are commonly used to treat adult OI, but have shown mixed efficacy. New treatments which consistently improve bone mass throughout the skeleton may improve patient outcomes. Neutralizing antibodies to sclerostin (Scl-Ab) are a novel anabolic therapy that have shown efficacy in preclinical studies by stimulating bone formation via the canonical wnt signaling pathway. The purpose of this study was to evaluate Scl-Ab in an adult 6 month old Brtl/+ model of OI that harbors a typical heterozygous OI-causing Gly > Cys substitution on Col1a1. Six-month-old WT and Brtl/+ mice were treated with Scl-Ab (25 mg/kg, 2×/week) or Veh for 5 weeks. OCN and TRACP5b serum assays, dynamic histomorphometry, microCT and mechanical testing were performed. Adult Brtl/+ mice demonstrated a strong anabolic response to Scl-Ab with increased serum osteocalcin and bone formation rate. This anabolic response led to improved trabecular and cortical bone mass in the femur. Mechanical testing revealed Scl-Ab increased Brtl/+ femoral stiffness and strength. Scl-Ab was successfully anabolic in an adult Brtl/+ model of OI.
Liu, X Sherry; Wang, Ji; Zhou, Bin; Stein, Emily; Shi, Xiutao; Adams, Mark; Shane, Elizabeth; Guo, X Edward
2013-07-01
Although high-resolution peripheral quantitative computed tomography (HR-pQCT) has advanced clinical assessment of trabecular bone microstructure, nonlinear microstructural finite element (µFE) prediction of yield strength using a HR-pQCT voxel model is impractical for clinical use due to its prohibitively high computational costs. The goal of this study was to develop an efficient HR-pQCT-based plate and rod (PR) modeling technique to fill the unmet clinical need for fast bone strength estimation. By using an individual trabecula segmentation (ITS) technique to segment the trabecular structure into individual plates and rods, a patient-specific PR model was implemented by modeling each trabecular plate with multiple shell elements and each rod with a beam element. To validate this modeling technique, predictions by HR-pQCT PR model were compared with those of the registered high-resolution micro-computed tomography (HR-µCT) voxel model of 19 trabecular subvolumes from human cadaveric tibia samples. Both the Young's modulus and yield strength of HR-pQCT PR models strongly correlated with those of µCT voxel models (r² = 0.91 and 0.86). Notably, the HR-pQCT PR models achieved major reductions in element number (>40-fold) and computer central processing unit (CPU) time (>1200-fold). Then, we applied PR model µFE analysis to HR-pQCT images of 60 postmenopausal women with (n = 30) and without (n = 30) a history of vertebral fracture. HR-pQCT PR model revealed significantly lower Young's modulus and yield strength at the radius and tibia in fracture subjects compared to controls. Moreover, these mechanical measurements remained significantly lower in fracture subjects at both sites after adjustment for areal bone mineral density (aBMD) T-score at the ultradistal radius or total hip. In conclusion, we validated a novel HR-pQCT PR model of human trabecular bone against µCT voxel models and demonstrated its ability to discriminate vertebral fracture
Zhang, Wenlong; Ding, Dongyan; Gu, Mingyuan
2012-12-01
A combination of finite-element calculation and tension-compression tests was employed to predict the yield strength difference between the pipe and plate of low-carbon microalloyed steel (LCMS) in the production of high-frequency straight bead welding pipes (HFSBWPs). The deformation process was divided into bending, flattening, and tension deformations. The bending and flattening deformations were simulated using a finite-element method in order to obtain circumferential strains at pipe wall positions along the wall thickness. These strains were the transition strains in the subsequent tension-compression-tension and compression-tension tests. The yield stresses (0.5 pct proof stresses) at the pipe wall positions were derived from the obtained stress-strain curves. The average of the obtained yield stresses was taken as the predicted yield strength of the pipes. It is found that the difference between the latter and the strength of the original steel plates is a result of the combined action of the Bauschinger effect and strain hardening caused by bending and reverse bending deformations. It is strongly dependent on the ratio of pipe wall thickness to pipe outer diameter ( T/D ratio). At low T/D ratios, the Bauschinger effect was dominant, resulting in a decreased yield strength. Strain hardening due to work hardening was dominant at higher T/D ratios, resulting in an increased yield strength. The increase in yield strength was greater at the inner pipe walls than at outer ones, indicating that strain hardening is stronger at inner pipe walls. The yield strength differences predicted with the presented approach are comparable with the values obtained from industrial productions of HFSBWPs, indicating that this approach can be used to predict the yield strength difference between pipe and plate of LCMS.
Pithan, Felix; Ackerman, Andrew; Angevine, Wayne M.; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian; Sandu, Irina; Steeneveld, Gert-Jan; Sterk, H. A. M.; Svensson, Gunilla; Vaillancourt, Paul A.; Zadra, Ayrton
2016-09-01
Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, partly because they lack or misrepresent physical processes that are specific to high latitudes. Observations have revealed two preferred states of the Arctic winter boundary layer. In the cloudy state, cloud liquid water limits surface radiative cooling, and temperature inversions are weak and elevated. In the radiatively clear state, strong surface radiative cooling leads to the build-up of surface-based temperature inversions. Many large-scale models lack the cloudy state, and some substantially underestimate inversion strength in the clear state. Here, the transformation from a moist to a cold dry air mass is modeled using an idealized Lagrangian perspective. The trajectory includes both boundary layer states, and the single-column experiment is the first Lagrangian Arctic air formation experiment (Larcform 1) organized within GEWEX GASS (Global atmospheric system studies). The intercomparison reproduces the typical biases of large-scale models: some models lack the cloudy state of the boundary layer due to the representation of mixed-phase microphysics or to the interaction between micro- and macrophysics. In some models, high emissivities of ice clouds or the lack of an insulating snow layer prevent the build-up of surface-based inversions in the radiatively clear state. Models substantially disagree on the amount of cloud liquid water in the cloudy state and on turbulent heat fluxes under clear skies. Observations of air mass transformations including both boundary layer states would allow for a tighter constraint of model behavior.
Yu Jingyuan
2011-08-01
Full Text Available In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template (F, centrifugal acceleration (v and sintering temperature (T, while the only output was the ultimate compressive strength (σ. According to the registered BP model, the effects of F, v, T on σ were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.
Howe, Lauren C; Krosnick, Jon A
2017-01-03
Attitude strength has been the focus of a huge volume of research in psychology and related sciences for decades. The insights offered by this literature have tremendous value for understanding attitude functioning and structure and for the effective application of the attitude concept in applied settings. This is the first Annual Review of Psychology article on the topic, and it offers a review of theory and evidence regarding one of the most researched strength-related attitude features: attitude importance. Personal importance is attached to an attitude when the attitude is perceived to be relevant to self-interest, social identification with reference groups or reference individuals, and values. Attaching personal importance to an attitude causes crystallizing of attitudes (via enhanced resistance to change), effortful gathering and processing of relevant information, accumulation of a large store of well-organized relevant information in long-term memory, enhanced attitude extremity and accessibility, enhanced attitude impact on the regulation of interpersonal attraction, energizing of emotional reactions, and enhanced impact of attitudes on behavioral intentions and action. Thus, important attitudes are real and consequential psychological forces, and their study offers opportunities for addressing behavioral change.
Yoram Nevo
Full Text Available The Ras superfamily of guanosine-triphosphate (GTP-binding proteins regulates a diverse spectrum of intracellular processes involved in inflammation and fibrosis. Farnesythiosalicylic acid (FTS is a unique and potent Ras inhibitor which decreased inflammation and fibrosis in experimentally induced liver cirrhosis and ameliorated inflammatory processes in systemic lupus erythematosus, neuritis and nephritis animal models. FTS effect on Ras expression and activity, muscle strength and fibrosis was evaluated in the dy(2J/dy(2J mouse model of merosin deficient congenital muscular dystrophy. The dy(2J/dy(2J mice had significantly increased RAS expression and activity compared with the wild type mice. FTS treatment significantly decreased RAS expression and activity. In addition, phosphorylation of ERK, a Ras downstream protein, was significantly decreased following FTS treatment in the dy(2J/dy(2J mice. Clinically, FTS treated mice showed significant improvement in hind limb muscle strength measured by electronic grip strength meter. Significant reduction of fibrosis was demonstrated in the treated group by quantitative Sirius Red staining and lower muscle collagen content. FTS effect was associated with significantly inhibition of both MMP-2 and MMP-9 activities. We conclude that active RAS inhibition by FTS was associated with attenuated fibrosis and improved muscle strength in the dy(2J/dy(2J mouse model of congenital muscular dystrophy.
Ciuchini, Marco; Mishima, Satoshi; Pierini, Maurizio; Reina, Laura; Silvestrini, Luca
2014-01-01
We present updated global fits of the Standard Model and beyond to electroweak precision data, taking into account recent progress in theoretical calculations and experimental measurements. From the fits, we derive model-independent constraints on new physics by introducing oblique and epsilon parameters, and modified $Zb\\bar{b}$ and $HVV$ couplings. Furthermore, we also perform fits of the scale factors of the Higgs-boson couplings to observed signal strengths of the Higgs boson.
Mulder, F. M.; Dingemans, T. J.; Schimmel, H. G.; Ramirez-Cuesta, A. J.; Kearley, G. J.
2008-07-01
Hydrogen adsorption in porous, high surface area, and stable metal organic frameworks (MOF's) appears a novel route towards hydrogen storage materials [N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O'Keeffe, O.M. Yaghi, Science 300 (2003) 1127; J.L.C. Rowsell, A.R. Millward, K. Sung Park, O.M. Yaghi, J. Am. Chem. Soc. 126 (2004) 5666; G. Ferey, M. Latroche, C. Serre, F. Millange, T. Loiseau, A. Percheron-Guegan, Chem. Commun. (2003) 2976; T. Loiseau, C. Serre, C. Huguenard, G. Fink, F. Taulelle, M. Henry, T. Bataille, G. Férey, Chem. Eur. J. 10 (2004) 1373]. A prerequisite for such materials is sufficient adsorption interaction strength for hydrogen adsorbed on the adsorption sites of the material because this facilitates successful operation under moderate temperature and pressure conditions. Here we report detailed information on the geometry of the hydrogen adsorption sites, based on the analysis of inelastic neutron spectroscopy (INS). The adsorption energies for the metal organic framework MOF5 equal about 800 K for part of the different sites, which is significantly higher than for nanoporous carbon materials (˜550 K) [H.G. Schimmel, G.J. Kearley, M.G. Nijkamp, C.T. Visser, K.P. de Jong, F.M. Mulder, Chem. Eur. J. 9 (2003) 4764], and is in agreement with what is found in first principles calculations [T. Sagara, J. Klassen, E. Ganz, J. Chem. Phys. 121 (2004) 12543; F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113]. Assignments of the INS spectra is realized using comparison with independently published model calculations [F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113] and structural data [T. Yildirim, M.R. Hartman, Phys. Rev. Lett. 95 (2005) 215504].
Sapin-de Brosses, Emilie; Jolivet, Erwan; Travert, Christophe; Mitton, David; Skalli, Wafa
2012-02-01
A finite element analysis on osteoporotic vertebrae. This study aims to validate subject-specific finite element models (FEMs) derived from a low-dose imaging system (EOS, Biospace Med, France) for the prediction of vertebral strength. The vertebrae are submitted to an eccentric compression force leading to compression and anterior bending. Given the aging population, osteoporosis and vertebral fractures are a major public health issue. A low bone mineral density (BMD) does not always explain incident fractures, and multifactorial analyses are required. In this context, FEMs based on quantitative computed tomography (QCT) have been proposed to predict vertebral strength in vitro or quantify effects of treatments. However, the clinical use of such a model for the in vivo follow-up of the whole spine is limited by the high-radiation dose induced by QCT and the lying position, which does not allow postural assessment with the same modality. Fourteen vertebrae were modeled using a parametric meshing method. The mesh was subject-specific using geometric parameters computed on the 3-dimensional (3D) reconstructions obtained from the EOS biplanar radiographs. The contribution of cortical bone was taken into account by modeling a cortico-cancellous shell whose properties were derived from experimental data. The effect of subject-specific bone Young's moduli derived from EOS vertebral areal BMD was quantified. The 3D position of the point-of-load application and the 3D orientation of the force was faithfully reproduced in the model to compare the predicted strength and experimental strength under the same loading conditions. The relative error of prediction decreased from 43% to 16% (2.5 times) when subject-specific mechanical properties, derived from EOS areal BMD, were implemented in the FEM compared with averaged material properties. The resulting subject-specific FEMs predicted vertebral strength with a level of significance close to the QCT-based models (r adjusted = 0
Simondsen, R P; Weber, P C; Salemme, F R; Tollin, G
1982-12-07
Electron transfer reactions between Clostridum pasteurianum flavodoxin semiquinone and various oxidants [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic [horse heart cytochrome c, ferricyanide, and ferric ethylenediaminetetraacetic acid (EDTA)] have been studied as a function of ionic strength by using stopped-flow spectrophotometry. The cytochrome c reaction is complicated by the existence of two cytochrome species which react at different rates and whose relative concentrations are ionic strength dependent. Only the faster of these two reactions is considered here. At low ionic strength, complex formation between cytochrome c and flavodoxin is indicated by a leveling off of the pseudo-first-order rate constant at high cytochrome c concentration. This is not observed for either ferricyanide or ferric EDTA. For cytochrome c, the rate and association constants for complex formation were found to increase with decreasing ionic strength, consistent with negative charges on flavodoxin interacting with the positively charged cytochrome electron transfer site. Both ferricyanide and ferric EDTA are negatively charged oxidants, and the rate data respond to ionic strength changes as would be predicted for reactants of the same charge sign. These results demonstrate that electrostatic interactions involving negatively charged groups are important in orienting flavodoxin with respect to oxidants during electron transfer. We have also carried out computer modeling studies of putative complexes of flavodoxin with cytochrome c and ferricyanide, which relate their structural properties to both the observed kinetic behavior and some more general features of physiological electron transfer processes. The results of this study are consistent with the ionic strength behavior described above.
Commitee III.1 Ultimate Strength
Jensen, Jørgen Juncher
1997-01-01
This report addresses the subject of ductile collapse of ships and offshore structures and their components due to buckling and excessive yielding under overload conditions. Consideration is given to load-deflection predictions for components with fabrication imperfections and in-service damage a...... and to the ultimate strength and post-ultimate behaviour of structural systems in order to identify the reserve strength. The effect of uncertainties in the modelling on the strength predictions is highlighted in two design examples....
Commitee III.1 Ultimate Strength
Jensen, Jørgen Juncher
1997-01-01
This report addresses the subject of ductile collapse of ships and offshore structures and their components due to buckling and excessive yielding under overload conditions. Consideration is given to load-deflection predictions for components with fabrication imperfections and in-service damage a...... and to the ultimate strength and post-ultimate behaviour of structural systems in order to identify the reserve strength. The effect of uncertainties in the modelling on the strength predictions is highlighted in two design examples....
Mohsen Shanbeh
2011-01-01
Full Text Available One of the main methods to reduce the production costs is waste recycling which is the most important challenge for the future. Cotton wastes collected from ginning process have desirable properties which could be used during spinning process. The purpose of this study was to develop predictive models of breaking strength and mass irregularity (CV% of cotton waste rotor-spun yarns containing cotton waste collected from ginning process by using the artificial neural network trained with backpropagation algorithm. Artificial neural network models have been developed based on rotor diameter, rotor speed, navel type, opener roller speed, ginning waste proportion and yarn linear density as input parameters. The parameters of artificial neural network model, namely, learning, and momentum rate, number of hidden layers and number of hidden processing elements (neurons were optimized to get the best predictive models. The findings showed that the breaking strength and mass irregularity of rotor spun yarns could be predicted satisfactorily by artificial neural network. The maximum error in predicting the breaking strength and mass irregularity of testing data was 8.34% and 6.65%, respectively.
The Distribution of Subjective Memory Strength: List Strength and Response Bias
Criss, Amy H.
2009-01-01
Models of recognition memory assume that memory decisions are based partially on the subjective strength of the test item. Models agree that the subjective strength of targets increases with additional time for encoding however the origin of the subjective strength of foils remains disputed. Under the fixed strength assumption the distribution of…
Arockia Bazil Raj, A; Arputha Vijaya Selvi, J; Durairaj, S
2015-02-01
Atmospheric parameters strongly affect the performance of free-space optical communication (FSOC) systems when the optical wave is propagating through the inhomogeneous turbulence transmission medium. Developing a model to get an accurate prediction of the atmospheric turbulence strength (C(n)(2)) according to meteorological parameters (weather data) becomes significant to understand the behavior of the FSOC channel during different seasons. The construction of a dedicated free-space optical link for the range of 0.5 km at an altitude of 15.25 m built at Thanjavur (Tamil Nadu) is described in this paper. The power level and beam centroid information of the received signal are measured continuously with weather data at the same time using an optoelectronic assembly and the developed weather station, respectively, and are recorded in a data-logging computer. Existing models that exhibit relatively fewer prediction errors are briefed and are selected for comparative analysis. Measured weather data (as input factors) and C(n)(2) (as a response factor) of size [177,147×4] are used for linear regression analysis and to design mathematical models more suitable in the test field. Along with the model formulation methodologies, we have presented the contributions of the input factors' individual and combined effects on the response surface and the coefficient of determination (R(2)) estimated using analysis of variance tools. An R(2) value of 98.93% is obtained using the new model, model equation V, from a confirmatory test conducted with a testing data set of size [2000×4]. In addition, the prediction accuracies of the selected and the new models are investigated during different seasons in a one-year period using the statistics of day, week-averaged, month-averaged, and seasonal-averaged diurnal Cn2 profiles, and are verified in terms of the sum of absolute error (SAE). A Cn2 prediction maximum average SAE of 2.3×10(-13) m(-2/3) is achieved using the new model in
Liu, Y.; Bhamji, I.; Withers, P. J.; Wolfe, D. E.; Motta, A. T.; Preuss, M.
2015-11-01
This paper investigates the residual stresses and interfacial shear strength of a TiAlN coating on Zr-Nb-Sn-Fe alloy (ZIRLO™) substrate designed to improve corrosion resistance of fuel cladding used in water-cooled nuclear reactors, both during normal and exceptional conditions, e.g. a loss of coolant event (LOCA). The distribution and maximum value of the interfacial shear strength has been estimated using a modified shear-lag model. The parameters critical to this analysis were determined experimentally. From these input parameters the interfacial shear strength between the TiAlN coating and ZIRLO™ substrate was inferred to be around 120 MPa. It is worth noting that the apparent strength of the coating is high (∼3.4 GPa). However, this is predominantly due to the large compressive residuals stress (3 GPa in compression), which must be overcome for the coating to fail in tension, which happens at a load just 150 MPa in excess of this.
Ultimate Strength, Committee III.1
Simonsen, Bo Cerup; Estefan, S.; Fasano, E.;
2003-01-01
Concern for the ductile of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and inservice damage and degradation on reserve strength. Uncertainties in strength models for design shall...
Schmid, Gernot; Hirtl, Rene
2016-06-01
The reference levels and maximum permissible exposure values for magnetic fields that are currently used have been derived from basic restrictions under the assumption of upright standing body models in a standard posture, i.e. with arms laterally down and without contact with metallic objects. Moreover, if anatomical modelling of the body was used at all, the skin was represented as a single homogeneous tissue layer. In the present paper we addressed the possible impacts of posture and skin modelling in scenarios of exposure to a 50 Hz uniform magnetic field on the in situ electric field strength in peripheral tissues, which must be limited in order to avoid peripheral nerve stimulation. We considered different body postures including situations where body parts form large induction loops (e.g. clasped hands) with skin-to-skin and skin-to-metal contact spots and compared the results obtained with a homogeneous single-layer skin model to results obtained with a more realistic two-layer skin representation consisting of a low-conductivity stratum corneum layer on top of a combined layer for the cellular epidermis and dermis. Our results clearly indicated that postures with loops formed of body parts may lead to substantially higher maximum values of induced in situ electric field strengths than in the case of standard postures due to a highly concentrated current density and in situ electric field strength in the skin-to-skin and skin-to-metal contact regions. With a homogeneous single-layer skin, as is used for even the most recent anatomical body models in exposure assessment, the in situ electric field strength may exceed the basic restrictions in such situations, even when the reference levels and maximum permissible exposure values are not exceeded. However, when using the more realistic two-layer skin model the obtained in situ electric field strengths were substantially lower and no violations of the basic restrictions occurred, which can be explained by the
Zhenjun He; Yupu Song
2008-01-01
An orthotropic constitutive relationship with temperature parameters for plain highstrength high-performance concrete (HSHPC) under biaxial compression is developed. It is based on the experiments performed for characterizing the strength and deformation behavior at two strength levels of HSHPC at 7 different stress ratios including α = σ2 : σ3 = 0.00 : -1, -0.20 : -1, -0.30 : -1, -0.40 : -1, -0.50 : -1, -0.75 : -1, -1.00 : -1, after the exposure to normal and high temperatures of 20, 200, 300, 400, 500 and 600℃, and using a large static-dynamic true triaxial machine. The biaxial tests were performed on 100 mm × 100 mm × 100 mm cubic specimens, and friction-reducing pads were used consisting of three layers of plastic membrane with glycerine in-between for the compressive loading plane. Based on the experimental results, failure modes of HSHPC specimens were described. The principal static compressive strengths, strains at the peak stress and stress-strain curves were measured; and the influence of the temperature and stress ratios on them was also analyzed. The experimental results showed that the uniaxial compressive strength of plain HSHPC after exposure to high temperatures does not decrease dramatically with the increase of temperature. The ratio of the biaxial to its uniaxial compressive strength depends on the stress ratios and brittleness-stiffness of HSHPC after exposure to different temperature levels. Comparison of the stress-strain results obtained from the theoretical model and the experimental data indicates good agreement.
Strength-permeability Model of Pervious Cement Concrete%透水性混凝土强度-渗透性模型试验研究
崔新壮; 欧金秋; 张娜; 高智珺; 隋伟
2013-01-01
High permeability is an important characteristic of pervious concrete . For the existing permeability testing devices of pervious concrete ,the specimen sidewall leakage is serious due to the large numbers of open pores on the surface of specimens . To solve the problem ,a new permeability testing method for pervious concrete was developed and a composite sidewall structure with waterproof daub , flexible rubber cushion and rigid sleeve sidewall was proposed .Meanwhile ,the strength and permeability of pervious cement concrete are incompatible with a reciprocal relationship .However ,limited research has been conducted on the relationship between them .Effects of water-cement ratio (W/C) ,aggregate-cement ratio and porosity on the properties of pervious concrete , including strength and permeability , were studied . Furthermore , strength-porosity model , permeability-porosity model and strength-permeability model were established .Tests reveal that :a) There is an optimum W/C of pervious concrete ,at which strength reaches the maximum ;b) The relationship between the strength and W/C shows a downward quadratic curve ,and the permeability is proportional to porosity and aggregate-cement ratio ;c) The relationship between strength and permeability of pervious cement concrete can be well fitted with the Lorentzian function ,and the strength decreases when the permeability increases ,but the rate of reduction decreases gradually .The optimum combination of strength and permeability should be determined based on the specific engineering requirements in design .%高透水性是透水性混凝土的重要特征，现有的透水性混凝土渗透系数测试装置存在试件侧壁渗漏问题，为此提出了一种试件侧面防水涂抹＋柔性夹层＋套筒刚性壁的防侧漏复合结构，提高了渗透系数测试精度。透水性混凝土的透水性和强度是一对矛盾体，此消彼长，但目前对它们之间关系缺乏系统的研究。通过
MODEL FOR PREDICTING SHEAR STRENGTH OF SATURATED SOFT CLAY AFTER IMPACT LOADING%冲击荷载作用下饱和软粘土强度预测模型
白冰
2004-01-01
Previous studies showed that the samples of saturated soft clay undergoing several stages of impact loading and reconsolidation show obvious quasi-overconsolidation state,and have an increased shear strength. In this paper,the definition of quasi-overconsolidation ratio is given,and furthermore a model for predicting the shear strength of saturated soft clay after impact loading is suggested. In this model,the conditions of partial drainage and stages of impact are taken into account. The calculation results by the proposed model are in good accordance with test data. Besides,the effect of disturbance consolidation on the undrained shear strength by this model is discussed.
Falland-Cheung, Lisa; Waddell, J Neil; Chun Li, Kai; Tong, Darryl; Brunton, Paul
2017-04-01
Conducting in vitro research for forensic, impact and injury simulation modelling generally involves the use of a skull simulant with mechanical properties similar to those found in the human skull. For this study epoxy resin, fibre filled epoxy resin, 3D-printing filaments (PETG, PLA) and self-cure acrylic denture base resin were used to fabricate the specimens (n=20 per material group), according to ISO 527-2 IBB and ISO20795-1. Tensile and flexural testing in a universal testing machine was used to measure their tensile/flexural elastic modulus and strength. The results showed that the epoxy resin and fibre filled epoxy resin had similar tensile elastic moduli (no statistical significant difference) with lower values observed for the other materials. The fibre filled epoxy resin had a considerably higher flexural elastic modulus and strength, possibly attributed to the presence of fibres. Of the simulants tested, epoxy resin had an elastic modulus and flexural strength close to that of mean human skull values reported in the literature, and thus can be considered as a suitable skull simulant for a skin/skull/brain model for lower impact forces that do not exceed the fracture stress. For higher impact forces a 3D printing filament (PLA) may be a more suitable skull simulant material, due to its closer match to fracture stresses found in human skull bone. Influencing factors were also anisotropy, heterogeneity and viscoelasticity of human skull bone and simulant specimens. Copyright © 2017 Elsevier Ltd. All rights reserved.
Majid Mapkhot Goaill
2013-01-01
Full Text Available Many recent studies emphasized the importance of retailer's satisfaction and commitment to manufacturer/supplier. These studies investigated the relationship between them as an overall relationship. However, there is a dearth of studies that investigated the dimensions of retailer's satisfaction on commitment, and analyzed the mysterious relationship via strength of manufacturer's brands as a moderating effect. Therefore, this study is an attempt to provide a value conceptual model that explains the theoretical linkages existing between dimensions of retailer's satisfaction and commitment, and tries to explain the in-depth meaning of this relationship through the moderating effect of manufacturer's brand strength in the context of social exchange theory. Additionally, hypotheses on the association between the constructs are presented as a basis for further study.
Direct shear strength model of rock mass with coplanar intermittent joints%共面断续节理岩体直剪强度特性模型
胡波; 王思敬; 刘晓丽
2012-01-01
采用理论分析和模型试验相结合方法,对共面闭合断续节理岩体直剪强度特性进行分析和研究.引入法向变形协调条件,基于Mohr-Coulomb理论,推导共面断续节理岩体模型的直剪强度公式.模型试验表明:全应力-应变曲线主要经历了线弹性增长、节理面错动、次生裂纹起裂稳态扩展、节理面贯通破坏和残余强度5个阶段；剪切应力峰值和残余强度都随正应力的增大而增大,而变形特性随正应力的变化规律性不强；抗剪峰值强度随节理连通率的增大而减小,低连通率时强度下降速度慢；节理分布形态对强度也有影响,节理在两边分布的试样强度普遍高于节理在中间的；理论计算结果与试验值吻合较好,能较好描述共面断续节理岩体的直剪强度特征.%According to theoretical analysis and model test, the direct shear strength behavior of rock mass with coplanar close intermittent joints was investigated. Through introducing deformation compatibility equation at normal direction, the direct shear strength formulation was deduced based on the Mohr-Coulomb theory. According to the complete stress strain curve obtained from model tests, there are five typical stages in the failure process with linear elastic increment, slippage of the joints, steady development of post-cracking, the coalescence failure of discontinuous joints and the residual strength. The peak and residual strength are increased by the increase of normal stress with poor relationship between deformation property and normal stress. The peak strength decreases with the increase of the joint connectivity rate, and the drop velocity is slow at low connectivity rate. The joint distribution has influence on the strength of rock mass, and the strength of model with joints on edge is bigger than that of the model with joints in the middle. The theoretical calculation results are in good consistency with experimental results to give
Lambert-Perlade, A.; Sturel, T.; Gourgues, A. F.; Besson, J.; Pineau, A.
2004-03-01
The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of martensite-austenite (M-A) constituents and of “crystallographic” bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probabilistic models (the “Master-curve” (MC) approach, the Beremin model, and a “double-barrier” (DB) model) are applied to account for the ductile-to-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.
Zhang, Ning; Shahsavari, Rouzbeh
2016-11-01
As the most widely used manufactured material on Earth, concrete poses serious societal and environmental concerns which call for innovative strategies to develop greener concrete with improved strength and toughness, properties that are exclusive in man-made materials. Herein, we focus on calcium silicate hydrate (C-S-H), the major binding phase of all Portland cement concretes, and study how engineering its nanovoids and portlandite particle inclusions can impart a balance of strength, toughness and stiffness. By performing an extensive +600 molecular dynamics simulations coupled with statistical analysis tools, our results provide new evidence of ductile fracture mechanisms in C-S-H - reminiscent of crystalline alloys and ductile metals - decoding the interplay between the crack growth, nanovoid/particle inclusions, and stoichiometry, which dictates the crystalline versus amorphous nature of the underlying matrix. We found that introduction of voids and portlandite particles can significantly increase toughness and ductility, specially in C-S-H with more amorphous matrices, mainly owing to competing mechanisms of crack deflection, voids coalescence, internal necking, accommodation, and geometry alteration of individual voids/particles, which together regulate toughness versus strength. Furthermore, utilizing a comprehensive global sensitivity analysis on random configuration-property relations, we show that the mean diameter of voids/particles is the most critical statistical parameter influencing the mechanical properties of C-S-H, irrespective of stoichiometry or crystalline or amorphous nature of the matrix. This study provides new fundamental insights, design guidelines, and de novo strategies to turn the brittle C-S-H into a ductile material, impacting modern engineering of strong and tough concrete infrastructures and potentially other complex brittle materials.
Cattell, R. B.; And Others
1985-01-01
Strength, super ego strength, ego, self sentiment, and both forms of the High School Personality Questionnaire were administered to 688 brothers and 2973 unrelated boys. Multiple abstract variance analysis (MAVA) Q-Data, and maximum likelihood analysis were used to assess heritability in their personality control system. (ABB)
Gerharz, E.W.; Mosekilde, Li.; Thomsen, J.S.
2003-01-01
; colocystoplasty; or sham operation (controls). After 8 months the lumbar vertebrae, femora, and tibiae were harvested at necropsy. Bone strength was assessed biomechanically at four different skeletal sites: vertebra L3, femoral middiaphysis, femoral neck, and distal femoral metaphysis. Bone mass and architecture...... were assessed using standard static histomorphometry of the proximal tibial metaphysis (trabecular bone volume [BV/TV]; trabecular number [Tb.N]) and ash weight. Statistically significant differences of biomechanical parameters between groups were observed at three skeletal sites with corresponding......, this is the first experimental study to demonstrate the relevance of histomorphometrically proven bone loss after enterocystoplasty in terms of biomechanical variables....
de Blas, Jorge; Franco, Enrico; Mishima, Satoshi; Pierini, Maurizio; Reina, Laura; Silvestrini, Luca
2016-01-01
We present results from a state-of-the-art fit of electroweak precision observables and Higgs-boson signal-strength measurements performed using 7 and 8 TeV data from the Large Hadron Collider. Based on the HEPfit package, our study updates the traditional fit of electroweak precision observables and extends it to include Higgs-boson measurements. As a result we obtain constraints on new physics corrections to both electroweak observables and Higgs-boson couplings. We present the projected accuracy of the fit taking into account the expected sensitivities at future colliders.
Large low-energy M1 strength for ^{56,57}Fe within the nuclear shell model.
Brown, B Alex; Larsen, A C
2014-12-19
A strong enhancement at low γ-ray energies has recently been discovered in the γ-ray strength function of ^{56,57}Fe. In this work, we have for the first time obtained theoretical γ decay spectra for states up to ≈8 MeV in excitation for ^{56,57}Fe. We find large B(M1) values for low γ-ray energies that provide an explanation for the experimental observations. The role of mixed E2 transitions for the low-energy enhancement is addressed theoretically for the first time, and it is found that they contribute a rather small fraction. Our calculations clearly show that the high-ℓ(=f) diagonal terms are most important for the strong low-energy M1 transitions. As such types of 0ℏω transitions are expected for all nuclei, our results indicate that a low-energy M1 enhancement should be present throughout the nuclear chart. This could have far-reaching consequences for our understanding of the M1 strength function at high excitation energies, with profound implications for astrophysical reaction rates.
Hreniuc, V.; Hreniuc, A.; Pescaru, A.
2017-08-01
Solving a general strength problem of a ship hull may be done using analytical approaches which are useful to deduce the buoyancy forces distribution, the weighting forces distribution along the hull and the geometrical characteristics of the sections. These data are used to draw the free body diagrams and to compute the stresses. The general strength problems require a large amount of calculi, therefore it is interesting how a computer may be used to solve such problems. Using computer programming an engineer may conceive software instruments based on analytical approaches. However, before developing the computer code the research topic must be thoroughly analysed, in this way being reached a meta-level of understanding of the problem. The following stage is to conceive an appropriate development strategy of the original software instruments useful for the rapid development of computer aided analytical models. The geometrical characteristics of the sections may be computed using a bool algebra that operates with ‘simple’ geometrical shapes. By ‘simple’ we mean that for the according shapes we have direct calculus relations. In the set of ‘simple’ shapes we also have geometrical entities bounded by curves approximated as spline functions or as polygons. To conclude, computer programming offers the necessary support to solve general strength ship hull problems using analytical methods.
Lee, Won Hee; Lisanby, Sarah H.; Laine, Andrew F.; Peterchev, Angel V.
2017-01-01
Background This study examines the strength and spatial distribution of the electric field induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). Methods The electric field induced by standard (bilateral, right unilateral, and bifrontal) and experimental (focal electrically administered seizure therapy and frontomedial) ECT electrode configurations as well as a circular MST coil configuration was simulated in an anatomically realistic finite element model of the human head. Maps of the electric field strength relative to an estimated neural activation threshold were used to evaluate the stimulation strength and focality in specific brain regions of interest for these ECT and MST paradigms and various stimulus current amplitudes. Results The standard ECT configurations and current amplitude of 800–900 mA produced the strongest overall stimulation with median of 1.8–2.9 times neural activation threshold and more than 94% of the brain volume stimulated at suprathreshold level. All standard ECT electrode placements exposed the hippocampi to suprathreshold electric field, although there were differences across modalities with bilateral and right unilateral producing respectively the strongest and weakest hippocampal stimulation. MST stimulation is up to 9 times weaker compared to conventional ECT, resulting in direct activation of only 21% of the brain. Reducing the stimulus current amplitude can make ECT as focal as MST. Conclusions The relative differences in electric field strength may be a contributing factor for the cognitive sparing observed with right unilateral compared to bilateral ECT, and MST compared to right unilateral ECT. These simulations could help understand the mechanisms of seizure therapies and develop interventions with superior risk/benefit ratio. PMID:27318858
Ito, G.; Moore, G. F.; Olive, J. A. L.; Weiss, J. R.
2015-12-01
Whereas seaward-verging thrust faults are, by far, the most common large faults associated with accretionary wedges, the importance of the globally rare, landward verging thrusts has recently been highlighted given the prominence of landward vergence along the Cascadia margin as well as along the Andaman-Sumatra subduction zone, especially in the rupture area of the great 2004 earthquake. The mechanical processes that lead to seaward- versus landward-verging thrusts in accretionary wedges has long been a topic of debate. A weak frictional décollement is one explanation that indeed promotes landward vergence, but not only so, because the typical pattern is of dual verging conjugate faults. A non-brittle, ductile décollement is a second explanation that has been shown in the laboratory to produce a wide sequence of only landward-verging thrusts, but the mechanical causes are not well understood and numerical modeling studies have yet to reproduce this behavior. A seaward-dipping backstop is a third explanation; it promotes landward vergence locally, but more distally the backstop effects diminish and the sense of vergence transitions back to seaward. Mohr-Coulomb and minimum work theory predict that landward vergence should predominate when the direction of maximum principal compression dips landward. We hypothesize that such a condition can arise due to the migration of pore fluids and the associated spatial heterogeneity in frictional strength within the wedge. We test this hypothesis using 2-D numerical models that use a finite-difference, particle-in-cell method for simulating the deformation of an accretionary wedge with a viscoelastic-plastic rheology. With a uniform internal frictional strength, the calculations reproduce many of the faulting behaviors seen in prior laboratory and numerical modeling studies. We are exploring the impacts of heterogeneity in pore fluid pressure and frictional strength on the pattern and vergence of thrust faults.
M.ª José HERNÁNDEZ AMORÓS
2013-01-01
Full Text Available This paper is the result of a research process developed to know which the students’ perceptions about the program of Secondary Teachers Training are, during the academic course 2011/2012, when it has already been developed for three years. For that, we have reached some information from 227 students who have completed an anonymous open questionnaire. It has been used an evaluative methodology which is typical of qualitative paradigm. The information has been analyzed by AQUAD 6 software program (Huber, 2006, which has allowed the classification of the different codes in nine categories that help us to organize the information and reach some conclusions. These dimensions are: assessment time and teachers, teachers’ development through training, training difficulties, benefits of training, concept of education, interest in teaching, expectations of professional development, basic principles of educational work and suggestions for improvement. Results, therefore, are useful for doing several reformulations in curriculum and for enhance strengths of curriculum, identified by the students.
Ardawi, Mohammed-Salleh M; Badawoud, Mohammed H; Hassan, Sherif M; Rouzi, Abdulrahim A; Ardawi, Jumanah M S; AlNosani, Nouf M; Qari, Mohammed H; Mousa, Shaker A
2016-02-01
Lycopene supplementation decreases oxidative stress and exhibits beneficial effects on bone health, but the mechanisms through which it alters bone metabolism in vivo remain unclear. The present study aims to evaluate the effects of lycopene treatment on postmenopausal osteoporosis. Six-month-old female Wistar rats (n=264) were sham-operated (SHAM) or ovariectomized (OVX). The SHAM group received oral vehicle only and the OVX rats were randomized into five groups receiving oral daily lycopene treatment (mg/kg body weight per day): 0 OVX (control), 15 OVX, 30 OVX, and 45 OVX, and one group receiving alendronate (ALN) (2μg/kg body weight per day), for 12weeks. Bone densitometry measurements, bone turnover markers, biomechanical testing, and histomorphometric analysis were conducted. Micro computed tomography was also used to evaluate changes in microarchitecture. Lycopene treatment suppressed the OVX-induced increase in bone turnover, as indicated by changes in biomarkers of bone metabolism: serum osteocalcin (s-OC), serum N-terminal propeptide of type 1 collagen (s-PINP), serum crosslinked carboxyterminal telopeptides (s-CTX-1), and urinary deoxypyridinoline (u-DPD). Significant improvement in OVX-induced loss of bone mass, bone strength, and microarchitectural deterioration was observed in lycopene-treated OVX animals. These effects were observed mainly at sites rich in trabecular bone, with less effect in cortical bone. Lycopene treatment down-regulated osteoclast differentiation concurrent with up-regulating osteoblast together with glutathione peroxidase (GPx) catalase (CAT) and superoxide dismutase (SOD) activities. These findings demonstrate that lycopene treatment in OVX rats primarily suppressed bone turnover to restore bone strength and microarchitecture.
Samuelson, J. E.; Koenen, M.; Tambach, T.
2011-12-01
Long-term sequestration of CO2, harvested from point sources such as coal burning power plants and cement manufactories, in depleted oil and gas reservoirs is considered to be one of the most attractive options for short- to medium-term mitigation of anthropogenic forcing of climate change. Many such reservoirs are laterally bounded by low-permeability fault zones which could potentially be reactivated either by changes in stress state during and after the injection process, and also by alterations in the frictional strength of fault gouge material. Of additional concern is how the stability of the fault zones will change as a result of the influence of supercritical CO2, specifically whether the rate and state frictional constitutive parameters (a, b, DC) of the fault zone will change in such a way as to enhance the likelihood of seismic activity on the fault zone. The short-term influence of CO2 on frictional strength and stability of simulated fault gouges prepared from mixtures of cap rock and reservoir rock has been analyzed recently [Samuelson et al., In Prep.], concluding that CO2 has little influence on frictional constitutive behavior on the timescale of a typical experiment (CO2 is intended to be sequestered, we have chosen to model the long-term mineralogical alteration of a fault zone with a simple starting mineralogy of 33% quartz, 33% illite, and 33% dolomite by weight using the geochemical modeling program PHREEQC and the THERMODDEM database, assuming instantaneous mixing of the CO2 with the fault gouge. The geochemical modeling predicts that equilibrium will be reached between fault gouge, reservoir brine, and CO2 in approximately 440 years, assuming an average grain-size (davg) of 20 μm, and ~90 years assuming davg =4 μm, a reasonable range of grain-sizes for natural fault gouges. The main change to gouge mineralogy comes from the complete dissolution of illite, and the precipitation of muscovite. The final equilibrium mineralogy of the fault
Mohammad Doustmohammadi
2014-12-01
Full Text Available Uniaxial compressive strength (UCS is one of the most significant factors on the stability of underground excavation projects. Most of the time, this factor can be obtained by exploratory boreholes evaluation. Due to the large distance between exploratory boreholes in the majority of geotechnical projects, the application of geostatistical methods has increased as an estimator of rock mass properties. The present paper ties the estimation of UCS values of intact rock to the distance between boreholes of the Behesht-Abad tunnel in central Iran, using SGEMS geostatistical program. Variography showed that UCS estimation of intact rock using geostatistical methods is reasonable. The model establishment and validation was done after assessment that the model was trustworthy. Cross validation proved the high accuracy (98% and reliability of the model to estimate uniaxial compressive strength. The UCS values were then estimated along the tunnel axis. Moreover, using geostatistical estimation led to better identification of the pros and cons of geotechnical explorations in each location of tunnel route.
Zare, Yasser
2016-05-15
In this paper, "a" interfacial parameter in Nicolais-Narkis model is expressed by thickness "ri" and strength "σi" of interphase between polymer and nanoparticles as well as material properties. "a" parameter is connected to "B1" interfacial parameter in modified Pukanszky model and the effects of "ri" and "σi" on "a" are explained. The negligible difference between "a" values calculated by fitting the experimental results to Nicolais-Narkis model and also, by "B1" results confirms the accurateness of the suggested relation between "a" and "B1" parameters. Additionally, an inverse relation is found between "a" and "B1" parameters for nanocomposites containing spherical nanoparticles. The results demonstrate that the slight levels of "ri" and "σi" data give a large value of "a" which indicates the poor interfacial adhesion.
Kristen D. Alexander
2012-01-01
Full Text Available We have employed capillary force deposition on ion beam patterned substrates to fabricate chains of 60 nm gold nanospheres ranging in length from 1 to 9 nanoparticles. Measurements of the surface-averaged SERS enhancement factor strength for these chains were then compared to the numerical predictions. The SERS enhancement conformed to theoretical predictions in the case of only a few chains, with the vast majority of chains tested not matching such behavior. Although all of the nanoparticle chains appear identical under electron microscope observation, the extreme sensitivity of the SERS enhancement to nanoscale morphology renders current nanofabrication methods insufficient for consistent production of coupled nanoparticle chains. Notwithstanding this fact, the aggregate data also confirmed that nanoparticle dimers offer a large improvement over the monomer enhancement while conclusively showing that, within the limitations imposed by current state-of-the-art nanofabrication techniques, chains comprising more than two nanoparticles provide only a marginal signal boost over the already considerable dimer enhancement.
Arora, Vivek K.; Scinocca, John F.
2016-07-01
Earth system models (ESMs) explicitly simulate the interactions between the physical climate system components and biogeochemical cycles. Physical and biogeochemical aspects of ESMs are routinely compared against their observation-based counterparts to assess model performance and to evaluate how this performance is affected by ongoing model development. Here, we assess the performance of version 4.2 of the Canadian Earth system model against four land carbon-cycle-focused, observation-based determinants of the global carbon cycle and the historical global carbon budget over the 1850-2005 period. Our objective is to constrain the strength of the terrestrial CO2 fertilization effect, which is known to be the most uncertain of all carbon-cycle feedbacks. The observation-based determinants include (1) globally averaged atmospheric CO2 concentration, (2) cumulative atmosphere-land CO2 flux, (3) atmosphere-land CO2 flux for the decades of 1960s, 1970s, 1980s, 1990s, and 2000s, and (4) the amplitude of the globally averaged annual CO2 cycle and its increase over the 1980 to 2005 period. The optimal simulation that satisfies constraints imposed by the first three determinants yields a net primary productivity (NPP) increase from ˜ 58 Pg C year-1 in 1850 to about ˜ 74 Pg C year-1 in 2005; an increase of ˜ 27 % over the 1850-2005 period. The simulated loss in the global soil carbon amount due to anthropogenic land use change (LUC) over the historical period is also broadly consistent with empirical estimates. Yet, it remains possible that these determinants of the global carbon cycle are insufficient to adequately constrain the historical carbon budget, and consequently the strength of terrestrial CO2 fertilization effect as it is represented in the model, given the large uncertainty associated with LUC emissions over the historical period.
Strength dynamics of weighted evolving networks
Wu Jian-Jun; Gao Zi-You; Sun Hui-Jun
2007-01-01
In this paper, a simple model for the strength dynamics of weighted evolving networks is proposed to characterize the weighted networks. By considering the congestion effects, this approach can yield power law strength distribution appeared on the many real weighted networks, such as traffic networks, internet networks. Besides, the relationship between strength and degree is given. Numerical simulations indicate that the strength distribution is strongly related to the strength dynamics decline. The model also provides us with a better description of the real weighted networks.
ZHANG Xiaogang; SONG Yupu; WU Zhimin
2005-01-01
By means of fracture testing on roller-compacted concrete (RCC) three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer's optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.
Strength and failure modes of ceramic multilayers
Sørensen, Bent F.; Toftegaard, Helmuth Langmaack; Linderoth, Søren
2012-01-01
A model was developed for the prediction of the tensile strength of thin, symmetric 3-layer sandwich specimens. The model predictions rationalize the effect of heat-treatment temperature on the strength of sandwich specimens consisting of an YSZ (Yttria-Stabilized Zirconia) substrate coated...... and propagating into the substrate. These predictions are consistent with microstructural observations of the fracture surfaces. A good agreement was found between the measured strength values and model predictions. © 2012 Elsevier Ltd. All rights reserved....
Lim, Young-il; Jørgensen, Sten Bay; Kim, In-Ho
2005-01-01
A packed-bed chromatographic model developed in this study includes adsorption isotherms considering steric mass action (SMA) as well as non-linearity in liquid/solid phases, adsorption kinetics and mass transport. For solving the nonlinear and nonequilibrium adsorption model described by a partial...... differential algebraic equation (PDAE) system, a fast and accurate numerical method (i.e., conservation element/solution element (CE/SE) method), is proposed. Sensitivity and elasticity of the model parameters (e.g., steric/shape factors, adsorption heat coefficient, effective protein charge, equilibrium...
Bourg, I.C.; Sposito, G.; Bourg, A.C.M.
2008-08-15
Assessments of bentonite barrier performance in waste management scenarios require an accurate description of the diffusion of water and solutes through the barrier. A two-compartment macropore/nanopore model (on which smectite interlayer nanopores are treated as a distinct compartment of the overall pore space) was applied to describe the diffusion of {sup 22}Na{sup +} in compacted, water-saturated Na-bentonites and then compared with the well-known surface diffusion model. The two-compartment model successfully predicted the observed weak ionic strength dependence of the apparent diffusion coefficient (D{sub a}) of Na{sup +}, whereas the surface diffusion model did not, thus confirming previous research indicating the strong influence of interlayer nanopores on the properties of smectite clay barriers. Since bentonite mechanical properties and pore water chemistry have been described successfully with two-compartment models, the results in the present study represent an important contribution toward the construction of a comprehensive two-compartment model of compacted bentonite barriers.
Lee, Jong-Won; Harris, Charles E.
1990-01-01
A mathematical model based on the Euler-Bermoulli beam theory is proposed for predicting the effective Young's moduli of piecewise isotropic composite laminates with local ply curvatures in the main load-carrying layers. Strains in corrugated layers, in-phase layers, and out-of-phase layers are predicted for various geometries and material configurations by assuming matrix layers as elastic foundations of different spring constants. The effective Young's moduli measured from corrugated aluminum specimens and aluminum/epoxy specimens with in-phase and out-of-phase wavy patterns coincide very well with the model predictions. Moire fringe analysis of an in-phase specimen and an out-of-phase specimen are also presented, confirming the main assumption of the model related to the elastic constraint due to the matrix layers. The present model is also compared with the experimental results and other models, including the microbuckling models, published in the literature. The results of the present study show that even a very small-scale local ply curvature produces a noticeable effect on the mechanical constitutive behavior of a laminated composite.
Stephenson, R. A.; Ershov, A.
2001-12-01
One way in which theoretical rheological models of the lithosphere can be constrained by geological data is through estimations of the lithosphere's integrated strength. When an applied force exceeds this, then the lithosphere should lose its integrity and undergo irreversible deformation (WLF - "whole lithosphere failure"). The geological expression of this kind of deformational regime is the development of rifts (in extension) and inverted structures (in compression). By considering intracratonic structures rather than marginal ones it is possible to exclude additional extraneous influences and infer the net effect of intraplate stresses. Here, actual intraplate structures are considered in terms of a rheological model in which the non-brittle part of the lithosphere deforms viscously (by creep) in response to applied forces. This is in contrast to conventional estimations of total lithosphere strength based on "yield stress envelopes" in which "ductile" deformation is taken to be time-invariant (plastic). Taking into account the implications of adopting a viscous rheology in place of a plastic one in evaluating the "strength" of the lithosphere, it is necessary to incorporate the time-dependence of stresses, strains and strain rates and also the dependence of the bulk strain rate on the total applied force. This means that the duration of loading of tectonic forces prior to eventual rifting or inversion is also an important model variable. The mechanism that controls strain rate and stress distribution in the lithosphere prior to WLF in the model is one of stress redistribution from ductile deformation zones into elastic ones, as determined by stress relaxation in the former and stress amplification in the latter given an assumed constant applied boundary force. A stable equilibrium regime of deformation occurs when, at each point within the lithosphere, the stress reduction effected by viscous relaxation equals the stress increase effected by the applied force
Takeshita, T.
2014-12-01
Seismologists have now believed that the fault interface is characterized by the asperity-matrix structure, where the upper and lower plates are strongly coupled at the asperity, and the matrix, which surrounds the asperity, is deformed by creeping. Earthquakes are generated by dynamic rupture only in the non-creeping hard asperity, where the strain energy is accumulated if the asperity and matrix are mechanically coupled to a certain degree. In this presentation, we will argue that this structure is developed as brittle fracturing proceeds aided by dissolution-precipitation creep in particular at the brittle-ductile transition zone, which leads to the strength reduction and seimogenesis in both crust and subduction zones. We have been studying deformation processes and mechanisms in rocks at brittle-ductile transition conditions, based on microstructural analyses in naturally deformed rocks. For example, we reported that pervasive micro-faulting in the high-P/T Sambagawa quartz schist at brittle-ductile transition conditions, where a volume fraction of micro-shear zones consisting of both very-fine grained dynamically recrystallized quartz and white mica increased with increasing deformation (Takeshita and El-Fakharani, 2013). We believe that the resultant structure, "undeformed lenses surrounded by microshear zones" can be correlated with the asperity-matrix structure in the thin section scale, which could have occurred in the mesoscopic to macroscopic scales (cf. Schrank et al., 2008). It is inferred that the rocks became softened with increasing volume fraction of micro-shear zones, because dissolution-precipitation creep could have occurred at low differential stresses in the sheared zones. Further, cataclasites were formed along the Median Tectonic Line in the Cretaceous to Paleogene, where new minerals precipitated from fluids in the space created by fracturing at the conditions of brittle-ductile transition. The fracturing was accompanied by element
Brilli, Lorenzo; Bechini, Luca; Bindi, Marco; Carozzi, Marco; Cavalli, Daniele; Conant, Richard; Dorich, Cristopher D; Doro, Luca; Ehrhardt, Fiona; Farina, Roberta; Ferrise, Roberto; Fitton, Nuala; Francaviglia, Rosa; Grace, Peter; Iocola, Ileana; Klumpp, Katja; Léonard, Joël; Martin, Raphaël; Massad, Raia Silvia; Recous, Sylvie; Seddaiu, Giovanna; Sharp, Joanna; Smith, Pete; Smith, Ward N; Soussana, Jean-Francois; Bellocchi, Gianni
2017-11-15
Biogeochemical simulation models are important tools for describing and quantifying the contribution of agricultural systems to C sequestration and GHG source/sink status. The abundance of simulation tools developed over recent decades, however, creates a difficulty because predictions from different models show large variability. Discrepancies between the conclusions of different modelling studies are often ascribed to differences in the physical and biogeochemical processes incorporated in equations of C and N cycles and their interactions. Here we review the literature to determine the state-of-the-art in modelling agricultural (crop and grassland) systems. In order to carry out this study, we selected the range of biogeochemical models used by the CN-MIP consortium of FACCE-JPI (http://www.faccejpi.com): APSIM, CERES-EGC, DayCent, DNDC, DSSAT, EPIC, PaSim, RothC and STICS. In our analysis, these models were assessed for the quality and comprehensiveness of underlying processes related to pedo-climatic conditions and management practices, but also with respect to time and space of application, and for their accuracy in multiple contexts. Overall, it emerged that there is a possible impact of ill-defined pedo-climatic conditions in the unsatisfactory performance of the models (46.2%), followed by limitations in the algorithms simulating the effects of management practices (33.1%). The multiplicity of scales in both time and space is a fundamental feature, which explains the remaining weaknesses (i.e. 20.7%). Innovative aspects have been identified for future development of C and N models. They include the explicit representation of soil microbial biomass to drive soil organic matter turnover, the effect of N shortage on SOM decomposition, the improvements related to the production and consumption of gases and an adequate simulations of gas transport in soil. On these bases, the assessment of trends and gaps in the modelling approaches currently employed to
FATIGUE STRENGTH OF HIGH-STRENGTH STEEL,
coldhardened by deforming to 83%. It was found that it has low static notch sensitivity (lower than that of heat-treated steels), that static strength ...is raised appreciably by increased cold plastic deformation, and that its fatigue strength is raised substantially by mechanical polishing. (Author)
Srivastava, Ankit; Ghassemi-Armaki, Hassan; Sung, Hyokyung; Chen, Peng; Kumar, Sharvan; Bower, Allan F.
2015-05-01
The micromechanics of plastic deformation and phase transformation in a three-phase advanced high strength steel are analyzed both experimentally and by microstructure-based simulations. The steel examined is a three-phase (ferrite, martensite and retained austenite) quenched and partitioned sheet steel with a tensile strength of ~980 MPa. The macroscopic flow behavior and the volume fraction of martensite resulting from the austenite-martensite transformation during deformation were measured. In addition, micropillar compression specimens were extracted from the individual ferrite grains and the martensite particles, and using a flat-punch nanoindenter, stress-strain curves were obtained. Finite element simulations idealize the microstructure as a composite that contains ferrite, martensite and retained austenite. All three phases are discretely modeled using appropriate crystal plasticity based constitutive relations. Material parameters for ferrite and martensite are determined by fitting numerical predictions to the micropillar data. The constitutive relation for retained austenite takes into account contributions to the strain rate from the austenite-martensite transformation, as well as slip in both the untransformed austenite and product martensite. Parameters for the retained austenite are then determined by fitting the predicted flow stress and transformed austenite volume fraction in a 3D microstructure to experimental measurements. Simulations are used to probe the role of the retained austenite in controlling the strain hardening behavior as well as internal stress and strain distributions in the microstructure.
Damaskin, B.B.; Ivanova, R.V.; Palm, U.V.; Salve, M.A.
1986-03-01
The adsorption parameters for the specific adsorption of Cs/sup +/ at the Hg/H/sub 2/O and Bi/H/sub 2/O interface from solutions are presented and the rms differences between theory and experiment found for these parameters are shown. The experimental data for the specific adsorption of Cs/sup +/ ions at the interfaces from the solutions obey the Grahame-Parsons model only to a first, rather than rough approximation, while more sensitive criteria reveal conflicts with this model.
Rahman, Tanzina; Millwater, Harry; Shipley, Heather J
2014-11-15
Aluminum oxide nanoparticles have been widely used in various consumer products and there are growing concerns regarding their exposure in the environment. This study deals with the modeling, sensitivity analysis and uncertainty quantification of one-dimensional transport of nano-sized (~82 nm) aluminum oxide particles in saturated sand. The transport of aluminum oxide nanoparticles was modeled using a two-kinetic-site model with a blocking function. The modeling was done at different ionic strengths, flow rates, and nanoparticle concentrations. The two sites representing fast and slow attachments along with a blocking term yielded good agreement with the experimental results from the column studies of aluminum oxide nanoparticles. The same model was used to simulate breakthrough curves under different conditions using experimental data and calculated 95% confidence bounds of the generated breakthroughs. The sensitivity analysis results showed that slow attachment was the most sensitive parameter for high influent concentrations (e.g. 150 mg/L Al2O3) and the maximum solid phase retention capacity (related to blocking function) was the most sensitive parameter for low concentrations (e.g. 50 mg/L Al2O3).
无
2001-01-01
A model, in which various seismic environmental factors areinvolved, has been developed in the paper on the bases of relevant data. The environmental factors include the crust structure, lithological conditions, fault plan attitude, the crust stress state, pore-fluid pressure and geothermal conditions, etc. The effect of each of the factors on the tectonic movement energy index has been analyzed. The model calculation results indicate that shear fractu-re energy of a fault generally increases with depth; it reached a peak value at a certain depth, then turns gradually attenuated. Of all the factors, the effects of pore-fluid pressure and geothermal conditions on the energy index are of prominence. High pore-fluid pressure and high temperature circumstance may result in decline of the peak value of the shear fracture energy curve, making the depths of the peak value and of the bell-waist value deepened. Such effects restrict strong seismic events, but suitable for micro-seismic activity and/or fault creep. The lower limit of focal depth under such an environment is relatively deep. Contrarily, low pore-fluid pressure and low geothermal temperature circumstance result in increase of the peak value of the shear fracture energy curve, and the curve becoming steep. The later circumstance is favorable to the formation of locked segment where possesses high strength and high-energy accumulation. If these two kind of segments are arranged interactively along a fault zone, such arrangement would boost the energy transition among the segments, forming mechanical circumstance of energy highly accumulated in one segment with adjacent segment(s) less-locked. Such contrast of the strength and energy would provide conditions for strong earthquakes with high stress drop. An analysis of the northwest seg-ment of the Honghe fault has provided some evidence for the modeling results.
Rivera, Gabriel; Stayton, C Tristan
2011-10-01
Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low-drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade-offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments; however, this flatter shape may also make the shells less capable of resisting predator-induced loads. We tested the idea that "lotic" shell shapes are weaker than "lentic" shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. "Lotic" shell shapes produced significantly higher stresses than "lentic" shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many-to-one mapping of shell shape onto strength, P. concinna experiences a trade-off in shell shape between hydrodynamic and mechanical performance. This trade-off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade-off in some cases, as changes in
Brose, Ulrich; Meyer, Katrin
2017-01-01
Knowledge on how functional responses (a measurement of feeding interaction strength) are affected by patch size and habitat complexity (represented by refuge availability) is crucial for understanding food-web stability and subsequently biodiversity. Due to their laborious character, it is almost impossible to carry out systematic empirical experiments on functional responses across wide gradients of patch sizes and refuge availabilities. Here we overcame this issue by using an individual-based model (IBM) to simulate feeding experiments. The model is based on empirically measured traits such as body-mass dependent speed and capture success. We simulated these experiments in patches ranging from sizes of petri dishes to natural patches in the field. Moreover, we varied the refuge availability within the patch independently of patch size, allowing for independent analyses of both variables. The maximum feeding rate (the maximum number of prey a predator can consume in a given time frame) is independent of patch size and refuge availability, as it is the physiological upper limit of feeding rates. Moreover, the results of these simulations revealed that a type III functional response, which is known to have a stabilizing effect on population dynamics, fitted the data best. The half saturation density (the prey density where a predator consumes half of its maximum feeding rate) increased with refuge availability but was only marginally influenced by patch size. Subsequently, we investigated how patch size and refuge availability influenced stability and coexistence of predator-prey systems. Following common practice, we used an allometric scaled Rosenzweig–MacArthur predator-prey model based on results from our in silico IBM experiments. The results suggested that densities of both populations are nearly constant across the range of patch sizes simulated, resulting from the constant interaction strength across the patch sizes. However, constant densities with
2011-01-01
One of the research emphases of application and investigation of high strength steel are laid on stability of axial compressed member. After analyzing stability of high strength steel and limitations of design method for stability of high strength steel analyzed, combined with the function of stability analysis of large finite element analysis software ANSYS and model test, stability for axial compressed members of high strength steel are researched, and formulae which parameter includes yield strength of material and slenderness ratio of member is put forward for calculation stability coefficient of axial compressed member of high strength steel. Some important conclusions are arrived at. The research is significant for application and investigation of high strength steel in future.%欧特克有限公司宣布，欧特克建筑信息模型（BIM）基础设施产品组合新增面向概念设计的Autodesk Infrastructure Modeler 2012软件。基于BIM的基础设施产品组合主要用于规划、设计、建设和管理更具可持续性的基础设施。新产品将与2012版欧特克基础设施设计套件配套，可帮助业内专业人士提高效率，并消除工作过程中产生的浪费。
T. Krauße
2011-03-01
Full Text Available The development of methods for estimating the parameters of hydrological models considering uncertainties has been of high interest in hydrological research over the last years. In particular methods which understand the estimation of hydrological model parameters as a geometric search of a set of robust performing parameter vectors by application of the concept of data depth found growing research interest. Bárdossy and Singh (2008 presented a first proposal and applied it for the calibration of a conceptual rainfall-runoff model with daily time step. Krauße and Cullmann (2011 further developed this method and applied it in a case study to calibrate a process oriented hydrological model with hourly time step focussing on flood events in a fast responding catchment. The results of both studies showed the potential of the application of the principle of data depth. However, also the weak point of the presented approach got obvious. The algorithm identifies a set of model parameter vectors with high model performance and subsequently generates a set of parameter vectors with high data depth with respect to the first set. These both steps are repeated iteratively until a stopping criterion is met. In the first step the estimation of the good parameter vectors is based on the Monte Carlo method. The major shortcoming of this method is that it is strongly dependent on a high number of samples exponentially growing with the dimensionality of the problem. In this paper we present another robust parameter estimation strategy which applies an approved search strategy for high-dimensional parameter spaces, the particle swarm optimisation in order to identify a set of good parameter vectors with given uncertainty bounds. The generation of deep parameters is according to Krauße and Cullmann (2011. The method was compared to the Monte Carlo based robust parameter estimation algorithm on the example of a case study in Krauße and Cullmann (2011 to
Kim, Hyunok; Kimchi, Menachem
2011-08-01
This paper presents a numerical modeling approach for predicting springback by considering the variations of elastic modulus on springback in stamping AHSS. Various stamping tests and finite-element method (FEM) simulation codes were used in this study. The cyclic loading-unloading tensile tests were conducted to determine the variations of elastic modulus for dual-phase (DP) 780 sheet steel. The biaxial bulge test was used to obtain plastic flow stress data. The non-linear reduction of elastic modulus for increasing the plastic strain was formulated by using the Yoshida model that was implemented in FEM simulations for springback. To understand the effects of material properties on springback, experiments were conducted with a simple geometry such as U-shape bending and the more complex geometry such as the curved flanging and S-rail stamping. Different measurement methods were used to confirm the final part geometry. Two different commercial FEM codes, LS-DYNA and DEFORM, were used to compare the experiments. The variable elastic modulus improved springback predictions in U-shape bending and curved flanging tests compared to FEM with the constant elastic modulus. However, in S-rail stamping tests, both FEM models with the isotropic hardening model showed limitations in predicting the sidewall curl of the S-rail part after springback. To consider the kinematic hardening and Bauschinger effects that result from material bending-unbending in S-rail stamping, the Yoshida model was used for FEM simulation of S-rail stamping and springback. The FEM predictions showed good improvement in correlating with experiments.
Kim, Hyunok; Mohr, William; Yang, Yu-Ping; Zelenak, Paul; Kimchi, Menachem
2011-08-01
Numerical modeling of local formability, such as hole-edge cracking and shear fracture in bending of AHSS, is one of the challenging issues for simulation engineers for prediction and evaluation of stamping and crash performance of materials. This is because continuum-mechanics-based finite element method (FEM) modeling requires additional input data, "failure criteria" to predict the local formability limit of materials, in addition to the material flow stress data input for simulation. This paper presents a numerical modeling approach for predicting hole-edge failures during static bend tests of AHSS structures. A local-strain-based failure criterion and a stress-triaxiality-based failure criterion were developed and implemented in LS-DYNA simulation code to predict hole-edge failures in component bend tests. The holes were prepared using two different methods: mechanical punching and water-jet cutting. In the component bend tests, the water-jet trimmed hole showed delayed fracture at the hole-edges, while the mechanical punched hole showed early fracture as the bending angle increased. In comparing the numerical modeling and test results, the load-displacement curve, the displacement at the onset of cracking, and the final crack shape/length were used. Both failure criteria also enable the numerical model to differentiate between the local formability limit of mechanical-punched and water-jet-trimmed holes. The failure criteria and static bend test developed here are useful to evaluate the local formability limit at a structural component level for automotive crash tests.
T. Krauße
2012-02-01
Full Text Available The development of methods for estimating the parameters of hydrologic models considering uncertainties has been of high interest in hydrologic research over the last years. In particular methods which understand the estimation of hydrologic model parameters as a geometric search of a set of robust performing parameter vectors by application of the concept of data depth found growing research interest. Bárdossy and Singh (2008 presented a first Robust Parameter Estimation Method (ROPE and applied it for the calibration of a conceptual rainfall-runoff model with daily time step. The basic idea of this algorithm is to identify a set of model parameter vectors with high model performance called good parameters and subsequently generate a set of parameter vectors with high data depth with respect to the first set. Both steps are repeated iteratively until a stopping criterion is met. The results estimated in this case study show the high potential of the principle of data depth to be used for the estimation of hydrologic model parameters. In this paper we present some further developments that address the most important shortcomings of the original ROPE approach. We developed a stratified depth based sampling approach that improves the sampling from non-elliptic and multi-modal distributions. It provides a higher efficiency for the sampling of deep points in parameter spaces with higher dimensionality. Another modification addresses the problem of a too strong shrinking of the estimated set of robust parameter vectors that might lead to overfitting for model calibration with a small amount of calibration data. This contradicts the principle of robustness. Therefore, we suggest to split the available calibration data into two sets and use one set to control the overfitting. All modifications were implemented into a further developed ROPE approach that is called Advanced Robust Parameter Estimation (AROPE. However, in this approach the estimation of
Ju CHEN; Wei-liang JIN
2008-01-01
In this study,the suitability of current design methods for the 0.2% proof yield strength of the comer regions for high strength cold-formed steel at norrnal room temperature was investigated.The current standard predictions are generally accurate for outer comer specimen but conservative for inner comer specimen.Based on the experimental results,an analytical model to predict the comer strength of high strength cold-formed steel at normal room temperature was also proposed.The comparison indicated that the proposed model predicted well the comer strength of high strength cold-formed steel not only at normal room temperature but also at elevated temperatures.It is shown that the predictions obtained from the proposed model agree well with the test results.Generally the comer strength enhancement of high strength cold-formed steel decreases when the temperature increases.
Kezhen Yan
2013-01-01
Full Text Available Compressive strength and splitting tensile strength are both important parameters that are utilized for characterization concrete mechanical properties. This paper aims to show a possible applicability of support vector machine (SVM to predict the splitting tensile strength of concrete from compressive strength of concrete, a SVM model was built, trained, and tested using the available experimental data gathered from the literature. All of the results predicted by the SVM model are compared with results obtained from experimental data, and we found that the predicted splitting tensile strength of concrete is in good agreement with the experimental data. The splitting tensile strength results predicted by SVM are also compared to those obtained by using empirical results of the building codes and various models. These comparisons show that SVM has strong potential as a feasible tool for predicting splitting tensile strength from compressive strength.
Weaver, C.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.
2014-01-01
We investigate the sensitivity of future spaceborne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations and a Lagrangian transport model to infer surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coal mines in Upper Silesia, Poland, and wetlands in southern Finland. The simulated methane surface concentrations capture at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. With this tool we can test whether proposed methane lidar instruments will be sensitive to changes in surface emissions. We show that future lidar instruments should be able to detect a 50% reduction in methane emissions from the Netherlands and Germany, at least during summer.
Yang, Ziheng; Nielsen, Rasmus
2008-01-01
Current models of codon substitution are formulated at the levels of nucleotide substitution and do not explicitly consider the separate effects of mutation and selection. They are thus incapable of inferring whether mutation or selection is responsible for evolution at silent sites. Here we...... to examine the null hypothesis that codon usage is due to mutation bias alone, not influenced by natural selection. Application of the test to the mammalian data led to rejection of the null hypothesis in most genes, suggesting that natural selection may be a driving force in the evolution of synonymous...... codon usage in mammals. Estimates of selection coefficients nevertheless suggest that selection on codon usage is weak and most mutations are nearly neutral. The sensitivity of the analysis on the assumed mutation model is discussed....
Changgui Gu
Full Text Available The suprachiasmatic nucleus (SCN is the master circadian clock in mammals and is composed of thousands of neuronal oscillators expressing different intrinsic periods. These oscillators form a coupled network with a free-running period around 24 h in constant darkness and entrainable to the external light-dark cycle (T cycle. Coupling plays an important role in setting the period of the network and its range of entrainment. Experiments in rats have shown that two subgroups of oscillators within the SCN, a ventrolateral (VL subgroup that receives photic input and a dorsomedial (DM subgroup that is coupled to VL, can be desynchronized under a short (22-h T cycle, with VL entrained to the cycle and DM free-running. We use a modified Goodwin model to understand how entrainment of the subgroups to short (22-h and long (26-h T cycles is influenced by light intensity, the proportion of neurons that receives photic input, and coupling heterogeneity. We find that the model's critical value for the proportion of photically-sensitive neurons is in accord with actual experimental estimates, while the model's inclusion of dispersed coupling can account for the experimental observation that VL and DM desynchronize more readily under the 22-h than under the 26-h T cycle. Heterogeneous intercellular coupling within the SCN is likely central to the generation of complex behavioral patterns.
Determination of the 25Mg( p, γ)26Al resonance strength at E c.m.=58 keV via shell model calculation
Li, ZhiHong; Su, Jun; Li, YunJu; Guo, Bing; Li, ErTao; Wang, YouBao; Yan, ShengQuan; Liu, WeiPing
2015-08-01
The observation of 26Al is an useful tool for γ-ray astronomy and in studies of galactic chemical evolution. The most likely mechanism for 26A1 nucleosynthesis is in the hydrogen burning MgAl cycle, and the 26A1 production reaction 25Mg( p, γ)26Al at the important temperature range below T = 0.2 GK is still not well known. The spectroscopic factor of 58 keV resonance level in 26A1 is determined with shell model calculation and then used to deduce the resonance strength of the 25Mg( p, γ)26Al reaction. The result provides a reference for the future 25Mg( p, γ)26Al direct measurement at Jinping underground laboratory.
2012-10-15
activation energies (-40 kJ/mol). Moreover, possible trapping sites will differ for precipitation hardened fee Ni-based alloys compared to ferrous ...FINAL REPORT Mechanism-Based Modeling of Hydrogen Environment Assisted Cracking (HEAC) in High Strength Alloys for Marine Applications: Prediction...the microscopic scale to enable threshold and crack growth rate predictions in Ni-based alloys which differ substantially from high strength steels
Righter, K.; Pando, K. M.; Danielson, L. R.
2015-01-01
Recent models for accretion of terrestrial bodies involve metal-silicate equilibrium as the metallic core formed during growth. Most elements considered are either refractory or well studied elements for which effects of pressure, temperature, oxygen fugacity, and metallic liquid composition are well known. There are a large number of elements that are both siderophile and volatile, whose fate in such models is unknown, largely due to a lack of data at comparable conditions and com-positions (FeNi core with light elements such as S, C, Si, and O). We have focused on Ge, In, As, Sb and determined the effect of Si and C on metal-silicate partitioning, and developed a thermo-dynamic model that allows application of these new data to a wide range of planetary bodies. New experiments: We have previously carried out experiments with FeSi metallic liquid at C-saturated conditions at 1600 and 1800 C [4]. In a new series of experiments we investigate the effect of Si in carbon-free systems at 1600 C for comparison. Experiments were carried out at 1 GPa in MgO capsules using the same basaltic starting composition as in previous studies. The MgO capsule reacts with the silicate melt to form more MgO-rich liquids that have 22-26 wt% MgO. Experimental met-als and silicates were analyzed using a combination of electron microprobe analysis and laser ablation ICP-MS. Results: The new results can be interpreted by considering Ge as an example, in the simple exchange equilibrium Fe + GeO = FeO + Ge, where the equilibrium constant Kd can be examined as a function of Si content of the metal. The slope of lnKd vs. (1-XSi) for this new series allows derivation of the epsilon interaction parameter for each of these four elements and Si (both C-saturated and C-free).All four elements have positive epsilon values, indicating that Si causes a decrease in the partition coefficients; values are 6.6, 6.5, 27.8 and 25.2 for In, Ge, As, and Sb, respectively, at 1 GPa and 1600 C. As an example of
Yousefvand, Hossein Reza
2017-07-01
In this paper a self-consistent numerical approach to study the temperature and bias dependent characteristics of mid-infrared (mid-IR) quantum cascade lasers (QCLs) is presented which integrates a number of quantum mechanical models. The field-dependent laser parameters including the nonradiative scattering times, the detuning and energy levels, the escape activation energy, the backfilling excitation energy and dipole moment of the optical transition are calculated for a wide range of applied electric fields by a self-consistent solution of Schrodinger-Poisson equations. A detailed analysis of performance of the obtained structure is carried out within a self-consistent solution of the subband population rate equations coupled with carrier coherent transport equations through the sequential resonant tunneling, by taking into account the temperature and bias dependency of the relevant parameters. Furthermore, the heat transfer equation is included in order to calculate the carrier temperature inside the active region levels. This leads to a compact predictive model to analyze the temperature and electric field dependent characteristics of the mid-IR QCLs such as the light-current (L-I), electric field-current (F-I) and core temperature-electric field (T-F) curves. For a typical mid-IR QCL, a good agreement was found between the simulated temperature-dependent L-I characteristic and experimental data, which confirms validity of the model. It is found that the main characteristics of the device such as output power and turn-on delay time are degraded by interplay between the temperature and Stark effects.
Topological strength of magnetic skyrmions
Bazeia, D.; Ramos, J. G. G. S.; Rodrigues, E. I. B.
2017-02-01
This work deals with magnetic structures that attain integer and half-integer skyrmion numbers. We model and solve the problem analytically, and show how the solutions appear in materials that engender distinct, very specific physical properties, and use them to describe their topological features. In particular, we found a way to model skyrmion with a large transition region correlated with the presence of a two-peak skyrmion number density. Moreover, we run into the issue concerning the topological strength of a vortex-like structure and suggest an experimental realization, important to decide how to modify and measure the topological strength of the magnetic structure.
Strength and Balance Exercises
... Peripheral Artery Disease Venous Thromboembolism Aortic Aneurysm More Strength and Balance Exercises Updated:Sep 8,2016 If ... Be Safe While Being Active - Stretching & Flexibility Exercises - Strength & Balance Exercises - Problems & Solutions for Being Active - FAQs ...
Goldberg, Robert K.
1999-01-01
Potential gas turbine applications will expose polymer matrix composites to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under extreme conditions. Specifically, analytical methods designed for these applications must have the capability of properly capturing the strain rate sensitivities and nonlinearities that are present in the material response. The Ramaswamy-Stouffer constitutive equations, originally developed to analyze the viscoplastic deformation of metals, have been modified to simulate the nonlinear deformation response of ductile, crystalline polymers. The constitutive model is characterized and correlated for two representative ductile polymers. Fiberite 977-2 and PEEK, and the computed results correlate well with experimental values. The polymer constitutive equations are implemented in a mechanics of materials based composite micromechanics model to predict the nonlinear, rate dependent deformation response of a composite ply. Uniform stress and uniform strain assumptions are applied to compute the effective stresses of a composite unit cell from the applied strains. The micromechanics equations are successfully verified for two polymer matrix composites. IM7/977-2 and AS4/PEEK. The ultimate strength of a composite ply is predicted with the Hashin failure criteria that were implemented in the composite micromechanics model. The failure stresses of the two composite material systems are accurately predicted for a variety of fiber orientations and strain rates. The composite deformation model is implemented in LS-DYNA, a commercially available transient dynamic explicit finite element code. The matrix constitutive equations are converted into an incremental form, and the model is implemented into LS-DYNA through the use of a user defined material subroutine. The deformation response of a bulk polymer and a polymer matrix composite are predicted by finite element analyses. The results
Connaughton, Daniel; Connaughton, Angela; Poor, Linda
2001-01-01
Strength training can be fun, safe, and appropriate for young girls and women and is an important component of any fitness program when combined with appropriate cardiovascular and flexibility activities. Concerns and misconceptions regarding girls' strength training are discussed, presenting general principles of strength training for children…
Connaughton, Daniel; Connaughton, Angela; Poor, Linda
2001-01-01
Strength training can be fun, safe, and appropriate for young girls and women and is an important component of any fitness program when combined with appropriate cardiovascular and flexibility activities. Concerns and misconceptions regarding girls' strength training are discussed, presenting general principles of strength training for children…
Sean P Parsons
2016-02-01
Full Text Available Pacemaker activities generated by networks of interstitial cells of Cajal (ICC, in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e. spatial noise with a long-tailed distribution, plateau steps occurred at points of low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency.
Parsons, Sean P.; Huizinga, Jan D.
2016-01-01
Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency. PMID:26869875
Parsons, Sean P; Huizinga, Jan D
2016-01-01
Pacemaker activities generated by networks of interstitial cells of Cajal (ICC), in conjunction with the enteric nervous system, orchestrate most motor patterns in the gastrointestinal tract. It was our objective to understand the role of network features of ICC associated with the myenteric plexus (ICC-MP) in the shaping of motor patterns of the small intestine. To that end, a model of weakly coupled oscillators (oscillators influence each other's phase but not amplitude) was created with most parameters derived from experimental data. The ICC network is a uniform two dimensional network coupled by gap junctions. All ICC generate pacemaker (slow wave) activity with a frequency gradient in mice from 50/min at the proximal end of the intestine to 40/min at the distal end. Key features of motor patterns, directly related to the underlying pacemaker activity, are frequency steps and dislocations. These were accurately mimicked by reduction of coupling strength at a point in the chain of oscillators. When coupling strength was expressed as a product of gap junction density and conductance, and gap junction density was varied randomly along the chain (i.e., spatial noise) with a long-tailed distribution, plateau steps occurred at pointsof low density. As gap junction conductance was decreased, the number of plateaus increased, mimicking the effect of the gap junction inhibitor carbenoxolone. When spatial noise was added to the natural interval gradient, as gap junction conductance decreased, the number of plateaus increased as before but in addition the phase waves frequently changed direction of apparent propagation, again mimicking the effect of carbenoxolone. In summary, key features of the motor patterns that are governed by pacemaker activity may be a direct consequence of biological noise, specifically spatial noise in gap junction coupling and pacemaker frequency.
Ledertoug, Mette Marie
Individual paper presentation: The ‘Strength Compass’. The results of a PhDresearch project among schoolchildren (age 6-16) identifying VIAstrengths concerning age, gender, mother-tongue-langue and possible child psychiatric diagnosis. Strengths-based interventions in schools have a theoretical...... foundation in research in VIA-strengths by Seligman & Peterson (2004) and in research on strengths by Linley (2008). Based on this research the VIA-test was created for adults and later for children and youths from the age of 10. For children younger than 10 years of age Peterson & Park (2011) have made...... interviews with the parents. For younger children there has been no possibility to test for strengths. In a Danish PhD project a tool to map children’s strengths was needed for children aged 6-16 and with permission from the VIA-institute ‘The Strength Compass’ was made in cooperation with The Danish...
Roy, S. G.; Tucker, G. E.; Koons, P. O.; Smith, S. M.; Upton, P.
2016-10-01
We explore two ways in which the mechanical properties of rock potentially influence fluvial incision and sediment transport within a watershed: rock erodibility is inversely proportional to rock cohesion, and fracture spacing influences the initial grain sizes produced upon erosion. Fault-weakened zones show these effects well because of the sharp strength gradients associated with localized shear abrasion. A natural example of fault erosion is used to motivate our calibration of a generalized landscape evolution model. Numerical experiments are used to study the sensitivity of river erosion and transport processes to variable degrees of rock weakening. In the experiments, rapid erosion and transport of fault gouge steers surface runoff, causing high-order channels to become confined within the structure of weak zones when the relative degree of rock weakening exceeds 1 order of magnitude. Erosion of adjacent, intact bedrock produces relatively coarser grained gravels that accumulate in the low relief of the eroded weak zone. The thickness and residence time of sediments stored there depends on the relief of the valley, which in these models depends on the degree of rock weakening. The frequency with which the weak zone is armored by bed load increases with greater weakening, causing the bed load to control local channel slope. Conversely, small tributaries feeding into the weak zone are predominantly detachment limited. Our results indicate that mechanical heterogeneity can exert strong controls on rates and patterns of erosion and should be considered in future landscape evolution studies to better understand the role of heterogeneity in structuring landscapes.
林鹏飞; 胡水平; 余伟; 宋晓波
2011-01-01
The test study for plastic deformation resistance of two kinds of high strength pipeline steels with different components was engaged in single pass compression test by Gleeble-3500. The influence of deforming temperature, deforming velocity and deforming degree on deformation resistance were analyzed and a new model of deformation resistance suitable for X70 and X80 steels was established. Through multiple linear regression analysis, this model proved to have good curve fitting characteristics and relatively high precision. The model has been successfully used in rolling production with relative error of rolling force less than eleven percent%利用Gleeble-3500热模拟试验机,对两种不同成分的高钢级管线钢进行单道次压缩实验的塑性变形抗力进行研究.分析了变形温度、变形速率、变形程度对变形抗力的影响,建立一种适合X70、X80高钢级管线钢的变形抗力模型.通过多元非线性进行回归分析,证明模型具有良好的曲线拟合特性.模型成功的应用于轧制生产的现场,计算出的轧制力值误差控制在11％以内.
Iyer, Saiganesh; Lerch, Brad (Technical Monitor)
2001-01-01
The magnitude of yield and flow stresses in aged Inconel 718 are observed to be different in tension and compression. This phenomenon, called the Strength differential (SD), contradicts the metal plasticity axiom that the second deviatoric stress invariant alone is sufficient for representing yield and flow. Apparently, at least one of the other two stress invariants is also significant. A unified viscoplastic model was developed that is able to account for the SD effect in aged Inconel 718. Building this model involved both theory and experiments. First, a general threshold function was proposed that depends on all three stress invariants and then the flow and evolution laws were developed using a potential-based thermodynamic framework. Judiciously chosen shear and axial tests were conducted to characterize the material. Shear tests involved monotonic loading, relaxation, and creep tests with different loading rates and load levels. The axial tests were tension and compression tests that resulted in sufficiently large inelastic strains. All tests were performed at 650 C. The viscoplastic material parameters were determined by optimizing the fit to the shear tests, during which the first and the third stress invariants remained zero. The threshold surface parameters were then fit to the tension and compression test data. An experimental procedure was established to quantify the effect of each stress invariant on inelastic deformation. This requires conducting tests with nonproportional three-dimensional load paths. Validation of the model was done using biaxial tests on tubular specimens of aged Inconel 718 using proportional and nonproportional axial-torsion loading. These biaxial tests also helped to determine the most appropriate form of the threshold function; that is, how to combine the stress invariants. Of the set of trial threshold functions, the ones that incorporated the third stress invariant give the best predictions. However, inclusion of the first
evaluating the strength of structural elements is examined. The book is intended for design engineers, factory laboratory personnel, scientific research workers, and the design institutes. (Author-PL)
Alberti, Mariza N; Polyhach, Yevhen; Tzirakis, Manolis D; Tödtli, Laura; Jeschke, Gunnar; Diederich, François
2016-07-11
The distal hydrogen bond (H-bond) in dioxygen-binding proteins is crucial for the discrimination of O2 with respect to CO or NO. We report the preparation and characterization of a series of Zn(II) porphyrins, with one of three meso-phenyl rings bearing both an alkyl-tethered proximal imidazole ligand and a heterocyclic distal H-bond donor connected by a rigid acetylene spacer. Previously, we had validated the corresponding Co(II) complexes as synthetic model systems for dioxygen-binding heme proteins and demonstrated the structural requirements for proper distal H-bonding to Co(II) -bound dioxygen. Here, we systematically vary the H-bond donor ability of the distal heterocycles, as predicted based on pKa values. The H-bond in the dioxygen adducts of the Co(II) porphyrins was directly measured by Q-band Davies-ENDOR spectroscopy. It was shown that the strength of the hyperfine coupling between the dioxygen radical and the distal H-atom increases with enhanced acidity of the H-bond donor.
A. Arul Lawrence Selvakumar
2012-01-01
Full Text Available Problem statement: Intrusion Detection System (IDS have become an important component of infrastructure protection mechanism to secure the current and emerging networks, its services and applications by detecting, alerting and taking necessary actions against the malicious activities. The network size, technology diversities and security policies make networks more challenging and hence there is a requirement for IDS which should be very accurate, adaptive, extensible and more reliable. Although there exists the novel framework for this requirement namely Mining Audit Data for Automated Models for Intrusion Detection (MADAM ID, it is having some performance shortfalls in processing the audit data. Approach: Few experiments were conducted on tcpdump data of DARPA and BCM audit files by applying the algorithms and tools of MADAM ID in the processing of audit data, mine patterns, construct features and build RIPPER classifiers. By putting it all together, four main categories of attacks namely DOS, R2L, U2R and PROBING attacks were simulated. Results: This study outlines the experimentation results of MADAM ID in testing the DARPA and BSM data on a simulated network environment. Conclusion: The strengths and weakness of MADAM ID has been identified thru the experiments conducted on tcpdump data and also on Pascal based audit files of Basic Security Module (BSM. This study also gives some additional directions about the future applications of MADAM ID.
van Woerkom, Marianne; Bakker, Arnold B; Nishii, Lisa H
2016-01-01
Absenteeism associated with accumulated job demands is a ubiquitous problem. We build on prior research on the benefits of counteracting job demands with resources by focusing on a still untapped resource for buffering job demands-that of strengths use. We test the idea that employees who are actively encouraged to utilize their personal strengths on the job are better positioned to cope with job demands. Based on conservation of resources (COR) theory, we hypothesized that job demands can accumulate and together have an exacerbating effect on company registered absenteeism. In addition, using job demands-resources theory, we hypothesized that perceived organizational support for strengths use can buffer the impact of separate and combined job demands (workload and emotional demands) on absenteeism. Our sample consisted of 832 employees from 96 departments (response rate = 40.3%) of a Dutch mental health care organization. Results of multilevel analyses indicated that high levels of workload strengthen the positive relationship between emotional demands and absenteeism and that support for strength use interacted with workload and emotional job demands in the predicted way. Moreover, workload, emotional job demands, and strengths use interacted to predict absenteeism. Strengths use support reduced the level of absenteeism of employees who experienced both high workload and high emotional demands. We conclude that providing strengths use support to employees offers organizations a tool to reduce absenteeism, even when it is difficult to redesign job demands.
Strength Training and Your Child
... Feeding Your 1- to 2-Year-Old Strength Training and Your Child KidsHealth > For Parents > Strength Training ... prevent injuries and speed up recovery. About Strength Training Strength training is the practice of using free ...
Nouh, M.R., E-mail: mragab73@yahoo.com [Department of Radiodiagnosis and Diagnostic Imaging, Faculty of Medicine, Alexandria University, 1 Kolya-El Teb St., Mahata El-Ramel, Alexandria (Egypt); Schweitzer, M.E., E-mail: mschweitzer@toh.on.ca [501 Smyth Module S-1, University of Ottawa, Ottawa, ON K1H 8L6 (Canada); Ragatte, Ravinder R., E-mail: Ravinder.regatte@nyumc.org [301 E17th Street, Department of Radiology, Hospital for Joint Disease, New York University, New York, NY 10003 (United States)
2011-11-15
Objectives: Protein binding and relaxivity are major determinants of the relative effectiveness of an MR arthrographic contrast agent. We sought to evaluate the optimal concentrations of high and usual relaxivity agents in two different proteinous environments at variable field strength for two MR contrast agents of different relaxivities. Materials and methods: At 1.5, 3.0 and 7.0 T, gadobenate dimeglumine (Multihance) with high-relaxivity in proteinous environment and gadoteridol (Prohance) with more typical behavior were studied at 1.25, 2.5, 5, and 10 mmol in 1.7 g/dL and 3 g/dL albumin (mimicking protein content of normal and inflammatory synovial fluids, respectively) vs. pure normal saline, as a control. Analysis of image signal intensity (SI) and relaxivity values was done. Results: In our study a change in concentration had no significant effect on T1 SI. In contrast, nearly every change in concentration led to a significant change in T2 SI. In 1.25 mmol concentration, there was no effect on T1 SI of either protein concentrations while higher concentrations showed significant decreased SI in either protein carrier compared to saline. The SI of Gadoteridol was significantly higher (p < 0.0001) than that of gadobenate at each of 3 T and 7 T, but was significantly lower (p < 0.001) at 1.5 T in saline solution while this was not significant for either protein carrier. Both protein carriers had significant effect on T1 (p = 0.0124) and T2 (p = 0.0118) relaxivities. Also solution concentration significantly (p < 0.01) affected both T1 and T2 relaxivities. Field strength did not affect T1 relaxivity (p = 0.02511) while it significantly affected T2 relaxivity (p < 0.001). This was significant (p = 0.035) in case of gadoteridol at 3 T. Conclusion: 1.25 mmol concentration of both gadoteridol and gadobenate solutions yields the best diagnostic T1 SI specially in higher fields (3 T and 7 T) and avoid the deleterious effect of increasing concentration on T2 SI
Strength of Cracked Reinforced Concrete Disks
Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...
Strengths of Remarried Families.
Knaub, Patricia Kain; And Others
1984-01-01
Focuses on remarried families' (N=80) perceptions of family strengths, marital satisfaction, and adjustment to the remarried situation. Results indicated that although most would like to make some changes, scores on the measurements used were high. A supportive environment was the most important predictor of family strength and success. (JAC)
Hill, Robert
1978-01-01
Comments on the feeling that the American family is disintegrating, and that many criticisms traditionally made about Black families are now made about White families. Suggests that people need to stress family strengths. As an example, five major strengths of Black families are described: flexibility, work and achievement ethics, religiosity, and…
BUZALAF, Marília Afonso Rabelo; HANNAS, Angélica Reis; MAGALHÃES, Ana Carolina; RIOS, Daniela; HONÓRIO, Heitor Marques; DELBEM, Alberto Carlos Botazzo
2010-01-01
Despite a plethora of in situ studies and clinical trials evaluating the efficacy of fluoridated dentifrices on caries control, in vitro pH cycling models are still broadly used because they mimic the dynamics of mineral loss and gain involved in caries formation. This paper critically reviews the current literature on existing pH-cycling models for the in vitro evaluation of the efficacy of fluoridated dentifrices for caries control, focusing on their strengths and limitations. A search was undertaken in the MEDLINE electronic journal database using the keywords "pH-cycling", "demineralization", "remineralization", "in vitro", "fluoride", "dentifrice". The primary outcome was the decrease of demineralization or the increase of remineralization as measured by different methods (e.g.: transverse microradiography) or tooth fluoride uptake. Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. One hundred and sixteen studies were included, of which 42 addressed specifically the comparison of dentifrices using different pH-cycling models. The other studies included meta-analysis or reviews, data about the effect of different fluoride sources on de-remineralization, different methods for analysis de-remineralization and chemical variables and characteristics of dental hard tissues that might have influence on de-remineralization processes. Generally, the studies presented ability to detect known results established by clinical trials, to demonstrate dose-related responses in the fluoride content of the dentifrices, and to provide repeatability and reproducibility between tests. In order to accomplish these features satisfactorily, it is mandatory to take into account the type of substrate and baseline artificial lesion, as well as the adequate response variables and statistical approaches to be used. This
Marília Afonso Rabelo Buzalaf
2010-08-01
Full Text Available Despite a plethora of in situ studies and clinical trials evaluating the efficacy of fluoridated dentifrices on caries control, in vitro pH cycling models are still broadly used because they mimic the dynamics of mineral loss and gain involved in caries formation. This paper critically reviews the current literature on existing pH-cycling models for the in vitro evaluation of the efficacy of fluoridated dentifrices for caries control, focusing on their strengths and limitations. A search was undertaken in the MEDLINE electronic journal database using the keywords "pH-cycling", "demineralization", "remineralization", "in vitro", "fluoride", "dentifrice". The primary outcome was the decrease of demineralization or the increase of remineralization as measured by different methods (e.g.: transverse microradiography or tooth fluoride uptake. Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. One hundred and sixteen studies were included, of which 42 addressed specifically the comparison of dentifrices using different pH-cycling models. The other studies included meta-analysis or reviews, data about the effect of different fluoride sources on de-remineralization, different methods for analysis de-remineralization and chemical variables and characteristics of dental hard tissues that might have influence on de-remineralization processes. Generally, the studies presented ability to detect known results established by clinical trials, to demonstrate dose-related responses in the fluoride content of the dentifrices, and to provide repeatability and reproducibility between tests. In order to accomplish these features satisfactorily, it is mandatory to take into account the type of substrate and baseline artificial lesion, as well as the adequate response variables and statistical approaches
Pheils, Denise M.
2010-01-01
This qualitative study explored the elements affecting an online student's performance and ability to succeed in an online course by offering a synthesized and enhanced model for online course development that considers the student holistically. The phenomenological study is grounded in the constructivist approach to learning and focused on the…
Asare-Addo, Kofi; Conway, Barbara R; Larhrib, Hassan; Levina, Marina; Rajabi-Siahboomi, Ali R; Tetteh, John; Boateng, Joshua; Nokhodchi, Ali
2013-11-01
The evaluation of the effects of different media ionic strengths and pH on the release of hydrochlorothiazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix was the objective of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the ionic strength had a profound effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength. For example, drug release after the 1h mark for the K100M matrices in water was 36%. Drug release in pH 1.2 after 1h was 30%. An increase of the pH 1.2 ionic strength to 0.4M saw a reduction of drug release to 26%. This was the general trend for the K4M and K15M matrices as well. The similarity factor f2 was calculated using drug release in water as a reference. Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2=64-72), increases of ionic strength at 0.2M and 0.4M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2=56-81). The values of f2 however reduced with increasing ionic strengths. DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices. There was an increase in
Pound, B.G.
1994-11-01
The ingress of hydrogen in various high-strength alloys was investigated with a view to characterizing their susceptibility to hydrogen embrittlement (HE). A potentiostatic pulse technique was applied to two precipitation-hardened iron-base alloys (AerMet 100 and alloy A-286), two Cu-containing alloys (Be-Cu and alloy K-500), and a superferritic stainless steel (UNS 544660) in 1 mol/L acetic acid-1 mol/L sodium acetate. The data were analyzed using a diffusion/trapping model to obtain the irreversible trapping constant (k) and hydrogen entry flux for each alloy. Irreversible trapping was negligible in overaged AerMet 100 but pronounced in the aged alloy. The order of the k values for AerMet 100 and two steels (4340 and 1 18Ni) previously studied inversely parallels their threshold stress intensities for stress corrosion cracking. Likewise, the k values of alloy A-286, 18Ni steel, and also alloy 718 from earlier work are consistent with test data for their relative resistance to HE. The results for AerMet 100 and alloy A-286 extend the previously reported correlation between k and HE resistance. Unaged Be-Cu is intrinsically more susceptible to HE than unaged alloy K- 500. The type of heat treatment has a marked effect on the rapping behavior of alloy K-500. The intrinsic susceptibility of the annealed and aged alloy is twice that or the direct-aged alloy. The propensity of the S44660 alloy to undergo HE at cathodic protection potentials can be attributed to the absence of an oxide and hence the relatively unrestricted entry of H.
Véronique Brault
2015-03-01
Full Text Available The trisomy of human chromosome 21 (Hsa21, which causes Down syndrome (DS, is the most common viable human aneuploidy. In contrast to trisomy, the complete monosomy (M21 of Hsa21 is lethal, and only partial monosomy or mosaic monosomy of Hsa21 is seen. Both conditions lead to variable physiological abnormalities with constant intellectual disability, locomotor deficits, and altered muscle tone. To search for dosage-sensitive genes involved in DS and M21 phenotypes, we created two new mouse models: the Ts3Yah carrying a tandem duplication and the Ms3Yah carrying a deletion of the Hspa13-App interval syntenic with 21q11.2-q21.3. Here we report that the trisomy and the monosomy of this region alter locomotion, muscle strength, mass, and energetic balance. The expression profiling of skeletal muscles revealed global changes in the regulation of genes implicated in energetic metabolism, mitochondrial activity, and biogenesis. These genes are downregulated in Ts3Yah mice and upregulated in Ms3Yah mice. The shift in skeletal muscle metabolism correlates with a change in mitochondrial proliferation without an alteration in the respiratory function. However, the reactive oxygen species (ROS production from mitochondrial complex I decreased in Ms3Yah mice, while the membrane permeability of Ts3Yah mitochondria slightly increased. Thus, we demonstrated how the Hspa13-App interval controls metabolic and mitochondrial phenotypes in muscles certainly as a consequence of change in dose of Gabpa, Nrip1, and Atp5j. Our results indicate that the copy number variation in the Hspa13-App region has a peripheral impact on locomotor activity by altering muscle function.
断续节理岩体模型试验及强度分析研究%Model Test and Strength Analysis Research on Intermittent Joint Rock Mass
胡波; 张楠; 王思敬; 陈俊生
2011-01-01
The theoretical analysis and model test are integrated to study the strength behavior of rock mass containing coplanar close intermittent joints in direct shear. Through introducing deformation compatibility equation in normal direction, the direct shear strength formulation is deducted based on the Mohr-Coulomb theory. According to the complete stress strain curve obtained from model tests, there are five typical stages in the failure process, namely linear elastic increment, slippage of the joints, steady development of post-cracking, the coalescence failure of discontinuous joints and the residual strength. The peak and residual strength increase with the increase of normal stress. There is no function to describe the relationship between deformation property and normal stress. The peak strength decreases with the increase of the joint connectivity rate, and the drop velocity is slow at low connectivity rate. The distribution of the joints also has influence on the strength of the rock mass. The similar material model test shows that the strength of model with joints on edge is bigger than that of the model with joints in the middle. The theoretical calculated results coincide well with experimental results.%采用理论分析同模型试验相结合的方法对共面闭合断续节理岩体的直剪强度特性进行研究.理论分析方面,引入法向变形协调条件,推导了模型的直剪强度公式.模型试验发现,全应力应变曲线主要经历了线弹性增长、节理面错动、次生裂纹起裂稳态扩展、节理面贯通破坏和残余强度五个阶段；峰值和残余强度都随正应力的增大而增大,而变形特性随正应力的变化规律性不强；峰值强度随节理连通率的增大而减小,低连通率时强度下降速度慢；节理两边分布的试样的强度普遍高于节理在中间的.对比发现,理论计算结果与试验值吻合较好.
Strength training for the warfighter.
Kraemer, William J; Szivak, Tunde K
2012-07-01
Optimizing strength training for the warfighter is challenged by past training philosophies that no longer serve the modern warfighter facing the "anaerobic battlefield." Training approaches for integration of strength with other needed physical capabilities have been shown to require a periodization model that has the flexibility for changes and is able to adapt to ever-changing circumstances affecting the quality of workouts. Additionally, sequencing of workouts to limit over-reaching and development of overtraining syndromes that end in loss of duty time and injury are paramount to long-term success. Allowing adequate time for rest and recovery and recognizing the negative influences of extreme exercise programs and excessive endurance training will be vital in moving physical training programs into a more modern perspective as used by elite strength-power anaerobic athletes in sports today. Because the warfighter is an elite athlete, it is time that training approaches that are scientifically based are updated within the military to match the functional demands of modern warfare and are given greater credence and value at the command levels. A needs analysis, development of periodized training modules, and individualization of programs are needed to optimize the strength of the modern warfighter. We now have the knowledge, professional coaches and nonprofit organization certifications with continuing education units, and modern training technology to allow this to happen. Ultimately, it only takes command decisions and implementation to make this possible.
2010-05-01
Shortfalls in units in $Mb Specialty Materials Beryllium Metal ST 36 $5.96M Beryllium Copper Master Alloy ST 0 $0.00M Beryl Ore ST 70 $0.01M...Boron MT 0 $0.00M Gallium KG 308 $0.17M Germanium KG 30,399 $30.34M Hafnium MT 0 $0.00M Indium Tr Oz 0 $0.00M Rhenium LB 32,753 $58.24M Rhodium...Beryllium Metalc ST 164 $26.96M Beryllium Copper Master Alloy ST 0 $0.00M Beryl Ored ST 1 $0.00M Boron MT 0 $0.00M Gallium KG 0 $0.00M Germanium KG
Bauer, Jan S., E-mail: jsb@tum.de [Department of Radiology, Technische Universität München, Munich (Germany); Department of Radiology, University of California, San Francisco, CA (United States); Max Planck Institute for Extraterrestrial Physics, Garching (Germany); Sidorenko, Irina [Max Planck Institute for Extraterrestrial Physics, Garching (Germany); Mueller, Dirk [Department of Radiology, Universität Köln (Germany); Baum, Thomas [Department of Radiology, Technische Universität München, Munich (Germany); Department of Radiology, University of California, San Francisco, CA (United States); Max Planck Institute for Extraterrestrial Physics, Garching (Germany); Issever, Ahi Sema [Department of Radiology, University of California, San Francisco, CA (United States); Department of Radiology, Charite, Berlin (Germany); Eckstein, Felix [Institute of Anatomy and Musculoskeletal Research, Paracelsus Medical University, Salzburg (Austria); Rummeny, Ernst J. [Department of Radiology, Technische Universität München, Munich (Germany); Link, Thomas M. [Department of Radiology, University of California, San Francisco, CA (United States); Raeth, Christoph W. [Max Planck Institute for Extraterrestrial Physics, Garching (Germany)
2014-01-15
Objectives: Finite-element-models (FEM) are a promising technology to predict bone strength and fracture risk. Usually, the highest spatial resolution technically available is used, but this requires excessive computation time and memory in numerical simulations of large volumes. Thus, FEM were compared at decreasing resolutions with respect to local strain distribution and prediction of failure load to (1) validate MDCT-based FEM and to (2) optimize spatial resolution to save computation time. Materials and methods: 20 cylindrical trabecular bone specimens (diameter 12 mm, length 15–20 mm) were harvested from elderly formalin-fixed human thoracic spines. All specimens were examined by micro-CT (isotropic resolution 30 μm) and whole-body multi-row-detector computed tomography (MDCT, 250 μm × 250 μm × 500 μm). The resolution of all datasets was lowered in eight steps to ∼2000 μm × 2000 μm × 500 μm and FEM were calculated at all resolutions. Failure load was determined by biomechanical testing. Probability density functions of local micro-strains were compared in all datasets and correlations between FEM-based and biomechanically measured failure loads were determined. Results: The distribution of local micro-strains was similar for micro-CT and MDCT at comparable resolutions and showed a shift toward higher average values with decreasing resolution, corresponding to the increasing apparent trabecular thickness. Small micro-strains (ε{sub eff} < 0.005) could be calculated down to 250 μm × 250 μm × 500 μm. Biomechanically determined failure load showed significant correlations with all FEM, up to r = 0.85 and did not significantly change with lower resolution but decreased with high thresholds, due to loss of trabecular connectivity. Conclusion: When choosing connectivity-preserving thresholds, both micro-CT- and MDCT-based finite-element-models well predicted failure load and still accurately revealed the distribution of local micro-strains in
Werner, C.; Kraus, D.; Mai, T. V.; Butterbach-Bahl, K.
2016-12-01
Agriculture is the economic backbone for over two thirds of Vietnam's population, providing food security, employment and income. However, agriculture in Vietnam is challenged by climate change and climate extremes and at the same time, agriculture remains a key source of greenhouse gas (GHG) emissions. The first bi-annual update report (BUR1), published in 2014 indicated that while the proportion of GHG emissions from agriculture had fallen from 43.1% to 33.2% from 2000 to 2010, the emission total increased from 65.1 mio to 88.4 mio t CO2e. Reducing GHG emissions from agriculture has thus become a key issue within the national strategy of GHG emission management. Here we present first data using IPCC Tier 3 modeling for quantifying the source strength of rice based crop systems for CH4 and N2O. We used LandscapeDNDC and linked it to a newly developed spatial landuse and land management database (climate, soil properties, and detailed field management data). Site application showed good agreement of simulated biomass, yield and GHG emissions with field observations, providing confidence for model use at national scale. Our results also show good agreement with national yield data and total annual emissions of the simulated period (2006-2015) ranged from 1060 - 1502 kt CH4 and 6.2 - 7.7 kt N2O, respectively. The dominating emission hotspot for CH4 is the Mekong Delta region with its double and triple rice cropping systems (819 kt CH4/yr, Fig. 1). With regard to N2O, emission hotspots have been identified to be closely related to regions with high fertilizer use and single to double rice cropping systems (Fig. 1). Though, our emission estimates are likely representing the best of current knowledge on national GHG emissions from rice based systems in Vietnam, the uncertainty is significant as information on rice system management remains vague. Sensitivity studies show that changes in field management affecting the soil organic carbon dynamics (duration of flooding
Rao, Samrat
2015-01-01
An atmospheric general circulation model (AGCM) with idealized and complete physics has been used to evaluate the Tropical Easterly Jet (TEJ) jet. In idealized physics, the role of upper tropospheric friction has been found to be important in getting realistic upper tropospheric zonal wind patterns in response to heating. In idealized physics, the location and strength of the TEJ as a response to Gill heating has been studied. Though the Gill model is considered to be widely successful in capturing the lower tropospheric response, it is found to be inadequate in explaining the location and strength of the upper level TEJ. Heating from the Gill model and realistic upper tropospheric friction does not lead to the formation of a TEJ.
Partial replacement of titanium carbide by tantalum carbide in three-phase WC-TiC-Co alloys tends to have a favorable effect on mechanical properties such as fatigue strength under bending and impact durability.
Prediction Model of High Temperature Rupture Strength of 00Cr18Ni10N Steel%00Cr18Ni10N钢高温持久强度的预测与验证
杨旭; 王正品; 要玉宏; 刘江南
2012-01-01
The high temperature rupture strength of 00Crl8Nil0N stainless steel is studied, The mathematical model of relation between the rupture strength at given temperature and the high temperature tensile strength of 00Crl8Ni10N steel is established by means of total differential and state function on the basis of Larson - Miller equation. The test data indicate: The rupture strength of 00Cr18Ni10N steel at 700 ℃ lasting 200 h calculated by the model conforms to the tested value. The relative error between them is 0. 6%.%研究了00Cr18Ni10N钢的高温持久强度.在Larson-Miller方程基础上,利用全微分和状态函数特征,建立了00Cr18Ni10N钢在给定温度条件下持久强度与高温抗拉强度之间关系的数学模型.通过试验结果表明,利用该数学理论模型预测00Cr18Ni10N钢在700℃,持久拉伸200 h理论与实测持久强度值相符,相对误差为0.6％.
吴世莲; 陆林侦; 曹明国; 查光玉
2011-01-01
Objective To study the influences of three kinds of disinfection methods on compressive strength of oral gypsum models. Methods On physical multi - function experimental bench the compressive strength of oral gypsum models was tested after microwave disinfection, pressure steam sterilization and ultraviolet irradiation disinfection. Results The compressive strength of three kinds of gypsum models including plaster, dental stone, high strength dental stone treated by microwave disinfection was slightly lower than that of the control group, but the difference had no statistical significance (P > 0.05). In addition to the gypsum models of high strength dental stone, the compressive strength of the other two kinds of gypsum models treated by ultraviolet irradiation disinfection was slightly lower too. The compressive strength of three kinds of gypsum models treated by pressure steam sterilization was significantly lower than that of the control group. Differences between the two groups of data were statistically significant (P < 0. 01). Conclusion Disinfection by microwave heating and ultraviolet irradiation do not obviously affect the compressive strength of oral gypsum models, but disinfection by pressure steam sterilization obviously affect the compressive strength of oral gypsum models.%目的 研究三种消毒方法对口腔石膏模型压缩强度的影响.方法 采用物理多功能试验台,对微波消毒法、压力蒸汽灭菌法和紫外线照射法消毒后的口腔石膏模型压缩强度进行了测试.结果 微波消毒法处理后的熟石膏、硬石膏和超硬石膏模型等种类石膏模型的压缩强度均略低于对照组压缩强度,但两组数据差异没有显著统计学意义(p＞0.05)；紫外线照射消毒法除超硬石膏模型之外,对另两种模型压缩强度也略有降低.压力蒸汽灭菌处理后的三种石膏模型的压缩强度明显低于对照,两组数据比较差异有显著统计学意义(p＜0.01).结论 微
王甲春; 阎培渝
2014-01-01
设计温度跟踪养护系统来模拟实际结构中混凝土所经历的温度历程，通过测试在标准养护条件20℃、恒温50℃和变温养护条件下不同强度等级的粉煤灰混凝土早龄期抗压强度的值，分析温度历程对粉煤灰混凝土早龄期抗压强度的影响。根据混凝土早龄期抗压强度的两个主要影响因素：温度和龄期，引入等效龄期理论建立了粉煤灰混凝土早龄期抗压强度的计算模型，并分析了模型参数。实际结构中的粉煤灰混凝土抗压强度可以通过测定温度场，利用计算模型进行相应龄期的抗压强度计算。研究结果表明，粉煤灰混凝土抗压强度计算模型能够较准确计算结构中粉煤灰混凝土的抗压强度，从而有效指导粉煤灰混凝土的工程应用。%Temperature tracking system is designed to simulate the actual curing concrete structure tem-perature history experienced .By the test standard curing conditions at 20℃, 50℃constant temperature and variable temperature curing conditions , early age compressive strength of different strength levels fly ash concrete is measured .According to the compressive strength of concrete at early age of the two main factors:temperature and age , the calculation model of compressive strength of fly ash concrete is estab-lished and analyze the model parameters with introduction of equivalent age theory .The compressive strength of fly ash concrete structures is predicted by measuring temperature field with computational mod -els.The results show that the compressive strength of fly ash concrete calculation model can accurately calculate the compressive strength of fly ash concrete structures , which can effectively guide the engineer-ing application of fly ash concrete .
Prediction of underwater target strength
WANG TongQing; Mohammad Amjad
2001-01-01
A model as well as its numerical method to calculate target strength of rigid body using Lighthill's acoustic analogy approach which developed from the propeller aircraft sound field study have been presented. The cases of ellipsoid target has been used to demonstrate the approach. The comparison of the numerical results with that of analytical formulation provides a satisfactory check for the validity of the approach. Some reasonable results have been discussed. The advantage of the present model is that it is suitable for any arbitrarily shaped rigid body moving with small Mach number.
Airborne field strength monitoring
J. Bredemeyer
2007-06-01
Full Text Available In civil and military aviation, ground based navigation aids (NAVAIDS are still crucial for flight guidance even though the acceptance of satellite based systems (GNSS increases. Part of the calibration process for NAVAIDS (ILS, DME, VOR is to perform a flight inspection according to specified methods as stated in a document (DOC8071, 2000 by the International Civil Aviation Organization (ICAO. One major task is to determine the coverage, or, in other words, the true signal-in-space field strength of a ground transmitter. This has always been a challenge to flight inspection up to now, since, especially in the L-band (DME, 1GHz, the antenna installed performance was known with an uncertainty of 10 dB or even more. In order to meet ICAO's required accuracy of ±3 dB it is necessary to have a precise 3-D antenna factor of the receiving antenna operating on the airborne platform including all losses and impedance mismatching. Introducing precise, effective antenna factors to flight inspection to achieve the required accuracy is new and not published in relevant papers yet. The authors try to establish a new balanced procedure between simulation and validation by airborne and ground measurements. This involves the interpretation of measured scattering parameters gained both on the ground and airborne in comparison with numerical results obtained by the multilevel fast multipole algorithm (MLFMA accelerated method of moments (MoM using a complex geometric model of the aircraft. First results will be presented in this paper.
Oxide driven strength evolution of silicon surfaces
Grutzik, Scott J.; Zehnder, Alan T., E-mail: atz2@cornell.edu [Field of Theoretical and Applied Mechanics, Cornell University, Ithaca, New York 14853 (United States); Milosevic, Erik [Department of Nanoengineering, SUNY Polytechnic University, Albany, New York 12203 (United States); Boyce, Brad L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-0889 (United States)
2015-11-21
Previous experiments have shown a link between oxidation and strength changes in single crystal silicon nanostructures but provided no clues as to the mechanisms leading to this relationship. Using atomic force microscope-based fracture strength experiments, molecular dynamics modeling, and measurement of oxide development with angle resolved x-ray spectroscopy we study the evolution of strength of silicon (111) surfaces as they oxidize and with fully developed oxide layers. We find that strength drops with partial oxidation but recovers when a fully developed oxide is formed and that surfaces intentionally oxidized from the start maintain their high initial strengths. MD simulations show that strength decreases with the height of atomic layer steps on the surface. These results are corroborated by a completely separate line of testing using micro-scale, polysilicon devices, and the slack chain method in which strength recovers over a long period of exposure to the atmosphere. Combining our results with insights from prior experiments we conclude that previously described strength decrease is a result of oxidation induced roughening of an initially flat silicon (1 1 1) surface and that this effect is transient, a result consistent with the observation that surfaces flatten upon full oxidation.
Examinations of factors influencing toe grip strength.
Soma, Masayuki; Murata, Shin; Kai, Yoshihiro; Nakae, Hideyuki; Satou, Yousuke; Murata, Jun; Miyazaki, Junya
2016-11-01
[Purpose] This study examined the relationship between toe grip strength and its associated factors by focusing on factors that were suggested to have a relationship with toe grip strength in previous studies, aiming to clarify the factors influencing the toe grip strength of healthy women. [Subjects and Methods] Twelve healthy young women were selected for this study. Their toe grip strength, angular changes in their ankle joint during toe grip, maximum voluntary contraction activities of the rectus femoris, biceps femoris, and tibialis anterior muscles, and the medial head of the gastrocnemius muscles were measured using electromyography. Their toe curl ability, foot-arch height ratio, and weight were also measured. [Results] Multiple regression analysis demonstrated that the predictors of toe grip strength in the resulting model were foot-arch height ratio and the percentage of integrated electromyography (%IEMG) of the tibialis anterior muscle, as the dependent variables. This reveals that women whose tibialis anterior muscle %IEMG values and foot-arch height ratio are high have greater %IEMG values have greater toe grip strength. [Conclusion] These findings suggest a significant relationship between foot-arch height ratio and toe grip strength, with a reciprocal interaction. These findings further indicate that the risk of falls by the elderly could be decreased if toe grip strength were enhanced, by increasing the height of a low foot-arch with the help of an inserted insole.
Burst strength of tubing and casing based on twin shear unified strength theory.
Lin, Yuanhua; Deng, Kuanhai; Sun, Yongxing; Zeng, Dezhi; Liu, Wanying; Kong, Xiangwei; Singh, Ambrish
2014-01-01
The internal pressure strength of tubing and casing often cannot satisfy the design requirements in high pressure, high temperature and high H2S gas wells. Also, the practical safety coefficient of some wells is lower than the design standard according to the current API 5C3 standard, which brings some perplexity to the design. The ISO 10400: 2007 provides the model which can calculate the burst strength of tubing and casing better than API 5C3 standard, but the calculation accuracy is not desirable because about 50 percent predictive values are remarkably higher than real burst values. So, for the sake of improving strength design of tubing and casing, this paper deduces the plastic limit pressure of tubing and casing under internal pressure by applying the twin shear unified strength theory. According to the research of the influence rule of yield-to-tensile strength ratio and mechanical properties on the burst strength of tubing and casing, the more precise calculation model of tubing-casing's burst strength has been established with material hardening and intermediate principal stress. Numerical and experimental comparisons show that the new burst strength model is much closer to the real burst values than that of other models. The research results provide an important reference to optimize the tubing and casing design of deep and ultra-deep wells.
Strength of Fibrous Composites
Huang, Zheng-Ming
2012-01-01
"Strength of Fibrous Composites" addresses evaluation of the strength of a fibrous composite by using its constituent material properties and its fiber architecture parameters. Having gone through the book, a reader is able to predict the progressive failure behavior and ultimate strength of a fibrous laminate subjected to an arbitrary load condition in terms of the constituent fiber and matrix properties, as well as fiber geometric parameters. The book is useful to researchers and engineers working on design and analysis for composite materials. Dr. Zheng-Ming Huang is a professor at the School of Aerospace Engineering & Applied Mechanics, Tongji University, China. Mr. Ye-Xin Zhou is a PhD candidate at the Department of Mechanical Engineering, the University of Hong Kong, China.
Notched Strength Allowables and Inplane Shear Strength of AS4/VRM-34 Textile Laminates
Grenoble, Ray W.; Johnston, William M.
2013-01-01
Notched and unnotched strength allowables were developed for a textile composite to provide input data to analytical structural models based on the Pultruded Rod Stiffened Efficient Unitized Structure (PRSEUS) concept. Filled-hole tensile strength, filled-hole compressive strength, and inplane shear strength along stitch lines have been measured. The material system evaluated in this study is based on warp-knitted preforms of AS4 carbon fibers and VRM-34 epoxy resin, which have been processed via resin infusion and oven curing. All specimens were tested in as-fabricated (dry) condition. Filled-hole strengths were evaluated with and without through-thickness stitching. The effects of scaling on filled-hole tensile strength were evaluated by testing specimens in two widths, but with identical width / hole-diameter ratios. Inplane shear specimens were stitched in two configurations, and two specimen thicknesses were tested for each stitch configuration.
Frederiksen, Henrik; Gaist, David; Petersen, Hans Christian
2002-01-01
in life is a major problem in terms of prevalence, morbidity, functional limitations, and quality of life. It is therefore of interest to find a phenotype reflecting physical functioning which has a relatively high heritability and which can be measured in large samples. Hand grip strength is known......-55%). A powerful design to detect genes associated with a phenotype is obtained using the extreme discordant and concordant sib pairs, of whom 28 and 77 dizygotic twin pairs, respectively, were found in this study. Hence grip strength is a suitable phenotype for identifying genetic variants of importance to mid...
Spin Resonance Strength Calculations
Courant, E. D.
2009-08-01
In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.
Spin resonance strength calculations
Courant,E.D.
2008-10-06
In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.
Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub
2012-06-05
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.
Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX
2010-08-31
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.
Strength of Cracked Reinforced Concrete Disks
Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The paper deals with models, based on the theory of plasticity, to be used in strength assessments of reinforced concrete disks suffering from different kinds of cracking. Based on the assumption that the sliding strength of concrete is reduced in sections where cracks are located, solutions...... for the shear strength of disks with initial cracks and disks suffering from isotropic cracking are presented. Furthermore, in the case of isotropicly cracked disks subjected to arbitrary in-plane loading, a general yield condition is derived....
Mapping strengths into virtues: The relation of the 24 VIA-strengths to six ubiquitous virtues
Willibald eRuch
2015-04-01
Full Text Available The Values-in-Action (VIA-classification distinguishes six core virtues and 24 strengths. As the assignment of the strengths to the virtues was done on theoretical grounds it still needs empirical verification. As an alternative to factor analytic investigations the present study utilizes expert judgments. In a pilot study the conceptual overlap among five sources of knowledge (strength’s name including synonyms, short definitions, brief descriptions, longer theoretical elaborations, and item content about a particular strength was examined. The results show that the five sources converged quite well, with the short definitions and the items being slightly different from the other. All strengths exceeded a cut-off value but the convergence was much better for some strengths (e.g., zest than for others (e.g., perspective. In the main study 70 experts (from psychology, philosophy, theology, etc. and 41 laypersons rated how prototypical the strengths are for each of the six virtues. The results showed that 10 were very good markers for their virtues, 9 were good markers, four were acceptable markers, and only one strength failed to reach the cut-off score for its assigned virtue. However, strengths were often markers for two or even three virtues, and occasionally they marked the other virtue more strongly than the one they were assigned to. The virtue prototypicality ratings were slightly positively correlated with higher coefficients being found for justice and humanity. A factor analysis of the 24 strengths across the ratings yielded the six factors with an only slightly different composition of strengths and double loadings. It is proposed to adjust either the classification (by reassigning strengths and by allowing strengths to be subsumed under more than one virtue or to change the definition of certain strengths so that they only exemplify one virtue. The results are discussed in the context of factor analytic attempts to verify the
The Character Strengths of Class Clowns
Willibald F. Ruch
2014-09-01
Full Text Available Class clowns traditionally were studied as a type concept and identified via sociometric procedures. In the present study a variable-centered approach was favored and class clown behaviors were studied in the context of character strengths, orientations to happiness and satisfaction with life. A sample of 672 Swiss children and adolescents filled in an 18 item self-report instrument depicting class clown behaviors. A hierarchical model of class clown behaviors was developed distinguishing a general factor and the four positively correlated dimensions of identified as a class clown, comic talent, disruptive rule-breaker, and subversive joker. Analysis of the general factor showed that class clowns were primarily male, and tended to be seen as class clowns by the teacher. Analyses of the 24 character strengths of the VIA-Youth (Park & Peterson, 2006 showed that class clowns were high in humor and leadership, and low in strengths like prudence, self-regulation, modesty, honesty, fairness, perseverance, and love of learning. An inspection of signature strengths revealed that 75% of class clowns had humor as a signature strength. Furthermore, generally class clown behaviors were shown by students indulging in a life of pleasure, but low life of engagement. The four dimensions yielded different character strengths profiles. While all dimensions of class clowns behaviors were low in temperance strengths, the factors identified as the class clown and comic talent were correlated with leadership strengths and the two negative factors (disruptive rule-breaker, subversive joker were low in other directed strengths. The disruptive rule breaking class clown was additionally low in intellectual strengths. While humor predicted life satisfaction, class clowning tended to go along with diminished satisfaction with life. It is concluded that different types of class clowns need to be kept apart and need different attention by teachers.
The character strengths of class clowns.
Ruch, Willibald; Platt, Tracey; Hofmann, Jennifer
2014-01-01
Class clowns traditionally were studied as a type concept and identified via sociometric procedures. In the present study a variable-centered approach was favored and class clown behaviors were studied in the context of character strengths, orientations to happiness and satisfaction with life. A sample of 672 Swiss children and adolescents filled in an 18 item self-report instrument depicting class clown behaviors. A hierarchical model of class clown behaviors was developed distinguishing a general factor and the four positively correlated dimensions of "identified as a class clown," "comic talent," "disruptive rule-breaker," and "subversive joker." Analysis of the general factor showed that class clowns were primarily male, and tended to be seen as class clowns by the teacher. Analyses of the 24 character strengths of the VIA-Youth (Park and Peterson, 2006) showed that class clowns were high in humor and leadership, and low in strengths like prudence, self-regulation, modesty, honesty, fairness, perseverance, and love of learning. An inspection of signature strengths revealed that 75% of class clowns had humor as a signature strength. Furthermore, class clown behaviors were generally shown by students indulging in a life of pleasure, but low life of engagement. The four dimensions yielded different character strengths profiles. While all dimensions of class clowns behaviors were low in temperance strengths, the factors "identified as the class clown" and "comic talent" were correlated with leadership strengths and the two negative factors ("disruptive rule-breaker," "subversive joker") were low in other directed strengths. The disruptive rule breaking class clown was additionally low in intellectual strengths. While humor predicted life satisfaction, class clowning tended to go along with diminished satisfaction with life. It is concluded that different types of class clowns need to be kept apart and need different attention by teachers.
Whitney, J. M.
1983-01-01
The notch strength of composites is discussed. The point stress and average stress criteria relate the notched strength of a laminate to the average strength of a relatively long tensile coupon. Tests of notched specimens in which microstrain gages have been placed at or near the edges of the holes have measured strains much larger that those measured in an unnotched tensile coupon. Orthotropic stress concentration analyses of failed notched laminates have also indicated that failure occurred at strains much larger than those experienced on tensile coupons with normal gage lengths. This suggests that the high strains at the edge of a hole can be related to the very short length of fiber subjected to these strains. Lockheed has attempted to correlate a series of tests of several laminates with holes ranging from 0.19 to 0.50 in. Although the average stress criterion correlated well with test results for hole sizes equal to or greater than 0.50 in., it over-estimated the laminate strength in the range of hole sizes from 0.19 to 0.38 in. It thus appears that a theory is needed that is based on the mechanics of failure and is more generally applicable to the range of hole sizes and the varieties of laminates found in aircraft construction.
The Strength of Varying Tie Strength
Bruggeman, Jeroen
2012-01-01
"The Strength of Weak Ties" argument (Granovetter 1973) says that the most valuable information is best collected through bridging ties with other social circles than one's own, and that those ties tend to be weak. Aral and Van Alstyne (2011) added that to access complex information, actors need strong ties ("high bandwidth") instead. These insights I generalize by pointing at actors' interest to avoid spending large resources on low value information. Weak ties are well-suited for relatively simple information at low transmission and tie maintenance costs, whereas for complex information, the best outcomes are expected for those actors who vary their bandwidths along with the value of information accessed. To support my claim I use all patents in the USA (two million) over the period 1975-1999. I also show that in rationalized fields, such as technology, bandwidth correlates highly with the value of information, which provides support for using this proxy if value can't be measured directly. Finally, I show ...
Strength-length scaling of elementary hemp fibers
Poriķe, E.; Andersons, J.
2013-03-01
The application of hemp fibers as a reinforcement of composite materials necessitates the characterization of fiber strength scatter and the effect of fiber length on its strength. With this aim, elementary hemp fibers were tested in tension at two different gage lengths. Due to the similar morphology of hemp and flax fibers, the probabilistic strength models derived and verified for the latter were applied to the former. The fiber strength was found to agree with the modified Weibull distribution. The modeling approaches developed for describing the variability of the strength and failure strain of elementary flax fibers are shown to be also applicable to hemp fibers.
Strength analysis of laser welded lap joint for ultra high strength steel
Jeong, Young Cheol; Kim, Cheol Hee; Cho, Young Tae; Jung, Yoon Gyo
2013-12-01
Several industries including the automotive industry have recently applied the process of welding high strength steel. High strength steel is steel that is harder than normal high strength steel, making it much stronger and stiffer. HSS can be formed in pieces that can be up to 10 to 15 percent thinner than normal steel without sacrificing strength, which enables weight reduction and improved fuel economy. Furthermore, HSS can be formed into complex shapes that can be welded into structural areas. This study is based on previous experiments and is aimed at establishing the stress distribution for laser welded high strength steel. Research on the stress distribution for laser welded high strength steel is conducted by using Solid Works, a program that analyzes the stress of a virtual model. In conclusion, we found that the stress distribution is changed depending on the shape of welded lap joint. In addition, the Influence of the stress distribution on welded high strength steel can be used to standard for high energy welding of high strength steel, and we can also predict the region in welded high strength steel that may cracked.
Strength evaluation code STEP for brittle materials
Ishihara, Masahiro [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Futakawa, Masatoshi
1997-12-01
In a structural design using brittle materials such as graphite and/or ceramics it is necessary to evaluate the strength of component under complex stress condition. The strength of ceramic materials is said to be influenced by the stress distribution. However, in the structural design criteria simplified stress limits had been adopted without taking account of the strength change with the stress distribution. It is, therefore, important to evaluate the strength of component on the basis of the fracture model for brittle material. Consequently, the strength evaluation program, STEP, on a brittle fracture of ceramic materials based on the competing risk theory had been developed. Two different brittle fracture modes, a surface layer fracture mode dominated by surface flaws and an internal fracture mode by internal flaws, are treated in the STEP code in order to evaluate the strength of brittle fracture. The STEP code uses stress calculation results including complex shape of structures analyzed by the generalized FEM stress analysis code, ABAQUS, so as to be possible to evaluate the strength of brittle fracture for the structures having complicate shapes. This code is, therefore, useful to evaluate the structural integrity of arbitrary shapes of components such as core graphite components in the HTTR, heat exchanger components made of ceramics materials etc. This paper describes the basic equations applying to the STEP code, code system with a combination of the STEP and the ABAQUS codes and the result of the verification analysis. (author)
Stochastic model of strength degradation based on P-S-N curve%基于 P-S-N 曲线的强度退化随机模型
安宗文; 高建雄; 刘波
2015-01-01
In general,strength degradation is a stochastic and irreversible process.Gamma process is an in-dependent nonnegative increment process which can be used to describe the characteristics of strength degradation.However,during strength degradation process,the degradation data that characterizes de-generate state (wear,crack,corrosion,etc.)is often difficult to measure directly,which is the typical missing data.But the P-S-N curve that characterizes material fatigue performance is generally easy to obtain.Therefore,this paper assumes that the shape parameter of Gamma process is a linear function, and estimates the characteristic parameters of Gamma process using material P-S-N curve.Then a stochastic model of strength degradation based on P-S-N curve is established.Finally,the validity of the proposed model is verified and analyzed by using the fatigue test data of 20CrMnTi steel.The results show that this model can effectively describe the macroscopic trend of material strength degradation.%强度退化一般具有随机性和不可逆性，而 Gamma 过程是一个独立非负的增量过程，具有描述强度退化特性的基本属性。由于强度退化过程中，表征退化状态(磨损、裂纹、腐蚀等)的数据很难直接测量，属于典型的缺失数据，而表征材料疲劳性能的 P-S-N 曲线一般易于获得。因此，本文假定 Gamma 过程的形状参数为线性函数，并利用材料的 P-S-N 曲线对 Gamma 过程的特征参数进行估计，由此建立基于 P-S-N 曲线的强度退化随机模型。最后，利用20CrMnTi 钢的疲劳试验数据对所建模型的有效性进行验证和分析。结果表明，所建模型能够有效描述材料强度退化的宏观趋势。
Sri Handayani
2008-01-01
Amalgam didefinisikan sebagai campuran dari dua atau beberapa logam (alloy) yang salah satunya adalali merkuri. Dental amalgam sendiri merupakan campuran dari merkuri (Hg), perak (Ag), timah (Sn), tembaga (Cu) dan bahan-bahan lain yang memiliki fungsinya masing-masing, dimana sebagian diantaranya akan saling mengatasi kekurangan yang ditimbulkan logam lain, jika logam tersebut dikombinasikan dengan perbandingan yang tepat. Amalgam mempunyai strength (kekuatan) yang cukup besar sehingga dap...
Character strengths and virtues
2015-01-01
The target of this work is to carry out a critical analysis about some of the underlying epistemological assumptions in Peterson and Seligman’s book Character Strengths and Virtues. A handbook and classifications (2004). This is a theoretical investigation that belongs to the epistemology of psychology field. According to the theory proposed by Serroni Copello (2003), a critic progress rational criterion is methodologically applied. The analysis points out some epistemological weakness that l...
Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.
2011-02-20
potential for erosion, it is important to compare the measured shear strength to penetrometer measurements and to develop a correlation (or correlations) between UCS measured by a pocket penetrometer and direct shear strength measurements for various homogeneous and heterogeneous simulants. This study developed 11 homogeneous simulants, whose shear strengths vary from 4 to 170 kPa. With these simulants, we developed correlations between UCS measured by a Geotest E-280 pocket penetrometer and shear strength values measured by a Geonor H-60 hand-held vane tester and a more sophisticated bench-top unit, the Haake M5 rheometer. This was achieved with side-by-side measurements of the shear strength and UCS of the homogeneous simulants. The homogeneous simulants developed under this study consist of kaolin clay, plaster of Paris, and amorphous alumina CP-5 with water. The simulants also include modeling clay. The shear strength of most of these simulants is sensitive to various factors, including the simulant size, the intensity of mixing, and the curing time, even with given concentrations of simulant components. Table S.1 summarizes these 11 simulants and their shear strengths.
Qafoku, Odeta; Felmy, Andrew R.
2007-01-01
The development of an accurate aqueous thermodynamic model is described for oxalate species in the Na-Ba-Ca-Mn-Sr-Cl-NO3-PO4-SO4-H2O system at 25°C. The model is valid to high ionic strength (as high as 10m) and from very acid (10m H2SO4) to neutral and basic conditions. The model is based upon the equations of Pitzer and co-workers. The necessary ion-interaction parameters are determined by comparison with experimental data taken from the literature or determined in this study. The proposed aqueous activity and solubility model is valid for a range of applications from interpretation of studies on mineral dissolution at circumneutral pH to the dissolution of high-level waste tank sludges under acidic conditions.
陈志辉; 程晓辉
2014-01-01
An approach is proposed for the undrained strength anisotropy of saturated clays based on a thermodynamic constitutive model, TTM (Tsinghua thermodynamic soil model). The model analyses and experiments indicate that the anisotropic consolidation or K0 consolidation can be an important cause for the strength anisotropy of geotechnical materials, and the strength anisotropy becomes more significant with the decrease of the consolidation stress ratio Kc. During the undrained loading, the direction of the principal stresses has a huge influence on the undrained strength and deformation of soils. Generally speaking, with the rotation of principal stresses from 0°to 90°, the undrained shear strength decreases while the peak strain increases. Besides, the anisotropic consolidation causes the non-coaxiality of the principal stresses and strains. Based on the proposed model, simulations and predictions are made for various test results of Kaolin clay and Boston blue clay, which indicate that TTM is able to show and predict the strength change and deformation behavior of soils under complex stress paths caused by the strength anisotropy, strain softening and rotation of direction of the principal axis of stress.%基于饱和土体TTM（Tsinghua thermodynamic soil model）热力学本构模型分析研究了饱和黏土的不排水抗剪强度各向异性问题。模型及试验研究表明：非等向或K0固结历史是引起土体强度各向异性的重要原因，固结应力比Kc越小，不排水强度各向异性越大。不排水加载过程中主应力轴的方向对土体不排水抗剪强度和变形有着重要影响。一般而言，当主应力轴方向从0°旋转到90°时，土体的不排水抗剪强度逐渐下降，峰值应变却逐渐增大。此外，非等向固结会导致土体主应力与主应变的非共轴性。利用TTM理论模型，对Kaolin Clay 和Boston Blue Clay的不同试验结果进行了模拟验证和预测。结果表明，TTM理
Strength Properties of Aalborg Clay
Iversen, Kirsten Malte; Nielsen, Benjaminn Nordahl; Augustesen, Anders Hust
resulted in many damaged buildings in Aalborg. To provide sufficient bearing capacity it is therefore necessary either to remove the fill or to construct the building on piles. Both methods imply that the strength of Aalborg Clay is important for the construction. This paper evaluates the strength...... of Aalborg Clay by use of triaxial tests from four different locations. Both the drained strength (c and ϕ) and the undrained strength (cu) are assessed through two different methods: one where the strength is assumed to vary with the effective stress and another where the strength is found to be constant....
Strength of precast concrete shear joints reinforced with high-strength wire ropes
Joergensen, Henrik B.; Hoang, Linh Cao; Hagsten, Lars German
2017-01-01
This paper concerns the in-plane shear strength of connections between precast concrete wall elements reinforced with looped high-strength wire ropes. The looped wire ropes are pre-installed in so-called ‘wire boxes’ which function as shear keys. Although only a small amount of research...... on the shear strength of such connections can be found in the literature, this type of connection is increasingly being used because wire ropes are much more construction-friendly than traditional U-bars. A rigid plastic upper bound model for the shear strength of wall connections reinforced with looped wire...... ropes that are pre-installed in wire boxes is presented along with test results on the shear strength of connections with double-wire boxes. It is shown that the plastic solution agrees well with both the obtained test results and results from previously conducted tests....
Peng, Qing; Wang, Guangyu; Liu, G. R.; de, Suvranu
2015-06-01
We investigate the elastic constants and equations of state (EOS) of the β-polymorph of cyclotetramethylene tetranitramine (HMX) energetic molecular crystal using density functional theory (DFT) calculations. The combination of vdW-DF2 van der Waals functionals and PBE exchange-correlation functionals gives optimized results. The DFT results are used to optimize the Reactive Force Field (ReaxFF). The material strength and EOS of beta-HMX at finite temperatures are then predicted from ReaxFF molecular dynamics simulations. Our results suggest that the optimized ReaxFF predicts the mechanics and EOS of beta-HMX well. The authors would like to acknowledge the generous financial support from the Defense Threat Reduction Agency (DTRA) Grant # HDTRA1-13-1-0025.
Collagen fibril diameter and leather strength.
Wells, Hannah C; Edmonds, Richard L; Kirby, Nigel; Hawley, Adrian; Mudie, Stephen T; Haverkamp, Richard G
2013-11-27
The main structural component of leather and skin is type I collagen in the form of strong fibrils. Strength is an important property of leather, and the way in which collagen contributes to the strength is not fully understood. Synchrotron-based small angle X-ray scattering (SAXS) is used to measure the collagen fibril diameter of leather from a range of animals, including sheep and cattle, that had a range of tear strengths. SAXS data were fit to a cylinder model. The collagen fibril diameter and tear strength were found to be correlated in bovine leather (r(2) = 0.59; P = 0.009), with stronger leather having thicker fibrils. There was no correlation between orientation index, i.e., fibril alignment, and fibril diameter for this data set. Ovine leather showed no correlation between tear strength and fibril diameter, nor was there a correlation across a selection of other animal leathers. The findings presented here suggest that there may be a different structural motif in skin compared with tendon, particularly ovine skin or leather, in which the diameter of the individual fibrils contributes less to strength than fibril alignment does.
FIELD STRENGTH MEASUREMENTS, PHASE I.
The program included the testing and evaluation of commercial and military field- strength meters. It also included a study of the interpretation of...field- strength measurement data taken under multipath conditions. As part of the field- strength meter evaluation, five instruments, the AN/TRM-7, NF...interpretation of the measured data is the variability of field- strength values obtained over an area. Such variability is caused by the presence of multipath
Asteroid airburst altitude vs. strength
Robertson, Darrel; Wheeler, Lorien; Mathias, Donovan
2016-10-01
Small NEO asteroids (<Ø140m) may not be a threat on a national or global level but can still cause a significant amount of local damage as demonstrated by the Chelyabinsk event where there was over $33 million worth of damage (1 billion roubles) and 1500 were injured, mostly due to broken glass. The ground damage from a small asteroid depends strongly on the altitude at which they "burst" where most of the energy is deposited in the atmosphere. The ability to accurately predict ground damage is useful in determining appropriate evacuation or shelter plans and emergency management.Strong asteroids, such as a monolithic boulder, fail and create peak energy deposition close to the altitude at which ram dynamic pressure exceeds the material cohesive strength. Weaker asteroids, such as a rubble pile, structurally fail at higher altitude, but it requires the increased aerodynamic pressure at lower altitude to disrupt and disperse the rubble. Consequently the resulting airbursts have a peak energy deposition at similar altitudes.In this study hydrocode simulations of the entry and break-up of small asteroids were performed to examine the effect of strength, size, composition, entry angle, and speed on the resulting airburst. This presentation will show movies of the simulations, the results of peak burst height, and the comparison to semi-analytical models.
Strength Development for Young Adolescents
McDaniel, Larry W.; Jackson, Allen; Gaudet, Laura
2009-01-01
Participation in strength training is important for older children or young adolescences who wish to improve fitness or participate in sports. When designing strength training programs for our youth this age group is immature anatomically, physiologically, and psychologically. For the younger or inexperienced group the strength training activities…
Strength Training and Children's Health.
Faigenbaum, Avery D.
2001-01-01
Provides an overview of the potential health benefits of strength training for children, discussing the role of strength training in preventing sports-related injuries and highlighting design considerations for such programs. The focus is on musculoskeletal adaptations to strength training that are observable in healthy children. Guidelines for…
Strength Training and Children's Health.
Faigenbaum, Avery D.
2001-01-01
Provides an overview of the potential health benefits of strength training for children, discussing the role of strength training in preventing sports-related injuries and highlighting design considerations for such programs. The focus is on musculoskeletal adaptations to strength training that are observable in healthy children. Guidelines for…
Strength of Rewelded Inconel 718
Bayless, E.; Lovoy, C. V.; Mcllwain, M. C.; Munafo, P.
1982-01-01
Inconel 718, nickel-based alloy used extensively for high-temperature structural service, welded repeatedly without detriment to its strength. According to NASA report, tests show 12 repairs on same weld joint do not adversely affect ultimate tensile strenth, yield strength, fatigue strength, metallurgical grain structures, or ability of weld joint to respond to post weld heat treatments.
Study on Neural Network Model of Shear Strength Index in Yunnan Laterite%云南红土抗剪强度指标的神经网络模型研究
杨玉婷; 黄英
2012-01-01
Based on the results of direct shear test about cement reinforced laterite,the artificial neural network model of shear strength index in Yunnan laterite is set up using the theory of artificial neural network. The input layer vector of the model includes the adding proportion of cement and samples curing time, the output layer vector includes two shear strength parameters which are cohesion and internal friction angle,the hidden layer transfer function is determined for tangent function, the output layer transfer function is determined for logarithmic function, the number of hidden layer neurons is determined as 5. The predicted results show that the neural network model can reflect the influence of adding proportion of cement and samples curing time on the shear strength of laterite, the prediction results of the shear strength index are close to the measured values , and the predicted effect is good.%以水泥加固红土的直剪试验结果为基础,运用人工神经网络理论建立起云南红土抗剪强度指标的神经网络模型.该模型的输入层向量包括水泥加入比例和试样养护时间两个影响因素,输出层向量为粘聚力和内摩擦角两个抗剪强度指标,隐层传递函数确定为正切函数,输出层传递函数确定为对数函数,隐层神经元数目确定为5.预测结果表明,该神经网络模型能够反映水泥加入比例和试样养护时间对红土抗剪强度的影响,预测的抗剪强度指标与实测值接近,预测效果较好.
Relationship between tensile strength and porosity for high porosity metals
刘培生; 付超; 李铁藩; 师昌绪
1999-01-01
An analysis model has been established according to the structure feature of high porosity metals, and the mathematical relationship between the tensile strength and porosity for this material has been derived from the model. Moreover, the corresponding theoretical formula has been proved good to reflect the variation law of tensile strength with porosity for high porosity metals by the example experiment on nickel foam.
Magnetic Field Strengths in Photodissociation Regions
Balser, Dana S; Jeyakumar, S; Bania, T M; Montet, Benjamin T; Shitanishi, J A
2015-01-01
We measure carbon radio recombination line (RRL) emission at 5.3 GHz toward four HII regions with the Green Bank Telescope (GBT) to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi (2007) suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic (MHD) waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B ~ 100-300 micro Gauss in W3 and NGC6334A. Our results for W49 and NGC6334D are less well constrained with total magnetic field strengths between B ~ 200-1000 micro Gauss. HI and OH Zeeman measurements of the line-of-sight magnetic field strength (B_los), taken from the literature, are between a facto...
Climate strength: a new direction for climate research.
Schneider, Benjamin; Salvaggio, Amy Nicole; Subirats, Montse
2002-04-01
Climate strength was conceptualized within D. Chan's (1998) discussion of compositional models and the concept of culture strength from the organizational culture literature. Climate strength was operationalized in terms of within-group variability in climate perceptions-the less within-group variability, the stronger the climate. The authors studied climate strength in the context of research linking employee service climate perceptions to customer satisfaction. The hypothesis was tested that climate strength moderates the relationship between employee perceptions of service climate and customer satisfaction experiences. Partial support for the hypothesis was reported in both a concurrent and predictive (3-year) test across 118 branches of a bank. In the predictive study only the interaction of climate and climate strength predicted customer satisfaction. Implications for future research on climate and climate strength are discussed.
The Strength-Interval Curve in Cardiac Tissue
Sunil M. Kandel
2013-01-01
Full Text Available The bidomain model describes the electrical properties of cardiac tissue and is often used to simulate the response of the heart to an electric shock. The strength-interval curve summarizes how refractory tissue is excited. This paper analyzes calculations of the strength-interval curve when a stimulus is applied through a unipolar electrode. In particular, the bidomain model is used to clarify why the cathodal and anodal strength-interval curves are different, and what the mechanism of the “dip” in the anodal strength-interval curve is.
Size Effect for Normal Strength Concrete in Uniaxial Tension
李庆斌; 尹玉先
2004-01-01
This paper presents a new size effect model for normal strength concrete subjected to uniaxial tension. The model is based on two extremes, sand cement paste in uniaxial tension and a sand-cement-paste/rock interface in uniaxial tension. Uniaxial tension tests with normal strength concrete measuring the tensile strength of normal strength concrete specimens with different geometrical shapes and different ratios of the aggregate size to the characteristic dimension of the concrete specimen show a significant size effect. The theoretical size effect law prediction agrees well with the experimental data.
On strength of porous material
Nielsen, Lauge Fuglsang
1999-01-01
The question of non-destructive testing of porous materials has always been of interest for the engineering profession. A number of empirically based MOE-MOR relations between stiffness (Modulus Of Elasticity) and strength (Modulus OF Rupture) of materials have been established in order to control...... to the theoretical research on non-destructive testing of such materials relating strength to stiffness and pore geometry.It is demonstrated that solutions for stiffness, tensile strength, and pore strength (damaging pore pressure, frost, fire) for some ideal porous materials can be determined theoretically only...... from knowing about pore geometry, solid phase stiffness, and zero-porosity strength. Pore geometry is the very important common denominator which controls both both stiffness and strength.The accurate results obtained are finally used to suggest generalizations with respect to strength in general...
Normative values of eccentric hip abduction strength in novice runners
Jørgensen, Daniel Ramskov; Pedersen, Mette Broen; Kastrup, Kristrian
2014-01-01
normative values of maximal eccentric hip abduction strength in novice runners. METHODS: Novice healthy runners (n = 831) were recruited through advertisements at a hospital and a university. Maximal eccentric hip abduction strength was measured with a hand-held dynamometer. The demographic variables......PURPOSE: Low eccentric strength of the hip abductors, might increase the risk of patellofemoral pain syndrome and iliotibial band syndrome in runners. No normative values for maximal eccentric hip abduction strength have been established. Therefore the purpose of this study was to establish...... associated with maximal eccentric hip abduction strength from a univariate analysis were included in a multivariate linear regression model. Based on the results from the regression model, a regression equation for normative hip abduction strength is presented. RESULTS: A SIGNIFICANT DIFFERENCE IN MAXIMAL...
Puydt, Quentin; Flouriot, Sylvain; Ringeval, Sylvain; De Geuser, Frédéric; Estevez, Rafael; Parry, Guillaume; Deschamps, Alexis
2014-12-01
This paper presents an experimental and modeling study of the mechanical behavior of an electron beam welded EN-AW 7020 aluminum alloy. The heterogeneous distribution of mechanical properties is characterized by micro-tensile tests and by strain field measurements using digital image correlation technic. These results are related to the microstructural observation presented in the companion paper. The mechanical behavior of the weld is simulated by a finite element model including a Gurson-type damage evolution model for void evolution. The model is shown to be capable of describing accurately experimental situations where the sample geometry is varied, resulting in stress triaxiality ratios ranging from 0.45 to 1.3.
Hao Wang
2016-01-01
Full Text Available Hysteresis characteristics of grain-oriented electrical steel were studied through the hysteresis loop. Existing hysteresis fitting simulation methods were summarized, and new Fe-3% Si grain-oriented electrical steel hysteresis loop model was proposed. Undetermined coefficients of the magnetic field intensity and magnetic flux density were determined by both the fixed angle method and the least squares method, and the hysteresis loop model was validated with high fitting degree by experimental data.
Tensile Strength of Snow using Centrifugal Technique
Agraj Upadhyay
2007-11-01
Full Text Available Tensile strength of snow was determined using indigenously developed automated centrifugalmachine. Processed snow (sintered at 20 °C for 4 days samples of dia: 65 mm andheight:130 mm were tested using this machine.The experiments were conducted on sieved snowat four temperature levels of 0 °C, 3 °C,6 °C and 9 °C at density ranging from 200-460 kg/m3.Results of these experiments have been compared with the earlier suggested models. Probabilitydistribution of snow strength on the basis of current experimental data has also been presented.
Distribution of crushing strength of tablets
Sonnergaard, Jørn
2002-01-01
as a material constant. However, the estimation of this parameter is laborious and subject to estimation problems. It is shown that the Weibull modulus is inherently connected to the coefficient of variation and that the information obtained from the modulus is unclear. The distribution of crushing strength...... data from nine model tablet formulations and four commercial tablets are shown to follow the normal distribution. The importance of proper cleaning of the crushing strength apparatus is demonstrated. Copyright © 2002 Elsevier Science B.V....
Neural Network Analysis of Tensile Strength of Austempered Ductile Iron
Z. Ławrynowicz; S. Dymski; M. Trepczyńska - Łent; T. Giętka
2007-01-01
The neural technique was applied to the analysis of the ultimate tensile strength and additionally the yield strength of austempered ductile iron (ADI). Austempered ductile iron is an excellent material and it possesses attractive properties as high strength, ductility and toughness. This paper begins with an introduction to neural networks and demonstrates the ability of the method to investigate new phenomena in cases where the information cannot be accessed experimentally. The model allows...
Hales, Patrick W; Kirkham, Fenella J; Clark, Christopher A
2016-02-01
Many MRI techniques require prior knowledge of the T1-relaxation time of blood (T1bl). An assumed/fixed value is often used; however, T1bl is sensitive to magnetic field (B0), haematocrit (Hct), and oxygen saturation (Y). We aimed to combine data from previous in vitro measurements into a mathematical model, to estimate T1bl as a function of B0, Hct, and Y. The model was shown to predict T1bl from in vivo studies with a good accuracy (± 87 ms). This model allows for improved estimation of T1bl between 1.5-7.0 T while accounting for variations in Hct and Y, leading to improved accuracy of MRI-derived perfusion measurements.
Neuromuscular adaptations following prepubescent strength training.
Ozmun, J C; Mikesky, A E; Surburg, P R
1994-04-01
Underlying mechanisms of prepubescent strength gains following resistance training are speculative. The purpose of this investigation was to determine the effects of 8 wk of resistance training on muscular strength, integrated EMG amplitude (IEMG), and arm anthropometrics of prepubescent youth. Sixteen subjects (8 males, 8 females) were randomly assigned to trained or control groups. All subjects (mean age = 10.3 yr) were of prepubertal status according to the criteria of Tanner. The trained group performed three sets (7-11 repetitions) of bicep curls with dumbbells three times per week for 8 wk. Pre- and posttraining measurements included isotonic and isokinetic strength of the elbow flexors, arm anthropometrics, and IEMG of the biceps brachii. Planned comparisons for a 2 x 2 (group by test) ANOVA model were used for data analysis. Significant isotonic (22.6%) and isokinetic (27.8%) strength gains were observed in the trained group without corresponding changes in arm circumference or skinfolds. The IEMG amplitude increased 16.8% (P < 0.05). The control group did not demonstrate any significant changes in the parameters measured. Early gains in muscular strength resulting from resistance training prepubescent children may be attributed to increased muscle activation.
Charles H Rundle
Full Text Available This study sought to determine if direct application of the lentiviral (LV-cyclooxygenase 2 (COX2 vector to the tendon-bone interface would promote osteointegration of the tendon graft in a rat model of biceps tenodesis. The LV-COX2 gene transfer strategy was chosen for investigation because a similar COX2 gene transfer strategy promoted bony bridging of the fracture gap during bone repair, which involves similar histologic transitions that occur in osteointegration. Briefly, a 1.14-mm diameter tunnel was drilled in the mid-groove of the humerus of adult Fischer 344 rats. The LV-COX2 or βgal control vector was applied directly into the bone tunnel and onto the end of the tendon graft, which was then pulled into the bone tunnel. A poly-L-lactide pin was press-fitted into the tunnel as interference fixation. Animals were sacrificed at 3, 5, or 8 weeks for histology analysis of osteointegration. The LV-COX2 gene transfer strategy enhanced neo-chondrogenesis at the tendon-bone interface but with only marginal effect on de novo bone formation. The tendon-bone interface of the LV-COX2-treated tenodesis showed the well-defined tendon-to-fibrocartilage-to-bone histologic transitions that are indicative of osteointegration of the tendon graft. The LV-COX2 in vivo gene transfer strategy also significantly enhanced angiogenesis at the tendon-bone interface. To determine if the increased osteointegration was translated into an improved pull-out mechanical strength property, the pull-out tensile strength of the LV-COX2-treated tendon grafts was determined with a pull-out mechanical testing assay. The LV-COX2 strategy yielded a significant improvement in the return of the pull-out strength of the tendon graft after 8 weeks. In conclusion, the COX2-based in vivo gene transfer strategy enhanced angiogenesis, osteointegration and improved return of the pull-out strength of the tendon graft. Thus, this strategy has great potential to be developed into an
孙蓟泉; 李双娇; 尹衍军
2014-01-01
High strength steel, the best choice for application in the lightweight technology of automotive body is limited to be used due to the forming technique. The principle, characteristics and present research developments of the advanced forming processes such as hydroforming tech-nology, laser butt welding technology and hot stamping technology are discussed. And also the constitutive model of the advanced high strength steel is explained in order to provide the basis for improving the forming property of the steel.%高强钢是汽车车身轻量化的首选材料，但其成型问题一直是限制其推广应用的重要因素。对高强钢的先进成型技术，如液压成型、激光拼焊、热冲压成型等的原理、特点及最新研究进展进行了论述。同时，对先进高强钢的本构模型进行了阐述，以期对改进高强钢成型性能提供依据。
Character strengths and virtues
Mariana Gancedo
2015-09-01
Full Text Available The target of this work is to carry out a critical analysis about some of the underlying epistemological assumptions in Peterson and Seligman’s book Character Strengths and Virtues. A handbook and classifications (2004. This is a theoretical investigation that belongs to the epistemology of psychology field. According to the theory proposed by Serroni Copello (2003, a critic progress rational criterion is methodologically applied. The analysis points out some epistemological weakness that leads to incongruences in the statements and conclusions of the investigations, such as: the absence of a unified theory, a candid search of objectivity, and the superposition of implicit paradigms. It also takes notice of a causal and elementary logic -which goes against today’s scientific paradigm-, and the strong American culture zeitgeist present in the principles of Positive Psychology. Finally, some ethic problems are displayed, in particular the step taken from a descriptive attitude –characteristic of science- toward a prescriptive attitude –characteristic of moral codes-.
Drach, M.; Andrzejewska, A.; Narkiewicz-Michalek, J.; Rudzinski, W.; Koopal, L.K.
2002-01-01
A theory of ionic surfactant aggregation on oppositely charged surfaces is presented. In the proposed model the adsorbed phase is considered as a mixture of singly dispersed surfactant molecules, monolayered and bilayered aggregates of various sizes and the ions of simple electrolyte added to the aq
FIELD STRENGTH MEASUREMENTS, PHASE II.
The measurement of the strength of radio frequency fields at high frequency and above has followed practices which are standard for the measurement...of field strength at medium and low frequencies. Variability of measurements made in practical situations and a lack of reproducibility of...measurements made under apparently identical conditions has prompted an investigation of equipment and methods used in the determinations. The field strength
Comelli, Raúl N; Seluy, Lisandro G; Isla, Miguel A
2016-12-25
This work focuses on the performance of ten commercial Saccharomyces yeast strains in the batch alcoholic fermentation of sugars contained in selected industrial wastewaters from the soft drink industry. Fermentation has been applied successfully to treat these effluents prior to their disposal. Although many strains were investigated, similar behaviour was observed between all of the Saccharomyces strains tested. When media were inoculated with 2gL(-1) of yeast, all strains were able to completely consume the available sugars in less than 14h. Thus, any of the strains studied in this work could be used in non-conventional wastewater treatment processes based on alcoholic fermentation. However, ethanol production varied between strains, and these differences could be significant from a production point of view. Saccharomyces bayanus produced the most ethanol, with a mean yield of 0.44gethanolgsugarconsumed(-1) and an ethanol specific production rate of 5.96gethanol (Lh)(-1). As the assayed soft drinks wastewaters contain about 105gsugar/L of fermentable sugars, the concentration of ethanol achieved after the fermentations process was 46.2gethanol/L. A rigorous kinetic modelling methodology was used to model the Saccharomyces bayanus fermentation process. The kinetic model included coupled mass balances and a minimal number of parameters. A simple unstructured model based on the Andrews equation (substrate inhibition) was developed. This model satisfactorily described biomass growth, sugar consumption and bioethanol production. In addition to providing insights into the fermentative performance of potentially relevant strains, this work can facilitate the design of large-scale ethanol production processes that use wastewaters from the sugar-sweetened beverage industry as feedstock. Copyright © 2016 Elsevier B.V. All rights reserved.
Physiological Effects of Strength Training and Various Strength Training Devices.
Wilmore, Jack H.
Current knowledge in the area of muscle physiology is a basis for a discussion on strength training programs. It is now recognized that the expression of strength is related to, but not dependent upon, the size of the muscle and is probably more related to the ability to recruit more muscle fibers in the contraction, or to better synchronize their…
Overview to Strength Development and Strength Trainings in Children
Mesut Hekim
2015-08-01
Full Text Available There are some important phases within psychomotor development process in children. Periods of movements related to sport appear in this phases. In this phase which contains 7-12 age period in children, a significant increment occurs in the physical and motoric development levels of children. Physical and motoric developments are supported by directing children in this age group to sport. In a plenty of studies, it was stated that participating to sports in children supports motoric features and physical development. Strength is one of the most important motoric features which develop via participating to sports. Children strength development is effected at positive direction by adaptation exercise made to support strength development. Psychomotor development basis are considered to obtain the best efficiency from workouts aimed strength development in children and to remove risks to be generate any injury/disability. In this research, strength development, contributions of participating in sports to strength development, strength training in children and children responses to strength training were all emphasized.
Compressive strength of continuous fiber unidirectional composites
Thompson, Ronald H.
Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. Four work streams comprise this study: first, development of a closed form analytical model; second, empirical methods development and model validation; third, creation and validation of a unit cell finite element model; and fourth, a patent application that leverages knowledge gained from the first three work streams. The analytical model characterizes the non-linearity of the matrix both with respect to shear and compressive loading. This improvement on existing analyses clearly shows why fiber modulus affects composite shear instability. Accounting for fiber misalignment in the model and experimental characterization of the fiber misalignment continuum are important contributions of this study. A simple method of compressive strength measurement of a small diameter monofilament glass-resin composite is developed. Sample definition and preparation are original, and necessary technologies are easily assessable to other researchers in this field. This study shows that glass fiber composites have the potential for high compressive strength. This potential is reached with excellent fiber alignment and suitable matrix characteristics, and results are consistent with model predictions. The unit cell three dimensional
C. Weaver
2013-07-01
Full Text Available We investigate the sensitivity of future space-borne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations, and a Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coalmines in Upper Silesia Poland, and wetlands in southern Finland. Our simulated methane surface concentration captures at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. With this tool we can perturb the surface fluxes and see the resulting changes in the simulated column methane measurements. For example, we show that future lidar instruments can detect a 50% reduction in methane emissions from the Netherlands and Germany, but only after averaging measurements on a monthly time scale.
Bynaum, R.V.; Free, S.J.; Moore, R.C.
1999-01-15
The organic ligands acetate, lactate, oxalate and EDTA have been identified as components of wastes targeted for disposal in the Waste Isolation Pilot Plant (WIPP) located in Southeastern New Mexico. The presence of these ligands is of concern because complexation of the actinides with the ligands may increase dissolved actinide concentrations and impact chemical retardation during transport. The current work considers the complexation of Am(III), Th (IV), Np(V), and U(W) with two of the organic ligands, acetate and lactate, in NaCl media from dilute through high concentration. A thermodynamic model for actinide complexation with the organic ligands has been developed based on the Pitzer activity coefficient formalism and the Harvie-Moller-Weare, Felmy-Weare database for describing brine evaporite systems. The model was parameterized using first apparent stability constant data from the literature. Because of complexation of other metal ions (Fe, Mg, Ni, Pb, etc.) present in the WIPP disposal room with the organic ligands, preliminary results from model calculations indicate the organic ligands do not significantly increase dissolved actinide concentrations.
Rudenko, A. N.; Katsnelson, M. I.; Roldán, R.
2017-02-01
The electronic properties of single-layer antimony are studied by a combination of first-principles and tight-binding methods. The band structure obtained from relativistic density functional theory is used to derive an analytic tight-binding model that offers an efficient and accurate description of single-particle electronic states in a wide spectral region up to the mid-UV. The strong (λ =0.34 eV) intra-atomic spin-orbit interaction plays a fundamental role in the band structure, leading to splitting of the valence band edge and to a significant reduction of the effective mass of the hole carriers. To obtain an effective many-body model of two-dimensional Sb we calculate the screened Coulomb interaction and provide numerical values for the on-site V¯00 (Hubbard) and intersite V¯i j interactions. We find that the screening effects originate predominantly from the 5 p states, and are thus fully captured within the proposed tight-binding model. The leading kinetic and Coulomb energies are shown to be comparable in magnitude, | t01|/ (V¯00-V¯01) ˜1.6 , which suggests a strongly correlated character of 5 p electrons in Sb. The results presented here provide an essential step toward the understanding and rational description of a variety of electronic properties of this two-dimensional material.
Biotic interaction strength and the intensity of selection.
Benkman, Craig W
2013-08-01
Although the ecological and evolutionary impacts of species interactions have been the foci of much research, the relationship between the strength of species interactions and the intensity of selection has been investigated only rarely. I develop a simple model demonstrating how the opportunity for selection varies with interaction strength, and then use the relationship between the maximum value of the selection differential and the opportunity for selection (Arnold & Wade 1984) to evaluate how selection differentials vary in relation to species interaction strength. This model predicts an initial deceleration and then an accelerating increase in the intensity of selection with increasing strength of antagonistic interactions and with decreasing strength of mutualistic interactions. Empirical data from several studies provide support for this model. These results further support an evolutionary mechanism for some striking patterns of evolutionary diversification including the latitudinal species gradient, and should be relevant to studies of eco-evolutionary dynamics.
Mayotte, Jean-Marc; Grabs, Thomas; Sutliff-Johansson, Stacy; Bishop, Kevin
2017-06-01
This study examined how the inactivation of bacteriophage MS2 in water was affected by ionic strength (IS) and dissolved organic carbon (DOC) using static batch inactivation experiments at 4 °C conducted over a period of 2 months. Experimental conditions were characteristic of an operational managed aquifer recharge (MAR) scheme in Uppsala, Sweden. Experimental data were fit with constant and time-dependent inactivation models using two methods: (1) traditional linear and nonlinear least-squares techniques; and (2) a Monte-Carlo based parameter estimation technique called generalized likelihood uncertainty estimation (GLUE). The least-squares and GLUE methodologies gave very similar estimates of the model parameters and their uncertainty. This demonstrates that GLUE can be used as a viable alternative to traditional least-squares parameter estimation techniques for fitting of virus inactivation models. Results showed a slight increase in constant inactivation rates following an increase in the DOC concentrations, suggesting that the presence of organic carbon enhanced the inactivation of MS2. The experiment with a high IS and a low DOC was the only experiment which showed that MS2 inactivation may have been time-dependent. However, results from the GLUE methodology indicated that models of constant inactivation were able to describe all of the experiments. This suggested that inactivation time-series longer than 2 months were needed in order to provide concrete conclusions regarding the time-dependency of MS2 inactivation at 4 °C under these experimental conditions.
Springback analysis of ultra high strength steel
Tenma, Kenji; Kina, Futoshi; Suzuki, Wataru
2013-12-01
It is an inevitable trend in the automotive industry to apply more and more high strength steels and even ultra-high strength steels. Even though these materials are more difficult to process the development time of forming tools must be reduced. In order to keep the development time under control, simulation tools are used to verify the forming process in advance. At Aoi Machine Industry a project has been executed to accurately simulate springback of ultra-high strength steels in order to reduce the tool tryout time. In the first phase of the project the simulation settings were optimized based on B-Pillar model A made of Dual Phase 980. In the second phase, it was verified with B-Pillar model B whether these simulation settings were usable as general setting. Results showed that with the right settings it is very well possible to accurately simulate springback of ultra-high strength steels. In the third phase the project the stamping of a B-Pillar of Dual Phase 1180 was studied.
王炳兴
2012-01-01
The maximum likelihood estimation and generalized confidence interval of the system reliability of general multi-component stress-strength model are derived when the component strengths and the stress are independent exponential random variables. The goodness-of-fit test of the model is discussed. The coverage probability of the proposed generalized confidence interval and the power of the test are evaluated by Monte Carlo simulation. The simulation results show that the proposed generalized confidence interval and test are very satisfactory even for small and moderate samples. Finally, an example is shown to illustrate the proposed procedures.%利用最大似然估计和广义区间估计方法,研究了元件的强度和承受的应力均服从指数分布时系统应力强度模型可靠度的估计问题,导出了可靠度的最大似然估计和广义区间估计.同时也讨论了模型的拟合检验问题.利用模拟方法研究了提出的广义置信区间的覆盖率和拟合检验的功效,模拟结果表明提出的广义置信区间的覆盖率与名义置信系数是一致的,提出的拟合检验的功效是好的.最后用一个例子说明提出的方法.
刘伯权; 刘喜; 吴涛
2015-01-01
Some models have been presented by domestic and foreign scholars for shear capacity of deep reinforced concrete flexural members,but there is still no generally accepted shear theory model.Bayesian theory has been applied to predict and design the bearing capacity for some reinforced concrete members,the reasonability,accuracy and superiority of which have been demonstrated,too.However,the calculation results and accuracy are different for different prior distributions.This paper develops probabilistic shear strength models for reinforced concrete deep flexural members by using of Bayesian multivariate statistical theory based on conjugate prior distribution.These probabilistic models are simplified through the Bayesian parameters removal process.Their performance is confirmed by comparison with 115 collected test results.This shows that the deep flexural members' shear strengths,as obtained by the simplified model based on Bayesian theory,are in good agreement with test results,and they are closer to the experimental values than the results given by models used in many nations' codes.The simplified models can be used in shear strength prediction and design for deep flexural members.%钢筋混凝土深受弯构件由于影响因素多、受力复杂,其计算模型和设计方法未形成统一定论.贝叶斯理论己被应用于钢筋混凝土部分构件承载力的预测和设计中,且合理性、准确性及优越性己得到证明,然其先验分布的选取不同,对计算结果的精度影响不同.采用共轭分布法推导了贝叶斯参数先验分布,利用贝叶斯多元统计理论,建立了基于共轭分布的钢筋混凝土深受弯构件受剪承载力贝叶斯概率模型,通过贝叶斯后验参数剔除法简化概率模型,并结合国内外学者己完成115组钢筋混凝土深受弯构件受剪性能试验结果验证模型.研究表明:基于贝叶斯简化模型得到的深受弯构件受剪承载力与试验结果吻合良好,较各
Pound, B.G.
1991-11-21
A potentiostatic pulse technique was used to study the ingress of hydrogen in titanium (pure and grade 2) in an acetate buffer. Hydrogen ingress did not occur with pure titanium, indicating that the surface oxide is an effective barrier to hydrogen entry. In contrast, the data for Ti grade 2 were shown to fit a model for hydrogen diffusion and trapping, allowing values to be determined for the irreversible trapping constant (k) and the flux of hydrogen into the metal. Two values of k were obtained, depending on the level of hydrogen present in the metal. The density of irreversible traps calculated from k for low hydrogen levels suggests that the principal irreversible traps may be interstitial nitrogen, but grain boundaries are another possibility. The additional trapping constant obtained for high hydrogen levels is thought to be associated with hydride formation. The irreversible trapping constants for Ti grade 2 are consistent with its susceptibility to hydrogen embrittlement relative to that of other alloys. The results demonstrate that multiple irreversible traps can be distinguished by using the diffusion/trapping model.
Pound, B.G.
1990-11-14
The objective of this research was to obtain the hydrogen ingress and trapping characteristics for a range of microstructures and so identify the dominant type of irreversible trap in different alloys. A diffusion/trapping model was used in conjunction with a potentiostatic pulse technique to study the ingress of hydrogen in three precipitation-hardened alloys (Inconel 718, Incoloy 925, and 18Ni maraging steel), two work-hardened alloys (Inconel 625 and Hastelloy C-276), titanium (pure and grade 2), and copper-enriched AISI 4340 steel in 1 mol/L acetic acid-1 mol/L sodium acetate containing 15 ppm arsenic oxide. In all cases except pure titanium, the data were shown to fit the interface-control form of the model and values were determined for the irreversible trapping constants (k) and the flux of hydrogen into the alloys. The density of irreversible trap defects were calculated from k and generally found to be in close agreement with the concentration of a specific heterogeneity in each alloy. Moreover, the trapping constants for the alloys were found to be consistent with their relative susceptibilities to hydrogen embrittlement.
Loading Conditions and Longitudinal Strength
Sørensen, Herman
1995-01-01
Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength.......Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength....
Loading Conditions and Longitudinal Strength
Sørensen, Herman
1995-01-01
Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength.......Methods for the calculation of the lightweight of the ship.Loading conditions satisfying draught, trim and intact stability requirements and analysis of the corresponding stillwater longitudinal strength....
Remolded Undrained Strength of Soils
HONG Zhen-shun(洪振舜); LIU Han-long(刘汉龙); NEGAMI Takehito
2003-01-01
Extensive data of undrained shear strength for various remolded soils are compiled to normalize the remolded undrained strength. Remolded soils have a wide spectrum of liquid limits ranging from 25% to 412%. It is found that the remolded undrained strength is a function of water content and liquid limit. Furthermore, a simple index designated as normalized water content w* is introduced for normalizing remolded undrained strength for various soils. The normalized water content w* is the ratio of water content to liquid limit. The relationship between the remolded undrained strength and the normalized water content can be expressed by a simple equation. The new simple equation is not only valuable theoretically for helping in assessing the in-situ mechanical behavior, but also useful to ocean engineering practice.
STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES
NOZEMTСEV Alexandr Sergeevich
2013-02-01
Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.
Simonsen, Karina T; Gallego, Sandra F; Færgeman, Nils J.
2012-01-01
For more than ten years the nematode Caenorhabditis elegans has proven to be a valuable model for studies of the host response to various bacterial and fungal pathogens. When exposed to a pathogenic organism, a clear response is elicited in the nematode, which is characterized by specific alterat...
Abnormality in fracture strength of polycrystalline silicene
Liu, Ning; Hong, Jiawang; Pidaparti, Ramana; Wang, Xianqiao
2016-09-01
Silicene, a silicon-based homologue of graphene, arouses great interest in nano-electronic devices due to its outstanding electronic properties. However, its promising electronic applications are greatly hindered by lack of understanding in the mechanical strength of silicene. Therefore, in order to design mechanically reliable devices with silicene, it is necessary to thoroughly explore the mechanical properties of silicene. Due to current fabrication methods, graphene is commonly produced in a polycrystalline form; the same may hold for silicene. Here we perform molecular dynamics simulations to investigate the mechanical properties of polycrystalline silicene. First, an annealing process is employed to construct a more realistic modeling structure of polycrystalline silicene. Results indicate that a more stable structure is formed due to the breaking and reformation of bonds between atoms on the grain boundaries. Moreover, as the grain size decreases, the efficiency of the annealing process, which is quantified by the energy change, increases. Subsequently, biaxial tensile tests are performed on the annealed samples in order to explore the relation between grain size and mechanical properties, namely in-plane stiffness, fracture strength and fracture strain etc. Results indicate that as the grain size decreases, the fracture strain increases while the fracture strength shows an inverse trend. The decreasing fracture strength may be partly attributed to the weakening effect from the increasing area density of defects which acts as the reservoir of stress-concentrated sites on the grain boundary. The observed crack localization and propagation and fracture strength are well-explained by a defect-pileup model.
The Strength Model of Self-Control：Progress in the Field of Sport%自我控制的力量模型：竞技领域中的研究进展
项明强; 张力为
2016-01-01
Based on strength model of self‐control ,it asserts that self‐control act can be de‐scribed as a process as well as human self‐control resources are limitied .After having worked on prior self‐control task ,the energy can deplete and is not immediately replenished .During this state ,termed ego depletion ,subsequent self‐control tasks may become worse performance . In this paper ,we report on a study on research and application of this model in the competitive field recently ,including perceptual motor ,sprint time ,decision making in sport ,the sport of training ,aggression in sport ,doping in sport ,and so on .Moreover ,in terms of ego depletion mechanism ,we discuss the limited energy theory ,energy allocation ,will power belief and shift‐ing priorities model .We also summarize the research approach to not only intergrate strength model of self‐control and attention control theory but also combine with strength model of self‐control and self‐determination theory .The findings provide further insights into our under‐standing of self control theory in the field of sport ,it is tentatively proposed that more scientif‐ic research paradigm and self‐control application reseach can be accessed based on the frame‐work of the dual‐process theories ,aiming to develop more ecological validity research methods , explore the mechanism of brain meanwhile improve the operability of ego‐depeltion coping and self‐control training .%自我控制的力量模型认为，自我控制行为是一个过程，且自我控制的能量有限，先前的自我控制任务所消耗的能量未得到及时恢复，就会出现自我损耗状态，进而导致后续自我控制任务的操作成绩下降。研究介绍了近年来该模型在竞技领域中的研究与应用，其中包括知觉动作、起跑反应时、运动决策、训练坚持性、运动攻击行为以及服用兴奋剂等。讨论了研究者在自我损耗机制方面提出的能量
J. J. Gómez-Navarro
2015-08-01
Full Text Available This study compares gridded European seasonal series of surface air temperature (SAT and precipitation (PRE reconstructions with a regional climate simulation over the period 1500–1990. The area is analysed separately for nine subareas that represent the majority of the climate diversity in the European sector. In their spatial structure, an overall good agreement is found between the reconstructed and simulated climate features across Europe, supporting consistency in both products. Systematic biases between both data sets can be explained by a priori known deficiencies in the simulation. Simulations and reconstructions, however, largely differ in the temporal evolution of past climate for European subregions. In particular, the simulated anomalies during the Maunder and Dalton minima show stronger response to changes in the external forcings than recorded in the reconstructions. Although this disagreement is to some extent expected given the prominent role of internal variability in the evolution of regional temperature and precipitation, a certain degree of agreement is a priori expected in variables directly affected by external forcings. In this sense, the inability of the model to reproduce a warm period similar to that recorded for the winters during the first decades of the 18th century in the reconstructions is indicative of fundamental limitations in the simulation that preclude reproducing exceptionally anomalous conditions. Despite these limitations, the simulated climate is a physically consistent data set, which can be used as a benchmark to analyse the consistency and limitations of gridded reconstructions of different variables. A comparison of the leading modes of SAT and PRE variability indicates that reconstructions are too simplistic, especially for precipitation, which is associated with the linear statistical techniques used to generate the reconstructions. The analysis of the co-variability between sea level pressure
Strength in Cognitive Self-Regulation
2013-01-01
Failures in self-regulation are predictive of adverse cognitive, academic and vocational outcomes, yet the interplay between cognition and self-regulation failure remains elusive. Two experiments tested the hypothesis that lapses in self-regulation, as predicted by the strength model, can be induced in individuals using cognitive paradigms and whether such failures are related to cognitive performance. In Experiments 1, the stop-signal task (SST) was used to show reduced behavioral inhibition...
Performance Optimization of Self-Piercing Rivets through Analytical Rivet Strength Estimation
Sun, Xin; Khaleel, Mohammad A.
2005-08-01
This paper presents the authors' work on strength optimization and failure mode prediction of self-piercing rivets (SPR) for automotive applications. The limit load-based strength estimator is used to estimate the static strength of an SPR under cross tension loading configuration. Failure modes associated with the estimated failure strength are also predicted. Experimental strength and failure mode observations are used to validate the model. It is shown that the strength of an SPR joint depends on the material and gage combinations, rivet design, die design and riveting direction. The rivet strength estimator is then used to optimize the rivet strength by comparing the measured rivet strength and failure mode with the predicted ones. Two illustrative examples are used in which rivet strength is optimized by changing rivet design and riveting direction from the original manufacturing parameters.
王少江; 侯力; 董璐; 肖华军
2012-01-01
在分析弧齿圆柱齿轮加工原理和数学建模的基础上,提出一种面向制造的弧齿圆柱齿轮建模新方法,解决长期以来弧齿圆柱齿轮3维造型和实际加工不一致的问题,保证后续分析、加工等工序的正确性。基于UG的二次开发,采用齿坯滚动进给、刀具旋转切削的方法,实现面向制造的弧齿圆柱齿轮的3维造型和快速原型制造,在此基础上深入分析刀具半径对弧齿圆柱齿轮的接触应力分布的影响,得出不同曲率下齿轮强度的变化规律。有限元分析结果表明同等条件下弧齿圆柱齿轮的接触强度较直齿轮有显著提高,其最大齿根应力仅为直齿圆柱齿轮的27%,弧齿圆柱齿轮齿根应力与弧齿线半径有明显的关系。此方法为弧齿圆柱齿轮在高速重载等工况下的工业应用提供理论依据和工程应用价值。%Based on the analysis of generating mechanism and mathematical model for the cylindrical gears with curvilinear shape teeth,a new way of modeling such gears for manufacture was proposed to solve the long existing inconsistencies between three-dimensional modeling and actual processing and to ensure the correctness of follow-up analysis of finite elements and gear machining.Adopting the secondary development of UG and the approach of gear blank＇s rolling feed and gear cutting tool＇s rotary,the three-dimensional model of such gears was accordingly built and proved to achieve rapid prototyping manufacture.Then,with the analysis of the model＇s strength and finite elements performed,it was confirmed that the contact strength of tooth surface of cylindrical gears with curvilinear shape teeth could be substantially improved,compared with that of spur gears,and that the maximal stress equivalent was only twenty-seven percent of spur gears＇.Meanwhile,the requirements of high speed and heavy duty gear transmission could be satisfied.Therefore,this approach was a good example of the
王誉瑾; 范峰; 钱宏亮; 翟希梅
2013-01-01
铝合金材料本构关系是铝合金结构分析和应用的基本问题之一,针对国产高强新牌号铝合金6082-T6的材料本构模型进行研究.对取自3种截面形式结构用6082-T6高强铝合金型材的90个材性试样进行了拉伸试验,统计规定非比例延伸强度、抗拉强度、弹性模量、断裂伸长率、泊松比等材料力学参数.分析Ramberg-Osgood本构模型中硬化指数n的各种计算方法,提出采用快速退火算法(fast simulated annealing,FSA)求解n的方法并且编制计算程序,从而获得,n的置信区间,所得结果比传统两点法更稳定.在此基础上得到了国产6082-T6高强铝合金材料本构模型,与试验实测应力-应变曲线的比较表明,提出的本构模型具有很好的预测性,可为铝合金结构的工程应用提供参考.%Material constitutive relationship is one of the basic problems for analysis and application of aluminum alloy structures.This paper systematically studied the material constitutive model of the domestic high-strength new grade aluminum alloy 6082-T6.Tensile testing was conducted for a total of 90 coupons that were cut from three cross-section shapes of the aluminum alloy 6082-T6.The measurement and statistical analysis of mechanical parameters were carried out,including non-proportional extension strengths,tensile strength,elastic modulus,breaking elongation,Poisson' s ratio,etc.Various methods for calculating hardening exponent n in the Ramberg-Osgood law were discussed.The fast simulated annealing (FSA) method for calculating n was proposed and the FSA code was written to obtain the confidence interval of n.Comparison of results between FSA and other methods indicates that the FSA can provide more stable results than the traditional two-point method.On this basis,the material constitutive model of the 6082-T6 aluminum alloy was obtained.The comparison of this model and the tested stress-strain curve demonstrates that the constitutive model
The dynamics of Bax channel formation: influence of ionic strength.
Ganesan, Vidyaramanan; Walsh, Timothy; Chang, Kai-Ti; Colombini, Marco
2012-08-08
Mitochondrial outer membrane permeabilization (MOMP) is a complex multistep process. Studies of MOMP in vivo are limited by the stochastic variability of MOMP between cells and rapid completion of IMS protein release within single cells. In vitro models have provided useful insights into MOMP. We have investigated the dynamics of Bax-mediated MOMP in isolated mitochondria using ionic strength as a tool to control the rate of MOMP. We find that Bax can induce both transient permeabilization, detected by protein release, and more substantial long-lasting permeabilization, measured by the rate of oxidation of added cytochrome c. We found that higher ionic strength causes Bax to form small channels quickly but the expansion of these early channels is impeded. This inhibitory effect of ionic strength is independent of tBid. Channels formed under low ionic strength are not destabilized by raising the ionic strength. Increase in ionic strength also increases the ability of Bcl-xL to inhibit Bax-mediated MOMP. Ionic strength does not affect Bax insertion into mitochondria. Thus, ionic strength influences the assembly of Bax molecules already in membrane into channels. Ionic strength can be used as an effective biophysical tool to study Bax-mediated channel formation.
裴国平; 陈培帅
2012-01-01
依托ABAQUS大型有限元程序，以坡体塑性区贯通和关键点位移突变为失稳判据，实现边坡强度折减法的参数化训练模型，计算了一个边坡算例，通过与Bishop极限平衡法计算结果的对比，验证了参数化训练模型的有效性和准确性，最后将研究成果应用于谷竹高速公路某段边坡，对坡体的安全性进行了分析，并提出了相关建议。%Based on ABAQUS large-scale finite element program, taking slope plasticity interpenetration and critical point displacement sudden change as the instability basis, the paper realizes the parametric training model of slope strength reduction method, calculates the side slope algo- rithm, compares it with the Bishop limit balance calculation method, and testifies the effectiveness and accuracy of parametric training model. In the end, it applies the research result into one side slope section of Gu-Zhu highway, and analyzes the security of the slope, and puts forward cor- responding suggestions.
Penetrator strength effect in long-rod critical ricochet angle
Daneshjou, K.; Shahravi, M. [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)
2008-11-15
3D numerical simulations were performed in order to further investigate the role of penetrator strength in the interaction of long-rods and oblique targets. Three distinctive regimes resulting from oblique impact depending on the obliquity, namely simple ricochet, critical ricochet and target perforation, were investigated in detail. Critical ricochet angles were calculated with a full 3D explicit finite element method for various impact velocities and strength of target plates and projectiles. Numerical predictions were compared with existing two-dimensional analytical models and test results. It was predicted that critical ricochet angle increases with decreasing impact velocity and that higher ricochet angles were expected if higher strength target materials are employed. But there are differences between analytical models and 3D numerical simulation results or test results. The causes for these discrepancies are established by numerical simulations which explore the validity of the penetrator strength parameter in the analytical model as a physical entity. As a matter of fact, in this paper we first investigate the role of penetrator dynamic strength using two-dimensional simulation which resulted in different penetrator strengths out of different impact velocities. Next, by applying these amounts for penetrator strength in Rosenberg analytical model the critical ricochet angle is calculated. Finally, a comparison between the present analytical method with the 3D simulation and test results shows that the new analytical approach leads to modified results with respect to Rosenberg ones
Muscle Strength and Poststroke Hemiplegia
Kristensen, Otto H; Stenager, Egon; Dalgas, Ulrik
2017-01-01
OBJECTIVES: To systematically review (1) psychometric properties of criterion isokinetic dynamometry testing of muscle strength in persons with poststroke hemiplegia (PPSH); and (2) literature that compares muscle strength in patients poststroke with that in healthy controls assessed by criterion...... isokinetic dynamometry. DATA SOURCES: A systematic literature search of 7 databases was performed. STUDY SELECTION: Included studies (1) enrolled participants with definite poststroke hemiplegia according to defined criteria; (2) assessed muscle strength or power by criterion isokinetic dynamometry; (3) had...... undergone peer review; and (4) were available in English or Danish. DATA EXTRACTION: The psychometric properties of isokinetic dynamometry were reviewed with respect to reliability, validity, and responsiveness. Furthermore, comparisons of strength between paretic, nonparetic, and comparable healthy muscles...
Hyperlipidemia affects multiscale structure and strength of murine femur.
Ascenzi, Maria-Grazia; Lutz, Andre; Du, Xia; Klimecky, Laureen; Kawas, Neal; Hourany, Talia; Jahng, Joelle; Chin, Jesse; Tintut, Yin; Nackenhors, Udo; Keyak, Joyce
2014-07-18
To improve bone strength prediction beyond limitations of assessment founded solely on the bone mineral component, we investigated the effect of hyperlipidemia, present in more than 40% of osteoporotic patients, on multiscale structure of murine bone. Our overarching purpose is to estimate bone strength accurately, to facilitate mitigating fracture morbidity and mortality in patients. Because (i) orientation of collagen type I affects, independently of degree of mineralization, cortical bone׳s micro-structural strength; and, (ii) hyperlipidemia affects collagen orientation and μCT volumetric tissue mineral density (vTMD) in murine cortical bone, we have constructed the first multiscale finite element (mFE), mouse-specific femoral model to study the effect of collagen orientation and vTMD on strength in Ldlr(-/-), a mouse model of hyperlipidemia, and its control wild type, on either high fat diet or normal diet. Each µCT scan-based mFE model included either element-specific elastic orthotropic properties calculated from collagen orientation and vTMD (collagen-density model) by experimentally validated formulation, or usual element-specific elastic isotropic material properties dependent on vTMD-only (density-only model). We found that collagen orientation, assessed by circularly polarized light and confocal microscopies, and vTMD, differed among groups and that microindentation results strongly correlate with elastic modulus of collagen-density models (r(2)=0.85, p=10(-5)). Collagen-density models yielded (1) larger strains, and therefore lower strength, in simulations of 3-point bending and physiological loading; and (2) higher correlation between mFE-predicted strength and 3-point bending experimental strength, than density-only models. This novel method supports ongoing translational research to achieve the as yet elusive goal of accurate bone strength prediction.
Prediction of Concrete Compressive Strength by Evolutionary Artificial Neural Networks
Mehdi Nikoo
2015-01-01
Full Text Available Compressive strength of concrete has been predicted using evolutionary artificial neural networks (EANNs as a combination of artificial neural network (ANN and evolutionary search procedures, such as genetic algorithms (GA. In this paper for purpose of constructing models samples of cylindrical concrete parts with different characteristics have been used with 173 experimental data patterns. Water-cement ratio, maximum sand size, amount of gravel, cement, 3/4 sand, 3/8 sand, and coefficient of soft sand parameters were considered as inputs; and using the ANN models, the compressive strength of concrete is calculated. Moreover, using GA, the number of layers and nodes and weights are optimized in ANN models. In order to evaluate the accuracy of the model, the optimized ANN model is compared with the multiple linear regression (MLR model. The results of simulation verify that the recommended ANN model enjoys more flexibility, capability, and accuracy in predicting the compressive strength of concrete.
2012-01-01
Diversity has always been science’s big secret, yet it’s a secret we’ve always been keen to share. CERN was founded on the basis of bringing a diverse mix of people together to pursue common aims, and it’s one of the things that’s driven this Organization’s success over the decades. Now, we are launching a new diversity programme aimed at strengthening our tradition of inclusiveness. This programme is being launched with a range of key goals in mind for the 2012-2014 timeframe. We’ll be striving to achieve a fair gender balance across all professional categories, and to provide strong gender role models across the Organization. We’ll be improving our career development processes to allow people to progress through both technical and managerial pathways, and we’ll be re-launching workshops that bring people from diverse professions and generations together to share their experience on key aspects of lif...
ROSETTA lander Philae - soil strength analysis
Roll, Reinhard; Witte, Lars; Arnold, Walter
2016-12-01
The landing of Philae, the lander of ESA's ROSETTA-mission, on November 12th 2014 on Comet 67P/Churyumov-Gerasimenko, was planned as a descent with passive landing activating a damper system and anchoring by harpoons at touch-down. The lander was not fixed to the ground at touch-down due to failing harpoons. The lander damper, however, was actuated for a length of 42.6 mm with a maximal speed of 0.08 m/s, while the lander speed was 1 m/s. Based on the damper data and a detailed mechanical model of Philae, an estimate can be made for the forces acting and the energy dissipated at touch-down inside the lander and the energy dissipated by ground penetration. The forces acting at ground penetration provide constraints on the mechanical strength of the soil. Two different soil models are investigated. Assuming constant compressive strength σ, one obtains σ ≈ 2 kPa. Assuming an increasing σs strength with penetration depth with results in σs = 3 kPa/m fits the damper data best.