Constitutive model with time-dependent deformations
DEFF Research Database (Denmark)
Krogsbøll, Anette
1998-01-01
are common in time as well as size. This problem is adressed by means of a new constitutive model for soils. It is able to describe the behavior of soils at different deformation rates. The model defines time-dependent and stress-related deformations separately. They are related to each other and they occur...... was the difference in time scale between the geological process of deposition (millions of years) and the laboratory measurements of mechanical properties (minutes or hours). In addition, the time scale relevant to the production history of the oil field was interesting (days or years)....
International Nuclear Information System (INIS)
Ren, W
2001-01-01
Time-dependent deformation behavior of a polymeric composite with chopped-glass-fiber reinforcement was investigated for automotive applications, The material under stress was exposed to representative automobile service environments. Results show that environment has substantial effects on time-dependent deformation behavior of the material. The data were analyzed and experimentally-based models developed for the time-dependent deformation behavior as a basis for automotive structural durability design criteria
Energy Technology Data Exchange (ETDEWEB)
Ren, W
2001-08-24
Time-dependent deformation behavior of a polymeric composite with chopped-glass-fiber reinforcement was investigated for automotive applications, The material under stress was exposed to representative automobile service environments. Results show that environment has substantial effects on time-dependent deformation behavior of the material. The data were analyzed and experimentally-based models developed for the time-dependent deformation behavior as a basis for automotive structural durability design criteria.
Evaluation of digital model accuracy and time-dependent deformation of alginate impressions.
Cesur, M G; Omurlu, I K; Ozer, T
2017-09-01
The aim of this study was to evaluate the accuracy of digital models produced with the three-dimensional dental scanner, and to test the dimensional stability of alginate impressions for durations of immediately (T0), 1 day (T1), and 2 days (T2). A total of sixty impressions were taken from a master model with an alginate, and were poured into plaster models in three different storage periods. Twenty impressions were directly scanned (negative digital models), after which plaster models were poured and scanned (positive digital models) immediately. The remaining 40 impressions were poured after 1 and 2 days. In total, 9 points and 11 linear measurements were used to analyze the plaster models, and negative and positive digital models. Time-dependent deformation of the alginate impressions and the accuracy of the conventional plaster models and digital models were evaluated separately. Plaster models, negative and positive digital models showed significant differences in nearly all measurements at T (0), T (1), and T (2) times (P 0.05), but they demonstrated statistically significant differences at T (2) time (P impressions is practicable method for orthodontists.
Modelling time-dependent mechanical behaviour of softwood using deformation kinetics
DEFF Research Database (Denmark)
Engelund, Emil Tang; Svensson, Staffan
2010-01-01
The time-dependent mechanical behaviour (TDMB) of softwood is relevant, e.g., when wood is used as building material where the mechanical properties must be predicted for decades ahead. The established mathematical models should be able to predict the time-dependent behaviour. However, these models...... are not always based on the actual physical processes causing time-dependent behaviour and the physical interpretation of their input parameters is difficult. The present study describes the TDMB of a softwood tissue and its individual tracheids. A model is constructed with a local coordinate system that follows...... macroscopic viscoelasticity, i.e., the time-dependent processes are to a significant degree reversible....
Deformation aspects of time dependent fracture
International Nuclear Information System (INIS)
Li, C.Y.; Turner, A.P.L.; Diercks, D.R.; Laird, C.; Langdon, T.G.; Nix, W.D.; Swindeman, R.; Wolfer, W.G.; Woodford, D.A.
1979-01-01
For all metallic materials, particularly at elevated temperatures, deformation plays an important role in fracture. On the macro-continuum level, the inelastic deformation behavior of the material determines how stress is distributed in the body and thus determines the driving force for fracture. At the micro-continuum level, inelastic deformation alters the elastic stress singularity at the crack tip and so determines the local environment in which crack advance takes place. At the microscopic and mechanistic level, there are many possibilities for the mechanisms of deformation to be related to those for crack initiation and growth. At elevated temperatures, inelastic deformation in metallic systems is time dependent so that the distribution of stress in a body will vary with time, affecting conditions for crack initiation and propagation. Creep deformation can reduce the tendency for fracture by relaxing the stresses at geometric stress concentrations. It can also, under suitable constraints, cause a concentration of stresses at specific loading points as a result of relaxation elsewhere in the body. A combination of deformation and unequal heating, as in welding, can generate large residual stress which cannot be predicted from the external loads on the body. Acceleration of deformation by raising the temperature can be an effective way to relieve such residual stresses
Xu, T.; Zhou, G. L.; Heap, Michael J.; Zhu, W. C.; Chen, C. F.; Baud, Patrick
2017-09-01
An understanding of the influence of temperature on brittle creep in granite is important for the management and optimization of granitic nuclear waste repositories and geothermal resources. We propose here a two-dimensional, thermo-mechanical numerical model that describes the time-dependent brittle deformation (brittle creep) of low-porosity granite under different constant temperatures and confining pressures. The mesoscale model accounts for material heterogeneity through a stochastic local failure stress field, and local material degradation using an exponential material softening law. Importantly, the model introduces the concept of a mesoscopic renormalization to capture the co-operative interaction between microcracks in the transition from distributed to localized damage. The mesoscale physico-mechanical parameters for the model were first determined using a trial-and-error method (until the modeled output accurately captured mechanical data from constant strain rate experiments on low-porosity granite at three different confining pressures). The thermo-physical parameters required for the model, such as specific heat capacity, coefficient of linear thermal expansion, and thermal conductivity, were then determined from brittle creep experiments performed on the same low-porosity granite at temperatures of 23, 50, and 90 °C. The good agreement between the modeled output and the experimental data, using a unique set of thermo-physico-mechanical parameters, lends confidence to our numerical approach. Using these parameters, we then explore the influence of temperature, differential stress, confining pressure, and sample homogeneity on brittle creep in low-porosity granite. Our simulations show that increases in temperature and differential stress increase the creep strain rate and therefore reduce time-to-failure, while increases in confining pressure and sample homogeneity decrease creep strain rate and increase time-to-failure. We anticipate that the
International Nuclear Information System (INIS)
Rutenberg, M.; Lux, K. H.
2011-01-01
Clay-stone rock masses are a reasonable alternative to e.g. salt rock masses as a host rock for underground radioactive waste repositories because of their very low permeability as well as their radionuclide retention capacity. Though clay-stone has been explored for many years, there is still a need for further research on its hydro-mechanical behaviour. Convergence measurements over a 4-year period in the tunnel system of the argillaceous Tournemire site in France yielded the presence of a time-dependent deformation behaviour in indurated clay. Moreover, a mine-by test was carried out with extensometer measurements capturing the rock mass deformation during the excavation process of a new gallery in 2003.This work focuses on the validation of a constitutive model by means of a three-dimensional (3D) simulation of the mine-by test. The utilised constitutive model Hou/Lux-T is based on the viscous constitutive model Lubby2 with which time-dependent deformation behaviour of salt rock can appropriately be simulated. It has been adapted to clay-stone by considering anisotropy effects, and in addition it features a strain-dependent fracture and failure criterion. The results of the mine-by-test simulation show that the calculated stresses and deformations in the rock mass seem to behave reasonably under this constitutive model with respect to time-dependency. A comparison of the 3D results to the results of a simplified two-dimensional (2D) simulation confirms the adequacy of using a 2D model with the constitutive model Hou/Lux-T for the setting at hand, described in the text (material parameters, time scale), in order to assess load-bearing capacity and deformability of the gallery near field away from heading face and tunnel crossing. Finally, a comparison of the 3D simulation results to the extensometer measurement results yields the principal ability of the used constitutive model to describe time-dependent evolutions of stresses and deformations during a three
Measuring time-dependent deformations in metallic MEMS
Bergers, L.I.J.C.; Hoefnagels, J.P.M.; Delhey, N.K.R.; Geers, M.G.D.
2011-01-01
The reliability of metallic microelectromechanical systems (MEMS) depends on time-dependent deformation such as creep. Key to this process is the interaction between microstructural length scales and dimensional length scales, so-called size-effects. As a first critical step towards studying these
Directory of Open Access Journals (Sweden)
Hayder Mohammed Salim Al-Maamori
2018-04-01
Full Text Available Effects of time-dependent deformation (TDD on a tunnel constructed using the micro-tunneling technique in Queenston shale (QS are investigated employing the finite element method. The TDD and strength parameters of the QS were measured from tests conducted on QS specimens soaked in water and lubricant fluids (LFs used in micro-tunneling such as bentonite and polymer solutions. The numerical model was verified using the results of TDD tests performed on QS samples, field measurements of some documented projects, and the closed-form solutions to circular tunnels in swelling rock. The verified model was then employed to conduct a parametric study considering important micro-tunneling design parameters, such as depth and diameter of the tunnel, in situ stress ratio (Ko, and the time lapse prior to replacing LFs with permanent cement grout around the tunnel. It was revealed that the time lapse plays a vital role in controlling deformations and associated stresses developed in the tunnel lining. The critical case of a pipe or tunnel in which the maximum tensile stress develops at its springline occurs when it is constructed at shallow depths in the QS layer. The results of the parametric study were used to suggest recommendations for the construction of tunnels in QS employing micro-tunneling. Keywords: Numerical model, Micro-tunneling, Queenston shale (QS, Lubricant fluids (LFs
Radiation effects on time-dependent deformation: Creep and growth
International Nuclear Information System (INIS)
Simonen, E.P.
1989-03-01
Observations of irradiation creep strain as well as irradiation growth strain and related microstructures are reviewed and compared to mechanisms for radiation effects on time-dependent deformation. Composition, microstructure, stress and temperature affect irradiation creep less than thermal creep. Irradiation creep rates can often dominate thermal creep rates, particularly at low temperatures and low stresses. Irradiation creep mechanisms are classified in two general categories: (1) stress-induced preferential absorption and (2) climb-glide. In the former, creep results from dislocation climb, whereas in the latter, creep results from dislocation glide. The effects of irradiation creep on failure modes in nuclear environments are discussed. 53 refs., 18 figs., 1 tab
International Nuclear Information System (INIS)
Rutenberg, M.; Lux, K.H.
2010-01-01
Document available in extended abstract form only. Modern repository research foregrounds physico-chemical processes (mechanical, hydraulic, thermal, chemical) and their interactions taking place in the near field and the far field of the geological system being explored. With regard to load bearing behaviour and preservation of barrier integrity, and with the general objective of complete confinement of the waste in the isolating rock zone, the focus is especially on geomechanical processes induced by excavation - including the influences on and by hydraulic, thermal, and chemical processes - as well as on thermal processes induced by heat generation of the deposited radioactive waste and their effects on mechanical and hydraulic processes. In order to improve assessments of the mechanical stability and, in case of a water saturated rock formation, of the hydraulic effects on the host rock of the repository, suitable physical models for numerical simulations of rock and rock mass behaviour have to be found and to be validated. Because of their radionuclide retention capacity, their low water permeability, and their resistance to water, clay-stone rock masses form a reasonable alternative to e.g. salt rock masses as a host rock for deep geological repositories. In past decades, various working groups at an international level have elaborated a broad experimental and theoretical understanding of the geomechanical and geo-hydraulic behaviour of clay-stones and applied this know-how to geologic repository components, e.g. in the context of engineering studies, or in the back-analysis of field tests. In this context, measurement results revealed a continuing convergence of drift walls lasting for a few years after completion of excavation. Possible reasons for this time-dependent deformation behaviour of the clay-stone rock mass might be: - viscous properties of the material from a phenomenological point of view, meaning a constant stress state leading to increasing
The Time-Dependency of Deformation in Porous Carbonate Rocks
Kibikas, W. M.; Lisabeth, H. P.; Zhu, W.
2016-12-01
Porous carbonate rocks are natural reservoirs for freshwater and hydrocarbons. More recently, due to their potential for geothermal energy generation as well as carbon sequestration, there are renewed interests in better understanding of the deformation behavior of carbonate rocks. We conducted a series of deformation experiments to investigate the effects of strain rate and pore fluid chemistry on rock strength and transport properties of porous limestones. Indiana limestone samples with initial porosity of 16% are deformed at 25 °C under effective pressures of 10, 30, and 50 MPa. Under nominally dry conditions, the limestone samples are deformed under 3 different strain rates, 1.5 x 10-4 s-1, 1.5 x 10-5 s-1 and 1.5 x 10-6 s-1 respectively. The experimental results indicate that the mechanical behavior is both rate- and pressure-dependent. At low confining pressures, post-yielding deformation changes from predominantly strain softening to strain hardening as strain rate decreases. At high confining pressures, while all samples exhibit shear-enhanced compaction, decreasing strain rate leads to an increase in compaction. Slower strain rates enhance compaction at all confining pressure conditions. The rate-dependence of deformation behaviors of porous carbonate rocks at dry conditions indicates there is a strong visco-elastic coupling for the degradation of elastic modulus with increasing plastic deformation. In fluid saturated samples, inelastic strain of limestone is partitioned among low temperature plasticity, cataclasis and solution transport. Comparison of inelastic behaviors of samples deformed with distilled water and CO2-saturated aqueous solution as pore fluids provide experimental constraints on the relative activities of the various mechanisms. Detailed microstructural analysis is conducted to take into account the links between stress, microstructure and the inelastic behavior and failure mechanisms.
Lee, Kyung Min; Tondiglia, Vincent P.; Bunning, Timothy J.; White, Timothy J.
2017-02-01
Recently, we reported direct current (DC) field controllable electro-optic (EO) responses of negative dielectric anisotropy polymer stabilized cholesteric liquid crystals (PSCLCs). A potential mechanism is: Ions in the liquid crystal mixtures are trapped in/on the polymer network during the fast photopolymerization process, and the movement of ions by the application of the DC field distorts polymer network toward the negative electrode, inducing pitch variation through the cell thickness, i.e., pitch compression on the negative electrode side and pitch expansion on positive electrode side. As the DC voltage is directly applied to a target voltage, charged polymer network is deformed and the reflection band is tuned. Interestingly, the polymer network deforms further (red shift of reflection band) with time when constantly applied DC voltage, illustrating DC field induced time dependent deformation of polymer network (creep-like behavior). This time dependent reflection band changes in PSCLCs are investigated by varying the several factors, such as type and concentration of photoinitiators, liquid crystal monomer content, and curing condition (UV intensity and curing time). In addition, simple linear viscoelastic spring-dashpot models, such as 2-parameter Kelvin and 3-parameter linear models, are used to investigate the time-dependent viscoelastic behaviors of polymer networks in PSCLC.
System reliability time-dependent models
International Nuclear Information System (INIS)
Debernardo, H.D.
1991-06-01
A probabilistic methodology for safety system technical specification evaluation was developed. The method for Surveillance Test Interval (S.T.I.) evaluation basically means an optimization of S.T.I. of most important system's periodically tested components. For Allowed Outage Time (A.O.T.) calculations, the method uses system reliability time-dependent models (A computer code called FRANTIC III). A new approximation, which was called Independent Minimal Cut Sets (A.C.I.), to compute system unavailability was also developed. This approximation is better than Rare Event Approximation (A.E.R.) and the extra computing cost is neglectible. A.C.I. was joined to FRANTIC III to replace A.E.R. on future applications. The case study evaluations verified that this methodology provides a useful probabilistic assessment of surveillance test intervals and allowed outage times for many plant components. The studied system is a typical configuration of nuclear power plant safety systems (two of three logic). Because of the good results, these procedures will be used by the Argentine nuclear regulatory authorities in evaluation of technical specification of Atucha I and Embalse nuclear power plant safety systems. (Author) [es
Time-dependent Hartree approximation and time-dependent harmonic oscillator model
International Nuclear Information System (INIS)
Blaizot, J.P.
1982-01-01
We present an analytically soluble model for studying nuclear collective motion within the framework of the time-dependent Hartree (TDH) approximation. The model reduces the TDH equations to the Schroedinger equation of a time-dependent harmonic oscillator. Using canonical transformations and coherent states we derive a few properties of the time-dependent harmonic oscillator which are relevant for applications. We analyse the role of the normal modes in the time evolution of a system governed by TDH equations. We show how these modes couple together due to the anharmonic terms generated by the non-linearity of the theory. (orig.)
Exact reconstruction in 2D dynamic CT: compensation of time-dependent affine deformations
International Nuclear Information System (INIS)
Roux, Sebastien; Desbat, Laurent; Koenig, Anne; Grangeat, Pierre
2004-01-01
This work is dedicated to the reduction of reconstruction artefacts due to motion occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensation algorithms, where the model of motion is included in the reconstruction formula. We address two fundamental questions. First what conditions on the deformation are required for the reconstruction of the object from projections acquired sequentially during the deformation, and second how do we reconstruct the object from those projections. Here we answer these questions in the particular case of 2D general time-dependent affine deformations, assuming the motion parameters are known. We treat the problem of admissibility conditions on the deformation in the parallel-beam and fan-beam cases. Then we propose exact reconstruction methods based on rebinning or sequential FBP formulae for each of these geometries and present reconstructed images obtained with the fan-beam algorithm on simulated data
Time-dependent source model of the Lusi mud volcano
Shirzaei, M.; Rudolph, M. L.; Manga, M.
2014-12-01
The Lusi mud eruption, near Sidoarjo, East Java, Indonesia, began erupting in May 2006 and continues to erupt today. Previous analyses of surface deformation data suggested an exponential decay of the pressure in the mud source, but did not constrain the geometry and evolution of the source(s) from which the erupting mud and fluids ascend. To understand the spatiotemporal evolution of the mud and fluid sources, we apply a time-dependent inversion scheme to a densely populated InSAR time series of the surface deformation at Lusi. The SAR data set includes 50 images acquired on 3 overlapping tracks of the ALOS L-band satellite between May 2006 and April 2011. Following multitemporal analysis of this data set, the obtained surface deformation time series is inverted in a time-dependent framework to solve for the volume changes of distributed point sources in the subsurface. The volume change distribution resulting from this modeling scheme shows two zones of high volume change underneath Lusi at 0.5-1.5 km and 4-5.5km depth as well as another shallow zone, 7 km to the west of Lusi and underneath the Wunut gas field. The cumulative volume change within the shallow source beneath Lusi is ~2-4 times larger than that of the deep source, whilst the ratio of the Lusi shallow source volume change to that of Wunut gas field is ~1. This observation and model suggest that the Lusi shallow source played a key role in eruption process and mud supply, but that additional fluids do ascend from depths >4 km on eruptive timescales.
Benson, P. M.; Fahrner, D.; Harnett, C. E.; Fazio, M.
2014-12-01
Time dependent deformation describes the process whereby brittle materials deform at a stress level below their short-term material strength (Ss), but over an extended time frame. Although generally well understood in engineering (where it is known as static fatigue or "creep"), knowledge of how rocks creep and fail has wide ramifications in areas as diverse as mine tunnel supports and the long term stability of critically loaded rock slopes. A particular hazard relates to the instability of volcano flanks. A large number of flank collapses are known such as Stromboli (Aeolian islands), Teide, and El Hierro (Canary Islands). Collapses on volcanic islands are especially complex as they necessarily involve the combination of active tectonics, heat, and fluids. Not only does the volcanic system generate stresses that reach close to the failure strength of the rocks involved, but when combined with active pore fluid the process of stress corrosion allows the rock mass to deform and creep at stresses far lower than Ss. Despite the obvious geological hazard that edifice failure poses, the phenomenon of creep in volcanic rocks at elevated temperatures has yet to be thoroughly investigated in a well controlled laboratory setting. We present new data using rocks taken from Stromboli, El Heirro and Teide volcanoes in order to better understand the interplay between the fundamental rock mechanics of these basalts and the effects of elevated temperature fluids (activating stress corrosion mechanisms). Experiments were conducted over short (30-60 minute) and long (8-10 hour) time scales. For this, we use the method of Heap et al., (2011) to impose a constant stress (creep) domain deformation monitored via non-contact axial displacement transducers. This is achieved via a conventional triaxial cell to impose shallow conditions of pressure (<25 MPa) and temperature (<200 °C), and equipped with a 3D laboratory seismicity array (known as acoustic emission, AE) to monitor the micro
Boundary-integral equation formulation for time-dependent inelastic deformation in metals
Energy Technology Data Exchange (ETDEWEB)
Kumar, V; Mukherjee, S
1977-01-01
The mathematical structure of various constitutive relations proposed in recent years for representing time-dependent inelastic deformation behavior of metals at elevated temperatues has certain features which permit a simple formulation of the three-dimensional inelasticity problem in terms of real time rates. A direct formulation of the boundary-integral equation method in terms of rates is discussed for the analysis of time-dependent inelastic deformation of arbitrarily shaped three-dimensional metallic bodies subjected to arbitrary mechanical and thermal loading histories and obeying constitutive relations of the kind mentioned above. The formulation is based on the assumption of infinitesimal deformations. Several illustrative examples involving creep of thick-walled spheres, long thick-walled cylinders, and rotating discs are discussed. The implementation of the method appears to be far easier than analogous BIE formulations that have been suggested for elastoplastic problems.
Constitutive relations describing creep deformation for multi-axial time-dependent stress states
McCartney, L. N.
1981-02-01
A THEORY of primary and secondary creep deformation in metals is presented, which is based upon the concept of tensor internal state variables and the principles of continuum mechanics and thermodynamics. The theory is able to account for both multi-axial and time-dependent stress and strain states. The wellknown concepts of elastic, anelastic and plastic strains follow naturally from the theory. Homogeneous stress states are considered in detail and a simplified theory is derived by linearizing with respect to the internal state variables. It is demonstrated that the model can be developed in such a way that multi-axial constant-stress creep data can be presented as a single relationship between an equivalent stress and an equivalent strain. It is shown how the theory may be used to describe the multi-axial deformation of metals which are subjected to constant stress states. The multi-axial strain response to a general cyclic stress state is calculated. For uni-axial stress states, square-wave loading and a thermal fatigue stress cycle are analysed.
International Nuclear Information System (INIS)
Ramaswamy, Ananth; Chandra Kishen, J.M.
2009-09-01
Time dependent deformations in concrete, both creep and shrinkage, play a critical role in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. These strains result in losses, through release of prestress, and thereby influence the safety of these structures. The present study comprises of an experimental and analytical program to assess the levels of creep and shrinkage in normal and heavy density concrete. The experimental program includes tests on creep using standard cylinder specimen, while shrinkage studies have been conducted using prism specimen, both under controlled environmental conditions. The experimental results suggest that creep and shrinkage strains are higher in heavy density concrete than in normal concrete. This may be attributed to the relatively smaller pore structure of heavy density concrete that results in larger availability of free water and a relatively slower hydration process in comparison to normal concrete. While there is some scatter in the results, creep strains decrease with age of loading and both creep and shrinkage strains are smaller when the relative humidity is higher. Statistical model reported in the literature for normal concrete is able to predict the test results for both normal and heavy density concrete quite well. Long term predictions of creep and shrinkage using this model, accounting for uncertainties, is also projected and shown to predict some long term measured results not used in the model calibration. The long term predictions are sensitive to the initial data used in model calibration. (author)
Numerical modelling of softwood time-dependent behaviour based on microstructure
DEFF Research Database (Denmark)
Engelund, Emil Tang
2010-01-01
The time-dependent mechanical behaviour of softwood such as creep or relaxation can be predicted, from knowledge of the microstructural arrangement of the cell wall, by applying deformation kinetics. This has been done several times before; however, often without considering the constraints defined...... by the basic physical mechanism behind the time-dependent behaviour. The mechanism causing time-dependency is thought to be sliding of the microfibrils past each other as a result breaking and re-bonding of hydrogen bonds. This can be incorporated in a numerical model by only allowing time-dependency in shear...
Characterization of Models for Time-Dependent Behavior of Soils
DEFF Research Database (Denmark)
Liingaard, Morten; Augustesen, Anders; Lade, Poul V.
2004-01-01
Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena ~ creep, stress relaxation, and rate effects ! observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part....... Special attention is paid to elastoviscoplastic models that combine inviscid elastic and time-dependent plastic behavior. Various general elastoviscoplastic models can roughly be divided into two categories: Models based on the concept of overstress and models based on nonstationary flow surface theory...
Meneses Gutierrez, A.; Sagiya, T.
2013-12-01
There is an ongoing concentrated deformation along the Japan Sea coast, which has been identified as Niigata Kobe Tectonic Zone (Sagiya et al., 2000). Large historical earthquakes have occurred in this area, and in recent years, Niigata has suffered the impact of two important events, known as the 2004 Mid-Niigata Prefecture earthquake (M 6.8) and The 2007 Niigata-ken Chuetsu-Oki earthquake (M 6.6), which considerately affected the crustal deformation pattern. For this reason, we review temporal variation of crustal deformation pattern in the mid Niigata region based on daily coordinates of 28 GPS sites from the GEONET network for three time windows: before 2004, 2004-2007 and after 2007 until March 2011, to avoid effects of crustal deformation associated with the 2011 Tohoku-Oki earthquake. We observed a migration of the deformation pattern in the East-West direction through the contraction belts for the above time windows. Before 2004, we recognize a clear shortening of 0.3ppm/yr in the area between the source regions of 2004 and 2007 quakes. After the 2004 Chuetsu earthquake, this shortening rate decreased. On the other hand, an accelerated contraction occurred to the east of this region, around the source region of the 2004 earthquake. After the 2007 earthquake, another contraction zone appeared to the northwest, near the 2007 source region. These time-dependent behaviors suggest there exists strong interaction between parallel fault segments in this area. It is crucially important to reveal such interaction to understand crustal deformation and seismogenesis in this region. We construct kinematic deformation models to interpret the time-dependent deformation pattern for each time period and to investigate mechanical interaction of coseismic as well as probably aseismic fault slips. Optimal faults parameters were established using a grid search, and computing the 95% confidence interval for each model parameter using the normalized Chi-squared distribution to
Time-dependent deformation of concrete under multiaxial stress conditions. Final report
International Nuclear Information System (INIS)
McDonald, J.E.
1975-10-01
An investigation was made on the time-dependent deformation behavior of concrete in the presence of temperature, moisture, and loading conditions similar to those encountered in a prestressed concrete reactor vessel (PCRV). This investigation encompassed one concrete strength (6000 psi at 28 days), three aggregate types (chert, limestone, and graywacke), one cement (Type II), two types of specimens (as-cast and air-dried), two levels of temperature during test (73 and 150 0 F), and four types of loading (uniaxial, hydrostatic, biaxial, and triaxial). This effort was intended primarily as a data report; the experimental procedures and results are presented in detail. A comprehensive evaluation of the effects of various parameters and their interactions on the behavior of concrete is not included. However, a number of general comparisons were made concerning the effect of the various test conditions on concrete behavior. Based on this limited evaluation of the data, general conclusions and recommendations for additional work were formulated
Neutrino flavor instabilities in a time-dependent supernova model
Directory of Open Access Journals (Sweden)
Sajad Abbar
2015-12-01
Full Text Available A dense neutrino medium such as that inside a core-collapse supernova can experience collective flavor conversion or oscillations because of the neutral-current weak interaction among the neutrinos. This phenomenon has been studied in a restricted, stationary supernova model which possesses the (spatial spherical symmetry about the center of the supernova and the (directional axial symmetry around the radial direction. Recently it has been shown that these spatial and directional symmetries can be broken spontaneously by collective neutrino oscillations. In this letter we analyze the neutrino flavor instabilities in a time-dependent supernova model. Our results show that collective neutrino oscillations start at approximately the same radius in both the stationary and time-dependent supernova models unless there exist very rapid variations in local physical conditions on timescales of a few microseconds or shorter. Our results also suggest that collective neutrino oscillations can vary rapidly with time in the regimes where they do occur which need to be studied in time-dependent supernova models.
Neutrino flavor instabilities in a time-dependent supernova model
Energy Technology Data Exchange (ETDEWEB)
Abbar, Sajad; Duan, Huaiyu, E-mail: duan@unm.edu
2015-12-17
A dense neutrino medium such as that inside a core-collapse supernova can experience collective flavor conversion or oscillations because of the neutral-current weak interaction among the neutrinos. This phenomenon has been studied in a restricted, stationary supernova model which possesses the (spatial) spherical symmetry about the center of the supernova and the (directional) axial symmetry around the radial direction. Recently it has been shown that these spatial and directional symmetries can be broken spontaneously by collective neutrino oscillations. In this letter we analyze the neutrino flavor instabilities in a time-dependent supernova model. Our results show that collective neutrino oscillations start at approximately the same radius in both the stationary and time-dependent supernova models unless there exist very rapid variations in local physical conditions on timescales of a few microseconds or shorter. Our results also suggest that collective neutrino oscillations can vary rapidly with time in the regimes where they do occur which need to be studied in time-dependent supernova models.
Considerations on assessment of different time depending models adequacy
International Nuclear Information System (INIS)
Constantinescu, C.
2015-01-01
The operating period of nuclear power plants can be prolonged if it can be shown that their safety has remained on a high level, and for this, it is necessary to estimate how the aged systems, structures and components (SSCs) influence the NPP reliability and safety. To emphasize the ageing aspects the case study presented in this paper will assess different time depending models for rate of occurrence of failures with the goal to obtain the best fitting model. A sensitivity analysis for the impact of burn-in failures was performed to improve the result of the goodness of fit test. Based on the analysis results, a conclusion about the existence or the absence of an ageing trend could be developed. A sensitivity analysis regarding of the reliability parameters was performed, and the results were used to observe the impact over the time-dependent rate of occurrence of failures. (authors)
Numerical simulation of time-dependent deformations under hygral and thermal transient conditions
International Nuclear Information System (INIS)
Roelfstra, P.E.
1987-01-01
Some basic concepts of numerical simulation of the formation of the microstructure of HCP are outlined. The aim is to replace arbitrary terms like aging by more realistic terms like bond density in the xerogel and bonds between hydrating particles of HCP. Actual state parameters such as temperature, humidity and degree of hydration can be determined under transient hygral and thermal conditions by solving numerically a series of appropriate coupled differential equations with given boundary conditions. Shrinkage of a composite structure without crack formation, based on calculated moisture distributions, has been determined with numerical concrete codes. The influence of crack formation, tensile strain-hardening and softening on the total deformation of a quasi-homogeneous drying material has been studied by means of model based on FEM. The difference between shrinkage without crack formation and shrinkage with crack formation can be quantified. Drying shrinkage and creep of concrete cannot be separated. The total deformation depends on the superimposed stress fields. Transient hygral deformation can be realistically predicted if the concept of point properties is applied rigorously. Transient thermal deformation has to be dealt with in the same way. (orig./HP)
Time dependent patient no-show predictive modelling development.
Huang, Yu-Li; Hanauer, David A
2016-05-09
Purpose - The purpose of this paper is to develop evident-based predictive no-show models considering patients' each past appointment status, a time-dependent component, as an independent predictor to improve predictability. Design/methodology/approach - A ten-year retrospective data set was extracted from a pediatric clinic. It consisted of 7,291 distinct patients who had at least two visits along with their appointment characteristics, patient demographics, and insurance information. Logistic regression was adopted to develop no-show models using two-thirds of the data for training and the remaining data for validation. The no-show threshold was then determined based on minimizing the misclassification of show/no-show assignments. There were a total of 26 predictive model developed based on the number of available past appointments. Simulation was employed to test the effective of each model on costs of patient wait time, physician idle time, and overtime. Findings - The results demonstrated the misclassification rate and the area under the curve of the receiver operating characteristic gradually improved as more appointment history was included until around the 20th predictive model. The overbooking method with no-show predictive models suggested incorporating up to the 16th model and outperformed other overbooking methods by as much as 9.4 per cent in the cost per patient while allowing two additional patients in a clinic day. Research limitations/implications - The challenge now is to actually implement the no-show predictive model systematically to further demonstrate its robustness and simplicity in various scheduling systems. Originality/value - This paper provides examples of how to build the no-show predictive models with time-dependent components to improve the overbooking policy. Accurately identifying scheduled patients' show/no-show status allows clinics to proactively schedule patients to reduce the negative impact of patient no-shows.
Development of constitutive model for composites exhibiting time dependent properties
International Nuclear Information System (INIS)
Pupure, L; Joffe, R; Varna, J; Nyström, B
2013-01-01
Regenerated cellulose fibres and their composites exhibit highly nonlinear behaviour. The mechanical response of these materials can be successfully described by the model developed by Schapery for time-dependent materials. However, this model requires input parameters that are experimentally determined via large number of time-consuming tests on the studied composite material. If, for example, the volume fraction of fibres is changed we have a different material and new series of experiments on this new material are required. Therefore the ultimate objective of our studies is to develop model which determines the composite behaviour based on behaviour of constituents of the composite. This paper gives an overview of problems and difficulties, associated with development, implementation and verification of such model
Time-dependent perturbation theory for nonequilibrium lattice models
International Nuclear Information System (INIS)
Jensen, I.; Dickman, R.
1993-01-01
The authors develop a time-dependent perturbation theory for nonequilibrium interacting particle systems. They focus on models such as the contact process which evolve via destruction and autocatalytic creation of particles. At a critical value of the destruction rate there is a continuous phase transition between an active steady state and the vacuum state, which is absorbing. They present several methods for deriving series for the evolution starting from a single seed particle, including expansions for the ultimate survival probability in the super- and subcritical regions, expansions for the average number of particles in the subcritical region, and short-time expansions. Algorithms for computer generation of the various expansions are presented. Rather long series (24 terms or more) and precise estimates of critical parameters are presented. 45 refs., 4 figs., 9 tabs
A simple shear limited, single size, time dependent flocculation model
Kuprenas, R.; Tran, D. A.; Strom, K.
2017-12-01
This research focuses on the modeling of flocculation of cohesive sediment due to turbulent shear, specifically, investigating the dependency of flocculation on the concentration of cohesive sediment. Flocculation is important in larger sediment transport models as cohesive particles can create aggregates which are orders of magnitude larger than their unflocculated state. As the settling velocity of each particle is determined by the sediment size, density, and shape, accounting for this aggregation is important in determining where the sediment is deposited. This study provides a new formulation for flocculation of cohesive sediment by modifying the Winterwerp (1998) flocculation model (W98) so that it limits floc size to that of the Kolmogorov micro length scale. The W98 model is a simple approach that calculates the average floc size as a function of time. Because of its simplicity, the W98 model is ideal for implementing into larger sediment transport models; however, the model tends to over predict the dependency of the floc size on concentration. It was found that the modification of the coefficients within the original model did not allow for the model to capture the dependency on concentration. Therefore, a new term within the breakup kernel of the W98 formulation was added. The new formulation results is a single size, shear limited, and time dependent flocculation model that is able to effectively capture the dependency of the equilibrium size of flocs on both suspended sediment concentration and the time to equilibrium. The overall behavior of the new model is explored and showed align well with other studies on flocculation. Winterwerp, J. C. (1998). A simple model for turbulence induced flocculation of cohesive sediment. .Journal of Hydraulic Research, 36(3):309-326.
Simulation of time-dependent Heisenberg models in one dimension
DEFF Research Database (Denmark)
Volosniev, A. G.; Hammer, H. -W.; Zinner, N. T.
2016-01-01
In this Letter, we provide a theoretical analysis of strongly interacting quantum systems confined by a time-dependent external potential in one spatial dimension. We show that such systems can be used to simulate spin chains described by Heisenberg Hamiltonians in which the exchange coupling...... constants can be manipulated by time-dependent driving of the shape of the external confinement. As illustrative examples, we consider a harmonic trapping potential with a variable frequency and an infinite square well potential with a time-dependent barrier in the middle....
Compensation of some time dependent deformations in two dimensional (2D) tomography
International Nuclear Information System (INIS)
Desbat, L.; Roux, S.; Grangeat, P.
2005-01-01
This work is a contribution to motion compensation in tomography. It has been shown that much more general deformations than affine transforms can be analytically compensated in dynamic tomography. The class of deformations that transformed only a parallel projection geometry into an other parallel projection geometry, or a divergent projection geometry into an other divergent geometry have been considered. Among these deformation, it has been shown that those involving only an affine deformation along each line (this affine deformation can vary from line to line), can be efficiently analytically compensated, i e within a F.B.P. algorithm. This class of deformations is much larger than the very small class of affine deformation. It involves more local deformation possibilities. Deformations from this considered class have been written as a composition of an affine transform and deformations that can be compensated with weighting and re-binning step, the admissibility conditions and the F.B.P. algorithm are the same those given. (N.C.)
Compensation of some time dependent deformations in two dimensional (2D) tomography
Energy Technology Data Exchange (ETDEWEB)
Desbat, L. [Universite Joseph Fourier, UMR CNRS 5525, 38 - Grenoble (France); Roux, S. [Universite Joseph Fourier, TIMC-IMAG, In3S, Faculte de Medecine, 38 - Grenoble (France)]|[CEA Grenoble, Lab. d' Electronique et de Technologie de l' Informatique (LETI), 38 (France); Grangeat, P. [CEA Grenoble, Lab. d' Electronique et de Technologie de l' Informatique (LETI), 38 (France)
2005-07-01
This work is a contribution to motion compensation in tomography. It has been shown that much more general deformations than affine transforms can be analytically compensated in dynamic tomography. The class of deformations that transformed only a parallel projection geometry into an other parallel projection geometry, or a divergent projection geometry into an other divergent geometry have been considered. Among these deformation, it has been shown that those involving only an affine deformation along each line (this affine deformation can vary from line to line), can be efficiently analytically compensated, i e within a F.B.P. algorithm. This class of deformations is much larger than the very small class of affine deformation. It involves more local deformation possibilities. Deformations from this considered class have been written as a composition of an affine transform and deformations that can be compensated with weighting and re-binning step, the admissibility conditions and the F.B.P. algorithm are the same those given. (N.C.)
Time-dependent Models of Magnetospheric Accretion onto Young Stars
Energy Technology Data Exchange (ETDEWEB)
Robinson, C. E.; Espaillat, C. C. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Owen, J. E. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Adams, F. C., E-mail: connorr@bu.edu [Physics Department, University of Michigan, Ann Arbor, MI 48109 (United States)
2017-04-01
Accretion onto Classical T Tauri stars is thought to take place through the action of magnetospheric processes, with gas in the inner disk being channeled onto the star’s surface by the stellar magnetic field lines. Young stars are known to accrete material in a time-variable manner, and the source of this variability remains an open problem, particularly on the shortest (∼day) timescales. Using one-dimensional time-dependent numerical simulations that follow the field line geometry, we find that for plausibly realistic young stars, steady-state transonic accretion occurs naturally in the absence of any other source of variability. However, we show that if the density in the inner disk varies smoothly in time with ∼day-long timescales (e.g., due to turbulence), this complication can lead to the development of shocks in the accretion column. These shocks propagate along the accretion column and ultimately hit the star, leading to rapid, large amplitude changes in the accretion rate. We argue that when these shocks hit the star, the observed time dependence will be a rapid increase in accretion luminosity, followed by a slower decline, and could be an explanation for some of the short-period variability observed in accreting young stars. Our one-dimensional approach bridges previous analytic work to more complicated multi-dimensional simulations and observations.
Time-dependent Models of Magnetospheric Accretion onto Young Stars
International Nuclear Information System (INIS)
Robinson, C. E.; Espaillat, C. C.; Owen, J. E.; Adams, F. C.
2017-01-01
Accretion onto Classical T Tauri stars is thought to take place through the action of magnetospheric processes, with gas in the inner disk being channeled onto the star’s surface by the stellar magnetic field lines. Young stars are known to accrete material in a time-variable manner, and the source of this variability remains an open problem, particularly on the shortest (∼day) timescales. Using one-dimensional time-dependent numerical simulations that follow the field line geometry, we find that for plausibly realistic young stars, steady-state transonic accretion occurs naturally in the absence of any other source of variability. However, we show that if the density in the inner disk varies smoothly in time with ∼day-long timescales (e.g., due to turbulence), this complication can lead to the development of shocks in the accretion column. These shocks propagate along the accretion column and ultimately hit the star, leading to rapid, large amplitude changes in the accretion rate. We argue that when these shocks hit the star, the observed time dependence will be a rapid increase in accretion luminosity, followed by a slower decline, and could be an explanation for some of the short-period variability observed in accreting young stars. Our one-dimensional approach bridges previous analytic work to more complicated multi-dimensional simulations and observations.
Recovery of time-dependent volatility in option pricing model
Deng, Zui-Cha; Hon, Y. C.; Isakov, V.
2016-11-01
In this paper we investigate an inverse problem of determining the time-dependent volatility from observed market prices of options with different strikes. Due to the non linearity and sparsity of observations, an analytical solution to the problem is generally not available. Numerical approximation is also difficult to obtain using most of the existing numerical algorithms. Based on our recent theoretical results, we apply the linearisation technique to convert the problem into an inverse source problem from which recovery of the unknown volatility function can be achieved. Two kinds of strategies, namely, the integral equation method and the Landweber iterations, are adopted to obtain the stable numerical solution to the inverse problem. Both theoretical analysis and numerical examples confirm that the proposed approaches are effective. The work described in this paper was partially supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region (Project No. CityU 101112) and grants from the NNSF of China (Nos. 11261029, 11461039), and NSF grants DMS 10-08902 and 15-14886 and by Emylou Keith and Betty Dutcher Distinguished Professorship at the Wichita State University (USA).
Constitutive modeling for uniaxial time-dependent ratcheting of SS304 stainless steel
International Nuclear Information System (INIS)
Kan Qianhua; Kang Guozheng; Zhang Juan
2007-01-01
Based on the experimental results of uniaxial time-dependent ratcheting behavior of SS304 stainless steel at room temperature and 973K, a new time-dependent constitutive model was proposed. The model describes the time-dependent ratcheting by adding a static/thermal recovery into the Abdel-Karim-Ohno non-linear kinematic hardening rule. The capability of the model to describe the time-dependent ratcheting was discussed by comparing the simulations with the corresponding experimental results. It is shown that the revised unified viscoplastic model can simulate the time-dependent ratcheting reasonably both at room and high temperatures. (authors)
Time-dependent evolution of rock slopes by a multi-modelling approach
Bozzano, F.; Della Seta, M.; Martino, S.
2016-06-01
This paper presents a multi-modelling approach that incorporates contributions from morpho-evolutionary modelling, detailed engineering-geological modelling and time-dependent stress-strain numerical modelling to analyse the rheological evolution of a river valley slope over approximately 102 kyr. The slope is located in a transient, tectonically active landscape in southwestern Tyrrhenian Calabria (Italy), where gravitational processes drive failures in rock slopes. Constraints on the valley profile development were provided by a morpho-evolutionary model based on the correlation of marine and river strath terraces. Rock mass classes were identified through geomechanical parameters that were derived from engineering-geological surveys and outputs of a multi-sensor slope monitoring system. The rock mass classes were associated to lithotechnical units to obtain a high-resolution engineering-geological model along a cross section of the valley. Time-dependent stress-strain numerical modelling reproduced the main morpho-evolutionary stages of the valley slopes. The findings demonstrate that a complex combination of eustatism, uplift and Mass Rock Creep (MRC) deformations can lead to first-time failures of rock slopes when unstable conditions are encountered up to the generation of stress-controlled shear zones. The multi-modelling approach enabled us to determine that such complex combinations may have been sufficient for the first-time failure of the S. Giovanni slope at approximately 140 ka (MIS 7), even without invoking any trigger. Conversely, further reactivations of the landslide must be related to triggers such as earthquakes, rainfall and anthropogenic activities. This failure involved a portion of the slope where a plasticity zone resulted from mass rock creep that evolved with a maximum strain rate of 40% per thousand years, after the formation of a river strath terrace. This study demonstrates that the multi-modelling approach presented herein is a useful
Time-dependent inhomogeneous jet models for BL Lac objects
Marlowe, A. T.; Urry, C. M.; George, I. M.
1992-05-01
Relativistic beaming can explain many of the observed properties of BL Lac objects (e.g., rapid variability, high polarization, etc.). In particular, the broadband radio through X-ray spectra are well modeled by synchrotron-self Compton emission from an inhomogeneous relativistic jet. We have done a uniform analysis on several BL Lac objects using a simple but plausible inhomogeneous jet model. For all objects, we found that the assumed power-law distribution of the magnetic field and the electron density can be adjusted to match the observed BL Lac spectrum. While such models are typically unconstrained, consideration of spectral variability strongly restricts the allowed parameters, although to date the sampling has generally been too sparse to constrain the current models effectively. We investigate the time evolution of the inhomogeneous jet model for a simple perturbation propagating along the jet. The implications of this time evolution model and its relevance to observed data are discussed.
TIME-DEPENDENT STOCHASTIC ACCELERATION MODEL FOR FERMI BUBBLES
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Kento; Asano, Katsuaki; Terasawa, Toshio, E-mail: kentos@icrr.u-tokyo.ac.jp, E-mail: asanok@icrr.u-tokyo.ac.jp, E-mail: terasawa@icrr.u-tokyo.ac.jp [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)
2015-12-01
We study stochastic acceleration models for the Fermi bubbles. Turbulence is excited just behind the shock front via Kelvin–Helmholtz, Rayleigh–Taylor, or Richtmyer–Meshkov instabilities, and plasma particles are continuously accelerated by the interaction with the turbulence. The turbulence gradually decays as it goes away from the shock fronts. Adopting a phenomenological model for the stochastic acceleration, we explicitly solve the temporal evolution of the particle energy distribution in the turbulence. Our results show that the spatial distribution of high-energy particles is different from those for a steady solution. We also show that the contribution of electrons that escaped from the acceleration regions significantly softens the photon spectrum. The photon spectrum and surface brightness profile are reproduced by our models. If the escape efficiency is very high, the radio flux from the escaped low-energy electrons can be comparable to that of the WMAP haze. We also demonstrate hadronic models with the stochastic acceleration, but they are unlikely in the viewpoint of the energy budget.
Evaluation of Digital Model Accuracy and Time-dependent ...
African Journals Online (AJOL)
2017-10-26
Oct 26, 2017 ... stability of alginate impressions for durations of immediately (T0), 1 day (T1), and 2 days (T2). ... 3D digital models were introduced in 1999 by OrthoCad, ..... printer either within or on the outside surface of the teeth.[18].
Time dependent mechanical modeling for polymers based on network theory
Energy Technology Data Exchange (ETDEWEB)
Billon, Noëlle [MINES ParisTech, PSL-Research University, CEMEF – Centre de mise en forme des matériaux, CNRS UMR 7635, CS 10207 rue Claude Daunesse 06904 Sophia Antipolis Cedex (France)
2016-05-18
Despite of a lot of attempts during recent years, complex mechanical behaviour of polymers remains incompletely modelled, making industrial design of structures under complex, cyclic and hard loadings not totally reliable. The non linear and dissipative viscoelastic, viscoplastic behaviour of those materials impose to take into account non linear and combined effects of mechanical and thermal phenomena. In this view, a visco-hyperelastic, viscoplastic model, based on network description of the material has recently been developed and designed in a complete thermodynamic frame in order to take into account those main thermo-mechanical couplings. Also, a way to account for coupled effects of strain-rate and temperature was suggested. First experimental validations conducted in the 1D limit on amorphous rubbery like PMMA in isothermal conditions led to pretty goods results. In this paper a more complete formalism is presented and validated in the case of a semi crystalline polymer, a PA66 and a PET (either amorphous or semi crystalline) are used. Protocol for identification of constitutive parameters is described. It is concluded that this new approach should be the route to accurately model thermo-mechanical behaviour of polymers using a reduced number of parameters of some physical meaning.
Nonperturbative Time Dependent Solution of a Simple Ionization Model
Costin, Ovidiu; Costin, Rodica D.; Lebowitz, Joel L.
2018-02-01
We present a non-perturbative solution of the Schrödinger equation {iψ_t(t,x)=-ψ_{xx}(t,x)-2(1 +α sinω t) δ(x)ψ(t,x)} , written in units in which \\hbar=2m=1, describing the ionization of a model atom by a parametric oscillating potential. This model has been studied extensively by many authors, including us. It has surprisingly many features in common with those observed in the ionization of real atoms and emission by solids, subjected to microwave or laser radiation. Here we use new mathematical methods to go beyond previous investigations and to provide a complete and rigorous analysis of this system. We obtain the Borel-resummed transseries (multi-instanton expansion) valid for all values of α, ω, t for the wave function, ionization probability, and energy distribution of the emitted electrons, the latter not studied previously for this model. We show that for large t and small α the energy distribution has sharp peaks at energies which are multiples of ω, corresponding to photon capture. We obtain small α expansions that converge for all t, unlike those of standard perturbation theory. We expect that our analysis will serve as a basis for treating more realistic systems revealing a form of universality in different emission processes.
Time dependent optimal switching controls in online selling models
Energy Technology Data Exchange (ETDEWEB)
Bradonjic, Milan [Los Alamos National Laboratory; Cohen, Albert [MICHIGAN STATE UNIV
2010-01-01
We present a method to incorporate dishonesty in online selling via a stochastic optimal control problem. In our framework, the seller wishes to maximize her average wealth level W at a fixed time T of her choosing. The corresponding Hamilton-Jacobi-Bellmann (HJB) equation is analyzed for a basic case. For more general models, the admissible control set is restricted to a jump process that switches between extreme values. We propose a new approach, where the optimal control problem is reduced to a multivariable optimization problem.
Mathematical model of SPOC with a time dependent reactive field
Energy Technology Data Exchange (ETDEWEB)
Ohtaki, Masako [Department of Physics, School of Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan)
2006-03-21
In general the muscle is in one of the two state possible states, relaxation or contraction. These contractions result from relative sliding of myosin and actin in the sarcomere, which is the contraction structure unit of skeletal muscle. The switching between two states is depending on the Ca2{sup +} concentrations. However another state has been detected between these two states. In the third state, that is SPontaneous Oscillatory Contraction (SPOC), sarcomere repeats contraction and extension spontaneously. Muscle fibers are composed of hundreds of sarcomeres in series and one sarcomea also is composed of hundreds of myosin. In microscopic, the force generated by actin and myosin interaction occurs stochastically. SPOC, however, is macroscopically observable and there are regular oscillations. To understand SPOC mechanism, we propose a model for SPOC based on chemical reaction including mechanical process.
Mathematical model of SPOC with a time dependent reactive field
International Nuclear Information System (INIS)
Ohtaki, Masako
2006-01-01
In general the muscle is in one of the two state possible states, relaxation or contraction. These contractions result from relative sliding of myosin and actin in the sarcomere, which is the contraction structure unit of skeletal muscle. The switching between two states is depending on the Ca2 + concentrations. However another state has been detected between these two states. In the third state, that is SPontaneous Oscillatory Contraction (SPOC), sarcomere repeats contraction and extension spontaneously. Muscle fibers are composed of hundreds of sarcomeres in series and one sarcomea also is composed of hundreds of myosin. In microscopic, the force generated by actin and myosin interaction occurs stochastically. SPOC, however, is macroscopically observable and there are regular oscillations. To understand SPOC mechanism, we propose a model for SPOC based on chemical reaction including mechanical process
Firework Model: Time Dependent Spectral Evolution of GRB
Barbiellini, Guido; Longo, Francesco; Ghirlanda, G.; Celotti, A.; Bosnjak, Z.
2004-09-01
The energetics of the long duration GRB phenomenon is compared with models of a rotating BH in a strong magnetic field generated by an accreting torus. The GRB energy emission is attributed to magnetic field vacuum breakdown that gives origin to a e +/- fireball. Its subsequent evolution is hypothesized in analogy with the in-flight decay of an elementary particle. An anisotropy in the fireball propagation is thus naturally produced. The recent discovery in some GRB of an initial phase characterized by a thermal spectrum could be interpreted as the photon emission of the fireball photosphere when it becomes transparent. In particular, the temporal evolution of the emission can be explained as the effect of a radiative deceleration of the out-moving ejecta.
Modeling caprock fracture, CO2 migration and time dependent fault healing: A numerical study.
MacFarlane, J.; Mukerji, T.; Vanorio, T.
2017-12-01
The Campi Flegrei caldera, located near Naples, Italy, is one of the highest risk volcanoes on Earth due to its recent unrest and urban setting. A unique history of surface uplift within the caldera is characterized by long duration uplift and subsidence cycles which are periodically interrupted by rapid, short period uplift events. Several models have been proposed to explain this history; in this study we will present a hydro-mechanical model that takes into account the caprock that seismic studies show to exist at 1-2 km depth. Specifically, we develop a finite element model of the caldera and use a modified version of fault-valve theory to represent fracture within the caprock. The model accounts for fault healing using a simplified, time-dependent fault sealing model. Multiple fracture events are incorporated by using previous solutions to test prescribed conditions and determine changes in rock properties, such as porosity and permeability. Although fault-valve theory has been used to model single fractures and recharge, this model is unique in its ability to model multiple fracture events. By incorporating multiple fracture events we can assess changes in both long and short-term reservoir behavior at Campi Flegrei. By varying the model inputs, we model the poro-elastic response to CO2 injection at depth and the resulting surface deformation. The goal is to enable geophysicists to better interpret surface observations and predict outcomes from observed changes in reservoir conditions.
Modelling long term rockslide displacements with non-linear time-dependent relationships
De Caro, Mattia; Volpi, Giorgio; Castellanza, Riccardo; Crosta, Giovanni; Agliardi, Federico
2015-04-01
Rockslides undergoing rapid changes in behaviour pose major risks in alpine areas, and require careful characterization and monitoring both for civil protection and mitigation activities. In particular, these instabilities can undergo very slow movement with occasional and intermittent acceleration/deceleration stages of motion potentially leading to collapse. Therefore, the analysis of such instabilities remains a challenging issue. Rockslide displacements are strongly conditioned by hydrologic factors as suggested by correlations with groundwater fluctuations, snowmelt, with a frequently observed delay between perturbation and system reaction. The aim of this work is the simulation of the complex time-dependent behaviour of two case studies for which also a 2D transient hydrogeological simulation has been performed: Vajont rockslide (1960 to 1963) and the recent Mt. de La Saxe rockslide (2009 to 2012). Non-linear time-dependent constitutive relationships have been used to describe long-term creep deformation. Analyses have been performed using a "rheological-mechanical" approach that fits idealized models (e.g. viscoelastic, viscoplastic, elasto-viscoplastic, Burgers, nonlinear visco-plastic) to the experimental behaviour of specific materials by means of numerical constants. Bidimensional simulations were carried out using the finite difference code FLAC. Displacements time-series, available for the two landslides, show two superimposed deformation mechanisms: a creep process, leading to movements under "steady state" conditions (e.g. constant groundwater level), and a "dynamic" process, leading to an increase in displacement rate due to changes of external loads (e.g. groundwater level). For both cases sliding mass is considered as an elasto-plastic body subject to its self-weight, inertial and seepage forces varying with time according to water table fluctuation (due to snowmelt or changing in reservoir level) and derived from the previous hydrogeological
Time-dependent Hartree-Fock dynamics and phase transition in Lipkin-Meshkov-Glick model
International Nuclear Information System (INIS)
Kan, K.; Lichtner, P.C.; Dworzecka, M.; Griffin, J.J.
1980-01-01
The time-dependent Hartree-Fock solutions of the two-level Lipkin-Meshkov-Glick model are studied by transforming the time-dependent Hartree-Fock equations into Hamilton's canonical form and analyzing the qualitative structure of the Hartree-Fock energy surface in the phase space. It is shown that as the interaction strength increases these time-dependent Hartree-Fock solutions undergo a qualitative change associated with the ground state phase transition previously studied in terms of coherent states. For two-body interactions stronger than the critical value, two types of time-dependent Hartree-Fock solutions (the ''librations'' and ''rotations'' in Hamilton's mechanics) exist simultaneously, while for weaker interactions only the rotations persist. It is also shown that the coherent states with the maximum total pseudospin value are determinants, so that time-dependent Hartree-Fock analysis is equivalent to the coherent state method
Skouri, K.; Konstantaras, I.
2009-01-01
An order level inventory model for seasonable/fashionable products subject to a period of increasing demand followed by a period of level demand and then by a period of decreasing demand rate (three branches ramp type demand rate) is considered. The unsatisfied demand is partially backlogged with a time dependent backlogging rate. In addition, the product deteriorates with a time dependent, namely, Weibull, deterioration rate. The model is studied under the following different replenishment p...
A time-dependent dusty gas dynamic model of axisymmetric cometary jets
International Nuclear Information System (INIS)
Korosmezey, A.; Gombosi, T.I.
1990-01-01
The present time-dependent, axisymmetric dusty gas dynamical model of inner cometary atmospheres solves the coupled and time-dependent equations of continuity, momentum, and energy for a gas-dust mixture between the surface of the nucleus and 100 km, using an axisymmetric 40 x 40 grid structure. A novel numerical method employing a second-order accurate Godunov-type scheme with dimensional splitting is used to solve the time-dependent pde system. It is established that a subsolar dust spike not predicted by previous calculations is generated by narrow axisymmetric jets, together with a jet cone whose opening angle depends on the jet length. 28 refs
Time-Dependent Global Sensitivity Analysis for Long-Term Degeneracy Model Using Polynomial Chaos
Directory of Open Access Journals (Sweden)
Jianbin Guo
2014-07-01
Full Text Available Global sensitivity is used to quantify the influence of uncertain model inputs on the output variability of static models in general. However, very few approaches can be applied for the sensitivity analysis of long-term degeneracy models, as far as time-dependent reliability is concerned. The reason is that the static sensitivity may not reflect the completed sensitivity during the entire life circle. This paper presents time-dependent global sensitivity analysis for long-term degeneracy models based on polynomial chaos expansion (PCE. Sobol’ indices are employed as the time-dependent global sensitivity since they provide accurate information on the selected uncertain inputs. In order to compute Sobol’ indices more efficiently, this paper proposes a moving least squares (MLS method to obtain the time-dependent PCE coefficients with acceptable simulation effort. Then Sobol’ indices can be calculated analytically as a postprocessing of the time-dependent PCE coefficients with almost no additional cost. A test case is used to show how to conduct the proposed method, then this approach is applied to an engineering case, and the time-dependent global sensitivity is obtained for the long-term degeneracy mechanism model.
Time-dependent Networks as Models to Achieve Fast Exact Time-table Queries
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Jacob, Rico
2001-01-01
We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....
Time-Dependent Networks as Models to Achieve Fast Exact Time-Table Queries
DEFF Research Database (Denmark)
Brodal, Gert Stølting; Jacob, Rico
2003-01-01
We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models.......We consider efficient algorithms for exact time-table queries, i.e. algorithms that find optimal itineraries for travelers using a train system. We propose to use time-dependent networks as a model and show advantages of this approach over space-time networks as models....
Towards the entropy of gravity time-dependent models via the Cardy-Verlinde formula
International Nuclear Information System (INIS)
Obregon, Octavio; Patino, Leonardo; Quevedo, Hernando
2003-01-01
For models with several time-dependent components, generalized entropies can be defined. This is shown for the Bianchi type IX model. We first derive the Cardy-Verlinde formula under the assumption that the first law of thermodynamics is valid. This leads to an explicit expression of the total entropy associated with this type of universe. Assuming the validity of the Cardy entropy formula, we obtain expressions for the corresponding Bekenstein, Bekenstein-Hawking and Hubble entropies. We discuss the validity of the Cardy-Verlinde formula and possible extensions of the outlined procedure to other time-dependent models
Directory of Open Access Journals (Sweden)
K. Skouri
2009-01-01
Full Text Available An order level inventory model for seasonable/fashionable products subject to a period of increasing demand followed by a period of level demand and then by a period of decreasing demand rate (three branches ramp type demand rate is considered. The unsatisfied demand is partially backlogged with a time dependent backlogging rate. In addition, the product deteriorates with a time dependent, namely, Weibull, deterioration rate. The model is studied under the following different replenishment policies: (a starting with no shortages and (b starting with shortages. The optimal replenishment policy for the model is derived for both the above mentioned policies.
Panwisawas, Chinnapat; D'Souza, Neil; Collins, David M.; Bhowmik, Ayan; Roebuck, Bryan
2018-05-01
Time-dependent plastic deformation through stress relaxation and creep deformation during in-situ cooling of the as-cast single-crystal superalloy CMSX-4® has been studied via neutron diffraction, transmission electron microscopy, electro-thermal miniature testing, and analytical modeling across two temperature regimes. Between 1000 °C and 900 °C, stress relaxation prevails and gives rise to softening as evidenced by a decreased dislocation density and the presence of long segment stacking faults in γ phase. Lattice strains decrease in both the γ matrix and γ' precipitate phases. A constitutive viscoplastic law derived from in-situ isothermal relaxation test under-estimates the equivalent plastic strain in the prediction of the stress and strain evolution during cooling in this case. It is thereby shown that the history dependence of the microstructure needs to be taken into account while deriving a constitutive law and which becomes even more relevant at high temperatures approaching the solvus. Higher temperature cooling experiments have also been carried out between 1300 °C and 1150 °C to measure the evolution of stress and plastic strain close to the γ' solvus temperature. In-situ cooling of samples using ETMT shows that creep dominates during high-temperature deformation between 1300 °C and 1220 °C, but below a threshold temperature, typically 1220 °C work hardening begins to prevail from increasing γ' fraction and resulting in a rapid increase in stress. The history dependence of prior accumulated deformation is also confirmed in the flow stress measurements using a single sample while cooling. The saturation stresses in the flow stress experiments show very good agreement with the stresses measured in the cooling experiments when viscoplastic deformation is dominant. This study demonstrates that experimentation during high-temperature deformation as well as the history dependence of the microstructure during cooling plays a key role in deriving
Panwisawas, Chinnapat; D'Souza, Neil; Collins, David M; Bhowmik, Ayan
2017-09-11
Time dependent plastic deformation in a single crystal nickel-base superalloy during cooling from casting relevant temperatures has been studied using a combination of in-situ neutron diffraction, transmission electron microscopy and modelling. Visco-plastic deformation during cooling was found to be dependent on the stress and constraints imposed to component contraction during cooling, which mechanistically comprises creep and stress relaxation. Creep results in progressive work hardening with dislocations shearing the γ' precipitates, a high dislocation density in the γ channels and near the γ/γ' interface and precipitate shearing. When macroscopic contraction is restricted, relaxation dominates. This leads to work softening from a decreased dislocation density and the presence of long segment stacking faults in γ phase. Changes in lattice strains occur to a similar magnitude in both the γ and γ' phases during stress relaxation, while in creep there is no clear monotonic trend in lattice strain in the γ phase, but only a marginal increase in the γ' precipitates. Using a visco-plastic law derived from in-situ experiments, the experimentally measured and calculated stresses during cooling show a good agreement when creep predominates. However, when stress relaxation dominates accounting for the decrease in dislocation density during cooling is essential.
The Limit Behavior of a Stochastic Logistic Model with Individual Time-Dependent Rates
Directory of Open Access Journals (Sweden)
Yilun Shang
2013-01-01
Full Text Available We investigate a variant of the stochastic logistic model that allows individual variation and time-dependent infection and recovery rates. The model is described as a heterogeneous density dependent Markov chain. We show that the process can be approximated by a deterministic process defined by an integral equation as the population size grows.
Stochastic time-dependent vehicle routing problem: Mathematical models and ant colony algorithm
Directory of Open Access Journals (Sweden)
Zhengyu Duan
2015-11-01
Full Text Available This article addresses the stochastic time-dependent vehicle routing problem. Two mathematical models named robust optimal schedule time model and minimum expected schedule time model are proposed for stochastic time-dependent vehicle routing problem, which can guarantee delivery within the time windows of customers. The robust optimal schedule time model only requires the variation range of link travel time, which can be conveniently derived from historical traffic data. In addition, the robust optimal schedule time model based on robust optimization method can be converted into a time-dependent vehicle routing problem. Moreover, an ant colony optimization algorithm is designed to solve stochastic time-dependent vehicle routing problem. As the improvements in initial solution and transition probability, ant colony optimization algorithm has a good performance in convergence. Through computational instances and Monte Carlo simulation tests, robust optimal schedule time model is proved to be better than minimum expected schedule time model in computational efficiency and coping with the travel time fluctuations. Therefore, robust optimal schedule time model is applicable in real road network.
Time-dependent reliability analysis of nuclear reactor operators using probabilistic network models
International Nuclear Information System (INIS)
Oka, Y.; Miyata, K.; Kodaira, H.; Murakami, S.; Kondo, S.; Togo, Y.
1987-01-01
Human factors are very important for the reliability of a nuclear power plant. Human behavior has essentially a time-dependent nature. The details of thinking and decision making processes are important for detailed analysis of human reliability. They have, however, not been well considered by the conventional methods of human reliability analysis. The present paper describes the models for the time-dependent and detailed human reliability analysis. Recovery by an operator is taken into account and two-operators models are also presented
Directory of Open Access Journals (Sweden)
Traykov Alexander
2015-01-01
Full Text Available Numerical studies are performed on computer models taking into account the stages of construction and time dependent material properties defined in two forms. A 2D model of three storey two spans frame is created. The first form deals with material defined in the usual design practice way - without taking into account the time dependent properties of the concrete. The second form creep and shrinkage of the concrete are taken into account. Displacements and internal forces in specific elements and sections are reported. The influence of the time dependent material properties on the displacement and the internal forces in the main structural elements is tracked down. The results corresponding to the two forms of material definition are compared together as well as with the results obtained by the usual design calculations. Conclusions on the influence of the concrete creep and shrinkage during the construction towards structural behaviour are made.
The solar modulation of galactic comic rays as described by a time-dependent drift model
International Nuclear Information System (INIS)
Le Roux, J.A.
1990-09-01
The modulation process is understood to be an interaction between cosmic rays and the solar wind. The heliosphere and the observed modulation of cosmic rays in the heliosphere was reviewed and the time-dependence nature of the long-term modulation of cosmic rays highligted. A two-dimensional time-dependent drift model that describes the long-term modulation of cosmic-rays is presented. Application of the time-dependent drift model during times of increased solar activity showed that drift should be reduced during such periods. Isolated Forbush decreases were also studied in an effort to explain some observed trends in the properties of the Forbush decrease as a function of radial distance. The magnitude of the Forbush decrease and its recovery time were therefore studied as a function of radial distance in the equatorial plane. 154 refs., 95 figs., 1 tab
The Spherical Deformation Model
DEFF Research Database (Denmark)
Hobolth, Asgar
2003-01-01
Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse the s...
A time-dependent event tree technique for modelling recovery operations
International Nuclear Information System (INIS)
Kohut, P.; Fitzpatrick, R.
1991-01-01
The development of a simplified time dependent event tree methodology is presented. The technique is especially applicable to describe recovery operations in nuclear reactor accident scenarios initiated by support system failures. The event tree logic is constructed using time dependent top events combined with a damage function that contains information about the final state time behavior of the reactor core. Both the failure and the success states may be utilized for the analysis. The method is illustrated by modeling the loss of service water function with special emphasis on the RCP [reactor coolant pump] seal LOCA [loss of coolant accident] scenario. 5 refs., 2 figs., 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Lasuik, J.; Shalchi, A., E-mail: andreasm4@yahoo.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada)
2017-09-20
Recently, a new theory for the transport of energetic particles across a mean magnetic field was presented. Compared to other nonlinear theories the new approach has the advantage that it provides a full time-dependent description of the transport. Furthermore, a diffusion approximation is no longer part of that theory. The purpose of this paper is to combine this new approach with a time-dependent model for parallel transport and different turbulence configurations in order to explore the parameter regimes for which we get ballistic transport, compound subdiffusion, and normal Markovian diffusion.
Modeling Time-Dependent Association in Longitudinal Data: A Lag as Moderator Approach
Selig, James P.; Preacher, Kristopher J.; Little, Todd D.
2012-01-01
We describe a straightforward, yet novel, approach to examine time-dependent association between variables. The approach relies on a measurement-lag research design in conjunction with statistical interaction models. We base arguments in favor of this approach on the potential for better understanding the associations between variables by…
Numerical modelling of the time-dependent mechanical behaviour of softwood
DEFF Research Database (Denmark)
Engelund, Emil Tang
2010-01-01
When using wood as a structural material it is important to consider its time-dependent mechanical behaviour and to predict this behaviour for decades ahead. For this purpose, several rheological mathematical models, spanning from fairly simple to very complex ones, have been developed over...
Diffeomorphic Statistical Deformation Models
DEFF Research Database (Denmark)
Hansen, Michael Sass; Hansen, Mads/Fogtman; Larsen, Rasmus
2007-01-01
In this paper we present a new method for constructing diffeomorphic statistical deformation models in arbitrary dimensional images with a nonlinear generative model and a linear parameter space. Our deformation model is a modified version of the diffeomorphic model introduced by Cootes et al....... The modifications ensure that no boundary restriction has to be enforced on the parameter space to prevent folds or tears in the deformation field. For straightforward statistical analysis, principal component analysis and sparse methods, we assume that the parameters for a class of deformations lie on a linear...... with ground truth in form of manual expert annotations, and compared to Cootes's model. We anticipate applications in unconstrained diffeomorphic synthesis of images, e.g. for tracking, segmentation, registration or classification purposes....
A Bimodal Hybrid Model for Time-Dependent Probabilistic Seismic Hazard Analysis
Yaghmaei-Sabegh, Saman; Shoaeifar, Nasser; Shoaeifar, Parva
2018-03-01
The evaluation of evidence provided by geological studies and historical catalogs indicates that in some seismic regions and faults, multiple large earthquakes occur in cluster. Then, the occurrences of large earthquakes confront with quiescence and only the small-to-moderate earthquakes take place. Clustering of large earthquakes is the most distinguishable departure from the assumption of constant hazard of random occurrence of earthquakes in conventional seismic hazard analysis. In the present study, a time-dependent recurrence model is proposed to consider a series of large earthquakes that occurs in clusters. The model is flexible enough to better reflect the quasi-periodic behavior of large earthquakes with long-term clustering, which can be used in time-dependent probabilistic seismic hazard analysis with engineering purposes. In this model, the time-dependent hazard results are estimated by a hazard function which comprises three parts. A decreasing hazard of last large earthquake cluster and an increasing hazard of the next large earthquake cluster, along with a constant hazard of random occurrence of small-to-moderate earthquakes. In the final part of the paper, the time-dependent seismic hazard of the New Madrid Seismic Zone at different time intervals has been calculated for illustrative purpose.
Integrable time-dependent Hamiltonians, solvable Landau-Zener models and Gaudin magnets
Yuzbashyan, Emil A.
2018-05-01
We solve the non-stationary Schrödinger equation for several time-dependent Hamiltonians, such as the BCS Hamiltonian with an interaction strength inversely proportional to time, periodically driven BCS and linearly driven inhomogeneous Dicke models as well as various multi-level Landau-Zener tunneling models. The latter are Demkov-Osherov, bow-tie, and generalized bow-tie models. We show that these Landau-Zener problems and their certain interacting many-body generalizations map to Gaudin magnets in a magnetic field. Moreover, we demonstrate that the time-dependent Schrödinger equation for the above models has a similar structure and is integrable with a similar technique as Knizhnik-Zamolodchikov equations. We also discuss applications of our results to the problem of molecular production in an atomic Fermi gas swept through a Feshbach resonance and to the evaluation of the Landau-Zener transition probabilities.
Wasim Akram Mandal; Sahidul Islam
2016-01-01
In this paper analyzes fuzzy inventory system for deterioration item with time depended demand. Shortages are allowed under fully backlogged. Fixed cost, deterioration cost, shortages cost, holding cost are the cost considered in this model. Fuzziness is applying by allowing the cost components (holding cost, deterioration, shortage cost, holding cost, etc). In fuzzy environment it considered all required parameter to be triangular fuzzy numbers. One numerical solution of the model is obtaine...
The Spherical Deformation Model
DEFF Research Database (Denmark)
Hobolth, Asgar
2003-01-01
Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse the s...... a single central section of the object. We use maximum-likelihood-based inference for this purpose and demonstrate the suggested methods on real data....
Prandtl-Ishlinskii hysteresis models for complex time dependent hysteresis nonlinearities
Czech Academy of Sciences Publication Activity Database
Al Janaideh, M.; Krejčí, Pavel
2012-01-01
Roč. 407, č. 9 (2012), s. 1365-1367 ISSN 0921-4526 R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : complex hysteresis * time dependent hysteresis * Prandtl-Ishlinskii model Subject RIV: BA - General Mathematics Impact factor: 1.327, year: 2012 http://www.sciencedirect.com/science/article/pii/S092145261100932X
Anderson, David F; Yuan, Chaojie
2018-04-18
A number of coupling strategies are presented for stochastically modeled biochemical processes with time-dependent parameters. In particular, the stacked coupling is introduced and is shown via a number of examples to provide an exceptionally low variance between the generated paths. This coupling will be useful in the numerical computation of parametric sensitivities and the fast estimation of expectations via multilevel Monte Carlo methods. We provide the requisite estimators in both cases.
Dynamics of the sub-Ohmic spin-boson model: A time-dependent variational study
International Nuclear Information System (INIS)
Wu Ning; Duan Liwei; Zhao Yang; Li Xin
2013-01-01
The Dirac-Frenkel time-dependent variation is employed to probe the dynamics of the zero temperature sub-Ohmic spin-boson model with strong friction utilizing the Davydov D 1 ansatz. It is shown that initial conditions of the phonon bath have considerable influence on the dynamics. Counterintuitively, even in the very strong coupling regime, quantum coherence features still manage to survive under the polarized bath initial condition, while such features are absent under the factorized bath initial condition. In addition, a coherent-incoherent transition is found at a critical coupling strength α≈ 0.1 for s= 0.25 under the factorized bath initial condition. We quantify how faithfully our ansatz follows the Schrödinger equation, finding that the time-dependent variational approach is robust for strong dissipation and deep sub-Ohmic baths (s≪ 1).
Energy Technology Data Exchange (ETDEWEB)
Nascimento, Daniel R.; DePrince, A. Eugene, E-mail: deprince@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390 (United States)
2015-12-07
We present a combined cavity quantum electrodynamics/ab initio electronic structure approach for simulating plasmon-molecule interactions in the time domain. The simple Jaynes-Cummings-type model Hamiltonian typically utilized in such simulations is replaced with one in which the molecular component of the coupled system is treated in a fully ab initio way, resulting in a computationally efficient description of general plasmon-molecule interactions. Mutual polarization effects are easily incorporated within a standard ground-state Hartree-Fock computation, and time-dependent simulations carry the same formal computational scaling as real-time time-dependent Hartree-Fock theory. As a proof of principle, we apply this generalized method to the emergence of a Fano-like resonance in coupled molecule-plasmon systems; this feature is quite sensitive to the nanoparticle-molecule separation and the orientation of the molecule relative to the polarization of the external electric field.
An economic production model for time dependent demand with rework and multiple production setups
Directory of Open Access Journals (Sweden)
S.R. Singh
2014-04-01
Full Text Available In this paper, we present a model for time dependent demand with multiple productions and rework setups. Production is demand dependent and greater than the demand rate. Production facility produces items in m production setups and one rework setup (m, 1 policy. The major reason of reverse logistic and green supply chain is rework, so it reduces the cost of production and other ecological problems. Most of the researchers developed a rework model without deteriorating items. A numerical example and sensitivity analysis is shown to describe the model.
An EOQ model for weibull distribution deterioration with time-dependent cubic demand and backlogging
Santhi, G.; Karthikeyan, K.
2017-11-01
In this article we introduce an economic order quantity model with weibull deterioration and time dependent cubic demand rate where holding costs as a linear function of time. Shortages are allowed in the inventory system are partially and fully backlogging. The objective of this model is to minimize the total inventory cost by using the optimal order quantity and the cycle length. The proposed model is illustrated by numerical examples and the sensitivity analysis is performed to study the effect of changes in parameters on the optimum solutions.
EBT time-dependent point model code: description and user's guide
International Nuclear Information System (INIS)
Roberts, J.F.; Uckan, N.A.
1977-07-01
A D-T time-dependent point model has been developed to assess the energy balance in an EBT reactor plasma. Flexibility is retained in the model to permit more recent data to be incorporated as they become available from the theoretical and experimental studies. This report includes the physics models involved, the program logic, and a description of the variables and routines used. All the files necessary for execution are listed, and the code, including a post-execution plotting routine, is discussed
Directory of Open Access Journals (Sweden)
Pengpeng Jiao
2014-01-01
Full Text Available Time-dependent turning movement flows are very important input data for intelligent transportation systems but are impossible to be detected directly through current traffic surveillance systems. Existing estimation models have proved to be not accurate and reliable enough during all intervals. An improved way to address this problem is to develop a combined model framework that can integrate multiple submodels running simultaneously. This paper first presents a back propagation neural network model to estimate dynamic turning movements, as well as the self-adaptive learning rate approach and the gradient descent with momentum method for solving. Second, this paper develops an efficient Kalman filtering model and designs a revised sequential Kalman filtering algorithm. Based on the Bayesian method using both historical data and currently estimated results for error calibration, this paper further integrates above two submodels into a Bayesian combined model framework and proposes a corresponding algorithm. A field survey is implemented at an intersection in Beijing city to collect both time series of link counts and actual time-dependent turning movement flows, including historical and present data. The reported estimation results show that the Bayesian combined model is much more accurate and stable than other models.
Random walk in degree space and the time-dependent Watts-Strogatz model
Casa Grande, H. L.; Cotacallapa, M.; Hase, M. O.
2017-01-01
In this work, we propose a scheme that provides an analytical estimate for the time-dependent degree distribution of some networks. This scheme maps the problem into a random walk in degree space, and then we choose the paths that are responsible for the dominant contributions. The method is illustrated on the dynamical versions of the Erdős-Rényi and Watts-Strogatz graphs, which were introduced as static models in the original formulation. We have succeeded in obtaining an analytical form for the dynamics Watts-Strogatz model, which is asymptotically exact for some regimes.
Time-dependent ionization balance model for non-LTE plasma
International Nuclear Information System (INIS)
Lee, Y.T.; Zimmerman, G.B.; Bailey, D.S.; Dickson, D.; Kim, D.
1986-01-01
We have developed a detailed configuration-accounting kinetic model for calculating time-dependent ionization-balance and ion-level populations in non-local thermal-equilibrium (non-LTE) plasmas. We use these population estimates in computing spectral line intensities, line ratios, and synthetic spectra, and in fitting these calculated values to experimental measurements. The model is also used to design laboratory x-ray laser experiments. For this purpose, it is self-consistently coupled to the hydrodynamics code LASNEX. 20 refs., 14 figs
Time-dependent approach to electron scattering and ionization in the s-wave model
International Nuclear Information System (INIS)
Ihra, W.; Draeger, M.; Handke, G.; Friedrich, H.
1995-01-01
The time-dependent Schroedinger equation is integrated for continuum states of two-electron atoms in the framework of the s-wave model, in which both electrons are restricted to having vanishing individual orbital angular momenta. The method is suitable for studying the time evolution of correlations in the two-electron wave functions and yields probabilities for elastic and inelastic electron scattering and for electron-impact ionization. The spin-averaged probabilities for electron-impact ionization of hydrogen in the s-wave model reproduce the shape of the experimentally observed integrated ionization cross section remarkably well for energies near and above the maximum
Random walk in degree space and the time-dependent Watts-Strogatz model
Grande, H. L. Casa; Cotacallapa, M.; Hase, M. O.
2016-01-01
In this work, we propose a scheme that provides an analytical estimate for the time-dependent degree distribution of some networks. This scheme maps the problem into a random walk in degree space, and then we choose the paths that are responsible for the dominant contributions. The method is illustrated on the dynamical versions of the Erd\\"os-R\\'enyi and Watts-Strogatz graphs, which were introduced as static models in the original formulation. We have succeeded in obtaining an analytical for...
Comparison of the surface friction model with the time-dependent Hartree-Fock method
International Nuclear Information System (INIS)
Froebrich, P.
1984-01-01
A comparison is made between the classical phenomenological surface friction model and a time-dependent Hartree-Fock study by Dhar for the system 208 Pb+ 74 Ge at E/sub lab/(Pb) = 1600 MeV. The general trends for energy loss, mean values for charge and mass, interaction times and energy-angle correlations turn out to be fairly similar in both methods. However, contrary to Dhar, the events close to capture are interpreted as normal deep-inelastic, i.e., not as fast fission processes
Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor under IFE Conditions
International Nuclear Information System (INIS)
Qiyang Hu; Shahram Sharafat; Nasr Ghoniem
2006-01-01
The High Average Power Laser (HAPL) program is a coordinated effort to develop Laser Inertial Fusion Energy. The implosion of the D-T target produces a spectrum of neutrons, X-rays, and charged particles, which arrive at the first wall (FW) at different times within about 2.5 μs at a frequency of 5 to 10 Hz. Helium is one of several high-energy charged particle constituents impinging on the candidate tungsten armored low activation ferritic steel First Wall. The spread of the implanted debris and burn helium energies results in a unique space-time dependent implantation profile that spans about 10 μm in tungsten. Co-implantation of X-rays and other ions results in spatially dependent damage profiles and rapid space-time dependent temperature spikes and gradients. The rate of helium transport and helium bubble formation will vary significantly throughout the implanted region. Furthermore, helium will also be transported via the migration of helium bubbles and non-equilibrium helium-vacancy clusters. The HEROS code was developed at UCLA to model the spatial and time-dependent helium bubble nucleation, growth, coalescence, and migration under transient damage rates and transient temperature gradients. The HEROS code is based on kinetic rate theory, which includes clustering of helium and vacancies, helium mobility, helium-vacancy cluster stability, cavity nucleation and growth and other microstructural features such as interstitial loop evolution, grain boundaries, and precipitates. The HEROS code is based on space-time discretization of reaction-diffusion type equations to account for migration of mobile species between neighboring bins as single atoms, clusters, or bubbles. HAPL chamber FW implantation conditions are used to model helium bubble evolution in the implanted tungsten. Helium recycling rate predictions are compared with experimental results of helium ion implantation experiments. (author)
Power Supply Interruption Costs: Models and Methods Incorporating Time Dependent Patterns
International Nuclear Information System (INIS)
Kjoelle, G.H.
1996-12-01
This doctoral thesis develops models and methods for estimation of annual interruption costs for delivery points, emphasizing the handling of time dependent patterns and uncertainties in the variables determining the annual costs. It presents an analytical method for calculation of annual expected interruption costs for delivery points in radial systems, based on a radial reliability model, with time dependent variables. And a similar method for meshed systems, based on a list of outage events, assuming that these events are found in advance from load flow and contingency analyses. A Monte Carlo simulation model is given which handles both time variations and stochastic variations in the input variables and is based on the same list of outage events. This general procedure for radial and meshed systems provides expectation values and probability distributions for interruption costs from delivery points. There is also a procedure for handling uncertainties in input variables by a fuzzy description, giving annual interruption costs as a fuzzy membership function. The methods are developed for practical applications in radial and meshed systems, based on available data from failure statistics, load registrations and customer surveys. Traditional reliability indices such as annual interruption time, power- and energy not supplied, are calculated as by-products. The methods are presented as algorithms and/or procedures which are available as prototypes. 97 refs., 114 figs., 62 tabs
Power Supply Interruption Costs: Models and Methods Incorporating Time Dependent Patterns
Energy Technology Data Exchange (ETDEWEB)
Kjoelle, G.H.
1996-12-01
This doctoral thesis develops models and methods for estimation of annual interruption costs for delivery points, emphasizing the handling of time dependent patterns and uncertainties in the variables determining the annual costs. It presents an analytical method for calculation of annual expected interruption costs for delivery points in radial systems, based on a radial reliability model, with time dependent variables. And a similar method for meshed systems, based on a list of outage events, assuming that these events are found in advance from load flow and contingency analyses. A Monte Carlo simulation model is given which handles both time variations and stochastic variations in the input variables and is based on the same list of outage events. This general procedure for radial and meshed systems provides expectation values and probability distributions for interruption costs from delivery points. There is also a procedure for handling uncertainties in input variables by a fuzzy description, giving annual interruption costs as a fuzzy membership function. The methods are developed for practical applications in radial and meshed systems, based on available data from failure statistics, load registrations and customer surveys. Traditional reliability indices such as annual interruption time, power- and energy not supplied, are calculated as by-products. The methods are presented as algorithms and/or procedures which are available as prototypes. 97 refs., 114 figs., 62 tabs.
Directory of Open Access Journals (Sweden)
L. Toledo Sesma
2016-01-01
Full Text Available We construct an effective four-dimensional model by compactifying a ten-dimensional theory of gravity coupled with a real scalar dilaton field on a time-dependent torus. This approach is applied to anisotropic cosmological Bianchi type I model for which we study the classical coupling of the anisotropic scale factors with the two real scalar moduli produced by the compactification process. Under this approach, we present an isotropization mechanism for the Bianchi I cosmological model through the analysis of the ratio between the anisotropic parameters and the volume of the Universe which in general keeps constant or runs into zero for late times. We also find that the presence of extra dimensions in this model can accelerate the isotropization process depending on the momenta moduli values. Finally, we present some solutions to the corresponding Wheeler-DeWitt (WDW equation in the context of standard quantum cosmology.
Reyes, Jonathan; Shadwick, B. A.
2016-10-01
Modeling the evolution of a short, intense laser pulse propagating through an underdense plasma is of particular interest in the physics of laser-plasma interactions. Numerical models are typically created by first discretizing the equations of motion and then imposing boundary conditions. Using the variational principle of Chen and Sudan, we spatially discretize the Lagrangian density to obtain discrete equations of motion and a discrete energy conservation law which is exactly satisfied regardless of the spatial grid resolution. Modifying the derived equations of motion (e.g., enforcing boundary conditions) generally ruins energy conservation. However, time-dependent terms can be added to the Lagrangian which force the equations of motion to have the desired boundary conditions. Although some foresight is needed to choose these time-dependent terms, this approach provides a mechanism for energy to exit the closed system while allowing the conservation law to account for the loss. An appropriate time discretization scheme is selected based on stability analysis and resolution requirements. We present results using this variational approach in a co-moving coordinate system and compare such results to those using traditional second-order methods. This work was supported by the U. S. Department of Energy under Contract No. DE-SC0008382 and by the National Science Foundation under Contract No. PHY- 1104683.
A simplified time-dependent recovery model as applied to RCP seal LOCAs
International Nuclear Information System (INIS)
Kohut, P.; Bozoki, G.; Fitzpatrick, R.
1991-01-01
In Westinghouse-designed reactors, the reactor coolant pump (RCP) seals constantly require a modest amount of cooling. This cooling function depends on the service water (SW) system. Upon the loss of the cooling function due to the unavailability of the SW, component cooling water system or electrical power (station blackout), the RCP seals may degrade, resulting in a loss-of-coolant accident (LOCA). Recent studies indicate that the frequency of the loss of SW initiating events is higher than previously thought. This change significantly increases the core damage frequency contribution from RCP seal failure. The most critical/dominant element in the loss of SW events was found to be the SW-induced RCP seal failure. For these potential accident scenarios, there are large uncertainties regarding the actual frequency of RCP seal LOCA, the resulting leakage rate, and time-dependent behavior. The roles of various recovery options based on the time evolution of the seal LOCA have been identified and taken into account in recent NUREG-1150 probabilistic risk assessment PRA analyses. In this paper, a consistent time-dependent recovery model is described that takes into account the effects of various recovery actions based on explicit considerations given to a spectrum of time- and flow-rate dependencies. The model represents a simplified approach but is especially useful when extensive seal leak rate and core uncovery information is unavailable
A GIS-based time-dependent seismic source modeling of Northern Iran
Hashemi, Mahdi; Alesheikh, Ali Asghar; Zolfaghari, Mohammad Reza
2017-01-01
The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran.
A time-dependent neutron transport model and its coupling to thermal-hydraulics
International Nuclear Information System (INIS)
Pautz, A.
2001-01-01
A new neutron transport code for time-dependent analyses of nuclear systems has been developed. The code system is based on the well-known Discrete Ordinates code DORT, which solves the steady-state neutron/photon transport equation in two dimensions for an arbitrary number of energy groups and the most common regular geometries. For the implementation of time-dependence a fully implicit first-order scheme was employed to minimize errors due to temporal discretization. This requires various modifications to the transport equation as well as the extensive use of elaborated acceleration mechanisms. The convergence criteria for fluxes, fission rates etc. had to be strongly tightened to ensure the reliability of results. To perform coupled analyses, an interface to the GRS system code ATHLET has been developed. The nodal power densities from the neutron transport code are passed to ATHLET to calculate thermal-hydraulic system parameters, e.g. fuel and coolant temperatures. These are in turn used to generate appropriate nuclear cross sections by interpolation of pre-calculated data sets for each time step. Finally, to demonstrate the transient capabilities of the coupled code system, the research reactor FRM-II has been analysed. Several design basis accidents were modelled, like the loss of off site power, loss of secondary heat sink and unintended control rod withdrawal. (author)
Exactly solvable quantum state reduction models with time-dependent coupling
International Nuclear Information System (INIS)
Brody, Dorje C; Constantinou, Irene C; Dear, James D C; Hughston, Lane P
2006-01-01
A closed-form solution to the energy-based stochastic Schroedinger equation with a time-dependent coupling is obtained. The solution is algebraic in character, and is expressed directly in terms of independent random data. The data consist of (i) a random variable H which has the distribution P(H=E i ) = π i , where π i is the transition probability vertical bar (ψ 0 vertical bar Φ i ) vertical bar 2 from the initial state vertical bar ψ 0 ) to the Lueders state vertical bar Φ i ) with energy E i , and (ii) an independent P-Brownian motion, where P is the physical probability measure associated with the dynamics of the reduction process. When the coupling is time independent, it is known that state reduction occurs asymptotically-that is to say, over an infinite time horizon. In the case of a time-dependent coupling, we show that if the magnitude of the coupling decreases sufficiently rapidly, then the energy variance will be reduced under the dynamics, but the state need not reach an energy eigenstate. This situation corresponds to the case of a 'partial' or 'incomplete' measurement of the energy. We also construct an example of a model where the opposite situation prevails, in which complete state reduction is achieved after the passage of a finite period of time
Directory of Open Access Journals (Sweden)
Akanda Md. Abdus Salam
2017-03-01
Full Text Available Individual heterogeneity in capture probabilities and time dependence are fundamentally important for estimating the closed animal population parameters in capture-recapture studies. A generalized estimating equations (GEE approach accounts for linear correlation among capture-recapture occasions, and individual heterogeneity in capture probabilities in a closed population capture-recapture individual heterogeneity and time variation model. The estimated capture probabilities are used to estimate animal population parameters. Two real data sets are used for illustrative purposes. A simulation study is carried out to assess the performance of the GEE estimator. A Quasi-Likelihood Information Criterion (QIC is applied for the selection of the best fitting model. This approach performs well when the estimated population parameters depend on the individual heterogeneity and the nature of linear correlation among capture-recapture occasions.
International Nuclear Information System (INIS)
Christian-Frear, T.; Freeze, G.
1997-01-01
Underground excavations produce damaged zones surrounding the excavations which have disturbed hydrologic and geomechanical properties. Prediction of fluid flow in these zones must consider both the mechanical and fluid flow processes. Presented here is a methodology which utilizes a mechanical model to predict damage and disturbed rock zone (DRZ) development around the excavation and then uses the predictions to develop time-dependent DRZ porosity relationships. These relationships are then used to adjust the porosity of the DRZ in the fluid flow model based upon the time and distance from the edge of the excavation. The application of this methodology is presented using a site-specific example from the Waste Isolation Pilot Plant, a US Department of Energy facility in bedded salts being evaluated for demonstration of the safe underground disposal of transuranic waste from US defense-related activities
Time-Dependent Diffusion MRI in Cancer: Tissue Modeling and Applications
Directory of Open Access Journals (Sweden)
Olivier Reynaud
2017-11-01
Full Text Available In diffusion weighted imaging (DWI, the apparent diffusion coefficient (ADC has been recognized as a useful and sensitive surrogate for cell density, paving the way for non-invasive tumor staging, and characterization of treatment efficacy in cancer. However, microstructural parameters, such as cell size, density and/or compartmental diffusivities affect diffusion in various fashions, making of conventional DWI a sensitive but non-specific probe into changes happening at cellular level. Alternatively, tissue complexity can be probed and quantified using the time dependence of diffusion metrics, sometimes also referred to as temporal diffusion spectroscopy when only using oscillating diffusion gradients. Time-dependent diffusion (TDD is emerging as a strong candidate for specific and non-invasive tumor characterization. Despite the lack of a general analytical solution for all diffusion times/frequencies, TDD can be probed in various regimes where systems simplify in order to extract relevant information about tissue microstructure. The fundamentals of TDD are first reviewed (a in the short time regime, disentangling structural and diffusive tissue properties, and (b near the tortuosity limit, assuming weakly heterogeneous media near infinitely long diffusion times. Focusing on cell bodies (as opposed to neuronal tracts, a simple but realistic model for intracellular diffusion can offer precious insight on diffusion inside biological systems, at all times. Based on this approach, the main three geometrical models implemented so far (IMPULSED, POMACE, VERDICT are reviewed. Their suitability to quantify cell size, intra- and extracellular spaces (ICS and ECS and diffusivities are assessed. The proper modeling of tissue membrane permeability—hardly a newcomer in the field, but lacking applications—and its impact on microstructural estimates are also considered. After discussing general issues with tissue modeling and microstructural parameter
Time-dependent diffusion MRI in cancer: tissue modeling and applications
Reynaud, Olivier
2017-11-01
In diffusion weighted imaging (DWI), the apparent diffusion coefficient has been recognized as a useful and sensitive surrogate for cell density, paving the way for non-invasive tumor staging, and characterization of treatment efficacy in cancer. However, microstructural parameters, such as cell size, density and/or compartmental diffusivities affect diffusion in various fashions, making of conventional DWI a sensitive but non-specific probe into changes happening at cellular level. Alternatively, tissue complexity can be probed and quantified using the time dependence of diffusion metrics, sometimes also referred to as temporal diffusion spectroscopy when only using oscillating diffusion gradients. Time-dependent diffusion (TDD) is emerging as a strong candidate for specific and non-invasive tumor characterization. Despite the lack of a general analytical solution for all diffusion times / frequencies, TDD can be probed in various regimes where systems simplify in order to extract relevant information about tissue microstructure. The fundamentals of TDD are first reviewed (a) in the short time regime, disentangling structural and diffusive tissue properties, and (b) near the tortuosity limit, assuming weakly heterogeneous media near infinitely long diffusion times. Focusing on cell bodies (as opposed to neuronal tracts), a simple but realistic model for intracellular diffusion can offer precious insight on diffusion inside biological systems, at all times. Based on this approach, the main three geometrical models implemented so far (IMPULSED, POMACE, VERDICT) are reviewed. Their suitability to quantify cell size, intra- and extracellular spaces (ICS and ECS) and diffusivities are assessed. The proper modeling of tissue membrane permeability – hardly a newcomer in the field, but lacking applications - and its impact on microstructural estimates are also considered. After discussing general issues with tissue modeling and microstructural parameter estimation (i
Treatment-time-dependence models of early and delayed radiation injury in rat small intestine
International Nuclear Information System (INIS)
Denham, James W.; Hauer-Jensen, Martin; Kron, Tomas; Langberg, Carl W.
2000-01-01
Background: The present study modeled data from a large series of experiments originally designed to investigate the influence of time, dose, and fractionation on early and late pathologic endpoints in rat small intestine after localized irradiation. The objective was to obtain satisfactory descriptions of the regenerative response to injury together with the possible relationships between early and late endpoints. Methods: Two- and 26-week pathologic radiation injury data in groups of Sprague-Dawley rats irradiated with 27 different fractionation schedules were modeled using the incomplete repair (IR) version of the linear-quadratic model with or without various time correction models. The following time correction models were tested: (1) No time correction; (2) A simple exponential (SE) regenerative response beginning at an arbitrary time after starting treatment; and (3) A bi-exponential response with its commencement linked to accumulated cellular depletion and fraction size (the 'intelligent response model' [INTR]). Goodness of fit of the various models was assessed by correlating the predicted biological effective dose for each dose group with the observed radiation injury score. Results: (1) The incomplete repair model without time correction did not provide a satisfactory description of either the 2- or 26-week data. (2) The models using SE time correction performed better, providing modest descriptions of the data. (3) The INTR model provided reasonable descriptions of both the 2- and 26-week data, confirming a treatment time dependence of both early and late pathological endpoints. (4) The most satisfactory descriptions of the data by the INTR model were obtained when the regenerative response was assumed to cease 2 weeks after irradiation rather than at the end of irradiation. A fraction-size-dependent delay of the regenerative response was also suggested in the best fitting models. (5) Late endpoints were associated with low-fractionation sensitivity
Resonance phenomena in a time-dependent, three-dimensional model of an idealized eddy
Rypina, I. I.; Pratt, L. J.; Wang, P.; Äe; -zgökmen, T. M.; Mezic, I.
2015-08-01
We analyze the geometry of Lagrangian motion and material barriers in a time-dependent, three-dimensional, Ekman-driven, rotating cylinder flow, which serves as an idealization for an isolated oceanic eddy and other overturning cells with cylindrical geometry in the ocean and atmosphere. The flow is forced at the top through an oscillating upper lid, and the response depends on the frequency and amplitude of lid oscillations. In particular, the Lagrangian geometry changes near the resonant tori of the unforced flow, whose frequencies are rationally related to the forcing frequencies. Multi-scale analytical expansions are used to simplify the flow in the vicinity of resonant trajectories and to investigate the resonant flow geometries. The resonance condition and scaling can be motivated by simple physical argument. The theoretically predicted flow geometries near resonant trajectories have then been confirmed through numerical simulations in a phenomenological model and in a full solution of the Navier-Stokes equations.
Time-dependent shell-model theory of dissipative heavy-ion collisions
International Nuclear Information System (INIS)
Ayik, S.; Noerenberg, W.
1982-01-01
A transport theory is formulated within a time-dependent shell-model approach. Time averaging of the equations for macroscopic quantities lead to irreversibility and justifies weak-coupling limit and Markov approximation for the (energy-conserving) one- and two-body collision terms. Two coupled equations for the occupation probabilities of dynamical single-particle states and for the collective variable are derived and explicit formulas for transition rates, dynamical forces, mass parameters and friction coefficients are given. The applicability of the formulation in terms of characteristic quantities of nuclear systems is considered in detail and some peculiarities due to memory effects in the initial equilibration process of heavy-ion collisions are discussed. (orig.)
Dynamical response of the Ising model to the time dependent magnetic field with white noise
Akıncı, Ümit
2018-03-01
The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.
Time-dependent 2-D modeling of edge plasma transport with high intermittency due to blobs
International Nuclear Information System (INIS)
Pigarov, A. Yu.; Krasheninnikov, S. I.; Rognlien, T. D.
2012-01-01
The results on time-dependent 2-D fluid modeling of edge plasmas with non-diffusive intermittent transport across the magnetic field (termed cross-field) based on the novel macro-blob approach are presented. The capability of this approach to simulate the long temporal evolution (∼0.1 s) of the background plasma and simultaneously the fast spatiotemporal dynamics of blobs (∼10 −4 s) is demonstrated. An analysis of a periodic sequence of many macro-blobs (PSMB) is given showing that the resulting plasma attains a dynamic equilibrium. Plasma properties in the dynamic equilibrium are discussed. In PSMB modeling, the effect of macro-blob generation frequency on edge plasma parameters is studied. Comparison between PSMB modeling and experimental profile data is given. The calculations are performed for the same plasma discharge using two different models for anomalous cross-field transport: time-average convection and PSMB. Parametric analysis of edge plasma variation with transport coefficients in these models is presented. The capability of the models to accurately simulate enhanced transport due to blobs is compared. Impurity dynamics in edge plasma with macro-blobs is also studied showing strong impact of macro-blob on profiles of impurity charge states caused by enhanced outward transport of high-charge states and simultaneous inward transport of low-charge states towards the core. Macro-blobs cause enhancement of sputtering rates, increase radiation and impurity concentration in plasma, and change erosion/deposition patterns.
Moloto, K. D.; Engelbrecht, N. E.; Burger, R. A.
2018-06-01
A simplified ab initio approach is followed to model cosmic-ray proton modulation, using a steady-state three-dimensional stochastic solver of the Parker transport equation that simulates some effects of time dependence. Standard diffusion coefficients based on Quasilinear Theory and Nonlinear Guiding Center Theory are employed. The spatial and temporal dependences of the various turbulence quantities required as inputs for the diffusion, as well as the turbulence-reduced drift coefficients, follow from parametric fits to results from a turbulence transport model as well as from spacecraft observations of these turbulence quantities. Effective values are used for the solar wind speed, magnetic field magnitude, and tilt angle in the modulation model to simulate temporal effects due to changes in the large-scale heliospheric plasma. The unusually high cosmic-ray intensities observed during the 2009 solar minimum follow naturally from the current model for most of the energies considered. This demonstrates that changes in turbulence contribute significantly to the high intensities during that solar minimum. We also discuss and illustrate how this model can be used to predict future cosmic-ray intensities, and comment on the reliability of such predictions.
Zhang, Wei; Wang, Jun
2017-09-01
In attempt to reproduce price dynamics of financial markets, a stochastic agent-based financial price model is proposed and investigated by stochastic exclusion process. The exclusion process, one of interacting particle systems, is usually thought of as modeling particle motion (with the conserved number of particles) in a continuous time Markov process. In this work, the process is utilized to imitate the trading interactions among the investing agents, in order to explain some stylized facts found in financial time series dynamics. To better understand the correlation behaviors of the proposed model, a new time-dependent intrinsic detrended cross-correlation (TDI-DCC) is introduced and performed, also, the autocorrelation analyses are applied in the empirical research. Furthermore, to verify the rationality of the financial price model, the actual return series are also considered to be comparatively studied with the simulation ones. The comparison results of return behaviors reveal that this financial price dynamics model can reproduce some correlation features of actual stock markets.
Alnaggar, Mohammed; Di Luzio, Giovanni; Cusatis, Gianluca
2017-04-28
Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.
3D static and time-dependent modelling of a dc transferred arc twin torch system
International Nuclear Information System (INIS)
Colombo, V; Ghedini, E; Boselli, M; Sanibondi, P; Concetti, A
2011-01-01
The transferred arc plasma torch device consists of two electrodes generating a plasma arc sustained by means of an electric current flowing through the body of the discharge. Modelling works investigating transferred electric arc discharges generated between two suspended metallic electrodes, in the so-called twin torch configuration, are scarce. The discharge generated by this particular plasma source configuration is characterized by a complex shape and fluid dynamics and needs a 3D description in order to be realistically predicted. The extended discharge length that goes from the tungsten pencil cathode to the flat copper anode without any particular confinement wall and the fluid dynamics and magnetic forces acting on the arc may induce an unsteady behaviour. In order to capture the dynamic behaviour of a twin torch discharge, a 3D time-dependent plasma arc model has been developed using a customized commercial code FLUENT form in both local thermodynamic equilibrium (LTE) and non-LTE. A two temperature (2T) model has been developed taking into account only the thermal non-equilibrium effects in argon plasma. The main differences between LTE and 2T models' results concern the increased extension of the horizontal section of the discharge and the predicted reduced (of about 60-80 V) voltage drop between the electrodes when using a 2T model.
Energy Technology Data Exchange (ETDEWEB)
Al Janaideh, Mohammad, E-mail: aljanaideh@gmail.com [Department of Mechatronics Engineering, The University of Jordan, 11942 Amman (Jordan)
2013-03-15
We present a time-dependent stop operator-based Prandtl–Ishlinskii model to characterize singular hysteresis loops in a piezoceramic actuator. The model is constructed based on the time-dependent threshold. The inverse time-dependent stop operator-based Prandtl–Ishlinskii model is obtained analytically and it can be applied as a feedforward compensator to compensate for singular hysteresis loops in a class of smart-material-based actuators. The objective of this study is to present an invertible Prandtl–Ishlinskii model that can be applied as a feedforward compensator to compensate for singular hysteresis loops without inserting a feedback control system.
International Nuclear Information System (INIS)
Al Janaideh, Mohammad
2013-01-01
We present a time-dependent stop operator-based Prandtl–Ishlinskii model to characterize singular hysteresis loops in a piezoceramic actuator. The model is constructed based on the time-dependent threshold. The inverse time-dependent stop operator-based Prandtl–Ishlinskii model is obtained analytically and it can be applied as a feedforward compensator to compensate for singular hysteresis loops in a class of smart-material-based actuators. The objective of this study is to present an invertible Prandtl–Ishlinskii model that can be applied as a feedforward compensator to compensate for singular hysteresis loops without inserting a feedback control system
A model for the time-dependent thermal distribution within an iceball surrounding a cryoprobe
International Nuclear Information System (INIS)
Rewcastle, J.C.; Sandison, G.A.; Hahn, L.J.; Saliken, J.C.; McKinnon, J.G.; Donnelly, B.J.
1998-01-01
The optimal cooling parameters to maximize cell necrosis in different types of tissue have yet to be determined. However, a critical isotherm is commonly adopted by cryosurgeons as a boundary of lethality for tissue. Locating this isotherm within an iceball is problematic due to the limitations of MRI, ultrasound and CT imaging modalities. This paper describes a time-dependent two-dimensional axisymmetric model of iceball formation about a single cryoprobe and extensively compares it with experimental data. Thermal histories for several points around a CRYOprobe are predicted to high accuracy (5 deg. C maximum discrepancy). A realistic three-dimensional probe geometry is specified and cryoprobe temperature may be arbitrarily set as a function of time in the model. Three-dimensional temperature distributions within the iceball, predicted by the model at different times, are presented. Isotherm locations, as calculated with the infinite cylinder approximation, are compared with those of the model in the most appropriate region of the iceball. Infinite cylinder approximations are shown to be inaccurate when applied to this commercial probe. Adopting the infinite cylinder approximation to locate the critical isotherm is shown to lead the user to an overestimate of the volume of target tissue enclosed by this isotherm which may lead to incomplete tumour ablation. (author)
A time-dependent model to determine the thermal conductivity of a nanofluid
Energy Technology Data Exchange (ETDEWEB)
Myers, T. G., E-mail: tmyers@crm.cat; MacDevette, M. M., E-mail: mmacdevette@crm.cat; Ribera, H. [Centre de Recerca Matematica (Spain)
2013-07-15
In this paper, we analyse the time-dependent heat equations over a finite domain to determine expressions for the thermal diffusivity and conductivity of a nanofluid (where a nanofluid is a fluid containing nanoparticles with average size below 100 nm). Due to the complexity of the standard mathematical analysis of this problem, we employ a well-known approximate solution technique known as the heat balance integral method. This allows us to derive simple analytical expressions for the thermal properties, which appear to depend primarily on the volume fraction and liquid properties. The model is shown to compare well with experimental data taken from the literature even up to relatively high concentrations and predicts significantly higher values than the Maxwell model for volume fractions approximately >1 %. The results suggest that the difficulty in reproducing the high values of conductivity observed experimentally may stem from the use of a static heat flow model applied over an infinite domain rather than applying a dynamic model over a finite domain.
Time dependent approach of TeV blazars based on a model of inhomogeneous stratified jet
International Nuclear Information System (INIS)
Boutelier, T.
2009-05-01
The study of the emission and variability mechanisms of TeV blazars has been the subject of intensive research for years. The homogeneous one-zone model commonly used is puzzling since it yields very high Lorentz factor, in contradiction with other observational evidences. In this work, I describe a new time dependent multi-zone approach, in the framework of the two-flow model. I compute the emission of a full jet, where relativistic electron-positron pairs distributed in pileup propagate. The evolution and the emission of the plasma is computed taking into account a turbulent heating term, some radiative cooling, and a pair production term due to photo-annihilation process. Applied to PKS 2155-304, the model allows the reproduction of the full spectra, as well as the simultaneous multi wavelength variability, with a relatively small Lorentz factor. The variability is explained by the instability of the pair creation process. Nonetheless, the value is still high to agree with other observational evidences in radio. Hence, I show in the last part of this work how to conciliate high Lorentz factor with the absence of apparent superluminal movement in radio, by taking into account the effect of the opening angle on the appearance of relativistic jets. (author)
Jackson, B. V.; Yu, H. S.; Hick, P. P.; Buffington, A.; Odstrcil, D.; Kim, T. K.; Pogorelov, N. V.; Tokumaru, M.; Bisi, M. M.; Kim, J.; Yun, J.
2017-12-01
The University of California, San Diego has developed an iterative remote-sensing time-dependent three-dimensional (3-D) reconstruction technique which provides volumetric maps of density, velocity, and magnetic field. We have applied this technique in near real time for over 15 years with a kinematic model approximation to fit data from ground-based interplanetary scintillation (IPS) observations. Our modeling concept extends volumetric data from an inner boundary placed above the Alfvén surface out to the inner heliosphere. We now use this technique to drive 3-D MHD models at their inner boundary and generate output 3-D data files that are fit to remotely-sensed observations (in this case IPS observations), and iterated. These analyses are also iteratively fit to in-situ spacecraft measurements near Earth. To facilitate this process, we have developed a traceback from input 3-D MHD volumes to yield an updated boundary in density, temperature, and velocity, which also includes magnetic-field components. Here we will show examples of this analysis using the ENLIL 3D-MHD and the University of Alabama Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) heliospheric codes. These examples help refine poorly-known 3-D MHD variables (i.e., density, temperature), and parameters (gamma) by fitting heliospheric remotely-sensed data between the region near the solar surface and in-situ measurements near Earth.
Considering Time-Dependency of Social Vulnerability in Crisis Modeling and Management
Aubrecht, C.; Steinnocher, K.; Freire, S.; Loibl, W.; Peters-Anders, J.; Ungar, J.
2012-04-01
and emergency management. The vulnerability of each relevant element at risk, including human beings and society in general and its time-dependent variation is characterized both by its pre-event status and by its possible evolution during a crisis. Particularly in metropolitan areas, the spatial distribution of population is highly time-dependent due to human activities and mobility. Identifying distinct day-/nighttime population distribution characteristics is a major improvement compared to standard residence-based models, but does however only display part of reality. New technologies and data processing capabilities allow moving into the field of real-time representation of human movement. The focus of this contribution will be on illustrating, through project examples and by putting it in an emergency and crisis management context, two main categories, (1) the mapping of cell phone user activity, and (2) the use of volunteered geographic information (VGI).
Distributed Cerebellar Motor Learning; a Spike-Timing-Dependent Plasticity Model
Directory of Open Access Journals (Sweden)
Niceto Rafael Luque
2016-03-01
Full Text Available Deep cerebellar nuclei neurons receive both inhibitory (GABAergic synaptic currents from Purkinje cells (within the cerebellar cortex and excitatory (glutamatergic synaptic currents from mossy fibres. Those two deep cerebellar nucleus inputs are thought to be also adaptive, embedding interesting properties in the framework of accurate movements. We show that distributed spike-timing-dependent plasticity mechanisms (STDP located at different cerebellar sites (parallel fibres to Purkinje cells, mossy fibres to deep cerebellar nucleus cells, and Purkinje cells to deep cerebellar nucleus cells in close-loop simulations provide an explanation for the complex learning properties of the cerebellum in motor learning. Concretely, we propose a new mechanistic cerebellar spiking model. In this new model, deep cerebellar nuclei embed a dual functionality: deep cerebellar nuclei acting as a gain adaptation mechanism and as a facilitator for the slow memory consolidation at mossy fibres to deep cerebellar nucleus synapses. Equipping the cerebellum with excitatory (e-STDP and inhibitory (i-STDP mechanisms at deep cerebellar nuclei afferents allows the accommodation of synaptic memories that were formed at parallel fibres to Purkinje cells synapses and then transferred to mossy fibres to deep cerebellar nucleus synapses. These adaptive mechanisms also contribute to modulate the deep-cerebellar-nucleus-output firing rate (output gain modulation towards optimising its working range.
Directory of Open Access Journals (Sweden)
Daniel Mellem
Full Text Available Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes.
Effects of a moving X-line in a time-dependent reconnection model
Directory of Open Access Journals (Sweden)
S. A. Kiehas
2007-02-01
Full Text Available In the frame of magnetized plasmas, reconnection appears as an essential process for the description of plasma acceleration and changing magnetic field topology. Under the variety of reconnection regions in our solar system, we focus our research onto the Earth's magnetotail. Under certain conditions a Near Earth Neutral Line (NENL is free to evolve in the current sheet of the magnetotail. Reconnection in this region leads to the formation of Earth- and tailward propagating plasma bulges, which can be detected by the Cluster or Geotail spacecraft. Observations give rise to the assumption that the evolved reconnection line does not provide a steady state behavior, but is propagating towards the tail (e.g., Baker et al., 2002. Based on a time-dependent variant of the Petschek model of magnetic reconnection, we present a method that includes an X-line motion and discuss the effects of such a motion. We focus our main interest on the shock structure and the magnetic field behavior, both for the switch-on and the switch-off phase.
Energy Technology Data Exchange (ETDEWEB)
Pleasant, J C; McDowell-Boyer, L M; Killough, G G
1982-06-01
RAGBEEF is a FORTRAN IV program that calculates radionuclide concentrations in beef as a result of ingestion of contaminated feeds, pasture, and pasture soil by beef cattle. The model implemented by RAGBEEF is dynamic in nature, allowing the user to consider age- and season-dependent aspects of beef cattle management in estimating concentrations in beef. It serves as an auxiliary code to RAGTIME, previously documented by the authors, which calculates radionuclide concentrations in agricultural crops in a dynamic manner, but evaluates concentrations in beef for steady-state conditions only. The time-dependent concentrations in feeds, pasture, and pasture soil generated by RAGTIME are used as input to the RAGBEEF code. RAGBEEF, as presently implemented, calculates radionuclide concentrations in the muscle of age-based cohorts in a beef cattle herd. Concentrations in the milk of lactating cows are also calculated, but are assumed age-dependent as in RAGTIME. Radionuclide concentrations in beef and milk are described in RAGBEEF by a system of ordinary linear differential equations in which the transfer rate of radioactivity between compartments is proportional to the inventory of radioactivity in the source compartment. This system is solved by use of the GEAR package for solution of systems of ordinary differential equations. The accuracy of this solution is monitored at various check points by comparison with explicit solutions of Bateman-type equations. This report describes the age- and season-dependent considerations making up the RAGBEEF model, as well as presenting the equations which describe the model and a documentation of the associated computer code. Listings of the RAGBEEF and updated RAGTIME codes are provided in appendices, as are the results of a sample run of RAGBEEF and a description of recent modifications to RAGTIME.
International Nuclear Information System (INIS)
Pleasant, J.C.; McDowell-Boyer, L.M; Killough, G.G.
1982-06-01
RAGBEEF is a FORTRAN IV program that calculates radionuclide concentrations in beef as a result of ingestion of contaminated feeds, pasture, and pasture soil by beef cattle. The model implemented by RAGBEEF is dynamic in nature, allowing the user to consider age- and season-dependent aspects of beef cattle management in estimating concentrations in beef. It serves as an auxiliary code to RAGTIME, previously documented by the authors, which calculates radionuclide concentrations in agricultural crops in a dynamic manner, but evaluates concentrations in beef for steady-state conditions only. The time-dependent concentrations in feeds, pasture, and pasture soil generated by RAGTIME are used as input to the RAGBEEF code. RAGBEEF, as presently implemented, calculates radionuclide concentrations in the muscle of age-based cohorts in a beef cattle herd. Concentrations in the milk of lactating cows are also calculated, but are assumed age-dependent as in RAGTIME. Radionuclide concentrations in beef and milk are described in RAGBEEF by a system of ordinary linear differential equations in which the transfer rate of radioactivity between compartments is proportional to the inventory of radioactivity in the source compartment. This system is solved by use of the GEAR package for solution of systems of ordinary differential equations. The accuracy of this solution is monitored at various check points by comparison with explicit solutions of Bateman-type equations. This report describes the age- and season-dependent considerations making up the RAGBEEF model, as well as presenting the equations which describe the model and a documentation of the associated computer code. Listings of the RAGBEEF and updated RAGTIME codes are provided in appendices, as are the results of a sample run of RAGBEEF and a description of recent modifications to RAGTIME
3D time-dependent flow computations using a molecular stress function model with constraint release
DEFF Research Database (Denmark)
Rasmussen, Henrik Koblitz
2002-01-01
The numerical simulation of time dependent viscoelastic flow (in three dimensions) is of interest in connection with a variety of polymer processing operations. The application of the numerical simulation techniques is in the analysis and design of polymer processing problems. This is operations,......, such as thermoforming, blow moulding, compression moulding, gas-assisted injection moulding, simultaneous multi-component injection moulding....
Time-dependent theoretical model of the polar wind: Preliminary results
International Nuclear Information System (INIS)
Gombosi, T.I.; Cravens, T.E.; Nagy, A.F.
1985-01-01
The coupled time dependent continuity, momentum and energy equations of a two ion (O + and H + ) quasineutral plasma were solved in order to extend our understanding of polar wind behavior. This numerical code allows studies of the time dependent behavior of polar wind-type flows into and out of the ionosphere. Initial studies indicate that the typical time constants for electron and ion temperature changes are of the order of minutes and tens of minutes, respectively. The response time of the minor high altitude ion O + is less than an hour, whereas that of the major ion, H + , is many hours. The initial test runs also demonstrate the fact that temporary supersonic flows of both O + and H + are possible, especially in the presence of significant ion heating
Charged particle motion in a time-dependent flux-driven ring: an exactly solvable model
International Nuclear Information System (INIS)
Luan, P-G; Tang, C-S
2007-01-01
We consider a charged particle driven by a time-dependent flux threading a quantum ring. The dynamics of the charged particle is investigated using a classical treatment, a Fourier expansion technique, a time-evolution method, and the Lewis-Riesenfeld approach. We have shown that, by properly managing the boundary conditions, a time-dependent wavefunction can be obtained using a general non-Hermitian time-dependent invariant, which is a specific linear combination of initial angular-momentum and azimuthal-angle operators. It is shown that the linear invariant eigenfunction can be realized as a Gaussian-type wavepacket with a peak moving along the classical angular trajectory, while the distribution of the wavepacket is determined by the ratio of the coefficient of the initial angle to that of the initial canonical angular momentum. From the topologically nontrivial nature as well as the classical trajectory and angular momentum, one can determine the dynamical motion of the wavepacket. It should be noted that the peak position is no longer an expectation value of the angle operator, and hence the Ehrenfest theorem is not directly applicable in such a topologically nontrivial system
International Nuclear Information System (INIS)
Revai, Janos.
1988-10-01
A model was attempted to construct which, on one hand, is flexible enough to imitate certain physical properties of real systems and, on the other hand, allows exact solution of its time dependent dynamics. This double goal is proposed to achieve by using separable interactions. A particle moving in an external field consisting of a stationary attractive and a time dependent repulsive part is proposed for the model in question. Due to the use of separable interactions, the time evolution dynamics can be solved exactly, and the model can be applied for studying time evolution of quasi-stationary states. (R.P.) 7 figs
Directory of Open Access Journals (Sweden)
Keiji Sawada
2016-12-01
Full Text Available A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below six is developed. The rovibrational X 1 Σ g + population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.
Modeling time-dependent corrosion fatigue crack propagation in 7000 series aluminum alloys
Mason, Mark E.; Gangloff, Richard P.
1994-01-01
Stress corrosion cracking and corrosion fatigue experiments were conducted with the susceptible S-L orientation of AA7075-T651, immersed in acidified and inhibited NaCl solution, to provide a basis for incorporating environmental effects into fatigue crack propagation life prediction codes such as NASA FLAGRO. This environment enhances da/dN by five to ten-fold compared to fatigue in moist air. Time-based crack growth rates from quasi-static load experiments are an order of magnitude too small for accurate linear superposition prediction of da/dN for loading frequencies above 0.001 Hz. Alternate methods of establishing da/dt, based on rising-load or ripple-load-enhanced crack tip strain rate, do not increase da/dt and do not improve linear superposition. Corrosion fatigue is characterized by two regimes of frequency dependence; da/dN is proportional to f(exp -1) below 0.001 Hz and to F(exp 0) to F(exp -0.1) for higher frequencies. Da/dN increases mildly both with increasing hold-time at K(sub max) and with increasing rise-time for a range of loading waveforms. The mild time-dependence is due to cycle-time-dependent corrosion fatigue growth. This behavior is identical for S-L nd L-T crack orientations. The frequency response of environmental fatigue in several 7000 series alloys is variable and depends on undefined compositional or microstructural variables. Speculative explanations are based on the effect of Mg on occluded crack chemistry and embritting hydrogen uptake, or on variable hydrogen diffusion in the crack tip process zone. Cracking in the 7075/NaCl system is adequately described for life prediction by linear superposition for prolonged load-cycle periods, and by a time-dependent upper bound relationship between da/dN and delta K for moderate loading times.
Modeling spiking behavior of neurons with time-dependent Poisson processes.
Shinomoto, S; Tsubo, Y
2001-10-01
Three kinds of interval statistics, as represented by the coefficient of variation, the skewness coefficient, and the correlation coefficient of consecutive intervals, are evaluated for three kinds of time-dependent Poisson processes: pulse regulated, sinusoidally regulated, and doubly stochastic. Among these three processes, the sinusoidally regulated and doubly stochastic Poisson processes, in the case when the spike rate varies slowly compared with the mean interval between spikes, are found to be consistent with the three statistical coefficients exhibited by data recorded from neurons in the prefrontal cortex of monkeys.
Avendaño-Valencia, Luis David; Fassois, Spilios D.
2017-12-01
The problem of vibration-based damage diagnosis in structures characterized by time-dependent dynamics under significant environmental and/or operational uncertainty is considered. A stochastic framework consisting of a Gaussian Mixture Random Coefficient model of the uncertain time-dependent dynamics under each structural health state, proper estimation methods, and Bayesian or minimum distance type decision making, is postulated. The Random Coefficient (RC) time-dependent stochastic model with coefficients following a multivariate Gaussian Mixture Model (GMM) allows for significant flexibility in uncertainty representation. Certain of the model parameters are estimated via a simple procedure which is founded on the related Multiple Model (MM) concept, while the GMM weights are explicitly estimated for optimizing damage diagnostic performance. The postulated framework is demonstrated via damage detection in a simple simulated model of a quarter-car active suspension with time-dependent dynamics and considerable uncertainty on the payload. Comparisons with a simpler Gaussian RC model based method are also presented, with the postulated framework shown to be capable of offering considerable improvement in diagnostic performance.
Hubbard, R.
1974-01-01
The radially-streaming particle model for broad quasar and Seyfert galaxy emission features is modified to include sources of time dependence. The results are suggestive of reported observations of multiple components, variability, and transient features in the wings of Seyfert and quasi-stellar emission lines.
Hout A. van den; Fox J.P.; Klein Entink R.H.
2015-01-01
Longitudinal data can be used to estimate the transition intensities between healthy and unhealthy states prior to death. An illness-death model for history of stroke is presented, where time-dependent transition intensities are regressed on a latent variable representing cognitive function. The
Performance Analysis of High-Order Numerical Methods for Time-Dependent Acoustic Field Modeling
Moy, Pedro Henrique Rocha
2012-07-01
The discretization of time-dependent wave propagation is plagued with dispersion in which the wavefield is perceived to travel with an erroneous velocity. To remediate the problem, simulations are run on dense and computationally expensive grids yielding plausible approximate solutions. This work introduces an error analysis tool which can be used to obtain optimal simulation parameters that account for mesh size, orders of spatial and temporal discretizations, angles of propagation, temporal stability conditions (usually referred to as CFL conditions), and time of propagation. The classical criteria of 10-15 nodes per wavelength for second-order finite differences, and 4-5 nodes per wavelength for fourth-order spectral elements are shown to be unrealistic and overly-optimistic simulation parameters for different propagation times. This work analyzes finite differences, spectral elements, optimally-blended spectral elements, and isogeometric analysis.
Electron localisation in static and time-dependent one-dimensional model systems
Durrant, T. R.; Hodgson, M. J. P.; Ramsden, J. D.; Godby, R. W.
2018-02-01
The most direct signature of electron localisation is the tendency of an electron in a many-body system to exclude other same-spin electrons from its vicinity. By applying this concept directly to the exact many-body wavefunction, we find that localisation can vary considerably between different ground-state systems, and can also be strongly disrupted, as a function of time, when a system is driven by an applied electric field. We use this measure to assess the well-known electron localisation function (ELF), both in its approximate single-particle form (often applied within density-functional theory) and its full many-particle form. The full ELF always gives an excellent description of localisation, but the approximate ELF fails in time-dependent situations, even when the exact Kohn-Sham orbitals are employed.
Making Deformable Template Models Operational
DEFF Research Database (Denmark)
Fisker, Rune
2000-01-01
for estimation of the model parameters, which applies a combination of a maximum likelihood and minimum distance criterion. Another contribution is a very fast search based initialization algorithm using a filter interpretation of the likelihood model. These two methods can be applied to most deformable template......Deformable template models are a very popular and powerful tool within the field of image processing and computer vision. This thesis treats this type of models extensively with special focus on handling their common difficulties, i.e. model parameter selection, initialization and optimization....... A proper handling of the common difficulties is essential for making the models operational by a non-expert user, which is a requirement for intensifying and commercializing the use of deformable template models. The thesis is organized as a collection of the most important articles, which has been...
Directory of Open Access Journals (Sweden)
Rakesh Prakash Tripathi
2014-05-01
Full Text Available In paper (2004 Chang studied an inventory model under a situation in which the supplier provides the purchaser with a permissible delay of payments if the purchaser orders a large quantity. Tripathi (2011 also studied an inventory model with time dependent demand rate under which the supplier provides the purchaser with a permissible delay in payments. This paper is motivated by Chang (2004 and Tripathi (2011 paper extending their model for exponential time dependent demand rate. This study develops an inventory model under which the vendor provides the purchaser with a credit period; if the purchaser orders large quantity. In this chapter, demand rate is taken as exponential time dependent. Shortages are not allowed and effect of the inflation rate has been discussed. We establish an inventory model for deteriorating items if the order quantity is greater than or equal to a predetermined quantity. We then obtain optimal solution for finding optimal order quantity, optimal cycle time and optimal total relevant cost. Numerical examples are given for all different cases. Sensitivity of the variation of different parameters on the optimal solution is also discussed. Mathematica 7 software is used for finding numerical examples.
Modeling Stepped Leaders Using a Time Dependent Multi-dipole Model and High-speed Video Data
Karunarathne, S.; Marshall, T.; Stolzenburg, M.; Warner, T. A.; Orville, R. E.
2012-12-01
In summer of 2011, we collected lightning data with 10 stations of electric field change meters (bandwidth of 0.16 Hz - 2.6 MHz) on and around NASA/Kennedy Space Center (KSC) covering nearly 70 km × 100 km area. We also had a high-speed video (HSV) camera recording 50,000 images per second collocated with one of the electric field change meters. In this presentation we describe our use of these data to model the electric field change caused by stepped leaders. Stepped leaders of a cloud to ground lightning flash typically create the initial path for the first return stroke (RS). Most of the time, stepped leaders have multiple complex branches, and one of these branches will create the ground connection for the RS to start. HSV data acquired with a short focal length lens at ranges of 5-25 km from the flash are useful for obtaining the 2-D location of these multiple branches developing at the same time. Using HSV data along with data from the KSC Lightning Detection and Ranging (LDAR2) system and the Cloud to Ground Lightning Surveillance System (CGLSS), the 3D path of a leader may be estimated. Once the path of a stepped leader is obtained, the time dependent multi-dipole model [ Lu, Winn,and Sonnenfeld, JGR 2011] can be used to match the electric field change at various sensor locations. Based on this model, we will present the time-dependent charge distribution along a leader channel and the total charge transfer during the stepped leader phase.
A Time-dependent Heliospheric Model Driven by Empirical Boundary Conditions
Kim, T. K.; Arge, C. N.; Pogorelov, N. V.
2017-12-01
Consisting of charged particles originating from the Sun, the solar wind carries the Sun's energy and magnetic field outward through interplanetary space. The solar wind is the predominant source of space weather events, and modeling the solar wind propagation to Earth is a critical component of space weather research. Solar wind models are typically separated into coronal and heliospheric parts to account for the different physical processes and scales characterizing each region. Coronal models are often coupled with heliospheric models to propagate the solar wind out to Earth's orbit and beyond. The Wang-Sheeley-Arge (WSA) model is a semi-empirical coronal model consisting of a potential field source surface model and a current sheet model that takes synoptic magnetograms as input to estimate the magnetic field and solar wind speed at any distance above the coronal region. The current version of the WSA model takes the Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model as input to provide improved time-varying solutions for the ambient solar wind structure. When heliospheric MHD models are coupled with the WSA model, density and temperature at the inner boundary are treated as free parameters that are tuned to optimal values. For example, the WSA-ENLIL model prescribes density and temperature assuming momentum flux and thermal pressure balance across the inner boundary of the ENLIL heliospheric MHD model. We consider an alternative approach of prescribing density and temperature using empirical correlations derived from Ulysses and OMNI data. We use our own modeling software (Multi-scale Fluid-kinetic Simulation Suite) to drive a heliospheric MHD model with ADAPT-WSA input. The modeling results using the two different approaches of density and temperature prescription suggest that the use of empirical correlations may be a more straightforward, consistent method.
A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)
National Research Council Canada - National Science Library
Pekker, Leonid
2008-01-01
.... The model includes a heat transfer radiation model based on a radiation database. This database has been constructed using commercially available radiation software PrismSPEC to calculate the radiation heat flux output from an uniform plasma slab...
A time dependent mixing model to close PDF equations for transport in heterogeneous aquifers
Schüler, L.; Suciu, N.; Knabner, P.; Attinger, S.
2016-10-01
Probability density function (PDF) methods are a promising alternative to predicting the transport of solutes in groundwater under uncertainty. They make it possible to derive the evolution equations of the mean concentration and the concentration variance, used in moment methods. The mixing model, describing the transport of the PDF in concentration space, is essential for both methods. Finding a satisfactory mixing model is still an open question and due to the rather elaborate PDF methods, a difficult undertaking. Both the PDF equation and the concentration variance equation depend on the same mixing model. This connection is used to find and test an improved mixing model for the much easier to handle concentration variance. Subsequently, this mixing model is transferred to the PDF equation and tested. The newly proposed mixing model yields significantly improved results for both variance modelling and PDF modelling.
Directory of Open Access Journals (Sweden)
Nikolay M. Bogoliubov
2009-04-01
Full Text Available The basic model of the non-equilibrium low dimensional physics the so-called totally asymmetric exclusion process is related to the 'crystalline limit' (q → ∞ of the SU_q(2 quantum algebra. Using the quantum inverse scattering method we obtain the exact expression for the time-dependent stationary correlation function of the totally asymmetric simple exclusion process on a one dimensional lattice with the periodic boundary conditions.
Effect of colored noise on the critical dynamics of the Time-Dependent Landau-Ginzburg Model A
International Nuclear Information System (INIS)
Korutcheva, E.; Rubia, J. de la
1999-08-01
By using the dynamical renormalization-group method, we show that the introduction of an additive colored noise with weak long-range correlations in the Time-Dependent Landau-Ginzburg Model A, does not give perturbative corrections for the dynamical critical exponent at least up to order O(ε 2 ). This result differs for a system with random quenched impurities, where a similar type of impurity correlation leads to corrections even of order O(ε). (author)
Optimal models of extreme volume-prices are time-dependent
International Nuclear Information System (INIS)
Rocha, Paulo; Boto, João Pedro; Raischel, Frank; Lind, Pedro G
2015-01-01
We present evidence that the best model for empirical volume-price distributions is not always the same and it strongly depends in (i) the region of the volume-price spectrum that one wants to model and (ii) the period in time that is being modelled. To show these two features we analyze stocks of the New York stock market with four different models: Γ, Γ-inverse, log-normal, and Weibull distributions. To evaluate the accuracy of each model we use standard relative deviations as well as the Kullback-Leibler distance and introduce an additional distance particularly suited to evaluate how accurate are the models for the distribution tails (large volume-price). Finally we put our findings in perspective and discuss how they can be extended to other situations in finance engineering
Viscoplastic discontinuum model of time-dependent fracture and seismicity effects in brittle rock
CSIR Research Space (South Africa)
Napier, JAL
1997-10-01
Full Text Available A model is proposed for the direct mechanistic simulation of seismic activity and stress transfer effects in deep level mines. The model uses a discontinuum viscoplastic formulation to relate the rate of slip on a crack to the shear stress acting...
Comments on a time-dependent version of the linear-quadratic model
International Nuclear Information System (INIS)
Tucker, S.L.; Travis, E.L.
1990-01-01
The accuracy and interpretation of the 'LQ + time' model are discussed. Evidence is presented, based on data in the literature, that this model does not accurately describe the changes in isoeffect dose occurring with protraction of the overall treatment time during fractionated irradiation of the lung. This lack of fit of the model explains, in part, the surprisingly large values of γ/α that have been derived from experimental lung data. The large apparent time factors for lung suggested by the model are also partly explained by the fact that γT/α, despite having units of dose, actually measures the influence of treatment time on the effect scale, not the dose scale, and is shown to consistently overestimate the change in total dose. The unusually high values of α/β that have been derived for lung using the model are shown to be influenced by the method by which the model was fitted to data. Reanalyses of the data using a more statistically valid regression procedure produce estimates of α/β more typical of those usually cited for lung. Most importantly, published isoeffect data from lung indicate that the true deviation from the linear-quadratic (LQ) model is nonlinear in time, instead of linear, and also depends on other factors such as the effect level and the size of dose per fraction. Thus, the authors do not advocate the use of the 'LQ + time' expression as a general isoeffect model. (author). 32 refs.; 3 figs.; 1 tab
Detection and modelling of time-dependent QTL in animal populations
DEFF Research Database (Denmark)
Lund, Mogens S; Sørensen, Peter; Madsen, Per
2008-01-01
A longitudinal approach is proposed to map QTL affecting function-valued traits and to estimate their effect over time. The method is based on fitting mixed random regression models. The QTL allelic effects are modelled with random coefficient parametric curves and using a gametic relationship...... matrix. A simulation study was conducted in order to assess the ability of the approach to fit different patterns of QTL over time. It was found that this longitudinal approach was able to adequately fit the simulated variance functions and considerably improved the power of detection of time-varying QTL...... effects compared to the traditional univariate model. This was confirmed by an analysis of protein yield data in dairy cattle, where the model was able to detect QTL with high effect either at the beginning or the end of the lactation, that were not detected with a simple 305 day model....
Potter, William J.
2018-01-01
Blazar jets are renowned for their rapid violent variability and multiwavelength flares, however, the physical processes responsible for these flares are not well understood. In this paper, we develop a time-dependent inhomogeneous fluid jet emission model for blazars. We model optically thick radio flares for the first time and show that they are delayed with respect to the prompt optically thin emission by ∼months to decades, with a lag that increases with the jet power and observed wavelength. This lag is caused by a combination of the travel time of the flaring plasma to the optically thin radio emitting sections of the jet and the slow rise time of the radio flare. We predict two types of flares: symmetric flares - with the same rise and decay time, which occur for flares whose duration is shorter than both the radiative lifetime and the geometric path-length delay time-scale; extended flares - whose luminosity tracks the power of particle acceleration in the flare, which occur for flares with a duration longer than both the radiative lifetime and geometric delay. Our model naturally produces orphan X-ray and γ-ray flares. These are caused by flares that are only observable above the quiescent jet emission in a narrow band of frequencies. Our model is able to successfully fit to the observed multiwavelength flaring spectra and light curves of PKS1502+106 across all wavelengths, using a transient flaring front located within the broad-line region.
A note on inventory model for ameliorating items with time dependent second order demand rate
Directory of Open Access Journals (Sweden)
Gobinda Chandra Panda
2013-03-01
Full Text Available Background: This paper is concerned with the development of ameliorating inventory models. The ameliorating inventory is the inventory of goods whose utility increases over the time by ameliorating activation. Material and Methods: This study is performed according to two areas: one is an economic order quantity (EOQ model for the items whose utility is ameliorating in accordance with Weibull distribution, and the other is a partial selling quantity (PSQ model developed for selling the surplus inventory accumulated by ameliorating activation with linear demand. The aim of this paper was to develop a mathematical model for inventory type concerned in the paper. Numerical examples were presented show the effect of ameliorating rate on inventory polices. Results and Conclusions: The inventory model for items with Weibull ameliorating is developed. For the case of small ameliorating rate (less than linear demand rate, EOQ model is developed, and for the case where ameliorating rate is greater than linear demand rate, PSQ model is developed. .
A time-dependent anisotropic plasma chemistry model of the Io plasma torus
Arridge, C. S.
2016-12-01
The physics of the Io plasma torus is typically modelled using one box neutral-plasma chemistry models, often referred to as neutral cloud theory models (e.g., Barbosa 1994; Delamere and Bagenal 2003). These models incorporate electron impact and photoionisation, charge exchange, molecular dissociation/recombination reactions, atomic radiatiative losses and Coulomb collisional heating. Isotropic Maxwellian distributions are usually assumed in the implementation of these models. Observationally a population of suprathermal electrons has been identified in the plasma torus and theoretically they have been shown to be important in reproducing the observed ionisation balance in the torus (e.g., Barbosa 1994). In this paper we describe an anisotropic plasma chemistry model for the Io torus that is inspired by ion cyclotron wave observations (Huddleston et al. 1994; Leisner et al. 2011), ion anisotropies due to pick up (Wilson et al. 2008), and theoretical ideas on the maintenance of the suprathermal electron population (Barbosa 1994). We present both steady state calculations and also time varying solutions (e.g., Delamere et al. 2004) where increases in the neutral source rate in the torus generates perturbations in ion anisotropies that subsequently decay over a timescale much longer than the duration of the initial perturbation. We also present a method for incorporating uncertainties in reaction rates into the model.
Vasilyev, V.; Ludwig, H.-G.; Freytag, B.; Lemasle, B.; Marconi, M.
2017-10-01
Context. Standard spectroscopic analyses of Cepheid variables are based on hydrostatic one-dimensional model atmospheres, with convection treated using various formulations of mixing-length theory. Aims: This paper aims to carry out an investigation of the validity of the quasi-static approximation in the context of pulsating stars. We check the adequacy of a two-dimensional time-dependent model of a Cepheid-like variable with focus on its spectroscopic properties. Methods: With the radiation-hydrodynamics code CO5BOLD, we construct a two-dimensional time-dependent envelope model of a Cepheid with Teff = 5600 K, log g = 2.0, solar metallicity, and a 2.8-day pulsation period. Subsequently, we perform extensive spectral syntheses of a set of artificial iron lines in local thermodynamic equilibrium. The set of lines allows us to systematically study effects of line strength, ionization stage, and excitation potential. Results: We evaluate the microturbulent velocity, line asymmetry, projection factor, and Doppler shifts. The microturbulent velocity, averaged over all lines, depends on the pulsational phase and varies between 1.5 and 2.7 km s-1. The derived projection factor lies between 1.23 and 1.27, which agrees with observational results. The mean Doppler shift is non-zero and negative, -1 km s-1, after averaging over several full periods and lines. This residual line-of-sight velocity (related to the "K-term") is primarily caused by horizontal inhomogeneities, and consequently we interpret it as the familiar convective blueshift ubiquitously present in non-pulsating late-type stars. Limited statistics prevent firm conclusions on the line asymmetries. Conclusions: Our two-dimensional model provides a reasonably accurate representation of the spectroscopic properties of a short-period Cepheid-like variable star. Some properties are primarily controlled by convective inhomogeneities rather than by the Cepheid-defining pulsations. Extended multi-dimensional modelling
Energy Technology Data Exchange (ETDEWEB)
Zachary M. Prince; Jean C. Ragusa; Yaqi Wang
2016-02-01
Because of the recent interest in reactor transient modeling and the restart of the Transient Reactor (TREAT) Facility, there has been a need for more efficient, robust methods in computation frameworks. This is the impetus of implementing the Improved Quasi-Static method (IQS) in the RATTLESNAKE/MOOSE framework. IQS has implemented with CFEM diffusion by factorizing flux into time-dependent amplitude and spacial- and weakly time-dependent shape. The shape evaluation is very similar to a flux diffusion solve and is computed at large (macro) time steps. While the amplitude evaluation is a PRKE solve where the parameters are dependent on the shape and is computed at small (micro) time steps. IQS has been tested with a custom one-dimensional example and the TWIGL ramp benchmark. These examples prove it to be a viable and effective method for highly transient cases. More complex cases are intended to be applied to further test the method and its implementation.
A Zero Dimensional Time-Dependent Model of High-Pressure Ablative Capillary Discharge (Preprint)
National Research Council Canada - National Science Library
Pekker, Leonid
2008-01-01
... plasma core and the ablative capillary walls. The model includes the thermodynamics of partially ionized plasmas and non-ideal effects taking place in the high density plasma and assumes local thermodynamic equilibrium (LTE...
Energy Technology Data Exchange (ETDEWEB)
Park, Byung Gi; Hwang, Il Soon [Seoul National Univ., Seoul (Korea, Republic of)
1999-10-01
REFIN model is applied to analyze a series of experiments that had been conducted by Tomczuk, et al. at Argonne National Laboratory (ANL) in the U.S.A.. Predicted results from REFIN model for the electrorefining experiment are compared with the published experimental results. It is demonstrated that REFIN model can predict faradic current of each element and electrochemical potential as a function of time over the entire campaign of the electrorefining experiment. The elemental concentration changes agree with the experimental results well. Elemental concentration changes during an open-circuit equilibration period are revealed to suggest that the electrorefining process could not be adequately described by the equilibrium model often applied for an electrode surface. Surface potential drop is changed according to equilibrium potential of chemical species with high activity in liquid metal.
International Nuclear Information System (INIS)
Paretzke, H.G.; Jacob, P.; Mueller, H.; Proehl, G.
1989-01-01
After major releases of radionuclides into the atmosphere fast reaction of authorities will be necessary to inform the public of potential consequences and to consider and optimize mitigating actions. These activities require availability of well designed computer models, adequate and fast measurements and prior training of responsible persons. The quantitative assessment models should be capable of taking into account of actual atmospheric dispersion conditions, actual deposition situation (dry, rain, snow, fog), seasonal status of the agriculture, food processing and distribution pathways, etc. In this paper the usefulness of such models will be discussed, their limitations, the relative importance of exposure pathways and a selection of important methods to decrease the activity in food products after an accident. Real-time reactor accident consequence models should be considered as a condition sine qua non for responsible use of nuclear power for electricity production
A full 3D time-dependent electromagnetic model for Roebel cables
DEFF Research Database (Denmark)
Rodriguez Zermeno, Victor Manuel; Grilli, Francesco; Sirois, Frederic
2013-01-01
High temperature superconductor Roebel cables are well known for their large current capacity and low AC losses. For this reason they have become attractive candidates for many power applications. The continuous transposition of their strands reduces the coupling losses while ensuring better...... is unavoidably a large scale computational problem. In this work, we present a full 3D model of a Roebel cable with 14 strands. The model is based on the H-formulation, widely used for 2D problems. In order to keep the 3D features of the cable (in particular the magnetization currents near the transpositions......), no simplifications are made other than the reduction of the modelled length according to the periodicity of the cable structure. The 3D model is used to study the dependence of AC losses on the amplitude of the AC applied magnetic field or transport current. Beyond the importance of simulating the Roebel cable...
International Nuclear Information System (INIS)
Zilio, Claudio; Patricelli, Luca
2014-01-01
The anti-ice systems are critical for airplane safety, but are also strongly affecting the fuel consumption of the aircraft. A complete model of this system allows the designers to investigate all possible combination of external parameters and improve the design of current anti-ice systems. The dynamic model of an anti-ice system is presented and the results of the model are validated thanks to a series of experimental tests. The model has been used to analyze the behavior of an anti-ice system at extreme high bleed air temperature which are typical of new generation aircraft engines. An innovative architecture for anti-ice system is studied and the benefits on aircraft fuel consumption for a standard day mission are shown. -- Highlights: • A detailed mathematical model of an anti-ice valves has been created. • Experimental results confirm the goodness of the developed model. • Instability of the valves has been studied. • A new architecture for the anti-ice systems is proposed and the impacts on the aircraft fuel consumption are analyzed
Two-dimensional time dependent hurricane overwash and erosion modeling at Santa Rosa Island
McCall, R.T.; Van Theil de Vries, J. S. M.; Plant, N.G.; Van Dongeren, A. R.; Roelvink, J.A.; Thompson, D.M.; Reniers, A.J.H.M.
2010-01-01
A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias - 0.21 m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response.
Cheng-Wu, Li; Hong-Lai, Xue; Cheng, Guan; Wen-biao, Liu
2018-04-01
Statistical analysis shows that in the coal matrix, the diffusion coefficient for methane is time-varying, and its integral satisfies the formula μt κ /(1 + β κ ). Therefore, a so-called dynamic diffusion coefficient model (DDC model) is developed. To verify the suitability and accuracy of the DDC model, a series of gas diffusion experiments were conducted using coal particles of different sizes. The results show that the experimental data can be accurately described by the DDC and bidisperse models, but the fit to the DDC model is slightly better. For all coal samples, as time increases, the effective diffusion coefficient first shows a sudden drop, followed by a gradual decrease before stabilizing at longer times. The effective diffusion coefficient has a negative relationship with the size of the coal particle. Finally, the relationship between the constants of the DDC model and the effective diffusion coefficient is discussed. The constant α (μ/R 2 ) denotes the effective coefficient at the initial time, and the constants κ and β control the attenuation characteristic of the effective diffusion coefficient.
Energy Technology Data Exchange (ETDEWEB)
Brics, Martins
2016-12-09
-called renormalized natural orbitals (RNOs), TDRNOT is benchmarked with the help of a numerically exactly solvable model helium atom in laser fields. In the special case of time-dependent two-electron systems the two-particle density matrix in terms of ONs and NOs is known exactly. Hence, in this case TDRNOT is exact, apart from the unavoidable truncation of the number of RNOs per particle taken into account in the simulation. It is shown that, unlike TDDFT, TDRNOT is able to describe doubly-excited states, Fano profiles in electron and absorption spectra, auto-ionization, Rabi oscillations, high harmonic generation, non-sequential ionization, and single-photon double ionization in excellent agreement with the corresponding TDSE results.
International Nuclear Information System (INIS)
Brics, Martins
2016-01-01
-called renormalized natural orbitals (RNOs), TDRNOT is benchmarked with the help of a numerically exactly solvable model helium atom in laser fields. In the special case of time-dependent two-electron systems the two-particle density matrix in terms of ONs and NOs is known exactly. Hence, in this case TDRNOT is exact, apart from the unavoidable truncation of the number of RNOs per particle taken into account in the simulation. It is shown that, unlike TDDFT, TDRNOT is able to describe doubly-excited states, Fano profiles in electron and absorption spectra, auto-ionization, Rabi oscillations, high harmonic generation, non-sequential ionization, and single-photon double ionization in excellent agreement with the corresponding TDSE results.
Using time-dependent models to investigate body condition and growth rate of the giant gartersnake
Coates, P.S.; Wylie, G.D.; Halstead, B.J.; Casazza, Michael L.
2009-01-01
Identifying links between phenotypic attributes and fitness is a primary goal of reproductive ecology. Differences in within-year patterns of body condition between sexes of gartersnakes in relation to reproduction and growth are not fully understood. We conducted an 11-year field study of body condition and growth rate of the giant gartersnake Thamnophis gigas across 13 study areas in the Central Valley of California, USA. We developed a priori mixed effects models of body condition index (BCI), which included covariates of time, sex and snout-vent length and reported the best-approximating models using an information theoretic approach. Also, we developed models of growth rate index (GRI) using covariates of sex and periods based on reproductive behavior. The largest difference in BCI between sexes, as predicted by a non-linear (cubic) time model, occurred during the mating period when female body condition (0.014??0.001 se) was substantially greater than males (-0.027??0.002 se). Males likely allocated energy to search for mates, while females likely stored energy for embryonic development. We also provided evidence that males use more body energy reserves than females during hibernation, perhaps because of different body temperatures between sexes. We found GRI of male snakes was substantially lower during the mating period than during a non-mating period, which indicated that a trade-off existed between searching for mates and growth. These findings contribute to our understanding of snake ecology in a Mediterranean climate. ?? 2009 The Zoological Society of London.
A Time-Dependent Λ and G Cosmological Model Consistent with Cosmological Constraints
Directory of Open Access Journals (Sweden)
L. Kantha
2016-01-01
Full Text Available The prevailing constant Λ-G cosmological model agrees with observational evidence including the observed red shift, Big Bang Nucleosynthesis (BBN, and the current rate of acceleration. It assumes that matter contributes 27% to the current density of the universe, with the rest (73% coming from dark energy represented by the Einstein cosmological parameter Λ in the governing Friedmann-Robertson-Walker equations, derived from Einstein’s equations of general relativity. However, the principal problem is the extremely small value of the cosmological parameter (~10−52 m2. Moreover, the dark energy density represented by Λ is presumed to have remained unchanged as the universe expanded by 26 orders of magnitude. Attempts to overcome this deficiency often invoke a variable Λ-G model. Cosmic constraints from action principles require that either both G and Λ remain time-invariant or both vary in time. Here, we propose a variable Λ-G cosmological model consistent with the latest red shift data, the current acceleration rate, and BBN, provided the split between matter and dark energy is 18% and 82%. Λ decreases (Λ~τ-2, where τ is the normalized cosmic time and G increases (G~τn with cosmic time. The model results depend only on the chosen value of Λ at present and in the far future and not directly on G.
An Inventory Model with Time-Dependent Demand and Limited Storage Facility under Inflation
Directory of Open Access Journals (Sweden)
Neeraj Kumar
2012-01-01
Full Text Available The main objective of this paper is to develop a two-warehouse inventory model with partial backordering and Weibull distribution deterioration. We consider inflation and apply the discounted cash flow in problem analysis. The discounted cash flow (DCF and optimization framework are presented to derive the optimal replenishment policy that minimizes the total present value cost per unit time. When only rented or own warehouse model is considered, the present value of the total relevant cost is higher than the case when two-warehouse is considered. The results have been validated with the help of a numerical example. Sensitivity analysis with respect to various parameters is also performed. From the sensitivity analysis, we show that the total cost of the system is influenced by the deterioration rate, the inflation rate, and the backordering ratio.
Tsivilskiy, I. V.; Nagulin, K. Yu.; Gilmutdinov, A. Kh.
2016-02-01
A full three-dimensional nonstationary numerical model of graphite electrothermal atomizers of various types is developed. The model is based on solution of a heat equation within solid walls of the atomizer with a radiative heat transfer and numerical solution of a full set of Navier-Stokes equations with an energy equation for a gas. Governing equations for the behavior of a discrete phase, i.e., atomic particles suspended in a gas (including gas-phase processes of evaporation and condensation), are derived from the formal equations molecular kinetics by numerical solution of the Hertz-Langmuir equation. The following atomizers test the model: a Varian standard heated electrothermal vaporizer (ETV), a Perkin Elmer standard THGA transversely heated graphite tube with integrated platform (THGA), and the original double-stage tube-helix atomizer (DSTHA). The experimental verification of computer calculations is carried out by a method of shadow spectral visualization of the spatial distributions of atomic and molecular vapors in an analytical space of an atomizer.
Directory of Open Access Journals (Sweden)
Sung Soo Kim
2016-02-01
Full Text Available We consider a discrete-time dependent Sparre Andersen risk model which incorporates multiple threshold levels characterizing an insurer’s minimal capital requirement, dividend paying situations, and external financial activities. We focus on the development of a recursive computational procedure to calculate the finite-time ruin probabilities and expected total discounted dividends paid prior to ruin associated with this model. We investigate several numerical examples and make some observations concerning the impact our threshold levels have on the finite-time ruin probabilities and expected total discounted dividends paid prior to ruin.
Spike solutions in Gierer#x2013;Meinhardt model with a time dependent anomaly exponent
Nec, Yana
2018-01-01
Experimental evidence of complex dispersion regimes in natural systems, where the growth of the mean square displacement in time cannot be characterised by a single power, has been accruing for the past two decades. In such processes the exponent γ(t) in ⟨r2⟩ ∼ tγ(t) at times might be approximated by a piecewise constant function, or it can be a continuous function. Variable order differential equations are an emerging mathematical tool with a strong potential to model these systems. However, variable order differential equations are not tractable by the classic differential equations theory. This contribution illustrates how a classic method can be adapted to gain insight into a system of this type. Herein a variable order Gierer-Meinhardt model is posed, a generic reaction- diffusion system of a chemical origin. With a fixed order this system possesses a solution in the form of a constellation of arbitrarily situated localised pulses, when the components' diffusivity ratio is asymptotically small. The pattern was shown to exist subject to multiple step-like transitions between normal diffusion and sub-diffusion, as well as between distinct sub-diffusive regimes. The analytical approximation obtained permits qualitative analysis of the impact thereof. Numerical solution for typical cross-over scenarios revealed such features as earlier equilibration and non-monotonic excursions before attainment of equilibrium. The method is general and allows for an approximate numerical solution with any reasonably behaved γ(t).
Cocco, M.
2001-12-01
Earthquake stress changes can promote failures on favorably oriented faults and modify the seismicity pattern over broad regions around the causative faults. Because the induced stress perturbations modify the rate of production of earthquakes, they alter the probability of seismic events in a specified time window. Comparing the Coulomb stress changes with the seismicity rate changes and aftershock patterns can statistically test the role of stress transfer in earthquake occurrence. The interaction probability may represent a further tool to test the stress trigger or shadow model. The probability model, which incorporate stress transfer, has the main advantage to include the contributions of the induced stress perturbation (a static step in its present formulation), the loading rate and the fault constitutive properties. Because the mechanical conditions of the secondary faults at the time of application of the induced load are largely unkown, stress triggering can only be tested on fault populations and not on single earthquake pairs with a specified time delay. The interaction probability can represent the most suitable tool to test the interaction between large magnitude earthquakes. Despite these important implications and the stimulating perspectives, there exist problems in understanding earthquake interaction that should motivate future research but at the same time limit its immediate social applications. One major limitation is that we are unable to predict how and if the induced stress perturbations modify the ratio between small versus large magnitude earthquakes. In other words, we cannot distinguish between a change in this ratio in favor of small events or of large magnitude earthquakes, because the interaction probability is independent of magnitude. Another problem concerns the reconstruction of the stressing history. The interaction probability model is based on the response to a static step; however, we know that other processes contribute to
Time-dependent modelling of environmental change: the effect of quaternary glaciations
International Nuclear Information System (INIS)
Boulton, G.S.
1990-01-01
The dominant amplitudes and frequencies of global climatic change over the last three million years can now be reconstructed with great precision. Extrapolations from this can then be used to simulate the future course of climatic change. Correlation between long oceanic records of global change and relatively brief, terrestrial geological records of regional and local changes, can be used to reconstruct long regional and local records. The precise evolution of many environmental processes driven by these local changes is inherently indeterminate, but by using the evidence from sediments produced by these changes as constraints on process models, it is possible to correlate regional climatic changes with regional process responses. Thus simulated climatic futures can be used to assess the character and magnitudes of processes which are important for waste disposal sites. 21 refs., 8 figs
A Quantitative, Time-Dependent Model of Oxygen Isotopes in the Solar Nebula: Step one
Nuth, J. A.; Paquette, J. A.; Farquhar, A.; Johnson, N. M.
2011-01-01
The remarkable discovery that oxygen isotopes in primitive meteorites were fractionated along a line of slope I rather than along the typical slope 0,52 terrestrial fractionation line occurred almost 40 years ago, However, a satisfactory, quantitative explanation for this observation has yet to be found, though many different explanations have been proposed, The first of these explanations proposed that the observed line represented the final product produced by mixing molecular cloud dust with a nucleosynthetic component, rich in O-16, possibly resulting from a nearby supernova explosion, Donald Clayton suggested that Galactic Chemical Evolution would gradually change the oxygen isotopic composition of the interstellar grain population by steadily producing O-16 in supernovae, then producing the heavier isotopes as secondary products in lower mass stars, Thiemens and collaborators proposed a chemical mechanism that relied on the availability of additional active rotational and vibrational states in otherwise-symmetric molecules, such as CO2, O3 or SiO2, containing two different oxygen isotopes and a second, photochemical process that suggested that differential photochemical dissociation processes could fractionate oxygen , This second line of research has been pursued by several groups, though none of the current models is quantitative,
From localized to extended states in a time-dependent quantum model
International Nuclear Information System (INIS)
Jose, J.V.
1986-01-01
The problem of a particle inside a rigid box with one of the walls oscillating periodically in time is studied quantum mechanically. In the classical limit, this model was introduced by Fermi in the context of cosmic ray physics. The classical solutions can go from being quasiperiodic to chaotic, as a function of the amplitude of the wall oscillation. In the quantum case, the authors calculate the spectral properties of the corresponding evolution operator, i.e.: the quasi-energy eigenvalues and eigenvectors. The specific form of the wall oscillation, e.g. iota(t) = √ 1 + 2δabsolute value of t, with absolute value of t ≤ 1/2, and iota(t + 1) = iota(t), is essential to the solutions presented here. It is found that as h increases with δ fixed, the nearest neighbor separation between quasi-energy eigenvalues changes from showing no energy level repulsion to energy level repulsion. This transition, from Poisson-like statistics to Gaussian-Orthogonal-Ensemble-like statistics is tested by looking at the distribution of quasi-energy level nearest neighbor separations and the Δ/sub e/(L) statistics. these results are also correlated to a transition between localized to extended states in energy space. The possible relevance of the results presented here to experiments in quasi-one-dimensional atoms is also discussed
Kinetic Ising model in a time-dependent oscillating external magnetic field: effective-field theory
International Nuclear Information System (INIS)
Deviren, Bayram; Canko, Osman; Keskin, Mustafa
2010-01-01
Recently, Shi et al. [2008 Phys. Lett. A 372 5922] have studied the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field and presented the dynamic phase diagrams by using an effective-field theory (EFT) and a mean-field theory (MFT). The MFT results are in conflict with those of the earlier work of Tomé and de Oliveira, [1990 Phys. Rev. A 41 4251]. We calculate the dynamic phase diagrams and find that our results are similar to those of the earlier work of Tomé and de Oliveira; hence the dynamic phase diagrams calculated by Shi et al. are incomplete within both theories, except the low values of frequencies for the MFT calculation. We also investigate the influence of external field frequency (ω) and static external field amplitude (h 0 ) for both MFT and EFT calculations. We find that the behaviour of the system strongly depends on the values of ω and h 0 . (general)
Chaturvedi, K.; Willenborg, B.; Sindram, M.; Kolbe, T. H.
2017-10-01
Semantic 3D city models play an important role in solving complex real-world problems and are being adopted by many cities around the world. A wide range of application and simulation scenarios directly benefit from the adoption of international standards such as CityGML. However, most of the simulations involve properties, whose values vary with respect to time, and the current generation semantic 3D city models do not support time-dependent properties explicitly. In this paper, the details of solar potential simulations are provided operating on the CityGML standard, assessing and estimating solar energy production for the roofs and facades of the 3D building objects in different ways. Furthermore, the paper demonstrates how the time-dependent simulation results are better-represented inline within 3D city models utilizing the so-called Dynamizer concept. This concept not only allows representing the simulation results in standardized ways, but also delivers a method to enhance static city models by such dynamic property values making the city models truly dynamic. The dynamizer concept has been implemented as an Application Domain Extension of the CityGML standard within the OGC Future City Pilot Phase 1. The results are given in this paper.
International Nuclear Information System (INIS)
King-Clayton, L.; Smith, Paul
1996-10-01
The report details the methodology and preliminary results from the modelling of radionuclide transport from a hypothetical repository based at the Aespoe site in Sweden. The work complements and utilizes the results from regional-scale, variable density flow modelling by Provost, in which the groundwater flow field is time dependent, reflecting the impact of climate evolution over the next 130,000 years. The climate evolution include development of permafrost conditions and ice sheet advance and retreat. The results indicate that temporal changes in flow conditions owing to future climate changes have a significant effect on the transport of radionuclides from a repository. In all cases modelled with time-dependent boundary conditions, the greatest radionuclide fluxes occur towards the end of the main glacial periods, and correspond to periods of high groundwater discharge at the margin of the modelled ice sheets. Fluxes to the biosphere may, for limited periods (2000 years or less), be three times higher than those from the near field. The study provides a quantitative way of illustrating the possible effects of future glaciations on radionuclide transport from the repository. Such effects are likely to be significant in any potential siting area predicted to be affected by future periods of ice cover. 8 refs, 22 tabs, 119 figs
Energy Technology Data Exchange (ETDEWEB)
Maitra, Neepa [Hunter College City University of New York, New York, NY (United States)
2016-07-14
This project investigates the accuracy of currently-used functionals in time-dependent density functional theory, which is today routinely used to predict and design materials and computationally model processes in solar energy conversion. The rigorously-based electron-ion dynamics method developed here sheds light on traditional methods and overcomes challenges those methods have. The fundamental research undertaken here is important for building reliable and practical methods for materials discovery. The ultimate goal is to use these tools for the computational design of new materials for solar cell devices of high efficiency.
International Nuclear Information System (INIS)
Fu Chuanji; Zhu Qinsheng; Wu Shaoyi
2010-01-01
Based on algebraic dynamics and the concept of the concurrence of the entanglement, we investigate the evolutive properties of the two-qubit entanglement that formed by Heisenberg XXX models under a time-depending external held. For this system, the property of the concurrence that is only dependent on the coupling constant J and total values of the external field is proved. Furthermore, we found that the thermal concurrence of the system under a static random external field is a function of the coupling constant J, temperature T, and the magnitude of external held. (general)
Antunes, Gabriela; Faria da Silva, Samuel F; Simoes de Souza, Fabio M
2018-06-01
Mirror neurons fire action potentials both when the agent performs a certain behavior and watches someone performing a similar action. Here, we present an original mirror neuron model based on the spike-timing-dependent plasticity (STDP) between two morpho-electrical models of neocortical pyramidal neurons. Both neurons fired spontaneously with basal firing rate that follows a Poisson distribution, and the STDP between them was modeled by the triplet algorithm. Our simulation results demonstrated that STDP is sufficient for the rise of mirror neuron function between the pairs of neocortical neurons. This is a proof of concept that pairs of neocortical neurons associating sensory inputs to motor outputs could operate like mirror neurons. In addition, we used the mirror neuron model to investigate whether channelopathies associated with autism spectrum disorder could impair the modeled mirror function. Our simulation results showed that impaired hyperpolarization-activated cationic currents (Ih) affected the mirror function between the pairs of neocortical neurons coupled by STDP.
Directory of Open Access Journals (Sweden)
Mitali Sarkar
2017-01-01
Full Text Available Recently, a major trend is going to redesign a production system by controlling or making variable the production rate within some fixed interval to maintain the optimal level. This strategy is more effective when the holding cost is time-dependent as it is interrelated with holding duration of products and rate of production. An effort is made to make a supply chain model (SCM to show the joint effect of variable production rate and time-varying holding cost for specific type of complementary products, where those products are made by two different manufacturers and a common retailer makes them bundle and sells bundles to end customers. Demand of each product is specified by stochastic reservation prices with a known potential market size. Those players of the SCM are considered with unequal power. Stackelberg game approach is employed to obtain global optimum solution of the model. An illustrative numerical example, graphical representation, and managerial insights are given to illustrate the model. Results prove that variable production rate and time-dependent holding cost save more than existing literature.
Chaplin, Vernon H.; Bellan, Paul M.
2015-12-01
A time-dependent two-fluid model has been developed to understand axial variations in the plasma parameters in a very high density (peak ne≳ 5 ×1019 m-3 ) argon inductively coupled discharge in a long 1.1 cm radius tube. The model equations are written in 1D with radial losses to the tube walls accounted for by the inclusion of effective particle and energy sink terms. The ambipolar diffusion equation and electron energy equation are solved to find the electron density ne(z ,t ) and temperature Te(z ,t ) , and the populations of the neutral argon 4s metastable, 4s resonant, and 4p excited state manifolds are calculated to determine the stepwise ionization rate and calculate radiative energy losses. The model has been validated through comparisons with Langmuir probe ion saturation current measurements; close agreement between the simulated and measured axial plasma density profiles and the initial density rise rate at each location was obtained at pA r=30 -60 mTorr . We present detailed results from calculations at 60 mTorr, including the time-dependent electron temperature, excited state populations, and energy budget within and downstream of the radiofrequency antenna.
Directory of Open Access Journals (Sweden)
Niklas Hübel
2014-12-01
Full Text Available The classical Hodgkin-Huxley (HH model neglects the time-dependence of ion concentrations in spiking dynamics. The dynamics is therefore limited to a time scale of milliseconds, which is determined by the membrane capacitance multiplied by the resistance of the ion channels, and by the gating time constants. We study slow dynamics in an extended HH framework that includes time-dependent ion concentrations, pumps, and buffers. Fluxes across the neuronal membrane change intra- and extracellular ion concentrations, whereby the latter can also change through contact to reservoirs in the surroundings. Ion gain and loss of the system is identified as a bifurcation parameter whose essential importance was not realized in earlier studies. Our systematic study of the bifurcation structure and thus the phase space structure helps to understand activation and inhibition of a new excitability in ion homeostasis which emerges in such extended models. Also modulatory mechanisms that regulate the spiking rate can be explained by bifurcations. The dynamics on three distinct slow times scales is determined by the cell volume-to-surface-area ratio and the membrane permeability (seconds, the buffer time constants (tens of seconds, and the slower backward buffering (minutes to hours. The modulatory dynamics and the newly emerging excitable dynamics corresponds to pathological conditions observed in epileptiform burst activity, and spreading depression in migraine aura and stroke, respectively.
Hübel, Niklas; Dahlem, Markus A
2014-12-01
The classical Hodgkin-Huxley (HH) model neglects the time-dependence of ion concentrations in spiking dynamics. The dynamics is therefore limited to a time scale of milliseconds, which is determined by the membrane capacitance multiplied by the resistance of the ion channels, and by the gating time constants. We study slow dynamics in an extended HH framework that includes time-dependent ion concentrations, pumps, and buffers. Fluxes across the neuronal membrane change intra- and extracellular ion concentrations, whereby the latter can also change through contact to reservoirs in the surroundings. Ion gain and loss of the system is identified as a bifurcation parameter whose essential importance was not realized in earlier studies. Our systematic study of the bifurcation structure and thus the phase space structure helps to understand activation and inhibition of a new excitability in ion homeostasis which emerges in such extended models. Also modulatory mechanisms that regulate the spiking rate can be explained by bifurcations. The dynamics on three distinct slow times scales is determined by the cell volume-to-surface-area ratio and the membrane permeability (seconds), the buffer time constants (tens of seconds), and the slower backward buffering (minutes to hours). The modulatory dynamics and the newly emerging excitable dynamics corresponds to pathological conditions observed in epileptiform burst activity, and spreading depression in migraine aura and stroke, respectively.
Meier-Hirmer, Carolina; Schumacher, Martin
2013-06-20
The aim of this article is to propose several methods that allow to investigate how and whether the shape of the hazard ratio after an intermediate event depends on the waiting time to occurrence of this event and/or the sojourn time in this state. A simple multi-state model, the illness-death model, is used as a framework to investigate the occurrence of this intermediate event. Several approaches are shown and their advantages and disadvantages are discussed. All these approaches are based on Cox regression. As different time-scales are used, these models go beyond Markov models. Different estimation methods for the transition hazards are presented. Additionally, time-varying covariates are included into the model using an approach based on fractional polynomials. The different methods of this article are then applied to a dataset consisting of four studies conducted by the German Breast Cancer Study Group (GBSG). The occurrence of the first isolated locoregional recurrence (ILRR) is studied. The results contribute to the debate on the role of the ILRR with respect to the course of the breast cancer disease and the resulting prognosis. We have investigated different modelling strategies for the transition hazard after ILRR or in general after an intermediate event. Including time-dependent structures altered the resulting hazard functions considerably and it was shown that this time-dependent structure has to be taken into account in the case of our breast cancer dataset. The results indicate that an early recurrence increases the risk of death. A late ILRR increases the hazard function much less and after the successful removal of the second tumour the risk of death is almost the same as before the recurrence. With respect to distant disease, the appearance of the ILRR only slightly increases the risk of death if the recurrence was treated successfully. It is important to realize that there are several modelling strategies for the intermediate event and that
Interactive Character Deformation Using Simplified Elastic Models
Luo, Z.
2016-01-01
This thesis describes the results of our research into realistic skin and model deformation methods aimed at the field of character deformation and animation. The main contributions lie in the properties of our deformation scheme. Our approach preserves the volume of the deformed object while
Steady-state and time-dependent modelling of parallel transport in the scrape-off layer
DEFF Research Database (Denmark)
Havlickova, E.; Fundamenski, W.; Naulin, Volker
2011-01-01
The one-dimensional fluid code SOLF1D has been used for modelling of plasma transport in the scrape-off layer (SOL) along magnetic field lines, both in steady state and under transient conditions that arise due to plasma turbulence. The presented work summarizes results of SOLF1D with attention...... given to transient parallel transport which reveals two distinct time scales due to the transport mechanisms of convection and diffusion. Time-dependent modelling combined with the effect of ballooning shows propagation of particles along the magnetic field line with Mach number up to M ≈ 1...... temperature calculated in SOLF1D is compared with the approximative model used in the turbulence code ESEL both for steady-state and turbulent SOL. Dynamics of the parallel transport are investigated for a simple transient event simulating the propagation of particles and energy to the targets from a blob...
Directory of Open Access Journals (Sweden)
Tripathi R.P.
2013-01-01
Full Text Available This study develops an inventory model for determining an optimal ordering policy for non-deteriorating items and time-dependent holding cost with delayed payments permitted by the supplier under inflation and time-discounting. The discounted cash flows approach is applied to study the problem analysis. Mathematical models have been derived under two different situations i.e. case I: The permissible delay period is less than cycle time for settling the account and case II: The permissible delay period is greater than or equal to cycle time for settling the account. An algorithm is used to obtain minimum total present value of the costs over the time horizon H. Finally, numerical example and sensitivity analysis demonstrate the applicability of the proposed model. The main purpose of this paper is to investigate the optimal cycle time and optimal payment time for an item so that annual total relevant cost is minimized.
Omi, Takahiro; Hirata, Yoshito; Aihara, Kazuyuki
2017-07-01
A Hawkes process model with a time-varying background rate is developed for analyzing the high-frequency financial data. In our model, the logarithm of the background rate is modeled by a linear model with a relatively large number of variable-width basis functions, and the parameters are estimated by a Bayesian method. Our model can capture not only the slow time variation, such as in the intraday seasonality, but also the rapid one, which follows a macroeconomic news announcement. By analyzing the tick data of the Nikkei 225 mini, we find that (i) our model is better fitted to the data than the Hawkes models with a constant background rate or a slowly varying background rate, which have been commonly used in the field of quantitative finance; (ii) the improvement in the goodness-of-fit to the data by our model is significant especially for sessions where considerable fluctuation of the background rate is present; and (iii) our model is statistically consistent with the data. The branching ratio, which quantifies the level of the endogeneity of markets, estimated by our model is 0.41, suggesting the relative importance of exogenous factors in the market dynamics. We also demonstrate that it is critically important to appropriately model the time-dependent background rate for the branching ratio estimation.
Omi, Takahiro; Hirata, Yoshito; Aihara, Kazuyuki
2017-07-01
A Hawkes process model with a time-varying background rate is developed for analyzing the high-frequency financial data. In our model, the logarithm of the background rate is modeled by a linear model with a relatively large number of variable-width basis functions, and the parameters are estimated by a Bayesian method. Our model can capture not only the slow time variation, such as in the intraday seasonality, but also the rapid one, which follows a macroeconomic news announcement. By analyzing the tick data of the Nikkei 225 mini, we find that (i) our model is better fitted to the data than the Hawkes models with a constant background rate or a slowly varying background rate, which have been commonly used in the field of quantitative finance; (ii) the improvement in the goodness-of-fit to the data by our model is significant especially for sessions where considerable fluctuation of the background rate is present; and (iii) our model is statistically consistent with the data. The branching ratio, which quantifies the level of the endogeneity of markets, estimated by our model is 0.41, suggesting the relative importance of exogenous factors in the market dynamics. We also demonstrate that it is critically important to appropriately model the time-dependent background rate for the branching ratio estimation.
International Nuclear Information System (INIS)
Seubert, A.; Velkov, K.; Langenbuch, S.
2008-01-01
This paper describes the time-dependent 3D discrete ordinates transport code TORT-TD. Thermal-hydraulic feedback is considered by coupling TORT-TD with the thermal-hydraulics system code ATHLET. The coupled code TORT-TD/ATHLET allows 3D pin-by-pin analyses of transients in few energy groups and anisotropic scattering by solving the time-dependent transport equation using the unconditionally stable implicit method. The nuclear cross sections are interpolated between pre-calculated table values of fuel temperature, moderator density and boron concentration. For verification of the implementation, selected test cases have been calculated by TORT-TD/ATHLET. They include a control rod ejection transient in a small PWR fuel assembly arrangement and a local boron concentration change in a single PWR fuel assembly. In the latter, special attention has been paid to study the influence of the thermal-hydraulic feedback modelling in ATHLET. The results obtained for a control rod ejection accident in a PWR quarter core demonstrate the applicability of TORT-TD/ATHLET. (authors)
Kinetics of the spin-2 Blume-Capel model under a time-dependent oscillating external field
International Nuclear Information System (INIS)
Keskin, M.; Canko, O.; Ertas, M.
2007-01-01
Within a mean-field approach and using the Glauber-type stochastic dynamics, we study the kinetics of the spin-2 Blume-Capel model in the presence of a time-varying (sinusoidal) magnetic field. We investigate the time dependence of the average order parameter and the behavior of the average order parameter in a period, which is also called the dynamic order parameter, as a function of the reduced temperature. The nature (continuous and discontinuous) of the transition is characterized by the dynamic order parameter. The dynamic phase transition points are obtained and the phase diagrams are presented in the reduced magnetic field amplitude and reduced temperature plane. The phase diagrams exhibit one dynamic tricritical point; besides a disordered and an ordered phases, there are three phase coexistence regions that are strongly dependent on the interaction parameter
Ichida, J M; Wassell, J T; Keller, M D; Ayers, L W
1993-02-01
Survival analysis methods are valuable for detecting intervention effects because detailed information from patient records and sensitive outcome measures are used. The burn unit at a large university hospital replaced routine bathing with total body bathing using chlorhexidine gluconate for antimicrobial effect. A Cox proportional hazards model was used to analyse time from admission until either infection with Staphylococcus aureus or discharge for 155 patients, controlling for burn severity and two time-dependent covariates: days until first wound excision and days until first administration of prophylactic antibiotics. The risk of infection was 55 per cent higher in the historical control group, although not statistically significant. There was also some indication that early wound excision may be important as an infection-control measure for burn patients.
Stökl, A.
2008-11-01
Context: In spite of all the advances in multi-dimensional hydrodynamics, investigations of stellar evolution and stellar pulsations still depend on one-dimensional computations. This paper devises an alternative to the mixing-length theory or turbulence models usually adopted in modelling convective transport in such studies. Aims: The present work attempts to develop a time-dependent description of convection, which reflects the essential physics of convection and that is only moderately dependent on numerical parameters and far less time consuming than existing multi-dimensional hydrodynamics computations. Methods: Assuming that the most extensive convective patterns generate the majority of convective transport, the convective velocity field is described using two parallel, radial columns to represent up- and downstream flows. Horizontal exchange, in the form of fluid flow and radiation, over their connecting interface couples the two columns and allows a simple circulating motion. The main parameters of this convective description have straightforward geometrical meanings, namely the diameter of the columns (corresponding to the size of the convective cells) and the ratio of the cross-section between up- and downdrafts. For this geometrical setup, the time-dependent solution of the equations of radiation hydrodynamics is computed from an implicit scheme that has the advantage of being unaffected by the Courant-Friedrichs-Lewy time-step limit. This implementation is part of the TAPIR-Code (short for The adaptive, implicit RHD-Code). Results: To demonstrate the approach, results for convection zones in Cepheids are presented. The convective energy transport and convective velocities agree with expectations for Cepheids and the scheme reproduces both the kinetic energy flux and convective overshoot. A study of the parameter influence shows that the type of solution derived for these stars is in fact fairly robust with respect to the constitutive numerical
International Nuclear Information System (INIS)
1983-04-01
VISCOT is a non-linear, transient, thermal-stress finite-element code designed to determine the viscoelastic, fiscoplastic, or elastoplastic deformation of a rock mass due to mechanical and thermal loading. The numerical solution of the nonlinear incremental equilibrium equations within VISCOT is performed by using an explicit Euler time-stepping scheme. The rock mass may be modeled as a viscoplastic or viscoelastic material. The viscoplastic material model can be described by a Tresca, von Mises, Drucker-Prager or Mohr-Coulomb yield criteria (with or without strain hardening) with an associated flow rule which can be a power or an exponential law. The viscoelastic material model within VISCOT is a temperature- and stress-dependent law which has been developed specifically for salt rock masses by Pfeifle, Mellegard and Senseny in ONWI-314 topical report (1981). Site specific parameters for this creep law at the Richton, Permian, Paradox and Vacherie salt sites have been calculated and are given in ONWI-314 topical report (1981). A major application of VISCOT (in conjunction with a SCEPTER heat transfer code such as DOT) is the thermomechanical analysis of a rock mass such as salt in which significant time-dependent nonlinear deformations are expected to occur. Such problems include room- and canister-scale studies during the excavation, operation, and long-term post-closure stages in a salt repository. In Section 1.5 of this document the code custodianship and control is described along with the status of verification, validation and peer review of this report
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Shu San Gan
2015-12-01
Full Text Available In this study we develop a model that optimizes the price for new and remanufactured short life-cycle products where demands are time-dependent and price sensitive. While there has been very few published works that attempt to model remanufacturing decisions for products with short life cycle, we believe that there are many situations where remanufacturing short life cycle products is rewarding economically as well as environmentally. The system that we model consists of a retailer, a manufacturer, and a collector of used product from the end customers. Two different scenarios are evaluated for the system. The first is the independent situation where each party attempts to maximize his/her own total profit and the second is the joint profit model where we optimize the combined total profit for all three members of the supply chain. Manufacturer acts as the Stackelberg leader in the independently optimized scenario, while in the other the intermediate prices are determined by coordinated pricing policy. The results suggest that (i reducing the price of new products during the decline phase does not give better profit for the whole system, (ii the total profit obtained from optimizing each player is lower than the total profit of the integrated model, and (iii speed of change in demand influences the robustness of the prices as well as the total profit gained.
Deformations of the Almheiri-Polchinski model
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Kyono, Hideki; Okumura, Suguru; Yoshida, Kentaroh [Department of Physics, Kyoto University, Kitashirakawa Oiwake-cho, Kyoto 606-8502 (Japan)
2017-03-31
We study deformations of the Almheiri-Polchinski (AP) model by employing the Yang-Baxter deformation technique. The general deformed AdS{sub 2} metric becomes a solution of a deformed AP model. In particular, the dilaton potential is deformed from a simple quadratic form to a hyperbolic function-type potential similarly to integrable deformations. A specific solution is a deformed black hole solution. Because the deformation makes the spacetime structure around the boundary change drastically and a new naked singularity appears, the holographic interpretation is far from trivial. The Hawking temperature is the same as the undeformed case but the Bekenstein-Hawking entropy is modified due to the deformation. This entropy can also be reproduced by evaluating the renormalized stress tensor with an appropriate counter-term on the regularized screen close to the singularity.
Strupczewski, Witold G.; Bogdanowich, Ewa; Debele, Sisay
2016-04-01
Under Polish climate conditions the series of Annual Maxima (AM) flows are usually a mixture of peak flows of thaw- and rainfall- originated floods. The northern, lowland regions are dominated by snowmelt floods whilst in mountainous regions the proportion of rainfall floods is predominant. In many stations the majority of AM can be of snowmelt origin, but the greatest peak flows come from rainfall floods or vice versa. In a warming climate, precipitation is less likely to occur as snowfall. A shift from a snow- towards a rain-dominated regime results in a decreasing trend in mean and standard deviations of winter peak flows whilst rainfall floods do not exhibit any trace of non-stationarity. That is why a simple form of trends (i.e. linear trends) are more difficult to identify in AM time-series than in Seasonal Maxima (SM), usually winter season time-series. Hence it is recommended to analyse trends in SM, where a trend in standard deviation strongly influences the time -dependent upper quantiles. The uncertainty associated with the extrapolation of the trend makes it necessary to apply a relationship for trend which has time derivative tending to zero, e.g. we can assume a new climate equilibrium epoch approaching, or a time horizon is limited by the validity of the trend model. For both winter and summer SM time series, at least three distributions functions with trend model in the location, scale and shape parameters are estimated by means of the GAMLSS package using the ML-techniques. The resulting trend estimates in mean and standard deviation are mutually compared to the observed trends. Then, using AIC measures as weights, a multi-model distribution is constructed for each of two seasons separately. Further, assuming a mutual independence of the seasonal maxima, an AM model with time-dependent parameters can be obtained. The use of a multi-model approach can alleviate the effects of different and often contradictory trends obtained by using and identifying
OL-DEC-MDP Model for Multiagent Online Scheduling with a Time-Dependent Probability of Success
Directory of Open Access Journals (Sweden)
Cheng Zhu
2014-01-01
Full Text Available Focusing on the on-line multiagent scheduling problem, this paper considers the time-dependent probability of success and processing duration and proposes an OL-DEC-MDP (opportunity loss-decentralized Markov Decision Processes model to include opportunity loss into scheduling decision to improve overall performance. The success probability of job processing as well as the process duration is dependent on the time at which the processing is started. The probability of completing the assigned job by an agent would be higher when the process is started earlier, but the opportunity loss could also be high due to the longer engaging duration. As a result, OL-DEC-MDP model introduces a reward function considering the opportunity loss, which is estimated based on the prediction of the upcoming jobs by a sampling method on the job arrival. Heuristic strategies are introduced in computing the best starting time for an incoming job by each agent, and an incoming job will always be scheduled to the agent with the highest reward among all agents with their best starting policies. The simulation experiments show that the OL-DEC-MDP model will improve the overall scheduling performance compared with models not considering opportunity loss in heavy-loading environment.
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Mohammad Rezaei
2015-06-01
Full Text Available Generally, longwall mining-induced stress results from the stress relaxation due to destressed zone that occurs above the mined panel. Knowledge of induced stress is very important for accurate design of adjacent gateroads and intervening pillars which helps to raise the safety and productivity of longwall mining operations. This study presents a novel time-dependent analytical model for determination of the longwall mining-induced stress and investigates the coefficient of stress concentration over adjacent gates and pillars. The model is developed based on the strain energy balance in longwall mining incorporated to a rheological constitutive model of caved materials with time-varying parameters. The study site is the Tabas coal mine of Iran. In the proposed model, height of destressed zone above the mined panel, total longwall mining-induced stress, abutment angle, induced vertical stress, and coefficient of stress concentration over neighboring gates and intervening pillars are calculated. To evaluate the effect of proposed model parameters on the coefficient of stress concentration due to longwall mining, sensitivity analysis is performed based on the field data and experimental constants. Also, the results of the proposed model are compared with those of existing models. The comparative results confirm a good agreement between the proposed model and the in situ measurements. According to the obtained results, it is concluded that the proposed model can be successfully used to calculate the longwall mining-induced stress. Therefore, the optimum design of gate supports and pillar dimensions would be attainable which helps to increase the mining efficiency.
3-D time-dependent numerical model of flow patterns within a large-scale Czochralski system
Nam, Phil-Ouk; O, Sang-Kun; Yi, Kyung-Woo
2008-04-01
Silicon single crystals grown through the Czochralski (Cz) method have increased in size to 300 mm, resulting in the use of larger crucibles. The objective of this study is to investigate the continuous Cz method in a large crucible (800 mm), which is performed by inserting a polycrystalline silicon rod into the melt. The numerical model is based on a time-dependent and three-dimensional standard k- ɛ turbulent model using the analytical software package CFD-ACE+, version 2007. Wood's metal melt, which has a low melting point ( Tm=70 °C), was used as the modeling fluid. Crystal rotation given in the clockwise direction with rotation rates varying from 0 to 15 rpm, while the crucible was rotated counter-clockwise, with rotation rates between 0 and 3 rpm. The results show that asymmetrical phenomena of fluid flow arise as results of crystal and crucible rotation, and that these phenomena move with the passage of time. Near the crystal, the flow moves towards the crucible at the pole of the asymmetrical phenomena. Away from the poles, a vortex begins to form, which is strongly pronounced in the region between the poles.
Time-dependent Bloch-Maxwell modelling of 1 mJ, 200 fs seeded soft x-ray laser
International Nuclear Information System (INIS)
Zeitoun, Ph.; Oliva, E.; Fajardo, M.; Velarde, P.; Ros, D.; Sebban, S.
2010-01-01
Complete text of publication follows. Seeding of high harmonic generation in a soft x-ray plasma amplifier has been first proposed and tested by T. Ditmire and collaborators. The experiment demonstrated low amplification (*2), with a very strong background coming from the soft x-ray laser ASE. Later seeding experiments reached very high amplification factors (up to 600) in both gas (Ph. Zeitoun et al.) and solid amplifiers (Wang et at.). Surprisingly, solid amplifiers extracted less energy (90 nJ) than gas amplifier (∼ 1 μJ) with equivalent pump energy. We recently demonstrated that 50-100 μJ is achievable with adequate plasma tailoring. However, this energy is still low as compared to the 10 mJ per pulse demonstrated on the ASE soft x-ray laser running at PALS facility (Czech Republic). In order to model the seeding process of PALS soft x-ray laser, we developed a time-dependent Bloch-Maxwell model that solves coherently the pumping, amplification and saturation processes. We demonstrated that direct seeding, with femtosecond pulse, a soft x-ray plasma amplifier having gain duration of several 100s of picosecond cannot extract the stored energy keeping the output beam energy in the 100 μJ range. We proposed and fully modelled a new seeding scheme that allows to achieve 10 mJ, 200 fs soft x-ray laser.
Hayashi, K.
2013-11-01
We present a model of a time-dependent three-dimensional magnetohydrodynamics simulation of the sub-Alfvenic solar corona and super-Alfvenic solar wind with temporally varying solar-surface boundary magnetic field data. To (i) accommodate observational data with a somewhat arbitrarily evolving solar photospheric magnetic field as the boundary value and (ii) keep the divergence-free condition, we developed a boundary model, here named Confined Differential Potential Field model, that calculates the horizontal components of the magnetic field, from changes in the vertical component, as a potential field confined in a thin shell. The projected normal characteristic method robustly simulates the solar corona and solar wind, in response to the temporal variation of the boundary Br. We conduct test MHD simulations for two periods, from Carrington Rotation number 2009 to 2010 and from Carrington Rotation 2074 to 2075 at solar maximum and minimum of Cycle 23, respectively. We obtained several coronal features that a fixed boundary condition cannot yield, such as twisted magnetic field lines at the lower corona and the transition from an open-field coronal hole to a closed-field streamer. We also obtained slight improvements of the interplanetary magnetic field, including the latitudinal component, at Earth.
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Mastichiadis Apostolos
2013-12-01
Full Text Available We apply a recently developed time-dependent one-zone leptohadronic model to study the emission of the blazar Mrk 421. Both processes involving proton-photon interactions, i.e. photopair (Bethe-Heitler and photopion, have been modeled in great detail using the results of Monte Carlo simulations, like the SOPHIA event generator, in a self-consistent scheme that couples energy losses and secondary injection. We find that TeV gamma-rays can be attributed to synchrotron radiation either from relativistic protons or, alternatively, from secondary leptons produced via photohadronic processes. We also study the variability patterns that each scenario predicts and we find that while the former is more energetically favored, it is the latter that produces, in a more natural way, the usual quadratic behavior between X-rays and TeV gamma-rays. We also use the obtained SEDs to calculate in detail the expected neutron and neutrino fluxes that each model predicts.
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Quan Wang
2017-08-01
Full Text Available The ability to learn sequential behaviors is a fundamental property of our brains. Yet a long stream of studies including recent experiments investigating motor sequence learning in adult human subjects have produced a number of puzzling and seemingly contradictory results. In particular, when subjects have to learn multiple action sequences, learning is sometimes impaired by proactive and retroactive interference effects. In other situations, however, learning is accelerated as reflected in facilitation and transfer effects. At present it is unclear what the underlying neural mechanism are that give rise to these diverse findings. Here we show that a recently developed recurrent neural network model readily reproduces this diverse set of findings. The self-organizing recurrent neural network (SORN model is a network of recurrently connected threshold units that combines a simplified form of spike-timing dependent plasticity (STDP with homeostatic plasticity mechanisms ensuring network stability, namely intrinsic plasticity (IP and synaptic normalization (SN. When trained on sequence learning tasks modeled after recent experiments we find that it reproduces the full range of interference, facilitation, and transfer effects. We show how these effects are rooted in the network's changing internal representation of the different sequences across learning and how they depend on an interaction of training schedule and task similarity. Furthermore, since learning in the model is based on fundamental neuronal plasticity mechanisms, the model reveals how these plasticity mechanisms are ultimately responsible for the network's sequence learning abilities. In particular, we find that all three plasticity mechanisms are essential for the network to learn effective internal models of the different training sequences. This ability to form effective internal models is also the basis for the observed interference and facilitation effects. This suggests that
Numerical modeling of time-dependent bio-convective stagnation flow of a nanofluid in slip regime
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Rakesh Kumar
Full Text Available A numerical investigation of unsteady stagnation point flow of bioconvective nanofluid due to an exponential deforming surface is made in this research. The effects of Brownian diffusion, thermophoresis, slip velocity and thermal jump are incorporated in the nanofluid model. By utilizing similarity transformations, the highly nonlinear partial differential equations governing present nano-bioconvective boundary layer phenomenon are reduced into ordinary differential system. The resultant expressions are solved for numerical solution by employing a well-known implicit finite difference approach termed as Keller-box method (KBM. The influence of involved parameters (unsteadiness, bioconvection Schmidt number, velocity slip, thermal jump, thermophoresis, Schmidt number, Brownian motion, bioconvection Peclet number on the distributions of velocity, temperature, nanoparticle and motile microorganisms concentrations, the coefficient of local skin-friction, rate of heat transport, Sherwood number and local density motile microorganisms are exhibited through graphs and tables. Keywords: Unsteadiness, Bio-convection, Slip regime, Stagnation point flow, Numerical modeling
International Nuclear Information System (INIS)
Shore, B.W.; Eberly, J.H.
1983-01-01
The definition of a time-dependent spectrum registered by an idealized spectrometer responding to a time-varying electromagnetic field as proposed by Eberly and Wodkiewicz and subsequently applied to the spectrum of laser-induced fluorescence by Eberly, Kunasz, and Wodkiewicz is here extended to allow a stochastically fluctuating (interruption model) environment: we provide an algorithm for numerical determination of the time-dependent fluorescence spectrum of an atom subject to excitation by an intense noisy laser and interruptive relaxation
International Nuclear Information System (INIS)
Durkee, J.W. Jr.
1983-01-01
The time-dependent convective-diffusion equation with radioactive decay is solved analytically in axisymmetric cylindrical geometry for laminar and slug velocity profiles under isothermal conditions. Concentration dependent diffusion is neglected. The laminar flow solution is derived using the method of separation of variables and Frobenius' technique for constructing a series expansion about a regular singular point. The slug flow multiregion solution is obtained using the method of separation of variables. The Davidon Variable Metric Minimization algorithm is used to compute the coupling coefficients. These solutions, which describe the transport of fission products in a flowing stream, are then used to determine the concentration of radioactive material deposited on a conduit wall using a standard mass transfer model. Fission product deposition measurements for five diffusion tubes in a Fort St. Vrain High-Temperature Gas-Cooled reactor plateout probe are analyzed. Using single region slug and laminar models, the wall mass transfer coefficients, diffusion coefficients, and inlet concentrations are determined using least squares analysis. The diffusion coefficients and inlet concentrations are consistent between tubes. The derived diffusion coefficients and wall mass transfer coefficients are in relative agreement with known literature values
Time Dependent Quantum Mechanics
Morrison, Peter G.
2012-01-01
We present a systematic method for dealing with time dependent quantum dynamics, based on the quantum brachistochrone and matrix mechanics. We derive the explicit time dependence of the Hamiltonian operator for a number of constrained finite systems from this formalism. Once this has been achieved we go on to calculate the wavevector as a function of time, in order to demonstrate the use of matrix methods with respect to several concrete examples. Interesting results are derived for elliptic ...
Riva, Federico; Agliardi, Federico; Amitrano, David; Crosta, Giovanni B.
2018-01-01
Large alpine rock slopes undergo long-term evolution in paraglacial to postglacial environments. Rock mass weakening and increased permeability associated with the progressive failure of deglaciated slopes promote the development of potentially catastrophic rockslides. We captured the entire life cycle of alpine slopes in one damage-based, time-dependent 2-D model of brittle creep, including deglaciation, damage-dependent fluid occurrence, and rock mass property upscaling. We applied the model to the Spriana rock slope (Central Alps), affected by long-term instability after Last Glacial Maximum and representing an active threat. We simulated the evolution of the slope from glaciated conditions to present day and calibrated the model using site investigation data and available temporal constraints. The model tracks the entire progressive failure path of the slope from deglaciation to rockslide development, without a priori assumptions on shear zone geometry and hydraulic conditions. Complete rockslide differentiation occurs through the transition from dilatant damage to a compacting basal shear zone, accounting for observed hydraulic barrier effects and perched aquifer formation. Our model investigates the mechanical role of deglaciation and damage-controlled fluid distribution in the development of alpine rockslides. The absolute simulated timing of rock slope instability development supports a very long "paraglacial" period of subcritical rock mass damage. After initial damage localization during the Lateglacial, rockslide nucleation initiates soon after the onset of Holocene, whereas full mechanical and hydraulic rockslide differentiation occurs during Mid-Holocene, supporting a key role of long-term damage in the reported occurrence of widespread rockslide clusters of these ages.
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Saito Ayumu
2010-04-01
Full Text Available Abstract Background With an accumulation of in silico data obtained by simulating large-scale biological networks, a new interest of research is emerging for elucidating how living organism functions over time in cells. Investigating the dynamic features of current computational models promises a deeper understanding of complex cellular processes. This leads us to develop a method that utilizes structural properties of the model over all simulation time steps. Further, user-friendly overviews of dynamic behaviors can be considered to provide a great help in understanding the variations of system mechanisms. Results We propose a novel method for constructing and analyzing a so-called active state transition diagram (ASTD by using time-course simulation data of a high-level Petri net. Our method includes two new algorithms. The first algorithm extracts a series of subnets (called temporal subnets reflecting biological components contributing to the dynamics, while retaining positive mathematical qualities. The second one creates an ASTD composed of unique temporal subnets. ASTD provides users with concise information allowing them to grasp and trace how a key regulatory subnet and/or a network changes with time. The applicability of our method is demonstrated by the analysis of the underlying model for circadian rhythms in Drosophila. Conclusions Building ASTD is a useful means to convert a hybrid model dealing with discrete, continuous and more complicated events to finite time-dependent states. Based on ASTD, various analytical approaches can be applied to obtain new insights into not only systematic mechanisms but also dynamics.
Chen, Chen; Xie, Yuanchang
2014-12-01
Driving hours and rest breaks are closely related to driver fatigue, which is a major contributor to truck crashes. This study investigates the effects of driving hours and rest breaks on commercial truck driver safety. A discrete-time logistic regression model is used to evaluate the crash odds ratios of driving hours and rest breaks. Driving time is divided into 11 one hour intervals. These intervals and rest breaks are modeled as dummy variables. In addition, a Cox proportional hazards regression model with time-dependent covariates is used to assess the transient effects of rest breaks, which consists of a fixed effect and a variable effect. Data collected from two national truckload carriers in 2009 and 2010 are used. The discrete-time logistic regression result indicates that only the crash odds ratio of the 11th driving hour is statistically significant. Taking one, two, and three rest breaks can reduce drivers' crash odds by 68%, 83%, and 85%, respectively, compared to drivers who did not take any rest breaks. The Cox regression result shows clear transient effects for rest breaks. It also suggests that drivers may need some time to adjust themselves to normal driving tasks after a rest break. Overall, the third rest break's safety benefit is very limited based on the results of both models. The findings of this research can help policy makers better understand the impact of driving time and rest breaks and develop more effective rules to improve commercial truck safety. Copyright © 2014 National Safety Council and Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Zhang Wei; Ye Youbin; Tong Yindong; Ou Langbo; Hu Dan; Wang Xuejun
2011-01-01
Understanding of the magnitude of urban runoff toxicity to aquatic organisms is important for effective management of runoff quality. In this paper, the aquatic toxicity of polycyclic aromatic hydrocarbons (PAHs) in urban road runoff was evaluated through a damage assessment model. Mortality probability of the organisms representative in aquatic environment was calculated using the monitored PAHs concentration in road runoff. The result showed that the toxicity of runoff in spring was higher than those in summer. Analysis of the time-dependent toxicity of series of runoff water samples illustrated that the toxicity of runoff water in the final phase of a runoff event may be as high as those in the initial phase. Therefore, the storm runoff treatment systems or strategies designed for capture and treatment of the initial portion of runoff may be inappropriate for control of runoff toxicity. - Research highlights: → Toxicity resulting from realistic exposure patterns of urban runoff is evaluated. → Toxicity of runoff water in the final phase is as high as the initial phase. → Treatment of the initial runoff portion is inappropriate to abate runoff toxicity. - Toxicity to aquatic organisms after sequential pulsed exposure to PAHs in urban road runoff is evaluated.
Vasilyev, V.; Ludwig, H.-G.; Freytag, B.; Lemasle, B.; Marconi, M.
2018-03-01
Context. Standard spectroscopic analyses of variable stars are based on hydrostatic 1D model atmospheres. This quasi-static approach has not been theoretically validated. Aim. We aim at investigating the validity of the quasi-static approximation for Cepheid variables. We focus on the spectroscopic determination of the effective temperature Teff, surface gravity log g, microturbulent velocity ξt, and a generic metal abundance log A, here taken as iron. Methods: We calculated a grid of 1D hydrostatic plane-parallel models covering the ranges in effective temperature and gravity that are encountered during the evolution of a 2D time-dependent envelope model of a Cepheid computed with the radiation-hydrodynamics code CO5BOLD. We performed 1D spectral syntheses for artificial iron lines in local thermodynamic equilibrium by varying the microturbulent velocity and abundance. We fit the resulting equivalent widths to corresponding values obtained from our dynamical model for 150 instances in time, covering six pulsational cycles. In addition, we considered 99 instances during the initial non-pulsating stage of the temporal evolution of the 2D model. In the most general case, we treated Teff, log g, ξt, and log A as free parameters, and in two more limited cases, we fixed Teff and log g by independent constraints. We argue analytically that our approach of fitting equivalent widths is closely related to current standard procedures focusing on line-by-line abundances. Results: For the four-parametric case, the stellar parameters are typically underestimated and exhibit a bias in the iron abundance of ≈-0.2 dex. To avoid biases of this type, it is favorable to restrict the spectroscopic analysis to photometric phases ϕph ≈ 0.3…0.65 using additional information to fix the effective temperature and surface gravity. Conclusions: Hydrostatic 1D model atmospheres can provide unbiased estimates of stellar parameters and abundances of Cepheid variables for particular
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Fuchs Regina
2017-01-01
Full Text Available The early-stage sintering of thin layers of micron-sized polystyrene (PS particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C, is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (rcrit ~ 1 μm below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than rcrit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.
Inglesfield, J. E.
2007-01-01
A method of solving the time-dependent Schr\\"odinger equation is presented, in which a finite region of space is treated explicitly, with the boundary conditions for matching the wave-functions on to the rest of the system replaced by an embedding term added on to the Hamiltonian. This time-dependent embedding term is derived from the Fourier transform of the energy-dependent embedding potential, which embeds the time-independent Schr\\"odinger equation. Results are presented for a one-dimensi...
International Nuclear Information System (INIS)
Rehman, Nasir; Shashiashvili, Malkhaz
2009-01-01
The classical Garman-Kohlhagen model for the currency exchange assumes that the domestic and foreign currency risk-free interest rates are constant and the exchange rate follows a log-normal diffusion process.In this paper we consider the general case, when exchange rate evolves according to arbitrary one-dimensional diffusion process with local volatility that is the function of time and the current exchange rate and where the domestic and foreign currency risk-free interest rates may be arbitrary continuous functions of time. First non-trivial problem we encounter in time-dependent case is the continuity in time argument of the value function of the American put option and the regularity properties of the optimal exercise boundary. We establish these properties based on systematic use of the monotonicity in volatility for the value functions of the American as well as European options with convex payoffs together with the Dynamic Programming Principle and we obtain certain type of comparison result for the value functions and corresponding exercise boundaries for the American puts with different strikes, maturities and volatilities.Starting from the latter fact that the optimal exercise boundary curve is left continuous with right-hand limits we give a mathematically rigorous and transparent derivation of the significant early exercise premium representation for the value function of the American foreign exchange put option as the sum of the European put option value function and the early exercise premium.The proof essentially relies on the particular property of the stochastic integral with respect to arbitrary continuous semimartingale over the predictable subsets of its zeros. We derive from the latter the nonlinear integral equation for the optimal exercise boundary which can be studied by numerical methods
Salditch, L.; Brooks, E. M.; Stein, S.; Spencer, B. D.; Campbell, M. R.
2017-12-01
A challenge for earthquake hazard assessment is that geologic records often show large earthquakes occurring in temporal clusters separated by periods of quiescence. For example, in Cascadia, a paleoseismic record going back 10,000 years shows four to five clusters separated by approximately 1,000 year gaps. If we are still in the cluster that began 1700 years ago, a large earthquake is likely to happen soon. If the cluster has ended, a great earthquake is less likely. For a Gaussian distribution of recurrence times, the probability of an earthquake in the next 50 years is six times larger if we are still in the most recent cluster. Earthquake hazard assessments typically employ one of two recurrence models, neither of which directly incorporate clustering. In one, earthquake probability is time-independent and modeled as Poissonian, so an earthquake is equally likely at any time. The fault has no "memory" because when a prior earthquake occurred has no bearing on when the next will occur. The other common model is a time-dependent earthquake cycle in which the probability of an earthquake increases with time until one happens, after which the probability resets to zero. Because the probability is reset after each earthquake, the fault "remembers" only the last earthquake. This approach can be used with any assumed probability density function for recurrence times. We propose an alternative, Long-Term Fault Memory (LTFM), a modified earthquake cycle model where the probability of an earthquake increases with time until one happens, after which it decreases, but not necessarily to zero. Hence the probability of the next earthquake depends on the fault's history over multiple cycles, giving "long-term memory". Physically, this reflects an earthquake releasing only part of the elastic strain stored on the fault. We use the LTFM to simulate earthquake clustering along the San Andreas Fault and Cascadia. In some portions of the simulated earthquake history, events would
Selles, Nathan; King, Andrew; Proudhon, Henry; Saintier, Nicolas; Laiarinandrasana, Lucien
2017-08-01
Double notched round bars made of semi-crystalline polymer polyamide 6 (PA6) were submitted to monotonic tensile and creep tests. The two notches had a root radius of 0.45 mm, which imposes a multiaxial stress state and a state of high triaxiality in the net (minimal) section of the specimens. Tests were carried out until the failure occurred from one of the notches. The other one, unbroken but deformed under steady strain rate or steady load, was inspected using the Synchrotron Radiation Computed Tomography (SRCT) technique. These 3D through thickness inspections allowed the study of microstructural evolution at the peak stress for the monotonic tensile test and at the beginning of the tertiary creep for the creep tests. Cavitation features were assessed with a micrometre resolution within the notched region. Spatial distributions of void volume fraction ( Vf) and void morphology were studied. Voiding mechanisms were similar under steady strain rates and steady loads. The maximum values of Vf were located between the axis of revolution of the specimens and the notch surface and voids were considered as flat cylinders with a circular basis perpendicular to the loading direction. A model, based on porous plasticity, was used to simulate the mechanical response of this PA6 material under high stress triaxiality. Both macroscopic behaviour (loading curves) and voiding micro-mechanisms (radial distributions of void volume fraction) were accurately predicted using finite element simulations.
Deformation of wrought uranium: Experiments and modeling
Energy Technology Data Exchange (ETDEWEB)
McCabe, R.J., E-mail: rmccabe@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Capolungo, L. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)] [UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Marshall, P.E.; Cady, C.M.; Tome, C.N. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2010-09-15
The room temperature deformation behavior of wrought polycrystalline uranium is studied using a combination of experimental techniques and polycrystal modeling. Electron backscatter diffraction is used to analyze the primary deformation twinning modes for wrought alpha-uranium. The {l_brace}1 3 0{r_brace}<3 1 0> twinning mode is found to be the most prominent twinning mode, with minor contributions from the '{l_brace}1 7 2{r_brace}'<3 1 2> and {l_brace}1 1 2{r_brace}'<3 7 2>' twin modes. Because of the large number of deformation modes, each with limited deformation systems, a polycrystalline model is employed to identify and quantify the activity of each mode. Model predictions of the deformation behavior and texture development agree reasonably well with experimental measures and provide reliable information about deformation systems.
Linking plate reconstructions with deforming lithosphere to geodynamic models
Müller, R. D.; Gurnis, M.; Flament, N.; Seton, M.; Spasojevic, S.; Williams, S.; Zahirovic, S.
2011-12-01
While global computational models are rapidly advancing in terms of their capabilities, there is an increasing need for assimilating observations into these models and/or ground-truthing model outputs. The open-source and platform independent GPlates software fills this gap. It was originally conceived as a tool to interactively visualize and manipulate classical rigid plate reconstructions and represent them as time-dependent topological networks of editable plate boundaries. The user can export time-dependent plate velocity meshes that can be used either to define initial surface boundary conditions for geodynamic models or alternatively impose plate motions throughout a geodynamic model run. However, tectonic plates are not rigid, and neglecting plate deformation, especially that of the edges of overriding plates, can result in significant misplacing of plate boundaries through time. A new, substantially re-engineered version of GPlates is now being developed that allows an embedding of deforming plates into topological plate boundary networks. We use geophysical and geological data to define the limit between rigid and deforming areas, and the deformation history of non-rigid blocks. The velocity field predicted by these reconstructions can then be used as a time-dependent surface boundary condition in regional or global 3-D geodynamic models, or alternatively as an initial boundary condition for a particular plate configuration at a given time. For time-dependent models with imposed plate motions (e.g. using CitcomS) we incorporate the continental lithosphere by embedding compositionally distinct crust and continental lithosphere within the thermal lithosphere. We define three isostatic columns of different thickness and buoyancy based on the tectonothermal age of the continents: Archean, Proterozoic and Phanerozoic. In the fourth isostatic column, the oceans, the thickness of the thermal lithosphere is assimilated using a half-space cooling model. We also
Deformation Models Tracking, Animation and Applications
Torres, Arnau; Gómez, Javier
2013-01-01
The computational modelling of deformations has been actively studied for the last thirty years. This is mainly due to its large range of applications that include computer animation, medical imaging, shape estimation, face deformation as well as other parts of the human body, and object tracking. In addition, these advances have been supported by the evolution of computer processing capabilities, enabling realism in a more sophisticated way. This book encompasses relevant works of expert researchers in the field of deformation models and their applications. The book is divided into two main parts. The first part presents recent object deformation techniques from the point of view of computer graphics and computer animation. The second part of this book presents six works that study deformations from a computer vision point of view with a common characteristic: deformations are applied in real world applications. The primary audience for this work are researchers from different multidisciplinary fields, s...
Johanson, I. A.; Miklius, A.; Okubo, P.; Montgomery-Brown, E. K.
2017-12-01
Mauna Loa volcano is the largest active volcano on earth and in the 20thcentury produced roughly one eruption every seven years. The 33-year quiescence since its last eruption 1984 has been punctuated by three inflation episodes where magma likely entered the shallow plumbing system, but was not erupted. The most recent began in 2014 and is ongoing. Unlike prior inflation episodes, the current one is accompanied by a significant increase in shallow seismicity, a pattern that is similar to earlier pre-eruptive periods. We apply the Kalman filter based Network Inversion Filter (NIF) to the 2014-present inflation episode using data from a 27 station continuous GPS network on Mauna Loa. The model geometry consists of a point volume source and tabular, dike-like body, which have previously been shown to provide a good fit to deformation data from a 2004-2009 inflation episode. The tabular body is discretized into 1km x 1km segments. For each day, the NIF solves for the rates of opening on the tabular body segments (subject to smoothing and positivity constraints), volume change rate in the point source, and slip rate on a deep décollement fault surface, which is constrained to a constant (no transient slip allowed). The Kalman filter in the NIF provides for smoothing both forwards and backwards in time. The model shows that the 2014-present inflation episode occurred as several sub-events, rather than steady inflation. It shows some spatial variability in the location of the inflation sub-events. In the model, opening in the tabular body is initially concentrated below the volcano's summit, in an area roughly outlined by shallow seismicity. In October, 2015 opening in the tabular body shifts to be centered beneath the southwest portion of the summit and seismicity becomes concentrated in this area. By late 2016, the opening rate on the tabular body decreases and is once again under the central part of summit. This modeling approach has allowed us to track these
Li, Jian; Chen, Rong; Yao, Qing-Yu; Liu, Sheng-Jun; Tian, Xiu-Yun; Hao, Chun-Yi; Lu, Wei; Zhou, Tian-Yan
2018-03-01
Dexamethasone (DEX) is the substrate of CYP3A. However, the activity of CYP3A could be induced by DEX when DEX was persistently administered, resulting in auto-induction and time-dependent pharmacokinetics (pharmacokinetics with time-dependent clearance) of DEX. In this study we investigated the pharmacokinetic profiles of DEX after single or multiple doses in human breast cancer xenograft nude mice and established a semi-mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) model for characterizing the time-dependent PK of DEX as well as its anti-cancer effect. The mice were orally given a single or multiple doses (8 mg/kg) of DEX, and the plasma concentrations of DEX were assessed using LC-MS/MS. Tumor volumes were recorded daily. Based on the experimental data, a two-compartment model with first order absorption and time-dependent clearance was established, and the time-dependence of clearance was modeled by a sigmoid E max equation. Moreover, a semi-mechanism-based PK/PD model was developed, in which the auto-induction effect of DEX on its metabolizing enzyme CYP3A was integrated and drug potency was described using an E max equation. The PK/PD model was further used to predict the drug efficacy when the auto-induction effect was or was not considered, which further revealed the necessity of adding the auto-induction effect into the final PK/PD model. This study established a semi-mechanism-based PK/PD model for characterizing the time-dependent pharmacokinetics of DEX and its anti-cancer effect in breast cancer xenograft mice. The model may serve as a reference for DEX dose adjustments or optimization in future preclinical or clinical studies.
International Nuclear Information System (INIS)
Jonas, M.; Olendrzynski, K.; Elzen, M. den
1991-10-01
The Intergovernmental Panel on Climate Change (IPCC) is placing increasing emphasis on the use of time-dependent impact models that are linked with energy-emission accounting frameworks and models that predict in a time-dependent fashion important variables such as atmospheric concentrations of greenhouse gases, surface temperature and precipitation. Integrating these tools (greenhouse gas emission strategies, atmospheric processes, ecological impacts) into what is called an integrated assessment model will assist policymakers in the IPCC and elsewhere to assess the impacts of a wide variety of emission strategies. The Integrated Model to Assess the Greenhouse Effect (IMAGE; developed at RIVM) represents such an integrated assessment model which already calculates historical and future effects of greenhouse gas emissions on global surface temperature, sea level rise and other ecological and socioeconomic impacts. However, to be linked to environmental impact models such as the Global Vegetation Model and the Timber Assessment Model, both of which are under development at RIVM and IIASA, IMAGE needs to be regionalized in terms of temperature and precipitation output. These key parameters will then enable the above environmental impact models to be run in a time-dependent mode. In this paper we lay the scientific and numerical basis for a two-dimensional Energy Balance Model (EBM) to be integrated into the climate module of IMAGE which will ultimately provide scenarios of surface temperature and precipitation, resolved with respect to latitude and height. This paper will deal specifically with temperature; following papers will deal with precipitation. So far, the relatively simple EBM set up in this paper resolves mean annual surface temperatures on a regional scale defined by 10 deg latitude bands. In addition, we can concentrate on the implementation of the EBM into IMAGE, i.e., on the steering mechanism itself. Both reasons justify the time and effort put into
Directory of Open Access Journals (Sweden)
Koktan Jiří
2014-12-01
Full Text Available The paper proposes an implementation of creep analysis of reinforced concrete structures which utilizes the B3 model and the direct stiffness method for reinforced concrete frames. The analysis is based on a numerical integration and it is implemented in an algorithmic programming language. There is presented a solution with the mentioned approaches which is compared with solution based on the EN 1992-1-1 technical standard.
International Nuclear Information System (INIS)
Piras, Daniele; Sadeghian, Hamed
2017-01-01
Ultrasound atomic force microscopy (US-AFM) has been used for subsurface imaging of nanostructures. The contact stiffness variations have been suggested as the origin of the image contrast. Therefore, to analyze the image contrast, the local changes in the contact stiffness due to the presence of subsurface features should be calculated. So far, only static simulations have been conducted to analyze the local changes in the contact stiffness and, consequently, the contrast in US-AFM. Such a static approach does not fully represent the real US-AFM experiment, where an ultrasound wave is launched either into the sample or at the tip, which modulates the contact stiffness. This is a time-dependent nonlinear dynamic problem rather than a static and stationary one. This paper presents dynamic 3D ultrasound analysis of contact stiffness in US-AFM (in contrast to static analysis) to realistically predict the changes in contact stiffness and thus the changes in the subsurface image contrast. The modulation frequency also influences the contact stiffness variations and, thus, the image contrast. The three-dimensional time-dependent ultrasound analysis will greatly aid in the contrast optimization of subsurface nano imaging with US-AFM. (paper)
Deformable Models for Eye Tracking
DEFF Research Database (Denmark)
Vester-Christensen, Martin; Leimberg, Denis; Ersbøll, Bjarne Kjær
2005-01-01
A deformable template method for eye tracking on full face images is presented. The strengths of the method are that it is fast and retains accuracy independently of the resolution. We compare the me\\$\\backslash\\$-thod with a state of the art active contour approach, showing that the heuristic...
Time dependent drift Hamiltonian
International Nuclear Information System (INIS)
Boozer, A.H.
1982-04-01
The motion of individual charged particles in a given magnetic and an electric fields is discussed. An idea of a guiding center distribution function f is introduced. The guiding center distribution function is connected to the asymptotic Hamiltonian through the drift kinetic equation. The general non-stochastic magnetic field can be written in a contravariant and a covariant forms. The drift Hamiltonian is proposed, and the canonical gyroradius is presented. The proposed drift Hamiltonian agrees with Alfven's drift velocity to lowest non-vanishing order in the gyroradius. The relation between the exact, time dependent equations of motion and the guiding center equation is clarified by a Lagrangian analysis. The deduced Lagrangian represents the drift motion. (Kato, T.)
International Nuclear Information System (INIS)
Menouar, Salah; Maamache, Mustapha; Choi, Jeong Ryeol
2010-01-01
The dynamics of the time-dependent coupled oscillator model for the motion of a charged particle subjected to a time-dependent external magnetic field is investigated. We use the canonical transformation approach for the classical treatment of the system, whereas the unitary transformation approach is used in managing the system in the framework of quantum mechanics. For both approaches, the original system is transformed into a much more simple system that is the sum of two independent harmonic oscillators with time-dependent frequencies. We therefore easily identify the wavefunctions in the transformed system with the help of an invariant operator of the system. The full wavefunctions in the original system are derived from the inverse unitary transformation of the wavefunctions associated with the transformed system.
Klinkusch, Stefan; Saalfrank, Peter; Klamroth, Tillmann
2009-09-21
We report simulations of laser-pulse driven many-electron dynamics by means of a simple, heuristic extension of the time-dependent configuration interaction singles (TD-CIS) approach. The extension allows for the treatment of ionizing states as nonstationary states with a finite, energy-dependent lifetime to account for above-threshold ionization losses in laser-driven many-electron dynamics. The extended TD-CIS method is applied to the following specific examples: (i) state-to-state transitions in the LiCN molecule which correspond to intramolecular charge transfer, (ii) creation of electronic wave packets in LiCN including wave packet analysis by pump-probe spectroscopy, and, finally, (iii) the effect of ionization on the dynamic polarizability of H(2) when calculated nonperturbatively by TD-CIS.
Shapes and dynamics from the time-dependent mean field
International Nuclear Information System (INIS)
Stevenson, P.D.; Goddard, P.M.; Rios, A.
2015-01-01
Explaining observed properties in terms of underlying shape degrees of freedom is a well-established prism with which to understand atomic nuclei. Self-consistent mean-field models provide one tool to understand nuclear shapes, and their link to other nuclear properties and observables. We present examples of how the time-dependent extension of the mean-field approach can be used in particular to shed light on nuclear shape properties, particularly looking at the giant resonances built on deformed nuclear ground states, and at dynamics in highly-deformed fission isomers. Example calculations are shown of 28 Si in the first case, and 240 Pu in the latter case
Zernike polynomial based Rayleigh-Ritz model of a piezoelectric unimorph deformable mirror
CSIR Research Space (South Africa)
Long, CS
2012-04-01
Full Text Available Piezoelectric bimorph- or unimorph-type deformable mirrors are commonly used in adaptive optics to correct for time-dependent phase aberrations. In the optics community, the surface deformations that deformable mirrors are required to achieve...
DEFF Research Database (Denmark)
Christensen, E; Altman, D G; Neuberger, J
1993-01-01
BACKGROUND: The precision of current prognostic models in primary biliary cirrhosis (PBC) is rather low, partly because they are based on data from just one time during the course of the disease. The aim of this study was to design a new, more precise prognostic model by incorporating follow......-up data in the development of the model. METHODS: We have performed Cox regression analyses with time-dependent variables in 237 PBC patients followed up regularly for up to 11 years. The validity of the obtained models was tested by comparing predicted and observed survival in 147 independent PBC...... patients followed for up to 6 years. RESULTS: In the obtained model the following time-dependent variables independently indicated a poor prognosis: high bilirubin, low albumin, ascites, gastrointestinal bleeding, and old age. When including histological variables, cirrhosis, central cholestasis, and low...
International Nuclear Information System (INIS)
Koo, Shigeru; Inagaki, Manabu
2010-06-01
In the high-level radioactive waste (HLW) disposal system, numerical evaluation for radionuclide transport with the time-dependent parameters is necessary to evaluate various scenarios. In H12 report, numerical calculation code MESHNOTE and TIGER were used for the evaluation of some natural phenomena scenarios that had to handle the time-dependent parameters. In the future, the necessity of handling the time-dependent parameters will be expected to increase, and more efficient calculation and improvement of quality control of input/output parameters will be required. Therefore, for the purpose of corresponding this requirement, a radionuclide transport model has been developed on the GoldSim platform. The GoldSim is a general simulation software, that was used for the computation modeling of Yucca Mountain Project. The conceptual model, the mathematical model and the verification of the GoldSim model are described in this report. In the future, application resources on this report will be able to upgrade for perturbation scenarios analysis model and other conceptual models. (author)
Frank, Till D; Kiyatkin, Anatoly; Cheong, Alex; Kholodenko, Boris N
2017-06-01
Signal integration determines cell fate on the cellular level, affects cognitive processes and affective responses on the behavioural level, and is likely to be involved in psychoneurobiological processes underlying mood disorders. Interactions between stimuli may subjected to time effects. Time-dependencies of interactions between stimuli typically lead to complex cell responses and complex responses on the behavioural level. We show that both three-factor models and time series models can be used to uncover such time-dependencies. However, we argue that for short longitudinal data the three factor modelling approach is more suitable. In order to illustrate both approaches, we re-analysed previously published short longitudinal data sets. We found that in human embryonic kidney 293 cells cells the interaction effect in the regulation of extracellular signal-regulated kinase (ERK) 1 signalling activation by insulin and epidermal growth factor is subjected to a time effect and dramatically decays at peak values of ERK activation. In contrast, we found that the interaction effect induced by hypoxia and tumour necrosis factor-alpha for the transcriptional activity of the human cyclo-oxygenase-2 promoter in HEK293 cells is time invariant at least in the first 12-h time window after stimulation. Furthermore, we applied the three-factor model to previously reported animal studies. In these studies, memory storage was found to be subjected to an interaction effect of the beta-adrenoceptor agonist clenbuterol and certain antagonists acting on the alpha-1-adrenoceptor / glucocorticoid-receptor system. Our model-based analysis suggests that only if the antagonist drug is administer in a critical time window, then the interaction effect is relevant. © The authors 2016. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.
International Nuclear Information System (INIS)
Tanaka, Yasunori
2006-01-01
A time-dependent, two-dimensional, two-temperature and chemical non-equilibrium model was developed for high-power Ar-N 2 pulse-modulated inductively coupled plasmas (PMICPs) at atmospheric pressure. The high-power PMICP is a new technique for sustaining high-power induction plasmas. It can control the plasma temperature and radical densities in the time domain. The PMICP promotes non-equilibrium effects by a sudden application of electric field, even in the high-power density plasmas. The developed model accounts separately for the time-dependent energy conservation equations of electrons and heavy particles. This model also considers reaction heat effects and energy transfer between electrons and heavy particles as well as enthalpy flow resulting from diffusion caused by the particle density gradient. Chemical non-equilibrium effects are also taken into account by solving time-dependent mass conservation equations for each particle, considering diffusion, convection and net production terms resulting from 30 chemical reactions. Transport and thermodynamic properties of Ar-N 2 plasmas are calculated self-consistently using the first order approximation of the Chapman-Enskog method at each position and iteration using the local particle composition, heavy particle temperature and electron temperature. This model is useful to discuss time evolution in temperature, gas flow fields and distribution of chemical species
Directory of Open Access Journals (Sweden)
Kundu Antara
2013-01-01
Full Text Available The present paper deals with an economic order quantity (EOQ model of an inventory problem with alternating demand rate: (i For a certain period, the demand rate is a non linear function of the instantaneous inventory level. (ii For the rest of the cycle, the demand rate is time dependent. The time at which demand rate changes, may be deterministic or uncertain. The deterioration rate of the item is time dependent. The holding cost and shortage cost are taken as a linear function of time. The total cost function per unit time is obtained. Finally, the model is solved using a gradient based non-linear optimization technique (LINGO and is illustrated by a numerical example.
2008-08-01
Current hurricane evacuation transportation modeling uses an approach fashioned after the : traditional four-step procedure applied in urban transportation planning. One of the limiting : features of this approach is that it models traffic in a stati...
Energy Technology Data Exchange (ETDEWEB)
Sarler, B [Institut Jozef Stefan, Ljubljana (Yugoslavia)
1987-07-01
The basic principles of the boundary element method numerical treatment of the radial flow heat diffusion equation are presented. The algorithm copes the time dependent Dirichlet and Neumann boundary conditions, temperature dependent material properties and regions from different materials in thermal contact. It is verified on the several analytically obtained test cases. The developed method is used for the modelling of unsteady radial heat flow in pressurized water reactor fuel rod. (author)
DEFF Research Database (Denmark)
Zhou, H. W.; Yi, H. Y.; Mishnaevsky, Leon
2017-01-01
A modeling approach to time-dependent property of Glass Fiber Reinforced Polymers (GFRP) composites is of special interest for quantitative description of long-term behavior. An electronic creep machine is employed to investigate the time-dependent deformation of four specimens of dog-bond-shaped......A modeling approach to time-dependent property of Glass Fiber Reinforced Polymers (GFRP) composites is of special interest for quantitative description of long-term behavior. An electronic creep machine is employed to investigate the time-dependent deformation of four specimens of dog......-bond-shaped GFRP composites at various stress level. A negative exponent function based on structural changes is introduced to describe the damage evolution of material properties in the process of creep test. Accordingly, a new creep constitutive equation, referred to fractional derivative Maxwell model...... by the fractional derivative Maxwell model proposed in the paper are in a good agreement with the experimental data. It is shown that the new creep constitutive model proposed in the paper needs few parameters to represent various time-dependent behaviors....
Energy Technology Data Exchange (ETDEWEB)
Verley, Jason C.; Axness, Carl L.; Hembree, Charles Edward; Keiter, Eric Richard; Kerr, Bert (New Mexico Institute of Mining and Technology, Socorro, NM)
2012-04-01
Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools such as SPICE [1] can be used to analyze these threats, and typically rely on compact models for individual electrical components such as transistors and diodes. Compact models consist of a handful of differential and/or algebraic equations, and are derived by making simplifying assumptions to any of the many semiconductor transport equations. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of qualitative approximation, rather than mathematically correct solutions to the ambipolar diffusion equation. A practical consequence of this inaccuracy is that a given model calibration is trustworthy over only a narrow range of operating conditions. This report describes work to produce improved compact models for photocurrent. Specifically, an analytic model is developed for epitaxial diode structures that have a highly doped subcollector. The analytic model is compared with both numerical TCAD calculations, as well as the compact model described in reference [2]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the compact model from reference [2].
Deformed baryons: constituent quark model vs. bag model
International Nuclear Information System (INIS)
Iwamura, Y.; Nogami, Y.
1985-01-01
Recently Bhaduri et al. developed a nonrelativistic constituent quark model for deformed baryons. In that model the quarks move in a deformable mean field, and the deformation parameters are determined by minimizing the quark energy subject to the constraint of volume conservation. This constraint is an ad hoc assumption. It is shown that, starting with a bag model, a model similar to that of Bhaduri et al. can be constructed. The deformation parameters are determined by the pressure balance on the bag surface. There is, however, a distinct difference between the two models with respect to the state dependence of the ''volume''. Implications of this difference are discussed
Modelling deformation and fracture in confectionery wafers
Energy Technology Data Exchange (ETDEWEB)
Mohammed, Idris K.; Charalambides, Maria N.; Williams, J. Gordon; Rasburn, John [Mechanical Engineering Department, Imperial College London, South Kensington, London, SW7 2AZ, United Kingdom and Nestec York Ltd., Nestlé Product Technology Centre, Haxby Road, PO Box 204, York YO91 1XY (United Kingdom)
2015-01-22
The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.
Extendable linearised adjustment model for deformation analysis
Hiddo Velsink
2015-01-01
Author supplied: "This paper gives a linearised adjustment model for the affine, similarity and congruence transformations in 3D that is easily extendable with other parameters to describe deformations. The model considers all coordinates stochastic. Full positive semi-definite covariance matrices
Extendable linearised adjustment model for deformation analysis
Velsink, H.
2015-01-01
This paper gives a linearised adjustment model for the affine, similarity and congruence transformations in 3D that is easily extendable with other parameters to describe deformations. The model considers all coordinates stochastic. Full positive semi-definite covariance matrices and correlation
On parameter estimation in deformable models
DEFF Research Database (Denmark)
Fisker, Rune; Carstensen, Jens Michael
1998-01-01
Deformable templates have been intensively studied in image analysis through the last decade, but despite its significance the estimation of model parameters has received little attention. We present a method for supervised and unsupervised model parameter estimation using a general Bayesian form...
Directory of Open Access Journals (Sweden)
Vinod Kumar Mishra
2013-06-01
Full Text Available Purpose: The purpose of this paper to develop an inventory model for instantaneous deteriorating items with the consideration of the facts that the deterioration rate can be controlled by using the preservation technology (PT and the holding cost & demand rate both are linear function of time which was treated as constant in most of the deteriorating inventory model. Design/methodology/approach: Developed the mathematical equation of deterministic deteriorating inventory model in which demand rate and holding cost both is linear function of time, deterioration rate is constant, backlogging rate is variable and depend on the length of the next replenishment, shortages are allowed and partially backlogged and obtain an analytical solution which optimizes the total cost of the proposed inventory model. Findings: The model can be applied for optimizing the total inventory cost of deteriorating items inventory for such business enterprises where they use the preservation technology to control the deterioration rate under other assumptions of the model. Originality/value: The inventory system for deteriorating items has been an object of study for a long time, but little is known about the effect of investing in reducing the rate of product deterioration and their significant impact in the business. The proposed model is effective as well as efficient for the business organization that uses the preservation technology to reduce the deterioration rate of the instantaneous deteriorating items of the inventory.
DEFF Research Database (Denmark)
Garcia-Aymerich, Judith; Lange, Peter; Serra, Ignasi
2008-01-01
PURPOSE: Results from longitudinal studies about the association between physical activity and chronic obstructive pulmonary disease (COPD) may have been biased because they did not properly adjust for time-dependent confounders. Marginal structural models (MSMs) have been proposed to address...... this type of confounding. We sought to assess the presence of time-dependent confounding in the association between physical activity and COPD development and course by comparing risk estimates between standard statistical methods and MSMs. METHODS: By using the population-based cohort Copenhagen City Heart...... Study, 6,568 subjects selected from the general population in 1976 were followed up until 2004 with three repeated examinations. RESULTS: Moderate to high compared with low physical activity was associated with a reduced risk of developing COPD both in the standard analysis (odds ratio [OR] 0.76, p = 0...
Benguigui, Madeleine; Alishekevitz, Dror; Timaner, Michael; Shechter, Dvir; Raviv, Ziv; Benzekry, Sebastien; Shaked, Yuval
2018-01-05
It has recently been suggested that pro-tumorigenic host-mediated processes induced in response to chemotherapy counteract the anti-tumor activity of therapy, and thereby decrease net therapeutic outcome. Here we use experimental data to formulate a mathematical model describing the host response to different doses of paclitaxel (PTX) chemotherapy as well as the duration of the response. Three previously described host-mediated effects are used as readouts for the host response to therapy. These include the levels of circulating endothelial progenitor cells in peripheral blood and the effect of plasma derived from PTX-treated mice on migratory and invasive properties of tumor cells in vitro . A first set of mathematical models, based on basic principles of pharmacokinetics/pharmacodynamics, did not appropriately describe the dose-dependence and duration of the host response regarding the effects on invasion. We therefore provide an alternative mathematical model with a dose-dependent threshold, instead of a concentration-dependent one, that describes better the data. This model is integrated into a global model defining all three host-mediated effects. It not only precisely describes the data, but also correctly predicts host-mediated effects at different doses as well as the duration of the host response. This mathematical model may serve as a tool to predict the host response to chemotherapy in cancer patients, and therefore may be used to design chemotherapy regimens with improved therapeutic outcome by minimizing host mediated effects.
Energy Technology Data Exchange (ETDEWEB)
Maurya, D. Ch., E-mail: dcmaurya563@gmail.com; Zia, R., E-mail: rashidzya@gmail.com; Pradhan, A., E-mail: pradhan.anirudh@gmail.com [GLA University, Department of Mathematics, Institute of Applied Sciences and Humanities (India)
2016-10-15
We discuss a spatially homogeneous and anisotropic string cosmological models in the Brans–Dicke theory of gravitation. For a spatially homogeneous metric, it is assumed that the expansion scalar θ is proportional to the shear scalar σ. This condition leads to A = kB{sup m}, where k and m are constants. With these assumptions and also assuming a variable scale factor a = a(t), we find solutions of the Brans–Dicke field equations. Various phenomena like the Big Bang, expanding universe, and shift from anisotropy to isotropy are observed in the model. It can also be seen that in early stage of the evolution of the universe, strings dominate over particles, whereas the universe is dominated by massive strings at the late time. Some physical and geometrical behaviors of the models are also discussed and observed to be in good agreement with the recent observations of SNe la supernovae.
CSIR Research Space (South Africa)
Bernhardi, EH
2008-01-01
Full Text Available that determines the temperature and the thermally induced stresses in isotropic rods is presented. Even though the model is developed for isotropic rods, it is shown that it can also be used to accurately estimate the thermal effects in anisotropic rods...
Zhang, Ziyu; Yuan, Lang; Lee, Peter D; Jones, Eric; Jones, Julian R
2014-11-01
Bone augmentation implants are porous to allow cellular growth, bone formation and fixation. However, the design of the pores is currently based on simple empirical rules, such as minimum pore and interconnects sizes. We present a three-dimensional (3D) transient model of cellular growth based on the Navier-Stokes equations that simulates the body fluid flow and stimulation of bone precursor cellular growth, attachment, and proliferation as a function of local flow shear stress. The model's effectiveness is demonstrated for two additive manufactured (AM) titanium scaffold architectures. The results demonstrate that there is a complex interaction of flow rate and strut architecture, resulting in partially randomized structures having a preferential impact on stimulating cell migration in 3D porous structures for higher flow rates. This novel result demonstrates the potential new insights that can be gained via the modeling tool developed, and how the model can be used to perform what-if simulations to design AM structures to specific functional requirements. © 2014 Wiley Periodicals, Inc.
An Efficient Virtual Trachea Deformation Model
Directory of Open Access Journals (Sweden)
Cui Tong
2016-01-01
Full Text Available In this paper, we present a virtual tactile model with the physically based skeleton to simulate force and deformation between a rigid tool and the soft organ. When the virtual trachea is handled, a skeleton model suitable for interactive environments is established, which consists of ligament layers, cartilage rings and muscular bars. In this skeleton, the contact force goes through the ligament layer, and produces the load effects of the joints , which are connecting the ligament layer and cartilage rings. Due to the nonlinear shape deformation inside the local neighbourhood of a contact region, the RBF method is applied to modify the result of linear global shape deformation by adding the nonlinear effect inside. Users are able to handle the virtual trachea, and the results from the examples with the mechanical properties of the human trachea are given to demonstrate the effectiveness of the approach.
Uthayakumar, R.; Tharani, S.
2017-12-01
Recently, much emphasis has given to study the control and maintenance of production inventories of the deteriorating items. Rework is one of the main issues in reverse logistic and green supply chain, since it can reduce production cost and the environmental problem. Many researchers have focused on developing rework model, but few of them have developed model for deteriorating items. Due to this fact, we take up productivity and rework with deterioration as the major concern in this paper. In this paper, a production-inventory model with deteriorative items in which one cycle has n production setups and one rework setup (n, 1) policy is considered for deteriorating items with stock-dependent demand in case 1 and exponential demand in case 2. An effective iterative solution procedure is developed to achieve optimal time, so that the total cost of the system is minimized. Numerical and sensitivity analyses are discussed to examine the outcome of the proposed solution procedure presented in this research.
Energy Technology Data Exchange (ETDEWEB)
Schneider, E.A. [Department of Mechanical Engineering, University of Texas, Austin, TX (United States); Deinert, M.R. [Theoretical and Applied Mechanics, Cornell University, 219 Kimball Hall, Ithaca, NY 14853 (United States)]. E-mail: mrd6@cornell.edu; Cady, K.B. [Theoretical and Applied Mechanics, Cornell University, 219 Kimball Hall, Ithaca, NY 14853 (United States)
2006-10-15
The balance of isotopes in a nuclear reactor core is key to understanding the overall performance of a given fuel cycle. This balance is in turn most strongly affected by the time and energy-dependent neutron flux. While many large and involved computer packages exist for determining this spectrum, a simplified approach amenable to rapid computation is missing from the literature. We present such a model, which accepts as inputs the fuel element/moderator geometry and composition, reactor geometry, fuel residence time and target burnup and we compare it to OECD/NEA benchmarks for homogeneous MOX and UOX LWR cores. Collision probability approximations to the neutron transport equation are used to decouple the spatial and energy variables. The lethargy dependent neutron flux, governed by coupled integral equations for the fuel and moderator/coolant regions is treated by multigroup thermalization methods, and the transport of neutrons through space is modeled by fuel to moderator transport and escape probabilities. Reactivity control is achieved through use of a burnable poison or adjustable control medium. The model calculates the buildup of 24 actinides, as well as fission products, along with the lethargy dependent neutron flux and the results of several simulations are compared with benchmarked standards.
Time-dependent crack growth and fracture in concrete
International Nuclear Information System (INIS)
Zhou Fan Ping.
1992-02-01
The objectives of this thesis are to study time-dependent fracture behaviour in concrete. The thesis consists of an experimental study, costitutive modelling and numerical analysis. The experimental study was undertaken to investigate the influences of time on material properties for the fracture process zone and on crack growth and fracture in plain concrete structures. The experiments include tensile relaxation tests, bending tests on notched beams to determine fracture energy at varying deflection rates, and sustained bending and compact tensile tests. From the tensile relaxation tests, the envelope of the σ-w relation does not seem to be influenced by holding periods, though some local detrimental effect does occur. Fracture energy seems to decrease as rates become slower. In the sustained loading tests, deformation (deflection or CMOD) growth curves display three stages, as usually observed in a creep rupture test. The secondary stage dominates the whole failure lifetime, and the secondary deformation rate appears to have good correlation with the failure lifetime. A crack model for time-dependent fracture is proposed, by applying the idea of the Fictitious Crack Model. In this model, a modified Maxwell model is introduced for the fracture process zone incorporated with the static σ-w curve as a failure criterion, based on the observation of the tensile relaxation tests. The time-dependent σ-w curve is expressed in an incremental law. The proposed model has been implemented in a finite element program and applied to simulating sustained flexural and compact tensile tests. Numerical analysis includes simulations of crack growth, load-CMOD curves, stress-failure lifetime curves, size effects on failure life etc. The numerical results indicate that the model seems to be able to properly predict the main features of time-dependent fracture behaviour in concrete, as compared with the experimental results. 97 refs
Molina-Romero, Miguel; Gómez, Pedro A; Sperl, Jonathan I; Czisch, Michael; Sämann, Philipp G; Jones, Derek K; Menzel, Marion I; Menze, Bjoern H
2018-03-23
The compartmental nature of brain tissue microstructure is typically studied by diffusion MRI, MR relaxometry or their correlation. Diffusion MRI relies on signal representations or biophysical models, while MR relaxometry and correlation studies are based on regularized inverse Laplace transforms (ILTs). Here we introduce a general framework for characterizing microstructure that does not depend on diffusion modeling and replaces ill-posed ILTs with blind source separation (BSS). This framework yields proton density, relaxation times, volume fractions, and signal disentanglement, allowing for separation of the free-water component. Diffusion experiments repeated for several different echo times, contain entangled diffusion and relaxation compartmental information. These can be disentangled by BSS using a physically constrained nonnegative matrix factorization. Computer simulations, phantom studies, together with repeatability and reproducibility experiments demonstrated that BSS is capable of estimating proton density, compartmental volume fractions and transversal relaxations. In vivo results proved its potential to correct for free-water contamination and to estimate tissue parameters. Formulation of the diffusion-relaxation dependence as a BSS problem introduces a new framework for studying microstructure compartmentalization, and a novel tool for free-water elimination. © 2018 International Society for Magnetic Resonance in Medicine.
International Nuclear Information System (INIS)
Requist, Ryan; Pankratov, Oleg
2011-01-01
We prove that if the two-body terms in the equation of motion for the one-body reduced density matrix are approximated by ground-state functionals, the eigenvalues of the one-body reduced density matrix (occupation numbers) remain constant in time. This deficiency is related to the inability of such an approximation to account for relative phases in the two-body reduced density matrix. We derive an exact differential equation giving the functional dependence of these phases in an interacting Landau-Zener model and study their behavior in short- and long-time regimes. The phases undergo resonances whenever the occupation numbers approach the boundaries of the interval [0,1]. In the long-time regime, the occupation numbers display correlation-induced oscillations and the memory dependence of the functionals assumes a simple form.
Directory of Open Access Journals (Sweden)
Max J Feldman
2017-06-01
Full Text Available Vertical growth of plants is a dynamic process that is influenced by genetic and environmental factors and has a pronounced effect on overall plant architecture and biomass composition. We have performed six controlled growth trials of an interspecific Setaria italica x Setaria viridis recombinant inbred line population to assess how the genetic architecture of plant height is influenced by developmental queues, water availability and planting density. The non-destructive nature of plant height measurements has enabled us to monitor height throughout the plant life cycle in both field and controlled environments. We find that plant height is reduced under water limitation and high density planting and affected by growth environment (field vs. growth chamber. The results support a model where plant height is a heritable, polygenic trait and that the major genetic loci that influence plant height function independent of growth environment. The identity and contribution of loci that influence height changes dynamically throughout development and the reduction of growth observed in water limited environments is a consequence of delayed progression through the genetic program which establishes plant height in Setaria. In this population, alleles inherited from the weedy S. viridis parent act to increase plant height early, whereas a larger number of small effect alleles inherited from the domesticated S. italica parent collectively act to increase plant height later in development.
Feldman, Max J; Paul, Rachel E; Banan, Darshi; Barrett, Jennifer F; Sebastian, Jose; Yee, Muh-Ching; Jiang, Hui; Lipka, Alexander E; Brutnell, Thomas P; Dinneny, José R; Leakey, Andrew D B; Baxter, Ivan
2017-06-01
Vertical growth of plants is a dynamic process that is influenced by genetic and environmental factors and has a pronounced effect on overall plant architecture and biomass composition. We have performed six controlled growth trials of an interspecific Setaria italica x Setaria viridis recombinant inbred line population to assess how the genetic architecture of plant height is influenced by developmental queues, water availability and planting density. The non-destructive nature of plant height measurements has enabled us to monitor height throughout the plant life cycle in both field and controlled environments. We find that plant height is reduced under water limitation and high density planting and affected by growth environment (field vs. growth chamber). The results support a model where plant height is a heritable, polygenic trait and that the major genetic loci that influence plant height function independent of growth environment. The identity and contribution of loci that influence height changes dynamically throughout development and the reduction of growth observed in water limited environments is a consequence of delayed progression through the genetic program which establishes plant height in Setaria. In this population, alleles inherited from the weedy S. viridis parent act to increase plant height early, whereas a larger number of small effect alleles inherited from the domesticated S. italica parent collectively act to increase plant height later in development.
Numerical Modeling of Subglacial Sediment Deformation
DEFF Research Database (Denmark)
Damsgaard, Anders
2015-01-01
may cause mass loss in the near future to exceed current best estimates. Ice flow in larger ice sheets focuses in fast-moving streams due to mechanical non-linearity of ice. These ice streams often move at velocities several magnitudes larger than surrounding ice and consequentially constitute...... glaciers move by deforming their sedimentary beds. Several modern ice streams, in particular, move as plug flows due to basal sediment deformation. An intense and long-winded discussion about the appropriate description for subglacial sediment mechanics followed this discovery, with good reason...... incompatible with commonly accepted till rheology models. Variation in pore-water pressure proves to cause reorganization in the internal stress network and leads to slow creeping deformation. The rate of creep is non-linearly dependent on the applied stresses. Granular creep can explain slow glacial...
International Nuclear Information System (INIS)
Hartmaier, Alexander; Buehler, Markus J.; Gao, Huajian
2005-01-01
The time-dependent irreversible deformation of polycrystalline thin metal films on substrates is investigated using two-dimensional discrete dislocation dynamics models incorporating essential parameters determined from atomistic studies. The work is focused on the mechanical properties of uncapped films, where diffusive processes play an important role. The simulations incorporate dislocation climb along the grain boundary as well as conservative glide. Despite of severe limitations of the two-dimensional dislocation models, the simulation results are found to largely corroborate experimental findings on different dominant deformation mechanisms at different film thicknesses
Kochukhov, O.; Ryabchikova, T. A.
2018-02-01
A series of recent theoretical atomic diffusion studies has address the challenging problem of predicting inhomogeneous vertical and horizontal chemical element distributions in the atmospheres of magnetic ApBp stars. Here we critically assess the most sophisticated of such diffusion models - based on a time-dependent treatment of the atomic diffusion in a magnetized stellar atmosphere - by direct comparison with observations as well by testing the widely used surface mapping tools with the spectral line profiles predicted by this theory. We show that the mean abundances of Fe and Cr are grossly underestimated by the time-dependent theoretical diffusion model, with discrepancies reaching a factor of 1000 for Cr. We also demonstrate that Doppler imaging inversion codes, based either on modelling of individual metal lines or line-averaged profiles simulated according to theoretical three-dimensional abundance distribution, are able to reconstruct correct horizontal chemical spot maps despite ignoring the vertical abundance variation. These numerical experiments justify a direct comparison of the empirical two-dimensional Doppler maps with theoretical diffusion calculations. This comparison is generally unfavourable for the current diffusion theory, as very few chemical elements are observed to form overabundance rings in the horizontal field regions as predicted by the theory and there are numerous examples of element accumulations in the vicinity of radial field zones, which cannot be explained by diffusion calculations.
A deformable bag model of hadrons, 1
International Nuclear Information System (INIS)
Ui, Haruo; Saito, Koich
1983-01-01
As a generalization of the MIT spherical bag model, we construct the spheroidal bag model of hadron with an arbitrary eccentricity. This generalization is made by slightly modifying the MIT linear boundary condition: The linear boundary condition is examined in detail. Our model always satisfies two necessary requirements of the MIT bag model - i.e., n.j = 0, no quark colour flux leaves the bag, and q-barq = 0, the scalar density of quark should vanish on the bag surface- and it reduces to the MIT spherical bag model in the limit of zero-eccentricity. Lagrangian formalism of our model is briefly described. The eigenfrequencies of a single massless quark confined in this spheroidal bag are numerically calculated. We obtain the level-splitting of the excited quark orbits, which is just analogous to the well-known Nilsson's splitting of single particle orbits in deformed nuclei. By using the numerical results of the lowest orbit, the effect of the bag-deformation on the mass of low-lying hadrons is estimated. It is found that, although the spherical bag is stable, the quark bag is extremely soft against the quadrupole deformation. Brief discussions are added on the mechanisms which make the spherical bag more stable. (author)
q-deformed Weinberg-Salam model and q-deformed Maxwell equations
International Nuclear Information System (INIS)
Alavi, S.A.; Sarbishaei, M.; Mokhtari, A.
2000-01-01
We study the q-deformation of the gauge part of the Weinberg-Salam model and show that the q-deformed theory involves new interactions. We then obtain q-deformed Maxwell equations from which magnetic monopoles appear naturally. (author)
Directory of Open Access Journals (Sweden)
Amir Hakimhashemi
2010-11-01
Full Text Available We apply here a forecasting model to the Italian region for the spatio-temporal distribution of seismicity based on a smoothing Kernel function, Coulomb stress variations, and a rate-and-state friction law. We tested the feasibility of this approach, and analyzed the importance of introducing time-dependency in forecasting future events. The change in seismicity rate as a function of time was estimated by calculating the Coulomb stress change imparted by large earthquakes. We applied our approach to the region of Italy, and used all of the cataloged earthquakes that occurred up to 2006 to generate the reference seismicity rate. For calculation of the time-dependent seismicity rate changes, we estimated the rate-and-state stress transfer imparted by all of the ML≥4.0 earthquakes that occurred during 2007 and 2008. To validate the results, we first compared the reference seismicity rate with the distribution of ML≥1.8 earthquakes since 2007, using both a non-declustered and a declustered catalog. A positive correlation was found, and all of the forecast earthquakes had locations within 82% and 87% of the study area with the highest seismicity rate, respectively. Furthermore, 95% of the forecast earthquakes had locations within 27% and 47% of the study area with the highest seismicity rate, respectively. For the time-dependent seismicity rate changes, the number of events with locations in the regions with a seismicity rate increase was 11% more than in the regions with a seismicity rate decrease.
Energy Technology Data Exchange (ETDEWEB)
Torres, Diego F.; Martin Rodriguez, Jonatan [Institute of Space Sciences (IEEC-CSIC), Campus UAB, Torre C5, 2a planta, E-08193 Barcelona (Spain); Cillis, Analia N. [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67-Suc. 28 (C1428ZAA), Buenos Aires (Argentina)
2013-01-20
We present a time-dependent spectral model of the nebula 3C 58 and compare it with available data. The model is for a leptonic nebula in which particles are subject to synchrotron, inverse Compton, self-synchrotron Compton, adiabatic, and bremsstrahlung processes. We find that 3C 58 is compatible with being a particle-dominated nebula, with a magnetic field of 35 {mu}G. A broken power-law injection fits well the multi-frequency data, with a break energy at about 40 GeV. We find that 3C 58 is not expected to appear in VERITAS or MAGIC II, unless the local IR background is a factor of {approx}20 off Galactic models' averages. For cases in which the cosmic microwave background dominates the inverse Compton contribution, we find that 3C 58 will not be visible either for the Cherenkov Telescope Array.
Directory of Open Access Journals (Sweden)
Khalid Ahmed Joudi
2017-01-01
Full Text Available This paper presents a computer simulation model of a thermally activated roof (TAR to cool a room using cool water from a wet cooling tower. Modeling was achieved using a simplified 1-D resistance-capacitance thermal network (RC model for an infinite slab. Heat transfer from the cooling pipe network was treated as 2-D heat flow. Only a limited number of nodes were required to obtain reliable results. The use of 6th order RC-thermal model produced a set of ordinary differential equations that were solved using MATLAB - R2012a. The computer program was written to cover all possible initial conditions, material properties, TAR system geometry and hourly solar radiation. The cool water supply was considered time dependent with the variation of the ambient wet bulb temperature. Results from RC-thermal modeling were compared with experimental measurements for a second story room measuring 5.5 m x 4 m x 3 m at Amarah city/ Iraq (31.865 ˚N, 47.128 ˚E for 21 July, 2013. The roof was constructed of 200 mm concrete slab, 150 mm turf and 50 mm insulation. Galvanized 13 mm steel pipe coils were buried in the roof slab with a pipe occupation ratio of 0.12. The walls were constructed of 240 mm common brick with 10mm cement plaster on the inside and outside surfaces and 20 mm Styrofoam insulation on the inside surface and covered with PVC panel. Thermistors were used to measure the indoor and outdoor temperatures, TAR system water inlet and outlet temperatures and temperature distribution inside the concrete slab. The effect of pipe spacing and water mass flow rate were evaluated. Agreement was good between the experimental and RC-thermal model. Concrete core temperature reaches the supply water temperature faster for lower pipe spacing. Heat extracted from the space increased with water mass flow rate to an optimum of 0.0088 kg/s.m².
International Nuclear Information System (INIS)
Heather, R.; Metiu, H.
1989-01-01
The time-dependent formulation of Raman scattering theory is used to study how nonadiabatic interactions affect the Raman spectrum of a model H + 3 system, which has two excited electronic states. We start with a formula derived by Heller which gives the Raman scattering cross section as the Fourier transform (over time) of a time-dependent overlap integral. The latter is calculated with a method proposed by Fleck, Morris, and Feit, and extended to curve crossing by Alvarellos and Metiu. In performing these calculations we are especially interested in displaying effects typical of systems having more than one upper state. If the incident laser populates two electronic states there are several ways (i.e., excite to state one and emit from state two, excite to state one, and emit from state one, etc.) by which the Raman process can reach a given final state, and this leads to quantum interference. This interference is manifested in the Raman cross section as approximate selection rules controlling which final states can be reached through the Raman process. These selection rules depend on the relative orientation of the transition dipoles that radiatively couple the ground electronic state with the excited electronic states. The magnitude of the nonadiabatic contribution to the Raman emission, e.g., the contribution from absorbing to state one and emitting from state two, can be determined from the polarization dependence of the Raman emission if the transition dipoles have neither parallel nor antiparallel relative orientation
Fukagawa, Masafumi; Kido, Ryo; Komaba, Hirotaka; Onishi, Yoshihiro; Yamaguchi, Takuhiro; Hasegawa, Takeshi; Kurita, Noriaki; Fukuma, Shingo; Akizawa, Tadao; Fukuhara, Shunichi
2014-06-01
Hemodialysis patients with mineral and bone disorders (MBDs) have an abnormally high relative risk of death, but their absolute risk of death is unknown. Further, previous studies have not accounted for possible time-dependent confounding of the association between MBD markers and death due to the effect of markers of MBD on treatments, which subsequently may affect MBD markers. Multicenter, 3-year, prospective, case-cohort study. 8,229 hemodialysis patients with secondary hyperparathyroidism (parathyroid hormone level ≥180 pg/mL and/or receiving vitamin D receptor activators) at 86 facilities in Japan. Serum phosphorus, calcium, and parathyroid hormone levels. All-cause mortality. Marginal structural models were used to compute absolute differences in all-cause mortality associated with different levels of predictors while accounting for time-dependent confounding. The association between phosphorus level and mortality appeared U-shaped, although only higher phosphorus level categories reached statistical significance: compared to those with phosphorus levels of 5.0-5.9 mg/dL (1.61-1.93 mmol/L), patients with the highest (≥9.0 mg/dL [≥2.90 mmol/L]) phosphorus levels had 9.4 excess deaths/100 person-years (rate ratio, 2.79 [95% CI, 1.26-6.15]), whereas no association was found for the lowest phosphorus category (secondary hyperparathyroidism. Copyright © 2014 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Kirchner, G.
1989-01-01
Following the Chernobyl accident, activity concentrations in grass from a pasture situated near Bremen and in milk from one particular cow grazing there were analyzed continuously in order to monitor the time-dependent transfer via the grass-cow-milk food chain. From these data weathering half lives on grass are calculated. Using a three compartment model, transfer rates for the transport of I-131 and Cs-137 into milk are determined. Transfer coefficients from feed to milk for use with equilibrium food chain models are derived. Generally, results are in the range of transfer data reported in the literature. Calculated weathering half lives, however, are in the lower range of values previously reported. (orig.)
Competing risks and time-dependent covariates
DEFF Research Database (Denmark)
Cortese, Giuliana; Andersen, Per K
2010-01-01
Time-dependent covariates are frequently encountered in regression analysis for event history data and competing risks. They are often essential predictors, which cannot be substituted by time-fixed covariates. This study briefly recalls the different types of time-dependent covariates......, as classified by Kalbfleisch and Prentice [The Statistical Analysis of Failure Time Data, Wiley, New York, 2002] with the intent of clarifying their role and emphasizing the limitations in standard survival models and in the competing risks setting. If random (internal) time-dependent covariates...
Fawzy, Diaa E.; Stȩpień, K.
2018-03-01
In the current study we present ab initio numerical computations of the generation and propagation of longitudinal waves in magnetic flux tubes embedded in the atmospheres of late-type stars. The interaction between convective turbulence and the magnetic structure is computed and the obtained longitudinal wave energy flux is used in a self-consistent manner to excite the small-scale magnetic flux tubes. In the current study we reduce the number of assumptions made in our previous studies by considering the full magnetic wave energy fluxes and spectra as well as time-dependent ionization (TDI) of hydrogen, employing multi-level Ca II atomic models, and taking into account departures from local thermodynamic equilibrium. Our models employ the recently confirmed value of the mixing-length parameter α=1.8. Regions with strong magnetic fields (magnetic filling factors of up to 50%) are also considered in the current study. The computed Ca II emission fluxes show a strong dependence on the magnetic filling factors, and the effect of time-dependent ionization (TDI) turns out to be very important in the atmospheres of late-type stars heated by acoustic and magnetic waves. The emitted Ca II fluxes with TDI included into the model are decreased by factors that range from 1.4 to 5.5 for G0V and M0V stars, respectively, compared to models that do not consider TDI. The results of our computations are compared with observations. Excellent agreement between the observed and predicted basal flux is obtained. The predicted trend of Ca II emission flux with magnetic filling factor and stellar surface temperature also agrees well with the observations but the calculated maximum fluxes for stars of different spectral types are about two times lower than observations. Though the longitudinal MHD waves considered here are important for chromosphere heating in high activity stars, additional heating mechanism(s) are apparently present.
Modeling plasticity by non-continuous deformation
Ben-Shmuel, Yaron; Altus, Eli
2017-10-01
Plasticity and failure theories are still subjects of intense research. Engineering constitutive models on the macroscale which are based on micro characteristics are very much in need. This study is motivated by the observation that continuum assumptions in plasticity in which neighbour material elements are inseparable at all-time are physically impossible, since local detachments, slips and neighbour switching must operate, i.e. non-continuous deformation. Material microstructure is modelled herein by a set of point elements (particles) interacting with their neighbours. Each particle can detach from and/or attach with its neighbours during deformation. Simulations on two- dimensional configurations subjected to uniaxial compression cycle are conducted. Stochastic heterogeneity is controlled by a single "disorder" parameter. It was found that (a) macro response resembles typical elasto-plastic behaviour; (b) plastic energy is proportional to the number of detachments; (c) residual plastic strain is proportional to the number of attachments, and (d) volume is preserved, which is consistent with macro plastic deformation. Rigid body displacements of local groups of elements are also observed. Higher disorder decreases the macro elastic moduli and increases plastic energy. Evolution of anisotropic effects is obtained with no additional parameters.
Head-Marsden, Kade; Mazziotti, David A
2015-02-07
For an open, time-dependent quantum system, Lindblad derived the most general modification of the quantum Liouville equation in the Markovian approximation that models environmental effects while preserving the non-negativity of the system's density matrix. While Lindblad's modification is correct for N-electron density matrices, solution of the Liouville equation with a Lindblad operator causes the one-electron reduced density matrix (1-RDM) to violate the Pauli exclusion principle. Consequently, after a short time, the 1-RDM is not representable by an ensemble N-electron density matrix (not ensemble N-representable). In this communication, we derive the necessary and sufficient constraints on the Lindbladian matrix within the Lindblad operator to ensure that the 1-RDM remains N-representable for all time. The theory is illustrated by considering the relaxation of an excitation in several molecules F2, N2, CO, and BeH2 subject to environmental noise.
International Nuclear Information System (INIS)
Menouar, Salah; Maamache, Mustapha; Choi, Jeong Ryeol
2010-01-01
The quantum states of time-dependent coupled oscillator model for charged particles subjected to variable magnetic field are investigated using the invariant operator methods. To do this, we have taken advantage of an alternative method, so-called unitary transformation approach, available in the framework of quantum mechanics, as well as a generalized canonical transformation method in the classical regime. The transformed quantum Hamiltonian is obtained using suitable unitary operators and is represented in terms of two independent harmonic oscillators which have the same frequencies as that of the classically transformed one. Starting from the wave functions in the transformed system, we have derived the full wave functions in the original system with the help of the unitary operators. One can easily take a complete description of how the charged particle behaves under the given Hamiltonian by taking advantage of these analytical wave functions.
Deformations of Geometric Structures in Topological Sigma Models
International Nuclear Information System (INIS)
Bytsenko, A. A.
2010-01-01
We study a Lie algebra of formal vector fields W n with it application to the perturbative deformed holomorphic symplectic structure in the A-model, and a Calabi-Yau manifold with boundaries in the B-model. We show that equivalent classes of deformations are described by a Hochschild cohomology of the DG-algebra A = (A,Q), Q = ∂-bar+∂ deform, which is defined to be the cohomology of (-1) n Q+d Hoch . Here ∂-bar is the initial non-deformed BRST operator while ∂ deform is the deformed part whose algebra is a Lie algebra of linear vector fields gl n .
Ponomarev, Artem L.; George, K.; Cucinotta, F. A.
2011-01-01
New experimental data show how chromosomal aberrations for low- and high-LET radiation are dependent on DSB repair deficiencies in wild-type, AT and NBS cells. We simulated the development of chromosomal aberrations in these cells lines in a stochastic track-structure-dependent model, in which different cells have different kinetics of DSB repair. We updated a previously formulated model of chromosomal aberrations, which was based on a stochastic Monte Carlo approach, to consider the time-dependence of DSB rejoining. The previous version of the model had an assumption that all DSBs would rejoin, and therefore we called it a time-independent model. The chromosomal-aberrations model takes into account the DNA and track structure for low- and high-LET radiations, and provides an explanation and prediction of the statistics of rare and more complex aberrations. We compared the program-simulated kinetics of DSB rejoining to the experimentally-derived bimodal exponential curves of the DSB kinetics. We scored the formation of translocations, dicentrics, acentric and centric rings, deletions, and inversions. The fraction of DSBs participating in aberrations was studied in relation to the rejoining time. Comparisons of simulated dose dependence for simple aberrations to the experimental dose-dependence for HF19, AT and NBS cells will be made.
A General Polygon-based Deformable Model for Object Recognition
DEFF Research Database (Denmark)
Jensen, Rune Fisker; Carstensen, Jens Michael
1999-01-01
We propose a general scheme for object localization and recognition based on a deformable model. The model combines shape and image properties by warping a arbitrary prototype intensity template according to the deformation in shape. The shape deformations are constrained by a probabilistic distr...
Multi-scale simulations of droplets in generic time-dependent flows
Milan, Felix; Biferale, Luca; Sbragaglia, Mauro; Toschi, Federico
2017-11-01
We study the deformation and dynamics of droplets in time-dependent flows using a diffuse interface model for two immiscible fluids. The numerical simulations are at first benchmarked against analytical results of steady droplet deformation, and further extended to the more interesting case of time-dependent flows. The results of these time-dependent numerical simulations are compared against analytical models available in the literature, which assume the droplet shape to be an ellipsoid at all times, with time-dependent major and minor axis. In particular we investigate the time-dependent deformation of a confined droplet in an oscillating Couette flow for the entire capillary range until droplet break-up. In this way these multi component simulations prove to be a useful tool to establish from ``first principles'' the dynamics of droplets in complex flows involving multiple scales. European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 642069. & European Research Council under the European Community's Seventh Framework Program, ERC Grant Agreement No 339032.
Schoeppner, M.; Plastino, W.; Budano, A.; De Vincenzi, M.; Ruggieri, F.
2012-04-01
Several nuclear reactors at the Fukushima Dai-ichi power plant have been severely damaged from the Tōhoku earthquake and the subsequent tsunami in March 2011. Due to the extremely difficult on-site situation it has been not been possible to directly determine the emissions of radioactive material. However, during the following days and weeks radionuclides of 137-Caesium and 131-Iodine (amongst others) were detected at monitoring stations throughout the world. Atmospheric transport models are able to simulate the worldwide dispersion of particles accordant to location, time and meteorological conditions following the release. The Lagrangian atmospheric transport model Flexpart is used by many authorities and has been proven to make valid predictions in this regard. The Flexpart software has first has been ported to a local cluster computer at the Grid Lab of INFN and Department of Physics of University of Roma Tre (Rome, Italy) and subsequently also to the European Mediterranean Grid (EUMEDGRID). Due to this computing power being available it has been possible to simulate the transport of particles originating from the Fukushima Dai-ichi plant site. Using the time series of the sampled concentration data and the assumption that the Fukushima accident was the only source of these radionuclides, it has been possible to estimate the time-dependent source-term for fourteen days following the accident using the atmospheric transport model. A reasonable agreement has been obtained between the modelling results and the estimated radionuclide release rates from the Fukushima accident.
Directory of Open Access Journals (Sweden)
A.K. Bhunia
2013-04-01
Full Text Available This paper deals with a deterministic inventory model developed for deteriorating items having two separate storage facilities (owned and rented warehouses due to limited capacity of the existing storage (owned warehouse with linear time dependent demand (increasing over a fixed finite time horizon. The model is formulated with infinite replenishment and the successive replenishment cycle lengths are in arithmetic progression. Partially backlogged shortages are allowed. The stocks of rented warehouse (RW are transported to the owned warehouse (OW in continuous release pattern. For this purpose, the model is formulated as a constrained non-linear mixed integer programming problem. For solving the problem, an advanced genetic algorithm (GA has been developed. This advanced GA is based on ranking selection, elitism, whole arithmetic crossover and non-uniform mutation dependent on the age of the population. Our objective is to determine the optimal replenishment number, lot-size of two-warehouses (OW and RW by maximizing the profit function. The model is illustrated with four numerical examples and sensitivity analyses of the optimal solution are performed with respect to different parameters.
International Nuclear Information System (INIS)
Pirouzmand, Ahmad; Hadad, Kamal; Suh, Kune Y.
2011-01-01
This paper considers the concept of analog computing based on a cellular neural network (CNN) paradigm to simulate nuclear reactor dynamics using a time-dependent second order form of the neutron transport equation. Instead of solving nuclear reactor dynamic equations numerically, which is time-consuming and suffers from such weaknesses as vulnerability to transient phenomena, accumulation of round-off errors and floating-point overflows, use is made of a new method based on a cellular neural network. The state-of-the-art shows the CNN as being an alternative solution to the conventional numerical computation method. Indeed CNN is an analog computing paradigm that performs ultra-fast calculations and provides accurate results. In this study use is made of the CNN model to simulate the space-time response of scalar flux distribution in steady state and transient conditions. The CNN model also is used to simulate step perturbation in the core. The accuracy and capability of the CNN model are examined in 2D Cartesian geometry for two fixed source problems, a mini-BWR assembly, and a TWIGL Seed/Blanket problem. We also use the CNN model concurrently for a typical small PWR assembly to simulate the effect of temperature feedback, poisons, and control rods on the scalar flux distribution
Integrable Time-Dependent Quantum Hamiltonians
Sinitsyn, Nikolai A.; Yuzbashyan, Emil A.; Chernyak, Vladimir Y.; Patra, Aniket; Sun, Chen
2018-05-01
We formulate a set of conditions under which the nonstationary Schrödinger equation with a time-dependent Hamiltonian is exactly solvable analytically. The main requirement is the existence of a non-Abelian gauge field with zero curvature in the space of system parameters. Known solvable multistate Landau-Zener models satisfy these conditions. Our method provides a strategy to incorporate time dependence into various quantum integrable models while maintaining their integrability. We also validate some prior conjectures, including the solution of the driven generalized Tavis-Cummings model.
Lozeau, Lindsay D; Rolle, Marsha W; Camesano, Terri A
2018-07-01
The human antimicrobial peptide LL37 is promising as an alternative to antibiotics due to its biophysical interactions with charged bacterial lipids. However, its clinical potential is limited due to its interactions with zwitterionic mammalian lipids leading to cytotoxicity. Mechanistic insight into the LL37 interactions with mammalian lipids may enable rational design of less toxic LL37-based therapeutics. To this end, we studied concentration- and time-dependent interactions of LL37 with zwitterionic model phosphatidylcholine (PC) bilayers with quartz crystal microbalance with dissipation (QCM-D). LL37 mass adsorption and PC bilayer viscoelasticity changes were monitored by measuring changes in frequency (Δf) and dissipation (ΔD), respectively. The Voigt-Kelvin viscoelastic model was applied to Δf and ΔD to study changes in bilayer thickness and density with LL37 concentration. At low concentrations (0.10-1.00 μM), LL37 adsorbed onto bilayers in a concentration-dependent manner. Further analyses of Δf, ΔD and thickness revealed that peptide saturation on the bilayers was a threshold for interactions observed above 2.00 μM, interactions that were rapid, multi-step, and reached equilibrium in a concentration- and time-dependent manner. Based on these data, we proposed a model of stable transmembrane pore formation at 2.00-10.0 μM, or transition from a primarily lipid to a primarily protein film with a transmembrane pore formation intermediate state at concentrations of LL37 > 10 μM. The concentration-dependent interactions between LL37 and PC bilayers correlated with the observed concentration-dependent biological activities of LL37 (antimicrobial, immunomodulatory and non-cytotoxic at 0.1-1.0 μM, hemolytic and some cytotoxicity at 2.0-13 μM and cytotoxic at >13 μM). Copyright © 2018 Elsevier B.V. All rights reserved.
Modeling knee joint endoprosthesis mode of deformation
Skeeba, V. Yu; Ivancivsky, V. V.
2018-03-01
The purpose of the work was to define the efficient design of the endoprosthesis, working in a multiple-cycle loading environment. Methodology and methods: triangulated surfaces of the base contact surfaces of endoprosthesis butt elements have been created using the PowerShape and SolidWorks software functional environment, and the assemblies of the possible combinations of the knee joint prosthetic designs have been prepared. The mode of deformation modeling took place in the multipurpose program complex ANSYS. Results and discussion: as a result of the numerical modeling, the following data were obtained for each of the developed knee joint versions: the distribution fields of absolute (total) and relative deformations; equivalent stress distribution fields; fatigue strength coefficient distribution fields. In the course of the studies, the following efficient design assembly has been established: 1) Ti-Al-V alloy composite femoral component with polymer inserts; 2) ceramic liners of the compound separator; 3) a Ti-Al-V alloy composite tibial component. The fatigue strength coefficient for the femoral component is 4.2; for the femoral component polymer inserts is 1.2; for the ceramic liners of the compound separator is 3.1; for the tibial component is 2.7. This promising endoprosthesis structure is recommended for further design and technological development.
Modelling Polymer Deformation during 3D Printing
McIlroy, Claire; Olmsted, Peter
Three-dimensional printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The fused deposition modelling technique involves melting a thermoplastic, followed by layer-by-layer extrusion to fabricate an object. The key to ensuring strength at the weld between layers is successful inter-diffusion. However, prior to welding, both the extrusion process and the cooling temperature profile can significantly deform the polymer micro-structure and, consequently, how well the polymers are able to ``re-entangle'' across the weld. In particular, polymer alignment in the flow can cause de-bonding of the layers and create defects. We have developed a simple model of the non-isothermal extrusion process to explore the effects that typical printing conditions and material rheology have on the conformation of a polymer melt. In particular, we incorporate both stretch and orientation using the Rolie-Poly constitutive equation to examine the melt structure as it flows through the nozzle, the subsequent alignment with the build plate and the resulting deformation due to the fixed nozzle height, which is typically less than the nozzle radius.
Directory of Open Access Journals (Sweden)
Bell Iris R
2012-10-01
Full Text Available Abstract Background This paper proposes a novel model for homeopathic remedy action on living systems. Research indicates that homeopathic remedies (a contain measurable source and silica nanoparticles heterogeneously dispersed in colloidal solution; (b act by modulating biological function of the allostatic stress response network (c evoke biphasic actions on living systems via organism-dependent adaptive and endogenously amplified effects; (d improve systemic resilience. Discussion The proposed active components of homeopathic remedies are nanoparticles of source substance in water-based colloidal solution, not bulk-form drugs. Nanoparticles have unique biological and physico-chemical properties, including increased catalytic reactivity, protein and DNA adsorption, bioavailability, dose-sparing, electromagnetic, and quantum effects different from bulk-form materials. Trituration and/or liquid succussions during classical remedy preparation create “top-down” nanostructures. Plants can biosynthesize remedy-templated silica nanostructures. Nanoparticles stimulate hormesis, a beneficial low-dose adaptive response. Homeopathic remedies prescribed in low doses spaced intermittently over time act as biological signals that stimulate the organism’s allostatic biological stress response network, evoking nonlinear modulatory, self-organizing change. Potential mechanisms include time-dependent sensitization (TDS, a type of adaptive plasticity/metaplasticity involving progressive amplification of host responses, which reverse direction and oscillate at physiological limits. To mobilize hormesis and TDS, the remedy must be appraised as a salient, but low level, novel threat, stressor, or homeostatic disruption for the whole organism. Silica nanoparticles adsorb remedy source and amplify effects. Properly-timed remedy dosing elicits disease-primed compensatory reversal in direction of maladaptive dynamics of the allostatic network, thus promoting
Calvi, Marta
2011-01-01
This review reports preliminary results of time-dependent measurements of decays of $B^0$ mesons and $B^0_s$ mesons coming from the analysis of about 36 pb$^{-1}$ of data collected by the LHCb experiment during the 2010 run of the Large Hadron Collider at $\\sqrt{s}$ = 7 TeV.
Calvi, Marta; Collaboration, for the LHCb
2011-01-01
This review reports preliminary results of time-dependent measurements of decays of B^0 mesons and B^0_s mesons coming from the analysis of about 36 pb^-1 of data collected by the LHCb experiment during the 2010 run of the Large Hadron Collider at sqrt(s)=7 TeV.
Time dependent view factor methods
International Nuclear Information System (INIS)
Kirkpatrick, R.C.
1998-03-01
View factors have been used for treating radiation transport between opaque surfaces bounding a transparent medium for several decades. However, in recent years they have been applied to problems involving intense bursts of radiation in enclosed volumes such as in the laser fusion hohlraums. In these problems, several aspects require treatment of time dependence
An electromechanical based deformable model for soft tissue simulation.
Zhong, Yongmin; Shirinzadeh, Bijan; Smith, Julian; Gu, Chengfan
2009-11-01
Soft tissue deformation is of great importance to surgery simulation. Although a significant amount of research efforts have been dedicated to simulating the behaviours of soft tissues, modelling of soft tissue deformation is still a challenging problem. This paper presents a new deformable model for simulation of soft tissue deformation from the electromechanical viewpoint of soft tissues. Soft tissue deformation is formulated as a reaction-diffusion process coupled with a mechanical load. The mechanical load applied to a soft tissue to cause a deformation is incorporated into the reaction-diffusion system, and consequently distributed among mass points of the soft tissue. Reaction-diffusion of mechanical load and non-rigid mechanics of motion are combined to govern the simulation dynamics of soft tissue deformation. An improved reaction-diffusion model is developed to describe the distribution of the mechanical load in soft tissues. A three-layer artificial cellular neural network is constructed to solve the reaction-diffusion model for real-time simulation of soft tissue deformation. A gradient based method is established to derive internal forces from the distribution of the mechanical load. Integration with a haptic device has also been achieved to simulate soft tissue deformation with haptic feedback. The proposed methodology does not only predict the typical behaviours of living tissues, but it also accepts both local and large-range deformations. It also accommodates isotropic, anisotropic and inhomogeneous deformations by simple modification of diffusion coefficients.
Reconstructing time-dependent dynamics
Clemson, Philip; Lancaster, Gemma; Stefanovska, Aneta
2016-01-01
The usefulness of the information extracted from biomedical data relies heavily on the underlying theory of the methods used in its extraction. The assumptions of stationarity and autonomicity traditionally applied to dynamical systems break down when considering living systems, due to their inherent time-variability. Living systems are thermodynamically open, and thus constantly interacting with their environment. This results in highly nonlinear, time-dependent dynamics. The aim of signal a...
Fermions in interaction with time dependent fields
International Nuclear Information System (INIS)
Falkensteiner, P.; Grosse, H.
1988-01-01
We solve a two dimensional model describing the interaction of fermions with time dependent external fields. We work out the second quantized formulation and obtain conditions for equivalence of representations at different times. This implies the existence of sectors which describe charged states. We obtain the time dependence of charges and observe that charge differences become integer for unitary equivalent states. For scattering we require the equivalence of in- and out-representations; nevertheless charged sectors may be reached by suitable interactions and ionization is possible. 20 refs. (Author)
Time-Dependent Damage Investigation of Rock Mass in an In Situ Experimental Tunnel
Jiang, Quan; Cui, Jie; Chen, Jing
2012-01-01
In underground tunnels or caverns, time-dependent deformation or failure of rock mass, such as extending cracks, gradual rock falls, etc., are a costly irritant and a major safety concern if the time-dependent damage of surrounding rock is serious. To understand the damage evolution of rock mass in underground engineering, an in situ experimental testing was carried out in a large belowground tunnel with a scale of 28.5 m in width, 21 m in height and 352 m in length. The time-dependent damage of rock mass was detected in succession by an ultrasonic wave test after excavation. The testing results showed that the time-dependent damage of rock mass could last a long time, i.e., nearly 30 days. Regression analysis of damage factors defined by wave velocity, resulted in the time-dependent evolutional damage equation of rock mass, which corresponded with logarithmic format. A damage viscoelastic-plastic model was developed to describe the exposed time-dependent deterioration of rock mass by field test, such as convergence of time-dependent damage, deterioration of elastic modules and logarithmic format of damage factor. Furthermore, the remedial measures for damaged surrounding rock were discussed based on the measured results and the conception of damage compensation, which provides new clues for underground engineering design.
DEFF Research Database (Denmark)
Garcia-Aymerich, J.; Lange, P.; Serra, I.
2008-01-01
this type of confounding. We sought to assess the presence of time-dependent confounding in the association between physical activity and COPD development and course by comparing risk estimates between standard statistical methods and MSMs. METHODS: By using the population-based cohort Copenhagen City Heart...
Selfsimilar time dependent shock structures
International Nuclear Information System (INIS)
Beck, R.; Drury, L.O.
1985-01-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The same argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions
Selfsimilar time dependent shock structures
Beck, R.; Drury, L. O.
1985-01-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.
Characterizing time-dependent mechanics in metallic MEMS
Directory of Open Access Journals (Sweden)
Geers M.G.D.
2010-06-01
parameters describing the time-dependent behavior, the experiments are simulated with FEM using a standardsolid material model and the exact test-structure geometry. Although this method is simple, yet precise, it lacks direct determination of stress and strain. Therefore a second method is designed: measuring time-dependent tensile behavior of these cantilevers with a custom nano-tensile stage. The wafer with specimen is fixed to and manipulated with nano-precision by piezos stacked on micro-manipulators. The piezos also serve as load actuators. The stage has a custom multirange load cell providing a load range of 0-100 mN at a minimum resolution of 10 nN. An electro-static force is generated between the top flat of the specimen’s free end and a mating flat on the load cell. Full-field displacement measurements through SEM/AFM/COP are enabled by a compact design. A final addition is a heating element allowing testing up to 150°. In short, the work will first discuss the performance of the numeric-experimental method for timedependent bending deformation characterization. Secondly, it will present the performance of the time-dependent tensile testing method along with preliminary measurements of time-dependent material behaviour.
Brant, Larry J; Ferrucci, Luigi; Sheng, Shan L; Concin, Hans; Zonderman, Alan B; Kelleher, Cecily C; Longo, Dan L; Ulmer, Hanno; Strasak, Alexander M
2010-12-01
Previous studies on blood pressure (BP) indices as a predictor of coronary heart disease (CHD) have provided equivocal results and generally relied on Cox proportional hazards regression methodology, with age and sex accounting for most of the predictive capability of the model. The aim of the present study was to use serially collected BP measurements to examine age-and gender-related differences in BP indices for predicting CHD. The predictive accuracy of time-dependent BP indices for CHD was investigated using a method of risk prediction based on posterior probabilities calculated from mixed-effects regression to utilize intraindividual differences in serial BP measurements according to age changes within gender groups. Data were collected prospectively from 2 community-dwelling cohort studies in the United States (Baltimore Longitudinal Study of Aging [BLSA]) and Europe (Vorarlberg Health Monitoring and Promotion Program [VHM&PP]). The study comprised 152,633 participants (aged 30-74 years) and 610,061 BP measurements. During mean follow-up of 7.5 years, 2457 nonfatal and fatal CHD events were observed. In both study populations, pulse pressure (PP) and systolic blood pressure (SBP) performed best as individual predictors of CHD in women (area under the receiver operating characteristic curve [AUC(ROC)] was between 0.83 and 0.85 for PP, and between 0.77 and 0.81 for SBP). Mean arterial pressure (MAP) and diastolic blood pressure (DBP) performed better for men (AUC(ROC) = 0.67 and 0.65 for MAP and DBP, respectively, in the BLSA; AUC(ROC) = 0.77 and 0.75 in the VHM&PP) than for women (AUC(ROC) = 0.60 for both MAP and DBP in the BLSA; AUC(ROC) = 0.75 and 0.52, respectively, in the VHM&PP). The degree of discrimination in both populations was overall greater but more varied for all BP indices for women (AUC(ROC) estimates between 0.85 [PP in the VHM&PP] and 0.52 [DBP in the VHM&PP]) than for men (AUC(ROC) estimates between 0.78 [MAP + PP in the VHM&PP] and 0.63 [PP
Betweenness in time dependent networks
International Nuclear Information System (INIS)
Alsayed, Ahmad; Higham, Desmond J.
2015-01-01
The concept of betweenness has given rise to a very useful class of network centrality measures. Loosely, betweenness quantifies the level of importance of a node in terms of its propensity to act as an intermediary when messages are passed around the network. In this work we generalize a walk-based betweenness measure to the case of time-dependent networks, such as those arising in telecommunications and on-line social media. We also introduce a new kind of betweenness measure, temporal betweenness, which quantifies the importance of a time-point. We illustrate the effectiveness of these new measures on synthetic examples, and also give results on real data sets involving voice call, email and Twitter
Sepehry-Fard, F.; Coulthard, Maurice H.
1995-01-01
The process of predicting the values of maintenance time dependent variable parameters such as mean time between failures (MTBF) over time must be one that will not in turn introduce uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. A minor deviation in the values of the maintenance time dependent variable parameters such as MTBF over time will have a significant impact on the logistics resources demands, International Space Station availability and maintenance support costs. There are two types of parameters in the logistics and maintenance world: a. Fixed; b. Variable Fixed parameters, such as cost per man hour, are relatively easy to predict and forecast. These parameters normally follow a linear path and they do not change randomly. However, the variable parameters subject to the study in this report such as MTBF do not follow a linear path and they normally fall within the distribution curves which are discussed in this publication. The very challenging task then becomes the utilization of statistical techniques to accurately forecast the future non-linear time dependent variable arisings and events with a high confidence level. This, in turn, shall translate in tremendous cost savings and improved availability all around.
Time-dependent 2-stream particle transport
International Nuclear Information System (INIS)
Corngold, Noel
2015-01-01
Highlights: • We consider time-dependent transport in the 2-stream or “rod” model via an attractive matrix formalism. • After reviewing some classical problems in homogeneous media we discuss transport in materials with whose density may vary. • There we achieve a significant contraction of the underlying Telegrapher’s equation. • We conclude with a discussion of stochastics, treated by the “first-order smoothing approximation.” - Abstract: We consider time-dependent transport in the 2-stream or “rod” model via an attractive matrix formalism. After reviewing some classical problems in homogeneous media we discuss transport in materials whose density may vary. There we achieve a significant contraction of the underlying Telegrapher’s equation. We conclude with a discussion of stochastics, treated by the “first-order smoothing approximation.”
Time dependent policy-based access control
DEFF Research Database (Denmark)
Vasilikos, Panagiotis; Nielson, Flemming; Nielson, Hanne Riis
2017-01-01
also on other attributes of the environment such as the time. In this paper, we use systems of Timed Automata to model distributed systems and we present a logic in which one can express time-dependent policies for access control. We show how a fragment of our logic can be reduced to a logic......Access control policies are essential to determine who is allowed to access data in a system without compromising the data's security. However, applications inside a distributed environment may require those policies to be dependent on the actual content of the data, the flow of information, while...... that current model checkers for Timed Automata such as UPPAAL can handle and we present a translator that performs this reduction. We then use our translator and UPPAAL to enforce time-dependent policy-based access control on an example application from the aerospace industry....
International Nuclear Information System (INIS)
Kemaneci, Efe; Graef, Wouter; Rahimi, Sara; Van Dijk, Jan; Kroesen, Gerrit; Carbone, Emile; Jimenez-Diaz, Manuel
2015-01-01
A microwave-induced oxygen plasma is simulated using both stationary and time-resolved modelling strategies. The stationary model is spatially resolved and it is self-consistently coupled to the microwaves (Jimenez-Diaz et al 2012 J. Phys. D: Appl. Phys. 45 335204), whereas the time-resolved description is based on a global (volume-averaged) model (Kemaneci et al 2014 Plasma Sources Sci. Technol. 23 045002). We observe agreement of the global model data with several published measurements of microwave-induced oxygen plasmas in both continuous and modulated power inputs. Properties of the microwave plasma reactor are investigated and corresponding simulation data based on two distinct models shows agreement on the common parameters. The role of the square wave modulated power input is also investigated within the time-resolved description. (paper)
Preliminary deformation model for National Seismic Hazard map of Indonesia
Energy Technology Data Exchange (ETDEWEB)
Meilano, Irwan; Gunawan, Endra; Sarsito, Dina; Prijatna, Kosasih; Abidin, Hasanuddin Z. [Geodesy Research Division, Faculty of Earth Science and Technology, Institute of Technology Bandung (Indonesia); Susilo,; Efendi, Joni [Agency for Geospatial Information (BIG) (Indonesia)
2015-04-24
Preliminary deformation model for the Indonesia’s National Seismic Hazard (NSH) map is constructed as the block rotation and strain accumulation function at the elastic half-space. Deformation due to rigid body motion is estimated by rotating six tectonic blocks in Indonesia. The interseismic deformation due to subduction is estimated by assuming coupling on subduction interface while deformation at active fault is calculated by assuming each of the fault‘s segment slips beneath a locking depth or in combination with creeping in a shallower part. This research shows that rigid body motion dominates the deformation pattern with magnitude more than 15 mm/year, except in the narrow area near subduction zones and active faults where significant deformation reach to 25 mm/year.
Time-Dependent Thermally-Driven Interfacial Flows in Multilayered Fluid Structures
Haj-Hariri, Hossein; Borhan, A.
1996-01-01
A computational study of thermally-driven convection in multilayered fluid structures will be performed to examine the effect of interactions among deformable fluid-fluid interfaces on the structure of time-dependent flow in these systems. Multilayered fluid structures in two models configurations will be considered: the differentially heated rectangular cavity with a free surface, and the encapsulated cylindrical liquid bridge. An extension of a numerical method developed as part of our recent NASA Fluid Physics grant will be used to account for finite deformations of fluid-fluid interfaces.
Intruder level and deformation in SD-pair shell model
International Nuclear Information System (INIS)
Luo Yan'an; Ning Pingzhi; Pan Feng
2004-01-01
The influence of intruder level on nuclear deformation is studied within the framework of the nucleon-pair shell model truncated to an SD-pair subspace. The results suggest that the intruder level has a tendency to reduce the deformation and plays an important role in determining the onset of rotational behavior. (authors)
Dissipative time-dependent quantum transport theory.
Zhang, Yu; Yam, Chi Yung; Chen, GuanHua
2013-04-28
A dissipative time-dependent quantum transport theory is developed to treat the transient current through molecular or nanoscopic devices in presence of electron-phonon interaction. The dissipation via phonon is taken into account by introducing a self-energy for the electron-phonon coupling in addition to the self-energy caused by the electrodes. Based on this, a numerical method is proposed. For practical implementation, the lowest order expansion is employed for the weak electron-phonon coupling case and the wide-band limit approximation is adopted for device and electrodes coupling. The corresponding hierarchical equation of motion is derived, which leads to an efficient and accurate time-dependent treatment of inelastic effect on transport for the weak electron-phonon interaction. The resulting method is applied to a one-level model system and a gold wire described by tight-binding model to demonstrate its validity and the importance of electron-phonon interaction for the quantum transport. As it is based on the effective single-electron model, the method can be readily extended to time-dependent density functional theory.
Deformations of vector-scalar models
Barnich, Glenn; Boulanger, Nicolas; Henneaux, Marc; Julia, Bernard; Lekeu, Victor; Ranjbar, Arash
2018-02-01
Abelian vector fields non-minimally coupled to uncharged scalar fields arise in many contexts. We investigate here through algebraic methods their consistent deformations ("gaugings"), i.e., the deformations that preserve the number (but not necessarily the form or the algebra) of the gauge symmetries. Infinitesimal consistent deformations are given by the BRST cohomology classes at ghost number zero. We parametrize explicitly these classes in terms of various types of global symmetries and corresponding Noether currents through the characteristic cohomology related to antifields and equations of motion. The analysis applies to all ghost numbers and not just ghost number zero. We also provide a systematic discussion of the linear and quadratic constraints on these parameters that follow from higher-order consistency. Our work is relevant to the gaugings of extended supergravities.
Complex structure-induced deformations of σ-models
Energy Technology Data Exchange (ETDEWEB)
Bykov, Dmitri [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut,Am Mühlenberg 1, D-14476 Potsdam-Golm (Germany); Steklov Mathematical Institute of Russ. Acad. Sci.,Gubkina str. 8, 119991 Moscow (Russian Federation)
2017-03-24
We describe a deformation of the principal chiral model (with an even-dimensional target space G) by a B-field proportional to the Kähler form on the target space. The equations of motion of the deformed model admit a zero-curvature representation. As a simplest example, we consider the case of G=S{sup 1}×S{sup 3}. We also apply a variant of the construction to a deformation of the AdS{sub 3}×S{sup 3}×S{sup 1} (super-)σ-model.
New deformation model of grain boundary strengthening in polycrystalline metals
International Nuclear Information System (INIS)
Trefilov, V.I.; Moiseev, V.F.; Pechkovskij, Eh.P.
1988-01-01
A new model explaining grain boundary strengthening in polycrystalline metals and alloys by strain hardening due to localization of plastic deformation in narrow bands near grain boundaries is suggested. Occurrence of localized deformation is caused by different flow stresses in grains of different orientation. A new model takes into account the active role of stress concentrator, independence of the strengthening coefficient on deformation, influence of segregations. Successful use of the model suggested for explanation of rhenium effect in molybdenum and tungsten is alloys pointed out
Jaynes-Cummings model and the deformed-oscillator algebra
International Nuclear Information System (INIS)
Crnugelj, J.; Martinis, M.; Mikuta-Martinis, V.
1994-01-01
We study the time evolution of the deformed Jaynes-Cummings model (DJCM). It is shown that the standard JCM and its recent non-linear generalizations involving the intensity-dependent coupling and/or the multiphoton coupling are only particular cases of the DJCM. The time evolution of the mean phonon number and the population inversion are evaluated. A special case of the q-deformed JCM is analyzed explicitly. The long time quasi-periodic revival effects of the q-deformed JCM are observed for q∼1 and an initially large mean photon number. For other values of the deformation parameter q we observe chaotic-like behaviour of the population inversion. Photons are assumed to be initially in the deformed coherent state. ((orig.))
The conservation laws for deformed classical models
International Nuclear Information System (INIS)
Klimek, M.
1994-01-01
The problem of deriving the conservation laws for deformed linear equations of motion is investigated. The conserved currents are obtained in explicit form and used in the construction of constants of motion. The equations for the set of non-interacting oscillators with arbitrary scale-time as well as the κ-Klein-Gordon equation are considered as an example of application of the method. (author) 9 refs
Nava, Nicoletta; Treccani, Giulia; Müller, Heidi Kaastrup; Popoli, Maurizio; Wegener, Gregers; Elfving, Betina
2017-01-01
It is well established that stress plays a major role in the pathogenesis of neuropsychiatric diseases. Stress-induced alteration of synaptic plasticity has been hypothesized to underlie the morphological changes observed by neuroimaging in psychiatric patients in key regions such as hippocampus and prefrontal cortex (PFC). We have recently shown that a single acute stress exposure produces significant short-term alterations of structural plasticity within medial PFC. These alterations were partially prevented by previous treatment with chronic desipramine (DMI). In the present study we evaluated the effects of acute Foot-shock (FS)-stress and pre-treatment with the traditional antidepressant DMI on the gene expression of key regulators of synaptic plasticity and structure. Expression of Homer, Shank, Spinophilin, Densin-180, and the small RhoGTPase related gene Rac1 and downstream target genes, Limk1, Cofilin1 and Rock1 were investigated 1 day (1d), 7 d and 14d after FS-stress exposure. We found that DMI specifically increases the short-term expression of Spinophilin, as well as Homer and Shank family genes, and that both acute stress and DMI exert significant long-term effects on mRNA levels of genes involved in spine plasticity. These findings support the knowledge that acute FS stress and antidepressant treatment induce both rapid and sustained time-dependent alterations in structural components of synaptic plasticity in rodent medial PFC. Copyright © 2016 Elsevier B.V. and ECNP. All rights reserved.
Safdar, Rabia; Imran, M.; Khalique, Chaudry Masood
2018-06-01
Exact solutions for velocity field and tangential stress for rotational flow of a generalized Burgers' fluid within an infinite circular pipe are derived by using the methods of Laplace and finite Hankel transformations. Firstly we take the position of fluid at rest and then the fluid flow due to the rotation of the pipe around the axis of flow having time dependant angular velocity. The exact solutions are presented in terms of the generalized Ga,b,c (., t) -functions. The corresponding results can be freely specified for the same results of Burgers', Oldroyd B, Maxwell, second grade and Newtonian fluids (performing the same motion) as particular cases of the results obtained earlier. The impact of the different parameters, individually and in comparison, are represented by graphical demonstrations. Secondly the numerical solutions for velocity and stress are also obtained with the help of Laplace transformation, Gaver Stehfest's algorithm and MATHCAD. Finally a comparison of both methods for the same problem is done and shows the consistency of results.
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Christian
2009-01-01
, lead-lag, pitch, trailing-edge flapping. In the linear region, the model reduces to the inviscid model, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa......The present work contains an extension of the Beddoes-Leishman-type dynamic stall model. In this work, a deformable trailing-edge flap has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave...... for the attached flow region and Hansen et al. The model is compared qualitatively to wind tunnel measurements of a Riso/ B1-18 blade section equipped with deformable trailing-edge flap devices in the form of piezoelectric devices. Copyright © 2009 John Wiley & Sons, Ltd....
A dynamic stall model for airfoils with deformable trailing edges
DEFF Research Database (Denmark)
Andersen, Peter Bjørn; Gaunaa, Mac; Bak, Dan Christian
2007-01-01
on an airfoil section undergoing arbitrary motion in heave, lead-lag, pitch, Trailing Edge (TE) flapping. In the linear region, the model reduces to the inviscid model of Gaunaa [4], which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed......The present work contains an extension of the Beddoes-Leishman (B-L) type dynamic stall model, as described by Hansen et al. [7]. In this work a Deformable Trailing Edge Geometry (DTEG) has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments...
Flat Knitting Loop Deformation Simulation Based on Interlacing Point Model
Directory of Open Access Journals (Sweden)
Jiang Gaoming
2017-12-01
Full Text Available In order to create realistic loop primitives suitable for the faster CAD of the flat-knitted fabric, we have performed research on the model of the loop as well as the variation of the loop surface. This paper proposes an interlacing point-based model for the loop center curve, and uses the cubic Bezier curve to fit the central curve of the regular loop, elongated loop, transfer loop, and irregular deformed loop. In this way, a general model for the central curve of the deformed loop is obtained. The obtained model is then utilized to perform texture mapping, texture interpolation, and brightness processing, simulating a clearly structured and lifelike deformed loop. The computer program LOOP is developed by using the algorithm. The deformed loop is simulated with different yarns, and the deformed loop is applied to design of a cable stitch, demonstrating feasibility of the proposed algorithm. This paper provides a loop primitive simulation method characterized by lifelikeness, yarn material variability, and deformation flexibility, and facilitates the loop-based fast computer-aided design (CAD of the knitted fabric.
Numerical modeling of the Indo-Australian intraplate deformation
Brandon, Vincent; Royer, Jean-Yves
2014-05-01
The Indo-Australian plate is perhaps the best example of wide intraplate deformation within an oceanic plate. The deformation is expressed by an unusual level of intraplate seismicity, including magnitude Mw > 8 events, large-scale folding and deep faulting of the oceanic lithosphere and reactivation of extinct fracture zones. The deformation pattern and kinematic data inversions suggest that the Indo-Australian plate can be viewed as a composite plate made of three rigid component plates - India, Capricorn, Australia - separated by wide and diffuse boundaries undergoing either extensional or compressional deformation. We tested this model using the SHELLS numerical code (Kong & Bird, 1995). The Indo-Australian plate is modeled by a mesh of 5281 spherical triangular finite elements. Mesh edges parallel the major extinct fracture zones so that they can be reactivated by reducing their friction rates. Strength of the plate is defined by the age of the lithosphere and seafloor topography. Model boundary conditions are only defined by the plate velocities predicted by the rotation vectors between rigid components of the Indo-Australian plate and their neighboring plates. Since the mesh limits all belong to rigid plates with fully defined Euler vectors, no conditions are imposed on the location, extent and limits of the diffuse and deforming zones. Using MORVEL plate velocities (DeMets et al., 2010), predicted deformation patterns are very consistent with that observed. Pre-existing structures of the lithosphere play an important role in the intraplate deformation and its distribution. The Chagos Bank focuses most of the extensional deformation between the Indian and Capricorn plates. Agreement between models and observation improves by weakening fossil fracture zones relative to the surrounding crust; however only limited sections of FZ's accommodate deformation. The reactivation of the Eocene FZ's in the Central Indian Basin (CIB) and Wharton Basin (WB) explains the
Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles.
Directory of Open Access Journals (Sweden)
Olga Kononova
2016-01-01
Full Text Available The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams modeling the particle structure. The beams' deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F-deformation (X spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young's moduli for Hertzian and bending deformations, and the structural damage dependent beams' survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications.
Van Kuiken, Benjamin E; Valiev, Marat; Daifuku, Stephanie L; Bannan, Caitlin; Strader, Matthew L; Cho, Hana; Huse, Nils; Schoenlein, Robert W; Govind, Niranjan; Khalil, Munira
2013-05-30
Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of Ru(II) and Ru(III) complexes in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6](4-) and Ru(II) polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5M(II)-CN-Ru(III)(NH3)5](-) (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.
Time-dependent Autler-Townes spectroscopy
International Nuclear Information System (INIS)
Qamar, Sajid; Zhu, S.-Y.; Zubairy, M Suhail
2003-01-01
Autler-Townes spontaneous emission spectroscopy is revisited for a time-dependent case. We report the results of spontaneous emission spectra for nonstationary scattered light signals using the definition of the time-dependent physical spectrum. This is a rare example of problems where time-dependent spectra can be calculated exactly
Time-dependent Autler-Townes spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Qamar, Sajid [Institute for Quantum Studies, Department of Physics, Texas A and M University, College Station, TX 77843-4242 (United States); Zhu, S.-Y. [Institute for Quantum Studies, Department of Physics, Texas A and M University, College Station, TX 77843-4242 (United States); Zubairy, M Suhail [Institute for Quantum Studies, Department of Physics, Texas A and M University, College Station, TX 77843-4242 (United States)
2003-04-01
Autler-Townes spontaneous emission spectroscopy is revisited for a time-dependent case. We report the results of spontaneous emission spectra for nonstationary scattered light signals using the definition of the time-dependent physical spectrum. This is a rare example of problems where time-dependent spectra can be calculated exactly.
Orientation sensitive deformation in Zr alloys: experimental and modeling studies
International Nuclear Information System (INIS)
Srivastava, D.; Keskar, N.; Manikrishna, K.V.; Dey, G.K.; Jha, S.K.; Saibaba, N.
2016-01-01
Zirconium alloys are used for fuel cladding and other structural components in pressurised heavy water nuclear reactors (PHWR's). Currently there is a lot of interest in developing alloys for structural components for higher temperature reactor operation. There is also need for development of cladding material with better corrosion and mechanical property of cladding material for higher and extended burn up applications. The performance of the cladding material is primarily influenced by the microstructural features of the material such as constituent phases their morphology, precipitates characteristics, nature of defects etc. Therefore, the microstructure is tailored as per the performance requirement by through controlled additions of alloying elements, thermo-mechanical- treatments. In order to obtain the desired microstructure, it is important to know the deformation behaviour of the material. Orientation dependent deformation behavior was studied in Zr using a combination of experimental and modeling (both discrete and atomistic dislocation dynamics) methods. Under the conditions of plane strain deformation, it was observed that single phase Zr, had significant extent of deformation heterogeneity based on local orientations. Discrete dislocation dynamics simulations incorporating multi slip systems had captured the orientation sensitive deformation. MD dislocations on the other hand brought the fundamental difference in various crystallographic orientations in determining the nucleating stress for the dislocations. The deformed structure has been characterized using X-ray, electron and neutron diffraction techniques. The various operating deformation mechanism will be discussed in this presentation. (author)
Geometric Aspects and Some Uses of Deformed Models of Thermostatistics
Directory of Open Access Journals (Sweden)
Alexandre Gavrilik
2018-02-01
Full Text Available We consider diverse deformed Bose gas models (DBGMs focusing on distributions and correlations of any order, and also on deformed thermodynamics. For so-called μ -deformed Bose gas model ( μ -DBGM, main thermodynamic aspects are treated: total number of particles, deformed partition function, etc. Using a geometric approach, we confirm the existence of critical behavior—Bose-like condensation; we find the critical temperature T c ( μ depending on μ so that T c ( μ > T c ( Bose for μ > 0 . This fact and other advantages of μ -DBGM relative to the usual Bose gas, e.g., stronger effective inter-particle attraction (controlled by the parameter μ , allow us to consider the condensate in μ -DBGM as a candidate for modeling dark matter. As another, quite successful application we discuss the usage of the two-parameter ( μ ˜ , q -deformed BGM for effective description of the peculiar (non-Bose like behavior of two-pion correlations observed in the STAR experiment at RHIC (Brookhaven. Herein, we point out the transparent role of the two deformation parameters μ ˜ and q as being responsible for compositeness and (effective account of interactions of pions, respectively.
Deformed Calogero-Sutherland model and fractional quantum Hall effect
Atai, Farrokh; Langmann, Edwin
2017-01-01
The deformed Calogero-Sutherland (CS) model is a quantum integrable system with arbitrary numbers of two types of particles and reducing to the standard CS model in special cases. We show that a known collective field description of the CS model, which is based on conformal field theory (CFT), is actually a collective field description of the deformed CS model. This provides a natural application of the deformed CS model in Wen's effective field theory of the fractional quantum Hall effect (FQHE), with the two kinds of particles corresponding to electrons and quasi-hole excitations. In particular, we use known mathematical results about super-Jack polynomials to obtain simple explicit formulas for the orthonormal CFT basis proposed by van Elburg and Schoutens in the context of the FQHE.
Holographic complexity for time-dependent backgrounds
Energy Technology Data Exchange (ETDEWEB)
Momeni, Davood, E-mail: davoodmomeni78@gmail.com [Eurasian International Center for Theoretical Physics and Department of General Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan); Faizal, Mir, E-mail: mirfaizalmir@googlemail.com [Irving K. Barber School of Arts and Sciences, University of British Columbia, Okanagan, 3333 University Way, Kelowna, British Columbia V1V 1V7 (Canada); Department of Physics and Astronomy, University of Lethbridge, Lethbridge, Alberta, T1K 3M4 (Canada); Bahamonde, Sebastian, E-mail: sebastian.beltran.14@ucl.ac.uk [Department of Mathematics, University College London, Gower Street, London, WC1E 6BT (United Kingdom); Myrzakulov, Ratbay [Eurasian International Center for Theoretical Physics and Department of General Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan)
2016-11-10
In this paper, we will analyze the holographic complexity for time-dependent asymptotically AdS geometries. We will first use a covariant zero mean curvature slicing of the time-dependent bulk geometries, and then use this co-dimension one spacelike slice of the bulk spacetime to define a co-dimension two minimal surface. The time-dependent holographic complexity will be defined using the volume enclosed by this minimal surface. This time-dependent holographic complexity will reduce to the usual holographic complexity for static geometries. We will analyze the time-dependence as a perturbation of the asymptotically AdS geometries. Thus, we will obtain time-dependent asymptotically AdS geometries, and we will calculate the holographic complexity for such time-dependent geometries.
Modeling steel deformation in the semi-solid state
Hojny, Marcin
2017-01-01
This book addresses selected aspects of steel-deformation modelling, both at very high temperatures and under the conditions in which the liquid and the solid phases coexist. Steel-deformation modelling with its simultaneous solidification is particularly difficult due to its specificity and complexity. With regard to industrial applications and the development of new, integrated continuous casting and rolling processes, the issues related to modelling are becoming increasingly important. Since the numerous industrial tests that are necessary when traditional methods are used to design the process of continuous casting immediately followed by rolling are expensive, new modelling concepts have been sought. Comprehensive tests were applied to solve problems related to the deformation of steel with a semi-solid core. Physical tests using specialist laboratory instruments (Gleeble 3800thermo-mechanical simulator, NANOTOM 180 N computer tomography, Zwick Z250 testing equipment, 3D blue-light scanning systems), and...
A Geometry Deformation Model for Braided Continuum Manipulators
Directory of Open Access Journals (Sweden)
S. M. Hadi Sadati
2017-06-01
Full Text Available Continuum manipulators have gained significant attention in the robotic community due to their high dexterity, deformability, and reachability. Modeling of such manipulators has been shown to be very complex and challenging. Despite many research attempts, a general and comprehensive modeling method is yet to be established. In this paper, for the first time, we introduce the bending effect in the model of a braided extensile pneumatic actuator with both stiff and bendable threads. Then, the effect of the manipulator cross-section deformation on the constant curvature and variable curvature models is investigated using simple analytical results from a novel geometry deformation method and is compared to experimental results. We achieve 38% mean reference error simulation accuracy using our constant curvature model for a braided continuum manipulator in presence of body load and 10% using our variable curvature model in presence of extensive external loads. With proper model assumptions and taking to account the cross-section deformation, a 7–13% increase in the simulation mean error accuracy is achieved compared to a fixed cross-section model. The presented models can be used for the exact modeling and design optimization of compound continuum manipulators by providing an analytical tool for the sensitivity analysis of the manipulator performance. Our main aim is the application in minimal invasive manipulation with limited workspaces and manipulators with regional tunable stiffness in their cross section.
Time-dependent seismic tomography
Julian, B.R.; Foulger, G.R.
2010-01-01
Of methods for measuring temporal changes in seismic-wave speeds in the Earth, seismic tomography is among those that offer the highest spatial resolution. 3-D tomographic methods are commonly applied in this context by inverting seismic wave arrival time data sets from different epochs independently and assuming that differences in the derived structures represent real temporal variations. This assumption is dangerous because the results of independent inversions would differ even if the structure in the Earth did not change, due to observational errors and differences in the seismic ray distributions. The latter effect may be especially severe when data sets include earthquake swarms or aftershock sequences, and may produce the appearance of correlation between structural changes and seismicity when the wave speeds are actually temporally invariant. A better approach, which makes it possible to assess what changes are truly required by the data, is to invert multiple data sets simultaneously, minimizing the difference between models for different epochs as well as the rms arrival-time residuals. This problem leads, in the case of two epochs, to a system of normal equations whose order is twice as great as for a single epoch. The direct solution of this system would require twice as much memory and four times as much computational effort as would independent inversions. We present an algorithm, tomo4d, that takes advantage of the structure and sparseness of the system to obtain the solution with essentially no more effort than independent inversions require. No claim to original US government works Journal compilation ?? 2010 RAS.
Multiscale modeling of large deformations in 3-D polycrystals
International Nuclear Information System (INIS)
Lu Jing; Maniatty, Antoinette; Misiolek, Wojciech; Bandar, Alexander
2004-01-01
An approach for modeling 3-D polycrystals, linking to the macroscale, is presented. A Potts type model is used to generate a statistically representative grain structures with periodicity to allow scale-linking. The grain structures are compared to experimentally observed grain structures to validate that they are representative. A macroscale model of a compression test is compared against an experimental compression test for an Al-Mg-Si alloy to determine various deformation paths at different locations in the samples. These deformation paths are then applied to the experimental grain structure using a scale-bridging technique. Preliminary results from this work will be presented and discussed
Directory of Open Access Journals (Sweden)
Hok Pan Yuen
2016-10-01
Full Text Available Joint modelling has emerged to be a potential tool to analyse data with a time-to-event outcome and longitudinal measurements collected over a series of time points. Joint modelling involves the simultaneous modelling of the two components, namely the time-to-event component and the longitudinal component. The main challenges of joint modelling are the mathematical and computational complexity. Recent advances in joint modelling have seen the emergence of several software packages which have implemented some of the computational requirements to run joint models. These packages have opened the door for more routine use of joint modelling. Through simulations and real data based on transition to psychosis research, we compared joint model analysis of time-to-event outcome with the conventional Cox regression analysis. We also compared a number of packages for fitting joint models. Our results suggest that joint modelling do have advantages over conventional analysis despite its potential complexity. Our results also suggest that the results of analyses may depend on how the methodology is implemented.
Simulation of quasistatic deformations using discrete rod models
Linn, J.; Stephan, T.
2008-01-01
Recently we developed a discrete model of elastic rods with symmetric cross section suitable for a fast simulation of quasistatic deformations [33]. The model is based on Kirchhoff’s geometrically exact theory of rods. Unlike simple models of “mass & spring” type typically used in VR applications, our model provides a proper coupling of bending and torsion. The computational approach comprises a variational formulation combined with a finite difference discretization of the continuum model. A...
A Deformable Template Model, with Special Reference to Elliptical Templates
DEFF Research Database (Denmark)
Hobolth, Asger; Pedersen, Jan; Jensen, Eva Bjørn Vedel
2002-01-01
This paper suggests a high-level continuous image model for planar star-shaped objects. Under this model, a planar object is a stochastic deformation of a star-shaped template. The residual process, describing the difference between the radius-vector function of the template and the object...
Star, Willem M.; Aalders, Maurice C. G.; Sac, Arnoldo; Sterenborg, Henricus J. C. M.
2002-01-01
We present a mathematical layer model to quantitatively calculate the diffusion of 5-aminolevulinic acid (ALA) in the skin in vivo, its uptake into the cells and its conversion to protoporphyrin IX (PpIX) and subsequently to heme. The model is a modification and extension of a recently presented
Semantic modeling of plastic deformation of polycrystalline rock
Babaie, Hassan A.; Davarpanah, Armita
2018-02-01
We have developed the first iteration of the Plastic Rock Deformation (PRD) ontology by modeling the semantics of a selected set of deformational processes and mechanisms that produce, reconfigure, displace, and/or consume the material components of inhomogeneous polycrystalline rocks. The PRD knowledge model also classifies and formalizes the properties (relations) that hold between instances of the dynamic physical and chemical processes and the rock components, the complex physio-chemical, mathematical, and informational concepts of the plastic rock deformation system, the measured or calculated laboratory testing conditions, experimental procedures and protocols, the state and system variables, and the empirical flow laws that define the inter-relationships among the variables. The ontology reuses classes and properties from several existing ontologies that are built for physics, chemistry, biology, and mathematics. With its flexible design, the PRD ontology is well positioned to incrementally develop into a model that more fully represents the knowledge of plastic deformation of polycrystalline rocks in the future. The domain ontology will be used to consistently annotate varied data and information related to the microstructures and the physical and chemical processes that produce them at different spatial and temporal scales in the laboratory and in the solid Earth. The PRDKB knowledge base, when built based on the ontology, will help the community of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and integration and query of heterogeneous experimental deformation data that originate from autonomous rock testing laboratories.
Directory of Open Access Journals (Sweden)
Laura Facchini
2017-10-01
Full Text Available Cell oxygenation and nutrition is vitally important for human and animal life. Oxygen and nutrients are transported by the blood stream and cross microvessel walls to penetrate the cell’s membrane. Pathological alterations in the transport of oxygen, and other nutrition elements, across microvessel walls may have serious consequences to cell life, possibly leading to localized cell necrosis. We present a transient model of plasma filtration and solute transport across microvessel walls by coupling flow and transport equations, the latter being non-linear in solute concentration. The microvessel wall is modeled through the superimposition of two or more membranes with different physical properties, representing key structural elements. With this model, the combined effect of the endothelial cells, the glycocalyx and other coating membranes specific of certain microvessels, can be analyzed. We investigate the role of transient external pressures in the study of trans-vascular filtration and solute exchange during the drop of blood capillary pressure due to the pathological decrease of blood volume called hypovolaemia, as well as hemorrhage. We discuss the advantage of using a multi-layered model, rather than a model considering the microvessel wall as a single and homogeneous membrane.
Time-dependent behavior of concrete
International Nuclear Information System (INIS)
Pfeiffer, P.A.; Tanabe, Tada-aki
1992-01-01
This paper is a condensed version of the material presented at the International Workshop on Finite Element Analysis of Reinforced Concrete, Session 4 -- Time Dependent Behavior, held at Columbia University, New York on June 3--6, 1991. Dr. P.A. Pfeiffer presented recent developments in time-dependent behavior of concrete and Professor T. Tanabe presented a review of research in Japan on time-dependent behavior of concrete. The paper discusses the recent research of time-dependent behavior of concrete in the past few years. 6 refs
Sommer, Harriet; Wolkewitz, Martin; Schumacher, Martin
2017-07-01
A variety of primary endpoints are used in clinical trials treating patients with severe infectious diseases, and existing guidelines do not provide a consistent recommendation. We propose to study simultaneously two primary endpoints, cure and death, in a comprehensive multistate cure-death model as starting point for a treatment comparison. This technique enables us to study the temporal dynamic of the patient-relevant probability to be cured and alive. We describe and compare traditional and innovative methods suitable for a treatment comparison based on this model. Traditional analyses using risk differences focus on one prespecified timepoint only. A restricted logrank-based test of treatment effect is sensitive to ordered categories of responses and integrates information on duration of response. The pseudo-value regression provides a direct regression model for examination of treatment effect via difference in transition probabilities. Applied to a topical real data example and simulation scenarios, we demonstrate advantages and limitations and provide an insight into how these methods can handle different kinds of treatment imbalances. The cure-death model provides a suitable framework to gain a better understanding of how a new treatment influences the time-dynamic cure and death process. This might help the future planning of randomised clinical trials, sample size calculations, and data analyses. Copyright © 2017 John Wiley & Sons, Ltd.
Kasper, Joseph M; Lestrange, Patrick J; Stetina, Torin F; Li, Xiaosong
2018-04-10
X-ray absorption spectroscopy is a powerful technique to probe local electronic and nuclear structure. There has been extensive theoretical work modeling K-edge spectra from first principles. However, modeling L-edge spectra directly with density functional theory poses a unique challenge requiring further study. Spin-orbit coupling must be included in the model, and a noncollinear density functional theory is required. Using the real-time exact two-component method, we are able to variationally include one-electron spin-orbit coupling terms when calculating the absorption spectrum. The abilities of different basis sets and density functionals to model spectra for both closed- and open-shell systems are investigated using SiCl 4 and three transition metal complexes, TiCl 4 , CrO 2 Cl 2 , and [FeCl 6 ] 3- . Although we are working in the real-time framework, individual molecular orbital transitions can still be recovered by projecting the density onto the ground state molecular orbital space and separating contributions to the time evolving dipole moment.
Time dependent fracture and cohesive zones
Knauss, W. G.
1993-01-01
This presentation is concerned with the fracture response of materials which develop cohesive or bridging zones at crack tips. Of special interest are concerns regarding crack stability as a function of the law which governs the interrelation between the displacement(s) or strain across these zones and the corresponding holding tractions. It is found that for some materials unstable crack growth can occur, even before the crack tip has experienced a critical COD or strain across the crack, while for others a critical COD will guarantee the onset of fracture. Also shown are results for a rate dependent nonlinear material model for the region inside of a craze for exploring time dependent crack propagation of rate sensitive materials.
Time-dependent dilatancy for brittle rocks
Directory of Open Access Journals (Sweden)
Jie Li
2017-12-01
Full Text Available This paper presents a theoretical study on time-dependent dilatancy behaviors for brittle rocks. The theory employs a well-accepted postulation that macroscopically observed dilatancy originates from the expansion of microcracks. The mechanism and dynamic process that microcracks initiate from local stress concentration and grow due to localized tensile stress are analyzed. Then, by generalizing the results from the analysis of single cracks, a parameter and associated equations for its evolution are developed to describe the behaviors of the microcracks. In this circumstance, the relationship between microcracking and dilatancy can be established, and the theoretical equations for characterizing the process of rock dilatancy behaviors are derived. Triaxial compression and creep tests are conducted to validate the developed theory. With properly chosen model parameters, the theory yields a satisfactory accuracy in comparison with the experimental results.
Schalge, Bernd; Rihani, Jehan; Haese, Barbara; Baroni, Gabriele; Erdal, Daniel; Haefliger, Vincent; Lange, Natascha; Neuweiler, Insa; Hendricks-Franssen, Harrie-Jan; Geppert, Gernot; Ament, Felix; Kollet, Stefan; Cirpka, Olaf; Saavedra, Pablo; Han, Xujun; Attinger, Sabine; Kunstmann, Harald; Vereecken, Harry; Simmer, Clemens
2017-04-01
Currently, an integrated approach to simulating the earth system is evolving where several compartment models are coupled to achieve the best possible physically consistent representation. We used the model TerrSysMP, which fully couples subsurface, land surface and atmosphere, in a synthetic study that mimicked the Neckar catchment in Southern Germany. A virtual reality run at a high resolution of 400m for the land surface and subsurface and 1.1km for the atmosphere was made. Ensemble runs at a lower resolution (800m for the land surface and subsurface) were also made. The ensemble was generated by varying soil and vegetation parameters and lateral atmospheric forcing among the different ensemble members in a systematic way. It was found that the ensemble runs deviated for some variables and some time periods largely from the virtual reality reference run (the reference run was not covered by the ensemble), which could be related to the different model resolutions. This was for example the case for river discharge in the summer. We also analyzed the spread of model states as function of time and found clear relations between the spread and the time of the year and weather conditions. For example, the ensemble spread of latent heat flux related to uncertain soil parameters was larger under dry soil conditions than under wet soil conditions. Another example is that the ensemble spread of atmospheric states was more influenced by uncertain soil and vegetation parameters under conditions of low air pressure gradients (in summer) than under conditions with larger air pressure gradients in winter. The analysis of the ensemble of fully coupled model simulations provided valuable insights in the dynamics of land-atmosphere feedbacks which we will further highlight in the presentation.
A Dynamic Stall Model for Airfoils with Deformable Trailing Edges
International Nuclear Information System (INIS)
Andersen, Peter Bjoern; Gaunaa, Mac; Bak, Christian; Hansen, Morten Hartvig
2007-01-01
The present work contains an extension of the Beddoes-Leishman (B-L) type dynamic stall model, as described by Hansen et al. In this work a Deformable Trailing Edge Geometry (DTEG) has been added to the dynamic stall model. The model predicts the unsteady aerodynamic forces and moments on an airfoil section undergoing arbitrary motion in heave, lead-lag, pitch, Trailing Edge (TE) flapping. In the linear region, the model reduces to the inviscid model of Gaunaa, which includes the aerodynamic effect of a thin airfoil with a deformable camberline in inviscid flow. Therefore, the proposed model can be considered a crossover between the work of Gaunaa for the attached flow region and Hansen et al. The model will be compared to wind tunnel measurements from Velux described by Bak et al
DEFF Research Database (Denmark)
Demetrescu, Crisan; Wilhelm, H.; Tumanian, M.
2007-01-01
in establishing the temperature field in the depth range of geothermal measurements. The lateral variation of the palaeoclimatically corrected surface heat flux from the centre of the Focsani Depression (40 mW m-2) to its margin and the foreland platform (70 mW m-2) is mainly the result of the lateral variation...... words: Carpathians foreland, geothermics, heat flow, lithosphere rheology, sedimentation, thermal modelling. ...
McClellan, Gene; Coleman, Margaret; Crary, David; Thurman, Alec; Thran, Brandolyn
2018-04-25
Military health risk assessors, medical planners, operational planners, and defense system developers require knowledge of human responses to doses of biothreat agents to support force health protection and chemical, biological, radiological, nuclear (CBRN) defense missions. This article reviews extensive data from 118 human volunteers administered aerosols of the bacterial agent Francisella tularensis, strain Schu S4, which causes tularemia. The data set includes incidence of early-phase febrile illness following administration of well-characterized inhaled doses of F. tularensis. Supplemental data on human body temperature profiles over time available from de-identified case reports is also presented. A unified, logically consistent model of early-phase febrile illness is described as a lognormal dose-response function for febrile illness linked with a stochastic time profile of fever. Three parameters are estimated from the human data to describe the time profile: incubation period or onset time for fever; rise time of fever; and near-maximum body temperature. Inhaled dose-dependence and variability are characterized for each of the three parameters. These parameters enable a stochastic model for the response of an exposed population through incorporation of individual-by-individual variability by drawing random samples from the statistical distributions of these three parameters for each individual. This model provides risk assessors and medical decisionmakers reliable representations of the predicted health impacts of early-phase febrile illness for as long as one week after aerosol exposures of human populations to F. tularensis. © 2018 Society for Risk Analysis.
Ohannessian, Robin; Gustin, Marie-Paule; Bénet, Thomas; Gerbier-Colomban, Solweig; Girard, Raphaele; Argaud, Laurent; Rimmelé, Thomas; Guerin, Claude; Bohé, Julien; Piriou, Vincent; Vanhems, Philippe
2018-04-10
The objective of the study was to estimate the length of stay of patients with hospital-acquired infections hospitalized in ICUs using a multistate model. Active prospective surveillance of hospital-acquired infection from January 1, 1995, to December 31, 2012. Twelve ICUs at the University of Lyon hospital (France). Adult patients age greater than or equal to 18 years old and hospitalized greater than or equal to 2 days were included in the surveillance. All hospital-acquired infections (pneumonia, bacteremia, and urinary tract infection) occurring during ICU stay were collected. None. The competitive risks of in-hospital death, transfer, or discharge were considered in estimating the change in length of stay due to infection(s), using a multistate model, time of infection onset. Thirty-three thousand four-hundred forty-nine patients were involved, with an overall hospital-acquired infection attack rate of 15.5% (n = 5,176). Mean length of stay was 27.4 (± 18.3) days in patients with hospital-acquired infection and 7.3 (± 7.6) days in patients without hospital-acquired infection. A multistate model-estimated mean found an increase in length of stay by 5.0 days (95% CI, 4.6-5.4 d). The extra length of stay increased with the number of infected site and was higher for patients discharged alive from ICU. No increased length of stay was found for patients presenting late-onset hospital-acquired infection, more than the 25th day after admission. An increase length of stay of 5 days attributable to hospital-acquired infection in the ICU was estimated using a multistate model in a prospective surveillance study in France. The dose-response relationship between the number of hospitalacquired infection and length of stay and the impact of early-stage hospital-acquired infection may strengthen attention for clinicians to focus interventions on early preventions of hospital-acquired infection in ICU.
Interactive collision detection for deformable models using streaming AABBs.
Zhang, Xinyu; Kim, Young J
2007-01-01
We present an interactive and accurate collision detection algorithm for deformable, polygonal objects based on the streaming computational model. Our algorithm can detect all possible pairwise primitive-level intersections between two severely deforming models at highly interactive rates. In our streaming computational model, we consider a set of axis aligned bounding boxes (AABBs) that bound each of the given deformable objects as an input stream and perform massively-parallel pairwise, overlapping tests onto the incoming streams. As a result, we are able to prevent performance stalls in the streaming pipeline that can be caused by expensive indexing mechanism required by bounding volume hierarchy-based streaming algorithms. At runtime, as the underlying models deform over time, we employ a novel, streaming algorithm to update the geometric changes in the AABB streams. Moreover, in order to get only the computed result (i.e., collision results between AABBs) without reading back the entire output streams, we propose a streaming en/decoding strategy that can be performed in a hierarchical fashion. After determining overlapped AABBs, we perform a primitive-level (e.g., triangle) intersection checking on a serial computational model such as CPUs. We implemented the entire pipeline of our algorithm using off-the-shelf graphics processors (GPUs), such as nVIDIA GeForce 7800 GTX, for streaming computations, and Intel Dual Core 3.4G processors for serial computations. We benchmarked our algorithm with different models of varying complexities, ranging from 15K up to 50K triangles, under various deformation motions, and the timings were obtained as 30 approximately 100 FPS depending on the complexity of models and their relative configurations. Finally, we made comparisons with a well-known GPU-based collision detection algorithm, CULLIDE [4] and observed about three times performance improvement over the earlier approach. We also made comparisons with a SW-based AABB
MULTISCALE SPARSE APPEARANCE MODELING AND SIMULATION OF PATHOLOGICAL DEFORMATIONS
Directory of Open Access Journals (Sweden)
Rami Zewail
2017-08-01
Full Text Available Machine learning and statistical modeling techniques has drawn much interest within the medical imaging research community. However, clinically-relevant modeling of anatomical structures continues to be a challenging task. This paper presents a novel method for multiscale sparse appearance modeling in medical images with application to simulation of pathological deformations in X-ray images of human spine. The proposed appearance model benefits from the non-linear approximation power of Contourlets and its ability to capture higher order singularities to achieve a sparse representation while preserving the accuracy of the statistical model. Independent Component Analysis is used to extract statistical independent modes of variations from the sparse Contourlet-based domain. The new model is then used to simulate clinically-relevant pathological deformations in radiographic images.
Resin flow/fiber deformation model for composites
International Nuclear Information System (INIS)
Gutowski, T.G.
1985-01-01
This paper presents a resin flow/fiber deformation model that can be used to predict the behavior of composites during the molding cycle. The model can take into account time varying pressure and viscosity and output the time history of the fiber volume fraction. With this known, the composite thickness, resin pressure, and fiber pressure can all be determined as a function of time. The results of this model are in good agreement with experimentally measured values. 10 references, 9 figures
A stochastic large deformation model for computational anatomy
DEFF Research Database (Denmark)
Arnaudon, Alexis; Holm, Darryl D.; Pai, Akshay Sadananda Uppinakudru
2017-01-01
In the study of shapes of human organs using computational anatomy, variations are found to arise from inter-subject anatomical differences, disease-specific effects, and measurement noise. This paper introduces a stochastic model for incorporating random variations into the Large Deformation...
Modelling the deformation process of flexible stamps for nanoimprint lithography
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard
of PTFE against steel on micro-scale is presented. The 2D axisymmetric model is verified through an experiment, in which a PTFE sheet with a predefined square grid pattern on the surface is deformed by a steel sphere mounted in a uniaxial tensile test machine. Good agreement between simulations...
Deformed shell model studies of spectroscopic properties of Zn and ...
Indian Academy of Sciences (India)
2014-04-05
Apr 5, 2014 ... April 2014 physics pp. 757–767. Deformed shell model studies of ... experiments without isotopical enrichment thereby reducing the cost considerably. By taking a large mass of the sample because of its low cost, one can ...
Nuclear deformation in the configuration-interaction shell model
Alhassid, Y.; Bertsch, G. F.; Gilbreth, C. N.; Mustonen, M. T.
2018-02-01
We review a method that we recently introduced to calculate the finite-temperature distribution of the axial quadrupole operator in the laboratory frame using the auxiliary-field Monte Carlo technique in the framework of the configuration-interaction shell model. We also discuss recent work to determine the probability distribution of the quadrupole shape tensor as a function of intrinsic deformation β,γ by expanding its logarithm in quadrupole invariants. We demonstrate our method for an isotope chain of samarium nuclei whose ground states describe a crossover from spherical to deformed shapes.
Stationary solution of a time dependent density matrix formalism
International Nuclear Information System (INIS)
Tohyama, Mitsuru
1994-01-01
A stationary solution of a time-dependent density-matrix formalism, which is an extension of the time-dependent Hartree-Fock theory to include the effects of two-body correlations, is obtained for the Lipkin model hamiltonian, using an adiabatic treatment of the two-body interaction. It is found that the obtained result is a reasonable approximation for the exact solution of the model. (author)
Cosmologies with a time dependent vacuum
International Nuclear Information System (INIS)
Sola, Joan
2011-01-01
The idea that the cosmological term Λ should be a time dependent quantity in cosmology is a most natural one. It is difficult to conceive an expanding universe with a strictly constant vacuum energy density, ρ Λ = Λ/(8π G), namely one that has remained immutable since the origin of time. A smoothly evolving vacuum energy density ρ Λ = ρ Λ (ξ(t)) that inherits its time-dependence from cosmological functions ξ = ξ(t), such as the Hubble rate H(t) or the scale factor a(t), is not only a qualitatively more plausible and intuitive idea, but is also suggested by fundamental physics, in particular by quantum field theory (QFT) in curved space-time. To implement this notion, is not strictly necessary to resort to ad hoc scalar fields, as usually done in the literature (e.g. in quintessence formulations and the like). A 'running' Λ term can be expected on very similar grounds as one expects (and observes) the running of couplings and masses with a physical energy scale in QFT. Furthermore, the experimental evidence that the equation of state (EOS) of the dark energy (DE) could be evolving with time/redshift (including the possibility that it might currently behave phantom-like) suggests that a time-variable Λ = Λ(t) term (possibly accompanied by a variable Newton's gravitational coupling too, G = G(t)) could account in a natural way for all these features. Remarkably enough, a class of these models (the 'new cosmon') could even be the clue for solving the old cosmological constant problem, including the coincidence problem.
Trost, A; Motloch, K; Bruckner, D; Schroedl, F; Bogner, B; Kaser-Eichberger, A; Runge, C; Strohmaier, C; Klein, B; Aigner, L; Reitsamer, H A
2015-07-01
Glaucoma is a group of neurodegenerative diseases characterized by the progressive loss of retinal ganglion cells (RGCs) and their axons, and is the second leading cause of blindness worldwide. Elevated intraocular pressure is a well known risk factor for the development of glaucomatous optic neuropathy and pharmacological or surgical lowering of intraocular pressure represents a standard procedure in glaucoma treatment. However, the treatment options are limited and although lowering of intraocular pressure impedes disease progression, glaucoma cannot be cured by the currently available therapy concepts. In an acute short-term ocular hypertension model in rat, we characterize RGC loss, but also microglial cell activation and vascular alterations of the retina at certain time points. The combination of these three parameters might facilitate a better evaluation of the disease progression, and could further serve as a new model to test novel treatment strategies at certain time points. Acute ocular hypertension (OHT) was induced by the injection of magnetic microbeads into the rat anterior chamber angle (n = 22) with magnetic position control, leading to constant elevation of IOP. At certain time points post injection (4d, 7d, 10d, 14d and 21d), RGC loss, microglial activation, and microvascular pericyte (PC) coverage was analyzed using immunohistochemistry with corresponding specific markers (Brn3a, Iba1, NG2). Additionally, the tightness of the retinal vasculature was determined via injections of Texas Red labeled dextran (10 kDa) and subsequently analyzed for vascular leakage. For documentation, confocal laser-scanning microscopy was used, followed by cell counts, capillary length measurements and morphological and statistical analysis. The injection of magnetic microbeads led to a progressive loss of RGCs at the five time points investigated (20.07%, 29.52%, 41.80%, 61.40% and 76.57%). Microglial cells increased in number and displayed an activated morphology
A Survey On Physical Methods For Deformation Modeling
Directory of Open Access Journals (Sweden)
Huda Basloom
2015-08-01
Full Text Available Much effort has been dedicated to achieving realism in the simulation of deformable objects such as cloth hair rubber sea water smoke and human soft tissue in surgical simulation. However the deformable object in these simulations will exhibit physically correct behaviors true to the behavior of real objects when any force is applied to it and sometimes this requires real-time simulation. No matter how complex the geometry is real-time simulation is still required in some applications. Surgery simulation is an example of the need for real-time simulation. This situation has attracted the attention of a wide community of researchers such as computer scientists mechanical engineers biomechanics and computational geometers. This paper presents a review of the existing techniques for modeling deformable objects which have been developed within the last three decades for different computer graphics interactive applications.
Fuzzy model for predicting the number of deformed wheels
Directory of Open Access Journals (Sweden)
Ž. Đorđević
2015-10-01
Full Text Available Deformation of the wheels damage cars and rails and affect on vehicle stability and safety. Repair and replacement cause high costs and lack of wagons. Planning of maintenance of wagons can not be done without estimates of the number of wheels that will be replaced due to wear and deformation in a given period of time. There are many influencing factors, the most important are: weather conditions, quality of materials, operating conditions, and distance between the two replacements. The fuzzy logic model uses the collected data as input variables to predict the output variable - number of deformed wheels for a certain type of vehicle in the defined period at a particular section of the railway.
Ishii, T; Niikura, Y; Kurata, K; Muroi, M; Tanamoto, K; Nagase, T; Sakaguchi, M; Yamashita, N
2018-03-01
House dust mites (HDMs) are a common source of allergens that trigger both allergen-specific and innate immune responses in humans. Here, we examined the effect of allergen concentration and the involvement of Toll-like receptor 4 (TLR4) in the process of sensitization to house dust mite allergens in an HDM extract-induced asthma mouse model. Intranasal administration of HDM extract induced an immunoglobulin E response and eosinophilic inflammation in a dose-dependent manner from 2.5 to 30 μg/dose. In TLR4-knockout mice, the infiltration of eosinophils and neutrophils into the lung was decreased compared with that in wild-type mice in the early phase of inflammation (total of three doses). However, in the late phase of inflammation (total of seven doses), eosinophil infiltration was significantly greater in TLR4-knockout mice than in wild-type mice. This suggests that the roles of TLR4 signaling are different between the early phase and the later phase of HDM allergen-induced inflammation. Thus, innate immune response through TLR4 regulated the response to HDM allergens, and the regulation was altered during the phase of inflammation. © 2018 The Foundation for the Scandinavian Journal of Immunology.
Modeling of 3D Aluminum Polycrystals during Large Deformations
International Nuclear Information System (INIS)
Maniatty, Antoinette M.; Littlewood, David J.; Lu Jing; Pyle, Devin
2007-01-01
An approach for generating, meshing, and modeling 3D polycrystals, with a focus on aluminum alloys, subjected to large deformation processes is presented. A Potts type model is used to generate statistically representative grain structures with periodicity to allow scale-linking. The grain structures are compared to experimentally observed grain structures to validate that they are representative. A procedure for generating a geometric model from the voxel data is developed allowing for adaptive meshing of the generated grain structure. Material behavior is governed by an appropriate crystal, elasto-viscoplastic constitutive model. The elastic-viscoplastic model is implemented in a three-dimensional, finite deformation, mixed, finite element program. In order to handle the large-scale problems of interest, a parallel implementation is utilized. A multiscale procedure is used to link larger scale models of deformation processes to the polycrystal model, where periodic boundary conditions on the fluctuation field are enforced. Finite-element models, of 3D polycrystal grain structures will be presented along with observations made from these simulations
Comparison of models discribing cladding deformations during LOCA
International Nuclear Information System (INIS)
Chakraborty, A.K.; Zipper, R.
1981-05-01
This report compares the important models for the determination of cladding deformations during LOCA. In addition to the comparisons of underlying assumptions of different models the same is done for the coefficients applied for the models. In order to assess the predictive capability of the models the calculated results are compared with the experimental results of the individual claddings. It was found out that the results of temperature ramp tests could be calculated better than that of the pressure ramp tests. The calculations revealed that even with the simplified assumption of the model used in TESPA the agreement of the calculated results with those of model NORA was relatively good. (orig.) [de
Jeong, Yoseok; Lee, Jaeha; Kim, WooSeok
2015-01-29
This paper aims at presenting the effects of short-term sustained load and temperature on time-dependent deformation of carbon fiber-reinforced polymer (CFRP) bonded to concrete and pull-off strength at room temperature after the sustained loading period. The approach involves experimental and numerical analysis. Single-lap shear specimens were used to evaluate temperature and short-term sustained loading effects on time-dependent behavior under sustained loading and debonding behavior under pull-off loading after a sustained loading period. The numerical model was parameterized with experiments on the concrete, FRP, and epoxy. Good correlation was seen between the numerical results and single-lap shear experiments. Sensitivity studies shed light on the influence of temperature, epoxy modulus, and epoxy thickness on the redistribution of interfacial shear stress during sustained loading. This investigation confirms the hypothesis that interfacial stress redistribution can occur due to sustained load and elevated temperature and its effect can be significant.
Time-dependent correlations in electricity markets
International Nuclear Information System (INIS)
Alvarez-Ramirez, Jose; Escarela-Perez, Rafael
2010-01-01
In the last years, many electricity markets were subjected to deregulated operation where prices are set by the action of market participants. In this form, producers and consumers rely on demand and price forecasts to decide their bidding strategies, allocate assets, negotiate bilateral contracts, hedge risks, and plan facility investments. A basic feature of efficient market hypothesis is the absence of correlations between price increments over any time scale leading to random walk-type behavior of prices, so arbitrage is not possible. However, recent studies have suggested that this is not the case and correlations are present in the behavior of diverse electricity markets. In this paper, a temporal quantification of electricity market correlations is made by means of detrended fluctuation and Allan analyses. The approach is applied to two Canadian electricity markets, Ontario and Alberta. The results show the existence of correlations in both demand and prices, exhibiting complex time-dependent behavior with lower correlations in winter while higher in summer. Relatively steady annual cycles in demand but unstable cycles in prices are detected. On the other hand, the more significant nonlinear effects (measured in terms of a multifractality index) are found for winter months, while the converse behavior is displayed during the summer period. In terms of forecasting models, our results suggest that nonlinear recursive models (e.g., feedback NNs) should be used for accurate day-ahead price estimation. In contrast, linear models can suffice for demand forecasting purposes. (author)
Energy Technology Data Exchange (ETDEWEB)
Yokogawa, D., E-mail: d.yokogawa@chem.nagoya-u.ac.jp [Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8602 (Japan)
2016-09-07
Theoretical approach to design bright bio-imaging molecules is one of the most progressing ones. However, because of the system size and computational accuracy, the number of theoretical studies is limited to our knowledge. To overcome the difficulties, we developed a new method based on reference interaction site model self-consistent field explicitly including spatial electron density distribution and time-dependent density functional theory. We applied it to the calculation of indole and 5-cyanoindole at ground and excited states in gas and solution phases. The changes in the optimized geometries were clearly explained with resonance structures and the Stokes shift was correctly reproduced.
Deformation modeling and the strain transient dip test
International Nuclear Information System (INIS)
Jones, W.B.; Rohde, R.W.; Swearengen, J.C.
1980-01-01
Recent efforts in material deformation modeling reveal a trend toward unifying creep and plasticity with a single rate-dependent formulation. While such models can describe actual material deformation, most require a number of different experiments to generate model parameter information. Recently, however, a new model has been proposed in which most of the requisite constants may be found by examining creep transients brought about through abrupt changes in creep stress (strain transient dip test). The critical measurement in this test is the absence of a resolvable creep rate after a stress drop. As a consequence, the result is extraordinarily sensitive to strain resolution as well as machine mechanical response. This paper presents the design of a machine in which these spurious effects have been minimized and discusses the nature of the strain transient dip test using the example of aluminum. It is concluded that the strain transient dip test is not useful as the primary test for verifying any micromechanical model of deformation. Nevertheless, if a model can be developed which is verifiable by other experimentts, data from a dip test machine may be used to generate model parameters
Modeling shockwave deformation via molecular dynamics
International Nuclear Information System (INIS)
Holian, B.L.
1987-01-01
Molecular dynamics (MD), where the equations of motion of up to thousands of interacting atoms are solved on the computer, has proven to be a powerful tool for investigating a wide variety of nonequilibrium processes from the atomistic viewpoint. Simulations of shock waves in three-dimensional (3D) solids and fluids have shown conclusively that shear-stress relaxation is achieved through atomic rearrangement. In the case of fluids, the transverse motion is viscous, and the constitutive model of Navier-Stokes hydrodynamics has been shown to be accurate - even on the time and distance scales of MD experiments. For strong shocks in solids, the plastic flow that leads to shear-stress relaxation in MD is highly localized near the shock front, involving a slippage along close-packed planes. For shocks of intermediate strength, MD calculations exhibit an elastic precursor running out in front of the steady plastic wave, where slippage similar in character to that in the very strong shocks leads to shear-stress relaxation. An interesting correlation between the maximum shear stress and the Hugoniot pressure jump is observed for both 3D and fluid shockwave calculations, which may have some utility in modeling applications. At low shock strengths, the MD simulations show only elastic compression, with no permanent transverse atomic strains. The result for perfect 3D crystals is also seen in calculations for 1D chains. It is speculated that, if it were practical, a very large MD system containing dislocations could be expected to exhibit more realistic plastic flow for weak shock waves, too
Ohlendorf, S. J.; Feigl, K.; Thurber, C. H.; Lu, Z.; Masterlark, T.
2011-12-01
Okmok Volcano is an active caldera located on Umnak Island in the Aleutian Island arc. Okmok, having recently erupted in 1997 and 2008, is well suited for multidisciplinary studies of magma migration and storage because it hosts a good seismic network and has been the subject of synthetic aperture radar (SAR) images that span the recent eruption cycle. Interferometric SAR can characterize surface deformation in space and time, while data from the seismic network provides important information about the interior processes and structure of the volcano. We conduct a complete time series analysis of deformation of Okmok with images collected by the ERS and Envisat satellites on more than 100 distinct epochs between 1993 and 2008. We look for changes in inter-eruption inflation rates, which may indicate inelastic rheologic effects. For the time series analysis, we analyze the gradient of phase directly, without unwrapping, using the General Inversion of Phase Technique (GIPhT) [Feigl and Thurber, 2009]. This approach accounts for orbital and atmospheric effects and provides realistic estimates of the uncertainties of the model parameters. We consider several models for the source, including the prolate spheroid model and the Mogi model, to explain the observed deformation. Using a medium that is a homogeneous half space, we estimate the source depth to be centered at about 4 km below sea level, consistent with the findings of Masterlark et al. [2010]. As in several other geodetic studies, we find the source to be approximately centered beneath the caldera. To account for rheologic complexity, we next apply the Finite Element Method to simulate a pressurized cavity embedded in a medium with material properties derived from body wave seismic tomography. This approach allows us to address the problem of unreasonably large pressure values implied by a Mogi source with a radius of about 1 km by experimenting with larger sources. We also compare the time dependence of the
CANDU fuel bundle deformation modelling with COMSOL multiphysics
International Nuclear Information System (INIS)
Bell, J.S.; Lewis, B.J.
2012-01-01
Highlights: ► The deformation behaviour of a CANDU fuel bundle was modelled. ► The model has been developed on a commercial finite-element platform. ► Pellet/sheath interaction and end-plate restraint effects were considered. ► The model was benchmarked against the BOW code and a variable-load experiment. - Abstract: A model to describe deformation behaviour of a CANDU 37-element bundle has been developed under the COMSOL Multiphysics finite-element platform. Beam elements were applied to the fuel elements (composed of fuel sheaths and pellets) and endplates in order to calculate the bowing behaviour of the fuel elements. This model is important to help assess bundle-deformation phenomena, which may lead to more restrictive coolant flow through the sub-channels of the horizontally oriented bundle. The bundle model was compared to the BOW code for the occurrence of a dry-out patch, and benchmarked against an out-reactor experiment with a variable load on an outer fuel element.
Semiautomated four-dimensional computed tomography segmentation using deformable models
International Nuclear Information System (INIS)
Ragan, Dustin; Starkschall, George; McNutt, Todd; Kaus, Michael; Guerrero, Thomas; Stevens, Craig W.
2005-01-01
The purpose of this work is to demonstrate a proof of feasibility of the application of a commercial prototype deformable model algorithm to the problem of delineation of anatomic structures on four-dimensional (4D) computed tomography (CT) image data sets. We acquired a 4D CT image data set of a patient's thorax that consisted of three-dimensional (3D) image data sets from eight phases in the respiratory cycle. The contours of the right and left lungs, cord, heart, and esophagus were manually delineated on the end inspiration data set. An interactive deformable model algorithm, originally intended for deforming an atlas-based model surface to a 3D CT image data set, was applied in an automated fashion. Triangulations based on the contours generated on each phase were deformed to the CT data set on the succeeding phase to generate the contours on that phase. Deformation was propagated through the eight phases, and the contours obtained on the end inspiration data set were compared with the original manually delineated contours. Structures defined by high-density gradients, such as lungs, cord, and heart, were accurately reproduced, except in regions where other gradient boundaries may have confused the algorithm, such as near bronchi. The algorithm failed to accurately contour the esophagus, a soft-tissue structure completely surrounded by tissue of similar density, without manual interaction. This technique has the potential to facilitate contour delineation in 4D CT image data sets; and future evolution of the software is expected to improve the process
Time-dependent crashworthiness of polyurethane foam
Basit, Munshi Mahbubul; Cheon, Seong Sik
2018-05-01
Time-dependent stress-strain relationship as well as crashworthiness of polyurethane foam was investigated under constant impact energy with different velocities, considering inertia and strain-rate effects simultaneously during the impact testing. Even though the impact energies were same, the percentage in increase in densification strain due to higher impact velocities was found, which yielded the wider plateau region, i.e. growth in crashworthiness. This phenomenon is analyzed by the microstructure of polyurethane foam obtained from scanning electron microscopy. The equations, coupled with the Sherwood-Frost model and the impulse-momentum theory, were employed to build the constitutive equation of the polyurethane foam and calculate energy absorption capacity of the foam. The nominal stress-strain curves obtained from the constitutive equation were compared with results from impact tests and were found to be in good agreement. This study is dedicated to guiding designer use polyurethane foam in crashworthiness structures such as an automotive bumper system by providing crashworthiness data, determining the crush mode, and addressing a mathematical model of the crashworthiness.
Microstructure based hygromechanical modelling of deformation of fruit tissue
Abera, M. K.; Wang, Z.; Verboven, P.; Nicolai, B.
2017-10-01
Quality parameters such as firmness and susceptibility to mechanical damage are affected by the mechanical properties of fruit tissue. Fruit tissue is composed of turgid cells that keep cell walls under tension, and intercellular gas spaces where cell walls of neighboring cells have separated. How the structure and properties of these complex microstructures are affecting tissue mechanics is difficult to unravel experimentally. In this contribution, a modelling methodology is presented to calculate the deformation of apple fruit tissue affected by differences in structure and properties of cells and cell walls. The model can be used to perform compression experiments in silico using a hygromechanical model that computes the stress development and water loss during tissue deformation, much like in an actual compression test. The advantage of the model is that properties and structure can be changed to test the influence on the mechanical deformation process. The effect of microstructure, turgor pressure, cell membrane permeability, wall thickness and damping) on the compressibility of the tissue was simulated. Increasing the turgor pressure and thickness of the cell walls results in increased compression resistance of apple tissue increases, as do decreasing cell size and porosity. Geometric variability of the microstructure of tissues plays a major role, affecting results more than other model parameters. Different fruit cultivars were compared, and it was demonstrated, that microstructure variations within a cultivar are so large that interpretation of cultivar-specific effects is difficult.
Time-dependent, Bianchi II, rotating universe
International Nuclear Information System (INIS)
Reboucas, M.J.
1981-01-01
An exact cosmological solution of Einstein's equations which has time-dependent rotation is presented. The t-constant sections are of Bianchi type II. The source of this geometry is a fluid which has not been thermalized. (Author) [pt
Topic 5: Time-Dependent Behavior
International Nuclear Information System (INIS)
Pfeiffer, P.A.; Tanabe, Tada-aki
1991-01-01
This chapter is a report of the material presented at the International Workshop on Finite Element Analysis of Reinforced Concrete, Session 4 -- Time Dependent Behavior, held at Columbia University, New York on June 3--6, 1991. Dr. P.A. Pfeiffer presented recent developments in time-dependent behavior of concrete and Professor T. Tanabe presented a review of research in Japan on time-dependent behavior of concrete. The chapter discusses the recent research of time-dependent behavior of concrete in the past few years in both the USA-European and Japanese communities. The author appreciates the valuable information provided by Zdenek P. Bazant in preparing the USA-European Research section
Chiral symmetry restoration and pion properties in a q-deformed NJL model
International Nuclear Information System (INIS)
Timoteo, V.S.; Lima, C.L.
2006-01-01
We review the implementation of a q-deformed fermionic algebra in the Nambu-Jona-Lasinio model (NJL). The gap equations obtained from a deformed condensate as well as from the deformation of the NJL Hamiltonian are discussed. The effect of both temperature and deformation in the chiral symmetry restoration process as well as in the pion properties is studied. (author)
Jeong, Chan-Yong; Kim, Hee-Joong; Hong, Sae-Young; Song, Sang-Hun; Kwon, Hyuck-In
2017-08-01
In this study, we show that the two-stage unified stretched-exponential model can more exactly describe the time-dependence of threshold voltage shift (ΔV TH) under long-term positive-bias-stresses compared to the traditional stretched-exponential model in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). ΔV TH is mainly dominated by electron trapping at short stress times, and the contribution of trap state generation becomes significant with an increase in the stress time. The two-stage unified stretched-exponential model can provide useful information not only for evaluating the long-term electrical stability and lifetime of the a-IGZO TFT but also for understanding the stress-induced degradation mechanism in a-IGZO TFTs.
A large deformation viscoelastic model for double-network hydrogels
Mao, Yunwei; Lin, Shaoting; Zhao, Xuanhe; Anand, Lallit
2017-03-01
We present a large deformation viscoelasticity model for recently synthesized double network hydrogels which consist of a covalently-crosslinked polyacrylamide network with long chains, and an ionically-crosslinked alginate network with short chains. Such double-network gels are highly stretchable and at the same time tough, because when stretched the crosslinks in the ionically-crosslinked alginate network rupture which results in distributed internal microdamage which dissipates a substantial amount of energy, while the configurational entropy of the covalently-crosslinked polyacrylamide network allows the gel to return to its original configuration after deformation. In addition to the large hysteresis during loading and unloading, these double network hydrogels also exhibit a substantial rate-sensitive response during loading, but exhibit almost no rate-sensitivity during unloading. These features of large hysteresis and asymmetric rate-sensitivity are quite different from the response of conventional hydrogels. We limit our attention to modeling the complex viscoelastic response of such hydrogels under isothermal conditions. Our model is restricted in the sense that we have limited our attention to conditions under which one might neglect any diffusion of the water in the hydrogel - as might occur when the gel has a uniform initial value of the concentration of water, and the mobility of the water molecules in the gel is low relative to the time scale of the mechanical deformation. We also do not attempt to model the final fracture of such double-network hydrogels.
Time-dependent EQPET analysis of TSC
International Nuclear Information System (INIS)
Takahashi, Akito
2006-01-01
Time-dependent fusion rates for 2D and 4D reactions are calculated for squeezing of tetrahedral symmetric condensate (TSC) from about 100 pm size to its minimum size (about 10 fm), within about 75 fs squeezing motion. Life time of the minimum TSC state is yet to be studied. Time-averaged fusion rates are given by assuming the life time of minimum TSC state is negligible. Time-averaged 2D fusion rate was given as 2.9x10 -25 f/s/pair, and time-averaged 4D fusion rate was 5.5x10 -8 f/s/cl. These values are compared with 1.0x10 -20 f/s/pair for 2D and 1.0x10 -9 f/s/cl for 4D, respectively, of previously estimated values by electronic quasi-particle expansion theory/TSC models. Effective fusion time by the TSC squeezing motion was estimated as 0.014 fs: namely fusions may happen in very short time interval. (author)
Description of deformed nuclei in the sdg boson model
International Nuclear Information System (INIS)
Li, S.C.; Kuyucak, S.
1996-01-01
We present a study of deformed nuclei in the framework of the sdg interacting boson model utilizing both numerical diagonalization and analytical 1/N expansion techniques. The focus is on the description of high-spin states which have recently become computationally accessible through the use of computer algebra in the 1/N expansion formalism. A systematic study is made of high-spin states in rare-earth and actinide nuclei. (orig.)
Description of deformed nuclei in the sdg boson model
Energy Technology Data Exchange (ETDEWEB)
Li, S.C. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences; Kuyucak, S. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences
1996-07-15
We present a study of deformed nuclei in the framework of the sdg interacting boson model utilizing both numerical diagonalization and analytical 1/N expansion techniques. The focus is on the description of high-spin states which have recently become computationally accessible through the use of computer algebra in the 1/N expansion formalism. A systematic study is made of high-spin states in rare-earth and actinide nuclei. (orig.).
Description of deformed nuclei in the sdg boson model
Li, S. C.; Kuyucak, S.
1996-02-01
We present a study of deformed nuclei in the framework of the sdg interacting boson model utilizing both numerical diagonalization and analytical {1}/{N} expansion techniques. The focus is on the description of high-spin states which have recently become computationally accessible through the use of computer algebra in the {1}/{N} expansion formalism. A systematic study is made of high-spin states in rare-earth and actinide nuclei.
Gurses, Ercan; El Sayed, Tamer S.
2011-01-01
In this work, a viscoplastic constitutive model for nanocrystalline metals is presented. The model is based on competing grain boundary and grain interior deformation mechanisms. In particular, inelastic deformations caused by grain boundary
Integrable higher order deformations of Heisenberg supermagnetic model
International Nuclear Information System (INIS)
Guo Jiafeng; Yan Zhaowen; Wang Shikun; Wu Ke; Zhao Weizhong
2009-01-01
The Heisenberg supermagnet model is an integrable supersymmetric system and has a close relationship with the strong electron correlated Hubbard model. In this paper, we investigate the integrable higher order deformations of Heisenberg supermagnet models with two different constraints: (i) S 2 =3S-2I for S is an element of USPL(2/1)/S(U(2)xU(1)) and (ii) S 2 =S for S is an element of USPL(2/1)/S(L(1/1)xU(1)). In terms of the gauge transformation, their corresponding gauge equivalent counterparts are derived.
Numerical modelling of stresses and deformations in casting processes
DEFF Research Database (Denmark)
Hattel, Jesper Henri
1997-01-01
Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method......Keywords: Stresses and deformations, casting, governing equations, thermal strain, control volume method...
Modelling of deformation and recrystallisation microstructures in rocks and ice
Bons, Paul D.; Evans, Lynn A.; Gomez-Rivas, Enrique; Griera, Albert; Jessell, Mark W.; Lebensohn, Ricardo; Llorens, Maria-Gema; Peternell, Mark; Piazolo, Sandra; Weikusat, Ilka; Wilson, Chris J. L.
2015-04-01
Microstructures both record the deformation history of a rock and strongly control its mechanical properties. As microstructures in natural rocks only show the final "post-mortem" state, geologists have attempted to simulate the development of microstructures with experiments and later numerical models. Especially in-situ experiments have given enormous insight, as time-lapse movies could reveal the full history of a microstructure. Numerical modelling is an alternative approach to simulate and follow the change in microstructure with time, unconstrained by experimental limitations. Numerical models have been applied to a range of microstructural processes, such as grain growth, dynamic recrystallisation, porphyroblast rotation, vein growth, formation of mylonitic fabrics, etc. The numerical platform "Elle" (www.elle.ws) in particular has brought progress in the simulation of microstructural development as it is specifically designed to include the competition between simultaneously operating processes. Three developments significantly improve our capability to simulate microstructural evolution: (1) model input from the mapping of crystallographic orientation with EBSD or the automatic fabric analyser, (2) measurement of grain size and crystallographic preferred orientation evolution using neutron diffraction experiments and (3) the implementation of the full-field Fast Fourier Transform (FFT) solver for modelling anisotropic crystal-plastic deformation. The latter enables the detailed modelling of stress and strain as a function of local crystallographic orientation, which has a strong effect on strain localisation such as, for example, the formation of shear bands. These models can now be compared with the temporal evolution of crystallographic orientation distributions in in-situ experiments. In the last decade, the possibility to combine experiments with numerical simulations has allowed not only verification and refinement of the numerical simulation
Heterogeneous Deformable Modeling of Bio-Tissues and Haptic Force Rendering for Bio-Object Modeling
Lin, Shiyong; Lee, Yuan-Shin; Narayan, Roger J.
This paper presents a novel technique for modeling soft biological tissues as well as the development of an innovative interface for bio-manufacturing and medical applications. Heterogeneous deformable models may be used to represent the actual internal structures of deformable biological objects, which possess multiple components and nonuniform material properties. Both heterogeneous deformable object modeling and accurate haptic rendering can greatly enhance the realism and fidelity of virtual reality environments. In this paper, a tri-ray node snapping algorithm is proposed to generate a volumetric heterogeneous deformable model from a set of object interface surfaces between different materials. A constrained local static integration method is presented for simulating deformation and accurate force feedback based on the material properties of a heterogeneous structure. Biological soft tissue modeling is used as an example to demonstrate the proposed techniques. By integrating the heterogeneous deformable model into a virtual environment, users can both observe different materials inside a deformable object as well as interact with it by touching the deformable object using a haptic device. The presented techniques can be used for surgical simulation, bio-product design, bio-manufacturing, and medical applications.
Time-dependent reliability analysis of flood defences
International Nuclear Information System (INIS)
Buijs, F.A.; Hall, J.W.; Sayers, P.B.; Gelder, P.H.A.J.M. van
2009-01-01
This paper describes the underlying theory and a practical process for establishing time-dependent reliability models for components in a realistic and complex flood defence system. Though time-dependent reliability models have been applied frequently in, for example, the offshore, structural safety and nuclear industry, application in the safety-critical field of flood defence has to date been limited. The modelling methodology involves identifying relevant variables and processes, characterisation of those processes in appropriate mathematical terms, numerical implementation, parameter estimation and prediction. A combination of stochastic, hierarchical and parametric processes is employed. The approach is demonstrated for selected deterioration mechanisms in the context of a flood defence system. The paper demonstrates that this structured methodology enables the definition of credible statistical models for time-dependence of flood defences in data scarce situations. In the application of those models one of the main findings is that the time variability in the deterioration process tends to be governed the time-dependence of one or a small number of critical attributes. It is demonstrated how the need for further data collection depends upon the relevance of the time-dependence in the performance of the flood defence system.
Deformations of N=4 SYM and integrable spin chain models
International Nuclear Information System (INIS)
Berenstein, David; Cherkis, Sergey A.
2004-01-01
Beginning with the planar limit of N=4 SYM theory, we study planar diagrams for field theory deformations of N=4 which are marginal at the free field theory level. We show that the requirement of integrability of the full one-loop dilatation operator in the scalar sector, places very strong constraints on the field theory, so that the only soluble models correspond essentially to orbifolds of N=4 SYM. For these, the associated spin chain model gets twisted boundary conditions that depend on the length of the chain, but which are still integrable. We also show that theories with integrable subsectors appear quite generically, and it is possible to engineer integrable subsectors to have some specific symmetry, however these do not generally lead to full integrability. We also try to construct a theory whose spin chain has quantum group symmetry SOq(6) as a deformation of the SO(6) R-symmetry structure of N=4 SYM. We show that it is not possible to obtain a spin chain with that symmetry from deformations of the scalar potential of N=4 SYM.We also show that the natural context for these questions can be better phrased in terms of multi-matrix quantum mechanics rather than in four-dimensional field theories
Static response of deformable microchannels: a comparative modelling study
Shidhore, Tanmay C.; Christov, Ivan C.
2018-02-01
We present a comparative modelling study of fluid-structure interactions in microchannels. Through a mathematical analysis based on plate theory and the lubrication approximation for low-Reynolds-number flow, we derive models for the flow rate-pressure drop relation for long shallow microchannels with both thin and thick deformable top walls. These relations are tested against full three-dimensional two-way-coupled fluid-structure interaction simulations. Three types of microchannels, representing different elasticity regimes and having been experimentally characterized previously, are chosen as benchmarks for our theory and simulations. Good agreement is found in most cases for the predicted, simulated and measured flow rate-pressure drop relationships. The numerical simulations performed allow us to also carefully examine the deformation profile of the top wall of the microchannel in any cross section, showing good agreement with the theory. Specifically, the prediction that span-wise displacement in a long shallow microchannel decouples from the flow-wise deformation is confirmed, and the predicted scaling of the maximum displacement with the hydrodynamic pressure and the various material and geometric parameters is validated.
Modeling the behaviour of shape memory materials under large deformations
Rogovoy, A. A.; Stolbova, O. S.
2017-06-01
In this study, the models describing the behavior of shape memory alloys, ferromagnetic materials and polymers have been constructed, using a formalized approach to develop the constitutive equations for complex media under large deformations. The kinematic and constitutive equations, satisfying the principles of thermodynamics and objectivity, have been derived. The application of the Galerkin procedure to the systems of equations of solid mechanics allowed us to obtain the Lagrange variational equation and variational formulation of the magnetostatics problems. These relations have been tested in the context of the problems of finite deformation in shape memory alloys and ferromagnetic materials during forward and reverse martensitic transformations and in shape memory polymers during forward and reverse relaxation transitions from a highly elastic to a glassy state.
Quasiequilibrium models for triaxially deformed rotating compact stars
International Nuclear Information System (INIS)
Huang Xing; Markakis, Charalampos; Sugiyama, Noriyuki; Uryu, Koji
2008-01-01
Quasiequilibrium models of rapidly rotating triaxially deformed stars are computed in general relativistic gravity, assuming a conformally flat spatial geometry (Isenberg-Wilson-Mathews formulation) and a polytropic equation of state. Highly deformed solutions are calculated on the initial slice covered by spherical coordinate grids, centered at the source, in all angular directions up to a large truncation radius. Constant rest mass sequences are calculated from nearly axisymmetric to maximally deformed triaxial configurations. Selected parameters are to model (proto-) neutron stars; the compactness is M/R=0.001, 0.1, 0.14, and 0.2 for polytropic index n=0.3 and M/R=0.001, 0.1, 0.12, and 0.14 for n=0.5, where M/R refers to that of a nonrotating spherical star having the same rest mass. We confirmed that the triaxial solutions exist for these parameters as in the case of Newtonian polytropes. However, it is also found that the triaxial sequences become shorter for higher compactness, and those disappear at a certain large compactness for the n=0.5 case. In the scenario of the contraction of proto-neutron stars being subject to strong viscosity and rapid cooling, it is plausible that, once the viscosity driven secular instability sets in during the contraction, the proto-neutron stars are always maximally deformed triaxial configurations, as long as the compactness and the equation of state parameters allow such triaxial sequences. Detection of gravitational waves from such sources may be used as another probe for the nuclear equation of state.
A nonaffine network model for elastomers undergoing finite deformations
Davidson, Jacob D.; Goulbourne, N. C.
2013-08-01
In this work, we construct a new physics-based model of rubber elasticity to capture the strain softening, strain hardening, and deformation-state dependent response of rubber materials undergoing finite deformations. This model is unique in its ability to capture large-stretch mechanical behavior with parameters that are connected to the polymer chemistry and can also be easily identified with the important characteristics of the macroscopic stress-stretch response. The microscopic picture consists of two components: a crosslinked network of Langevin chains and an entangled network with chains confined to a nonaffine tube. These represent, respectively, changes in entropy due to thermally averaged chain conformations and changes in entropy due to the magnitude of these conformational fluctuations. A simple analytical form for the strain energy density is obtained using Rubinstein and Panyukov's single-chain description of network behavior. The model only depends on three parameters that together define the initial modulus, extent of strain softening, and the onset of strain hardening. Fits to large stretch data for natural rubber, silicone rubber, VHB 4905 (polyacrylate rubber), and b186 rubber (a carbon black-filled rubber) are presented, and a comparison is made with other similar constitutive models of large-stretch rubber elasticity. We demonstrate that the proposed model provides a complete description of elastomers undergoing large deformations for different applied loading configurations. Moreover, since the strain energy is obtained using a clear set of physical assumptions, this model may be tested and used to interpret the results of computer simulation and experiments on polymers of known microscopic structure.
Investigations of Low Temperature Time Dependent Cracking
Energy Technology Data Exchange (ETDEWEB)
Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J
2002-09-30
The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.
ACCUMULATED DEFORMATION MODELING OF PERMANENT WAY BASED ON ENTROPY SYSTEM
Directory of Open Access Journals (Sweden)
D. M. Kurhan
2015-07-01
Full Text Available Purpose. The work provides a theoretical research about the possibility of using methods that determine the lifetime of a railway track not only in terms of total stresses, and accounting its structure and dynamic characteristics. The aim of these studies is creation the model of deformations accumulation for assessment of service life of a railway track taking into account these features. Methodology. To simulate a gradual change state during the operation (accumulation of deformations the railway track is presented as a system that consists of many particles of different materials collected in a coherent design. It is appropriate to speak not about the appearance of deformations of a certain size in a certain section of the track, and the probability of such event on the site. If to operate the probability of occurrence of deviations, comfortable state of the system is characterized by the number of breaks of the conditional internal connections. The same state of the system may correspond to different combinations of breaks. The more breaks, the more the number of options changes in the structure of the system appropriate to its current state. Such a process can be represented as a gradual transition from an ordered state to a chaotic one. To describe the characteristics of the system used the numerical value of the entropy. Findings. Its entropy is constantly increasing at system aging. The growth of entropy is expressed by changes in the internal energy of the system, which can be determined using mechanical work forces, which leads to deformation. This gives the opportunity to show quantitative indication of breaking the bonds in the system as a consequence of performing mechanical work. According to the results of theoretical research methods for estimation of the timing of life cycles of railway operation considering such factors as the structure of the flow of trains, construction of the permanent way, the movement of trains at high
Deformable object model and simulation. Application to lung cancer treatment
International Nuclear Information System (INIS)
Baudet, V.
2006-06-01
Ionising treatment against cancers such as conformal radiotherapy and hadron therapy are set with error margins that take into account statistics of tumour motions, for instance. We are looking for reducing these margins by searching deformable models that would simulate displacements occurring in lungs during a treatment. It must be personalized with the geometry obtained from CT scans of the patient and also it must be parameterized with physiological measures of the patient. In this Ph. D. thesis, we decided to use a mass-spring system to model lungs because of its fast and physically realist deformations obtained in animation. As a starting point, we chose the model proposed by Van Gelder in order to parameterize a mass-spring system with rheological characteristics of an homogeneous, linear elastic isotropic material in two dimensions (2D). However, we tested this model and proved it was false. Hence we did a Lagrangian study in order to obtain a parametric model with rectangular in 2D (cubic in 3D) elements. We also determined the robustness by testing with stretching, inflating, shearing and bending experiments and also by comparing results with other infinite element method. Thus, in this Ph.D. thesis, we explain how to obtain this parametric model, and how it will be linked to physiological data and how accurate it will be. (author)
Time dependent convection electric fields and plasma injection
International Nuclear Information System (INIS)
Kaye, S.M.; Kivelson, M.G.
1979-01-01
Large-scale electric fields associated with storms or substorms are responsible for inward convection and energization of plasma sheet plasma. Calculations based on steady state convection theory show that the response to such electric fields qualitatively accounts for many features of the injected particle distribution, but quantitative agreement with the theory has not yet been obtained. It is known that the predictions can be improved by introducing the concept of convection in response to a time dependent electric field. On the other hand, time dependent calculations are sensitive to the choice of initial conditions, and most models have failed to incorporate these conditions in a realistic and self-consistent manner. In this paper we present a more complete model consisting of realisic initial conditions and time dependent convection to explain a typical substorm-associated electron injection event. We find very good agreement between the observed electron flux changes and those predicted by our model
Dynamic skin deformation simulation using musculoskeletal model and soft tissue dynamics
Institute of Scientific and Technical Information of China (English)
Akihiko Murai; Q. Youn Hong; Katsu Yamane; Jessica K. Hodgins
2017-01-01
Deformation of skin and muscle is essential for bringing an animated character to life. This deformation is difficult to animate in a realistic fashion using traditional techniques because of the subtlety of the skin deformations that must move appropriately for the character design. In this paper, we present an algorithm that generates natural, dynamic, and detailed skin deformation (movement and jiggle) from joint angle data sequences. The algorithm has two steps: identification of parameters for a quasi-static muscle deformation model, and simulation of skin deformation. In the identification step, we identify the model parameters using a musculoskeletal model and a short sequence of skin deformation data captured via a dense marker set. The simulation step first uses the quasi-static muscle deformation model to obtain the quasi-static muscle shape at each frame of the given motion sequence (slow jump). Dynamic skin deformation is then computed by simulating the passive muscle and soft tissue dynamics modeled as a mass–spring–damper system. Having obtained the model parameters, we can simulate dynamic skin deformations for subjects with similar body types from new motion data. We demonstrate our method by creating skin deformations for muscle co-contraction and external impacts from four different behaviors captured as skeletal motion capture data. Experimental results show that the simulated skin deformations are quantitatively and qualitatively similar to measured actual skin deformations.
Dynamic skin deformation simulation using musculoskeletal model and soft tissue dynamics
Institute of Scientific and Technical Information of China (English)
Akihiko Murai; Q.Youn Hong; Katsu Yamane; Jessica K.Hodgins
2017-01-01
Deformation of skin and muscle is essential for bringing an animated character to life. This deformation is difficult to animate in a realistic fashion using traditional techniques because of the subtlety of the skin deformations that must move appropriately for the character design. In this paper, we present an algorithm that generates natural, dynamic, and detailed skin deformation(movement and jiggle) from joint angle data sequences. The algorithm has two steps: identification of parameters for a quasi-static muscle deformation model, and simulation of skin deformation. In the identification step, we identify the model parameters using a musculoskeletal model and a short sequence of skin deformation data captured via a dense marker set. The simulation step first uses the quasi-static muscle deformation model to obtain the quasi-static muscle shape at each frame of the given motion sequence(slow jump). Dynamic skin deformation is then computed by simulating the passive muscle and soft tissue dynamics modeled as a mass–spring–damper system. Having obtained the model parameters, we can simulate dynamic skin deformations for subjects with similar body types from new motion data. We demonstrate our method by creating skin deformations for muscle co-contraction and external impacts from four different behaviors captured as skeletal motion capture data. Experimental results show that the simulated skin deformations are quantitatively and qualitatively similar to measured actual skin deformations.
Sun, Haoyu; Calabrese, Edward J; Zheng, Min; Wang, Dali; Pan, Yongzheng; Lin, Zhifen; Liu, Ying
2018-08-01
Hormesis occurs frequently in broadly ranging biological areas (e.g. plant biology, microbiology, biogerontology), toxicology, pharmacology and medicine. While numerous mechanisms (e.g. receptor and pathway mediated pathway responses) account for stimulatory and inhibitory features of hormetic dose responses, the vast majority emphasizes the inclusion of many doses but only one timepoint or use of a single optimized dose that is assessed over a broad range of timepoints. In this paper, a toxicity study was designed using a large number of properly spaced doses with responses determined over a large number of timepoints, which could help us reveal the underlying mechanism of hormesis. We present the results of a dose-time-response study on hormesis using five antibacterial chemicals on the bioluminescence of Aliivibrio fischeri, measuring expression of protein mRNA based on quorum sensing, simulating bioluminescent reaction and analyzing toxic actions of test chemicals. The findings show dose-time-dependent responses conforming to the hormetic dose-response model, while revealing unique response dynamics between agent induced stimulatory and inhibitory effects within bacterial growth phase dynamics. These dynamic dose-time features reveal a type of biological seesaw model that integrates stimulatory and inhibitory responses within unique growth phase, dose and time features, which has faultlessly explained the time-dependent hormetic phenomenon induced by five antibacterial chemicals (characterized by low-dose stimulation and high-dose inhibition). This study offers advances in understanding cellular dynamics, the biological integration of diverse and opposing responses and their role in evolutionary adaptive strategies to chemicals, which can provide new insight into the mechanistic investigation of hormesis. Copyright © 2018 Elsevier Ltd. All rights reserved.
Soliton-like excitations in a deformable spin model
International Nuclear Information System (INIS)
Nguenang, Jean-Pierre; Kenfack, Aurelien J; Kofane, Timoleon C
2004-01-01
Nonlinear excitations in a one-dimensional deformable, discrete, classical, ferromagnetic chain are numerically investigated. In the continuum limit the equations of motion are reduced to a Klein-Gordon equation, with a Remoissenet-Peyrard substrate potential. From a numerical computation of the discrete system with a suitable choice of the deformability parameters, the soliton solutions are shown to exist and move both with a monotonic oscillating (i.e. nanopteron) and a monotonic nonoscillating tail, and also with a non-oscillating tail but with a splitting propagating shape. The stability of all these various soliton shapes is confirmed numerically in a range of the reduced magnetic fields greater than for a rigid magnetic chain i.e. 0 ≤ b ≤0.33. From a kink-antikink and a kink-kink colliding simulation, we found various effects, including a bound state of a kink and an antikink, as well as a moving kink profile with higher topological charge that appears to be the bound state of two kinks. For some values of the deformability parameter, with a suitable choice of the initial velocity, we observed that the presence of an internal mode leads to the combination of an attractive and a repulsive phenomenon, that arises when the kink-kink collision is engaged. The fact that this collision happens only in the centre of the magnetic chain with the presence of a minimal distance between the two kinks as long as the collision is produced is also a feature of the deformability effect in the dynamics of a magnetic chain. From our results, it appears that the value of the shape parameter of the substrate potential or the modified Zeeman energy is a factor of utmost importance when modelling magnetic chains
Facial Performance Transfer via Deformable Models and Parametric Correspondence.
Asthana, Akshay; de la Hunty, Miles; Dhall, Abhinav; Goecke, Roland
2012-09-01
The issue of transferring facial performance from one person's face to another's has been an area of interest for the movie industry and the computer graphics community for quite some time. In recent years, deformable face models, such as the Active Appearance Model (AAM), have made it possible to track and synthesize faces in real time. Not surprisingly, deformable face model-based approaches for facial performance transfer have gained tremendous interest in the computer vision and graphics community. In this paper, we focus on the problem of real-time facial performance transfer using the AAM framework. We propose a novel approach of learning the mapping between the parameters of two completely independent AAMs, using them to facilitate the facial performance transfer in a more realistic manner than previous approaches. The main advantage of modeling this parametric correspondence is that it allows a "meaningful" transfer of both the nonrigid shape and texture across faces irrespective of the speakers' gender, shape, and size of the faces, and illumination conditions. We explore linear and nonlinear methods for modeling the parametric correspondence between the AAMs and show that the sparse linear regression method performs the best. Moreover, we show the utility of the proposed framework for a cross-language facial performance transfer that is an area of interest for the movie dubbing industry.
Asymptotic time dependent neutron transport in multidimensional systems
International Nuclear Information System (INIS)
Nagy, M.E.; Sawan, M.E.; Wassef, W.A.; El-Gueraly, L.A.
1983-01-01
A model which predicts the asymptotic time behavior of the neutron distribution in multi-dimensional systems is presented. The model is based on the kernel factorization method used for stationary neutron transport in a rectangular parallelepiped. The accuracy of diffusion theory in predicting the asymptotic time dependence is assessed. The use of neutron pulse experiments for predicting the diffusion parameters is also investigated
Time dependent resonating Hartree-Bogoliubov theory
International Nuclear Information System (INIS)
Nishiyama, Seiya; Fukutome, Hideo.
1989-01-01
Very recently, we have developed a theory of excitations in superconducting Fermion systems with large quantum fluctuations that can be described by resonance of time dependent non-orthogonal Hartree-Bogoliubov (HB) wave functions with different correlation structures. We have derived a new kind of variation equation called the time dependent Resonating HB equation, in order to determine both the time dependent Resonating HB wave functions and coefficients of a superposition of the HB wave functions. Further we have got a new approximation for excitations from time dependent small fluctuations of the Resonating HB ground state, i.e., the Resonating HB RPA. The Res HB RPA equation is represented in a given single particle basis. It, however, has drawbacks that the constraints for the Res HB RPA amplitudes are not taken into account and the equation contains equations which are not independent. We shall derive another form of the Res HB RPA equation eliminating these drawbacks. The Res HB RPA gives a unified description of the vibrons and resonons and their interactions. (author)
Time-dependent Dyson orbital theory
Gritsenko, O.V.; Baerends, E.J.
2016-01-01
Although time-dependent density functional theory (TDDFT) has become the tool of choice for real-time propagation of the electron density ρN(t) of N-electron systems, it also encounters problems in this application. The first problem is the neglect of memory effects stemming from the, in TDDFT
Biological repair with time-dependent irradiation
International Nuclear Information System (INIS)
Broyles, A.A.; Shapiro, C.S.
1985-01-01
Recent experiments have provided new data that explore the effectiveness of biological repair in assessing damage due to exposures from ionizing radiation. These data are mainly from experiments conducted at constant dose rates, to study the effectiveness per unit dose of different dose rates. Here, we develop new formulae to estimate the effectiveness of an arbitrary time-dependent dose rate exposure
Scheduling with time-dependent execution times
Woeginger, G.J.
1995-01-01
We consider systems of tasks where the task execution times are time-dependent and where all tasks have some common deadline. We describe how to compute in polynomial time a schedule that minimizes the number of late tasks. This answers a question raised in a recent paper by Ho, Leung and Wei.
Hartree--Fock time-dependent problem
Energy Technology Data Exchange (ETDEWEB)
Bove, A; Fano, G [Bologna Univ. (Italy). Istituto di Fisica; Istituto Nazionale di Fisica Nucleare, Bologna (Italy)); Da Prato, G [Rome Univ. (Italy). Istituto di Matematica
1976-06-01
A previous result is generalized. An existence and uniqueness theorem is proved for the Hartree--Fock time-dependent problem in the case of a finite Fermi system interacting via a two body potential which is supposed to be dominated by the kinetic energy part of the one-particle Hamiltonian.
Micromechanical modeling of the deformation of HCP metals
Energy Technology Data Exchange (ETDEWEB)
Graff, S. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung
2008-12-04
Nowadays, intense research is conducted to understand the relation between microstructural features and mechanical properties of hexagonal close-packed (hcp) metals. Due to their hexagonal structure, hcp metals exhibit mechanical properties such as strong anisotropy, which is more pronounced than for construction metals with cubic crystal structure, and tension/compression asymmetry. Deformation mechanisms in hcp metals, dislocation motion on specific slip systems and activation of twinning, are not yet completely understood. The purpose of this work is to link the physical mechanisms developing during deformation of magnesium (Mg) on the microscale with the macroscopic yielding properties of texture Mg samples. It will be shown that the mechanical behavior of hcp metals may be understood and reproduced with the help of a visco-plastic model for crystal plasticity and a phenomenological yield criterion with appropriate hardening behavior. The study of single crystal specimens subjected to channel die compression tests reveals the active slip systems and twinning systems of the material considered. The material anisotropy at mesoscale is reproduced by using adequate critical resolved shear stresses (CRSS) for the considered deformation mechanisms. In order to describe the macroscopic behavior, texture is incorporated into polycrystalline Representative Volume Elements (RVEs) and various mechanical properties of extruded bars and rolled plates can be predicted. For RVEs exhibiting the texture of rolled plates the numerical results reveal the plate's anisotropic yielding and hardening behavior on a mesoscale. In order to extend the modeling possibilities to process simulations and to allow for time-saving simulations of structural behavior, a phenomenological yield surface accounting for anisotropy and tension/compression asymmetry has been established and implemented in a finite element code. Its numerous model parameters are calibrated by an optimization
Doehmann, M.; Brune, S.; Nardini, L.; Rybacki, E.; Dresen, G.
2017-12-01
Strain localization is an ubiquitous process in earth materials observed over a broad range of scales in space and time. Localized deformation and the formation of shear zones and faults typically involves material softening by various processes, like shear heating and grain size reduction. Numerical modeling enables us to study the complex physical and chemical weakening processes by separating the effect of individual parameters and boundary conditions. Using simple piece-wise linear functions for the parametrization of weakening processes allows studying a system at a chosen (lower) level of complexity (e.g. Cyprych et al., 2016). In this study, we utilize a finite element model to test two weakening laws that reduce the strength of the material depending on either the I) amount of accumulated strain or II) deformational work. Our 2D Cartesian models are benchmarked to single inclusion torsion experiments performed at elevated temperatures of 900 °C and pressures of up to 400 MPa (Rybacki et al., 2014). The experiments were performed on Carrara marble samples containing a weak Solnhofen limestone inclusion at a maximum strain rate of 2.0*10-4 s-1. Our models are designed to reproduce shear deformation of a hollow cylinder equivalent to the laboratory setup, such that material leaving one side of the model in shear direction enters again on the opposite side using periodic boundary conditions. Similar to the laboratory tests, we applied constant strain rate and constant stress boundary conditions.We use our model to investigate the time-dependent distribution of stress and strain and the effect of different parameters. For instance, inclusion rotation is shown to be strongly dependent on the viscosity ratio between matrix and inclusion and stronger ductile weakening increases the localization rate while decreasing shear zone width. The most suitable weakening law for representation of ductile rock is determined by combining the results of parameter tests with
Wave function for time-dependent harmonically confined electrons in a time-dependent electric field.
Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht
2013-09-21
The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential.
Progress Report on Alloy 617 Time Dependent Allowables
Energy Technology Data Exchange (ETDEWEB)
Wright, Julie Knibloe [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-06-01
Time dependent allowable stresses are required in the ASME Boiler and Pressure Vessel Code for design of components in the temperature range where time dependent deformation (i.e., creep) is expected to become significant. There are time dependent allowable stresses in Section IID of the Code for use in the non-nuclear construction codes, however, there are additional criteria that must be considered in developing time dependent allowables for nuclear components. These criteria are specified in Section III NH. St is defined as the lesser of three quantities: 100% of the average stress required to obtain a total (elastic, plastic, primary and secondary creep) strain of 1%; 67% of the minimum stress to cause rupture; and 80% of the minimum stress to cause the initiation of tertiary creep. The values are reported for a range of temperatures and for time increments up to 100,000 hours. These values are determined from uniaxial creep tests, which involve the elevated temperature application of a constant load which is relatively small, resulting in deformation over a long time period prior to rupture. The stress which is the minimum resulting from these criteria is the time dependent allowable stress St. In this report data from a large number of creep and creep-rupture tests on Alloy 617 are analyzed using the ASME Section III NH criteria. Data which are used in the analysis are from the ongoing DOE sponsored high temperature materials program, form Korea Atomic Energy Institute through the Generation IV VHTR Materials Program and historical data from previous HTR research and vendor data generated in developing the alloy. It is found that the tertiary creep criterion determines St at highest temperatures, while the stress to cause 1% total strain controls at low temperatures. The ASME Section III Working Group on Allowable Stress Criteria has recommended that the uncertainties associated with determining the onset of tertiary creep and the lack of significant
Recent progress in modelling 3D lithospheric deformation
Kaus, B. J. P.; Popov, A.; May, D. A.
2012-04-01
Modelling 3D lithospheric deformation remains a challenging task, predominantly because the variations in rock types, as well as nonlinearities due to for example plastic deformation result in sharp and very large jumps in effective viscosity contrast. As a result, there are only a limited number of 3D codes available, most of which are using direct solvers which are computationally and memory-wise very demanding. As a result, the resolutions for typical model runs are quite modest, despite the use of hundreds of processors (and using much larger computers is unlikely to bring much improvement in this situation). For this reason we recently developed a new 3D deformation code,called LaMEM: Lithosphere and Mantle Evolution Model. LaMEM is written on top of PETSc, and as a result it runs on massive parallel machines and we have a large number of iterative solvers available (including geometric and algebraic multigrid methods). As it remains unclear which solver combinations work best under which conditions, we have implemented most currently suggested methods (such as schur complement reduction or Fully coupled iterations). In addition, we can use either a finite element discretization (with Q1P0, stabilized Q1Q1 or Q2P-1 elements) or a staggered finite difference discretization for the same input geometry, which is based on a marker and cell technique). This gives us he flexibility to test various solver methodologies on the same model setup, in terms of accuracy, speed, memory usage etc. Here, we will report on some features of LaMEM, on recent code additions, as well as on some lessons we learned which are important for modelling 3D lithospheric deformation. Specifically we will discuss: 1) How we combine a particle-and-cell method to make it work with both a finite difference and a (lagrangian, eulerian or ALE) finite element formulation, with only minor code modifications code 2) How finite difference and finite element discretizations compare in terms of
Marginal deformations of heterotic G 2 sigma models
Fiset, Marc-Antoine; Quigley, Callum; Svanes, Eirik Eik
2018-02-01
Recently, the infinitesimal moduli space of heterotic G 2 compactifications was described in supergravity and related to the cohomology of a target space differential. In this paper we identify the marginal deformations of the corresponding heterotic nonlinear sigma model with cohomology classes of a worldsheet BRST operator. This BRST operator is nilpotent if and only if the target space geometry satisfies the heterotic supersymmetry conditions. We relate this to the supergravity approach by showing that the corresponding cohomologies are indeed isomorphic. We work at tree-level in α' perturbation theory and study general geometries, in particular with non-vanishing torsion.
Modeling and Simulation of Grasping of Deformable Objects
DEFF Research Database (Denmark)
Fugl, Andreas Rune
Automated robot solutions have for decades been increasing productivity around the world. They are attractive for being fast, accurate and able to work in dangerous and repetitive environments. In traditional applications the grasped object is kinematically attached to the Tool Center Point....... The purpose of this thesis is to address the modeling and simulation of deformable objects, as applied to robotic grasping and manipulation. The main contributions of this work are: An evaluation of 3D linear elasticity used for robot grasping as implemented by a Finite Difference Method supporting regular...
A model to accumulate fractionated dose in a deforming organ
International Nuclear Information System (INIS)
Yan Di; Jaffray, D.A.; Wong, J.W.
1999-01-01
Purpose: Measurements of internal organ motion have demonstrated that daily organ deformation exists throughout the course of radiation treatment. However, a method of constructing the resultant dose delivered to the organ volume remains a difficult challenge. In this study, a model to quantify internal organ motion and a method to construct a cumulative dose in a deforming organ are introduced. Methods and Materials: A biomechanical model of an elastic body is used to quantify patient organ motion in the process of radiation therapy. Intertreatment displacements of volume elements in an organ of interest is calculated by applying an finite element method with boundary conditions, obtained from multiple daily computed tomography (CT) measurements. Therefore, by incorporating also the measurements of daily setup error, daily dose delivered to a deforming organ can be accumulated by tracking the position of volume elements in the organ. Furthermore, distribution of patient-specific organ motion is also predicted during the early phase of treatment delivery using the daily measurements, and the cumulative dose distribution in the organ can then be estimated. This dose distribution will be updated whenever a new measurement becomes available, and used to reoptimize the ongoing treatment. Results: An integrated process to accumulate dosage in a daily deforming organ was implemented. In this process, intertreatment organ motion and setup error were systematically quantified, and incorporated in the calculation of the cumulative dose. An example of the rectal wall motion in a prostate treatment was applied to test the model. The displacements of volume elements in the rectal wall, as well as the resultant doses, were calculated. Conclusion: This study is intended to provide a systematic framework to incorporate daily patient-specific organ motion and setup error in the reconstruction of the cumulative dose distribution in an organ of interest. The realistic dose
Watching excitons move: the time-dependent transition density matrix
Ullrich, Carsten
2012-02-01
Time-dependent density-functional theory allows one to calculate excitation energies and the associated transition densities in principle exactly. The transition density matrix (TDM) provides additional information on electron-hole localization and coherence of specific excitations of the many-body system. We have extended the TDM concept into the real-time domain in order to visualize the excited-state dynamics in conjugated molecules. The time-dependent TDM is defined as an implicit density functional, and can be approximately obtained from the time-dependent Kohn-Sham orbitals. The quality of this approximation is assessed in simple model systems. A computational scheme for real molecular systems is presented: the time-dependent Kohn-Sham equations are solved with the OCTOPUS code and the time-dependent Kohn-Sham TDM is calculated using a spatial partitioning scheme. The method is applied to show in real time how locally created electron-hole pairs spread out over neighboring conjugated molecular chains. The coupling mechanism, electron-hole coherence, and the possibility of charge separation are discussed.
Time-dependent scattering in resonance lines
International Nuclear Information System (INIS)
Kunasz, P.B.
1983-01-01
A numerical finite-difference method is presented for the problem of time-dependent line transfer in a finite slab in which material density is sufficiently low that the time of flight between scatterings greatly exceeds the relaxation time of the upper state of the scattering transition. The medium is assumed to scatter photons isotropically, with complete frequency redistribution. Numerical solutions are presented for a homogeneous, time-independent slab illuminated by an externally imposed radiation field which enters the slab at t = 0. Graphical results illustrate relaxation to steady state of trapped internal radiation, emergent energy, and emergent profiles. A review of the literature is also given in which the time-dependent line transfer problem is discussed in the context of recent analytical work
Time-dependent problems and difference methods
Gustafsson, Bertil; Oliger, Joseph
2013-01-01
Praise for the First Edition "". . . fills a considerable gap in the numerical analysis literature by providing a self-contained treatment . . . this is an important work written in a clear style . . . warmly recommended to any graduate student or researcher in the field of the numerical solution of partial differential equations."" -SIAM Review Time-Dependent Problems and Difference Methods, Second Edition continues to provide guidance for the analysis of difference methods for computing approximate solutions to partial differential equations for time-de
Shell-model-based deformation analysis of light cadmium isotopes
Schmidt, T.; Heyde, K. L. G.; Blazhev, A.; Jolie, J.
2017-07-01
Large-scale shell-model calculations for the even-even cadmium isotopes 98Cd-108Cd have been performed with the antoine code in the π (2 p1 /2;1 g9 /2) ν (2 d5 /2;3 s1 /2;2 d3 /2;1 g7 /2;1 h11 /2) model space without further truncation. Known experimental energy levels and B (E 2 ) values could be well reproduced. Taking these calculations as a starting ground we analyze the deformation parameters predicted for the Cd isotopes as a function of neutron number N and spin J using the methods of model independent invariants introduced by Kumar [Phys. Rev. Lett. 28, 249 (1972), 10.1103/PhysRevLett.28.249] and Cline [Annu. Rev. Nucl. Part. Sci. 36, 683 (1986), 10.1146/annurev.ns.36.120186.003343].
Multi Scale Models for Flexure Deformation in Sheet Metal Forming
Directory of Open Access Journals (Sweden)
Di Pasquale Edmondo
2016-01-01
Full Text Available This paper presents the application of multi scale techniques to the simulation of sheet metal forming using the one-step method. When a blank flows over the die radius, it undergoes a complex cycle of bending and unbending. First, we describe an original model for the prediction of residual plastic deformation and stresses in the blank section. This model, working on a scale about one hundred times smaller than the element size, has been implemented in SIMEX, one-step sheet metal forming simulation code. The utilisation of this multi-scale modeling technique improves greatly the accuracy of the solution. Finally, we discuss the implications of this analysis on the prediction of springback in metal forming.
Multi-view and 3D deformable part models.
Pepik, Bojan; Stark, Michael; Gehler, Peter; Schiele, Bernt
2015-11-01
As objects are inherently 3D, they have been modeled in 3D in the early days of computer vision. Due to the ambiguities arising from mapping 2D features to 3D models, 3D object representations have been neglected and 2D feature-based models are the predominant paradigm in object detection nowadays. While such models have achieved outstanding bounding box detection performance, they come with limited expressiveness, as they are clearly limited in their capability of reasoning about 3D shape or viewpoints. In this work, we bring the worlds of 3D and 2D object representations closer, by building an object detector which leverages the expressive power of 3D object representations while at the same time can be robustly matched to image evidence. To that end, we gradually extend the successful deformable part model [1] to include viewpoint information and part-level 3D geometry information, resulting in several different models with different level of expressiveness. We end up with a 3D object model, consisting of multiple object parts represented in 3D and a continuous appearance model. We experimentally verify that our models, while providing richer object hypotheses than the 2D object models, provide consistently better joint object localization and viewpoint estimation than the state-of-the-art multi-view and 3D object detectors on various benchmarks (KITTI [2] , 3D object classes [3] , Pascal3D+ [4] , Pascal VOC 2007 [5] , EPFL multi-view cars[6] ).
Modelling Polymer Deformation and Welding Behaviour during 3D Printing
McIlroy, Claire; Olmsted, Peter
2016-11-01
3D printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The most common method, fused deposition modelling, involves melting a thermoplastic, followed by layer-by-layer extrusion of the material to fabricate a three-dimensional object. The key to the ensuring strength at the weld between these layers is successful inter-diffusion. However, as the printed layer cools towards the glass transition temperature, the time available for diffusion is limited. In addition, the extrusion process significantly deforms the polymer micro-structure prior to welding and consequently affects how the polymers "re-entangle" across the weld. We have developed a simple model of the non-isothermal printing process to explore the effects that typical printing conditions and amorphous polymer rheology have on the ultimate weld structure. In particular, we incorporate both the stretch and orientation of the polymer using the Rolie-Poly constitutive equation to examine how the melt flows through the nozzle and is deposited onto the build plate. We then address how this deformation relaxes and contributes to the thickness and structure of the weld. National Institute for Standards and Technology (NIST) and Georgetown University.
Non-proportional deformation paths for sheet metal: experiments and models
van den Boogaard, Antonius H.; van Riel, M.; Hora, P.
2009-01-01
For mild steel, after significant plastic deformation in one direction, a subsequent deformation in an orthogonal direction shows a typical stress overshoot compared to monotonic deformation. This phenomenon is investigated experimentally and numerically on a DC06 material. Two models that
DISCRETE DEFORMATION WAVE DYNAMICS IN SHEAR ZONES: PHYSICAL MODELLING RESULTS
Directory of Open Access Journals (Sweden)
S. A. Bornyakov
2016-01-01
Full Text Available Observations of earthquake migration along active fault zones [Richter, 1958; Mogi, 1968] and related theoretical concepts [Elsasser, 1969] have laid the foundation for studying the problem of slow deformation waves in the lithosphere. Despite the fact that this problem has been under study for several decades and discussed in numerous publications, convincing evidence for the existence of deformation waves is still lacking. One of the causes is that comprehensive field studies to register such waves by special tools and equipment, which require sufficient organizational and technical resources, have not been conducted yet.The authors attempted at finding a solution to this problem by physical simulation of a major shear zone in an elastic-viscous-plastic model of the lithosphere. The experiment setup is shown in Figure 1 (A. The model material and boundary conditions were specified in accordance with the similarity criteria (described in detail in [Sherman, 1984; Sherman et al., 1991; Bornyakov et al., 2014]. The montmorillonite clay-and-water paste was placed evenly on two stamps of the installation and subject to deformation as the active stamp (1 moved relative to the passive stamp (2 at a constant speed. The upper model surface was covered with fine sand in order to get high-contrast photos. Photos of an emerging shear zone were taken every second by a Basler acA2000-50gm digital camera. Figure 1 (B shows an optical image of a fragment of the shear zone. The photos were processed by the digital image correlation method described in [Sutton et al., 2009]. This method estimates the distribution of components of displacement vectors and strain tensors on the model surface and their evolution over time [Panteleev et al., 2014, 2015].Strain fields and displacements recorded in the optical images of the model surface were estimated in a rectangular box (220.00×72.17 mm shown by a dot-and-dash line in Fig. 1, A. To ensure a sufficient level of
Hamilton, H. B.; Strangas, E.
1980-01-01
The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.
Mechanical modelling of the Singoe deformation zone. Site descriptive modelling Forsmark stage 2.1
Energy Technology Data Exchange (ETDEWEB)
Glamheden, Rune; Maersk Hansen, Lars; Fredriksson, Anders; Bergkvist, Lars; Markstroem, Ingemar; Elfstroem, Mats [Golder Associates AB (Sweden)
2007-02-15
This project aims at demonstrating the theoretical approach developed by SKB for determination of mechanical properties of large deformation zones, in particular the Singoe deformation zone. Up to now, only bedrock and minor deformation zones have been characterized by means of this methodology, which has been modified for this project. The Singoe deformation zone is taken as a reference object to get a more comprehensive picture of the structure, which could be incorporated in a future version of the SDM of Forsmark. Furthermore, the Singoe Zone has been chosen because of available data from four tunnels. Scope of work has included compilation and analysis of geological information from site investigations and documentation of existing tunnels. Results have been analyzed and demonstrated by means of RVS-visualization. Numerical modelling has been used to obtain mechanical properties. Numerical modelling has also been carried out in order to verify the results by comparison of calculated and measured deformations. Compilation of various structures in the four tunnels coincides largely with a magnetic anomaly and also with the estimated width. Based on the study it is clear that the Singoe deformation zone has a heterogeneous nature. The number of fracture zones associated with the deformation zone varies on either side of the zone, as does the transition zone between host rock and the Singoe zone. The overall impression from the study is that the results demonstrate that the methodology used for simulating of equivalent mechanical properties is an applicable and adequate method, also in case of large deformation zones. Typical rock mechanical parameters of the Singoe deformations that can be used in the regional stress model considering the zone to be a single fracture are: 200 MPa/m in normal stiffness, 10-15 MPa/m in shear stiffness, 0.4 MPa in cohesion and 31.5 degrees in friction angle.
Mechanical modelling of the Singoe deformation zone. Site descriptive modelling Forsmark stage 2.1
International Nuclear Information System (INIS)
Glamheden, Rune; Maersk Hansen, Lars; Fredriksson, Anders; Bergkvist, Lars; Markstroem, Ingemar; Elfstroem, Mats
2007-02-01
This project aims at demonstrating the theoretical approach developed by SKB for determination of mechanical properties of large deformation zones, in particular the Singoe deformation zone. Up to now, only bedrock and minor deformation zones have been characterized by means of this methodology, which has been modified for this project. The Singoe deformation zone is taken as a reference object to get a more comprehensive picture of the structure, which could be incorporated in a future version of the SDM of Forsmark. Furthermore, the Singoe Zone has been chosen because of available data from four tunnels. Scope of work has included compilation and analysis of geological information from site investigations and documentation of existing tunnels. Results have been analyzed and demonstrated by means of RVS-visualization. Numerical modelling has been used to obtain mechanical properties. Numerical modelling has also been carried out in order to verify the results by comparison of calculated and measured deformations. Compilation of various structures in the four tunnels coincides largely with a magnetic anomaly and also with the estimated width. Based on the study it is clear that the Singoe deformation zone has a heterogeneous nature. The number of fracture zones associated with the deformation zone varies on either side of the zone, as does the transition zone between host rock and the Singoe zone. The overall impression from the study is that the results demonstrate that the methodology used for simulating of equivalent mechanical properties is an applicable and adequate method, also in case of large deformation zones. Typical rock mechanical parameters of the Singoe deformations that can be used in the regional stress model considering the zone to be a single fracture are: 200 MPa/m in normal stiffness, 10-15 MPa/m in shear stiffness, 0.4 MPa in cohesion and 31.5 degrees in friction angle
Modeling level structures of odd-odd deformed nuclei
International Nuclear Information System (INIS)
Hoff, R.W.; Kern, J.; Piepenbring, R.; Boisson, J.P.
1984-01-01
A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation were derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated configuration-specific values for the Gallagher-Moszkowski splittings were used. Calculated and experimental level structures for 238 Np, 244 Am, and 250 Bk are compared, as well as those for several nuclei in the rare-earth region. The agreement for the actinide species is excellent, with bandhead energies deviating 22 keV and rotational parameters 5%, on the average. Corresponding average deviations for five rare-earth nuclei are 47 keV and 7%. Several applications of this modeling technique are discussed. 18 refs., 5 figs., 4 tabs
Time dependent variational method in quantum mechanics
International Nuclear Information System (INIS)
Torres del Castillo, G.F.
1987-01-01
Using the fact that the solutions to the time-dependent Schodinger equation can be obtained from a variational principle, by restricting the evolution of the state vector to some surface in the corresponding Hilbert space, approximations to the exact solutions can be obtained, which are determined by equations similar to Hamilton's equations. It is shown that, in order for the approximate evolution to be well defined on a given surface, the imaginary part of the inner product restricted to the surface must be non-singular. (author)
Time-dependent angularly averaged inverse transport
International Nuclear Information System (INIS)
Bal, Guillaume; Jollivet, Alexandre
2009-01-01
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. Such measurement settings find applications in medical and geophysical imaging. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain
Time dependent black holes and thermal equilibration
International Nuclear Information System (INIS)
Bak, Dongsu; Gutperle, Michael; Karch, Andreas
2007-01-01
We study aspects of a recently proposed exact time dependent black hole solution of IIB string theory using the AdS/CFT correspondence. The dual field theory is a thermal system in which initially a vacuum density for a non-conserved operator is turned on. We can see that in agreement with general thermal field theory expectation the system equilibrates: the expectation value of the non-conserved operator goes to zero exponentially and the entropy increases. In the field theory the process can be described quantitatively in terms of a thermofield state and exact agreement with the gravity answers is found
Royer, J.; Brandon, V.
2011-12-01
The large-scale deformation observed in the Indo-Australian plate seems to challenge tenets of plate tectonics: plate rigidity and narrow oceanic plate boundaries. Its distribution along with kinematic data inversions however suggest that the Indo-Australian plate can be viewed as a composite plate made of three rigid component plates - India, Capricorn, Australia - separated by wide and diffuse boundaries either extensional or compressional. We tested this model using the SHELLS numerical code (Kong & Bird, 1995) where the Indo-Australian plate was meshed into 5281 spherical triangular finite elements. Model boundary conditions are defined only by the plate velocities of the rigid parts of the Indo-Australian plate relative to their neighboring plates. Different plate velocity models were tested. From these boundary conditions, and taking into account the age of the lithosphere, seafloor topography, and assumptions on the rheology of the oceanic lithosphere, SHELLS predicts strain rates within the plate. We also tested the role of fossil fracture zones as potential lithospheric weaknesses. In a first step, we considered different component plate pairs (India/Capricorn, Capricorn/Australia, India/Australia). Since the limits of their respective diffuse boundary (i.e. the limits of the rigid component plates) are not known, we let the corresponding edge free. In a second step, we merged the previous meshes to consider the whole Indo-Australian plate. In this case, the velocities on the model boundaries are all fully defined and were set relative to the Capricorn plate. Our models predict deformation patterns very consistent with that observed. Pre-existing structures of the lithosphere play an important role in the intraplate deformation and its distribution. The Chagos Bank focuses the extensional deformation between the Indian and Capricorn plates. Reactivation of fossil fracture zones may accommodate large part of the deformation both in extensional areas, off
Numerical modeling of intraplate seismicity with a deformable loading plate
So, B. D.; Capitanio, F. A.
2017-12-01
We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic
3D Face modeling using the multi-deformable method.
Hwang, Jinkyu; Yu, Sunjin; Kim, Joongrock; Lee, Sangyoun
2012-09-25
In this paper, we focus on the problem of the accuracy performance of 3D face modeling techniques using corresponding features in multiple views, which is quite sensitive to feature extraction errors. To solve the problem, we adopt a statistical model-based 3D face modeling approach in a mirror system consisting of two mirrors and a camera. The overall procedure of our 3D facial modeling method has two primary steps: 3D facial shape estimation using a multiple 3D face deformable model and texture mapping using seamless cloning that is a type of gradient-domain blending. To evaluate our method's performance, we generate 3D faces of 30 individuals and then carry out two tests: accuracy test and robustness test. Our method shows not only highly accurate 3D face shape results when compared with the ground truth, but also robustness to feature extraction errors. Moreover, 3D face rendering results intuitively show that our method is more robust to feature extraction errors than other 3D face modeling methods. An additional contribution of our method is that a wide range of face textures can be acquired by the mirror system. By using this texture map, we generate realistic 3D face for individuals at the end of the paper.
Constitutive modelling in the range of inelastic deformations
International Nuclear Information System (INIS)
Bruhns, O.T.; White, P.S.; Chaboche, J.L.; Eikhoff, J.V.D.
1988-01-01
The main objective of this report is to describe the state of the art in constitutive modelling in the range of inelastic deformations, with particular consideration of the practical use of these models in the field of fast reactors, rather than to formulate new models. An outline is given of the constitutive equations for high-temperature reactor materials developed at the Oak Ridge National Laboratory. Two forms of equations are considered, a semi-classical treatment in terms of separate plasticity and creep and unified equations in which the classical plasticity does not explicitly occur. The fraction model originally proposed by Besseling is described. The basic concept of this model is that the material is thought to be subdivided into a number of parallel fractions, each with simple conventional properties. The more complicated behaviour of real material is thus approximated by choosing a number of parallel fractions with suitable models and model parameters. Three time-independent formulations of plasticity are considered and compared. Attention is focused on the kinematic hardening in the multi-yield surface theory of Mroz and the non-linear kinematic rule intensively used at Enset and Onera. Some connections are pointed out with the two-surface model of Dafalias and Popov, and the range of applicability of the different models is studied in detail. Finally, the constitutive equations of the Interatom model are presented. They are mainly based on the concept of overstresses, expressing the rate-dependence of the material by the magnitude of these overstresses. This model furthermore comprises a combination of general non-linear isotropic and kinematic hardening, with a smooth transition from isotropic to kinematic hardening as a function of process time
Holographic superconductor in a deformed four-dimensional STU model
Energy Technology Data Exchange (ETDEWEB)
Pourhassan, B.; Bagheri-Mohagheghi, M.M. [Damghan University, School of Physics, Damghan (Iran, Islamic Republic of)
2017-11-15
In this paper, we consider a deformed STU model in four dimensions including both electric and magnetic charges. Using the AdS/CFT correspondence, we study holographic superconductors and obtain transport properties like electrical and thermal conductivities. We obtain transport properties in terms of the magnetic charge of the black hole and interpret it as the magnetic monopole of dual field theory. We find that the presence of the magnetic charge is necessary to have maximum conductivities, and the existence of a magnetic monopole with a critical charge (137 e) to reach the maximum superconductivity is important. Also, we show that the thermal conductivity increases with increasing of the magnetic charge. It may be concluded that the origin of superconductivity is the magnetic monopole. (orig.)
Examining the time dependence of DAMA's modulation amplitude
Kelso, Chris; Savage, Christopher; Sandick, Pearl; Freese, Katherine; Gondolo, Paolo
2018-03-01
If dark matter is composed of weakly interacting particles, Earth's orbital motion may induce a small annual variation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a 9.3σ confidence level such an annual modulation in their event rate over two detector iterations, DAMA/NaI and DAMA/LIBRA, each with ˜ 7 years of observations. This data is well fit by a constant modulation amplitude for the two iterations of the experiment. We statistically examine the time dependence of the modulation amplitudes, which "by eye" appear to be decreasing with time in certain energy ranges. We perform a chi-squared goodness of fit test of the average modulation amplitudes measured by the two detector iterations which rejects the hypothesis of a consistent modulation amplitude at greater than 80, 96, and 99.6% for the 2-4, 2-5 and 2-6 keVee energy ranges, respectively. We also find that among the 14 annual cycles there are three ≳ 3σ departures from the average in our estimated data in the 5-6 keVee energy range. In addition, we examined several phenomenological models for the time dependence of the modulation amplitude. Using a maximum likelihood test, we find that descriptions of the modulation amplitude as decreasing with time are preferred over a constant modulation amplitude at anywhere between 1σ and 3σ , depending on the phenomenological model for the time dependence and the signal energy range considered. A time dependent modulation amplitude is not expected for a dark matter signal, at least for dark matter halo morphologies consistent with the DAMA signal. New data from DAMA/LIBRA-phase2 will certainly aid in determining whether any apparent time dependence is a real effect or a statistical fluctuation.
Research on geometrical model and mechanism for metal deformation based on plastic flow
International Nuclear Information System (INIS)
An, H P; Li, X; Rui, Z Y
2015-01-01
Starting with general conditions of metal plastic deformation, it analyses the relation between the percentage spread and geometric parameters of a forming body with typical machining process are studied. A geometrical model of deforming metal is set up according to the characteristic of a flowing metal particle. Starting from experimental results, the effect of technological parameters and friction between workpiece and dies on plastic deformation of a material were studied and a slippage deformation model of mass points within the material was proposed. Finally, the computing methods for strain and deformation energy and temperature rise are derived from homogeneous deformation. The results can be used to select technical parameters and compute physical quantities such as strain, deformation energy, and temperature rise. (paper)
Modelling of reactive fluid transport in deformable porous rocks
Yarushina, V. M.; Podladchikov, Y. Y.
2009-04-01
One outstanding challenge in geology today is the formulation of an understanding of the interaction between rocks and fluids. Advances in such knowledge are important for a broad range of geologic settings including partial melting and subsequent migration and emplacement of a melt into upper levels of the crust, or fluid flow during regional metamorphism and metasomatism. Rock-fluid interaction involves heat and mass transfer, deformation, hydrodynamic flow, and chemical reactions, thereby necessitating its consideration as a complex process coupling several simultaneous mechanisms. Deformation, chemical reactions, and fluid flow are coupled processes. Each affects the others. Special effort is required for accurate modelling of the porosity field through time. Mechanical compaction of porous rocks is usually treated under isothermal or isoentropic simplifying assumptions. However, joint consideration of both mechanical compaction and reactive porosity alteration requires somewhat greater than usual care about thermodynamic consistency. Here we consider the modelling of multi-component, multi-phase systems, which is fundamental to the study of fluid-rock interaction. Based on the conservation laws for mass, momentum, and energy in the form adopted in the theory of mixtures, we derive a thermodynamically admissible closed system of equations describing the coupling of heat and mass transfer, chemical reactions, and fluid flow in a deformable solid matrix. Geological environments where reactive transport is important are located at different depths and accordingly have different rheologies. In the near surface, elastic or elastoplastic properties would dominate, whereas viscoplasticity would have a profound effect deeper in the lithosphere. Poorly understood rheologies of heterogeneous porous rocks are derived from well understood processes (i.e., elasticity, viscosity, plastic flow, fracturing, and their combinations) on the microscale by considering a
Time-dependent Cooling in Photoionized Plasma
Energy Technology Data Exchange (ETDEWEB)
Gnat, Orly, E-mail: orlyg@phys.huji.ac.il [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
2017-02-01
I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts ( z = 0 − 3), for a range of temperatures (10{sup 8}–10{sup 4} K), densities (10{sup −7}–10{sup 3} cm{sup −3}), and metallicities (10{sup −3}–2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibrium (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard; Smistrup, K.; Hannibal, Morten
2015-01-01
-viscoplastic. This behavior was described in a temperature dependent constitutive model consisting of a Zenerbody for the viscoelastic deformation and the Johnson-Cook model for the description of the viscoplastic deformation. The constitutive model was implemented in the general purpose finite element software ABAQUS...
Soliton like excitations on a deformable spin model
International Nuclear Information System (INIS)
Nguenang, Jean-Pierre; Kenfack, Aurelien J.; Kofane, Timoleon C.
2003-07-01
We study numerically non-linear excitations on a one-dimensional deformable discrete classical ferromagnetic chain. In the continuum limits the equations of motion are reduced to a Klein-Gordon equation with a Remoissenet - Peyrard substrate potential. From a numerical computation of the discrete system with a suitable choice of the deformability parameters, the solitons solutions are shown to exist and move both with a monotonic oscillating (i.e. nanopteron) and a monotonic non- oscillating tails and also with a non- oscillating tails but with a splitting propagating shape. The stability of all these various solitons shape is confirmed numerically in a greater range of the reduced magnetic field 0≤b≤0.61 compared to the case of a rigid magnetic chain i.e. 0≤b≤0.33. From a kink- antikink and a kink-kink colliding simulation, we found various effects including a bound state of a kink and an antikink as well as a moving kink profile with higher topological charge that appears to be the bound state of two kinks. We also observed a three particles interaction that also arises from a kink-kink collision. The breather that intercalates between the two kinks has length that varies from its minimal value to the maximal one as far as the alternation between an attractive and a repulsive phenomenon is produced. From our results it appears that the value of the shape parameter of the substrate potential or the modified Zeeman energy is a factor of outmost importance when modelling magnetic chains. (author)
The time-dependent simplified P2 equations: Asymptotic analyses and numerical experiments
International Nuclear Information System (INIS)
Shin, U.; Miller, W.F. Jr.
1998-01-01
Using an asymptotic expansion, the authors found that the modified time-dependent simplified P 2 (SP 2 ) equations are robust, high-order, asymptotic approximations to the time-dependent transport equation in a physical regime in which the conventional time-dependent diffusion equation is the leading-order approximation. Using diffusion limit analysis, they also asymptotically compared three competitive time-dependent equations (the telegrapher's equation, the time-dependent SP 2 equations, and the time-dependent simplified even-parity equation). As a result, they found that the time-dependent SP 2 equations contain higher-order asymptotic approximations to the time-dependent transport equation than the other competitive equations. The numerical results confirm that, in the vast majority of cases, the time-dependent SP 2 solutions are significantly more accurate than the time-dependent diffusion and the telegrapher's solutions. They have also shown that the time-dependent SP 2 equations have excellent characteristics such as rotational invariance (which means no ray effect), good diffusion limit behavior, guaranteed positivity in diffusive regimes, and significant accuracy, even in deep-penetration problems. Through computer-running-time tests, they have shown that the time-dependent SP 2 equations can be solved with significantly less computational effort than the conventionally used, time-dependent S N equations (for N > 2) and almost as fast as the time-dependent diffusion equation. From all these results, they conclude that the time-dependent SP 2 equations should be considered as an important competitor for an improved approximately transport equations solver. Such computationally efficient time-dependent transport models are important for problems requiring enhanced computational efficiency, such as neutronics/fluid-dynamics coupled problems that arise in the analyses of hypothetical nuclear reactor accidents
A simulation model for analysing brain structure deformations
Energy Technology Data Exchange (ETDEWEB)
Bona, Sergio Di [Institute for Information Science and Technologies, Italian National Research Council (ISTI-8211-CNR), Via G Moruzzi, 1-56124 Pisa (Italy); Lutzemberger, Ludovico [Department of Neuroscience, Institute of Neurosurgery, University of Pisa, Via Roma, 67-56100 Pisa (Italy); Salvetti, Ovidio [Institute for Information Science and Technologies, Italian National Research Council (ISTI-8211-CNR), Via G Moruzzi, 1-56124 Pisa (Italy)
2003-12-21
Recent developments of medical software applications from the simulation to the planning of surgical operations have revealed the need for modelling human tissues and organs, not only from a geometric point of view but also from a physical one, i.e. soft tissues, rigid body, viscoelasticity, etc. This has given rise to the term 'deformable objects', which refers to objects with a morphology, a physical and a mechanical behaviour of their own and that reflects their natural properties. In this paper, we propose a model, based upon physical laws, suitable for the realistic manipulation of geometric reconstructions of volumetric data taken from MR and CT scans. In particular, a physically based model of the brain is presented that is able to simulate the evolution of different nature pathological intra-cranial phenomena such as haemorrhages, neoplasm, haematoma, etc and to describe the consequences that are caused by their volume expansions and the influences they have on the anatomical and neuro-functional structures of the brain.
Validity of scale modeling for large deformations in shipping containers
International Nuclear Information System (INIS)
Burian, R.J.; Black, W.E.; Lawrence, A.A.; Balmert, M.E.
1979-01-01
The principal overall objective of this phase of the continuing program for DOE/ECT is to evaluate the validity of applying scaling relationships to accurately assess the response of unprotected model shipping containers severe impact conditions -- specifically free fall from heights up to 140 ft onto a hard surface in several orientations considered most likely to produce severe damage to the containers. The objective was achieved by studying the following with three sizes of model casks subjected to the various impact conditions: (1) impact rebound response of the containers; (2) structural damage and deformation modes; (3) effect on the containment; (4) changes in shielding effectiveness; (5) approximate free-fall threshold height for various orientations at which excessive damage occurs; (6) the impact orientation(s) that tend to produce the most severe damage; and (7) vunerable aspects of the casks which should be examined. To meet the objective, the tests were intentionally designed to produce extreme structural damage to the cask models. In addition to the principal objective, this phase of the program had the secondary objectives of establishing a scientific data base for assessing the safety and environmental control provided by DOE nuclear shipping containers under impact conditions, and providing experimental data for verification and correlation with dynamic-structural-analysis computer codes being developed by the Los Alamos Scientific Laboratory for DOE/ECT
Non-proportional deformation paths for sheet metal: experiments and models
van den Boogaard, Antonius H.; van Riel, M.; Hora, P.
2009-01-01
For mild steel, after significant plastic deformation in one direction, a subsequent deformation in an orthogonal direction shows a typical stress overshoot compared to monotonic deformation. This phenomenon is investigated experimentally and numerically on a DC06 material. Two models that incorporate the observed overshoot are compared. In the Teodosiu-Hu model, pre-strain influences the rate of kinematic hardening by a rather complex set of evolution equations. The shape of the elastic doma...
International Nuclear Information System (INIS)
Kornienko, V.T.
1991-01-01
A method is suggested to estimate microstructural non-uniformity of deformation in metals by means of modelling. This method includes measurement of deformation in metals by small-dimensioned dividing grid cells as well as calculation of parameters by means of model representation of microdeformation distribution. It is shown that the method of modelling gives an opportunity to objectively estimate deformation non-uniformity in metals irrespective of the selected dimension of a dividing grid cells. New structural characteristics: base and wave of variations, reflecting a degree of dividing or uniting grains in metals according to the non-uniformity of deformation are introduced
Transcriptional dynamics with time-dependent reaction rates
Nandi, Shubhendu; Ghosh, Anandamohan
2015-02-01
Transcription is the first step in the process of gene regulation that controls cell response to varying environmental conditions. Transcription is a stochastic process, involving synthesis and degradation of mRNAs, that can be modeled as a birth-death process. We consider a generic stochastic model, where the fluctuating environment is encoded in the time-dependent reaction rates. We obtain an exact analytical expression for the mRNA probability distribution and are able to analyze the response for arbitrary time-dependent protocols. Our analytical results and stochastic simulations confirm that the transcriptional machinery primarily act as a low-pass filter. We also show that depending on the system parameters, the mRNA levels in a cell population can show synchronous/asynchronous fluctuations and can deviate from Poisson statistics.
Transcriptional dynamics with time-dependent reaction rates
International Nuclear Information System (INIS)
Nandi, Shubhendu; Ghosh, Anandamohan
2015-01-01
Transcription is the first step in the process of gene regulation that controls cell response to varying environmental conditions. Transcription is a stochastic process, involving synthesis and degradation of mRNAs, that can be modeled as a birth–death process. We consider a generic stochastic model, where the fluctuating environment is encoded in the time-dependent reaction rates. We obtain an exact analytical expression for the mRNA probability distribution and are able to analyze the response for arbitrary time-dependent protocols. Our analytical results and stochastic simulations confirm that the transcriptional machinery primarily act as a low-pass filter. We also show that depending on the system parameters, the mRNA levels in a cell population can show synchronous/asynchronous fluctuations and can deviate from Poisson statistics. (paper)
Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures
Mishra, Himanshu; Schrader, Alex M.; Lee, Dong Woog; Gallo, Adair; Chen, Szu-Ying; Kaufman, Yair; Das, Saurabh; Israelachvili, Jacob N.
2015-01-01
Wetting of rough surfaces involves time-dependent effects, such as surface deformations, non-uniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 10-7-10-4 m. Under saturated vapor conditions, we found that in the short-term (<1 min), the contact angle of a sessile water droplet on the templated PDMS, θSDT = 140° ± 3°, was accurately described by the Cassie-Baxter model (predicted θSDT = 137°); however, after 90 min, θSDT fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θSDT to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θSDT to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and
Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures
Mishra, Himanshu
2015-12-28
Wetting of rough surfaces involves time-dependent effects, such as surface deformations, non-uniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 10-7-10-4 m. Under saturated vapor conditions, we found that in the short-term (<1 min), the contact angle of a sessile water droplet on the templated PDMS, θSDT = 140° ± 3°, was accurately described by the Cassie-Baxter model (predicted θSDT = 137°); however, after 90 min, θSDT fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θSDT to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θSDT to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and
Time-Dependent Variations of Accretion Disk
Directory of Open Access Journals (Sweden)
Hye-Weon Na
1987-06-01
Full Text Available In dward nova we assume the primary star as a white dwarf and the secondary as the late type star which filled Roche lobe. Mass flow from the secondary star leads to the formation of thin accretion disk around the white dwarf. We use the α parameter as viscosity to maintain the disk form and propose that the outburst in dwarf nova cause the steep increase of source term. With these assumptions we solve the basic equations of stellar structure using Newton-Raphson method. We show the physical parameters like temperature, density, pressure, opacity, surface density, height and flux to the radius of disk. Changing the value of α, we compare several parameters when mass flow rate is constant with those of when luminosity of disk is brightest. At the same time, we obtain time-dependent variations of luminosity and mass of disk. We propose the suitable range of α is 0.15-0.18 to the difference of luminosity. We compare several parameters of disk with those of the normal late type stars which have the same molecular weight of disk is lower. Maybe the outburst in dwarf nova is due to the variation of the α value instead of increment of mass flow from the secondary star.
Time dependent mean-field games
Gomes, Diogo A.
2014-01-06
We consider time dependent mean-field games (MFG) with a local power-like dependence on the measure and Hamiltonians satisfying both sub and superquadratic growth conditions. We establish existence of smooth solutions under a certain set of conditions depending both on the growth of the Hamiltonian as well as on the dimension. In the subquadratic case this is done by combining a Gagliardo-Nirenberg type of argument with a new class of polynomial estimates for solutions of the Fokker-Planck equation in terms of LrLp- norms of DpH. These techniques do not apply to the superquadratic case. In this setting we recur to a delicate argument that combines the non-linear adjoint method with polynomial estimates for solutions of the Fokker-Planck equation in terms of L1L1-norms of DpH. Concerning the subquadratic case, we substantially improve and extend the results previously obtained. Furthermore, to the best of our knowledge, the superquadratic case has not been addressed in the literature yet. In fact, it is likely that our estimates may also add to the current understanding of Hamilton-Jacobi equations with superquadratic Hamiltonians.
Xing, X.; Yuan, Z.; Chen, L. F.; Yu, X. Y.; Xiao, L.
2018-04-01
The stability control is one of the major technical difficulties in the field of highway subgrade construction engineering. Building deformation model is a crucial step for InSAR time series deformation monitoring. Most of the InSAR deformation models for deformation monitoring are pure empirical mathematical models, without considering the physical mechanism of the monitored object. In this study, we take rheology into consideration, inducing rheological parameters into traditional InSAR deformation models. To assess the feasibility and accuracy for our new model, both simulation and real deformation data over Lungui highway (a typical highway built on soft clay subgrade in Guangdong province, China) are investigated with TerraSAR-X satellite imagery. In order to solve the unknows of the non-linear rheological model, three algorithms: Gauss-Newton (GN), Levenberg-Marquarat (LM), and Genetic Algorithm (GA), are utilized and compared to estimate the unknown parameters. Considering both the calculation efficiency and accuracy, GA is chosen as the final choice for the new model in our case study. Preliminary real data experiment is conducted with use of 17 TerraSAR-X Stripmap images (with a 3-m resolution). With the new deformation model and GA aforementioned, the unknown rheological parameters over all the high coherence points are obtained and the LOS deformation (the low-pass component) sequences are generated.
Description of the hexadecapole deformation parameter in the sdg interacting boson model
International Nuclear Information System (INIS)
Liu Yuxin; Sun Di; Wang Jiajun; Han Qizhi
1998-01-01
The hexadecapole deformation parameter β 4 of the rare-earth and actinide nuclei is investigated in the framework of the sdg interacting boson model. An explicit relation between the geometric hexadecapole deformation parameter β 4 and the intrinsic deformation parameters ε 4 , ε 2 are obtained. The deformation parameters β 4 of the rare-earths and actinides are determined without any free parameter. The calculated results agree with experimental data well. It also shows that the SU(5) limit of the sdg interacting boson model can describe the β 4 systematics as well as the SU(3) limit
Description of the Hexadecapole Deformation Parameter in the sdg Interacting Boson Model
Liu, Yu-xin; Sun, Di; Wang, Jia-jun; Han, Qi-zhi
1998-04-01
The hexadecapole deformation parameter β4 of the rare-earth and actinide nuclei is investigated in the framework of the sdg interacing boson model. An explicit relation between the geometric hexadecapole deformation parameter β4 and the intrinsic deformation parameters epsilon4, epsilon2 are obtained. The deformation parameters β4 of the rare-earths and actinides are determined without any free parameter. The calculated results agree with experimental data well. It also shows that the SU(5) limit of the sdg interacting boson model can describe the β4 systematics as well as the SU(3) limit.
Nonlinear time-dependent simulation of helix traveling wave tubes
International Nuclear Information System (INIS)
Peng Wei-Feng; Yang Zhong-Hai; Hu Yu-Lu; Li Jian-Qing; Lu Qi-Ru; Li Bin
2011-01-01
A one-dimensional nonlinear time-dependent theory for helix traveling wave tubes is studied. A generalized electromagnetic field is applied to the expression of the radio frequency field. To simulate the variations of the high frequency structure, such as the pitch taper and the effect of harmonics, the spatial average over a wavelength is substituted by a time average over a wave period in the equation of the radio frequency field. Under this assumption, the space charge field of the electron beam can be treated by a space charge wave model along with the space charge coefficient. The effects of the radio frequency and the space charge fields on the electrons are presented by the equations of the electron energy and the electron phase. The time-dependent simulation is compared with the frequency-domain simulation for a helix TWT, which validates the availability of this theory. (interdisciplinary physics and related areas of science and technology)
Time-dependent generalized Gibbs ensembles in open quantum systems
Lange, Florian; Lenarčič, Zala; Rosch, Achim
2018-04-01
Generalized Gibbs ensembles have been used as powerful tools to describe the steady state of integrable many-particle quantum systems after a sudden change of the Hamiltonian. Here, we demonstrate numerically that they can be used for a much broader class of problems. We consider integrable systems in the presence of weak perturbations which break both integrability and drive the system to a state far from equilibrium. Under these conditions, we show that the steady state and the time evolution on long timescales can be accurately described by a (truncated) generalized Gibbs ensemble with time-dependent Lagrange parameters, determined from simple rate equations. We compare the numerically exact time evolutions of density matrices for small systems with a theory based on block-diagonal density matrices (diagonal ensemble) and a time-dependent generalized Gibbs ensemble containing only a small number of approximately conserved quantities, using the one-dimensional Heisenberg model with perturbations described by Lindblad operators as an example.
Induced voltage due to time-dependent magnetisation textures
International Nuclear Information System (INIS)
Kudtarkar, Santosh Kumar; Dhadwal, Renu
2010-01-01
We determine the induced voltage generated by spatial and temporal magnetisation textures (inhomogeneities) in metallic ferromagnets due to the spin diffusion of non-equilibrium electrons. Using time dependent semi-classical theory as formulated in Zhang and Li and the drift-diffusion model of transport it is shown that the voltage generated depends critically on the difference in the diffusion constants of up and down spins. Including spin relaxation results in a crucial contribution to the induced voltage. We also show that the presence of magnetisation textures results in the modification of the conductivity of the system. As an illustration, we calculate the voltage generated due to a time dependent field driven helimagnet by solving the Landau-Lifshitz equation with Gilbert damping and explicitly calculate the dependence on the relaxation and damping parameters.
International Nuclear Information System (INIS)
Chakraborty, A.K.; Schubert, J.D.
1983-01-01
For calculation of clad ballooning from single rod and rod bundle experiments a model considering the influences of azimuthal temperature gradients due to the existing eccentricity of the pellets has been developed. This model is based on the secondary creep model of Norton and on the concentric deformation model ending in cladding burst as proposed by F. Erbacher. The new model considers the azimuthal temperature differences along the cladding and the resulting differences in deformations. With this model, calculations of cladding burst deformations from single rod and rod bundle experiments are performed with good agreement
The Simulation and Correction to the Brain Deformation Based on the Linear Elastic Model in IGS
Institute of Scientific and Technical Information of China (English)
MU Xiao-lan; SONG Zhi-jian
2004-01-01
@@ The brain deformation is a vital factor affecting the precision of the IGS and it becomes a hotspot to simulate and correct the brain deformation recently.The research organizations, which firstly resolved the brain deformation with the physical models, have the Image Processing and Analysis department of Yale University, Biomedical Modeling Lab of Vanderbilt University and so on. The former uses the linear elastic model; the latter uses the consolidation model.The linear elastic model only needs to drive the model using the surface displacement of exposed brain cortex,which is more convenient to be measured in the clinic.
A Novel Method of Modeling the Deformation Resistance for Clad Sheet
International Nuclear Information System (INIS)
Hu Jianliang; Yi Youping; Xie Mantang
2011-01-01
Because of the excellent thermal conductivity, the clad sheet (3003/4004/3003) of aluminum alloy is extensively used in various heat exchangers, such as radiator, motorcar air conditioning, evaporator, and so on. The deformation resistance model plays an important role in designing the process parameters of hot continuous rolling. However, the complex behaviors of the plastic deformation of the clad sheet make the modeling very difficult. In this work, a novel method for modeling the deformation resistance of clad sheet was proposed by combining the finite element analysis with experiments. The deformation resistance model of aluminum 3003 and 4004 was proposed through hot compression test on the Gleeble-1500 thermo-simulation machine. And the deformation resistance model of clad sheet was proposed through finite element analysis using DEFORM-2D software. The relationship between cladding ratio and the deformation resistance was discussed in detail. The results of hot compression simulation demonstrate that the cladding ratio has great effects on the resistance of the clad sheet. Taking the cladding ratio into consideration, the mathematical model of the deformation resistance for clad sheet has been proved to have perfect forecasting precision of different cladding ratio. Therefore, the presented model can be used to predict the rolling force of clad sheet during the hot continuous rolling process.
Time-dependent radioactivity distribution in MAFF
International Nuclear Information System (INIS)
Nebel, F.; Zech, E.; Faestermann, T.; Kruecken, R.; Maier-Komor, P.; Assmann, W.; Szerypo, J.; Gross, M.; Kester, O.; Thirolf, P.G.; Groetzschel, R.
2006-01-01
The Munich Accelerator for Fission Fragments is planned to be installed at the FRM II in Garching. It will operate a uranium-carbide-loaded graphite matrix as a target for neutron-induced fission. The radioactive reaction fragments leave the ion source as both, atoms and ions. For radiation safety it is imperative to have a basic understanding of the fragment distribution within the beam line. Atoms leaving the graphite matrix will spread like a gas and stick to surfaces depending on their species. A probabilistic Monte-Carlo approach is used to predict the surface coating of internal surfaces of the beam line for all fission nuclides. To decrease calculation time, the problem is reduced to two dimensions with the surface areas being a measure for the probability, that they are hit by a particle. The program is completely time dependent to implement radioactive decay. Ions leaving the fission ion source are transported by electrostatic means towards the mass pre-separator, a low-resolution dipole magnet with a complex slit system in the focal plane. All unwanted ions are stopped at the slits, resulting in a high level of radioactive contamination. While it is advantageous for shielding purposes to have the majority of the contamination in one point, precautions must be taken to ensure that it stays that way. Material corrosion caused by sputtering will release previously implanted radionuclides. To reduce this effect, different methods are under investigation, one of which is changing the slit geometry. The considered designs will be described and experimental results will be shown
Zhuang, Jinda; Ju, Y Sungtaek
2015-09-22
The deformation and rupture of axisymmetric liquid bridges being stretched between two fully wetted coaxial disks are studied experimentally and theoretically. We numerically solve the time-dependent Navier-Stokes equations while tracking the deformation of the liquid-air interface using the arbitrary Lagrangian-Eulerian (ALE) moving mesh method to fully account for the effects of inertia and viscous forces on bridge dynamics. The effects of the stretching velocity, liquid properties, and liquid volume on the dynamics of liquid bridges are systematically investigated to provide direct experimental validation of our numerical model for stretching velocities as high as 3 m/s. The Ohnesorge number (Oh) of liquid bridges is a primary factor governing the dynamics of liquid bridge rupture, especially the dependence of the rupture distance on the stretching velocity. The rupture distance generally increases with the stretching velocity, far in excess of the static stability limit. For bridges with low Ohnesorge numbers, however, the rupture distance stay nearly constant or decreases with the stretching velocity within certain velocity windows due to the relative rupture position switching and the thread shape change. Our work provides an experimentally validated modeling approach and experimental data to help establish foundation for systematic further studies and applications of liquid bridges.
Application of the Periodic Average System Model in Dam Deformation Analysis
Directory of Open Access Journals (Sweden)
Yueqian Shen
2015-01-01
Full Text Available Dams are among the most important hydraulic engineering facilities used for water supply, flood control, and hydroelectric power. Monitoring of dams is crucial since deformation might have occurred. How to obtain the deformation information and then judge the safe conditions is the key and difficult problem in dam deformation monitoring field. This paper proposes the periodic average system model and creates the concept of “settlement activity” based on the dam deformation issue. Long-term deformation monitoring data is carried out in a pumped-storage power station, this model combined with settlement activity is used to make the single point deformation analysis, and then the whole settlement activity profile is drawn by clustering analysis. Considering the cumulative settlement value of every point, the dam deformation trend is analyzed in an intuitive effect way. The analysis mode of combined single point with multipoints is realized. The results show that the key deformation information of the dam can be easily grasped by the application of the periodic average system model combined with the distribution diagram of settlement activity. And, above all, the ideas of this research provide an effective method for dam deformation analysis.
Development of zircaloy deformation model to describe the zircaloy-4 cladding tube during accidents
International Nuclear Information System (INIS)
Raff, S.
1978-01-01
The development of a high-temperature deformation model for Zircaloy-4 cans is primarily based on numerous well-parametrized tensile tests to get the material behaviour including statistical variance. It is shown that plastic deformation may be described by a power creep law, the coefficients of which show strong dependence on temperature in the relevant temperature region. These coefficients have been determined. A model based on these coefficients has been established which, apart from best estimate deformation, gives upper and lower bounds of possible deformation. The model derived from isothermal uniaxial tests is being verified against isothermal and transient tube burst tests. The influence of preoxidation and increased oxygen concentration during deformation is modeled on the basis of the pseudobinary Zircaloy-oxygen phase diagram. (author)
Effect of material property heterogeneity on biomechanical modeling of prostate under deformation
International Nuclear Information System (INIS)
Samavati, Navid; McGrath, Deirdre M; Ménard, Cynthia; Jewett, Michael A S; Van der Kwast, Theo; Brock, Kristy K
2015-01-01
Biomechanical model based deformable image registration has been widely used to account for prostate deformation in various medical imaging procedures. Biomechanical material properties are important components of a biomechanical model. In this study, the effect of incorporating tumor-specific material properties in the prostate biomechanical model was investigated to provide insight into the potential impact of material heterogeneity on the prostate deformation calculations. First, a simple spherical prostate and tumor model was used to analytically describe the deformations and demonstrate the fundamental effect of changes in the tumor volume and stiffness in the modeled deformation. Next, using a clinical prostate model, a parametric approach was used to describe the variations in the heterogeneous prostate model by changing tumor volume, stiffness, and location, to show the differences in the modeled deformation between heterogeneous and homogeneous prostate models. Finally, five clinical prostatectomy examples were used in separately performed homogeneous and heterogeneous biomechanical model based registrations to describe the deformations between 3D reconstructed histopathology images and ex vivo magnetic resonance imaging, and examine the potential clinical impact of modeling biomechanical heterogeneity of the prostate. The analytical formulation showed that increasing the tumor volume and stiffness could significantly increase the impact of the heterogeneous prostate model in the calculated displacement differences compared to the homogeneous model. The parametric approach using a single prostate model indicated up to 4.8 mm of displacement difference at the tumor boundary compared to a homogeneous model. Such differences in the deformation of the prostate could be potentially clinically significant given the voxel size of the ex vivo MR images (0.3 × 0.3 × 0.3 mm). However, no significant changes in the registration accuracy were
Time-Dependent Neutron and Photon Dose-Field Analysis
Energy Technology Data Exchange (ETDEWEB)
Wooten, Hasani Omar [Georgia Inst. of Technology, Atlanta, GA (United States)
2005-08-01
A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The Pandemonium code, originally designed to determine flux and dose-rates only, is improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. A primary benefit of this work has been an extensive analysis and improvement of the photon model that is not limited to the application described in this thesis. The photon model has been extended in energy range to 10 MeV to include photons from fission and new photon buildup factors have been included that account for the effects of photon buildup at slant-path thicknesses as a function of angle, where the mean free path thickness has been preserved. The overall system of codes is user-friendly and it is directly applicable to facilities such as the plutonium facility at Los Alamos National Laboratory, where high-intensity neutron and photon emitters are regularly used. The codes may be used to determine a priori doses for given work scenarios in an effort to supply dose information to process models which will in turn assist decision makers on ensuring as low as reasonably achievable (ALARA) compliance. In addition, coupling the computational results of these tools with the process model visualization tools will help to increase worker safety and radiological safety awareness.
Comparative Analysis of Bulge Deformation between 2D and 3D Finite Element Models
Directory of Open Access Journals (Sweden)
Qin Qin
2014-02-01
Full Text Available Bulge deformation of the slab is one of the main factors that affect slab quality in continuous casting. This paper describes an investigation into bulge deformation using ABAQUS to model the solidification process. A three-dimensional finite element analysis model of the slab solidification process has been first established because the bulge deformation is closely related to slab temperature distributions. Based on slab temperature distributions, a three-dimensional thermomechanical coupling model including the slab, the rollers, and the dynamic contact between them has also been constructed and applied to a case study. The thermomechanical coupling model produces outputs such as the rules of bulge deformation. Moreover, the three-dimensional model has been compared with a two-dimensional model to discuss the differences between the two models in calculating the bulge deformation. The results show that the platform zone exists in the wide side of the slab and the bulge deformation is affected strongly by the ratio of width-to-thickness. The indications are also that the difference of the bulge deformation for the two modeling ways is little when the ratio of width-to-thickness is larger than six.
A Statistical Model of Head Asymmetry in Infants with Deformational Plagiocephaly
DEFF Research Database (Denmark)
Lanche, Stéphanie; Darvann, Tron Andre; Ólafsdóttir, Hildur
2007-01-01
Deformational plagiocephaly is a term describing cranial asymmetry and deformation commonly seen in infants. The purpose of this work was to develop a methodology for assessment and modelling of head asymmetry. The clinical population consisted of 38 infants for whom 3-dimensional surface scans...... quantitative description of the asymmetry present in the dataset....
RAPS: Robust and Efficient Automatic Construction of Person-Specific Deformable Models
Sagonas, Christos; Panagakis, Yannis; Zafeiriou, Stefanos; Pantic, Maja
The construction of Facial Deformable Models (FDMs) is a very challenging computer vision problem, since the face is a highly deformable object and its appearance drastically changes under different poses, expressions, and illuminations. Although several methods for generic FDMs construction, have
Anelastic deformation processes in metallic glasses and activation energy spectrum model
Ocelik, [No Value; Csach, K; Kasardova, A; Bengus, VZ; Ocelik, Vaclav
1997-01-01
The isothermal kinetics of anelastic deformation below the glass transition temperature (so-called 'stress induced ordering' or 'creep recovery' deformation) was investigated in Ni-Si-B metallic glass. The relaxation time spectrum model and two recently developed methods for its calculation from the
Modelling and simulations in hot deformation of steels
International Nuclear Information System (INIS)
Cabrera, J.M.
2002-01-01
Traditionally, hot forming has been employed to provide shape to metals. Nowadays, however, hot working not only produces the desired geometry, but also the mechanical characteristics required. An understanding of the thermomechanical behaviour of metals, and particularly steels, is essential in the simulation and control of the hot forming operations. Moreover, a right prediction of the final properties needs from accurate descriptions of the microstructural features occurring during the shaping step. For this purpose, the determination of constitutive equations describing the stress σ - strain ε relationships at a given strain rate ε, temperature T and initial microstructure, is a useful task. In this sense, computer simulations of hot working processes proportionate a benchmark to engineers and researchers and allow decreasing the cost of developing products and processes. With regard to the prediction of the final microstructure, the simulation of the hot plastic deformation usually gives unsatisfactory results. This is due to the inadequate constitutive equations employed by the conventional and commercial software available to describe the hot flow behaviour. There are scarce models which couple the typical hot working variables (temperature, strain and strain rate) with microstructural characteristics such as grain size. In this review work is presented how the latter limitation can be overcome by using physical-based constitutive equations, some of which have been partially developed by the present authors, where account of the interaction between microstructure and processing variables is taken. Moreover, a practical derivation of the latter expressions on an AISI-304 steel is presented. To conclude, some examples of industrial applications of the latter approach are also presented. Copyright (2002) AD-TECH - International Foundation for the Advancement of Technology Ltd
DEFORMATION DEPENDENT TUL MULTI-STEP DIRECT MODEL
International Nuclear Information System (INIS)
WIENKE, H.; CAPOTE, R.; HERMAN, M.; SIN, M.
2007-01-01
The Multi-Step Direct (MSD) module TRISTAN in the nuclear reaction code EMPIRE has been extended in order to account for nuclear deformation. The new formalism was tested in calculations of neutron emission spectra emitted from the 232 Th(n,xn) reaction. These calculations include vibration-rotational Coupled Channels (CC) for the inelastic scattering to low-lying collective levels, ''deformed'' MSD with quadrupole deformation for inelastic scattering to the continuum, Multi-Step Compound (MSC) and Hauser-Feshbach with advanced treatment of the fission channel. Prompt fission neutrons were also calculated. The comparison with experimental data shows clear improvement over the ''spherical'' MSD calculations and JEFF-3.1 and JENDL-3.3 evaluations
Deformation dependent TUL multi-step direct model
International Nuclear Information System (INIS)
Wienke, H.; Capote, R.; Herman, M.; Sin, M.
2008-01-01
The Multi-Step Direct (MSD) module TRISTAN in the nuclear reaction code EMPIRE has been extended to account for nuclear deformation. The new formalism was tested in calculations of neutron emission spectra emitted from the 232 Th(n,xn) reaction. These calculations include vibration-rotational Coupled Channels (CC) for the inelastic scattering to low-lying collective levels, 'deformed' MSD with quadrupole deformation for inelastic scattering to the continuum, Multi-Step Compound (MSC) and Hauser-Feshbach with advanced treatment of the fission channel. Prompt fission neutrons were also calculated. The comparison with experimental data shows clear improvement over the 'spherical' MSD calculations and JEFF-3.1 and JENDL-3.3 evaluations. (authors)
Discrete element modeling of deformable particles in YADE
Directory of Open Access Journals (Sweden)
Martin Haustein
2017-01-01
Full Text Available In this paper we describe the open-source discrete element framework YADE and the implementation of a new deformation engine. YADE is a highly expandable software package that allows the simulation of current industrial problems in the field of granular materials using particle-based numerical methods. The description of the compaction of powders and granular material like metal pellets is now possible with a pure and simple discrete element approach in a modern DEM-framework. The deformation is realized by expanding the radius of the spherical particles, depending on their overlap, so that the volume of the material is kept constant.
Recent Progress on Modeling Slip Deformation in Shape Memory Alloys
Sehitoglu, H.; Alkan, S.
2018-03-01
This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non- Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.
An Efficient Data-driven Tissue Deformation Model
DEFF Research Database (Denmark)
Mosbech, Thomas Hammershaimb; Ersbøll, Bjarne Kjær; Christensen, Lars Bager
2009-01-01
empirical data; 10 pig carcasses are subjected to deformation from a controlled source imitating the cutting tool. The tissue deformation is quantified by means of steel markers inserted into the carcass as a three-dimensional lattice. For each subject marker displacements are monitored through two...... find an association between the first principal mode and the lateral movement. Furthermore, there is a link between this and the ratio of meat-fat quantity - a potentially very useful finding since existing tools for carcass grading and sorting measure equivalent quantities....
Recent Progress on Modeling Slip Deformation in Shape Memory Alloys
Sehitoglu, H.; Alkan, S.
2018-03-01
This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non-Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.
Energy Technology Data Exchange (ETDEWEB)
Cornu, T.
2001-01-01
The present work deals with three-dimensional deformation of sedimentary basins. The main goal of the work was to propose new ways to study tectonic deformation and to insert it into basin-modeling environment for hydrocarbon migration applications. To handle the complexity of the deformation, the model uses kinematic laws, a discrete approach, and the construction of a code that allows the greatest diversity in the deformation mechanisms we can take into account. The 3-D-volume deformation is obtained through the calculation of the behavior of the neutral surface of each basin layer. The main idea is to deform the neutral surface of each layer with the help of geometrical laws and to use the result to rebuild the volume deformation of the basin. The constitutive algorithm includes three characteristic features. The first one deals with the mathematical operator we use to describe the flexural-slip mechanism which is a combination of the translation of the neutral surface nodes and the rotation of the vertical edges attached to these nodes. This performs the reversibility that was required for the basin modeling. The second one is about. the use of a discrete approach, which gives a better description of the global deformation and offers to locally control volume evolutions. The knowledge of volume variations can become a powerful tool in structural geology analysis and the perfect complement for a field study. The last one concerns the modularity of the developed code. Indeed, the proposed model uses three main mechanisms of deformation. But the architecture of the code allows the insertion of new mechanisms or a better interaction between them. The model has been validated first with 2-D cases, then with 3-D natural cases. They give good results from a qualitative point of view. They also show the capacity of the model to provide a deformation path that is geologically acceptable, and its ability to control the volume variations of the basin through the
Erickson, Gary E.
2013-01-01
A video-based photogrammetric model deformation system was established as a dedicated optical measurement technique at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. This system was used to measure the wing twist due to aerodynamic loads of two supersonic commercial transport airplane models with identical outer mold lines but different aeroelastic properties. One model featured wings with deflectable leading- and trailing-edge flaps and internal channels to accommodate static pressure tube instrumentation. The wings of the second model were of single-piece construction without flaps or internal channels. The testing was performed at Mach numbers from 1.6 to 2.7, unit Reynolds numbers of 1.0 million to 5.0 million, and angles of attack from -4 degrees to +10 degrees. The video model deformation system quantified the wing aeroelastic response to changes in the Mach number, Reynolds number concurrent with dynamic pressure, and angle of attack and effectively captured the differences in the wing twist characteristics between the two test articles.
Twisted supersymmetry in a deformed Wess-Zumino model in (2+1) dimensions
Energy Technology Data Exchange (ETDEWEB)
Palechor, C.; Ferrari, A.F.; Quinto, A.G. [Universidade Federal do ABC - UFABC,Avenida dos Estados 5001, 0910-580, Santo André, SP (Brazil)
2017-01-12
Non-anticommutative deformations have been studied in the context of supersymmetry (SUSY) in three and four space-time dimensions, and the general picture is that highly nontrivial to deform supersymmetry in a way that still preserves some of its important properties, both at the formal algebraic level (e.g., preserving the associativity of the deformed theory) as well as at the physical level (e.g., maintaining renormalizability). The Hopf algebra formalism allows the definition of algebraically consistent deformations of SUSY, but this algebraic consistency does not guarantee that physical models build upon these structures will be consistent from the physical point of view. We will investigate a deformation induced by a Drinfel’d twist of the N=1 SUSY algebra in three space-time dimensions. The use of the Hopf algebra formalism allows the construction of deformed N=1 SUSY algebras that should still preserve a deformed version of supersymmetry. We will construct the simplest deformed version of the Wess-Zumino model in this context, but we will show that despite the consistent algebraic structure, the model in question is not invariant under SUSY transformation and is not renormalizable. We will comment on the relation of these results with previous ones discussed in the literature regarding similar four-dimensional constructions.
Two Back Stress Hardening Models in Rate Independent Rigid Plastic Deformation
Yun, Su-Jin
In the present work, the constitutive relations based on the combination of two back stresses are developed using the Armstrong-Frederick, Phillips and Ziegler’s type hardening rules. Various evolutions of the kinematic hardening parameter can be obtained by means of a simple combination of back stress rate using the rule of mixtures. Thus, a wide range of plastic deformation behavior can be depicted depending on the dominant back stress evolution. The ultimate back stress is also determined for the present combined kinematic hardening models. Since a kinematic hardening rule is assumed in the finite deformation regime, the stress rate is co-rotated with respect to the spin of substructure obtained by incorporating the plastic spin concept. A comparison of the various co-rotational rates is also included. Assuming rigid plasticity, the continuum body consists of the elastic deformation zone and the plastic deformation zone to form a hybrid finite element formulation. Then, the plastic deformation behavior is investigated under various loading conditions with an assumption of the J2 deformation theory. The plastic deformation localization turns out to be strongly dependent on the description of back stress evolution and its associated hardening parameters. The analysis for the shear deformation with fixed boundaries is carried out to examine the deformation localization behavior and the evolution of state variables.
[Research progress on real-time deformable models of soft tissues for surgery simulation].
Xu, Shaoping; Liu, Xiaoping; Zhang, Hua; Luo, Jie
2010-04-01
Biological tissues generally exhibit nonlinearity, anisotropy, quasi-incompressibility and viscoelasticity about material properties. Simulating the behaviour of elastic objects in real time is one of the current objectives of virtual surgery simulation which is still a challenge for researchers to accurately depict the behaviour of human tissues. In this paper, we present a classification of the different deformable models that have been developed. We present the advantages and disadvantages of each one. Finally, we make a comparison of deformable models and perform an evaluation of the state of the art and the future of deformable models.
Energy Technology Data Exchange (ETDEWEB)
Follin, Sven (SF GeoLogic AB, Taeby (SE)); Leven, Jakob (Swedish Nuclear Fuel and Waste Management Co., Stockholm (SE)); Hartley, Lee; Jackson, Peter; Joyce, Steve; Roberts, David; Swift, Ben (Serco Assurance, Harwell (GB))
2007-09-15
The work reported here collates the structural-hydraulic information gathered in 21 cored boreholes and 32 percussion-drilled boreholes belonging to Forsmark site description, modelling stage 2.2. The analyses carried out provide the hydrogeological input descriptions of the bedrock in Forsmark needed by the end users Repository Engineering, Safety Assessment and Environmental Impact Assessment; that is, hydraulic properties of deformation zones and fracture domains. The same information is also needed for constructing 3D groundwater flow models of the Forsmark site and surrounding area. The analyses carried out render the following conceptual model regarding the observed heterogeneity in deformation zone transmissivity: We find the geological division of the deterministically modelled deformation zones into eight categories (sets) useful from a hydrogeological point of view. Seven of the eight categories are steeply dipping, WNW, NW, NNW, NNE, NE, ENE and EW, and on is gently dipping, G. All deformation zones, regardless of orientation (strike and dip), are subjected to a substantial decrease in transmissivity with depth. The data gathered suggest a contrast of c. 20,000 times for the uppermost one kilometre of bedrock, i.e. more than four orders of magnitude. The hydraulic properties below this depth are not investigated. The lateral heterogeneity is also substantial but more irregular in its appearance. For instance, for a given elevation and deformation zone category (orientation), the spatial variability in transmissivity within a particular deformation zone appears to be as large as the variability between all deformation zones. This suggests that the lateral correlation length is shorter than the shortest distance between two adjacent observation points and shorter than the category spacing. The observation that the mean transmissivity of the gently-dipping deformation zones is c. one to two orders of magnitude greater than the mean transmissivities of all
Numerical modelling of river processes: flow and river bed deformation
Tassi, P.A.
2007-01-01
The morphology of alluvial river channels is a consequence of complex interaction among a number of constituent physical processes, such as flow, sediment transport and river bed deformation. This is, an alluvial river channel is formed from its own sediment. From time to time, alluvial river
Modeling polyolefin deformation resistance in a growing microparticle
Agarwal, U.S.
2004-01-01
When polyolefins are produced on heterogeneous catalysts, they encapsulate the catalyst fragments and present diffusional resistance to further monomer transport to the catalyst fragments. In addition, the deposited polymer layer brings in viscoelastic resistance, since it must be deformed to make
Time Dependent Hartree Fock Equation: Gateway to Nonequilibrium Plasmas
International Nuclear Information System (INIS)
Dufty, James W.
2007-01-01
This is the Final Technical Report for DE-FG02-2ER54677 award 'Time Dependent Hartree Fock Equation - Gateway to Nonequilibrium Plasmas'. Research has focused on the nonequilibrium dynamics of electrons in the presence of ions, both via basic quantum theory and via semi-classical molecular dynamics (MD) simulation. In addition, fundamental notions of dissipative dynamics have been explored for models of grains and dust, and for scalar fields (temperature) in turbulent edge plasmas. The specific topics addressed were Quantum Kinetic Theory for Metallic Clusters, Semi-classical MD Simulation of Plasmas , and Effects of Dissipative Dynamics.
Time-dependent coolant velocity measurements in an operating BWR
International Nuclear Information System (INIS)
Luebbesmeyer, D.; Crowe, R.D.
1980-01-01
A method to measure time-dependent fluid velocities in BWR-bundle elements by noise analysis of the incore-neutron-detector signals is shown. Two application examples of the new method are given. The time behaviour of the fluid velocity in the bundle element during a scheduled power excursion of the plant. The change of power was performed by changing the coolant flow through the core The apparent change of the fluid velocity due to thermal elongation of the helix-drive of the TIP-system. A simplified mathematical model was derived for this elongation to use as a reference to check the validity of the new method. (author)
Queues with waiting time dependent service
DEFF Research Database (Denmark)
Bekker, R.; Koole, G. M.; Nielsen, Bo Friis
2011-01-01
Motivated by service levels in terms of the waiting-time distribution seen, for instance, in call centers, we consider two models for systems with a service discipline that depends on the waiting time. The first model deals with a single server that continuously adapts its service rate based...... derive steady-state waiting-time distributions for both models. The results are illustrated with numerical examples....... on the waiting time of the first customer in line. In the second model, one queue is served by a primary server which is supplemented by a secondary server when the waiting of the first customer in line exceeds a threshold. Using level crossings for the waiting-time process of the first customer in line, we...
Soft tissue deformation modelling through neural dynamics-based reaction-diffusion mechanics.
Zhang, Jinao; Zhong, Yongmin; Gu, Chengfan
2018-05-30
Soft tissue deformation modelling forms the basis of development of surgical simulation, surgical planning and robotic-assisted minimally invasive surgery. This paper presents a new methodology for modelling of soft tissue deformation based on reaction-diffusion mechanics via neural dynamics. The potential energy stored in soft tissues due to a mechanical load to deform tissues away from their rest state is treated as the equivalent transmembrane potential energy, and it is distributed in the tissue masses in the manner of reaction-diffusion propagation of nonlinear electrical waves. The reaction-diffusion propagation of mechanical potential energy and nonrigid mechanics of motion are combined to model soft tissue deformation and its dynamics, both of which are further formulated as the dynamics of cellular neural networks to achieve real-time computational performance. The proposed methodology is implemented with a haptic device for interactive soft tissue deformation with force feedback. Experimental results demonstrate that the proposed methodology exhibits nonlinear force-displacement relationship for nonlinear soft tissue deformation. Homogeneous, anisotropic and heterogeneous soft tissue material properties can be modelled through the inherent physical properties of mass points. Graphical abstract Soft tissue deformation modelling with haptic feedback via neural dynamics-based reaction-diffusion mechanics.
International Nuclear Information System (INIS)
Yaguchi, Masatsugu; Takahashi, Yukio
2001-01-01
A series of ratchetting deformation tests was conducted on modified 9Cr-1Mo steel at 550degC under uniaxial and multiaxial stress conditions. Ratchetting behavior depended on various parameters such as mean stress, stress/strain rate and those range, hold time and prior cyclic deformation. Under uniaxial conditions, untraditional ratchetting behavior was observed; the ratchetting deformation rate was the fastest when the stress ratio was equal to -1, while no ratchetting deformation was predicted by conventional constitutive models. In order to discuss the reason for this untraditional ratchetting behavior, a lot of monotonic compression tests were conducted and compared with tension data. The material showed a difference of deformation resistance of about 30 MPa between tension and compression at high strain rates. Furthermore, the authors' previous model and Ohno-Wang model were applied to the test conditions to evaluate their description capability for ratchetting behavior of the material. It was shown that the authors' model has a tendency to overestimate the ratchetting deformation and that the Ohno-Wang model has a tendency to underestimate the uniaxial ratchetting deformation at small stress rates. (author)
The Electromagnetic Field of Elementary Time-Dependent Toroidal Sources
International Nuclear Information System (INIS)
Afanas'ev, G.N.; Stepanovskij, Yu.P.
1994-01-01
The radiation field of toroidal-like time-dependent current configurations is investigated. Time-dependent charge-current sources are found outside which the electromagnetic strengths disappear but the potentials survive. This can be used to carry out time-dependent Aharonov-Bohm-like experiments and the information transfer. Using the Neumann-Helmholtz parametrization of the current density we present the time-dependent electromagnetic field in a form convenient for applications. 17 refs
Time-dependent problems in quantum-mechanical state reconstruction
International Nuclear Information System (INIS)
Leonhardt, U.; Bardroff, P. J.
1997-01-01
We study the state reconstruction of wave packets that travel in time-dependent potentials. We solve the problem for explicitly time-dependent potentials. We solve the problem for explicitly time-dependent harmonic oscillators and sketch a general adaptive technique for finding the wave function that matches and observed evolution. (authors)
Crustal deformation mechanism in southeastern Tibetan Plateau: Insights from numerical modeling
Li, Y.; Liu, S.; Chen, L.
2017-12-01
The Indo-Asian collision developed the complicated crustal deformation around the southeastern Tibetan plateau. Numerous models have proposed to explain the crustal deformation, but the mechanism remains controversial, especially the increasing multi-geophysics data, which demonstrate the existence of lower velocity, lower resistivity and high conductivity, implying that lower crustal flow is responsible for the crustal deformation, arguing for the lower crust flow model. To address the relations between the crust flow and the surface deformation, we employ a three-dimensional viscoelastic finite model to investigate the possible influence on the surface deformation, and discuss the stress field distribution under the model. Our preliminary results suggest that lower crustal flow plays an important role in crustal deformation in southeastern Tibetan plateau. The best fitting is achieved when the flow velocity of the lower crust is approximately 10-11 mm/a faster than that of the upper crust. Crustal rheological properties affect regional crustal deformation, when the viscosity of the middle and lower crust in the South China block reaches 1022 and 1023 Pa.s, respectively; the predicted match observations well, especially for the magnitude within the South China block. The maximum principal stress field exhibits clear zoning, gradually shifting from an approximately east-west orientation in the northern Bayan Har block to southeast in the South China block, southwest in the western Yunnan block, and a radially divergent distribution in the Middle Yunnan and Southern Yunnan blocks.
Dembo, N.; Granot, R.; Hamiel, Y.
2017-12-01
The intraplate crustal deformation found in the northern part of the Sinai Microplate, located near the northern Dead Sea Fault plate boundary, is examined. Previous studies have suggested that distributed deformation in Lebanon is accommodated by regional uniform counterclockwise rigid block rotations. However, remanent magnetization directions observed near the Lebanese restraining bend are not entirely homogeneous suggesting that an unexplained and complex internal deformation pattern exists. In order to explain the variations in the amount of vertical-axis rotations we construct a mechanical model of the major active faults in the region that simulates the rotational deformation induced by motion along these faults. The rotational pattern calculated by the mechanical modeling predicts heterogeneous distribution of rotations around the faults. The combined rotation field that considers both the fault induced rotations and the already suggested regional block rotations stands in general agreement with the observed magnetization directions. Overall, the modeling results provide a more detailed and complete picture of the deformation pattern in this region and show that rotations induced by motion along the Dead Sea Fault act in parallel to rigid block rotations. Finally, the new modeling results unravel important insights as to the fashion in which crustal deformation is distributed within the northern part of the Sinai Microplate and propose an improved deformational mechanism that might be appropriate for other plate margins as well.
Numerical model for the deformation of nucleated cells by optical stretchers
Sraj, Ihab; Francois, Joshua; Marr, David W M; Eggleton, Charles D.
2015-01-01
In this paper, we seek to numerically study the deformation of nucleated cells by single diode-laser bar optical stretchers. We employ a recently developed computational model, the dynamic ray-tracing method, to determine the force distribution
Modeling, Calibration and Control for Extreme-Precision MEMS Deformable Mirrors, Phase I
National Aeronautics and Space Administration — Iris AO will develop electromechanical models and actuator calibration methods to enable open-loop control of MEMS deformable mirrors (DMs) with unprecedented...
National Research Council Canada - National Science Library
Grishber, R
1997-01-01
A constitutive model for deformation of a novel laminated metal composite (LMC) which is comprised of 21 alternating layers of Al 5182 alloy and Al 6090/SiC/25p metal matrix composite (MMC) has been proposed...