Varying vacuum energy of a self-interacting scalar field
Trachenko, K.
2015-11-01
Understanding mechanisms capable of altering the vacuum energy is currently of interest in field theories and cosmology. We consider an interacting scalar field and show that the vacuum energy naturally takes any value between its maximum and zero because interaction affects the number of operating field modes, the assertion that involves no assumptions or postulates. The mechanism is similar to the recently discussed temperature evolution of collective modes in liquids. The cosmological implication concerns the evolution of scalar field ϕ during the inflation of the Universe. ϕ starts with all field modes operating and maximal vacuum energy in the early inflation-dominated epoch. As a result of inflation, ϕ undergoes a dynamical crossover and arrives in the state with one long-wavelength longitudinal mode and small positive vacuum energy predicted to be asymptotically decreasing to zero in the late epoch. Accordingly, we predict that the currently observed cosmological constant will decrease in the future, and comment on the possibility of a cyclic Universe.
Vacuum Stability of Standard Model^{++}
Anchordoqui, Luis A.; Goldberg, Haim; Huang, Xing; Lust, Dieter; Taylor, Tomasz R.; Vlcek, Brian
2013-01-01
The latest results of the ATLAS and CMS experiments point to a preferred narrow Higgs mass range (m_h \\simeq 124 - 126 GeV) in which the effective potential of the Standard Model (SM) develops a vacuum instability at a scale 10^{9} -10^{11} GeV, with the precise scale depending on the precise value of the top quark mass and the strong coupling constant. Motivated by this experimental situation, we present here a detailed investigation about the stability of the SM^{++} vacuum, which is characterized by a simple extension of the SM obtained by adding to the scalar sector a complex SU(2) singlet that has the quantum numbers of the right-handed neutrino, H", and to the gauge sector an U(1) that is broken by the vacuum expectation value of H". We derive the complete set of renormalization group equations at one loop. We then pursue a numerical study of the system to determine the triviality and vacuum stability bounds, using a scan of 10^4 random set of points to fix the initial conditions. We show that, if there...
Thermodynamical aspects of running vacuum models
Energy Technology Data Exchange (ETDEWEB)
Lima, J.A.S. [Universidade de Sao Paulo, Departamento de Astronomia, Sao Paulo (Brazil); Basilakos, Spyros [Academy of Athens, Research Center for Astronomy and Applied Mathematics, Athens (Greece); Sola, Joan [Univ. de Barcelona, High Energy Physics Group, Dept. d' Estructura i Constituents de la Materia, Institut de Ciencies del Cosmos (ICC), Barcelona, Catalonia (Spain)
2016-04-15
The thermal history of a large class of running vacuum models in which the effective cosmological term is described by a truncated power series of the Hubble rate, whose dominant term is Λ(H) ∝ H{sup n+2}, is discussed in detail. Specifically, by assuming that the ultrarelativistic particles produced by the vacuum decay emerge into space-time in such a way that its energy density ρ{sub r} ∝ T{sup 4}, the temperature evolution law and the increasing entropy function are analytically calculated. For the whole class of vacuum models explored here we find that the primeval value of the comoving radiation entropy density (associated to effectively massless particles) starts from zero and evolves extremely fast until reaching a maximum near the end of the vacuum decay phase, where it saturates. The late-time conservation of the radiation entropy during the adiabatic FRW phase also guarantees that the whole class of running vacuum models predicts the same correct value of the present day entropy, S{sub 0} ∝ 10{sup 87}-10{sup 88} (in natural units), independently of the initial conditions. In addition, by assuming Gibbons¨CHawking temperature as an initial condition, we find that the ratio between the late-time and primordial vacuum energy densities is in agreement with naive estimates from quantum field theory, namely, ρ{sub Λ0}/ρ{sub ΛI} 10{sup -123}. Such results are independent on the power n and suggests that the observed Universe may evolve smoothly between two extreme, unstable, non-singular de Sitter phases. (orig.)
Dynamic Models of Vacuum-Evaporator Plants for Dairy Industry
Directory of Open Access Journals (Sweden)
G. M. Airapetiants
2009-01-01
Full Text Available The paper studies problems of linearized dynamic models intended for synthesis of automatic temperature control systems and vacuum depth in vacuum evaporators. А single-casing vacuum evaporator plant is considered as an object of automatic control. Disturbance input channels are discerned and transfer functions permitting to determine laws of temperature and vacuum regulation and optimum parameters for setting automatic regulators used for various operational modes of vacuum-evaporator plants are obtained on the basis of the executed analysis.
On the Vacuum Structure of the 3-2 Model
Shacham, Tomer
2012-01-01
The 3-2 model of dynamical supersymmetry breaking is revisited, with some incidentally new observations on the vacuum structure. Extra matter is then added, and the vacuum structure is further studied. The parametric dependence of the location of the vacuum provides a consistency check of Seiberg duality.
On the vacuum structure of the 3-2 model
Shacham, Tomer
2012-05-01
The 3-2 model of dynamical supersymmetry breaking is revisited, with some incidentally new observations on the vacuum structure. Extra matter is then added, and the vacuum structure is further studied. The parametric dependence of the location of the vacuum provides a consistency check of Seiberg duality.
Novel vacuum conditions in inflationary collapse models
Bengochea, Gabriel R.; León, Gabriel
2017-11-01
Within the framework of inflationary models that incorporate a spontaneous reduction of the wave function for the emergence of the seeds of cosmic structure, we study the effects on the primordial scalar power spectrum by choosing a novel initial quantum state that characterizes the perturbations of the inflaton. Specifically, we investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities when the standard Bunch-Davies vacuum is replaced by another one that minimizes the renormalized stress-energy tensor via a Hadamard procedure. We think that this new prescription for selecting the vacuum state is better suited for the self-induced collapse proposal than the traditional one in the semiclassical gravity picture. We show that the parametrization for the time of collapse, considered in previous works, is maintained. Also, we obtain an angular spectrum for the CMB temperature anisotropies consistent with the one that best fits the observational data. Therefore, we conclude that the collapse mechanism might be of a more fundamental character than previously suspected.
Detailed Modeling of Flat Plate Solar Collector with Vacuum Glazing
Viacheslav Shemelin; Tomas Matuska
2017-01-01
A theoretical analysis of flat plate solar collectors with a vacuum glazing is presented. Different configurations of the collector have been investigated by a detailed theoretical model based on a combined external and internal energy balance of the absorber. Performance characteristics for vacuum flat plate collector alternatives have been derived. Subsequently, annual energy gains have been evaluated for a selected variant and compared with state-of-the-art vacuum tube collectors. The resu...
Flash vacuum pyrolysis of lignin model compounds
Energy Technology Data Exchange (ETDEWEB)
Cooney, M.J.; Britt, P.F.; Buchanan, A.C. III
1997-03-01
Despite the extensive research into the pyrolysis of lignin, the underlying chemical reactions that lead to product formation are poorly understood. Detailed mechanistic studies on the pyrolysis of biomass and lignin under conditions relevant to current process conditions could provide insight into utilizing this renewable resource for the production of chemicals and fuel. Currently, flash or fast pyrolysis is the most promising process to maximize the yields of liquid products (up to 80 wt %) from biomass by rapidly heating the substrate to moderate temperatures, typically 500{degrees}C, for short residence times, typically less than two seconds. To provide mechanistic insight into the primary reaction pathways under process relevant conditions, we are investigating the flash vacuum pyrolysis (FVP) of lignin model compounds that contain a {beta}-ether. linkage and {alpha}- or {gamma}-alcohol, which are key structural elements in lignin. The dominant products from the FVP of PhCH{sub 2}CH{sub 2}OPh (PPE), PhC(OH)HCH{sub 2}OPh, and PhCH{sub 2}CH(CH{sub 2}OH)OPh at 500{degrees}C can be attributed to homolysis of the weakest bond in the molecule (C-O bond) or 1,2-elimination. Surprisingly, the hydroxy-substituent dramatically increases the decomposition of PPE. It is proposed that internal hydrogen bonding is accelerating the reaction.
Detailed Modeling of Flat Plate Solar Collector with Vacuum Glazing
Directory of Open Access Journals (Sweden)
Viacheslav Shemelin
2017-01-01
Full Text Available A theoretical analysis of flat plate solar collectors with a vacuum glazing is presented. Different configurations of the collector have been investigated by a detailed theoretical model based on a combined external and internal energy balance of the absorber. Performance characteristics for vacuum flat plate collector alternatives have been derived. Subsequently, annual energy gains have been evaluated for a selected variant and compared with state-of-the-art vacuum tube collectors. The results of modeling indicate that, in the case of using advanced vacuum glazing with optimized low-emissivity coating (emissivity 0.20, solar transmittance 0.85, it is possible to achieve efficiency parameters similar to or even better than vacuum tube collectors. The design presented in this paper can be considered promising for the extension of the applicability range of FPC and could be used in applications, which require low-to-medium temperature level.
Conceptual Modeling of Time-Varying Information
DEFF Research Database (Denmark)
Gregersen, Heidi; Jensen, Christian Søndergaard
2004-01-01
A wide range of database applications manage information that varies over time. Many of the underlying database schemas of these were designed using the Entity-Relationship (ER) model. In the research community as well as in industry, it is common knowledge that the temporal aspects of the mini-world...... are important, but difficult to capture using the ER model. Several enhancements to the ER model have been proposed in an attempt to support the modeling of temporal aspects of information. Common to the existing temporally extended ER models, few or no specific requirements to the models were given...
Efficient Estimation in Heteroscedastic Varying Coefficient Models
Directory of Open Access Journals (Sweden)
Chuanhua Wei
2015-07-01
Full Text Available This paper considers statistical inference for the heteroscedastic varying coefficient model. We propose an efficient estimator for coefficient functions that is more efficient than the conventional local-linear estimator. We establish asymptotic normality for the proposed estimator and conduct some simulation to illustrate the performance of the proposed method.
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Bianchi Type-I cosmological models containing perfect fluid with time varying and have been presented. The solutions obtained represent an expansion scalar bearing a constant ratio to the anisotropy in the direction of space-like unit vector . Of the two models obtained, one has negative vacuum energy density, ...
KINETIC MODELS STUDY OF HYDRODESULPHURIZATION VACUUM DISTILLATE REACTION
Directory of Open Access Journals (Sweden)
AbdulMunem A. Karim
2013-05-01
Full Text Available This study deals with kinetics of hydrodesulphurization (HDS reaction of vacuum gas oil (611-833 K which was distillated from Kirkuk crude oil and which was obtained by blending the fractions, light vacuum gas oil (611 - 650 K, medium vacuum gas oil (650-690 K, heavy vacuum gas oil (690-727 K and very heavy vacuum gas oil (727-833 K. The vacuum gas oil was hydrotreated on a commercial cobalt-molybdenum alumina catalyst presulfied at specified conditions in a laboratory trickle bed reactor. The reaction temperature range (583-643 K,liquid hourly space velocity range (1.5-3.75 h-1 and hydrogen pressure was kept constant at 3.5 MPa with hydrogen to oil ratio about 250 lt/lt. The conversion results for desulphurization reaction appeared to obey the second order reaction. According to this model, the rate constants for desulphurization reaction were determined. Finally, the apparent activation energy (Ea, enthalpy of activation ( H* and entropy ( S* were calculated based on the values of rate constant (k2 and were equal 80.3792 KJ/mole, 75.2974 KJ/mole and 197.493 J/mole, respectively.
Cosmological model with decaying vacuum energy from quantum mechanics
Szydłowski, Marek
2015-06-01
We construct the cosmological model to explain the cosmological constant problem. We built the extension of the standard cosmological model Λ CDM by consideration of decaying vacuum energy represented by the running cosmological term. From the principles of quantum mechanics one can find that in the long-term behavior survival probability of unstable states is a decreasing function of the cosmological time and has the inverse powerlike form. This implies that cosmological constant ρvac=Λ (t )=Λbare+α/t2 where Λbare and α are constants. We investigate the dynamics of this model using dynamical system methods due to a link to the Λ (H ) cosmologies. We have found the exact solution for the scale factor as well as the indicators of its variability like the deceleration parameter and the jerk. From the calculation of the jerk we obtain a simple test of the decaying vacuum in the Friedman-Robertson-Walker universe. Using astronomical data [SNIa, H (z ), CMB, BAO] we have estimated the model parameters and compared this model with the Λ CDM model. Our statistical results indicate that the decaying vacuum model is a little worse than the Λ CDM model. But the decaying vacuum cosmological model explains the small value of the cosmological constant today.
Thermal conductivity model for powdered materials under vacuum based on experimental studies
Directory of Open Access Journals (Sweden)
N. Sakatani
2017-01-01
Full Text Available The thermal conductivity of powdered media is characteristically very low in vacuum, and is effectively dependent on many parameters of their constituent particles and packing structure. Understanding of the heat transfer mechanism within powder layers in vacuum and theoretical modeling of their thermal conductivity are of great importance for several scientific and engineering problems. In this paper, we report the results of systematic thermal conductivity measurements of powdered media of varied particle size, porosity, and temperature under vacuum using glass beads as a model material. Based on the obtained experimental data, we investigated the heat transfer mechanism in powdered media in detail, and constructed a new theoretical thermal conductivity model for the vacuum condition. This model enables an absolute thermal conductivity to be calculated for a powder with the input of a set of powder parameters including particle size, porosity, temperature, and compressional stress or gravity, and vice versa. Our model is expected to be a competent tool for several scientific and engineering fields of study related to powders, such as the thermal infrared observation of air-less planetary bodies, thermal evolution of planetesimals, and performance of thermal insulators and heat storage powders.
Modelling of nectarine drying under near infrared - Vacuum conditions.
Alaei, Behnam; Chayjan, Reza Amiri
2015-01-01
Drying of nectarine slices was performed to determine the thermal and physical properties in order to reduce product deterioration due to chemical reactions, facilitate storage and lower transportation costs. Because nectarine slices are sensitive to heat with long drying period, the selection of a suitable drying approach is a challenging task. Infrared-vacuum drying can be used as an appropriate method for susceptible materials with high moisture content such as nectarine slices. Modelling of nectarine slices drying was carried out in a thin layer near infraredvacuum conditions. Drying of the samples was implemented at the absolute pressures of 20, 40 and 60 kPa and drying temperatures of 50, 60 and 70°C. Drying behaviour of nectarine slices, as well as the effect of drying conditions on moisture loss trend, drying rate, effective diffusion coefficient, activation energy, shrinkage, colour and energy consumption of nectarine slices, dried in near infrared-vacuum dryer are discussed in this study. Six mathematical models were used to predict the moisture ratio of the samples in thin layer drying. The Midilli model had supremacy in prediction of nectarine slices drying behaviour. The maximum drying rates of the samples were between 0.014-0.047 gwater/gdry material·min. Effective moisture diffusivity of the samples was estimated in the ranges of 2.46·10-10 to 6.48·10-10 m2/s. Activation energy were computed between 31.28 and 35.23 kJ/mol. Minimum shrinkage (48.4%) and total colour difference (15.1) were achieved at temperature of 50°C and absolute pressure of 20 kPa. Energy consumption of the tests was estimated in the ranges of 0.129 to 0.247 kWh. Effective moisture diffusivity was increased with decrease of vacuum pressure and increase of drying temperature but effect of drying temperature on effective moisture diffusivity of nectarine slices was more than vacuum pressure. Activation energy was decreased with decrease in absolute pressure. Total colour
Standard Model Vacuum Stability and Weyl Consistency Conditions
DEFF Research Database (Denmark)
Antipin, Oleg; Gillioz, Marc; Krog, Jens
2013-01-01
At high energy the standard model possesses conformal symmetry at the classical level. This is reflected at the quantum level by relations between the different beta functions of the model. These relations are known as the Weyl consistency conditions. We show that it is possible to satisfy them...... order by order in perturbation theory, provided that a suitable coupling constant counting scheme is used. As a direct phenomenological application, we study the stability of the standard model vacuum at high energies and compare with previous computations violating the Weyl consistency conditions....
Time Varying Parameterization of Hydrological Models
Bardossy, A.; Singh, S. K.
2007-12-01
Hydrological models are frequently used for forecasting, water management or design to provide information for decision making. Due to the simplification of the complex natural processes and the limited availability of observations the parameters of these models cannot be identified perfectly. Usually the parameters of the models are assumed to be time independent. However some properties of the catchments might change in from one event to another in an unpredictable manner. The purpose of this paper is to develop a methodology to estimate selected model parameters as random variables changing in time. The distribution of the model parameter is assessed in calibration phase using different assumptions. During the application of the model these distributions are used to estimate the expected hydrological behavior and the uncertainty too. The methodology will be demonstrated on mezo-scale catchments in the Neckar basin in South-West Germany. The systematic differences between model behavior and observations are demonstrated using a set of selected events. Calibration and uncertainty estimation are demonstrated by an example application to a distributed HBV model. The model residual distributions are presented and compared to a standard calibration method. Further, it is shown that the new methodology leads to more realistic confidence intervals for model simulations.
EOQ Models with Varying Holding Cost
Directory of Open Access Journals (Sweden)
Naser Ghasemi
2013-01-01
Full Text Available Models of inventory management contain different parameters. An issue is observable in the classical models which can be related to the determination of the quantity of the economic order and the quantity of the economic production. In these models, the parameters like setup and holding costs and also the rate of demands are fixed. This matter causes the quantity of the economic ordering in classic model to have some differences in comparison with the real-world conditions. It should be stated that holding cost of spoiled and useless products is not always fixed and so the costs increase by passing the time. This paper is an attempt to develop classical EOQ models by considering holding cost as an increasing function of the ordering cycle length. So the classical EOQ models are developed, and the related optimum quantity to the ordering cycle length, economic ordering quantity, and the optimum total cost are determined.
ELECTRON AVALANCHE MODEL OF DIELECTRIC-VACUUM SURFACE BREAKDOWN
Energy Technology Data Exchange (ETDEWEB)
Lauer, E J
2007-02-21
The model assumes that an 'initiating event' results in positive ions on the surface near the anode and reverses the direction of the normal component of electric field so that electrons in vacuum are attracted to the dielectric locally. A sequence of surface electron avalanches progresses in steps from the anode to the cathode. For 200 kV across 1 cm, the spacing of avalanches is predicted to be about 13 microns. The time for avalanches to step from the anode to the cathode is predicted to be about a ns.
EOQ Models with Varying Holding Cost
National Research Council Canada - National Science Library
Ghasemi, Naser; Afshar Nadjafi, Behrouz
2013-01-01
.... This paper is an attempt to develop classical EOQ models by considering holding cost as an increasing function of the ordering cycle length. So the classical EOQ models are developed, and the related optimum quantity to the ordering cycle length, economic ordering quantity, and the optimum total cost are determined.
Estimating varying coefficients for partial differential equation models.
Zhang, Xinyu; Cao, Jiguo; Carroll, Raymond J
2017-09-01
Partial differential equations (PDEs) are used to model complex dynamical systems in multiple dimensions, and their parameters often have important scientific interpretations. In some applications, PDE parameters are not constant but can change depending on the values of covariates, a feature that we call varying coefficients. We propose a parameter cascading method to estimate varying coefficients in PDE models from noisy data. Our estimates of the varying coefficients are shown to be consistent and asymptotically normally distributed. The performance of our method is evaluated by a simulation study and by an empirical study estimating three varying coefficients in a PDE model arising from LIDAR data. © 2017, The International Biometric Society.
Modeling non-Gaussian time-varying vector autoregressive process
National Aeronautics and Space Administration — We present a novel and general methodology for modeling time-varying vector autoregressive processes which are widely used in many areas such as modeling of chemical...
Modeling Vacuum Arcs On Spacecraft Solar Panel Arrays Project
National Aeronautics and Space Administration — Spacecraft charging and subsequent vacuum arcing poses a significant threat to satellites in LEO and GEO plasma conditions. Localized arc discharges can cause a...
Mathematical Models of IABG Thermal-Vacuum Facilities
Doring, Daniel; Ulfers, Hendrik
2014-06-01
IABG in Ottobrunn, Germany, operates thermal-vacuum facilities of different sizes and complexities as a service for space-testing of satellites and components. One aspect of these tests is the qualification of the thermal control system that keeps all onboard components within their save operating temperature band. As not all possible operation / mission states can be simulated within a sensible test time, usually a subset of important and extreme states is tested at TV facilities to validate the thermal model of the satellite, which is then used to model all other possible mission states. With advances in the precision of customer thermal models, simple assumptions of the test environment (e.g. everything black & cold, one solar constant of light from this side) are no longer sufficient, as real space simulation chambers do deviate from this ideal. For example the mechanical adapters which support the spacecraft are usually not actively cooled. To enable IABG to provide a model that is sufficiently detailed and realistic for current system tests, Munich engineering company CASE developed ESATAN models for the two larger chambers. CASE has many years of experience in thermal analysis for space-flight systems and ESATAN. The two models represent the rather simple (and therefore very homogeneous) 3m-TVA and the extremely complex space simulation test facility and its solar simulator. The cooperation of IABG and CASE built up extensive knowledge of the facilities thermal behaviour. This is the key to optimally support customers with their test campaigns in the future. The ESARAD part of the models contains all relevant information with regard to geometry (CAD data), surface properties (optical measurements) and solar irradiation for the sun simulator. The temperature of the actively cooled thermal shrouds is measured and mapped to the thermal mesh to create the temperature field in the ESATAN part as boundary conditions. Both models comprise switches to easily
Vacuum assisted resin transfer molding (VARTM): Model development and verification
Song, Xiaolan
2003-06-01
In this investigation, a comprehensive Vacuum Assisted Resin Transfer Molding (VARTM) process simulation model was developed and verified. The model incorporates resin flow through the preform, compaction and relaxation of the preform, and viscosity and cure kinetics of the resin. The computer model can be used to analyze the resin flow details, track the thickness change of the preform, predict the total infiltration time and final fiber volume fraction of the parts, and determine whether the resin could completely infiltrate and uniformly wet out the preform. Flow of resin through the preform is modeled as flow through porous media. Darcy's law combined with the continuity equation for an incompressible Newtonian fluid forms the basis of the flow model. During the infiltration process, it is well accepted that the total pressure is shared by the resin pressure and the pressure supported by the fiber network. With the progression of the resin, the net pressure applied to the preform decreases as a result of increasing local resin pressure. This leads to the springback of the preform, and is called the springback mechanism. On the other side, the lubrication effect of the resin causes the rearrangement of the fiber network and an increase in the preform compaction. This is called the wetting compaction mechanism. The thickness change of the preform is determined by the relative magnitude of the springback and wetting deformation mechanisms. In the compaction model, the transverse equilibrium equation is used to calculate the net compaction pressure applied to the preform, and the compaction test results are fitted to give the compressive constitutive law of the preform. The Finite Element/Control Volume (FE/CV) method is adopted to find the flow front location and the fluid pressure. The code features the ability of simultaneous integration of 1-D, 2-D and 3-D element types in a single simulation, and thus enables efficient modeling of the flow in complex mold
Modelling Acoustic Wave Propagation in Axisymmetric Varying-Radius Waveguides
DEFF Research Database (Denmark)
Bæk, David; Willatzen, Morten
2008-01-01
A computationally fast and accurate model (a set of coupled ordinary differential equations) for fluid sound-wave propagation in infinite axisymmetric waveguides of varying radius is proposed. The model accounts for fluid heat conduction and fluid irrotational viscosity. The model problem is solved...
Flash vacuum pyrolysis of methoxy-substituted lignin model compounds
Energy Technology Data Exchange (ETDEWEB)
Britt, P.F.; Buchanan, A.C.; Cooney, M.J.; Martineau, D.R. [Oak Ridge National Laboratory, Oak Ridge, IN (USA). Chemical and Analytical Science Division
2000-07-01
The flash vacuum pyrolysis (FVP) of methoxy-substituted beta-0-4-lignin model compounds was studied at 500{degree}C to provide mechanistic insight into the primary reaction pathways that occur under conditions of fast pyrolysis. FVP of PhCH{sub 2}CH{sub 2}OPh (PPE) a model of the dominance beta-0-4 linkage in lignin, proceeds by C-O and C-C cleavage, in a 37:1 ratio, to produce styrene plus phenol as the dominant products and, minor amounts of toluene, bibenzyl, and benzaldehyde. From the deuterium isotope effect in the FVP of PhCD{sub 2}CH{sub 2}OPh, it was shown that C-O cleavage occurs by homolysis and by 1,2-elimination in a ratio of 1.4:1, respectively. Methoxy substituents enhance the homolysis of the beta-0-4 linkage, relative to PPE, in o-CH{sub 3}O-C{sub 6}H{sub 4}OCH{sub 2}CH{sub 2}Ph (o-CN{sub 3}O-PPE) and (o-CH{sub 3}O){sub 2}-C{sub 6}H{sub 3}OCH{sub 2}CH{sub 2}Ph((o-CH{sub 3}O){sub 2}-PPE). The methoxy-substituted phenoxy radicals undergo a complex series of reactions, which are dominated by 1.5- 1.6-, and 1.4-intramolecular hydrogen abstraction, rearrangement, and beta-scission reactions.
Nonlinear MPC Design for Identified Nonlinear Parameter Varying (NPV Model
Directory of Open Access Journals (Sweden)
Jiangang Lu
2012-09-01
Full Text Available In this paper, a novel nonlinear model predictive controller (MPC is proposed based on an identified nonlinear parameter varying (NPV model. Firstly, an NPV model scheme is present for process identification, which is featured by its nonlinear hybrid Hammerstein model structure and varying model parameters. The hybrid Hammerstein model combines a normalized static artificial neural network with a linear transfer function to identify general nonlinear systems at each fixed working point. Meanwhile, a model interpolating philosophy is utilized to obtain the global model across the whole operation domain. The NPV model considers both the nonlinearity of transition dynamics due to the variation of the working-point and the nonlinear mapping from the input to the output at fixed working points. Moreover, under the new NPV framework, the control action is computed via a multistep linearization method aimed for nonlinear optimization problems. In the proposed scheme, only low cost tests are needed for system identification and the controller can achieve better output performance than MPC methods based on linear parameter varying (LPV models. Numerical examples validate the effectiveness of the proposed approach. Keywords: Nonlinear parameter varying (NPV, Hammerstein model, nonlinear MPC.
A Semiparametric Recurrent Events Model with Time-varying Coefficients
Yu, Zhangsheng; Liu, Lei; Bravata, Dawn M.; Williams, Linda S.; Tepper, Robert S.
2013-01-01
SUMMARY We consider a recurrent events model with time-varying coefficients motivated by two clinical applications. A random effects (Gaussian frailty) model is used to describe the intensity of recurrent events. The model can accommodate both time-varying and time-constant coefficients. The penalized spline method is used to estimate the time-varying coefficients. Laplace approximation is used to evaluate the penalized likelihood without a closed form. The smoothing parameters are estimated in a similar way to variance components. We conduct simulations to evaluate the performance of the estimates for both time-varying and time-independent coefficients. We apply this method to analyze two data sets: a stroke study and a child wheeze study. PMID:22903343
Partially linear varying coefficient models stratified by a functional covariate
Maity, Arnab
2012-10-01
We consider the problem of estimation in semiparametric varying coefficient models where the covariate modifying the varying coefficients is functional and is modeled nonparametrically. We develop a kernel-based estimator of the nonparametric component and a profiling estimator of the parametric component of the model and derive their asymptotic properties. Specifically, we show the consistency of the nonparametric functional estimates and derive the asymptotic expansion of the estimates of the parametric component. We illustrate the performance of our methodology using a simulation study and a real data application.
Modelling Flow over Stepped Spillway with Varying Chute Geometry ...
African Journals Online (AJOL)
This study has modeled some characteristics of the flows over stepped spillway with varying chute geometry through a laboratory investigation. Using six physically built stepped spillway models, with each having six horizontal plain steps at 4cm constant height, 30 cm width and respective chute slope angles at 310, 320, ...
Flashover of a vacuum-insulator interface: A statistical model
Directory of Open Access Journals (Sweden)
W. A. Stygar
2004-07-01
Full Text Available We have developed a statistical model for the flashover of a 45° vacuum-insulator interface (such as would be found in an accelerator subject to a pulsed electric field. The model assumes that the initiation of a flashover plasma is a stochastic process, that the characteristic statistical component of the flashover delay time is much greater than the plasma formative time, and that the average rate at which flashovers occur is a power-law function of the instantaneous value of the electric field. Under these conditions, we find that the flashover probability is given by 1-exp(-E_{p}^{β}t_{eff}C/k^{β}, where E_{p} is the peak value in time of the spatially averaged electric field E(t, t_{eff}≡∫[E(t/E_{p}]^{β}dt is the effective pulse width, C is the insulator circumference, k∝exp(λ/d, and β and λ are constants. We define E(t as V(t/d, where V(t is the voltage across the insulator and d is the insulator thickness. Since the model assumes that flashovers occur at random azimuthal locations along the insulator, it does not apply to systems that have a significant defect, i.e., a location contaminated with debris or compromised by an imperfection at which flashovers repeatedly take place, and which prevents a random spatial distribution. The model is consistent with flashover measurements to within 7% for pulse widths between 0.5 ns and 10 μs, and to within a factor of 2 between 0.5 ns and 90 s (a span of over 11 orders of magnitude. For these measurements, E_{p} ranges from 64 to 651 kV/cm, d from 0.50 to 4.32 cm, and C from 4.96 to 95.74 cm. The model is significantly more accurate, and is valid over a wider range of parameters, than the J. C. Martin flashover relation that has been in use since 1971 [J. C. Martin on Pulsed Power, edited by T. H. Martin, A. H. Guenther, and M. Kristiansen (Plenum, New York, 1996]. We have generalized the statistical model to estimate the total-flashover probability of an
Norton, Brian; Eames, Philip; Fang, Yueping; Hyde, Trevor; Hewitt, Neil
2008-01-01
The thermal performance of vacuum glazing was predicted using two dimensional (2-D) finite element and three dimensional (3-D) finite volume models. In the 2-D model, the vacuum space, including the pillar arrays, was represented by a material whose effective thermal conductivity was determined from the specified vacuum space width, the heat conduction through the pillar array and the calculated radiation heat transfer between the two interior glass surfaces within the vacuum gap. In the 3-D ...
A five-dimensional model of varying fine structure constant
Indian Academy of Sciences (India)
A five-dimensional model of varying fine structure constant. J P MBELEK. Service d'Astrophysique, C.E. Saclay, F-91191 Gif-sur-Yvette Cedex, France. Abstract. The cosmological variation of the fine structure constant « is explored from an effective theory, under the form of an improved version of the 5D Kaluza-Klein theory.
A five-dimensional model of varying fine structure constant
Indian Academy of Sciences (India)
dimensional model of varying fine structure constant. J P Mbelek. Cosmology Volume 62 Issue 3 March 2004 pp 741-743. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/pram/062/03/0741-0743 ...
Wong, Cat S. M.; Snider, L. A.; Lo, Edward W. C.; Chung, T. S.
Switching of induction motors with vacuum circuit breakers continues to be a concern. In this paper the influence on statistical overvoltages of the stochastic characteristics of vacuum circuit breakers, high frequency models of motors and transformers, and network characteristics, including cable lengths and network topology are evaluated and a general view of the overvoltages phenomena is presented. Finally, a real case study on the statistical voltage levels and risk-of-failure resulting from switching of a vacuum circuit breaker in an industrial installation in Hong Kong is presented.
Modeling maximum daily temperature using a varying coefficient regression model
Han Li; Xinwei Deng; Dong-Yum Kim; Eric P. Smith
2014-01-01
Relationships between stream water and air temperatures are often modeled using linear or nonlinear regression methods. Despite a strong relationship between water and air temperatures and a variety of models that are effective for data summarized on a weekly basis, such models did not yield consistently good predictions for summaries such as daily maximum temperature...
Modelling of pressure increase protection system for the vacuum vessel of W7-X device
Energy Technology Data Exchange (ETDEWEB)
Kaliatka, Tadas, E-mail: tadas.kaliatka@lei.lt; Uspuras, Eugenijus; Kaliatka, Algirdas
2016-11-01
Highlights: • Two in-vessel LOCAs (partial and guillotine break of 40 mm diameter pipe of cooling system) for Wendelstein 7-X fusion device were analyzed. • The analysis of the processes in the cooling system, vacuum vessel and pressure increase protection system were performed using thermal-hydraulic RELAP5 Mod3.3 code. • The suitability of pressure increase protection system was assessed. - Abstract: In fusion devices, plasma is contained in a vacuum vessel. The vacuum vessel cannot withstand a pressure above atmospheric. Any damage of in-vessel components could lead to water ingress and may lead to pressure increase and possible damage of vacuum vessel. In order to avoid such undesirable consequences, the pressure increase protection system is designed. In this article, the processes occurring in the vacuum vessel and pressure increase protection system of W7-X device during LOCA (small and guillotine pipe break) event are analyzed. The model of W7-X cooling system, vacuum vessel and pressure increase protection system was developed using RELAP5 code. Numerical analysis of partial and guillotine break of 40 mm diameter pipe of cooling system was performed. Calculation results showed that burst disc of the pressure increase protection system does not open when the cross section area of partial break in the cooling system is smaller than 1 mm{sup 2}. During the guillotine break of cooling system, the burst disc opens, but pressure increase protection system is capable to prevent overpressure of the vacuum vessel.
Robust linear parameter varying induction motor control with polytopic models
Directory of Open Access Journals (Sweden)
Dalila Khamari
2013-01-01
Full Text Available This paper deals with a robust controller for an induction motor which is represented as a linear parameter varying systems. To do so linear matrix inequality (LMI based approach and robust Lyapunov feedback controller are associated. This new approach is related to the fact that the synthesis of a linear parameter varying (LPV feedback controller for the inner loop take into account rotor resistance and mechanical speed as varying parameter. An LPV flux observer is also synthesized to estimate rotor flux providing reference to cited above regulator. The induction motor is described as a polytopic model because of speed and rotor resistance affine dependence their values can be estimated on line during systems operations. The simulation results are presented to confirm the effectiveness of the proposed approach where robustness stability and high performances have been achieved over the entire operating range of the induction motor.
Naturalness, vacuum stability, and leptogenesis in the minimal seesaw model
Bambhaniya, Gulab; Bhupal Dev, P. S.; Goswami, Srubabati; Khan, Subrata; Rodejohann, Werner
2017-05-01
The right-handed neutrinos within the type-I seesaw mechanism can induce large radiative corrections to the Higgs mass, and naturalness arguments can then be used to set limits on their mass scale and Yukawa couplings. Driven by minimality, we consider the presence of two degenerate right-handed neutrinos. We compare the limits from naturalness with the ones from the stability of the electroweak vacuum and from lepton flavor violation. Implications from neutrinoless double beta decay are also discussed and renormalization effects for the light neutrino parameters are presented. Adding small perturbations to the degenerate heavy neutrino spectrum allows for successful leptogenesis.
Dynamics of a Delay-Varying Computer Virus Propagation Model
Directory of Open Access Journals (Sweden)
Jianguo Ren
2012-01-01
Full Text Available By considering the varying latency period of computer virus, we propose a novel model for computer virus propagation in network. Under this model, we give the threshold value determining whether or not the virus finally dies out, and study the local stability of the virus-free and virus equilibrium. It is found that the model may undergo a Hopf bifurcation. Next, we use different methods to prove the global asymptotic stability of the equilibria: the virus-free equilibrium by using the direct Lyapunov method and virus equilibrium by using a geometric approach. Finally, some numerical examples are given to support our conclusions.
Modeling information diffusion in time-varying community networks
Cui, Xuelian; Zhao, Narisa
2017-12-01
Social networks are rarely static, and they typically have time-varying network topologies. A great number of studies have modeled temporal networks and explored social contagion processes within these models; however, few of these studies have considered community structure variations. In this paper, we present a study of how the time-varying property of a modular structure influences the information dissemination. First, we propose a continuous-time Markov model of information diffusion where two parameters, mobility rate and community attractiveness, are introduced to address the time-varying nature of the community structure. The basic reproduction number is derived, and the accuracy of this model is evaluated by comparing the simulation and theoretical results. Furthermore, numerical results illustrate that generally both the mobility rate and community attractiveness significantly promote the information diffusion process, especially in the initial outbreak stage. Moreover, the strength of this promotion effect is much stronger when the modularity is higher. Counterintuitively, it is found that when all communities have the same attractiveness, social mobility no longer accelerates the diffusion process. In addition, we show that the local spreading in the advantage group has been greatly enhanced due to the agglomeration effect caused by the social mobility and community attractiveness difference, which thus increases the global spreading.
A hierarchical nest survival model integrating incomplete temporally varying covariates
Converse, Sarah J.; Royle, J. Andrew; Adler, Peter H.; Urbanek, Richard P.; Barzan, Jeb A.
2013-01-01
Nest success is a critical determinant of the dynamics of avian populations, and nest survival modeling has played a key role in advancing avian ecology and management. Beginning with the development of daily nest survival models, and proceeding through subsequent extensions, the capacity for modeling the effects of hypothesized factors on nest survival has expanded greatly. We extend nest survival models further by introducing an approach to deal with incompletely observed, temporally varying covariates using a hierarchical model. Hierarchical modeling offers a way to separate process and observational components of demographic models to obtain estimates of the parameters of primary interest, and to evaluate structural effects of ecological and management interest. We built a hierarchical model for daily nest survival to analyze nest data from reintroduced whooping cranes (Grus americana) in the Eastern Migratory Population. This reintroduction effort has been beset by poor reproduction, apparently due primarily to nest abandonment by breeding birds. We used the model to assess support for the hypothesis that nest abandonment is caused by harassment from biting insects. We obtained indices of blood-feeding insect populations based on the spatially interpolated counts of insects captured in carbon dioxide traps. However, insect trapping was not conducted daily, and so we had incomplete information on a temporally variable covariate of interest. We therefore supplemented our nest survival model with a parallel model for estimating the values of the missing insect covariates. We used Bayesian model selection to identify the best predictors of daily nest survival. Our results suggest that the black fly Simulium annulus may be negatively affecting nest survival of reintroduced whooping cranes, with decreasing nest survival as abundance of S. annulus increases. The modeling framework we have developed will be applied in the future to a larger data set to evaluate the
Modelling Time-Varying Volatility in Financial Returns
DEFF Research Database (Denmark)
Amado, Cristina; Laakkonen, Helinä
2014-01-01
The “unusually uncertain” phase in the global financial markets has inspired many researchers to study the effects of ambiguity (or “Knightian uncertainty”) on the decisions made by investors and their implications for the capital markets. We contribute to this literature by using a modified...... being captured by a stable GARCH(1,1) process and the second driven by the level of uncertainty in the financial market....... version of the time-varying GARCH model of Amado and Teräsvirta (2013) to analyze whether the increasing uncertainty has caused excess volatility in the US and European government bond markets. In our model, volatility is multiplicatively decomposed into two time-varying conditional components: the first...
A von Bertalanffy growth model with a seasonally varying coefficient
Cloern, James E.; Nichols, Frederic H.
1978-01-01
The von Bertalanffy model of body growth is inappropriate for organisms whose growth is restricted to a seasonal period because it assumes that growth rate is invariant with time. Incorporation of a time-varying coefficient significantly improves the capability of the von Bertalanffy equation to describe changing body size of both the bivalve mollusc Macoma balthicain San Francisco Bay and the flathead sole, Hippoglossoides elassodon, in Washington state. This simple modification of the von Bertalanffy model should offer improved predictions of body growth for a variety of other aquatic animals.
Microstructural Model of Ignition for Time Varying Loading Conditions
Browning, Richard V.; Scammon, Richard J.
2002-07-01
A micro-mechanical based model of ignition was developed about five years ago based on a simple inter-granular friction model of mechanical dissipation coupled with a fit to extensive direct numerical simulations of the resulting thermally induced decomposition. The chemical model used was the McGuire-Tarver ODTX based model for HMX decomposition. The resulting power law type model has been reasonably successful in predicting threshold conditions for Steven type experiments. The final power law form was obtained by assuming a constant time history for both the pressure and shear strain rate, resulting in time independent loading conditions for the chemical model. Here we propose to extend the model to handle time varying loading conditions. This is done using a linear operator that models reactive heat transfer simulations done for a wide variety of loading conditions. The linear operator is represented by a convolution integral with Prony series kernel form for efficient numerical implementation. To complete the model the same inter-granular friction model used previously is employed. Comparisons are made with results of numerical simulations and experiments. The technique used here is based on the notion of linearizing the reactive heat transfer problem. Although the chemical model involves four reactions and is highly nonlinear, we effectively linearize the problem around ignition conditions with a linear operator fit. We use a simple power law approximation that gives useful accuracy over at least 4 orders of magnitude in time and fluence. A non-dimensional scaling method is used to determine the final form. We believe the techniques used here could also be used with more detailed chemical models and with other types of mechanical dissipation models.
Pilot Wave Model for Impulsive Thrust from RF Test Device Measured in Vacuum
White, Harold; Lawrence, James; Sylvester, Andre; Vera, Jerry; Chap, Andrew; George, Jeff
2017-01-01
A physics model is developed in detail and its place in the taxonomy of ideas about the nature of the quantum vacuum is discussed. The experimental results from the recently completed vacuum test campaign evaluating the impulsive thrust performance of a tapered RF test article excited in the TM212 mode at 1,937 megahertz (MHz) are summarized. The empirical data from this campaign is compared to the predictions from the physics model tools. A discussion is provided to further elaborate on the possible implications of the proposed model if it is physically valid. Based on the correlation of analysis prediction with experimental data collected, it is proposed that the observed anomalous thrust forces are real, not due to experimental error, and are due to a new type of interaction with quantum vacuum fluctuations.
Temperature-induced stresses in vacuum glazing: modelling and experimental validation
Energy Technology Data Exchange (ETDEWEB)
Simko, T.M.; Collins, R.E. [University of Sydney (Australia). School of Physics; Fischer-Cripps, A.C. [University of Technology, Sydney (Australia). Dept. of Applied Physics
1998-07-01
A temperature difference across a sample of vacuum glazing causes differential expansion of one glass sheet relative to the other. In vacuum glazing with a fused edge seal, this results in tensile and compressive stresses in the glass sheets, and bending of the structure. The physical origins of these stresses and deflections are discussed, and a finite element model is used to determine their magnitude. The model has been validated by comparison with experimental data for a well-characterised sample of vacuum glazing under accurately defined external conditions. Modelling data are presented for two glazing designs which have properties that are characteristic of the extremes of performance of this type of glazing. It is shown that mechanical edge constraints can profoundly alter the spatial distribution of stresses in the glazing. (author)
Integrodifference models for persistence in temporally varying river environments.
Jacobsen, Jon; Jin, Yu; Lewis, Mark A
2015-02-01
To fully understand population persistence in river ecosystems, it is necessary to consider the effect of the water flow, which varies tremendously with seasonal fluctuations of water runoff and snow melt. In this paper, we study integrodifference models for growth and dispersal in the presence of advective flow with both periodic (alternating) and random kernel parameters. For the alternating kernel model, we obtain the principal eigenvalue of the linearization operator to determine population persistence and derive a boundary value problem to calculate it. For the random model, we establish two persistence metrics: a generalized spectral radius and the asymptotic growth rate, which are mathematically equivalent but can be understood differently, to determine population persistence or extinction. The theoretical framework and methods for calculations are provided, and the framework is applied to calculating persistence in highly variable river environments.
The hadronic vacuum polarization contribution to the muon g - 2 in the quark-resonance model
Pallante, E.
1994-01-01
The hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is parametrized by using the quark-resonance model formulated elsewhere. In this context a recent prediction obtained within the ENJL model can be affected by two additional contributions: the next to leading
Model microswimmers in channels with varying cross section
Malgaretti, Paolo; Stark, Holger
2017-05-01
We study different types of microswimmers moving in channels with varying cross section and thereby interacting hydrodynamically with the channel walls. Starting from the Smoluchowski equation for a dilute suspension, for which interactions among swimmers can be neglected, we derive analytic expressions for the lateral probability distribution between plane channel walls. For weakly corrugated channels, we extend the Fick-Jacobs approach to microswimmers and thereby derive an effective equation for the probability distribution along the channel axis. Two regimes arise dominated either by entropic forces due to the geometrical confinement or by the active motion. In particular, our results show that the accumulation of microswimmers at channel walls is sensitive to both the underlying swimming mechanism and the geometry of the channels. Finally, for asymmetric channel corrugation, our model predicts a rectification of microswimmers along the channel, the strength and direction of which strongly depends on the swimmer type.
Pressure Model for the Vacuum System for the Electron Gun and Injector for LCLS Final Design Report
Energy Technology Data Exchange (ETDEWEB)
Tung, L S; Eriksson, L
2006-04-28
The vacuum system of the injector for the Linac Coherent Light Source (LCLS) has been analyzed and configured by the Lawrence Livermore National Laboratory's New Technologies Engineering Division (NTED) as requested by the SLAC/LCLS program. The vacuum system layout and detailed analyses for the injector are presented in this final design report. The vacuum system was analyzed and optimized using a coupled gas load balance model of sub-volumes of the components to be evacuated.
Tree level vacuum stability in two-Higgs-doublet models
Velhinho, J.; Santos, R.; Barroso, A.
1994-02-01
We study the two-Higgs-doublet models with CP conservation. In particular, we consider the special form of the potential which has a single CP invariant stable minimum. We also comment on the bounds for the Higgs masses and couplings derived in these models.
Directory of Open Access Journals (Sweden)
Jingjin Liu
2017-10-01
Full Text Available Problems continue to be encountered concerning the traditional vacuum preloading method in field during the treatment of newly deposited dredger fills. In this paper, an improved multiple-vacuum preloading method was developed to consolidate newly dredger fills that are hydraulically placed in seawater for land reclamation in Lingang Industrial Zone of Tianjin City, China. With this multiple-vacuum preloading method, the newly deposited dredger fills could be treated effectively by adopting a novel moisture separator and a rapid improvement technique without sand cushion. A series of model tests was conducted in the laboratory for comparing the results from the multiple-vacuum preloading method and the traditional one. Ten piezometers and settlement plates were installed to measure the variations in excess pore water pressures and moisture content, and vane shear strength was measured at different positions. The testing results indicate that water discharge–time curves obtained by the traditional vacuum preloading method can be divided into three phases: rapid growth phase, slow growth phase, and steady phase. According to the process of fluid flow concentrated along tiny ripples and building of larger channels inside soils during the whole vacuum loading process, the fluctuations of pore water pressure during each loading step are divided into three phases: steady phase, rapid dissipation phase, and slow dissipation phase. An optimal loading pattern which could have a best treatment effect was proposed for calculating the water discharge and pore water pressure of soil using the improved multiple-vacuum preloading method. For the newly deposited dredger fills at Lingang Industrial Zone of Tianjin City, the best loading step was 20 kPa and the loading of 40–50 kPa produced the highest drainage consolidation. The measured moisture content and vane shear strength were discussed in terms of the effect of reinforcement, both of which indicate
A mathematical model for distribution of calcium in silicon by vacuum directional solidification
Directory of Open Access Journals (Sweden)
Zheng D.
2016-01-01
Full Text Available Calcium is one of the main impurity elements in silicon. The removal of calcium strongly affects the quality of the polycrystalline silicon ingot produced by a vacuum directional solidification method. Based on the considerations of the theory of segregation, mass transfer and evaporation during vacuum directional solidification process, a mathematical model for calcium distribution in silicon was proposed and it can be used to explain the removal mechanism. In order to confirm the mathematical model, an industrial scale experiment on UMG-Si with an initial purity of 99.98 wt. % was performed. Since the reaction temperature strongly influences both the evaporation and segregation of calcium, the dependences of effective segregation coefficient (keff and the evaporation coefficient (kE on temperature were carefully investigated. The results showed that the proposed mathematical model was highly consistent with the experimental data and the calcium removal efficiency mainly relied on the evaporation step.
Structure and chemistry of model catalysts in ultrahigh vacuum
Walker, Joshua D.
The study of catalysis is a key area of focus not only in the industrial sector but also in the nature and biological systems. The market for catalysis is a multi-billion dollar industry. Many of the materials and products we use on a daily basis are formed through a catalytic process. The quest to understanding and improving catalytic mechanisms is ongoing. Many model catalysts use transition metals as a support for chemical reactions to take place due to their selectivity and activity. Palladium, gold, and copper metals are studied in this work and show the ability to be catalytically reactive. It is important to understand the characteristics and properties of these surfaces. A well-known example of catalysis is the conversion of carbon monoxide (CO), a very harmful gas to carbon dioxide (CO2) which is less harmful. This reaction is mainly seen in the automotive industry. This reaction is investigated in this work on a Au(111) single crystal, which is normally inert but becomes reactivity with the adsorption of oxygen on the surface. Temperature Programmed Desorption (TPD) is used to understand some of the chemistry and effects with and without the addition of H2O. The oxidation of CO is shown to be enhanced by the addition of water, but warrants further analysis too fully understand the different mechanisms and reaction pathways existing. The field of nano-electronics is rapidly growing as technology continues to challenge scientists to create innovative ideas. The trend to produce smaller electronic products is increasing as consumer demands persist. It has been shown previously that 1,4-phenlyene diisocyanobenzene (1,4-PDI) on Au(111) react to form one-dimensional oligomer chains comprising alternating gold and 1,4-PDI units on the Au(111) surface. A similar compound 1,3-phenlyene diisocyanobenzene (1,3-PDI) was studied in order to investigate whether the oligomerization found for 1,4-PDI is a general phenomenon and to ultimately explore the effect of
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Hyde, Trevor; Hewitt, Neil [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB Northern Ireland (United Kingdom); Eames, Philip C. [Centre for Research in Renewable Energy Science and Technology, University of Loughborough (United Kingdom); Norton, Brian [Dublin Energy Lab, Dublin Institute of Technology, Aungier Street, Dublin 2 (Ireland)
2009-09-15
Thermal performance of vacuum glazing predicted by using two-dimensional (2-D) finite element and three-dimensional (3-D) finite volume models are presented. In the 2-D model, the vacuum space, including the pillar arrays, was represented by a material whose effective thermal conductivity was determined from the specified vacuum space width, the heat conduction through the pillar array and the calculated radiation heat transfer between the two interior glass surfaces within the vacuum gap. In the 3-D model, the support pillar array was incorporated and modelled within the glazing unit directly. The predicted difference in overall heat transfer coefficients between the two models for the vacuum window simulated was less than 3%. A guarded hot box calorimeter was used to determine the experimental thermal performance of vacuum glazing. The experimentally determined overall heat transfer coefficient and temperature profiles along the central line of the vacuum glazing are in very good agreement with the predictions made using the 2-D and 3-D models. (author)
Li, Dongling; Wen, Zhiyu; Wen, Zhongquan; He, Xuefeng; Yang, Yinchuan; Shang, Zhengguo
2009-01-01
A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %.
Directory of Open Access Journals (Sweden)
Zhengguo Shang
2009-05-01
Full Text Available A novel high-precision vacuum microelectronic accelerometer has been successfully fabricated and tested in our laboratory. This accelerometer has unique advantages of high sensitivity, fast response, and anti-radiation stability. It is a prototype intended for navigation applications and is required to feature micro-g resolution. This paper briefly describes the structure and working principle of our vacuum microelectronic accelerometer, and the mathematical model is also established. The performances of the accelerometer system are discussed after Matlab modeling. The results show that, the dynamic response of the accelerometer system is significantly improved by choosing appropriate parameters of signal detecting circuit, and the signal detecting circuit is designed. In order to attain good linearity and performance, the closed-loop control mode is adopted. Weak current detection technology is studied, and integral T-style feedback network is used in I/V conversion, which will eliminate high-frequency noise at the front of the circuit. According to the modeling parameters, the low-pass filter is designed. This circuit is simple, reliable, and has high precision. Experiments are done and the results show that the vacuum microelectronic accelerometer exhibits good linearity over -1 g to +1 g, an output sensitivity of 543 mV/g, and a nonlinearity of 0.94 %.
Internal vacuum-assisted closure device in the swine model of severe liver injury
Directory of Open Access Journals (Sweden)
Everett Christopher B
2012-12-01
Full Text Available Abstract Objectives The authors present a novel approach to nonresectional therapy in major hepatic trauma utilizing intraabdominal perihepatic vacuum assisted closure (VAC therapy in the porcine model of Grade V liver injury. Methods A Grade V injury was created in the right lobe of the liver in a healthy pig. A Pringle maneuver was applied (4.5 minutes total clamp time and a vacuum assisted closure device was placed over the injured lobe and connected to suction. The device consisted of a perforated plastic bag placed over the liver, followed by a 15 cm by 15cm VAC sponge covered with a nonperforated plastic bag. The abdomen was closed temporarily. Blood loss, cardiopulmonary parameters and bladder pressures were measured over a one-hour period. The device was then removed and the animal was euthanized. Results Feasibility of device placement was demonstrated by maintenance of adequate vacuum suction pressures and seal. VAC placement presented no major technical challenges. Successful control of ongoing liver hemorrhage was achieved with the VAC. Total blood loss was 625 ml (20ml/kg. This corresponds to class II hemorrhagic shock in humans and compares favorably to previously reported estimated blood losses with similar grade liver injuries in the swine model. No post-injury cardiopulmonary compromise or elevated abdominal compartment pressures were encountered, while hepatic parenchymal perfusion was maintained. Conclusion These data demonstrate the feasibility and utility of a perihepatic negative pressure device for the treatment of hemorrhage from severe liver injury in the porcine model.
Fully kinetic model of breakdown during sheath expansion after interruption of vacuum arcs
Wang, Zhenxing; Wang, Haoran; Zhou, Zhipeng; Tian, Yunbo; Geng, Yingsan; Wang, Jianhua; Liu, Zhiyuan
2016-08-01
Research on sheath expansion is critical to the understanding of the dielectric recovery process in a vacuum interrupter after interruption of vacuum arcs. In this paper, we investigated how residual plasma affects breakdown in the sheath expansion period after the current zero. To simulate sheath expansion and breakdown, we developed a fully kinetic particle-in-cell Monte Carlo collision model with one spatial dimension and three velocity dimensions. The model accounted for various collisions, including ionization, excitation, elastic collisions, charge exchange, and momentum exchange, and we added an external circuit to the model to make the calculations self-consistent. The existence of metal vapor slowed the sheath expansion in the gap and caused high electric field formation in front of the cathode surface. The initial residual plasma, which was at sufficiently low density, seemed to have a limited impact on breakdown, and the metal vapor dominated the breakdown in this case. Additionally, the breakdown probability was sensitive to the initial plasma density if the value exceeded a specific threshold, and plasma at sufficiently high density could mean that breakdown would occur more easily. We found that if the simulation does not take the residual plasma into account, it could overestimate the critical value of the metal vapor density, which is always used to describe the boundary of breakdown after interruption of vacuum arcs. We discussed the breakdown mechanism in sheath expansion, and the breakdown is determined by a combination of metal vapor, residual plasma, and the electric field in front of the cathode surface.
Internal vacuum-assisted closure device in the swine model of severe liver injury
2012-01-01
Objectives The authors present a novel approach to nonresectional therapy in major hepatic trauma utilizing intraabdominal perihepatic vacuum assisted closure (VAC) therapy in the porcine model of Grade V liver injury. Methods A Grade V injury was created in the right lobe of the liver in a healthy pig. A Pringle maneuver was applied (4.5 minutes total clamp time) and a vacuum assisted closure device was placed over the injured lobe and connected to suction. The device consisted of a perforated plastic bag placed over the liver, followed by a 15 cm by 15cm VAC sponge covered with a nonperforated plastic bag. The abdomen was closed temporarily. Blood loss, cardiopulmonary parameters and bladder pressures were measured over a one-hour period. The device was then removed and the animal was euthanized. Results Feasibility of device placement was demonstrated by maintenance of adequate vacuum suction pressures and seal. VAC placement presented no major technical challenges. Successful control of ongoing liver hemorrhage was achieved with the VAC. Total blood loss was 625 ml (20ml/kg). This corresponds to class II hemorrhagic shock in humans and compares favorably to previously reported estimated blood losses with similar grade liver injuries in the swine model. No post-injury cardiopulmonary compromise or elevated abdominal compartment pressures were encountered, while hepatic parenchymal perfusion was maintained. Conclusion These data demonstrate the feasibility and utility of a perihepatic negative pressure device for the treatment of hemorrhage from severe liver injury in the porcine model. PMID:23217091
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
the value Ωtotal = 1, predicted by inflationary theory. Several physical models have been proposed to give a consistent physical interpretation of these observational facts. The observational and theoretical features suggest that the most natural candidate for the missing energy is the vacuum energy density or the cosmologi-.
Naidu, Gayathri
2016-08-27
The application of vacuum to direct contact membrane distillation (vacuum enhanced direct contact membrane distillation, V-DCMD) removed condensable gasses and reduced partial pressure in the membrane pores, achieving 37.6% higher flux than DCMD at the same feed temperature. Transfer mechanism and temperature distribution profile in V-DCMD were studied. The empirical flux decline (EFD) model represented fouling profiles of V-DCMD. In a continuous V-DCMD operation with moderate temperature (55 degrees C) and permeate pressure (300 mbar) for treating wastewater ROC, a flux of 16.0 +/- 0.3 L/m(2) h and high quality distillate were achieved with water flushing, showing the suitability of V-DCMD for ROC treatment. (C) 2016 Elsevier B.V. All rights reserved.
Model of Mass and Heat Transfer during Vacuum Freeze-Drying for Cornea
Directory of Open Access Journals (Sweden)
Zou Huifen
2012-01-01
Full Text Available Cornea is the important apparatus of organism, which has complex cell structure. Heat and mass transfer and thermal parameters during vacuum freeze-drying of keeping corneal activity are studied. The freeze-drying cornea experiments were operated in the homemade vacuum freeze dryer. Pressure of the freeze-drying box was about 50 Pa and temperature was about −10°C by controlled, and operating like this could guarantee survival ratio of the corneal endothelium over the grafting normal. Theory analyzing of corneal freeze-drying, mathematical model of describing heat and mass transfer during vacuum freeze-drying of cornea was established. The analogy computation for the freeze-drying of cornea was made by using finite-element computational software. When pressure of the freeze-drying box was about 50 Pa and temperature was about −10°C, time of double-side drying was 170 min. In this paper, a moving-grid finite-element method was used. The sublimation interface was tracked continuously. The finite-element mesh is moved continuously such that the interface position always coincides with an element node. Computational precision was guaranteed. The computational results were agreed with the experimental results. It proved that the mathematical model was reasonable. The finite-element software is adapted for calculating the heat and mass transfer of corneal freeze-drying.
Study of Two Bioactive Peptides in Vacuum and Solvent by Molecular Modeling
Yaşar, F.; Demir, K.
The thermodynamic and structural properties of Tyrosine-Glycine-Leusine-Phenylalanine (YGLF, in a one letter code) and Lysine-Valine-Leusine-Proline-Valine-Proline-Glutamine (KVLPVPQ) peptide sequences were studied by three-dimensional molecular modeling in vacuum and solution. All the three-dimensional conformations of each peptide sequences were obtained by multicanonical simulations with using ECEPP/2 force field and each simulation started from completely random initial conformation. Solvation contributions are included by a term that is proportional to solvent-accessible surface areas of peptides. In the present study, we calculated the average values of total energy, specific heat, fourth-order cumulant and end-to-end distance for two peptide sequences of milk protein as a function of temperature. With using major advantage of this simulation technique, Ramachandran plots were prepared and analysed to predict the relative occurrence probabilities of β-turn, γ-turn and helical structures. Although structural predictions of these sequences indicate both the presence of high level of γ-turns and low level of β-turns in vacuum and solvent, it was observed that these probabilities in vacuum were higher than the ones in solvent model.
Numerical modeling and validation of squeezed-film damping in vacuum-packaged industrial MEMS
Syed, Wajih U.; Brimmo, Ayoola; Waheed, Owais; Bojesomo, Alabi; Hassan Ali, Mohamed; Ocak, Ilker; Chengliang, Sun; Chatterjee, Aveek; Elfadel, Ibrahim (Abe M.
2017-07-01
Several high-performance, industrial micro-electromechanical (MEM) devices, such as gyroscopes, magnetometers, high-Q resonators and piezoelectric energy harvesters, require wafer bonding and packaging under near-vacuum conditions. One very challenging aspect of the design, verification and characterisation of these devices is to predict their performance characteristics in the presence of any residual gases post-packaging. Such gases contribute to the energy losses resulting from device surfaces squeezing or sliding against the gas films within the device cavities. In this paper, we fully expose the modelling assumptions used in commercial FEM tools to estimate the squeezed-film damping (SFD) experienced by MEM devices that are packaged under near-vacuum conditions. We also explain the various meshing options to enable the extraction of the most accurate Q factors under existing SFD assumptions. In addition, we compare the computational results across a variety of commercial FEM codes against measurements obtained under realistic vacuum conditions for an industrial high-Q magnetometer. These measurements suggest that existing computational models may deviate by as much as 25% on Q factor values for gas flow regimes under operating cavity pressures of less than 1 Torr.
Thin layer modeling of tom yum herbs in vacuum heat pump dryer.
Artnaseaw, A; Theerakulpisut, S; Benjapiyaporn, C
2010-04-01
Thin layer vacuum heat pump drying experiments were conducted to determine drying models for Tom Yum herbs (chili, lemon grass, kaffir lime leaf and galangal slice). The drying experiments were conducted in a vacuum heat pump dryer at a constant drying pressure of 0.2 bars and drying temperatures ranging from 50 °C to 65 °C. The experimental results were fitted to a number of well-known thin layer drying models and it was found, for the range of drying temperature tested, that the Midilli model is the best model for all Tom Yum herbs. To account for the influence of drying temperature, the constants and coefficients of model were formulated as functions of the drying temperature. Statistical tests of agreement between the model and experimental results were performed by determining the coefficient of determination (R²) , reduced chi-square (χ²) and root mean square error (RMSE). It was found that the model is in very good agreement with the experimental results.
Dynamics of microparticles in vacuum breakdown: Cranberg’s scenario updated by numerical modeling
Directory of Open Access Journals (Sweden)
B. Seznec
2017-07-01
Full Text Available Microparticles (MP and thermofield emission in vacuum are mainly caused by the roughness present at the surface of electrodes holding a high voltage. They can act as a trigger for breakdown, especially under high vacuum. This theoretical study discusses the interactions between one MP and the thermofield emission electron current as well as the consequences on the MP’s transit. Starting from Cranberg’s assumptions, new phenomena have been taken into account such as MP charge variation due to the secondary electron emission induced by energetic electron bombardment. Hence, the present model can be solved only numerically. Four scenarios have been identified based on the results, depending on the electron emission current from the cathode roughness (tip and the size of the MP released at the anode, namely (i one way; (ii back and forth; (iii oscillation; and (iv vaporization. A crash study of the MP on the cathode shows that the electron emission can decrease if the MP covers the thermoemissive tip, i.e., if the MP is larger than the tip size—a phenomenon often called “conditioning”—and helping to increase the voltage holding in vacuum without breakdown.
A potato model intercomparison across varying climates and productivity levels
DEFF Research Database (Denmark)
H. Fleisher, David; Condori, Bruno; Quiroz, Roberto
2017-01-01
decreased from 38% to 20% between P1 and P2. Model uncertainty increased with inter-annual variability, and predictions for all agronomic variables were significantly different from one model to another (p ... in carbon dioxide (C), but increased as much as 41 and 23% for yield and ET respectively as temperature (T) or rainfall (W) moved away from historical levels. Increases in T accounted for the highest amount of uncertainty, suggesting that methods and parameters for T sensitivity represent a considerable...... unknown among models. Using median model ensemble values, yield increased on average 6% per 100-ppm C, declined 4.6% per °C, and declined 2% for every 10% decrease in rainfall (for non-irrigated sites). Differences in predictions due to model representation of light utilization were significant (p
Electroweak vacuum stability in classically conformal B - L extension of the standard model
Energy Technology Data Exchange (ETDEWEB)
Das, Arindam; Okada, Nobuchika; Papapietro, Nathan [University of Alabama, Department of Physics and Astronomy, Alabama (United States)
2017-02-15
We consider the minimal U(1){sub B-L} extension of the standard model (SM) with the classically conformal invariance, where an anomaly-free U(1){sub B-L} gauge symmetry is introduced along with three generations of right-handed neutrinos and a U(1){sub B-L} Higgs field. Because of the classically conformal symmetry, all dimensional parameters are forbidden. The B - L gauge symmetry is radiatively broken through the Coleman-Weinberg mechanism, generating the mass for the U(1){sub B-L} gauge boson (Z{sup '} boson) and the right-handed neutrinos. Through a small negative coupling between the SM Higgs doublet and the B - L Higgs field, the negative mass term for the SM Higgs doublet is generated and the electroweak symmetry is broken. In this model context, we investigate the electroweak vacuum instability problem in the SM. It is well known that in the classically conformal U(1){sub B-L} extension of the SM, the electroweak vacuum remains unstable in the renormalization group analysis at the one-loop level. In this paper, we extend the analysis to the two-loop level, and perform parameter scans. We identify a parameter region which not only solve the vacuum instability problem, but also satisfy the recent ATLAS and CMS bounds from search for Z{sup '} boson resonance at the LHC Run-2. Considering self-energy corrections to the SM Higgs doublet through the right-handed neutrinos and the Z{sup '} boson, we derive the naturalness bound on the model parameters to realize the electroweak scale without fine-tunings. (orig.)
MODEL OF HYDRODYNAMIC MIXING OF CARBONIC POWDERS IN VACUUMATOR, USED IN STEEL-MAKING OF RUP “BMZ”
Directory of Open Access Journals (Sweden)
A. N. Chichko
2005-01-01
Full Text Available The mathematical model of the mixing and dissolving process of carbonic powder in a system '"vacuumator-bowl” under influence of circulating argon is offered. The spatial distribution of hydrodynamic currents at mixing of carbonic powder, received on the basis of computer calculations is presented. The character of distribution of hydrodynamic speeds of melt (circulating currents in industrial bowl and vacuumator for different time slots of mixing is determined.
A Heuristic Model for the Active Galactic Nucleus Based on the Planck Vacuum Theory
Directory of Open Access Journals (Sweden)
Daywitt W. C.
2009-07-01
Full Text Available The standard explanation for an active galactic nucleus (AGN is a "central engine" consisting of a hot accretion disk surrounding a supermassive black hole. Energy is generated by the gravitational infall of material which is heated to high temperatures in this dissipative accretion disk. What follows is an alternative model for the AGN based on the Planck vacuum (PV theory, where both the energy of the AGN and its variable luminosity are explained in terms of a variable photon flux emanating from the PV.
Flash Vacuum Pyrolysis of Lignin Model Compounds: Reaction Pathways of Aromatic Methoxy Groups
Energy Technology Data Exchange (ETDEWEB)
Britt, P.F.; Buchanan, A.C., III; Martineau, D.R.
1999-03-21
Currently, there is interest in utilizing lignin, a major constituent of biomass, as a renewable source of chemicals and fuels. High yields of liquid products can be obtained from the flash or fast pyrolysis of biomass, but the reaction pathways that lead to product formation are not understood. To provide insight into the primary reaction pathways under process relevant conditions, we are investigating the flash vacuum pyrolysis (FVP) of lignin model compounds at 500 C. This presentation will focus on the FVP of {beta}-ether linkages containing aromatic methoxy groups and the reaction pathways of methoxy-substituted phenoxy radicals.
Eichmeier, Joseph A
2008-01-01
Nineteen experts from the electronics industry, research institutes and universities have joined forces to prepare this book. ""Vacuum Electronics"" covers the electrophysical fundamentals, the present state of the art and applications, as well as the future prospects of microwave tubes and systems, optoelectronics vacuum devices, electron and ion beam devices, light and X-ray emitters, particle accelerators and vacuum interrupters. These topics are supplemented by useful information about the materials and technologies of vacuum electronics and vacuum technology.
modelling flow over stepped spillway with varying chute geometry
African Journals Online (AJOL)
2012-07-02
Jul 2, 2012 ... stepped Spillway, chute Slope, energy dissipated, hydraulic models. 1. Introduction. Stepped spillways (cascades) are commonly used for river training, debris dam structures, storm water sys- tems and aeration cascades [1]. Stepped cascade flows are characterized by the strong kinetic energy of flow.
Some Inhomogeneous Magnetized Viscous Fluid Cosmological Models with Varying $\\Lambda$
Pradhan,Anirudh; Srivastav, Sudhir Kumar; Jotania, Kanti R.
2003-01-01
Some cylindrically symmetric inhomogeneous viscous fluid cosmological models with electro-magnetic field are obtained. To get a solution a supplementary condition between metric potentials is used. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Without assumin g any {\\it ad hoc} law, we obtain a cosmological constant as a decreasing function of time. The behaviour of the electro-magnetic field tensor together with some p hysical aspects of t...
Gao, Yujie; Li, Xingang; Ding, Hui
2015-08-01
A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1Pa, heating temperature of 923K, heating time of 60.0min, particle size of 70 mesh (0.212mm) and initial mass of 5.25g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny-Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation. Copyright © 2015 Elsevier Ltd. All rights reserved.
Service-life limitations in vacuum glazing: A transient pressure balance model
Energy Technology Data Exchange (ETDEWEB)
Koebel, Matthias M.; Manz, Heinrich; Emanuel Mayerhofer, Karl; Keller, Beat (Swiss Federal Laboratories for Materials Research and Testing, Empa, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland.)
2010-06-15
Windows constitute a weak link in the building envelope and hence contribute significantly to the heating energy demand. By evacuating the glazing cavity, heat transfer rates two to five times lower than those of gas-filled conventional glazing units are predicted in theory and have been practically confirmed in a few cases. Of central importance to any practical realization of vacuum glazing is the edge-sealing problem because the technology used defines many secondary and tertiary parameters and strongly influences service life. This work establishes a correlation between the sealing method and its effect on the products service life. A cavity pressure balance model is presented, which takes into account four possible sources to the total pressure increase. Using this model a set of critical parameters is defined and the range of tolerable values for each parameter can be extracted. These findings underline the importance of choosing a sealing process, which is carried out in a high-vacuum environment. A possible source of pressure increase not considered in detail so far is the photofragmentation of long-chain organic adsorbate contaminants on the inner glazing surfaces. It was shown that a surface treatment via UV/ozone cleaning reduces the surface concentration of a model surface contaminant sodium dodecyl sulfate (SDS) by approximately 3 orders of magnitude. (author)
Modeling a nonperturbative spinor vacuum interacting with a strong gravitational wave
Energy Technology Data Exchange (ETDEWEB)
Dzhunushaliev, Vladimir [Al-Farabi Kazakh National University, Department of Theoretical and Nuclear Physics, Almaty (Kazakhstan); Al-Farabi Kazakh National University, Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Folomeev, Vladimir [Institute of Physicotechnical Problems and Material Science, NAS of the Kyrgyz Republic, Bishkek (Kyrgyzstan)
2015-07-15
We consider the propagation of strong gravitational waves interacting with a nonperturbative vacuum of spinor fields. To described the latter, we suggest an approximate model. The corresponding Einstein equation has the form of the Schroedinger equation. Its gravitational-wave solution is analogous to the solution of the Schroedinger equation for an electron moving in a periodic potential. The general solution for the periodic gravitational waves is found. The analog of the Kronig-Penney model for gravitational waves is considered. It is shown that the suggested gravitational-wave model permits the existence of weak electric charge and current densities concomitant with the gravitational wave. Based on this observation, a possible experimental verification of the model is suggested. (orig.)
Modeling deep ocean shipping noise in varying acidity conditions.
Udovydchenkov, Ilya A; Duda, Timothy F; Doney, Scott C; Lima, Ivan D
2010-09-01
Possible future changes of ambient shipping noise at 0.1-1 kHz in the North Pacific caused by changing seawater chemistry conditions are analyzed with a simplified propagation model. Probable decreases of pH would cause meaningful reduction of the sound absorption coefficient in near-surface ocean water for these frequencies. The results show that a few decibels of increase may occur in 100 years in some very quiet areas very far from noise sources, with small effects closer to noise sources. The use of ray physics allows sound energy attenuated via volume absorption and by the seafloor to be compared.
Numerical modeling of rapidly varying flows using HEC-RAS and WSPG models.
Rao, Prasada; Hromadka, Theodore V
2016-01-01
The performance of two popular hydraulic models (HEC-RAS and WSPG) for modeling hydraulic jump in an open channel is investigated. The numerical solutions are compared with a new experimental data set obtained for varying channel bottom slopes and flow rates. Both the models satisfactorily predict the flow depths and location of the jump. The end results indicate that the numerical models output is sensitive to the value of chosen roughness coefficient. For this application, WSPG model is easier to implement with few input variables.
Aidani, Emad; Hadadkhodaparast, Mohammadhossein; Kashaninejad, Mahdi
2017-05-01
In this work, we tried to evaluate mass transfer during a combined infrared-vacuum drying of kiwifruits. Infrared radiation power (200-300 W) and system pressure (5-15 kPa), as drying parameters, are evaluated on drying characteristics of kiwifruits. Both the infrared lamp power and vacuum pressure affected the drying time of kiwifruit slices. Nine different mathematical models were evaluated for moisture ratios using nonlinear regression analysis. The results of regression analysis indicated that the quadratic model is the best to describe the drying behavior with the lowest SE values and highest R value. Also, an increase in the power led to increase in the effective moisture diffusivity between 1.04 and 2.29 × 10-9 m2/s. A negative effect was observed on the ΔE with increasing in infrared power and with rising in infrared radiation power it was increased. Chroma values decreased during drying.
Šumić, Zdravko; Vakula, Anita; Tepić, Aleksandra; Čakarević, Jelena; Vitas, Jasmina; Pavlić, Branimir
2016-07-15
Fresh red currants were dried by vacuum drying process under different drying conditions. Box-Behnken experimental design with response surface methodology was used for optimization of drying process in terms of physical (moisture content, water activity, total color change, firmness and rehydratation power) and chemical (total phenols, total flavonoids, monomeric anthocyanins and ascorbic acid content and antioxidant activity) properties of dried samples. Temperature (48-78 °C), pressure (30-330 mbar) and drying time (8-16 h) were investigated as independent variables. Experimental results were fitted to a second-order polynomial model where regression analysis and analysis of variance were used to determine model fitness and optimal drying conditions. The optimal conditions of simultaneously optimized responses were temperature of 70.2 °C, pressure of 39 mbar and drying time of 8 h. It could be concluded that vacuum drying provides samples with good physico-chemical properties, similar to lyophilized sample and better than conventionally dried sample. Copyright © 2016 Elsevier Ltd. All rights reserved.
New model for colour kinetics of plum under infrared vacuum condition and microwave drying.
Chayjan, Reza Amiri; Alaei, Behnam
2016-01-01
Quality of dried foods is affected by the drying method and physiochemical changes in tissue. The drying method affects properties such as colour. The colour of processed food is one of the most important quality indices and plays a determinant role in consumer acceptability of food materials and the processing method. The colour of food materials can be used as an indirect factor to determine changes in quality, since it is simpler and faster than chemical methods. The study focused on the kinetics of colour changes of plum slices, under infrared vacuum and microwave conditions. Drying the samples was implemented at the absolute pressures of 20 and 60 kPa, drying temperatures of 50 and 60°C and microwave power of 90, 270, 450 and 630 W. Colour changes were quantified by the tri-stimulus L* (whiteness/darkness), a* (redness/greenness) and b* (yellowness/blueness) model, which is an international standard for color measurement developed by the Commission Internationale d'Eclairage (CIE). These values were also used to calculate total colour change (∆E), chroma, hue angle, and browning index (BI). A new model was used for mathematical modelling of colour change kinetics. The drying process changed the colour parameters of L*, a*, and b*, causing a colour shift toward the darker region. The values of L* and hue angle decreased, whereas the values of a*, b*, ∆E, chroma and browning index increased during exposure to infrared vacuum conditions and microwave drying. Comparing the results obtained using the new model with two conventional models of zero-order and first-order kinetics indicated that the new model presented more compatibility with the data of colour kinetics for all colour parameters and drying conditions. All kinetic changes in colour parameters can be explained by the new model presented in this study. The hybrid drying system included infrared vacuum conditions and microwave power for initial slow drying of plum slices and provided the desired
Modelling suction instabilities in soils at varying degrees of saturation
Directory of Open Access Journals (Sweden)
Buscarnera Giuseppe
2016-01-01
Full Text Available Wetting paths imparted by the natural environment and/or human activities affect the state of soils in the near-surface, promoting transitions across different regimes of saturation. This paper discusses a set of techniques aimed at quantifying the role of hydrologic processes on the hydro-mechanical stability of soil specimens subjected to saturation events. Emphasis is given to the mechanical conditions leading to coupled flow/deformation instabilities. For this purpose, energy balance arguments for three-phase systems are used to derive second-order work expressions applicable to various regimes of saturation. Controllability analyses are then performed to relate such work input with constitutive singularities that reflect the loss of strength under coupled and/or uncoupled hydro-mechanical forcing. A suction-dependent plastic model is finally used to track the evolution of stability conditions in samples subjected to wetting, thus quantifying the growth of the potential for coupled failure modes upon increasing degree of saturation. These findings are eventually linked with the properties of the field equations that govern pore pressure transients, thus disclosing a conceptual link between the onset of coupled hydro-mechanical failures and the evolution of suction with time. Such results point out that mathematical instabilities caused by a non-linear suction dependent behaviour play an important role in the advanced constitutive and/or numerical tools that are commonly used for the analysis of geomechanical problems in the unsaturated zone, and further stress that the relation between suction transients and soil deformations is a key factor for the interpretation of runaway failures caused by intense saturation events.
DEFF Research Database (Denmark)
Bak, Claus Leth; Borghetti, Alberto; Glasdam, Jakob Bærholm
2018-01-01
for both VCB sizing and insulation coordination studies of the components nearby the switching device. In this respect, their accurate modelling, which is the object of the paper, becomes crucial. In particular, the paper presents (the concept of) a VCB model and two relevant applications showing the model......Vacuum circuit breakers (VCBs) are widely used for medium voltage applications when low maintenance, long operating life, and large number of allowable switching cycles are required. The accurate estimation of the transient recovery voltages (TRVs) associated with their manoeuvres is indispensable...... capabilities of simulating TRVs due to opening/closing manoeuvres, namely the switching of large electrical motors and the switching of cables collecting offshore wind farms (OWFs). Data from digital fault recorder (DFR) in a water-pumping plant and from a measurement campaign in an OWF using a high...
Mager, R; Balzereit, C; Gust, K; Hüsch, T; Herrmann, T; Nagele, U; Haferkamp, A; Schilling, D
2016-05-01
Passive removal of stone fragments in the irrigation stream is one of the characteristics in continuous-flow PCNL instruments. So far the physical principle of this so-called vacuum cleaner effect has not been fully understood yet. The aim of the study was to empirically prove the existence of the vacuum cleaner effect and to develop a physical hypothesis and generate a mathematical model for this phenomenon. In an empiric approach, common low-pressure PCNL instruments and conventional PCNL sheaths were tested using an in vitro model. Flow characteristics were visualized by coloring of irrigation fluid. Influence of irrigation pressure, sheath diameter, sheath design, nephroscope design and position of the nephroscope was assessed. Experiments were digitally recorded for further slow-motion analysis to deduce a physical model. In each tested nephroscope design, we could observe the vacuum cleaner effect. Increase in irrigation pressure and reduction in cross section of sheath sustained the effect. Slow-motion analysis of colored flow revealed a synergism of two effects causing suction and transportation of the stone. For the first time, our model showed a flow reversal in the sheath as an integral part of the origin of the stone transportation during vacuum cleaner effect. The application of Bernoulli's equation provided the explanation of these effects and confirmed our experimental results. We widen the understanding of PCNL with a conclusive physical model, which explains fluid mechanics of the vacuum cleaner effect.
Higgs mass range from standard model false vacuum inflation in scalar-tensor gravity
DEFF Research Database (Denmark)
Masina, I.; Notari, A.
2012-01-01
If the standard model is valid up to very high energies it is known that the Higgs potential can develop a local minimum at field values around 10(15)-10(17) GeV, for a narrow band of values of the top quark and Higgs masses. We show that in a scalar-tensor theory of gravity such Higgs false vacuum...... can give rise to viable inflation if the potential barrier is very shallow, allowing for tunneling and relaxation into the electroweak scale true vacuum. The amplitude of cosmological density perturbations from inflation is directly linked to the value of the Higgs potential at the false minimum....... Requiring the top quark mass, the amplitude and spectral index of density perturbations to be compatible with observations, selects a narrow range of values for the Higgs mass, m(H) = 126.0 +/- 3.5 GeV, where the error is mostly due to the theoretical uncertainty of the 2-loop renormalization group equation...
National Research Council Canada - National Science Library
Sznaier, Mario
2001-01-01
.... In this chapter we propose a suboptimal regulator for nonlinear parameter varying, control affine systems based upon the combination of model predictive and control Lyapunov function techniques...
Experimental validation of a numerical model for heat transfer in vacuum glazing
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Eames, Philip C.; Hyde, Trevor J. [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB, N. Ireland (United Kingdom); Norton, Brian [Dublin Institute of Technology, Aungier Street, Dublin 2 (Ireland)
2006-05-15
Flat vacuum glazings consisting of a narrow evacuated space between two glass panes separated by an array of small support pillars have been fabricated. A guarded hot box calorimeter was designed and constructed to measure their heat transfer coefficients. Experimental measurements of temperatures and rates of heat transfer were found to be in very good agreement with those predicted using a developed finite element model. A method for determining the heat transfer coefficient of the evacuated gap has been established and comparisons are made between the measured and predicted glass surface temperature profiles of the exposed glass area and the heat transfer coefficients of the total glazing system in order to validated the model. (author)
Model of liquid-metal splashing in the cathode spot of a vacuum arc discharge
Energy Technology Data Exchange (ETDEWEB)
Gashkov, M. A.; Zubarev, N. M., E-mail: nick@iep.uran.ru; Zubareva, O. V.; Mesyats, G. A.; Uimanov, I. V. [Russian Academy of Sciences, Institute of Electrophysics, Ural Branch (Russian Federation)
2016-04-15
The formation of microjets is studied during the extrusion of a melted metal by the plasma pressure from craters formed on a cathode in a burning vacuum arc. An analytic model of liquid-metal splashing that includes two stages is proposed. At the first stage, the liquid motion has the axial symmetry and a liquid-metal wall surrounding the crater is formed. At the second stage, the axial symmetry is broken due to the development of the Plateau–Rayleigh instability in the upper part of the wall. The wall breakup process is shown to have a threshold. The minimal plasma pressure and the minimal electric current flowing through the crater required for obtaining the liquid-metal splashing regime are found. The basic spatial and temporal characteristics of the jet formation process are found using the analytic model.
DEFF Research Database (Denmark)
Maagaard, Mathilde; Oestergaard, Jeanett; Johansen, Marianne
2012-01-01
Objectives. To develop and validate an Objective Structured Assessment of Technical Skills (OSATS) scale for vacuum extraction. Design. Two part study design: Primarily, development of a procedure-specific checklist for vacuum extraction. Hereafter, validationof the developed OSATS scale for vacuum...
Thermo-optical vacuum testing of IRNSS laser retroreflector array qualification model
Porcelli, L.; Boni, A.; Ciocci, E.; Contessa, S.; Dell'Agnello, S.; Delle Monache, G.; Intaglietta, N.; Martini, M.; Mondaini, C.; Patrizi, G.; Salvatori, L.; Tibuzzi, M.; Lops, C.; Cantone, C.; Tuscano, P.; Maiello, M.; Venkateswaran, R.; Chakraborty, P.; Ramana Reddy, C. V.; Sriram, K. V.
2017-09-01
We describe the activities performed by SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory) of INFN-LNF for the thermo-optical vacuum testing activity of a IRNSS (Indian Regional Navigation Satellite System) LRA (Laser Retroreflector Array), under contract for ISRO-LEOS. To our knowledge, this is the first publication on the characterization of the optical performance of an LRA operating at about 36,000 km altitude (typical of regional GNSS segments, namely QZSS, COMPASS-G) executed in fully representative, carefully lab-simulated space conditions. In particular, this is the only such publication concerning IRNSS. Since laser ranging to its altitude is more challenging than to GNSS altitudes (from about 19,100 km for GLONASS to about 23,200 km for Galileo), comparative measurements were long awaited by ILRS (International Laser Ranging Service) and we present measurements of the absolute laser return to ground stations of the ILRS in terms of lidar OCS (Optical Cross Section) at the IRNSS relevant value of velocity aberration, in turn derived from measurements of the full FFDP (Far Field Diffraction Pattern) over a very large range of velocity aberrations. These measurements were acquired: (i) on a full-size qualification model of a IRNSS CCR (Cube Corner Retroreflector) LRA that ISRO-LEOS provided to INFN-LNF; (ii) during the lab-simulation of a 1/4 orbit segment, in which the LRA CCRs are exposed to the perturbation of the sun heat at varying angles, from grazing incidence (90° with respect to the direction perpendicular to the plane of array), up to the perpendicular to the LRA, with a same time variation consistent with the actual space orbit. In this 1/4 orbit condition, the LRA experiences potentially large thermal degradations of the OCS, depending on the detailed thermal and mechanical design of the LRA. Since all GNSS constellations have different LRA designs or configurations, this is another
Todd E. Clark; Francesco Ravazzolo
2012-01-01
This paper compares alternative models of time-varying macroeconomic volatility on the basis of the accuracy of point and density forecasts of macroeconomic variables. In this analysis, we consider both Bayesian autoregressive and Bayesian vector autoregressive models that incorporate some form of time-varying volatility, precisely stochastic volatility (both with constant and time-varying autoregressive coeffi cients), stochastic volatility following a stationary AR process, stochastic volat...
Wigley, D. A.; Sandefur, P. G., Jr.; Lawing, P. L.
1981-01-01
The results of initial experiments show that high-strength void-free bonds can be formed by vacuum brazing of stainless steels using copper and nickel-based filler metals. In Nitronic 40, brazed joints have been formed with strengths in excess of the yield strength of the parent metal, and even at liquid nitrogen temperatures the excellent mechanical properties of the parent metal are only slightly degraded. The poor toughness of 15-5 P.H. stainless steel at cryogenic temperatures is lowered even further by the presence of the brazed bonds investigated. It is highly unlikely that the technique would be used for any critical areas of aerofoil models intended for low-temperature service. Nevertheless, the potential advantages of this simplified method of construction still have attractions for use at ambient temperatures.
Gauge-Independent Scales Related to the Standard Model Vacuum Instability
Espinosa, Jose R.; Konstandin, Thomas; Riotto, Antonio
2017-01-01
The measured (central) values of the Higgs and top quark masses indicate that the Standard Model (SM) effective potential develops an instability at high field values. The scale of this instability, determined as the Higgs field value at which the potential drops below the electroweak minimum, is about $10^{11}$ GeV. However, such a scale is unphysical as it is not gauge-invariant and suffers from a gauge-fixing uncertainty of up to two orders of magnitude. Subjecting our system, the SM, to several probes of the instability (adding higher order operators to the potential; letting the vacuum decay through critical bubbles; heating up the system to very high temperature; inflating it) and asking in each case physical questions, we are able to provide several gauge-invariant scales related with the Higgs potential instability.
Modeling of acetylene pyrolysis under steel vacuum carburizing conditions in a tubular flow reactor.
Khan, Rafi Ullah; Bajohr, Siegfried; Graf, Frank; Reimert, Rainer
2007-03-02
In the present work, the pyrolysis of acetylene was studied under steel vacuum carburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from 650 degrees C to 1050 degrees C. The partial pressure of acetylene in the feed mixture was 10 and 20 mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressure of the mixture was 1.6 bar. A kinetic mechanism which consists of seven species and nine reactions has been used in the commercial computational fluid dynamics (CFD) software Fluent. The species transport and reaction model of Fluent was used in the simulations. A comparison of simulated and experimental results is presented in this paper.
Difermion condensates in vacuum in 2-4D four-fermion interaction models
Bang-Rong, Zhou
2007-01-01
Theoretical analysis of interplay between the condensates $$ and $$ in vacuum is generally made by relativistic effective potentials in the mean field approximation in 2D, 3D and 4D models with two flavor and $N_c$ color massless fermions. It is found that in ground states of these models, interplay between the two condensates mainly depend on the ratio $G_S/H_S$ for 2D and 4D case or $G_S/H_P$ for 3D case, where $G_S$, $H_S$ and $H_P$ are respectively the coupling constants in a scalar $(\\bar{q}q)$, a scalar $(qq)$ and a pseudoscalar $(qq)$ channel. In ground states of all the models, only pure $$ condensates could exist if $G_S/H_S$ or $G_S/H_P$ is bigger than the critical value $2/N_c$, the ratio of the color numbers of the fermions entering into the condensates $$ and $$. As $G_S/H_S$ or $G_S/H_P$ decreases to the region below $2/N_c$, differences of the models will manifest themselves. Depending on different models, and also on $N_c$ in 3D model, one will have or have no the coexistence phase of the two ...
Modelling time-varying effects in Cox model under order restrictions
Salanti, Georgia; Ulm, Kurt
2003-01-01
The violation of the proportional hazards assumption in Cox model occurs quite often in studies concerning solid tumours or leukaemia. Then the time varying coefficients model is its most popular extension used. The function f(t) that measures the time variation of a covariate, can be assessed through several smoothing techniques, such as cubic splines. However, for practical propose, it is more convenient to assess f(t) by a step function. The main drawback of this approach is the lack of s...
Estimation of time-varying selectivity in stock assessments using state-space models
DEFF Research Database (Denmark)
Nielsen, Anders; Berg, Casper Willestofte
2014-01-01
-varying selectivity pattern. The fishing mortality rates are considered (possibly correlated) stochastic processes, and the corresponding process variances are estimated within the model. The model is applied to North Sea cod and it is verified from simulations that time-varying selectivity can be estimated......Time-varying selectivity is one of the main challenges in single species age-based assessment models. In classical deterministic VPA-type models the fishing mortality rates are unfiltered representations of the observed catches. As a consequence the selectivity becomes time......-varying, but this representation is too fluctuating, because it includes the observation noise. In parametric statistical catch at age models a common assumption is that the selectivity is constant in all years, although time-varying selectivity can be introduced by splitting the data period in blocks with different selectivities...
Directory of Open Access Journals (Sweden)
WAN Xin
2006-02-01
Full Text Available Under vacuum, heat transfer in porous corundum shell of investment casting depends on the characteristics of the solid materials and the spatial arrangement of solids and pores. In this study, we present a modified fractal approach to model the pore structure of corundum shell and to describe its influence on the thermal conductivity. We assumed that there is no heat convection in the shell. A sectioned view of porous corundum shell was studied and used to describe the geometric structure and to calculate the fractal dimension d. Based on the fractal dimension d, we obtained the relationship between volumetric solid content and pore arrangement in different measure scales. A heat transfer model was thus established using a network of resistors in which we applied an equivalent approach to calculate the effective thermal conductivity of real porous corundum shell that include the effects of heat conduction and heat radiation of solid. From the obtained results we discuss these effects on the effective thermal conductivity including the scale of measurement, the structure of pore and the temperature. At last these results were compared with other empirical model, which computed by assuming even porosity in which effect of pore structure was not being considered. Though the thermal conductivity calculated essentially in agreement with that obtained from empirical model, model used in this study is more close to the real heat transfer process.
Energy Technology Data Exchange (ETDEWEB)
Zayakin, Andrey V.
2011-01-17
This Thesis is dedicated to a comparison of the two means of studying the electromagnetic properties of the QCD vacuum - holography and resummed field theory. I compare two classes of distinct models for the dynamics of the condensates. The first class consists of the so-called holographic models of QCD. Based upon the Maldacena conjecture, it tries to establish the properties of QCD correlation functions from the behavior of classical solutions of field equations in a higher-dimensional theory. Yet in many aspects the holographic approach has been found to be in an excellent agreement with data. These successes are the prediction of the very small viscosity-to-entropy ratio and the predictions of meson spectra up to 5% accuracy in several models. On the other hand, the resummation methods in field theory have not been discarded so far. Both classes of methods have access to condensates. Thus a comprehensive study of condensates becomes possible, in which I compare my calculations in holography and resummed field theory with each other, as well as with lattice results, field theory and experiment. I prove that the low-energy theorems of QCD keep their validity in holographic models with a gluon condensate in a non-trivial way. I also show that the so-called decoupling relation holds in holography models with chiral and gluon condensates, whereas this relation fails in the Dyson-Schwinger approach. On the contrary, my results on the chiral magnetic effect in holography disagree with the weak-field prediction; the chiral magnetic effect (that is, the electric current generation in a magnetic field) is three times less than the current in the weakly-coupled QCD. The chiral condensate behavior is found to be quadratic in external field both in the Dyson-Schwinger approach and in holography, yet we know that in the exact limit the condensate must be linear, thus both classes of models are concluded to be deficient for establishing the correct condensate behaviour in the
Modeling of cathode spot crater formation and development in vacuum arc
Zhang, Xiao; Wang, Lijun; Jia, Shenli; Shmelev, D. L.
2017-11-01
A two-dimensional (2D) rotary axisymmetric model has been developed to describe the formation and development of cathode spot in vacuum arc. The model includes hydrodynamic equations and heat transfer equation which considers surface evaporation and Joule heating. Parameters used in this model, such as the distributions of pressure, energy flux density, and current density, come from experiments and other researchers’ work. In this model, cathode spot maintains 30 ns and during this time, all parameters are fixed. The simulation results show that when the energy flux density is 1.5–3 × 1012 W, discharge current is 1–6 A and the pressure is 1–3 × 108 Pa, the crater radius is 1.4–4.1 µm, the crater depth is 1.4–2.1 µm, the velocity of liquid metal is 154–428 m s‑1 and the maximum temperature is 2145–5342 K which is located in the area with radius 0.5–1.5 µm. Besides, on the chromium cathode, the maximum temperature is higher mainly because of the lower thermal conductivity.
State-of-the-Art Calculation of the Decay Rate of Electroweak Vacuum in the Standard Model
Chigusa, So; Moroi, Takeo; Shoji, Yutaro
2017-11-01
The decay rate of the electroweak (EW) vacuum is calculated in the framework of the standard model (SM) of particle physics, using the recent progress in the understanding of the decay rate of metastable vacuum in gauge theories. We give a manifestly gauge-invariant expression of the decay rate. We also perform a detailed numerical calculation of the decay rate. With the best-fit values of the SM parameters, we find that the decay rate of the EW vacuum per unit volume is about 10-554 Gyr-1 Gpc-3 ; with the uncertainty in the top mass, the decay rate is estimated as 10-284- 10-1371 Gyr-1 Gpc-3 .
Directory of Open Access Journals (Sweden)
G. F. Dugan
2015-04-01
Full Text Available This paper compares measurements and calculations of scattering of photons from technical vacuum chamber surfaces typical of accelerators. Synchrotron radiation generated by a charged particle beam in the accelerator is either absorbed, specularly reflected, or scattered by the vacuum chamber surface. This phenomenon has important implications on the operation of the accelerator. Measurements of photon scattering were made at the BESSY-II synchrotron radiation facility using samples of aluminum vacuum chamber from Cornell electron storage ring (CESR. A description of the analytic model used in the calculation is given, which takes into account the reflectivity of the material, the surface features of the sample, the wavelengths and the incident angles of the photons. The surface properties used in these calculations were obtained from measurements made from an atomic force microscope.
Optimal Control of a Delay-Varying Computer Virus Propagation Model
Ren, Jianguo; Xu, Yonghong; Zhang, Chunming
2013-01-01
By incorporating the objective of keeping a low number of infected nodes and a high number of recovered nodes at a lower cost into a known computer virus model (the delay-varying SIRC model) extended by introducing quarantine, a novel model is described by means of the optimal control strategy and theoretically analyzed. Through the comparison of simulation results, it is shown that the propagation of computer virus with varying latency period can be suppressed effectively by the optimal cont...
Overcoming Challenges in Kinetic Modeling of Magnetized Plasmas and Vacuum Electronic Devices
Omelchenko, Yuri; Na, Dong-Yeop; Teixeira, Fernando
2017-10-01
We transform the state-of-the art of plasma modeling by taking advantage of novel computational techniques for fast and robust integration of multiscale hybrid (full particle ions, fluid electrons, no displacement current) and full-PIC models. These models are implemented in 3D HYPERS and axisymmetric full-PIC CONPIC codes. HYPERS is a massively parallel, asynchronous code. The HYPERS solver does not step fields and particles synchronously in time but instead executes local variable updates (events) at their self-adaptive rates while preserving fundamental conservation laws. The charge-conserving CONPIC code has a matrix-free explicit finite-element (FE) solver based on a sparse-approximate inverse (SPAI) algorithm. This explicit solver approximates the inverse FE system matrix (``mass'' matrix) using successive sparsity pattern orders of the original matrix. It does not reduce the set of Maxwell's equations to a vector-wave (curl-curl) equation of second order but instead utilizes the standard coupled first-order Maxwell's system. We discuss the ability of our codes to accurately and efficiently account for multiscale physical phenomena in 3D magnetized space and laboratory plasmas and axisymmetric vacuum electronic devices.
Chitanvis, Shirish M.
1989-03-01
The analogy between chemical reactions and cascade ionization is exploited to study the spatial and temporal dynamics of plasma formation in the vapor that is formed on a metallic aerosol that is being irradiated by a high-energy laser beam, in vacuum. The present hydrodynamic model is valid for relatively low laser fluences and pulses of the order of nanoseconds or less, when the diffusive approximation may be safely invoked. The main result of the paper is to show that the laser-induced plasma layer around aerosols shows a crossover, from being transparent to being opaque, as the fluence incident upon the aerosol is increased. The model of cascade ionization is used to show that for the laser fluxes for which the model is valid, the plasma in the vapor layer surrounding an aluminuim metallic sphere is not dense enough to obscure the laser beam. For flux levels of 10 to the 11th W/sq cm or higher and pulse lengths of 10 ns or longer, the plasma around individual aluminum aerosols becomes very absorbing.
Gordon, H.S.
1959-09-15
An improved adsorption vacuum trap for use in vacuum systems was designed. The distinguishing feature is the placement of a plurality of torsionally deformed metallic fins within a vacuum jacket extending from the walls to the central axis so that substantially all gas molecules pass through the jacket will impinge upon the fin surfaces. T fins are heated by direct metallic conduction, thereby ol taining a uniform temperature at the adeorbing surfaces so that essentially all of the condensible impurities from the evacuating gas are removed from the vacuum system.
NARX-based BPSO modelling for time-varying steam temperature of ...
African Journals Online (AJOL)
This paper focuses on a nonlinear modelling for a time-varying process of steam temperature by employing a polynomial Nonlinear Auto-Regressive with Exogenous Input (NARX) structure based on Binary Particle Swarm Optimization (BPSO) algorithm. The system identification time-varying steam temperature data was ...
Energy Technology Data Exchange (ETDEWEB)
Biltoft, P J
2004-10-15
The environmental condition called vacuum is created any time the pressure of a gas is reduced compared to atmospheric pressure. On earth we typically create a vacuum by connecting a pump capable of moving gas to a relatively leak free vessel. Through operation of the gas pump the number of gas molecules per unit volume is decreased within the vessel. As soon as one creates a vacuum natural forces (in this case entropy) work to restore equilibrium pressure; the practical effect of this is that gas molecules attempt to enter the evacuated space by any means possible. It is useful to think of vacuum in terms of a gas at a pressure below atmospheric pressure. In even the best vacuum vessels ever created there are approximately 3,500,000 molecules of gas per cubic meter of volume remaining inside the vessel. The lowest pressure environment known is in interstellar space where there are approximately four molecules of gas per cubic meter. Researchers are currently developing vacuum technology components (pumps, gauges, valves, etc.) using micro electro mechanical systems (MEMS) technology. Miniature vacuum components and systems will open the possibility for significant savings in energy cost and will open the doors to advances in electronics, manufacturing and semiconductor fabrication. In conclusion, an understanding of the basic principles of vacuum technology as presented in this summary is essential for the successful execution of all projects that involve vacuum technology. Using the principles described above, a practitioner of vacuum technology can design a vacuum system that will achieve the project requirements.
Verification of spectral stabilization and numerically modeled external vacuum in NIMROD
Sovinec, C. R.; Bunkers, K. J.
2013-10-01
Revisions to the NIMROD algorithm (JCP 195, 355) aim to improve its utility for tokamak computations. The standard spectral-element expansion of all physical fields in continuous bases leads to convergence on MHD interchange from the unstable side in conditions of weak dissipation. This is a numerical impediment in nonlinear computations (Lutjens, CPC 95, 47). Adapting 1D numerical results (Sovinec, BAPS 57, No. 12) to NIMROD's elements, we consider incomplete modal expansions for auxiliary flow-divergence and parallel-vorticity fields. Their bases are just the highest order Legendre polynomial of each element. We show that convergence from the stable side is achieved when the auxiliary fields are used for either hyperbolic or parabolic correction terms, as verified in cylindrical interchange and toroidal ballooning computations. Separate development on applying distinct physical models to different regions of a domain allows coupling to external vacuum regions, suitable for modeling vertical displacement events and resistive wall modes. Results from initial tests are reported. Work supported by U.S. Dept. of Energy.
Modeling and simulation of a time-varying inertia aircraft in aerial refueling
National Research Council Canada - National Science Library
Wang Haitao Dong Xinmin Xue Jianping Liu Jiaolong Wang Jian
2016-01-01
Studied in this paper is dynamic modeling and simulation application of the receiver aircraft with the time-varying mass and inertia property in an integrated simulation environment which includes two...
Long Memory of Financial Time Series and Hidden Markov Models with Time-Varying Parameters
DEFF Research Database (Denmark)
Nystrup, Peter; Madsen, Henrik; Lindström, Erik
2016-01-01
Hidden Markov models are often used to model daily returns and to infer the hidden state of financial markets. Previous studies have found that the estimated models change over time, but the implications of the time-varying behavior have not been thoroughly examined. This paper presents an adaptive...... to reproduce with a hidden Markov model. Capturing the time-varying behavior of the parameters also leads to improved one-step density forecasts. Finally, it is shown that the forecasting performance of the estimated models can be further improved using local smoothing to forecast the parameter variations....
Hackwood, Susan; Belinski, Steven E.; Beni, Gerardo
1989-01-01
The discipline of vacuum mechatronics is defined as the design and development of vacuum-compatible computer-controlled mechanisms for manipulating, sensing and testing in a vacuum environment. The importance of vacuum mechatronics is growing with an increased application of vacuum in space studies and in manufacturing for material processing, medicine, microelectronics, emission studies, lyophylisation, freeze drying and packaging. The quickly developing field of vacuum mechatronics will also be the driving force for the realization of an advanced era of totally enclosed clean manufacturing cells. High technology manufacturing has increasingly demanding requirements for precision manipulation, in situ process monitoring and contamination-free environments. To remove the contamination problems associated with human workers, the tendency in many manufacturing processes is to move towards total automation. This will become a requirement in the near future for e.g., microelectronics manufacturing. Automation in ultra-clean manufacturing environments is evolving into the concept of self-contained and fully enclosed manufacturing. A Self Contained Automated Robotic Factory (SCARF) is being developed as a flexible research facility for totally enclosed manufacturing. The construction and successful operation of a SCARF will provide a novel, flexible, self-contained, clean, vacuum manufacturing environment. SCARF also requires very high reliability and intelligent control. The trends in vacuum mechatronics and some of the key research issues are reviewed.
Directory of Open Access Journals (Sweden)
Jamaluddin Jamaluddin
2012-05-01
Full Text Available The natural colour of fruit flaky product is one of specific property prefered by consumer. To maintain the natural colourof the fruit flaky during frying, it is necessary to pay attention the characteristic changes of raw material and control the process in order not to have much changes to get the intended colour. The objective of this research is to develop empirically mathematical model of fruit flaky colour changes during vacuum frying process by considering the change of water and sucrose contents in the product. Sample of the research were jack fruits fried in the temperature of 70–100OC, frying duration of 15–60 minutes, and vacuum pressure of 13-23 kPa. The observed parameters are colour (L, colour (a, colour (b, water and sukrose contents before and after frying. The result showed that colour changes (L, a and b were influenced by free water vaporization and sukrose decreasing in product, so empirically, the developed mathematical model of colour changes (L, a and b can be used to predict fruit flaky colour changes during vacuum frying. ABSTRAK Warna alami pada produk keripik buah adalah merupakan salah satu sifat khas yang disukai oleh konsumen, untukmempertahankan warna alami keripik buah agar tidak banyak mengalami perubahan selama dalam penggorengan, perlu diperhatikan perubahan karakteristik bahan baku dan pengendalian proses, agar warna keripik buah yang dihasilkan sesuai dengan yang diinginkan. Penelitian ini bertujuan untuk mengembangkan secara empirik model matematik perubahan warna keripik buah selama dalam proses penggorengan vakum dengan mempertimbangkan ke dalam model perubahan kadar air dan kadar sukrosa di dalam padatan. Sampel penelitian adalah buah nangka digoreng pada suhu70-100 OC, lama penggorengan 15-60 menit dan tekanan vakum 13-23 kPa. Parameter yang diamati adalah warna (L, warna (a, warna (b, kadar air dan kadar sukrosa sebelum dan setelah sampel digoreng. Hasil penelitian menunjukkan perubahan warna L, a
One-Dimensional Vacuum Steady Seepage Model of Unsaturated Soil and Finite Difference Solution
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Feng Huang
2017-01-01
Full Text Available Vacuum tube dewatering method and light well point method have been widely used in engineering dewatering and foundation treatment. However, there is little research on the calculation method of unsaturated seepage under the effect of vacuum pressure which is generated by the vacuum well. In view of this, the one-dimensional (1D steady seepage law of unsaturated soil in vacuum field has been analyzed based on Darcy’s law, basic equations, and finite difference method. First, the gravity drainage ability is analyzed. The analysis presents that much unsaturated water can not be drained off only by gravity effect because of surface tension. Second, the unsaturated vacuum seepage equations are built up in conditions of flux boundary and waterhead boundary. Finally, two examples are analyzed based on the relationship of matric suction and permeability coefficient after boundary conditions are determined. The results show that vacuum pressure will significantly enhance the drainage ability of unsaturated water by improving the hydraulic gradient of unsaturated water.
Derivation of a Vacuum Refractive Index in a Stringy Space-Time Foam Model
Ellis, Jonathan Richard; Nanopoulos, D V
2008-01-01
It has been suggested that energetic photons propagating in vacuo should experience a non-trivial refractive index due to the foamy structure of space-time induced by quantum-gravitational fluctuations. The sensitivity of recent astrophysical observations, particularly of AGN Mk501 by the MAGIC Collaboration, approaches the Planck scale for a refractive index depending linearly on the photon energy. We present here a new derivation of this quantum-gravitational vacuum refraction index, based on a stringy analogue of the interaction of a photon with internal degrees of freedom in a conventional medium. We model the space-time foam as a gas of D-particles in the bulk space-time of a higher-dimensional cosmology where the observable Universe is a D3-brane. The interaction of an open string representing a photon with a D-particle stretches and excites the string, which subsequently decays and re-emits the photon with a time delay that increases linearly with the photon energy and is related to stringy uncertainty...
From calls to communities: a model for time varying social networks
Laurent, Guillaume; Karsai, Márton
2015-01-01
Social interactions vary in time and appear to be driven by intrinsic mechanisms, which in turn shape the emerging structure of the social network. Large-scale empirical observations of social interaction structure have become possible only recently, and modelling their dynamics is an actual challenge. Here we propose a temporal network model which builds on the framework of activity-driven time-varying networks with memory. The model also integrates key mechanisms that drive the formation of social ties - social reinforcement, focal closure and cyclic closure, which have been shown to give rise to community structure and the global connectedness of the network. We compare the proposed model with a real-world time-varying network of mobile phone communication and show that they share several characteristics from heterogeneous degrees and weights to rich community structure. Further, the strong and weak ties that emerge from the model follow similar weight-topology correlations as real-world social networks, i...
Directory of Open Access Journals (Sweden)
Liu K.
2014-01-01
Full Text Available The vacuum distillation of aluminum from Si-Fe-Al ternary alloy with high content of Al is studied by a molecular interaction volume model (MIVM in this paper. The vapor-liquid phase equilibrium of the Si-Fe-Al system in vacuum distillation has been calculated using only the properties of pure components and the activity coefficients. A significant advantage of the model lies in its ability to predict the thermodynamic properties of liquid alloys using only binary infinite dilution activity coefficients. The thermodynamic activities and activity coefficients of components of the related Si-Fe, Si- Al and Fe-Al binary and the Si-Fe-Al ternary alloy systems are calculated based on the MIVM. The computational activity values are presented graphically, and evaluated with the reported experiment data in the literature, which shows that the prediction effect of the proposed model is of stability and reliability.
Block Empirical Likelihood for Longitudinal Single-Index Varying-Coefficient Model
Directory of Open Access Journals (Sweden)
Yunquan Song
2013-01-01
Full Text Available In this paper, we consider a single-index varying-coefficient model with application to longitudinal data. In order to accommodate the within-group correlation, we apply the block empirical likelihood procedure to longitudinal single-index varying-coefficient model, and prove a nonparametric version of Wilks’ theorem which can be used to construct the block empirical likelihood confidence region with asymptotically correct coverage probability for the parametric component. In comparison with normal approximations, the proposed method does not require a consistent estimator for the asymptotic covariance matrix, making it easier to conduct inference for the model's parametric component. Simulations demonstrate how the proposed method works.
International Stock Market Efficiency: A Non-Bayesian Time-Varying Model Approach
Mikio Ito; Akihiko Noda; Tatsuma Wada
2012-01-01
This paper develops a non-Bayesian methodology to analyze the time-varying structure of international linkages and market efficiency in G7 countries. We consider a non-Bayesian time-varying vector autoregressive (TV-VAR) model, and apply it to estimate the joint degree of market efficiency in the sense of Fama (1970, 1991). Our empirical results provide a new perspective that the international linkages and market efficiency change over time and that their behaviors correspond well to historic...
Helbich, M; Griffith, D
2016-01-01
Real estate policies in urban areas require the recognition of spatial heterogeneity in housing prices to account for local settings. In response to the growing number of spatially varying coefficient models in housing applications, this study evaluated four models in terms of their spatial patterns
Liu, Qun; Jiang, Daqing; Shi, Ningzhong; Hayat, Tasawar; Alsaedi, Ahmed
2017-03-01
In this paper, we develop a mathematical model for a tuberculosis model with constant recruitment and varying total population size by incorporating stochastic perturbations. By constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of an ergodic stationary distribution as well as extinction of the disease to the stochastic system.
Model reference adaptive control for linear time varying and nonlinear systems
Abida, L.; Kaufman, H.
1982-01-01
Model reference adaptive control is applied to linear time varying systems and to nonlinear systems amenable to virtual linearization. Asymptotic stability is guaranteed even if the perfect model following conditions do not hold, provided that some sufficient conditions are satisfied. Simulations show the scheme to be capable of effectively controlling certain nonlinear systems.
Quark-Antiquark and Diquark Condensates in Vacuum in a 3D Two-Flavor Gross-Neveu Model
Bang-Rong, Zhou
2007-01-01
The effective potential analysis indicates that, in a 3D two-flavor Gross-Neveu model in vacuum, depending on less or bigger than the critical value 2/3 of $G_S/H_P$, where $G_S$ and $H_P$ are respectively the coupling constants of scalar quark-antiquark channel and pseudoscalar diquark channel, the system will have the ground state with pure diquark condensates or with pure quark-antiquark condensates, but no the one with coexistence of the two forms of condensates. The similarities and differences in the interplay between the quark-antiquark and the diquark condensates in vacuum in the 2D, 3D and 4D two-flavor four-fermion interaction models are summarized.
Robles-Pérez, Salvador
2017-11-01
We apply the Lewis-Riesenfeld invariant method for the harmonic oscillator with time dependent mass and frequency to the modes of a charged scalar field that propagates in a curved, homogeneous and isotropic spacetime. We recover the Bunch-Davies vacuum in the case of a flat DeSitter spacetime, the equivalent one in the case of a closed DeSitter spacetime and the invariant vacuum in a curved spacetime that evolves adiabatically. In the three cases, it is computed the thermodynamical magnitudes of entanglement between the modes of the particles and antiparticles of the invariant vacuum, and the modification of the Friedmann equation caused by the existence of the energy density of entanglement. The amplitude of the vacuum fluctuations are also computed.
Energy Technology Data Exchange (ETDEWEB)
Chernin, Artur D [P.K. Shternberg State Astronomical Institute at the M.V. Lomonosov Moscow State University, Moscow (Russian Federation)
2001-11-30
Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered. (reviews of topical problems)
Franchetti, G
2013-01-01
This paper continues the presentation of pumps begun in ‘Vacuum I’. The main topic here is gauges and partial-pressure measurements. Starting from the kinetics of gases, the various strategies for measuring vacuum pressures are presented at an introductory level, with some reference to hardware devices. Partial-pressure measurement techniques are introduced, showing that the principles of ion selection have a direct similarity to particle dynamics in accelerators.
Silva, Nathália Buss da; Longhi, Daniel Angelo; Martins, Wiaslan Figueiredo; Laurindo, João Borges; Aragão, Gláucia Maria Falcão de; Carciofi, Bruno Augusto Mattar
2017-01-02
Lactic acid bacteria (LAB) are responsible for spoiling vacuum-packed meat products, such as ham. Since the temperature is the main factor affecting the microbial dynamic, the use of mathematical models describing the microbial behavior into a non-isothermal environment can be very useful for predicting food shelf life. In this study, the growth of Lactobacillus viridescens was measured in vacuum-packed sliced ham under non-isothermal conditions, and the predictive ability of primary (Baranyi and Roberts, 1994) and secondary (Square Root) models were assessed using parameters estimated in MRS culture medium under isothermal conditions (between 4 and 30°C). Fresh ham piece was sterilized, sliced, inoculated, vacuum-packed, and stored in a temperature-controlled incubator at five different non-isothermal conditions (between 4 and 25°C) and one isothermal condition (8°C). The mathematical models obtained in MRS medium were assessed by comparing predicted values with L. viridescens growth data in vacuum-packed ham. Its predictive ability was assessed through statistical indexes, with good results (bias factor between 0.95 and 1.03; accuracy factor between 1.04 and 1.07, and RMSE between 0.76 and 1.33), especially in increasing temperature, which predictions were safe. The model parameters obtained from isothermal growth data in MRS medium enabled to estimate the shelf life of a commercial ham under non-isothermal conditions in the temperature range analyzed. Copyright Â© 2016 Elsevier B.V. All rights reserved.
Performance Optimizing Adaptive Control with Time-Varying Reference Model Modification
Nguyen, Nhan T.; Hashemi, Kelley E.
2017-01-01
This paper presents a new adaptive control approach that involves a performance optimization objective. The control synthesis involves the design of a performance optimizing adaptive controller from a subset of control inputs. The resulting effect of the performance optimizing adaptive controller is to modify the initial reference model into a time-varying reference model which satisfies the performance optimization requirement obtained from an optimal control problem. The time-varying reference model modification is accomplished by the real-time solutions of the time-varying Riccati and Sylvester equations coupled with the least-squares parameter estimation of the sensitivities of the performance metric. The effectiveness of the proposed method is demonstrated by an application of maneuver load alleviation control for a flexible aircraft.
Modeling of Electricity Demand for Azerbaijan: Time-Varying Coefficient Cointegration Approach
Directory of Open Access Journals (Sweden)
Jeyhun I. Mikayilov
2017-11-01
Full Text Available Recent literature has shown that electricity demand elasticities may not be constant over time and this has investigated using time-varying estimation methods. As accurate modeling of electricity demand is very important in Azerbaijan, which is a transitional country facing significant change in its economic outlook, we analyze whether the response of electricity demand to income and price is varying over time in this economy. We employed the Time-Varying Coefficient cointegration approach, a cutting-edge time-varying estimation method. We find evidence that income elasticity demonstrates sizeable variation for the period of investigation ranging from 0.48% to 0.56%. The study has some useful policy implications related to the income and price aspects of the electricity consumption in Azerbaijan.
Energy Technology Data Exchange (ETDEWEB)
Vasileiadis, N.; Tatsios, G.; Misdanitis, S.; Valougeorgis, D., E-mail: diva@mie.uth.gr
2016-02-15
Highlights: • An integrated s/w for modeling complex rarefied gas distribution systems is presented. • Analysis is based on kinetic theory of gases. • Code effectiveness is demonstrated by simulating the ITER divertor pumping system. • The present s/w has the potential to support design work in large vacuum systems. - Abstract: An integrated software tool for modeling and simulation of complex gas distribution systems operating under any vacuum conditions is presented and validated. The algorithm structure includes (a) the input geometrical and operational data of the network, (b) the definition of the fundamental set of network loops and pseudoloops, (c) the formulation and solution of the mass and energy conservation equations, (d) the kinetic data base of the flow rates for channels of any length in the whole range of the Knudsen number, supporting, in an explicit manner, the solution of the conservation equations and (e) the network output data (mainly node pressures and channel flow rates/conductance). The code validity is benchmarked under rough vacuum conditions by comparison with hydrodynamic solutions in the slip regime. Then, its feasibility, effectiveness and potential are demonstrated by simulating the ITER torus vacuum system with the six direct pumps based on the 2012 design of the ITER divertor. Detailed results of the flow patterns and paths in the cassettes, in the gaps between the cassettes and along the divertor ring, as well as of the total throughput for various pumping scenarios and dome pressures are provided. A comparison with previous results available in the literature is included.
Directory of Open Access Journals (Sweden)
Sepehr Sadighi
2013-12-01
Full Text Available An artificial neural network (ANN and kinetic-based models for a pilot scale vacuum gas oil (VGO hydrocracking plant are presented in this paper. Reported experimental data in the literature were used to develop, train, and check these models. The proposed models are capable of predicting the yield of all main hydrocracking products including dry gas, light naphtha, heavy naphtha, kerosene, diesel, and unconverted VGO (residue. Results showed that kinetic-based and artificial neural models have specific capabilities to predict yield of hydrocracking products. The former is able to accurately predict the yield of lighter products, i.e. light naphtha, heavy naphtha and kerosene. However, ANN model is capable of predicting yields of diesel and residue with higher precision. The comparison shows that the ANN model is superior to the kinetic-base models. © 2013 BCREC UNDIP. All rights reservedReceived: 9th April 2013; Revised: 13rd August 2013; Accepted: 18th August 2013[How to Cite: Sadighi, S., Zahedi, G.R. (2013. Comparison of Kinetic-based and Artificial Neural Network Modeling Methods for a Pilot Scale Vacuum Gas Oil Hydrocracking Reactor. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (2: 125-136. (doi:10.9767/bcrec.8.2.4722.125-136][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.2.4722.125-136
National Research Council Canada - National Science Library
Barmpalia-Davis, Ioanna M; Geornaras, Ifigenia; Kendall, Patricia A; Sofos, John N
2008-01-01
Listeria monocytogenes counts were determined during storage (82 days, 4°C) in vacuum packages of inoculated bologna and salami slices and after exposure to a simulated dynamic model of the stomach and small intestine...
Modeling the Time-Varying Nature of Student Exceptionality Classification on Achievement Growth
Nese, Joseph F. T.; Stevens, Joseph J.; Schulte, Ann C.; Tindal, Gerald; Elliott, Stephen N.
2017-01-01
Our purpose was to examine different approaches to modeling the time-varying nature of exceptionality classification. Using longitudinal data from one state's mathematics achievement test for 28,829 students in Grades 3 to 8, we describe the reclassification rate within special education and between general and special education, and compare four…
Artificial neural network modeling of DDGS flowability with varying process and storage parameters
Neural Network (NN) modeling techniques were used to predict flowability behavior in distillers dried grains with solubles (DDGS) prepared with varying CDS (10, 15, and 20%, wb), drying temperature (100, 200, and 300°C), cooling temperature (-12, 0, and 35°C) and cooling time (0 and 1 month) levels....
Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia ...
Time-varying coefficient estimation in SURE models. Application to portfolio management
DEFF Research Database (Denmark)
Casas, Isabel; Ferreira, Eva; Orbe, Susan
This paper provides a detailed analysis of the asymptotic properties of a kernel estimator for a Seemingly Unrelated Regression Equations model with time-varying coefficients (tv-SURE) under very general conditions. Theoretical results together with a simulation study differentiates the cases for...
Schliep, E. M.; Gelfand, A. E.; Holland, D. M.
2015-12-01
There is considerable demand for accurate air quality information in human health analyses. The sparsity of ground monitoring stations across the United States motivates the need for advanced statistical models to predict air quality metrics, such as PM2.5, at unobserved sites. Remote sensing technologies have the potential to expand our knowledge of PM2.5 spatial patterns beyond what we can predict from current PM2.5 monitoring networks. Data from satellites have an additional advantage in not requiring extensive emission inventories necessary for most atmospheric models that have been used in earlier data fusion models for air pollution. Statistical models combining monitoring station data with satellite-obtained aerosol optical thickness (AOT), also referred to as aerosol optical depth (AOD), have been proposed in the literature with varying levels of success in predicting PM2.5. The benefit of using AOT is that satellites provide complete gridded spatial coverage. However, the challenges involved with using it in fusion models are (1) the correlation between the two data sources varies both in time and in space, (2) the data sources are temporally and spatially misaligned, and (3) there is extensive missingness in the monitoring data and also in the satellite data due to cloud cover. We propose a hierarchical autoregressive spatially varying coefficients model to jointly model the two data sources, which addresses the foregoing challenges. Additionally, we offer formal model comparison for competing models in terms of model fit and out of sample prediction of PM2.5. The models are applied to daily observations of PM2.5 and AOT in the summer months of 2013 across the conterminous United States. Most notably, during this time period, we find small in-sample improvement incorporating AOT into our autoregressive model but little out-of-sample predictive improvement.
Lan Liu; Ryan K. L. Ko; Guangming Ren; Xiaoping Xu
2017-01-01
As the adoption of Software Defined Networks (SDNs) grows, the security of SDN still has several unaddressed limitations. A key network security research area is in the study of malware propagation across the SDN-enabled networks. To analyze the spreading processes of network malware (e.g., viruses) in SDN, we propose a dynamic model with a time-varying community network, inspired by research models on the spread of epidemics in complex networks across communities. We assume subnets of the ne...
A hepatitis C virus infection model with time-varying drug effectiveness: solution and analysis.
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Jessica M Conway
2014-08-01
Full Text Available Simple models of therapy for viral diseases such as hepatitis C virus (HCV or human immunodeficiency virus assume that, once therapy is started, the drug has a constant effectiveness. More realistic models have assumed either that the drug effectiveness depends on the drug concentration or that the effectiveness varies over time. Here a previously introduced varying-effectiveness (VE model is studied mathematically in the context of HCV infection. We show that while the model is linear, it has no closed-form solution due to the time-varying nature of the effectiveness. We then show that the model can be transformed into a Bessel equation and derive an analytic solution in terms of modified Bessel functions, which are defined as infinite series, with time-varying arguments. Fitting the solution to data from HCV infected patients under therapy has yielded values for the parameters in the model. We show that for biologically realistic parameters, the predicted viral decay on therapy is generally biphasic and resembles that predicted by constant-effectiveness (CE models. We introduce a general method for determining the time at which the transition between decay phases occurs based on calculating the point of maximum curvature of the viral decay curve. For the parameter regimes of interest, we also find approximate solutions for the VE model and establish the asymptotic behavior of the system. We show that the rate of second phase decay is determined by the death rate of infected cells multiplied by the maximum effectiveness of therapy, whereas the rate of first phase decline depends on multiple parameters including the rate of increase of drug effectiveness with time.
Bayesian Forecasting of WWW Traffic on the Time Varying Poisson Model
Koizumi, Daiki; Matsushima, Toshiyasu; Hirasawa, Shigeichi
2009-01-01
Traffic forecasting from past observed traffic data with small calculation complexity is one of important problems for planning of servers and networks. Focusing on World Wide Web (WWW) traffic as fundamental investigation, this paper would deal with Bayesian forecasting of network traffic on the time varying Poisson model from a viewpoint from statistical decision theory. Under this model, we would show that the estimated forecasting value is obtained by simple arithmetic calculation and exp...
Xu, Hang; Greenland, Kasey; Bloswick, Donald; Zhao, Jie; Merryweather, Andrew
2017-05-24
The elevated vacuum suspension system (EVSS) has demonstrated unique health benefits for amputees, but the effect of vacuum pressure values on knee contact force (KCF) is still unclear. The objective of this study was to investigate the effect of vacuum levels on KCF for unilateral transtibial amputees (UTA) using the EVSS. Three-dimensional gait was modeled for 9 UTA with five vacuum levels (0-20inHg [67.73kPa], 5inHg [16.93kPa] increments) and 9 non-amputees based on kinematic and ground reaction force data. The results showed that the vacuum level effects were significant for peak axial KCF, which had a relatively large value at 0 and 20inHg (67.73kPa). The intact limb exhibited a comparable peak axial KCF to the non-amputees at 15inHg (50.79kPa). At moderate vacuum levels (5inHg [16.93kPa] to 15inHg [50.79kPa]), co-contraction of quadriceps and hamstrings at peak axial KCF was similar for the intact limb, but was smaller for the residual limb comparing with the non-amputees. The intact limb showed a similar magnitude of quadriceps and hamstrings force at 15inHg (50.79kPa) to the non-amputees, but the muscle coordination patterns varied between the residual and intact limbs. These findings indicate that a proper vacuum level may partially compensate for the lack of ankle plantarflexor and reduce the knee loading. Of the tested vacuum levels, 15inHg (50.79kPa) appears most favorable, although additional analyses with more amputees are suggested to confirm these results prior to establishing clinical guidelines. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Nikolova Maria
2017-01-01
Full Text Available The thermochemical treatments of tool steels improve the performance of the components with respect to surface hardness, wear and tribological performance as well as corrosion resistance. Compared to the conventional gas ferritic nitrocarburizing process, the original vacuum oxy-nitrocarburizing is a time-, cost-effective and environmentally-friendly gas process. Because of the oxidizing nature of the gas atmosphere, there is no need to perform subsequent post-oxidation.In this study, a vacuum oxynitrocarburizing process was carried out onto four tool steels (AISI H10, H11, H21 and D2 at 570 °C, after hardening and single tempering. The structural analysis of the compound and diffusion layers was performed by optical and electron microscopy, X-ray diffraction and glow discharge optical emission spectrometry (GDOES methods. A largely monophase ε- layer is formed with a carbon accumulation at the substrate adjacent area. The overlaying oxides adjacent to the ε-carbonitride phase contained Fe3O4 (magnetite as a main constituent. A thermodynamic modelling approach was also performed to understand and optimize the process. The “Equilib module” of FactSage software which uses Gibbs energy minimization method, was used to estimate the possible products during vacuum oxynitrocarburising process.
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Muzher M. Ibraheem
2013-05-01
Full Text Available The aim of this research is to study the kinetic reaction models for catalytic hydrogenation of aromatic content for Basrah crude oil (BCO and vacuum gas oil (VGO derived from Kirkuk crude oil which has the boiling point rang of (611-833K. This work is performed using a hydrodesulphurization (HDS pilot plant unit located in AL-Basil Company. A commercial (HDS catalyst cobalt-molybdenum (Co-Mo supported in alumina (γ-Al2O3 is used in this work. The feed is supplied by North Refinery Company in Baiji. The reaction temperatures range is (600-675 K over liquid hourly space velocity (LHSV range of (0.7-2hr-1 and hydrogen pressure is 3 MPa with H2/oil ratio of 300 of Basrah Crude oil (BCO, while the corresponding conditions for vacuum gas oil (VGO are (583-643 K, (1.5-3.75 hr-1, 3.5 MPa and 250 respectively . The results showed that the reaction kinetics is of second order for both types of feed. Activation energies are found to be 30.396, 38.479 kJ/mole for Basrah Crude Oil (BCO and Vacuum Gas Oil (VGO respectively.
Vacuum stability in U(1-prime extensions of the Standard Model with TeV scale right handed neutrinos
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Claudio Corianò
2014-11-01
Full Text Available We investigate a minimal U(1′ extension of the Standard Model with one extra complex scalar and generic gauge charge assignments. We use a type-I seesaw mechanism with three heavy right handed neutrinos to illustrate the constraints on the charges, on their mass and on the mixing angle of the two scalars, derived by requiring the vacuum stability of the scalar potential. We focus our study on a scenario which could be accessible at the LHC, by selecting a vacuum expectation value of the extra Higgs in the TeV range and determining the constraints that emerge in the parameter space. To illustrate the generality of the approach, specific gauge choices corresponding to U(1B−L, U(1R and U(1χ are separately analyzed. Our results are based on a modified expression of one of the β functions of the quartic couplings of the scalar potential compared to the previous literature. This is due to a change in the coefficient of the Yukawa term of the right handed neutrinos. Differently from previous analysis, we show that this coupling may destabilize the vacuum.
Modeling and Analysis of a Piezoelectric Energy Harvester with Varying Cross-Sectional Area
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Maiara Rosa
2014-01-01
Full Text Available This paper reports on the modeling and on the experimental verification of electromechanically coupled beams with varying cross-sectional area for piezoelectric energy harvesting. The governing equations are formulated using the Rayleigh-Ritz method and Euler-Bernoulli assumptions. A load resistance is considered in the electrical domain for the estimate of the electric power output of each geometric configuration. The model is first verified against the analytical results for a rectangular bimorph with tip mass reported in the literature. The experimental verification of the model is also reported for a tapered bimorph cantilever with tip mass. The effects of varying cross-sectional area and tip mass on the electromechanical behavior of piezoelectric energy harvesters are also discussed. An issue related to the estimation of the optimal load resistance (that gives the maximum power output on beam shape optimization problems is also discussed.
New Inference Procedures for Semiparametric Varying-Coefficient Partially Linear Cox Models
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Yunbei Ma
2014-01-01
Full Text Available In biomedical research, one major objective is to identify risk factors and study their risk impacts, as this identification can help clinicians to both properly make a decision and increase efficiency of treatments and resource allocation. A two-step penalized-based procedure is proposed to select linear regression coefficients for linear components and to identify significant nonparametric varying-coefficient functions for semiparametric varying-coefficient partially linear Cox models. It is shown that the penalized-based resulting estimators of the linear regression coefficients are asymptotically normal and have oracle properties, and the resulting estimators of the varying-coefficient functions have optimal convergence rates. A simulation study and an empirical example are presented for illustration.
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Pierre-Henri Chavanis
2013-01-01
Full Text Available We consider a cosmological model based on a quadratic equation of state (where is the Planck density and is the cosmological density “unifying” vacuum energy, radiation, and dark energy. For , it reduces to leading to a phase of early accelerated expansion (early inflation with a constant density equal to the Planck density g/m3 (vacuum energy. For , we recover the equation of state of radiation . For , we get leading to a phase of late accelerated expansion (late inflation with a constant density equal to the cosmological density g/m3 (dark energy. The temperature is determined by a generalized Stefan-Boltzmann law. We show a nice “symmetry” between the early universe (vacuum energy + radiation and the late universe (radiation + dark energy. In our model, they are described by two polytropic equations of state with index and respectively. Furthermore, the Planck density in the early universe plays a role similar to that of the cosmological density in the late universe. They represent fundamental upper and lower density bounds differing by 122 orders of magnitude. We add the contribution of baryonic matter and dark matter considered as independent species and obtain a simple cosmological model describing the whole evolution of the universe. We study the evolution of the scale factor, density, and temperature. This model gives the same results as the standard CDM model for , where is the Planck time and completes it by incorporating the phase of early inflation in a natural manner. Furthermore, this model does not present any singularity at and exists eternally in the past (although it may be incorrect to extrapolate the solution to the infinite past. Our study suggests that vacuum energy, radiation, and dark energy may be the manifestation of a unique form of “generalized radiation.” By contrast, the baryonic and dark matter components of the universe are treated as different species. This is at variance with usual models
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Hamada, Yuta [KEK Theory Center, IPNS, KEK, Tsukuba, Ibaraki (Japan); Yamada, Masatoshi [Kanazawa University, Institute for Theoretical Physics, Kanazawa (Japan)
2017-09-15
The null result in the LHC may indicate that the standard model is not drastically modified up to very high scales, such as the GUT/string scale. Having this in the mind, we suggest a novel leptogenesis scenario realized in the false vacuum of the Higgs field. If the Higgs field develops a large vacuum expectation value in the early universe, a lepton number violating process is enhanced, which we use for baryogenesis. To demonstrate the scenario, several models are discussed. For example, we show that the observed baryon asymmetry is successfully generated in the standard model with higher-dimensional operators. (orig.)
1974-01-01
This valve was used in the Intersecting Storage Rings (ISR) to protect against the shock waves that would be caused if air were to enter the vacuum tube. Some of the ISR chambers were very fragile, with very thin walls - a design required by physicists on the lookout for new particles.
Modelling time-varying volatility in the Indian stock returns: Some empirical evidence
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Trilochan Tripathy
2015-12-01
Full Text Available This paper models time-varying volatility in one of the Indian main stock markets, namely, the National Stock Exchange (NSE located in Mumbai, investigating whether it has been affected by the recent global financial crisis. A Chow test indicates the presence of a structural break. Both symmetric and asymmetric GARCH models suggest that the volatility of NSE returns is persistent and asymmetric and has increased as a result of the crisis. The model under the Generalized Error Distribution appears to be the most suitable one. However, its out-of-sample forecasting performance is relatively poor.
Fitting Social Network Models Using Varying Truncation Stochastic Approximation MCMC Algorithm
Jin, Ick Hoon
2013-10-01
The exponential random graph model (ERGM) plays a major role in social network analysis. However, parameter estimation for the ERGM is a hard problem due to the intractability of its normalizing constant and the model degeneracy. The existing algorithms, such as Monte Carlo maximum likelihood estimation (MCMLE) and stochastic approximation, often fail for this problem in the presence of model degeneracy. In this article, we introduce the varying truncation stochastic approximation Markov chain Monte Carlo (SAMCMC) algorithm to tackle this problem. The varying truncation mechanism enables the algorithm to choose an appropriate starting point and an appropriate gain factor sequence, and thus to produce a reasonable parameter estimate for the ERGM even in the presence of model degeneracy. The numerical results indicate that the varying truncation SAMCMC algorithm can significantly outperform the MCMLE and stochastic approximation algorithms: for degenerate ERGMs, MCMLE and stochastic approximation often fail to produce any reasonable parameter estimates, while SAMCMC can do; for nondegenerate ERGMs, SAMCMC can work as well as or better than MCMLE and stochastic approximation. The data and source codes used for this article are available online as supplementary materials. © 2013 American Statistical Association, Institute of Mathematical Statistics, and Interface Foundation of North America.
Modeling the time--varying subjective quality of HTTP video streams with rate adaptations.
Chen, Chao; Choi, Lark Kwon; de Veciana, Gustavo; Caramanis, Constantine; Heath, Robert W; Bovik, Alan C
2014-05-01
Newly developed hypertext transfer protocol (HTTP)-based video streaming technologies enable flexible rate-adaptation under varying channel conditions. Accurately predicting the users' quality of experience (QoE) for rate-adaptive HTTP video streams is thus critical to achieve efficiency. An important aspect of understanding and modeling QoE is predicting the up-to-the-moment subjective quality of a video as it is played, which is difficult due to hysteresis effects and nonlinearities in human behavioral responses. This paper presents a Hammerstein-Wiener model for predicting the time-varying subjective quality (TVSQ) of rate-adaptive videos. To collect data for model parameterization and validation, a database of longer duration videos with time-varying distortions was built and the TVSQs of the videos were measured in a large-scale subjective study. The proposed method is able to reliably predict the TVSQ of rate adaptive videos. Since the Hammerstein-Wiener model has a very simple structure, the proposed method is suitable for online TVSQ prediction in HTTP-based streaming.
Perperoglou, Aris
2016-12-10
Flexible survival models are in need when modelling data from long term follow-up studies. In many cases, the assumption of proportionality imposed by a Cox model will not be valid. Instead, a model that can identify time varying effects of fixed covariates can be used. Although there are several approaches that deal with this problem, it is not always straightforward how to choose which covariates should be modelled having time varying effects and which not. At the same time, it is up to the researcher to define appropriate time functions that describe the dynamic pattern of the effects. In this work, we suggest a model that can deal with both fixed and time varying effects and uses simple hypotheses tests to distinguish which covariates do have dynamic effects. The model is an extension of the parsimonious reduced rank model of rank 1. As such, the number of parameters is kept low, and thus, a flexible set of time functions, such as b-splines, can be used. The basic theory is illustrated along with an efficient fitting algorithm. The proposed method is applied to a dataset of breast cancer patients and compared with a multivariate fractional polynomials approach for modelling time-varying effects. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Multi-Step Time Series Forecasting with an Ensemble of Varied Length Mixture Models.
Ouyang, Yicun; Yin, Hujun
2017-11-13
Many real-world problems require modeling and forecasting of time series, such as weather temperature, electricity demand, stock prices and foreign exchange (FX) rates. Often, the tasks involve predicting over a long-term period, e.g. several weeks or months. Most existing time series models are inheritably for one-step prediction, that is, predicting one time point ahead. Multi-step or long-term prediction is difficult and challenging due to the lack of information and uncertainty or error accumulation. The main existing approaches, iterative and independent, either use one-step model recursively or treat the multi-step task as an independent model. They generally perform poorly in practical applications. In this paper, as an extension of the self-organizing mixture autoregressive (AR) model, the varied length mixture (VLM) models are proposed to model and forecast time series over multi-steps. The key idea is to preserve the dependencies between the time points within the prediction horizon. Training data are segmented to various lengths corresponding to various forecasting horizons, and the VLM models are trained in a self-organizing fashion on these segments to capture these dependencies in its component AR models of various predicting horizons. The VLM models form a probabilistic mixture of these varied length models. A combination of short and long VLM models and an ensemble of them are proposed to further enhance the prediction performance. The effectiveness of the proposed methods and their marked improvements over the existing methods are demonstrated through a number of experiments on synthetic data, real-world FX rates and weather temperatures.
A river water quality model for time varying BOD discharge concentration
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Oppenheimer Seth F.
1999-01-01
Full Text Available We consider a model for biochemical oxygen demand (BOD in a semi-infinite river where the BOD is prescribed by a time varying function at the left endpoint. That is, we study the problem with a time varying boundary loading. We obtain the well-posedness for the model when the boundary loading is smooth in time. We also obtain various qualitative results such as ordering, positivity, and boundedness. Of greatest interest, we show that a periodic loading function admits a unique asymptotically attracting periodic solution. For non-smooth loading functions, we obtain weak solutions. Finally, for certain special cases, we show how to obtain explicit solutions in the form of infinite series.
Zhou, Bang-Rong
2007-01-01
By means of a relativistic effective potential, we analytically research competition between the quark-antiquark condensates langlebar qqrangle and the diquark condensates langleqqrangle in vacuum in ground state of a two-flavor Nambu-Jona-Lasinio (NJL) model and obtain the GS-HS phase diagram, where GS and HS are the respective four-fermion coupling constants in scalar quark-antiquark channel and scalar color anti-triplet diquark channel. The results show that, in the chiral limit, there is only the pure langlebar qqrangle phase when GS/HS>2/3, and as GS/HS decreases to 2/3>GS/HS>=0 one will first have a coexistence phase of the condensates langlebar qqrangle and langleqqrangle and then a pure langleqqrangle phase. In non-zero bare quark mass case, the critical value of GS/HS at which the pure langlebar qqrangle phase will transfer to the coexistence phase of the condensates langlebar qqrangle and langleqqrangle will be less than 2/3. Our theoretical results, combined with present phenomenological fact that there is no diquark condensates in the vacuum of QCD, will also impose a real restriction to any given two-flavor NJL model which is intended to simulate QCD, i.e. in such model the resulting smallest ratio GS/HS after the Fierz transformations in the Hartree approximation must be larger than 2/3. A few phenomenological QCD-like NJL models are checked and analyzed.
Estimation and Properties of a Time-Varying GQARCH(1,1-M Model
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Sofia Anyfantaki
2011-01-01
analysis of these models computationally infeasible. This paper outlines the issues and suggests to employ a Markov chain Monte Carlo algorithm which allows the calculation of a classical estimator via the simulated EM algorithm or a simulated Bayesian solution in only ( computational operations, where is the sample size. Furthermore, the theoretical dynamic properties of a time-varying GQARCH(1,1-M are derived. We discuss them and apply the suggested Bayesian estimation to three major stock markets.
New LHC resonance with mass 750 GeV and the vacuum stability in the Standard Model
Das, C. R.; Laperashvili, L. V.; Nielsen, H. B.
2017-09-01
In the present talk we show that the correction to the Higgs mass coming from the bound state S of 6 t + 6 t̅ quarks, predicted early by C.D. Froggatt and ourselves, leads to the just borderline of the Standard Model vacuum stability thereby confirming the accuracy of the multiple point principle (principle of degenerate vacua), if a mass of the bound state S coincides with the mass 750 GeV of the new diphoton state recently observed by LHC.
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Gabriel Rodríguez
2016-06-01
Full Text Available Following Xu and Perron (2014, I applied the extended RLS model to the daily stock market returns of Argentina, Brazil, Chile, Mexico and Peru. This model replaces the constant probability of level shifts for the entire sample with varying probabilities that record periods with extremely negative returns. Furthermore, it incorporates a mean reversion mechanism with which the magnitude and the sign of the level shift component vary in accordance with past level shifts that deviate from the long-term mean. Therefore, four RLS models are estimated: the Basic RLS, the RLS with varying probabilities, the RLS with mean reversion, and a combined RLS model with mean reversion and varying probabilities. The results show that the estimated parameters are highly significant, especially that of the mean reversion model. An analysis of ARFIMA and GARCH models is also performed in the presence of level shifts, which shows that once these shifts are taken into account in the modeling, the long memory characteristics and GARCH effects disappear. Also, I find that the performance prediction of the RLS models is superior to the classic models involving long memory as the ARFIMA(p,d,q models, the GARCH and the FIGARCH models. The evidence indicates that except in rare exceptions, the RLS models (in all its variants are showing the best performance or belong to the 10% of the Model Confidence Set (MCS. On rare occasions the GARCH and the ARFIMA models appear to dominate but they are rare exceptions. When the volatility is measured by the squared returns, the great exception is Argentina where a dominance of GARCH and FIGARCH models is appreciated.
SEIR Model of Rumor Spreading in Online Social Network with Varying Total Population Size
Dong, Suyalatu; Deng, Yan-Bin; Huang, Yong-Chang
2017-10-01
Based on the infectious disease model with disease latency, this paper proposes a new model for the rumor spreading process in online social network. In this paper what we establish an SEIR rumor spreading model to describe the online social network with varying total number of users and user deactivation rate. We calculate the exact equilibrium points and reproduction number for this model. Furthermore, we perform the rumor spreading process in the online social network with increasing population size based on the original real world Facebook network. The simulation results indicate that the SEIR model of rumor spreading in online social network with changing total number of users can accurately reveal the inherent characteristics of rumor spreading process in online social network. Supported by National Natural Science Foundation of China under Grant Nos. 11275017 and 11173028
Gendron, Paul J
2017-04-01
A hierarchical Gaussian mixture model has been proposed to characterize sparse space-time varying shallow water acoustic response functions [Gendron, J. Acoust. Soc. Am. 139, 1923-1937 (2016)]. Considered here is an extension of this model to a uniform linear vertical array in order to provide an empirical validation of the mixture model for receivers of small aperture. An acoustic environment between source and moving receiver is predicated on a small proportion of relatively coherent paths obeying an ensemble frequency-angle-Doppler distribution. Provided are quantile-quantile plots of the discrete mixture model versus the empirical channel coefficients that lend credence to its use as a sparse model for acoustic response functions.
Using video modeling with substitutable loops to teach varied play to children with autism.
Dupere, Sally; MacDonald, Rebecca P F; Ahearn, William H
2013-01-01
Children with autism often engage in repetitive play with little variation in the actions performed or items used. This study examined the use of video modeling with scripted substitutable loops on children's pretend play with trained and untrained characters. Three young children with autism were shown a video model of scripted toy play that included a substitutable loop that allowed various characters to perform the same actions and vocalizations. Three characters were modeled with the substitutable loop during training sessions, and 3 additional characters were present in the video but never modeled. Following video modeling, all the participants incorporated untrained characters into their play, but the extent to which they did so varied. © Society for the Experimental Analysis of Behavior.
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Jamalludin Jamalludin
2012-05-01
Full Text Available Recently, vacuum frying flaky products have been popularly consumed by people as they have spesific characteristics, good taste, crispy, and crunchy. During vacuum frying process, heat and mass transfer simultanously occur. Heat transfer takes place from hot frying oil to the fruit, and water in the fruit comes out. At the same time, the fruit absobes oil. The objective of is this research to develop mathematical model of simultant heat and mass transfer during vacuum fruit frying. Sample of the research is jack fruit vacuumly fried in the temperature of 70-100 oC, duration of 15-60 minutes, and pressure of 13-23 kPa. The model includes changes of water, oil, extract, sukrose, reduction glucosa, and β-karoten content in product. The developed model is based on the one order simultan ordinary differential equation solved by Runge-Kutta numerical method. Simulation result showed that increasing temperature, decreasing water content, and oil absorbtion during the vacuum frying process describe that the developed mathematical model is good enough to explain simultanously heat and mass transfer phenomena during the process of vacuum fruit frying. ABSTRAK Saat ini produk keripik buah hasil proses penggorengan vakum sudah populer dikonsumsi oleh masyarakat, karena produk keripik buah mempunyai sifat yang khas, enak, gurih dan renyah jika dimakan. Selama proses penggorengan buah pada keadaan vakum, perpindahan panas dan massa terjadi secara simultan. Pepindahan panas dari minyak panas ke permukaan kemudian merambat ke dalam buah dan kandungan air di dalam buah keluar ke permukaan, pada saat yang bersamaan buah menyerap minyak. Penelitian ini bertujuan untuk mengembangkan model matematik perpindahan panas dan massa secara simultan pada penggorengan buah pada keadaan vakum. Sampel penelitian adalah buah nangka digoreng pada suhu 70-100 oC, lama penggorengan 15-60 menit dan tekanan vakum 13-23 kPa. Model meliputi perubahan kadar air, kadar minyak
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Wu Kun-Shan
2002-01-01
Full Text Available In this paper, an EOQ inventory model is depleted not only by time varying demand but also by Weibull distribution deterioration, in which the inventory is permitted to start with shortages and end without shortages. A theory is developed to obtain the optimal solution of the problem; it is then illustrated with the aid of several numerical examples. Moreover, we also assume that the holding cost is a continuous, non-negative and non-decreasing function of time in order to extend the EOQ model. Finally, sensitivity of the optimal solution to changes in the values of different system parameters is also studied.
Energy Technology Data Exchange (ETDEWEB)
Martinez, P., E-mail: pablomiguel.martinez@ciemat.es [CIEMAT-LNF (Laboratorio Nacional de Fusion), Madrid (Spain); Moreno, C. [CIEMAT-LNF (Laboratorio Nacional de Fusion), Madrid (Spain); Martinez, I. [SENER Ingenieria y Sistemas, Provenca 392, 4a 08025 Barcelona (Spain); Sedano, L. [CIEMAT-LNF (Laboratorio Nacional de Fusion), Madrid (Spain)
2012-08-15
The Permeator Against Vacuum (PAV) has been conceived as the simplest, cost effective and reliable technology system dedicated to tritium extraction from breeding liquid metals. An optimal design of a PAV requires a detailed hydraulic design optimization for established operational ranges (HCLL at low velocities of {approx}1 mm/s or DCLL in the ranges of tens of cm/s). The present work analyses the PAV extraction efficiency dependency on the design parameters as optimum on-line Tritium Extraction System (TES). Three different models have been built for that purpose: one through physically refined 1D tritium transport computation using TMAP7 (unique simulation tool with QA for ITER); and two further detailed models on 2D/3D FEM tool (COMSOL Multi-physics 4.0). The geometry used in this work is a simplification of Fuskite{sup Registered-Sign} conceptual design developed at CIEMAT, consisting of a set of cylindrical and concentric {alpha}-Fe double membranes enclosing a vacuumed space and in contact with in-pipe flowing LiPb eutectic. The aim of this paper is to give the first steps to establish the optimal design parameters of a PAV and evaluate the state-of-the-art of these models.
A behavioral asset pricing model with a time-varying second moment
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Chiarella, Carl [School of Finance and Economics, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007 (Australia)]. E-mail: carl.chiarella@uts.edu.au; He Xuezhong [School of Finance and Economics, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007 (Australia); Wang, Duo [LMAM, Department of Financial Mathematics, School of Mathematical Sciences, Peking University, Beijing 100871 (China)
2006-08-15
We develop a simple behavioral asset pricing model with fundamentalists and chartists in order to study price behavior in financial markets when chartists estimate both conditional mean and variance by using a weighted averaging process. Through a stability, bifurcation, and normal form analysis, the market impact of the weighting process and time-varying second moment are examined. It is found that the fundamental price becomes stable (unstable) when the activities from both types of traders are balanced (unbalanced). When the fundamental price becomes unstable, the weighting process leads to different price dynamics, depending on whether the chartists act as either trend followers or contrarians. It is also found that a time-varying second moment of the chartists does not change the stability of the fundamental price, but it does influence the stability of the bifurcations. The bifurcation becomes stable (unstable) when the chartists are more (less) concerned about the market risk characterized by the time-varying second moment. Different routes to complicated price dynamics are also observed. The analysis provides an analytical foundation for the statistical analysis of the corresponding stochastic version of this type of behavioral model.
Chen, Lihong; Wei, Fengying
2017-10-01
In this paper, the dynamics of a stochastic susceptible-infected-removed model in a population with varying size is investigated. We firstly show that the stochastic epidemic model has a unique global positive solution with any positive initial value. Then we verify that random perturbations lead to extinction when some conditions are being valid. Moreover, we prove that the solution of the stochastic epidemic model is persistent in the mean by building up a suitable Lyapunov function and using generalized Itô's formula. Further, the stochastic epidemic model admits a stationary distribution around the endemic equilibrium when parameters satisfy some sufficient conditions. To end this contribution and to check the validity of the main results, numerical simulations are separately carried out to illustrate these results.
Model-free adaptive fractional order control of stable linear time-varying systems.
Yakoub, Z; Amairi, M; Chetoui, M; Saidi, B; Aoun, M
2017-03-01
This paper presents a new model-free adaptive fractional order control approach for linear time-varying systems. An online algorithm is proposed to determine some frequency characteristics using a selective filtering and to design a fractional PID controller based on the numerical optimization of the frequency-domain criterion. When the system parameters are time-varying, the controller is updated to keep the same desired performances. The main advantage of the proposed approach is that the controller design depends only on the measured input and output signals of the process. The effectiveness of the proposed method is assessed through a numerical example. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Schaefer, Jacob; Hanson, Curt; Johnson, Marcus A.; Nguyen, Nhan
2011-01-01
Three model reference adaptive controllers (MRAC) with varying levels of complexity were evaluated on a high performance jet aircraft and compared along with a baseline nonlinear dynamic inversion controller. The handling qualities and performance of the controllers were examined during failure conditions that induce coupling between the pitch and roll axes. Results from flight tests showed with a roll to pitch input coupling failure, the handling qualities went from Level 2 with the baseline controller to Level 1 with the most complex MRAC tested. A failure scenario with the left stabilator frozen also showed improvement with the MRAC. Improvement in performance and handling qualities was generally seen as complexity was incrementally added; however, added complexity usually corresponds to increased verification and validation effort required for certification. The tradeoff between complexity and performance is thus important to a controls system designer when implementing an adaptive controller on an aircraft. This paper investigates this relation through flight testing of several controllers of vary complexity.
Spectrum Sensing Based on Censored Observations in Time-Varying Channels using AR-1 Model
Directory of Open Access Journals (Sweden)
Dhaval K Patel
2015-01-01
Full Text Available Non-parametric sensing algorithms are preferred in cognitive radio. In this paper, spectrum sensing method based on censored observations is proposed. We evaluate the performance of Censored Anderson-Darling (CAD sensing method in time-varying and flat-fading channel using Monte Carlo simulations. We have shown the performance of the CAD sensing in terms of receiver operating characteristic (ROC. The considered channel is modeled by Gaussian variables and characterized by a first ordered autoregressive process ($AR1$. It is shown that the proposed method outperforms prevailing techniques such as the Energy detection (ED sensing and Order-statistic (OS based sensing in time-varying channel at lower signal to noise ratio.
A boundary element model for diffraction of water waves on varying water depth
Energy Technology Data Exchange (ETDEWEB)
Poulin, Sanne
1997-12-31
In this thesis a boundary element model for calculating diffraction of water waves on varying water depth is presented. The varying water depth is approximated with a perturbed constant depth in the mild-slope wave equation. By doing this, the domain integral which is a result of the varying depth is no longer a function of the unknown wave potential but only a function of position and the constant depth wave potential. The number of unknowns is the resulting system of equations is thus reduced significantly. The integration procedures in the model are tested very thoroughly and it is found that a combination of analytical integration in the singular region and standard numerical integration outside works very well. The gradient of the wave potential is evaluated successfully using a hypersingular integral equation. Deviations from the analytical solution are only found on the boundary or very close to, but these deviations have no significant influence on the accuracy of the solution. The domain integral is evaluated using the dual reciprocity method. The results are compared with a direct integration of the integral, and the accuracy is quite satisfactory. The problem with irregular frequencies is taken care of by the CBIEM (or CHIEF-method) together with a singular value decomposition technique. This method is simple to implement and works very well. The model is verified using Homma`s island as a test case. The test cases are limited to shallow water since the analytical solution is only valid in this region. Several depth ratios are examined, and it is found that the accuracy of the model increases with increasing wave period and decreasing depth ratio. Short waves, e.g. wind generated waves, can allow depth variations up to approximately 2 before the error exceeds 10%, while long waves can allow larger depth ratios. It is concluded that the perturbation idea is highly usable. A study of (partially) absorbing boundary conditions is also conducted. (EG)
Changing Dynamics : Time-Varying Autoregressive Models Using Generalized Additive Modeling
Bringmann, L.F.; Hamaker, E.L.; Vigo, D.E.; Aubert, A.; Borsboom, D.; Tuerlinckx, F.
In psychology, the use of intensive longitudinal data has steeply increased during the past decade. As a result, studying temporal dependencies in such data with autoregressive modeling is becoming common practice. However, standard autoregressive models are often suboptimal as they assume that
1997-01-01
Under a Space Act Agreement between the Kirby company and Lewis Research Center, NASA technology was applied to a commercial vacuum cleaner product line. Kirby engineers were interested in advanced operational concepts, such as particle flow behavior and vibration, critical factors to improve vacuum cleaner performance. An evaluation of the company 1994 home care system, the Kirby G4, led to the refinement of the new G5 and future models. Under the cooperative agreement, Kirby had access to Lewis' holography equipment, which added insight into how long a vacuum cleaner fan would perform, as well as advanced computer software that can simulate the flow of air through fans. The collaboration resulted in several successes including fan blade redesign and continuing dialogue on how to improve air-flow traits in various nozzle designs.
Specification and testing of Multiplicative Time-Varying GARCH models with applications
DEFF Research Database (Denmark)
Amado, Cristina; Teräsvirta, Timo
2017-01-01
In this article, we develop a specification technique for building multiplicative time-varying GARCH models of Amado and Teräsvirta (2008, 2013). The variance is decomposed into an unconditional and a conditional component such that the unconditional variance component is allowed to evolve smoothly...... over time. This nonstationary component is defined as a linear combination of logistic transition functions with time as the transition variable. The appropriate number of transition functions is determined by a sequence of specification tests. For that purpose, a coherent modelling strategy based...... on statistical inference is presented. It is heavily dependent on Lagrange multiplier type misspecification tests. The tests are easily implemented as they are entirely based on auxiliary regressions. Finite-sample properties of the strategy and tests are examined by simulation. The modelling strategy...
Lebedev, Dmitry V; Steil, Jochen J; Ritter, Helge J
2005-04-01
We introduce a new type of neural network--the dynamic wave expansion neural network (DWENN)--for path generation in a dynamic environment for both mobile robots and robotic manipulators. Our model is parameter-free, computationally efficient, and its complexity does not explicitly depend on the dimensionality of the configuration space. We give a review of existing neural networks for trajectory generation in a time-varying domain, which are compared to the presented model. We demonstrate several representative simulative comparisons as well as the results of long-run comparisons in a number of randomly-generated scenes, which reveal that the proposed model yields dominantly shorter paths, especially in highly-dynamic environments.
Estimation of Bid Curves in Power Exchanges using Time-varying Simultaneous-Equations Models
Ofuji, Kenta; Yamaguchi, Nobuyuki
Simultaneous-equations model (SEM) is generally used in economics to estimate interdependent endogenous variables such as price and quantity in a competitive, equilibrium market. In this paper, we have attempted to apply SEM to JEPX (Japan Electric Power eXchange) spot market, a single-price auction market, using the publicly available data of selling and buying bid volumes, system price and traded quantity. The aim of this analysis is to understand the magnitude of influences to the auctioned prices and quantity from the selling and buying bids, than to forecast prices and quantity for risk management purposes. In comparison with the Ordinary Least Squares (OLS) estimation where the estimation results represent average values that are independent of time, we employ a time-varying simultaneous-equations model (TV-SEM) to capture structural changes inherent in those influences, using State Space models with Kalman filter stepwise estimation. The results showed that the buying bid volumes has that highest magnitude of influences among the factors considered, exhibiting time-dependent changes, ranging as broad as about 240% of its average. The slope of the supply curve also varies across time, implying the elastic property of the supply commodity, while the demand curve remains comparatively inelastic and stable over time.
Performance of growth mixture models in the presence of time-varying covariates.
Diallo, Thierno M O; Morin, Alexandre J S; Lu, HuiZhong
2017-10-01
Growth mixture modeling is often used to identify unobserved heterogeneity in populations. Despite the usefulness of growth mixture modeling in practice, little is known about the performance of this data analysis technique in the presence of time-varying covariates. In the present simulation study, we examined the impacts of five design factors: the proportion of the total variance of the outcome explained by the time-varying covariates, the number of time points, the error structure, the sample size, and the mixing ratio. More precisely, we examined the impact of these factors on the accuracy of parameter and standard error estimates, as well as on the class enumeration accuracy. Our results showed that the consistent Akaike information criterion (CAIC), the sample-size-adjusted CAIC (SCAIC), the Bayesian information criterion (BIC), and the integrated completed likelihood criterion (ICL-BIC) proved to be highly reliable indicators of the true number of latent classes in the data, across design conditions, and that the sample-size-adjusted BIC (SBIC) also proved quite accurate, especially in larger samples. In contrast, the Akaike information criterion (AIC), the entropy, the normalized entropy criterion (NEC), and the classification likelihood criterion (CLC) proved to be unreliable indicators of the true number of latent classes in the data. Our results also showed that substantial biases in the parameter and standard error estimates tended to be associated with growth mixture models that included only four time points.
Effects of varying microbial distributions when modelling pore-scale biodegradation
Schmidt, S. I.; Picioreanu, C.; Mackay, R.; Thullner, M.; Kreft, J. U.
2012-04-01
We have developed a numerical model to study the impact of single cell processes and micro-scale heterogeneities on biodegradation in contaminated aquifers on the pore level (pore of 1 mm length). The model is able to consider the spatial distribution of solutes along the length and width of the pore and of individual microbial cells and cell clusters along the pore wall. The model was applied to study biodegradation of easily degradable substances as well as of more refractory contaminants. The interplay between total biomass (varying from 100,000 to 10,000,000 cells/cm3), cell distribution (biomass distributed homogeneously, as a film along the wall, or clustered in two colonies with various distance), and flow rate (between 0.1 and 7 m/d) was tested. First results indicated that scenarios where the inflow concentration was smaller than approximately 5 times the Monod half-saturation constant, degradation varied considerably (up to 50 percent points) between the different microbial distribution types tested. At higher inflow concentration, extent of degradation depended only on the biomass density, not cell distribution. We conclude that depending on how the biomass is distributed, especially for the easier-to-degrade substances, micro-scale distribution of degrader cells matters.
National Aeronautics and Space Administration — The overall goal of the project is to develop reliable reduced order modeling technologies to automatically generate nonlinear, parameter-varying (PV),...
A Test of the Adaptive Market Hypothesis using a Time-Varying AR Model in Japan
Akihiko Noda
2012-01-01
This study examines the adaptive market hypothesis (AMH) in Japanese stock markets (TOPIX and TSE2). In particular, we measure the degree of market efficiency by using a time-varying model approach. The empirical results show that (1) the degree of market efficiency changes over time in the two markets, (2) the level of market efficiency of the TSE2 is lower than that of the TOPIX in most periods, and (3) the market efficiency of the TOPIX has evolved, but that of the TSE2 has not. We conclud...
Directory of Open Access Journals (Sweden)
Lili Jiang
2010-04-01
Full Text Available Escherichia coli chemotactic motion in spatiotemporally varying environments is studied by using a computational model based on a coarse-grained description of the intracellular signaling pathway dynamics. We find that the cell's chemotaxis drift velocity v(d is a constant in an exponential attractant concentration gradient [L] proportional, variantexp(Gx. v(d depends linearly on the exponential gradient G before it saturates when G is larger than a critical value G(C. We find that G(C is determined by the intracellular adaptation rate k(R with a simple scaling law: G(C infinity k(1/2(R. The linear dependence of v(d on G = d(ln[L]/dx directly demonstrates E. coli's ability in sensing the derivative of the logarithmic attractant concentration. The existence of the limiting gradient G(C and its scaling with k(R are explained by the underlying intracellular adaptation dynamics and the flagellar motor response characteristics. For individual cells, we find that the overall average run length in an exponential gradient is longer than that in a homogeneous environment, which is caused by the constant kinase activity shift (decrease. The forward runs (up the gradient are longer than the backward runs, as expected; and depending on the exact gradient, the (shorter backward runs can be comparable to runs in a spatially homogeneous environment, consistent with previous experiments. In (spatial ligand gradients that also vary in time, the chemotaxis motion is damped as the frequency omega of the time-varying spatial gradient becomes faster than a critical value omega(c, which is controlled by the cell's chemotaxis adaptation rate k(R. Finally, our model, with no adjustable parameters, agrees quantitatively with the classical capillary assay experiments where the attractant concentration changes both in space and time. Our model can thus be used to study E. coli chemotaxis behavior in arbitrary spatiotemporally varying environments. Further experiments are
Model and simulation of a vacuum sieve tray for T extraction from liquid PbLi breeding blankets
Energy Technology Data Exchange (ETDEWEB)
Mertens, M.A.J., E-mail: merlijn.mertens@ugent.be [Ghent University, Department of Materials Science and Engineering, Center of Molecular Modeling, Technologiepark 903, B-9052 Zwijnaarde (Belgium); Demange, D., E-mail: david.demange@kit.edu [Karlsruhe Institute of Technology, Institute for Technical Physics, Tritium Laboratory Karlsruhe, Hermann-von-Helmholtz Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Frances, L., E-mail: laetitia.frances@kit.edu [Karlsruhe Institute of Technology, Institute for Technical Physics, Tritium Laboratory Karlsruhe, Hermann-von-Helmholtz Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)
2016-11-15
Highlights: • A simulation tool was developed to analyse, optimise and scale up VST set-ups. • This tool predicts that efficiencies higher than 90% can be reached. • Upscaling to DEMO breeding blanket flow rates results in feasibly sized designs. - Abstract: Tritium self-sufficiency within a nuclear fusion reactor is necessary to demonstrate nuclear fusion as a viable source of energy. Tritium can be produced within liquid eutectic PbLi but then has to be extracted to be refuelled to the plasma. The vacuum sieve tray (VST) method is based on the extraction of tritium from millimetre-scaled oscillating PbLi droplets falling inside a vacuum chamber. A simulation tool was developed describing the fluid dynamics occurring along the PbLi flow and was used to study the influence of the different geometrical and operational parameters on the VST performance. The simulation predicts that extraction efficiencies over 90% can be easily reached according to theory and previous experimental results. The size of the VST extraction unit for a fusion reactor is estimated based on the findings from our single-nozzle model and assuming no T reabsorption. It is found to be in the feasible range. Nevertheless, two approaches are discussed which may further reduce this size by up to 90%. The simulation tool proved to be an easy and powerful way to analyse and optimise VST set-ups at any scale.
A time-varying subjective quality model for mobile streaming videos with stalling events
Ghadiyaram, Deepti; Pan, Janice; Bovik, Alan C.
2015-09-01
Over-the-top mobile video streaming is invariably influenced by volatile network conditions which cause playback interruptions (stalling events), thereby impairing users' quality of experience (QoE). Developing models that can accurately predict users' QoE could enable the more efficient design of quality-control protocols for video streaming networks that reduce network operational costs while still delivering high-quality video content to the customers. Existing objective models that predict QoE are based on global video features, such as the number of stall events and their lengths, and are trained and validated on a small pool of ad hoc video datasets, most of which are not publicly available. The model we propose in this work goes beyond previous models as it also accounts for the fundamental effect that a viewer's recent level of satisfaction or dissatisfaction has on their overall viewing experience. In other words, the proposed model accounts for and adapts to the recency, or hysteresis effect caused by a stall event in addition to accounting for the lengths, frequency of occurrence, and the positions of stall events - factors that interact in a complex way to affect a user's QoE. On the recently introduced LIVE-Avvasi Mobile Video Database, which consists of 180 distorted videos of varied content that are afflicted solely with over 25 unique realistic stalling events, we trained and validated our model to accurately predict the QoE, attaining standout QoE prediction performance.
AST: Activity-Security-Trust driven modeling of time varying networks.
Wang, Jian; Xu, Jiake; Liu, Yanheng; Deng, Weiwen
2016-02-18
Network modeling is a flexible mathematical structure that enables to identify statistical regularities and structural principles hidden in complex systems. The majority of recent driving forces in modeling complex networks are originated from activity, in which an activity potential of a time invariant function is introduced to identify agents' interactions and to construct an activity-driven model. However, the new-emerging network evolutions are already deeply coupled with not only the explicit factors (e.g. activity) but also the implicit considerations (e.g. security and trust), so more intrinsic driving forces behind should be integrated into the modeling of time varying networks. The agents undoubtedly seek to build a time-dependent trade-off among activity, security, and trust in generating a new connection to another. Thus, we reasonably propose the Activity-Security-Trust (AST) driven model through synthetically considering the explicit and implicit driving forces (e.g. activity, security, and trust) underlying the decision process. AST-driven model facilitates to more accurately capture highly dynamical network behaviors and figure out the complex evolution process, allowing a profound understanding of the effects of security and trust in driving network evolution, and improving the biases induced by only involving activity representations in analyzing the dynamical processes.
Directory of Open Access Journals (Sweden)
Jorge A. Orrego-Ruiz
2014-06-01
Full Text Available In this work, prediction models of Saturates, Aromatics, Resins and Asphaltenes fractions (SARA from thirty-seven vacuum residues of representative Colombian crudes and eighteen fractions of molecular distillation process were obtained. Mid-Infrared (MIR Attenuated Total Reflection (ATR spectroscopy in combination with partial least squares (PLS regression analysis was used to estimate accurately SARA analysis in these kind of samples. Calibration coefficients of prediction models were for saturates, aromatics, resins and asphaltenes fractions, 0.99, 0.96, 0.97 and 0.99, respectively. This methodology permits to control the molecular distillation process since small differences in chemical composition can be detected. Total time elapsed to give the SARA analysis per sample is 10 minutes.
Stojkovic, D B
2001-01-01
In this thesis we explore different field theory models containing massive neutrinos. We analyze the theoretical background of neutrino masses and mixings and consequences for the zero mode and vacuum structures of the standard model and its various extensions. We first consider the most general neutrino masses and mixings including Dirac mass terms, MD, as well as right- and left-handed Majorana masses, MR and ML. We show that for three generations, diagonalization of the Hamiltonian to obtain the propagating eigenstates in the general case requires diagonalization of a 12 x 12 Hermitian matrix, rather than the traditional 6 x 6 symmetric mass matrix. Although the standard “see-saw” mechanism remains valid, and the eigenvalues obtained are identical to the standard ones, the correct description of diagonalization and mixing is more complicated. The analogs of the CKM matrix for the light and the heavy neutrinos need not to be unitary, enriching the opportunities for CP violation in the fu...
Thermally driven classical Heisenberg model in 1D with a local time varying field
Bagchi, Debarshee
2013-12-01
We study thermal transport in the one-dimensional classical Heisenberg model driven by boundary heat baths and in the presence of a local time varying magnetic field. We find that, in the steady state, the energy current shows thermal resonance as the frequency of the time-periodic forcing is varied. Even in the absence of a thermal bias a steady nonzero energy current can be induced in the system, whereas for the thermally driven system a current reversal can be achieved in the bulk by suitably tuning the system parameters. When the amplitude of the forcing field is increased the system exhibits multiple resonance peaks. Thermal resonance survives in the thermodynamic limit and their magnitude increases as the temperature of the system is decreased. We find that the resonance frequency is an intrinsic frequency of the model and is related to its spin wave dispersion spectrum. Finally we show that, similar to other generic force-driven systems, there is no thermal pumping despite the current reversal in the bulk of the system.
Models of quality-adjusted life years when health varies over time
DEFF Research Database (Denmark)
Hansen, Kristian Schultz; Østerdal, Lars Peter Raahave
2006-01-01
time tradeoff (TTO) and standard gamble (SG) scores. We investigate deterministic and probabilistic models and consider five different families of discounting functions in all. The second part of the paper discusses four issues recurrently debated in the literature. This discussion includes questioning...... the SG method as the gold standard for estimation of the health state index, reexamining the role of the constantproportional tradeoff condition, revisiting the problem of double discounting of QALYs, and suggesting that it is not a matter of choosing between TTO and SG procedures as the combination...... of these two can be used to disentangle risk aversion from discounting. We find that caution must be taken when drawing conclusions from models with chronic health states to situations where health varies over time. One notable difference is that in the former case, risk aversion may be indistinguishable from...
Models of Quality-Adjusted Life Years when Health varies over Time: Survey and Analysis
DEFF Research Database (Denmark)
Hansen, Kristian Schultz; Østerdal, Lars Peter
2006-01-01
time trade-off (TTO) and standard gamble (SG) scores. We investigate deterministic and probabilistic models and consider five different families of discounting functions in all. This discussion includes questioning the SG method as the gold standard of the health state index, re-examining the role...... of the constant-proportional trade-off condition, revisiting the problem of double discounting of QALYs, and suggesting that it is not a matter of choosing between TTO and SG procedures as the combination of these two can be used to disentangle risk aversion from discounting. We find that caution must be taken...... when drawing conclusions from models with chronic health states to situations where health varies over time. One notable difference is that in the former case, risk aversion may be indistinguishable from discounting....
Comparison of Constant-Posture Force-Varying EMG-Force Dynamic Models About the Elbow.
Dai, Chenyun; Bardizbanian, Berj; Clancy, Edward A
2017-09-01
Numerous techniques have been used to minimize error in relating the surface electromyogram (EMG) to elbow joint torque. We compare the use of three techniques to further reduce error. First, most EMG-torque models only use estimates of EMG standard deviation as inputs. We studied the additional features of average waveform length, slope sign change rate and zero crossing rate. Second, multiple channels of EMG from the biceps, and separately from the triceps, have been combined to produce two low-variance model inputs. We contrasted this channel combination with using each EMG separately. Third, we previously modeled nonlinearity in the EMG-torque relationship via a polynomial. We contrasted our model versus that of the classic exponential power law of Vredenbregt and Rau (1973). Results from 65 subjects performing constant-posture, force-varying contraction gave a "baseline" comparison error (i.e., error with none of the new techniques) of 5.5 ± 2.3% maximum flexion voluntary contraction (%MVC F ). Combining the techniques of multiple features with individual channels reduced error to 4.8 ± 2.2 %MVC F , while combining individual channels with the power-law model reduced error to 4.7 ± 2.0 %MVC F . The new techniques further reduced error from that of the baseline by ≈ 15 %.
Almirall, Daniel; Griffin, Beth Ann; McCaffrey, Daniel F.; Ramchand, Rajeev; Yuen, Robert A.; Murphy, Susan A.
2014-01-01
This article considers the problem of examining time-varying causal effect moderation using observational, longitudinal data in which treatment, candidate moderators, and possible confounders are time varying. The structural nested mean model (SNMM) is used to specify the moderated time-varying causal effects of interest in a conditional mean model for a continuous response given time-varying treatments and moderators. We present an easy-to-use estimator of the SNMM that combines an existing regression-with-residuals (RR) approach with an inverse-probability-of-treatment weighting (IPTW) strategy. The RR approach has been shown to identify the moderated time-varying causal effects if the time-varying moderators are also the sole time-varying confounders. The proposed IPTW+RR approach provides estimators of the moderated time-varying causal effects in the SNMM in the presence of an additional, auxiliary set of known and measured time-varying confounders. We use a small simulation experiment to compare IPTW+RR versus the traditional regression approach and to compare small and large sample properties of asymptotic versus bootstrap estimators of the standard errors for the IPTW+RR approach. This article clarifies the distinction between time-varying moderators and time-varying confounders. We illustrate the methodology in a case study to assess if time-varying substance use moderates treatment effects on future substance use. PMID:23873437
Directory of Open Access Journals (Sweden)
Bubnov A.F.
2016-01-01
Full Text Available In this paper, we consider vacuum polarization effects in the model of charged fermions with anomalous magnetic moment and axial-vector interaction term in a uniform magnetic field. Nontrivial orrections to the effective Lagrangian from the anomalous moment and axial-vector term are calculated with account for various configurations of parameters of the model.
Charbonneau, Jeremy
As the perceived quality of a product is becoming more important in the manufacturing industry, more emphasis is being placed on accurately predicting the sound quality of everyday objects. This study was undertaken to improve upon current prediction techniques with regard to the psychoacoustic descriptor of loudness and an improved binaural summation technique. The feasibility of this project was first investigated through a loudness matching experiment involving thirty-one subjects and pure tones of constant sound pressure level. A dependence of binaural summation on frequency was observed which had previously not been a subject of investigation in the reviewed literature. A follow-up investigation was carried out with forty-eight volunteers and pure tones of constant sensation level. Contrary to existing theories in literature the resulting loudness matches revealed an amplitude versus frequency relationship which confirmed the perceived increase in loudness when a signal was presented to both ears simultaneously as opposed to one ear alone. The resulting trend strongly indicated that the higher the frequency of the presented signal, the greater the increase in observed binaural summation. The results from each investigation were summarized into a single binaural summation algorithm and inserted into an improved time-varying loudness model. Using experimental techniques, it was demonstrated that the updated binaural summation algorithm was a considerable improvement over the state of the art approach for predicting the perceived binaural loudness. The improved function retained the ease of use from the original model while additionally providing accurate estimates of diotic listening conditions from monaural WAV files. It was clearly demonstrated using a validation jury test that the revised time-varying loudness model was a significant improvement over the previously standardized approach.
SILICON REFINING BY VACUUM TREATMENT
Directory of Open Access Journals (Sweden)
André Alexandrino Lotto
2014-12-01
Full Text Available This work aims to investigate the phosphorus removal by vacuum from metallurgical grade silicon (MGSi (98.5% to 99% Si. Melting experiments were carried out in a vacuum induction furnace, varying parameters such as temperature, time and relation area exposed to the vacuum / volume of molten silicon. The results of chemical analysis were obtained by inductively coupled plasma (ICP, and evaluated based on thermodynamic and kinetic aspects of the reaction of vaporization of the phosphorus in the silicon. The phosphorus was decreased from 33 to approximately 1.5 ppm after three hours of vacuum treatment, concluding that the evaporation step is the controlling step of the process for parameters of temperature, pressure and agitation used and refining by this process is technically feasible.
A Bayesian probit model with spatially varying coefficients for brain decoding using fMRI data.
Zhang, Fengqing; Jiang, Wenxin; Wong, Patrick; Wang, Ji-Ping
2016-10-30
Recent advances in human neuroimaging have shown that it is possible to accurately decode how the brain perceives information based only on non-invasive functional magnetic resonance imaging measurements of brain activity. Two commonly used statistical approaches, namely, univariate analysis and multivariate pattern analysis often lead to distinct patterns of selected voxels. One current debate in brain decoding concerns whether the brain's representation of sound categories is localized or distributed. We hypothesize that the distributed pattern of voxels selected by most multivariate pattern analysis models can be an artifact due to the spatial correlation among voxels. Here, we propose a Bayesian spatially varying coefficient model, where the spatial correlation is modeled through the variance-covariance matrix of the model coefficients. Combined with a proposed region selection strategy, we demonstrate that our approach is effective in identifying the truly localized patterns of the voxels while maintaining robustness to discover truly distributed pattern. In addition, we show that localized or clustered patterns can be artificially identified as distributed if without proper usage of the spatial correlation information in fMRI data. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Directory of Open Access Journals (Sweden)
Lan Liu
2017-01-01
Full Text Available As the adoption of Software Defined Networks (SDNs grows, the security of SDN still has several unaddressed limitations. A key network security research area is in the study of malware propagation across the SDN-enabled networks. To analyze the spreading processes of network malware (e.g., viruses in SDN, we propose a dynamic model with a time-varying community network, inspired by research models on the spread of epidemics in complex networks across communities. We assume subnets of the network as communities and links that are dense in subnets but sparse between subnets. Using numerical simulation and theoretical analysis, we find that the efficiency of network malware propagation in this model depends on the mobility rate q of the nodes between subnets. We also find that there exists a mobility rate threshold qc. The network malware will spread in the SDN when the mobility rate q>qc. The malware will survive when q>qc and perish when q
Toy Models of Universe with an Effective Varying Λ-Term in Lyra Manifold
Directory of Open Access Journals (Sweden)
Martiros Khurshudyan
2015-01-01
Full Text Available Research on the accelerated expansion of our Universe captures a lot of attention. The dark energy (DE is a way to explain it. In this paper we will consider scalar field quintessence DE with ωDE>-1 EoS, where the dynamics of the DE models related to the dynamics of the scalar field. We are interested in the study of the behavior of the Universe in the presence of interacting quintessence DE models in Lyra manifold with a varying Λt. In a considered framework we also would like to propose a new form for Λt. We found that the models correspond to the transit Universe, which will enter the accelerated expansion phase and will remain there with a constant deceleration parameter q. We found also that the Λt is a decreasing function which takes a small positive value with Ωm≠0 and ΩQ→const dominating Ωm in the old Universe. Observational constraints are applied and causality issue via CS2 is discussed as a possible way to either reject or accept the models.
Using the power balance model to simulate cross-country skiing on varying terrain.
Moxnes, John F; Sandbakk, Oyvind; Hausken, Kjell
2014-01-01
The current study adapts the power balance model to simulate cross-country skiing on varying terrain. We assumed that the skier's locomotive power at a self-chosen pace is a function of speed, which is impacted by friction, incline, air drag, and mass. An elite male skier's position along the track during ski skating was simulated and compared with his experimental data. As input values in the model, air drag and friction were estimated from the literature based on the skier's mass, snow conditions, and speed. We regard the fit as good, since the difference in racing time between simulations and measurements was 2 seconds of the 815 seconds racing time, with acceptable fit both in uphill and downhill terrain. Using this model, we estimated the influence of changes in various factors such as air drag, friction, and body mass on performance. In conclusion, the power balance model with locomotive power as a function of speed was found to be a valid tool for analyzing performance in cross-country skiing.
Bachnas A.A.; Toth R.; Ludlage J.H.A.; Mesbah A.
2014-01-01
Model-based control strategies are widely used for optimal operation of chemical processes to respond to the increasing performance demands in the chemical industry. Yet, obtaining accurate models to describe the inherently nonlinear, time-varying dynamics of chemical processes remains a challenge in most model-based control applications. This paper reviews data-driven, Linear Parameter-Varying (LPV) modeling approaches for process systems by exploring and comparing various identification met...
Directory of Open Access Journals (Sweden)
Jian Liu
2015-09-01
Full Text Available Liquid–solid extrusion directly following vacuum infiltration (LSEVI is an infiltration–extrusion integrated forming technique, and transverse weld between upper residual magnesium alloy and magnesium matrix composites is a common internal defect, which can severely reduce the yield of composite products. To improve current understanding on the mechanism of transverse welding phenomenon, a thermo-mechanical numerical model of LSEVI for magnesium matrix composites was developed. The formation of transverse weld during extrusion was visualized using finite element simulation method, and the formation mechanism was discussed from the aspect of velocity field using a point tracking technique. The simulation results were verified by the experimental results in term of weld shape.
Gravitational Waves in Decaying Vacuum Cosmologies
David Alejandro Tamayo Ramirez
2015-01-01
In the present monograph we study in detail the primordial gravitational waves in cosmologies with a decaying vacuum. The decaying vacuum models are an alternative to solve the cosmological constant problem attributing a dynamic to the vacuum energy. The problem of primordial gravitational waves is discussed in the framework of an expanding, flat, spatially homogeneous and isotropic FLRW Universe described by General Relativity theory with decaying vacuum energy density of the type $\\\\Lambda ...
Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.
2016-02-01
Recent years have shown an increase in harmful algal blooms in the Northwest Arabian Sea and Gulf of Oman, raising the question of whether climate change will accelerate this trend. This has led us to examine whether the Earth System Models used to simulate phytoplankton productivity accurately capture bloom dynamics in this region - both in terms of the annual cycle and interannual variability. Satellite data (SeaWIFS ocean color) show two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. On a regional scale, interannual variability of the wintertime bloom is dominated by cyclonic eddies which vary in location from one year to another. Two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The models fail to capture both the magnitude of the wintertime bloom and its modulation by eddies in part because of their failure to capture the observed sharp thermocline and/or nutricline in this region. When CM2.6 is able to capture such features in the Southern part of the basin, eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). For the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf - something that is poorly done in global models.
Kadum, Hawwa; Rockel, Stanislav; Holling, Michael; Peinke, Joachim; Cal, Raul Bayon
2017-11-01
The wake behind a floating model horizontal axis wind turbine during pitch motion is investigated and compared to a fixed wind turbine wake. An experiment is conducted in an acoustic wind tunnel where hot-wire data are acquired at five downstream locations. At each downstream location, a rake of 16 hot-wires was used with placement of the probes increasing radially in the vertical, horizontal, and diagonally at 45 deg. In addition, the effect of turbulence intensity on the floating wake is examined by subjecting the wind turbine to different inflow conditions controlled through three settings in the wind tunnel grid, a passive and two active protocols, thus varying in intensity. The wakes are inspected by statistics of the point measurements, where the various length/time scales are considered. The wake characteristics for a floating wind turbine are compared to a fixed turbine, and uncovering its features; relevant as the demand for exploiting deep waters in wind energy is increasing.
Segmentation of Locally Varying Numbers of Outer Retinal Layers by a Model Selection Approach.
Novosel, Jelena; Yzer, Suzanne; Vermeer, Koenraad A; van Vliet, Lucas J
2017-06-01
Extraction of image-based biomarkers, such as the presence, visibility, or thickness of a certain layer, from 3-D optical coherence tomography data provides relevant clinical information. We present a method to simultaneously determine the number of visible layers in the outer retina and segment them. The method is based on a model selection approach with special attention given to the balance between the quality of a fit and model complexity. This will ensure that a more complex model is selected only if this is sufficiently supported by the data. The performance of the method was evaluated on healthy and retinitis pigmentosa (RP) affected eyes. In addition, the reproducibility of automatic method and manual annotations was evaluated on healthy eyes. Good agreement between the segmentation performed manually by a medical doctor and results obtained from the automatic segmentation was found. The mean unsigned deviation for all outer retinal layers in healthy and RP affected eyes varied between 2.6 and 4.9 μm. The reproducibility of the automatic method was similar to the reproducibility of the manual segmentation. Overall, the method provides a flexible and accurate solution for determining the visibility and location of outer retinal layers and could be used as an aid for the disease diagnosis and monitoring.
Directory of Open Access Journals (Sweden)
Zhang Yang
2017-12-01
Full Text Available The authors develop slim and light-weight vacuum insulation panels (VIPs by producing vacuum layers with spacers and plastic plates. The developed VIPs have the advantages of a low cost and easy installation, thus facilitating retrofitting insulation of existing buildings. In addition, one of the developed VIPs is slim and translucent so it can be easily used for windows in an internal installation. In this paper, the authors first propose a vacuum layer type slim translucent VIP and focus on a reasonable design method. Next, the authors introduce the design process in which the structural design is obtained with element mechanical analysis and a three-dimensional analysis is conducted for the VIP element. In the study, a heat transfer model is used to predict the insulation performance through finite element analysis (FEA. Subsequently, the authors perform an experiment to measure the thermal conductivity in a guarded hot plate apparatus to validate the performance prediction. Finally, case studies are performed to confirm how the different design conditions affect the insulation performance. The optimum design of the vacuum layer type slim and translucent VIP will have a sufficient structural strength to hold and maintain the vacuum layer. The thermal conductivity is approximately 0.007 W / ( m · K , which can effectively improve the insulation performance in applications.
A Fragment-Cloud Model for Breakup of Asteroids with Varied Internal Structures
Wheeler, Lorien; Mathias, Donovan; Stokan, Ed; Brown, Peter
2016-01-01
As an asteroid descends toward Earth, it deposits energy in the atmosphere through aerodynamic drag and ablation. Asteroid impact risk assessments rely on energy deposition estimates to predict blast overpressures and ground damage that may result from an airburst, such as the one that occurred over Chelyabinsk, Russia in 2013. The rates and altitudes at which energy is deposited along the entry trajectory depend upon how the bolide fragments, which in turn depends upon its internal structure and composition. In this work, we have developed an analytic asteroid fragmentation model to assess the atmospheric energy deposition of asteroids with a range of structures and compositions. The modeling approach combines successive fragmentation of larger independent pieces with aggregate debris clouds released with each fragmentation event. The model can vary the number and masses of fragments produced, the amount of mass released as debris clouds, the size-strength scaling used to increase the robustness of smaller fragments, and other parameters. The initial asteroid body can be seeded with a distribution of independent fragment sizes amid a remaining debris mass to represent loose rubble pile conglomerations, can be given an outer regolith later, or can be defined as a coherent or fractured monolith. This approach enables the model to represent a range of breakup behaviors and reproduce detailed energy deposition features such as multiple flares due to successive burst events, high-altitude regolith blow-off, or initial disruption of rubble piles followed by more energetic breakup of the constituent boulders. These capabilities provide a means to investigate sensitivities of ground damage to potential variations in asteroid structure.
A Loudness Model for Time-Varying Sounds Incorporating Binaural Inhibition
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Brian C. J. Moore
2016-12-01
Full Text Available This article describes a model of loudness for time-varying sounds that incorporates the concept of binaural inhibition, namely, that the signal applied to one ear can reduce the internal response to a signal at the other ear. For each ear, the model includes the following: a filter to allow for the effects of transfer of sound through the outer and middle ear; a short-term spectral analysis with greater frequency resolution at low than at high frequencies; calculation of an excitation pattern, representing the magnitudes of the outputs of the auditory filters as a function of center frequency; application of a compressive nonlinearity to the output of each auditory filter; and smoothing over time of the resulting instantaneous specific loudness pattern using an averaging process resembling an automatic gain control. The resulting short-term specific loudness patterns are used to calculate broadly tuned binaural inhibition functions, the amount of inhibition depending on the relative short-term specific loudness at the two ears. The inhibited specific loudness patterns are summed across frequency to give an estimate of the short-term loudness for each ear. The overall short-term loudness is calculated as the sum of the short-term loudness values for the two ears. The long-term loudness for each ear is calculated by smoothing the short-term loudness for that ear, again by a process resembling automatic gain control, and the overall loudness impression is obtained by summing the long-term loudness across ears. The predictions of the model are more accurate than those of an earlier model that did not incorporate binaural inhibition.
A Loudness Model for Time-Varying Sounds Incorporating Binaural Inhibition.
Moore, Brian C J; Glasberg, Brian R; Varathanathan, Ajanth; Schlittenlacher, Josef
2016-01-01
This article describes a model of loudness for time-varying sounds that incorporates the concept of binaural inhibition, namely, that the signal applied to one ear can reduce the internal response to a signal at the other ear. For each ear, the model includes the following: a filter to allow for the effects of transfer of sound through the outer and middle ear; a short-term spectral analysis with greater frequency resolution at low than at high frequencies; calculation of an excitation pattern, representing the magnitudes of the outputs of the auditory filters as a function of center frequency; application of a compressive nonlinearity to the output of each auditory filter; and smoothing over time of the resulting instantaneous specific loudness pattern using an averaging process resembling an automatic gain control. The resulting short-term specific loudness patterns are used to calculate broadly tuned binaural inhibition functions, the amount of inhibition depending on the relative short-term specific loudness at the two ears. The inhibited specific loudness patterns are summed across frequency to give an estimate of the short-term loudness for each ear. The overall short-term loudness is calculated as the sum of the short-term loudness values for the two ears. The long-term loudness for each ear is calculated by smoothing the short-term loudness for that ear, again by a process resembling automatic gain control, and the overall loudness impression is obtained by summing the long-term loudness across ears. The predictions of the model are more accurate than those of an earlier model that did not incorporate binaural inhibition.
Linear parameter-varying modeling and control of the steam temperature in a Canadian SCWR
Energy Technology Data Exchange (ETDEWEB)
Sun, Peiwei, E-mail: sunpeiwei@mail.xjtu.edu.cn; Zhang, Jianmin; Su, Guanghui
2017-03-15
Highlights: • Nonlinearity of Canadian SCWR is analyzed based on step responses and Nyquist plots. • LPV model is derived through Jacobian linearization and curve fitting. • An output feedback H{sub ∞} controller is synthesized for the steam temperature. • The control performance is evaluated by step disturbances and wide range operation. • The controller can stabilize the system and reject the reactor power disturbance. - Abstract: The Canadian direct-cycle Supercritical Water-cooled Reactor (SCWR) is a pressure-tube type SCWR under development in Canada. The dynamics of the steam temperature have a high degree of nonlinearity and are highly sensitive to reactor power disturbances. Traditional gain scheduling control cannot theoretically guarantee stability for all operating regions. The control performance can also be deteriorated when the controllers are switched. In this paper, a linear parameter-varying (LPV) strategy is proposed to solve such problems. Jacobian linearization and curve fitting are applied to derive the LPV model, which is verified using a nonlinear dynamic model and determined to be sufficiently accurate for control studies. An output feedback H{sub ∞} controller is synthesized to stabilize the steam temperature system and reject reactor power disturbances. The LPV steam temperature controller is implemented using a nonlinear dynamic model, and step changes in the setpoints and typical load patterns are carried out in the testing process. It is demonstrated through numerical simulation that the LPV controller not only stabilizes the steam temperature under different disturbances but also efficiently rejects reactor power disturbances and suppresses the steam temperature variation at different power levels. The LPV approach is effective in solving control problems of the steam temperature in the Canadian SCWR.
Dynamic linear models to explore time-varying suspended sediment-discharge rating curves
Ahn, Kuk-Hyun; Yellen, Brian; Steinschneider, Scott
2017-06-01
This study presents a new method to examine long-term dynamics in sediment yield using time-varying sediment-discharge rating curves. Dynamic linear models (DLMs) are introduced as a time series filter that can assess how the relationship between streamflow and sediment concentration or load changes over time in response to a wide variety of natural and anthropogenic watershed disturbances or long-term changes. The filter operates by updating parameter values using a recursive Bayesian design that responds to 1 day-ahead forecast errors while also accounting for observational noise. The estimated time series of rating curve parameters can then be used to diagnose multiscale (daily-decadal) variability in sediment yield after accounting for fluctuations in streamflow. The technique is applied in a case study examining changes in turbidity load, a proxy for sediment load, in the Esopus Creek watershed, part of the New York City drinking water supply system. The results show that turbidity load exhibits a complex array of variability across time scales. The DLM highlights flood event-driven positive hysteresis, where turbidity load remained elevated for months after large flood events, as a major component of dynamic behavior in the rating curve relationship. The DLM also produces more accurate 1 day-ahead loading forecasts compared to other static and time-varying rating curve methods. The results suggest that DLMs provide a useful tool for diagnosing changes in sediment-discharge relationships over time and may help identify variability in sediment concentrations and loads that can be used to inform dynamic water quality management.
Modeling broadband ocean acoustic transmissions with time-varying sea surfaces.
Siderius, Martin; Porter, Michael B
2008-07-01
Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is "frozen" in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1-50 kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface adds complexity and often leads to a statistical description for the variations in received signals. A purely statistical description likely limits the insight that modeling generally provides. In this paper, time-domain modeling approaches to the sea-surface scattering problem are described. As a benchmark for comparison, the Helmholtz integral equation is used for solutions to static, time-harmonic rough surface problems. The integral equation approach is not practical for time-evolving rough surfaces and two alternatives are formulated. The first approach is relatively simple using ray theory. This is followed with a ray-based formulation of the Helmholtz integral equation with a time-domain Kirchhoff approximation.
The varying cosmological constant: A new approximation to the Friedmann equations and universe model
Öztaş, Ahmet M.; Dil, Emre; Smith, Michael L.
2018-01-01
We investigate the time-dependent nature of the cosmological constant, Λ, of the Einstein Field Equation (EFE). Beginning with the Einstein-Hilbert action as our fundamental principle we develop a modified version of the EFE allowing the value of Λ to vary as a function of time, Λ(t), indirectly, for an expanding universe. We follow the evolving Λ presuming 4-dimensional spacetime and a flat universe geometry and present derivations of Λ(t) as functions of the Hubble constant, matter density and volume changes which can be traced back to the radiation epoch. The models are more detailed descriptions of the Λ dependence on cosmological factors than previous, allowing calculations of the important parameters, Ωm and Ωr, to deep lookback times. Since we derive these without the need for extra dimensions or other special conditions our derivations are useful for model evaluation with astronomical data. This should aid resolution of several difficult problems of astronomy such as the best value for the Hubble constant at present and at recombination.
Directory of Open Access Journals (Sweden)
Corentin Herbert
2013-07-01
Full Text Available It has been suggested that the maximum entropy production (MEP principle, or MEP hypothesis, could be an interesting tool to compute climatic variables like temperature. In this climatological context, a major limitation of MEP is that it is generally assumed to be applicable only for stationary systems. It is therefore often anticipated that critical climatic features like the seasonal cycle or climatic change cannot be represented within this framework. We discuss here several possibilities in order to introduce time- varying climatic problems using the MEP formalism. We will show that it is possible to formulate a MEP model which accounts for time evolution in a consistent way. This formulation leads to physically relevant results as long as the internal time scales associated with thermal inertia are small compared to the speed of external changes. We will focus on transient changes as well as on the seasonal cycle in a conceptual climate box-model in order to discuss the physical relevance of such an extension of the MEP framework.
Atwell, Matthew J.; Hurlbert, Eric A.; Melcher, J. C.; Morehead, Robert L.
2017-01-01
An integrated cryogenic liquid oxygen, liquid methane (LOX/LCH4) reaction control system (RCS) was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under vacuum and thermal vacuum conditions. The RCS is a subsystem of the Integrated Cryogenic Propulsion Test Article (ICPTA), a pressure-fed LOX/LCH4 propulsion system composed of a single 2,800 lbf main engine, two 28 lbf RCS engines, and two 7 lbf RCS engines. Propellants are stored in four 48 inch diameter 5083 aluminum tanks that feed both the main engine and RCS engines in parallel. Helium stored cryogenically in a composite overwrapped pressure vessel (COPV) flows through a heat exchanger on the main engine before being used to pressurize the propellant tanks to a design operating pressure of 325 psi. The ICPTA is capable of simultaneous main engine and RCS operation. The RCS engines utilize a coil-on-plug (COP) ignition system designed for operation in a vacuum environment, eliminating corona discharge issues associated with a high voltage lead. There are two RCS pods on the ICPTA, with two engines on each pod. One of these two engines is a heritage flight engine from Project Morpheus. Its sea level nozzle was removed and replaced by an 85:1 nozzle machined using Inconel 718, resulting in a maximum thrust of 28 lbf under altitude conditions. The other engine is a scaled down version of the 28 lbf engine, designed to match the core and overall mixture ratios as well as other injector characteristics. This engine can produce a maximum thrust of 7 lbf with an 85:1 nozzle that was additively manufactured using Inconel 718. Both engines are film-cooled and capable of limited duration gas-gas and gas-liquid operation, as well as steady-state liquid-liquid operation. Each pod contains one of each version, such that two engines of the same thrust level can be fired as a couple on opposite pods. The RCS feed system is composed of symmetrical 3/8 inch lines
Yanagawa, Youichi; Ohsaka, Hiromichi; Jitsuiki, Kei; Yoshizawa, Toshihiko; Takeuchi, Ikuto; Omori, Kazuhiko; Oode, Yasumasa; Ishikawa, Kouhei
2016-08-01
This article describes the theory of the formation of the vacuum phenomenon (VP), the detection of the VP, the different medical causes, the different locations of the presentation of the VP, and the differential diagnoses. In the human body, the cavitation effect is recognized on radiological studies; it is called the VP. The mechanism responsible for the formation of the VP is as follows: if an enclosed tissue space is allowed to expand as a rebound phenomenon after an external impact, the volume within the enclosed space will increase. In the setting of expanding volume, the pressure within the space will decrease. The solubility of the gas in the enclosed space will decrease as the pressure of the space decreases. Decreased solubility allows a gas to leave a solution. Clinically, the pathologies associated with the VP have been reported to mainly include the normal joint motion, degeneration of the intervertebral discs or joints, and trauma. The frequent use of CT for trauma patients and the high spatial resolution of CT images might produce the greatest number of chances to detect the VP in trauma patients. The VP is observed at locations that experience a traumatic impact; thus, an analysis of the VP may be useful for elucidating the mechanism of an injury. When the VP is located in the abdomen, it is important to include perforation of the digestive tract in the differential diagnosis. The presence of the VP in trauma patients does not itself influence the final outcome.
Expanding space-time and variable vacuum energy
Parmeggiani, Claudio
2017-08-01
The paper describes a cosmological model which contemplates the presence of a vacuum energy varying, very slightly (now), with time. The constant part of the vacuum energy generated, some 6 Gyr ago, a deceleration/acceleration transition of the metric expansion; so now, in an aged Universe, the expansion is inexorably accelerating. The vacuum energy varying part is instead assumed to be eventually responsible of an acceleration/deceleration transition, which occurred about 14 Gyr ago; this transition has a dynamic origin: it is a consequence of the general relativistic Einstein-Friedmann equations. Moreover, the vacuum energy (constant and variable) is here related to the zero-point energy of some quantum fields (scalar, vector, or spinor); these fields are necessarily described in a general relativistic way: their structure depends on the space-time metric, typically non-flat. More precisely, the commutators of the (quantum field) creation/annihilation operators are here assumed to depend on the local value of the space-time metric tensor (and eventually of its curvature); furthermore, these commutators rapidly decrease for high momentum values and they reduce to the standard ones for a flat metric. In this way, the theory is ”gravitationally” regularized; in particular, the zero-point (vacuum) energy density has a well defined value and, for a non static metric, depends on the (cosmic) time. Note that this varying vacuum energy can be negative (Fermi fields) and that a change of its sign typically leads to a minimum for the metric expansion factor (a ”bounce”).
DEFF Research Database (Denmark)
Bak, Claus Leth; Borghetti, Alberto; Glasdam, Jakob Bærholm
2017-01-01
for both VCB sizing and insulation coordination studies of the components nearby the switching device. In this respect, their accurate modelling, which is the object of the paper, becomes crucial. In particular, the paper presents (the concept of) a VCB model and two relevant applications showing the model......-bandwidth GPS-synchronised measurement system, respectively, are used for model validation. It is shown that the inclusion of detailed VCB models significantly improves the agreement between the measurements related to both pre- and restrikes and the corresponding simulation results obtained by using two well...
Moldoványi, N.; Abonyi, J.
2009-01-01
Crystallisers are essentially multivariable systems with high interaction amongst the process variables. Model Predictive Controllers (MPC) can handle such highly interacting multivariable systems efficiently due to their coordinated approach. In the absence of a real continuous crystalliser, a detailed momentum-model was applied using the process simulator in Simulink. This process has been controlled by a model predictive controller widely used in industry. A new framework has been worke...
Directory of Open Access Journals (Sweden)
Huiguo Chen
2017-01-01
Full Text Available Based on the Kanai-Tajimi power spectrum filtering method proposed by Du Xiuli et al., a genetic algorithm and a quadratic optimization identification technique are employed to improve the bimodal time-varying modified Kanai-Tajimi power spectral model and the parameter identification method proposed by Vlachos et al. Additionally, a method for modeling time-varying power spectrum parameters for ground motion is proposed. The 8244 Orion and Chi-Chi earthquake accelerograms are selected as examples for time-varying power spectral model parameter identification and ground motion simulations to verify the feasibility and effectiveness of the improved bimodal time-varying modified Kanai-Tajimi power spectral model. The results of this study provide important references for designing ground motion inputs for seismic analyses of major engineering structures.
Detecting a Local Cohort Effect for Cancer Mortality Data Using a Varying Coefficient Model
Directory of Open Access Journals (Sweden)
Tetsuji Tonda
2015-11-01
Full Text Available Background: Cancer mortality is increasing with the aging of the population in Japan. Cancer information obtained through feasible methods is therefore becoming the basis for planning effective cancer control programs. There are three time-related factors affecting cancer mortality, of which the cohort effect is one. Past descriptive epidemiologic studies suggest that the cohort effect is not negligible in cancer mortality. Methods: In this paper, we develop a statistical method for automatically detecting a cohort effect and assessing its statistical significance for cancer mortality data using a varying coefficient model. Results: The proposed method was applied to liver and lung cancer mortality data on Japanese men for illustration. Our method detected significant positive or negative cohort effects. The relative risk was 1.54 for liver cancer mortality in the cohort born around 1934 and 0.83 for lung cancer in the cohort born around 1939. Conclusions: Cohort effects detected using the proposed method agree well with previous descriptive epidemiologic findings. In addition, the proposed method is expected to be sensitive enough to detect smaller, previously undetected birth cohort effects.
A two-locus model of spatially varying stabilizing or directional selection on a quantitative trait.
Geroldinger, Ludwig; Bürger, Reinhard
2014-06-01
The consequences of spatially varying, stabilizing or directional selection on a quantitative trait in a subdivided population are studied. A deterministic two-locus two-deme model is employed to explore the effects of migration, the degree of divergent selection, and the genetic architecture, i.e., the recombination rate and ratio of locus effects, on the maintenance of genetic variation. The possible equilibrium configurations are determined as functions of the migration rate. They depend crucially on the strength of divergent selection and the genetic architecture. The maximum migration rates are investigated below which a stable fully polymorphic equilibrium or a stable single-locus polymorphism can exist. Under stabilizing selection, but with different optima in the demes, strong recombination may facilitate the maintenance of polymorphism. However usually, and in particular with directional selection in opposite direction, the critical migration rates are maximized by a concentrated genetic architecture, i.e., by a major locus and a tightly linked minor one. Thus, complementing previous work on the evolution of genetic architectures in subdivided populations subject to diversifying selection, it is shown that concentrated architectures may aid the maintenance of polymorphism. Conditions are obtained when this is the case. Finally, the dependence of the phenotypic variance, linkage disequilibrium, and various measures of local adaptation and differentiation on the parameters is elaborated. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.
Modelling shallow debris flows of the Coulomb-mixture type over temporally varying topography
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Y. C. Tai
2012-02-01
Full Text Available We propose a saturated binary mixture model for debris flows of the Coulomb-mixture type over temporally varying topography, where the effects of erosion and deposition are considered. Due to the deposition or erosion processes, the interface between the moving material and the stagnant base is a non-material singular surface. The motion of this singular surface is determined by the mass exchange between the flowing layer and the ground. The ratio of the relative velocity between the two constituents to the velocity of the solid phase is assumed to be small, so that the governing equations can be reduced to a system of the quasi-single-phase type. A shock-capturing numerical scheme is implemented to solve the derived equation system. The deposition shapes of a finite mass sliding down an inclined planary chute are investigated for a range of mixture ratios. The geometric evolution of the deposition is presented, which allows the possibility of mimicking the development of levee deposition.
Scherer, Sandra Saja; Pietramaggiori, Giorgio; Mathews, Jasmine C; Orgill, Dennis P
2009-11-01
The vacuum-assisted closure device is a widely used mechanical modulator of wound healing; however, the optimal time kinetics of application have not been determined. The objective of the study was to optimize the kinetics of vacuum-assisted closure application. Full-thickness wounds in seven diabetic mice per study group were treated with either an occlusive dressing alone, the vacuum-assisted closure device for 6 or 12 hours, or the vacuum-assisted closure device periodically for 4 hours every other day or continuously for 7 days. Wound closure and tissue response were evaluated by macroscopic, histologic, and immunohistochemical analyses on day 7. Wound closure was significantly faster after short initial vacuum-assisted closure (6-hour and 12-hour groups) when compared with continuous treatment. Increased granulation tissue formation was seen in the 12-hour group (2.4-fold increase) and in those treated periodically for 4 hours every other day (3.2-fold increase) compared with the dressing-alone controls. Significant stimulation of cell proliferation was seen after all vacuum-assisted closure patterns (3.6- to 5.3-fold increase), whereas angiogenesis was augmented only after the device was applied for either three times for 4 hours (4.3-fold) or continuously (4.7-fold) when compared with dressing-treated wounds. Treatment three times for 4 hours showed a superior angiogenic effect also when compared with short initial applications (6-hour and 12-hour groups). Short vacuum-assisted closure treatment induced an extended biological response in the wound. A total of 12 hours of periodically applied vacuum-assisted closure reached a similar wound tissue response as continuously applied vacuum-assisted closure for 7 days. These findings suggest new clinical approaches for mechanical wound-healing devices.
Edge conduction in vacuum glazing
Energy Technology Data Exchange (ETDEWEB)
Simko, T.M.; Collins, R.E. [Sydney Univ., NSW (Australia). Dept. of Applied Physics; Beck, F.A.; Arasteh, D. [Lawrence Berkeley Lab., CA (United States)
1995-03-01
Vacuum glazing is a form of low-conductance double glazing using in internal vacuum between the two glass sheets to eliminate heat transport by gas conduction and convection. An array of small support pillars separates the sheets; fused solder glass forms the edge seal. Heat transfer through the glazing occurs by radiation across the vacuum gap, conduction through the support pillars, and conduction through the bonded edge seal. Edge conduction is problematic because it affects stresses in the edge region, leading to possible failure of the glazing; in addition, excessive heat transfer because of thermal bridging in the edge region can lower overall window thermal performance and decrease resistance to condensation. Infrared thermography was used to analyze the thermal performance of prototype vacuum glazings, and, for comparison, atmospheric pressure superwindows. Research focused on mitigating the edge effects of vacuum glazings through the use of insulating trim, recessed edges, and framing materials. Experimentally validated finite-element and finite-difference modeling tools were used for thermal analysis of prototype vacuum glazing units and complete windows. Experimental measurements of edge conduction using infrared imaging were found to be in good agreement with finite-element modeling results for a given set of conditions. Finite-element modeling validates an analytic model developed for edge conduction.
Modeling the absorption spectrum of the permanganate ion in vacuum and in aqueous solution
DEFF Research Database (Denmark)
Olsen, Jógvan Magnus Haugaard; Hedegård, Erik Donovan
2017-01-01
The absorption spectrum of the MnO4(-) ion has been a test-bed for quantum-chemical methods over the last decades. Its correct description requires highly-correlated multiconfigurational methods, which are incompatible with the inclusion of finite-temperature and solvent effects due to their high...... computational demands. Therefore, implicit solvent models are usually employed. Here we show that implicit solvent models are not sufficiently accurate to model the solvent shift of MnO4(-), and we analyze the origins of their failure. We obtain the correct solvent shift for MnO4(-) in aqueous solution...
The modelling of the cathode sheath of an electrical arc in vacuum
Energy Technology Data Exchange (ETDEWEB)
Rossignol, J [Laboratoire de Recherches sur la Reactivite des Solides, UMR 5613 CNRS, Universite de Bourgogne 21078 Dijon (France); Clain, S [Laboratoire de Mathematiques Appliquees, UMR 6620 CNRS, Universite Blaise Pascal, 63177 Aubiere (France); Abbaoui, M [Laboratoire Arc Electrique et Plasmas Thermiques, CNRS UPES-A 6069, Universite Blaise Pascal 63177 Aubiere (France)
2003-07-07
This paper presents a simple model of the fragment in the cathode electrical arc root taking into account the physical phenomena occurring on the cathode surface and the sheath. The goal is the obtainment of characteristics values of the heat flux, the electrons, and atoms density in the sheath. Computation is carried out on a one-dimensional model with a coupling between the equation obtained in the sheath and an enthalpy model of the cathode to describe the temperature evolution. In the modelling, we introduce a friction zone above the sheath edge to characterize the heavy particle interactions. Numerical simulation shows that the ionic friction phenomenon deriving from ion-atom collision regulates the heat flux lightening the surface, and the crucial necessity to obtain a good evaluation of the cross section of the charge exchange.
PARAFFIN SEPARATION VACUUM DISTILLATION
Directory of Open Access Journals (Sweden)
Zaid A. Abdulrahman
2013-05-01
Full Text Available Simulated column performance curves were constructed for existing paraffin separation vacuum distillation column in LAB plant (Arab Detergent Company/Baiji-Iraq. The variables considered in this study are the thermodynamic model option, top vacuum pressure, top and bottom temperatures, feed temperature, feed composition & reflux ratio. Also simulated columns profiles for the temperature, vapor & liquid flow rates composition were constructed. Four different thermodynamic model options (SRK, TSRK, PR, and ESSO were used, affecting the results within 1-25% variation for the most cases.The simulated results show that about 2% to 8 % of paraffin (C10, C11, C12, & C13 present at the bottom stream which may cause a problem in the LAB plant. The major variations were noticed for the top temperature & the paraffin weight fractions at bottom section with top vacuum pressure. The bottom temperature above 240 oC is not recommended because the total bottom flow rate decreases sharply, where as the weight fraction of paraffins decrease slightly. The study gives evidence about a successful simulation with CHEMCAD
Conditions for vacuum stability in an S{sub 3} extension of the Standard Model
Energy Technology Data Exchange (ETDEWEB)
Beltran, O Felix [Fac. de Cs. de la Electronica, BUAP, Apdo. Postal 542, Puebla, Pue. 72570 (Mexico); Mondragon, M [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 20-364, Mexico, D.F. 01000 (Mexico); RodrIguez-Jauregui, E, E-mail: ezequiel.rodriguez@correo.fisica.uson.m [Departamento de Fisica, UNISON, Apdo. Postal 1626, Hermosillo, Son. 83000 (Mexico)
2009-06-01
In this work we study the Higgs sector in the minimal S{sub 3} extension of the Standard Model. The S{sub 3} extended Standard Model, which has three Higgs doublets fields that belong to the three-dimensional reducible representation of the permutation group S{sub 3}, has naturally new phenomena: there are several Higgs bosons, charged, neutral and pseuodscalar ones, and more than one potential minimum. We analyzed the stability of the minimal S3 invariant extension of the Higgs potential and show that at tree-level, the potential minimum preserving electric charge and CP symmetries, when it exists, is the global one.
A thermodynamic model of plasma generation by pulsed laser irradiation in vacuum
Tosto, S
2003-01-01
This paper introduces a thermodynamic model to determine composition, temperature and pressure of the plasma cloud induced by pulsed laser irradiation in the case where a relevant thermal sputtering mechanism is operating at the surface of a molten layer. The model concerns in particular pulse lengths of the order of several nanoseconds and completes the results of a previous paper concerning the physics of the evaporation and boiling driven thermal sputtering (Tosto S 2002 J. Phys. D: Appl. Phys. 35); the recession rate and temperature at the molten surface are linked to the pulse fluence and plasma properties in the frame of a unique physical model. This paper shows that the plasma properties depend critically on the non-equilibrium character of the surface evaporation and boiling mechanisms. The extension of the model to the case of continuous laser irradiation is also discussed. Some examples of computer simulation aim to show the results available in the particular case of a metal target; the comparison ...
Lu, Tao; Wang, Min; Liu, Guangying; Dong, Guang-Hui; Qian, Feng
2016-01-01
It is well known that there is strong relationship between HIV viral load and CD4 cell counts in AIDS studies. However, the relationship between them changes during the course of treatment and may vary among individuals. During treatments, some individuals may experience terminal events such as death. Because the terminal event may be related to the individual's viral load measurements, the terminal mechanism is non-ignorable. Furthermore, there exists competing risks from multiple types of events, such as AIDS-related death and other death. Most joint models for the analysis of longitudinal-survival data developed in literatures have focused on constant coefficients and assume symmetric distribution for the endpoints, which does not meet the needs for investigating the nature of varying relationship between HIV viral load and CD4 cell counts in practice. We develop a mixed-effects varying-coefficient model with skewed distribution coupled with cause-specific varying-coefficient hazard model with random-effects to deal with varying relationship between the two endpoints for longitudinal-competing risks survival data. A fully Bayesian inference procedure is established to estimate parameters in the joint model. The proposed method is applied to a multicenter AIDS cohort study. Various scenarios-based potential models that account for partial data features are compared. Some interesting findings are presented.
Koroteev, A. A.; Nagel, Yu. A.; Filatov, N. I.
2015-12-01
The basic results of space tests of liquid droplet cooler-radiator models as the main elements of frameless systems for low-grade heat rejection are considered. The studies carried out have been analyzed and intermediate elaboration's results are summarized, which concern (1) the development of generators of droplet propellant flows, (2) revealing an operational behavior of fluid collectors of various types and analysis of unsolved problems associated with droplet collection upon the open trajectory's section passage, and (3) provision of the coolant circulation contour's closing. The necessity is substantiated for the activization of works directed to carrying out space experiments with improved radiator models and new promising propellants in order to provide a possibility of creating new space power plants characterized by megawatt power levels.
Zhang, Wen; Liu, Xiaolong; He, Wei; Dong, Mingli; Zhu, Lianqing
2017-09-01
For the improvement of monitoring accuracy, a vibration monitoring for aircraft wing model using a fiber Bragg grating (FBG) array packaged by vacuum-assisted resin transfer molding (VARTM) is proposed. The working principle of the vibration monitoring using FBG array has been explained, which can theoretically support the idea of this paper. VARTM has been explained in detail, which is suitable for not only the single FBG sensor but also the FBG array within a relatively large area. The calibration experiment has been performed using the FBG sensor packaged by VARTM. The strain sensitivity of the VARTM package is 1.35 pm/μɛ and the linearity is 0.9999. The vibration monitoring experiment has been carried out using FBG array packaged by VARTM. The measured rate of strain changes across the aluminum test board used to simulate the aircraft wing is 0.69 μɛ/mm and the linearity is 0.9931. The damping ratio is 0.16, which could be further used for system performance evaluation. Experimental results demonstrate that the vibration monitoring using FBG sensors packaged by VARTM can be efficiently used for the structural health monitoring. Given the validation and great performance, this method is quite promising for in-flight monitoring and holds great reference value in other similar engineering structures.
Silvennoinen, Annestiina; Terasvirta, Timo
2017-01-01
A new multivariate volatility model that belongs to the family of conditional correlation GARCH models is introduced. The GARCH equations of this model contain a multiplicative deterministic component to describe long-run movements in volatility and, in addition, the correlations are deterministically time-varying. Parameters of the model are estimated jointly using maximum likelihood. Consistency and asymptotic normality of maximum likelihood estimators is proved. Numerical aspects of the es...
Directory of Open Access Journals (Sweden)
Fengxia Xu
2014-01-01
Full Text Available U-model can approximate a large class of smooth nonlinear time-varying delay system to any accuracy by using time-varying delay parameters polynomial. This paper proposes a new approach, namely, U-model approach, to solving the problems of analysis and synthesis for nonlinear systems. Based on the idea of discrete-time U-model with time-varying delay, the identification algorithm of adaptive neural network is given for the nonlinear model. Then, the controller is designed by using the Newton-Raphson formula and the stability analysis is given for the closed-loop nonlinear systems. Finally, illustrative examples are given to show the validity and applicability of the obtained results.
The Investigation of EM Scattering from the Time-Varying Overturning Wave Crest Model by the IEM
Directory of Open Access Journals (Sweden)
Xiao Meng
2016-01-01
Full Text Available Investigation of the electromagnetic (EM scattering of time-varying overturning wave crests is a worthwhile endeavor. Overturning wave crest is one of the reasons of sea spike generation, which increases the probability of false radar alarms and reduces the performance of multitarget detection in the environment. A three-dimensional (3D time-varying overturning wave crest model is presented in this paper; this 3D model is an improvement of the traditional two-dimensional (2D time-varying overturning wave crest model. The integral equation method (IEM was employed to investigate backward scattering radar cross sections (RCS at various incident angles of the 3D overturning wave crest model. The super phenomenon, where the intensity of horizontal polarization scattering is greater than that of vertical polarization scattering, is an important feature of sea spikes. Simulation results demonstrate that super phenomena may occur in some time samples as variations in the overturning wave crest.
A novel vacuum assisted closure therapy model for use with percutaneous devices.
Cook, Saranne J; Nichols, Francesca R; Brunker, Lucille B; Bachus, Kent N
2014-06-01
Long-term maintenance of a dermal barrier around a percutaneous prosthetic device remains a common clinical problem. A technique known as Negative Pressure Wound Therapy (NPWT) uses negative pressure to facilitate healing of impaired and complex soft tissue wounds. However, the combination of using negative pressure with percutaneous prosthetic devices has not been investigated. The goal of this study was to develop a methodology to apply negative pressure to the tissues surrounding a percutaneous device in an animal model; no tissue healing outcomes are presented. Specifically, four hairless rats received percutaneous porous coated titanium devices implanted on the dorsum and were bandaged with a semi occlusive film dressing. Two of these animals received NPWT; two animals received no NPWT and served as baseline controls. Over a 28-day period, both the number of dressing changes required between the two groups as well as the pressures were monitored. Negative pressures were successfully applied to the periprosthetic tissues in a clinically relevant range with a manageable number of dressing changes. This study provides a method for establishing, maintaining, and quantifying controlled negative pressures to the tissues surrounding percutaneous devices using a small animal model. Published by Elsevier Ltd.
Disrupted bandcount doubling in an AC-DC boost PFC circuit modeled by a time varying map
DEFF Research Database (Denmark)
Avrutin, Viktor; Zhusubaliyev, Zhanybai T.; Aroudi, Abdelali El
2016-01-01
averaged models. In this paper, we derive a time varying discretetime map modeling the behavior of a power factor correction AC-DC boost converter. This map is derived in closed-form and is able to faithfully reproduce the system behavior under realistic conditions. In the chaotic regime the map exhibits...
Directory of Open Access Journals (Sweden)
Hong Zhang
2014-01-01
Full Text Available This paper is concerned with a nonautonomous fishing model with a time-varying delay. Under proper conditions, we employ a novel argument to establish a criterion on the global exponential stability of positive almost periodic solutions of the model with almost periodic coefficients and delays. Moreover, an example and its numerical simulation are given to illustrate the main results.
Modeling the time-varying interaction between surface water and groundwater bodies
Gliege, Steffen; Steidl, Jörg; Lischeid, Gunnar; Merz, Christoph
2016-04-01
The countless kettle holes (small lakes) in the Late Pleistocene landscapes of Northern Europe have important ecological and hydrological functions. On the one hand they act as depressions in which water and solutes of mainly agriculturally used catchments accumulate. On the other hand they operate as biochemical reactors with respect to greenhouse gas emissions, carbon sequestration, and as major sinks for nutrients and contaminants. Even small kettle holes often are hydraulically connected to the uppermost groundwater system: Groundwater discharges into the kettle hole on one side, and the aquifer is recharged from the kettle hole water body on the other side. Thus kettle hole biogeochemical processes are both affected by groundwater and vice versa. Groundwater flow direction and velocity into and out of the kettle hole often is not stable over time. Groundwater flow direction might reverse at the downstream part, resulting in repeated recycling of groundwater and corresponding solute turnover within the kettle holes. A sound understanding of this intricate interplay is a necessary prerequisite for better understanding of the biogeochemistry of this terrestrial-aquatic interface. A numerical experiment was used to quantify the lateral solute exchange between a kettle hole and the surrounding groundwater. A vertical cross section through the real existing catchment of a kettle hole was chosen. Glacial till represents the lower boundary. The heterogeneity of the subsurface was reproduced by various parameterizations of the soil hydraulic properties as well as varying the thickness of the unconfined aquifer or the lateral boundary conditions. In total 24 different parameterizations were implemented in the modeling software HydroGeoSphere (HGS). HGS is suitable to calculate the fluid exchange between surface and subsurface simultaneously and in a physically based way. The simulation runs were done for the period from November 1994 to October 2014. All results were
Spatially-varied erosion modeling using WEPP for timber harvested and burned hillslopes
Peter R. Robichaud; T. M. Monroe
1997-01-01
Spatially-varied hydrologic surface conditions exist on steep hillslopes after timber harvest operation and site preparation burning treatments. Site preparation burning creates low- and high-severity burn surface conditions or disturbances. In this study, a hillslope was divided into multiple combinations of surface conditions to determine how their spatial...
Trip, Sebastian; Buerger, Mathias; De Persis, Claudio
This paper studies the problem of frequency regulation in power grids under unknown and possible time-varying load changes, while minimizing the generation costs. We formulate this problem as an output agreement problem for distribution networks and address it using incremental passivity and
DEFF Research Database (Denmark)
Andersen, P.; Skjærbæk, P. S.; Kirkegaard, Poul Henning
with the smoothed quanties which have been obtained from SARCOF. The results show the usefulness of the technique for identification of a time varying civil engineering structure. It is found that all the techniques give reliable estiates of the frequencies of the two lowest modes and the first mode shape. Only...
RELATION BETWEEN FUNCTION AND FORM IN VACUUM CLEANERS DESIGN
RADU Ștefan
2015-01-01
The paper analyses how robotic vacuum cleaner works, describing their cleaning capabilities and additional features. The paper illustrates advantages of using robotic vacuum cleaners that have intelligent programming and a vacuum cleaning system, the components of a robotic vacuum cleaner. The paper develops aspects concerning to create 2D scale models for the evaluation of specific features of the new components for a prototype robotic vacuum cleaner.
RELATION BETWEEN FUNCTION AND FORM IN VACUUM CLEANERS DESIGN
Directory of Open Access Journals (Sweden)
RADU Ștefan
2015-11-01
Full Text Available The paper analyses how robotic vacuum cleaner works, describing their cleaning capabilities and additional features. The paper illustrates advantages of using robotic vacuum cleaners that have intelligent programming and a vacuum cleaning system, the components of a robotic vacuum cleaner. The paper develops aspects concerning to create 2D scale models for the evaluation of specific features of the new components for a prototype robotic vacuum cleaner.
Lu, Fengbin; Qiao, Han; Wang, Shouyang; Lai, Kin Keung; Li, Yuze
2017-01-01
This paper proposes a new time-varying coefficient vector autoregressions (VAR) model, in which the coefficient is a linear function of dynamic lagged correlation. The proposed model allows for flexibility in choices of dynamic correlation models (e.g. dynamic conditional correlation generalized autoregressive conditional heteroskedasticity (GARCH) models, Markov-switching GARCH models and multivariate stochastic volatility models), which indicates that it can describe many types of time-varying causal effects. Time-varying causal relations between West Texas Intermediate (WTI) crude oil and the US Standard and Poor's 500 (S&P 500) stock markets are examined by the proposed model. The empirical results show that their causal relations evolve with time and display complex characters. Both positive and negative causal effects of the WTI on the S&P 500 in the subperiods have been found and confirmed by the traditional VAR models. Similar results have been obtained in the causal effects of S&P 500 on WTI. In addition, the proposed model outperforms the traditional VAR model. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Residual currents generated from vacuum by an electric field pulse in 2+1 dimensional QED models
Directory of Open Access Journals (Sweden)
Smolyansky S.A.
2017-01-01
Full Text Available In the framework of strong field QED, the generation of a residual alternating polarization current is demonstrated, which remains after switching off an external field pulse. This effect is stipulated by inertial properties of the physical vacuum. In the standard vacuum D = 2+1 QED, this current is rapidly damped fast but can be available, apparently, for observation in the graphene, where the Fermi velocity vF ≪ c plays an analogous role as the light velocity.
Koszela, K.; OtrzÄ sek, J.; Zaborowicz, M.; Boniecki, P.; Mueller, W.; Raba, B.; Lewicki, A.; Przybył, K.
2014-04-01
The farming area for vegetables in Poland is constantly changed and modified. Each year the cultivation structure of particular vegetables is different. However, it is the cultivation of carrots that plays a significant role among vegetables. According to the Main Statistical Office (GUS), in 2012 carrot held second position among the cultivated root vegetables, and it was estimated at 835 thousand tons. In the world we are perceived as the leading producer of carrot, due to the fourth place in the ranking of global producers. Poland is the largest producer of this vegetable in the EU [1]. It is also noteworthy, that the demand for dried vegetables is still increasing. This tendency affects the development of drying industry in our country, contributing to utilization of the product surplus. Dried vegetables are used increasingly often in various sectors of food products industry, due to high nutrition value, as well as to changing alimentary preferences of consumers [2-3]. Dried carrot plays a crucial role among dried vegetables, because of its wide scope of use and high nutrition value. It contains a lot of carotene and sugar present in the form of crystals. Carrot also undergoes many different drying processes, which makes it difficult to perform a reliable quality assessment and classification of this dried material. One of many qualitative properties of dried carrot, having important influence on a positive or negative result of the quality assessment, is color and shape. The aim of the research project was to develop a method for the analysis of microwave-vacuum dried carrot images, and its application for the classification of individual fractions in the sample studied for quality assessment. During the research digital photographs of dried carrot were taken, which constituted the basis for assessment performed by a dedicated computer programme developed as a part of the research. Consequently, using a neural model, the dried material was classified [4-6].
Goldhaber-Fiebert, Jeremy D; Brandeau, Margaret L
2015-02-01
Risk factors increase the incidence and severity of chronic disease. To examine future trends and develop policies addressing chronic diseases, it is important to capture the relationship between exposure and disease development, which is challenging given limited data. To develop parsimonious risk factor models embeddable in chronic disease models, which are useful when longitudinal data are unavailable. The model structures encode relevant features of risk factors (e.g., time-varying, modifiable) and can be embedded in chronic disease models. Calibration captures time-varying exposures for the risk factor models using available cross-sectional data. We illustrate feasibility with the policy-relevant example of smoking in India. The model is calibrated to the prevalence of male smoking in 12 Indian regions estimated from the 2009-2010 Indian Global Adult Tobacco Survey. Nelder-Mead searches (250,000 starting locations) identify distributions of starting, quitting, and restarting rates that minimize the difference between modeled and observed age-specific prevalence. We compare modeled life expectancies to estimates in the absence of time-varying risk exposures and consider gains from hypothetical smoking cessation programs delivered for 1 to 30 years. Calibration achieves concordance between modeled and observed outcomes. Probabilities of starting to smoke rise and fall with age, while quitting and restarting probabilities fall with age. Accounting for time-varying smoking exposures is important, as not doing so produces smaller estimates of life expectancy losses. Estimated impacts of smoking cessation programs delivered for different periods depend on the fact that people who have been induced to abstain from smoking longer are less likely to restart. The approach described is feasible for important risk factors for numerous chronic diseases. Incorporating exposure-change rates can improve modeled estimates of chronic disease outcomes and of the long
Lagona, Francesco; Jdanov, Dmitri; Shkolnikova, Maria
2014-10-15
Longitudinal data are often segmented by unobserved time-varying factors, which introduce latent heterogeneity at the observation level, in addition to heterogeneity across subjects. We account for this latent structure by a linear mixed hidden Markov model. It integrates subject-specific random effects and Markovian sequences of time-varying effects in the linear predictor. We propose an expectationŰ-maximization algorithm for maximum likelihood estimation, based on data augmentation. It reduces to the iterative maximization of the expected value of a complete likelihood function, derived from an augmented dataset with case weights, alternated with weights updating. In a case study of the Survey on Stress Aging and Health in Russia, the model is exploited to estimate the influence of the observed covariates under unobserved time-varying factors, which affect the cardiovascular activity of each subject during the observation period. Copyright © 2014 John Wiley & Sons, Ltd.
National Research Council Canada - National Science Library
Singer, Philipp; Helic, Denis; Taraghi, Behnam; Strohmaier, Markus
2014-01-01
One of the most frequently used models for understanding human navigation on the Web is the Markov chain model, where Web pages are represented as states and hyperlinks as probabilities of navigating...
Precipitation is a key control on watershed hydrologic modelling output, with errors in rainfall propagating through subsequent stages of water quantity and quality analysis. Most watershed models incorporate precipitation data from rain gauges; higher-resolution data sources are...
Constructing Regional Groundwater Models from Geophysical Data of Varying Type, Age, and Quality
DEFF Research Database (Denmark)
Vest Christiansen, Anders; Auken, Esben; Marker, Pernille Aabye
-casing a study from Denmark were a regional groundwater model is constructed by including lithological information from 3100 boreholes over an 710 sqkm area. The geophysical models spans more than 30 years of data collection and includes approx. 225,000 DC models, and 35,000 EM models, airborne as well...... geophysical datasets covering the entire domain. Using boreholes to link between hydrostratigraphical classes and resistivity is efficient and emphasizes the need for an all-inclusive data interpretation procedure that can be integrated in groundwater model calibration. We present an automatic method...... for parameterization of a 3D model of the subsurface, integrating lithological information from boreholes with resistivity models. The objective is to create a direct input to regional groundwater models for sedimentary areas, where the sand/clay distribution governs the groundwater flow. The resistivity input is all...
Shields Richard K; Frey Law Laura A
2005-01-01
Abstract Background Mathematical muscle models may be useful for the determination of appropriate musculoskeletal stresses that will safely maintain the integrity of muscle and bone following spinal cord injury. Several models have been proposed to represent paralyzed muscle, but there have not been any systematic comparisons of modelling approaches to better understand the relationships between model parameters and muscle contractile properties. This sensitivity analysis of simulated muscle ...
Time-varying disaster risk models: An empirical assessment of the Rietz-Barro hypothesis
DEFF Research Database (Denmark)
Irarrazabal, Alfonso; Parra-Alvarez, Juan Carlos
This paper revisits the fit of disaster risk models where a representative agent has recursive preferences and the probability of a macroeconomic disaster changes over time. We calibrate the model as in Wachter (2013) and perform two sets of tests to assess the empirical performance of the model...
Liu, Bo; Stevenson, R Jan
2017-12-31
Site grouping by regions or typologies, site-specific modeling and varying metrics among site groups are four approaches that account for natural variation, which can be a major source of error in ecological assessments. Using a data set from the 2007 National Lakes Assessment project of the USEPA, we compared performances of multimetric indices (MMI) of biological condition that were developed: (1) with different lake grouping methods, ecoregions or diatom typologies; (2) by varying or not varying metrics among site groups; and (3) with different statistical techniques for modeling diatom metric values expected for minimally disturbed condition for each lake. Hierarchical modeling of MMIs, i.e. grouping sites by ecoregions or typologies and then modeling natural variability in metrics among lakes within groups, substantially improved MMI performance compared to using either ecoregions or site-specific modeling alone. Compared with MMIs based on ecoregion site groups, MMI precision and sensitivity to human disturbance were better when sites were grouped by diatom typologies and assessing performance nationwide. However, when MMI performance was evaluated at site group levels, as some government agencies often do, there was little difference in MMI performance between the two site grouping methods. Low numbers of reference and highly impacted sites in some typology groups likely limited MMI performance at the group level of analysis. Varying metrics among site groups did not improve MMI performance. Random forest models for site-specific expected metric values performed better than classification and regression tree and multiple linear regression, except when numbers of reference sites were small in site groups. Then classification and regression tree models were most precise. Based on our results, we recommend hierarchical modeling in future large scale lake assessments where lakes are grouped by ecoregions or diatom typologies and site-specific metric models are
Influence of Joint Angle on EMG-Torque Model During Constant-Posture, Torque-Varying Contractions.
Liu, Pu; Liu, Lukai; Clancy, Edward A
2015-11-01
Relating the electromyogram (EMG) to joint torque is useful in various application areas, including prosthesis control, ergonomics and clinical biomechanics. Limited study has related EMG to torque across varied joint angles, particularly when subjects performed force-varying contractions or when optimized modeling methods were utilized. We related the biceps-triceps surface EMG of 22 subjects to elbow torque at six joint angles (spanning 60° to 135°) during constant-posture, torque-varying contractions. Three nonlinear EMG σ -torque models, advanced EMG amplitude (EMG σ ) estimation processors (i.e., whitened, multiple-channel) and the duration of data used to train models were investigated. When EMG-torque models were formed separately for each of the six distinct joint angles, a minimum "gold standard" error of 4.01±1.2% MVC(F90) resulted (i.e., error relative to maximum voluntary contraction at 90° flexion). This model structure, however, did not directly facilitate interpolation across angles. The best model which did so achieved a statistically equivalent error of 4.06±1.2% MVC(F90). Results demonstrated that advanced EMG σ processors lead to improved joint torque estimation as do longer model training durations.
H. Li; X. Deng; Andy Dolloff; E. P. Smith
2015-01-01
A novel clustering method for bivariate functional data is proposed to group streams based on their waterâair temperature relationship. A distance measure is developed for bivariate curves by using a time-varying coefficient model and a weighting scheme. This distance is also adjusted by spatial correlation of streams via the variogram. Therefore, the proposed...
2017-10-25
competitively low computational burden. It is hoped that the compactness of this mathematical representation will facilitate more rapid development... Literature Survey ................................................................................................... 2 2. MATHEMATICAL BACKGROUND...approach to modeling clutter which has not received much attention in the literature is to use tools from linear time-varying system theory. A linear
Gentry, Robert
2011-04-01
Physicists who identify the big bang with the early universe should have first noted from Hawking's A Brief History of Time, p. 42, that he ties Hubble's law to Doppler shifts from galaxy recession from a nearby center, not to bb's unvalidated and thus problematical expansion redshifts. Our PRL submission LJ12135 describes such a model, but in it Hubble's law is due to Doppler and vacuum gravity effects, the 2.73K CBR is vacuum gravity shifted blackbody cavity radiation from an outer galactic shell, and its (1 + z)-1 dilation and (M,z) relations closely fit high-z SNe Ia data; all this strongly implies our model's vacuum energy is the elusive dark energy. We also find GPS operation's GR effects falsify big bang's in-flight expansion redshift paradigm, and hence the big bang, by showing λ changes occur only at emission. Surprisingly we also discover big bang's CBR prediction is T 0, while galactic photons shrink dλ/dt < 0. Contrary to a PRL editor's claim, the above results show LJ12135 fits PRL guidelines for papers that replace established theories. For details see alphacosmos.net.
How Do Various Maize Crop Models Vary in Their Responses to Climate Change Factors?
Bassu, Simona; Brisson, Nadine; Grassini, Patricio; Durand, Jean-Louis; Boote, Kenneth; Lizaso, Jon; Jones, James W.; Rosenzweig, Cynthia; Ruane, Alex C.; Adam, Myriam;
2014-01-01
Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO2], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly -0.5 Mg ha(sup 1) per degC. Doubling [CO2] from 360 to 720 lmol mol 1 increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO2] among models. Model responses to temperature and [CO2] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.
Modelling plasma response to RMP fields in ASDEX Upgrade with varying edge safety factor and triangularity
Li, L.; Liu, Y. Q.; Kirk, A.; Wang, N.; Liang, Y.; Ryan, D.; Suttrop, W.; Dunne, M.; Fischer, R.; Fuchs, J. C.; Kurzan, B.; Piovesan, P.; Willensdorfer, M.; Zhong, F. C.; the ASDEX Upgrade Team; the EUROfusion MST1 Team
2016-12-01
Toroidal computations are performed using the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), in order to understand correlations between the plasma response and the observed mitigation of the edge localized modes (ELM) using resonant magnetic perturbation fields in ASDEX Upgrade. In particular, systematic numerical scans of the edge safety factor reveal that the amplitude of the resonant poloidal harmonic of the response radial magnetic field near the plasma edge, as well as the plasma radial displacement near the X-point, can serve as good indicators for predicting the optimal toroidal phasing between the upper and lower rows of coils in ASDEX Upgrade. The optimal coil phasing scales roughly linearly with the edge safety factor {{q}95} , for various choices of the toroidal mode number n = 1-4 of the coil configuration. The optimal coil phasing is also predicted to vary with the upper triangularity of the plasma shape in ASDEX Upgrade. Furthermore, multiple resonance effects of the plasma response, with continuously varying {{q}95} , are computationally observed and investigated.
Wright, Aidan G.C.; Hallquist, Michael N.; Swartz, Holly A.; Frank, Ellen; Cyranowski, Jill M.
2014-01-01
Objective We demonstrate the utility of the time-varying effect model (TVEM) for the analysis of psychotherapy data, with the aim of elucidating complex patterns of change over time and dynamic associations between constructs of interest. Specifically, we examine the association between depression and co-occurring anxiety in a sample of adults treated with interpersonal psychotherapy for depression (IPT) or a variant designed to address both depression and co-occurring anxiety (IPT-PS, IPT for depression with panic and anxiety symptoms). Method Seventy-eight (82% female) adult outpatients with major depression and co-occurring anxiety were assessed at each of 16 outpatient treatment sessions using the Hamilton rating scales for depression and anxiety. Results On average, depressive symptoms declined in a quadratic form over the course of treatment. While the association between anxiety and depression was modest early in treatment, it strengthened over the middle and latter treatment phases. Finally, exploratory analyses suggest that while IPT and IPT-PS were similarly effective in reducing depressive symptoms, IPT-PS may be more effective at uncoupling the association between core anxiety and depressive symptoms. Conclusions Findings point to the utility of the TVEM for psychotherapy research, and the importance of assessing anxiety in the course of treating depression, especially following the initial phase of treatment (i.e., after session 5). PMID:24041230
Modelling the solidification of ductile cast iron parts with varying wall thicknesses
DEFF Research Database (Denmark)
Bjerre, Mathias Karsten; Tiedje, Niels Skat; Thorborg, Jesper
2015-01-01
] with a 2D FE solution of the heat conduction equation is developed in an in-house code and model parameters are calibrated using experimental data from representative castings made of ductile cast iron. The main focus is on the influence of casting thickness and resulting local cooling conditions......In the present paper modelling the solidification of cast iron parts is considered. Common for previous efforts in this field is that they have mainly considered thin walled to medium thickness castings. Hence, a numerical model combining the solidification model presented by Lesoultet al. [1...
Plane Symmetric Viscous Fluid Cosmological Models with Varying Λ-Term
Pradhan, Anirudh; Pandey, Purnima; Jotania, Kanti; Yadav, Mahesh Kumar
2007-11-01
Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.
Consumer acceptance of model soup system with varying levels of herbs and salt.
Wang, Chao; Lee, Youngsoo; Lee, Soo-Yeun
2014-10-01
Although herbs have been reported as one of the most common saltiness enhancers, few studies have focused on the effect of herbs on reducing added sodium as well as the impact of herbs on consumers' overall liking of foods. Therefore, the objectives of this study were to determine the effect of varying levels of herbs on reducing added sodium and consumers' overall liking of soups and identify the impact of salt levels on consumers' overall liking of soups. Overall liking of freshly prepared and retorted canned soups with varying levels of herbs was evaluated before and after adding salt by consumers ad libitum until the saltiness of the soup was just about right for them. The results of the study demonstrated that when the perceived herb flavor increased, the amount of salt consumers added to fresh soups decreased (P ≤ 0.006); however, consumers' overall liking decreased (P ≤ 0.013) as well for the highest level of herb tested in the study. Although overall liking of all canned soups was not significantly decreased by herbs, the amount of salt consumers added was also not significantly decreased when herbs were used. Overall liking of all soups significantly increased after more salt was added (P ≤ 0.001), which indicates that salt level was a dominant factor in affecting consumers' overall liking of soups with varying levels of herbs. These findings imply the role of herbs in decreasing salt intake, and the adequate amount of herbs to be added in soup systems. It is challenging for the food industry to reduce sodium in foods without fully understanding the impact of sodium reduction on sensory properties of foods. Herbs are recommended to use in reducing sodium; however, little has been reported regarding the effect of herbs on sodium reduction and how herbs influence consumers’ acceptance of foods. This study provides findings that herbs may aid in decreasing the amount of salt consumers need to add for freshly prepared soups. It was also found that high
Ishibashi, Nobuyuki; Iwata, Yusuke; Okamura, Toru; Zurakowski, David; Lidov, Hart G.W.; Jonas, Richard A.
2010-01-01
Objective We investigated whether the degree of vulnerability of different areas in the developing brain varies according to the specific mechanism of the insults caused by cardiopulmonary bypass. Methods A meta-analysis of two experimental studies (n = 80) was conducted. The end points of the otherwise identical studies were tissue oxygen index in experiment one while cerebral micro-vessel vasoconstriction and inflammatory response of endothelial cells were directly visualized in the second study. We assigned ultra-low flow bypass at 25°C for 60 min as Control; circulatory arrest at 25°C for 60 min as ischemic stress under circulatory arrest (Ischemia-CA); and ultra-low flow bypass at 34°C for 60 min as the stress under ultra-low flow bypass (Ischemia-ULF). Histological neuronal damage was the primary outcome. Secondary measures included neurological recovery. Results Vasoconstriction following ischemia and inflammation after bypass were independent predictors of severe histological damage. The caudate nucleus was significantly vulnerable to Ischemia-CA and was significantly influenced by vasoconstriction. In contrast, the hippocampus was significantly vulnerable to Ischemia-ULF. The different forms of ischemic insults did not influence Purkinje cells, while Purkinje damage significantly correlated with inflammation. Tissue oxygen index had the ability to differentiate accurately regional damage. Neurological recovery under Ischemia-CA was significantly worse compared with Ischemia-ULF. Neurological recovery correlated with neuronal damage in the caudate nucleus, but did not correlate with damage in the hippocampus. Conclusion Neuronal vulnerability in different areas of the developing brain varies according to mechanisms of bypass-induced ischemic stress. Certain regional damage may not be apparent in assessing acute neurological recovery. PMID:20434176
Time-Varying Scheme for Non-Centralized Model Predictive Control of Large-scale Systems
Nunez Vicencio, A.A.; Ocampo-Martinez, C.; Maestre, J.M.; De Schutter, B.H.K.
2015-01-01
The Non-Centralized Model Predictive Control (NC-MPC) framework refers in this paper to any distributed, hierarchical, or decentralized model predictive controller (or a combination of them) the structure of which can change over time and the control actions of which are not obtained based on a
Modeling time-varying exposure using inverse probability of treatment weights
Grafféo, Nathalie; Latouche, Aurélien; Geskus, Ronald B.; Chevret, Sylvie
2017-01-01
For estimating the causal effect of treatment exposure on the occurrence of adverse events, inverse probability weights (IPW) can be used in marginal structural models to correct for time-dependent confounding. The R package ipw allows IPW estimation by modeling the relationship between the exposure
The Office of Pesticide Programs models daily aquatic pesticide exposure values for 30 years in its risk assessments. However, only a fraction of that information is typically used in these assessments. The population model employed herein is a deterministic, density-dependent pe...
Representing time-varying cyclic dynamics using multiple-subject state-space models
Chow, Sy-Miin; Hamaker, E.L.; Fujita, Frank; Boker, Steven M.
2009-01-01
Over the last few decades, researchers have become increasingly aware of the need to consider intraindividual variability in the form of cyclic processes. In this paper, we review two contemporary cyclic state-space models: Young and colleagues' dynamic harmonic regression model and Harvey and
Cylindrically symmetric inhomogeneous cosmological models with viscous fluid and varying Λ
Pradhan, Anirudh; Singh, Prashant Kumar; Jotania, R. Kanti
2006-06-01
Cylindrically symmetric non-static cosmological models representing a bulk viscous fluid distribution have been obtained which are inhomogeneous and anisotropic. Without assuming any adhoc law, we obtain a cosmological constant as a decreasing function of time. Various physical and geometrical features of the models are also discussed.
Sotero, Roberto C; Shmuel, Amir
2012-06-01
Several studies posit energy as a constraint on the coding and processing of information in the brain due to the high cost of resting and evoked cortical activity. This suggestion has been addressed theoretically with models of a single neuron and two coupled neurons. Neural mass models (NMMs) address mean-field based modeling of the activity and interactions between populations of neurons rather than a few neurons. NMMs have been widely employed for studying the generation of EEG rhythms, and more recently as frameworks for integrated models of neurophysiology and functional MRI (fMRI) responses. To date, the consequences of energy constraints on the activity and interactions of ensembles of neurons have not been addressed. Here we aim to study the impact of constraining energy consumption during the resting-state on NMM parameters. To this end, we first linearized the model, then used stochastic control theory by introducing a quadratic cost function, which transforms the NMM into a stochastic linear quadratic regulator (LQR). Solving the LQR problem introduces a regime in which the NMM parameters, specifically the effective connectivities between neuronal populations, must vary with time. This is in contrast to current NMMs, which assume a constant parameter set for a given condition or task. We further simulated energy-constrained stochastic control of a specific NMM, the Wilson and Cowan model of two coupled neuronal populations, one of which is excitatory and the other inhibitory. These simulations demonstrate that with varying weights of the energy-cost function, the NMM parameters show different time-varying behavior. We conclude that constraining NMMs according to energy consumption may create more realistic models. We further propose to employ linear NMMs with time-varying parameters as an alternative to traditional nonlinear NMMs with constant parameters.
Directory of Open Access Journals (Sweden)
Miholca CONSTANTIN
2008-07-01
Full Text Available The paper presents a method of mathematical modelling of a solar converter using the results of full-scale testing. The advantages of analytical modelling method applied to photovoltaic systems are also presented; this is because the model parameters are directly measurable by data acquisition from the photovoltaic field consisting of photovoltaic cells type Z - (mono-crystalline photovoltaic. The model parameter also includes both the photovoltaic cell characteristics as a device (forming the photovoltaic field and the temperature influence on the photovoltaic field performance. The results of the photovoltaic model numerical simulation (PV to the major parameters conversion variation can also be used to design and assess the performance of low and medium - power photovoltaic systems operating in single regime (to supply the home appliances.
Molecular dynamics simulations of proteins: can the explicit water model be varied?
Energy Technology Data Exchange (ETDEWEB)
Nutt, David [University of Heidelberg; Smith, Jeremy C [ORNL
2007-03-01
In molecular mechanics simulations of biological systems, the solvation water is typically represented by a default water model which is an integral part of the force field. Indeed, protein nonbonding parameters are chosen in order to obtain a balance between water-water and protein-water interactions and hence a reliable description of protein solvation. However, less attention has been paid to the question of whether the water model provides a reliable description of the water properties under the chosen simulation conditions, for which more accurate water models often exist. Here we consider the case of the CHARMM protein force field, which was parameterized for use with a modified TIP3P model. Using quantum mechanical and molecular mechanical calculations, we investigate whether the CHARMM force field can be used with other water models: TIP4P and TIP5P. Solvation properties of N-methylacetamide (NMA), other small solute molecules, and a small protein are examined. The results indicate differences in binding energies and minimum energy geometries, especially for TIP5P, but the overall description of solvation is found to be similar for all models tested. The results provide an indication that molecular mechanics simulations with the CHARMM force field can be performed with water models other than TIP3P, thus enabling an improved description of the solvent water properties.
Molecular Dynamics Simulations of Proteins: Can the Explicit Water Model Be Varied?
Energy Technology Data Exchange (ETDEWEB)
Smith, Jeremy C [ORNL; Nutt, David [University of Heidelberg
2007-01-01
In molecular mechanics simulations of biological systems, the solvation water is typically represented by a default water model which is an integral part of the force field. Indeed, protein nonbonding parameters are chosen in order to obtain a balance between water-water and protein-water interactions and hence a reliable description of protein solvation. However, less attention has been paid to the question of whether the water model provides a reliable description of the water properties under the chosen simulation conditions, for which more accurate water models often exist. Here we consider the case of the CHARMM protein force field, which was parameterized for use with a modified TIP3P model. Using quantum mechanical and molecular mechanical calculations, we investigate whether the CHARMM force field can be used with other water models: TIP4P and TIP5P. Solvation properties of N-methylacetamide (NMA), other small solute molecules, and a small protein are examined. The results indicate differences in binding energies and minimum energy geometries, especially for TIP5P, but the overall description of solvation is found to be similar for all models tested. The results provide an indication that molecular mechanics simulations with the CHARMM force field can be performed with water models other than TIP3P, thus enabling an improved description of the solvent water properties.
Directory of Open Access Journals (Sweden)
Philipp Singer
Full Text Available One of the most frequently used models for understanding human navigation on the Web is the Markov chain model, where Web pages are represented as states and hyperlinks as probabilities of navigating from one page to another. Predominantly, human navigation on the Web has been thought to satisfy the memoryless Markov property stating that the next page a user visits only depends on her current page and not on previously visited ones. This idea has found its way in numerous applications such as Google's PageRank algorithm and others. Recently, new studies suggested that human navigation may better be modeled using higher order Markov chain models, i.e., the next page depends on a longer history of past clicks. Yet, this finding is preliminary and does not account for the higher complexity of higher order Markov chain models which is why the memoryless model is still widely used. In this work we thoroughly present a diverse array of advanced inference methods for determining the appropriate Markov chain order. We highlight strengths and weaknesses of each method and apply them for investigating memory and structure of human navigation on the Web. Our experiments reveal that the complexity of higher order models grows faster than their utility, and thus we confirm that the memoryless model represents a quite practical model for human navigation on a page level. However, when we expand our analysis to a topical level, where we abstract away from specific page transitions to transitions between topics, we find that the memoryless assumption is violated and specific regularities can be observed. We report results from experiments with two types of navigational datasets (goal-oriented vs. free form and observe interesting structural differences that make a strong argument for more contextual studies of human navigation in future work.
Singer, Philipp; Helic, Denis; Taraghi, Behnam; Strohmaier, Markus
2014-01-01
One of the most frequently used models for understanding human navigation on the Web is the Markov chain model, where Web pages are represented as states and hyperlinks as probabilities of navigating from one page to another. Predominantly, human navigation on the Web has been thought to satisfy the memoryless Markov property stating that the next page a user visits only depends on her current page and not on previously visited ones. This idea has found its way in numerous applications such as Google's PageRank algorithm and others. Recently, new studies suggested that human navigation may better be modeled using higher order Markov chain models, i.e., the next page depends on a longer history of past clicks. Yet, this finding is preliminary and does not account for the higher complexity of higher order Markov chain models which is why the memoryless model is still widely used. In this work we thoroughly present a diverse array of advanced inference methods for determining the appropriate Markov chain order. We highlight strengths and weaknesses of each method and apply them for investigating memory and structure of human navigation on the Web. Our experiments reveal that the complexity of higher order models grows faster than their utility, and thus we confirm that the memoryless model represents a quite practical model for human navigation on a page level. However, when we expand our analysis to a topical level, where we abstract away from specific page transitions to transitions between topics, we find that the memoryless assumption is violated and specific regularities can be observed. We report results from experiments with two types of navigational datasets (goal-oriented vs. free form) and observe interesting structural differences that make a strong argument for more contextual studies of human navigation in future work.
DEFF Research Database (Denmark)
Silvennoinen, Annestiina; Terasvirta, Timo
A new multivariate volatility model that belongs to the family of conditional correlation GARCH models is introduced. The GARCH equations of this model contain a multiplicative deterministic component to describe long-run movements in volatility and, in addition, the correlations are deterministi......A new multivariate volatility model that belongs to the family of conditional correlation GARCH models is introduced. The GARCH equations of this model contain a multiplicative deterministic component to describe long-run movements in volatility and, in addition, the correlations...... are deterministically time-varying. Parameters of the model are estimated jointly using maximum likelihood. Consistency and asymptotic normality of maximum likelihood estimators is proved. Numerical aspects of the estimation algorithm are discussed. A bivariate empirical example is provided....
Analysis of credit linked demand in an inventory model with varying ordering cost.
Banu, Ateka; Mondal, Shyamal Kumar
2016-01-01
In this paper, we have considered an economic order quantity model for deteriorating items with two-level trade credit policy in which a delay in payment is offered by a supplier to a retailer and also an another delay in payment is offered by the retailer to his/her all customers. Here, it is proposed that the demand function is dependent on the length of the customer's credit period and also the duration of offering the credit period. In this article, it is considered that the retailer's ordering cost per order depends on the number of replenishment cycles. The objective of this model is to establish a deterministic EOQ model of deteriorating items for the retailer to decide the position of customers credit period and the number of replenishment cycles in finite time horizon such that the retailer gets the maximum profit. Also, the model is explained with the help of some numerical examples.
Nanoscale Vacuum Channel Transistor.
Han, Jin-Woo; Moon, Dong-Il; Meyyappan, M
2017-04-12
Vacuum tubes that sparked the electronics era had given way to semiconductor transistors. Despite their faster operation and better immunity to noise and radiation compared to the transistors, the vacuum device technology became extinct due to the high power consumption, integration difficulties, and short lifetime of the vacuum tubes. We combine the best of vacuum tubes and modern silicon nanofabrication technology here. The surround gate nanoscale vacuum channel transistor consists of sharp source and drain electrodes separated by sub-50 nm vacuum channel with a source to gate distance of 10 nm. This transistor performs at a low voltage (3 microamperes). The nanoscale vacuum channel transistor can be a possible alternative to semiconductor transistors beyond Moore's law.
Consumption and credit: a model of time-varying liquidity constraints
Sydney Ludvigson
1996-01-01
This paper investigates the role of consumer credit in determining real consumption growth in aggregate, post-war U.S. data. This paper presents evidence that predictable growth in consumer credit is significantly related to consumption growth. The finding is inconsistent with the predictions of (I) the permanent income/life cycle hypothesis, (ii) the "rule of thumb" models where some agents simply consume their current income, and (iii) models of liquidity constraints where individuals face ...
Some Inhomogeneous Magnetized Viscous-Fluid Cosmological Models with Varying Λ
Pradhan, Anirudh; Srivastav, Sudhir Kumar; Jotania, Kanti R.
2004-02-01
Some cylindrically symmetric inhomogeneous viscous-fluid cosmological models with electromagnetic field are obtained. To get a solution a supplementary condition between metric potentials is used. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Without assuming any ad hoc law, we obtain a cosmological constant as a decreasing function of time. The behaviour of the electromagnetic field tensor together with some physical aspects of the model are also discussed.
Modeling time-varying exposure using inverse probability of treatment weights.
Grafféo, Nathalie; Latouche, Aurélien; Geskus, Ronald B; Chevret, Sylvie
2017-12-27
For estimating the causal effect of treatment exposure on the occurrence of adverse events, inverse probability weights (IPW) can be used in marginal structural models to correct for time-dependent confounding. The R package ipw allows IPW estimation by modeling the relationship between the exposure and confounders via several regression models, among which is the Cox model. For right-censored data and time-dependent exposures such as treatment switches, the ipw package allows a single switch, assuming that patients are treated once and for all. However, to accommodate multiple switches, we extend this package by implementing a function that allows for multiple and intermittent exposure status in the estimation of IPW using a survival model. This extension allows for the whole exposure treatment trajectory in the estimation of IPW. The impact of the estimated weights on the estimated causal effect, with both methods, is assessed in a simulation study. Then, the function is illustrated on a real dataset from a nationwide prospective observational cohort including patients with inflammatory bowel disease. In this study, patients received one or multiple medications (thiopurines, methotrexate, and anti-TNF) over time. We used a Cox marginal structural model to assess the effect of thiopurines exposure on the cause-specific hazard for cancer incidence considering other treatments as confounding factors. To this end, we used our extended function which is available online in the Supporting Information. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Georgiou, George K; Aro, Mikko; Liao, Chen-Huei; Parrila, Rauno
2016-03-01
The purpose of this study was twofold: (a) to contrast the prominent theoretical explanations of the rapid automatized naming (RAN)-reading relationship across languages varying in orthographic consistency (Chinese, English, and Finnish) and (b) to examine whether the same accounts can explain the RAN-spelling relationship. In total, 304 Grade 4 children (102 Chinese-speaking Taiwanese children, 117 English-speaking Canadian children, and 85 Finnish-speaking children) were assessed on measures of RAN, speed of processing, phonological processing, orthographic processing, reading fluency, and spelling. The results of path analysis indicated that RAN had a strong direct effect on reading fluency that was of the same size across languages and that only in English was a small proportion of its predictive variance mediated by orthographic processing. In contrast, RAN did not exert a significant direct effect on spelling, and a substantial proportion of its predictive variance was mediated by phonological processing (in Chinese and Finnish) and orthographic processing (in English). Given that RAN predicted reading fluency equally well across languages and that phonological/orthographic processing had very little to do with this relationship, we argue that the reason why RAN is related to reading fluency should be sought in domain-general factors such as serial processing and articulation. Copyright © 2015 Elsevier Inc. All rights reserved.
Modular use of human body models of varying levels of complexity: Validation of head kinematics.
Decker, William; Koya, Bharath; Davis, Matthew L; Gayzik, F Scott
2017-05-29
The significant computational resources required to execute detailed human body finite-element models has motivated the development of faster running, simplified models (e.g., GHBMC M50-OS). Previous studies have demonstrated the ability to modularly incorporate the validated GHBMC M50-O brain model into the simplified model (GHBMC M50-OS+B), which allows for localized analysis of the brain in a fraction of the computation time required for the detailed model. The objective of this study is to validate the head and neck kinematics of the GHBMC M50-O and M50-OS (detailed and simplified versions of the same model) against human volunteer test data in frontal and lateral loading. Furthermore, the effect of modular insertion of the detailed brain model into the M50-OS is quantified. Data from the Navy Biodynamics Laboratory (NBDL) human volunteer studies, including a 15g frontal, 8g frontal, and 7g lateral impact, were reconstructed and simulated using LS-DYNA. A five-point restraint system was used for all simulations, and initial positions of the models were matched with volunteer data using settling and positioning techniques. Both the frontal and lateral simulations were run with the M50-O, M50-OS, and M50-OS+B with active musculature for a total of nine runs. Normalized run times for the various models used in this study were 8.4 min/ms for the M50-O, 0.26 min/ms for the M50-OS, and 0.97 min/ms for the M50-OS+B, a 32- and 9-fold reduction in run time, respectively. Corridors were reanalyzed for head and T1 kinematics from the NBDL studies. Qualitative evaluation of head rotational accelerations and linear resultant acceleration, as well as linear resultant T1 acceleration, showed reasonable results between all models and the experimental data. Objective evaluation of the results for head center of gravity (CG) accelerations was completed via ISO TS 18571, and indicated scores of 0.673 (M50-O), 0.638 (M50-OS), and 0.656 (M50-OS+B) for the 15g frontal impact
Comparison of the kinetics of different Markov models for ligand binding under varying conditions.
Martini, Johannes W R; Habeck, Michael
2015-03-07
We recently derived a Markov model for macromolecular ligand binding dynamics from few physical assumptions and showed that its stationary distribution is the grand canonical ensemble [J. W. R. Martini, M. Habeck, and M. Schlather, J. Math. Chem. 52, 665 (2014)]. The transition probabilities of the proposed Markov process define a particular Glauber dynamics and have some similarity to the Metropolis-Hastings algorithm. Here, we illustrate that this model is the stochastic analog of (pseudo) rate equations and the corresponding system of differential equations. Moreover, it can be viewed as a limiting case of general stochastic simulations of chemical kinetics. Thus, the model links stochastic and deterministic approaches as well as kinetics and equilibrium described by the grand canonical ensemble. We demonstrate that the family of transition matrices of our model, parameterized by temperature and ligand activity, generates ligand binding kinetics that respond to changes in these parameters in a qualitatively similar way as experimentally observed kinetics. In contrast, neither the Metropolis-Hastings algorithm nor the Glauber heat bath reflects changes in the external conditions correctly. Both converge rapidly to the stationary distribution, which is advantageous when the major interest is in the equilibrium state, but fail to describe the kinetics of ligand binding realistically. To simulate cellular processes that involve the reversible stochastic binding of multiple factors, our pseudo rate equation model should therefore be preferred to the Metropolis-Hastings algorithm and the Glauber heat bath, if the stationary distribution is not of only interest.
Implications of Time Varying Cosmological Constant on Kaluza-Klein Cosmological Model
Jain, Namrata I.; Bhoga, S. S.; Khadekar, G. S.
2013-12-01
In this paper, the cosmological model with variable in Kaluza-Klein metric have been studied. Here α and β are dimensionless parameters. The solutions to Einstein field equations which assume that the Universe is filled with perfect fluid have been obtained by using the Gamma Law Equation p=( γ-1) ρ; in which the parameter γ is constant and power law equation A( t)= R n ( t)—where A( t) is scale factor for extra dimension and R( t) is scale factor for space dimensions. The fifth dimension for the radiation dominated phases is more prominent with this model. Other physical parameters i.e. density, pressure, deceleration parameter, Hubble parameter have been determined for this model. It is observed physical parameters depends upon constants α, β and n. Neo-classical tests have also been studied in this paper.
Directory of Open Access Journals (Sweden)
A. N. Chichko
2013-01-01
Full Text Available The computer simulation of the characteristics of manufacturing technology of the iron casting «body» for different correlations of feeder, slag traps and riser, recommended for the molds obtained by vacuum-film forming is carried out. The volume evolution of filling of the casting is calculated and dependences of speed instability and its projections on period of filling in assigned points of the mold are established.
Lin, Hao-Cheng; Yang, Wen-Li; Zhang, Jun-Lan; Dai, Yu-Tian; Wang, Run
2013-01-01
Our previous study showed that vacuum erectile device (VED) therapy has improved erectile function in rats with bilateral cavernous nerve crush (BCNC) injuries. This study was designed to explore the mechanism of VED in penile rehabilitation by analyzing cavernous oxygen saturation (SO2) and to examine the effect of VED therapy on preventing penile shrinkage after BCNC. Thirty adult Sprague–Dawley rats were randomly assigned into three groups: group 1, sham surgery; group 2, BCNC; and group 3...
Vacuum alignment with and without elementary scalars
DEFF Research Database (Denmark)
Alanne, Tommi; Gertov, Helene; Meroni, Aurora
2016-01-01
We systematically elucidate differences and similarities of the vacuum alignment issue in composite and renormalizable elementary extensions of the Standard Model featuring a pseudo-Goldstone Higgs. We also provide general conditions for the stability of the vacuum in the elementary framework...
Nitric oxide levels in the aqueous humor vary in different ocular hypertension experimental models
Directory of Open Access Journals (Sweden)
Da-Wen Lu
2014-12-01
Full Text Available This study investigated the relationships among intraocular pressure (IOP, nitric oxide (NO levels, and aqueous flow rates in experimental ocular hypertension models. A total of 75 rabbits were used. One of four different materials [i.e., α-chymotrypsin, latex microspheres (Polybead, red blood cell ghosts, or sodium hyaluronate (Healon GV] was injected into the eyes of the 15 animals in each experimental group; the remaining 15 rabbits were reserved for a control group. The IOP changes in the five groups were recorded on postinduction Days 1–3, Day 7, Day 14, Day 30, Day 60, Day 90, and Day 120. On postinduction Day 7, the dynamics and NO levels in the aqueous humor were recorded. Significant IOP elevations were induced by α-chymotrypsin (p < 0.01 and Polybead (p < 0.01 on each postinduction day. In the red blood cell ghosts model, significant elevations (p < 0.01 were found on postinduction Days 1–3; Healon GV significantly elevated IOP (p < 0.01 on postinduction Day 1 and Day 2. On postinduction Day 7, the aqueous humor NO levels increased significantly in the models of α-chymotrypsin, Polybead, and red blood cell ghosts (all p < 0.01, while the aqueous flow rates were significantly reduced in the models of α-chymotrypsin and Polybead (p < 0.005. Persistent ocular hypertension models were induced with α-chymotrypsin and Polybead in the rabbits. The Polybead model exhibited the characteristic of an increased aqueous humor NO level, similar to human eyes with acute angle-closure glaucoma and neovascular glaucoma.
The influence of temperature on ozone production under varying NOx conditions - a modelling study
Coates, Jane; Mar, Kathleen A.; Ojha, Narendra; Butler, Tim M.
2016-09-01
Surface ozone is a secondary air pollutant produced during the atmospheric photochemical degradation of emitted volatile organic compounds (VOCs) in the presence of sunlight and nitrogen oxides (NOx). Temperature directly influences ozone production through speeding up the rates of chemical reactions and increasing the emissions of VOCs, such as isoprene, from vegetation. In this study, we used an idealised box model with different chemical mechanisms (Master Chemical Mechanism, MCMv3.2; Common Representative Intermediates, CRIv2; Model for OZone and Related Chemical Tracers, MOZART-4; Regional Acid Deposition Model, RADM2; Carbon Bond Mechanism, CB05) to examine the non-linear relationship between ozone, NOx and temperature, and we compared this to previous observational studies. Under high-NOx conditions, an increase in ozone from 20 to 40 °C of up to 20 ppbv was due to faster reaction rates, while increased isoprene emissions added up to a further 11 ppbv of ozone. The largest inter-mechanism differences were obtained at high temperatures and high-NOx emissions. CB05 and RADM2 simulated more NOx-sensitive chemistry than MCMv3.2, CRIv2 and MOZART-4, which could lead to different mitigation strategies being proposed depending on the chemical mechanism. The increased oxidation rate of emitted VOC with temperature controlled the rate of Ox production; the net influence of peroxy nitrates increased net Ox production per molecule of emitted VOC oxidised. The rate of increase in ozone mixing ratios with temperature from our box model simulations was about half the rate of increase in ozone with temperature observed over central Europe or simulated by a regional chemistry transport model. Modifying the box model set-up to approximate stagnant meteorological conditions increased the rate of increase of ozone with temperature as the accumulation of oxidants enhanced ozone production through the increased production of peroxy radicals from the secondary degradation of
Indian Vacuum Society: The Indian Vacuum Society
Saha, T. K.
2008-03-01
The Indian Vacuum Society (IVS) was established in 1970. It has over 800 members including many from Industry and R & D Institutions spread throughout India. The society has an active chapter at Kolkata. The society was formed with the main aim to promote, encourage and develop the growth of Vacuum Science, Techniques and Applications in India. In order to achieve this aim it has conducted a number of short term courses at graduate and technician levels on vacuum science and technology on topics ranging from low vacuum to ultrahigh vacuum So far it has conducted 39 such courses at different parts of the country and imparted training to more than 1200 persons in the field. Some of these courses were in-plant training courses conducted on the premises of the establishment and designed to take care of the special needs of the establishment. IVS also regularly conducts national and international seminars and symposia on vacuum science and technology with special emphasis on some theme related to applications of vacuum. A large number of delegates from all over India take part in the deliberations of such seminars and symposia and present their work. IVS also arranges technical visits to different industries and research institutes. The society also helped in the UNESCO sponsored post-graduate level courses in vacuum science, technology and applications conducted by Mumbai University. The society has also designed a certificate and diploma course for graduate level students studying vacuum science and technology and has submitted a syllabus to the academic council of the University of Mumbai for their approval, we hope that some colleges affiliated to the university will start this course from the coming academic year. IVS extended its support in standardizing many of the vacuum instruments and played a vital role in helping to set up a Regional Testing Centre along with BARC. As part of the development of vacuum education, the society arranges the participation of
Directory of Open Access Journals (Sweden)
M. Lockwood
2004-01-01
Full Text Available This paper presents a numerical model for predicting the evolution of the pattern of ionospheric convection in response to general time-dependent magnetic reconnection at the dayside magnetopause and in the cross-tail current sheet of the geomagnetic tail. The model quantifies the concepts of ionospheric flow excitation by Cowley and Lockwood (1992, assuming a uniform spatial distribution of ionospheric conductivity. The model is demonstrated using an example in which travelling reconnection pulses commence near noon and then move across the dayside magnetopause towards both dawn and dusk. Two such pulses, 8min apart, are used and each causes the reconnection to be active for 1min at every MLT that they pass over. This example demonstrates how the convection response to a given change in the interplanetary magnetic field (via the reconnection rate depends on the previous reconnection history. The causes of this effect are explained. The inherent assumptions and the potential applications of the model are discussed. Key words. Ionosphere (ionosphere-magnetosphere interactions; plasma convection – Magnetospheric physics (magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions
Slab detachment in laterally varying subduction zones: 3-D numerical modeling
Duretz, T.; Gerya, T.V.; Spakman, W.|info:eu-repo/dai/nl/074103164
Understanding the three-dimensional (3-D) dynamics of subduction-collision systems is a longstanding challenge in geodynamics. We investigate the impact of slab detachment in collision systems that are subjected to along-trench variations. High-resolution thermomechanical numerical models,
Modeling complex flow structures and drag around a submerged plant of varied posture
Boothroyd, Richard J.; Hardy, Richard J.; Warburton, Jeff; Marjoribanks, Timothy I.
2017-04-01
Although vegetation is present in many rivers, the bulk of past work concerned with modeling the influence of vegetation on flow has considered vegetation to be morphologically simple and has generally neglected the complexity of natural plants. Here we report on a combined flume and numerical model experiment which incorporates time-averaged plant posture, collected through terrestrial laser scanning, into a computational fluid dynamics model to predict flow around a submerged riparian plant. For three depth-limited flow conditions (Reynolds number = 65,000-110,000), plant dynamics were recorded through high-definition video imagery, and the numerical model was validated against flow velocities collected with an acoustic Doppler velocimeter. The plant morphology shows an 18% reduction in plant height and a 14% increase in plant length, compressing and reducing the volumetric canopy morphology as the Reynolds number increases. Plant shear layer turbulence is dominated by Kelvin-Helmholtz type vortices generated through shear instability, the frequency of which is estimated to be between 0.20 and 0.30 Hz, increasing with Reynolds number. These results demonstrate the significant effect that the complex morphology of natural plants has on in-stream drag, and allow a physically determined, species-dependent drag coefficient to be calculated. Given the importance of vegetation in river corridor management, the approach developed here demonstrates the necessity to account for plant motion when calculating vegetative resistance.
DEFF Research Database (Denmark)
Topping, C; Ostergaard, S; Pertoldi, C
2003-01-01
heterogeneity. Results showed that both spatial and temporal heterogeneity exerted an influence on the rate of loss of genetic diversity, but the precise effect was a balance between the effects of population sub-structuring, the frequency of founder effects and population size. These were in turn related...... conditions, but exclude factors such as animal behaviour, environmental structure, and breeding biology, all of which influence genetic diversity. Most populations are unique in some of these characteristics, and therefore may be unsuitable for the classical approach. Here, an alternative approach using...... a genetically explicit individual-based model (IBM) coupled to a dynamic landscape model was used to obtain measures for the genetic status of simulated vole populations. The rate of loss of expected heterozygosity (H-e) was calculated for simulated populations using two levels of spatial and temporal...
Cutaneous and systemic effects of varying doses of brown recluse spider venom in a rabbit model.
McGlasson, David L; Harroff, Hugh H; Sutton, Jackie; Dick, Edward; Elston, Dirk M
2007-01-01
To ascertain whether a dose response exists between the dose of brown recluse spider venom (BRSV) and the cutaneous and coagulation effects in a rabbit model. Cutaneous necrosis is a serious complication of brown recluse spider envenomation (spider bite with venom). Disseminated intravascular coagulation (DIC) is a dreaded complication of brown recluse envenomation in humans. New Zealand white (NZW) rabbits have proved to be a model for the study of therapeutic regimens to prevent skin necrosis after spider bites. We studied the venom's effects on the skin and the coagulation mechanism in this rabbit model to determine if a clear dose-response relationship could be established. Establishment of a dose-response relationship is an important first step in determining if the NZW rabbit is a suitable model to study both cutaneous and systemic effects of the venom. Thirty-six NZW rabbits were divided into three groups. One group received a saline injection, and the other two groups received a 4.0 microg or a 10.0 microg dose of purified BRSV intradermally into the skin on the dorsum of the back. Blood was collected at baseline, 24, 48, and 72 hours. Tissue specimens were obtained after seven days during the animal necropsy and gross and microscopic pathology examination was conducted to assess tissue damage. Measurements included complete blood count (CBC); platelets; PT; activated partial thromboplastin time (APTT); fibrinogen (clottable, immunological); coagulation factors II, V, VII, VIII, IX, X, XI, XII; anti-thrombin (AT); alpha-2 antiplasmin (AP); Protein C (PC); mixing studies; lupus anticoagulant screening; plasminogen; thrombin-antithrombin; fibrin degradation products (FDP); d-dimer; and thrombin time. Gross pathology results were consistent with previous studies that used higher doses of BRSV. The WBC and platelet counts decreased at 24 hours in the two groups receiving the BRSV (p brown recluse envenomation. Further studies to identify this factor could shed
DEFF Research Database (Denmark)
Kepler, Jørgen Asbøl; Hansen, Michael Rygaard
2007-01-01
thickness but significantly smaller than panel length dimensions. Experimental data for the total loss in impactor kinetic energy and momentum and estimated damage energy are described. For a selection of impactor tip shapes, the numerical model is used to evaluate different simplified force histories...... between the impactor and the panel during penetration. The force histories are selected from a primary criterion of conservation of linear momentum in the impactor-panel system, and evaluated according to agreement with the total measured energy balance....
Sedigh Marvasti, S.; A. Gnanadesikan; A. A. Bidokhti; Dunne, J. P.; Ghader, S.
2016-01-01
Recent years have shown an increase in harmful algal blooms in the Northwest Arabian Sea and Gulf of Oman, raising the question of whether climate change will accelerate this trend. This has led us to examine whether the Earth System Models used to simulate phytoplankton productivity accurately capture bloom dynamics in this region – both in terms of the annual cycle and interannual variability. Satellite data (SeaWIFS ocean color) show two climatological blooms in this regi...
On the Use of Maps and Models in Conservation and Resource Management (Warning: Results May Vary
Directory of Open Access Journals (Sweden)
Vincent Lecours
2017-09-01
Full Text Available Conservation planning and management typically require accurate and spatially explicit data at scales that are relevant for conservation objectives. In marine conservation, these data are often combined with spatial analytical techniques to produce marine habitat maps. While marine habitat mapping is increasingly used to inform conservation efforts, this field is still relatively young and its methods are rapidly evolving. Because conservation efforts do not always specify standards or guidelines for the production of habitat maps, results can vary dramatically. As representations of real environmental characteristics, habitat maps are highly sensitive to how they are produced. In this review paper, I present four concepts that are known to cause variation in spatial representation and prediction of habitats: the methodology used, the quality and scale of the data, and the choice of variables in regards to fitness for use. I then discuss the potential antinomy associated with the use of habitat maps in conservation: while habitat maps have become an invaluable tool to inform and assist decision-making, maps of the same area built using different methods and data may provide dissimilar representations, thus providing different information and possibly leading to different decisions. Exploring the theories and methods that have proved effective in terrestrial conservation and the spatial sciences, and how they can be integrated in marine habitat mapping practices, could help improve maps used to support marine conservation efforts and result in more reliable products to inform conservation decisions. Having a strong, consistent, transparent, repeatable, and science-based protocol for data collection and mapping is essential for effectively supporting decision-makers in developing conservation and management plans. The development of user-friendly tools to assist in the application of such protocol is crucial to a widespread improvement in
E Fesmire, J.; Ancipink, J. B.; Swanger, A. M.; White, S.; Yarbrough, D.
2017-12-01
Thermal conductivity of low-density materials in thermal insulation systems varies dramatically with the environment: cold vacuum pressure, residual gas composition, and boundary temperatures. Using a reference material of aerogel composite blanket (reinforcement fibers surrounded by silica aerogel), an experimental basis for the physical heat transmission model of aerogel composites and other low-density, porous materials is suggested. Cryogenic-vacuum testing between the boundary temperatures of 78 K and 293 K is performed using a one meter cylindrical, absolute heat flow calorimeter with an aerogel blanket specimen exposed to different gas environments of nitrogen, helium, argon, or CO2. Cold vacuum pressures include the full range from 1×10-5 torr to 760 torr. The soft vacuum region, from about 0.1 torr to 10 torr, is complex and difficult to model because all modes of heat transfer – solid conduction, radiation, gas conduction, and convection – are significant contributors to the total heat flow. Therefore, the soft vacuum tests are emphasized for both heat transfer analysis and practical thermal data. Results for the aerogel composite blanket are analyzed and compared to data for its component materials. With the new thermal conductivity data, future applications of aerogel-based insulation systems are also surveyed. These include Mars exploration and surface systems in the 5 torr CO2 environment, field joints for vacuum-jacketed cryogenic piping systems, common bulkhead panels for cryogenic tanks on space launch vehicles, and liquid hydrogen cryofuel systems with helium purged conduits or enclosures.
Simulations and Vacuum Tests of a CLIC Accelerating Structure
Garion, C
2011-01-01
The Compact LInear Collider, under study, is based on room temperature high gradient structures. The vacuum specificities of these cavities are low conductance, large surface areas and a non-baked system. The main issue is to reach UHV conditions (typically 10-7 Pa) in a system where the residual vacuum is driven by water outgassing. A finite element model based on an analogy thermal/vacuum has been built to estimate the vacuum profile in an accelerating structure. Vacuum tests are carried out in a dedicated set-up, the vacuum performances of different configurations are presented and compared with the predictions.
Nguyen, Nhan T.; Hashemi, Kelley E.; Yucelen, Tansel; Arabi, Ehsan
2017-01-01
This paper presents a new adaptive control approach that involves a performance optimization objective. The problem is cast as a multi-objective optimal control. The control synthesis involves the design of a performance optimizing controller from a subset of control inputs. The effect of the performance optimizing controller is to introduce an uncertainty into the system that can degrade tracking of the reference model. An adaptive controller from the remaining control inputs is designed to reduce the effect of the uncertainty while maintaining a notion of performance optimization in the adaptive control system.
The efficacy of nisin can drastically vary when produced in situ in model cheeses.
Aly, Samar; Floury, Juliane; Piot, Michel; Lortal, Sylvie; Jeanson, Sophie
2012-10-01
Nisin, a bacteriocin produced by strains of Lactococcus lactis, has a broad inhibitory effect against Gram-positive bacteria. This study investigated the efficacy of nisin Z against Lactobacillus sakei when produced by a nisin-producing strain L. lactis in model cheeses manufactured with ultrafiltrated milk. These cheeses, containing 0, 4 or 10% of gelatin in their dry matter, were inoculated with both strains. Measurement of Lb. sakei loss of viability was an indirect indicator of nisin in situ efficacy. After 24 h, the loss of viability of Lb. sakei was from 0.73 ± 0.14 to 3.30 ± 0.60 log(10) cfu g(-1) in the cheeses with 0 and 10% of gelatin, respectively, indicating a better in situ efficacy of nisin when gelatin was incorporated. However, the concentration of nisin produced by Lactococcus was similar (3.5 μg g(-1)) in all model cheeses when measured using an enzyme-linked immune sorbent assay (ELISA). The growth of Lactococcus was slightly improved when gelatin was incorporated, leading to a higher lactate concentration, which is one of the factors explaining the increased nisin efficacy. These results reinforced previous observations that prediction of nisin efficacy in complex food systems remains difficult. Copyright © 2012 Elsevier Ltd. All rights reserved.
Modelling antecedents of blood donation motivation among non-donors of varying age and education.
Lemmens, K P H; Abraham, C; Ruiter, R A C; Veldhuizen, I J T; Dehing, C J G; Bos, A E R; Schaalma, H P
2009-02-01
Understanding blood donation motivation among non-donors is prerequisite to effective recruitment. Two studies explored the psychological antecedents of blood donation motivation and the generalisability of a model of donation motivation across groups differing in age and educational level. An older well-educated population and a younger less well-educated population were sampled. The studies assessed the role of altruism, fear of blood/needles and donation-specific cognitions including attitudes and normative beliefs derived from an extended theory of planned behaviour (TPB). Across both samples, results showed that affective attitude, subjective norm, descriptive norm, and moral norm were the most important correlates of blood donation intentions. Self-efficacy was more important among the younger less well-educated group. Altruism was related to donation motivation but only indirectly through moral norm. Similarly, fear of blood/needles only had an indirect effect on motivation through affective attitude and self-efficacy. Additional analyses with the combined data set found no age or education moderation effects, suggesting that this core model of donation-specific cognitions can be used to inform future practical interventions recruiting new blood donors in the general population.
Nitric oxide levels in the aqueous humor vary in different ocular hypertension experimental models.
Lu, Da-Wen; Chen, Yi-Hao; Chang, Charn-Jung; Chiang, Chiao-Hsi; Yao, Hsin-Yu
2014-12-01
This study investigated the relationships among intraocular pressure (IOP), nitric oxide (NO) levels, and aqueous flow rates in experimental ocular hypertension models. A total of 75 rabbits were used. One of four different materials [i.e., α-chymotrypsin, latex microspheres (Polybead), red blood cell ghosts, or sodium hyaluronate (Healon GV)] was injected into the eyes of the 15 animals in each experimental group; the remaining 15 rabbits were reserved for a control group. The IOP changes in the five groups were recorded on postinduction Days 1-3, Day 7, Day 14, Day 30, Day 60, Day 90, and Day 120. On postinduction Day 7, the dynamics and NO levels in the aqueous humor were recorded. Significant IOP elevations were induced by α-chymotrypsin (p humor NO levels increased significantly in the models of α-chymotrypsin, Polybead, and red blood cell ghosts (all p humor NO level, similar to human eyes with acute angle-closure glaucoma and neovascular glaucoma. Copyright © 2014. Published by Elsevier Taiwan.
HIGH PRODUCTIVITY VACUUM BLASTING SYSTEM
Energy Technology Data Exchange (ETDEWEB)
William S. McPhee
1999-05-31
The objective of this project is to improve the productivity and lower the expense of existing vacuum blasting technology. This technology is used to remove radioactive contamination, PCBs, and lead-based paint and provides worker protection by continuously recycling the material and dust for the decontamination tasks. The proposed work would increase the cleaning rate and provide safe and cost-effective decontamination of the DOE sites. This work focuses on redesigning and improving existing vacuum blasting technology including blast head nozzles, ergonomic handling of the blast head by reducing its weight; brush-ring design, vacuum level regulator, efficiency of the dust separator, and operational control sensors. The redesign is expected to enhance the productivity and economy of the vacuum blasting system by at least 50% over current vacuum blasting systems. There are three phases in the project. Phase I consists of developing and testing mathematical models. Phase II consists of pre-prototype design and fabrication and pre-prototype unit testing. Phase III consists of prototype design and field verification testing. In phase I, mathematical models are developed and analyzed for the nozzle, blast head, wind curtain, and dust separator, first as individual devices and then combined as an integrated model. This allows study of respective airflow and design parameters. The Contractor shall, based on the results of the mathematical modeling studies, design experimental models of the components and test these models. In addition, the Contractor shall develop sensors to detect the relationship of the blast head to the blast surfaces and controls to minimize the dependency on an operator's skill and judgment to obtain optimum positioning, as well as real-time characterization sensors to determine as the blast head is moving the depth to which coatings must be removed, thereby improving production and minimizing waste. In phase II, the Contractor shall design and
Zhu, Zichen; Wang, Yongzhi; Bian, Shuhua; Hu, Zejian; Liu, Jianqiang; Liu, Lejun
2017-11-01
We modified the sediment incipient motion in a numerical model and evaluated the impact of this modification using a study case of the coastal area around Weihai, China. The modified and unmodified versions of the model were validated by comparing simulated and observed data of currents, waves, and suspended sediment concentrations (SSC) measured from July 25th to July 26th, 2006. A fitted Shields diagram was introduced into the sediment model so that the critical erosional shear stress could vary with time. Thus, the simulated SSC patterns were improved to more closely reflect the observed values, so that the relative error of the variation range decreased by up to 34.5% and the relative error of simulated temporally averaged SSC decreased by up to 36%. In the modified model, the critical shear stress values of the simulated silt with a diameter of 0.035 mm and mud with a diameter of 0.004 mm varied from 0.05 to 0.13 N/m2, and from 0.05 to 0.14 N/m 2, respectively, instead of remaining constant in the unmodified model. Besides, a method of applying spatially varying fractions of the mixed grain size sediment improved the simulated SSC distribution to fit better to the remote sensing map and reproduced the zonal area with high SSC between Heini Bay and the erosion groove in the modified model. The Relative Mean Absolute Error was reduced by between 6% and 79%, depending on the regional attributes when we used the modified method to simulate incipient sediment motion. But the modification achieved the higher accuracy in this study at a cost of computation speed decreasing by 1.52%.
DEFF Research Database (Denmark)
Nielsen, Jesper Bo
2010-01-01
PURPOSE: Following dermal exposure to chemicals causing systemic toxicity, the general advice to avoid further systemic exposure is to wash the skin. The present study uses four model compounds (benzoic acid, glyphosat, caffeine, malathion) with varying size and solubility to substantiate...... this advice and quantify the effect of skin wash following 6 h dermal exposure on subsequent extent of skin penetration and deposition within the skin compartment. METHOD: Percutaneous penetration through human skin is studied in an in vitro model with static diffusion cells. RESULTS: The study demonstrates...
Modelling optical scattering artefacts for varying pathlength in a gel dosimeter phantom
Energy Technology Data Exchange (ETDEWEB)
Bosi, Stephen G [Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW 2031 (Australia); Brown, Saxby; Sarabipour, Sarvenaz; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); De Deene, Yves [Division of Radiotherapy, University Hospital of Ghent, de Pintelaan 185, 9000 Ghent (Belgium)], E-mail: s.bosi@physics.usyd.edu.au
2009-01-21
A gelatin phantom containing an optically scattering funnel-shaped region of elevated optical density (OD) was used to examine light-scattering-induced artefacts in a cone-beam optical CT scanner used for gel dosimetry. To simulate polymer gel dosimeters, the opacity was introduced by adding a colloidal scatterer to the gelatin. Scatter results in an underestimate of OD (hence dose). In line profiles of OD taken from 3D reconstructions of the funnel, those profiles with a long pathlength through high OD regions exhibited a 'dishing' (or 'cupping') artefact, while those of short pathlength exhibited the opposite effect-'doming'. These phenomena are accounted for by a model that includes the effect of stray, scattered light.
Remer, D. S.
1977-01-01
A mathematical model is developed for calculating the life cycle costs for a project where the operating costs increase or decrease in a linear manner with time. The life cycle cost is shown to be a function of the investment costs, initial operating costs, operating cost gradient, project life time, interest rate for capital and salvage value. The results show that the life cycle cost for a project can be grossly underestimated (or overestimated) if the operating costs increase (or decrease) uniformly over time rather than being constant as is often assumed in project economic evaluations. The following range of variables is examined: (1) project life from 2 to 30 years; (2) interest rate from 0 to 15 percent per year; and (3) operating cost gradient from 5 to 90 percent of the initial operating costs. A numerical example plus tables and graphs is given to help calculate project life cycle costs over a wide range of variables.
Semiparametric time varying coefficient model for matched case-crossover studies.
Ortega-Villa, Ana Maria; Kim, Inyoung; Kim, H
2017-03-15
In matched case-crossover studies, it is generally accepted that the covariates on which a case and associated controls are matched cannot exert a confounding effect on independent predictors included in the conditional logistic regression model. This is because any stratum effect is removed by the conditioning on the fixed number of sets of the case and controls in the stratum. Hence, the conditional logistic regression model is not able to detect any effects associated with the matching covariates by stratum. However, some matching covariates such as time often play an important role as an effect modification leading to incorrect statistical estimation and prediction. Therefore, we propose three approaches to evaluate effect modification by time. The first is a parametric approach, the second is a semiparametric penalized approach, and the third is a semiparametric Bayesian approach. Our parametric approach is a two-stage method, which uses conditional logistic regression in the first stage and then estimates polynomial regression in the second stage. Our semiparametric penalized and Bayesian approaches are one-stage approaches developed by using regression splines. Our semiparametric one stage approach allows us to not only detect the parametric relationship between the predictor and binary outcomes, but also evaluate nonparametric relationships between the predictor and time. We demonstrate the advantage of our semiparametric one-stage approaches using both a simulation study and an epidemiological example of a 1-4 bi-directional case-crossover study of childhood aseptic meningitis with drinking water turbidity. We also provide statistical inference for the semiparametric Bayesian approach using Bayes Factors. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Julias, Margaret; Buettner, Helen M; Shreiber, David I
2011-02-01
During traditional acupuncture, fine needles are inserted subcutaneously and rotated, which causes loose fascial tissue to wind around the needle. This coupling is stronger at acupuncture points, which tend to fall above intermuscular fascial planes, than control points, which lay above skeletal muscle. These different anatomical constraints may affect the mechanical coupling. Fascia at acupuncture points is bounded on two sides by skeletal muscle, but at control points is essentially unbounded. These differences were approximated in simple in vitro models. To emulate the narrower boundary within the intermuscular plane, type I collagen was cast in circular gels of different radii. To model the channel-like nature of these planes, collagen was cast in elliptical gels with major and minor axes matching the large and small circular gels, respectively, and in planar gels constrained on two sides. Acupuncture needles were inserted into the gels and rotated via a computer-controlled motor while capturing the evolution of fiber alignment under cross-polarization. Small circular gels aligned faster, but failed earlier than large circular gels. Rotation in elliptical and planar gels generated more alignment-per-revolution than circular gels. Planar gels were particularly resistant to failure. Fiber alignment in circular gels was isotropic, but was stronger in the direction of the minor axis in elliptical and planar gels. In fibroblast-populated gels, cells followed the alignment of the collagen fibers, and also became denser in regions of stronger alignment. These results suggest that the anatomy at acupuncture points provides unique boundaries that accentuate the mechanical response to needle manipulation. 2010 Wiley-Liss, Inc.
Energy Technology Data Exchange (ETDEWEB)
Schellekens, H.
1989-05-01
After showing the extended experience of Holec with vacuum disconnectors, the difficulties encountered in developing the type SVS vacuum bottle are indicated. The implications of demands imposed on price and dimensions are translated into design features. The function and the design of the getter is explained to show how Holec guarantees a 20 year approved vacuum in the bottle. Finally, the results of switching tests are mentioned to explain the reliability and capability of the new disconnector. 12 figs.
Kissoon, N; Spenceley, N; Krahn, G; Milner, R
2010-09-01
We compared saturations from a paediatric central venous oximetry catheter with co-oximetry values with changes in drug infusions, intravascular blood volume and hypoxia in an animal model. Piglets (large white) were anaesthetised, intubated and mechanically ventilated. PediaSat oximetry catheters were placed in the superior vena cava via jugular vein cut-down and in the inferior vena cava percutaneously via the femoral vein. A carotid arterial catheter was placed via cut-down for blood sampling and pressure monitoring. Anaesthesia was maintained with continuous thiopentone and supplemental morphine. Haemodynamics (heart rate, mean arterial blood, central venous pressure), fibreoptic ScvO2 (ScvO2-inferior) from inferior vena cava, fibreoptic ScvO2 (ScvO2-superior) from superior vena cava and blood gas oximetry (ScvO2-co-ox) were measured simultaneously at predetermined intervals during increasing adrenaline and sodium nitroprusside infusions and during increasing hypoxia and hypovolaemia. There was good agreement of both superior vena cava and inferior vena cava ScvO2 catheters with co-oximetry during adrenaline and sodium nitroprusside infusions. During the hypoxia study there was good agreement between the co-oximeter to ScvO2-superior catheter but poor agreement with to the inferior vena cava catheter samples. In the hypovolaemic phase of the experiment there was good agreement between the measured co-oximetry value and ScvO2-superior catheter until the mean blood pressure reached 43 mmHg. The oximetry catheter is capable of identifying changes in ScvO2 under physiological conditions usually encountered in clinical medicine but was less accurate at the extremes of physiology and when placed in the inferior vena cava catheter especially during hypovolaemia and hypoxia.
Jiang, Sanyuan; Jomaa, Seifeddine; Rode, Michael
2013-04-01
The rivers in central Germany are moderately to heavily polluted by nutrient inputs from point and diffuse sources. The objectives of this study are (i) to assess the new HYPE model (HYdrological Predictions for the Environment) for simulating runoff and inorganic nitrogen (IN) emissions at nested and spatially heterogeneous mesoscale catchments; (ii) to investigate the temporal and spatial variations of IN leaching and (iii) to investigate effects of calibration data on hydrological parameter identification. A multi-site and multi-objective calibration approach with help of Markov chain Monte Carlo (MCMC) was employed for parameter optimisation and uncertainty analysis. Results showed that parameters related to evapotranspiration were most sensitive in runoff simulation, while the nitrogen processes were mainly controlled by plant uptake and denitrification. Runoff was reproduced quite well for both calibration (1994-1999) and validation (1999-2004) periods (including the extreme dry year of 2003) at all three gauge stations, with a lowest Nash-Sutcliffe (NSE) of 0.86. The dynamics of soil moisture during extreme climatological events were well captured. Corresponding to spatial variability of hydrological regimes and land use, IN concentrations showed an increase in magnitude and a decrease in dynamics from upstream to downstream, reflecting the combined effects of increasing nutrient inputs and decreasing IN in-stream retention. The IN load was simulated well at monthly time intervals, with a lowest NSE of 0.69. Results revealed high IN emissions in winter and low values in summer; the area-weighted IN emission load decreased along the stream channel. Therefore, it is concluded that the IN emission is mainly controlled by runoff in this study catchment. From the preliminary result, we found that the 95% parameter confidence intervals of hydrological parameters decreased when IN concentration observations were included in hydrological parameter calibration. In
Pei, Yifei; Zhang, Jingchuan; Zhang, Luosha; Liu, Yang; Zhang, Lina; Chen, Shiyu
2018-01-01
To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, two different kinds of sleeve compactly single model fiber covered by acrylate and polyimide are researched. Influence of the cover to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, transmission characteristic of single model fiber in high vacuum thermal environment is analyzed by solve the equation of heat conduction. Then, experimental program of influence on FBG reflection spectrum characteristics is designed and a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG in different coating single-mode transmission fiber under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different coating single-mode transmission fiber dropped to -196 ° from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the theoretical and experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ° 25 ° temperature cycle) .
Oscillations of a polarizable vacuum
Directory of Open Access Journals (Sweden)
James G. Gilson
1991-01-01
Full Text Available A classical basis for one-dimensional Schrödinger quantum theory is constructed from simple vacuum polarization harmonic oscillators within standard stochastic theory. The model is constructed on a two-dimensional phase configuration surface with phase velocity vectors that have a speed of light zitterbewegung behaviour character. The system supplies a natural Hermitian scalar product describing probability density which is derived from angular momentum considerations. The generality of the model which is extensive is discussed.
Vacuum and ultravacuum physics and technology
Bello, Igor
2018-01-01
Vacuum technology has enormous impact on human life in many aspects and fields, such as metallurgy, material development and production, food and electronic industry, microelectronics, device fabrication, physics, materials science, space science, engineering, chemistry, technology of low temperature, pharmaceutical industry, and biology. All decorative coatings used in jewelries and various daily productsincluding shiny decorative papers, the surface finish of watches, and light fixturesare made using vacuum technological processes. Vacuum analytical techniques and vacuum technologies are pillars of the technological processes, material synthesis, deposition, and material analysesall of which are used in the development of novel materials, increasing the value of industrial products, controlling the technological processes, and ensuring the high product quality. Based on physical models and calculated examples, the book provides a deeper look inside the vacuum physics and technology.
Directory of Open Access Journals (Sweden)
Raymond F. Hamilton
2018-01-01
Full Text Available Functionalization has been shown to alter toxicity of multi-walled carbon nanotube (MWCNT in several studies. This study varied the degree of functionalization (viz., amount of MWCNT surface carboxylation to define the relationship between the extent of carboxylation and effects in a variety of in vitro cell models and short-term ex vivo/in vivo particle exposures. Studies with vitamin D3 plus phorbol ester transformed THP-1 macrophages demonstrated that functionalization, regardless of amount, corresponded with profoundly decreased NLRP3 inflammasome activation. However, all MWCNT variants were slightly toxic in this model. Alternatively, studies with A549 epithelial cells showed some varied effects. For example, IL-33 and TNF-α release were related to varying amounts of functionalization. For in vivo particle exposures, autophagy of alveolar macrophages, measured using green fluorescent protein (GFP- fused-LC3 transgenic mice, increased for all MWCNT tested three days after exposure, but, by Day 7, autophagy was clearly dependent on the amount of carboxylation. The instilled source MWCNT continued to produce cellular injury in alveolar macrophages over seven days. In contrast, the more functionalized MWCNT initially showed similar effects, but reduced over time. Dark-field imaging showed the more functionalized MWCNTs were distributed more uniformly throughout the lung and not isolated to macrophages. Taken together, the results indicated that in vitro and in vivo bioactivity of MWCNT decreased with increased carboxylation. Functionalization by carboxylation eliminated the bioactive potential of the MWCNT in the exposure models tested. The observation that maximally functionalized MWCNT distribute more freely throughout the lung with the absence of cellular damage, and extended deposition, may establish a practical use for these particles as a safer alternative for unmodified MWCNT.
Directory of Open Access Journals (Sweden)
Li Yang
2017-01-01
Full Text Available Paste-like tailings slurry (PTLS is always simplified as a Bingham plastic fluid, leading to excessive computational errors in the calculation of the hydraulic gradient. In the case of paste-like tailings in long-distance pipeline transportation, to explore a high-precision and reliable hydraulic gradient formula, the rheological behavior of paste-like tailings slurry was analyzed, a time-varying hydraulic gradient model was constructed, and a series of laboratory shear tests were conducted. The results indicate that the PTLS shows noticeable shear-thinning characteristics in constant shear tests; the calculated hydraulic gradient declined by about 56%, from 4.44 MPa·km−1 to 1.95 MPa·km−1 within 253 s, and remained constant for the next four hours during the pipeline transportation. Comparing with the balance hydraulic gradient obtained in a semi-industrial loop test, the computational errors of those calculated by using the time-varying hydraulic gradient model, Jinchuan formula, and Shanxi formula are 15%, 78%, and 130%, respectively. Therefore, our model is a feasible and high-precision solution for the calculation of the hydraulic gradient of paste-like tailings in long-distance pipeline transportation.
Fecher, T.; Pail, R.; Gruber, T.
2017-05-01
GOCO05c is a gravity field model computed as a combined solution of a satellite-only model and a global data set of gravity anomalies. It is resolved up to degree and order 720. It is the first model applying regionally varying weighting. Since this causes strong correlations among all gravity field parameters, the resulting full normal equation system with a size of 2 TB had to be solved rigorously by applying high-performance computing. GOCO05c is the first combined gravity field model independent of EGM2008 that contains GOCE data of the whole mission period. The performance of GOCO05c is externally validated by GNSS-levelling comparisons, orbit tests, and computation of the mean dynamic topography, achieving at least the quality of existing high-resolution models. Results show that the additional GOCE information is highly beneficial in insufficiently observed areas, and that due to the weighting scheme of individual data the spectral and spatial consistency of the model is significantly improved. Due to usage of fill-in data in specific regions, the model cannot be used for physical interpretations in these regions.
Density perturbations in f (R ,ϕ ) gravity with an application to the varying-power-law model
Hammad, Fayçal
2017-09-01
Density perturbations in the cosmic microwave background within general f (R ,ϕ ) models of gravity are investigated. The general dynamical equations for the tensor and scalar modes in any f (R ,ϕ )-gravity model are derived. An application of the equations to the varying-power-law modified gravity toy model is then made. Formulas and numerical values for the tensor-to-scalar ratio, the scalar tilt, and the tensor tilt are all obtained within this specific model. While the model cannot provide a theoretical reason for the value of the energy scale at which inflation should occur, it is found, based on the latest observations of the density perturbations in the sky, that the model requires inflation to occur at an energy scale less than the grand unified theory scale, namely, ˜1014 GeV . The different energy intervals examined here show that the density perturbations recently obtained from observations are recovered naturally, with very high precision, and without fine tuning the model's parameters.
Vaysman, Ya I.; Surkov, AA; Surkova, Yu I.; Kychkin, AV
2017-06-01
The article is devoted to the use of renewable energy sources and the assessment of the feasibility of their use in the climatic conditions of the Western Urals. A simulation model that calculates the efficiency of a combined power installations (CPI) was (RES) developed. The CPI consists of the geothermal heat pump (GHP) and the vacuum solar collector (VCS) and is based on the research model. This model allows solving a wide range of problems in the field of energy and resource efficiency, and can be applied to other objects using RES. Based on the research recommendations for optimizing the management and the application of CPI were given. The optimization system will give a positive effect in the energy and resource consumption of low-rise residential buildings projects.
Microfabricated triggered vacuum switch
Roesler, Alexander W [Tijeras, NM; Schare, Joshua M [Albuquerque, NM; Bunch, Kyle [Albuquerque, NM
2010-05-11
A microfabricated vacuum switch is disclosed which includes a substrate upon which an anode, cathode and trigger electrode are located. A cover is sealed over the substrate under vacuum to complete the vacuum switch. In some embodiments of the present invention, a metal cover can be used in place of the trigger electrode on the substrate. Materials used for the vacuum switch are compatible with high vacuum, relatively high temperature processing. These materials include molybdenum, niobium, copper, tungsten, aluminum and alloys thereof for the anode and cathode. Carbon in the form of graphitic carbon, a diamond-like material, or carbon nanotubes can be used in the trigger electrode. Channels can be optionally formed in the substrate to mitigate against surface breakdown.
Insulation vacuum and beam vacuum overpressure release
Parma, V
2009-01-01
There is evidence that the incident of 19th September caused a high pressure build-up inside the cryostat insulation vacuum which the existing overpressure devices could not contain. As a result, high longitudinal forces acting on the insulation vacuum barriers developed and broke the floor and the floor fixations of the SSS with vacuum barriers. The consequent large longitudinal displacements of the SSS damaged chains of adjacent dipole cryo-magnets. Estimates of the helium mass flow and the pressure build- up experienced in the incident are presented together with the pressure build-up for an even more hazardous event, the Maximum Credible Incident (MCI). The strategy of limiting the maximum pressure by the installation of addition pressure relieve devices is presented and discussed. Both beam vacuum lines were ruptured during the incident in sector 3-4 giving rise to both mechanical damage and pollution of the system. The sequence, causes and effects of this damage will be briefly reviewed. We will then an...
Modeling Water Flux at the Base of the Rooting Zone for Soils with Varying Glacial Parent Materials
Naylor, S.; Ellett, K. M.; Ficklin, D. L.; Olyphant, G. A.
2013-12-01
Soils of varying glacial parent materials in the Great Lakes Region (USA) are characterized by thin unsaturated zones and widespread use of agricultural pesticides and nutrients that affect shallow groundwater. To better our understanding of the fate and transport of contaminants, improved models of water fluxes through the vadose zones of various hydrogeologic settings are warranted. Furthermore, calibrated unsaturated zone models can be coupled with watershed models, providing a means for predicting the impact of varying climate scenarios on agriculture in the region. To address these issues, a network of monitoring sites was developed in Indiana that provides continuous measurements of precipitation, potential evapotranspiration (PET), soil volumetric water content (VWC), and soil matric potential to parameterize and calibrate models. Flux at the base of the root zone is simulated using two models of varying complexity: 1) the HYDRUS model, which numerically solves the Richards equation, and 2) the soil-water-balance (SWB) model, which assumes vertical flow under a unit gradient with infiltration and evapotranspiration treated as separate, sequential processes. Soil hydraulic parameters are determined based on laboratory data, a pedo-transfer function (ROSETTA), field measurements (Guelph permeameter), and parameter optimization. Groundwater elevation data are available at three of six sites to establish the base of the unsaturated zone model domain. Initial modeling focused on the groundwater recharge season (Nov-Feb) when PET is limited and much of the annual vertical flux occurs. HYDRUS results indicate that base of root zone fluxes at a site underlain by glacial ice-contact parent materials are 48% of recharge season precipitation (VWC RMSE=8.2%), while SWB results indicate that fluxes are 43% (VWC RMSE=3.7%). Due in part to variations in surface boundary conditions, more variable fluxes were obtained for a site underlain by alluvium with the SWB model (68
Barrow, John D
2009-01-01
We review properties of cosmological theories for the variation of the fine structure 'constant'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that are consistent with time-variation in the fine structure 'constant' since a redshift of 3.5.
Scale covariance and G-varying cosmology. IV - The log N-log S relation. [radio source models
Canuto, V. M.; Owen, J. R.
1979-01-01
The traditional radio counts N(S) and radio source models are studied within the framework of the scale-covariant cosmology developed to investigate whether the relative strength of the gravitational and electromagnetic constants is a function of cosmological epoch. It is found that a gravitational constant G varying as the inverse of t, where t is the epoch in atomic units, is consistent with all the data analyzed. For a wide class of models the present cosmology allows a finer discrimination of the deceleration parameter than does standard theory. The results, when combined with those of previous papers, namely, those from radio and optical flux and angular-diameter data analysis, favor an open universe.
Einstein Equations from Varying Complexity
Czech, Bartłomiej
2018-01-01
A recent proposal equates the circuit complexity of a quantum gravity state with the gravitational action of a certain patch of spacetime. Since Einstein's equations follow from varying the action, it should be possible to derive them by varying complexity. I present such a derivation for vacuum solutions of pure Einstein gravity in three-dimensional asymptotically anti-de Sitter space. The argument relies on known facts about holography and on properties of tensor network renormalization, an algorithm for coarse-graining (and optimizing) tensor networks.
Lim, J. T.; Wilkerson, G. G.; Raper, C. D. Jr; Gold, H. J.
1990-01-01
A differential equation model of vegetative growth of the soya bean plant (Glycine max (L.) Merrill cv. Ransom') was developed to account for plant growth in a phytotron system under variation of root temperature and nitrogen concentration in nutrient solution. The model was tested by comparing model outputs with data from four different experiments. Model predictions agreed fairly well with measured plant performance over a wide range of root temperatures and over a range of nitrogen concentrations in nutrient solution between 0.5 and 10.0 mmol NO3- in the phytotron environment. Sensitivity analyses revealed that the model was most sensitive to changes in parameters relating to carbohydrate concentration in the plant and nitrogen uptake rate.
Wilusz, D. C.; Harman, C. J.; Ball, W. P.
2014-12-01
Modeling the dynamics of chemical transport from the landscape to streams is necessary for water quality management. Previous work has shown that estimates of the distribution of water age in streams, the transit time distribution (TTD), can improve prediction of the concentration of conservative tracers (i.e., ones that "follow the water") based on upstream watershed inputs. A major challenge however has been accounting for climate and transport variability when estimating TDDs at the catchment scale. In this regard, Harman (2014, in review) proposed the Omega modeling framework capable of using watershed hydraulic fluxes to approximate the time-varying TTD. The approach was previously applied to the Plynlimon research watershed in Wales to simulate stream concentration dynamics of a conservative tracer (chloride) including 1/f attenuation of the power spectra density. In this study we explore the extent to which TTDs estimated by the Omega model vary with the concentration of non-conservative tracers (i.e., ones whose concentrations are also affected by transformations and interactions with other phases). First we test the hypothesis that the TTD calibrated in Plynlimon can explain a large part of the variation in non-conservative stream water constituents associated with storm flow (acidity, Al, DOC, Fe) and base flow (Ca, Si). While controlling for discharge, we show a correlation between the percentage of water of different ages and constituent concentration. Second, we test the hypothesis that TTDs help explain variation in stream nitrate concentration, which is of particular interest for pollution control but can be highly non-conservative. We compare simulation runs from Plynlimon and the agricultural Choptank watershed in Maryland, USA. Following a top-down approach, we estimate nitrate concentration as if it were a conservative tracer and examine the structure of residuals at different temporal resolutions. Finally, we consider model modifications to
Jia, Shenli; Mo, Yongpeng; Shi, Zongqian; Li, Junliang; Wang, Lijun
2017-10-01
The post-arc dielectric recovery process has a decisive effect on the current interruption performance in a vacuum circuit breaker. The dissipation of residual plasma at the moment of current zero under the transient recovery voltage, which is the first stage of the post-arc dielectric recovery process and forms the post-arc current, has attracted many concerns. A one-dimensional particle-in-cell model is developed to simulate the measured post-arc current in the vacuum circuit breaker in this paper. At first, the parameters of the residual plasma are estimated roughly by the waveform of the post-arc current which is taken from measurements. After that, different components of the post-arc current, which are formed by the movement of charged particles in the residual plasma, are discussed. Then, the residual plasma density is adjusted according to the proportion of electrons and ions absorbed by the post-arc anode derived from the particle-in-cell simulation. After this adjustment, the post-arc current waveform obtained from the simulation is closer to that obtained from measurements.
A simulation of cross-country skiing on varying terrain by using a mathematical power balance model.
Moxnes, John F; Sandbakk, Oyvind; Hausken, Kjell
2013-01-01
The current study simulated cross-country skiing on varying terrain by using a power balance model. By applying the hypothetical inductive deductive method, we compared the simulated position along the track with actual skiing on snow, and calculated the theoretical effect of friction and air drag on skiing performance. As input values in the model, air drag and friction were estimated from the literature, whereas the model included relationships between heart rate, metabolic rate, and work rate based on the treadmill roller-ski testing of an elite cross-country skier. We verified this procedure by testing four models of metabolic rate against experimental data on the treadmill. The experimental data corresponded well with the simulations, with the best fit when work rate was increased on uphill and decreased on downhill terrain. The simulations predicted that skiing time increases by 3%-4% when either friction or air drag increases by 10%. In conclusion, the power balance model was found to be a useful tool for predicting how various factors influence racing performance in cross-country skiing.
Sridhar, A.; Pullin, D. I.; Cheng, W.
2016-11-01
An empirical model is presented, after Rotta (1962), that describes the development of a fully-developed turbulent boundary layer in the presence of surface roughness with nominal roughness length-scale ks that varies with stream-wise distance x. For Rex =Ue (x) x / ν large, use is made of the log-wake model of the local turbulent mean-velocity profile that contains the Hama roughness correction ΔU+ (ks+) for the asymptotic, fully rough regime. It is shown that the skin friction coefficient Cf is constant in x only for ks = αx , where α is a dimensionless number. For Ue (x) = Axm , this then gives a two-parameter (α , m) family of solutions for boundary-layer flows that are self similar in the variable z / (α x) where z is the wall-normal co-ordinate. Trends observed in this model are supported by wall-modeled LES of the zero-pressure-gradient turbulent boundary layer (m = 0) at very large Rex . It is argued that the present results suggest that, in the sense that Cf is spatially constant and independent of Rex , this class of flows can be interpreted as providing the asymptotically-rough equivalent of Moody-like diagrams for boundary layers in the presence of small-scale roughness. Supported partially by KAUST OCRF Award No. URF/1/1394-01 and partially by NSF award CBET 1235605.
McNab, A.; Stagni, F.; Ubeda Garcia, M.
2014-06-01
We present a model for the operation of computing nodes at a site using Virtual Machines (VMs), in which VMs are created and contextualized for experiments by the site itself. For the experiment, these VMs appear to be produced spontaneously "in the vacuum" rather having to ask the site to create each one. This model takes advantage of the existing pilot job frameworks adopted by many experiments. In the Vacuum model, the contextualization process starts a job agent within the VM and real jobs are fetched from the central task queue as normal. An implementation of the Vacuum scheme, Vac, is presented in which a VM factory runs on each physical worker node to create and contextualize its set of VMs. With this system, each node's VM factory can decide which experiments' VMs to run, based on site-wide target shares and on a peer-to-peer protocol in which the site's VM factories query each other to discover which VM types they are running. A property of this system is that there is no gate keeper service, head node, or batch system accepting and then directing jobs to particular worker nodes, avoiding several central points of failure. Finally, we describe tests of the Vac system using jobs from the central LHCb task queue, using the same contextualization procedure for VMs developed by LHCb for Clouds.
Tsetsos, Konstantinos; Gao, Juan; McClelland, James L; Usher, Marius
2012-01-01
When people make decisions, do they give equal weight to evidence arriving at different times? A recent study (Kiani et al., 2008) using brief motion pulses (superimposed on a random moving dot display) reported a primacy effect: pulses presented early in a motion observation period had a stronger impact than pulses presented later. This observation was interpreted as supporting the bounded diffusion (BD) model and ruling out models in which evidence accumulation is subject to leakage or decay of early-arriving information. We use motion pulses and other manipulations of the timing of the perceptual evidence in new experiments and simulations that support the leaky competing accumulator (LCA) model as an alternative to the BD model. While the LCA does include leakage, we show that it can exhibit primacy as a result of competition between alternatives (implemented via mutual inhibition), when the inhibition is strong relative to the leak. Our experiments replicate the primacy effect when participants must be prepared to respond quickly at the end of a motion observation period. With less time pressure, however, the primacy effect is much weaker. For 2 (out of 10) participants, a primacy bias observed in trials where the motion observation period is short becomes weaker or reverses (becoming a recency effect) as the observation period lengthens. Our simulation studies show that primacy is equally consistent with the LCA or with BD. The transition from primacy-to-recency can also be captured by the LCA but not by BD. Individual differences and relations between the LCA and other models are discussed.
Hu, Jiazhong; Chen, Wenlan; Vendeiro, Zachary; Urvoy, Alban; Braverman, Boris; Vuletić, Vladan
2017-11-01
We investigate the generation of entanglement (spin squeezing) in an optical-transition atomic clock through the coupling to an optical cavity in its vacuum state. We show that if each atom is prepared in a superposition of the ground state and a long-lived electronic excited state, and viewed as a spin-1/2 system, then the collective vacuum light shift entangles the atoms, resulting in a squeezed distribution of the ensemble collective spin, without any light applied. This scheme reveals that even an electromagnetic vacuum can constitute a useful resource for entanglement and quantum manipulation. By rotating the spin direction while coupling to the vacuum, the scheme can be extended to implement two-axis twisting resulting in stronger squeezing.
2016-01-01
This comprehensive, standard work has been updated to remain an important resource for all those needing detailed knowledge of the theory and applications of vacuum technology. With many numerical examples and illustrations to visualize the theoretical issues.
Federal Laboratory Consortium — Located near the K-Basins (see K-Basins link) in Hanford's 100 Area is a facility called the Cold Vacuum Drying Facility (CVDF).Between 2000 and 2004, workers at the...
... the birth canal. The vacuum uses a soft plastic cup that attaches to the baby's head with suction. ... a numbing medicine placed in the vagina. The plastic cup will be placed on the baby's head. Then, ...
CERN. Geneva
2001-01-01
A short introduction for some basic facts and equations. Subsquently, discussion about: Building blocks of an ultrahigh vacuum system - Various types of pumps required to reach uhv and methods to reduce these effects - Outgassing phenomena induced by the presence of a particle beam and the most common methods to reduce these effects It will be given some practical examples from existing CERN accelerators and discuss the novel features of the future LHC vacuum system.
Whitaker, Jerry
2012-01-01
Providing examples of applications, Power Vacuum Tubes Handbook, Third Edition examines the underlying technology of each type of power vacuum tube device in common use today. The author presents basic principles, reports on new development efforts, and discusses implementation and maintenance considerations. Supporting mathematical equations and extensive technical illustrations and schematic diagrams help readers understand the material. Translate Principles into Specific Applications This one-stop reference is a hands-on guide for engineering personnel involved in the design, specification,
Directory of Open Access Journals (Sweden)
Daywitt W. C.
2009-04-01
Full Text Available Both the big-bang and the quasi-steady-state cosmologies originate in some type of Planck state. This paper presents a new cosmological theory based on the Planck- vacuum negative-energy state, a state consisting of a degenerate collection of negative- energy Planck particles. A heuristic look at the Einstein field equation provides a con- vincing argument that such a vacuum state could provide a theoretical explanation for the visible universe.
Akanda, A. S.; Jutla, A. S.; Eltahir, E. A.; Islam, S.
2011-12-01
Despite major advances in the ecological and microbiological understanding of the bacterium Vibrio cholerae, the role of underlying large-scale processes in the progression of the cholera disease in space and time is not well understood. Here, we present a spatially explicit and seasonally varying coupled hydroclimatology-epidemiology model for understanding regional scale cholera prevalence in response to large scale hydroclimatic and environmental forcings. Our results show that environmental cholera transmission can be modulated by two spatially and seasonally distinct mechanisms - influenced by dry and wet season hydrologic determinants. The model is applied to the Ganges-Brahmaputra-Meghna Basin areas in Bangladesh to simulate spatially explicit cholera prevalence rates, and validated with long-term cholera data from Dhaka and shorter-term records from regional surveillance locations. The model reproduces the variability of cholera prevalence at monthly, seasonal, and interannual timescales and highlights the role of asymmetric large scale hydroclimatic processes as the dominant controls. Our findings have important implications for formulating effective cholera intervention strategies, and for understanding the impacts of changing climate patterns on seasonal cholera transmission.
Wang, Jing; Qi, Zhaohui; Wang, Gang
2017-10-01
The dynamic analysis of cable-pulley systems is investigated in this paper, where the time-varying length characteristic of the cable as well as the coupling motion between the cable and the pulleys are considered. The dynamic model for cable-pulley systems are presented based on the principle of virtual power. Firstly, the cubic spline interpolation is adopted for modeling the flexible cable elements and the virtual 1powers of tensile strain, inertia and gravity forces on the cable are formulated. Then, the coupled motions between the cable and the movable or fixed pulley are described by the input and output contact points, based on the no-slip assumption and the spatial description. The virtual powers of inertia, gravity and applied forces on the contact segment of the cable, the movable and fixed pulleys are formulated. In particular, the internal node degrees of freedom of spline cable elements are reduced, which results in that only the independent description parameters of the nodes connected to the pulleys are included in the final governing dynamic equations. At last, two cable-pulley lifting mechanisms are considered as demonstrative application examples where the vibration of the lifting process is investigated. The comparison with ADAMS models is given to prove the validity of the proposed method.
Liu, Zhuqing; Bartsch, Andreas J; Berrocal, Veronica J; Johnson, Timothy D
2018-01-01
Spatial resolution plays an important role in functional magnetic resonance imaging studies as the signal-to-noise ratio increases linearly with voxel volume. In scientific studies, where functional magnetic resonance imaging is widely used, the standard spatial resolution typically used is relatively low which ensures a relatively high signal-to-noise ratio. However, for pre-surgical functional magnetic resonance imaging analysis, where spatial accuracy is paramount, high-resolution functional magnetic resonance imaging may play an important role with its greater spatial resolution. High spatial resolution comes at the cost of a smaller signal-to-noise ratio. This begs the question as to whether we can leverage the higher signal-to-noise ratio of a standard functional magnetic resonance imaging study with the greater spatial accuracy of a high-resolution functional magnetic resonance imaging study in a pre-operative patient. To answer this question, we propose to regress the statistic image from a high resolution scan onto the statistic image obtained from a standard resolution scan using a mixed-effects model with spatially varying coefficients. We evaluate our model via simulation studies and we compare its performance with a recently proposed model that operates at a single spatial resolution. We apply and compare the two models on data from a patient awaiting tumor resection. Both simulation study results and the real data analysis demonstrate that our newly proposed model indeed leverages the larger signal-to-noise ratio of the standard spatial resolution scan while maintaining the advantages of the high spatial resolution scan.
Lowe, Douglas; Topping, David; McFiggans, Gordon
2017-04-01
Gas to particle partitioning of atmospheric compounds occurs through disequilibrium mass transfer rather than through instantaneous equilibrium. However, it is common to treat only the inorganic compounds as partitioning dynamically whilst organic compounds, represented by the Volatility Basis Set (VBS), are partitioned instantaneously. In this study we implement a more realistic dynamic partitioning of organic compounds in a regional framework and assess impact on aerosol mass and microphysics. It is also common to assume condensed phase water is only associated with inorganic components. We thus also assess sensitivity to assuming all organics are hygroscopic according to their prescribed molecular weight. For this study we use WRF-Chem v3.4.1, focusing on anthropogenic dominated North-Western Europe. Gas-phase chemistry is represented using CBM-Z whilst aerosol dynamics are simulated using the 8-section MOSAIC scheme, including a 9-bin VBS treatment of organic aerosol. Results indicate that predicted mass loadings can vary significantly. Without gas phase ageing of higher volatility compounds, dynamic partitioning always results in lower mass loadings downwind of emission sources. The inclusion of condensed phase water in both partitioning models increases the predicted PM mass, resulting from a larger contribution from higher volatility organics, if present. If gas phase ageing of VBS compounds is allowed to occur in a dynamic model, this can often lead to higher predicted mass loadings, contrary to expected behaviour from a simple non-reactive gas phase box model. As descriptions of aerosol phase processes improve within regional models, the baseline descriptions of partitioning should retain the ability to treat dynamic partitioning of organics compounds. Using our simulations, we discuss whether derived sensitivities to aerosol processes in existing models may be inherently biased. This work was supported by the Natural Environment Research Council within
Kamran, M. Ahmad; Hong, Keum-Shik
2013-10-01
Objective. Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive brain imaging technique that measures brain activities by using near-infrared light of 650-950 nm wavelength. The major advantages of fNIRS are its low cost, portability, and good temporal resolution as a plausible solution to real-time imaging. Recent research has shown the great potential of fNIRS as a tool for brain-computer interfaces. Approach. This paper presents the first novel technique for fNIRS-based modelling of brain activities using the linear parameter-varying (LPV) method and adaptive signal processing. The output signal of each channel is assumed to be an output of an LPV system with unknown coefficients that are optimally estimated by the affine projection algorithm. The parameter vector is assumed to be Gaussian. Main results. The general linear model (GLM) is very popular and is a commonly used method for the analysis of functional MRI data, but it has certain limitations in the case of optical signals. The proposed model is more efficient in the sense that it allows the user to define more states. Moreover, unlike most previous models, it is online. The present results, showing improvement, were verified by random finger-tapping tasks in extensive experiments. We used 24 states, which can be reduced or increased depending on the cost of computation and requirements. Significance. The t-statistics were employed to determine the activation maps and to verify the significance of the results. Comparison of the proposed technique and two existing GLM-based algorithms shows an improvement in the estimation of haemodynamic response. Additionally, the convergence of the proposed algorithm is shown by error reduction in consecutive iterations.
Amira, Touil; Roman, Peczalski; Fethi, Zagrouba
2016-11-01
The aim of this work was to monitor in-line and at a real time, the solid-state forms during pharmaceuticals manufacturing. It concerns the dehydration behavior and the solid-state transitions of theophylline in an agitated vacuum contact dryer. First, a near infrared spectroscopy (NIRS) method was performed using a reflectance diffuse probe to measure the in-line and in-situ exact composition of the mixture of different forms of theophylline and water content during drying. A multivariate modeling has been investigated to build a robust model which can predict four components at the same time during drying process. The XRPD analysis was used as a reference method in the process of calibration of NIRS. The indicators of the accuracy in quantitative spectral analysis confirm the robustness of the model and the efficiency of the method of calibration. Second, the kinetics of solid state transformations were investigated. It was shown that the dehydration advanced first by the formation of the metastable anhydrate and after a lag time of the stable one. Once the stable form appeared, formation of the metastable form came to an end. The temperature was found out to be the main factor controlling the overall process rate but also the final contents of the stable and metastable anhydrates for the considered dryer and operating conditions range. Finally, a semi-empirical drying model was proposed and significant quantitative differences were found, particularly at the product temperature which was probably caused by the excessive simplicity of the model.
Maheshwari, Rajesh; Tracy, Mark; Hinder, Murray; Wright, Audrey
2017-08-01
The aim of this study was to compare mask leak with three different peak inspiratory pressure (PIP) settings during T-piece resuscitator (TPR; Neopuff) mask ventilation on a neonatal manikin model. Participants were neonatal unit staff members. They were instructed to provide mask ventilation with a TPR with three PIP settings (20, 30, 40 cm H2 O) chosen in a random order. Each episode was for 2 min with 2-min rest period. Flow rate and positive end-expiratory pressure (PEEP) were kept constant. Airway pressure, inspiratory and expiratory tidal volumes, mask leak, respiratory rate and inspiratory time were recorded. Repeated measures analysis of variance was used for statistical analysis. A total of 12 749 inflations delivered by 40 participants were analysed. There were no statistically significant differences (P > 0.05) in the mask leak with the three PIP settings. No statistically significant differences were seen in respiratory rate and inspiratory time with the three PIP settings. There was a significant rise in PEEP as the PIP increased. Failure to achieve the desired PIP was observed especially at the higher settings. In a neonatal manikin model, the mask leak does not vary as a function of the PIP when the flow rate is constant. With a fixed rate and inspiratory time, there seems to be a rise in PEEP with increasing PIP. © 2017 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).
Ahmad, Sahar; Khan, Muhammad Faisal
2015-12-01
In this paper, we present a new non-rigid image registration method that imposes a topology preservation constraint on the deformation. We propose to incorporate the time varying elasticity model into the deformable image matching procedure and constrain the Jacobian determinant of the transformation over the entire image domain. The motion of elastic bodies is governed by a hyperbolic partial differential equation, generally termed as elastodynamics wave equation, which we propose to use as a deformation model. We carried out clinical image registration experiments on 3D magnetic resonance brain scans from IBSR database. The results of the proposed registration approach in terms of Kappa index and relative overlap computed over the subcortical structures were compared against the existing topology preserving non-rigid image registration methods and non topology preserving variant of our proposed registration scheme. The Jacobian determinant maps obtained with our proposed registration method were qualitatively and quantitatively analyzed. The results demonstrated that the proposed scheme provides good registration accuracy with smooth transformations, thereby guaranteeing the preservation of topology. Copyright © 2015 Elsevier Ltd. All rights reserved.
Nielsen, Jesper Bo
2010-08-01
Following dermal exposure to chemicals causing systemic toxicity, the general advice to avoid further systemic exposure is to wash the skin. The present study uses four model compounds (benzoic acid, glyphosat, caffeine, malathion) with varying size and solubility to substantiate this advice and quantify the effect of skin wash following 6 h dermal exposure on subsequent extent of skin penetration and deposition within the skin compartment. Percutaneous penetration through human skin is studied in an in vitro model with static diffusion cells. The study demonstrates that percutaneous penetration continues after end of exposure due to the reservoir present in the skin. However, penetration rate will decrease significantly, and it is evident that simple hand-wash after end of exposure not only reduces the amount of residue present in the upper skin compartment but also significantly reduces the total absorption of test substance, most so for the hydrophilic compounds. Our observations support the continuing initiatives from occupational hygienists to urge people with dermal exposure hazards to wash potentially exposed skin areas.
Zhang, Zhen; Yan, Peng; Jiang, Huan; Ye, Peiqing
2014-09-01
In this paper, we consider the discrete time-varying internal model-based control design for high precision tracking of complicated reference trajectories generated by time-varying systems. Based on a novel parallel time-varying internal model structure, asymptotic tracking conditions for the design of internal model units are developed, and a low order robust time-varying stabilizer is further synthesized. In a discrete time setting, the high precision tracking control architecture is deployed on a Voice Coil Motor (VCM) actuated servo gantry system, where numerical simulations and real time experimental results are provided, achieving the tracking errors around 3.5‰ for frequency-varying signals. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.
LCLS XTOD Tunnel Vacuum System (XVTS)
Energy Technology Data Exchange (ETDEWEB)
Beale, R; Duffy, P; Kishiyama, K; Mckernan, M; McMahon, D; Lewis, S; Trent, J; Tung, L; Shen, S
2005-11-04
The vacuum system of the XVTS (X-Ray Vacuum Transport System) for the LCLS (Linac Coherent Light Source) XTOD (X-ray Transport, Optics and Diagnostics) system has been analyzed and configured by the Lawrence Livermore National Laboratory's NTED (New Technologies Engineering Division) as requested by the SLAC/LCLS program. The system layout, detailed analyses and selection of the vacuum components for the XTOD tunnel section are presented in this preliminary design report. The vacuum system was analyzed and optimized using a coupled gas load balance model of sub-volumes of the components to be evacuated. Also included are the plans for procurement, mechanical integration, and the cost estimates.
Ali, M Sanni; Groenwold, Rolf H H|info:eu-repo/dai/nl/30481203X; Belitser, Svetlana V; Souverein, Patrick C; Martín, Elisa; Gatto, Nicolle M; Huerta, Consuelo; Gardarsdottir, Helga|info:eu-repo/dai/nl/321858131; Roes, Kit C B|info:eu-repo/dai/nl/115147020; Hoes, Arno W|info:eu-repo/dai/nl/101111762; de Boer, Antonius; Klungel, Olaf H|info:eu-repo/dai/nl/181447649
2016-01-01
BACKGROUND: Observational studies including time-varying treatments are prone to confounding. We compared time-varying Cox regression analysis, propensity score (PS) methods, and marginal structural models (MSMs) in a study of antidepressant [selective serotonin reuptake inhibitors (SSRIs)] use and
Bui, Quang M; Huggins, Richard M; Hwang, Wen-Han; White, Victoria; Erbas, Bircan
2010-01-01
Anti-smoking advertisements are an effective population-based smoking reduction strategy. The Quitline telephone service provides a first point of contact for adults considering quitting. Because of data complexity, the relationship between anti-smoking advertising placement, intensity, and time trends in total call volume is poorly understood. In this study we use a recently developed semi-varying coefficient model to elucidate this relationship. Semi-varying coefficient models comprise parametric and nonparametric components. The model is fitted to the daily number of calls to Quitline in Victoria, Australia to estimate a nonparametric long-term trend and parametric terms for day-of-the-week effects and to clarify the relationship with target audience rating points (TARPs) for the Quit and nicotine replacement advertising campaigns. The number of calls to Quitline increased with the TARP value of both the Quit and other smoking cessation advertisement; the TARP values associated with the Quit program were almost twice as effective. The varying coefficient term was statistically significant for peak periods with little or no advertising. Semi-varying coefficient models are useful for modeling public health data when there is little or no information on other factors related to the at-risk population. These models are well suited to modeling call volume to Quitline, because the varying coefficient allowed the underlying time trend to depend on fixed covariates that also vary with time, thereby explaining more of the variation in the call model.
Vacuum induced photoresist outgassing
Waterman, Justin; Mbanaso, Chimaobi; Denbeaux, Gregory
2008-03-01
In order to continue the trend toward smaller feature sizes in lithography, new methods of lithography will be needed. A likely method for printing features 32 nm and smaller is extreme ultraviolet (EUV) lithography. EUV allows for features to be printed that are smaller than the current methods can achieve. However, outgassing of the photoresist is a concern for EUV lithography. The outgassed components can lead to contamination of the optics, degrading the reflectivity and hence lowering throughput of the exposure tools. Outgassing due to EUV exposure has been investigated by many groups. However, there were no complete investigations available of vacuum induced outgassing. In this paper, several methods were employed to investigate the outgassing due to vacuum. It was found that the vacuum induced outgassing outgassed a similar number of molecules as the outgassing due to EUV exposure. Furthermore, almost all of the outgassing was completed after about two minutes in vacuum. To mitigate the potential concern of outgassing due to vacuum causing contamination of optics, this work shows that photoresist coated silicon wafers only require about two minutes of pumping prior to insertion near the optics within EUV lithography tools.
Directory of Open Access Journals (Sweden)
Zheng Yang
2013-01-01
Full Text Available Torsional spring-loaded antibacklash gear which can improve the transmission precision is widely used in many precision transmission fields. It is very important to investigate the dynamic characteristics of antibacklash gear. In the paper, applied force analysis is completed in detail. Then, defining the starting point of double-gear meshing as initial position, according to the meshing characteristic of antibacklash gear, single- or double-tooth meshing states of two gear pairs and the transformation relationship at any moment are determined. Based on this, a nonlinear model of antibacklash gear with time-varying friction and meshing stiffness is proposed. The influences of friction and variations of torsional spring stiffness, damping ratio and preload on dynamic transmission error (DTE are analyzed by numerical calculation and simulation, and the results show that antibacklash gear can increase the composite meshing stiffness; when the torsional spring stiffness is large enough, the oscillating components of the DTE (ODTE and the RMS of the DTE (RDTE trend to be a constant value; the variations of ODTE and RDTE are not significant, unless preload exceeds a certain value.
Faruq, Samia; McOwan, Peter W; Chittka, Lars
2013-08-20
The perceived color of an object depends on its spectral reflectance and the spectral composition of the illuminant. Thus when the illumination changes, the light reflected from the object also varies. This would result in a different color sensation if no color constancy mechanism is put in place-that is, the ability to form consistent representation of colors across various illuminants and background scenes. We explore the quantitative benefits of various color constancy algorithms in an agent-based model of foraging bees, where agents select flower color based on reward. Each simulation is based on 100 "meadows" with five randomly selected flower species with empirically determined spectral reflectance properties, and each flower species is associated with realistic distributions of nectar rewards. Simulated foraging bees memorize the colors of flowers that they have experienced as most rewarding, and their task is to discriminate against other flower colors with lower rewards, even in the face of changing illumination conditions. We compared the performance of von Kries, White Patch, and Gray World constancy models with (hypothetical) bees with perfect color constancy, and color-blind bees. A bee equipped with trichromatic color vision but no color constancy performed only ∼20% better than a color-blind bee (relative to a maximum improvement at 100% for perfect color constancy), whereas the most powerful recovery of reflectance in the face of changing illumination was generated by a combination of von Kries photoreceptor adaptation and a White Patch calibration (∼30% improvement relative to a bee without color constancy). However, none of the tested algorithms generated perfect color constancy.
Brown, I.
2013-12-16
The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.
Energy Technology Data Exchange (ETDEWEB)
Lorenci, V.A. de; Svaiter, N.F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1996-11-01
It was investigated which mapping has to be used to compare measurements made in a rotating frame to those made in an inertial frame. Using a non-Galilean coordinate transformation, the creation-annihilation operators of a massive scalar field in the rotating frame are not the same as those of an inertial observer. This leads to a new vacuum state(a rotating vacuum) which is a superposition of positive and negative frequency Minkowski particles. Polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view were analysed. 65 refs.
1964-01-01
Handbook of Vacuum Physics, Volume 3: Technology is a handbook of vacuum physics, with emphasis on the properties of miscellaneous materials such as mica, oils, greases, waxes, and rubber. Accurate modern tables of physical constants, properties of materials, laboratory techniques, and properties of commercial pumps, gauges, and leak detectors are presented. This volume is comprised of 12 chapters and begins with a discussion on pump oils, divided into rotary pump oils and vapor pump oils. The next chapter deals with the properties and applications of greases, including outgassing and vapor pr
Development of a Modified Vacuum Cleaner for Lunar Surface Systems
Toon, Katherine P.; Lee, Steve A.; Edgerly, Rachel D.
2010-01-01
The National Aeronautics and Space Administration (NASA) mission to expand space exploration will return humans to the Moon with the goal of maintaining a long-term presence. One challenge that NASA will face returning to the Moon is managing the lunar regolith found on the Moon's surface, which will collect on extravehicular activity (EVA) suits and other equipment. Based on the Apollo experience, the issues astronauts encountered with lunar regolith included eye/lung irritation, and various hardware failures (seals, screw threads, electrical connectors and fabric contamination), which were all related to inadequate lunar regolith mitigation. A vacuum cleaner capable of detaching, transferring, and efficiently capturing lunar regolith has been proposed as a method to mitigate the lunar regolith problem in the habitable environment on lunar surface. In order to develop this vacuum, a modified "off-the-shelf' vacuum cleaner will be used to determine detachment efficiency, vacuum requirements, and optimal cleaning techniques to ensure efficient dust removal in habitable lunar surfaces, EVA spacesuits, and air exchange volume. During the initial development of the Lunar Surface System vacuum cleaner, systematic testing was performed with varying flow rates on multiple surfaces (fabrics and metallics), atmospheric (14.7 psia) and reduced pressures (10.2 and 8.3 psia), different vacuum tool attachments, and several vacuum cleaning techniques in order to determine the performance requirements for the vacuum cleaner. The data recorded during testing was evaluated by calculating particulate removal, relative to the retained simulant on the tested surface. In addition, optical microscopy was used to determine particle size distribution retained on the surface. The scope of this paper is to explain the initial phase of vacuum cleaner development, including historical Apollo mission data, current state-of-the-art vacuum cleaner technology, and vacuum cleaner testing that has
Dermody, Sarah S; Thomas, Katherine M; Hopwood, Christopher J; Durbin, C Emily; Wright, Aidan G C
2017-06-01
This paper demonstrates a recently-popularized quantitative method, the time-varying effect model (TVEM), in describing dynamic, momentary interpersonal processes implicated by Interpersonal Theory. We investigated moment-to-moment complementarity in affiliation and control behaviors (i.e., correspondence in affiliation and reciprocity in control between married dyad members) in a five-minute interaction (N=135), and how complementarity changed over time. Overall, results supported complementarity in affiliation and control. Moreover, effects were time-varying: Complementarity in affiliation increased over time and complementary in control changed over time in a cyclical manner. Dyadic adjustment moderated the strength in complementarity in control during specific timeframes. We discuss implications of these results and future directions. The findings support the utility of TVEM for studying dynamic and time-dependent interpersonal processes.
Technology handbook of vacuum physics
Beck, A H
2013-01-01
Handbook of Vacuum Physics, Volume 3: Technology is part of a series of publications that presents articles featuring the whole spectrum of vacuum physics. This particular volume presents materials that deal with technology concerns in vacuum mechanics. The first material talks about the utilization of ceramic materials in the construction of vacuum devices. The next paper details the application of vacuum physics in soldering and brazing process. The last article deals with the utilization of vacuum technology in high frequency heating. The book will be of great use to professionals involved
Energy Technology Data Exchange (ETDEWEB)
Benedito, J., E-mail: jjbenedi@tal.upv.e [Grupo de Analisis y Simulacion de Procesos Agroalimentarios, Departamento Tecnologia de Alimentos, Universidad Politecnica de Valencia, Cami de Vera S/n, E46022 Valencia (Spain); Cambero, M.I. [Departamento de Nutricion, Bromatologia y Tecnologia de los Alimentos, Facultad de Veterinaria, Universidad Complutense de Madrid, E28040 Madrid (Spain); Ortuno, C. [Grupo de Analisis y Simulacion de Procesos Agroalimentarios, Departamento Tecnologia de Alimentos, Universidad Politecnica de Valencia, Cami de Vera S/n, E46022 Valencia (Spain); Cabeza, M.C.; Ordonez, J.A.; Hoz, L. de la [Departamento de Nutricion, Bromatologia y Tecnologia de los Alimentos, Facultad de Veterinaria, Universidad Complutense de Madrid, E28040 Madrid (Spain)
2011-03-15
The E-beam irradiation of vacuum-packaged RTE cooked ham was carried out to establish the dose required to achieve the food safety objective (FSO) and to minimize changes in selected sensory attributes. Cooked ham was irradiated with doses ranging 1-4 kGy. After the treatment, the microbial inactivation of Listeria monocytogenes, the shelf-life of the product and some sensory attributes (appearance, odor, and flavor) were determined. The inactivation of L. monocytogenes was satisfactorily described by a first-order kinetics equation (R2=0.99). The influence of the irradiation dose on appearance, odor, and flavor was modeled through Gompertz (R2=0.99, for appearance) and Activation/Inactivation (R2=0.99, for odor and flavor) equations. A model was also developed to determine the shelf-life of irradiated cooked ham depending on the irradiation dose (R2>0.91). The dose that maximized the scores of the sensory attributes was 0.96 kGy resulting in an acceptable sensory quality for 80 days. It is possible to apply up to 2 kGy to ensure microbial safety, while provoking no significant changes in the above mentioned sensory attributes.
Pradhan, Anirudh; Jotania, Kanti
2010-08-01
In this paper we have obtained some new exact solutions of Einstein’s field equations in a spatially homogeneous and anisotropic Bianchi type-V space-time with perfect fluid distribution along with heat-conduction and decaying vacuum energy density Λ by applying the variation law for generalized Hubble’s parameter that yields a constant value of deceleration parameter. We find that the constant value of deceleration parameter is reasonable for the present day universe. The variation law for Hubble’s parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein’s field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. The cosmological constant Λ is found to be a decreasing function of time and positive which is corroborated by results from recent supernovae Ia observations. Expressions for look-back time-redshift, neoclassical tests (proper distance d( z)), luminosity distance red-shift and event horizon are derived and their significance are described in detail. The physical and geometric properties of spatially homogeneous and anisotropic cosmological models are discussed.
1983-01-01
This is a cut-out of a LEP vacuum chamber for dipole magnets showing the beam channel and the pumping channel with the getter (NEG) strip and its insulating supports. A water pipe connected to the cooling channel can also be seen at the back.The lead radiation shield lining is also shown. See also 8305563X.
2007-01-01
"Modern physics has shown that the vacuum, previously thought of as a stated of total nothingness, is really a seething background of virtual particles springing in and out of eixstence until they can seize enough energy to materialize as "real" particles." (1,5 page)
CERN PhotoLab
1983-01-01
Final prototype for the LEP vacuum chamber, see 8305170 for more details. Here we see the strips of the NEG pump, providing "distributed pumping". The strips are made from a Zr-Ti-Fe alloy. By passing an electrical current, they were heated to 700 deg C.
CERN PhotoLab
1971-01-01
Some of the most important components of the vacuum system are shown. At the left, the rectangular box is a sputter-ion pump inside its bake-out oven. The assembly in the centre includes a sector valve, three roughing valves, a turbomolecular pump, a rotary backing pump and auxiliary equipment. At the right, the small elbow houses a Bayard-
Furnace brazing under partial vacuum
Mckown, R. D.
1979-01-01
Brazing furnace utilizing partial-vacuum technique reduces tooling requirements and produces better bond. Benefit in that partial vacuum helps to dissociate metal oxides that inhibit metal flow and eliminates heavy tooling required to hold parts together during brazing.
Tritium handling in vacuum systems
Energy Technology Data Exchange (ETDEWEB)
Gill, J.T. [Monsanto Research Corp., Miamisburg, OH (United States). Mound Facility; Coffin, D.O. [Los Alamos National Lab., NM (United States)
1986-10-01
This report provides a course in Tritium handling in vacuum systems. Topics presented are: Properties of Tritium; Tritium compatibility of materials; Tritium-compatible vacuum equipment; and Tritium waste treatment.
Computational Simulation of VARI Fluid Process Molding for Stiffened Panel Structural Composites
Directory of Open Access Journals (Sweden)
XIAO Fei
2016-08-01
Full Text Available The resin filling time can be predicted and the flow pattern of resin can be simulated in Composites VARI Fluid Process Molding with simulation software PAM-RTM. The permeability is important parameter in VARI process. In-plane and transverse permeability are usually tested with complicate and expensive enclosed mold.A set of model with simple structure, easy operation, low cost, was built to obtain accurate permeability by using a process of vacuum-assisted resin infusion (VARI. Besides, the method of equivalent model was employed. The simulation results of effective model is compared with those of experimental VARI process. The filling times for simulation method is 254 s which is shorter than 301 s of the experimental process. Based on flow runner project with equivalent model, the stiffened panel structural composite is prepared to validate the selective process.
Energy Technology Data Exchange (ETDEWEB)
Burda, Philipp [Racah Institute of Physics, Hebrew University,Jerusalem 91904 (Israel); Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada); Moss, Ian G. [School of Mathematics and Statistics, Newcastle University,Newcastle Upon Tyne, NE1 7RU (United Kingdom)
2016-06-06
We have recently suggested that tiny black holes can act as nucleation seeds for the decay of the metastable Higgs vacuum. Previous results applied only to the nucleation of thin-wall bubbles, and covered a very small region of parameter space. This paper considers bubbles of arbitrary profile and reaches the same conclusion: black holes seed rapid vacuum decay. Seeded and unseeded nucleation rates are compared, and the gravitational back reaction of the bubbles is taken into account. The evolution of the bubble interior is described for the unseeded nucleation. Results are presented for the renormalisation group improved Standard Model Higgs potential, and a simple effective model representing new physics.
Lu, Tao; Huang, Yangxin
2017-06-01
In AIDS clinical study, two biomarkers, HIV viral load and CD4 cell counts, play important roles. It is well known that there is inverse relationship between the two. Nevertheless, the relationship is not constant but time varying. The mixed-effects varying-coefficient model is capable of capturing the time varying nature of such relationship from both population and individual perspective. In practice, the nucleic acid sequence-based amplification assay is used to measure plasma HIV-1 RNA with a limit of detection (LOD) and the CD4 cell counts are usually measured with much noise and missing data often occur during the treatment. Furthermore, most of the statistical models assume symmetric distribution, such as normal, for the response variables. Often time, normality assumption does not hold in practice. Therefore, it is important to explore all these factors when modeling the real data. In this article, we establish a joint model that accounts for asymmetric and LOD data for the response variable, and covariate measurement error and missingness simultaneously in the mixed-effects varying-coefficient modeling framework. A Bayesian inference procedure is developed to estimate the parameters in the joint model. The proposed model and method are applied to a real AIDS clinical study and various comparisons of a few models are performed.
Adams, K R; Niebuhr, S E; Dickson, J S
2015-12-01
The objectives of this study were to determine the dissolved CO2 and O2 concentrations in the purge of vacuum-packaged pork chops over a 60 day storage period, and to elucidate the relationship of dissolved CO2 and O2 to the microbial populations and shelf life. As the populations of spoilage bacteria increased, the dissolved CO2 increased and the dissolved O2 decreased in the purge. Lactic acid bacteria dominated the spoilage microflora, followed by Enterobacteriaceae and Brochothrix thermosphacta. The surface pH decreased to 5.4 due to carbonic acid and lactic acid production before rising to 5.7 due to ammonia production. A mathematical model was developed which estimated microbial populations based on dissolved CO2 concentrations. Scanning electron microscope images were also taken of the packaging film to observe the biofilm development. The SEM images revealed a two-layer biofilm on the packaging film that was the result of the tri-phase growth environment. Copyright © 2015 Elsevier Ltd. All rights reserved.
Masina, Isabella; Notari, Alessio
2012-05-11
For a narrow band of values of the top quark and Higgs boson masses, the standard model Higgs potential develops a false minimum at energies of about 10(16) GeV, where primordial inflation could have started in a cold metastable state. A graceful exit to a radiation-dominated era is provided, e.g., by scalar-tensor gravity models. We pointed out that if inflation happened in this false minimum, the Higgs boson mass has to be in the range 126.0±3.5 GeV, where ATLAS and CMS subsequently reported excesses of events. Here we show that for these values of the Higgs boson mass, the inflationary gravitational wave background has be discovered with a tensor-to-scalar ratio at hand of future experiments. We suggest that combining cosmological observations with measurements of the top quark and Higgs boson masses represent a further test of the hypothesis that the standard model false minimum was the source of inflation in the universe.
Vacuum cleaner emissions as a source of indoor exposure to airborne particles and bacteria.
Knibbs, Luke D; He, Congrong; Duchaine, Caroline; Morawska, Lidia
2012-01-03
Vacuuming can be a source of indoor exposure to biological and nonbiological aerosols, although there are few data that describe the magnitude of emissions from the vacuum cleaner itself. We therefore sought to quantify emission rates of particles and bacteria from a large group of vacuum cleaners and investigate their potential determinants, including temperature, dust bags, exhaust filters, price, and age. Emissions of particles between 0.009 and 20 μm and bacteria were measured from 21 vacuums. Ultrafine (vacuums, which was largely not attributable to the range of determinant factors we assessed. Vacuum cleaner emissions contribute to indoor exposure to nonbiological and biological aerosols when vacuuming, and this may vary markedly depending on the vacuum used.
Analysis of RFQ vacuum system for HINS tests at MDB
Energy Technology Data Exchange (ETDEWEB)
Piekarz, Henryk; /Fermilab
2009-07-01
The arrangement of RFQ vacuum system is briefly described. The projections of the vacuum level using standard out-gassing rates for the RFQ major components are compared with measurements. The permeation of water through the Viton O-rings of the LCW manifold inside the RFQ vacuum vessel is analyzed and compared with RGA data. A model where the out-gassing water from the vanes inner surfaces affects seriously RFQ operation is devised and compared with RFQ performance. The rate of a hydrogen gas spill from the LEBT into the RFQ vacuum space is also projected. Suggestions to correct and improve RFQ operation are presented.
Vacuum fluctuations of the supersymmetric field in curved background
Energy Technology Data Exchange (ETDEWEB)
Bilic, Neven, E-mail: bilic@thphys.irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia); Domazet, Silvije, E-mail: sdomazet@irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia); Guberina, Branko, E-mail: guberina@thphys.irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia)
2012-01-16
We study a supersymmetric model in curved background spacetime. We calculate the effective action and the vacuum expectation value of the energy momentum tensor using a covariant regularization procedure. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density and pressure. Assuming the presence of a cosmic fluid in addition to the vacuum fluctuations of the supersymmetric field an effective equation of state is derived in a self-consistent approach at one loop order. The net effect of the vacuum fluctuations of the supersymmetric fields in the leading adiabatic order is a renormalization of the Newton and cosmological constants.
Nonperturbative QED vacuum birefringence
Denisov, V. I.; Dolgaya, E. E.; Sokolov, V. A.
2017-05-01
In this paper we represent nonperturbative calculation for one-loop Quantum Electrodynamics (QED) vacuum birefringence in presence of strong magnetic field. The dispersion relations for electromagnetic wave propagating in strong magnetic field point to retention of vacuum birefringence even in case when the field strength greatly exceeds Sauter-Schwinger limit. This gives a possibility to extend some predictions of perturbative QED such as electromagnetic waves delay in pulsars neighbourhood or wave polarization state changing (tested in PVLAS) to arbitrary magnetic field values. Such expansion is especially important in astrophysics because magnetic fields of some pulsars and magnetars greatly exceed quantum magnetic field limit, so the estimates of perturbative QED effects in this case require clarification.
Energy Technology Data Exchange (ETDEWEB)
Hamer, J.A.; Burg, C.J. Van Der; Kanbier, D.; Heijden, P. Van Der.
1990-09-18
This invention relates to a vacuum distillation device comprising a vacuum distillation column, a furnace provided with a heat exchange tube, and a connecting conduit between the column and the heat exchange tube. Such a device is used to fractionate a hydrocarbon-containing feed sometimes referred to as long residue. An object of this invention is to provide a vacuum distillation device which allows vaporization of a major part of the feed upstream of the column inlet. To this end, the device according to the invention comprises a vacuum distillation device as described above, in which the inner diameter of the heat exchange tube increases along its length to between 2.4 and 3 times the inner diameter of the tube inlet, and in which the inner diameter of the connecting conduit gradually increases along its length to between 2.5 and 5.4 times the inner diameter of the tube outlet. During normal operation of the device of the invention, only less than 50 wt % of the feed is vaporized in the heat exchange tube in the furnace, and more feed is vaporized in the connecting conduit, so that at the outlet end of the conduit the feed comprises about 0.9 kg vapor per kg of feed. The invention provides improved heat transfer in the heat exchange tubes such that fouling is reduced, consequently more heat can be applied per unit of time in the heat exchange tube. This allows either heating of the feed to a higher temperature or increasing the throughput for the same temperature.
Structural design for a 10-GWh SMES vacuum vessel
Energy Technology Data Exchange (ETDEWEB)
Bennett, J.G.; Anderson, C.A.
1978-01-01
An approximate solution to the problem of the nonlinear elastic deformation of a periodically point-supported cylindrical shell is obtained. This solution is used to investigate the structural design of the vacuum vessel for the large underground superconducting magnetic energy storage (SMES) concept. Vacuum vessel designs are evaluated by varying such parameters as shell thickness, support spacing, material properties and physical configuration to keep the amount of material used and construction cost to a minimum.
Szalai, Emily B.; Fleischer, Guy W.; Bence, James R.
2003-01-01
A concurrent increase in lakewide abundance and decrease in size-at-age of bloater (Coregonus hoyi) in Lake Michigan have suggested density-dependent growth regulation. We investigated these temporal patterns by fitting a dynamic von Bertalanffy model and lengthweight relationship with time-varying parameters to mean length- and weight-at-ages (ages 17) from annual surveys (1965-1999). We modeled yearling length, asymptotic size (L‰), and the parameters of a power relationship between mean weight and mean length (α and β) as changing slowly over time using a random walk model. The Brody growth coefficient (k) was modeled as a linear function of L‰ with year-specific random deviations. Our results support a positive relationship between L‰ and k, indicating that under conditions supporting larger asymptotic lengths, individuals approach the asymptote more rapidly. We explored the relationship between year-specific growth parameters and indices of lakewide bloater abundance and found evidence of density-dependent growth. However, in the most recent years, L‰ and yearling length have remained low in Lake Michigan despite low bloater abundances, suggesting the occurrence of a fundamental shift in the food web.
SNS Vacuum Instrumentation and Control System
Energy Technology Data Exchange (ETDEWEB)
J. Y. Tang; L. A. Smart; H. C. Hseuh; P. S. Marroquin; L. R. Dalesio; S. A. Lewis; C. A. Lionberger; K. Kishiyama; D. P. Gurd; M. Hechler; W. Schneider
2001-11-01
The Spallation Neutron Source (SNS) vacuum instrumentation and control systems are being designed at Lawrence Berkeley National Laboratory (LBNL), Brookhaven National Laboratory (BNL), Thomas Jefferson National Accelerator facility (TJNAF) and Los Alamos National Laboratory (LANL). Each participating lab is responsible for a different section of the machine: LBNL for the Front-End section, LANL for the warm LINAC section, TJNAF for the cold LINAC section and BNL for the Ring and transfer line sections. The vacuum instrumentation and control systems are scheduled to be installed and be in operation at Oak Ridge National Laboratory in 2004 or 2005. Although the requirements vary for different sections of the machine, a collaborative effort has been made to standardize vacuum instrumentation components and the global control system interfaces. This paper summarizes the design of each sub-section of vacuum instrumentation and control system and discusses SNS standards for Ion Pump and Gauge controllers, Programmable Logic Controller (PLC) interfaces, Ladder Logic programming and the SNS global control system interfaces.
Lane, J. E.; Metzger, P. T.
2010-01-01
A simple trajectory model has been developed and is presented. The particle trajectory path is estimated by computing the vertical position as a function of the horizontal position using a constant horizontal velocity and a vertical acceleration approximated as a power law. The vertical particle position is then found by solving the differential equation of motion using a double integral of vertical acceleration divided by the square of the horizontal velocity, integrated over the horizontal position. The input parameters are: x(sub 0) and y(sub 0), the initial particle starting point; the derivative of the trajectory at x(sub 0) and y(sub 0), s(sub 0) = s(x(sub 0))= dx(y)/dy conditional expectation y = y((sub 0); and b where bx(sub 0)/y(sub 0) is the final trajectory angle before gravity pulls the particle down. The final parameter v(sub 0) is an approximation to a constant horizontal velocity. This model is time independent, providing vertical position x as a function of horizontal distance y: x(y) = (x(sub 0) + s(sub 0) (y-y(sub 0))) + bx(sub 0) -(s(sub 0)y(sub 0) ((y - y(sub 0)/y(sub 0) - ln((y/y(sub 0)))-((g(y-y(sub 0)(exp 2))/ 2((v(sub 0)(exp 2). The first term on the right in the above equation is due to simple ballistics and a spherically expanding gas so that the trajectory is a straight line intersecting (0,0), which is the point at the center of the gas impingement on the surface. The second term on the right is due to vertical acceleration, which may be positive or negative. The last term on the right is the gravity term, which for a particle with velocities less than escape velocity will eventually bring the particle back to the ground. The parameters b, s(sub 0), and in some cases v(sub 0), are taken from an interpolation of similar parameters determined from a CFD simulation matrix, coupled with complete particle trajectory simulations.
2017-12-08
formulae for the clutter autocorrelation with the hope that these mathematical tools can be useful in the design of clutter mitigation signal...varying (LTV) system theory, particularly in the case of wide-sense stationary uncorrelated scattering (WSSUS) was first put on firm mathematical ...is only valid over a single coherent processing interval (CPI) • Over a single CPI, the range to target(s) is roughly constant • The lag variable τ
Katarina Anthony
2012-01-01
The NA62 straw tracker is using pioneering CERN technology to measure charged particles from very rare kaon decays. For the first time, a large straw tracker with a 4.4 m2 coverage will be placed directly into an experiment’s vacuum tank, allowing physicists to measure the direction and momentum of charged particles with extreme precision. NA62 measurements using this technique will help physicists take a clear look at the kaon decay rate, which might be influenced by particles and processes that are not included in the Standard Model. Straw ends are glued to an aluminium frame, a crucial step in the assembly of a module. The ends are then visually inspected before a leak test is performed. “Although straw detectors have been around since the 1980s, what makes the NA62 straw trackers different is that they can work under vacuum,” explains Hans Danielsson from the PH-DT group leading the NA62 straw project. Straw detectors are basically small drift cha...
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Hyde, Trevor J.; Hewitt, Neil [Ulster Univ., Newtownabbey, Northern Ireland (United Kingdom). Centre for Sustainable Technologies; Eames, Philip C. [Warwick Univ., Coventry (United Kingdom). Warwick Inst. for Sustainable Energy and Resources
2008-07-01
Details of theoretical and experimental studies of the change in vacuum pressure within a vacuum glazing after extreme thermal cycling are presented. The vacuum glazing was fabricated at low temperature using an indium edge seal. It comprised two 4 mm thick 0.4 m by 0.4 m low-emittance glass panes separated by an array of stainless steel pillars with a diameter of 0.32 mm and a height of 0.2 mm. After thermal cycling in the temperature range -30 C to +50 C on one side of the sample, while maintaining 22 C on the other side, it was found that the glass to glass heat conductance of the sample had increased by 8.2%. The vacuum pressure within the evacuated gap was determined to have increased from 0.01 Pa to 0.15 Pa using the model of Corrucini. This is at the upper limit of the range where the effect of gas pressure on the thermal performance of vacuum glazing can be ignored. The degradation of vacuum level determined was corroborated by the change in glass surface temperatures. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Hyde, Trevor; Hewitt, Neil [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB N. Ireland (United Kingdom); Eames, Philip C. [Centre for Renewable Energy Research, University of Loughborough (United Kingdom)
2009-09-15
Details of theoretical and experimental studies of the change in vacuum pressure within a vacuum glazing after extreme thermal cycling are presented. The vacuum glazing was fabricated at low temperature using an indium-copper-indium edge seal. It comprised two 4 mm thick 0.4 m by 0.4 m glass panes with low-emittance coatings separated by an array of stainless steel support pillars spaced at 25 mm with a diameter of 0.4 mm and a height of 0.15 mm. Thermal cycling tests were undertaken in which the air temperature on one side of the sample was taken from -30 C to +50 C and back to -30 C 15 times while maintaining an air temperature of 22 C on the other side. After this test procedure, it was found that the glass to glass heat conductance at the centre glazing area had increased by 10.1% from which the vacuum pressure within the evacuated space was determined to have increased from the negligible level of less than 0.1 Pa to 0.16 Pa using the model of Corrucini. Previous research has shown that if the vacuum pressure is less than 0.1 Pa, the effect of conduction through the residual gas on the total glazing heat transfer is negligible. The degradation of vacuum level determined was corroborated by the change in glass surface temperatures. (author)
McNab, A.
2017-10-01
This paper describes GridPP’s Vacuum Platform for managing virtual machines (VMs), which has been used to run production workloads for WLCG and other HEP experiments. The platform provides a uniform interface between VMs and the sites they run at, whether the site is organised as an Infrastructure-as-a-Service cloud system such as OpenStack, or an Infrastructure-as-a-Client system such as Vac. The paper describes our experience in using this platform, in developing and operating VM lifecycle managers Vac and Vcycle, and in interacting with VMs provided by LHCb, ATLAS, ALICE, CMS, and the GridPP DIRAC service to run production workloads.
Vacuum ultraviolet spectroscopy I
Samson, James A; Lucatorto, Thomas
1998-01-01
This volume is for practitioners, experimentalists, and graduate students in applied physics, particularly in the fields of atomic and molecular physics, who work with vacuum ultraviolet applications and are in need of choosing the best type of modern instrumentation. It provides first-hand knowledge of the state-of-the-art equipment sources and gives technical information on how to use it, along with a broad reference bibliography.Key Features* Aimed at experimentalists who are in need of choosing the best type of modern instrumentation in this applied field* Contains a detailed chapter on la
Energy Technology Data Exchange (ETDEWEB)
Mapes, M.; Smart, L.; Weiss, D.; Steszyn, A.; Todd, R.
2010-01-01
The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The
Tu, Jun; Xia, Zong-Guo
2008-12-15
Traditional regression techniques such as ordinary least squares (OLS) can hide important local variations in the model parameters, and are not able to deal with spatial autocorrelations existing in the variables. A recently developed technique, geographically weighted regression (GWR), is used to examine the relationships between land use and water quality in eastern Massachusetts, USA. GWR models make great improvements of model performance over OLS models, which is proved by F-test and comparisons of model R2 and corrected Akaike Information Criterion (AICc) from both GWR and OLS. GWR models also improve the reliabilities of the relationships by reducing spatial autocorrelations. The application of GWR models finds that the relationships between land use and water quality are not constant over space but show great spatial non-stationarity. GWR models are able to reveal the information previously ignored by OLS models on the local causes of water pollution, and so improve the model ability to explain local situation of water quality. The results of this study suggest that GWR technique has the potential to serve as a useful tool for environmental research and management at watershed, regional, national and even global scales.
Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.
2018-01-01
The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Bøknæs, Niels; Nielsen, P.L.
developed. The mathematical model has been formulated from mechanistic understanding of the process. The resulting coupled model equations were solved using the Finite Element Method (COMSOL Multiphysics® version 4.3b). Experiments were carried out using a newly developed laboratory-scale ohmic heater where...
Katarina Anthony
2015-01-01
A new LHCb programme is delving into uncharted waters for the LHC: exploring how protons interact with noble gases inside the machine pipe. While, at first glance, it may sound risky for the overall quality of the vacuum in the machine, the procedure is safe and potentially very rich in rewards. The results could uncover the high-energy helium-proton cross-section (with all the implications thereof), explore new boundaries of the quark-gluon plasma and much more. As the beam passes through LHCb, interactions with neon gas allow the experiment to measure the full beam profile. In this diagram, beam 1 (blue) and beam 2 (red) are measured by the surrounding VELO detector. It all begins with luminosity. In 2011, LHCb set out to further improve its notoriously precise measurements of the beam profile, using the so-called Beam-Gas Imaging (BGI) method. BGI does exactly what it says on the tin: a small amount of gas is inserted into the vacuum, increasing the rate of collisions around the interaction ...
Gröbner, Oswald
1999-01-01
The Large Hadron Collider (LHC) project, now in the advanced construction phase at CERN, comprises two proton storage rings with colliding beams of 7-TeV energy. The machine is housed in the existing LEP tunnel with a circumference of 26.7 km and requires a bending magnetic field of 8.4 T with 14-m long superconducting magnets. The beam vacuum chambers comprise the inner 'cold bore' walls of the magnets. These magnets operate at 1.9 K, and thus serve as very good cryo-pumps. In order to reduce the cryogenic power consumption, both the heat load from synchrotron radiation emitted by the proton beams and the resistive power dissipation by the beam image currents have to be absorbed on a 'beam screen', which operates between 5 and 20 K and is inserted inside the vacuum chamber. The design of this beam screen represents a technological challenge in view of the numerous and often conflicting requirements and the very tight mechanical tolerances imposed. The synchrotron radiation produces strong outgassing from the...
An overview of the technology of vacuum glazing
Energy Technology Data Exchange (ETDEWEB)
Simko, T. M.; Collins, R. E.; Turner, G. M.; Tang, J-Z. [Sydney Univ., NSW (Australia). School of Physics; Fischer-Cripps, A. C. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Garrison, J. D. [San Diego State Univ., CA (United States). Dept. of Physics
1995-12-01
The technology of vacuum glazing was discussed as an alternative to the argon and krypton gas fills in double paned windows. A vacuum between the two panes insulates in the same way that a Dewar flask insulates. Aside from patent literature, few reports have been published in the scientific literature on the use of vacuum glazing. Over 500 samples of vacuum glazing have been produced in the laboratory. Manufacturing methods have been similar to those used in the production of picture tubes. It was shown that high internal vacuums may be maintained over several years. Design of vacuum glazing required a trade-off between heat flow through pillars and internal stresses. Modelling showed that internal stresses were tolerable for temperature differentials of up to 40 degrees. Relationships between mechanical stress, fracture probability and thermal performance were in the process of being quantified. Physical mechanisms of vacuum degradation were also being studied. Practical applicability of vacuum glazing will depend on the extent to which field trials confirm results of lab experiments and numerical modelling. High thermal insulation, with a very thin glazing and moderate cost were expected in the future. 4 figs., 14 refs.
Vacuum science, technology, and applications
Naik, Pramod K
2018-01-01
Vacuum plays an important role in science and technology. The study of interaction of charged particles, neutrals and radiation with each other and with solid surfaces requires a vacuum environment for reliable investigations. Vacuum has contributed immensely to advancements made in nuclear science, space, metallurgy, electrical/electronic technology, chemical engineering, transportation, robotics and many other fields. This book is intended to assist students, scientists, technicians and engineers to understand the basics of vacuum science and technology for application in their projects. The fundamental theories, concepts, devices, applications, and key inventions are discussed.
Ultra-high vacuum in superconducting accelerator rings
Bazanov, A. M.; Butenko, A. V.; Galimov, A. R.; Lugovnin, A. K.; Smirnov, A. V.
2016-12-01
Achieving the ultra-high vacuum (UHV) in the collider and booster of the NICA project is one of the main challenges when creating this device. It determines the need for a serious approach to this issue and conducting research in this direction. First, it is necessary to understand the effect of the various components of the vacuum systems on the degree of vacuum. It is also necessary to carry out studies of pumping devices for producing the required vacuum (10-9 Pa) in the beam chamber and choose the most optimal pumping scheme. At the same time, it is necessary to figure out how various operations are carried out with the vacuum chamber: preparation of vacuum surfaces, letting in the atmosphere, and warming the chamber after closing the influence on the degree of vacuum and the composition of the residual gas. The temperature may vary from room temperature to liquid helium temperature due to the difficulty of keeping the beam-chamber walls at a constant temperature, including the inner components. This complicates the processes taking place within it. Additional complexity arises due the heating of the chamber walls by various processes during the operation of the accelerator (for example, cycling the magnetic field).
Directory of Open Access Journals (Sweden)
K. Rankinen
2002-01-01
Full Text Available As a first step in applying the Integrated Nitrogen model for CAtchments (INCA to the Simojoki river basin (3160 km2, this paper focuses on calibration of the hydrological part of the model and nitrogen (N dynamics in the river during the 1980s and 1990s. The model application utilised the GIS land-use and forest classification of Finland together with a recent forest inventory based on remote sensing. In the INCA model, the Hydrologically Effective Rainfall (HER is used to drive the water flow and N fluxes through the catchment system. HER was derived from the Watershed Simulation and Forecast System (WSFS. The basic component of the WSFS is a conceptual hydrological model which simulates runoff using precipitation, potential evapotranspiration and temperature data as inputs. Spatially uniform, lumped input data were calculated for the whole river basin and spatially semi-distributed input data were calculated for each of the nine sub-basins. When comparing discharges simulated by the INCA model with observed values, a better fit was obtained with the semi-distributed data than with the spatially uniform data (R2 0.78 v. 0.70 at Hosionkoski and 0.88 v. 0.78 at the river outlet. The timing of flow peaks was simulated rather well with both approaches, although the semi-distributed input data gave a more realistic simulation of low flow periods and the magnitude of spring flow peaks. The river basin has a relatively closed N cycle with low input and output fluxes of inorganic N. During 1982-2000, the average total N flux to the sea was 715 tonnes yr–1, of which 6% was NH4-N, 14% NO3-N, and 80% organic N. Annual variation in river flow and the concentrations of major N fractions in river water, and factors affecting this variation are discussed. Keywords: northern river basin, nitrogen, forest management, hydrology, dynamic modelling, semi-distributed modelling
Directory of Open Access Journals (Sweden)
Bo Chen
2014-01-01
Full Text Available This paper aims to carry out the condition assessment on solar radiation model and thermal loading of bridges. A modification factor is developed to change the distribution of solar intensities during a whole day. In addition, a new solar radiation model for civil engineering structures is proposed to consider the shelter effects induced by cloud, mountains, and surrounding structures. The heat transfer analysis of bridge components is conducted to calculate the temperature distributions based on the proposed new solar radiation model. By assuming that the temperature along the bridge longitudinal direction is constant, one typical bridge segment is specially studied. Fine finite element models of deck plates and corrugate sheets are constructed to examine the temperature distributions and thermal loading of bridge components. The feasibility and validity of the proposed solar radiation model are investigated through detailed numerical simulation and parametric study. The numerical results are compared with the field measurement data obtained from the long-term monitoring system of the bridge and they shows a very good agreement in terms of temperature distribution in different time instants and in different seasons. The real application verifies effectiveness and validity of the proposed solar radiation and heat transfer analysis.
Multiple (Two) Met Bel 601 In Series Ultimate Vacuum Testing
Energy Technology Data Exchange (ETDEWEB)
Restivo, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2016-09-30
SRNL Environmental and Chemical Process Technology (E&CPT) was requested to perform testing of vacuum pumps per a verbal request from the Customer, SRNL Hydrogen Processing Technology. Tritium Operations is currently having difficulties procuring the Normetex™® Model 15 m^{3}/hr (9 CFM) vacuum pump (formerly Normetex Pompes, now Eumeca_{SARL}). One possible solution proposed by Hydrogen Processing Technology personnel is to use two Senior Aerospace Metal Bellows MB-601 vacuum pumps piped with the heads in series, and the pumps in series (Figure 1 below). This memorandum documents the ultimate vacuum testing that was performed to determine if this concept was a viable alternate vacuum pump strategy. This testing dovetails with previous pump evaluations documented in references 1 and 2.
Vacuum energy sequestering and graviton loops
Kaloper, Nemanja; Padilla, Antonio
2017-01-01
We recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy sequestering mechanism to also cancel all the vacuum energy loops involving virtual gravitons, in addition to the vacuum energy generated by matter fields alone.
Zainudin, W. N. R. A.; Ramli, N. A.
2017-09-01
In 2010, Energy Commission (EC) had introduced Incentive Based Regulation (IBR) to ensure sustainable Malaysian Electricity Supply Industry (MESI), promotes transparent and fair returns, encourage maximum efficiency and maintains policy driven end user tariff. To cater such revolutionary transformation, a sophisticated system to generate policy driven electricity tariff structure is in great need. Hence, this study presents a data analytics framework that generates altered revenue function based on varying power consumption distribution and tariff charge function. For the purpose of this study, the power consumption distribution is being proxy using proportion of household consumption and electricity consumed in KwH and the tariff charge function is being proxy using three-tiered increasing block tariff (IBT). The altered revenue function is useful to give an indication on whether any changes in the power consumption distribution and tariff charges will give positive or negative impact to the economy. The methodology used for this framework begins by defining the revenue to be a function of power consumption distribution and tariff charge function. Then, the proportion of household consumption and tariff charge function is derived within certain interval of electricity power. Any changes in those proportion are conjectured to contribute towards changes in revenue function. Thus, these changes can potentially give an indication on whether the changes in power consumption distribution and tariff charge function are giving positive or negative impact on TNB revenue. Based on the finding of this study, major changes on tariff charge function seems to affect altered revenue function more than power consumption distribution. However, the paper concludes that power consumption distribution and tariff charge function can influence TNB revenue to some great extent.
DEFF Research Database (Denmark)
Liu, Guanchen; Jæger, Tanja C.; Nielsen, Søren B.
2017-01-01
To better understand the interactions between nanoparticulated whey protein (NWP) and other milk proteins during acidification, milk model systems were diluted to 0.5% protein concentration and adjusted to pH of 6.0-4.5 following homogenisation and heat treatment. The diluted systems with different...
Gil, Enrique A; Aubert, Xavier L; Beersma, Domien G M
In this work, we introduce a number of models for human circadian phase estimation in ambulatory conditions using various sensor modalities. Machine learning techniques have been applied to ambulatory recordings of wrist actigraphy, light exposure, electrocardiograms (ECG), and distal and proximal
Price, G.W.
1954-08-01
A protector device is described for use in controlling the pressure within a cyclotron. In particular, an electrical circuit functions to actuate a vacuum pump when a predetermined low pressure is reached and disconnect the pump when the pressure increases abcve a certain value. The principal feature of the control circuit lies in the use of a voltage divider network at the input to a relay control tube comprising two parallel, adjustable resistances wherein one resistor is switched into the circuit when the relay connects the pump to a power source. With this arrangement the relay is energized at one input level received from a sensing element within the cyclotron chamber and is de-energized when a second input level, representing the higher pressure limit, is reached.
Mirus, B.B.; Perkins, K.S.; Nimmo, J.R.; Singha, K.
2009-01-01
To understand their relation to pedogenic development, soil hydraulic properties in the Mojave Desert were investi- gated for three deposit types: (i) recently deposited sediments in an active wash, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. Eff ective parameter values were estimated for a simplifi ed model based on Richards' equation using a fl ow simulator (VS2D), an inverse algorithm (UCODE-2005), and matric pressure and water content data from three ponded infi ltration experiments. The inverse problem framework was designed to account for the eff ects of subsurface lateral spreading of infi ltrated water. Although none of the inverse problems converged on a unique, best-fi t parameter set, a minimum standard error of regression was reached for each deposit type. Parameter sets from the numerous inversions that reached the minimum error were used to develop probability distribu tions for each parameter and deposit type. Electrical resistance imaging obtained for two of the three infi ltration experiments was used to independently test fl ow model performance. Simulations for the active wash and Holocene soil successfully depicted the lateral and vertical fl uxes. Simulations of the more pedogenically developed Pleistocene soil did not adequately replicate the observed fl ow processes, which would require a more complex conceptual model to include smaller scale heterogeneities. The inverse-modeling results, however, indicate that with increasing age, the steep slope of the soil water retention curve shitis toward more negative matric pressures. Assigning eff ective soil hydraulic properties based on soil age provides a promising framework for future development of regional-scale models of soil moisture dynamics in arid environments for land-management applications. ?? Soil Science Society of America.
Abdominal intrauterine vacuum aspiration.
Tjalma, W A A
2014-01-01
Evaluating and "cleaning" of the uterine cavity is probably the most performed operation in women. It is done for several reasons: abortion, evaluation of irregular bleeding in premenopausal period, and postmenopausal bleeding. Abortion is undoubtedly the number one procedure with more than 44 million pregnancies terminated every year. This procedure should not be underestimated and a careful preoperative evaluation is needed. Ideally a sensitive pregnancy test should be done together with an ultrasound in order to confirm a uterine pregnancy, excluding extra-uterine pregnancy, and to detect genital and/or uterine malformations. Three out of four abortions are performed by surgical methods. Surgical methods include a sharp, blunt, and suction curettage. Suction curettage or vacuum aspiration is the preferred method. Despite the fact that it is a relative safe procedure with major complications in less than one percent of cases, it is still responsible for 13% of all maternal deaths. All the figures have not declined in the last decade. Trauma, perforation, and bleeding are a danger triage. When there is a perforation, a laparoscopy should be performed immediately, in order to detect intra-abdominal lacerations and bleeding. The bleeding should be stopped as soon as possible in order to not destabilize the patient. When there is a perforation in the uterus, this "entrance" can be used to perform the curettage. This is particularly useful if there is trauma of the isthmus and uterine wall, and it is difficult to identify the uterine canal. A curettage is a frequent performed procedure, which should not be underestimated. If there is a perforation in the uterus, then this opening can safely be used for vacuum aspiration.
ULTRARAPID VACUUM-MICROWAVE HISTOPROCESSING
KOK, LP; BOON, ME
A novel histoprocessing method for paraffin sections is presented in which the combination of vacuum and microwave exposure is the key element. By exploiting the decrease in boiling temperature under vacuum, the liquid molecules in the tissues have been successfully extracted and exchanged at
Vacuum Technology for Superconducting Devices
Chiggiato, P
2014-01-01
The basic notions of vacuum technology for superconducting applications are presented, with an emphasis on mass and heat transport in free molecular regimes. The working principles and practical details of turbomolecular pumps and cryopumps are introduced. The specific case of the Large Hadron Collider’s cryogenic vacuum system is briefly reviewed.
Rahmann, Sven; Gräfe, Christine
2004-11-22
In order to assess the stability of DNA-DNA hybridizations-for example during PCR primer design or oligonucleotide selection for microarrays-one needs to predict the change in Gibbs free energy DeltaG during hybridization. The nearest neighbor model provides a good compromise between accuracy and computational simplicity for this task. To determine optimal combinations of reaction parameters (temperature, salt concentration, oligonucleotide length and GC-content), one would like to understand how DeltaG depends on all of these parameters simultaneously. We derive analytic results about the distribution of nearest neighbor DeltaG values for a Bernoulli random sequence model (specified by oligonucleotide length and average GC-content) under given experimental conditions. We find that the distribution of DeltaG values is approximately Gaussian and provide exact formulas for expectation and variance.
E. M. Schliep; A. E. Gelfand; Holland, D. M.
2015-01-01
There is considerable demand for accurate air quality information in human health analyses. The sparsity of ground monitoring stations across the United States motivates the need for advanced statistical models to predict air quality metrics, such as PM2.5, at unobserved sites. Remote sensing technologies have the potential to expand our knowledge of PM2.5 spatial patterns beyond what we can predict from current PM2.5 monitoring networks. Data from satellites have an additio...
Vacuum Large Current Parallel Transfer Numerical Analysis
Directory of Open Access Journals (Sweden)
Enyuan Dong
2014-01-01
Full Text Available The stable operation and reliable breaking of large generator current are a difficult problem in power system. It can be solved successfully by the parallel interrupters and proper timing sequence with phase-control technology, in which the strategy of breaker’s control is decided by the time of both the first-opening phase and second-opening phase. The precise transfer current’s model can provide the proper timing sequence to break the generator circuit breaker. By analysis of the transfer current’s experiments and data, the real vacuum arc resistance and precise correctional model in the large transfer current’s process are obtained in this paper. The transfer time calculated by the correctional model of transfer current is very close to the actual transfer time. It can provide guidance for planning proper timing sequence and breaking the vacuum generator circuit breaker with the parallel interrupters.
Possible form of vacuum deformation by heavy particles
Mackenzie, R.; Wilczek, F.; Zee, A.
1984-01-01
The possibility is discussed that the lowest-energy state for certain quantum numbers involves a Higgs field polarized into a skyrmion-type configuration. In some models a new type of vacuum instability arises. Phenomenological consequences are indicated schematically.
Heinrici, Axel; Bjelajac, Goran; Jonkers, Jeroen; Jakobs, Stefan; Olschok, Simon; Reisgen, Uwe
2017-02-01
Research and development carried out by the ISF Welding and Joining Institute of RWTH Aachen University has proven that combining high power laser and low vacuum atmosphere provides a welding performance and quality, which is comparable to electron beam welding. The developed welding machines are still using a beam forming which takes place outside the vacuum and the focusing laser beam has to be introduced to the vacuum via a suitable window. This inflexible design spoils much of the flexibility of modern laser welding. With the target to bring a compact, lightweight flying optics with flexible laser transport fibers into vacuum chambers, a high power fiber-fiber coupler has been adapted by II-VI HIGHYAG that includes a reliable vacuum interface. The vacuum-fiber-fiber coupler (V-FFC) is tested with up to 16 kW sustained laser power and the design is flexible in terms of a wide variety of laser fiber plug systems and vacuum flanges. All that is needed to implement the V-FFC towards an existing or planned vacuum chamber is an aperture of at least 100 mm (4 inch) diameter with any type of vacuum or pressure flange. The V-FFC has a state-of-the-art safety interface which allows for fast fiber breakage detection for both fibers (as supported by fibers) by electric wire breakage and short circuit detection. Moreover, the System also provides connectors for cooling and electric signals for the laser beam optics inside the vacuum. The V-FFC has all necessary adjustment options for coupling the laser radiation to the receiving fiber.
Abduljalil, Khaled; Jamei, Masoud; Rostami-Hodjegan, Amin; Johnson, Trevor N
2014-05-01
Although both POPPK and physiologically based pharmacokinetic (PBPK) models can account for age and other covariates within a paediatric population, they generally do not account for real-time growth and maturation of the individuals through the time course of drug exposure; this may be significant in prolonged neonatal studies. The major objective of this study was to introduce age progression into a paediatric PBPK model, to allow for continuous updating of anatomical, physiological and biological processes in each individual subject over time. The Simcyp paediatric PBPK model simulator system parameters were reanalysed to assess the impact of re-defining the individual over the study period. A schedule for re-defining parameters within the Simcyp paediatric simulator, for each subject, over a prolonged study period, was devised to allow seamless prediction of pharmacokinetics (PK). The model was applied to predict concentration-time data from multiday studies on sildenafil and phenytoin performed in neonates. Among PBPK system parameters, CYP3A4 abundance was one of the fastest changing covariates and a 1-h re-sampling schedule was needed for babies below age 3.5 days in order to seamlessly predict PK (age increased, reaching biweekly by 6 months of age. The PK of both sildenafil and phenytoin were predicted better at the end of a prolonged study period using the time varying vs fixed PBPK models. Paediatric PBPK models which account for time-varying system parameters during prolonged studies may provide more mechanistic PK predictions in neonates and infants.
Energy Technology Data Exchange (ETDEWEB)
Lynch, Miranda L., E-mail: Miranda_Lynch@urmc.rochester.edu [University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States); Huang, Li-Shan [University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States); Cox, Christopher [Johns Hopkins Bloomberg School of Public Health, Baltimore, MD (United States); Strain, J.J. [University of Ulster, Coleraine, Northern Ireland (United Kingdom); Myers, Gary J. [University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States); Bonham, Maxine P. [University of Ulster, Coleraine, Northern Ireland (United Kingdom); Shamlaye, Conrad F. [Ministry of Health, Republic of Seychelles (Seychelles); Stokes-Riner, Abbie [University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States); Wallace, Julie M.W.; Duffy, Emeir M. [University of Ulster, Coleraine, Northern Ireland (United Kingdom); Clarkson, Thomas W.; Davidson, Philip W. [University of Rochester School of Medicine and Dentistry, Rochester, NY 14642 (United States)
2011-01-15
Maternal consumption of fish during the gestational period exposes the fetus to both nutrients, especially the long-chain polyunsaturated fatty acids (LCPUFAs), believed to be beneficial for fetal brain development, as well as to the neurotoxicant methylmercury (MeHg). We recently reported that nutrients present in fish may modify MeHg neurotoxicity. Understanding the apparent interaction of MeHg exposure and nutrients present in fish is complicated by the limitations of modeling methods. In this study we fit varying coefficient function models to data from the Seychelles Child Development Nutrition Study (SCDNS) cohort to assess the association of dietary nutrients and children's development. This cohort of mother-child pairs in the Republic of Seychelles had fish consumption averaging 9 meals per week. Maternal nutritional status was assessed for five different nutritional components known to be present in fish (n-3 LCPUFA, n-6 LCPUFA, iron status, iodine status, and choline) and associated with children's neurological development. We also included prenatal MeHg exposure (measured in maternal hair). We examined two child neurodevelopmental outcomes (Bayley Scales Infant Development-II (BSID-II) Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI)), each administered at 9 and at 30 months. The varying coefficient models allow the possible interactions between each nutritional component and MeHg to be modeled as a smoothly varying function of MeHg as an effect modifier. Iron, iodine, choline, and n-6 LCPUFA had little or no observable modulation at different MeHg exposures. In contrast the n-3 LCPUFA docosahexaenoic acid (DHA) had beneficial effects on the BSID-II PDI that were reduced or absent at higher MeHg exposures. This study presents a useful modeling method that can be brought to bear on questions involving interactions between covariates, and illustrates the continuing importance of viewing fish consumption during pregnancy
49 CFR 570.56 - Vacuum brake assist unit and vacuum brake system.
2010-10-01
... 49 Transportation 6 2010-10-01 2010-10-01 false Vacuum brake assist unit and vacuum brake system... Vehicles With GVWR of More Than 10,000 Pounds § 570.56 Vacuum brake assist unit and vacuum brake system. The following requirements apply to vehicles with vacuum brake assist units and vacuum brake systems...
Fisher, Aaron J; Reeves, Jonathan W; Chi, Cyrus
2016-07-01
Expanding on recently published methods, the current study presents an approach to estimating the dynamic, regulatory effect of the parasympathetic nervous system on heart period on a moment-to-moment basis. We estimated second-to-second variation in respiratory sinus arrhythmia (RSA) in order to estimate the contemporaneous and time-lagged relationships among RSA, interbeat interval (IBI), and respiration rate via vector autoregression. Moreover, we modeled these relationships at lags of 1 s to 10 s, in order to evaluate the optimal latency for estimating dynamic RSA effects. The IBI (t) on RSA (t-n) regression parameter was extracted from individual models as an operationalization of the regulatory effect of RSA on IBI-referred to as dynamic RSA (dRSA). Dynamic RSA positively correlated with standard averages of heart rate and negatively correlated with standard averages of RSA. We propose that dRSA reflects the active downregulation of heart period by the parasympathetic nervous system and thus represents a novel metric that provides incremental validity in the measurement of autonomic cardiac control-specifically, a method by which parasympathetic regulatory effects can be measured in process. © 2016 Society for Psychophysiological Research.
Zhou, Si-Da; Ma, Yuan-Chen; Liu, Li; Kang, Jie; Ma, Zhi-Sai; Yu, Lei
2018-01-01
Identification of time-varying modal parameters contributes to the structural health monitoring, fault detection, vibration control, etc. of the operational time-varying structural systems. However, it is a challenging task because there is not more information for the identification of the time-varying systems than that of the time-invariant systems. This paper presents a vector time-dependent autoregressive model and least squares support vector machine based modal parameter estimator for linear time-varying structural systems in case of output-only measurements. To reduce the computational cost, a Wendland's compactly supported radial basis function is used to achieve the sparsity of the Gram matrix. A Gamma-test-based non-parametric approach of selecting the regularization factor is adapted for the proposed estimator to replace the time-consuming n-fold cross validation. A series of numerical examples have illustrated the advantages of the proposed modal parameter estimator on the suppression of the overestimate and the short data. A laboratory experiment has further validated the proposed estimator.
Particles and Antiparticles in the Planck Vacuum Theory
Directory of Open Access Journals (Sweden)
Daywitt W. C.
2011-01-01
Full Text Available This short note sheds some light on the negative energy vacuum state by expanding the Planck vacuum (PV model and taking a closer look at the particle-antiparticle nature of the Dirac equation. Results of the development are briefly discussed with regard to the complexity of the PV interaction with the massless free charge, the Dirac electron, and the proton; an exercise that may lead to a better proton model.
Zorilă, Tudor-Cătălin; Stylianou, Yannis; Flanagan, Sheila; Moore, Brian Cecil
2017-01-01
A model for the loudness of time-varying sounds [Glasberg and Moore (2012). J. Audio. Eng. Soc. 50, 331-342] was assessed for its ability to predict the loudness of sentences that were processed to either decrease or increase their dynamic fluctuations. In a paired-comparison task, subjects compared the loudness of unprocessed and processed sentences that had been equalized in (1) root-mean square (RMS) level; (2) the peak long-term loudness predicted by the model; (3) the mean long-term loud...
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Debashis Dutta
2015-10-01
Full Text Available This paper proposes a differential equation inventory model that incorporates partial backlogging and deterioration. Holding cost and demand rate are time dependent. Shortages are allowed and assumed to be partially backlogged. Two versions are presented, the first one with deterministic values of the parameters and the second one taking into the account the interval uncertainty of the parameters. In the crisp case, Taylor’s series expansion is used, and graphically shown that the cost function is convex. While, in the case of intervals, the interval arithmetic is used and then the problem is transformed into a multi-objective non-linear optimization problem and an interval objective function. To solve this problem, the weighted-sum method is used. The proposed procedure is validated with the help of a numerical example. Sensitivity analysis on various parameters has also been carried out.
Cohen, Dale J; Quinlan, Philip T
2016-12-01
How do people derive meaning from numbers? Here, we instantiate the primary theories of numerical representation in computational models and compare simulated performance to human data. Specifically, we fit simulated data to the distributions for correct and incorrect responses, as well as the pattern of errors made, in a traditional "relative quantity" task. The results reveal that no current theory of numerical representation can adequately account for the data without additional assumptions. However, when we introduce repeated, error-prone sampling of the stimulus (e.g., Cohen, 2009) superior fits are achieved when the underlying representation of integers reflects linear spacing with constant variance. These results provide new insights into (i) the detailed nature of mental numerical representation, and, (ii) general perceptual processes implemented by the human visual system. Copyright © 2016 Elsevier Inc. All rights reserved.
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Fang eShen
2014-09-01
Full Text Available Tree shrews represent a suitable animal model to study the pathogenesis of human diseases as they are phylogenetically close to primates and have a well-developed central nervous system that possesses many homologies with primates. Therefore, in our study, we investigated whether tree shrews can be used to explore the addictive behaviors induced by morphine. Firstly, to investigate the psychoactive effect of morphine on tree shrews’ behavior, the number of jumping and shuttling, which represent the vertical and horizontal locomotor activity respectively, was examined following the injection of different dosage of morphine. Our results showed intramuscular (IM injection of morphine (5 or 10 mg/kg significantly increased the locomotor activity of tree shrews 30-60 min post-injection. Then, using the conditioned place preference/aversion (CPP/CPA paradigm, we found morphine-conditioned tree shrews exhibited place preference in the morphine-paired chamber on the test day. In addition, naloxone-precipitated withdrawal induced place aversion in the chronic morphine-dependent tree shrews. We evaluated the craving for morphine drinking by assessing the break point that reflects the maximum effort animals will expend to get the drug. Our data showed the break point was significantly increased when compared to the baseline on the 1st, 7th and 14th day after the abstinence. Moreover, in the intravenous morphine self-administration experiment, tree shrews conditioned with morphine responded on the active lever significantly more frequently than on the inactive lever after training. These results suggest that tree shrew may be a potential candidate for study the addictive behaviors and the underling neurological mechanisms.
Twu, Pamela; Zhao, Qichao; Pitner, William R; Acree, William E; Baker, Gary A; Anderson, Jared L
2011-08-05
Ionic liquids (ILs) are promising gas chromatography (GC) stationary phases due to their high thermal stability, negligible vapor pressure, and ability to solvate a broad range of analytes. The tunability of ILs allows for structure modification in pursuit of enhanced separation selectivity and control of analyte elution order. In this study, the solvation parameter model is used to characterize the solvation interactions of fifteen ILs containing various cationic functional groups (i.e., dimethylamino, hydroxyl, and ether) and cation types paired with various counter anions, namely, tris(pentafluoroethyl)trifluorophosphate (FAP(-)), bis[(trifluoromethyl)sulfonyl]imide (NTf(2)(-)), thiocyanate (SCN(-)), tricyanomethide (C(CN)(3)(-)), tetracyanoborate (B(CN)(4)(-)), and bis[oxalate(2-)]borate (BOB(-)). The presence of functional groups affected the hydrogen bond basicity, hydrogen bond acidity, as well as dispersion interactions of the resulting ILs, while the change of cation type yielded modest influence on the dipolarity. The switch of counter anions in unfunctionalized ILs produced compounds with higher dipolarity and hydrogen bond basicity. The dipolarity and hydrogen bond basicity of ILs possessing cyano-containing anions appeared to be inversely proportional to the cyano content of the anion. The modification of IL structure resulted in a significant effect on the retention behavior as well as separation selectivity for many solutes, including reversed elution orders of some analytes. This study provides one of the most comprehensive examinations up-to-date on the relation between IL structure and the resulting solvation characteristics and gives tremendous insight into choosing suitable ILs as GC stationary phases for solute specific separations. Copyright © 2011 Elsevier B.V. All rights reserved.
Creativity Doesn't Develop in a Vacuum
Barbot, Baptiste; Baer, John
2016-01-01
The skills, knowledge, attitudes, motivations, and personality traits that lead to creative thinking and creative behavior do not exist--and do not develop--in a vacuum. They are inextricably tied to content, to domains, in particular, and they therefore vary by domains. The more we learn about creativity, the more we discover how domain specific…
Yang, Hanyu; Cranford, James A; Li, Runze; Buu, Anne
2015-02-20
This study proposes a generalized time-varying effect model that can be used to characterize a discrete longitudinal covariate process and its time-varying effect on a later outcome that may be discrete. The proposed method can be applied to examine two important research questions for daily process data: measurement reactivity and predictive validity. We demonstrate these applications using health risk behavior data collected from alcoholic couples through an interactive voice response system. The statistical analysis results show that the effect of measurement reactivity may only be evident in the first week of interactive voice response assessment. Moreover, the level of urge to drink before measurement reactivity takes effect may be more predictive of a later depression outcome. Our simulation study shows that the performance of the proposed method improves with larger sample sizes, more time points, and smaller proportions of zeros in the binary longitudinal covariate. Copyright © 2014 John Wiley & Sons, Ltd.
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E. D. Chertov
2015-01-01
Full Text Available The work is devoted to the creation of a new type of mixer to produce homogeneous mixtures of dissimilar materials applied to recycling of housing and communal services waste. The article describes the design of a dual-chamber device of the original high-temperature vacuum mixer, there investigated the processes occurring in the chambers of such devices. The results of theoretical and experimental research of the process of mixing recycled polyethylene with a mixture of "grinded food waste – Eco wool” are presented. The problem of the optimum choice of bending the curvilinear blades in the working volume of the seal, which is achieved by setting their profile in the form of involute arc of several circles of different radii, is examined . The dependences, allowing to define the limits of the changes of the main mode parameters the angular velocity of rotation of the working body of the mixer using two ways of setting the profile of the curvilinear blade mixer are obtained. Represented design of the mixer is proposed to use for a wide range of tasks associated with the mixing of the components with a strongly pronounced difference of physic al chemical properties and, in particular, in the production of composites out of housing and communal services waste.
Experimental tests of vacuum energy
CERN. Geneva
2015-01-01
While the current vacuum energy of the Universe is very small, in our standard cosmological picture it has been much larger at earlier epochs. We try to address the question of what are possible ways to try to experimentally verify this. One direction is to look for systems where vacuum energy constitutes a non-negligible fraction of the total energy, and study the properties of those. Another possibility is to focus on the epochs around cosmic phase transitions, when the vacuum energy is of the same order as the total energy. Along these lines we investigate properties of neutron stars and the imprint of phase transitions on primordial gravitational waves.
Task sequencing for autonomous robotic vacuum cleaners
Gorbenko, Anna; Popov, Vladimir
2017-07-01
Various planning problems for robotic systems are of considerable interest. One of such problems is the problem of task sequencing. In this paper, we consider the problem of task sequencing for autonomous vacuum floor cleaning robots. We consider a graph model for the problem. We propose an efficient approach to solve the problem. In particular, we use an explicit reduction from the decision version of the problem to the satisfiability problem. We present the results of computational experiments for different satisfiability algorithms.
On stability of electroweak vacuum during inflation
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A. Shkerin
2015-06-01
Full Text Available We study Coleman–De Luccia tunneling of the Standard Model Higgs field during inflation in the case when the electroweak vacuum is metastable. We verify that the tunneling rate is exponentially suppressed. The main contribution to the suppression is the same as in flat space–time. We analytically estimate the corrections due to the expansion of the universe and an effective mass term in the Higgs potential that can be present at inflation.
Electroweak vacuum stabilized by moduli during/after inflation
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Yohei Ema
2016-10-01
Full Text Available It is known that the present electroweak vacuum is likely to be metastable and it may lead to a serious instability during/after inflation. We propose a simple solution to the problem of vacuum instability during/after inflation. If there is a moduli field which has Planck-suppressed interactions with the standard model fields, the Higgs quartic coupling in the early universe naturally takes a different value from the present one. A slight change of the quartic coupling in the early universe makes the Higgs potential absolutely stable and hence we are free from the vacuum instability during/after inflation.
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Yi Ren
2013-01-01
Full Text Available Transplantation is often the only viable treatment for pediatric patients with end-stage liver disease. Making well-informed decisions on when to proceed with transplantation requires accurate predictors of transplant survival. The standard Cox proportional hazards (PH model assumes that covariate effects are time-invariant on right-censored failure time; however, this assumption may not always hold. Gray’s piecewise constant time-varying coefficients (PC-TVC model offers greater flexibility to capture the temporal changes of covariate effects without losing the mathematical simplicity of Cox PH model. In the present work, we examined the Cox PH and Gray PC-TVC models on the posttransplant survival analysis of 288 pediatric liver transplant patients diagnosed with cancer. We obtained potential predictors through univariable (P<0.15 and multivariable models with forward selection (P<0.05 for the Cox PH and Gray PC-TVC models, which coincide. While the Cox PH model provided reasonable average results in estimating covariate effects on posttransplant survival, the Gray model using piecewise constant penalized splines showed more details of how those effects change over time.
Alumina barrier for vacuum brazing
Beuyukian, C. S.
1980-01-01
Heating platens of vacuum-brazing press will not stick to workpiece if aluminum oxide "paper" is interposed. Paper does not disintegrate in press, will not contaminate braze alloy, and helps form smoothly contoured, regular fillet at brazed edges.
[Endoscopic vacuum-assisted closure].
Wedemeyer, J; Lankisch, T
2013-03-01
Anastomotic leakage in the upper and lower intestinal tract is associated with high morbidity and mortality. Within the last 10 years endoscopic treatment options have been accepted as sufficient treatment option of these surgical complications. Endoscopic vacuum assisted closure (E-VAC) is a new innovative endoscopic therapeutic option in this field. E-VAC transfers the positive effects of vacuum assisted closure (VAC) on infected cutaneous wounds to infected cavities that can only be reached endoscopically. A sponge connected to a drainage tube is endoscopically placed in the leakage and a continuous vacuum is applied. Sponge and vacuum allow removal of infected fluids and promote granulation of the leakage. This results in clean wound grounds and finally allows wound closure. Meanwhile the method was also successfully used in the treatment of necrotic pancreatitis.
Cosmic R-string, R-tube and vacuum instability
Energy Technology Data Exchange (ETDEWEB)
Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Hamada, Yuta; Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ohashi, Keisuke [Osaka City Univ. (Japan). Dept. of Mathematics and Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research
2012-11-15
We show that a cosmic string associated with spontaneous U(1) R symmetry breaking gives a constraint for supersymmetric model building. In some models, the string can be viewed as a tube-like domain wall with a winding number interpolating a false vacuum and a true vacuum. Such string causes inhomogeneous decay of the false vacuum to the true vacuum via rapid expansion of the radius of the tube and hence its formation would be inconsistent with the present Universe. However, we demonstrate that there exist metastable solutions which do not expand rapidly. Furthermore, when the true vacua are degenerate, the structure inside the tube becomes involved. As an example, we show a ''bamboo''-like solution, which suggests a possibility observing an information of true vacua from outside of the tube through the shape and the tension of the tube.
Lagana, Rastislav
The reliability of wood structures is strongly affected by duration of loading and environmental conditions. The goal of this study was to develop a simple method for measuring the mechano-sorptive character of the hygro-mechanical behavior of wood and to develop a model capable of predicting long term beam behavior under changing climates. The model predictions were compared with experimental results. Red spruce was the species selected for investigation. The mechano-sorptive properties were measured in tension and compression on thin specimens where moisture content variation within the material was minimal when exposed to a varying environment. The measured mechano-sorptive deformation in compression was significantly greater than that measured in tension (4 times higher at cumulative MC 60% than in tension). However, the developed compression protocol was less accurate, with a tendency to overestimate the magnitude of subsequent experimental creep behavior. A multi-physics model of hygro-mechanical uniaxial beam behavior was developed that rigorously couples spatially varying time-dependent moisture content with the uniaxial stress-strain relations. To verify the model and accuracy of the measured uniaxial mechano-sorptive characteristic of red spruce, the behavior of beams loaded by four point bending was measured in cyclically varying climate over 2.5 months. Although the model did not properly account for the immediate effect of moisture content change on mid-span deflection, as was observed in real beams, the overall trend of the predicted deflection was in good agreement with experimental results. An additional part of the thesis dealt with development of an analytical model to predict the hygro-mechanical behavior of multi-directional polymer matrix composite laminates which incorporate the mechano-sorptive effects of a phenol resorcinol formal-dehyde resin. E-glass/phenol resorcinol formaldehyde resin composite material parameters were used in the model
Vacuum production; Produccion de vacio
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Segovia, J. L. de
2010-07-01
Since the advent of ultra high vacuum in 1958 has been a great demand for new as means of production and to meet the process needs to be done: industry heavy, high technology and space research areas, large accelerator systems particles or nuclear fusion. In this paper we explore the modern media production: dry vacuum pumps, turbo pumps, pump status diffusion ion pumps and cryopumps. (Author)
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James A Wiley
Full Text Available We put forward a new item response model which is an extension of the binomial error model first introduced by Keats and Lord. Like the binomial error model, the basic latent variable can be interpreted as a probability of responding in a certain way to an arbitrarily specified item. For a set of dichotomous items, this model gives predictions that are similar to other single parameter IRT models (such as the Rasch model but has certain advantages in more complex cases. The first is that in specifying a flexible two-parameter Beta distribution for the latent variable, it is easy to formulate models for randomized experiments in which there is no reason to believe that either the latent variable or its distribution vary over randomly composed experimental groups. Second, the elementary response function is such that extensions to more complex cases (e.g., polychotomous responses, unfolding scales are straightforward. Third, the probability metric of the latent trait allows tractable extensions to cover a wide variety of stochastic response processes.
Vacuum-assisted cesarean section
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McQuivey RW
2017-03-01
Full Text Available Ross W McQuivey,1 Jon E Block2 1Clinical Innovations, Salt Lake City, UT, 2Independent consultant, San Francisco, CA, USA Abstract: There has been a dramatic rise in the frequency of cesarean sections, surpassing 30% of all deliveries in the US. This upsurge, coupled with a decreasing willingness to allow vaginal birth after cesarean section, has resulted in an expansion of the use of vacuum assistance to safely extract the fetal head. By avoiding the use of a delivering hand or forceps blade, the volume being delivered through the uterine incision can be decreased when the vacuum is used properly. Reducing uterine extensions with their associated complications (eg, excessive blood loss in difficult cases is also a theoretical advantage of vacuum delivery. Maternal discomfort related to excessive fundal pressure may also be lessened. To minimize the risk of neonatal morbidity, proper cup placement over the “flexion point” remains essential to maintain vacuum integrity and reduce the chance of inadvertent detachment and uterine extensions. Based on the published literature and pragmatic clinical experience, utilization of the vacuum device is a safe and effective technique to assist delivery during cesarean section. Keywords: cesarean section, vacuum, forceps, birth, delivery
Technical specification for vacuum systems
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Khaw, J. (ed.)
1987-01-01
The vacuum systems at the Stanford Linear Accelerator Center (SLAC) are primarily of all-metal construction and operate at pressures from 10/sup -5/ to 10/sup -11/ Torr. The primary gas loads during operation result from thermal desorption and beam-induced desorption from the vacuum chamber walls. These desorption rates can be extremely high in the case of hydrocarbons and other contaminants. These specifications place a major emphasis on eliminating contamination sources. The specifications and procedures have been written to insure the cleanliness and vacuum integrity of all SLAC vacuum systems, and to assist personnel involved with SLAC vacuum systems in choosing and designing components that are compatible with existing systems and meet the quality and reliability of SLAC vacuum standards. The specification includes requirements on design, procurement, fabrication, chemical cleaning, clean room practices, welding and brazing, helium leak testing, residual gas analyzer testing, bakeout, venting, and pumpdown. Also appended are specifications regarding acceptable vendors, isopropyl alcohol, bakeable valve cleaning procedure, mechanical engineering safety inspection, notes on synchrotron radiation, and specifications of numerous individual components. (LEW)
Electroweak vacuum metastability and low-scale inflation
Ema, Yohei; Mukaida, Kyohei; Nakayama, Kazunori
2017-12-01
We study the stability of the electroweak vacuum in low-scale inflation models whose Hubble parameter is much smaller than the instability scale of the Higgs potential. In general, couplings between the inflaton and Higgs are present, and hence we study effects of these couplings during and after inflation. We derive constraints on the couplings between the inflaton and Higgs by requiring that they do not lead to catastrophic electroweak vacuum decay, in particular, via resonant production of the Higgs particles.
Vacuum polarization and photon mass in inflation
Prokopec, T; Prokopec, Tomislav; Woodard, Richard P.
2004-01-01
We give a pedagogical review of a mechanism through which long wave length photons can become massive during inflation. Our account begins with a discussion of the period of exponentially rapid expansion known as inflation. We next describe how, when the universe is not expanding, quantum fluctuations in charged particle fields cause even empty space to behave as a polarizable medium. This is the routinely observed phenomenon of vacuum polarization. We show that the quantum fluctuations of low mass, scalar fields are enormously amplified during inflation. If one of these fields is charged, the vacuum polarization effect of flat space is strengthened to the point that long wave length photons acquire mass. Our result for this mass is shown to agree with a simple model in which the massive photon electrodynamics of Proca emerges from applying the Hartree approximation to scalar quantum electrodynamics during inflation. One does not measure a huge photon mass today because the original phase of inflation ended w...
Thermal Vacuum Chamber Repressurization with Instrument Purging
Woronowicz, Michael
2017-01-01
At the end of James Webb Space Telescope (JWST) OTIS (Optical Telescope Element-OTE-Integrated Science Instrument Module-ISIM) cryogenic vacuum testing in NASA Johnson Space Centers (JSCs) thermal vacuum (TV) Chamber A, contamination control (CC) engineers are mooting the idea that chamber particulate material stirred up by the repressurization process may be kept from falling into the ISIM interior to some degree by activating instrument purge flows over some initial period before opening the chamber valves. This memo describes development of a series of models designed to describe this process. These are strung together in tandem to estimate overpressure evolution from which net outflow velocity behavior may be obtained. Creeping flow assumptions are then used to determine the maximum particle size that may be kept suspended above the ISIM aperture, keeping smaller particles from settling within the instrument module.
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Jelena Parlov Vuković
2015-03-01
Full Text Available NMR spectroscopy in combination with statistical methods was used to study vacuum residues and vacuum gas oils from 32 crude oils of different origin. Two chemometric metodes were applied. Firstly, principal component analysis on complete spectra was used to perform classification of samples and clear distinction between vacuum residues and vacuum light and heavy gas oils were obtained. To quantitatively predict the composition of asphaltenes, principal component regression models using areas of resonance signals spaned by 11 frequency bins of the 1H NMR spectra were build. The first 5 principal components accounted for more than 94 % of variations in the input data set and coefficient of determination for correlation between measured and predicted values was R2 = 0.7421. Although this value is not significant, it shows the underlying linear dependence in the data. Pseudo two-dimensional DOSY NMR experiments were used to assess the composition and structural properties of asphaltenes in a selected crude oil and its vacuum residue on the basis of their different hydrodynamic behavior and translational diffusion coefficients. DOSY spectra showed the presence of several asphaltene aggregates differing in size and interactions they formed. The obtained results have shown that NMR techniques in combination with chemometrics are very useful to analyze vacuum residues and vacuum gas oils. Furthermore, we expect that our ongoing investigation of asphaltenes from crude oils of different origin will elucidate in more details composition, structure and properties of these complex molecular systems.
The survival and recovery of bacteria in vacuum cleaner dust.
Haysom, I W; Sharp, K
2003-03-01
The possibility exists that environmental dust could be a source of gastro-intestinal infection in the domestic environment and that the causative microbes are collected during vacuum cleaning. This study examines the survival of total bacterial populations, Enterobacteriaceae and salmonella species in vacuum cleaner dust in vitro and in use. Total counts remain constant at around 10(6)-10(8) colony forming units (cfu) g-1 for at least 60 days. Enterobacteriaceae showed only a slight decline over the same period. Recovery of salmonellae artificially inoculated into vacuum dust was dose and time dependent: even relatively small inocula (vacuum cleaner dust samples were received from 76 households. A significant association was found between total bacterial counts and whether the household was in a rural or urban situation and the number of people in the household. No association was found between total bacterial counts and the number of children in the household, the presence of pets, wearing shoes indoors, the makes, model and age of the vacuum cleaner, the type of dust collector or dust bag, how often the vacuum cleaner was used and the length of time between sample collection and microbiological testing. Salmonella species were isolated from vacuum cleaner dust from three of the 76 households although no factors could be identified linking the homes. This study shows that vacuum cleaners are effective collectors and reservoirs of microbial contamination and that these contaminants are able to survive for up to two months. Vacuum cleaner dust could thus be a useful indicator of environmental contamination in the home.
Reyes, J. J.; Tague, N.; Kruger, C. E.; Johnson, K.; Adam, J. C.
2015-12-01
Grasses in rangeland ecosystems cover a large portion of the contiguous United States and are used to support the production of livestock. These grasslands experience a wide range of precipitation and temperature regimes, as well as management activities like grazing. Assessing the coupled response of biomass to both climatic change and human activities is important to decision makers to ensure the sustainable management of their lands. The objective of this study is to examine the sensitivity of biomass under co-varying conditions of climate and grazing management. For this, we used the Regional Hydro-ecologic Simulation System (RHESSys), a physically-based model that simulates coupled water and biogeochemical processes. We selected representative grassland sites using the Köppen-Geiger climate classification system and information on major grass species. Historical data on precipitation, temperature, and grazing patterns (intensity, frequency, duration) were incrementally perturbed to simulate climatic change and possible changes in management. To visualize this multi-dimensional parameter space, we created surface response plots of varying climate and grazing factors for the mean and variance of both aboveground and belowground biomass, as well as the ratio between the two. Mean biomass generally increased with warmer temperatures and decreased with more intense grazing. The sensitivity of biomass (i.e. variance) increased with more extreme perturbations in climate and intense types of grazing management. However, co-varying climate conditions with either grazing intensity, frequency, or duration revealed different biomass responses and tradeoffs. For example, some changes in grazing duration could be reversed by changes in climate. Effects of high intensity grazing could be buffered depending on the timing of grazing (i.e. start/end date). Using simple perturbations with process-based modeling provides useful information for land managers for future planning.
Lynch, Miranda L.; Huang, Li-Shan; Cox, Christopher; Strain, J.J.; Myers, Gary J.; Bonham, Maxine P.; Shamlaye, Conrad F.; Stokes-Riner, Abbie; Wallace, Julie M.W.; Duffy, Emeir M.; Clarkson, Thomas W.; Davidson, Philip W.
2010-01-01
Maternal consumption of fish during the gestational period exposes the fetus to both nutrients, especially the long-chain polyunsaturated fatty acids (LCPUFAs), believed to be beneficial for fetal brain development, as well as to the neurotoxicant methylmercury (MeHg). We recently reported that nutrients present in fish may modify MeHg neurotoxicity. Understanding the apparent interaction of MeHg exposure and nutrients present in fish is complicated by the limitations of modeling methods. In this study we fit varying coefficient function models to data from the Seychelles Child Development Nutrition Study (SCDNS) cohort to assess the association of dietary nutrients and children’s development. This cohort of mother-child pairs in the Republic of Seychelles had fish consumption averaging 9 meals per week. Maternal nutritional status was assessed for five different nutritional components known to be present in fish (n-3 LCPUFA, n-6 LCPUFA, iron status, iodine status, and choline) and associated with children’s neurological development. We also included prenatal MeHg exposure (measured in maternal hair). We examined two child neurodevelopmental outcomes (Bayley Scales Infant Development-II (BSID-II) Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI)), each administered at 9 and at 30 months. The varying coefficient models allow the possible interactions between each nutritional component and MeHg to be modeled as a smoothly varying function of MeHg as an effect modifier. Iron, iodine, choline, and n-6 LCPUFA had little or no observable modulation at different MeHg exposures. In contrast the n-3 LCPUFA docosahexaenoic acid (DHA) had beneficial effects on the BSID-II PDI that were reduced or absent at higher MeHg exposures. This study presents a useful modeling method that can be brought to bear on questions involving interactions between covariates, and illustrates the continuing importance of viewing fish consumption during pregnancy as a
Ali, M Sanni; Groenwold, Rolf H H; Belitser, Svetlana V; Souverein, Patrick C; Martín, Elisa; Gatto, Nicolle M; Huerta, Consuelo; Gardarsdottir, Helga; Roes, Kit C B; Hoes, Arno W; de Boer, Antonius; Klungel, Olaf H
2016-03-01
Observational studies including time-varying treatments are prone to confounding. We compared time-varying Cox regression analysis, propensity score (PS) methods, and marginal structural models (MSMs) in a study of antidepressant [selective serotonin reuptake inhibitors (SSRIs)] use and the risk of hip fracture. A cohort of patients with a first prescription for antidepressants (SSRI or tricyclic antidepressants) was extracted from the Dutch Mondriaan and Spanish Base de datos para la Investigación Farmacoepidemiológica en Atención Primaria (BIFAP) general practice databases for the period 2001-2009. The net (total) effect of SSRI versus no SSRI on the risk of hip fracture was estimated using time-varying Cox regression, stratification and covariate adjustment using the PS, and MSM. In MSM, censoring was accounted for by inverse probability of censoring weights. The crude hazard ratio (HR) of SSRI use versus no SSRI use on hip fracture was 1.75 (95%CI: 1.12, 2.72) in Mondriaan and 2.09 (1.89, 2.32) in BIFAP. After confounding adjustment using time-varying Cox regression, stratification, and covariate adjustment using the PS, HRs increased in Mondriaan [2.59 (1.63, 4.12), 2.64 (1.63, 4.25), and 2.82 (1.63, 4.25), respectively] and decreased in BIFAP [1.56 (1.40, 1.73), 1.54 (1.39, 1.71), and 1.61 (1.45, 1.78), respectively]. MSMs with stabilized weights yielded HR 2.15 (1.30, 3.55) in Mondriaan and 1.63 (1.28, 2.07) in BIFAP when accounting for censoring and 2.13 (1.32, 3.45) in Mondriaan and 1.66 (1.30, 2.12) in BIFAP without accounting for censoring. In this empirical study, differences between the different methods to control for time-dependent confounding were small. The observed differences in treatment effect estimates between the databases are likely attributable to different confounding information in the datasets, illustrating that adequate information on (time-varying) confounding is crucial to prevent bias. Copyright © 2016 John Wiley & Sons, Ltd.
A modified pump-out technique used for fabrication of low temperature metal sealed vacuum glazing
Energy Technology Data Exchange (ETDEWEB)
Zhao, Jun Fu; Hyde, Trevor J.; Fang, Yueping [Center for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, Co. Antrim BT37 0QB, Northern Ireland (United Kingdom); Eames, Philip C.; Wang, Jinlei [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom)
2007-09-15
A modified pump-out technique, incorporating a novel pump-out hole sealing process, has been developed that enables a high level of vacuum to be achieved between the panes of a vacuum glazing. The modified pump-out method provides several potential opportunities for the fabrication of a vacuum glazing with improved thermal performance. In particular, improved flexibility for production of a wide range of glazing sizes may allow a lower cost of manufacture to be achieved by avoiding the expense of a high vacuum oven which would otherwise be required for commercial production of high performance, large-scale vacuum glazings. The thermal performance of the vacuum glazing fabricated using the pump-out technique was characterized using a guarded hotbox calorimeter and theoretically analyzed using a finite volume model. The excellent experimentally determined thermal performance of the fabricated vacuum glazing was in good agreement with that predicted theoretically. (author)
Low emittance coatings and the thermal performance of vacuum glazing
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Hyde, Trevor J.; Zhao, Junfu; Wang, Jinlei; Huang, Ye [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB, N. Ireland (United Kingdom); Eames, Philip C. [School of Engineering, University of Warwick, Coventry, CV4 7AL (United Kingdom); Norton, Brian [Dublin Institute of Technology, Aungier Street, Dublin 2 (Ireland)
2007-01-15
The thermal performances of vacuum glazings employing coatings with emittance between 0.02 and 0.16 were simulated using a three-dimensional finite volume model. Physical samples of vacuum glazings with hard and soft coatings with emittance of 0.04, 0.12 and 0.16 were fabricated and their thermal performance characterised experimentally using a guarded hot box calorimeter. Good agreement was found between experimental and theoretical thermal performances for both a vacuum glazing with a soft coating (emittance 0.04) and those with hard coatings (emittance 0.12 and 0.16). Simulations showed that for a low value of emittance (e.g. 0.02), the use of two low-emittance coatings gives limited improvement in thermal performance of the glazing system. The use of a single high performance low-emittance coating in a vacuum glazing has been shown to provide excellent performance. (author)
Observation of the Phononic Lamb Shift with a Synthetic Vacuum
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T. Rentrop
2016-11-01
Full Text Available In contrast to classical empty space, the quantum vacuum fundamentally alters the properties of embedded particles. This paradigm shift allows one to explain the discovery of the celebrated Lamb shift in the spectrum of the hydrogen atom. Here, we engineer a synthetic vacuum, building on the unique properties of ultracold atomic gas mixtures, offering the ability to switch between empty space and quantum vacuum. Using high-precision spectroscopy, we observe the phononic Lamb shift, an intriguing many-body effect originally conjectured in the context of solid-state physics. We find good agreement with theoretical predictions based on the Fröhlich model. Our observations establish this experimental platform as a new tool for precision benchmarking of open theoretical challenges, especially in the regime of strong coupling between the particles and the quantum vacuum.
Mathot, S
2008-01-01
The aim of this paper is to describe the vacuum brazing procedure used at CERN for the brazing of Radio Frequency Quadrupole (RFQ). The RFQ is made of high precision machined OFE copper pieces assembled together. Vacuum brazing is one of the most promising techniques used to join the individual components leading to vacuum tightness and high precision alignment. The RFQ modules brazed at CERN are made of four 100 or 120 cm long vanes (two major and two minor vanes). Our brazing procedure consists of two steps. The first step involves the brazing of the four vanes in a horizontal position. The second step consists of brazing the vacuum stainless steel flanges to the copper structure in a vertical position. The paper describes the problems encountered with the alignment and the vacuum tightness. The difficulties related to the stress relaxation of the machined copper pieces during the brazing heat treatment are discussed. In addition, the solutions developed to improve the alignment of the brazed RFQâs are...
Measurement of partial pressures in vacuum technology and vacuum physics
Huber, W. K.
1986-01-01
It is pointed out that the measurement of gaseous pressures of less than 0.0001 torr is based on the ionization of gas atoms and molecules due to collisions with electrons. The particle density is determined in place of the pressure. The ionization cross sections for molecules of various gases are discussed. It is found that the true pressure in a vacuum system cannot be determined with certainty if it is unknown which gas is present. Effects of partial pressure determination on the condition of the vacuum system are discussed together with ion sources, systems of separation, and ion detection.
Pan, Shin-Liang; Chen, Hsiu-Hsi
2010-09-01
The rates of functional recovery after stroke tend to decrease with time. Time-varying Markov processes (TVMP) may be more biologically plausible than time-invariant Markov process for modeling such data. However, analysis of such stochastic processes, particularly tackling reversible transitions and the incorporation of random effects into models, can be analytically intractable. We make use of ordinary differential equations to solve continuous-time TVMP with reversible transitions. The proportional hazard form was used to assess the effects of an individual's covariates on multi-state transitions with the incorporation of random effects that capture the residual variation after being explained by measured covariates under the concept of generalized linear model. We further built up Bayesian directed acyclic graphic model to obtain full joint posterior distribution. Markov chain Monte Carlo (MCMC) with Gibbs sampling was applied to estimate parameters based on posterior marginal distributions with multiple integrands. The proposed method was illustrated with empirical data from a study on the functional recovery after stroke. Copyright 2010 Elsevier Inc. All rights reserved.
Vacuum membrane distillation of liquid desiccants Utilizing Hollow Fiber Membranes
Lefers, Ryan
2018-01-31
This paper documents the testing of a vacuum membrane distillation system intended for use with liquid desiccants. Liquid desiccants offer the possibility for low-energy, ambient temperature dehumidification. Effective desalination and purification of diluted desiccants outputs two important products: a concentrated desiccant for reuse in dehumidification and fresh water. In this study, vacuum membrane distillation was used in the laboratory to purify diluted liquid desiccants. Calcium chloride and magnesium chloride were the desiccants selected for testing. Desiccant solutions were pumped through the lumens of poly(vinylidene fluoride) (PVDF) hollow fiber membranes at varying feed inlet temperatures, solution velocity rates and vacuum set points during membrane distillation. An average flux of 8 kg m-2 h-1 was obtained using 30 wt% magnesium chloride solution at a temperature of 50 °C while applying vacuum to achieve 25 mbar absolute pressure on the air side of the membrane. The results are promising for the development of a full-scale vacuum membrane distillation process for desiccant solution regeneration and fresh water recovery. In addition, the recovered condensate was of sufficient quality for use in agricultural irrigation or drinking water.
Microscale Digital Vacuum Electronic Gates
Manohara, Harish (Inventor); Mojarradi, Mohammed M. (Inventor)
2014-01-01
Systems and methods in accordance with embodiments of the invention implement microscale digital vacuum electronic gates. In one embodiment, a microscale digital vacuum electronic gate includes: a microscale field emitter that can emit electrons and that is a microscale cathode; and a microscale anode; where the microscale field emitter and the microscale anode are disposed within at least a partial vacuum; where the microscale field emitter and the microscale anode are separated by a gap; and where the potential difference between the microscale field emitter and the microscale anode is controllable such that the flow of electrons between the microscale field emitter and the microscale anode is thereby controllable; where when the microscale anode receives a flow of electrons, a first logic state is defined; and where when the microscale anode does not receive a flow of electrons, a second logic state is defined.
Carbon nanotubes based vacuum gauge
Rudyk, N. N.; Il’in, O. I.; Il’ina, M. V.; Fedotov, A. A.; Klimin, V. S.; Ageev, O. A.
2017-11-01
We have created an ionization type Vacuum gauge with sensor element based on an array of vertically aligned carbon nanotubes. Obtained asymmetrical current-voltage characteristics at different voltage polarity on the electrode with the CNTs. It was found that when applying a negative potential on an electrode with the CNTs, the current in the gap is higher than at a positive potential. In the pressure range of 1 ÷ 103 Torr vacuum gauge sensitivity was 6 mV/Torr (at a current of 4.5·10-5 A) and in the range of 10-5 ÷ 1 Torr was 10 mV/Torr (at a current of 1.3·10-5 A). It is shown that the energy efficiency of vacuum gauge can be increased in the case where electrode with CNT operates as an emitter of electrons.
Dynamical pions and kaons in the glueball condensate vacuum
Energy Technology Data Exchange (ETDEWEB)
Hansson, T.H.; Klabuar, D.; Zahed, I.
1987-07-01
The model for pions as collective modes in the glueball condensate vacuum is extended to incorporate time-independent fields and massive quarks. The quark mass dependence of
Kim, Jongrae; Bates, Declan G; Postlethwaite, Ian; Heslop-Harrison, Pat; Cho, Kwang-Hyun
2008-05-15
Inherent non-linearities in biomolecular interactions make the identification of network interactions difficult. One of the principal problems is that all methods based on the use of linear time-invariant models will have fundamental limitations in their capability to infer certain non-linear network interactions. Another difficulty is the multiplicity of possible solutions, since, for a given dataset, there may be many different possible networks which generate the same time-series expression profiles. A novel algorithm for the inference of biomolecular interaction networks from temporal expression data is presented. Linear time-varying models, which can represent a much wider class of time-series data than linear time-invariant models, are employed in the algorithm. From time-series expression profiles, the model parameters are identified by solving a non-linear optimization problem. In order to systematically reduce the set of possible solutions for the optimization problem, a filtering process is performed using a phase-portrait analysis with random numerical perturbations. The proposed approach has the advantages of not requiring the system to be in a stable steady state, of using time-series profiles which have been generated by a single experiment, and of allowing non-linear network interactions to be identified. The ability of the proposed algorithm to correctly infer network interactions is illustrated by its application to three examples: a non-linear model for cAMP oscillations in Dictyostelium discoideum, the cell-cycle data for Saccharomyces cerevisiae and a large-scale non-linear model of a group of synchronized Dictyostelium cells. The software used in this article is available from http://sbie.kaist.ac.kr/software
Liu, Qiang; McVicar, Tim R.; Yang, Zhifeng; Donohue, Randall J.; Liang, Liqiao; Yang, Yuting
2016-12-01
Vegetation patterns are affected by water availability, which, in turn, influences the hydrological partitioning and regional water balance, especially in water-limited regions. Considering the important role of vegetation in partitioning the catchment water yield, the recently developed Budyko-Choudhury-Porporato (or BCP) model incorporated Porporato's model of key ecohydrological processes into Choudury's form of the Budyko hydroclimatic framework. Here we extend the steady state BCP model by incorporating dynamic ecohydrological processes into it and combining it with a typical bucket soil water balance model (resulting in the dynamic BCP, or dBCP, model). The dBCP model is used here to assess the impacts of vegetation on the water balance in a temperate water-limited basin (i.e., the Yellow River Basin (YRB) in north China), where growing season phenology is primarily constrained by low temperatures. The results show that: (i) the incorporation of dynamic growing season (fs) and dynamic effective rooting depth (Ze) conditions into the dBCP model improves results when compared to the original BCP model; (ii) dBCP model's results vary depending on time-step used (i.e., we tested mean-annual to monthly), which reflected the influence of catchment variables, e.g., catchment area, catchment-average air temperature, dryness index and Ze; and (iii) actual evapotranspiration (E) is more sensitive to changes in mean storm depth (α), followed by P, Ze, and Ep. When taking into account observed variability of each of four ecohydrological variables, changes in Ze cause the greatest variability in E, generally followed by variability in P and α, and then Ep. The dBCP results indicate that incorporating dynamic ecohydrological processes into the Budyko framework can improve the estimation of inter-annual variability of the regional water balance. This can help to understand the water requirement and to establish suitable water management strategies to adapt to climate
Vacuum Cleaner Fan Being Improved
Tweedt, Daniel L.
1997-01-01
As part of the technology utilization program at the NASA Lewis Research Center, efforts are underway to transfer aerospace technologies to new areas of practical application. One such effort involves using advanced computational fluid dynamics (CFD) codes for turbomachinery to analyze the internal fluid dynamics of low-speed fans and blowers. This year, the Kirby Company in Cleveland, Ohio, approached NASA with a request for technologies that could help them improve their vacuum cleaners. Of particular interest to Kirby is the high-frequency blade-passing noise generation of their vacuum cleaner fan at low airflow rates.
Vacuum gaps in pulsars and PSR J2144-3933
Gil, J; Gil, Janusz; Mitra, Dipanjan
2001-01-01
In this paper we revisit the radio pulsar death line problem within the framework of curvature radiation and/or inverse compton scattering induced vacuum gap model above neutron star polar caps. Our special interest is in the recently detected pulsar PSR J2144-3933 with extremal period 8.5 seconds, which lies far beyond conventional death lines. We argue, that formation of vacuum gaps requires a complicated multipolar surface magnetic field, with a strenght $B_s$ much higher than the surface dipolar component $B_d$, and radii of curvature ${\\cal R}$ much smaller than the neutron star radius $R=10^6$ cm. Such a multipolar surface field is also consistent with death lines including the extremal pulsar PSR J2144-3933. Since vacuum gap models produce sparks, our paper naturally supports the spark related models of subpulse drift phenomenon as well as to the spark associated models of coherent pulsar radio emission.
Energy Technology Data Exchange (ETDEWEB)
Girault, M; Rouizi, Y; Favennec, Y J; Petit, D [Laboratoire d' Etudes Thermiques, UMR CNRS 6608, ENSMA, Teleport 2, 1 avenue Clement Ader, BP40109, 86961 Futuroscope Chasseneuil Cedex (France); Maillet, D [Laboratoire d' Energetique et de Mecanique Theorique et Appliquee, UMR CNRS 7563, ENSEM-INPL, 2 avenue de la foret de Haye, BP160, F-54504 Vandoeuvre les Nancy (France)], E-mail: manuel.girault@let.ensma.fr, E-mail: Denis.Maillet@ensem.inpl-nancv.fr, E-mail: yassine.rouizi@let.ensma.fr, E-mail: yann.favennec@let.ensma.fr, E-mail: daniel.petit@let.ensma.fr
2008-11-01
This numerical study deals with the estimation of both unknown position and intensity of a heat source in diffusive problems, from the knowledge of local temperature data. The source is assumed to be fixed but its intensity varies with time. The originality of this paper lies in the use of reduced models to solve the inverse problem. The source position being unknown, a specific approach is proposed, involving the Modal Identification Method (MIM) allowing us to obtain a RM relative to a set of output temperatures. The source is modelled as f(r,r{sub s})u(t), where f covers the whole domain and mimics a source centred in r{sub s}. Starting with initial guess for r{sub s}, RMs relative to outputs and their first derivatives with respect to r{sub s}, are identified. A Quasi-Newton algorithm is used for searching r{sub s}, and according to a Taylor expansion, new RMs are built for current r{sub s} to estimate u(f) and compute sensitivities. When r{sub s} cannot be modified anymore by the iterative algorithm, the Detailed Model is called to update the RMs series. The approach is first described in detail for a ID case, then expressions for 2D and 3D cases are given. An academic 3D heat diffusion problem illustrates the method.
Cosmological implications of the transition from the false vacuum to the true vacuum state
Energy Technology Data Exchange (ETDEWEB)
Stachowski, Aleksander [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Szydlowski, Marek [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Jagiellonian University, Mark Kac Complex Systems Research Centre, Krakow (Poland); Urbanowski, Krzysztof [University of Zielona Gora, Institute of Physics, Zielona Gora (Poland)
2017-06-15
We study cosmology with running dark energy. The energy density of dark energy is obtained from the quantum process of transition from the false vacuum state to the true vacuum state. We use the Breit-Wigner energy distribution function to model the quantum unstable systems and obtain the energy density of the dark energy parametrization ρ{sub de}(t). We also use Krauss and Dent's idea linking properties of the quantum mechanical decay of unstable states with the properties of the observed Universe. In the cosmological model with this parametrization there is an energy transfer between dark matter and dark energy. The intensity of this process, measured by a parameter α, distinguishes two scenarios. As the Universe starts from the false vacuum state, for the small value of α (0 < α < 0.4) it goes through an intermediate oscillatory (quantum) regime of the density of dark energy, while for α > 0.4 the density of the dark energy jumps down. In both cases the present value of the density of dark energy is reached. From a statistical analysis we find this model to be in good agreement with the astronomical data and practically indistinguishable from the ΛCDM model. (orig.)
Gases and vacua handbook of vacuum physics
Beck, A H
2013-01-01
Handbook of Vacuum Physics, Volume 1: Gases and Vacua provides information on the many aspects of vacuum technology, from material on the quantum theoretical aspects of the complex semi-conductors used for thermionic and photo-electric emission to data on the performance of commercially available pumps, gauges, and high-vacuum materials. The handbook satisfies the need of workers using vacuum apparatuses or works on the diverse applications of high-vacuum technology in research and industry. The book is a compilation of long articles prepared by experts in vacuum technology. Sufficient theoret
Vacuum-Structure and a Relativistic Pilot Wave
Salehi, Hadi; Motavali, Hossein; Golshani, Mehdi
2000-01-01
We study a model for analyzing the effect of a principal violation of the Lorentz-invariance on the structure of vacuum. The model is based on the divergence theory developed by Salehi (1997). It is shown that the divergence theory can be used to model an ensemble of particles. The ensemble is characterized by the condition that its members are basically at rest in the rest frame of a preferred inertial observer in vacuum. In this way we find a direct dynamical interplay between a particle an...
Microwave-vacuum drying of flax fiber for biocomposite production.
Panigrahi, Satyanarayan; Rana, Anup; Meda, Venkatesh; Chang, Peter R
2009-01-01
Flax fiber is one of the important bast fiber available in North America which has low density and good mechanical properties for reinforcing various polymers to develop industrial biocomposite. But the hydrophilic nature of the fiber leads to poor adhesion between the fiber and the polymer matrices which, in turn, leads to poor dimensional stability. To enhance the adhesion between polymer matrix and fiber, chemical treatments of the fiber are necessary. After these treatments, the fiber needs to be uniformly dried to minimum moisture content for better compounding of flax in polymer matrices. Drying by conventional dryers at higher temperature usually results in overall quality loss due to surface drying, and it is also time consuming and energy intensive. In recent years, the microwave has been effectively used for enhancing bulk drying of biomaterials especially when coupled with vacuum. Such a volumetric heat transfer mechanism coupled with drying in vacuum provides an ideal low-temperature drying technique resulting in better organoleptic quality. In this study, the drying characteristics of flax fiber were studied under microwave-vacuum condition. The drying experiments were conducted in Enwave Microwave-vacuum dryer using three different process variables viz., microwave power (750 W and 375 W), vacuum level (25, 10, and 0 in Hg) and time of drying (0 to 14 mins). In order to select the appropriate drying curve equation, the drying data was fitted in three different models viz., Page model, single exponential model and approximation of diffusion model.
External Cylindrical Nozzle with Controlled Vacuum
Directory of Open Access Journals (Sweden)
V. N. Pil'gunov
2015-01-01
Full Text Available There is a developed design of the external cylindrical nozzle with a vacuum camera. The paper studies the nozzle controllability of flow rate via regulated connection of the evacuated chamber to the atmosphere through an air throttle. Working capacity of the nozzle with inlet round or triangular orifice are researched. The gap is provided in the nozzle design between the external wall of the inlet orifice and the end face of the straight case in the nozzle case. The presented mathematical model of the nozzle with the evacuated chamber allows us to estimate the expected vacuum amount in the compressed section of a stream and maximum permissible absolute pressure at the inlet orifice. The paper gives experimental characteristics of the fluid flow process through the nozzle for different values of internal diameter of a straight case and an extent of its end face remoteness from an external wall of the inlet orifice. It estimates how geometry of nozzle constructive elements influences on the volume flow rate. It is established that the nozzle capacity significantly depends on the shape of inlet orifice. Triangular orifice nozzles steadily work in the mode of completely filled flow area of the straight case at much more amounts of the limit pressure of the flow. Vacuum depth in the evacuated chamber also depends on the shape of inlet orifice: the greatest vacuum is reached in a nozzle with the triangular orifice which 1.5 times exceeds the greatest vacuum with the round orifice. Possibility to control nozzle capacity through the regulated connection of the evacuated chamber to the atmosphere was experimentally estimated, thus depth of flow rate regulation of the nozzle with a triangular orifice was 45% in comparison with 10% regulation depth of the nozzle with a round orifice. Depth of regulation calculated by a mathematical model appeared to be much more. The paper presents experimental dependences of the flow coefficients of nozzle input orifice
Energy Technology Data Exchange (ETDEWEB)
Morfin, Franck; Piccolo, Laurent [Institut de recherches sur la catalyse et l' environnement de Lyon (IRCELYON), UMR 5256 CNRS and Université Lyon 1, 2 avenue Albert Einstein, F-69626 Villeurbanne (France)
2013-09-15
A small-volume reaction cell for catalytic or photocatalytic testing of solid materials at pressures up to 1000 Torr has been coupled to a surface-science setup used for standard sample preparation and characterization under ultrahigh vacuum (UHV). The reactor and sample holder designs allow easy sample transfer from/to the UHV chamber, and investigation of both planar and small amounts of powder catalysts under the same conditions. The sample is heated with an infrared laser beam and its temperature is measured with a compact pyrometer. Combined in a regulation loop, this system ensures fast and accurate temperature control as well as clean heating. The reaction products are automatically sampled and analyzed by mass spectrometry and/or gas chromatography (GC). Unlike previous systems, our GC apparatus does not use a recirculation loop and allows working in clean conditions at pressures as low as 1 Torr while detecting partial pressures smaller than 10{sup −4} Torr. The efficiency and versatility of the reactor are demonstrated in the study of two catalytic systems: butadiene hydrogenation on Pd(100) and CO oxidation over an AuRh/TiO{sub 2} powder catalyst.
varying elastic parameters distributions
Moussawi, Ali
2014-12-01
The experimental identication of mechanical properties is crucial in mechanics for understanding material behavior and for the development of numerical models. Classical identi cation procedures employ standard shaped specimens, assume that the mechanical elds in the object are homogeneous, and recover global properties. Thus, multiple tests are required for full characterization of a heterogeneous object, leading to a time consuming and costly process. The development of non-contact, full- eld measurement techniques from which complex kinematic elds can be recorded has opened the door to a new way of thinking. From the identi cation point of view, suitable methods can be used to process these complex kinematic elds in order to recover multiple spatially varying parameters through one test or a few tests. The requirement is the development of identi cation techniques that can process these complex experimental data. This thesis introduces a novel identi cation technique called the constitutive compatibility method. The key idea is to de ne stresses as compatible with the observed kinematic eld through the chosen class of constitutive equation, making possible the uncoupling of the identi cation of stress from the identi cation of the material parameters. This uncoupling leads to parametrized solutions in cases where 5 the solution is non-unique (due to unknown traction boundary conditions) as demonstrated on 2D numerical examples. First the theory is outlined and the method is demonstrated in 2D applications. Second, the method is implemented within a domain decomposition framework in order to reduce the cost for processing very large problems. Finally, it is extended to 3D numerical examples. Promising results are shown for 2D and 3D problems.
Energy Technology Data Exchange (ETDEWEB)
Fang, Yueping; Eames, Philip C. [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey, BT37 0QB, N. Ireland (United Kingdom)
2006-10-16
The thermal performance of an electrochromic vacuum glazing and a vacuum glazing with a range of low-emittance coatings and frame rebate depths were simulated for insolations between 0 and 1000Wm{sup -2} using a three-dimensional finite volume model. The vacuum glazing simulated comprised two 0.4mx0.4m glass panes separated by a 0.12mm wide evacuated space supported by a 0.32mm diameter pillar array spaced at 25mm. The two glass sheets were sealed contiguously by a 6mm wide metal edge seal and had either one or two low-emittance coatings. For the electrochromic vacuum glazing, a third glass pane on which an electrochromic layer was deposited was assumed to be sealed to an evacuated glass unit, to enable control of visible light transmittance and solar gain and thus improve occupant thermal comfort. It is shown that for both vacuum glazing and electrochromic vacuum glazings, when the coating emittance value is very low (close to 0.02), the use of two low-emittance coatings only gives limited improvement in glazing performance. The use of a single currently expensive low-emittance coating in both systems provided acceptable performance. Deeper frame rebate depths gave significant improvements in thermal performance for both glazing systems. (author)
Clemons, J. M.; Penn, B. G.; Ledbetter, Frank E., III; Daniels, J. G.
1987-01-01
Improvement upon recommended procedures saves time and expense. Autoclave molding in vacuum bag cleaner if adhesive-backed covering placed around caul plate as well as on mold plate. Covering easy to remove after curing and leaves caul plate free of resin deposits.
Brine Distribution after Vacuum Saturation
DEFF Research Database (Denmark)
Hedegaard, Kathrine; Andersen, Bertel Lohmann
1999-01-01
Experiments with the vacuum saturation method for brine in plugs of chalk showed that a homogeneous distribution of brine cannot be ensured at saturations below 20% volume. Instead of a homogeneous volume distribution the brine becomes concentrated close to the surfaces of the plugs...
Quantum Vacuum Structure and Cosmology
Energy Technology Data Exchange (ETDEWEB)
Rafelski, Johann; Labun, Lance; Hadad, Yaron; /Arizona U. /Munich U.; Chen, Pisin; /Taiwan, Natl. Taiwan U. /KIPAC, Menlo Park /SLAC
2011-12-05
Contemporary physics faces three great riddles that lie at the intersection of quantum theory, particle physics and cosmology. They are: (1) The expansion of the universe is accelerating - an extra factor of two appears in the size; (2) Zero-point fluctuations do not gravitate - a matter of 120 orders of magnitude; and (3) The 'True' quantum vacuum state does not gravitate. The latter two are explicitly problems related to the interpretation and the physical role and relation of the quantum vacuum with and in general relativity. Their resolution may require a major advance in our formulation and understanding of a common unified approach to quantum physics and gravity. To achieve this goal we must develop an experimental basis and much of the discussion we present is devoted to this task. In the following, we examine the observations and the theory contributing to the current framework comprising these riddles. We consider an interpretation of the first riddle within the context of the universe's quantum vacuum state, and propose an experimental concept to probe the vacuum state of the universe.
LEP vacuum chamber, early prototype
CERN PhotoLab
1978-01-01
The same vacuum chamber as in 7810256, read the detailed description there. Here, the 4 strip-shaped ion-getter pumps are poised at the entrance to their slots. Ion-getter pumps were not retained, thermal getter pumps were chosen instead (see 8301153 and 8305170).
Katarina Anthony
2013-01-01
Last month, the Vacuum, Surfaces and Coatings (VSC) group was tasked with an unusually delicate operation in the LHCb experiment cavern: removing the LHC beam pipe while keeping the sensitive Vertex Locator vacuum vessel (VELO) completely isolated from the action. The VSC group seal off the VELO beam pipe with a flange. Image: Gloria Corti. LHCb’s VELO detector is one of the crown jewels of the experiment. With detector elements surrounded by a vacuum, it gets as close as 5 cm from the beam. Fantastic for physics, but difficult for all-important access. “Because of the sensitivity of the VELO detector and its proximity to the beam, the collaboration decided not to bake (see box) its portion of the beam pipe,” says Giulia Lanza (TE-VSC-LBV), the expert in charge of the beam vacuum operation. “Our group was therefore asked to remove the rest of the LHC beam pipe while keeping the VELO portion of the pipe completely isolated. This work...
Vacuum assisted closure in coloproctology
Bemelman, W.A.
2009-01-01
Vacuum-assisted closure has earned its indications in coloproctology. It has been described with variable results in the treatment of large perineal defects after abdominoperineal excision, in the treatment of stoma dehiscence and perirectal abscesses. The most promising indication for
High Vacuum Techniques for Anionic Polymerization
Ratkanthwar, Kedar
2015-09-01
Anionic polymerization high vacuum techniques (HVTs) are the most suitable for the preparation of polymer samples with well-defined complex macromolecular architectures. Though HVTs require glassblowing skill for designing and making polymerization reactor, it is the best way to avoid any termination of living polymers during the number of steps for the synthesis of polymers with complex structure. In this chapter, we describe the different polymerization reactors and HVTs for the purification of monomers, solvents, and other reagents for anionic polymerization as well as few model reactions for the synthesis of polymers with simple to complex structure.
DEFF Research Database (Denmark)
Christoffersen, Peter; Feunoua, Bruno; Jeon, Yoontae
We estimate a continuous-time model with stochastic volatility and dynamic crash probability for the S&P 500 index and find that market illiquidity dominates other factors in explaining the stock market crash risk. While the crash probability is time-varying, its dynamic depends only weakly...
Energy Technology Data Exchange (ETDEWEB)
Hayes, R R; Newill, P A; Podd, F J W; York, T A; Grieve, B D; Dorn, O, E-mail: Robert.Hayes@postgrad.manchester.ac.uk
2010-11-01
A new visualisation tool is being developed for seed breeders, providing on-line data for each individual plant in a screening programme. It will be used to indicate how efficiently each plant utilises the water and nutrients available in the surrounding soil. This will facilitate early detection of desirable genetic traits with the aim of increased efficiency in identification and delivery of tomorrow's drought tolerant food crops. Visualisation takes the form of Electrical Capacitance Tomography (ECT), a non-destructive and non-intrusive imaging technique. Measurements are to be obtained for an individual plant thus allowing water and nutrient absorption levels for an individual specimen to be inferred. This paper presents the inverse problem, discusses the inherent challenges and presents the early experimental results. Two mixture models are evaluated for the prediction of electrical capacitance measurement data for varying effective soil saturation levels using a finite element model implemented in COMSOL Multiphysics. These early studies have given the research team an understanding of the technical challenges that must now be addressed to take the current research into the world of agri-science and food supply.
Directory of Open Access Journals (Sweden)
Ankita Chatterjee
2017-11-01
Full Text Available To combat decrease in rice productivity under different stresses, an understanding of rice metabolism is needed. Though there are different genome scale metabolic models (GSMs of Oryza sativa japonica, no GSM with gene-protein-reaction association exist for Oryza sativa indica. Here, we report a GSM, OSI1136 of O.s. indica, which includes 3602 genes and 1136 metabolic reactions and transporters distributed across the cytosol, mitochondrion, peroxisome, and chloroplast compartments. Flux balance analysis of the model showed that for varying RuBisCO activity (Vc/Vo (i the activity of the chloroplastic malate valve increases to transport reducing equivalents out of the chloroplast under increased photorespiratory conditions and (ii glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase can act as source of cytosolic ATP under decreased photorespiration. Under increasing light conditions we observed metabolic flexibility, involving photorespiration, chloroplastic triose phosphate and the dicarboxylate transporters of the chloroplast and mitochondrion for redox and ATP exchanges across the intracellular compartments. Simulations under different enzymatic cost conditions revealed (i participation of peroxisomal glutathione-ascorbate cycle in photorespiratory H2O2 metabolism (ii different modes of the chloroplastic triose phosphate transporters and malate valve, and (iii two possible modes of chloroplastic Glu–Gln transporter which were related with the activity of chloroplastic and cytosolic isoforms of glutamine synthetase. Altogether, our results provide new insights into plant metabolism.
Directory of Open Access Journals (Sweden)
Mohammad Bagher Abolhasani Jabali
2017-07-01
Full Text Available Detecting critical power system events for Dynamic Security Assessment (DSA is required for reliability improvement. The approach proposed in this paper investigates the effects of events on dynamic behavior during nonlinear system response while common approaches use steady-state conditions after events. This paper presents some new and enhanced indices for event ranking based on time-domain simulation and polytopic linear parameter-varying (LPV modeling of a power system. In the proposed approach, a polytopic LPV representation is generated via linearization about some points of the nonlinear dynamic behavior of power system using wide-area measurement system (WAMS concepts and then event ranking is done based on the frequency response of the system models on the vertices. Therefore, the nonlinear behaviors of the system in the time of fault occurrence are considered for events ranking. The proposed algorithm is applied to a power system using nonlinear simulation. The comparison of the results especially in different fault conditions shows the advantages of the proposed approach and indices.
Vacuum polarization and Hawking radiation
Rahmati, Shohreh
Quantum gravity is one of the interesting fields in contemporary physics which is still in progress. The purpose of quantum gravity is to present a quantum description for spacetime at 10-33cm or find the 'quanta' of gravitational interaction.. At present, the most viable theory to describe gravitational interaction is general relativity which is a classical theory. Semi-classical quantum gravity or quantum field theory in curved spacetime is an approximation to a full quantum theory of gravity. This approximation considers gravity as a classical field and matter fields are quantized. One interesting phenomena in semi-classical quantum gravity is Hawking radiation. Hawking radiation was derived by Stephen Hawking as a thermal emission of particles from the black hole horizon. In this thesis we obtain the spectrum of Hawking radiation using a new method. Vacuum is defined as the possible lowest energy state which is filled with pairs of virtual particle-antiparticle. Vacuum polarization is a consequence of pair creation in the presence of an external field such as an electromagnetic or gravitational field. Vacuum polarization in the vicinity of a black hole horizon can be interpreted as the cause of the emission from black holes known as Hawking radiation. In this thesis we try to obtain the Hawking spectrum using this approach. We re-examine vacuum polarization of a scalar field in a quasi-local volume that includes the horizon. We study the interaction of a scalar field with the background gravitational field of the black hole in the desired quasi-local region. The quasi-local volume is a hollow cylinder enclosed by two membranes, one inside the horizon and one outside the horizon. The net rate of particle emission can be obtained as the difference of the vacuum polarization from the outer boundary and inner boundary of the cylinder. Thus we found a new method to derive Hawking emission which is unitary and well defined in quantum field theory.
Quark see-saw, Higgs mass and vacuum stability
Indian Academy of Sciences (India)
2015-12-29
Dec 29, 2015 ... The issue of vacuum stability of standard model (SM) is discussed by embedding it within the TeV scale left–right quark see-saw model. The Higgs potential in this case has only two coupling parameters (1, 2) and two mass parameters. There are only two physical neutral Higgs bosons (ℎ, ), the lighter ...
Quark see-saw, Higgs mass and vacuum stability
Indian Academy of Sciences (India)
Abstract. The issue of vacuum stability of standard model (SM) is discussed by embedding it within the TeV scale left–right quark see-saw model. The Higgs potential in this case has only two coupling parameters (λ1,λ2) and two mass parameters. There are only two physical neutral. Higgs bosons (h, H ), the lighter one ...
Robot Vacuum Cleaner Personality and Behavior
Hendriks, A.F.M.; Meerbeek, B.W.; Boess, S.; Pauws, S.C.; Sonneveld, M.
2011-01-01
In this paper we report our study on the user experience of robot vacuum cleaner behavior. How do people want to experience this new type of cleaning appliance? Interviews were conducted to elicit a desired robot vacuum cleaner personality. With this knowledge in mind, behavior was designed for a future robot vacuum cleaner. A video prototype was used to evaluate how people experienced the behavior of this robot vacuum cleaner. The results indicate that people recognizedthe intended personali...