An Annular Gap Acceleration Model for γ-ray Emission of Pulsars
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
If the binding energy of the pulsar's surface is not so high (the case of a neutron star), both negative and positive charges will flow out freely from the surface of the star. An annular free flow model for γ-ray emission of pulsars is suggested. It is emphasized that:(1) Two kinds of acceleration regions (annular and core) need to be taken into account. The annular acceleration region is defined by the magnetic field lines that cross the null charge surface within the light cylinder. (2) If the potential drop in the annular region of a pulsar is high enough (normally the case for young pulsars), charges in both the annular and the core regions could be accelerated and produce primary gamma-rays. Secondary pairs are generated in both regions and stream outwards to power the broadband radiations. (3) The potential drop grows more rapidly in the annular region than in the core region. The annular acceleration process is a key process for producing the observed wide emission beams. (4)The advantages of both the polar cap and outer gap models are retained in this model. The geometric properties of the γ-ray emission from the annular flow are analogous to that presented in a previous work by Qiao et al., which match the observations well. (5) Since charges with different signs leave the pulsar through the annular and the core regions respectively, the current closure problem can be partially solved.
International Nuclear Information System (INIS)
For severe accident assessment in a light water reactor, heat transfer models in a narrow annular gap between the overheated core debris and the reactor pressure vessel (RPV) are important for evaluating RPV integrity and emergency procedures. Using existing data, the authors developed heat transfer models on the average critical heat flux (CHF) restricted by countercurrent flow limitation (CCFL) and local boiling heat fluxes, and showed that the average CHF depended on the steam-water flow pattern in the narrow gap and that the local heat fluxes were similar to the pool boiling curve. We evaluated the validity of heat transfer models by simple calculations for ALPHA experiments performed at Japan Atomic Energy Research Institute. Calculated results showed that heat fluxes on the crust surface were restricted mainly by thermal resistance of the crust after the crust formation, and emissivity on the crust surface did not have much effect on the heat fluxes. The calculated vessel temperature during the heat-up process and peak vessel temperature agreed well with the measurements, which confirmed the validity of the average CHF correlation. However, the vessel cooling rate was underestimated mainly due to underestimation of the gap size.
Directory of Open Access Journals (Sweden)
G. Egbo
2014-12-01
Full Text Available Annular gaps of 0.010m, 0.015m, 0.020m, 0.025m, 0.030m, 0.035m, 0.040m, 0.045m, 0.050m and 0.055m are used to simulate the performance of the solar parabolic-trough collector, while maintaining the same geometric dimension of the reflector, the same absorber-tube design features, as well as the same meteorological and radiation data, employing developed thermal energy equations. The higher the annular gap between the absorber-tube and the enveloping glass-cover, with corresponding increase in the diameter of the enveloping glass-cover, the more is the total heat loss of the system and therefore, the lower is the thermal efficiency of the system.
A magnetorheological valve with both annular and radial fluid flow resistance gaps
International Nuclear Information System (INIS)
In order to increase the efficiency of magnetorheological (MR) valves, Ai et al (2006) proposed an MR valve simultaneously possessing annular and radial fluid flow resistance channels with the assumption that the magnetic flux densities at the annular and radial fluid flow gaps are identical. In this paper, an MR valve simultaneously possessing annular and radial fluid flow resistance channels is designed, fabricated, modeled and tested. A model for the developed MR valve is produced and its performances are theoretically predicted based on the average magnetic flux densities in the annular and radial fluid flow gaps through finite element analysis. The theoretical results for the developed MR valve are compared with the experimental results. In addition, the performances of the developed MR valve are theoretically and experimentally compared with those of the MR valve with only annular fluid flow gaps. It has been shown that the theoretical results match well with the experimental results. Mainly attributed to the radial fluid flow gaps, the pressure drops across the MR valve with both annular and radial fluid flow gaps are larger than those across the MR valve with only annular fluid flow gaps for varying valve parameters. The radial fluid flow gaps in the MR valve can reach a higher efficiency and larger controllable range than those by annular fluid flow gaps to some extent
Heat transfer coefficient for flow boiling in an annular mini gap
Hożejowska Sylwia; Musiał Tomasz; Piasecka Magdalena
2016-01-01
The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the numbe...
Study of film boiling dispersed two phase in narrow annular gap
International Nuclear Information System (INIS)
Experimental investigation on film boiling dispersed two phase friction pressure drop in narrow annular gap with deionized water was performed in three types of narrow annular gap. The friction pressure drop differences were compared between narrow annular gap and circular channel was compared in the paper. The influence of narrow annular gap on friction pressure drop was examined in this paper. Results showed that the modified Sadatomi's correlation can be used to calculate film boiling dispersed two-phase friction pressure drop in narrow annular gap for engineering application
Effects of annular air gaps surrounding an emplaced nuclear waste canister in deep geologic storage
International Nuclear Information System (INIS)
Annular air spaces surrounding an emplaced nuclear waste canister in deep geologic storage will have significant effects on the long-term performance of the waste form. Addressed specifically in this analysis is the influence of a gap on the thermal response of the waste package. Three dimensional numerical modeling predicts temperature effects for a series of parameter variations, including the influence of gap size, surface emissivities, initial thermal power generation of the canister, and the presence/absence of a sleeve. Particular emphasis is placed on determining the effects these variables have on the canister surface temperature. We have identified critical gap sizes at which the peak transient temperature occurs when gap widths are varied for a range of power levels. It is also shown that high emissivities for the heat exchanging surfaces are desirable, while that of the canister surface has the greatest influence. Gap effects are more pronounced, and therefore more effort should be devoted to optimal design, in situations where the absolute temperature of the near field medium is high. This occurs for higher power level emplacements and in geomedia with low thermal conductivities. Finally, loosely inserting a sleeve in the borehole effectively creates two gaps and drastically raises the canister peak temperature. It is possible to use these results in the design of an optimum package configuration which will maintain the canister at acceptable temperature levels. A discussion is provided which relates these findings to NRC regulatory considerations
Experimental Study on Convective Boiling Heat Transfer in Vertical Narrow Gap Annular Tube
Institute of Scientific and Technical Information of China (English)
Li Bin; He Anding; Wang Yueshe; Zhou Fangde
2001-01-01
Experiments are conducted to investigate the characteristics of single-phase forced-flow convection and boiling heat transfer of R113 flowing through annular tube with gap of 1, 1.5 and 2.5 mm, and also the visualization test are carried out to get two-phase flow regime. The data show that the Nusselt numbers for the narrow-gap are higher than those predicted by traditional large channel correlation and boiling heat transfer is enhanced. Based on the data obtained in this investigation, correlations for single-phase, forced convection and flow boiling in annular tube of different gap size has been developed.
Absolute photonic band gap in 2D honeycomb annular photonic crystals
International Nuclear Information System (INIS)
Highlights: • A two-dimensional honeycomb annular photonic crystal (PC) is proposed. • The absolute photonic band gap (PBG) is studied. • Annular PCs show larger PBGs than usual air-hole PCs for high refractive index. • Annular PCs with anisotropic rods show large PBGs for low refractive index. • There exist optimal parameters to open largest band gaps. - Abstract: Using the plane wave expansion method, we investigate the effects of structural parameters on absolute photonic band gap (PBG) in two-dimensional honeycomb annular photonic crystals (PCs). The results reveal that the annular PCs possess absolute PBGs that are larger than those of the conventional air-hole PCs only when the refractive index of the material from which the PC is made is equal to 4.5 or larger. If the refractive index is smaller than 4.5, utilization of anisotropic inner rods in honeycomb annular PCs can lead to the formation of larger PBGs. The optimal structural parameters that yield the largest absolute PBGs are obtained
Heat transfer coefficient for flow boiling in an annular mini gap
Hożejowska, Sylwia; Musiał, Tomasz; Piasecka, Magdalena
2016-03-01
The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface - fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two-phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.
Heat transfer coefficient for flow boiling in an annular mini gap
Directory of Open Access Journals (Sweden)
Hożejowska Sylwia
2016-01-01
Full Text Available The aim of this paper was to present the concept of mathematical models of heat transfer in flow boiling in an annular mini gap between the metal pipe with enhanced exterior surface and the external glass pipe. The one- and two-dimensional mathematical models were proposed to describe stationary heat transfer in the gap. A set of experimental data governed both the form of energy equations in cylindrical coordinates and the boundary conditions. The models were formulated to minimize the number of experimentally determined constants. Known temperature distributions in the enhanced surface and in the fluid helped to determine, from the Robin condition, the local heat transfer coefficients at the enhanced surface – fluid contact. The Trefftz method was used to find two-dimensional temperature distributions for the thermal conductive filler layer, enhanced surface and flowing fluid. The method of temperature calculation depended on whether the area of single-phase convection ended with boiling incipience in the gap or the two-phase flow region prevailed, with either fully developed bubbly flow or bubbly-slug flow. In the two–phase flow, the fluid temperature was calculated by Trefftz method. Trefftz functions for the Laplace equation and for the energy equation were used in the calculations.
International Nuclear Information System (INIS)
A theoretical vibration model of a pressurized water reactor is established and studied which takes into account the fluid-structure interaction of the coupled three-dimensional system reactor pressure vessel-core barrel (reactor cavity). Vibration differential equations are derived only for the two-dimensional movement; the eigenfrequencies and amplitude ratios of the undamped system as well as a dimensionless damping factor of cavity vibrations are calculated with the data of the WWER-440, and discussed. (orig.)
Heat transfer models in narrow gap
International Nuclear Information System (INIS)
For severe accident assessment in a light water reactor (LWR), heat transfer models in a narrow annular gap between the overheated core debris and the reactor pressure vessel (RPV) are important to evaluate the integrity of RPV and emergency procedures. Some heat transfer models have been proposed as gap cooling CHF (critical heat flux) but the effects of superheat on the heat transfer surface were not taken into account. This paper presents the effects of superheat based on existing data and heat transfer models in a narrow gap. (author)
MHD stability analysis of a liquid sodium flow at the annular gap of an EM pump
International Nuclear Information System (INIS)
Highlights: ► A MHD stability analysis on an electromagnetic pump was carried out. ► Small perturbations for MHD fields were considered in sinusoidal form. ► Critical Reynolds number depends on the Hartman number and perturbed wave number. ► A magnetic field has a significant stabilizing effect on liquid sodium flow. - Abstract: A stability analysis of a viscous, incompressible, and electrically conducting liquid sodium flow in an annular linear induction electromagnetic pump for sodium coolant circulation of a Sodium Fast Reactor (SFR) was carried out when transverse magnetic fields permeate the sodium fluid across the narrow annular gap. Due to a negligible skin effect and the presence of a magnetic core outside the gap, radial magnetic field is assumed to be constant over the narrow channel gap, and the steady state solution of the axial velocity is obtained as a function of radius. Small perturbations for MHD fields were considered in sinusoidal form as a function of the angular frequency and wave number, and the resulting equations were linearized. The solutions of the perturbed equations were sought in the form of a linear combination of independent orthogonal functions in a non-dimensional radial interval (0, 1), and each orthogonal function was chosen to satisfy the boundary conditions of adhesion to the solid walls of the channel. Under the assumption that solutions of the equations were not oscillated rapidly according to the radial coordinate, finite numbers of orthogonal polynomials were considered. As a result, simultaneous equations with coefficients of steady-state solutions were arranged, and dispersion relations between angular frequency and wave number of perturbed state were sought. The imaginary part of the angular frequency was taken into consideration from the condition of existence of a nontrivial solution of the system, which leads to the relation between critical Reynolds number (Recr) and Hartmann number (Ha). In the present study
International Nuclear Information System (INIS)
Several methods to predict the dynamic behavior of a rod subjected to annular flow have been developed. These include the linearized potential flow theory based model by Mateescu, Paidoussis and Sim, and the pressure-loss model by Hobson and Langthjem. Recently, Kang, Mureithi and Pettigrew proposed a theory based on the pressure-loss model with consideration of flow friction. They showed the critical flow velocity of a simply-supported cylinder could go down to a dimensionless velocity of 2.4. The basic dynamics due to annular flow are known by virtue of these models. For heat exchanger tubes, the support causes highly confined annular flow with a divergent or convergent flow at the exit or the entrance of the support, which is due to chamfering of the support hole for manufacturing convenience. Gorman, Goden, and Planchard qualitatively reported that a finite-length diffuser caused a thimble tube in a pressurized water reactor to reach dynamic instability. Yasuo and Paidoussis tried to solve the flow induced instability problem of heat exchanger tubes subjected to axial flow in a diffuser-shaped, loose intermediate support. They suggested critical flow velocity equations either for divergence or flutter. Application of this theory to practical problems is, however, limited because of the inaccurate prediction of the critical flow velocity for flutter. The purpose of this study is to obtain experimentally the critical flow velocity of a cylinder subjected to annular flow in a finite-length narrow-gap support at the middle of the cylinder and to identify instability
Modeling of annular film dryout with Cobra-TF
International Nuclear Information System (INIS)
The COBRA-TF computer code uses a two-fluid, three-field and three-dimensional formulation to model a two-phase flow field in a specific geometry. The liquid phase is divided in a continuous liquid field and a separate dispersed field, which is used to describe the entrained liquid drops. For each space dimension, the code solves three momentum equations, three mass conservation equations and two energy conservation equations. Entrainment and depositions models are implemented into the code to model the mass transfer between the two liquid fields. In annular flow condition critical heat flux is caused by annular film dryout. Film dryout is a complex function of the film flow rate, the applied heat flux, and the entrainment from the liquid film to the continuous vapor region, and the deposition of entrained droplets back to the liquid film. Because of the three-field approach, COBRA-TF hydrodynamic equations are able to predict dry-out by solving directly the film dry-out as a hydrodynamic process rather than using an empirical dry-out correlation. The dry-out is driven by the hydraulic calculation and the prediction is the result of the combined effect of the entrainment, the deposition models and interfacial heat transfer. The paper discusses the annular film entrainment and deposition models used in the code as well as the logic, which is used to determine the dry-out phenomena as the film thickness decreases. The obtained results with COBRA-TF are compared with the test data from the Bennett Tube Dry-out Experiments. In general, the COBRA-TF prediction of the dry-out location is in good agreement with Bennett test data. In particular, results show that the predicted dry-out length tends to be longer than the measured value and in the post dry-out region the wall temperature, which is dependent on vapor superheat, tends to be underestimated by the code. (authors)
Mathematical model for multicomponent separations on the continuous annular chromatograph
International Nuclear Information System (INIS)
A model for multicomponent separations on ion exchange columns has been adapted for use in studying the performance of the continuous annular chromatograph. The model accurately predicts solute peak positions in the column effluent and qualitatively predicts trends in solute effluent resolution as a function of increasing bandwidth of the solute feed pulse. The major virtues of the model are its simplicity in terms of the calculations involved and the fact that it incorporates the nonlinear solute-resin binding isotherms common in many ion exchange separations. Because dispersion effects are not accounted for in the model, discrepancies exist between the shapes of the effluent peaks predicted by the model and those determined experimentally
Mathematical model for multicomponent separations on the continuous annular chromatograph
Energy Technology Data Exchange (ETDEWEB)
Bratzler, R.L.; Begovich, J.M.
1980-12-01
A model for multicomponent separations on ion exchange columns has been adapted for use in studying the performance of the continuous annular chromatograph. The model accurately predicts solute peak positions in the column effluent and qualitatively predicts trends in solute effluent resolution as a function of increasing bandwidth of the solute feed pulse. The major virtues of the model are its simplicity in terms of the calculations involved and the fact that it incorporates the nonlinear solute-resin binding isotherms common in many ion exchange separations. Because dispersion effects are not accounted for in the model, discrepancies exist between the shapes of the effluent peaks predicted by the model and those determined experimentally.
Annular fuel pin heat transfer and lumped model correction
International Nuclear Information System (INIS)
Fuel pin heat transfer studies are important in nuclear reactor accident analysis. Based on the requirement of accuracy and the speed of the computation, a simple lumped heat transfer method or detailed numerical methods are chosen to solve the heat transfer equations. In a nuclear reactor design calculations, accuracy of the solution is very important than the speed. In a nuclear reactor simulator, the speed is important. Lumped model assumes fuel pellet is solid without central hole and the heat transfer coefficient is constant across the fuel pin. In the present study a new modified lumped heat transfer model is developed to consider the annular fuel pin's central hole, and the heat transfer coefficient is made as a function of average fuel pin temperature. Transient analyses are carried out with the above said modifications for a typical LMFBR annular fuel pin. The results of lumped heat transfer model are almost matching with the accurate numerical schemes like Crank-Nicolson method. Comparisons of results with Crank-Nicolson methods are good for small step reactivity addition, ramp reactivity insertion and large step reactivity addition, ramp reactivity insertion with and without reactivity feedbacks. Comparisons of results are good for LOFA also, with and without reactivity feedbacks. With the consideration of reactivity feedbacks, fuel temperature calculated through the present modified lumped model is matching well with Crank-Nicolson methods, and the nominal power also matching well. The modified lumped heat transfer model can be used in nuclear reactor simulation studies and in conservative accident analyses where fastness of the solution is a matter of concern. (author)
Entrance and exit region friction factor models for annular seal analysis. Ph.D. Thesis
Elrod, David Alan
1988-01-01
The Mach number definition and boundary conditions in Nelson's nominally-centered, annular gas seal analysis are revised. A method is described for determining the wall shear stress characteristics of an annular gas seal experimentally. Two friction factor models are developed for annular seal analysis; one model is based on flat-plate flow theory; the other uses empirical entrance and exit region friction factors. The friction factor predictions of the models are compared to experimental results. Each friction model is used in an annular gas seal analysis. The seal characteristics predicted by the two seal analyses are compared to experimental results and to the predictions of Nelson's analysis. The comparisons are for smooth-rotor seals with smooth and honeycomb stators. The comparisons show that the analysis which uses empirical entrance and exit region shear stress models predicts the static and stability characteristics of annular gas seals better than the other analyses. The analyses predict direct stiffness poorly.
International Nuclear Information System (INIS)
Highlights: ► Two-phase natural circulation flow induced in insulation gap was investigated. ► Half-scaled non-heating experiments were performed to evaluate flow behavior. ► The loop-integrated momentum equation was formulated and solved asymptotically. ► First-order approximate solution was obtained and agreed with experimental data. - Abstract: The process of two-phase natural circulation flow induced in the annular gap between the reactor vessel and the insulation under external reactor vessel cooling conditions was investigated experimentally and analytically in this study. HERMES-HALF experiments were performed to observe and quantify the induced two-phase natural circulation flow in the annular gap. A half-scaled non-heating experimental facility was designed by utilizing the results of a scaling analysis to simulate the APR1400 reactor and its insulation system. The behavior of the boiling-induced two-phase natural circulation flow in the annular gap was observed, and the liquid mass flow rates driven by the natural circulation loop and the void fraction distribution were measured. Direct flow visualization revealed that choking would occur under certain flow conditions in the minimum gap region near the shear keys. Specifically, large recirculation flows were observed in the minimum gap region for large air injection rates and small outlet areas. Under such conditions, the injected air could not pass through the minimum gap region, resulting in the occurrence of choking near the minimum gap with a periodical air back flow being generated. Therefore, a design modification of the minimum gap region needs to be done to facilitate steam venting and to prevent choking from occurring. To complement the HERMES-HALF experimental effort, an analytical study of the dependence of the induced natural circulation mass flow rate on the inlet area and the volumetric air injection rate was performed using a loop integration of the momentum equation. The loop
MCNP/MCNPX model of the annular core research reactor.
Energy Technology Data Exchange (ETDEWEB)
DePriest, Kendall Russell; Cooper, Philip J.; Parma, Edward J., Jr. (.,; .)
2006-10-01
Many experimenters at the Annular Core Research Reactor (ACRR) have a need to predict the neutron/gamma environment prior to testing. In some cases, the neutron/gamma environment is needed to understand the test results after the completion of an experiment. In an effort to satisfy the needs of experimenters, a model of the ACRR was developed for use with the Monte Carlo N-Particle transport codes MCNP [Br03] and MCNPX [Wa02]. The model contains adjustable safety, transient, and control rods, several of the available spectrum-modifying cavity inserts, and placeholders for experiment packages. The ACRR model was constructed such that experiment package models can be easily placed in the reactor after being developed as stand-alone units. An addition to the 'standard' model allows the FREC-II cavity to be included in the calculations. This report presents the MCNP/MCNPX model of the ACRR. Comparisons are made between the model and the reactor for various configurations. Reactivity worth curves for the various reactor configurations are presented. Examples of reactivity worth calculations for a few experiment packages are presented along with the measured reactivity worth from the reactor test of the experiment packages. Finally, calculated neutron/gamma spectra are presented.
Olsen, W K., Jamie Morgan.
2004-01-01
EXECUTIVE SUMMARYIntroductionThere has been little change in the full-time gender pay gap since the mid 1990s andin the female part-time/male full-time pay gap since the mid 1970s. The gender gapin hourly earnings for those employed full-time in Britain in 2003 was 18 per cent,while that between women working part-time and men working full-time was 40 percent.This research uses statistical methods to identify how much of the gender pay gap isassociated with different factors. The data set ana...
Modeling and analysis of thermoacoustic instabilities in an annular combustor
Murthy, Sandeep; Sayadi, Taraneh; Le Chenadec, Vincent; Schmid, Peter
2015-11-01
A simplified model is introduced to study thermo-acoustic instabilities in axisymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber's geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al., 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.
Numerical modeling of a horizontal annular flow experiment using a droplet entrainment model
International Nuclear Information System (INIS)
Highlights: • A new droplet entrainment model within the AIAD framework is proposed. • The approach was validated against a horizontal annular flow experiment. • Important flow phenomena could be calculated and analyzed. - Abstract: One limitation in current simulating horizontal annular flows is the lack of treatment of droplet formation mechanisms. For self-generating annular flows in horizontal pipes, the interfacial momentum exchange and the turbulence parameters have to be modelled correctly. Furthermore the understanding of the mechanism of droplet entrainment in annular flow regimes for heat and mass transfer processes is of great importance in the chemical and nuclear industry. A new entrainment model is proposed. It assumes that due to liquid turbulence the interface gets rough and wavy and forms droplets. The new approach is validated with HZDR annular flow experiments. Important phenomena like the pressure drop, the wave pumping effect, the droplet entrainment, the liquid film formation and the transient flow behavior could be calculated, analyzed and some of the phenomena compared with the measurement
Energy Technology Data Exchange (ETDEWEB)
Cao, Xiaobin
2011-01-15
The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T{sub c} in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the
International Nuclear Information System (INIS)
The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above Tc in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the quasi
Characterization and modeling of annular two-phase flows
International Nuclear Information System (INIS)
Three aspects of annular two-phase flow are studied: (a) wave motion on falling films, (b) flow transition from downflow to upflow, and (c) the upflow. For the case of wave motion on falling films, it is shown that the assumption of the Nusselt velocity profile for finite-amplitude waves is solution of the wave profile, wave velocity, and velocity components within the wave is developed. An algorithm based on collocation methods is also detailed and can be applied to extend the model to solve for higher order terms in the velocity profile. Comparisons with experimental studies show good agreement. Flow transition and the upflow experiments are conducted in a 5.08 x 10-2m inner diameter, 6.5m long Plexiglas column. The liquid rates are varied from 0 to 0.126 kg/s and the gas rates from 0 to 0.0524 kg/s. At four measuring stations along the length of the column, an electrical conductance technique which employs two electrodes mounted flush with the wall is utilized to measure film thickness and pressure transducers are used to make the pressure measurements. Flow visualization studies indicate that flooding takes place as a result of entrainment from the crests of large waves. The effect of column length and pore size of the feed device on flooding velocities is studied. No previous correlation or theory is found to be fully adequate. A speculative interaction among system parameters is proposed to form a basis for a physical model for flooding phenomena
International Nuclear Information System (INIS)
Two-phase annular flow with heat transfer is prevalent in many processes such as industrial and energy reformation processes. Recently, advances in high performance electronic chips and the miniaturisation of electronic circuits in which high heat flux will be created and other compact systems such as Integrated Nuclear Power Device (INPD), the refrigeration/air conditioning, automobile environment control systems have resulted in a great demand for developing efficient heat transfer techniques to accommodate these high heat fluxes. It has been studied by many researchers because of its successful application in many areas, but its influence factor and mechanism of heat transfer remain somewhat unknown yet. In order to understand the heat transfer and flow mechanism in the narrow annular channel, experimental and theoretical study of dryout and post-dryout heat transfer of steam-water two-phase flow in annular channel with narrow gap (1.0 mm and 1.5 mm) have been carried out. The working fluid is deionized water. The range of experimental pressure is 1.0 ∼ 6.OMPa. In correspondence with two different narrow gaps, two kinds of test sections were designed. The test sections were made of specially processed straight stainless steel tubes with linearity error less than 0.01% to form narrow concentric annuli. It also needs a good sealed performance at high pressure and high temperature. The experiments were carried out to investigate the characteristics and occurring conditions of the dryout point. The former Soviet researcher Kutateladse's correlation, based on round tube, was quoted and modified to apply barrow annuli under low flow conditions. At full conditions of the influencing factors, such as geometry of test section, pressure, mass flux, heat flux etc., an empirical correlation was developed to apply to bilaterally heated annuli and it had a good agreement with the experimental data A new analytical model for the dryout point of critical quality in
Energy Technology Data Exchange (ETDEWEB)
Bouafia, M. [Cemif, Centre d`Etudes mecanique d`ile-de-France, 91 - Evry (France); Ziouchi, A. [IAP de Boumerdes (Algeria); Bertin, Y.; Saulnier, J.B. [Centre National de la Recherche Scientifique (CNRS), 86 - Poitiers (France). Laboratoire d`etudes thermiques, UMR 6608
1999-07-01
The convective heat transfer between the walls of an annular gap with a rotating inner cylinder are studied experimentally and numerically. Two geometrical configurations are analysed: the surfaces of the cylinders are either smooth, or the moving wall is smooth and the other is axially grooved. The experimental study allowed us to appreciate the increase of heat transfer in the presence of grooves for values of Taylor number up to 2.10{sup 7}. The study of the flow and of the heat transfer has also been conducted by numerical simulation by means of three-dimensional laminar model for the grooved gap, and of an axisymmetric model for the smooth gap; the comparison of numerical and experimental data have shown a good agreement of the Nusselt number for values of Taylor number up to 4.10{sup 5}. (authors) 16 refs.
International Nuclear Information System (INIS)
In Indian Pressurised Heavy Water Reactors (PHWRs), the PT (pressure tube) is designed to be nominally concentric with the encircling CT (calandria tube). Due to various factors PT becomes eccentric with respect to CT over the life of reactor. If this becomes excessive, hot PT will come in contact with cold CT. Such a cold spot could act as potential location for initiating blister formation and premature failure of PT. Hence it is important to periodically measure annular gap between PT and CT. An advanced eddy current technique has been successfully developed and incorporated in BARCIS (BARC Channel Inspection System) for measurement of PT-CT gap. (author). 4 refs., 3 figs
The Organisational Gap Model for Hotel Management
Maja Uran
2010-01-01
This paper describes the development of the organisational gap model for hotel management. It descries a management measurement instrument that helps to assess the 3 organizational service gaps that are preconditions for delivering service quality (the positioning gap, specification gap and evaluation gap). The described theoretical model was constructed based upon the four organisational gaps of the Parasuraman et al. service quality model, then redefined and reassessed. Data were gathered o...
International Nuclear Information System (INIS)
Countercurrent flow limitation (CCFL) is the dominant dryout phenomenon in a debris bed that may be formed during a severe accident such as that observed at Three Mile Island unit 2. The actual CCFL situation in a debris bed is very complex, and it is difficult to treat. An annular flow model was developed to predict CCFL in a pipe. If a hypothetical flow channel were assumed, CCFL in a debris bed could be treated in the same manner as CCFL in a pipe. The purpose of this study is to investigate whether the annular flow model developed for CCFL in a pipe is applicable for CCFL in a debris bed
Frolov, S. M.; Dubrovskii, A. V.; Ivanov, V. S.
2016-07-01
The possibility of integrating the Continuous Detonation Chamber (CDC) in a gas turbine engine (GTE) is demonstrated by means of three-dimensional (3D) numerical simulations, i. e., the feasibility of the operation process in the annular combustion chamber with a wide gap and with separate feeding of fuel (hydrogen) and oxidizer (air) is proved computationally. The CDC with an upstream isolator damping pressure disturbances propagating towards the compressor is shown to exhibit a gain in the total pressure of 15% as compared with the same combustion chamber operating in the deflagration mode.
The Organisational Gap Model for Hotel Management
Directory of Open Access Journals (Sweden)
Maja Uran
2010-12-01
Full Text Available This paper describes the development of the organisational gap model for hotel management. It descries a management measurement instrument that helps to assess the 3 organizational service gaps that are preconditions for delivering service quality (the positioning gap, specification gap and evaluation gap. The described theoretical model was constructed based upon the four organisational gaps of the Parasuraman et al. service quality model, then redefined and reassessed. Data were gathered on the sample of 500 questionnaires from the Slovenian hotel industry and analysed with exploratory factor analysis and structural equation modelling. The results can be useful guidelines for hotel management on how to improve the service delivery process.
... page: //medlineplus.gov/ency/article/001142.htm Annular pancreas To use the sharing features on this page, please enable JavaScript. An annular pancreas is a ring of pancreatic tissue that encircles ...
CFD model of diabatic annular two-phase flow using the Eulerian–Lagrangian approach
International Nuclear Information System (INIS)
Highlights: • A CFD model of annular two-phase flow with evaporating liquid film has been developed. • A two-dimensional liquid film model is developed assuming that the liquid film is sufficiently thin. • The liquid film model is coupled to the gas core flow, which is represented using the Eulerian–Lagrangian approach. - Abstract: A computational fluid dynamics (CFD) model of annular two-phase flow with evaporating liquid film has been developed based on the Eulerian–Lagrangian approach, with the objective to predict the dryout occurrence. Due to the fact that the liquid film is sufficiently thin in the diabatic annular flow and at the pre-dryout conditions, it is assumed that the flow in the wall normal direction can be neglected, and the spatial gradients of the dependent variables tangential to the wall are negligible compared to those in the wall normal direction. Subsequently the transport equations of mass, momentum and energy for liquid film are integrated in the wall normal direction to obtain two-dimensional equations, with all the liquid film properties depth-averaged. The liquid film model is coupled to the gas core flow, which currently is represented using the Eulerian–Lagrangian technique. The mass, momentum and energy transfers between the liquid film, gas, and entrained droplets have been taken into account. The resultant unified model for annular flow has been applied to the steam–water flow with conditions typical for a Boiling Water Reactor (BWR). The simulation results for the liquid film flow rate show favorable agreement with the experimental data, with the potential to predict the dryout occurrence based on criteria of critical film thickness or critical film flow rate
Silva. EDF two-phase 1D annular model of a CFB boiler furnace
Energy Technology Data Exchange (ETDEWEB)
Montat, D.; Fauquet, Ph. [Electricite de France (EDF), 78 - Chatou (France). Researckh and Development Div.; Lafanechere, L.; Bursi, J.M. [Electricite de France (EDF) (France). Construction Div.
1997-01-01
SILVA computer code is used for the modelling of the thermal-hydraulics and of the combustion of a coal-fired CFBC solid loop. In a first step, only the furnace is considered. The model is based on a 1D annular two phases description of the hydrodynamics. The model is based on particle mass balances and pressure drop calculations. A basic combustion model is incorporated into this model. The coal combustion is divided in two phases, the combustion of volatile matter and the heterogeneous combustion. The model has been developed within LEGO software and can be included into the global model of the solid loop developed by EDF. (author) 26 refs.
Miller, R. L.; Schmidt, G. A.; Shindell, D. T.
2006-09-01
We examine the annular mode within each hemisphere (defined here as the leading empirical orthogonal function and principal component of hemispheric sea level pressure) as simulated by the Intergovernmental Panel on Climate Change Fourth Assessment Report ensembles of coupled ocean-atmosphere models. The simulated annular patterns exhibit a high spatial correlation with the observed patterns during the late 20th century, though the mode represents too large a percentage of total temporal variability within each hemisphere. In response to increasing concentrations of greenhouse gases and tropospheric sulfate aerosols, the multimodel average exhibits a positive annular trend in both hemispheres, with decreasing sea level pressure (SLP) over the pole and a compensating increase in midlatitudes. In the Northern Hemisphere, the trend agrees in sign but is of smaller amplitude than that observed during recent decades. In the Southern Hemisphere, decreasing stratospheric ozone causes an additional reduction in Antarctic surface pressure during the latter half of the 20th century. While annular trends in the multimodel average are positive, individual model trends vary widely. Not all models predict a decrease in high-latitude SLP, although no model exhibits an increase. As a test of the models' annular sensitivity, the response to volcanic aerosols in the stratosphere is calculated during the winter following five major tropical eruptions. The observed response exhibits coupling between stratospheric anomalies and annular variations at the surface, similar to the coupling between these levels simulated elsewhere by models in response to increasing GHG concentration. The multimodel average is of the correct sign but significantly smaller in magnitude than the observed annular anomaly. This suggests that the models underestimate the coupling of stratospheric changes to annular variations at the surface and may not simulate the full response to increasing GHGs.
Gap Model for Dual Customer Values
Institute of Scientific and Technical Information of China (English)
HOU Lun; TANG Xiaowo
2008-01-01
The customer value, the key problem in customer relationship management (CRM), was studied to construct a gap model for dual customer values. A basic description of customer values is given, and then the gaps between products and services in different periods for the customers and companies are analyzed based on the product or service life-cycle. The main factors that influence the perceived customer value were analyzed to define the "recognized value gap" and a gap model for the dual customer values was constructed to supply companies with a tool to analyze existing customer value gaps and improve customer relationship management.
Development of heat transfer models for gap cooling
International Nuclear Information System (INIS)
In a severe accident of a light water reactor (LWR), heat transfer models in a narrow annular gap between superheated core debris and a reactor pressure vessel (RPV) are important to evaluate the integrity of RPV and emergency procedures. This paper discusses the effects of superheat on the heat flux based on existing data. In low superheat conditions, the heat flux in the narrow gap is higher than the heat flux in pool nucleate boiling due to restricted flow area. It approaches the nucleate boiling heat flux as superheat increasing and reaches a critical value subject to the counter-current flow limiting (CCFL) at the top end of the gap. A heat transfer correlation was derived as a function of dimensionless superheat and a Kutateladze-type CCFL correlation was deduced for critical heat flux (CHF) restricted by CCFL, which gave good prediction for a wide range of the CHF data. Effect of an angle of inclination of the gap could also be incorporated in the CCFL correlation. In high superheat conditions, the heat flux in the narrow gap maintains a similar shape to the pool boiling curve but shifts the position to a higher superheated side than the pool boiling except film boiling, which could be expressed by the typical pool film boiling correlation. Incorporating quench test data, the heat flux correlation was derived as a function of dimensionless superheat using the same formula for the low superheat and the Kutateladze-type CCFL correlation was deduced for CHF. The CHF at the high superheat was 3-4 times as large as CHF at the low superheat and this difference was well predicted by different flow patterns in the gap and the balance of pressure gradients between gas and liquid phases. (author)
Dwenger, Richard Dale
1995-01-01
An experimental study was conducted in annular combustor model to provide a better understanding of the flowfield. Combustor model configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets were investigated. The purpose of this research was to provide a better understanding of combustor flows and to provide a data base for comparison with computational models. The first part of this research used a laser Doppler velocimeter to measure mean velocity and statistically calculate root-mean-square velocity in two coordinate directions. From this data, one Reynolds shear stress component and a two-dimensional turbulent kinetic energy term was determined. Major features of the flowfield included recirculating flow, primary and annular jet interaction, and high turbulence. The most pronounced result from this data was the effect the primary jets had on the flowfield. The primary jets were seen to reduce flow asymmetries, create larger recirculation zones, and higher turbulence levels. The second part of this research used a technique called marker nephelometry to provide mean concentration values in the combustor. Results showed the flow to be very turbulent and unsteady. All configurations investigated were highly sensitive to alignment of the primary and annular jets in the model and inlet conditions. Any imbalance between primary jets or misalignment of the annular jets caused severe flow asymmetries.
International Nuclear Information System (INIS)
A two-dimensional two-fluid analytical model is formulated to deal with the inverted annular film boiling (IAFB) heat transfer. The irregular variation of vapour annulus makes solving partial differential conservation equations difficulty. A relative coordinate system is proposed, through which a curve side mesh is mapped into rectangular one. The governing equations could then be solved a standard finite difference method. The model predicts Stewart's experiments well and reasonably confirms the influence of various components on vapour film. A comparison has been made between one-dimensional analytical system and this model. The wall temperature is a bit higher if the radial component is omitted. (orig./DG)
Interpreting the nature of Northern and Southern Annular Mode variability in CMIP5 Models
Schenzinger, V.; Osprey, S. M.
2015-11-01
Characteristic timescales for the Northern Annular Mode (NAM) and Southern Annular Mode (SAM) variability are diagnosed in historical simulations submitted to the Coupled Model Intercomparison Project Phase 5 (CMIP5) and are compared to the European Centre for Medium-Range Weather Forecasts ERA-Interim data. These timescales are calculated from geopotential height anomaly spectra using a recently developed method, where spectra are divided into low-frequency (Lorentzian) and high-frequency (exponential) parts to account for stochastic and chaotic behaviors, respectively. As found for reanalysis data, model spectra at high frequencies are consistent with low-order chaotic behavior, in contrast to an AR1 process at low frequencies. This places the characterization of the annular mode timescales in a more dynamical rather than purely stochastic context. The characteristic high-frequency timescales for the NAM and SAM derived from the model spectra at high frequencies are ˜5 days, independent of season, which is consistent with the timescales of ERA-Interim. In the low-frequency domain, however, models are slightly biased toward too long timescales, but within the error bars, a finding which is consistent with previous studies of CMIP3 models. For the SAM, low-frequency timescales in November, December, January, and February are overestimated in the models compared to ERA-Interim. In some models, the overestimation in the SAM austral summer timescale is partly due to interannual variability, which can inflate these timescales by up to ˜40% in the models but only accounts for about 5% in the ERA-Interim reanalysis.
Modeling Mist to Annular Flow Development in the Discharge of a Compressor
Wujek, Scott S.; Hrnjak, Predrag S.
2012-01-01
A model has been created to describe the development of flow leaving a compressor as it transitions from mist to annular flow. Flow parameters such as the drop size, drop speed, drop concentration, film thickness, and film velocity change as a function of length. Parameters such as refrigerant flow rates, oil in circulation ratios, and fluid properties are accounted for in these models. While some flow development work is found in the open literature for air-water or steam-water flows, little...
Annular Planar Monopole Antennas
Chen, Z. N.; Ammann, Max; Chia, W.Y. W.; See, T.S. P.
2002-01-01
A type of annular planar monopole antenna is presented. The impedance and radiation characteristics of the monopole with different holes and feed gaps are experimentally examined. The measured results demonstrate that the proposed antenna is capable of providing significantly broad impedance bandwidth with acceptable radiation performance.
International Nuclear Information System (INIS)
A model is developed to describe the transition of annular flow to intermittent flow in a vertical two-phase flow system. The instability of the disturbance wave, which is a dominant wave shape at the boundary between annular flow and intermittent flow, is considered as the governing mechanism and this instability is described by the concept of hyperbolicity breaking in the characteristic equation. The developed model is validated by comparing its predictions of gas superficial velocity for the transition with the experimental data available from the literature, and comparing those with the predictions of the other correlations. The comparison results show that the developed model gives better predictions for the transition condition than the existing correlations and the effects of fluid properties, geometry and liquid flow rate on the transition are well considered by the developed model. It is found that the predictions of the developed model have much smaller bias than those of the other correlations; the average of the prediction error is 3% for the present model. The standard deviation of the prediction errors of the present model reaches 28%, which is the smallest among the models compared here. Through the core uncovery experiments, it has been known that the low power and high power core boil-off patterns are observed in the high pressure core uncovery following a small-break loss-of-coolant accident. The developed model for the annular to intermittent flow regime transition was applied to the classification of low power boil-off and high power boil-off patterns. At first, the applicability of the developed criterion to the rod-bundle geometry is demonstrated using the flow pattern transition data taken by Bergles et al. and Venkateswararao. It is shown that the developed criterion well predicts the boundary between low power boil-off and high power boil-off through the comparisons of the predicted annular to intermittent flow transition conditions with
Kilbane, J.; Polzin, K. A.
2014-01-01
An annular linear induction pump (ALIP) that could be used for circulating liquid-metal coolant in a fission surface power reactor system is modeled in the present work using the computational COMSOL Multiphysics package. The pump is modeled using a two-dimensional, axisymmetric geometry and solved under conditions similar to those used during experimental pump testing. Real, nonlinear, temperature-dependent material properties can be incorporated into the model for both the electrically-conducting working fluid in the pump (NaK-78) and structural components of the pump. The intricate three-phase coil configuration of the pump is implemented in the model to produce an axially-traveling magnetic wave that is qualitatively similar to the measured magnetic wave. The model qualitatively captures the expected feature of a peak in efficiency as a function of flow rate.
START-3 code gap conductance modelling
International Nuclear Information System (INIS)
A model of integral fuel performance code START-3 for calculation of heat transfer across the fuel-cladding gap in nuclear fuel elements is presented. The model allows to determine heat transfer coefficient in various condition of fuel in relation to cladding: contact, gap. The contribution radiation component of coefficient of a heat transfer is also taken into account which, however for steady-state operation does not exceed 1%. Comparisons are made between the prediction of gap conductance model and out-of-pile experiments, and the results are presented. The START-3 code has been used to predict central line temperature data available from the Halden reactor. The calculations have been made for two different fuel rod internal gas (helium, xenon). The results of the comparison between the prediction of gap conductance model and out-of-pile experiments are presented. The agreement between model predictions and experimental data is satisfactory. (author)
Jenkins Model Based Ferrofluid Lubrication of a Curved Rough Annular Squeeze Film with Slip Velocity
Directory of Open Access Journals (Sweden)
J.R. Patel
2015-06-01
Full Text Available This paper deals with the combined effect of roughness and slip velocity on the performance of a Jenkins model based ferrofluid squeeze film in curved annular plates. Beavers and Joseph’s slip model has been adopted to incorporate the effect of slip velocity. The stochastic model of Christensen and Tonder has been deployed to evaluate the effect of surface roughness. The associated stochastically averaged Reynolds type equation is solved to derive the pressure distribution, leading to the calculation of load carrying capacity. The graphical representation makes it clear that although, the effect of transverse surface roughness is adverse in general, Jenkins model based ferrofluid lubrication provides some measures in mitigating the adverse effect and this becomes more manifest when the slip parameter is reduced and negatively skewed roughness occurs. Of course, a judicious choice of curvature parameters and variance (-ve add to this positive effect.
Kalman filter-based gap conductance modeling
International Nuclear Information System (INIS)
Geometric and thermal property uncertainties contribute greatly to the problem of determining conductance within the fuel-clad gas gap of a nuclear fuel pin. Accurate conductance values are needed for power plant licensing transient analysis and for test analyses at research facilities. Recent work by Meek, Doerner, and Adams has shown that use of Kalman filters to estimate gap conductance is a promising approach. A Kalman filter is simply a mathematical algorithm that employs available system measurements and assumed dynamic models to generate optimal system state vector estimates. This summary addresses another Kalman filter approach to gap conductance estimation and subsequent identification of an empirical conductance model
A two-dimensional parabolic model for vertical annular two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Fernandez, F.M.; Toledo, A. Alvarez; Paladino, E.E. [Graduate Program in Mechanical Engineering, Universidade Federal de Rio Grande do Norte, Natal, RN (Brazil)], e-mail: emilio@ct.ufrn.br
2010-07-01
This work presents a solution algorithm for predicting hydrodynamic parameters for developing and equilibrium, adiabatic, annular, vertical two-phase flow. It solves mass and momentum transport differential equations for both the core and the liquid film across their entire domains. Thus, the velocity and shear stress distributions from the tube center to the wall are obtained, together with the average film thickness and the pressure gradient, making no use of empirical closure relations nor assuming any known velocity profile to solve the triangular relationship in the liquid film. The model was developed using the Finite Volume Method and an iterative procedure is proposed to solve all flow variables for given phase superficial velocities. The procedure is validated against the analytical solution for laminar flow and experimental data for gas-liquid turbulent flow with entrainment. For the last case, an algebraic turbulence model is used for turbulent viscosity calculation for both, liquid film and gas core. (author)
Sun, Shufeng; Wu, Yuyuan; Zhao, Rongyi
2001-04-01
According to a separated phase flow model for vertical annular two-phase flow in an annular channel, the liquid film thickness, distributions of velocities and temperatures in the liquid layer are predicted in the range of heat fluxes: 6000-12000 W/m 2, mass flux: 500-1100 kg/m2 s. The pressure drop along the flow channel and heat transfer coefficient are also calculated. The liquid film thickness is in the order of micrometers and heat transfer coefficient is 2800-7800 W/m2 K of liquid nitrogen boiling in narrow annular channels. The measured heat transfer coefficient is 29% higher than the calculated values. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop and heat transfer coefficient increase.
A grillage model for predicting wrinkles in annular graphene under circular shearing
International Nuclear Information System (INIS)
This paper is concerned with a Timoshenko grillage model for modeling the wrinkling phenomenon in annular graphene under circular shearing applied at its inner edge. By calibrating the grillage model results against the molecular mechanics (MM) results, the grillage model comprising beams of elliptical cross-section orientated along the carbon-carbon bond has section dimensions of 0.06 nm for the major axis length and 0.036 nm for the minor axis length. Moreover, the beams are connected to one another at 0.00212 nm from the geometric centric. This eccentric connection of beams allows the proposed grillage model to cater for the cross-couplings among bonds that produce the out-of-plane wrinkling pattern. The out-of-plane to in-plane bending stiffnesses' ratio is 0.36, and the cross bending stiffness provided by the ellipse eccentricity is 0.025 times that of the in-plane bending stiffness. Besides furnishing identical wave numbers as well as amplitudes and wavelengths that are in good agreement with MM results, the grillage model can capture wrinkling patterns with a boundary layer, whereas plate and membrane models could not mimic the boundary layer.
Diffractive analysis of annular resonators.
Morin, M; Bélanger, P A
1992-04-20
The modal properties of annular resonators are investigated by using an approximate version of the Kirchhoff-Fresnel integral. It is shown that the radial diffraction of a thin annular beam with a large inside radius is similar to that of a cylindrical field distribution. This permits the formal demonstration of the equivalence that exists between large Fresnel number annular resonators and infinite strip resonators. The model explains the properties of annular resonators that have been observed either experimentally or numerically by others, such as the lack of azimuthal discrimination. PMID:20720842
An assessment of the annular flow transition criteria and interphase friction models in RELAP5/MOD2
International Nuclear Information System (INIS)
An assessment of the annular flow transition criteria and interphase friction models for two-phase flow in tubes used in RELAP5/MOD2 code is described. The assessment examines the theoretical bases for the criteria and models and considers the results of comparisons with experimental data. Several deficiencies in the transition criteria are identified and appropriate improvements proposed. The interphase friction models are found to be adequate for PWR analyses. (author)
Directory of Open Access Journals (Sweden)
Patel Jimit R.
2015-01-01
Full Text Available This paper analyzes the combined effect of slip velocity and transverse roughness on the performance of a Jenkins model based ferrofluid lubrication of a squeeze film in curved rough annular plates. The slip model of Beavers and Joseph has been invoked to evaluate the effect of slip velocity. In order to find the effect of surface roughness the stochastic averaging model of Christensen and Tonder has been used. The pressure distribution is obtained by solving the concerned stochastically averaged Reynolds type equation. The load carrying capacity is calculated. The graphical representations of the results indicate that the effect of transverse surface roughness is adverse in general, however, the situation is relatively better in the case of negatively skewed roughness. Further, Jenkins model based ferrofluid lubrication offers some measures in reducing the adverse effect of roughness when slip parameter is kept at reduced level with a suitable ratio of curvature parameters. Lastly, the positive effect of magnetization gets a boost due to the combined effect of variance (-ve and negatively skewed roughness suitably choosing the aspect ratio.
International Nuclear Information System (INIS)
Highlights: → Knowledge of the interfacial wave structure is essential for making an accurate prediction of the amount of entrained droplets. → A new droplet entrainment model based on the force balance of interfacial waves in vertical annular flow. → An analytic wave shape function was developed. → A new droplet entrainment model was validated using the experimental data reported by Hewitt and Pulling and by Keeys et al. - Abstract: Droplets are generated at the interface of annular flow due to an interaction between a liquid film and gas core flow. Therefore, knowledge of the interfacial wave structure is essential for making an accurate prediction of the amount of entrained droplets. A new droplet entrainment model was proposed based on the force balance of interfacial waves in vertical annular flow. An analytic wave shape function was developed reflecting the detailed experimental findings, and was used in the development of a new model. The model was validated using the experimental data reported by Hewitt and Pulling at low pressures and by Keeys et al. at high pressures, which had been performed in adiabatic vertical tubes. The root-mean-square error of the prediction of the amount of entrainment was approximately 27% when the model was implemented into COBRA-TF code, which is approximately 23% less than that determined by the Wuertz model. The models proposed by Okawa et al. and Stevanovic et al. were also implemented into COBRA-TF and compared with the proposed model.
Parmentier, Jean-François; Salas, Pablo; Wolf, Pierre; Staffelbach, Gabriel; Nicoud, Franck; Poinsot, Thierry
2012-01-01
This study describes a simple analytical method to compute the azimuthal modes appearing in annular combustion chambers and help analyzing experimental, acoustic and large eddy simulation (LES) data obtained in these combustion chambers. It is based on a one-dimensional zero Mach number formulation where N burners are connected to a single annular chamber. A manipulation of the corresponding acoustic equations in this configuration leads to a simple dispersion relation which can be solved by ...
Quantifying paleo-reconstruction skill of the Southern Annular Mode in a model framework
Huiskamp, Willem; McGregor, Shayne; Batehup, Ryan
2016-04-01
The Southern Annular Mode (SAM) is the leading mode of atmospheric variability in the Southern Hemisphere. It impacts rainfall and surface air temperature throughout the hemisphere and is also responsible for a significant proportion of the variability in air-sea carbon exchange. The recent positive trend in the SAM over the last ~40 years has been linked to potential changes in ocean heat and carbon uptake, which could have a significant impact on the rate of anthropogenic warming. To investigate whether trends like this have occurred in the past, and how they may affect regional climate and atmospheric CO2, paleo-reconstructions of the SAM have been created spanning roughly the last millennium. Using the GFDL CM2.1 climate model, we attempt to assess the expected skill of these reconstructions using a pseudo-proxy approach and the popular weighted Composite Plus Scaling reconstruction method. This study covers non-stationary proxy-SAM relationships, the effects of calibration period length on reconstruction skill, the number of sites included in a reconstruction and the problem of relying too heavily on a single continent when sourcing proxies. We find that maximising the calibration window size, as well as sourcing proxies from a geographically diverse range of sites provides the most reliable reconstructions, accounting for up up to 58% of the model SAM variability (with realistic 31 year calibration window and 70 proxies).
Theoretical thermal dosimetry produced by an annular phased array system in CT-based patient models
International Nuclear Information System (INIS)
Theoretical calculations for the specific absorption rate (SAR) and the resulting temperature distributions produced by an annular phased array (APA) type system are made. The finite element numerical method is used in the formulation of both the electromagnetic (EM) and the thermal boundary value problems. A number of detailed patient models based on CT-scan data from the pelvic, visceral, and thoracic regions are generated to stimulate a variety of tumor locations and surrounding normal tissues. The SAR values from the EM solution are input into the bioheat transfer equation, and steady-rate temperature distributions are calculated for a wide variety of blood flow rates. Based on theoretical modeling, the APA shows no preferential heating of superficial over deep-seated tumors. However, in most cases satisfactory thermal profiles (therapeutic volume near 60%) are obtained in all three regions of the human trunk only for tumors with little or no blood flow. Unsatisfactory temperature patterns (therapeutic volume <50%) are found for tumors with moderate to high perfusion rates. These theoretical calculations should aid the clinician in the evaluation of the effectiveness of APA type devices in heating tumors located in the trunk region
Gupta, Diptesh; Hess, Brian; Bachegowda, Lohith
2010-01-01
We present a case of a 77-year-old, diabetic male with a 20-year history of a migratory erythematous, asymptomatic, generalized, nonscaly, and nonitchy rash that started over the dorsum of his left hand. On examination, there were multiple annular erythematous plaques, distributed symmetrically and diffusely over his torso and arms, with central clearing and no scales. A punch biopsy of the skin helped us to arrive at the diagnosis of a generalized granuloma annulare (GA). GA is a benign, self-limiting skin condition of unknown etiology that is often asymptomatic. The cause of this condition is unknown, but it has been associated with diabetes mellitus, infections such as HIV, and malignancies such as lymphoma. These lesions typically start as a ring of flesh-colored papules that slowly progress with central clearing. Lack of symptoms, scaling, or associated vesicles helps to differentiate GA from other skin conditions such as tinea corporis, pityriasis rosea, psoriasis, or erythema annulare centrifugum. Treatment is often not needed as the majority of these lesions are self-resolving within 2 years. Treatment may be pursued for cosmetic reasons. Available options include high-dose steroid creams, PUVA, cryotherapy, or drugs such as niacinamide, infliximab, Dapsone, and topical calcineurin inhibitors. PMID:20209383
Boiling two-phase flow and heat transfer in concentric annular tube
International Nuclear Information System (INIS)
The boiling flow resistance and heat transfer characteristics is experimentally investigated under the outer tube wall heating condition in a concentric annular tube with 2.1 mm gap size. The results show that the flow resistance in the annular tube is greater than that in circular tube, as well as the boiling heat transfer becomes enhanced. The heat transfer coefficient has close relationship with the pressure, thermal equilibrium quality, mass flux, heat flux, gap size of the annular tube, and heat models as well. The physical explanation about the enhancement boiling heat transfer in the annular tube is proposed with both micro-film evaporation mechanics and bubble disturbance mechanics. The correlations to calculate the flow friction coefficient and heat transfer coefficient are proposed based on the experimental data. (authors)
Flow Measurement Model of Ultrasonic Flowmeter for Gas-Liquid Two-Phase Stratified and Annular Flows
Lanchang Xing; Chenquan Hua; Hao Zhu; Wolfgang Drahm
2014-01-01
An error correction model for ultrasonic gas flowmeter was proposed to explore the potential of an ultrasonic flowmeter for metering gas-liquid stratified and annular flows. The gas and liquid mass flowrates could be obtained provided that the gas quality and physical prosperities were known. A single-path ultrasonic flowmeter was investigated and the error of the apparent volumetric flowrate was considered as mainly resulting from the shrinkage of the gas flow path due to the presence of a l...
Adaptive Linked Gap Element for FE-Based Gap Conductance Model
International Nuclear Information System (INIS)
A light water reactor (LWR) fuel rod consists of a zirconium alloy cladding tube and uranium dioxide pellets with a slight gap between them. The modeling of the heat transfer across the gap between fuel pellets and the protective cladding is essential to understanding the fuel behavior under irradiated conditions. Based on the Ross and Stoute model, the gap conductance that specifies the temperature gradient within the gap is very sensitive to the gap thickness in a certain region. Many researchers have been being developing fuel performance codes based on a finite element method (FE) to calculate the temperature, stress, and strain for a multidimensional analysis. The gap conductance model for multi-dimension is a difficult issue in terms of convergence and nonlinearity because the gap conductance is a function of gap thickness which depends on the mechanical analysis at each iteration step. In this paper, an adaptive linked gap element (AGE) has been proposed to resolve the convergence issue and nonlinear characteristic of multidimensional gap conductance. The elements that link the node of a pellet surface with the node of the cladding surface virtually are generated, so as to transfer heat as a function of gap thickness at every iteration step. To evaluate the proposed methodology for the simulation of the gap conductance, a thermo-mechanical coupled FE model has been established using ANSYS Parametric Design Language (APDL). In terms of the calculation accuracy and convergence efficiency, the proposed model has been evaluated for variable cases. (author)
Dynamic Model of Gap Loop for HCW Mill
Institute of Scientific and Technical Information of China (English)
YANG Jing-ming; YANG Qiu-xia; CHE Hai-jun; CHANG Ling-fang
2004-01-01
The hydraulic automatic gauge control system using gap loop for cold mill was designed. The stiffness of HCW cold mill was defined for gap loop, and the dynamic model of gauge control system for gap loop was built with mechanism analysis. The stiffness for gap loop and the cylinder displacement loop were measured.
Analysis of Design Variables of Annular Linear Induction Electromagnetic Pump using an MHD Model
International Nuclear Information System (INIS)
The generated force is affected by lots of factors including electrical input, hydrodynamic flow, geometrical shape, and so on. These factors, which are the design variables of an ALIP, should be suitably analyzed to optimally design an ALIP. Analysis on the developed pressure and efficiency of the ALIP according to the change of design variables is required for the ALIP satisfying requirements. In this study, the design variables of the ALIP are analyzed by using ideal MHD analysis model. Electromagnetic force and efficiency are derived by analyzing the main design variables such as pump core length, inner core diameter, flow gap and turns of coils. The developed pressure and efficiency of the ALIP were derived and analyzed on the change of the main variables such as pump core length, inner core diameter, flow gap, and turns of coils of the ALIP
Analysis of Design Variables of Annular Linear Induction Electromagnetic Pump using an MHD Model
Energy Technology Data Exchange (ETDEWEB)
Kwak, Jae Sik; Kim, Hee Reyoung [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)
2015-05-15
The generated force is affected by lots of factors including electrical input, hydrodynamic flow, geometrical shape, and so on. These factors, which are the design variables of an ALIP, should be suitably analyzed to optimally design an ALIP. Analysis on the developed pressure and efficiency of the ALIP according to the change of design variables is required for the ALIP satisfying requirements. In this study, the design variables of the ALIP are analyzed by using ideal MHD analysis model. Electromagnetic force and efficiency are derived by analyzing the main design variables such as pump core length, inner core diameter, flow gap and turns of coils. The developed pressure and efficiency of the ALIP were derived and analyzed on the change of the main variables such as pump core length, inner core diameter, flow gap, and turns of coils of the ALIP.
International Nuclear Information System (INIS)
A model is developed to describe the transition from annular flow to intermittent flow in a vertical two-phase flow system. Since the instability of the disturbance wave, which is a dominant wave shape at the boundary between annular flow and intermittent flow, is considered as a governing mechanism, this instability described by the concept of hyperbolicity breaking in the characteristic equation is included in the model. The developed model is validated by comparing its predictions of gas superficial velocity for the transition with experimental data available in the literature, and comparing those with the predictions of the other correlations. The comparison results show that the model gives better predictions for the transition condition than existing correlations, and the effects of fluid properties, geometry and liquid flow rate on the transition are well considered by the developed model. The average of prediction errors is 3% for the present model. The standard deviation of the prediction errors of the model reaches 28%, which is the smallest among the models compared here. (author)
A self-standing two-fluid CFD model for vertical upward two-phase annular flow
Energy Technology Data Exchange (ETDEWEB)
Liu, Y., E-mail: yang_liu@mail.dlut.edu.c [Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning Province (China); Li, W.Z.; Quan, S.L. [Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024, Liaoning Province (China)
2011-05-15
Research highlights: A mathematic model for two-phase annular flow is established in this paper. Pressure loss and wall shear stress increase with inlet gas and liquid flow velocities. Droplet mass fraction distribution exhibits a concave profile radially. - Abstract: In this paper, a new two-fluid CFD (computational fluid dynamics) model is proposed to simulate the vertical upward two-phase annular flow. This model solves the basic mass and momentum equations for the gas core region flow and the liquid film flow, where the basic governing equations are accounted for by the commercial CFD package Fluent6.3.26. The liquid droplet flow and the interfacial inter-phase effects are accounted for by the programmable interface of Fluent, UDF (user defined function). Unlike previous models, the present model includes the effect of liquid roll waves directly determined from the CFD code. It is able to provide more detailed and, the most important, self-standing information for both the gas core flow and the film flow as well as the inner tube wall situations.
International Nuclear Information System (INIS)
Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy, derived for a two-phase flow by volume averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration, bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities make the rigorously formulated terms useless for computational purposes, modelling of these terms is discussed. 3 figs., 15 refs
Energy Technology Data Exchange (ETDEWEB)
Bottoni, M.; Ajuha, S. [Argonne National Lab., IL (United States). Energy Technology Div.; Sengpiel, W. [Kernforschungszentrum Karlsruhe (Germany). Inst. fur Reaktorsicherheit
1994-12-31
Starting from the rigorous formulation of the conservation equations for mass, momentum and enthalpy derived for a two-phase flow by volume-averaging microscopic balance equations over Eulerian control cells, the article discusses the formulation of the terms describing exchanges between the phases. Two flow regimes are taken into consideration; bubbly flow, applicable for small or medium void fractions, and annular flow, for large void fractions. When lack of knowledge of volume-averaged physical quantities makes the rigorously formulated terms useless for computational purposes, modeling of these terms is discussed.
International Nuclear Information System (INIS)
Maintaining the PWR components under reliable operating conditions requires a complex design to prevent various damaging processes including wear problems due to flow induced vibration. To improve wear prediction in PWR components, EDF has undertaken a comprehensive program oriented both on experimental and computational studies. The present paper illustrates one aspect of this program, proposing a numerical model for fluid-structure coupling of a cylindrical center body submitted to an axial annular flow. This model has been developed in the case of an incompressible, single phase, viscous fluid, and for a confined geometry with variable section passage. The structural response is expended in terms of the normal modes of the system. Due to the particular geometry of the problem, a specific numerical procedure has been implemented to provide a good approximate solution of the unsteady Navier-Stokes equations. The boundary conditions and dissipative terms taken into account in the modelization are of particular interest and are developed in detail. In the stable operating region, it provides the evolution versus flow velocity, of the modal characteristics of the coupled fluid-structure system. Consequently, the critical flow velocity can be computed as the velocity at which the damping ratio becomes zero. As a final step, an experimental validation is presented: the results obtained with the numerical model are compared to previously published experimental data concerning an oscillating cylinder submitted to an unsteady annular flow. (authors). 5 figs., 15 refs
Review of seismic gaps and gap model for the South American subduction zone
Roth, Frank; Dahm, Torsten; Hainzl, Sebastian
2016-04-01
The seismic gap hypothesis describes a long-period decrease of the probability of earthquake occurrence after major earthquakes, as a consequence of the induced stress shadow. The gap model assumes that the continuous build-up of tectonic strain and stress is released by characteristic major earthquakes. The size of the characteristic earthquakes is for instance controlled by structural heterogeneities or the geometry of the plate boundaries. The gap model is commonly accepted by geologists and a fundamental assumption of our approaches to estimate seismic hazard and time dependent earthquake probability. Interestingly, systematic and rigorous tests to verify the seismic gap model have often failed. In this study we analyze the historical record of major earthquakes at the South American plate boundary with a special look to seismic gaps. The aim of our study is to compare and proof different seismic gap models. We discuss whether the characteristic earthquakes assumption is justified for the South American plate boundary. Two different gap models are discussed: (a) a traditional quasi-periodic recurrence model involving time dependent conditional occurrence probabilities, and (b) a new model describing earthquake rates by rate and state seismicity models considering the estimated spatial pattern of stress drop during major earthquakes.
Lockett, R. D.; Greenhalgh, D.A.
2010-01-01
Planar laser induced fluorescence (PLIF) was employed in a three sector, low NOx double annular combustor in order to characterise the combusting fuel spray. Naphthalene was employed as a fluorescent agent in odourless kerosene in order to determine the behavior of the light fractions in the fuel vapour, and the light to medium fractions in the fuel spray, while 2,5 di-phenyl oxizol (ppo) was employed to determine the behavior of the heavy fractions in the fuel spray. Counter-swirl air blast ...
A Simple Analytical Model for Gaps in Protoplanetary Disks
Duffell, Paul C
2015-01-01
An analytical model is presented for calculating the surface density as a function of radius $\\Sigma(r)$ in protoplanetary disks in which a planet has opened a gap. This model is also applicable to circumbinary disks with extreme binary mass ratios. The gap profile can be solved for algebraically, without performing any numerical integrals. In contrast with previous one-dimensional gap models, this model correctly predicts that low-mass (sub-Jupiter) planets can open gaps in sufficiently low-viscosity disks, and it correctly recovers the power-law dependence of gap depth on planet-to-star mass ratio $q$, disk aspect ratio $h/r$, and dimensionless viscosity $\\alpha$ found in previous numerical studies. Analytical gap profiles are compared with numerical calculations over a range of parameter space in $q$, $h/r$, and $\\alpha$, demonstrating accurate reproduction of the "partial gap" regime, and general agreement over a wide range of parameter space.
THE EXTENSION OF THE GAP-MODEL FOR SERVICES
DINA ASWAD
2012-01-01
The customer oriented marketing has significant correlation with logistical concept, only its tools and methods are different; therefore, the logistical services should be implemented in to the gap-model. The goal of the model is to identify the gaps between the customer's expectation and the services provided at different stages of services and to disappear the gap and improve the customer services. In my work, the original model [5] has been completed with additional elements including buye...
Sensitivity Analysis of the Gap Heat Transfer Model in BISON.
Energy Technology Data Exchange (ETDEWEB)
Swiler, Laura Painton; Schmidt, Rodney C.; Williamson, Richard (INL); Perez, Danielle (INL)
2014-10-01
This report summarizes the result of a NEAMS project focused on sensitivity analysis of the heat transfer model in the gap between the fuel rod and the cladding used in the BISON fuel performance code of Idaho National Laboratory. Using the gap heat transfer models in BISON, the sensitivity of the modeling parameters and the associated responses is investigated. The study results in a quantitative assessment of the role of various parameters in the analysis of gap heat transfer in nuclear fuel.
International Nuclear Information System (INIS)
Dryout of the liquid coolant film on fuel pins at the top of boiling water reactor (BWR) cores constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is a limiting factor in the thermal power, and therefore the economy, of BWRs. Ongoing research on multiphase annular flow, specifically the liquid film thickness, is fundamental not only to nuclear reactor safety and operation but also to that of evaporators, condensers, and pipelines in a general industrial context. We have performed cold neutron tomography of adiabatic air water annular flow in a scaled up model of the subchannel geometry found in BWR fuel assemblies today. All imaging has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institut in Switzerland. Neutron tomography is shown to excel in investigating the interactions of air water two phase flows with spacer vanes of different geometry. The high resolution, high contrast measurements provide spatial distributions of the coolant on top of the surfaces of the spacer, including the vanes, and in the subchannel downstream of the spacers.
International Nuclear Information System (INIS)
The development of thermal hydraulic analysis code for Gas-Cooled Reactors (GCRs) and for annular fuel and its application to various types of nuclear reactors, and the assessment of the Korea Advanced Institute of Science and Technology (KAIST) Departure from Nucleate Boiling (DNB)-type theoretical Critical Heat Flux (CHF) model for rod bundles with non-uniform axial power shapes were investigated. Thermal hydraulic characteristics of thorium-based fuel assemblies with annular seed pins were analyzed using Thermal-Hydraulic analysis code for Annular Fuel (THAF) combined with Multichannel Analyzer for steady states and Transients in Rod Arrays (MATRA), and compared with those of existing thorium-based assemblies. This study investigates the possibilities of using annular fuel pins in a pressurized water reactor with emphasis on coolant flow distribution and heat transfer fraction in internal and external sub-channels. MATRA and THAF showed good agreements for the pressure drops at the internal sub-channels. Mass fluxes were high in inner sub-channels of the seed pins due to the grid form losses in the outer sub-channels. About 43% of heat generated from the seed pin flowed into the inner sub-channel. The remaining heat flowed into the outer sub-channel. The inner to outer wall heat flux ratio was approximately 1.2. Maximum temperatures of annular seed pins were slightly above 500 .deg. C. Minimum DNB Ratios (MDNBRs) of the assemblies loaded with annular seed pins were higher than those of the existing assemblies. Temperatures and enthalpies were higher in the inner sub-channels due to the fact that inter-channel mixing cannot occur in the inner sub-channels. A thermal-hydraulic analysis code for annular fuel-based Liquid Metal Reactors (LMRs) has been developed. About 41% of the heat generated from the fuel pin flowed into the inner sub-channel and the rest into the outer sub-channel. The inner to outer wall heat flux ratio was equal to approximately 1.44. A new 37
Annular Flow Distribution test
International Nuclear Information System (INIS)
This report documents the Babcock and Wilcox (B ampersand W) Annular Flow Distribution testing for the Savannah River Laboratory (SRL). The objective of the Annular Flow Distribution Test Program is to characterize the flow distribution between annular coolant channels for the Mark-22 fuel assembly with the bottom fitting insert (BFI) in place. Flow rate measurements for each annular channel were obtained by establishing ''hydraulic similarity'' between an instrumented fuel assembly with the BFI removed and a ''reference'' fuel assembly with the BFI installed. Empirical correlations of annular flow rates were generated for a range of boundary conditions
Electroosmotic flow and Joule heating in preparative continuous annular electrochromatography.
Laskowski, René; Bart, Hans-Jörg
2015-09-01
An openFOAM "computational fluid dynamic" simulation model was developed for the description of local interaction of hydrodynamics and Joule heating in annular electrochromatography. A local decline of electrical conductivity of the background eluent is caused by an electrokinetic migration of ions resulting in higher Joule heat generation. The model equations consider the Navier-Stokes equation for incompressible fluids, the energy equation for stationary temperature fields, and the mass transfer equation for the electrokinetic flow. The simulations were embedded in commercial ANSYS Fluent software and in open-source environment openFOAM. The annular gap (1 mm width) contained an inorganic C8 reverse-phase monolith as stationary phase prepared by an in situ sol-gel process. The process temperature generated by Joule heating was determined by thermal camera system. The local hydrodynamics in the prototype was detected by a gravimetric contact-free measurement method and experimental and simulated values matched quite well. PMID:25997390
Communication: Fragment-based Hamiltonian model of electronic charge-excitation gaps and gap closure
International Nuclear Information System (INIS)
Capturing key electronic properties such as charge excitation gaps within models at or above the atomic scale presents an ongoing challenge to understanding molecular, nanoscale, and condensed phase systems. One strategy is to describe the system in terms of properties of interacting material fragments, but it is unclear how to accomplish this for charge-excitation and charge-transfer phenomena. Hamiltonian models such as the Hubbard model provide formal frameworks for analyzing gap properties but are couched purely in terms of states of electrons, rather than the states of the fragments at the scale of interest. The recently introduced Fragment Hamiltonian (FH) model uses fragments in different charge states as its building blocks, enabling a uniform, quantum-mechanical treatment that captures the charge-excitation gap. These gaps are preserved in terms of inter-fragment charge-transfer hopping integrals T and on-fragment parameters U(FH). The FH model generalizes the standard Hubbard model (a single intra-band hopping integral t and on-site repulsion U) from quantum states for electrons to quantum states for fragments. We demonstrate that even for simple two-fragment and multi-fragment systems, gap closure is enabled once T exceeds the threshold set by U(FH), thus providing new insight into the nature of metal-insulator transitions. This result is in contrast to the standard Hubbard model for 1d rings, for which Lieb and Wu proved that gap closure was impossible, regardless of the choices for t and U
International Nuclear Information System (INIS)
It's necessary to choose a good turbulence model for the reliable numerical simulation of the pump in hydraulic optimization. In this paper, the four widely used turbulence models are selected and compared in three dimensional steady numerical simulations for a large annular volute-type pump with the diffuser. The pump performance is verified by the experiments in an open test rig. The results show that the SST turbulence model gets closer values to the experiment in predicting head. The trend of the pressure distribution at design condition for the four models on pressure side is very similar, which first increases and then decreases along the streamline. There are a minimum at 0.05 and a maximum at 0.8 of the length of the streamline, due to the existence of vortices. The predicted pressure distribution on the suction side is more similar. With the increase of flow rate, the flow field in the impeller becomes more uniform, and the number as well as the size of the vortices decrease. Secondary flow is observed in the volute and three vortices are found near the upside of the volute
Heckmann, Andreas; Hartweg, Stefan; Kaiser, Ingo
2011-01-01
The bending deformation of rotating annular plates and the associated vibration behaviour is important in engineering applications which range from automotive or railway brake systems to discs that form essential components in turbomachinery. In order to extend the capabilities of the DLR FlexibleBodies library for such use cases, a new Modelica class has been implemented which is based on the analytical description of an annular Kirchhoff plate. In addition the so-called Arbitray Langra...
Bone compaction enhances implant fixation in a canine gap model
DEFF Research Database (Denmark)
Kold, Søren; Rahbek, Ole; Toft, Marianne;
2005-01-01
A new bone preparation technique, compaction, has increased fixation of implants inserted with exact-fit or press-fit to bone. Furthermore, a demonstrated spring-back effect of compacted bone might be of potential value in reducing the initial gaps that often exist between clinical inserted...... implants and bone. However, it is unknown whether the compression and breakage of trabeculae during the compaction procedure results in impaired gap-healing of compacted bone. Therefore, we compared compaction with conventional drilling in a canine gap model. Grit-blasted titanium implants (diameter 6 mm...... that the beneficial effect of reduced gap size, as compacted bone springs back, is not eliminated by an impaired gap-healing of compacted bone....
Local Structural Alignment of RNA with Affine Gap Model
Wong, Thomas K. F.; Cheung, Brenda W. Y.; Lam, T. W.; Yiu, S. M.
Predicting new non-coding RNAs (ncRNAs) of a family can be done by aligning the potential candidate with a member of the family with known sequence and secondary structure. Existing tools either only consider the sequence similarity or cannot handle local alignment with gaps. In this paper, we consider the problem of finding the optimal local structural alignment between a query RNA sequence (with known secondary structure) and a target sequence (with unknown secondary structure) with the affine gap penalty model. We provide the algorithm to solve the problem. Based on a preliminary experiment, we show that there are ncRNA families in which considering local structural alignment with gap penalty model can identify real hits more effectively than using global alignment or local alignment without gap penalty model.
International Nuclear Information System (INIS)
The Supercritical-Water-Cooled Reactor (SCWR) is a high-temperature, high-pressure water cooled reactor that operates above the critical pressure of water. In order to perform efficiently the thermal design of the SCWR, it is important to assess the thermal-hydraulics in rod bundles of the core. The experimental conditions of mockup tests, however, have to be limited because of technical and financial reasons. Therefore, it is required to establish an analytical design technique which can extrapolate experimental data to various design conditions of the reactor. JAEA (Japan Atomic Energy Agency) have been improved the three-dimensional two-fluid model analysis code ACE-3D, which has been developed originally for the two-phase flow thermal hydraulics of light water reactors, to handle the thermal hydraulic properties of water at supercritical region. In the present paper, heat transfer experiments of supercritical water flowing in a vertical annular channel around a heater pin, which simulates the core flow around a fuel rod, were analyzed with the improved ACE-3D to assess the prediction performance of the code. As a result, it was confirmed that the calculated wall surface temperature agreed with the measured results and the code is applicable to prediction of heat transfer of supercritical water in the system that simulates the SCWR core. (author)
Magnetostatic penumbra models with field-free gaps
Scharmer, G B
2006-01-01
We present numerical 2D magnetostatic models for sunspot penumbrae consisting of radially aligned field-free gaps in a potential magnetic field, as proposed by Spruit and Scharmer (2006). The shape of the gaps and the field configurations around them are computed consistently from the condition of magnetostatic pressure balance between the gap and the magnetic field. The results show that field-free gaps in the {\\it inner} penumbra are cusp-shaped and bounded by a magnetic field inclined by about $70^\\circ$ from the vertical. Here, the magnetic component has a Wilson depression on the order 200--300 km relative to the top of the field-free gap; the gaps should thus appear as noticeably elevated features. This structure explains the large variations in field strength in the inner penumbra inferred from magnetograms and two-component inversions, and the varying appearance of the inner penumbra with viewing angle. In the {\\it outer} penumbra, on the other hand, the gaps are flat-topped with a horizontal magnetic...
The Binding Energy, Spin-Excitation Gap, and Charged Gap in the Boson-Fermion Model
Institute of Scientific and Technical Information of China (English)
YANG Kai-Hua; TIAN Guang-Shan; HAN Ru-Qi
2003-01-01
In this paper, by applying a simplified version of Lieb 's spin-refleetion-positivity method, which was recentlydeveloped by one of us [G.S. Tian and J.G. Wang, J. Phys. A: Math. Gen. 35 (2002) 941], we investigate some generalproperties of the boson-fermion Hamiltonian, which has been widely used as a phenomenological model to describe thereal-space pairing of electrons. On a mathematically rigorous basis, we prove that for either negative or positive couplingV, which represents the spontaneous decay and recombination process between boson and fermion in the model, thepairing energy of electrons is nonzero. Furthermore, we also show that the spin-excitation gap of the boson-fermionHamiltonian is always larger than its charged gap, as predicted by the pre-paired electron theory.
The Binding Energy, Spin－Excitation Gap, and Charged Gap in the Boson－Fermion Model
Institute of Scientific and Technical Information of China (English)
YANGKai-Hua; Guang-Shan; HANRu-Qi
2003-01-01
In this paper, by applying a simplified version of Lieb's spin-reflection-positivity method, which was recently developed by one of us [G.S. Tian and J.G. Wang, J. Phys. A: Math. Gen. 35 (2002) 941], we investigate some general properties of the boeon-fermion Hamiltonlan, which has been widely used as a phenomenological model to describe the real-space pairing of electrons. On a mathematically rigorous basis, we prove that for either negative or positive couping V, which represents the spontaneous decay and recombination process between boson and fermion in the model, the pairing energy of electrons is nonzero. Furthermore, we also show that the spin-excitation gap of the boson-fermion Hamiltonian is always larger than its charged gap, as predicted by the pre-palred electron theory.
An Improved Linear Model for Rotors Subject to Dissipative Annular Flows
Moreira, Miguel; J. Antunes; Pina, H.
2000-01-01
In a previous paper, Antunes, Axisa and co-workers developed a linearized model for the dynamic of rotors under moderate fluid confinement, based on classical perturbation analysis covering two different cases: (i) dissipative motions of a centered rotor; (ii) motions of an eccentric rotor for a frictionless flow. Following the same procedures and assumptions, we derive here an improved model to cover the more general case of a dissipative linearized motion of an eccentric rotor. Besides the ...
International Nuclear Information System (INIS)
A series of experiments has been carried out in order to characterize a MAPA applicator prior to possible clinical implementation. The energy deposition patterns were determined in several human limb models of different complexities. The maximum energy deposition observed in a homogeneous cylindrical phantom was found to be at the middle of the applicator. For more realistically shaped, homogeneous limb models, the point of maximum energy deposition was shifted towards a smaller cross-sectional region; this was also the case for isolated human legs. Furthermore, significant heating was observed in the bone of the isolated legs. Such phenomena illustrate the limitation of using classical 2-D numerical models for predicting the energy deposition patterns in heterogeneous bodies
Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment
Energy Technology Data Exchange (ETDEWEB)
Mitran, Sorin, E-mail: mitran@unc.edu
2013-07-01
The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale.
Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment
International Nuclear Information System (INIS)
The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale
Optimizing a gap conductance model applicable to VVER-1000 thermal–hydraulic model
International Nuclear Information System (INIS)
Highlights: ► Two known conductance models for application in VVER-1000 thermal–hydraulic code are examined. ► An optimized gap conductance model is developed which can predict the gap conductance in good agreement with FSAR data. ► The licensed thermal–hydraulic code is coupled with the gap conductance model predictor externally. -- Abstract: The modeling of gap conductance for application in VVER-1000 thermal–hydraulic codes is addressed. Two known models, namely CALZA-BINI and RELAP5 gap conductance models, are examined. By externally linking of gap conductance models and COBRA-EN thermal hydraulic code, the acceptable range of each model is specified. The result of each gap conductance model versus linear heat rate has been compared with FSAR data. A linear heat rate of about 9 kW/m is the boundary for optimization process. Since each gap conductance model has its advantages and limitation, the optimized gap conductance model can predict the gap conductance better than each of the two other models individually.
BMP13 Prevents the Effects of Annular Injury in an Ovine Model
Directory of Open Access Journals (Sweden)
Aiqun Wei, Lisa A Williams, Divya Bhargav, Bojiang Shen, Thomas Kishen, Neil Duffy, Ashish D Diwan
2009-01-01
Full Text Available Chronic back pain is a global health problem affecting millions of people worldwide and carries significant economic and social morbidities. Intervertebral disc damage and degeneration is a major cause of back pain, characterised by histological and biochemical changes that have been well documented in animal models. Recently there has been intense interest in early intervention in disc degeneration using growth factors or stem cell transplantation, to replenish the diseased tissues. Bone Morphogenetic Proteins (BMPs have been approved for clinical use in augmenting spinal fusions, and may represent candidate molecules for intervertebral disc regeneration. BMP13 has an important role in embryonic development and recent genetic evidence shows a role in the development of the human spine. This study explores the effect of BMP13 on a damaged intervertebral disc in an ovine model of discal degeneration. We found that, when injected at the time of injury, BMP13 reversed or arrested histological changes that occurred in the control discs such as loss of extracellular matrix proteins. In addition, BMP13 injected discs retained greater hydration after 4months, and possessed more cells in the NP. Taken together, BMP13 may be a potent clinical therapeutic agent when used early in the degeneration cascade to promote healthy disc tissue.
Annular pancreas is an abnormal ring or collar of pancreatic tissue that encircles the duodenum (the part of the ... intestine that connects to stomach). This portion of pancreas can constrict the duodenum and block or impair ...
Electric field modelling for point-plane gap
International Nuclear Information System (INIS)
The electric field distribution for point-plane gap is modelled both for stressed point and stressed plane electrodes. In simulations, the influence of the discharge chamber walls is taken into account. The size of an avalanche and the corresponding current pulse are calculated. The results are compared with those got other field distribution approximations. (author)
CFD Simulation of Annular Centrifugal Extractors
Directory of Open Access Journals (Sweden)
S. Vedantam
2012-01-01
Full Text Available Annular centrifugal extractors (ACE, also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.
Gap junction modulation by extracellular signaling molecules: the thymus model
Directory of Open Access Journals (Sweden)
Alves L.A.
2000-01-01
Full Text Available Gap junctions are intercellular channels which connect adjacent cells and allow direct exchange of molecules of low molecular weight between them. Such a communication has been described as fundamental in many systems due to its importance in coordination, proliferation and differentiation. Recently, it has been shown that gap junctional intercellular communication (GJIC can be modulated by several extracellular soluble factors such as classical hormones, neurotransmitters, interleukins, growth factors and some paracrine substances. Herein, we discuss some aspects of the general modulation of GJIC by extracellular messenger molecules and more particularly the regulation of such communication in the thymus gland. Additionally, we discuss recent data concerning the study of different neuropeptides and hormones in the modulation of GJIC in thymic epithelial cells. We also suggest that the thymus may be viewed as a model to study the modulation of gap junction communication by different extracellular messengers involved in non-classical circuits, since this organ is under bidirectional neuroimmunoendocrine control.
International Nuclear Information System (INIS)
An investigation has been carried out concerning the transmission of thermal and fast neutrons in air filled annular ducts through laminated Fe-D2O shields. Measurements have been made with annular air gaps of 0.5, 1.0, 1.5 and 2.0 cm, at a duct length of half a meter. The neutron fluxes were determined with a foil activation technique. The thermal flux was theoretically and experimentally divided into three components, a streaming, a leakage and an albedo component. The fast flux was similarly divided into a streaming component and a 'leakage' component. A calculational model to predict the components was then developed and fitted, to the data obtained by experiments. The model reported here for prediction of neutron attenuation in ducted configurations may be applied to straight annular ducts of arbitrary dimensions and material configurations but is especially designed for the problems met with in short ducts
Bogdanovich, B. Yu.; L'vov, E. I.; Nesterovich, A. V.; Sukhanova, L. A.; Khlestkov, Yu. A.
2016-04-01
A scheme of forming an annular high-current relativistic beam (HCRB) from a directly propagating HCRB in a diode with magnetic insulation and toroidal chamber with a constant magnet is described. The code KARAT is used to analyze numerically the HCRB dynamics. It is demonstrated that for a proper relationship of the system parameters the directly propagating HCRB is rolled up into a torus.
Telzer, Eva H; Yuen, Cynthia; Gonzales, Nancy; Fuligni, Andrew J
2016-07-01
The acculturation gap-distress model purports that immigrant children acculturate faster than do their parents, resulting in an acculturation gap that leads to family and youth maladjustment. However, empirical support for the acculturation gap-distress model has been inconclusive. In the current study, 428 Mexican-American adolescents (50.2 % female) and their primary caregivers independently completed questionnaires assessing their levels of American and Mexican cultural orientation, family functioning, and youth adjustment. Contrary to the acculturation gap-distress model, acculturation gaps were not associated with poorer family or youth functioning. Rather, adolescents with higher levels of Mexican cultural orientations showed positive outcomes, regardless of their parents' orientations to either American or Mexican cultures. Findings suggest that youths' heritage cultural maintenance may be most important for their adjustment. PMID:26759225
International Nuclear Information System (INIS)
As the study of two-phase flows is required to assess or optimize the performance of many industrial systems in chemical, thermal or nuclear engineering, this research thesis in fluid mechanics aims at describing the evolution of a two-phase flow in a dispersed annular configuration when passing a convergent nozzle. The study focused on the elaboration of simple, one-dimensional and permanent flows, and is based on experiments performed in the case of a liquid annular injection. The author discusses the mapping of two-phase flows, proposes an overview of their modelling, and proposes a model with its instantaneous local equations and time- and space-averaged equations. He addresses the issues of closure laws for two-field models (friction laws on the walls and at the interfaces, discussion of published experimental results), and of mass transfer laws for three-field models. He reports the development of a droplet carryover rate law and the analysis of published experiments by using the three-field model
International Nuclear Information System (INIS)
For the purpose of the nuclear material accountancy and control for NUCEF: the Nuclear Fuel Cycle Safety Engineering Research Facility, the vessel calibration data analysis program: VESCAL is revised, and a new model for non-linear parts of annular and slab tanks is added to the program. The new model has three unknown parameters, and liquid level is expressed as a square root function with respect to liquid volume. Using the new model, an accurate calibration function on the level and volume data for non-linear parts of annular and slab tanks can be obtained with the smaller number of unknown parameters, compared with a polynomial function model. As a result of benchmark tests for this revision, it was proved that numerical results computed with VESCAL well agreed with those by a statistical analysis program package which is widely used. In addition, the new model would be useful for carrying out data analyses on the vessel calibration at the other bulk handling facilities as well as at NUCEF. This paper describes summary of the program, computational methods and results of benchmark tests concerning this revision. (author)
Thermal bidirectional gap probability model for row crop canopies and validation
Institute of Scientific and Technical Information of China (English)
YAN; Guangjian(阎广建); IANG; Lingmei(蒋玲梅); WANG; Jindi(王锦地); CHEN; Liangfu(陈良富); LI; Xiaowen(李小文)
2003-01-01
Based on the row structure model of Kimes and the mean gap probability model in single direction, we develop a bidirectional gap probability model for row crop canopies. A concept of overlap index is introduced in this model to consider the gaps and their correlation between the sun and view directions. Multiangular thermal emission data sets were measured in Shunyi, Beijing, and these data are used in model validation in this paper. By comparison with the Kimes model that does not consider the gap probability, and the model considering the gap in view direction only, it is found that our bidirectional gap probability model fits the field measurements over winter wheat much better.
Development of Dual Cooled Annular Fuel Temperature Analysis Program
Energy Technology Data Exchange (ETDEWEB)
Yang, Yong Sik; Shin, C. H.; Bang, J. G.; Kim, D. H.; Kim, S. K.; Lim, I. S.; Koo Yang Hyun [KAERI, Daejeon (Korea, Republic of)
2010-09-15
To calculate the temperature distribution of dual cooled annular fuel, the DUOS program has been developed. Various thermal hydraulic models to determine the inner channel and outer channel flow distribution were established based on equal pressure drop condition at the top of fuel rod. The effect of gap width change was considered by employing thermal deformation model of pellet and claddings. Heat conduction model in the pellet was solved by finite difference method to consider burnup and power difference according to pellet radius. Pellet temperature model was validated by comparison with calculated temperature profile, which was determined by analytical solution of heat conduction equation under controlled input condition. Accuracy of thermal hydraulic models of DUOS were validated by core sub-channel analysis code MATRA-AF. Coolant bulk temperature of inner/outer channel and pressure drop prediction results of DUOS program show good agreement with that of MATRA-AF. Further models should be added in DUOS program to describe dual cooled annular fuel in-pile behavior, but basic thermal analysis structure has been established successfully
Development of Dual Cooled Annular Fuel Temperature Analysis Program
International Nuclear Information System (INIS)
To calculate the temperature distribution of dual cooled annular fuel, the DUOS program has been developed. Various thermal hydraulic models to determine the inner channel and outer channel flow distribution were established based on equal pressure drop condition at the top of fuel rod. The effect of gap width change was considered by employing thermal deformation model of pellet and claddings. Heat conduction model in the pellet was solved by finite difference method to consider burnup and power difference according to pellet radius. Pellet temperature model was validated by comparison with calculated temperature profile, which was determined by analytical solution of heat conduction equation under controlled input condition. Accuracy of thermal hydraulic models of DUOS were validated by core sub-channel analysis code MATRA-AF. Coolant bulk temperature of inner/outer channel and pressure drop prediction results of DUOS program show good agreement with that of MATRA-AF. Further models should be added in DUOS program to describe dual cooled annular fuel in-pile behavior, but basic thermal analysis structure has been established successfully
Modeling of the Inductance of a Blumlein Circuit Spark Gap
Aboites, V.; Rendón, L.; Hernández, A. I.; Valdés, E.
2015-01-01
In this paper we present an analysis of the time-varying inductance in the spark gap of a Blumlein circuit. We assume several mathematical expressions to describe the inductance and compare theoretical and computational calculations with experimental results. The time-varying inductance is approximated by a constant, a straight line and two parables which differ in their concavity. This is the first time to our knowledge, in which the time-varying ignition inductance of a nitrogen laser is modeled.
Modeling of the Inductance of a Blumlein Circuit Spark Gap
International Nuclear Information System (INIS)
In this paper we present an analysis of the time-varying inductance in the spark gap of a Blumlein circuit. We assume several mathematical expressions to describe the inductance and compare theoretical and computational calculations with experimental results. The time-varying inductance is approximated by a constant, a straight line and two parables which differ in their concavity. This is the first time to our knowledge, in which the time-varying ignition inductance of a nitrogen laser is modeled
International Nuclear Information System (INIS)
Highlights: → Annular flows w/wo functional spacers are investigated by cold neutron imaging. → Liquid film thickness distribution on fuel pins and on spacer vanes is measured. → The influence of the spacers on the liquid film distributions has been quantified. → The cross-sectional averaged liquid hold-up significantly affected by the spacers. → The sapers affect the fraction of the entrained liquid hold up in the gas core. - Abstract: Dryout of the coolant liquid film at the upper part of the fuel pins of a boiling water reactor (BWR) core constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is both a safety concern and a limiting factor in the thermal power and thus for the economy of BWRs. We have investigated adiabatic, air-water annular flows in a scaled-up model of two neighboring subchannels as found in BWR fuel assemblies using cold-neutron tomography. The imaging of the double suchannel has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institute, Switzerland. Cold-neutron tomography is shown here to be an excellent tool for investigating air-water annular flows and the influence of functional spacers of different geometries on such flows. The high-resolution, high-contrast measurements provide the spatial distributions of the coolant liquid film thickness on the fuel pin surfaces as well as on the surfaces of the spacer vanes. The axial variations of the cross-section averaged liquid hold-up and its fraction in the gas core shows the effect of the spacers on the redistribution of the two phases.
Modeling for water penetration into narrow gap in CAMP code
International Nuclear Information System (INIS)
An analytical code, CAMP, is being developed at JAERI for thermo-fluiddynamics of a molten core in the lower plenum of the reactor pressure vessel (RPV). Models for the water penetration into narrow gaps based on the flooding of a two-phase flow have been recently incorporated in CAMP code. The in-vessel debris coolability experiments performed at Japan Atomic Energy Research Institute (JAERI), where an Al2O3 melt was poured into a water-filled lower head experimental vessel and the interfacial gap between the solidified Al2O3 and the vessel was supposed to form, were analyzed with CAMP code. It was found that temperature histories at the vessel outer surface were qualitatively reproduced using the water penetration model. The analysis also implied that an appropriate flooding correlation are needed to increase the predictability of CAMP code and that the steam generation in the interfacial gap, which largely influences on the flooding, was dominated by thermal radiation from the surface of the solidified Al2O3 to the penetrating water. (author)
Evaluation of Cost Models and Needs & Gaps Analysis
DEFF Research Database (Denmark)
Kejser, Ulla Bøgvad
2014-01-01
his report ’D3.1—Evaluation of Cost Models and Needs & Gaps Analysis’ provides an analysis of existing research related to the economics of digital curation and cost & benefit modelling. It reports upon the investigation of how well current models and tools meet stakeholders’ needs for calculating...... for amore efficient use of resources for digital curation. To facilitate and clarify the model evaluation the report first outlines a basic terminology and a generaldescription of the characteristics of cost and benefit models.The report then describes how the ten current and emerging cost and benefit...... breakdown costs. This is followed by an in depth analysis of stakeholders’ needs for financial information derived from the 4C project stakeholder consultation.The stakeholders’ needs analysis indicated that models should:• support accounting, but more importantly they should enable budgeting• be able to...
Dazhuan Wu; Leqin Wang; Qinglei Jiang; Lulu Zhai
2011-01-01
The current paper studies the influence of annular seal flow on the transient response of centrifugal pump rotors during the start-up period. A single rotor system and three states of annular seal flow were modeled. These models were solved using numerical integration and finite difference methods. A fluid-structure interaction method was developed. In each time step one of the three annular seal models was chosen to simulate the annular seal flow according to the state of rotor systems. The ...
Generalized granuloma annulare
Directory of Open Access Journals (Sweden)
Khatri M
1995-01-01
Full Text Available A 35-years-old female patient had generalized pruritic papular lesions, distributed like dermatitis herpetiformis for last 4 years. Histopathologic changes were typical of granuloma annulare with negative results of direct immunofluorescence. The patient did not have association of diabetes mellitus or any other systemic disease. She failed to respond to dapsone therapy and 13-cis-retinoic acid.
Oscillating annular liquid membranes
International Nuclear Information System (INIS)
The response of annular liquid membranes (e.g. used as protection systems in laser fusion reactors) to sinusoidal mass flow rate fluctuations at the nozzle exit is analyzed as a function of the amplitude and frequency of the axial velocity fluctuations at the nozzle exit and thermodynamic compression of the gas enclosed by the membrane. The pressure of the gases enclosed by the annular membrane and the axial distance at which the annular membrane merges on the symmetry axis are periodic functions of time which have the same period as that of the mass flow rate fluctuations at the nozzle exit. They are also nearly sinusoidal functions of time for small amplitudes of the mass flow rate fluctuations at the nozzle exit, and exhibit delay and lag times with respect to the sinusoidal axial velocity fluctuations at the nozzle exit. The delay and the lag times are functions of the amplitude and frequency of the mass flow rate fluctuations at the nozzle exit and the polytropic exponent. The amplitudes of both the pressure of the gases enclosed by the annular liquid membrane and the convergence length increase and decrease, resp., as the amplitude and frequency of the mass flow rate fluctuations at the nozzle exit, resp., are increased. They also increase as the polytropic exponent is increased. (orig.)
U.S. Geological Survey Gap Analysis Program Species Distribution Models
U.S. Geological Survey, Department of the Interior — GAP distribution models represent the areas where species are predicted to occur based on habitat associations. GAP distribution models are the spatial arrangement...
Linking Gap Model with MODIS Biophysical Products for Biomass Estimation
Wang, D.; Sun, G.; Cai, Y.; Guo, Z.; Fu, A.; Ni, W.; Liu, D.
With the development of earth observation technology and data processing technology biophysical data from remote sensing means such as MODIS LAI and NPP are accessible now However it is still difficult for direct measurement of biomass from remote sensors One possibility for overcoming this problem is using ecological models to link the vegetation parameters currently available from remote sensing to biomass In this paper a combined work is done for estimating forest biomass A calibrated gap model ZELIG was run to simulate the forest development in a temperate forested area in NE China The output relationship between age and biomass was linked to registered MODIS LAI NPP and land cover type images of the same area From the above work forest age or biomass was estimated from existing remote sensed data Obviously there is a lot of work to be done such as optimal combination of biophysical parameters to improve the linkage between MODIS product and ecological modeling
Lilley, D. G.; Sander, G. F.
1983-01-01
In connection with the desirability of optimizing the design of a gas turbine combustion chamber, there exists a need for a more complete understanding of the fluid dynamics of the flow in such chambers. In order to satisfy this need, experimental and theoretical research is being conducted with the objective to study two-dimensional axisymmetric geometries under low speed, nonreacting, turbulent, swirling flow conditions. The flow enters the test section and proceeds into a larger chamber. Inlet swirl vanes are adjustable to a variety of vane angles. The present investigation concentrates on the time-mean flow characteristics which are generated by the upstream annular swirler. The investigation makes use of a five-hole pitot probe technique. A theoretical analysis of swirl numbers associated with several idealized exit velocity profiles is included, and values of the ratio of maximum swirl velocity to maximum axial velocity at different swirl strengths are given for each case.
An alternative finite element model for simulation of frictional gap
International Nuclear Information System (INIS)
This study is an attempt to modeling a frictional gap in a crack closure process under compressive loading conditions in which the crack surfaces are in touch and the effects of friction between them are significant. An iterative finite element (FE) solution is developed to model a finite crack in an interfacial layer with varying material properties. A mere application of a Lagrange multiplier formulation (node-to-node, NTN, or node-to-segment, NTS) in a developed FE framework to fulfill the contact constraints between contacting surfaces is discussed which improves the penalty formulation used in ANSYS. We then argue that the penalty formulation allows for a certain amount of crack surface interpenetration whereas the Lagrange multiplier formulation fulfils the contact constraints more accurately. This technique is easy to implement and offers higher accuracy than the equivalent FE solution, available in commercial FE software such as ANSYS 9.0, to the same system.
Stability of cantilevered coaxial shells with internal and annular flow
International Nuclear Information System (INIS)
This paper is a theoretical study of the stability of cantilevered coaxial cylindrical shells conveying incompressible fluid in the annular space in- between and within the inner shell. The viscous effects of the mean flow are taken into account, but the perturbations of the equilibrium state on the basis of which stability is assessed is carried out by means of potential flow theory, thus neglecting unsteady viscous effects which are known to become important for narrow annular flows. Shell displacements are described by Flugge's equations of motion. Solution of the coupled fluid-structure equations is carried out by means of the Fourier Transform Method. The main finding of this research is that stability is lost by flutter for internal flow, according to both the inviscid and viscous variants of the theory; for annular flow, however, whereas inviscid theory predicts loss of stability by flutter, viscous theory (with dissipative effects included) predicts that the shell loses stability by divergence and then, at appreciably higher flow, by flutter. Reduction of the annular gap generally destabilizes the system; while increased steady viscous effects slightly stabilize the system for internal flow, they strongly destabilize it for annular flow. Increasing the length of the shell destabilizes the system for both internal and annular flows. The presence of internal flow in addition to annular flow tends to stabilize the system vis-a-vis the case of annular flow, but only at low flow velocities, having the opposite effect at higher flows; the same effects arise when the main flow is internal and an annular flow added to the system
Directory of Open Access Journals (Sweden)
Srisharan G. Govindarajan
2013-01-01
Full Text Available This paper considers a composite cylindrical structure, with low-enriched uranium (LEU foil enclosed between two aluminum 6061-T6 cylinders. A recess is cut all around the outer circumference of the inner tube to accommodate the LEU foil of open-cross section. To obtain perfect contact at the interfaces of the foil and the tubes, an internal pressure is applied to the inner tube, thereby plastically and elastically deforming it. The residual stresses resulting from the assembly process are used along with a thermal stress model to predict the stress margins in the cladding during irradiation. The whole process was simulated as a steady-state two-dimensional problem using the commercial finite element code Abaqus FEA. The irradiation behavior of the annular target has been presented, and the effect of the assembly residual stresses has been discussed.
Confocal Annular Josephson Tunnel Junctions
Monaco, Roberto
2016-04-01
The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.
Confocal Annular Josephson Tunnel Junctions
Monaco, Roberto
2016-09-01
The physics of Josephson tunnel junctions drastically depends on their geometrical configurations and here we show that also tiny geometrical details play a determinant role. More specifically, we develop the theory of short and long annular Josephson tunnel junctions delimited by two confocal ellipses. The behavior of a circular annular Josephson tunnel junction is then seen to be simply a special case of the above result. For junctions having a normalized perimeter less than one, the threshold curves in the presence of an in-plane magnetic field of arbitrary orientations are derived and computed even in the case with trapped Josephson vortices. For longer junctions, a numerical analysis is carried out after the derivation of the appropriate motion equation for the Josephson phase. We found that the system is modeled by a modified and perturbed sine-Gordon equation with a space-dependent effective Josephson penetration length inversely proportional to the local junction width. Both the fluxon statics and dynamics are deeply affected by the non-uniform annulus width. Static zero-field multiple-fluxon solutions exist even in the presence of a large bias current. The tangential velocity of a traveling fluxon is not determined by the balance between the driving and drag forces due to the dissipative losses. Furthermore, the fluxon motion is characterized by a strong radial inward acceleration which causes electromagnetic radiation concentrated at the ellipse equatorial points.
On the modeling of narrow gaps using the standard BEM
DEFF Research Database (Denmark)
Henriquez, Vicente Cutanda; Juhl, P.M.; Jacobsen, Finn
2001-01-01
the literature. A simple integration technique that can extend the range of thicknesses/widths tractable by the otherwise unmodified standard formulation is presented and tested. This technique is valid for both cases. The modeling of acoustic transducers Like sound intensity probes and condenser......Numerical methods based on the Helmholtz integral equation are well suited for solving acoustic scattering and diffraction problems at relatively low frequencies. However, it is well known that the standard method becomes degenerate if the objects that disturb the sound field are very thin. This...... paper makes use of a standard axisymmetric Helmholtz integral equation formulation and its boundary element method (BEM) implementation to study the behavior of the method on two test cases: a thin rigid disk of variable thickness and two rigid cylinders separated by a gap of variable width. Both...
Institute of Scientific and Technical Information of China (English)
李斌; 何安定; 王跃社; 周芳德
2001-01-01
The friction resistance performance of the single-phase flow and double-phase flow was studied when R-113 rized vertically in tho narrow-gap annular tube with various sizes, both single-phase flow and double-phase flow were different from the common flow in tubes. The transition Re Number of the flow in the narrow-gap was 500-1000,the friction resistance of double-bhase flow was bigger than that of the flow in common cycle tubes.Some important data were described,and the relation was proposed for calculating the friction resistance of the single-phase flow and the double-phase flow in the narrow-gap tube annular, the biggest relative error between the testing value and the calculating value was not more than 7.2％.%主要研究不同尺寸窄缝环形管内R-113垂直向上单相和两相流动沸腾时的摩擦阻力特性。研究发现，无论是单相还是两相流动都不同于普通管内流动，流体在窄缝环形管内流动的转变雷诺数Re为500～1000，两相流动摩擦阻力比普通圆管内的大。研究获取了重要的实验数据，并提出了计算窄缝环形管内单相和两相流动摩擦阻力的关系式，试验值与计算值的最大相对误差不超过7.2％。
Modeling charged defects inside density functional theory band gaps
International Nuclear Information System (INIS)
Density functional theory (DFT) has emerged as an important tool to probe microscopic behavior in materials. The fundamental band gap defines the energy scale for charge transition energy levels of point defects in ionic and covalent materials. The eigenvalue gap between occupied and unoccupied states in conventional DFT, the Kohn–Sham gap, is often half or less of the experimental band gap, seemingly precluding quantitative studies of charged defects. Applying explicit and rigorous control of charge boundary conditions in supercells, we find that calculations of defect energy levels derived from total energy differences give accurate predictions of charge transition energy levels in Si and GaAs, unhampered by a band gap problem. The GaAs system provides a good theoretical laboratory for investigating band gap effects in defect level calculations: depending on the functional and pseudopotential, the Kohn–Sham gap can be as large as 1.1 eV or as small as 0.1 eV. We find that the effective defect band gap, the computed range in defect levels, is mostly insensitive to the Kohn–Sham gap, demonstrating it is often possible to use conventional DFT for quantitative studies of defect chemistry governing interesting materials behavior in semiconductors and oxides despite a band gap problem
Energy Technology Data Exchange (ETDEWEB)
G. Terrones; F.J. Souto; R.F. Shea; M.W.Burkett; E.S. Idar
2005-09-30
In order to understand the implications that cookoff of plastic-bonded explosive-9501 could have on safety assessments, we analyzed the available data from the large-scale annular cookoff (LSAC) assembly series of experiments. In addition, we examined recent data regarding hypotheses about pre-ignition that may be relevant to post-ignition behavior. Based on the post-ignition data from Shot 6, which had the most complete set of data, we developed an approximate equation of state (EOS) for the gaseous products of deflagration. Implementation of this EOS into the multimaterial hydrodynamics computer program PAGOSA yielded good agreement with the inner-liner collapse sequence for Shot 6 and with other data, such as velocity interferometer system for any reflector and resistance wires. A metric to establish the degree of symmetry based on the concept of time of arrival to pin locations was used to compare numerical simulations with experimental data. Several simulations were performed to elucidate the mode of ignition in the LSAC and to determine the possible compression levels that the metal assembly could have been subjected to during post-ignition.
Effect of annular secondary conductor in a linear electromagnetic stirrer
Indian Academy of Sciences (India)
R Madhavan; V Ramanarayanan
2008-10-01
This paper presents the variation of average axial force density in the annular secondary conductor of a linear electromagnetic stirrer. Different geometries of secondaries are considered for numerical and experimental validation namely, 1. hollow annular ring, 2. annular ring with a solid cylinder and 3. solid cylinder. Experimental and numerical simulations are performed for a 2-pole in house built 15 kW linear electromagnetic stirrer (EMS). It is observed for a supply current of 200 A at 30 Hz the force densities in the hollow annular ring is 67% higher than the equivalent solid cylinder. The same values are 33% for annular ring with a solid cylinder. Force density variation with supply frequency and current are also reported. Numerical simulations using ﬁnite element model are validated with experimental results.
Directory of Open Access Journals (Sweden)
Ekbal Rashid
2013-06-01
Full Text Available This paper tries to introduce a new mathematical model to understand the state of quality of software by calculating parameters such as the time gap and quality gap with relation to some predefinedstandard software quality or in relation to some chalked out software quality plan. The paper also suggests methods to calculate the difference in quality of the software being developed and the modelsoftware which has been decided upon as the criteria for comparison. These methods can be employed to better understand the state of quality as compared to other standards. In order to obtain the graphical representation of data we have used Microsoft office 2007 graphical chart. Which facilitate easy simulation of time and quality gap.
Principle of radial transport in low temperature annular plasmas
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yunchao, E-mail: yunchao.zhang@anu.edu.au; Charles, Christine; Boswell, Rod [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Bldg 60, Mills Road, Australian Capital Territory 2601 (Australia)
2015-07-15
Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electric field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number.
Fabrication and Resintering of Annular UO2 Pellet
International Nuclear Information System (INIS)
Nuclear fuel is one of the most important components in a PWR affecting its safety and economy. The traditional PWR fuel pellet has a shape of cylindrical tablets of about 800 μm in diameter with a chamfer and dishes. A significant reduction in its failure rate has resulted from the improvements in fuel and cladding quality. Enhanced fuel assembly design allowed appreciable power density increases. However, it is difficult to achieve a significant increase of a power density under the current fuel pin design. Recently, Massachusetts Institute of Technology (MIT) has proposed an annular UO2 fuel with an internal cooling of each fuel rod. Annular fuel pellets with a voided central region have been used in VVER reactors without an internal cooling. Annular fuels with both internal and external cooling have been proposed for high temperature gas cooled reactors. However, commercial PWR reactors have not used such annular internally and externally cooled fuel rods, yet. There must be a lot of considerations in the various fields to introduce an annular internally and externally cooled fuel to commercial PWR reactors. The dimension tolerance and the thermal stability of a pellet are very important from the viewpoint of fabrication technology, because they have an influence on the size of the gap between the pellet and the inner/outer claddings. In this study, annular UO2 pellets with various densities were fabricated and then a resintering test was conducted. The changes of dimension and density of the sintered pellets were characterized
Model-based Measures of Output Gap: Application to the Thai Economy
Vimut Vanitcharearnthum
2012-01-01
In this paper we compare two model-based measures of the output gap. The first measure, as proposed by Gali (2011), defines output gap as the difference between actual output and the output level that would be if the economy operates under a perfectly competitive market without price or wage stickiness. We used annual data of relevant variables for Thailand and computed the output gap under this approach. The calculated output gap for Thailand shows that the Thai economy performs consistently...
Modeling GD-1 Gaps in a Milky-Way Potential
Carlberg, Raymond G
2015-01-01
The GD-1 star stream is currently the best available for identifying density fluctuations, "gaps", along its length as a test of the LCDM prediction of large numbers of dark matter sub-halos orbiting in the halo. Density variations of some form are present, since the variance of the density along the stream is three times that expected from the empirically estimated variation in the filtered mean star counts. The density variations are characterized with filters that approximate the shape of sub-halo induced stream gaps, which locates gaps and measures their amplitude, leading to a measurement of the distribution of gap widths. To gain understanding of the gap width distribution, a suite of n-body simulations for a GD-1 like orbit in a Milky Way-like potential provides a dynamically realistic statistical prediction of the gap distribution. The simulations show that every location in the stream has been disturbed to some degree by a sub-halo. The small gaps emerging from the filtering are largely noise. Larger...
Bridging the gap with the five-factor model.
Costa, Paul T; McCrae, Robert R
2010-04-01
Comments on the original article Personality traits and the classification of mental Disorders: Toward a more complete integration in DSM-5 and an empirical model of psychopathology by Robert F. Krueger and Nicholas R. Eaton (see record 2010-13810-003). Some researchers had hoped the forthcoming Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) would ask psychiatrists (and the clinical psychologists and researchers who are also tied to the DSM) to leap the gap and embrace a trait-based taxonomy of personality pathology (Widiger & Trull, 2007). Krueger and Eaton (pp. 97-118, this issue) take a more pragmatic stance: They hope to coax psychiatrists across by introducing personality dimensions as an adjunct to familiar PD types; they envision that DSM-5 might serve "as a bridge" (p. 110, this issue) to a fully dimensional Diagnostic and Statistical Manual of Mental Disorders, Sixth Edition (DSM-6). We acknowledge the wisdom of this strategy and suggest ways to strengthen it. PMID:22448624
Modeling of Photonic Band Gap Crystals and Applications
Energy Technology Data Exchange (ETDEWEB)
Ihab Fathy El-Kady
2002-08-27
In this work, the authors have undertaken a theoretical approach to the complex problem of modeling the flow of electromagnetic waves in photonic crystals. The focus is to address the feasibility of using the exciting phenomena of photonic gaps (PBG) in actual applications. The authors start by providing analytical derivations of the computational electromagnetic methods used in their work. They also present a detailed explanation of the physics underlying each approach, as well as a comparative study of the strengths and weaknesses of each method. The Plane Wave expansion, Transfer Matrix, and Finite Difference time Domain Methods are addressed. They also introduce a new theoretical approach, the Modal Expansion Method. They then shift the attention to actual applications. They begin with a discussion of 2D photonic crystal wave guides. The structure addressed consists of a 2D hexagonal structure of air cylinders in a layered dielectric background. Comparison with the performance of a conventional guide is made, as well as suggestions for enhancing it. The studies provide an upper theoretical limit on the performance of such guides, as they assumed no crystal imperfections and non-absorbing media. Next, they study 3D metallic PBG materials at near infrared and optical wavelengths. The main objective is to study the importance of absorption in the metal and the suitability of observing photonic band gaps in such structures. They study simple cubic structures where the metallic scatters are either cubes or interconnected metallic rods. Several metals are studied (aluminum, gold, copper, and silver). The effect of topology is addressed and isolated metallic cubes are found to be less lossy than the connected rod structures. The results reveal that the best performance is obtained by choosing metals with a large negative real part of the dielectric function, together with a relatively small imaginary part. Finally, they point out a new direction in photonic crystal
A bi-directional gap model for simulating the directional thermal radiance of row crops
Institute of Scientific and Technical Information of China (English)
CHEN; Liangfu; (陈良富); LIU; Qinhuo; (柳钦火); FAN; Wenjie; (范闻捷); LI; Xiaowen; (李小文); XIAO; Qing; (肖青); YAN; Guangjian; (闫广建); TIAN; Guoliang; (田国良)
2002-01-01
Row crops are a kind of typical vegetation canopy between discrete canopy and continuous canopy. Kimes et al. studied the directional thermal radiation of row crops using the geometrical optical model, which simplified row structure as "box" and neglected the gap among foliage and did not consider the emissivity effects. In this work we take account of the gaps along illumination and viewing directions and propose a bi-direction gap model on the basis of the idea of gap probability of discrete vegetation canopy introduced by "Li-Strahler" and inter-correlation of continuous vegetation developed by Kuusk. It can be used to explain "hot spot" effects in thermal infrared region. The gap model has been validated by field experiment on winter wheat planted in shape of rows and results show that the gap model is better than Kimes' model in describing the directionality of thermal infrared emission for row crops.
Directory of Open Access Journals (Sweden)
JIMITKUMAR PATEL
2016-01-01
Full Text Available This paper theoretically analyzes the combined effect of slip velocity and surface roughness on the performance of Jenkins model based ferrofluid squeeze film in curved annular plates. The effect of slip velocity has been studied resorting to the slip model of Beavers and Joseph. The stochastically averaging method of Christensen and Tonders has been deployed for studying the effect of surface roughness. The pressure distribution is derived by solving the associated stochastically averaged Reynolds type equation with suitable boundary conditions, leading to the computation of load carrying capacity. The graphical representations reveal that the transverse surface roughness adversely affects the bearing performance. However, Jenkins model based ferrofluid lubrication offers some scopes in minimizing this adverse effect when the slip parameter is kept at minimum. Of course, an appropriate choice of curvature parameters adds to this positive effect in the case of negatively skewed roughness. Moreover, it is established that this type of bearing system supports certain amount of load; even when there is no flow which does not happen in the case of conventional lubricant based bearing system.
Venkatakrishnan, S V; Drummy, Lawrence F; Jackson, Michael A; De Graef, Marc; Simmons, Jeff; Bouman, Charles A
2013-11-01
High angle annular dark field (HAADF)-scanning transmission electron microscope (STEM) data is increasingly being used in the physical sciences to research materials in 3D because it reduces the effects of Bragg diffraction seen in bright field TEM data. Typically, tomographic reconstructions are performed by directly applying either filtered back projection (FBP) or the simultaneous iterative reconstruction technique (SIRT) to the data. Since HAADF-STEM tomography is a limited angle tomography modality with low signal to noise ratio, these methods can result in significant artifacts in the reconstructed volume. In this paper, we develop a model based iterative reconstruction algorithm for HAADF-STEM tomography. We combine a model for image formation in HAADF-STEM tomography along with a prior model to formulate the tomographic reconstruction as a maximum a posteriori probability (MAP) estimation problem. Our formulation also accounts for certain missing measurements by treating them as nuisance parameters in the MAP estimation framework. We adapt the iterative coordinate descent algorithm to develop an efficient method to minimize the corresponding MAP cost function. Reconstructions of simulated as well as experimental data sets show results that are superior to FBP and SIRT reconstructions, significantly suppressing artifacts and enhancing contrast. PMID:23955748
Institute of Scientific and Technical Information of China (English)
王一平; 陈为强; 黄群武; 冯加和; 崔勇
2016-01-01
Based on the momentum conservation approach, a theoretical model was developed to predict the su-perficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular exter-nal-loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm2/s(2cs-SiO)and 5.0 mm2/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predic-tions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to pre-dict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.
Hydrogeologic Model for the Gable Gap Area, Hanford Site
Energy Technology Data Exchange (ETDEWEB)
Bjornstad, Bruce N.; Thorne, Paul D.; Williams, Bruce A.; Last, George V.; Thomas, Gregory S.; Thompson, Michael D.; Ludwig, Jami L.; Lanigan, David C.
2010-09-30
Gable Gap is a structural and topographic depression between Gable Mountain and Gable Butte within the central Hanford Site. It has a long and complex geologic history, which includes tectonic uplift synchronous with erosional downcutting associated with the ancestral Columbia River during both Ringold and Cold Creek periods, and by the later Ice Age (mostly glacial Lake Missoula) floods. The gap was subsequently buried and partially backfilled by mostly coarse-grained, Ice Age flood deposits (Hanford formation). Erosional remnants of both the Ringold Formation and Cold Creek unit locally underlie the high-energy flood deposits. A large window exists in the gap where confined basalt aquifers are in contact with the unconfined suprabasalt aquifer. Several paleochannels, of both Hanford and Ringold Formation age, were eroded into the basalt bedrock across Gable Gap. Groundwater from the Central Plateau presently moves through Gable Gap via one or more of these shallow paleochannels. As groundwater levels continue to decline in the region, groundwater flow may eventually be cut off through Gable Gap.
International Nuclear Information System (INIS)
High-thermal performance PWR (pressurized water reactor) spacer grids require both low pressure loss and high critical heat flux (CHF) properties. Numerical investigations on the effect of angles and position of mixing vanes and to understand in more details the main physical phenomena (wall boiling, entrainment of bubbles in the wakes, recondensation) are required. In the field of fuel assembly analysis or design by means of CFD codes, the overwhelming majority of the studies are carried out using two-equation eddy viscosity models (EVM), especially the standard K-ε model, while the use of Reynolds Stress Transport Models (RSTM) remains exceptional. But extensive testing and application over the past three decades have revealed a number of shortcomings and deficiencies in eddy viscosity models. In fact, the K-ε model is totally blind to rotation effects and the swirling flows can be regarded as a special case of fluid rotation. This aspect is crucial for the simulation of a hot channel in a fuel assembly. In fact, the mixing vanes of the spacer grids generate a swirl in the coolant water, to enhance the heat transfer from the rods to the coolant in the hot channels and to limit boiling. First, we started to evaluate computational fluid dynamics results against the AGATE-mixing experiment: single-phase liquid water tests, with Laser-Doppler liquid velocity measurements upstream and downstream of mixing blades. The comparison of computed and experimental azimuthal (circular component in a horizontal plane) liquid velocity downstream of a mixing vane for the AGATE-mixing test shows that the rotating flow is qualitatively well reproduced by CFD calculations but azimuthal liquid velocity is underestimated with the K-ε model. Before comparing performance of EVM and RSTM models on fuel assembly geometry, we performed calculations with a simpler geometry, the ASU-annular channel case. A wall function model dedicated to boiling flows is also proposed.
Axisymmetric annular curtain stability
International Nuclear Information System (INIS)
A temporal stability analysis was carried out to investigate the stability of an axially moving viscous annular liquid jet subject to axisymmetric disturbances in surrounding co-flowing viscous gas media. We investigated in this study the effects of inertia, surface tension, the gas-to-liquid density ratio, the inner-to-outer radius ratio and the gas-to-liquid viscosity ratio on the stability of the jet. With an increase in inertia, the growth rate of the unstable disturbances is found to increase. The dominant (or most unstable) wavenumber decreases with increasing Reynolds number for larger values of the gas-to-liquid viscosity ratio. However, an opposite tendency for the most unstable wavenumber is predicted for small viscosity ratio in the same inertia range. The surrounding gas density, in the presence of viscosity, always reduces the growth rate, hence stabilizing the flow. There exists a critical value of the density ratio above which the flow becomes stable for very small viscosity ratio, whereas for large viscosity ratio, no stable flow appears in the same range of the density ratio. The curvature has a significant destabilizing effect on the thin annular jet, whereas for a relatively thick jet, the maximum growth rate decreases as the inner radius increases, irrespective of the surrounding gas viscosity. The degree of instability increases with Weber number for a relatively large viscosity ratio. In contrast, for small viscosity ratio, the growth rate exhibits a dramatic dependence on the surface tension. There is a small Weber number range, which depends on the viscosity ratio, where the flow is stable. The viscosity ratio always stabilizes the flow. However, the dominant wavenumber increases with increasing viscosity ratio. The range of unstable wavenumbers is affected only by the curvature effect. (paper)
Analysis of a Segmented Annular Coplanar Capacitive Tilt Sensor with Increased Sensitivity.
Guo, Jiahao; Hu, Pengcheng; Tan, Jiubin
2016-01-01
An investigation of a segmented annular coplanar capacitor is presented. We focus on its theoretical model, and a mathematical expression of the capacitance value is derived by solving a Laplace equation with Hankel transform. The finite element method is employed to verify the analytical result. Different control parameters are discussed, and each contribution to the capacitance value of the capacitor is obtained. On this basis, we analyze and optimize the structure parameters of a segmented coplanar capacitive tilt sensor, and three models with different positions of the electrode gap are fabricated and tested. The experimental result shows that the model (whose electrode-gap position is 10 mm from the electrode center) realizes a high sensitivity: 0.129 pF/° with a non-linearity of <0.4% FS (full scale of ± 40°). This finding offers plenty of opportunities for various measurement requirements in addition to achieving an optimized structure in practical design. PMID:26805844
International Nuclear Information System (INIS)
Inverted-annular film-boiling (IAFB) is one of the post-burnout heat transfer modes taking place, in particular, during the reflooding phase of the loss-of-coolant accident, when the liquid at the quench front is subcooled. Under IAFB conditions, a continuous liquid core is separated from the wall by a superheated vapour film. The heat transfer rate in IAFB is influenced by the flooding rate, liquid subcooling, pressure, and the wall geometry and temperature. These influences can be accounted by a two-fluid model with physically sound closure laws for mass, momentum and heat transfer between the wall, the vapour film, the vapour-liquid interface, and the liquid core. The applicability of existing IAFB two-fluid models is limited. This is attributed to shortcomings in the description of heat transfer within the liquid core, to use of certain correlations outside their validity range, and to a limited use of experimental information on IAFB. The usual approach has been to develop models employing generally applicable closure laws including, however, adjustable parameters, and to adjust these using global experimental results. The present approach has been to develop IAFB-specific closure laws in such a form that they could be adjusted separately using detailed, IAFB-relevant, experimental result. Steady-state results, including heat flux, wall temperature and void fraction data have been used for the adjustment. A key issue in IAFB modeling is to predict how the heat flux reaching the vapour-liquid interface is split into a liquid heating term and a vaporization term. In the model proposed, convective liquid heating is related to the liquid velocity relative to the interface, and not to the absolute liquid velocity, as in previous models. This relative velocity is deduced from the interfacial shear stress, using the liquid-interface friction law. With this modification, the prediction of the experimental trends is greatly improved. (author) figs., tabs., refs
International Nuclear Information System (INIS)
A supercritical-water-cooled reactor (SCWR) is a high-temperature, high-pressure water cooled reactor that operates above the critical pressure of water. In order to perform efficiently the thermal design of the SCWR, it is important to assess the thermal hydraulics in rod bundles of the core. Experimental conditions of mockup tests, however, may be limited because of technical and financial reasons. Therefore, it is required to establish an analytical design technique that can extrapolate experimental data to various design conditions of the reactor. Japan Atomic Energy Agency (JAEA) has improved the three-dimensional two-fluid model analysis code ACE-3D, which was originally developed for the two-phase flow thermal hydraulics of light water reactors, to handle the thermal hydraulic properties of water in the supercritical region. In the present study, heat transfer experiments of supercritical water flowing in a vertical annular channel around a heater pin, which were performed at JAEA, were analyzed with the improved ACE-3D to assess the prediction performance of the code. As a result, it was implied that the ACE-3D code is applicable to the prediction of wall temperatures of a single rod that simulates the fuel bundle geometry of the SCWR core. (author)
Modelling of hydrocarbon redeposition in the gaps of castellated structures
International Nuclear Information System (INIS)
Castellated armor tiles are proposed for the first wall and the divertor area in ITER. However, there is a critical issue of fuel (tritium) retention and impurity transport in the gaps between the castellated tiles. The previous calculation reproduces the tritium profiles observed on the gap sides of the TFTR bumper limiter. In this study, we have performed a simulation calculation of transport and deposition of hydrocarbons on the castellated structure in order to understand the mechanisms of co-deposition and to mitigate carbon deposition in the gaps by changing castellated geometry. Reflection/sticking coefficients of the tile surface in realistic conditions were investigated by using molecular dynamics (MD) of collisions with all hydrocarbons that result from chemical sputtering. A new castellation geometry of unit cells with a tilted surface is proposed and the optimization of the shape of the cell is very likely to work to minimize the redeposition rate in the gaps. The tile geometry is important to reduce the in-vessel tritium inventory for the safety operation of fusion reactors. (author)
Annular Hybrid Rocket Motor Project
National Aeronautics and Space Administration — Engineers at SpaceDev have conducted a preliminary design and analysis of a proprietary annular design concept for a hybrid motor. A U.S. Patent application has...
Manufacture of annular cermet articles
Forsberg, Charles W.; Sikka, Vinod K.
2004-11-02
A method to produce annular-shaped, metal-clad cermet components directly produces the form and avoids multiple fabrication steps such as rolling and welding. The method includes the steps of: providing an annular hollow form with inner and outer side walls; filling the form with a particulate mixture of ceramic and metal; closing, evacuating, and hermetically sealing the form; heating the form to an appropriate temperature; and applying force to consolidate the particulate mixture into solid cermet.
Non newtonian annular alloy solidification in mould
Energy Technology Data Exchange (ETDEWEB)
Moraga, Nelson O.; Garrido, Carlos P. [Universidad de La Serena, Departamento de Ingenieria Mecanica, La Serena (Chile); Castillo, Ernesto F. [Universidad de Santiago de Chile, Departamento de Ingenieria Mecanica, Santiago (Chile)
2012-08-15
The annular solidification of an aluminium-silicon alloy in a graphite mould with a geometry consisting of horizontal concentric cylinders is studied numerically. The analysis incorporates the behavior of non-Newtonian, pseudoplastic (n=0.2), Newtonian (n=1), and dilatant (n=1.5) fluids. The fluid mechanics and heat transfer coupled with a transient model of convection diffusion are solved using the finite volume method and the SIMPLE algorithm. Solidification is described in terms of a liquid fraction of a phase change that varies linearly with temperature. The final results make it possible to infer that the fluid dynamics and heat transfer of solidification in an annular geometry are affected by the non-Newtonian nature of the fluid, speeding up the process when the fluid is pseudoplastic. (orig.)
Interfacial friction in low flowrate vertical annular flow
International Nuclear Information System (INIS)
During boil-off and reflood transients in nuclear reactors, the core liquid inventory and inlet flowrate are largely determined by the interfacial friction in the reactor core. For these transients, annular flow occurs at relatively modest liquid flowrates and at the low heat fluxes typical of decay heat conditions. The resulting low vapor Reynolds numbers, are out of the data range used to develop the generally accepted interfacial friction relations for annular flow. In addition, most existing annular flow data comes from air/liquid adiabatic experiments with fully developed flows. By contrast, in a reactor core, the flow is continuously developing along the heated length as the vapor flowrate increases and the flow regimes evolve from bubbly to annular flow. Indeed, the entire annular flow regime may exist only over tens of L/D's. Despite these limitations, many of the advanced reactor safety analysis codes employ the Wallis model for interfacial friction in annular flow. Our analyses of the conditions existing at the end-of-reflood in the PERICLES tests have indicated that the Wallis model seriously underestimates the interfacial shear for low vapor velocity cocurrent upflow. To extend the annular flow data base to diabatic low flowrate conditions, the DADINE tests were re-analyzed. In these tests, both pressure drop and local cross-section averaged void fractions were measured. Thus, both the wall and interfacial shear can be deduced. Based on the results of this analysis, a new correlation is proposed for interfacial friction in annular flow. (authors). 5 figs., 12 refs
Dilemma of Facts and Perceptions: The Crisis Communication Model of Expectation Gaps
Directory of Open Access Journals (Sweden)
Rui-Xiang Wang
2015-11-01
Full Text Available Crisis communication theories suggest that crisis communications must appeal to publics’ perceptions and expectations. But in crisis there could be gaps between communicators and audiences about communicated objects. There were two kinds of gaps could happen: crisis situations and expected strategies. The gaps between the organization and publics in crisis communication dynamic are still unexplored. This research designed virtual crisis situations and communication strategies, surveyed the subject’s responses, analysed how gaps influence the communication effect, found the acceptability of explanations was crucial of crisis communication effect. This research constructed a model, theoretical and practical implications also discussed.
Capacity Prediction Model Based on Limited Priority Gap-Acceptance Theory at Multilane Roundabouts
Directory of Open Access Journals (Sweden)
Zhaowei Qu
2014-01-01
Full Text Available Capacity is an important design parameter for roundabouts, and it is the premise of computing their delay and queue. Roundabout capacity has been studied for decades, and empirical regression model and gap-acceptance model are the two main methods to predict it. Based on gap-acceptance theory, by considering the effect of limited priority, especially the relationship between limited priority factor and critical gap, a modified model was built to predict the roundabout capacity. We then compare the results between Raff’s method and maximum likelihood estimation (MLE method, and the MLE method was used to predict the critical gaps. Finally, the predicted capacities from different models were compared, with the observed capacity by field surveys, which verifies the performance of the proposed model.
The influence of annular seal clearance to the critical speed of the multistage pump
International Nuclear Information System (INIS)
In the multistage pump of high head, pressure difference in two ends of annular seal clearance and rotor eccentric would produce the sealing fluid force, the effect of which can be expressed by a damping and stiffness coefficient. It has a great influence on the critical speed of the rotor system. In order to research the influence of the annular seal to the rotor system, this paper used CFD method to conduct the numerical simulation for the flow field of annular seal clearance. The radial and tangential forces were obtained to calculate the annular dynamic coefficients. Also dynamic coefficient were obtained by Matlab. The rotor system was modeled using ANSYS finite software and the critical speed with and without annular seal clearance were calculated. The result shows: annular seal's fluid field is under the comprehensive effect of pressure difference and rotor entrainment. Due to the huge pressure difference in front annular seal, fluid flows under pressure difference; the low pressure difference results in the more obvious effect on the clearance field in back annular seal. The first order critical speed increases greatly with the annular seal clearance; while the average growth rate of the second order critical speed is only 3.2%; the third and fourth critical speed decreases little. Based on the above result, the annular seal has great influence to the first order speed, while has little influence on the rest
Srivastava, Sanjeev K.; Aghajamali, Alireza
2016-05-01
Theoretical investigation of photonic band gaps or reflection bands in one-dimensional annular photonic crystal (APC) containing double negative (DNG) metamaterials and air has been presented. The proposed structure consists of the alternate layers of dispersive DNG material and air immersed in free space. In order to study photonic band gaps we obtain the reflectance spectrum of the annular PC by employing the transfer matrix method (TMM) in the cylindrical waves for both TE and TM polarizations. In this work we study the effect of azimuthal mode number (m) and starting radius (ρ0) on the three band gaps viz. zero averaged refractive index (zero-nbar) gap, zero permittivity (zero- ε) and zero permeability (zero- μ) gaps. It is found that for m ≥ 1 , zero- μ gap appears in TE mode and zero- ε gap appears in TM mode. The width of both zero- μ and zero- ε gap increases by increasing m values, but the enhancement of zero- μ gap is more appreciable. Also, the effect of ρ0 on the three band gaps (reflection bands) of annular PC structure at the given m-number has been studied, for both TE and TM polarizations. The result shows that in both polarizations zero- ε and zero- μ gaps decreases when ρ0 increases, whereas zero-nbar gap remains invariant.
Efficient Computation of Info-Gap Robustness for Finite Element Models
International Nuclear Information System (INIS)
A recent research effort at LANL proposed info-gap decision theory as a framework by which to measure the predictive maturity of numerical models. Info-gap theory explores the trade-offs between accuracy, that is, the extent to which predictions reproduce the physical measurements, and robustness, that is, the extent to which predictions are insensitive to modeling assumptions. Both accuracy and robustness are necessary to demonstrate predictive maturity. However, conducting an info-gap analysis can present a formidable challenge, from the standpoint of the required computational resources. This is because a robustness function requires the resolution of multiple optimization problems. This report offers an alternative, adjoint methodology to assess the info-gap robustness of Ax = b-like numerical models solved for a solution x. Two situations that can arise in structural analysis and design are briefly described and contextualized within the info-gap decision theory framework. The treatments of the info-gap problems, using the adjoint methodology are outlined in detail, and the latter problem is solved for four separate finite element models. As compared to statistical sampling, the proposed methodology offers highly accurate approximations of info-gap robustness functions for the finite element models considered in the report, at a small fraction of the computational cost. It is noted that this report considers only linear systems; a natural follow-on study would extend the methodologies described herein to include nonlinear systems.
Adiabatic Steam-Water Annular Flow in an Annular Geometry
DEFF Research Database (Denmark)
Andersen, P. S.; Würtz, J.
1981-01-01
Experimental results for fully developed steam-water annular flow in annular geometries are presented. Rod and tube film flow rates and axial pressure gradients were measured for mass fluxes between 500 and 2000 kg/m2s, steam qualities between 20 and 60 per cent and pressures ranging from 3 to 9...... MPa. It was found that the measured tube film flow rate per unit tube perimeter is always many times greater than the corresponding rod film flow rate. Possible explanations for this asymmetry are discussed....
International Nuclear Information System (INIS)
A theoretical and numerical model to predict film condensation heat transfer in mini, micro and ultra micro-channels of different internal shapes is presented in this thesis. The model is based on a finite volume formulation of the Navier-Stokes and energy equations and it includes the contributions of the unsteady terms, surface tension, axial shear stresses, gravitational forces and wall thermal conduction. Notably, interphase mass transfer and near-to-wall effects (disjoining pressure) are also included. This model has been validated versus various benchmark cases and versus published experimental results from three different laboratories, predicting micro-channel heat transfer data with an average error of 20 % or better. The conjugate heat transfer problem arising from the coupling between the thin film fluid dynamics, the heat transfer in the condensing fluid and the heat conduction in the channel wall has been studied and analyzed. The work has focused on the effects of three external wall boundary conditions: a uniform wall temperature, a non uniform wall heat flux and single-phase convective cooling. The thermal axial and peripheral conduction occurring in the wall of the channel can affect the behavior of the condensate film, not only because it redistributes the heat, but also because the annular laminar film condensation process is dependent on the local saturation to wall temperature difference. When moving from mini to micro and ultra-micro channels, the results shows that the axial conduction effects can become very important in the prediction of the wall temperature profile and they can not be ignored. Under these conditions, the overall performances of the heat exchanger become dependent not only on the fluid properties and the operative conditions but also on the geometry and wall material. Results obtained for steady state conditions are presented for circular, elliptical and flattened shape cross sections for R-134a and ammonia, for hydraulic
An Experimental study on the critical heat flux in gap
Energy Technology Data Exchange (ETDEWEB)
Chang, Soon Heung; Baek, Won Pil; Yang, Soo Hyung; Kim, Soo Hyoung; Chung, Yong Hun [Kora Advanced Institute of Science and Technology, Taejon (Korea)
1998-04-01
Experimental study of Critical Heat Flux in annular gap was conducted and the results can be summarized as follows: (1) Current research results and understandings about CHF in gap which are needed to know for analysis the accident f plate-type research reactor and to understand the interaction of tubes and baffles of steam-generator are hard to apply to large gap geometry. (2) Preliminary analysis results about the cooling mechanism of melted core through gap show that the mechanism is only one parts of the scenarios of various severe accidents. (3) CHF experiments were performed to know the effects of the size of gap and the inclination angle of test section. The results show that CHF's are decrease as gap and angle are decreased. (4) Semi-emperical correlation was developed using homogeneous flow model and experimental data. That correlation can be applicable to 30 mm < w < 60 mm, 30 < 1 < 200 mm and 0.25 < s < 3.5 mm. (5) Analysis of the database of CHF in gap show than Monde's correlation can be applicable only small gap size lower than sub-milimeter. (6) Analysis results of the CHFG of SONATA-IV shows that flooding is the mechanism of CHF in gap and critical width is related with Rayleigh-Taylor instability wave length and not with the circumference of gap. And CHF occurrence by flooding means low heat removal capability of gap. (author). 18 refs., 30 figs., 2 tabs.
The Domestic and Foreign Price Gaps in the P-STAR Model; Evidence from Spain
Alicia García-Herrero; Manoj Vasant Pradhan
1999-01-01
The paper uses the P-STAR model to analyze Spanish prices from 1970 to 1996, adding the foreign price gap to the standard domestic definition of the P-STAR model (the domestic price gap) to assess the role German price movements played in Spanish inflation. The domestic price gap turns out to be the major explanatory variable for inflation, even after the entrance of Spain in the exchange rate mechanism (ERM). This result suggests that the successful disinflation experienced in Spain in the p...
Neural network modeling of data with gaps: method of principal curves, Carleman's formula, and other
Gorban, A. N.; Rossiev, A. A.; Wunsch II, D. C.
2003-01-01
A method of modeling data with gaps by a sequence of curves has been developed. The new method is a generalization of iterative construction of singular expansion of matrices with gaps. Under discussion are three versions of the method featuring clear physical interpretation: linear - modeling the data by a sequence of linear manifolds of small dimension; quasilinear - constructing "principal curves: (or "principal surfaces"), univalently projected on the linear principal components; essentia...
Application of Gap Model in the Researches of Hotel Services Quality
Directory of Open Access Journals (Sweden)
Ivana Blešić
2011-01-01
Full Text Available This work presents the research results of the hotel services quality by applying Gap model and SERVQUAL questionnaire. The research was conducted in five health spa centers in the West Morava river valley region during August and September 2008. The reach is aimed at testing of Gap model, i.e. identification of exceptions when the hotel services quality in the observed sample is concerned.
An alternative model for the origin of gaps in circumstellar disks
Vorobyov, Eduard I; Guedel, Manuel; Lin, D N C
2016-01-01
Motivated by recent observational and numerical studies suggesting that collapsing protostellar cores may be replenished from the local environment, we explore the evolution of protostellar cores submerged in the external counter-rotating environment. These models predict the formation of counter-rotating disks with a deep gap in the gas surface density separating the inner disk (corotating with the star) and the outer counter-rotating disk. The properties of these gaps are compared to those of planet-bearing gaps that form in disks hosting giant planets. We employ numerical hydrodynamics simulations of collapsing cores that are replenished from the local counter-rotating environment, as well as numerical hydrodynamic simulations of isolated disks hosting giant planets, to derive the properties of the gaps that form in both cases. Our numerical simulations demonstrate that counter-rotating disks can form for a wide range of mass and angular momentum available in the local environment. The gap that separates b...
Phase Space Distribution for Two-Gap Solution in Unitary Matrix Model
Dutta, Parikshit
2015-01-01
We analyze the dynamics of weakly coupled finite temperature $U(N)$ gauge theories on $S^3$ by studying a class of effective unitary matrix model. Solving Dyson-Schwinger equation at large $N$, we find that different phases of gauge theories are characterized by gaps in eigenvalue distribution over a unit circle. In particular, we obtain no-gap, one-gap and two-gap solutions at large $N$ for a class of matrix model we are considering. The same effective matrix model can equivalently be written as a sum over representations (or Young diagrams) of unitary group. We show that at large $N$, Young diagrams corresponding to different phases can be classified in terms of discontinuities in number of boxes in two consecutive rows. More precisely, the representation, where there is no discontinuity, corresponds to no-gap and one-gap solution, where as, a diagram with one discontinuity corresponds to two-gap phase, mentioned above. This observation allows us to write a one to one relation between eigenvalue distributio...
Institute of Scientific and Technical Information of China (English)
2013-01-01
高炉煤气净化、环缝洗涤塔下段循环水系统生产中常出现循环水泵气蚀、水泵检修及机械、液压、电气、计器系统等异常，造成水封水位升高，威胁生产。为解决这一问题增加了应急泄水管，保证了安全稳定。%Cavitation erosion of circulating water pump often occurs in production of the circulating water system of blast furnace gas purification and of the lower part of annular gap scrubbing tower. The abnormal phenomena take place in water pump maintenance and in the testing systems of machinery, hydraulic pressure, electric and gauge, causing high water level of water seal and a threat to production. In order to solve this problem, it is necessary to add emergency drainage pipes to ensure stable and safety production.
Development of Lateral Loss Coefficient Model on Heterogeneous Gap of Mixed Core
Energy Technology Data Exchange (ETDEWEB)
Kwon, Hyuk; Kim, S. J.; Hwang, D. H.; Lee, W. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2013-10-15
Model on lateral loss coefficient model in conventional PWR that is crucial parameter to evaluate the cross flow is not needed due to the homogeneous gap. In conventional thermal-hydraulic design, lateral loss coefficients use the constant or Idel 'chik's Reynolds number dependent model that is not considered on the P/D effect. In order to develop a lateral loss coefficient model applied to the heterogeneous gap in mixed core, 2-D CFD analysis is performed to calculate the pressure distribution and velocity field. MATRA code, subchannel code developed by KAERI, adopted the model is used to estimate the compatibility of FCM assembly with the reference fuel assembly of the conventional PWR. Lateral loss coefficient model was developed considering the heterogeneous gap in mixed core that is consisted of conventional 16 by 16 and FCM assembly. Developed model implemented in MATRA code was well applied on the subchannel calculation of mixed core.
Anomalous behavior of the energy gap in the one-dimensional quantum XY model.
Okuyama, Manaka; Yamanaka, Yuuki; Nishimori, Hidetoshi; Rams, Marek M
2015-11-01
We reexamine the well-studied one-dimensional spin-1/2 XY model to reveal its nontrivial energy spectrum, in particular the energy gap between the ground state and the first excited state. In the case of the isotropic XY model, the XX model, the gap behaves very irregularly as a function of the system size at a second order transition point. This is in stark contrast to the usual power-law decay of the gap and is reminiscent of the similar behavior at the first order phase transition in the infinite-range quantum XY model. The gap also shows nontrivial oscillatory behavior for the phase transitions in the anisotropic model in the incommensurate phase. We observe a close relation between this anomalous behavior of the gap and the correlation functions. These results, those for the isotropic case in particular, are important from the viewpoint of quantum annealing where the efficiency of computation is strongly affected by the size dependence of the energy gap. PMID:26651656
Phase flow rate measurements of annular flows
Al-Yarubi, Qahtan
2010-01-01
In the international oil and gas industry multiphase annular flow in pipelines and wells is extremely important, but not well understood. This thesis reports the development of an efficient and cheap method for measuring the phase flow rates in two phase annular and annular mist flow, in which the liquid phase is electrically conducting, using ultrasonic and conductance techniques. The method measures changes in the conductance of the liquid film formed during annular flow and uses these to c...
SAR Observation and Modeling of Gap Winds in the Prince William Sound of Alaska
Directory of Open Access Journals (Sweden)
Karl Volz
2008-08-01
Full Text Available AlaskaÃ¢Â€Â™s Prince William Sound (PWS is a unique locale tending to have strong gap winds, especially in the winter season. To characterize and understand these strong surface winds, which have great impacts on the local marine and aviation activities, the surface wind retrieval from the Synthetic Aperture Radar data (SAR-wind is combined with a numerical mesoscale model. Helped with the SAR-wind observations, the mesoscale model is used to study cases of strong winds and relatively weak winds to depict the nature of these winds, including the area of extent and possible causes of the wind regimes. The gap winds from the Wells Passage and the Valdez Arm are the most dominant gap winds in PWS. Though the Valdez Arm is north-south trending and Wells Passage is east-west oriented, gap winds often develop simultaneously in these two places when a low pressure system is present in the Northern Gulf of Alaska. These two gap winds often converge at the center of PWS and extend further out of the Sound through the Hinchinbrook Entrance. The pressure gradients imposed over these areas are the main driving forces for these gap winds. Additionally, the drainage from the upper stream glaciers and the blocking effect of the banks of the Valdez Arm probably play an important role in enhancing the gap wind.
Clathrin and Cx43 gap junction plaque endoexocytosis
International Nuclear Information System (INIS)
In earlier transmission electron microscopic studies, we have described pentilaminar gap junctional membrane invaginations and annular gap junction vesicles coated with short, electron-dense bristles. The similarity between these electron-dense bristles and the material surrounding clathrin-coated pits led us to suggest that the dense bristles associated with gap junction structures might be clathrin. To confirm that clathrin is indeed associated with annular gap junction vesicles and gap junction plaques, quantum dot immuno-electron microscopic techniques were used. We report here that clathrin associates with both connexin 43 (Cx43) gap junction plaques and pentilaminar gap junction vesicles. An important finding was the preferential localization of clathrin to the cytoplasmic surface of the annular or of the gap junction plaque membrane of one of the two contacting cells. This is consistent with the possibility that the direction of gap junction plaque internalization into one of two contacting cells is regulated by clathrin
Modeling and Identification of a Large Gap Magnetic Suspension System
Cox, David E. (Editor); Groom, Nelson J. (Editor); Hsiao, Min-Hung; Huang, Jen-Kuang
1996-01-01
This paper presents the results of modeling and system identification efforts on the NASA Large-Angle Magnetic Suspension Test Fixture (LAMSTF). The LAMSTF consists of a cylindrical permanent magnet which is levitated above a planar array of five electromagnets mounted in a circular configuration. The analytical model is first developed and open-loop characteristics are described. The system is shown to be highly unstable and requires feedback control in order to apply system identification. Limitations on modeling accuracy due to the effect of eddy-currents on the system are discussed. An algorithm is derived to identify a state-space model for the system from input/output data acquired during closed-loop operation. The algorithm is tested on both the baseline system and a perturbed system which has an increased presence of eddy currents. It is found that for the baseline system the analytic model adequately captures the dynamics, although the identified model improves the simulation accuracy. For the system perturbed by additional unmodeled eddy-currents the analytic model is no longer adequate and a higher-order model, determined through system identification, is required to accurately predict the system's time response.
Connexin43 Cardiac Gap Junction Remodeling: Lessons from Genetically Engineered Murine Models
Remo, Benjamin F.; Giovannone, Steven; Fishman, Glenn I.
2012-01-01
Sudden cardiac death is responsible for several hundred thousand deaths each year in the United States. Multiple lines of evidence suggest that perturbation of gap junction expression and function in the heart, or what has come to be known as cardiac gap junction remodeling, plays a key mechanistic role in the pathophysiology of clinically significant cardiac arrhythmias. Here we review recent studies from our laboratory using genetically engineered murine models to explore mechanisms implica...
Subcutaneous granuloma annulare: radiologic appearance
International Nuclear Information System (INIS)
Objective. Granuloma annulare is an uncommon benign inflammatory dermatosis characterized by the formation of dermal papules with a tendency to form rings. There are several clinically distinct forms. The subcutaneous form is the most frequently encountered by radiologists, with the lesion presenting as a superficial mass. There are only a few scattered reports of the imaging appearance of this entity in the literature. We report the radiologic appearance of five cases of subcutaneous granuloma annulare. Design and patients. The radiologic images of five patients (three male, two female) with subcutaneous granuloma annulare were retrospectively studied. Mean patient age was 6.4 years (range, 2-13 years). The lesions occurred in the lower leg (two), foot, forearm, and hand. MR images were available for all lesions, gadolinium-enhanced imaging in three cases, radiographs in four, and bone scintigraphy in one. Results. Radiographs showed unmineralized nodular masses localized to the subcutaneous adipose tissue. The size range, in greatest dimension on imaging studies, was 1-4 cm. MR images show a mass with relatively decreased signal intensity on all pulse sequences, with variable but generally relatively well defined margins. There was extensive diffuse enhancement following gadolinium administration. Conclusion. The radiologic appearance of subcutaneous granuloma annulare is characteristic, typically demonstrating a nodular soft-tissue mass involving the subcutaneous adipose tissue. MR images show a mass with relatively decreased signal intensity on all pulse sequences and variable but generally well defined margins. There is extensive diffuse enhancement following gadolinium administration. Radiographs show a soft-tissue mass or soft-tissue swelling without evidence of bone involvement or mineralization. This radiologic appearance in a young individual is highly suggestive of subcutaneous granuloma annulare. (orig.)
Annular diffraction of very unstable light nuclei
International Nuclear Information System (INIS)
Because they are brittle, unstable light nuclei can produce an annular diffraction pattern observed on their decay products with large cross sections. With such a simple model, the 9Li angular distribution observed in the 11Li fragmentation have been reproduced together with the reaction cross-section and the fragmentation yield provided recoil effects from neutron emission are included. It results that for this projectile and for light targets, diffraction is the main source of transverse momentum for 9Li whereas for neutrons it originates from its emission energy in the 11Li center of mass
Modeling of deep gaps created by giant planets in protoplanetary discs
Kanagawa, K D; Muto, T; Tanigawa, T
2016-01-01
A giant planet embedded in a protoplanetary disc creates a gap. This process is important for both theory and observations. Gap openings are intimately connected with orbital migration and the mass growth of a planet. It has recently been observed that discs around young stars are rich in structure, and the interaction between a planet and a disc is considered to be one possible origin of this structure. We performed two-dimensional hydrodynamic simulations, varying the planet mass, disc aspect ratio, and viscosity in a wide range of parameters. This relationship enables us to judge whether an observed gap is likely to have been caused by an embedded planet. It is also possible to predict the planet mass from observations of the gap shape. Based on the results of hydrodynamic simulations, we present an empirical model of wave excitation and damping with deep gaps. Using this model of wave excitation and damping, we constructed a semianalytical model of the gap surface density distribution, and it reproduces t...
Annular-Efficient Triangulations of 3-manifolds
Jaco, William
2011-01-01
A triangulation of a compact 3-manifold is annular-efficient if it is 0-efficient and the only normal, incompressible annuli are thin edge-linking. If a compact 3-manifold has an annular-efficient triangulation, then it is irreducible, boundary-irreducible, and an-annular. Conversely, it is shown that for a compact, irreducible, boundary-irreducible, and an-annular 3-manifold, any triangulation can be modified to an annular-efficient triangulation. It follows that for a manifold satisfying this hypothesis, there are only a finite number of boundary slopes for incompressible and boundary-incompressible surfaces of a bounded Euler characteristic.
Explaining the Gender Wage Gap: Estimates from a Dynamic Model of Job Changes and Hours Changes
Liu, Kai
2015-01-01
I address the causes of the gender wage gap with a new dynamic model of wage, hours, and job changes that permits me to decompose the gap into a portion due to gender differences in preferences for hours of work and in constraints. The dynamic model allows the differences in constraints to reflect possible gender differences in job arrival rates, job destruction rates, the mean and variance of the wage offer distribution, and the wage cost of part-time work. The model is estimated using the 1...
Osmotic forces and gap junctions in spreading depression: a computational model
Shapiro, B. E.
2001-01-01
In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K+ is allowed to move through gap junctions. SD waves of [K+]out approximately 25 to approximately 60 mM moving at approximately 2 to approximately 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to approximately 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na+ currents are predicted to facilitate SD, while SK and A-type K+ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.
International Nuclear Information System (INIS)
The impedance of a diode having an annular cathode and indented anode that terminates a coaxial MITL (magnetically insulated transmission line) is measured and compared with a semiempirical model developed from calculations made using the magIc code. The measurements were made on the 16-Ω electron accelerator HELIA (high-energy linear induction accelerator) operating at 3 MV. The model agrees with the measurements within the 10% measuring error and shows that the diode operates in either a load- or line-dominated regime depending on AK (anode-cathode) gap spacing. In the load-dominated regime, which corresponds to small AK gaps, the diode impedance is controlled by an effective anode-cathode gap, and the flow is approximately axial. In the line-dominated regime, which corresponds to large AK gaps, the impedance is independent of the AK gap and corresponds to the impedance associated with the minimum current solution of the MITL, with the flow becoming more radial as the AK gap is increased
Constraining Gamma-Ray Pulsar Gap Models with a Simulated Pulsar Population
Pierbattista, Marco; Grenier, I. A.; Harding, A. K.; Gonthier, P. L.
2012-01-01
With the large sample of young gamma-ray pulsars discovered by the Fermi Large Area Telescope (LAT), population synthesis has become a powerful tool for comparing their collective properties with model predictions. We synthesised a pulsar population based on a radio emission model and four gamma-ray gap models (Polar Cap, Slot Gap, Outer Gap, and One Pole Caustic). Applying gamma-ray and radio visibility criteria, we normalise the simulation to the number of detected radio pulsars by a select group of ten radio surveys. The luminosity and the wide beams from the outer gaps can easily account for the number of Fermi detections in 2 years of observations. The wide slot-gap beam requires an increase by a factor of 10 of the predicted luminosity to produce a reasonable number of gamma-ray pulsars. Such large increases in the luminosity may be accommodated by implementing offset polar caps. The narrow polar-cap beams contribute at most only a handful of LAT pulsars. Using standard distributions in birth location and pulsar spin-down power (E), we skew the initial magnetic field and period distributions in a an attempt to account for the high E Fermi pulsars. While we compromise the agreement between simulated and detected distributions of radio pulsars, the simulations fail to reproduce the LAT findings: all models under-predict the number of LAT pulsars with high E , and they cannot explain the high probability of detecting both the radio and gamma-ray beams at high E. The beaming factor remains close to 1.0 over 4 decades in E evolution for the slot gap whereas it significantly decreases with increasing age for the outer gaps. The evolution of the enhanced slot-gap luminosity with E is compatible with the large dispersion of gamma-ray luminosity seen in the LAT data. The stronger evolution predicted for the outer gap, which is linked to the polar cap heating by the return current, is apparently not supported by the LAT data. The LAT sample of gamma-ray pulsars
Vibration Analysis of Annular Sector Plates under Different Boundary Conditions
Directory of Open Access Journals (Sweden)
Dongyan Shi
2014-01-01
Full Text Available An analytical framework is developed for the vibration analysis of annular sector plates with general elastic restraints along each edge of plates. Regardless of boundary conditions, the displacement solution is invariably expressed as a new form of trigonometric expansion with accelerated convergence. The expansion coefficients are treated as the generalized coordinates and determined using the Rayleigh-Ritz technique. This work allows a capability of modeling annular sector plates under a variety of boundary conditions and changing the boundary conditions as easily as modifying the material properties or dimensions of the plates. Of equal importance, the proposed approach is universally applicable to annular sector plates of any inclusion angles up to 2π. The reliability and accuracy of the current method are adequately validated through numerical examples.
Concentric Coplanar Capacitive Sensor System with Quantitative Model
Bowler, Nicola (Inventor); Chen, Tianming (Inventor)
2014-01-01
A concentric coplanar capacitive sensor includes a charged central disc forming a first electrode, an outer annular ring coplanar with and outer to the charged central disc, the outer annular ring forming a second electrode, and a gap between the charged central disc and the outer annular ring. The first electrode and the second electrode may be attached to an insulative film. A method provides for determining transcapacitance between the first electrode and the second electrode and using the transcapacitance in a model that accounts for a dielectric test piece to determine inversely the properties of the dielectric test piece.
An alternative model for the origin of gaps in circumstellar disks
Vorobyov, Eduard I.; Regaly, Zsolt; Guedel, Manuel; Lin, Doug N. C.
2016-03-01
Aims: Motivated by recent observational and numerical studies suggesting that collapsing protostellar cores may be replenished from the local environment, we explore the evolution of protostellar cores submerged in the external counter-rotating environment. These models predict the formation of counter-rotating disks with a deep gap in the gas surface density separating the inner disk (corotating with the star) and the outer counter-rotating disk. The properties of these gaps are compared to those of planet-bearing gaps that form in disks hosting giant planets. Methods: We employ numerical hydrodynamics simulations of collapsing cores that are replenished from the local counter-rotating environment and numerical hydrodynamics simulations of isolated disks hosting giant planets to derive the properties of the gaps that form in both cases. Results: Our numerical simulations demonstrate that counter-rotating disks can form for a wide range of mass and angular momentum available in the local environment. The gap that separates both disks has a substantial depletion factor, can be located at a distance from ten to over a hundred AU from the star, and can propagate inward with velocity ranging from 1 AU Myr-1 to >100 AU Myr-1. Unlike our previous conclusion, the gap can therefore be a long-lived phenomenon that is, in some case, comparable to the lifetime of the disk itself. For a proper choice of the planetary mass, the viscous α-parameter and disk mass, the planet-bearing gaps and gaps in counter-rotating disks may show a remarkable similarity in the gas density profile and depletion factor, which may complicate their observational differentiation.
Thermal hydraulic performance assessment of dual-cooled annular nuclear fuel for OPR-1000
Energy Technology Data Exchange (ETDEWEB)
Shin, Chang-Hwan, E-mail: shinch@kaeri.re.kr [LWR Fuel Development Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Chun, Tae-Hyun, E-mail: thchun@kaeri.re.kr [LWR Fuel Development Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); Oh, Dong-Seok, E-mail: dsoh1@kaeri.re.kr [LWR Fuel Development Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of); In, Wang-Kee, E-mail: wkin@kaeri.re.kr [LWR Fuel Development Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-Gu, Daejeon 305-353 (Korea, Republic of)
2012-02-15
Highlights: Black-Right-Pointing-Pointer A thermal hydraulic performance of a 12 Multiplication-Sign 12 annular fuel array is evaluated. Black-Right-Pointing-Pointer The subchannel analysis code for the dual-cooled annular fuel, MATRA-AF is validated. Black-Right-Pointing-Pointer We evaluate the sensitivity for geometry tolerances and operating parameter. Black-Right-Pointing-Pointer We decide the essential design parameters to uprate the power generation by dual-cooled annular fuel. Black-Right-Pointing-Pointer A thermal margin amount accommodating a 20% power-uprate seems viable. - Abstract: An internally and externally cooled annular fuel was proposed for an advance PWR, which can endure substantial power uprating. KAERI is pursuing the development for a reloading of power uprated annular fuel for the operating PWR reactors of OPR-1000. In this paper, the characteristics and verification of the MATRA-AF are described. The thermal hydraulic performance of a 12 Multiplication-Sign 12 annular fuel is calculated for the major design parameters and its performance is compared against the reference 16 Multiplication-Sign 16 cylindrical fuel assembly. In particular, the enhancements of the thermal hydraulic performance of dual-cooled annular fuel are estimated for the 100% normal power reactor core. The purpose of this study is to estimate a normal power for OPR-1000 with dual-cooled annular fuel, and ultimately to assess the feasibility of 120% core power. The parametric study was carried out for the fuel rod dimension, gap conductance, thermal diffusion coefficients, and pressure loss of the spacer grids. As a result of the analysis on the nominal power, annular fuel showed a sufficient margin available on DNB and fuel pellet temperature relative to cylindrical fuel. The margin amount seems accommodating a 20% power-uprate seems viable.
CHARACTERIZING DETONATING LX-17 CHARGES CROSSING A TRANSVERSE AIR GAP WITH EXPERIMENTS AND MODELING
Energy Technology Data Exchange (ETDEWEB)
Lauderbach, L M; Souers, P C; Garcia, F; Vitello, P; Vandersall, K S
2009-06-26
Experiments were performed using detonating LX-17 (92.5% TATB, 7.5% Kel-F by weight) charges with various width transverse air gaps with manganin peizoresistive in-situ gauges present. The experiments, performed with 25 mm diameter by 25 mm long LX-17 pellets with the transverse air gap in between, showed that transverse gaps up to about 3 mm could be present without causing the detonation wave to fail to continue as a detonation. The Tarantula/JWL{sup ++} code was utilized to model the results and compare with the in-situ gauge records with some agreement to the experimental data with additional work needed for a better match to the data. This work will present the experimental details as well as comparison to the model results.
Dwoyer, D. L.; Newman, P. A.; Thames, F. C.; Melson, N. D.
1981-01-01
The problem of predicting aerodynamic loads on the insulating tiles of the space shuttle thermal protection system (TPS) is discussed and seen to require a method for predicting pressure and mass flux in the gaps between tiles. A mathematical model of the tile-gap flow is developed, based upon a slow viscous (Stokes) flow analysis, and is verified against experimental data. The tile-gap pressure field is derived from a solution of the two-dimensional Laplace equation; the mass-flux vector is then calculated from the pressure gradient. The means for incorporating this model into a lumped-parameter network analogy for porous-media flow is given. The means for incorporating this model into a lumped-parameter network analogy for porous-media flow is given. The flow model shows tile-gap mass flux to be very sensitive to the gap width indicating a need for coupling the TPS flow and tile displacement calculation. Analytical and experimental work to improve TPS flow predictions and a possible shuttle TPS hardware modification are recommended.
ACRIM-gap and TSI trend issue resolved using a surface magnetic flux TSI proxy model
Scafetta, Nicola; Willson, Richard C.
2009-03-01
The ACRIM-gap (1989.5-1991.75) continuity dilemma for satellite TSI observations is resolved by bridging the satellite TSI monitoring gap between ACRIM1 and ACRIM2 results with TSI derived from Krivova et al.'s (2007) proxy model based on variations of the surface distribution of solar magnetic flux. `Mixed' versions of ACRIM and PMOD TSI composites are constructed with their composites' original values except for the ACRIM gap, where Krivova modeled TSI is used to connect ACRIM1 and ACRIM2 results. Both `mixed' composites demonstrate a significant TSI increase of 0.033 %/decade between the solar activity minima of 1986 and 1996, comparable to the 0.037 % found in the ACRIM composite. The finding supports the contention of Willson (1997) that the ERBS/ERBE results are flawed by uncorrected degradation during the ACRIM gap and refutes the Nimbus7/ERB ACRIM gap adjustment Fröhlich and Lean (1998) employed in constructing the PMOD.
Mechanistic Modeling Reveals the Critical Knowledge Gaps in Bile Acid–Mediated DILI
Woodhead, J L; Yang, K.; Brouwer, K L R; Siler, S. Q.; Stahl, S H; Ambroso, J L; Baker, D; Watkins, P B; Howell, B A
2014-01-01
Bile salt export pump (BSEP) inhibition has been proposed to be an important mechanism for drug-induced liver injury (DILI). Modeling can prioritize knowledge gaps concerning bile acid (BA) homeostasis and thus help guide experimentation. A submodel of BA homeostasis in rats and humans was constructed within DILIsym, a mechanistic model of DILI. In vivo experiments in rats with glibenclamide were conducted, and data from these experiments were used to validate the model. The behavior of DILIs...
Improvement of image processing algorithms for annular flow
International Nuclear Information System (INIS)
Annular flow occurs in a wide range of industrial heat-transfer equipment, including the top of a BWR core, in the steam generator of a PWR, and in postulated accident scenarios including critical heat flux (CHF) by dryout. The modeling of annular flow often requires information regarding the average thickness of liquid film at the periphery of the flow channel as a measurement of film roughness (film roughness concept). More recently, two-region modeling efforts require wave intermittency as a measurement of disturbance wave (as opposed to base film thickness) contribution to gas-to-liquid momentum transfer and pressure loss. The present work focuses on the characterization of film behaviors in annular flow using quantitative visualization. The data reduction codes for planar laser-induced flourescence (PLIF) imaging and back-lit quartz tube imaging have been further developed to improve measurement accuracy. Film thickness distribution (base film and wave), disturbance wave length, and wave intermittency estimates have been updated and applied to a recent two-region annular flow model. Outputs of average film thickness, pressure gradient, and average wave velocity have been modeled with mean absolute errors of 8.70%, 17.42%, and 19.14%, respectively. (author)
Annular beam shaping and optical trepanning
Zeng, Danyong
Percussion drilling and trepanning are two laser drilling methods. Percussion drilling is accomplished by focusing the laser beam to approximately the required diameter of the hole, exposing the material to one or a series of laser pulses at the same spot to melt and vaporize the material. Drilling by trepanning involves cutting a hole by rotating a laser beam with an optical element or an x-y galvo-scanner. Optical trepanning is a new laser drilling method using an annular beam. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a traditional circular laser beam. Heating depth is important for drilling application. Since there are no good ways to measure the temperature inside substrate during the drilling process, an analytical model for optical trepanning has been developed by considering an axisymmetric, transient heat conduction equation, and the evolutions of the melting temperature isotherm, which is referred to as the melt boundary in this study, are calculated to investigate the influences of the laser pulse shapes and intensity profiles on the hole geometry. This mathematical model provides a means of understanding the thermal effect of laser irradiation with different annular beam shapes. To take account of conduction in the solid, vaporization and convection due to the melt flow caused by an assist gas, an analytical two-dimensional model is developed for optical trepanning. The influences of pulse duration, laser pulse length, pulse repetition rate, intensity profiles and beam radius are investigated to examine their effects on the recast layer thickness, hole depth and taper. The ray tracing technique of geometrical optics is employed to design the necessary optics to transform a Gaussian laser beam into an annular beam of different intensity profiles. Such profiles include half Gaussian with maximum intensities at the inner and outer
Hydrodynamics of annular-dispersed flow
International Nuclear Information System (INIS)
The interfacial drag, droplet entrainment, and droplet size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The drag correlations for multiple fluid particle systems have been developed from a similarity hypothesis based on the mixture viscosity model. The results show that the drag coefficient depends on the particle Reynolds number and droplet concentration. The onset on droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet size distribution have been obtained from a simple model in collaboration with a large number of data
Fit Gap Analysis – The Role of Business Process Reference Models
Directory of Open Access Journals (Sweden)
Dejan Pajk
2013-12-01
Full Text Available Enterprise resource planning (ERP systems support solutions for standard business processes such as financial, sales, procurement and warehouse. In order to improve the understandability and efficiency of their implementation, ERP vendors have introduced reference models that describe the processes and underlying structure of an ERP system. To select and successfully implement an ERP system, the capabilities of that system have to be compared with a company’s business needs. Based on a comparison, all of the fits and gaps must be identified and further analysed. This step usually forms part of ERP implementation methodologies and is called fit gap analysis. The paper theoretically overviews methods for applying reference models and describes fit gap analysis processes in detail. The paper’s first contribution is its presentation of a fit gap analysis using standard business process modelling notation. The second contribution is the demonstration of a process-based comparison approach between a supply chain process and an ERP system process reference model. In addition to its theoretical contributions, the results can also be practically applied to projects involving the selection and implementation of ERP systems.
Bridging the Gap between Practitioners and E-learning Standards: A Domain-specific Modeling Approach
Miao, Yongwu; Sodhi, Tim; Brouns, Francis; Sloep, Peter; Koper, Rob
2009-01-01
Miao, Y., Sodhi, T., Brouns, F., Sloep, P. B., & Koper, R. (2008). Bridging the Gap between Practitioners and E-learning Standards: A Domain-Specific Modeling Approach. Presentation at the ECTEL 2008 conference. September, 16-19, 2008, Maastricht, The Netherlands.
Temperature dependence of band gaps in Si and Ge in the quasi-ion model
Klenner, M.; Falter, C.; Ludwig, W.
We have calculated the temperature dependence of the direct and indirect band gaps in silicon and germanium. The electron-phonon potential as well as the phonon frequencies and eigenvectors are calculated consistently within the rigid quasi-ion model. Comparison is made with experiment and with the theoretical results of Allen and Cardona and Lautenschlager et al.
Spectral Gap and Edge Excitations of d-Dimensional PVBS Models on Half-Spaces
Bishop, Michael; Nachtergaele, Bruno; Young, Amanda
2016-03-01
We analyze a class of quantum spin models defined on half-spaces in the d-dimensional hypercubic lattice bounded by a hyperplane with inward unit normal vector min {R}^d. The family of models was previously introduced as the single species Product Vacua with Boundary States (PVBS) model, which is a spin-1/2 model with a XXZ-type nearest neighbor interactions depending on parameters λ _jin (0,∞), one for each coordinate direction. For any given values of the parameters, we prove an upper bound for the spectral gap above the unique ground state of these models, which vanishes for exactly one direction of the normal vector m. For all other choices of m we derive a positive lower bound of the spectral gap, except for the case λ _1 =\\cdots =λ _d=1, which is known to have gapless excitations in the bulk.
Comparative Research on Prediction Model of China’s Urban-rural Residents’ Income Gap
Institute of Scientific and Technical Information of China (English)
2011-01-01
By using the data concerning China’s urban-rural residents’ income gap from 1978 to 2010,this paper mainly researches the application of several kinds of models in predicting China’s urban-rural residents’ income gap.By conducting empirical analysis,we establish ARIMA prediction model,grey prediction model and quadratic-polynomial prediction model and conduct accuracy comparison.The results show that quadratic-polynomial prediction model has excellent fitting effect.By using quadratic-polynomial prediction model,this paper conducts prediction on trend of China’s urban-rural residents’ income gap from 2011 to 2013,and the prediction value of income gap of urban-rural residents in China from 2011 to 2013 is 14 173.20,15 212.92 and 16 289.67 yuan respectively.Finally,on the basis of analysis,corresponding countermeasures are put forward,in order to provide scientific basis for energy planning and policy formulation:first,strengthen government’s function of public service,coordinate resources,and strive to provide an equal opportunity of development for social members,so as to promote people’s welfare and promote social equality;second,breach industrial monopoly and bridge income gap between employees in monopoly industry and general industry;last but not the least,support,encourage and call for government to establish social relief fund,adjust residents’ income distribution from the non-governmental perspective,and endeavor to promote the income level of low-income class.
CFD Simulation of Annular Centrifugal Extractors
Vedantam, S.; Wardle, K. E.; Tamhane, T. V.; Ranade, V. V.; Joshi, J. B.
2012-01-01
Annular centrifugal extractors (ACE), also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of cent...
Granuloma annulare in herpes zoster scars.
Ohata, C; Shirabe, H; Takagi, K; Kawatsu, T
2000-03-01
A 54-year-old Japanese female developed granuloma annulare twice in herpes zoster scars. Soon after the second event, she developed ulcerative colitis, which was well controlled by sulfonamides and corticosteroid suppository. She had no history of diabetes mellitus. There was no recurrence of granuloma annulare by June of 1999. Granuloma annulare might have contributed to the complications of ulcerative colitis, although this had not been noticed before. PMID:10774142
Behaviour of the energy gap in a model of Josephson coupled Bose-Einstein condensates
International Nuclear Information System (INIS)
In this work we investigate the energy gap between the ground state and the first excited state in a model of two single-mode Bose-Einstein condensates coupled via Josephson tunnelling. The energy gap is never zero when the tunnelling interaction is non-zero. The gap exhibits no local minimum below a threshold coupling which separates a delocalized phase from a self-trapping phase that occurs in the absence of the external potential. Above this threshold point one minimum occurs close to the Josephson regime, and a set of minima and maxima appear in the Fock regime. Expressions for the position of these minima and maxima are obtained. The connection between these minima and maxima and the dynamics for the expectation value of the relative number of particles is analysed in detail. We find that the dynamics of the system changes as the coupling crosses these points
Particle flux in an annular gap about a sphere
International Nuclear Information System (INIS)
We develop a method for joining diffusion theory to a void region in a consistent manner. In particular, we apply the theory to a three region problem with a central solid core, surrounded by a concentric void shell and this in turn is surrounded by a concentric shell of another solid material. The sources can be either incident on the outer surface or uniformly distributed in the inner and outer regions. The void flux is calculated from the free streaming Boltzmann equation and is linked to the diffusion equations by assuming that the angular distribution on the surfaces follows the form A + B cosθ, where A and B are related to the diffusion theory fluxes in the inner and outer regions. This procedure allows us to calculate the flux throughout the solid and void regions without making any diffusion theory assumptions in the void. Numerical results are given to illustrate the method and comparisons with exact transport calculations are given to establish the accuracy. An extension of the method to deal with axially symmetric systems is also given in Appendix B. The theory will apply to neutrons and photons
The Three-Dimensional Velocity Distribution of Wide Gap Taylor-Couette Flow Modelled by CFD
Directory of Open Access Journals (Sweden)
David Shina Adebayo
2016-01-01
Full Text Available A numerical investigation is conducted for the flow between two concentric cylinders with a wide gap, relevant to bearing chamber applications. This wide gap configuration has received comparatively less attention than narrow gap journal bearing type geometries. The flow in the gap between an inner rotating cylinder and an outer stationary cylinder has been modelled as an incompressible flow using an implicit finite volume RANS scheme with the realisable k-ε model. The model flow is above the critical Taylor number at which axisymmetric counterrotating Taylor vortices are formed. The tangential velocity profiles at all axial locations are different from typical journal bearing applications, where the velocity profiles are quasilinear. The predicted results led to two significant findings of impact in rotating machinery operations. Firstly, the axial variation of the tangential velocity gradient induces an axially varying shear stress, resulting in local bands of enhanced work input to the working fluid. This is likely to cause unwanted heat transfer on the surface in high torque turbomachinery applications. Secondly, the radial inflow at the axial end-wall boundaries is likely to promote the transport of debris to the junction between the end-collar and the rotating cylinder, causing the build-up of fouling in the seal.
Sensitivity analysis of a forest gap model concerning current and future climate variability
Energy Technology Data Exchange (ETDEWEB)
Lasch, P.; Suckow, F.; Buerger, G.; Lindner, M.
1998-07-01
The ability of a forest gap model to simulate the effects of climate variability and extreme events depends on the temporal resolution of the weather data that are used and the internal processing of these data for growth, regeneration and mortality. The climatological driving forces of most current gap models are based on monthly means of weather data and their standard deviations, and long-term monthly means are used for calculating yearly aggregated response functions for ecological processes. In this study, the results of sensitivity analyses using the forest gap model FORSKA{sub -}P and involving climate data of different resolutions, from long-term monthly means to daily time series, including extreme events, are presented for the current climate and for a climate change scenario. The model was applied at two sites with differing soil conditions in the federal state of Brandenburg, Germany. The sensitivity of the model concerning climate variations and different climate input resolutions is analysed and evaluated. The climate variability used for the model investigations affected the behaviour of the model substantially. (orig.)
Systematic comparison of the use of annular and Zernike circle polynomials for annular wavefronts
Mahajan, V.N.; Aftab, M.
2010-01-01
The theory of wavefront analysis of a noncircular wavefront is given and applied for a systematic comparison of the use of annular and Zernike circle polynomials for the analysis of an annular wavefront. It is shown that, unlike the annular coefficients, the circle coefficients generally change as t
A single-particle model of Cherenkov FEL with cylindrical waveguides
International Nuclear Information System (INIS)
A single-particle model is used to investigate Cherenkov free electron laser with annular relativistic electron beams contained in dielectric-loaded cylindrical waveguides. Frequency tunability is discussed and growth rate is derived. The threshold current for overcoming the cavity losses is calculated. Results show that the gap between the beam and the dielectric can degrade the beam-mode coupling. The growth rate for an annular beam may be higher than that for a solid beam
Yu, Hong; Vikhe Patil, Kim; Han, Chul; Fabella, Brian; Canlon, Barbara; Someya, Shinichi; Cederroth, Christopher R
2016-01-01
Gap detection or gap pre-pulse inhibition of the acoustic startle (GPIAS) has been successfully used in rat and guinea pig models of tinnitus, yet this system has been proven to have low efficacy in CBA mice, with low basal GPIAS and subtle tinnitus-like effects. Here, we tested five mouse strains (CBA, BalbC, CD-1, C57BL/6 and 129sv) for pre-pulse inhibition (PPI) and gap detection with varying interstimulus intervals (ISI) and found that mice from a CBA genetic background had the poorest capacities of suppressing the startle response in the presence of a pre-pulse or a gap. CD-1 mice displayed variable responses throughout all ISI. Interestingly, C57BL/6, 129sv and BalbC showed efficient suppression with either pre-pulses or gaps with shorter ISI. The glutamate aspartate transporter (GLAST) is expressed in support cells from the cochlea and buffers the excess of glutamate. We hypothesized that loss of GLAST function could sensitize the ear to tinnitus-inducing agents, such as salicylate. Using shorter ISI to obtain a greater dynamic range to assess tinnitus-like effects, we found that disruption of gap detection by salicylate was exacerbated across various intensities of a 32-kHz narrow band noise gap carrier in GLAST knockout (KO) mice when compared to their wild-type (WT) littermates. Auditory brainstem responses (ABR) and distortion-product otoacoustic emission (DPOAE) were performed to evaluate the effects on hearing functions. Salicylate caused greater auditory threshold shifts (near 15 dB) in GLAST KO mice than in WT mice across all tested frequencies, despite similarly reduced DPOAE. Despite these changes, inhibition using broad-band gap carriers and 32 kHz pre-pulses were not affected. Our study suggests that GLAST deficiency could become a useful experimental model to decipher the mechanisms underlying drug-induced tinnitus. Future studies addressing the neurological correlates of tinnitus in this model could provide additional insights into the
Dipole Emission In Finite Photonic Band-Gap Structures an Exactly Solvable One-Dimensional Model
Dowling, J P
1999-01-01
I consider an exact model of atomic spontaneous dipole emission and classical dipole radiation in a finite photonic band-gap structure. The full 3D or 2D problem is reduced to a finite 1D model, and then this is solved for analytically using algebraic matrix transfer techniques. The results give insight to the electromagnetic emission process in periodic dielectrics, quantitative predictions for emission in 1D dielectric stacks, and qualitative formulas for the 2D and 3D problem.
Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP
Connelly, Michael J.
2015-02-01
Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs.
Band-gap shrinkage calculations and analytic model for strained bulk InGaAsP
International Nuclear Information System (INIS)
Band-gap shrinkage is an important effect in semiconductor lasers and optical amplifiers. In the former it leads to an increase in the lasing wavelength and in the latter an increase in the gain peak wavelength as the bias current is increased. The most common model used for carrier-density dependent band-gap shrinkage is a cube root dependency on carrier density, which is strictly only true for high carrier densities and low temperatures. This simple model, involves a material constant which is treated as a fitting parameter. Strained InGaAsP material is commonly used to fabricate polarization insensitive semiconductor optical amplifiers (SOAs). Most mathematical models for SOAs use the cube root bandgap shrinkage model. However, because SOAs are often operated over a wide range of drive currents and input optical powers leading to large variations in carrier density along the amplifier length, for improved model accuracy it is preferable to use band-gap shrinkage calculated from knowledge of the material bandstructure. In this letter the carrier density dependent band-gap shrinkage for strained InGaAsP is calculated by using detailed non-parabolic conduction and valence band models. The shrinkage dependency on temperature and both tensile and compressive strain is investigated and compared to the cube root model, for which it shows significant deviation. A simple power model, showing an almost square-root dependency, is derived for carrier densities in the range usually encountered in InGaAsP laser diodes and SOAs. (paper)
Estimating New Zealand’s Output Gap Using a Small Macro Model
Kam Leong Szeto
2013-01-01
The Treasury has been testing the assumptions on the potential growth rate of the New Zealand economy. In this paper, we estimate a small macro model using Bayesian techniques, which allows us to assess the level of uncertainty of the estimates of the output gap. The model is based on the work of Benes et al. (2010) with some modifications reflecting New Zealand economic conditions. Although this new technique does not reduce the uncertainty in measures of potential output as indicated by lar...
Female Brain Drains and Women's Rights Gaps: A Gravity Model Analysis of Bilateral Migration Flows
Naghsh Nejad, Maryam; Young, Andrew
2014-01-01
In this paper we model the migration decisions of high-skilled women as a function of the benefits associated with moving from an origin with relatively low women's rights to a destination with a relatively high level of women's rights. However, the costs faced by women are decreasing in the level of women's rights provided. The model predicts a non-linear relationship between the relative levels of women's rights in destination versus origin countries (the women's rights gap) and the gender ...
Bridging the gap between gene expression and metabolic phenotype via kinetic models
Vital-Lopez, Francisco G; Wallqvist, Anders; Reifman, Jaques
2013-01-01
Background Despite the close association between gene expression and metabolism, experimental evidence shows that gene expression levels alone cannot predict metabolic phenotypes, indicating a knowledge gap in our understanding of how these processes are connected. Here, we present a method that integrates transcriptome, fluxome, and metabolome data using kinetic models to create a mechanistic link between gene expression and metabolism. Results We developed a modeling framework to construct ...
Model for synchronization of pancreatic beta-cells by gap junction coupling.
Sherman, A.; Rinzel, J
1991-01-01
Pancreatic beta-cells coupled by gap junctions in sufficiently large clusters exhibit regular electrical bursting activity, which is described by the Chay-Keizer model and its variants. According to most reports, however, isolated cells exhibit disorganized spiking. We have previously (Sherman, A. J. Rinzel, and J. Keizer, 1988. Biophys. J. 54:411-425) modeled these behaviors by hypothesizing that stochastic channel fluctuations disrupt the bursts. We showed that when cells are coupled by inf...
Diametric Tolerance Control of Dual Cooled Annular Fuel Pellet without Inner Surface Grinding
International Nuclear Information System (INIS)
A dual cooled fuel consists of internal and external cladding tubes in which annular pellets are stacked and cooling water flows in both internal and external coolant passages. It is recently being reconsidered as a promising option for a power up-rate of a pressurized water reactor fuel assembly because an annular fuel shows a lot of advantages from the point of a fuel safety and its economy due to an increased heat transfer area and a thin pellet thickness. Many technical issues might cause a serious problem to adopt the dual cooled annular fuel to the commercial PWR reactors. One of the most important issues is a heat flux split toward an internal cladding and an external cladding due to the gap conductance asymmetry which results from a preferential expansion of a fuel pellet toward the outside during an irradiation. Gap conductance is directly related to the inner and outer gap thicknesses. Initial gap thicknesses can vary with a pellet's dimensions which are affected by a reactor operation condition. Recently, it is suggested that a fuel rod with a smaller inner gap and a larger outer gap can reduce this gap conductance asymmetry. This approach can be effective only after precise tolerance technology is achieved. Because of an inhomogeneous green density distribution along the compact height, an hour-glassing usually occurred in a sintered cylindrical PWR fuel pellet fabricated by a conventional double-acting press. Thus, a sintered pellet usually undergoes a center-less grinding process in order to secure a pellet's specifications. In the case of an annular pellet fabrication using a conventional double-acting press, the same hour-glass shape would probably occur. The outer diameter tolerance of an annular pellet can be controlled easily similar to that of a conventional cylindrical PWR pellet through a center-less grinding. However, it appears not to be simple in the case of an inner surface grinding. It would be the best way to satisfy the specifications
Model based studies of some optical and electronic properties of narrow and wide gap materials
Ravindra, N. M.; Kumar, K. S.; Srivastava, V. K.; Bhardwaj, R. P.
1981-11-01
Studies are reported concerning the optical and electronic properties of narrow and wide gap materials in the groups IV, V, VI, III-V, II-VI, I-VII, IV-VI, and IV-IV, with emphasis on the high-frequency dielectric constant and its related properties. The relevance of this work to solar cells is discussed, and a comparative assessment of the models proposed by Penn (1962), Van Vechten (1969), Breckenridge et al. (1974) and Grimes and Cowley (1975) is presented. It is found that, although all of the models give adequate estimates of the Penn gap, none of them are universally applicable. In addition, studies are presented of the temperature and pressure dependence of the Penn and energy gaps and the high frequency dielectric constant, followed by an evaluation of the electron-phonon contribution to the total temperature dependence of the energy gap and the refractive index. The inverse square law governing the variation of deformation potential with the lattice parameter is found to be valid for a large number of semiconductors.
Yim Ling Loo; Alicia Y.C. Tang; Azhana Ahmad
2015-01-01
Agent-based modeling had been revolving to be established approach in modeling simulation systems which are used to understand and predict certain real-life scenarios in specific domains. Past researches which are domain-specific caused repetitive building of new models from scratch and restrict replication and reuse because of limitation of models’ description. This paper presents a review of gaps between domain-specific agent-based simulation modeling and the recent practices of agent-based...
Bioavailability and efficacy of a gap junction enhancer (PQ7 in a mouse mammary tumor model.
Directory of Open Access Journals (Sweden)
Stephanie N Shishido
Full Text Available The loss of gap junctional intercellular communication is characteristic of neoplastic cells, suggesting that the restoration with a gap junction enhancer may be a new therapeutic treatment option with less detrimental effects than traditional antineoplastic drugs. A gap junction enhancer, 6-methoxy-8-[(2-furanylmethyl amino]-4-methyl-5-(3-trifluoromethylphenyloxy quinoline (PQ7, on the normal tissue was evaluated in healthy C57BL/6J mice in a systemic drug distribution study. Immunoblot analysis of the vital organs indicates a reduction in Cx43 expression in PQ7-treated animals with no observable change in morphology. Next the transgenic strain FVB/N-Tg(MMTV-PyVT 634Mul/J (also known as PyVT was used as a spontaneous mammary tumor mouse model to determine the biological and histological effects of PQ7 on tumorigenesis and metastasis at three stages of development: Pre tumor, Early tumor, and Late tumor formation. PQ7 was assessed to have a low toxicity through intraperitoneal administration, with the majority of the compound being detected in the heart, liver, and lungs six hours post injection. The treatment of tumor bearing animals with PQ7 had a 98% reduction in tumor growth, while also decreasing the total tumor burden compared to control mice during the Pre stage of development. PQ7 treatment increased Cx43 expression in the neoplastic tissue during Pre-tumor formation; however, this effect was not observed in Late stage tumor formation. This study shows that the gap junction enhancer, PQ7, has low toxicity to normal tissue in healthy C57BL/6J mice, while having clinical efficacy in the treatment of spontaneous mammary tumors of PyVT mice. Additionally, gap junctional intercellular communication and neoplastic cellular growth are shown to be inversely related, while treatment with PQ7 inhibits tumor growth through targeting gap junction expression.
Fabrication of Annular Pellet for HANARO Irradiation Test of Dual Cooled Fuel
International Nuclear Information System (INIS)
One of the most important components in a Pressurized Water Reactor affecting its safety and economy is a nuclear fuel. The traditional PWR fuel pellet has a shape of cylindrical tablets of about 8 mm in diameter with a chamfer and dishes. A significant reduction in its failure rate has resulted from the improvements in the fuel and cladding quality. Enhanced fuel assembly design allowed appreciable power density increases. However, it is difficult to achieve a significant increase of a power density under the current fuel pin design. An internally and externally cooled annular fuel has been considered seriously as a promising solution for an extended power uprate of a PWR fuel assembly. A dual cooled annular fuel shows a lot of advantages from the point of a fuel safety and its economy due to its unique configurational merit such as an increased heat transfer area and a thin pellet thickness. There must be a lot of considerations in the various fields to introduce an annular internally and externally cooled fuel to commercial PWR reactors. The dimensional changes of the annular fuel pellets during the early irradiation stage are very important, because they have an influence on the size of the gap between the pellet and the inner/outer claddings. In order to gain an insight to how the annular pellets deform, a HANARO irradiation test is planned for annular pellets with 5 different types. The detailed specification of the annular pellet was shown in Table 1. It is noted that Type C has the same pore structure as a commercial PWR pellet. The purpose of this paper is to report on the manufacturing process of an annular fuel pellet for a HANARO irradiation test
Meer, van der P.J.; Jorritsma, I.T.M.; Kramer, K.
2002-01-01
The sensitivity of forest development to climate change is assessed using a gap model. Process descriptions in the gap model of growth, phenology, and seed production were adjusted for climate change effects using a detailed process-based growth modeland a regression analysis. Simulation runs over 4
Soliton bunching in annular Josephson junctions
DEFF Research Database (Denmark)
Vernik, I.V; Lazarides, Nickos; Sørensen, Mads Peter;
1996-01-01
By studying soliton (fluxon) motion in long annular Josephson junctions it is possible to avoid the influence of the boundaries and soliton-soliton collisions present in linear junctions. A new experimental design consisting of a niobium coil placed on top of an annular junction has been used to...
Bistability and hysteresis of annular impinging jets
Tisovsky, Tomas
2016-06-01
In present study, the bistability and hysteresis of annular impinging jets is investigated. Annular impinging jets are simulated using open source CFD code - OpenFOAM. Both flow field patterns of interest are obtained and hysteresis is found by means of dynamic mesh simulation. Effect of nozzle exit velocity on resulting hysteresis loop is also illustrated.
A mathematical model of a three-gap thyratron simulating turn-on
International Nuclear Information System (INIS)
Kicker magnets are required for all ring-to-ring transfers in the 5 rings of the proposed KAON factory synchrotron. The kick must rise/fall from 1% to 99% of full strength during the time interval of gaps created in the beam (80 ns to 160 ns) so that the beam can be extracted with minimum losses. Approximately one-third of the injection and extraction kicker magnets will operate continuously at a rate of 50 pulses per second: the others operate at 10 pulses per second. The kicker magnet PFN voltages will be in the range 50kV to 80kV, hence multi-gap thyratrons will be used for the injection and extraction kicker systems. Displacement current arising from turn-on of a multi-gap thyratron flows in the external circuit and can thus increase the effective rise-time of the kick. A mathematical model of a three-gap thyratron, which includes the drift spaces, has been developed for simulating turn-on, and is described in this paper. The thyratron model has been used to investigate ways to suppress the effects of displacement current on the kick, and to reduce thyratron switching loss. A ferrite saturating inductor may be connected adjacent to each thyratron to reduce switching loss, so that thyratron life can be extended and the kick rise-time improved. This inductor can also be used to reduce the effect of anode displacement current during turn-on of a multi-gap thyratron. The research has culminated in a predicted kick rise time (1% to 99%) of less than 50 ns for a TRIUMF 10 cell prototype kicker magnet. The proposed improvements are currently being implemented on our prototype kicker system. (author). 15 refs., 11 figs
Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model
Banik, Ivan; Kubliha, Marián; Lukovičová, Jozefa; Pavlendová, Gabriela
2015-12-01
The physical mechanism of photoluminescence spectrum formation of chalcogenide glasses (CHG) belongs to the important unsolved problems in physics of non-crystalline materials. Photoluminescence is an important means of the electron spectrum investigation. PL spectrum in CHG is produced mostly in the middle of the band gap, and its profile is normal - Gaussian. Several features of PL spectra in CHG is still a great mystery. The aim of the paper is to make reader acquainted with the new insight into the problem. In this article we also deal with the issue of clarifying the nature of mid-gap absorption. From the experiments it is known that after excitation of the glass As2S3 (or As2Se3) with primary radiation from Urbach-tail region the glass will be able to absorb the photons of low energy (IR) radiation from mid-gap region of spectra. This low photon absorption without action of the primary excitation radiation of the higher photon energy is impossible. Mid-gap absorption yields boost in the photoluminescence. The paper gives the reader the new insights into some, until now, unexplained effects and contexts in chalcogenide glasses from the position of barrier-cluster-heating model.
Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model
Energy Technology Data Exchange (ETDEWEB)
Banik, Ivan, E-mail: ivan.banik@stuba.sk; Kubliha, Marián; Lukovičová, Jozefa; Pavlendová, Gabriela [Faculty of Civil Engineering, Slovak University of Technology, 813 68 Bratislava (Slovakia)
2015-12-07
The physical mechanism of photoluminescence spectrum formation of chalcogenide glasses (CHG) belongs to the important unsolved problems in physics of non-crystalline materials. Photoluminescence is an important means of the electron spectrum investigation. PL spectrum in CHG is produced mostly in the middle of the band gap, and its profile is normal - Gaussian. Several features of PL spectra in CHG is still a great mystery. The aim of the paper is to make reader acquainted with the new insight into the problem. In this article we also deal with the issue of clarifying the nature of mid-gap absorption. From the experiments it is known that after excitation of the glass As{sub 2}S{sub 3} (or As{sub 2}Se{sub 3}) with primary radiation from Urbach-tail region the glass will be able to absorb the photons of low energy (IR) radiation from mid-gap region of spectra. This low photon absorption without action of the primary excitation radiation of the higher photon energy is impossible. Mid-gap absorption yields boost in the photoluminescence. The paper gives the reader the new insights into some, until now, unexplained effects and contexts in chalcogenide glasses from the position of barrier-cluster-heating model.
Laser-induced retinal damage thresholds for annular retinal beam profiles
Kennedy, Paul K.; Zuclich, Joseph A.; Lund, David J.; Edsall, Peter R.; Till, Stephen; Stuck, Bruce E.; Hollins, Richard C.
2004-07-01
The dependence of retinal damage thresholds on laser spot size, for annular retinal beam profiles, was measured in vivo for 3 μs, 590 nm pulses from a flashlamp-pumped dye laser. Minimum Visible Lesion (MVL)ED50 thresholds in rhesus were measured for annular retinal beam profiles covering 5, 10, and 20 mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 μm, respectively, on the primate retina. Annular beam profiles at the retinal plane were achieved using a telescopic imaging system, with the focal properties of the eye represented as an equivalent thin lens, and all annular beam profiles had a 37% central obscuration. As a check on experimental data, theoretical MVL-ED50 thresholds for annular beam exposures were calculated using the Thompson-Gerstman granular model of laser-induced thermal damage to the retina. Threshold calculations were performed for the three experimental beam diameters and for an intermediate case with an outer beam diameter of 230 μm. Results indicate that the threshold vs. spot size trends, for annular beams, are similar to the trends for top hat beams determined in a previous study; i.e., the threshold dose varies with the retinal image area for larger image sizes. The model correctly predicts the threshold vs. spot size trends seen in the biological data, for both annular and top hat retinal beam profiles.
Spontaneous calcium signals induced by gap junctions in a network model of astrocytes
Kazantsev, V. B.
2009-01-01
The dynamics of a network model of astrocytes coupled by gap junctions is investigated. Calcium dynamics of the single cell is described by the biophysical model comprising the set of three nonlinear differential equations. Intercellular dynamics is provided by the diffusion of inositol 1,4,5-trisphosphate (IP3) through gap junctions between neighboring astrocytes. It is found that the diffusion induces the appearance of spontaneous activity patterns in the network. Stability of the network steady state is analyzed. It is proved that the increase of the diffusion coefficient above a certain critical value yields the generation of low-amplitude subthreshold oscillatory signals in a certain frequency range. It is shown that such spontaneous oscillations can facilitate calcium pulse generation and provide a certain time scale in astrocyte signaling.
Skov, Søren Nielsen; Røpcke, Diana Mathilde; Ilkjær, Christine; Rasmussen, Jonas; Tjørnild, Marcell Juan; Jimenez, Jorge H; Yoganathan, Ajit P; Nygaard, Hans; Nielsen, Sten Lyager; Jensen, Morten Olgaard
2016-03-21
Limited knowledge exists about the forces acting on mitral valve annuloplasty repair devices. The aim of this study was to develop a new mitral annular force transducer to measure the forces acting on clinically used mitral valve annuloplasty devices. The design of an X-shaped transducer in the present study was optimized for simultaneous in- and out-of-plane force measurements. Each arm was mounted with strain gauges on four circumferential elements to measure out-of-plane forces, and the central parts of the X-arms were mounted with two strain gauges to measure in-plane forces. A dedicated calibration setup was developed to calibrate isolated forces with tension and compression for in- and out-of-plane measurements. With this setup, it was possible with linear equations to isolate and distinguish measured forces between the two planes and minimize transducer arm crosstalk. An in-vitro test was performed to verify the crosstalk elimination method and the assumptions behind it. The force transducer was implanted and evaluated in an 80kg porcine in-vivo model. Following crosstalk elimination, in-plane systolic force accumulation was found to be in average 4.0±0.1N and the out-of-plane annular segments experienced an average force of 1.4±0.4N. Directions of the systolic out-of-plane forces indicated movements towards a saddle shaped annulus, and the transducer was able to measure independent directional forces in individual annular segments. Further measurements with the new transducer coupled with clinical annuloplasty rings will provide a detailed insight into the biomechanical dynamics of these devices. PMID:26903412
Bridging the Gap: A Conceptual Model of the Access of Digital Libraries
Pan, Bing; Hembrooke, Helene; Gay, Geri; Gonsalves, Gerald C.
2006-01-01
This paper proposes a general conceptual model for the access of digital libraries based on relevant research in information retrieval, information seeking and foraging, and activity based design theory. The authors reveal that a gap exists in current digital library design practices in which a digital library is disconnected from its targeted user community. Search engines have disintermediated many digital library interfaces and their related evaluation and usability efforts....
Lattice Hamiltonian approach to the massless Schwinger model. Precise extraction of the mass gap
Energy Technology Data Exchange (ETDEWEB)
Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Kujawa-Cichy, Agnieszka [Poznan Univ. (Poland). Faculty of Physics; Szyniszewski, Marcin [Poznan Univ. (Poland). Faculty of Physics; Manchester Univ. (United Kingdom). NOWNano DTC
2012-12-15
We present results of applying the Hamiltonian approach to the massless Schwinger model. A finite basis is constructed using the strong coupling expansion to a very high order. Using exact diagonalization, the continuum limit can be reliably approached. This allows to reproduce the analytical results for the ground state energy, as well as the vector and scalar mass gaps to an outstanding precision better than 10{sup -6} %.
Lattice Hamiltonian approach to the massless Schwinger model. Precise extraction of the mass gap
International Nuclear Information System (INIS)
We present results of applying the Hamiltonian approach to the massless Schwinger model. A finite basis is constructed using the strong coupling expansion to a very high order. Using exact diagonalization, the continuum limit can be reliably approached. This allows to reproduce the analytical results for the ground state energy, as well as the vector and scalar mass gaps to an outstanding precision better than 10-6 %.
Modelling of streamer propagation in hydrocarbon liquids in point-plane gaps
International Nuclear Information System (INIS)
A model of streamer dynamics in hydrocarbon liquids is developed that accounts for liquid vaporization and formation of a gaseous filament behind the streamer head. Results of simulation of streamer propagation in cyclohexane in a short point-plane gap at various hydrostatic pressures and applied voltages are presented. Obtained characteristics of streamer propagation (streamer velocity, stopping length, electric current) and parameters of streamer plasma (number density of electrons, electric field in streamer channel) are compared with available experimental data. (paper)
Wendl, Michael C; Robert H Waterston
2002-01-01
We develop an extension to the Lander-Waterman theory for characterizing gaps in bacterial artificial chromosome fingerprint mapping and shotgun sequencing projects. It supports a larger set of descriptive statistics and is applicable to a wider range of project parameters. We show that previous assertions regarding inconsistency of the Lander-Waterman theory at higher coverages are incorrect and that another well-known but ostensibly different model is in fact the same. The apparent paradox ...
Mathematical modeling of gap junction coupling and electrical activity in human β-cells
Loppini, Alessandro; Braun, Matthias; Filippi, Simonetta; Gram Pedersen, Morten
2015-12-01
Coordinated insulin secretion is controlled by electrical coupling of pancreatic β-cells due to connexin-36 gap junctions. Gap junction coupling not only synchronizes the heterogeneous β-cell population, but can also modify the electrical behavior of the cells. These phenomena have been widely studied with mathematical models based on data from mouse β-cells. However, it is now known that human β-cell electrophysiology shows important differences to its rodent counterpart, and although human pancreatic islets express connexin-36 and show evidence of β-cell coupling, these aspects have been little investigated in human β-cells. Here we investigate theoretically, the gap junction coupling strength required for synchronizing electrical activity in a small cluster of cells simulated with a recent mathematical model of human β-cell electrophysiology. We find a lower limit for the coupling strength of approximately 20 pS (i.e., normalized to cell size, ˜2 pS pF-1) below which spiking electrical activity is asynchronous. To confront this theoretical lower bound with data, we use our model to estimate from an experimental patch clamp recording that the coupling strength is approximately 100-200 pS (10-20 pS pF-1), similar to previous estimates in mouse β-cells. We then investigate the role of gap junction coupling in synchronizing and modifying other forms of electrical activity in human β-cell clusters. We find that electrical coupling can prolong the period of rapid bursting electrical activity, and synchronize metabolically driven slow bursting, in particular when the metabolic oscillators are in phase. Our results show that realistic coupling conductances are sufficient to promote synchrony in small clusters of human β-cells as observed experimentally, and provide motivation for further detailed studies of electrical coupling in human pancreatic islets.
Modeling of air-gap membrane distillation process: A theoretical and experimental study
Alsaadi, Ahmad Salem
2013-06-03
A one dimensional (1-D) air gap membrane distillation (AGMD) model for flat sheet type modules has been developed. This model is based on mathematical equations that describe the heat and mass transfer mechanisms of a single-stage AGMD process. It can simulate AGMD modules in both co-current and counter-current flow regimes. The theoretical model was validated using AGMD experimental data obtained under different operating conditions and parameters. The predicted water vapor flux was compared to the flux measured at five different feed water temperatures, two different feed water salinities, three different air gap widths and two MD membranes with different average pore sizes. This comparison showed that the model flux predictions are strongly correlated with the experimental data, with model predictions being within +10% of the experimentally determined values. The model was then used to study and analyze the parameters that have significant effect on scaling-up the AGMD process such as the effect of increasing the membrane length, and feed and coolant flow rates. The model was also used to analyze the maximum thermal efficiency of the AGMD process by tracing changes in water production rate and the heat input to the process along the membrane length. This was used to understand the gain in both process production and thermal efficiency for different membrane surface areas and the resultant increases in process capital and water unit cost. © 2013 Elsevier B.V.
International Nuclear Information System (INIS)
Evaluation of global diffusion potential of learning technologies and their timely specific cost development across regions is always a challenging issue for the future technology policy preparation. Further the process of evaluation gains interest especially by endogenous treatment of energy technologies under uncertainty in learning rates with technology gap across the regions in global regional cluster learning approach. This work devised, implemented, and examined new methodologies on technology gaps (a practical problem), using two broad concepts of knowledge deficit and time lag approaches in global learning, applying the floor cost approach methodology. The study was executed in a multi-regional, technology-rich and long horizon bottom-up linear energy system model on The Integrated MARKAL EFOM System (TIMES) framework. Global learning selects highest learning technologies in maximum uncertainty of learning rate scenario, whereas any form of technology gap retards the global learning process and discourages the technologies deployment. Time lag notions of technology gaps prefer heavy utilization of learning technologies in developed economies for early reduction of specific cost. Technology gaps of any kind should be reduced among economies through the promotion and enactment of various policies by governments, in order to utilize the technological resources by mass deployment to combat ongoing climate change. (author)
International Nuclear Information System (INIS)
Evaluation of global diffusion potential of learning technologies and their timely specific cost development across regions is always a challenging issue for the future technology policy preparation. Further the process of evaluation gains interest especially by endogenous treatment of energy technologies under uncertainty in learning rates with technology gap across the regions in global regional cluster learning approach. This work devised, implemented, and examined new methodologies on technology gaps (a practical problem), using two broad concepts of knowledge deficit and time lag approaches in global learning, applying the floor cost approach methodology. The study was executed in a multi-regional, technology-rich and long horizon bottom-up linear energy system model on The Integrated MARKAL EFOM System (TIMES) framework. Global learning selects highest learning technologies in maximum uncertainty of learning rate scenario, whereas any form of technology gap retards the global learning process and discourages the technologies deployment. Time lag notions of technology gaps prefer heavy utilization of learning technologies in developed economies for early reduction of specific cost. Technology gaps of any kind should be reduced among economies through the promotion and enactment of various policies by governments, in order to utilize the technological resources by mass deployment to combat ongoing climate change.
A model for thickness effect on the band gap of amorphous germanium film
Wang, Xiao-Dong; Wang, Hai-Feng; Chen, Bo; Li, Yun-Peng; Ma, Yue-Ying
2013-05-01
A Mott-Davis-Paracrystalline model was proposed to interpret thickness effect of the band gap for amorphous germanium (a-Ge). We believe that a-Ge has a semiconductor-alloy-like structure, it may contain medium-range order (MRO) and continuous random network (CRN) simultaneously and there is a dependence of MRO/CRN ratio on film thickness and preparation methods/parameters. For MRO is dominant, thickness effect can be described by one-dimensional quantum confinement (ODQC) effect of nanocrystals and strain-induced shrinkage of the band gap; For CRN is dominant, thickness dependence can be interpreted by changes in the quality of a CRN and ODQC effect of nanoamorphous phase.
Institute of Scientific and Technical Information of China (English)
Xiaofang; ZOU; Xueqin; JIANG
2014-01-01
The increasingly widening income gap between urban and rural areas is affected by many factors. Using the stepwise regression analysis,we find that urbanization level,socio-economic development,education level,financial development scale and financial development efficiency have the greatest impact on the income gap between urban and rural areas. By cointegration test,it is found that there is a long-term equilibrium relationship between these five variables and the income gap between urban and rural areas. We build the state-space model to research the dynamic impact of these factors on the income gap between urban and rural areas. The results show that by improving the level of urbanization,we can effectively narrow the income gap between urban and rural areas,while socio-economic development,the improvement of education level,expansion of financial development scale and financial development efficiency all significantly expand the income gap between urban and rural areas.
Delsanto, P. P.; Griffa, M.; Condat, C. A.; Delsanto, S.; Morra, L.
2005-04-01
Multicellular tumor spheroids are valuable experimental tools in cancer research. By introducing an intermediate model, we have been able to successfully relate mesoscopic and macroscopic descriptions of spheroid growth. Since these descriptions stem from completely different roots (cell dynamics, and energy conservation and scaling arguments, respectively), their consistency validates both approaches and allows us to establish a direct correspondence between parameters characterizing processes occurring at different scales. Our approach may find applications as an example of bridging the gap between models at different scale levels in other contexts.
How the Human Capital Model Explains Why the Gender Wage Gap Narrowed
Solomon W. Polachek
2004-01-01
This paper explores secular changes in women?s pay relative to men?s pay. It shows how the human capital model predicts a smaller gender wage gap as male-female lifetime work expectations become more similar. The model explains why relative female wages rose almost unabated from 1890 to the early-1990s in the United States (with the exception of about 1940-1980), and why this relative wage growth tapered off since 1993. In addition to the US, the paper presents evidence from nine other countr...
Etizolam-induced superficial erythema annulare centrifugum.
Kuroda, K; Yabunami, H; Hisanaga, Y
2002-01-01
Erythema annulare centrifugum (EAC) is characterized by slowly enlarging annular erythematous lesions. Although the origin is not clear in most cases, EAC has been associated with infections, medications, and in rare cases, underlying malignancy. We describe a patient who developed annular erythematous lesions after etizolam administration. The eruptions were typical of the superficial form of EAC, both clinically and histopathologically. The lesions disappeared shortly after discontinuation of the medication. Patch testing with etizolam gave positive results. To our knowledge this is the first reported case of etizolam-induced superficial EAC. PMID:11952667
X-ray diffraction from bone employing annular and semi-annular beams
International Nuclear Information System (INIS)
There is a compelling need for accurate, low cost diagnostics to identify osteo-tissues that are associated with a high risk of fracture within an individual. To satisfy this requirement the quantification of bone characteristics such as ‘bone quality’ need to exceed that provided currently by densitometry. Bone mineral chemistry and microstructure can be determined from coherent x-ray scatter signatures of bone specimens. Therefore, if these signatures can be measured, in vivo, to an appropriate accuracy it should be possible by extending terms within a fracture risk model to improve fracture risk prediction.In this preliminary study we present an examination of a new x-ray diffraction technique that employs hollow annular and semi-annular beams to measure aspects of ‘bone quality’. We present diffractograms obtained with our approach from ex vivo bone specimens at Mo Kα and W Kα energies. Primary data is parameterized to provide estimates of bone characteristics and to indicate the precision with which these can be determined. (paper)
A generation/recombination model assisted with two trap centers in wide band-gap semiconductors
Yamaguchi, Ken; Kuwabara, Takuhito; Uda, Tsuyoshi
2013-03-01
A generation/recombination (GR) model assisted with two trap centers has been proposed for studying reverse current on pn junctions in wide band-gap semiconductors. A level (Et1) has been assumed to be located near the bottom of the conduction band and the other (Et2) to be near the top of the valence band. The GR model has been developed by assuming (1) a high-electric field; F, (2) a short distance; d, between trap centers, (3) reduction in an energy-difference; Δeff = |Et1 - Et2| - eFd, and (4) hopping or tunneling conductions between trap centers with the same energy-level (Δeff ≈ 0). The GR rate has been modeled by trap levels, capture cross-sections, trap densities, and transition rate between trap centers. The GR rate, about 1010 greater than that estimated from the single-level model, has been predicted on pn junctions in a material with band-gap of 3.1 eV. Device simulations using the proposed GR model have been demonstrated for SiC diodes with and without a guard ring. A reasonable range for reverse current at room temperature has been simulated and stable convergence has been obtained in a numerical scheme for analyzing diodes with an electrically floating region.
Analysis of a Low-Angle Annular Expander Nozzle
Directory of Open Access Journals (Sweden)
Kyll Schomberg
2015-01-01
Full Text Available An experimental and numerical analysis of a low-angle annular expander nozzle is presented to observe the variance in shock structure within the flow field. A RANS-based axisymmetric numerical model was used to evaluate flow characteristics and the model validated using experimental pressure readings and schlieren images. Results were compared with an equivalent converging-diverging nozzle to determine the capability of the wake region in varying the effective area of a low-angle design. Comparison of schlieren images confirmed that shock closure occurred in the expander nozzle, prohibiting the wake region from affecting the area ratio. The findings show that a low angle of deflection is inherently unable to influence the effective area of an annular supersonic nozzle design.
Production of annular flat-topped vortex beams
Institute of Scientific and Technical Information of China (English)
Jiannong Chen; Yongjiang Yu; Feifei Wang
2011-01-01
@@ A model of an annular flat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.%A model of an annular fiat-topped vortex beam based on multi-Gaussian superimposition is proposed. We experimentally produce this beam with a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient. This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.
Issues for Achieving an Experimental Model Concerning Bubble Deck Concrete Slab with Spherical Gaps
Directory of Open Access Journals (Sweden)
Sergiu Călin
2010-01-01
Full Text Available After realizing numerous constructions in the world, which use Bubble Deck concrete slabs with spherical gaps, valuable information were gathered, allowing a rigorous processing and systematization, with the purpose of realizing an experimental and documentary study. The paper presents some experimental programs which refer to concrete slabs with spherical gaps, existing in similar execution and loading conditions as those from a real construction; this implies the realization of a monolithic slab element at a scale of 1:1, which will be subjected to static gravitational loadings in order to determine the deformation (deflection, cracking and failing characteristics. The resultant conclusions will be used in defining the failing mechanisms, very useful in the formulation of an adequate mathematical model. The research proposed in the project offers an answer to the major objectives of the development of calculus methods and existent prescriptions of the concrete slabs with spherical gaps. The realization of the proposed objectives involves documentation activities, theoretical study, collaboration with different other partners, gathering and processing of the results obtained in laboratory and even in situ.
Large Eddy Simulation of ignition in an annular multi-injector combustor
Vicquelin, Ronan; Philip, Maxime; Boileau, Matthieu; Schmitt, Thomas; Bourgoin, Jean-François; Durox, Daniel; Candel, Sébastien
2013-11-01
The present work deals with validating the LES methodology for transient ignition simulations, and in particular elucidating the mechanisms that control the light round sequence in a laboratory annular combustor, representative of many practical industrial systems. The simulation benefits from the unique experimental database built at EM2C on a fully transparent annular chamber equipped with 16 premixed swirled injectors. The F-TACLES combustion model is used for its ability to properly represent the flame propagation.
The numerical solution of flow field of short-annular combustion chamber
Xu, H.; Ning, H.
1986-05-01
The recirculating flow field of a short-annular combustion chamber has been studied. The body-fitting coordinate system and the 'simple' method combined with a constant viscosity model have been employed to solve the Navier-Stokes equations in a regime containing a complicated curved boundary. The result could provide the theoretical reference for the design and improvement of short-annular combustion chambers.
A research on the mechanisms of transition from annular flow in two-phase pipeline flow
International Nuclear Information System (INIS)
Various kinds mechanisms of transitions from two-phase annular flow in tubes were studied and modelled, and the affection factors on the transitions were also discussed. Some mathematical equations and transition criteria for every mechanisms presented were derived, and an unified general criterion for the annular flow transitions in whole range of pipe inclinations was recommended. The boundaries predicted show good agreement with the air-water two-phase experimental data
Rutkowski, David; Rutkowski, Leslie; Plucker, Jonathan A.
2012-01-01
A recent study in the USA documented the existence and growth of "excellence gaps" among students. These gaps are similar to the minimum competency achievement gaps that proliferate in policy discussions in many Western countries, but excellence gaps focus on the highest level of achievement rather than minimum competency. We extend this research…
Divergent Field Annular Ion Engine Project
National Aeronautics and Space Administration — The proposed work investigates an approach that would allow an annular ion engine geometry to achieve ion beam currents approaching the Child-Langmuir limit. In...
Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere
Kim, Junsu; Reichler, Thomas
2015-10-01
The proper simulation of the annular mode time scale may be regarded as an important benchmark for climate models. Previous research demonstrated that this time scale is systematically overestimated by climate models. As suggested by the fluctuation-dissipation theorem, this may imply that climate models are overly sensitive to external forcings. Previous research also made it clear that calculating the AM time scale is a slowly converging process, necessitating relatively long time series and casting doubts on the usefulness of the historical reanalysis record to constrain climate models in terms of the annular mode time scale. Here, we use long control simulations with the coupled and uncoupled version of the GFDL climate model, CM2.1 and AM2.1, respectively, to study the effects of internal atmospheric variability and forcing from the lower boundary on the stability of the annular mode time scale. In particular, we ask whether a model's annular mode time scale and dynamical sensitivity can be constrained from the 50-year-long reanalysis record. We find that internal variability attaches large uncertainty to the annular mode time scale when diagnosed from decadal records. Even under the fixed forcing conditions of our long control run at least 100 years of data are required in order to keep the uncertainty in the annular mode time scale of the Northern Hemisphere to 10 %; over the Southern Hemisphere, the required length increases to 200 years. If nature's annular mode time scale over the Northern Hemisphere is similarly variable, there is no guarantee that the historical reanalysis record is a fully representative target for model evaluation. Over the Southern Hemisphere, however, the discrepancies between model and reanalysis are sufficiently large to conclude that the model is unable to reproduce the observed time scale structure correctly. The effects of ocean coupling lead to a considerable increase in time scale and uncertainty in time scale, effects which
Directory of Open Access Journals (Sweden)
Qinglei Jiang
2011-01-01
Full Text Available The current paper studies the influence of annular seal flow on the transient response of centrifugal pump rotors during the start-up period. A single rotor system and three states of annular seal flow were modeled. These models were solved using numerical integration and finite difference methods. A fluid-structure interaction method was developed. In each time step one of the three annular seal models was chosen to simulate the annular seal flow according to the state of rotor systems. The objective was to obtain a transient response of rotor systems under the influence of fluid-induced forces generated by annular seal flow. This method overcomes some shortcomings of the traditional FSI method by improving the data transfer process between two domains. Calculated results were in good agreement with the experimental results. The annular seal was shown to have a supportive effect on rotor systems. Furthermore, decreasing the seal clearance would enhance this supportive effect. In the transient process, vibration amplitude and critical speed largely changed when the acceleration of the rotor system increased.
Pressure dependence of a charge-transfer gap and a three-band Hubbard model
International Nuclear Information System (INIS)
The three-band Hubbard Hamiltonian with an attractive oxygen-oxygen interaction Upp is investigated using the Hartree-Fock approximation. Such a Hamiltonian is assumed to be a generic model for CuO2 planes of high-Tc superconductors. Both superconducting and antiferromagnetic phases are found in the separate regions of the numerically obtained (Upp,δ) phase diagrams, where δ is the hole doping. It is found that the region of stability of the superconducting phase is enhanced with decreasing values of the charge-transfer gap, in good qualitative agreement with the experimental findings
A numerical model to analyse the impact between piping and gapped restraints
International Nuclear Information System (INIS)
An algorithm to solve the impact between deformable bodies and rigid gapped restrains is presented. This kind of problem occurs in structures of nuclear power plants. This algorithm combines the Newmark method with an impact model which simulates the impulsive force as a retangular pulse. When several restraints are presented the equilibrium and the unilateral conditions are simultaneously attained by means of an iterative scheme which deals with a reduced flexibility matrix, of the order of the number of unilateral restraints, to avoid the use of the whole matrix of the system. Some numerical examples solved with the proposed algorithm show that no numerical instabilities occur. (author)
Modelling of the negative discharge in long air gaps under impulse voltages
International Nuclear Information System (INIS)
This paper presents a self-consistent model enabling the description of the whole negative discharge sequence, initiated in long air gaps under impulse voltage waves. This sequence includes the different phases of the propagation such as the initiation of the first corona, the pilot leader, the electrode and space leaders, and their junction. The model consists of using a RLC equivalent electrical network, the parameters of which vary with time according to the discharge characteristics and geometry (R, L and C being, respectively, the resistance, the inductance and the capacitance). This model provides the spatial and temporal evolution of the entire discharge, the current and the corresponding electrical charge, the power and energy injected into the gap and the velocity. It also allows us to simulate an image converter working in streak or frame mode and the leader propagation velocities as well as the trajectory of the discharge obtained from a probabilistic distribution. The computed results are compared with experimental data. Good agreement between computed and experimental results was obtained for various test configurations
Fabrication of Mn-Al doped UO{sub 2} Annular Pellet with High Thermal Stability
Energy Technology Data Exchange (ETDEWEB)
Kim, Dong Joo; Rhee, Young Woo; Yang, Jae Ho; Oh, Jang Soo; Kim, Jong Hun; Nam, Ik Hui; Kim, Keon Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2012-05-15
For a higher burnup and extended cycle, one of the innovative nuclear fuel concepts being developed has a new fuel geometry design that is of an annular sintered pellet, inner and outer cladding, and a dual cooling system which is cooled by both an internal and external coolant (dual cooled fuel). The advantages of dual cooled fuel are considerably lower surface heat flux and lower fuel temperature than those of solid fuel. While the lower heat flux gives a higher DNB (Departure from Nucleate Boiling) margin for the same power rate, the lower temperature reduces the stored energy of the fuel and cladding peak temperature. The dual cooled fuel has promising potential to increase both the reactor economy and safety. In the development of a nuclear fuel pellet, the improvement of fuel performance to reduce the FGR (Fission Gas Release) and increase the resistance to the PCI (Pellet Cladding Interaction) is a technical challenge. As in the annular fuel pellet, the in-reactor performance of dual cooled fuel can be definitely enhanced by an improvement in PCI and FGR. In the development of the dual cooled fuel concept, a 'heat split' behavior of the fuel is one of the issues that must be significantly considered. The heat split is a phenomenon with an unbalanced distribution of heat flux between inner and outer coolant-direction. In the densification of the annular pellet, inner gap of fuel will be changed narrower than outer gap of fuel. And then, the thermal resistance of inner gap will decrease lower than that of outer gap. Finally, the heat flux of inner coolant-direction will rise higher, and the temperature of inner coolant and cladding will increase. Therefore, if an annular sintered pellet with a higher thermal stability can be fabricated, the dual cooled fuel performance in the reactor can be remarkably improved. That is to say, the annular pellet with a minimized dimensional change by densification needed. In this study, an annular sintered pellet
L. Zhu; Jiang, S. Z.; Zhu, Z Q; Chan, C. C.
2009-01-01
We present a simple lumped magnetic circuit model for interior permanent-magnet (IPM) machines with multisegment and multilayer permanent magnets. We derived analytically the open-circuit air-gap field distribution, average air-gap flux density, and leakage fluxes. To verify the developed models and analytical method, we adopted finite-element analysis (FEA). We show that for prototype machines, the errors between the FEA and analytically predicted results are $≪$1% for multisegment IPM machi...
Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump
Kaushik, S. C.; Manikandan, S.; Hans, Ranjana
2016-07-01
In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter ( S r = r 2 /r 1), dimensionless temperature ratio ( θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.
Energy and Exergy Analysis of an Annular Thermoelectric Heat Pump
Kaushik, S. C.; Manikandan, S.; Hans, Ranjana
2016-04-01
In this paper, the concept of an annular thermoelectric heat pump (ATEHP) has been introduced. An exoreversible thermodynamic model of the ATEHP considering the Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for dimensionless heating power, optimum current at the maximum energy, exergy efficiency conditions and dimensionless irreversibilities in the ATEHP are derived. The results show that the heating power, energy and exergy efficiency of the ATEHP are lower than the flat-plate thermoelectric heat pump. The effects of annular shape parameter (S r = r 2 /r 1), dimensionless temperature ratio (θ = T h /T c) and the electrical contact resistances on the heating power, energy/exergy efficiency of an ATEHP have been studied. This study will help in the designing of actual ATEHP systems.
Mechanistic Modeling Reveals the Critical Knowledge Gaps in Bile Acid-Mediated DILI.
Woodhead, J L; Yang, K; Brouwer, K L R; Siler, S Q; Stahl, S H; Ambroso, J L; Baker, D; Watkins, P B; Howell, B A
2014-01-01
Bile salt export pump (BSEP) inhibition has been proposed to be an important mechanism for drug-induced liver injury (DILI). Modeling can prioritize knowledge gaps concerning bile acid (BA) homeostasis and thus help guide experimentation. A submodel of BA homeostasis in rats and humans was constructed within DILIsym, a mechanistic model of DILI. In vivo experiments in rats with glibenclamide were conducted, and data from these experiments were used to validate the model. The behavior of DILIsym was analyzed in the presence of a simulated theoretical BSEP inhibitor. BSEP inhibition in humans is predicted to increase liver concentrations of conjugated chenodeoxycholic acid (CDCA) and sulfate-conjugated lithocholic acid (LCA) while the concentration of other liver BAs remains constant or decreases. On the basis of a sensitivity analysis, the most important unknowns are the level of BSEP expression, the amount of intestinal synthesis of LCA, and the magnitude of farnesoid-X nuclear receptor (FXR)-mediated regulation. PMID:25006780
International Nuclear Information System (INIS)
This study develops the hybrid meta frontier DEA model for which inputs are distinguished into radial inputs that change proportionally and non-radial inputs that change non-proportionally, in order to measure the technical efficiency and technology gap ratios (TGR) of four different regions: Asia, Africa, America, and Europe. This paper selects 87 countries that are members of the World Energy Council from 2005 to 2007. The input variables are industry and population, while the output variances are gross domestic product (GDP) and the amount of fossil-fuel CO2 emissions. The result shows that countries’ efficiency ranking among their own region presents more implied volatility. In view of the Technology Gap Ratio, Europe is the most efficient of any region, but during the same period, Asia has a lower efficiency than other regions. Finally, regions with higher industry (or GDP) might not have higher efficiency from 2005 to 2007. And higher CO2 emissions or population also might not mean lower efficiency for other regions. In addition, Brazil is not OECD member, but it is higher efficiency than other OECD members in emerging countries case. OECD countries are better efficiency than non-OECD countries and Europe is higher than Asia to control CO2 emissions. If non-OECD countries or Asia countries could reach the best efficiency score, they should try to control CO2 emissions. - Highlights: ► The new meta frontier Model for evaluating the efficiency and technology gap ratios. ► Higher CO2 emissions might not lower efficiency than any other regions, like Europe. ► Asia’s output and CO2 emissions simultaneously increased and lower of its efficiency. ► Non-OECD or Asia countries should control CO2 emissions to reach best efficiency score.
A model describing the pressure dependence of the band gap energy for the group III-V semiconductors
Zhao, Chuan-Zhen; Wei, Tong; Sun, Xiao-Dong; Wang, Sha-Sha; Lu, Ke-Qing
2016-08-01
A model describing the pressure dependence of the band gap energy for the group III-V semiconductors has been developed. It is found that the model describes the pressure dependence of the band gap energy very well. It is also found that, although the pressure dependence of the band gap energy for both the conventional III-V semiconductors and the dilute nitride alloys can be described well by the model in this work, the physical mechanisms for them are different. In addition, the influence of the nonlinear compression of the lattice on the band gap energy is smaller than that of the coupling interaction between the N level and the conduction band minimum of the host material.
Band gap engineering in finite elongated graphene nanoribbon heterojunctions: Tight-binding model
International Nuclear Information System (INIS)
A simple model based on the divide and conquer rule and tight-binding (TB) approximation is employed for studying the role of finite size effect on the electronic properties of elongated graphene nanoribbon (GNR) heterojunctions. In our model, the GNR heterojunction is divided into three parts: a left (L) part, middle (M) part, and right (R) part. The left part is a GNR of width WL, the middle part is a GNR of width WM, and the right part is a GNR of width WR. We assume that the left and right parts of the GNR heterojunction interact with the middle part only. Under this approximation, the Hamiltonian of the system can be expressed as a block tridiagonal matrix. The matrix elements of the tridiagonal matrix are computed using real space nearest neighbor orthogonal TB approximation. The electronic structure of the GNR heterojunction is analyzed by computing the density of states. We demonstrate that for heterojunctions for which WL = WR, the band gap of the system can be tuned continuously by varying the length of the middle part, thus providing a new approach to band gap engineering in GNRs. Our TB results were compared with calculations employing divide and conquer rule in combination with density functional theory (DFT) and were found to agree nicely
Gap Analysis to Support Modeling the Long-Term Degradation of Used Nuclear Fuel Canisters
Energy Technology Data Exchange (ETDEWEB)
Jensen, Philip J.; Sunderland, Dion J.; Ross, Steven B.; Montgomery, Robert O.; Hanson, Brady D.; Devanathan, Ram
2015-04-01
Welded stainless steel canisters are being used worldwide for dry storage of used nuclear fuel (UNF) assemblies, and the number of canisters in use is steadily increasing. In support of work currently being pursued at Pacific Northwest National Laboratory to understand the atmospheric corrosion behavior of spent fuel dry storage systems, a gap analysis is underway to assess the state of knowledge for modeling of the long-term degradation of a UNF canister. The fundamental aim of this work is to inform research and development (R&D) efforts to establish a sound technical basis to support the extended dry storage of UNF for 100+ years. The analysis is considering all major components of the atmosphere corrosion degradation processes, ranging from contaminant sources and climatic interactions to regional conditions of particle transport and deposition, to microscale effects leading to stress corrosion cracking. The results of this gap analysis will be used to define the R&D pathway to develop an integrated multi-scale atmospheric corrosion modeling capability for UNF in dry storage canisters that can support the safe and reliable performance of these structures for more than 100 years.
Band gap engineering in finite elongated graphene nanoribbon heterojunctions: Tight-binding model
Energy Technology Data Exchange (ETDEWEB)
Tayo, Benjamin O. [Physics Department, Pittsburg State University, Pittsburg, KS 66762 (United States)
2015-08-15
A simple model based on the divide and conquer rule and tight-binding (TB) approximation is employed for studying the role of finite size effect on the electronic properties of elongated graphene nanoribbon (GNR) heterojunctions. In our model, the GNR heterojunction is divided into three parts: a left (L) part, middle (M) part, and right (R) part. The left part is a GNR of width W{sub L}, the middle part is a GNR of width W{sub M}, and the right part is a GNR of width W{sub R}. We assume that the left and right parts of the GNR heterojunction interact with the middle part only. Under this approximation, the Hamiltonian of the system can be expressed as a block tridiagonal matrix. The matrix elements of the tridiagonal matrix are computed using real space nearest neighbor orthogonal TB approximation. The electronic structure of the GNR heterojunction is analyzed by computing the density of states. We demonstrate that for heterojunctions for which W{sub L} = W{sub R}, the band gap of the system can be tuned continuously by varying the length of the middle part, thus providing a new approach to band gap engineering in GNRs. Our TB results were compared with calculations employing divide and conquer rule in combination with density functional theory (DFT) and were found to agree nicely.
Annular electron beam production on gamble II using a magnetically insulated splitter
International Nuclear Information System (INIS)
Annular electron beams have been tested using a post-hole convolute or magnetically insulated splitter (MIS) to feed current to both sides of a ring cathode. Beams were produced on the BLACKJACK 3 generator using a coaxial feed and from BLACKJACK 5 with a triplate feed. On BLACKJACK 3, annular cathodes with 5 cm and 10 cm mean diameters were tested. The cathodes were fed in four places by a MIS. The cathodes were 1.2 cm wide made from stainless steel or brass. Typical anode/cathode gap spacings were 0.6 cm. Experiments were performed at power levels of about 0.6 TW and energies of 30-40 kJ. Typical voltages were 0:6-1 MV with currents of about 0.8 MA. Diagnostics were diode voltage, diode current, and an X-ray pinhole camera. For the 10 cm cathode, current was measured before and after the MIS. The current on each side of the ring was measured separately. The beam voltage was determined from the diode voltage by an inductive correction. The annular beams had a linear current density of about 30 kA/cm and about 60 kA/cm for the 10 cm and 5 cm, respectively. The beam diameter at the cathode could be varied by changing the inductance on each side of the ring cathode and thereby the current balance. The impedance behavior could be modeled using the critical current formulation with a closure velocity of 3.5-4.5 cm/us. The BLACKJACK 5 geometry was a triplate feed. The ring cathode was fed by generators of 0.5 and 0.75 Ω, respectively. The MIS was used to combine the power before the cathode. The cathode had a mean diameter of 25 cm and width of 1.5-3 cm. Experiments were performed at power levels up to about6 TW and energies greater than or equal to200 kJ. Typical operating parameters were about 2 MV and 3 MA
Al-Kayiem, A. H. H.; Ibrahim, M. A.
2015-12-01
The flow behaviour and the pressure drop throughout an annular flow test section was investigated in order to evaluate and justify the reliability of experimental flow loop for wax deposition studies. The specific objective of the present paper is to assess and highlight the influence of the equivalent diameter method on the analysis of the hydrodynamic behaviour of the flow and the pressure drop throughout the annular test section. The test section has annular shape of 3 m length with three flow passages, namely; outer thermal control jacket, oil annular flow and inner pipe flow of a coolant. The oil annular flow has internal and external diameters of 0.0422 m and 0.0801 m, respectively. Oil was re-circulated in the annular passage while a cold water-glycol mixture was re-circulated in the inner pipe counter currently to the oil flow. The experiments were carried out at oil Reynolds number range of 2000 to 17000, covering laminar, transition and turbulent flow regimes. Four different methods of equivalent diameter of the annulus have been considered in this hydraulic analysis. The correction factor model for frictional pressure drop was also considered in the investigations. All methods addressed the high deviation of the prediction from the experimental data, which justified the need of a suitable pressure prediction correlation for the annular test section. The conventional hydraulic diameter method is a convenient substitute for characterizing physical dimension of a non-circular duct, and it leads to fairly good correlation between turbulent fluid flow and heat transfer characteristic of annular ducts.
Energy Technology Data Exchange (ETDEWEB)
Carbajo, Juan (Oak Ridge National Laboratory, Oak Ridge, TN); Jeong, Hae-Yong (Korea Atomic Energy Research Institute, Daejeon, Korea); Wigeland, Roald (Idaho National Laboratory, Idaho Falls, ID); Corradini, Michael (University of Wisconsin, Madison, WI); Schmidt, Rodney Cannon; Thomas, Justin (Argonne National Laboratory, Argonne, IL); Wei, Tom (Argonne National Laboratory, Argonne, IL); Sofu, Tanju (Argonne National Laboratory, Argonne, IL); Ludewig, Hans (Brookhaven National Laboratory, Upton, NY); Tobita, Yoshiharu (Japan Atomic Energy Agency, Ibaraki-ken, Japan); Ohshima, Hiroyuki (Japan Atomic Energy Agency, Ibaraki-ken, Japan); Serre, Frederic (Centre d' %C3%94etudes nucl%C3%94eaires de Cadarache %3CU%2B2013%3E CEA, France)
2011-06-01
This report summarizes the results of an expert-opinion elicitation activity designed to qualitatively assess the status and capabilities of currently available computer codes and models for accident analysis and reactor safety calculations of advanced sodium fast reactors, and identify important gaps. The twelve-member panel consisted of representatives from five U.S. National Laboratories (SNL, ANL, INL, ORNL, and BNL), the University of Wisconsin, the KAERI, the JAEA, and the CEA. The major portion of this elicitation activity occurred during a two-day meeting held on Aug. 10-11, 2010 at Argonne National Laboratory. There were two primary objectives of this work: (1) Identify computer codes currently available for SFR accident analysis and reactor safety calculations; and (2) Assess the status and capability of current US computer codes to adequately model the required accident scenarios and associated phenomena, and identify important gaps. During the review, panel members identified over 60 computer codes that are currently available in the international community to perform different aspects of SFR safety analysis for various event scenarios and accident categories. A brief description of each of these codes together with references (when available) is provided. An adaptation of the Predictive Capability Maturity Model (PCMM) for computational modeling and simulation is described for use in this work. The panel's assessment of the available US codes is presented in the form of nine tables, organized into groups of three for each of three risk categories considered: anticipated operational occurrences (AOOs), design basis accidents (DBA), and beyond design basis accidents (BDBA). A set of summary conclusions are drawn from the results obtained. At the highest level, the panel judged that current US code capabilities are adequate for licensing given reasonable margins, but expressed concern that US code development activities had stagnated and that the
Droplet sizes, dynamics and deposition in vertical annular flow
International Nuclear Information System (INIS)
The role of droplets in vertical upwards annular flow is investigated, focusing on the droplet size distributions, dynamics, and deposition phenomena. An experimental program was performed based on a new laser optical technique developed in these laboratories and implemented here for annular flow. This permitted the simultaneous measurement of droplet size, axial and radial velocity. The dependence of droplet size distributions on flow conditions is analyzed. The Upper-Log Normal function proves to be a good model for the size distribution. The mechanism controlling the maximum stable drop size was found to result from the interaction of the pressure fluctuations of the turbulent flow of the gas core with the droplet. The average axial droplet velocity showed a weak dependence on gas rates. This can be explained once the droplet size distribution and droplet size-velocity relationship are analyzed simultaneously. The surprising result from the droplet conditional analysis is that larger droplet travel faster than smaller ones. This dependence cannot be explained if the drag curves used do not take into account the high levels of turbulence present in the gas core in annular flow. If these are considered, then interesting new situations of multiplicity and stability of droplet terminal velocities are encountered. Also, the observed size-velocity relationship can be explained. A droplet deposition is formulated based on the particle inertia control. This permitted the calculation of rates of drop deposition directly from the droplet size and velocities data
The spectral gap of the 2-D stochastic Ising model with nearly single-spin boundary conditions
Alexander, Kenneth S.
2000-01-01
We establish upper bounds for the spectral gap of the stochastic Ising model at low temperature in an N-by-N box, with boundary conditions which are ``plus'' except for small regions at the corners which are either free or ``minus.'' The spectral gap decreases exponentially in the size of the corner regions, when these regions are of size at least of order \\log N. This means that removing as few as O(\\log N) plus spins from the corners produces a spectral gap far smaller than the order N^{-2}...
Energy Technology Data Exchange (ETDEWEB)
Wright, Catherine S.; Berends, Rebecca F. [Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, 70 Cowcaddens Road, Glasgow G4 0BA (United Kingdom); Flint, David J. [Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE (United Kingdom); Martin, Patricia E.M., E-mail: Patricia.Martin@gcu.ac.uk [Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, 70 Cowcaddens Road, Glasgow G4 0BA (United Kingdom)
2013-02-15
Reducing Cx43 expression stimulates skin wound healing. This is mimicked in models when Cx43 function is blocked by the connexin mimetic peptide Gap27. IGF-I also stimulates wound healing with IGFBP-5 attenuating its actions. Further, the IGF-I to IGFBP-5 ratio is altered in diabetic skin, where wound closure is impaired. We investigated whether Gap27 remains effective in augmenting scrape-wound closure in human skin wound models simulating diabetes-induced changes, using culture conditions with raised glucose, insulin and IGFBP-5. Gap27 increased scrape-wound closure in normal glucose and insulin (NGI) and to a lesser extent in high glucose and insulin (HGI). IGF-I enhanced scrape-wound closure in keratinocytes whereas IGFBP-5 inhibited this response. Gap27 overcame the inhibitory effects of IGFBP-5 on IGF-I activity. Connexin-mediated communication (CMC) was reduced in HGI, despite raised Cx43, and Gap27 significantly decreased CMC in NGI and HGI. IGF-I and IGFBP-5 did not affect CMC. IGF-I increased keratinocyte proliferation in NGI, and Gap27 increased proliferation in NGI to a greater extent than in HGI. We conclude that IGF-I and Gap27 stimulate scrape-wound closure by independent mechanisms with Gap27 inhibiting Cx43 function. Gap27 can enhance wound closure in diabetic conditions, irrespective of the IGF-I:IGFBP-5 balance. - Highlights: ► Human organotypic and keratinocyte ‘diabetic’ skin models were used to demonstrate the ability of Gap27 to improve scrape-wound closure. ► Gap27 enhanced scrape-wound closure by reducing Cx43-mediated communication, whereas IGFBP-5 retarded cell migration. ► IGF-I and IGFBP-5 did not affect connexin-mediated pathways. ► Gap27 can override altered glucose, insulin, IGF-I, and IGFBP-5 in ‘diabetic’ skin models and thus has therapeutic potential.
International Nuclear Information System (INIS)
Reducing Cx43 expression stimulates skin wound healing. This is mimicked in models when Cx43 function is blocked by the connexin mimetic peptide Gap27. IGF-I also stimulates wound healing with IGFBP-5 attenuating its actions. Further, the IGF-I to IGFBP-5 ratio is altered in diabetic skin, where wound closure is impaired. We investigated whether Gap27 remains effective in augmenting scrape-wound closure in human skin wound models simulating diabetes-induced changes, using culture conditions with raised glucose, insulin and IGFBP-5. Gap27 increased scrape-wound closure in normal glucose and insulin (NGI) and to a lesser extent in high glucose and insulin (HGI). IGF-I enhanced scrape-wound closure in keratinocytes whereas IGFBP-5 inhibited this response. Gap27 overcame the inhibitory effects of IGFBP-5 on IGF-I activity. Connexin-mediated communication (CMC) was reduced in HGI, despite raised Cx43, and Gap27 significantly decreased CMC in NGI and HGI. IGF-I and IGFBP-5 did not affect CMC. IGF-I increased keratinocyte proliferation in NGI, and Gap27 increased proliferation in NGI to a greater extent than in HGI. We conclude that IGF-I and Gap27 stimulate scrape-wound closure by independent mechanisms with Gap27 inhibiting Cx43 function. Gap27 can enhance wound closure in diabetic conditions, irrespective of the IGF-I:IGFBP-5 balance. - Highlights: ► Human organotypic and keratinocyte ‘diabetic’ skin models were used to demonstrate the ability of Gap27 to improve scrape-wound closure. ► Gap27 enhanced scrape-wound closure by reducing Cx43-mediated communication, whereas IGFBP-5 retarded cell migration. ► IGF-I and IGFBP-5 did not affect connexin-mediated pathways. ► Gap27 can override altered glucose, insulin, IGF-I, and IGFBP-5 in ‘diabetic’ skin models and thus has therapeutic potential
Directory of Open Access Journals (Sweden)
Esmaeil Kavousy
2011-07-01
Full Text Available This article aims to study the expectations gap between the status quo and desired status of tourism industry based on cultural indices in public and private sectors in Iran and present a model for determining such expectation gap. It initially deals with the most common definition of tourism and reviews types of tourism and travel incentives in Iran, and then introduces the research conceptual model based on the theory of Edgar Schein. The results from the study shows that there is a meaningful and deep difference and deviations in the expectation gap between the status quo of tourism industry and the desired status in the future prospects of this industry in the country and it is better to offer some practical solutions to reduce the distance or fill the gap between these two statuses.
Design and performance evaluation of a novel magnetorheological valve with a tunable resistance gap
International Nuclear Information System (INIS)
This paper outlines the design and development of a novel magnetorheological (MR) valve with a tunable resistance gap that varies from 1 mm to 2 mm by rotating a valve spool. The finite element modelling and analysis of this proposed MR valve was carried out using ANSYS/Emag software, including achieving the optimal magnetic field distribution and magnetic flux density. A mathematical model of the pressure drop in the MR valve was built to study the pressure drop mechanism while considering the conical annular resistance gap. Moreover, this proposed MR valve with a tunable resistance gap was prototyped and evaluated experimentally, showing that the MR valve has significantly improved its efficiency. (technical note)
Calibrating and testing a gap model for simulating forest management in the Oregon Coast Range
Pabst, R.J.; Goslin, M.N.; Garman, S.L.; Spies, T.A.
2008-01-01
The complex mix of economic and ecological objectives facing today's forest managers necessitates the development of growth models with a capacity for simulating a wide range of forest conditions while producing outputs useful for economic analyses. We calibrated the gap model ZELIG to simulate stand-level forest development in the Oregon Coast Range as part of a landscape-scale assessment of different forest management strategies. Our goal was to incorporate the predictive ability of an empirical model with the flexibility of a forest succession model. We emphasized the development of commercial-aged stands of Douglas-fir, the dominant tree species in the study area and primary source of timber. In addition, we judged that the ecological approach of ZELIG would be robust to the variety of other forest conditions and practices encountered in the Coast Range, including mixed-species stands, small-scale gap formation, innovative silvicultural methods, and reserve areas where forests grow unmanaged for long periods of time. We parameterized the model to distinguish forest development among two ecoregions, three forest types and two site productivity classes using three data sources: chronosequences of forest inventory data, long-term research data, and simulations from an empirical growth-and-yield model. The calibrated model was tested with independent, long-term measurements from 11 Douglas-fir plots (6 unthinned, 5 thinned), 3 spruce-hemlock plots, and 1 red alder plot. ZELIG closely approximated developmental trajectories of basal area and large trees in the Douglas-fir plots. Differences between simulated and observed conifer basal area for these plots ranged from -2.6 to 2.4 m2/ha; differences in the number of trees/ha ???50 cm dbh ranged from -8.8 to 7.3 tph. Achieving these results required the use of a diameter-growth multiplier, suggesting some underlying constraints on tree growth such as the temperature response function. ZELIG also tended to overestimate
Lee, Joohwi; Seko, Atsuto; Shitara, Kazuki; Nakayama, Keita; Tanaka, Isao
2016-03-01
Machine learning techniques are applied to make prediction models of the G0W0 band gaps for 270 inorganic compounds using Kohn-Sham (KS) band gaps, cohesive energy, crystalline volume per atom, and other fundamental information of constituent elements as predictors. Ordinary least squares regression (OLSR), least absolute shrinkage and selection operator, and nonlinear support vector regression (SVR) methods are applied with two levels of predictor sets. When the KS band gap by generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) or modified Becke-Johnson (mBJ) is used as a single predictor, the OLSR model predicts the G0W0 band gap of randomly selected test data with the root-mean-square error (RMSE) of 0.59 eV. When KS band gap by PBE and mBJ methods are used together with a set of predictors representing constituent elements and compounds, the RMSE decreases significantly. The best model by SVR yields the RMSE of 0.24 eV. Band gaps estimated in this way should be useful as predictors for virtual screening of a large set of materials.
Probing gamma-ray emissions of Fermi-LAT pulsars with a non-stationary outer gap model
Takata, J; Cheng, K S
2015-01-01
We explore a non-stationary outer gap scenario for gamma-ray emission process in pulsar magnetosphere. Electrons/positrons that migrate along the magnetic field line and enter the outer gap from the outer/inner boundaries activate the pair-creation cascade and high-energy emission process. In our model, the rate of the particle injection at the gap boundaries is key physical quantity to control the gap structure and properties of the gamma-ray spectrum. Our model assumes that the injection rate is time variable and the observed gamma-ray spectrum are superposition of the emissions from different gap structures with different injection rates at the gap boundaries. The calculated spectrum superposed by assuming power law distribution of the particle injection rate can reproduce sub-exponential cut-off feature in the gamma-ray spectrum observed by Fermi-LAT. We fit the phase-averaged spectra for 43 young/middle-age pulsars and 14 millisecond pulsars with the model. Our results imply that (1) a larger particle in...
Ni, Haibin; Wang, Ming; Shen, Tianyi; Zhou, Jing
2015-02-24
Surface plasmons that propagate along cylindrical metal/dielectric interfaces in annular apertures in metal films, called cylindrical surface plasmons (CSPs), exhibit attractive optical characteristics. However, it is challenging to fabricate these nanocoaxial structures. Here, we demonstrate a practical low-cost route to manufacture highly ordered, large-area annular cavity arrays (ACAs) that can support CSPs with great tunability. By employing a sol-gel coassembly method, reactive ion etching and metal sputtering techniques, regular, highly ordered ACAs in square-centimeter-scale with a gap width tunable in the range of several to hundreds of nanometers have been produced with good reproducibility. Ag ACAs with a gap width of 12 nm and a gap height of 635 nm are demonstrated. By finite-difference time-domain simulation, we confirm that the pronounced dips in the reflectance spectra of ACAs are attributable to CSP resonances excited in the annular gaps. By adjusting etching time and Ag film thickness, the CSP dips can be tuned to sweep the entire optical range of 360 to 1800 nm without changing sphere size, which makes them a promising candidate for forming integrated plasmonic sensing arrays. The high tunability of the CSP resonant frequencies together with strong electric field enhancement in the cavities make the ACAs promising candidates for surface plasmon sensors and SERS substrates, as, for example, they have been used in liquid refractive index (RI) sensing, demonstrating a sensitivity of 1505 nm/RIU and a figure of merit of 9. One of the CSP dips of ACAs with a certain geometry size is angle- (0-70 degrees) and polarization-independent and can be used as a narrow-band absorber. Furthermore, the nano annular cavity arrays can be used to construct solar cells, nanolasers and nanoparticle plasmonic tweezers. PMID:25639937
Energy Technology Data Exchange (ETDEWEB)
D' Ambros, Alder C.; Vitorassi, Pedro H.; Franco, Admilson T.; Morales, Rigoberto E.M. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Matins, Andre Leibsohn [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Tecnologia de Engenharia de Perfuracao
2008-07-01
The success of oil well drilling process depends on the correct prediction of the velocities and stresses fields inside the gap between the drill string and the rock formation. Using CFD is possible to predict the behavior of the drilling fluid flow along the annular space, from the bottom to the top of the well. Commonly the drilling fluid is modeled as a Herschel-Bulkley fluid. An alternative is to employ a non-linear viscoelastic model, like the one developed by Phan-Thien-Tanner (PTT). In the present work the PTT constitutive equation is used to model the drilling fluid flow along the annular space. Thus, this work investigates the influence of the Deborah number on the laminar flow pattern through the numerical solution of the equations formed by the coupled velocity-pressure-stress fields. The results are analyzed and validated against the analytical solution for the fully developed annular pipe flow. The relation between the Deborah number (De) and the entry length is investigated, along with the influence of high values of Deborah number on the friction factor, stress and velocity fields. (author)
Bridging the Gap between RF and Optical Patch Antenna Analysis via the Cavity Model
Unal, G. S.; Aksun, M. I.
2015-11-01
Although optical antennas with a variety of shapes and for a variety of applications have been proposed and studied, they are still in their infancy compared to their radio frequency (rf) counterparts. Optical antennas have mainly utilized the geometrical attributes of rf antennas rather than the analysis tools that have been the source of intuition for antenna engineers in rf. This study intends to narrow the gap of experience and intuition in the design of optical patch antennas by introducing an easy-to-understand and easy-to-implement analysis tool in rf, namely, the cavity model, into the optical regime. The importance of this approach is not only its simplicity in understanding and implementation but also its applicability to a broad class of patch antennas and, more importantly, its ability to provide the intuition needed to predict the outcome without going through the trial-and-error simulations with no or little intuitive guidance by the user.
González-Jiménez, Nicolás; Reisenegger, Andreas
2014-01-01
When a rotating neutron star loses angular momentum, the progressive reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (rotochemical heating). This effect has previously been studied by Fern\\'andez & Reisenegger (2005) for non-superfluid neutron stars and by Petrovich & Reisenegger (2010) for superfluid millisecond pulsars. Both studies found that pulsars reach a quasi-steady state in which the compression driving the matter out of beta equilibrium is balanced by the reactions trying to restore the equilibrium. We extend previous studies by considering the effect of density-dependence and anisotropy of the superfluid energy gaps, for the case in which the dominant reactions are the modified Urca processes, the protons are non-superconducting, and the neutron superfluidity is parametrized by models proposed in the literature. By comparing our prediction...
Annular bilayer magnetoelectric composites: theoretical analysis.
Guo, Mingsen; Dong, Shuxiang
2010-01-01
The laminated bilayer magnetoelectric (ME) composites consist of magnetostrictive and piezoelectric layers are known to have giant ME coefficient due to the high coupling efficiency in bending mode. In our previous report, the bar-shaped bilayer composite has been investigated by using a magnetoelectric-coupling equivalent circuit. Here, we propose an annular bilayer ME composite, which consists of magnetostrictive and piezoelectric rings. This composite has a much lower resonance frequency of bending mode compared with its radial mode. In addition, the annular bilayer ME composite is expected to respond to vortex magnetic field as well as unidirectional magnetic field. In this paper, we investigate the annular bilayer ME composite by using impedance-matrix method and predict the ME coefficients as a function of geometric parameters of the composites. PMID:20178914
Berge, Joel; Christophe, Bruno; Liorzou, Françoise
Theories beyond the standard model aim to face several challenges: connect gravitation with the other three known forces, and shed light on dark matter and dark energy. Although General Relativity has been incredibly successful at passing laboratory / Solar System scales tests to date, it is a classical theory (hence, incompatible with quantum physics scales) and it fails at explaining large scale astrophysical observations such as galaxy rotation curves and the accelerated expansion of the Universe without introducing dark matter and dark energy. Thus, most theories beyond the standard model explore modifications to General Relativity. Those modifications, whether they consist in adding an extra scalar field or adding a scale-dependence to the gravitation laws, allow us to predict small deviations from General Relativity at laboratory / Solar System scales. For instance, such a deviation could have explained the Pioneer anomaly, where the Pioneer probes were measured to undergo an unexpected acceleration. Although this anomaly has recently been accounted for by an instrumental thermal radiation, precise measurements of the non-gravitational forces applied to the probes would have helped decide whether the observed behavior was due to gravitational or non-gravitational physics. As a result, several missions have been proposed to embark an accelerometer on-board an interplanetary probe. Indeed, an accelerometer will measure the non-gravitational accelerations applied to the probe, thereby separating the potentially measured departures from a pure geodetic trajectory into their gravitational and non-gravitational components, and allowing us to easily constrain General Relativity in deep space. The Gravity Advanced Package (GAP) is an instrument developed for this purpose. It is composed of a 3-axes electrostatic accelerometer called MicroSTAR and a rotating platform called Bias Rejection System. It aims to provide an unbiased measurement of a spacecraft's non
Sanchez-Vila, X.; Ackerer, P.; Delay, F.; Guadagnini, A.
2016-03-01
We analyze drawdown reciprocity gaps emerging in interference tests performed in a confined fissured karstic formation. Modeling the system as a dual porosity continuum allows characterizing the dynamics of the relative contribution of the connected fractures and the rock matrix to the total flow rate extracted at the pumping wells. Observed lack of reciprocity of drawdowns can then be linked to the occurrence of processes that are not accounted for in the classical flow models based on a single-continuum representation of the system through flow equations grounded on Darcy's law only. We show that interpreting the system as a dual porosity continuum can cause drawdown reciprocity gaps to emerge as a consequence of local effects associated with an identifiable contribution of the matrix to the total fluid extracted at the well location during pumping. These theoretical results are then employed to identify the contribution to the flow being supplied to the pumping well by the low conductivity matrix constituting the host rock formation, in contrast to that provided by the fractures. An application to data from two interference tests performed at the Hydrogeological Experimental Site (HES) in Poitiers, France, illustrates the approach. We show that, whenever the matrix is assumed to provide a contribution to the total flow rate extracted, nonreciprocity is expected, the latter being linked to the occurrence of a differential drawdown between fracture and matrix at the pumping well. This difference decreases with time in the example presented, displaying a power law late time behavior, with nonreciprocity effects persisting up to remarkably long times.
Modelling of impurity deposition in gaps of castellated structures in TEXTOR with the 3DGap code
International Nuclear Information System (INIS)
In fusion devices, fuel-rich redeposited layers are formed on plasma shadowed areas and especially in narrow gaps between surface tiles. The Monte-Carlo neutral transport code 3DGap has been developed to study impurity deposition in such gaps. Coupling with Particle-in-Cell simulations allows accounting for plasma penetration into the gaps. The code is applied to study carbon deposition in gaps of the ITER-like castellated test limiter (CTL) and between tiles of the toroidal belt limiter ALT-II of TEXTOR. In case of CTL, the deposition on gap sides can be quantitatively reproduced. However, certain discrepancies remain for the gap bottom. Similarly, deposition at side walls and at the bottom was observed in ALT-II gaps. In this experiment, boronization and normal plasma operation phases were alternated. Atomic ratio boron/carbon of about 3 in the deposit at the bottom in gaps was measured, while carbon dominates deposition near the gap entrance. This issue will be addressed together with the poloidal-toroidal asymmetry of carbon deposition in gaps.
FRANCO, Finite Element Method (FEM) Fuel Rod Analysis for Solid and Annular Configurations
International Nuclear Information System (INIS)
1 - Description of program or function: The FRANCO code is a quasi- static two-dimensional fuel rod analysis code, that calculates the fuel temperature and material deformation as a function of heat generation rate. Both solid and annular fuel configurations are modeled. 2 - Method of solution: FRANCO uses two-dimensional finite element theory and applications for mechanical deformation and heat conduction, and determines the temperature distribution from the fuel center to the coolant adjacent to the clad at a position along the fuel rod axis. FRANCO calculates the average temperature of each radial division, the nodal displacement, and strain and stress within the fuel pellet and clad. The principal stresses, which represent maximum and minimum stresses within an element, result from Mohr's circle relationship between normal stresses. FRANCO is capable of predicting the thermo-mechanical behavior in the radial direction of a single fuel rod for both boiling water reactors (BWR's) and pressurized water reactors (PWR's). The cross sectional plane geometry of fuel rod is modeled using three-node constant strain triangular finite elements, and both thermal and mechanical solutions are computed with the same finite element configurations. The local linear heat generation rate is modeled as a uniform heat source in a fuel pellet, and the coolant temperature and heat transfer coefficient are applied as known boundary conditions at the boundary of the cladding surface. The total load to form the global force vector consists of the thermal load that results from thermal expansion of the material and the mechanical load exerted by pressure. FRANCO assumes the fuel-cladding gap region to be conductive material in order to simplify the analysis, and this gap is simulated by either an open gap or a closed gap model. A time- dependent problem can be simulated by FRANCO using quasi-static analysis when time-dependent parameters are provided. FRANCO can treat a steady-state or
Stitching algorithm for annular subaperture interferometry
Institute of Scientific and Technical Information of China (English)
Xi Hou; Fan Wu; Li Yang; Shibin Wu; Qiang Chen
2006-01-01
@@ Annular subaperture interferometry (ASI) has been developed for low cost and flexible test of rotationally symmetric aspheric surfaces, in which accurately combining the subaperture measurement data corrupted by misalignments and noise into a complete surface figure is the key problem. By introducing the Zernike annular polynomials which are orthogonal over annulus, a method that eliminates the coupling problem in the earlier algorithm based on Zernike circle polynomials is proposed. Vector-matrix notation is used to simplify the description and calculations. The performance of this reduction method is evaluated by numerical simulation. The results prove this method with high precision and good anti-noise capability.
Optimal Thrust Vectoring for an Annular Aerospike Nozzle Project
National Aeronautics and Space Administration — Recent success of an annular aerospike flight test by NASA Dryden has prompted keen interest in providing thrust vector capability to the annular aerospike nozzle...
Dilemma of Facts and Perceptions: The Crisis Communication Model of Expectation Gaps
Rui-Xiang Wang; Hui-Chung Yao
2015-01-01
Crisis communication theories suggest that crisis communications must appeal to publics’ perceptions and expectations. But in crisis there could be gaps between communicators and audiences about communicated objects. There were two kinds of gaps could happen: crisis situations and expected strategies. The gaps between the organization and publics in crisis communication dynamic are still unexplored. This research designed virtual crisis situations and communication strategies, surveyed the su...
Experimental model of a bone gap by radial ostectomy in rabbits
Directory of Open Access Journals (Sweden)
Antonio Carlos Cunha Lacreta Junior
2010-09-01
Full Text Available A lot of experimental models have been used to study the process of a fracture’s consolidation, but the problem is that due to anatomic, biologic and technical differences, these models do not always have appropriate parameters for the exact species, for which the experiment was done. The rabbit is an experimental model that is widely used in studies involving bone physiopatology in the face of fractures and their different types of treatment, corresponding to approximately 35% of all the musculoskeletic system’s scientific studies. Several surgical techniques have been used on rabbit’s bone for experimental studies, and the partial ostectomy of the radius bone is one of them. In this study, 14 rabbits (Oryctolagus cuniculus familiaris, males, adults, of white New Zeland breed, neutered, with weight between three and four kilograms, were used. Clinically, the animals did not present any alterations that compromised the study. There were evaluated through radiographic exam on days zero, 30 and 60 after the surgery, visualizing the quality of the gap and the relevant alteration of bone proliferation. The histologic exam elucidated the neoformed bone architecture and its components. The efficacy of the techinique was proved and it could be reproduced for many purposes in orthopedic surgery.
Observational Properties of Proto-planetary Disk Gaps
Varniere, Peggy; Bjorkman, J. E.; Quillen, Adam Frank Alice C.; Carciofi, A. C.; Whitney, Barbara A.; Wood, Kenneth
2005-01-01
We study the effects of an annular gap induced by an embedded proto-planet on disk scattered light images and the infrared spectral energy distribution. We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within in the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given ...
Directory of Open Access Journals (Sweden)
Riedel M.
2013-04-01
Full Text Available The laser-optical research of the flow inside the lubricating gap of a journal bearing model is one important task in a larger overall project. The long-term objective is the development of an easy-to-work calculation tool which delivers information about the causes and consequences of cavitation processes in hydrodynamically lubricated journal bearings. Hence, it will be possible to find statements for advantageous and disadvantageous geometrical shapes of the bushings. In conclusion such a calculation tool can provide important insights for the construction and design of future journal bearings. Current design programs are based on a two-dimensional approach for the lubricating gap. The first dimension is the breath of the bearing and the second dimension is the circumferential direction of the bearing. The third dimension, the expansion of the gap in radial direction, will be neglected. Instead of an exact resolution of the flow pattern inside the gap, turbulence models are in use. Past studies on numerical and experimental field have shown that inside the lubricating gap clearly organized and predominantly laminar flow structures can be found. Thus, for a detailed analysis of the reasons and effects of cavitation bubbles, a three-dimensional resolution of the lubricating gap is inevitable. In addition to the qualitative evaluation of the flow with visualization experiments it is possible to perform angle-based velocity measurements inside the gap with the help of a triggered Laser-Doppler- Velocimeter (LDV. The results of these measurements are used to validate three-dimensional CFD flow simulations, and to optimize the numerical mesh structure and the boundary conditions. This paper will present the experimental setup of the bearing model, some exemplary results of the visualization experiments and LDV measurements as well as a comparison between experimental and numerical results.
Directory of Open Access Journals (Sweden)
Judith Somekh
2012-12-01
Full Text Available We propose a Conceptual Model-based Systems Biology framework for qualitative modeling, executing, and eliciting knowledge gaps in molecular biology systems. The framework is an adaptation of Object-Process Methodology (OPM, a graphical and textual executable modeling language. OPM enables concurrent representation of the system's structure-the objects that comprise the system, and behavior-how processes transform objects over time. Applying a top-down approach of recursively zooming into processes, we model a case in point-the mRNA transcription cycle. Starting with this high level cell function, we model increasingly detailed processes along with participating objects. Our modeling approach is capable of modeling molecular processes such as complex formation, localization and trafficking, molecular binding, enzymatic stimulation, and environmental intervention. At the lowest level, similar to the Gene Ontology, all biological processes boil down to three basic molecular functions: catalysis, binding/dissociation, and transporting. During modeling and execution of the mRNA transcription model, we discovered knowledge gaps, which we present and classify into various types. We also show how model execution enhances a coherent model construction. Identification and pinpointing knowledge gaps is an important feature of the framework, as it suggests where research should focus and whether conjectures about uncertain mechanisms fit into the already verified model.
A New Annular Shear Piezoelectric Accelerometer
DEFF Research Database (Denmark)
Liu, Bin; Kriegbaum, B.
2000-01-01
This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...
Azimuthally forced flames in an annular combustor
Worth, Nicholas; Dawson, James; Mastorakos, Epaminondas
2015-11-01
Thermoacoustic instabilities are more likely to occur in lean burn combustion systems, making their adoption both difficult and costly. At present, our knowledge of such phenomena is insufficient to produce an inherently stable combustor by design, and therefore an improved understanding of these instabilities has become the focus of a significant research effort. Recent experimental and numerical studies have demonstrated that the symmetry of annular chambers permit a range of self-excited azimuthal modes to be generated in annular geometry, which can make the study of isolated modes difficult. While acoustic forcing is common in single flame experiments, no equivalent for forced azimuthal modes in an annular chamber have been demonstrated. The present investigation focuses on the novel application of acoustic forcing to a laboratory scale annular combustor, in order to generate azimuthal standing wave modes at a prescribed frequency and amplitude. The results focus on the ability of the method to isolate the mode of oscillation using experimental pressure and high speed OH* measurements. The successful excitation of azimuthal modes demonstrated represents an important step towards improving our fundamental understanding of this phenomena in practically relevant geometry.
Animating Research with Counseling Values: A Training Model to Address the Research-to-Practice Gap
Lee, Kristi A.; Dewell, John A.; Holmes, Courtney M.
2014-01-01
The persistent research-to-practice gap poses a problem for counselor education. The gap may be caused by conflicts between the humanistic values that guide much of counseling and the values that guide research training. In this article, the authors address historical concerns regarding research training for students and the conducting of research…
Hydro-economic Modeling: Reducing the Gap between Large Scale Simulation and Optimization Models
Forni, L.; Medellin-Azuara, J.; Purkey, D.; Joyce, B. A.; Sieber, J.; Howitt, R.
2012-12-01
The integration of hydrological and socio economic components into hydro-economic models has become essential for water resources policy and planning analysis. In this study we integrate the economic value of water in irrigated agricultural production using SWAP (a StateWide Agricultural Production Model for California), and WEAP (Water Evaluation and Planning System) a climate driven hydrological model. The integration of the models is performed using a step function approximation of water demand curves from SWAP, and by relating the demand tranches to the priority scheme in WEAP. In order to do so, a modified version of SWAP was developed called SWEAP that has the Planning Area delimitations of WEAP, a Maximum Entropy Model to estimate evenly sized steps (tranches) of water derived demand functions, and the translation of water tranches into crop land. In addition, a modified version of WEAP was created called ECONWEAP with minor structural changes for the incorporation of land decisions from SWEAP and series of iterations run via an external VBA script. This paper shows the validity of this integration by comparing revenues from WEAP vs. ECONWEAP as well as an assessment of the approximation of tranches. Results show a significant increase in the resulting agricultural revenues for our case study in California's Central Valley using ECONWEAP while maintaining the same hydrology and regional water flows. These results highlight the gains from allocating water based on its economic compared to priority-based water allocation systems. Furthermore, this work shows the potential of integrating optimization and simulation-based hydrologic models like ECONWEAP.ercentage difference in total agricultural revenues (EconWEAP versus WEAP).
Strategy and gaps for modeling, simulation, and control of hybrid systems
Energy Technology Data Exchange (ETDEWEB)
Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Garcia, Humberto E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hovsapian, Rob [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mesina, George L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bragg-Sitton, Shannon M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Boardman, Richard D. [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-04-01
, dynamic energy systems requires multiple simulation tools, potentially developed in several programming languages and resolved on separate time scales. Whereas further investigation and development of hybrid concepts will provide a more complete understanding of the joint computational and physical modeling needs, this report highlights areas in which co-simulation capabilities are warranted. The current development status, quality assurance, availability and maintainability of simulation tools that are currently available for hybrid systems modeling is presented. Existing gaps in the modeling and simulation toolsets and development needs are subsequently discussed. This effort will feed into a broader Roadmap activity for designing, developing, and demonstrating hybrid energy systems.
Tian, Junfang; Ma, Shoufeng; Zhu, Chenqiang; Jiang, Rui; Ding, YaoXian
2015-01-01
This paper proposes an improved cellular automaton traffic flow model based on the brake light model, which takes into account that the desired time gap of vehicles is remarkably larger than one second. Although the hypothetical steady state of vehicles in the deterministic limit corresponds to a unique relationship between speeds and gaps in the proposed model, the traffic states of vehicles dynamically span a two-dimensional region in the plane of speed versus gap, due to the various randomizations. It is shown that the model is able to well reproduce (i) the free flow, synchronized flow, jam as well as the transitions among the three phases; (ii) the evolution features of disturbances and the spatiotemporal patterns in a car-following platoon; (iii) the empirical time series of traffic speed obtained from NGSIM data. Therefore, we argue that a model can potentially reproduce the empirical and experimental features of traffic flow, provided that the traffic states are able to dynamically span a 2D speed-gap...
Energy Technology Data Exchange (ETDEWEB)
Wardle, K.E. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
2013-07-01
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup.
International Nuclear Information System (INIS)
Liquid-liquid contacting equipment used in solvent extraction processes has the dual purpose of mixing and separating two immiscible fluids. Consequently, such devices inherently encompass a wide variety of multiphase flow regimes. A hybrid multiphase computational fluid dynamics (CFD) solver which combines the Eulerian multi-fluid method with VOF (volume of fluid) sharp interface capturing has been developed for application to annular centrifugal contactors. This solver has been extended to enable prediction of mean droplet size and liquid-liquid interfacial area through a single moment population balance method. Simulations of liquid-liquid mixing in a simplified geometry and a model annular centrifugal contactor are reported with droplet breakup/coalescence models being calibrated versus available experimental data. Quantitative comparison is made for two different housing vane geometries and it is found that the predicted droplet size is significantly smaller for vane geometries which result in higher annular liquid holdup
Modelling and design of complete photonic band gaps in two-dimensional photonic crystals
Indian Academy of Sciences (India)
Yogita Kalra; R K Sinha
2008-01-01
In this paper, we investigate the existence and variation of complete photonic band gap size with the introduction of asymmetry in the constituent dielectric rods with honeycomb lattices in two-dimensional photonic crystals (PhC) using the plane-wave expansion (PWE) method. Two examples, one consisting of elliptical rods and the other comprising of rectangular rods in honeycomb lattices are considered with a view to estimate the design parameters for maximizing the complete photonic band gap. Further, it has been shown that complete photonic band gap size changes with the variation in the orientation angle of the constituent dielectric rods.
Sabbe, Maarten; Reyniers, Marie-Françoise; Reuter, Karsten
2012-01-01
Electronic structure calculations have emerged as a key contributor in modern heterogeneous catalysis research, though their application in chemical reaction engineering remains largely limited to academia. This perspective aims at encouraging the judicious use of first-principles kinetic models in industrial settings based on a critical discussion of present-day best practices, identifying existing gaps, and defining where further progress is needed.
Management of Periocular Granuloma Annulare Using Topical Dapsone
Patel, Mayha; Shitabata, Paul; Horowitz, David
2015-01-01
Granuloma annulare is a disease characterized by granulomatous inflammation of the dermis. Localized granuloma annulare may resolve spontaneously, while generalized granuloma annulare may persist for decades. The authors present the case of a 41-year-old Hispanic man with a two-week history of periocular granuloma annulare. Due to previously reported success in the use of systemic dapsone for the treatment of granuloma annulare, and the periocular proximity of the patient’s lesion, topical dapsone was used for treatment. Various additional therapies for the management of granuloma annulare have been reported, such as topical and systemic steroids, isotretinoin, pentoxifylline, cyclosporine, Interferon gamma, potassium iodide, nicotinamide, niacinamide, salicylic acid, fumaric acid ester, etanercept, infliximab, and hydroxychloroquine. Additional clinical trials are necessary to further evaluate the effectiveness of topical dapsone in the management of granuloma annulare. PMID:26203321
International Nuclear Information System (INIS)
In this note, we use ideas of Farhi et al. [Int. J. Quantum. Inf. 6, 503 (2008) and Quantum Inf. Comput. 11, 840 (2011)] who link a lower bound on the run time of their quantum adiabatic search algorithm to an upper bound on the energy gap above the ground-state of the generators of this algorithm. We apply these ideas to the quantum random energy model (QREM). Our main result is a simple proof of the conjectured exponential vanishing of the energy gap of the QREM
A model for the direct-to-indirect band-gap transition in monolayer MoSe2 under strain
Indian Academy of Sciences (India)
Ruma Das; Priya Mahadevan
2015-06-01
A monolayer of MoSe2 is found to be a direct band-gap semiconductor. We show, within ab-initio electronic structure calculations, that a modest biaxial tensile strain of 3% can drive it into an indirect band-gap semiconductor with the valence band maximum (VBM) shifting from point to point. An analysis of the charge density reveals that while Mo–Mo interactions contribute to the VBM at 0% strain, Mo–Se interactions contribute to the highest occupied band at point. A scaling of the hopping interaction strengths within an appropriate tight binding model can capture the transition.
Energy Technology Data Exchange (ETDEWEB)
Adame, J.; Warzel, S., E-mail: warzel@ma.tum.de [Zentrum Mathematik, TU München, Boltzmannstr. 3, 85747 Garching (Germany)
2015-11-15
In this note, we use ideas of Farhi et al. [Int. J. Quantum. Inf. 6, 503 (2008) and Quantum Inf. Comput. 11, 840 (2011)] who link a lower bound on the run time of their quantum adiabatic search algorithm to an upper bound on the energy gap above the ground-state of the generators of this algorithm. We apply these ideas to the quantum random energy model (QREM). Our main result is a simple proof of the conjectured exponential vanishing of the energy gap of the QREM.
Wright, Russell Eric
2000-01-01
The purpose of this project was to study the effects of anodic electrically stimulated silver-coated stainless steel implants and bacterial contamination in a canine radius fracture gap model. Twelve skeletally mature canines weighing 19.2-23.2 kg were used. Dogs were randomly assigned to into control and contaminated groups. A 5 mm ostectomy gap was made in both radii of each dog. One radius of each dog was stabilized with a silver-coated stainless steel bone plate and the other with ...
A Parametric Study on the Thermal Hydraulic Design for an Annular Fuel Assembly
Energy Technology Data Exchange (ETDEWEB)
Shin, C. H.; Seo, K. W.; Chun, T. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2008-10-15
Recently, MIT proposed an internally and externally cooled annular fuel for an advanced PWR which can endure a substantial power uprating. To apply this annular fuel in the conventional reactors such as OPR-1000, it is desirable to investigate its a structural compatibility for its reloading to operating PWR reactors of OPR-1000 as well as other compatibilities like the fuel to moderator ratio, amount of fissile material and coolant flow area. Conventional fuel assembly has a 16x16 solid rod array with four big guide tubes and one instrumentation tube. A 12x12 annular fuel assembly design which can meet the above compatibilities was proposed, which is structurally compatible with the existing internals of OPR-1000. Actually the advantage of an annular fuel comes from the fuel performance and thermal hydraulics. In the thermal hydraulic analysis, the mixing effect between the neighboring channels has to be carried out in a subchannel analysis. A subchannel analysis code, MATRA has been developed by KAERI. However, MATRA dose not have the capability to model both an internally and externally cooled annular fuel. A subchannel code, MATRA-AF which can be coupled to MATRA and can calculate the coolant flow distribution and heat transfer fraction in the internal and external subchannels has been developed. In this paper, the characteristics and the verification of the MATRA-AF are described. The effects of the thermal hydraulic parameters are estimated through a single fuel assembly.
A Parametric Study on the Thermal Hydraulic Design for an Annular Fuel Assembly
International Nuclear Information System (INIS)
Recently, MIT proposed an internally and externally cooled annular fuel for an advanced PWR which can endure a substantial power uprating. To apply this annular fuel in the conventional reactors such as OPR-1000, it is desirable to investigate its a structural compatibility for its reloading to operating PWR reactors of OPR-1000 as well as other compatibilities like the fuel to moderator ratio, amount of fissile material and coolant flow area. Conventional fuel assembly has a 16x16 solid rod array with four big guide tubes and one instrumentation tube. A 12x12 annular fuel assembly design which can meet the above compatibilities was proposed, which is structurally compatible with the existing internals of OPR-1000. Actually the advantage of an annular fuel comes from the fuel performance and thermal hydraulics. In the thermal hydraulic analysis, the mixing effect between the neighboring channels has to be carried out in a subchannel analysis. A subchannel analysis code, MATRA has been developed by KAERI. However, MATRA dose not have the capability to model both an internally and externally cooled annular fuel. A subchannel code, MATRA-AF which can be coupled to MATRA and can calculate the coolant flow distribution and heat transfer fraction in the internal and external subchannels has been developed. In this paper, the characteristics and the verification of the MATRA-AF are described. The effects of the thermal hydraulic parameters are estimated through a single fuel assembly
Electrorheological damper with annular ducts for seismic protection applications
Makris, Nicos; Burton, Scott A.; Taylor, Douglas P.
1996-10-01
This paper presents the design, analysis, testing and modeling of an electrorheological (ER) fluid damper developed for vibration and seismic protection of civil structures. The damper consists of a main cylinder and a piston rod that pushes an ER fluid through a stationary annular duct. The behavior of the damper can be approximated with Hagen - Poiseuille flow theory. The basic equations that describe the fluid flow across an annular duct are derived. Experimental results on the damper response with and without the presence of electric field are presented. As the rate of deformation increases, viscous stresses prevail over field-induced yield stresses and a smaller fraction of the total damper force can be controlled. Simple physically motivated phenomenological models are considered to approximate the damper response with and without the presence of electric field. Subsequently, the performance of a multilayer neural network constructed and trained by an efficient algorithm known as the Dependence Identification Algorithm is examined to predict the response of the electrorheological damper. A combination of a simple phenomenological model and a neural network is then proposed as a practical tool to approximate the nonlinear and velocity-dependent damper response.
Investigation of azimuthal staging concepts in annular gas turbines
Noiray, Nicolas; Bothien, Mirko; Schuermans, Bruno
2011-10-01
In this work, the influence of azimuthal staging concepts on the thermoacoustic behavior of annular combustion chambers is assessed theoretically and numerically. Staging is a well-known and effective method to abate thermoacoustic pulsations in combustion chambers. However, in the case of, for example, fuel staging the associated inhomogeneity of equivalence ratio may result in increased levels of NOx emissions. In order to minimize this unwanted effect a staging concept is required in which the transfer functions of the burners are changed while affecting the equivalence ratio as little as possible. In order to achieve this goal, a theoretical framework for predicting the influence of staging concepts on pulsations has been developed. Both linear and nonlinear analytical approaches are presented and it is shown that the dynamics of azimuthal modes can be described by coupled Van der Pol oscillators. A criterion based on the thermoacoustic coupling strength and on the asymmetry degree provides the modal behavior in the annular combustor, i.e. standing or traveling waves. The model predictions have been verified by numerical simulations of a heavy-duty gas turbine using an in-house thermoacoustic network-modeling tool. The interaction between the heat release of the flame and the acoustic field was modeled using measured transfer functions and source terms. These numerical simulations confirmed the original theoretical considerations.
Gaps in Data and Modeling Tools for Understanding Fire and Fire Effects in Tundra Ecosystems
French, N. H.; Miller, M. E.; Loboda, T. V.; Jenkins, L. K.; Bourgeau-Chavez, L. L.; Suiter, A.; Hawkins, S. M.
2013-12-01
As the ecosystem science community learns more about tundra ecosystems and disturbance in tundra, a review of base data sets and ecological field data for the region shows there are many gaps that need to be filled. In this paper we will review efforts to improve our knowledge of the occurrence and impacts of fire in the North American tundra region completed under a NASA Terrestrial Ecology grant. Our main source of information is remote sensing data from satellite sensors and ecological data from past and recent field data collections by our team, collaborators, and others. Past fire occurrence is not well known for this region compared with other North American biomes. In this presentation we review an effort to use a semi-automated detection algorithm to identify past fire occurrence using the Landsat TM/ETM+ archives, pointing out some of the still-unaddressed issues for a full understanding of fire regime for the region. For this task, fires in Landsat scenes were mapped using the Random Forest classifier (Breiman 2001) to automatically detect potential burn scars. Random Forests is an ensemble classifier that employs machine learning to build a large collection of decision trees that are grown from a random selection of user supplied training data. A pixel's classification is then determined by which class receives the most 'votes' from each tree. We also review the use fire location records and existing modeling methods to quantify emissions from these fires. Based on existing maps of vegetation fuels, we used the approach developed for the Wildland Fire Emissions Information System (WFEIS; French et al. 2011) to estimate emissions across the tundra region. WFEIS employs the Consume model (http://www.fs.fed.us/pnw/fera/research/smoke/consume/index.shtml) to estimate emissions by applying empirically developed relationships between fuels, fire conditions (weather-based fire indexes), and emissions. Here again, we will review the gaps in data and modeling
Darquenne, Chantal; Fleming, John S; Katz, Ira; Martin, Andrew R; Schroeter, Jeffry; Usmani, Omar S; Venegas, Jose; Schmid, Otmar
2016-04-01
Development of a new drug for the treatment of lung disease is a complex and time consuming process involving numerous disciplines of basic and applied sciences. During the 2015 Congress of the International Society for Aerosols in Medicine, a group of experts including aerosol scientists, physiologists, modelers, imagers, and clinicians participated in a workshop aiming at bridging the gap between basic research and clinical efficacy of inhaled drugs. This publication summarizes the current consensus on the topic. It begins with a short description of basic concepts of aerosol transport and a discussion on targeting strategies of inhaled aerosols to the lungs. It is followed by a description of both computational and biological lung models, and the use of imaging techniques to determine aerosol deposition distribution (ADD) in the lung. Finally, the importance of ADD to clinical efficacy is discussed. Several gaps were identified between basic science and clinical efficacy. One gap between scientific research aimed at predicting, controlling, and measuring ADD and the clinical use of inhaled aerosols is the considerable challenge of obtaining, in a single study, accurate information describing the optimal lung regions to be targeted, the effectiveness of targeting determined from ADD, and some measure of the drug's effectiveness. Other identified gaps were the language and methodology barriers that exist among disciplines, along with the significant regulatory hurdles that need to be overcome for novel drugs and/or therapies to reach the marketplace and benefit the patient. Despite these gaps, much progress has been made in recent years to improve clinical efficacy of inhaled drugs. Also, the recent efforts by many funding agencies and industry to support multidisciplinary networks including basic science researchers, R&D scientists, and clinicians will go a long way to further reduce the gap between science and clinical efficacy. PMID:26829187
Experimental research on dryout point of flow boiling in narrow annular channels
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
An experimental research on the dryout point of flow boiling in narrow annular channels under low mass flux with 1.55 mm and 1.05 mm annular gap, respectively, is conducted. Distilled water is used as working fluid and the range of pressure is limited within 2.0～4.0 MPa and that of mass flux is 26.0～69.0 kg·m-2·s-1. The relation of critical heat flux (CHF) and critical qualities with mass flux and pressure are revealed. It is found that the critical qualities decrease with the increasing mass flux and increase with the increasing inlet qualities in externally heated annuli.Under the same conditions, critical qualities in the outer tube are always larger than those in the inner tube. The appearance of dryout point in bilaterally heated narrow annuli can be judged according to the ratio of qo/qi.
The effect of inlet swirl on the dynamics of long annular seals in centrifugal pumps
Ismail, M.; Brown, R. D.; France, D.
1994-01-01
This paper describes additional results from a continuing research program which aims to identify the dynamics of long annular seals in centrifugal pumps. A seal test rig designed at Heriot-Watt University and commissioned at Weir Pumps Research Laboratory in Alloa permits the identification of mass, stiffness, and damping coefficients using a least-squares technique based on the singular value decomposition method. The analysis is carried out in the time domain using a multi-fiequency forcing function. The experimental method relies on the forced excitation of a flexibly supported stator by two hydraulic shakers. Running through the stator embodying two symmetrical balance drum seals is a rigid rotor supported in rolling element bearings. The only physical connection between shaft and stator is the pair of annular gaps filled with pressurized water discharged axially. The experimental coefficients obtained from the tests are compared with theoretical values.
International Nuclear Information System (INIS)
A method of droplet behavior simulation in an annular dispersed flow has been developed. In this method, both droplet deposition and entrainment from liquid film are considered. The Lagrangian method and stochastic model are used to analyze droplet diffusion and deposition behavior in a turbulent flow, and droplet entrainment from liquid film is calculated by an entrainment correlation. For the verification of this method, Gill's experiment is analyzed, in which the transition from annular flow with no entrainment to equilibrium annular dispersed flow was observed. Analysis results can also show the similar transition tendency. The experimental results of radial distribution of droplet mass flux are compared with analysis results. The agreement is good for low liquid flow rate, but entrainment rate must be adjusted for high liquid flow rate, in which gas turbulence is thought to be modified by high droplet density. In future work the effect of high droplet density on turbulence should be considered. (author)
Wohlman, Sarah J.; Wendy M Murray
2013-01-01
The thumb is required for a majority of tasks of daily living. Biomechanical modeling is a valuable tool, with the potential to help us bridge the gap between our understanding of the mechanical actions of individual thumb muscles, derived from anatomical cadaveric experiments, and our understanding of how force is produced by the coordination of all of the thumb muscles, derived from studies involving human subjects. However, current biomechanical models do not replicate muscle force product...
Performance of annular high frequency thermoacoustic engines
Rodriguez, Ivan A.
This thesis presents studies of the behavior of miniature annular thermoacoustic prime movers and the imaging of the complex sound fields using PIV inside the small acoustic wave guides when driven by a temperature gradient. Thermoacoustic engines operating in the standing wave mode are limited in their acoustic efficiency by a high degree of irreversibility that is inherent in how they work. Better performance can be achieved by using traveling waves in the thermoacoustic devices. This has led to the development of an annular high frequency thermoacoustic prime mover consisting of a regenerator, which is a random stack in-between a hot and cold heat exchanger, inside an annular waveguide. Miniature devices were developed and studied with operating frequencies in the range of 2-4 kHz. This corresponds to an average ring circumference of 11 cm for the 3 kHz device, the resonator bore being 6 mm. A similar device of 11 mm bore, length of 18 cm was also investigated; its resonant frequency was 2 kHz. Sound intensities as high as 166.8 dB were generated with limited heat input. Sound power was extracted from the annular structure by an impedance-matching side arm. The nature of the acoustic wave generated by heat was investigated using a high speed PIV instrument. Although the acoustic device appears symmetric, its performance is characterized by a broken symmetry and by perturbations that exist in its structure. Effects of these are observed in the PIV imaging; images show axial and radial components. Moreover, PIV studies show effects of streaming and instabilities which affect the devices' acoustic efficiency. The acoustic efficiency is high, being of 40% of Carnot. This type of device shows much promise as a high efficiency energy converter; it can be reduced in size for microcircuit applications.
Annular Alopecia Areata: Report of Two Cases
Bansal, Manish; Manchanda, Kajal; Pandey, SS
2013-01-01
Alopecia areata (AA) is an auto-immune disorder characterized by the appearance of non-scarring bald patches affecting the hair bearing areas of the body. Scalp is the most common site of involvement. AA can affect any age group. The usual pattern of the hair loss is oval or round. We hereby, report two cases of annular and circinate pattern of AA due to its unusual morphology.
Annular pancreas associated with duodenal carcinoma
Institute of Scientific and Technical Information of China (English)
Enrico; Bronnimann; Silke; Potthast; Tatjana; Vlajnic; Daniel; Oertli; Oleg; Heizmann
2010-01-01
Annular pancreas (AP) is a rare congenital anomaly. Coexisting malignancy has been reported only in a few cases. We report what is, to the best of our knowledge, the first case in the English literature of duodenal adenocarcinoma in a patient with AP. In a 55-year old woman with duodenal outlet stenosis magnetic resonance cholangiopancreatography showed an aberrant pancreatic duct encircling the duodenum. Duodenojejunostomy was performed. Eight weeks later she presented with painless jaundice. Duodenopancre...
Al-Talibi, A. Adhim
An estimated 4% of national energy consumption is used for drinking water and wastewater services. Despite the awareness and optimization initiatives for energy conservation, energy consumption is on the rise owing to population and urbanization expansion and to commercial and industrial business advancement. The principal concern is since energy consumption grows, the higher will be the energy production demand, leading to an increase in CO2 footprints and the contribution to global warming potential. This research is in the area of energy-water nexus, focusing on wastewater treatment plant (WWTP) energy trilogy -- the group of three related entities, which includes processes: (1) consuming energy, (2) producing energy, and (3) the resulting -- CO2 equivalents. Detailed and measurable energy information is not readily obtained for wastewater facilities, specifically during facility preliminary design phases. These limitations call for data-intensive research approach on GHG emissions quantification, plant efficiencies and source reduction techniques. To achieve these goals, this research introduced a model integrating all plant processes and their pertinent energy sources. In a comprehensive and "Energy Source-to-Effluent Discharge" pattern, this model is capable of bridging the gaps of WWTP energy, facilitating plant designers' decision-making for meeting energy assessment, sustainability and the environmental regulatory compliance. Protocols for estimating common emissions sources are available such as for fuels, whereas, site-specific emissions for other sources have to be developed and are captured in this research. The dissertation objectives were met through an extensive study of the relevant literature, models and tools, originating comprehensive lists of processes and energy sources for WWTPs, locating estimation formulas for each source, identifying site specific emissions factors, and linking the sources in a mathematical model for site specific CO2 e
Goodenough, Daniel A.; Paul, David L.
2009-01-01
Gap junctions are aggregates of intercellular channels that permit direct cell–cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hex...
Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik
2012-01-01
Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of ...
A contoured gap coaxial plasma gun with injected plasma armature
Witherspoon, F. Douglas; Case, Andrew; Messer, Sarah J.; Bomgardner, Richard; Phillips, Michael W.; Brockington, Samuel; Elton, Raymond
2009-08-01
A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 μg of plasma with density above 1017 cm-3 to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 μg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.
A contoured gap coaxial plasma gun with injected plasma armature
International Nuclear Information System (INIS)
A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 μg of plasma with density above 1017 cm-3 to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 μg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.
Vibration analysis of annular-like plates
Cheng, L.; Li, Y. Y.; Yam, L. H.
2003-05-01
The existence of eccentricity of the central hole for an annular plate results in a significant change in the natural frequencies and mode shapes of the structure. In this paper, the vibration analysis of annular-like plates is presented based on numerical and experimental approaches. Using the finite element analysis code Nastran, the effects of the eccentricity, hole size and boundary condition on vibration modes are investigated systematically through both global and local analyses. The results show that analyses for perfect symmetric conditions can still roughly predict the mode shapes of "recessive" modes of the plate with a slightly eccentric hole. They will, however, lead to erroneous results for "dominant" modes. In addition, the residual displacement mode shape is verified as an effective parameter for identifying damage occurring in plate-like structures. Experimental modal analysis on a clamped-free annular-like plate is performed, and the results obtained reveal good agreement with those obtained by numerical analysis. This study provides guidance on modal analysis, vibration measurement and damage detection of plate-like structures.
Directory of Open Access Journals (Sweden)
Liu Jun S
2004-10-01
Full Text Available Abstract Background Certain protein families are highly conserved across distantly related organisms and belong to large and functionally diverse superfamilies. The patterns of conservation present in these protein sequences presumably are due to selective constraints maintaining important but unknown structural mechanisms with some constraints specific to each family and others shared by a larger subset or by the entire superfamily. To exploit these patterns as a source of functional information, we recently devised a statistically based approach called contrast hierarchical alignment and interaction network (CHAIN analysis, which infers the strengths of various categories of selective constraints from co-conserved patterns in a multiple alignment. The power of this approach strongly depends on the quality of the multiple alignments, which thus motivated development of theoretical concepts and strategies to improve alignment of conserved motifs within large sets of distantly related sequences. Results Here we describe a hidden Markov model (HMM, an algebraic system, and Markov chain Monte Carlo (MCMC sampling strategies for alignment of multiple sequence motifs. The MCMC sampling strategies are useful both for alignment optimization and for adjusting position specific background amino acid frequencies for alignment uncertainties. Associated statistical formulations provide an objective measure of alignment quality as well as automatic gap penalty optimization. Improved alignments obtained in this way are compared with PSI-BLAST based alignments within the context of CHAIN analysis of three protein families: Giα subunits, prolyl oligopeptidases, and transitional endoplasmic reticulum (p97 AAA+ ATPases. Conclusion While not entirely replacing PSI-BLAST based alignments, which likewise may be optimized for CHAIN analysis using this approach, these motif-based methods often more accurately align very distantly related sequences and thus can
Modeling of Particle Transport on Channels and Gaps Exposed to Plasma Fluxes
Nieto-Pérez, Martin
2008-04-01
Many problems in particle transport in fusion devices involve the transport of plasma or eroded particles through channels or gaps, such as in the case of trying to assess damage to delicate optical diagnostics collecting light through a slit or determining the deposition and codeposition on the gaps between tiles of plasma-facing components. A dynamic-composition Monte Carlo code in the spirit of TRIDYN, previously developed to study composition changes on optical mirrors subject to ion bombardment, has been upgraded to include motion of particles through a volume defined by sets of plane surfaces. Particles sputtered or reflected from the walls of the channel/gap can be tracked as well, allowing the calculation of wall impurity transport, either back to the plasma (for the case of a gap) or to components separated from the plasma by a channel/slit (for the case of optical diagnostics). Two examples of the code application to particle transport in fusion devices will be presented in this work: one will evaluate the erosion/impurity deposition rate on a mirror separated from a plasma source by a slit; the other case will look at the enhanced emission of tile material in the region of the gap between two tiles.
Modeling of Particle Transport on Channels and Gaps Exposed to Plasma Fluxes
International Nuclear Information System (INIS)
Many problems in particle transport in fusion devices involve the transport of plasma or eroded particles through channels or gaps, such as in the case of trying to assess damage to delicate optical diagnostics collecting light through a slit or determining the deposition and codeposition on the gaps between tiles of plasma-facing components. A dynamic-composition Monte Carlo code in the spirit of TRIDYN, previously developed to study composition changes on optical mirrors subject to ion bombardment, has been upgraded to include motion of particles through a volume defined by sets of plane surfaces. Particles sputtered or reflected from the walls of the channel/gap can be tracked as well, allowing the calculation of wall impurity transport, either back to the plasma (for the case of a gap) or to components separated from the plasma by a channel/slit (for the case of optical diagnostics). Two examples of the code application to particle transport in fusion devices will be presented in this work: one will evaluate the erosion/impurity deposition rate on a mirror separated from a plasma source by a slit; the other case will look at the enhanced emission of tile material in the region of the gap between two tiles
Spark gap switch with spiral gas flow
Brucker, John P.
1989-01-01
A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.
Development of a Debye heat capacity model for vibrational modes with a gap in the density of states
International Nuclear Information System (INIS)
Low-energy vibrational modes that have a gap in the density of states (DOS) have often been observed in heat capacity data in the form of ‘boson’ peaks, but the functions used to model these modes are often inadequate or are not physically meaningful. We have adapted the Debye model to represent these gapped modes and have derived the heat capacity equations for these modes in one, two, and three dimensions. Applying these equations to the low-temperature heat capacity data fitting for a large variety of materials substantially improves the fit quality relative to conventional fits. From the fitting parameters, the underlying DOS were estimated, which we show to be comparable to those reported in the literature. This model expands the methods of theoretical low-temperature heat capacity data analysis and improves the procedure of approximating a material’s DOS from its low-temperature heat capacity. (paper)
Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia
International Nuclear Information System (INIS)
Highlights: • Astrocytes exhibit characteristic changes in [Ca2+]i under OGD. • Astrocytic [Ca2+]i increase is synchronized with a neuronal anoxic depolarization. • Gap junctional couplings protect neurons as well as astrocytes during OGD. - Abstract: Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca2+]i) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca2+]i oscillations followed by larger and sustained [Ca2+]i increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca2+]i increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca2+]i increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca2+]i increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage during the acute phase of ischemia
Astrocytic gap junctional networks suppress cellular damage in an in vitro model of ischemia
Energy Technology Data Exchange (ETDEWEB)
Shinotsuka, Takanori; Yasui, Masato; Nuriya, Mutsuo, E-mail: mnuriya@z2.keio.jp
2014-02-07
Highlights: • Astrocytes exhibit characteristic changes in [Ca{sup 2+}]{sub i} under OGD. • Astrocytic [Ca{sup 2+}]{sub i} increase is synchronized with a neuronal anoxic depolarization. • Gap junctional couplings protect neurons as well as astrocytes during OGD. - Abstract: Astrocytes play pivotal roles in both the physiology and the pathophysiology of the brain. They communicate with each other via extracellular messengers as well as through gap junctions, which may exacerbate or protect against pathological processes in the brain. However, their roles during the acute phase of ischemia and the underlying cellular mechanisms remain largely unknown. To address this issue, we imaged changes in the intracellular calcium concentration ([Ca{sup 2+}]{sub i}) in astrocytes in mouse cortical slices under oxygen/glucose deprivation (OGD) condition using two-photon microscopy. Under OGD, astrocytes showed [Ca{sup 2+}]{sub i} oscillations followed by larger and sustained [Ca{sup 2+}]{sub i} increases. While the pharmacological blockades of astrocytic receptors for glutamate and ATP had no effect, the inhibitions of gap junctional intercellular coupling between astrocytes significantly advanced the onset of the sustained [Ca{sup 2+}]{sub i} increase after OGD exposure. Interestingly, the simultaneous recording of the neuronal membrane potential revealed that the onset of the sustained [Ca{sup 2+}]{sub i} increase in astrocytes was synchronized with the appearance of neuronal anoxic depolarization. Furthermore, the blockade of gap junctional coupling resulted in a concurrent faster appearance of neuronal depolarizations, which remain synchronized with the sustained [Ca{sup 2+}]{sub i} increase in astrocytes. These results indicate that astrocytes delay the appearance of the pathological responses of astrocytes and neurons through their gap junction-mediated intercellular network under OGD. Thus, astrocytic gap junctional networks provide protection against tissue damage
The prototype GAPS (pGAPS) experiment
International Nuclear Information System (INIS)
The General Antiparticle Spectrometer (GAPS) experiment is a novel approach for the detection of cosmic ray antiparticles. A prototype GAPS (pGAPS) experiment was successfully flown on a high-altitude balloon in June of 2012. The goals of the pGAPS experiment were: to test the operation of lithium drifted silicon (Si(Li)) detectors at balloon altitudes, to validate the thermal model and cooling concept needed for engineering of a full-size GAPS instrument, and to characterize cosmic ray and X-ray backgrounds. The instrument was launched from the Japan Aerospace Exploration Agency's (JAXA) Taiki Aerospace Research Field in Hokkaido, Japan. The flight lasted a total of 6 h, with over 3 h at float altitude (∼33km). Over one million cosmic ray triggers were recorded and all flight goals were met or exceeded
Model Evidence of a Superconducting State with a Full Energy Gap in Small Cuprate Islands
Black-Schaffer, Annica M.; Golubev, Dmitri S.; Bauch, Thilo; Lombardi, Floriana; Fogelström, Mikael
2013-05-01
We investigate subdominant order parameters stabilizing at low temperatures in nanoscale high-Tc cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa2Cu3O7-δ [D. Gustafsson et al., Nature Nanotech. 8, 25 (2013)]. Using complementary quasiclassical and tight-binding Bogoliubov-de Gennes methods, we show on distinctly different properties dependent on the symmetry being dx2-y2+is or dx2-y2+idxy. We find that a surface-induced dx2-y2+is phase creates a global spectroscopic gap which increases with an applied magnetic field, consistent with experimental observation.
Julin, Jan; Shiraiwa, Manabu; Miles, Rachael E H; Reid, Jonathan P; Pöschl, Ulrich; Riipinen, Ilona
2013-01-17
The condensational growth of submicrometer aerosol particles to climate relevant sizes is sensitive to their ability to accommodate vapor molecules, which is described by the mass accommodation coefficient. However, the underlying processes are not yet fully understood. We have simulated the mass accommodation and evaporation processes of water using molecular dynamics, and the results are compared to the condensation equations derived from the kinetic gas theory to shed light on the compatibility of the two. Molecular dynamics simulations were performed for a planar TIP4P-Ew water surface at four temperatures in the range 268-300 K as well as two droplets, with radii of 1.92 and 4.14 nm at T = 273.15 K. The evaporation flux from molecular dynamics was found to be in good qualitative agreement with that predicted by the simple kinetic condensation equations. Water droplet growth was also modeled with the kinetic multilayer model KM-GAP of Shiraiwa et al. [Atmos. Chem. Phys. 2012, 12, 2777]. It was found that, due to the fast transport across the interface, the growth of a pure water droplet is controlled by gas phase diffusion. These facts indicate that the simple kinetic treatment is sufficient in describing pure water condensation and evaporation. The droplet size was found to have minimal effect on the value of the mass accommodation coefficient. The mass accommodation coefficient was found to be unity (within 0.004) for all studied surfaces, which is in agreement with previous simulation work. Additionally, the simulated evaporation fluxes imply that the evaporation coefficient is also unity. Comparing the evaporation rates of the mass accommodation and evaporation simulations indicated that the high collision flux, corresponding to high supersaturation, present in typical molecular dynamics mass accommodation simulations can under certain conditions lead to an increase in the evaporation rate. Consequently, in such situations the mass accommodation coefficient
DEFF Research Database (Denmark)
Kramer Overgaard, Majken; Broeng, Jes; Jensen, Monika Luniewska;
Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ventures.......Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ventures....
Kramer Overgaard, Majken; Broeng, Jes; Jensen, Monika Luniewska; Murdock, Karen; Schmidt, Iben Julie
2015-01-01
Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ventures. Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ve...
Existence, uniqueness and multiplicity of rotating fluxon waves in annular Josephson junctions
Katriel, Guy
2007-01-01
We prove that the equation modelling an annular Josephson junction has a rotating fluxon wave solution for all values of the parameters. We also obtain results on uniqueness of the rotating fluxon wave in some parameter regimes, and on multiplicity of rotating fluxon waves in other parameter regimes.
Effect of Annular Slit Geometry on Characteristics of Spiral Jet
Institute of Scientific and Technical Information of China (English)
Shigeru Matsuo; Kwon-Hee Lee; Shinsuke Oda; Toshiaki Setoguchi; Heuy-Dong Kim
2003-01-01
A spiral flow using an annular slit connected to a conical cylinder does not need special device to generate a tangential velocity component of the flow and differs from swirling flows. Pressurized fluid is supplied to an annular chamber and injected into the convergent nozzle through the annular slit. The annular jet develops into the spiral flow. In the present study, a spiral jet discharged out of nozzle exit was obtained by using a convergent nozzle and an annular slit set in nozzle inlet, and the effect of annular slit geometry on characteristics of the spiral jet was investigated by using a Laser Doppler Velocimeter (LDV) experimentally. Furthermore, velocity distributions of the spiral jet were compared with those of a normal jet.
Inertial Wave Excitation and Wave Attractors in an Annular Tank: DNS
Klein, Marten; Ghasemi, Abouzar; Harlander, Uwe; Will, Andreas
2014-05-01
Rotation is the most relevant aspect of geophysical fluid dynamics, manifesting itself by the Coriolis force. Small perturbations to the state of rigid body rotation can excite inertial waves (waves restored by Coriolis force) with frequencies in the range 0 fluid so that inertial waves remain the only waves in the mathematical model, which can transport kinetic energy and angular momentum. In geophysics, inertial waves have received a lot attention over the last decades. A spherical shell, for instance, is already non-simple in a sense that its inertial mode's spatial structures are complex, forming so-called wave attractors [1]. But also other containers have been investigated, e.g., cylinders and boxes from the viewpoints of normal mode excitation [2,3], mean flow generation and boundary layer flow [4]. A simple wave attractor was found in a prism, which can be seen as idealized ocean basin [5]. However, local mechanisms of wave excitation are still not very well understood. In order to contribute to the ongoing discussion, we consider an annular geometry. Its rectangular symmetry was broken by replacing the inner cylinder with a frustum of apex half-angle α = 5.7°. The annular gap is filled with a fluid of kinematic viscosity ν. The whole vessel rotates with a mean angular velocity Ω0 around its axis of symmetry. Ekman numbers investigated are 1 ≠« E = ν(Ω0H2)-1 ≥ 10-5. Similarly to [1-5] we perturb the system by longitudinal libration, Ω(t) = Ω0(1 + ɛsinωt), where ω > 0 denotes the frequency and 0 Fluids (2012), vol. 24, 076602. [3] A. Sauret, D. Cébron, M. Le Bars and S. Le Dizès, Phys. Fluids (2012), vol. 24, 026603. [4] F. H. Busse, Physica D, vol. 240 (2011), pp. 208-211. [5] L. R. M. Maas, J. Fluid Mech. (2001), vol. 437, pp. 13-28.
Gamma-ray pulsar physics: gap-model populations and light-curve analyses in the Fermi era
International Nuclear Information System (INIS)
This thesis research focusses on the study of the young and energetic isolated ordinary pulsar population detected by the Fermi gamma-ray space telescope. We compared the model expectations of four emission models and the LAT data. We found that all the models fail to reproduce the LAT detections, in particular the large number of high E objects observed. This inconsistency is not model dependent. A discrepancy between the radio-loud/radio-quiet objects ratio was also found between the observed and predicted samples. The Lγ α E0.5 relation is robustly confirmed by all the assumed models with particular agreement in the slot gap (SG) case. On luminosity bases, the intermediate altitude emission of the two pole caustic SG model is favoured. The beaming factor fΩ shows an E dependency that is slightly visible in the SG case. Estimates of the pulsar orientations have been obtained to explain the simultaneous gamma and radio light-curves. By analysing the solutions we found a relation between the observed energy cutoff and the width of the emission slot gap. This relation has been theoretically predicted. A possible magnetic obliquity α alignment with time is rejected -for all the models- on timescale of the order of 106 years. The light-curve morphology study shows that the outer magnetosphere gap emission (OGs) are favoured to explain the observed radio-gamma lag. The light curve moment studies (symmetry and sharpness) on the contrary favour a two pole caustic SG emission. All the model predictions suggest a different magnetic field layout with an hybrid two pole caustic and intermediate altitude emission to explain both the pulsar luminosity and light curve morphology. The low magnetosphere emission mechanism of the polar cap model, is systematically rejected by all the tests done. (author)
Ultrasonogrphic diagnosis of snapping annular ligament in the elbow
Energy Technology Data Exchange (ETDEWEB)
Chai, Jee Won; Kim Su Jin; Lim, Hyun Kyong; Bae, Kee Jeong [SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul (Korea, Republic of)
2015-01-15
Elbow snapping by annular ligament is rare and may be difficult to diagnose, when this Epub ahead of print condition is not familiar. We report a case of elbow snapping by annular ligament diagnosed by ultrasonography, which was confirmed by arthroscopic observation. The ultrasonographic findings were thickening of the annular ligament and snapping in and out of the radiocapitellar joint during elbow flexion and extension on dynamic ultrasonography.
Belley, Philippe; Nathalie HAVET; Lacroix, Guy
2012-01-01
The paper focuses on the early career patterns of young male and female workers. It investigates potential dynamic links between statistical discrimination, mobility, tenure and wage profiles. The model assumes that it is more costly for an employer to assess female workers' productivity and that the noise/signal ratio tapers off more rapidly for male workers. These two assumptions yield numerous theoretical predictions pertaining to gender wage gaps. These predictions are tested using data f...
Granuloma annulare localized to the shaft of the penis
DEFF Research Database (Denmark)
Trap, R; Wiebe, B
1993-01-01
A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis.......A case of granuloma annulare localized to the shaft of the penis is reported. The differential diagnoses are discussed. Penile granuloma annulare is a rare disorder and it is concluded that biopsies of penile lesions are recommended to verify the correct diagnosis....
Liquid transfer and entrainment correlation for droplet-annular flow
International Nuclear Information System (INIS)
A correlation for the amount of entrained liquid in annular flow has been developed from a simple model and experimental data. There are basically two different regions of entrainment, namely, the entrance and quasi-equilibrium regions. The correlation for the equilibrium region is expressed in terms of the dimensionless gas flux, diameter, cand total liquid Reynolds number. The entrance effect is taken into account by an exponential relaxation function. It has been shown that this new model can satisfactorily correlate wide ranges of experimental data for water. Furthermore, the necessary distance for the development of entrainment is identified. These correlations, therefore, can supply accurate information on entrainment which has not been available previously
Florentin, Éric
2010-04-23
Today, the identification ofmaterialmodel parameters is based more and more on full-field measurements. This article explains how an appropriate use of the constitutive equation gap method (CEGM) can help in this context. The CEGM is a well-known concept which, until now, has been used mainly for the verification of finite element simulations. This has led to many developments, especially concerning the techniques for constructing statically admissible stress fields. The originality of the present study resides in the application of these recent developments to the identification problem. The proposed CEGM is described in detail, then evaluated through the identification of heterogeneous isotropic elastic properties. The results obtained are systematically compared with those of the equilibrium gap method, which is a well-known technique for the resolution of such identification problems. We prove that the use of the enhanced CEGM significantly improves the quality of the results. © Springer-Verlag 2010.
Experimental investigation of transonic flow in 2-D model of clearance gap
Czech Academy of Sciences Publication Activity Database
Luxa, Martin; Dvořák, Rudolf; Šimurda, David; Vimmr, J.
Praha: Ústav termomechaniky AV ČR, v. v. i., 2008 - (Příhoda, J.; Kozel, K.), s. 67-70 ISBN 978-80-87012-09-3. [Topical Problems of Fluid Mechanics 2008. Praha (CZ), 20.02.2008-22.02.2008] R&D Projects: GA ČR GA101/07/1508 Institutional research plan: CEZ:AV0Z20760514 Keywords : clearance gap * schlieren method * transonic flow Subject RIV: BK - Fluid Dynamics
Numerical and experimental investigation of transonic flow through 2-D model of clearance gap
Czech Academy of Sciences Publication Activity Database
Vimmr, J.; Bublík, O.; Luxa, Martin; Dvořák, Rudolf; Šimurda, David
Prague: Institute of Thermomechanics AS CR, v. v. i., 2008 - (Fuis, V.; Pásek, M.), s. 1121-1132 ISBN 978-80-87012-11-6. [Engineering Mechanics 2008. Svratka (CZ), 12.05.2008-15.05.2008] R&D Projects: GA ČR(CZ) GA101/08/0623 Institutional research plan: CEZ:AV0Z20760514 Keywords : clearance gap * transonic flow * numerical investigation * experimental investigation * schlieren method Subject RIV: BK - Fluid Dynamics
Thread-annular flow in vertical pipes
Frei, Ch.; Lüscher, P.; Wintermantel, E.
2000-05-01
Thread injection is a promising method for different minimally invasive medical applications. This paper documents an experimental study dealing with an axially moving thread in annular pipe flow. Mass flow and axial force on the thread are measured for a 0.46 mm diameter thread in pipes with diameters between 0.55 and 1.35 mm. The experiments with thread velocities of up to 1.5 ms[minus sign]1 confirm the findings of theoretical studies that for clinical requirements the radius ratio between thread and pipe is crucial for the adjustments of mass ow and force on the thread.
Deep variant of Erythema Annulare Centrifugum
Ahu Yorulmaz; Ferda Artuz; Devrim Tuba Unal
2014-01-01
A 29-year-old woman came to our outpatient clinic with a several-month history of itchy red lesions over her trunk. There was no family history and past history of any other diseases or medication. Dermatological examination revealed annular and oval-shaped plaques up to several cm’s in size, one of which was polycyclic in configuration, on back of the patient (Fig. 1). It was also noticed that lesions had erythematous indurated bordes with paler central areas (Fig. 1).
Deep variant of Erythema Annulare Centrifugum
Directory of Open Access Journals (Sweden)
Ahu Yorulmaz
2014-10-01
Full Text Available A 29-year-old woman came to our outpatient clinic with a several-month history of itchy red lesions over her trunk. There was no family history and past history of any other diseases or medication. Dermatological examination revealed annular and oval-shaped plaques up to several cm’s in size, one of which was polycyclic in configuration, on back of the patient (Fig. 1. It was also noticed that lesions had erythematous indurated bordes with paler central areas (Fig. 1.
Visualization of the annular synthetic jet
Czech Academy of Sciences Publication Activity Database
Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, Pavel
Praha: Ústav termomechaniky AV ČR, v. v. i, 2012 - (Šimurda, D.; Kozel, K.), s. 13-16 ISBN 978-80-87012-40-6. [Topical Problems of Fluid Mechanics 2012. Praha (CZ), 15.02.2012-17.02.2012] R&D Projects: GA AV ČR(CZ) IAA200760801; GA ČR(CZ) GCP101/11/J019 Institutional research plan: CEZ:AV0Z20760514 Keywords : synthetic jet * annular jet * visualization Subject RIV: BK - Fluid Dynamics
Wave turbulence in annular wave tank
Onorato, Miguel; Stramignoni, Ettore
2014-05-01
We perform experiments in an annular wind wave tank at the Dipartimento di Fisica, Universita' di Torino. The external diameter of the tank is 5 meters while the internal one is 1 meter. The tank is equipped by two air fans which can lead to a wind of maximum 5 m/s. The present set up is capable of studying the generation of waves and the development of wind wave spectra for large duration. We have performed different tests including different wind speeds. For large wind speed we observe the formation of spectra consistent with Kolmogorv-Zakharov predictions.
Interfacial friction in cocurrent upward annular flow
Hossfeld, L. M.; Bharathan, D.; Wallis, G. B.; Richter, H. J.
1982-03-01
Cocurrent upward annular flow is investigated, with an emphasis on correlating and predicting pressure drop. Attention is given to the characteristics of the liquid flow in the film, and the interaction of the core with the film. Alternate approaches are discussed for correlating suitably defined interfacial friction factors. Both approaches are dependent on knowledge of the entrainment in order to make predictions. Dimensional analysis is used to define characteristic parameters of the flow and an effort is made to determine, to the extent possible, the influences of these parameters on the interfacial friction factor.
Air-water countercurrent annular flow
Energy Technology Data Exchange (ETDEWEB)
Bharathan, D.
1979-09-01
Countercurrent annular flow of air and water in circular tubes of diameters ranging from 6.4 to 152 mm is investigated. Experimental measurements include liquid fraction, pressure gradients and countercurrent gas and liquid fluxes. Influences of tube end geometries on the countercurrent fluxes are isolated. Analogies between countercurrent flow, open channel flow, and compressible flow are established. Interfacial momentum transfer between the phases are characterized by empirical friction factors. The dependence of interfacial friction factors on tube diameter is shown to yield a basis for extending the present results to larger tubes.
Air-water countercurrent annular flow
International Nuclear Information System (INIS)
Countercurrent annular flow of air and water in circular tubes of diameters ranging from 6.4 to 152 mm is investigated. Experimental measurements include liquid fraction, pressure gradients and countercurrent gas and liquid fluxes. Influences of tube end geometries on the countercurrent fluxes are isolated. Analogies between countercurrent flow, open channel flow, and compressible flow are established. Interfacial momentum transfer between the phases are characterized by empirical friction factors. The dependence of interfacial friction factors on tube diameter is shown to yield a basis for extending the present results to larger tubes
Experiments and numerical simulations of plate gap model for high energetic materials
International Nuclear Information System (INIS)
Experimental and numerical study for detonation propagation was conducted using the system in which the high energy materials and air gaps alternately stacked. The aim of this simulation is an extraction of information of the EOS for detonation product at arbitrary initial density from the numerical simulation with EOS at TMD (theoretical maximum density). In this report, we described the numerical procedure and an example of the calculation result. On the other hand, the experiment was designed for confirmation of the validity of our reactive flow simulation. The experimental system for this study consists of the pellet explosives and PMMA rings, PMMA pipe and booster explosive part. The pellets and the rings were alternately stacked in the PMMA pipe to make the system. The diameter of the pellet was 20 mm and the thicknesses were 10 or 5 mm. The thickness of the ring was varied to adjust the size of the air gaps between the pellets. The sample explosive was a composition A5 (RDX 98.8 wt%). The relationship between the bulk density which was estimated by the thicknesses of the pellets and the air gaps and the average detonation velocity was compared with the data for RDX. The slopes of those relationships differed mutually. Although the experimental results can be used for confirmation of the validity of the numerical procedure, it does not simulate the detonation wave in the powdered explosive. It may show the interesting process that consists of the shock wave in air, shock to detonation transition and steady detonation.
Tomaskovic-Devey, Donald; Hällsten, Martin; Avent-Holt, Dustin
2015-01-01
The authors propose a strategy for observing and explaining workplace variance in categorically linked inequalities. Using Swedish economy-wide linked employer-employee panel data, the authors examine variation in workplace wage inequalities between native Swedes and non-Western immigrants. Consistent with relational inequality theory, the authors' findings are that immigrant-native wage gaps vary dramatically across workplaces, even net of strong human capital controls. The authors also find that, net of observed and fixed-effect controls for individual traits, workplace immigrant-native wage gaps decline with increased workplace immigrant employment and managerial representation and increase when job segregation rises. These results are stronger in high-inequality workplaces and for white-collar employees: contexts in which one expects status-based claims on organizational resources, the central causal mechanism identified by relational inequality theory, to be stronger. The authors conclude that workplace variation in the non-Western immigrant-native wage gaps is contingent on organizational variationin the relative power of groups and the institutional context in which that power is exercised. PMID:26046226
Hurlbatt, A.; O’Connell, D.; Gans, T.
2016-08-01
Analytical and numerical models allow investigation of complicated discharge phenomena and the interplay that makes plasmas such a complex environment. Global models are quick to implement and can have almost negligible computation cost, but provide only bulk or spatially averaged values. Full fluid models take longer to develop, and can take days to solve, but provide accurate spatio-temporal profiles of the whole plasma. The work presented here details a different type of model, analytically similar to fluid models, but computationally closer to a global model, and able to give spatially resolved solutions for the challenging environment of electronegative plasmas. Included are non-isothermal electrons, gas heating, and coupled neutral dynamics. Solutions are reached in seconds to minutes, and spatial profiles are given for densities, fluxes, and temperatures. This allows the semi-analytical model to fill the gap that exists between global and full fluid models, extending the tools available to researchers. The semi-analytical model can perform broad parameter sweeps that are not practical with more computationally expensive models, as well as exposing non-trivial trends that global models cannot capture. Examples are given for a low pressure oxygen CCP. Excellent agreement is shown with a full fluid model, and comparisons are drawn with the corresponding global model.
Directory of Open Access Journals (Sweden)
RAJDEEP SINGH
2010-07-01
Full Text Available Service firms like other organizations are realizing the significance of customer-centered philosophies and are turning to quality management approaches to help managing their businesses. This paper has started with the concept of service quality and has demonstrated the model of service quality gaps. SERVQUAL methodology was applied for faculty as a customer to identify the gap between customer expectations and perceptions of the actual service received taking higher education as a service industry. Outcomes of the study outlined the major gaps of expectations and perceptions of the faculty of higher education and therefore give a framework for prioritizing critical factors to close the gap.
Detonation diffraction from an annular channel
Meredith, James; Ng, Hoi Dick; Lee, John H. S.
2010-12-01
In this study, gaseous detonation diffraction from an annular channel was investigated with a streak camera and the critical pressure for transmission of the detonation wave was obtained. The annular channel was used to approximate an infinite slot resulting in cylindrically expanding detonation waves. Two mixtures, stoichiometric acetylene-oxygen and stoichiometric acetylene-oxygen with 70% Ar dilution, were tested in a 4.3 and 14.3 mm channel width ( W). The undiluted and diluted mixtures were found to have values of the critical channel width over the cell size around 3 and 12 respectively. Comparing these results to values of the critical diameter ( d c ), in which a spherical detonation occurs, a value of critical d c / W c near 2 is observed for the highly diluted mixture. This value corresponds to the geometrical factor of the curvature term between a spherical and cylindrical diverging wave. Hence, the result is in support of Lee's proposed mechanism [Lee in Dynamics of Exothermicity, pp. 321, Gordon and Breach, Amsterdam, 1996] for failure due to diffraction based on curvature in stable mixtures such as those highly argon diluted with very regular detonation cellular patterns.
A 3-Dimensional Model of Water-Bearing Sequences in the Dominguez Gap Region, Long Beach, California
Ponti, Daniel J.; Ehman, Kenneth D.; Edwards, Brian D.; Tinsley, John C., III; Hildenbrand, Thomas; Hillhouse, John W.; Hanson, Randall T.; McDougall, Kristen; Powell, Charles L.; Wan, Elmira; Land, Michael; Mahan, Shannon; Sarna-Wojcicki, Andrei M.
2007-01-01
A 3-dimensional computer model of the Quaternary sequence stratigraphy in the Dominguez gap region of Long Beach, California has been developed to provide a robust chronostratigraphic framework for hydrologic and tectonic studies. The model consists of 13 layers within a 16.5 by 16.1 km (10.25 by 10 mile) square area and extends downward to an altitude of -900 meters (-2952.76 feet). Ten sequences of late Pliocene to Holocene age are identified and correlated within the model. Primary data to build the model comes from five reference core holes, extensive high-resolution seismic data obtained in San Pedro Bay, and logs from several hundred water and oil wells drilled in the region. The model is best constrained in the vicinity of the Dominguez gap seawater intrusion barrier where a dense network of subsurface data exist. The resultant stratigraphic framework and geologic structure differs significantly from what has been proposed in earlier studies. An important new discovery from this approach is the recognition of ongoing tectonic deformation throughout nearly all of Quaternary time that has impacted the geometry and character of the sequences. Anticlinal folding along a NW-SE trend, probably associated with Quaternary reactivation of the Wilmington anticline, has uplifted and thinned deposits along the fold crest, which intersects the Dominguez gap seawater barrier near Pacific Coast Highway. A W-NW trending fault system that approximately parallels the fold crest has also been identified. This fault progressively displaces all but the youngest sequences down to the north and serves as the southern termination of the classic Silverado aquifer. Uplift and erosion of fining-upward paralic sequences along the crest of the young fold has removed or thinned many of the fine-grained beds that serve to protect the underlying Silverado aquifer from seawater contaminated shallow groundwater. As a result of this process, the potential exists for vertical migration of
Stability of forced-convection subcooled boiling in steady-state and transient annular flow
International Nuclear Information System (INIS)
A semi-analytical model developed by Lee and Bankoff for OFI in round tubes is extended to annular or parallel-plate flows with unequal heat fluxes, and shown to compare well with data by Dougherty, et al. and by Whittle and Forgan. The model is a better fit in the high Peclet number range than the Saha-Zuber model, and is simple to use
Stability of forced-convection subcooled boiling in steady-state and transient annular flow
Energy Technology Data Exchange (ETDEWEB)
Gehrke, V.; Bankoff, S.G. [SGB Associates, Evanston, IL (United States)
1993-06-01
A semi-analytical model developed by Lee and Bankoff for OFI in round tubes is extended to annular or parallel-plate flows with unequal heat fluxes, and shown to compare well with data by Dougherty, et al. and by Whittle and Forgan. The model is a better fit in the high Peclet number range than the Saha-Zuber model, and is simple to use.
International Nuclear Information System (INIS)
Thermal modeling and numerical simulations have been performed to describe the ultrafast thermal response of band gap materials upon optical excitation. A model was established by extending the conventional two-temperature model that is adequate for metals, but not for semiconductors. It considers the time- and space-dependent density of electrons photoexcited to the conduction band and accordingly allows a more accurate description of the transient thermal equilibration between the hot electrons and lattice. Ultrafast thermal behaviors of bismuth, as a model system, were demonstrated using the extended two-temperature model with a view to elucidating the thermal effects of excitation laser pulse fluence, electron diffusivity, electron-hole recombination kinetics, and electron-phonon interactions, focusing on high-density excitation
Energy Technology Data Exchange (ETDEWEB)
Shin, Taeho [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Samsung Advanced Institute of Technology, Suwon 443-803 (Korea, Republic of); Teitelbaum, Samuel W.; Wolfson, Johanna; Nelson, Keith A., E-mail: kanelson@mit.edu [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Kandyla, Maria [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens 116-35 (Greece)
2015-11-21
Thermal modeling and numerical simulations have been performed to describe the ultrafast thermal response of band gap materials upon optical excitation. A model was established by extending the conventional two-temperature model that is adequate for metals, but not for semiconductors. It considers the time- and space-dependent density of electrons photoexcited to the conduction band and accordingly allows a more accurate description of the transient thermal equilibration between the hot electrons and lattice. Ultrafast thermal behaviors of bismuth, as a model system, were demonstrated using the extended two-temperature model with a view to elucidating the thermal effects of excitation laser pulse fluence, electron diffusivity, electron-hole recombination kinetics, and electron-phonon interactions, focusing on high-density excitation.
Shin, Taeho; Teitelbaum, Samuel W; Wolfson, Johanna; Kandyla, Maria; Nelson, Keith A
2015-11-21
Thermal modeling and numerical simulations have been performed to describe the ultrafast thermal response of band gap materials upon optical excitation. A model was established by extending the conventional two-temperature model that is adequate for metals, but not for semiconductors. It considers the time- and space-dependent density of electrons photoexcited to the conduction band and accordingly allows a more accurate description of the transient thermal equilibration between the hot electrons and lattice. Ultrafast thermal behaviors of bismuth, as a model system, were demonstrated using the extended two-temperature model with a view to elucidating the thermal effects of excitation laser pulse fluence, electron diffusivity, electron-hole recombination kinetics, and electron-phonon interactions, focusing on high-density excitation. PMID:26590551
Missed Monteggia fracture in children: Is annular ligament reconstruction always required?
Directory of Open Access Journals (Sweden)
Bhaskar Atul
2009-01-01
Full Text Available Background: Chronic (neglected radiocapitellar joint dislocation is one of the feared complications of Monteggia fractures especially when associated with subtle fracture of the ulna bone. Many treatment strategies have been described to manage chronic Monteggia fracture and the need for annular ligament reconstruction is not always clear. The purpose of this study is to highlight the management of missed Monteggia fracture with particular emphasis on utility of annular ligament reconstruction by comparing the two groups of patients. Materials and Methods: In a prospective study 12 patients with mean age of 7.4 years, who presented with neglected Monteggia fractures, were studied. All children underwent open reduction of the radiocapitellar joint. Five children (Group A were treated with angulation-distraction osteotomy of ulna and annular ligament reconstruction and six cases (Group B required only angulation-distraction osteotomy of ulna without ligament reconstruction. In one case an open reduction of the radiocapitellar joint was sufficient to reduce the radial head and this was included in Group B. The gap between injury and presentation was from 3 months to 18 months (mean 9 months. Ten patients were classified as Bado I, and one each as Bado II and III respectively. We used the Kim′s criteria to score our results. Result: The mean follow-up period was 22 months. All ulna osteotomies healed uneventfully. The mean loss of pronation was 15 degree in Group A and 10 degree in Group B. Elbow flexion improved from the preoperative range and no child complained of pain, deformity and restriction of activity. The elbow score was excellent in 10 cases, and good in two cases. Conclusion: Distraction-angulation osteotomy of the ulna suffices in most cases of missed monteggia fracture and the need for annular ligament reconstruction is based on intraoperative findings of radial head instability.
Investigation of a low NOx full-scale annular combustor
1982-01-01
An atmospheric test program was conducted to evaluate a low NOx annular combustor concept suitable for a supersonic, high-altitude aircraft application. The lean premixed combustor, known as the vortex air blast (VAB) concept, was tested as a 22.0-cm diameter model in the early development phases to arrive at basic design and performance criteria. Final demonstration testing was carried out on a full scale combustor of 0.66-m diameter. Variable geometry dilution ports were incorporated to allow operation of the combustor across the range of conditions between idle (T(in) = 422 K, T(out) = 917 K) and cruise (T(in) = 833 K, T(out) - 1778 K). Test results show that the design could meet the program NOx goal of 1.0 g NO2/kg fuel at a one-atmospheric simulated cruise condition.
Dynamic Response of Three-Layered Annular Plate with Imperfections
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Pawlus Dorota
2015-02-01
Full Text Available This paper presents the imperfection sensitivity of annular plate with three-layered structure. The plate composed of thin elastic facings and a thicker elastic core is loaded in facing plane. The classical issue of a three-layered plate was solved for dynamic deflection problem using the approximation methods: orthogonalization and finite difference. The solution includes the axisymmetric and asymmetric plate modes of the dynamic stability loss. The evaluation of the rate of plate sensitivity to imperfection of plate preliminary geometry has been enriched by the analysis of plate models built of finite elements. The ABAQUS program has been used. The numerous calculation results in the form of deflection characteristics, buckling modes, values of critical parameters create the view of response of dynamic plate structure with different rate of imperfection and linear in time loading growth, too.
Annular modes and apparent eddy feedbacks in the Southern Hemisphere
Byrne, Nicholas J.; Shepherd, Theodore G.; Woollings, Tim; Plumb, R. Alan
2016-04-01
Lagged correlation analysis is often used to infer intraseasonal dynamical effects but is known to be affected by nonstationarity. We highlight a pronounced quasi 2 year peak in the anomalous zonal wind and eddy momentum flux convergence power spectra in the Southern Hemisphere, which is prima facie evidence for nonstationarity. We then investigate the consequences of this nonstationarity for the Southern Annular Mode and for eddy momentum flux convergence. We argue that positive lagged correlations previously attributed to the existence of an eddy feedback are more plausibly attributed to nonstationary interannual variability external to any potential feedback process in the midlatitude troposphere. The findings have implications for the diagnosis of feedbacks in both models and reanalysis data as well as for understanding the mechanisms underlying variations in the zonal wind.
75 FR 23582 - Annular Casing Pressure Management for Offshore Wells
2010-05-04
... Recommended Practice (RP) 90. As explained in API RP 90, Section 3, Annular Casing Pressure Management Program... Institute's Recommended Practice for managing annular casing pressure. New regulations are needed because... Continental Shelf lessees to follow best industry practices for wells with sustained casing pressure....
Obtention of an empirical equation for annular channels
International Nuclear Information System (INIS)
Using a trial circuit, the experimental heat transfer coefficient is determined, in forced convection at one phase only within an annular channel in which water flows ascendantly and for this reason an empirical equation is determined. This work tries to contribute to the understanding of the forced convection phenomena in non tubular geometries like the annular channels. (Author)
Limited Diffraction Maps for Pulsed Wave Annular Arrays
DEFF Research Database (Denmark)
Fox, Paul D.
2002-01-01
A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained...
Holm, J. A.; Chambers, J. Q.; Collins, W.
2013-12-01
Uncertainties surrounding vegetation and carbon responses to increased disturbance rates associated with climate change remains a major global change issue for Amazon forests. To help quantify the impacts of increased disturbances on climate and the earth system, the fidelity of tree mortality and disturbance algorithms in global land surface models (here the Community Land Model, CLM) warrant critical evaluation. In order to address this issue, we parameterized and calibrated ZELIG-TROP, a dynamic vegetation gap model, to simulate a complex Central Amazon forest toward improving disturbance-recovery processes in CLM. To evaluate the long-term consequences of increased disturbance rates in ZELIG-TROP and CLM for a Central Amazon rainforest, we 1) doubled background tree mortality rates (i.e., high disturbance treatment), and 2) applied a periodic disturbance treatment of removing 20% of stems every 50 years (i.e., periodic treatment) and compared model results. For the high disturbance treatment, ZELIG-TROP predicted that AGB and ANPP decreased by an average of 110 Mg ha-1 and 0.48 Mg C ha-1 yr-1 respectively (41.9% and 7.7%). The net carbon loss due to the periodic treatment, with four large-scale disturbances, was not as extreme as the loss from the high disturbance treatment, due to recovery dynamics. AGB only decreased by 15.9% (vs. 41.9%), however ANPP decreased by 19% (vs. 7.7%). For the high disturbance treatment in ZELIG-TROP, there were a higher proportion of smaller stems and a decrease in larger stems. This resulted in a decrease in coarse litter (trunks and large branches >10 cm in diameter) production rates (Mg C ha-1 yr-1) by 11.5%. For the periodic disturbance the average coarse litter production rates increased by 11.2% due to the four large-scale disturbance events. A comparison of the biomass response of ZELIG-TROP and CLM from simulated disturbance and recovery events displayed the same pattern between the two models, and for both disturbance
Directory of Open Access Journals (Sweden)
P. Ravinder Reddy
1997-01-01
Full Text Available The quadratic isoparametric elements which embody the inverse squareroot singularity were used to determine the stress intensity factor in an annular disk made of Boron-Epoxy composite material. The displacements and stresses were determined in a rectangular orthotropic composite annular disk using isoparametric finite elements. The singularity in the strain field was provided by means of 8-noded isoparametric elements (4-nodes at the four corners and four mid-side nodes each at l/4th distance from the edge. The results were obtained for various material properties and fibre orientation. The geometry of the annular disk was reported when subjected to a boundary radial and tangential. The r singularity was provided at the boundary of the circular hole and the rest of the annular disk was modelled with ordinary isoparametric elements. The apparent stress intensity factor (K/sub I/= was computed from the stress data near the circular hole, when it was subjected to uniform tension. A curve was drawn for apparent stress intensity factor versus the distance from the crack edge and was extrapolated to r = 0, the actual stress intensity factor was found on the y-axis.
International Nuclear Information System (INIS)
Highlights: • Exergy analysis in the annular thermoelectric generator (ATEG) system is proposed. • Analytical expressions for the power output, exergy efficiency of an ATEG is derived. • The effects of Sr, RL, and θ in Pout and exergy efficiency of an ATEG is studied. • The influence of Thomson effect in Pout and exergy efficiency of an ATEG is studied. - Abstract: The exoreversible thermodynamic model of an annular thermoelectric generator (ATEG) considering Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction has been investigated using exergy analysis. New expressions for optimum current at the maximum power output and maximum energy, exergy efficiency conditions, and dimensionless irreversibilities in the ATEG are derived. The modified expression for figure of merit of a thermoelectric generator considering the Thomson effect has also been obtained. The results show that the power output, energy and exergy efficiency of the ATEG is lower than the flat plate thermoelectric generator. The effects of annular shape parameter (Sr = r2/r1), load resistance (RL), dimensionless temperature ratio (θ = Th/Tc) and the thermal and electrical contact resistances in power output, energy/exergy efficiency of the ATEG have been studied. It has also been proved that because of the influence of Thomson effect, the power output and energy/exergy efficiency of the ATEG is reduced. This study will help in the designing of the actual annular thermoelectric generation systems
The effects of annular flow on dynamics of AP1000 reactor coolant pump rotor
International Nuclear Information System (INIS)
The feature of AP1000 RCP rotor system is that the whole rotor system is immersed in the annular flow. The rotor in annular flow induces fluctuating fluid forces, thereby causes vibration and noise, even rotor instability. The effects of annular flow on AP1000 RCP rotor system are different from that in bearings and seals and should be considered in a new approach. Based on the turbulent bulk flow theory and perturbation analysis, the rotor-flow coupled linear dynamic model is developed to predict the dynamics of AP1000 RCP immersed rotor. During the analysis, the rotor eccentricity, stator and rotor wall friction effects are emphasized. The analytic results show the rotor eccentricity induces divergence instability and significant decrease of instability speed for system with moderate or large eccentricity; however, stator and rotor wall friction effects distinctly suppress divergence instability and increase instability speed for system with small or moderate eccentricity. Finally, we can have the conclusion that the flow-structure interaction induced by annular flow has great effects on the dynamics of AP1000 RCP immersed rotor, which should be considered in rotor dynamic analysis and design of AP1000 RCP. The method and results in the paper have theoretical significance and practical importance. (author)
International Nuclear Information System (INIS)
During normal operation, the collapsible CANDU® fuel sheath deforms, especially, it may deform into longitudinal ridges or collapse instantaneously into the axial gaps between the end pellet and endcap or between two neighbouring pellets. These phenomena occur under certain conditions, such as the coolant pressure exceeding critical pressures for longitudinal ridging or axial collapse. Both longitudinal ridging and axial collapse phenomena result from plastic instability in the sheath under coolant pressure. Longitudinal ridging features one or multiple lobes or 'ridges' (outward from the sheath surface) formed along the sheath in the longitudinal direction. Axial collapse features a 'valley' around the sheath circumference. Both phenomena can lead to sheath overstrain, which in turn potentially leads to sheath failure. The LONGER code, which contains empirical correlations, has been used to predict the critical pressures for these two sheath deformation phenomena. To study fuel behaviour outside of the application ranges of the LONGER empirical correlations, a mechanistic model is needed. FEAST (Finite Element Analysis for Stresses) is an AECL computer code used to assess the structural integrity of the CANDU fuel element. The FEAST code has recently been developed (to Version 3.1) to model processes occurring during longitudinal ridge formation and instantaneous collapse into the axial gap. The new models include those for geometric non-linearity (large deformation, large material rotation), non-linear stress-strain curve for plastic deformation, Zr-4 sheath creep law, and variable Young’s Modulus etc. This paper describes the mechanistic model (FEAST 3.1) development for analyses of longitudinal ridging and instantaneous collapse into axial gap, and the comparison with the results from empirical correlations in LONGER. (author)
International Nuclear Information System (INIS)
Experiments and particle-in-cell simulations of femtosecond laser-stimulated electrical discharges in submicrometre gaps between scanning tunnelling microscope tip cathodes and gold film anodes are described. In experiments at applied potentials of 35 V and less, discharges were detected either as self-terminating low-current pulses with durations less than 10 ns and magnitudes less than 200 mA or as higher-current, longer-duration current waveforms. The probability of occurrence of low-current pulses increased as applied potential was decreased, being certain at low potentials of 20-25 V. Low-current pulse waveforms and surface melting of gold anodes predicted by the simulations were compared with experiments. Laser stimulation was modelled by introducing partially ionized electrode materials into the simulation domain at a controlled rate. Simulation results showed that the duration of low-current pulses was influenced by the time over which material was added to the gap region, establishing the importance of electrode vaporization on discharge duration. Subsequently, partially ionized electrode materials were preloaded into the gap in controlled amounts in subsequent simulations. Peak currents predicted by these simulations were nearly equal to the low-current pulse measurements but simulated pulse durations were shorter than experiments. Thus, the time axis of simulation current profiles was normalized for equality of charge transfer with experiments. Anode temperatures and melt diameters calculated from normalized simulated heat input profiles were well matched to experimental measurements.
Directory of Open Access Journals (Sweden)
Mindaugas Snipas
2015-01-01
Full Text Available The primary goal of this work was to study advantages of numerical methods used for the creation of continuous time Markov chain models (CTMC of voltage gating of gap junction (GJ channels composed of connexin protein. This task was accomplished by describing gating of GJs using the formalism of the stochastic automata networks (SANs, which allowed for very efficient building and storing of infinitesimal generator of the CTMC that allowed to produce matrices of the models containing a distinct block structure. All of that allowed us to develop efficient numerical methods for a steady-state solution of CTMC models. This allowed us to accelerate CPU time, which is necessary to solve CTMC models, ∼20 times.
Lee, Sang Hoon; Kim, Song Yee; Kim, Dong Soon; Kim, Young Whan; Chung, Man Pyo; Uh, Soo Taek; Park, Choon Sik; Jeong, Sung Hwan; Park, Yong Bum; Lee, Hong Lyeol; Shin, Jong Wook; Lee, Eun Joo; Lee, Jin Hwa; Jegal, Yangin; Lee, Hyun Kyung; Kim, Yong Hyun; Song, Jin Woo; Park, Moo Suk
2016-01-01
Abstract Although a multidisciplinary approach has become an important criterion for an idiopathic pulmonary fibrosis (IPF) diagnosis, lung biopsies remain crucial. However, the prognosis of patients with surgically diagnosed IPF (sIPF) is uncertain. We aimed to investigate the prognosis of patients with clinically diagnosed IPF (cIPF) and sIPF. In this retrospective observational study, the Korean Interstitial Lung Disease Study Group conducted a national survey to evaluate the clinical, physiological, radiological, and survival characteristics of patients with IPF from January 1, 2003 to December 31, 2007. Patients were recruited from 54 universities and teaching hospitals across the Republic of Korea. IPF diagnoses were established according to the 2002 American Thoracic Society (ATS)/European Respiratory Society criteria (ERS) guideline. A total of 1685 patients with IPF (1027 cIPF and 658 sIPF) were enrolled. Patients with sIPF were significantly younger, predominantly female, and nonsmokers (all P < 0.001). sIPF group had significantly better initial pulmonary function. The proportion of computed tomography-based honeycomb findings of patients with cIPF was higher than in those with sIPF (P < 0.001). A Kaplan-Meier analysis showed that the sIPF group had a better prognosis (P = 0.001). A survival analysis showed that age, pulmonary function parameters, pulmonary oxygen tension, honeycombing change, and combined lung cancer had a significant influence on patient prognosis. However, there was no significant difference in prognosis between the cIPF and sIPF groups after adjusting for GAP (gender, age, physiology) stage. The patients with sIPF had better clinical features than those with cIPF. However, after adjusting for GAP stage, the sIPF group showed similar prognoses as the cIPF group. This study showed that after adjusting for GAP stage, the prognosis of patients with IPF is the same regardless of the diagnostic method used. PMID:26986154
DEFF Research Database (Denmark)
Lyles, Marjorie; Pedersen, Torben; Petersen, Bent
2003-01-01
, assimilating, and utilizing knowledge - are crucial determinants ofknowledge gap elimination. In contrast, the two factors deemed essential in traditionalinternationalization process theory - elapsed time of operations and experientiallearning - are found to have no or limited effect.Key words...
Critical behavior of the Higgs- and Goldstone-mass gaps for the two-dimensional S=1 XY model
Directory of Open Access Journals (Sweden)
Yoshihiro Nishiyama
2015-08-01
Full Text Available Spectral properties for the two-dimensional quantum S=1 XY model were investigated with the exact diagonalization method. In the symmetry-broken phase, there appear the massive Higgs and massless Goldstone excitations, which correspond to the longitudinal and transverse modes of the spontaneous magnetic moment, respectively. The former excitation branch is embedded in the continuum of the latter, and little attention has been paid to the details, particularly, in proximity to the critical point. The finite-size-scaling behavior is improved by extending the interaction parameters. An analysis of the critical amplitude ratio for these mass gaps is made.
Mishonov, T. M.; Donkov, A. A.; Koleva, R. K.; Penev, E. S.
2000-01-01
The oxygen O2p_sigma and copper Cu4s and Cu3d_x^2-y^2 orbitals are involved in a simple LCAO model for determination of the conduction band and the oxygen-oxygen hopping is considered as a small parameter with respect to the transition amplitude between nearest neighbours. The traditional Cooper pairing is obtained by taking into account the double-electron exchange between the nearest neighbours within the two-dimensional CuO_2 plane. The equation for the superconducting gap is obtained as a...
Dual-Band Annular-Ring Microstrip Patch Antenna for Satellite Applications
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Tvs Divakar
2014-08-01
Full Text Available A dual-band circularly polarized antenna fed by four apertures that covers the bands of GPS, Galileo, is introduced. The ARSAs designed using FR4 substrates in the L and S bands have 3-dB axial-ratio bandwidths (ARBWs of as large as 37% and 52%, respectively, whereas the one using an RT5880 substrate in the L band, 61%. In these 3-dB axial-ratio bands, impedance matching with VSWR<=1.8 is also achieved. Three wideband planar baluns are used to achieve good axial ratio and VSWR. The results of the annular-ring microstrip antenna show good performance of a dual-band operation, which meets the requirement of Global Navigation Satellite System (GNSS applications.
Directory of Open Access Journals (Sweden)
William Hansen
2014-11-01
Full Text Available Different kinds of omissions sometimes occur, or are perceived to occur, in traditional narratives and in tradition-inspired literature. A familiar instance is when a narrator realizes that he or she does not fully remember the story that he or she has begun to tell, and so leaves out part of it, which for listeners may possibly result in an unintelligible narrative. But many instances of narrative gap are not so obvious. From straightforward, objective gaps one can distinguish less-obvious subjective gaps: in many cases narrators do not leave out anything crucial or truly relevant from their exposition, and yet readers perceive gaps and take steps to fill them. The present paper considers four examples of subjective gaps drawn from ancient Greek literature (the Pandora myth, ancient Roman literature (the Pygmalion legend, ancient Hebrew literature (the Joseph legend, and early Christian literature (the Jesus legend. I consider the quite varied ways in which interpreters expand the inherited texts of these stories, such as by devising names, manufacturing motives, creating backstories, and in general filling in biographical ellipses. Finally, I suggest an explanation for the phenomenon of subjective gaps, arguing that, despite their variety, they have a single cause.
Facility modernization Annular Core Research Reactor
International Nuclear Information System (INIS)
The Annular Core Research Reactor (ACRR) has undergone numerous modifications since its conception in response to program needs. The original reactor fuel, which was special U-ZrH TRIGA fuel designed primarily for pulsing, has been replaced with a higher pulsing capacity BeO fuel. Other advanced operating modes which use this increased capability, in addition to the pulse and steady state, have been incorporated to tailor power histories and fluences to the experiments. Various experimental facilities have been developed that range from a radiography facility to a 50 cm diameter External Fuel Ring Cavity (FREC) using 180 of the original ZrH fuel elements. Currently a digital reactor console is being produced with GA, which will give enhanced monitoring capabilities of the reactor parameters while leaving the safety-related shutdown functions with analog technology. (author)
Recurrent Annular Peripheral Choroidal Detachment after Trabeculectomy
Directory of Open Access Journals (Sweden)
Shaohui Liu
2013-10-01
Full Text Available We report a challenging case of recurrent flat anterior chamber without hypotony after trabeculectomy in a 54-year-old Black male with a remote history of steroid-treated polymyositis, cataract surgery, and uncontrolled open angle glaucoma. The patient presented with a flat chamber on postoperative day 11, but had a normal fundus exam and intraocular pressure (IOP. Flat chamber persisted despite treatment with cycloplegics, steroids, and a Healon injection into the anterior chamber. A transverse B-scan of the peripheral fundus revealed a shallow annular peripheral choroidal detachment. The suprachoroidal fluid was drained. The patient presented 3 days later with a recurrent flat chamber and an annular peripheral choroidal effusion. The fluid was removed and reinforcement of the scleral flap was performed with the resolution of the flat anterior chamber. A large corneal epithelial defect developed after the second drainage. The oral prednisone was tapered quickly and the topical steroid was decreased. One week later, his vision decreased to count fingers with severe corneal stromal edema and Descemet's membrane folds that improved to 20/50 within 24 h of resumption of the oral steroid and frequent topical steroid. The patient's visual acuity improved to 20/20 following a slow withdrawal of the oral and topical steroid. Eight months after surgery, the IOP was 15 mm Hg without glaucoma medication. The detection of a shallow anterior choroidal detachment by transverse B-scan is critical to making the correct diagnosis. Severe cornea edema can occur if the steroid is withdrawn too quickly. Thus, steroids should be tapered cautiously in steroid-dependent patients.
Annular MHD Physics for Turbojet Energy Bypass
Schneider, Steven J.
2011-01-01
The use of annular Hall type MHD generator/accelerator ducts for turbojet energy bypass is evaluated assuming weakly ionized flows obtained from pulsed nanosecond discharges. The equations for a 1-D, axisymmetric MHD generator/accelerator are derived and numerically integrated to determine the generator/accelerator performance characteristics. The concept offers a shockless means of interacting with high speed inlet flows and potentially offers variable inlet geometry performance without the complexity of moving parts simply by varying the generator loading parameter. The cycle analysis conducted iteratively with a spike inlet and turbojet flying at M = 7 at 30 km altitude is estimated to have a positive thrust per unit mass flow of 185 N-s/kg. The turbojet allowable combustor temperature is set at an aggressive 2200 deg K. The annular MHD Hall generator/accelerator is L = 3 m in length with a B(sub r) = 5 Tesla magnetic field and a conductivity of sigma = 5 mho/m for the generator and sigma= 1.0 mho/m for the accelerator. The calculated isentropic efficiency for the generator is eta(sub sg) = 84 percent at an enthalpy extraction ratio, eta(sub Ng) = 0.63. The calculated isentropic efficiency for the accelerator is eta(sub sa) = 81 percent at an enthalpy addition ratio, eta(sub Na) = 0.62. An assessment of the ionization fraction necessary to achieve a conductivity of sigma = 1.0 mho/m is n(sub e)/n = 1.90 X 10(exp -6), and for sigma = 5.0 mho/m is n(sub e)/n = 9.52 X 10(exp -6).
Energy Technology Data Exchange (ETDEWEB)
Budzianowski, W.M. [Wroclaw Univ. of Technology, Wroclaw (Poland). Div. of Chemical and Biochemical Processes, Faculty of Chemistry; Miller, R. [Wroclaw Univ. of Technology, Wroclaw (Poland). Inst. of Power Engineering and Fluid Mechanics, Faculty of Mechanical and Power Engineering
2008-08-15
This study investigated the auto-thermal combustion of lean gaseous fuels in a recuperative annular double-layer catalytic converter. An analysis of the stationary and transient performance of annular converters was presented. The feasibility of lean gaseous mixture combustion in auto-thermally operated recuperative annular double-layer catalytic converters was investigated. The aim of the study was to build a process model using mass, energy, and momentum differential balances. The model was used to study the static behaviour of a recuperative annular double layer converter; an annular converter operating in transient conditions; and energy accumulation and recuperation interactions. The effects of fuel temperature, external cooling, and fuel concentration were examined. Results of the study showed that a substantial reduction of the inter- and intra-phase resistances to mass and heat transfer was obtained. It was demonstrated that the use of a low value for the substrate's thermal conductivity accelerated ignition and retarded extinction. The recuperative converter was able to transfer short-time inlet disturbances of various parameters due to the energy accumulation and temporal reversed recuperation which counteracted destructive overheating of the catalysts. The stability analyses showed stable and unstable branches of solutions for the different parameters of the recuperative converter. 21 refs., 1 tab., 23 figs.
Jugroot, M.; Bayle, P.; Yousfi, M.; Eichwald, O.
1999-01-01
A self-consistent model of charged and neutral particle dynamics is developed for the case of high pressure short-gap discharges in helium 0022-3727/32/2/007/img7 and hydrogen 0022-3727/32/2/007/img8 and 0022-3727/32/2/007/img9. Boundary wall effects on the electron swarm parameters are first investigated by a Monte Carlo method in order to verify the validity of the classical local field approximation in short-gap discharges. The hydrodynamic transport equations of the self-consistent model are then described with an emphasis on the different terms involved in the close coupling between charged and neutral particles and the electric field. These equations are solved by powerful two-dimensional numerical schemes for both transport and electrical field equations. The discharges are studied from an initial electronic cloud to the first stages of breakdown. Cathode emission is discussed in terms of its prime importance in the spatio-temporal evolution of the short-gap discharges and it is shown that the principal difference between helium and hydrogen discharges is due to the mode of cathode emission. The particular observations in the luminosity in hydrogen are discussed in terms of ionization of the gas and secondary emission processes at the surface. A detailed analysis reveals a complex distribution of charged particles due to the superposition of ionization and transport effects. Furthermore, Joule heating of the neutral medium is evaluated in the entire time scale of the discharge and its influence on the discharge evolution is discussed.
GAP Analysis Program (GAP) Raster
Kansas Data Access and Support Center — The Kansas GAP Land Cover database depicts 43 land cover classes for the state of Kansas. The database was generated using a two-stage hybrid classification of...
Koonprasert, Sanoe; Sangsawang, Rilrada
2008-09-01
This paper presents the analytical solutions and symbolic computations for the temperature distribution of the annular fin under fully-wet surface condition. During the process of dehumidification, the annular fin is separated into two regions. The mathematical models for each region are based on the conservation of energy principle. An assumption used in this paper is the humidity ratio of the saturated air on the wet surface varies linearly with the local fin temperature. The mathematical models are solved by the Cauchy-Euler Equation and modified Bessel Equation to form analytical solutions. Besides, the symbolic computations are shown by the Maple software to visualize the temperature distribution along the fin.
International Nuclear Information System (INIS)
Objective: To determine the effect of recombinant canine somatotropin (STH) on radiographic, densitometric, and biomechanical aspects of bone healing using an unstable ostectomy gap model. Study Design: After an ostectomy of the midshaft radius, bone healing was evaluated over an 8-week period in control dogs (n = 4) and dogs receiving recombinant canine STH (n = 4). Animals Or Sample Population: Eight sexually intact female Beagle dogs, 4 to 5 years old. Methods: Bone healing was evaluated by qualitative and quantitative evaluation of serial radiographs every 2 weeks. Terminal dual-energy x-ray absorptiometry and three-point bending biomechanical testing were also performed. Results: Dogs receiving STH had more advanced radiographic healing of ostectomy sites. Bone area, bone mineral content, and bone density were two to five times greater at the ostectomy sites of treated dogs. Ultimate load at failure and stiffness were three and five times greater in dogs receiving STH. Conclusions: Using the ostectomy gap model, recombinant canine STH enhanced the radiographic, densitometric, and biomechanical aspects of bone healing in dogs. Clinical Relevance: Dogs at risk for delayed healing of fractures may benefit from treatment with recombinant canine STH
Abbiendi, G; Åkesson, P F; Alexander, G; Allison, J; Amaral, P; Anagnostou, G; Anderson, K J; Arcelli, S; Asai, S; Axen, D A; Azuelos, Georges; Bailey, I; Barberio, E; Barlow, R J; Batley, J Richard; Bechtle, P; Behnke, T; Bell, K W; Bell, P J; Bella, G; Bellerive, A; Benelli, G; Bethke, Siegfried; Biebel, O; Bock, P; Boeriu, O; Boutemeur, M; Braibant, S; Brigliadori, L; Brown, R M; Burckhart, H J; Büsser, K; Campana, S; Carnegie, R K; Caron, B; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Csilling, Akos; Cuffiani, M; Dado, S; de Roeck, A; De Wolf, E A; Desch, Klaus; Dienes, B; Donkers, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Etzion, E; Fabbri, Franco Luigi; Feld, L; Ferrari, P; Fiedler, F; Fleck, I; Ford, M; Frey, A; Fürtjes, A; Gagnon, P; Gary, J W; Gaycken, G; Geich-Gimbel, C; Giacomelli, G; Giacomelli, P; Giunta, M; Goldberg, J; Gross, E; Grunhaus, Jacob; Gruwé, M; Günther, P O; Hajdu, C; Hamann, M; Hanson, G G; Harder, K; Harel, A; Harin-Dirac, M; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Hensel, C; Herten, G; Heuer, R D; Hill, J C; Hoffman, K; Horváth, D; Igo-Kemenes, P; Ishii, K; Jeremie, H; Jovanovic, P; Junk, T R; Kanaya, N; Kanzaki, J; Karapetian, G V; Karlen, Dean A; Kawagoe, K; Kawamoto, T; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Kim, D H; Klein, K; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Komamiya, S; Kormos, L L; Kramer, T; Krieger, P; Von Krogh, J; Krüger, K; Kupper, M; Kühl, T; Lafferty, G D; Landsman, Hagar Yaël; Lanske, D; Layter, J G; Leins, A; Lellouch, D; Letts, J; Levinson, L; Lillich, J; Lloyd, S L; Loebinger, F K; Lü, J; Ludwig, J; MacPherson, A; Mader, W; Marcellini, S; Martin, A J; Masetti, G; Mashimo, T; McDonald, W J; McKenna, J A; McMahon, T J; McPherson, R A; Meijers, F; Menges, W; Merritt, F S; Mes, H; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Moed, S; Mohr, W; Mori, T; Mutter, A; Mättig, P; Nagai, K; Nakamura, I; Nanjo, H; Neal, H A; Nisius, R; O'Neale, S W; Oh, A; Okpara, A N; Oreglia, M J; Orito, S; Pahl, C; Pater, J R; Patrick, G N; Pilcher, J E; Pinfold, J L; Plane, D E; Poli, B; Polok, J; Pooth, O; Przybycien, M B; Pásztor, G; Quadt, A; Rabbertz, K; Rembser, C; Renkel, P; Roney, J M; Rosati, S; Rozen, Y; Runge, K; Sachs, K; Saeki, T; Sarkisyan-Grinbaum, E; Schaile, A D; Schaile, O; Scharff-Hansen, P; Schieck, J; Schröder, M; Schumacher, M; Schwick, C; Schörner-Sadenius, T; Scott, W G; Sen-Gupta, A; Seuster, R; Shears, T G; Shen, B C; Sherwood, P; Siroli, G P; Skuja, A; Smith, A M; Sobie, R J; Spanó, F; Stahl, A; Stephens, K; Strom, D; Ströhmer, R; Söldner-Rembold, S; Tarem, S; Tasevsky, M; Taylor, R J; Teuscher, R; Thomson, M A; Torrence, E; Toya, D; Tran, P; Trigger, I; Trócsányi, Z L; Tsur, E; Turner-Watson, M F; Ueda, I; Ujvári, B; Vannerem, P; Vertesi, R; Verzocchi, M; Vollmer, C F; Voss, H; Vossebeld, Joost Herman; Waller, D; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wengler, T; Wermes, N; Wetterling, D; Wilson, G W; Wilson, J A; Wolf, G; Wyatt, T R; Yamashita, S; Zer-Zion, D; Zivkovic, L
2004-01-01
Gluon jets with a mean energy of 22 GeV and purity of 95% are selected from hadronic Z0 decay events produced in e+e- annihilations. A subsample of these jets is identified which exhibits a large gap in the rapidity distribution of particles within the jet. After imposing the requirement of a rapidity gap, the gluon jet purity is 86%. These jets are observed to demonstrate a high degree of sensitivity to the presence of color reconnection, i.e. higher order QCD processes affecting the underlying color structure. We use our data to test three QCD models which include a simulation of color reconnection: one in the Ariadne Monte Carlo, one in the Herwig Monte Carlo, and the other by Rathsman in the Pythia Monte Carlo. We find the Rathsman and Ariadne color reconnection models can describe our gluon jet measurements only if very large values are used for the cutoff parameters which serve to terminate the parton showers, and that the description of inclusive Z0 data is significantly degraded in this case. We concl...
Vibrational characteristics of fluid filled gap support systems
International Nuclear Information System (INIS)
A fluid filled gap support system is a hydrodynamic support system, which is composed of an inner cylinder and an outer restraint cylinder surrounding the inner cylinder, with a small gap between them filled with fluid. In pool type LMFBRs, the fluid filled gap support system is considered to be efficient as a seismic support system for internal components, such as pumps, IHXs etc., which are suspended from the deck. Because this support system has no mechanical connections with internal components, and accommodates the thermal deformation without causing thermal stress. This support system fundamentally has a two concentric cylindrical geometry separated by an annular fluid region. Previously, two dimensional analyses on this cylindrical structure were performed, neglecting axial flows in the annular region, by Fritz and Chen. It has been proved analytically and experimentally that the fluid filled gap support system was effective to restrain component vibration, and that axial flows in the annular gap reduced supporting effects. So, it is expected that the system will be improved in performance by suppressing axial flows in the annular gap. In this study, a device using seal rings was designed to suppress the axial flow described above. Analyses were performed to evaluate vibrational characteristics for the system, such as added mass and damping factors. Also, vibration tests with the seal rings were performed to examine the validity of the analytical method, and vibration test without the seal rings were performed in a large response amplitude to examine the vibration characteristics. Finally, a design calculation for a core support cylinder was performed for the evaluation of support systems. 5 refs, 12 figs, 2 tabs
Mind the Gaps: Wikipedia as an education model and public duty for scientists
Boustead, Greg; Wiki Education Foundation
2016-06-01
Search for almost any scientific term on the Internet, and chances are that a Wikipedia page will be the first result. Wikipedia’s content reaches more than 450 million readers around the world, at a rate of about 8,000 readers a second. That makes Wikipedia one of the most powerful platforms for the dissemination of science information in the world. Although Wikipedia’s coverage of science topics is robust, clear gaps remain — especially with subject matter that requires technical or specialized expertise. Some information is woefully out of date; and, while a minority, some scientific entries on Wikipedia are simply inaccurate. Furthermore, the underrepresentation of women, and diversity in general, remains a real issue. The Wikipedia Year of Science 2016 is an unprecedented targeted initiative designed to improve Wikipedia’s potential for communicating science to the public. The multi-faceted effort is a program conceived by the Wiki Education Foundation, with support from the Simons Foundation and Google. This talk will provide a brief overview of the Wikipedia Year of Science initiative, and ways AAS members can get involved — during the meeting, in the classroom, and beyond.
Detonation Initiation by Annular Jets and Shock Waves
Shepherd, Joseph E.
2005-01-01
The objective of this research is to experimentally determine the feasibility of initiating detonation in fuel-air mixtures using only the energy in hot, compressed air. The existing 6-inch shock tube at Caltech was used to create hot, high-pressure air behind a reflected shock wave. The hot air created an imploding annular shock wave when it jetted through an annular orifice into a 76-mm-diameter, 1-m-long tube attached to the end of the shock tube. A special test section with an annular ...
Institute of Scientific and Technical Information of China (English)
蒲鹏飞; 潘良明; 李午申; 黄永军
2005-01-01
对竖直矩形狭缝通道内有液滴卷吸环状流阶段流动沸腾进行分析.以液膜紊流的动量方程和能量方程为基础,加上相应的边界条件和使控制方程组封闭的经验关系式,建立了环状流的数学模型并进行数值计算,得到了矩形狭缝通道内的液膜厚度分布、沸腾传热系数等结果;将模型预测的换热系数同实验关系式作比较,最大相对误差为17.8%.
Computation of Flow through an Annular Diffuser and Volute Exhaust
Directory of Open Access Journals (Sweden)
M. Arun
2006-04-01
Full Text Available Turbulent flow in a diffuser with swirl occurs in many commonly used fluid mechanicaldevices,eg, diffusers located downstream of a gas turbine, and in certain types of combustionchambers. Diffusers are widely used for converting kinetic energy to pressure, and a reliableprediction method of such flows with the required flow conditions would lead to the design offluid machinery with improved efficiency. As a first step, turbulent swirling flow through a 12oincluded angle conical diffuser for a swirl parameter, m = 0.18 was numerically investigated usingvarious turbulence models like standard k- , RNG-based k- , shear-stress transport (SST kandReynolds stress model (RSM. Though the comparison between the experimental and thepredicted mean velocity profile by RSM is superior to that by RNG kandSST models, the lattertwo models give closer comparison with the experimental pressure distribution. Subsequently,computation of flow inside a complex duct involving axisymmetric annular diffuser, transitionfrom rectangular to circular cross section, and exit pipe have been carried out using RNG kandSST k models.The comparison of computed and experimental results indicates that theSST k modelgives predictions with reasonable accuracy.
DCH dispersal and entrainment experiment in a scaled annular cavity
International Nuclear Information System (INIS)
The objective of this experiment was to measure the amount of corium dispersal and the droplet size distribution during high pressure melt ejection from a CE reactor. The melt and the steam flowed to the containment through a narrow annular cavity. The experiment was carried out on a 1/20th scaled model of the cavity and the containment. The scaling was based on dimensionless numbers obtained from a two-phase flow model of the dispersal and entrainment mechanisms in the cavity. Furthermore, the model shows that the flow in the cavity was choked, so high levels of dispersal and entrainment were possible. The experiment consisted of air-water, air-helium, air-woods metal and helium-woods metal tests; the main result being that the level of dispersal was very high in all cases. The woods metal data supported a separated flow model in the cavity, implying that the gas choked velocity was very high and the droplets very small. In contrast, the measured drop sizes for the water tests were much larger than the separated flow model predictions. This discrepancy could not be resolved because the entrainment mechanism is not properly understood at the present time. (orig.)
Wohlman, Sarah J; Murray, Wendy M
2013-03-15
The thumb is required for a majority of tasks of daily living. Biomechanical modeling is a valuable tool, with the potential to help us bridge the gap between our understanding of the mechanical actions of individual thumb muscles, derived from anatomical cadaveric experiments, and our understanding of how force is produced by the coordination of all of the thumb muscles, derived from studies involving human subjects. However, current biomechanical models do not replicate muscle force production at the thumb-tip. We hypothesized that accurate representations of the axes of rotation of the thumb joints were necessary to simulate the magnitude of endpoint forces produced by human subjects. We augmented a musculoskeletal model with axes of rotation derived from experimental measurements (Holzbaur et al., 2005) by defining muscle-tendon paths and maximum isometric force-generating capacity for the five intrinsic muscles. We then evaluated if this augmented model replicated a broad range of experimental data from the literature and identified which parameters most influenced model performance. The simulated endpoint forces generated by the combined action of all thumb muscles in our model yielded comparable forces in magnitude to those produced by nonimpaired subjects. A series of 8 sets of Monte Carlo simulations demonstrated that the difference in the axes of rotation of the thumb joints between studies best explains the improved performance of our model relative to previous work. In addition, we demonstrate that the endpoint forces produced by individual muscles cannot be replicated with existing experimental data describing muscle moment arms. PMID:23332233
DEFF Research Database (Denmark)
Zhu, Jun; Rasmussen, Jakob Gulddahl; Møller, Jesper;
2008-01-01
Studies of forest declines are important, because they both reduce timber production and affect successional trajectories of landscapes and ecosystems. Of particular interest is the decline of red pines, which is characterized by expanding areas of dead and chlorotic trees in plantations throughout...... the Great Lakes region. Here we examine the impact of two bark beetle groups, red turpentine beetles and pine engraver bark beetles, on tree mortality and the subsequent gap formation over time in a plantation in Wisconsin. We construct spatial-temporal statistical models that quantify the relations...... among red turpentine beetle colonization, pine engraver bark beetle colonization, and mortality of red pine trees while accounting for correlation across space and over time. We extend traditional Markov random-field models to include temporal terms and multiple-response variables aimed at developing a...
DEFF Research Database (Denmark)
Zhu, J.; Rasmussen, Jakob Gulddahl; Møller, Jesper;
Studies of forest declines are important, because they both reduce timber production and aect successional trajectories of landscapes and ecosystems. Of partic- ular interest is the decline of red pines which is characterized by expanding areas of dead and chlorotic trees in plantations throughout...... the Great Lakes Region. Here we examine the impact of two bark beetle groups, namely red turpentine beetles and pine engraver bark beetles, on tree mortality and the subsequent gap formation over time in a plantation in Wisconsin. We construct spatial-temporal statistical models that quantify the...... relations among red turpentine beetle coloniza- tion, pine engraver bark beetle colonization, and mortality of red pine trees, while accounting for correlation across space and over time. For statistical inference, we adopt a Bayesian hierarchical model and devise Markov chain Monte Carlo algorithms for...
Experimental model of a bone gap by radial ostectomy in rabbits
Antonio Carlos Cunha Lacreta Junior; Everton Regonato; Lucas Bahdour Cossi; Ciro Alexandre Teixeira Cruvinel; Júlio Carlos Canola
2010-01-01
A lot of experimental models have been used to study the process of a fracture’s consolidation, but the problem is that due to anatomic, biologic and technical differences, these models do not always have appropriate parameters for the exact species, for which the experiment was done. The rabbit is an experimental model that is widely used in studies involving bone physiopatology in the face of fractures and their different types of treatment, corresponding to approximately 35% of all the mus...
A Numerical and an Experimental Study for Optimization of a Small Annular Combustor
Iki, Norihiko; Gruber, Andrea; Yoshida, Hiro
The small annular combustor of a micro gas turbine fueled with methane is investigated experimentally and numerically in order to improve the overall efficiency of the small engine. The CFD analysis of the tiny combustor relies on a low Reynolds number turbulence model coupled to the Eddy Dissipation Concept (EDC) and provides important insight about the turbulent flow pattern, flame shape, position and optimal flame anchoring. For the experimental observation, a model combustor, representing 120 degrees of the original annular combustor, is fabricated, which enables us to visualize internal flow. The burning area in the combustion chamber moves to downstream with increase of air flow rate. At full-load, some fuel remains at the combustion chamber exit. Moreover, temperatures are measured and compared with the numerical simulations. The results shown here will form the basis for future optimization of the micro gas turbine with minimal or no increase in combustor pressure loss.
Ghodsi, Seyed Hamed; Kerachian, Reza; Estalaki, Siamak Malakpour; Nikoo, Mohammad Reza; Zahmatkesh, Zahra
2016-02-01
In this paper, two deterministic and stochastic multilateral, multi-issue, non-cooperative bargaining methodologies are proposed for urban runoff quality management. In the proposed methodologies, a calibrated Storm Water Management Model (SWMM) is used to simulate stormwater runoff quantity and quality for different urban stormwater runoff management scenarios, which have been defined considering several Low Impact Development (LID) techniques. In the deterministic methodology, the best management scenario, representing location and area of LID controls, is identified using the bargaining model. In the stochastic methodology, uncertainties of some key parameters of SWMM are analyzed using the info-gap theory. For each water quality management scenario, robustness and opportuneness criteria are determined based on utility functions of different stakeholders. Then, to find the best solution, the bargaining model is performed considering a combination of robustness and opportuneness criteria for each scenario based on utility function of each stakeholder. The results of applying the proposed methodology in the Velenjak urban watershed located in the northeastern part of Tehran, the capital city of Iran, illustrate its practical utility for conflict resolution in urban water quantity and quality management. It is shown that the solution obtained using the deterministic model cannot outperform the result of the stochastic model considering the robustness and opportuneness criteria. Therefore, it can be concluded that the stochastic model, which incorporates the main uncertainties, could provide more reliable results.
Gamma-ray pulsar physics: gap-model populations and light-curve analyses in the FERMI era
Pierbattista, Marco
2013-01-01
This thesis research focusses on the study of the young and energetic isolated ordinary pulsar population detected by the Fermi gamma-ray space telescope. We compared the model expectations of four emission models and the LAT data. We found that all the models fail to reproduce the LAT detections, in particular the large number of high spin-down power objects observed. This inconsistency is not model dependent. A discrepancy between the radio-loud/radio-quiet objects ratio was also found between the observed and predicted samples. The gamma-ray luminosity proportional to the 0.5 power of the spin-down power relation is robustly confirmed by all the assumed models with particular agreement in the slot gap (SG) case. On luminosity bases, the intermediate altitude emission of the two pole caustic SG model is favoured. The beaming factor shows an spin-down power dependency that is slightly visible in theSG case. Estimates of the pulsar orientations have been obtained to explain the simultaneous gamma and radio li...
Quan, M.; Lockman, W. K.
1975-01-01
Results are presented which were obtained from tests in a hypersonic wind tunnel to determine aerodynamic heating rates in a gap running parallel or slightly askew to the flow direction. The model used was a flat plate instrumented in thin-skin sections with chromelconstantan thermocouples. Heating rate profiles lengthwise along and down into the gap were obtained, and additional data were obtained from a total temperature probe and rake fabricated during the test to investigate an apparent aerodynamic cooling trend in the gap. Model variables were width, depth, length, and orientation of the gap relative to the flow direction. The tests were conducted at Mach 5.1 and Reynolds numbers per foot of 500,000, 1,000,000, and 2,000,000.
Annular flow entrainment rate experiment in a small vertical pipe
International Nuclear Information System (INIS)
Two-fluid model predictions of film dryout in annular flow, leading to nuclear reactor fuel failure, are limited by the uncertainties in the constitutive relations for the entrainment rate of droplets from the liquid film. The main cause of these uncertainties is the lack of separate-effects experimental data in the range of the operating conditions in nuclear power reactors. An air-water experiment has been performed to measure the entrainment rate in a small pipe. The current data extend the available database in the literature to higher gas and liquid flows and also to higher pressures. The measurements were made with the film extraction technique. A mechanistic model was obtained based on Kelvin-Helmholtz' instability theory. The dimensionless model includes the Weber number of the gas and the liquid film Reynolds number. Kataoka and Ishii's correlation (Kataoka, I., Ishii, M., (1982)) is modified based on this model and the new data. The new correlation collapses the present air-water data and Cousins and Hewitt's data (Cousins, L.B. (1968)) The effects of pressure and surface tension were considered in the derivation so it may be applied for boiling water reactor operating conditions. (orig.)
Nonlinear modelling of cancer: bridging the gap between cells and tumours
International Nuclear Information System (INIS)
Despite major scientific, medical and technological advances over the last few decades, a cure for cancer remains elusive. The disease initiation is complex, and including initiation and avascular growth, onset of hypoxia and acidosis due to accumulation of cells beyond normal physiological conditions, inducement of angiogenesis from the surrounding vasculature, tumour vascularization and further growth, and invasion of surrounding tissue and metastasis. Although the focus historically has been to study these events through experimental and clinical observations, mathematical modelling and simulation that enable analysis at multiple time and spatial scales have also complemented these efforts. Here, we provide an overview of this multiscale modelling focusing on the growth phase of tumours and bypassing the initial stage of tumourigenesis. While we briefly review discrete modelling, our focus is on the continuum approach. We limit the scope further by considering models of tumour progression that do not distinguish tumour cells by their age. We also do not consider immune system interactions nor do we describe models of therapy. We do discuss hybrid-modelling frameworks, where the tumour tissue is modelled using both discrete (cell-scale) and continuum (tumour-scale) elements, thus connecting the micrometre to the centimetre tumour scale. We review recent examples that incorporate experimental data into model parameters. We show that recent mathematical modelling predicts that transport limitations of cell nutrients, oxygen and growth factors may result in cell death that leads to morphological instability, providing a mechanism for invasion via tumour fingering and fragmentation. These conditions induce selection pressure for cell survivability, and may lead to additional genetic mutations. Mathematical modelling further shows that parameters that control the tumour mass shape also control its ability to invade. Thus, tumour morphology may serve as a predictor of
The thermophysical properties of gases determined using an annular acoustic resonator
Buxton, A. J.
1997-01-01
A novel annular acoustic resonator was constructed for measurements of the speed of sound in gases at pressures below 1 MPa. The resonator was designed to allow measurements of the speed and absorption of sound at low pressure in gases with large bulk viscosities. Measurements in propene, for which the speed of sound is known, served to characterise the geometry of the resonator and provide a test of the acoustic model for the system. A detailed description of the resonator whi...
Direct and ozone-mediated forcing of the Southern Annular Mode by greenhouse gases
Morgenstern, Olaf; ZENG Guang; Dean, Sam M.; Joshi, Manoj; Abraham, N. Luke; Osprey, Annette
2014-01-01
We assess the roles of long-lived greenhouse gases and ozone depletion in driving meridional surface pressure gradients in the southern extratropics; these gradients are a defining feature of the Southern Annular Mode. Stratospheric ozone depletion is thought to have caused a strengthening of this mode during summer, with increasing long-lived greenhouse gases playing a secondary role. Using a coupled atmosphere-ocean chemistry-climate model, we show that there is cancelation between the dire...
Applicability of the limiting cases for axial annular flow of power-law fluids
Czech Academy of Sciences Publication Activity Database
Filip, Petr; David, Jiří
Fukuoka: WSEAS Press, 2013 - ( Fujita , H.; Tuba, M.; Sasaki, J.), s. 45-48 ISBN 978-1-61804-177-7. ISSN 1790-5117. [Recent advances in automatic control, modelling and simulation. Morioka City (JP), 23.04.2013-25.04.2013] R&D Projects: GA ČR GA103/09/2066 Institutional support: RVO:67985874 Keywords : annular flow * power-law fluids * poiseuille flow * flow rate * pressure drop Subject RIV: BK - Fluid Dynamics
Influence of the Southern Annular Mode on the sea ice-ocean system
W. Lefebvre; Goosse, H.; Timmermann, R.; Fichefet, T.
2004-01-01
[1] The global sea ice - ocean model ORCA2-LIM, driven by the NCEP/NCAR ( National Centers for Environmental Prediction-National Center for Atmospheric Research) reanalysis daily 2-m air temperatures and 10-m winds and by monthly climatologies for precipitation, cloud cover, and relative humidity, is used to investigate the impact of the Southern Annular Mode (SAM) on the Antarctic sea ice-ocean system. Our results suggest that the response of the circumpolar Southern Ocean consists of an ann...
RAJDEEP SINGH; Dinesh Khanduja
2010-01-01
Service firms like other organizations are realizing the significance of customer-centered philosophies and are turning to quality management approaches to help managing their businesses. This paper has started with the concept of service quality and has demonstrated the model of service quality gaps. SERVQUAL methodology was applied for faculty as a customer to identify the gap between customer expectations and perceptions of the actual service received taking higher education as a service i...
Assessment of Inner Channel Blockage on the Annular Fuel Rod
Energy Technology Data Exchange (ETDEWEB)
Shin, C. H.; In, W. K.; Oh, D. S.; Chun, T. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2010-10-15
A dual-cooled annular fuel for a pressurized water reactor (PWR) has been introduced for a significant amount of reactor power uprate. The Korea Atomic Energy Research Institute (KAERI) has been performing a research to develop a dual-cooled annular fuel for the power uprate of 20% in an optimized PWR in Korea, OPR1000. An inner channel blockage is principal one of technical issues of the annular fuel rod. The inner channel in an annular fuel is isolated from the neighbor channels unlike the outer channels. The inner channel will be faced with a DNB accident by the partial blockage. In this paper, the largest fractional channel blockage was assessed by subchannel analysis code MATRA-AF and an end plug design to complement inlet blockage of inner channel was estimated by CFD code, CFD-ACE
Annular linear induction pump with an externally supported duct
International Nuclear Information System (INIS)
An annular linear induction pump of increased efficiency is described, capable of being readily disassembled for repair or replacement of parts, and having one pass flow of the liquid metal through the pump. (U.K.)
Predicted congestions never occur. On the gap between transport modeling and human behavior
Directory of Open Access Journals (Sweden)
Harald FREY
2011-01-01
Full Text Available This paper presents an introduction to meso-scale transport modeling and issues of human behaviour in transport systems. Along with other examples of the human ability to learn in transport systems we look at the comparison of real life data and the prediction of modeling tools for the closure of Vienna’s inner ring road during the 2008 European Football Championship (EURO 2008. Some light is shed on the scientific question, whether currently used modeling tools are able to adequately reproduce the real-life behaviour of human beings in the transport system and should be used for transport policy decision making.
Institute of Scientific and Technical Information of China (English)
孙玉昕; 赵旭峰; 吴波
2012-01-01
In the present study, the convective heat transfer characteristic of air gap between rotating inner cylinder and concentric fixed outer cylinder has been simulated using commercial Computation Fluid Dynamic (CFD) software. Distributions of velocity field, temperature field and heat flux have been analyzed at different Taylor number. Comparing with the Nusselt number calculated by empirical formula, the average relative error of the averaged Nusselt number calculated by CFD simulation is at a reasonable scope, which validates the effectiveness of numerical simulation. Results show that, due to the existence of Taylor vortexes, distributions of velocity field, temperature field and heat flux fluctuate periodically along axial direction, and the frequency of the fluctuation correspond with the number of vortexes in the fluid field. Fluctuation of velocity and temperature has same change trend, while the trend of heat flux is opposite. Averaged Nusselt number enlarges with the increase of Taylor number, and the larger Nusselt number is, the better convective heat transfer performance is. Additionally, the convective heat transfer characteristic of air gap with slots has also been simulated, and reasons why Taylor-Couette Flow can enhance heat and mass transfer have been analyzed.%本文利用商用CFD软件对发电机气隙简化模型——同心旋转圆柱体间环形气隙内流体对流换热情况进行数值模拟，得到了不同泰勒数Ta下流场的速度分布、温度分布和热流密度分布。将模拟得出的平均努赛尔数Nu与经验公式的计算值进行了对比，误差在合理的范围之内，证明了数值模拟的有效性。计算结果表明，受流场中泰勒涡的影响，速度、温度、以及热流密度沿轴向的分布呈现周期性波动，波动频率与泰勒涡的数量相同，其中，速度与温度分布波动的变化趋势相同，热流密度波动的变化趋势与前两者相反；泰勒数Ta越大，流
AFSC/RACE/GAP/Laman: Model Results of Aleutian Island POP distributions
National Oceanic and Atmospheric Administration, Department of Commerce — The data supporting the "Model Results of Aleutian Island POP distributions" manuscript are distribution and abundance of Pacific ocean perch from RACEBase,...
Bridging the gap: From computational agent-based models to analytical tractability
Dyson, Louise; Lafuerza, Luis F.; McKane, Alan J.; Edmonds, Bruce
2014-03-01
In order to investigate complex inter-dependent systems such as those found in the biological and social sciences, one is often left trying to examine complicated, descriptive models. To aid in understanding these it would be helpful to develop tools for examining how these relate to simpler models with understandable and analysable mechanisms. We describe a way of analysing the formation of a social network in a complex computational model that represents voting patterns in a population of agents who may live, work and form friendships together. Once the network is formed, we examine the spread of ``intention to vote'' and compare our findings with those found in the descriptive, agent-based model.
The Relationship between Profitability, Innovation and Technology Gap: A Basic Model
Directory of Open Access Journals (Sweden)
Krčál Ondřej
2014-09-01
Full Text Available This paper introduces a model of innovation that explains some of the stylized facts presented in recent empirical literature. In the model, firms choose R&D expenditures that maximize their expected profits under the assumption that R&D expenditures of firms might be constrained by the size of their profits. Optimal decisions of firms generate relationships between profitability and innovation of individual firms that may create the observed patterns at the industry level. In particular, the model is able to explain an inverted-U relationship between profitability and innovation in the industry together with decreasing or flat and concave relationships between profitability and the dispersion of productivity in the industry. Additionally, the paper investigates the parameter space for which the model generates the observed relationships.
Carroll, Kathleen M.; Rounsaville, Bruce J
2003-01-01
Many behavioral and pharmacologic treatments for which there is strong empirical support are rarely used in clinical practice in the treatment of substance dependence. In an effort to facilitate greater emphasis on issues such as utility, practicality, and cost earlier in the evaluation of promising therapies, the authors propose a hybrid model to link efficacy and effectiveness research. A hybrid model may foster broader use of empirically validated treatments in substance abuse treatment pr...
Thomas, R E; Johnson, M F; Frostick, L.E.; Parsons, D. R.; T. J. Bouma; Dijkstra, J.T.; Eiff, O.; Gobert, S.; Henry, P.; Kemp, P; McLelland, S.J.; Moulin, F.Y.; Myrhaug, D.; Neyts, A.; Paul, M
2014-01-01
Physical modelling is a key tool for generating understanding of the complex interactions between aquatic organisms and hydraulics, which is important for management of aquatic environments under environmental change and our ability to exploit ecosystem services. Many aspects of this field remain poorly understood and the use of physical models within eco-hydraulics requires advancement in methodological application and substantive understanding. This paper presents a review of the emergent t...
Sameh Eid; Adam Zalewski; Martin Smieško; Beat Ernst; Angelo Vedani
2013-01-01
In the current era of high-throughput drug discovery and development, molecular modeling has become an indispensable tool for identifying, optimizing and prioritizing small-molecule drug candidates. The required background in computational chemistry and the knowledge of how to handle the complex underlying protocols, however, might keep medicinal chemists from routinely using in silico technologies. Our objective is to encourage those researchers to exploit existing modeling technologies more...
The Relationship between Profitability, Innovation and Technology Gap: A Basic Model
Krčál Ondřej
2014-01-01
This paper introduces a model of innovation that explains some of the stylized facts presented in recent empirical literature. In the model, firms choose R&D expenditures that maximize their expected profits under the assumption that R&D expenditures of firms might be constrained by the size of their profits. Optimal decisions of firms generate relationships between profitability and innovation of individual firms that may create the observed patterns at the industry level. In particular, the...
An analytical model for predicting dryout point in bilaterally heated vertical narrow annuli
International Nuclear Information System (INIS)
Based on the the droplet-diffusion model by Kirillov and Smogalev (1969, 1972), a new analytical model of dryout point prediction in the steam-water flow for bilaterally and uniformly heated narrow annular gap was developed. Comparison of the present model predictions with experimental results indicated that a good agreement in accuracy for the experimental parametric range (pressure from 0.8 to 3.5 MPa, mass flux of 60.39 to 135.6 kg·-2·s-1 and the heat flus of 50 kW·m-2. Prediction of dryout point was experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap heated by AC power supply. (author)
An analytical model for predicting dryout point in bilaterally heated vertical narrow annuli
Institute of Scientific and Technical Information of China (English)
AYE Myint; TIAN Wen-Xi; JIA Dou-Nan; LI Zhi-Hui; LI Hao
2005-01-01
Based on the droplet-diffusion model by Kirillov and Smogalev (1969, 1972), a new analytical model of dryout point prediction in the steam-water flow for bilaterally and uniformly heated narrow annular gap was developed. Comparisons of the present model predictions with experimental results indicated that a good agreement in ac curacy for the experimental parametric range (pressure from 0.8 to 3.5 MPa, mass flux of 60.39 to 135.6 kg·m-2·s-1 and heat flux of 5 to 50 kW·m-2). Prediction of dryout point was experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap heated by AC power supply.
Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis
Rishi Hassan; P Arunprasath; Padmavathy, L.; K Srivenkateswaran
2016-01-01
Annular elastolytic giant cell granuloma (AEGCG) is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the clas...
Annular bright and dark field imaging of soft materials
International Nuclear Information System (INIS)
Here polyethylene, as an example of an important soft material, was studied by STEM annular bright and dark field. The contrast as function of the probe size/shape and the detector collection angle are discussed. The results are compared to conventional bright field transmission electron microscopy, electron energy filtered imaging and energy dispersive spectroscopy mapping. Annular bright and dark field gave a higher contrast than conventional transmission and analytical mapping techniques
Delany, Clare M; Edwards, Ian; Jensen, Gail M; Skinner, Elizabeth
2010-07-01
Physical therapist practice has a distinct focus that is holistic (ie, patient centered) and at the same time connected to a range of other providers within health care systems. Although there is a growing body of literature in physical therapy ethics knowledge, including clinical obligations and underlying philosophical principles, less is known about the unique ethical issues that physical therapists encounter, and how and why they make ethical decisions. As moral agents, physical therapists are required to make autonomous clinical and ethical decisions based on connections and relationships with their patients, other health care team members, and health institutions and policies. This article identifies specific ethical dimensions of physical therapist practice and highlights the development and focus of ethics knowledge in physical therapy over the last several decades. An applied ethics model, called the "active engagement model," is proposed to integrate clinical and ethical dimensions of practice with the theoretical knowledge and literature about ethics. The active engagement model has 3 practical steps: to listen actively, to think reflexively, and to reason critically. The model focuses on the underlying skills, attitudes, and actions that are required to build a sense of moral agency and purpose within physical therapist practice and to decrease gaps between the ethical dimensions of physical therapist practice and physical therapy ethics knowledge and scholarship. A clinical case study is provided to illustrate how the ethics engagement model might be used to analyze and provide insight into the ethical dimensions of physical therapist practice. PMID:20448105
Institute of Scientific and Technical Information of China (English)
Guangjun ZHANG; Shanben CHEN; Lin WU
2005-01-01
As the base of the research work on the weld shape control during pulsed gas tungsten arc welding (GTAW) with wire filler, this paper addressed the modeling of the dynamic welding process. Topside length Lt, maximum width Wt and half-length ratio Rh1 were selected to depict topside weld pool shape, and were measured on-line by vision sensing. A dynamic neural network model was constructed to predict the usually unmeasured backside width and topside height of the weld through topside shape parameters and welding parameters. The inputs of the model were the welding parameters (peak current, pulse duty ratio, welding speed, filler rate), the joint gap, the topside pool shape parameters (Lt, Wt, and Rhl), and their history values at two former pulse, a total of 24 numbers. The validating experiment results proved that the artificial neural network (ANN) model had high precision and could be used in process control. At last, with the developed dynamic model, steady and dynamic behavior was analyzed by simulation experiments, which discovered the variation rules of weld pool shape parameters under different welding parameters, and further knew well the characteristic of the welding process.
Non-Newtonian ﬂuid ﬂow in annular pipes and entropy generation: Temperature-dependent viscosity
Indian Academy of Sciences (India)
M Yürüsoy; B S Yilbaş; M Pakdemirli
2006-12-01
Non-Newtonian ﬂuid ﬂow in annular pipes is considered and the entropy generation due to ﬂuid friction and heat transfer in them is formulated. A third-grade ﬂuid is employed to account for the non-Newtonian effect, while the Reynolds model is accommodated for temperature-dependent viscosity. Closed-form solutions for velocity, temperature, and entropy ﬁelds are presented. It is found that entropy generation number increases with reducing non-Newtonian parameter, while it is the reverse for the viscosity parameter, which is more pronounced in the region close to the annular pipe inner wall.
Ma, Ding; Hassanzadeh, Pedram; Kuang, Zhiming
2016-01-01
A linear response function (LRF) that relates the temporal tendency of zonal mean temperature and zonal wind to their anomalies and external forcing is used to accurately quantify the strength of the eddy-jet feedback associated with the annular mode in an idealized GCM. Following a simple feedback model, the results confirm the presence of a positive eddy-jet feedback in the annular mode dynamics, with a feedback strength of 0.137 day$^{-1}$ in the idealized GCM. Statistical methods proposed...
Sonographic evaluation of digital annular pulley tears
International Nuclear Information System (INIS)
Objective. To evaluate the sonographic (US) appearance of digital annular pulley (DAP) tears in high-level rock climbers. Design and patients. We performed a retrospective analysis of the US examinations of 16 high-level rock climbers with clinical signs of DAP lesions. MRI and surgical evaluation were performed in five and three patients respectively. The normal US and MRI appearances of DAP were evaluated in 40 and three normal fingers respectively. Results. Nine of 16 patients presented a DAP tear. In eight subjects (seven with complete tears involving the fourth finger and one the fifth finger), US diagnosis was based on the indirect sign of volar bowstringing of the flexor tendons. Injured pulleys were not appreciated by US. Tears concerned the A2 and A3 in six patients and the A3 and A4 in two patients. A2 pulley thickening and hypoechogenicity compatible with a partial tear was demonstrated in one patient. MRI and surgical data correlated well with the US findings. Four patients had tenosynovitis of the flexor tendons but no evidence of pulley disruption. US examinations of three patients were normal. In the healthy subjects US demonstrated DAP in 16 of 40 digits. Conclusion. US can diagnose DAP tears and correlates with the MRI and surgical data. Because of its low cost and non-invasiveness we suggest US as the first imaging modality in the evaluation of injuries of the digital pulley. (orig.)
Annular burnout data from rod bundle experiments
International Nuclear Information System (INIS)
Burnout data for annular flow in a rod bundle are presented for both transient and steady-state conditions. Tests were performed at the Oak Ridge National Laboratory in the Thermal Hydraulic Test Facility (THTF), a pressurized-water loop containing an electrically heated 64-rod bundle. The bundle configuration is typical of later generation pressurized-water reactors with 17 x 17 fuel arrays. Both axial and radial power profiles are flat. All experiments were carried out in upflow with subcooled inlet conditions, insuring accurate flow measurement. Conditions within the bundle were typical of those which could be encountered during a nuclear reactor loss-of-coolant accident. Level average fluid conditions within the test section were calculated using steady-state mass and energy conservation considerations for the steady-state tests and a transient, homogeneous, equilibrium computer code for the transient tests. Unlike tube dryout, burnout within a rod bundle does not necessarily occur at one distinct axial level. The location of individual rod dryout was determined by scanning rods axially and locating the position where rod superheat increased from approx. =0 to 30 K or greater. Thermocouple instrumentation within the bundle allows the location of dryout to be determined to within approximately +.5 cm for many of the tests
2D Axisymmetric vs 1D: A PIC/DSMC Model of Breakdown in Triggered Vacuum Spark Gaps
Moore, Stan; Moore, Chris; Boerner, Jeremiah
2015-09-01
Last year at GEC14, we presented results of one-dimensional PIC/DSMC simulations of breakdown in triggered vacuum spark gaps. In this talk, we extend the model to two-dimensional axisymmetric and compare the results to the previous 1D case. Specially, we vary the fraction of the cathode that emits electrons and neutrals (holding the total injection rates over the cathode surface constant) and show the effects of the higher dimensionality on the time to breakdown. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Thomas, R.E.; Johnson, M.F.; Frostick, L.E.; Parsons, D.R.; Bouma, T.J.; Dijkstra, J.T.; Eiff, O.; Gobert, S.; Henry, P.; Kemp, P.; McLelland, S.J.; Moulin, F.Y.; Myrhaug, D.; Neyts, A.; Paul, M.; Penning, W.E.; Puijalon, S.; Rice, S.P.; Stanica, A.; Tagliapietra, D.; Tal, M.; Torum, A.; Vousdoukas, M.I.
2014-01-01
Physical modelling is a key tool for generating understanding of the complex interactions between aquatic organisms and hydraulics, which is important for management of aquatic environments under environmental change and our ability to exploit ecosystem services. Many aspects of this field remain po
On the modeling of narrow gaps using the standard boundary element method
DEFF Research Database (Denmark)
Cutanda Henríquez, Vicente; Juhl, Peter Møller; Jacobsen, Finn
2001-01-01
the literature. A simple integration technique that can extend the range of thicknesses/widths tractable by the otherwise unmodified standard formulation is presented and tested. This technique is valid for both cases. The modeling of acoustic transducers Like sound intensity probes and condenser...
Energy Technology Data Exchange (ETDEWEB)
Tso, C.P.; Mahulikar, S.P. [Nanyang Technological University, Singapore (Singapore). School of Mechanical and Production Engineering
2000-03-01
Surface radiation interchange in an annular enclosure is numerically modeled together with evaporating meniscus-driven convection, for investigating the application of the concept for cooling in microelectronic devices. The geometry is axially discretised into ring elements, where the wall and fluid temperatures within each element are unknowns. The governing algebraic energy equations for convection and surface radiation for each element are formulated for steady-state operating conditions for heat generating cylinders. These equations are then solved simultaneously for all the elements, together with the integral form of the momentum equation, which equates the driving force due to the meniscus curvature to the weight of the coolant and the frictional resistance, and solely dictates the coolant rise length in the microchannel. The results reveal the coupling of fluid flow and heat transfer in the annular microchannel, and the relative importance of radiation. (author)
Stability analysis of a liquid fuel annular combustion chamber. M.S. Thesis
Mcdonald, G. H.
1979-01-01
The problems of combustion instability in an annular combustion chamber are investigated. A modified Galerkin method was used to produce a set of modal amplitude equations from the general nonlinear partial differential acoustic wave equation. From these modal amplitude equations, the two variable perturbation method was used to develop a set of approximate equations of a given order of magnitude. These equations were modeled to show the effects of velocity sensitive combustion instabilities by evaluating the effects of certain parameters in the given set of equations. By evaluating these effects, parameters which cause instabilities to occur in the combustion chamber can be ascertained. It is assumed that in the annular combustion chamber, the liquid propellants are injected uniformly across the injector face, the combustion processes are distributed throughout the combustion chamber, and that no time delay occurs in the combustion processes.
Charged annular disks and Reissner-Nordstroem type black holes from extremal dust
International Nuclear Information System (INIS)
We present the first analytical superposition of a charged black hole with an annular disk of extremal dust. In order to obtain the solutions, we first solve the Einstein-Maxwell field equations for sources that represent disklike configurations of matter in confomastatic spacetimes by assuming a functional dependence among the metric function, the electric potential, and an auxiliary function, which is taken as a solution of the Laplace equation. We then employ the Lord Kelvin inversion method applied to models of finite extension in order to obtain annular disks. The structures obtained extend to infinity, but their total masses are finite and all the energy conditions are satisfied. Finally, we observe that the extremal Reissner-Nordstroem black hole can be embedded into the center of the disks by adding a boundary term in the inversion.
Charged Annular Disks and Reissner-Nordstro ?m Type Black Holes from Extremal Dust
Lora-Clavijo, F D; Pedraza, J F
2010-01-01
We present the first analytical superposition of a charged black hole with an annular disk of extremal dust. In order to obtain the solutions, we first solve the Einstein-Maxwell field equations for sources that represent disk-like configurations of matter in confomastatic spacetimes by assuming a functional dependence between the metric function, the electric potential and an auxiliary function, which is taken as a solution of the Laplace equation. We then employ the Lord Kelvin Inversion Method applied to models of finite extension in order to obtain annular disks. The structures obtained extend to infinity, but their total masses are finite and all the energy conditions are satisfied. Finally, we observe that the extremal Reissner-Nordstr\\"om black hole can be embedded into the center of the disks by adding a boundary term in the inversion.
Annular Seals of High Energy Centrifugal Pumps: Presentation of Full Scale Measurement
Florjancic, S.; Stuerchler, R.; Mccloskey, T.
1991-01-01
Prediction of rotordynamic behavior for high energy concentration centrifugal pumps is a challenging task which still imposes considerable difficulties. While the mechanical modeling of the rotor is solved most satisfactorily by finite element techniques, accurate boundary conditions for arbitrary operating conditions are known for journal bearings only. Little information is available on the reactive forces of annular seals, such as neck ring and interstage seals and balance pistons, and on the impeller interaction forces. The present focus is to establish reliable boundary conditions at annular seals. For this purpose, a full scale test machine was set up and smooth and serrated seal configurations measured. Dimensionless coefficients are presented and compared with a state of the art theory.
Entrainment rate of droplets in the ripple-annular regime for small vertical tubes
International Nuclear Information System (INIS)
Two-fluid model predictions of film dryout in annular flow are limited by the uncertainties in the constitutive relations for the entrainment rate of droplets from the liquid film. The main cause of these uncertainties is the lack of separate effects experimental data in the range of the operating conditions in nuclear power reactors. Air/water and Freon-113 entrainment rate data have been obtained in 10 mm tubes using the film extraction technique. These experiments have been scaled to approach high pressure steam-water flow conditions. The effects of surface tension and density ratio, missing from most previous data sets, have been systematically tested. The entrainment rate mechanism is assumed to be a Kelvin-Helmholtz instability. Based on this analysis and two previous correlations, a new correlation is proposed that is valid for low viscosity fluids in small ducts in the ripple annular regime
Harper, E. B.; Stella, J. C.; Fremier, A. K.
2009-12-01
Fremont cottonwood (Populus fremontii) is an important component of semi-arid riparian ecosystems throughout western North America, but its populations are in decline due to flow regulation. Achieving a balance between human resource needs and riparian ecosystem function requires a mechanistic understanding of the multiple geomorphic and biological factors affecting tree recruitment and survival, including the timing and magnitude of river flows, and the concomitant influence on suitable habitat creation and mortality from scour and sedimentation burial. Despite a great deal of empirical research on some components of the system, such as factors affecting cottonwood recruitment, other key components are less studied. Yet understanding the relative influence of the full suite of physical and life-history drivers is critical to modeling whole-population dynamics under changing environmental conditions. We addressed these issues for the Fremont cottonwood population along the Sacramento River, CA using a sensitivity analysis approach to quantify uncertainty in parameters on the outcomes of a patch-based, dynamic population model. Using a broad range of plausible values for 15 model parameters that represent key physical, biological and climatic components of the ecosystem, we ran 1,000 population simulations that consisted of a subset of 14.3 million possible combinations of parameter estimates to predict the frequency of patch colonization and total forest habitat predicted to occur under current hydrologic conditions after 175 years. Results indicate that Fremont cottonwood populations are highly sensitive to the interactions among flow regime, sedimentation rate and the depth of the capillary fringe (Fig. 1). Estimates of long-term floodplain sedimentation rate would substantially improve model accuracy. Spatial variation in sediment texture was also important to the extent that it determines the depth of the capillary fringe, which regulates the availability of
Directory of Open Access Journals (Sweden)
M. Scherstjanoi
2014-02-01
Full Text Available To be able to simulate climate change effects on forest dynamics over the whole of Switzerland, we adapted the second generation DGVM LPJ-GUESS to the Alpine environment. We modified model functions, tuned model parameters, and implemented new tree species to represent the potential natural vegetation of Alpine landscapes. Furthermore, we increased the computational efficiency of the model to enable area-covering simulations in a fine resolution (1 km sufficient for the complex topography of the Alps, which resulted in more than 32 000 simulation grid cells. To this aim, we applied the recently developed method GAPPARD (Scherstjanoi et al., 2013 to LPJ-GUESS. GAPPARD derives mean output values from a combination of simulation runs without disturbances and a patch age distribution defined by the disturbance frequency. With this computationally efficient method, that increased the model's speed by approximately the factor 8, we were able to faster detect shortcomings of LPJ-GUESS functions and parameters. We used the adapted LPJ-GUESS together with GAPPARD to assess the influence of one climate change scenario on dynamics of tree species composition and biomass throughout the 21st century in Switzerland. To allow for comparison with the original model, we additionally simulated forest dynamics along a north-south-transect through Switzerland. The results from this transect confirmed the high value of the GAPPARD method despite some limitations towards extreme climatic events. It allowed for the first time to obtain area-wide, detailed high resolution LPJ-GUESS simulation results for a large part of the Alpine region.
Quantitative Modeling of Acid Wormholing in Carbonates- What Are the Gaps to Bridge
Qiu, Xiangdong
2013-01-01
Carbonate matrix acidization extends a well\\'s effective drainage radius by dissolving rock and forming conductive channels (wormholes) from the wellbore. Wormholing is a dynamic process that involves balance between the acid injection rate and reaction rate. Generally, injection rate is well defined where injection profiles can be controlled, whereas the reaction rate can be difficult to obtain due to its complex dependency on interstitial velocity, fluid composition, rock surface properties etc. Conventional wormhole propagation models largely ignore the impact of reaction products. When implemented in a job design, the significant errors can result in treatment fluid schedule, rate, and volume. A more accurate method to simulate carbonate matrix acid treatments would accomodate the effect of reaction products on reaction kinetics. It is the purpose of this work to properly account for these effects. This is an important step in achieving quantitative predictability of wormhole penetration during an acidzing treatment. This paper describes the laboratory procedures taken to obtain the reaction-product impacted kinetics at downhole conditions using a rotating disk apparatus, and how this new set of kinetics data was implemented in a 3D wormholing model to predict wormhole morphology and penetration velocity. The model explains some of the differences in wormhole morphology observed in limestone core flow experiments where injection pressure impacts the mass transfer of hydrogen ions to the rock surface. The model uses a CT scan rendered porosity field to capture the finer details of the rock fabric and then simulates the fluid flow through the rock coupled with reactions. Such a validated model can serve as a base to scale up to near wellbore reservoir and 3D radial flow geometry allowing a more quantitative acid treatment design.
A Coupled Multiphase Fluid Flow And Heat And Vapor Transport Model For Air-Gap Membrane Distillation
Mukhopadhyay, Sumit
2010-05-01
Membrane distillation (MD) is emerging as a viable desalination technology because of its low energy requirements that can be provided from low-grade, waste heat and because it causes less fouling. In MD, desalination is accomplished by transporting water vapour through a porous hydrophobic membrane. The vapour transport process is governed by the vapour pressure difference between the two sides of a membrane. A variety of configurations have been tested to impose this vapour pressure gradient, however, the air-gap membrane distillation (AGMD) has been found to be the most efficient. The separation mechanism of AGMD and its overall efficiency is based on vapour-liquid equilibrium (VLE). At present, little knowledge is available about the optimal design of such a transmembrane VLE-based evaporation, and subsequent condensation processes. While design parameters for MD have evolved mostly through experimentations, a comprehensive mathematical model is yet to be developed. This is primarily because the coupling and non-linearity of the equations, the interactions between the flow, heat and mass transport regimes, and the complex geometries involved pose a challenging modelling and simulation problem. Yet a comprehensive mathematical model is needed for systematic evaluation of the processes, design parameterization, and performance prediction. This paper thus presents a coupled fluid flow, heat and mass transfer model to investigate the main processes and parameters affecting the performance of an AGMD.
Directory of Open Access Journals (Sweden)
Tao Yuan
2013-02-01
Full Text Available The partial discharge (PD process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk of the liquid. In this paper, a microscopic model describing the dynamics of the charge carriers is implemented. The model consists of drift-diffusion equations of electrons, positive and negative ions coupled with Poisson’s equation. The stochastic feature of PD events is included in the equation. First the model is validated through comparison between the calculated PD current and experimental data. Then experiments are conducted to study the effects of the amplitude of the applied voltage, gap distance and electrode type on the PD process. The PD currents under each condition are recorded. Simulations based on the model have been conducted to analyze the dynamics of the PD events under each condition, and thus explain the mechanism of how these factors influence the PD events. The space charge generated in the PD process is revealed as the main reason affecting the microscopic process of the PD events.
Alzheimer’s disease biomarkers in animal models: closing the translational gap
Sabbagh, Jonathan J.; Kinney, Jefferson W.; Cummings, Jeffrey L.
2013-01-01
The rising prevalence of Alzheimer’s disease (AD) is rapidly becoming one of the largest health and economic challenges in the world. There is a growing need for the development and implementation of reliable biomarkers for AD that can be used to assist in diagnosis, inform disease progression, and monitor therapeutic efficacy. Preclinical models permit the evaluation of candidate biomarkers and assessment of pipeline agents before clinical trials are initiated and provide a translational opp...
Bridging The Gap For Destination Extreme Sports - A Model of Sports Tourism Customer Experience
Klaus, Philipp "Phil"; Maklan, Stan
2011-01-01
This longitudinal study proposes a conceptual model of sports tourism customer experience in the context of a mountain-biking extreme sport camp. Customer experience is conceptualised as a three-dimensional framework consisting of five dimensions: hedonic pleasure, personal progression, social interaction, efficiency and surreal feeling. Using the means-end approach in 89 semi-structured interviews with clients of a mountain-biking camp, conducted over three years, the authors identified hedo...
VandeVord, Pamela J; Leonardi, Alessandra Dal Cengio; Ritzel, David
2016-01-01
Recent military combat has heightened awareness to the complexity of blast-related traumatic brain injuries (bTBI). Experiments using animal, cadaver, or biofidelic physical models remain the primary measures to investigate injury biomechanics as well as validate computational simulations, medical diagnostics and therapies, or protection technologies. However, blast injury research has seen a range of irregular and inconsistent experimental methods for simulating blast insults generating results which may be misleading, cannot be cross-correlated between laboratories, or referenced to any standard for exposure. Both the US Army Medical Research and Materiel Command and the National Institutes of Health have noted that there is a lack of standardized preclinical models of TBI. It is recommended that the blast injury research community converge on a consistent set of experimental procedures and reporting of blast test conditions. This chapter describes the blast conditions which can be recreated within a laboratory setting and methodology for testing in vivo models within the appropriate environment. PMID:27604715
Measurement of large aspheric surfaces by annular subaperture stitching interferometry
Institute of Scientific and Technical Information of China (English)
Xiaokun Wang; Lihui Wang; Longhai Yin; Binzhi Zhang; Di Fan; Xuejun Zhang
2007-01-01
A new method for testing aspheric surfaces by annular subaperture stitching interferometry is introduced.It can test large-aperture and large-relative-aperture aspheric surfaces at high resolution, low cost, and high efficiency without auxiliary null optics. The basic principle of the method is described, the synthetical optimization stitching model and effective algorithm are established based on simultaneous least-square fitting. A hyperboloid with an aperture of 350 mm is tested by this method. The obtained peak-to-valley (PV) and root-mean-square (RMS) values of the surface error after stitching are 0.433λ and 0.052λ (λis 632.8 nm), respectively. The reconstructed surface map is coincide with the entire surface map from null test, and the difference of PV and RMS errors between them are 0.031λ and 0.005λ, respectively.This stitching model provides another quantitive method for testing large aspheric surfaces besides null compensation.
DEFF Research Database (Denmark)
Kaplan, Sigal; Prato, Carlo Giacomo
2012-01-01
not account for individual-related spatiotemporal constraints. This paper reduces the gap by proposing a route choice model incorporating spatiotemporal constraints and latent traits. The proposed approach combines stochastic route generation with a latent variable semi-compensatory model representing...
Self-organized Hydrodynamics in an Annular Domain: Modal Analysis and Nonlinear Effects
Degond, Pierre; Yu, Hui
2014-01-01
The Self-Organized Hydrodynamics model of collective behavior is studied on an annular domain. A modal analysis of the linearized model around a perfectly polarized steady-state is conducted. It shows that the model has only pure imaginary modes in countable number and is hence stable. Numerical computations of the low-order modes are provided. The fully non-linear model is numerically solved and nonlinear mode-coupling is then analyzed. Finally, the efficiency of the modal decomposition to a...
Directory of Open Access Journals (Sweden)
Sameh Eid
2013-01-01
Full Text Available In the current era of high-throughput drug discovery and development, molecular modeling has become an indispensable tool for identifying, optimizing and prioritizing small-molecule drug candidates. The required background in computational chemistry and the knowledge of how to handle the complex underlying protocols, however, might keep medicinal chemists from routinely using in silico technologies. Our objective is to encourage those researchers to exploit existing modeling technologies more frequently through easy-to-use graphical user interfaces. In this account, we present two innovative tools (which we are prepared to share with academic institutions facilitating computational tasks commonly utilized in drug discovery and development: (1 the VirtualDesignLab estimates the binding affinity of small molecules by simulating and quantifying their binding to the three-dimensional structure of a target protein; and (2 the MD Client launches molecular dynamics simulations aimed at exploring the time-dependent stability of ligand–protein complexes and provides residue-based interaction energies. This allows medicinal chemists to identify sites of potential improvement in their candidate molecule. As a case study, we present the application of our tools towards the design of novel antagonists for the FimH adhesin.
Sea Carousel—A benthic, annular flume
Amos, Carl L.; Grant, J.; Daborn, G. R.; Black, K.
1992-06-01
A benthic annular flume (Sea Carousel) has been developed and tested to measure in situ the erodibility of cohesive sediments. The flume is equipped with three optical backscatter sensors, a lid rotation switch, and an electromagnetic (EM) flow meter capable of detecting azimuthal and vertical components of flow. Data are logged at rates up to 10·66 Hz. Erodibility is inferred from the rate of change in suspended sediment concentration detected in the annulus. The energy-density/wave number spectrum of azimuthal flow showed peaks in the energy spectrum at paddle rotation wave numbers (k) of 14 and 7 m -1 (macroturbulent time scales) but were not significant. Friction velocity ( U*), measured (1) at 1 Hz using a flush-mounted hot-film sensor, and (2) derived from measured velocity profiles in the inner part of the logarithmic layer gave comparable results for Ū* 0·32 m s -1. Radial velocity gradients were proportional to ( Ū y - 0·32 m s -1). Maximum radial differences in U* were 10% for Ū y = 0·5 ms -1. Suspended sediment mass concentration ( S) in the annulus resulted in a significant decrease (10·5%) in Ū* derived by method (1) over the range 0calibration with changes in S. Subaerial deployments of Sea Carousel caused severe substrate disturbance, water losses, and aeration of the annulus. Submarine deployments produced stable results, though dispersion of turbid flume water took place. Results clearly demonstrated the existence of 'Type I' and 'Type II' erosion documented from laboratory studies.
Darden, C.; Carroll, B.; Lapenta, W.; Jedlovec, G.; Goodman, S.; Bradshaw, T.; Gordon, J.; Arnold, James E. (Technical Monitor)
2002-01-01
The National Weather Service Office (WFO) in Huntsville, Alabama (HUN) is slated to begin full-time operations in early 2003. With the opening of the Huntsville WFO, a unique opportunity has arisen for close and productive collaboration with scientists at NASA Marshall Space Flight Center (MSFC) and the University of Alabama Huntsville (UAH). As a part of the collaboration effort, NASA has developed the Short-term Prediction Research and Transition (SPoRT) Center. The mission of the SPoRT center is to incorporate NASA earth science technology and research into the NWS operational environment. Emphasis will be on improving mesoscale and short-term forecasting in the first 24 hours of the forecast period. As part of the collaboration effort, the NWS and NASA will develop an implementation and evaluation plan to streamline the integration of the latest technologies and techniques into the operational forecasting environment. The desire of WFO HUN, NASA, and UAH is to provide a model for future collaborative activities between research and operational communities across the country.
DEFF Research Database (Denmark)
Lehmann, Richard J.; Hermansen, John Erik; Fritz, Melanie;
2011-01-01
Several global developments such as diminishing production resources, limits in the availability of water and the growing demand for bio-energy as well as sector-wide crises (e.g. BSE, swine fever, dioxin) have led to a changing attitude of society towards the conse-quences of the food system‘s a....... The models support different parties involved in pork production, such as enterprises, system developers and consultants, in developing enterprise or network specific solutions.......Several global developments such as diminishing production resources, limits in the availability of water and the growing demand for bio-energy as well as sector-wide crises (e.g. BSE, swine fever, dioxin) have led to a changing attitude of society towards the conse-quences of the food system......‘s activities for social, economic and environmental issues, cap-tured in the term of sustainability. As a consequence, consumers show increasing interest in the characteristics of food, and in turn, on the availability of related information and guaran-tees. The paper introduces different information reference...
Yuan, Jinxian; Huang, Hao; Zhou, Xin; Liu, Xi; Ou, Shu; Xu, Tao; Li, Ruohan; Ma, Limin; Chen, Yangmei
2016-01-01
Increasing evidence suggests that epilepsy is the result of synaptic reorganization and pathological excitatory loop formation in the central nervous system; however, the mechanisms that regulate this process are not well understood. We proposed that microRNA-132 (miR-132) and p250GAP might play important roles in this process by activating the downstream Rho GTPase family. We tested this hypothesis using a magnesium-free medium-induced epileptic model of cultured hippocampal neurons. We investigated whether miR-132 regulates GTPase activity through p250GAP and found that Cdc42 was significantly activated in our experimental model. Silencing miR-132 inhibited the electrical excitability level of cultured epileptic neurons, whereas silencing p250GAP had an opposite effect. In addition, we verified the effect of miR-132 in vivo and found that silencing miR-132 inhibited the aberrant formation of dendritic spines and chronic spontaneous seizure in a lithium-pilocarpine-induced epileptic mouse model. Finally, we confirmed that silencing miR-132 has a neuroprotective effect on cultured epileptic neurons; however, this effect did not occur through the p250GAP pathway. Generally, silencing miR-132 may suppress spontaneous seizure activity through the miR-132/p250GAP/Cdc42 pathway by regulating the morphology and electrophysiology of dendritic spines; therefore, miR-132 may serve as a potential target for the development of antiepileptic drugs. PMID:27579184
Huang, Hao; Zhou, Xin; Liu, Xi; Xu, Tao; Ma, Limin
2016-01-01
Increasing evidence suggests that epilepsy is the result of synaptic reorganization and pathological excitatory loop formation in the central nervous system; however, the mechanisms that regulate this process are not well understood. We proposed that microRNA-132 (miR-132) and p250GAP might play important roles in this process by activating the downstream Rho GTPase family. We tested this hypothesis using a magnesium-free medium-induced epileptic model of cultured hippocampal neurons. We investigated whether miR-132 regulates GTPase activity through p250GAP and found that Cdc42 was significantly activated in our experimental model. Silencing miR-132 inhibited the electrical excitability level of cultured epileptic neurons, whereas silencing p250GAP had an opposite effect. In addition, we verified the effect of miR-132 in vivo and found that silencing miR-132 inhibited the aberrant formation of dendritic spines and chronic spontaneous seizure in a lithium-pilocarpine-induced epileptic mouse model. Finally, we confirmed that silencing miR-132 has a neuroprotective effect on cultured epileptic neurons; however, this effect did not occur through the p250GAP pathway. Generally, silencing miR-132 may suppress spontaneous seizure activity through the miR-132/p250GAP/Cdc42 pathway by regulating the morphology and electrophysiology of dendritic spines; therefore, miR-132 may serve as a potential target for the development of antiepileptic drugs.
International Nuclear Information System (INIS)
Ultrasonic guided waves are fast emerging as a reliable tool for continuous structural health monitoring. Their multi-modal nature along with their long range propagation characteristics offer several possibilities for interrogating structures. Transducers commonly used to generate guided waves in structures excite multiple modes at any frequency; their complex scattering and reflection from defects and boundaries often complicates the extraction of useful information. Often it is desirable to control the guided wave modes propagating in a structure to take advantage of their unique properties for different applications. Earlier attempts at guided wave mode control involved developing fixed wavelength linear and annular array transducers. Their only disadvantage is that the transducer is limited to a particular wavelength and a change in wavelength necessitates a change in the transducer. In this paper, we propose the development of an annular array transducer that can generate mode controlled omnidirectional guided waves by independently controlling the amplitude and phase of the array elements. A simplified actuator model that approximates the transducer loading on the structure to a constant pressure load under the array elements is assumed and an optimization problem is set up to compute the excitation voltage and phase of the elements. A five element annular array transducer is designed utilizing 1–3 type piezocomposite materials. The theoretical computations are experimentally verified on an aluminum plate like structure by exciting A0 and S0 guided wave modes. (paper)
Effects study on the thermal stresses in a LEU metal foil annular target
International Nuclear Information System (INIS)
The effects of fission gas pressure, uranium swelling and thermal contact conductance on the thermal–mechanical behavior of an annular target containing a low-enriched uranium foil (LEU) encapsulated in a nickel foil have been presented in this paper. The draw-plug assembly method is simulated to obtain the residual stresses, which are applied to the irradiation model as initial inputs, and the integrated assembly-irradiation process is simulated as an axisymmetric problem using the commercial finite element code Abaqus FEA. Parametric studies were performed on the LEU heat generation rate and the results indicate satisfactory irradiation performance of the annular target. The temperature and stress margins have been provided along with a discussion of the results. - Highlights: • Analyzed the thermal stresses in a low-enriched uranium foil based annular target. • Included fission gas, uranium swelling, and thermal contact conductance effects. • Worst case scenarios for temperature and stresses were found to be different. • Sensitivity studies on the foil heat generation rates were performed. • Temperature and stress were found to be within acceptable limits
Institute of Scientific and Technical Information of China (English)
Wang Zhiyuan; Sun Baojiang
2009-01-01
It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.
Bauerheim, M.; Nicoud, F.; Poinsot, T.
2016-02-01
Longitudinal low-frequency thermoacoustic unstable modes in combustion chambers have been intensively studied experimentally, numerically, and theoretically, leading to significant progress in both understanding and controlling these acoustic modes. However, modern annular gas turbines may also exhibit azimuthal modes, which are much less studied and feature specific mode structures and dynamic behaviors, leading to more complex situations. Moreover, dealing with 10-20 burners mounted in the same chamber limits the use of high fidelity simulations or annular experiments to investigate these modes because of their complexity and costs. Consequently, for such circumferential acoustic modes, theoretical tools have been developed to uncover underlying phenomena controlling their stability, nature, and dynamics. This review presents recent progress in this field. First, Galerkin and network models are described with their pros and cons in both the temporal and frequency framework. Then, key features of such acoustic modes are unveiled, focusing on their specificities such as symmetry breaking, non-linear modal coupling, forcing by turbulence. Finally, recent works on uncertainty quantifications, guided by theoretical studies and applied to annular combustors, are presented. The objective is to provide a global view of theoretical research on azimuthal modes to highlight their complexities and potential.
Energy Technology Data Exchange (ETDEWEB)
Li, H.; Huang, P; Zhang, D; Sun, Y; Chen, H; Zhang, J; Huang, P; Kong, X; Lee-Huang, S
2010-01-01
We report here the high-resolution atomic structures of GAP31 crystallized in the presence of HIV-LTR DNA oligonucleotides systematically designed to examine the adenosine glycosidase activity of this anti-HIV and anti-tumor plant protein. Structural analysis and molecular modeling lead to several novel findings. First, adenine is bound at the active site in the crystal structures of GAP31 to HIV-LTR duplex DNA with 5' overhanging adenosine ends, such as the 3'-processed HIV-LTR DNA but not to DNA duplex with blunt ends. Second, the active site pocket of GAP31 is ideally suited to accommodate the 5' overhanging adenosine of the 3'-processed HIV-LTR DNA and the active site residues are positioned to perform the adenosine glycosidase activity. Third, GAP31 also removes the 5'-end adenine from single-stranded HIV-LTR DNA oligonucleotide as well as any exposed adenosine, including that of single nucleotide dAMP but not from AMP. Fourth, GAP31 does not de-purinate guanosine from di-nucleotide GT. These results suggest that GAP31 has DNA adenosine glycosidase activity against accessible adenosine. This activity is distinct from the generally known RNA N-glycosidase activity toward the 28S rRNA. It may be an alternative function that contributes to the antiviral and anti-tumor activities of GAP31. These results provide molecular insights consistent with the anti-HIV mechanisms of GAP31 in its inhibition on the integration of viral DNA into the host genome by HIV-integrase as well as irreversible topological relaxation of the supercoiled viral DNA.
Energy Technology Data Exchange (ETDEWEB)
Li, Hui-Guang [Department of Biochemistry, New York University School of Medicine, New York, NY 10016 (United States); Huang, Philip L. [American Biosciences, Boston, MA 02114 (United States); Zhang, Dawei; Sun, Yongtao [Department of Biochemistry, New York University School of Medicine, New York, NY 10016 (United States); Chen, Hao-Chia [Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892 (United States); Zhang, John [Department of Chemistry, New York University, New York, NY 10003 (United States); Huang, Paul L. [Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02114 (United States); Kong, Xiang-Peng, E-mail: xiangpeng.kong@med.nyu.edu [Department of Biochemistry, New York University School of Medicine, New York, NY 10016 (United States); Lee-Huang, Sylvia, E-mail: sylvia.lee-huang@med.nyu.edu [Department of Biochemistry, New York University School of Medicine, New York, NY 10016 (United States)
2010-01-01
We report here the high-resolution atomic structures of GAP31 crystallized in the presence of HIV-LTR DNA oligonucleotides systematically designed to examine the adenosine glycosidase activity of this anti-HIV and anti-tumor plant protein. Structural analysis and molecular modeling lead to several novel findings. First, adenine is bound at the active site in the crystal structures of GAP31 to HIV-LTR duplex DNA with 5' overhanging adenosine ends, such as the 3'-processed HIV-LTR DNA but not to DNA duplex with blunt ends. Second, the active site pocket of GAP31 is ideally suited to accommodate the 5' overhanging adenosine of the 3'-processed HIV-LTR DNA and the active site residues are positioned to perform the adenosine glycosidase activity. Third, GAP31 also removes the 5'-end adenine from single-stranded HIV-LTR DNA oligonucleotide as well as any exposed adenosine, including that of single nucleotide dAMP but not from AMP. Fourth, GAP31 does not de-purinate guanosine from di-nucleotide GT. These results suggest that GAP31 has DNA adenosine glycosidase activity against accessible adenosine. This activity is distinct from the generally known RNA N-glycosidase activity toward the 28S rRNA. It may be an alternative function that contributes to the antiviral and anti-tumor activities of GAP31. These results provide molecular insights consistent with the anti-HIV mechanisms of GAP31 in its inhibition on the integration of viral DNA into the host genome by HIV-integrase as well as irreversible topological relaxation of the supercoiled viral DNA.
International Nuclear Information System (INIS)
We report here the high-resolution atomic structures of GAP31 crystallized in the presence of HIV-LTR DNA oligonucleotides systematically designed to examine the adenosine glycosidase activity of this anti-HIV and anti-tumor plant protein. Structural analysis and molecular modeling lead to several novel findings. First, adenine is bound at the active site in the crystal structures of GAP31 to HIV-LTR duplex DNA with 5' overhanging adenosine ends, such as the 3'-processed HIV-LTR DNA but not to DNA duplex with blunt ends. Second, the active site pocket of GAP31 is ideally suited to accommodate the 5' overhanging adenosine of the 3'-processed HIV-LTR DNA and the active site residues are positioned to perform the adenosine glycosidase activity. Third, GAP31 also removes the 5'-end adenine from single-stranded HIV-LTR DNA oligonucleotide as well as any exposed adenosine, including that of single nucleotide dAMP but not from AMP. Fourth, GAP31 does not de-purinate guanosine from di-nucleotide GT. These results suggest that GAP31 has DNA adenosine glycosidase activity against accessible adenosine. This activity is distinct from the generally known RNA N-glycosidase activity toward the 28S rRNA. It may be an alternative function that contributes to the antiviral and anti-tumor activities of GAP31. These results provide molecular insights consistent with the anti-HIV mechanisms of GAP31 in its inhibition on the integration of viral DNA into the host genome by HIV-integrase as well as irreversible topological relaxation of the supercoiled viral DNA.
Characterization of Novel Calorimeters in the Annular Core Research Reactor *
Directory of Open Access Journals (Sweden)
Hehr Brian D.
2016-01-01
Full Text Available A series of pulsed irradiation experiments have been performed in the central cavity of Sandia National Laboratories' Annular Core Research Reactor (ACRR to characterize the responses of a set of elemental calorimeter materials including Si, Zr, Sn, Ta, W, and Bi. Of particular interest was the perturbing effect of the calorimeter itself on the ambient radiation field – a potential concern in dosimetry applications. By placing the calorimeter package into a neutron-thermalizing lead/polyethylene (LP bucket and irradiating both with and without a cadmium wrapper, it was demonstrated that prompt capture gammas generated inside the calorimeters can be a significant contributor to the measured dose in the active disc region. An MCNP model of the experimental setup was shown to replicate measured dose responses to within 10%. The internal (n,γ contribution was found to constitute as much as 50% of the response inside the LP bucket and up to 20% inside the nominal (unmodified cavity environment, with Ta and W exhibiting the largest enhancement due to their sizable (n,γ cross sections. Capture reactions in non-disc components of the calorimeter were estimated to be responsible for up to a few percent of the measured response.
Characterization of Novel Calorimeters in the Annular Core Research Reactor
Hehr, Brian D.; Parma, Edward J.; Peters, Curtis D.; Naranjo, Gerald E.; Luker, S. Michael
2016-02-01
A series of pulsed irradiation experiments have been performed in the central cavity of Sandia National Laboratories' Annular Core Research Reactor (ACRR) to characterize the responses of a set of elemental calorimeter materials including Si, Zr, Sn, Ta, W, and Bi. Of particular interest was the perturbing effect of the calorimeter itself on the ambient radiation field - a potential concern in dosimetry applications. By placing the calorimeter package into a neutron-thermalizing lead/polyethylene (LP) bucket and irradiating both with and without a cadmium wrapper, it was demonstrated that prompt capture gammas generated inside the calorimeters can be a significant contributor to the measured dose in the active disc region. An MCNP model of the experimental setup was shown to replicate measured dose responses to within 10%. The internal (n,γ) contribution was found to constitute as much as 50% of the response inside the LP bucket and up to 20% inside the nominal (unmodified) cavity environment, with Ta and W exhibiting the largest enhancement due to their sizable (n,γ) cross sections. Capture reactions in non-disc components of the calorimeter were estimated to be responsible for up to a few percent of the measured response. This work was supported by the United States Department of Energy under Contract DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.
Criticality Benchmark Analysis of the HTTR Annular Startup Core Configurations
Energy Technology Data Exchange (ETDEWEB)
John D. Bess
2009-11-01
One of the high priority benchmarking activities for corroborating the Next Generation Nuclear Plant (NGNP) Project and Very High Temperature Reactor (VHTR) Program is evaluation of Japan's existing High Temperature Engineering Test Reactor (HTTR). The HTTR is a 30 MWt engineering test reactor utilizing graphite moderation, helium coolant, and prismatic TRISO fuel. A large amount of critical reactor physics data is available for validation efforts of High Temperature Gas-cooled Reactors (HTGRs). Previous international reactor physics benchmarking activities provided a collation of mixed results that inaccurately predicted actual experimental performance.1 Reevaluations were performed by the Japanese to reduce the discrepancy between actual and computationally-determined critical configurations.2-3 Current efforts at the Idaho National Laboratory (INL) involve development of reactor physics benchmark models in conjunction with the International Reactor Physics Experiment Evaluation Project (IRPhEP) for use with verification and validation methods in the VHTR Program. Annular cores demonstrate inherent safety characteristics that are of interest in developing future HTGRs.
Criticality Benchmark Analysis of the HTTR Annular Startup Core Configurations
International Nuclear Information System (INIS)
One of the high priority benchmarking activities for corroborating the Next Generation Nuclear Plant (NGNP) Project and Very High Temperature Reactor (VHTR) Program is evaluation of Japan's existing High Temperature Engineering Test Reactor (HTTR). The HTTR is a 30 MWt engineering test reactor utilizing graphite moderation, helium coolant, and prismatic TRISO fuel. A large amount of critical reactor physics data is available for validation efforts of High Temperature Gas-cooled Reactors (HTGRs). Previous international reactor physics benchmarking activities provided a collation of mixed results that inaccurately predicted actual experimental performance.1 Reevaluations were performed by the Japanese to reduce the discrepancy between actual and computationally-determined critical configurations.2-3 Current efforts at the Idaho National Laboratory (INL) involve development of reactor physics benchmark models in conjunction with the International Reactor Physics Experiment Evaluation Project (IRPhEP) for use with verification and validation methods in the VHTR Program. Annular cores demonstrate inherent safety characteristics that are of interest in developing future HTGRs.
Seyedhosseini, Seyed Mohammad; Makui, Ahmad; Shahanaghi, Kamran; Torkestani, Sara Sadat
2016-05-01
Determining the best location to be profitable for the facility's lifetime is the important decision of public and private firms, so this is why discussion about dynamic location problems (DLPs) is a critical significance. This paper presented a comprehensive review from 1968 up to most recent on published researches about DLPs and classified them into two parts. First, mathematical models developed based on different characteristics: type of parameters (deterministic, probabilistic or stochastic), number and type of objective function, numbers of commodity and modes, relocation time, number of relocation and relocating facilities, time horizon, budget and capacity constraints and their applicability. In second part, It have been also presented solution algorithms, main specification, applications and some real-world case studies of DLPs. At the ends, we concluded that in the current literature of DLPs, distribution systems and production-distribution systems with simple assumption of the tackle to the complexity of these models studied more than any other fields, as well as the concept of variety of services (hierarchical network), reliability, sustainability, relief management, waiting time for services (queuing theory) and risk of facility disruption need for further investigation. All of the available categories based on different criteria, solution methods and applicability of them, gaps and analysis which have been done in this paper suggest the ways for future research.
Dhar-Chowdhury, Parnali; Haque, C Emdad; Driedger, S Michelle
2016-05-01
Worldwide, more than 50 million cases of dengue fever are reported every year in at least 124 countries, and it is estimated that approximately 2.5 billion people are at risk for dengue infection. In Bangladesh, the recurrence of dengue has become a growing public health threat. Notably, knowledge and perceptions of dengue disease risk, particularly among the public, are not well understood. Recognizing the importance of assessing risk perception, we adopted a comparative approach to examine a generic methodology to assess diverse sets of beliefs related to dengue disease risk. Our study mapped existing knowledge structures regarding the risk associated with dengue virus, its vector (Aedes mosquitoes), water container use, and human activities in the city of Dhaka, Bangladesh. "Public mental models" were developed from interviews and focus group discussions with diverse community groups; "expert mental models" were formulated based on open-ended discussions with experts in the pertinent fields. A comparative assessment of the public's and experts' knowledge and perception of dengue disease risk has revealed significant gaps in the perception of: (a) disease risk indicators and measurements; (b) disease severity; (c) control of disease spread; and (d) the institutions responsible for intervention. This assessment further identifies misconceptions in public perception regarding: (a) causes of dengue disease; (b) dengue disease symptoms; (c) dengue disease severity; (d) dengue vector ecology; and (e) dengue disease transmission. Based on these results, recommendations are put forward for improving communication of dengue risk and practicing local community engagement and knowledge enhancement in Bangladesh. PMID:26387980
Ruane, Alex C.; Goldberg, Richard; Chryssanthacopoulos, James
2014-01-01
The AgMERRA and AgCFSR climate forcing datasets provide daily, high-resolution, continuous, meteorological series over the 1980-2010 period designed for applications examining the agricultural impacts of climate variability and climate change. These datasets combine daily resolution data from retrospective analyses (the Modern-Era Retrospective Analysis for Research and Applications, MERRA, and the Climate Forecast System Reanalysis, CFSR) with in situ and remotely-sensed observational datasets for temperature, precipitation, and solar radiation, leading to substantial reductions in bias in comparison to a network of 2324 agricultural-region stations from the Hadley Integrated Surface Dataset (HadISD). Results compare favorably against the original reanalyses as well as the leading climate forcing datasets (Princeton, WFD, WFD-EI, and GRASP), and AgMERRA distinguishes itself with substantially improved representation of daily precipitation distributions and extreme events owing to its use of the MERRA-Land dataset. These datasets also peg relative humidity to the maximum temperature time of day, allowing for more accurate representation of the diurnal cycle of near-surface moisture in agricultural models. AgMERRA and AgCFSR enable a number of ongoing investigations in the Agricultural Model Intercomparison and Improvement Project (AgMIP) and related research networks, and may be used to fill gaps in historical observations as well as a basis for the generation of future climate scenarios.
Gas-liquid annular flow in vertical circular tubes with liquid penetrated in nucleus
International Nuclear Information System (INIS)
A semi-analytical model is proposed for fully developed upward gas-liquid annular flow inside vertical circular tubes, by utilizing wall-known turbulence algebraic models for single-phase flows, within both streams, combined with empirical correlations for the gas-liquid interface friction factor. Direct integration of the associated momentum equations provide the velocity distribution for each phase, as well as overall quantities of practical interest such as liquid film thickness and pressure gradient. The effects of liquid droplets entrainment in the gas is specialized empirical correlations. Extensive comparisons with experimental results are made in order to demonstrate the consistency of the proposed model. (author)
Energy Technology Data Exchange (ETDEWEB)
Collison, M.
2007-04-15
Heavy oil is more difficult and costly to produce and refine than conventional light oil. Almost 50 per cent of the oil currently produced in Canada is classified as heavy oil. This article provided details of a heavy oil technology pilot project conducted by the Alberta Research Council (ARC) and Husky Energy. The ARC has now formed a steering committee of industry members to analyze new technologies and find ways to implement them. As part of their technology program, ARC hired, trained and placed an engineer with Husky Energy to execute a field application at Lloydminster of a heavy oil reservoir simulation software program. The biggest barrier to production in the Lloydminster play is the sand mixed throughout the viscous oil. In order to address the problem, Husky has spent 20 years developing a process known as cold heavy oil production with sand (CHOPS). The process employs a cavity pump which can tolerate extremely large amounts of sand in viscous oil. The pump has a corkscrew metal rotor placed inside a rubber covering, which rotates and pumps up the heavy oil, sand, natural gas, and water. The sand and oil are pumped into huge settling tanks which are heated by the natural gas that is stripped out of the oil. The sand sinks out the warm floating oil and settles in the tanks. Although it is very difficult to model a situation where sand flows from the reservoir along with the oil, ARC has developed a model of the process using data collected by Husky throughout its use of the CHOPS technique. A number of wells have been successfully modelled using the simulation tool. It was concluded that use of the CHOPS model has allowed researchers to test different operating strategies and extrapolate them to the field to predict possible oil production for various heavy oil recovery processes. 1 fig.
Far-field Diffraction Properties of Annular Walsh Filters
Directory of Open Access Journals (Sweden)
Pubali Mukherjee
2013-01-01
Full Text Available Annular Walsh filters are derived from the rotationally symmetric annular Walsh functions which form a complete set of orthogonal functions that take on values either +1 or −1 over the domain specified by the inner and outer radii of the annulus. The value of any annular Walsh function is taken as zero from the centre of the circular aperture to the inner radius of the annulus. The three values 0, +1, and −1 in an annular Walsh function can be realized in a corresponding annular Walsh filter by using transmission values of zero amplitude (i.e., an obscuration, unity amplitude and zero phase, and unity amplitude and phase, respectively. Not only the order of the Walsh filter but also the size of the inner radius of the annulus provides an additional degree of freedom in tailoring of point spread function by using these filters for pupil plane filtering in imaging systems. In this report, we present the far-field amplitude characteristics of some of these filters to underscore their potential for effective use in several demanding applications like high-resolution microscopy, optical data storage, microlithography, optical encryption, and optical micromanipulation.
Rotordynamic Analysis of Textured Annular Seals With Multiphase (Bubbly Flow
Directory of Open Access Journals (Sweden)
Gérard PINEAU
2011-09-01
Full Text Available For some applications it must be considered that the flow in the annular seal contains a mixture of liquid and gas. The multiphase character of the flow is described by the volume fraction of gas (usually air contained in the liquid under the form of bubbles.The fluid is then a homogenous mixture of air and liquid all thru the annular seal. Its local gas volume fraction depends on the pressure field and is calculated by using a simplified form of the Rayleigh-Plesset equation.The influence of such of a multiphase (bubbly flow on the dynamic characteristics of a straight annular seal is minimal because the volume of the fluid is reduced.The situation is quite different for textured annular (damper seals provided with equally spaced deep cavities intended to increase the damping capabilities and to reduce the leakage flow rate.As a by-product, the volume of the fluid in the seal increases drastically and the compressibility effects stemming from the bubbly nature of the flow are largely increased even for a low gas volume fraction. The present work depicts the influence of the gas volume fraction on the dynamic characteristics of a textured annular seal. It is shown that variations of the gas volume fraction between 1% and 0.1% can lead to frequency dependent stiffness, damping and added mass coefficients.
Zheng, Y.; Han, F.; Wu, B.
2013-12-01
Process-based, spatially distributed and dynamic models provide desirable resolutions to watershed-scale water management. However, their reliability in solving real management problems has been seriously questioned, since the model simulation usually involves significant uncertainty with complicated origins. Uncertainty analysis (UA) for complex hydrological models has been a hot topic in the past decade, and a variety of UA approaches have been developed, but mostly in a theoretical setting. Whether and how a UA could benefit real management decisions remains to be critical questions. We have conducted a series of studies to investigate the applicability of classic approaches, such as GLUE and Markov Chain Monte Carlo (MCMC) methods, in real management settings, unravel the difficulties encountered by such methods, and tailor the methods to better serve the management. Frameworks and new algorithms, such as Probabilistic Collocation Method (PCM)-based approaches, were also proposed for specific management issues. This presentation summarize our past and ongoing studies on the role of UA in real water management. Challenges and potential strategies to bridge the gap between UA for complex models and decision-making for management will be discussed. Future directions for the research in this field will also be suggested. Two common water management settings were examined. One is the Total Maximum Daily Loads (TMDLs) management for surface water quality protection. The other is integrated water resources management for watershed sustainability. For the first setting, nutrients and pesticides TMDLs in the Newport Bay Watershed (Orange Country, California, USA) were discussed. It is a highly urbanized region with a semi-arid Mediterranean climate, typical of the western U.S. For the second setting, the water resources management in the Zhangye Basin (the midstream part of Heihe Baisn, China), where the famous 'Silk Road' came through, was investigated. The Zhangye
González-Carrasco, J. F.; Gonzalez, G.; Aránguiz, R.; Catalan, P. A.; Cienfuegos, R.; Urrutia, A.; Shrivastava, M. N.; Yagi, Y.; Moreno, M.
2015-12-01
Tsunami inundation maps are a powerful tool to design evacuation plans of coastal communities, additionally can be used as a guide to territorial planning and assessment of structural damages in port facilities and critical infrastructure (Borrero et al., 2003; Barberopoulou et al., 2011; Power et al., 2012; Mueller et al., 2015). The accuracy of inundation estimation is highly correlated with tsunami initial conditions, e.g. seafloor vertical deformation, displaced water volume and potential energy (Bolshakova et al., 2011). Usually, the initial conditions are estimated using homogeneous rupture models based in historical worst-case scenario. However tsunamigenic events occurred in central Chilean continental margin showed a heterogeneous slip distribution of source with patches of high slip, correlated with fully-coupled interseismic zones (Moreno et al., 2012). The main objective of this work is to evaluate the predictive capacity of interseismic coupling models based on geodetic data comparing them with homogeneous fault slip model constructed using scaling laws (Blaser et al., 2010) to estimate inundation and runup in coastal areas. To test our hypothesis we select a seismic gap of Maule, where occurred the last large tsunamigenic earthquake in the chilean subduction zone, using the interseismic coupling models (ISC) proposed by Moreno et al., 2011 and Métois et al., 2013. We generate a slip deficit distribution to build a tsunami source supported by geological information such as slab depth (Hayes et al., 2012), strike, rake and dip (Dziewonski et al., 1981; Ekström et al., 2012) to model tsunami generation, propagation and shoreline impact using Neowave 2D (Yamazaki et al., 2009). We compare the tsunami scenario of Mw 8.8, Maule based in coseismic slip distribution proposed by Moreno et al., 2012 with homogeneous and heterogeneous models to identify the accuracy of our results with sea level time series and regional runup data (Figure 1). The estimation of
Heat-and-mass transfer during a laminar dissociating gas flow in eccentric annular channels
International Nuclear Information System (INIS)
An algorithm to calculate heat-and-mass transfer processes during dissociating gas laminar flow in an eccentric annular channels is considered. Analytical solutions of the heat transfer equations for a rod clodding and gap with boundary conditions of conjugation of temperatures and heat fluxes have been used to determine temperature field. This has made it possible to proceed from slution of the conjugate problem to solution of the equation of energy only for the coolant. The results of calculation of temperature distribution along the cladding for different values of its eccentricity and thermal conductivity coefficient both for the case of frozen flow and in the presence of chemical reactions in the flow are given. When calculating temperatures with conjugation boundary conditions temperature gradients in azimuthal direction are far less and heat transfer in concentration diffusion is carried out mainly in radial direction
Fehler, Manuel; Kleinhenz, Marco; Klügl, Franziska; Puppe, Frank; Tautz, Jürgen
2007-08-01
In addition to heat production on the comb surface, honeybee workers frequently visit open cells (“gaps”) that are scattered throughout the sealed brood area, and enter them to incubate adjacent brood cells. We examined the efficiency of this heating strategy under different environmental conditions and for gap proportions from 0 to 50%. For gap proportions from 4 to 10%, which are common to healthy colonies, we find a significant reduction in the incubation time per brood cell to maintain the correct temperature. The savings make up 18 to 37% of the time, which would be required for this task in completely sealed brood areas without any gaps. For unnatural high proportions of gaps (>20%), which may be the result of inbreeding or indicate a poor condition of the colony, brood nest thermoregulation becomes less efficient, and the incubation time per brood cell has to increase to maintain breeding temperature. Although the presence of gaps is not essential to maintain an optimal brood nest temperature, a small number of gaps make heating more economical by reducing the time and energy that must be spent on this vital task. As the benefit depends on the availability, spatial distribution and usage of gaps by the bees, further studies need to show the extent to which these results apply to real colonies.
Turbulent structure at the midsection of an annular flow
Ghaemi, S.; Rafati, S.; Bizhani, M.; Kuru, E.
2015-10-01
The turbulent flow in the midsection of an annular gap between two concentric tubes at Reynolds number of 59 200-90 800 based on hydraulic diameter (dh = 57 mm) and average velocity is experimentally investigated. Measurements are carried out using particle tracking velocimetry (PTV) and planar particle image velocimetry (PIV) with spatial resolution of 0.0068dh (size of the binning window) and 0.0129dh (size of the interrogation window), respectively. Both PTV and PIV results show that the location of maximum mean streamwise velocity (yU) does not coincide with the locations of zero shear stress (yuv), minimum streamwise velocity fluctuation (yu2), and minimum radial velocity fluctuation (yv2). The separation between yU and yuv is 0.013dh based on PTV while PIV underestimates the separation distance as 0.0063dh. Conditional averages of turbulent fluctuations based on the four quadrants across the annulus demonstrate that the inner and outer wall flows overlap in the midsection. In the midsection, the flow is subject to opposing sweep/ejection events originating from both the inner and outer walls. The opposite quadrant events of the two boundary layers cancel out at yuv while the local minimum of spatial correlation of u (maximum mixing of the two wall flows) occurs at yU. Investigation of the budget of Reynolds shear stress showed that production and advection terms act towards the coincidence of the yU and yuv while the dissipation term works against the coincidence of the two points. The location of max also overlaps with zero dissipation of . The production of turbulent kinetic energy is slightly negative in the narrow region between yU and yuv. This negative production acts towards smoothing the mean velocity profile at the joint of the two wall flows by equalizing its curvature (∂2/∂y2) on the two sides of yU. The small separation distance of the yU and yuv is associated with slight deviation from the fully developed condition.
Hydrodynamic stability of inverted annular flow in an adiabatic simulation
International Nuclear Information System (INIS)
In experiments, inverted annular flow was simulated adiabatically with turbulent water jets, issuing downward from long aspect nozzles, enclosed in gas annuli. Velocities, diameters, and gas species were varied, and core jet length, shape, break-up mode, and dispersed-core droplet sizes were recorded at approximately 750 data points. Inverted annular flow was observed to develop into inverted slug flow at low relative velocities, and into dispersed droplet flow at high relative velocities. For both of the above transitions from inverted annular flow, a correlation for core jet length was developed by extending work done on free liquid jets to include this new, coaxial, jet disintegration phenomenon. The result, showing length dependence upon diameter, jet Reynolds number, jet Weber number, void fraction, and gas Weber number, correlates the data well, especially at moderate-to-large relative velocities
Fluidic Analysis in an Annular Centrifugal Contactor for Fuel Reprocessing
International Nuclear Information System (INIS)
An annular centrifugal contactor (ACC) is a promising device for fuel reprocessing process, because it offers several advantages—a smaller size, a smaller holdup volume, and a higher separation performance—over conventional contactors such as a mixer-settler and a pulse column. Fluid dynamics and dispersion in an ACC, which has a combined mixer/centrifuge structure, are closely related to its separation performance and capacity, and this information is useful in improving equipment design. In this paper, experimental and computational fluid dynamics (CFD) studies were conducted to analyze fluidic and dispersion behavior in ACCs. Multiphase mixing (water/TBP-dodecane/air) in the annular zone was observed by Particle Imaging Velocimetry, and the change in the fluidic and dispersion behavior was ascertained under several operational conditions. The results of the CFD studies, which considered multiphase turbulent flow in the annular and rotor interior zones, were in a good agreement with the experimental data. (author)
Air entrainment into annular water flows in a vertical pipe
International Nuclear Information System (INIS)
An experimental investigation was carried out on air entrainment into water flowing downward in a vertical pipe. Local flow rates of water and air in a fluid layer of annular flow, formed on the pipe wall, were measured precisely by using a small tube probe. Measurements were also made of local flow rates of water and air in bubbly flow downstream of annular water flow. Distributions of local flow rates in the radial direction of the pipe for annular flow regime indicate that the fluid layer consists of a water layer adjacent to the pipe wall and a water-air (two-phase fluid) layer located inside of the water layer. The water-air layer is formed as a result of air entrainment. The departure of air bubbles from a water pool to air phase was found for bubbly flow regime. (author)
Service Quality Gaps & Six Sigma
Ali Dehghan; Arash Shahin; Bahman Zenouzi
2011-01-01
Nowadays almost all organizations are realizing the significance of customer centered philosophies. One of the key challenges they are facing is how to manage service quality, which holds a great importance to customer satisfaction. This paper has attempted to investigate the gap between customers, service providers and managers in terms of service quality dimensions. For this purpose, gaps 1 and 6 of the SERVQUAL model have been studied, as well as two new gaps, proposed for comparing custo...
Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis
Directory of Open Access Journals (Sweden)
Rishi Hassan
2016-01-01
Full Text Available Annular elastolytic giant cell granuloma (AEGCG is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the classical clinical and histological findings of the disease and its rare co-existence with Hashimoto's thyroiditis.
Annular elastolytic giant cell granuloma in association with Hashimoto's thyroiditis.
Hassan, Rishi; Arunprasath, P; Padmavathy, L; Srivenkateswaran, K
2016-01-01
Annular elastolytic giant cell granuloma (AEGCG) is a rare granulomatous skin disease characterized clinically by annular plaques with elevated borders and atrophic centers found mainly on sun-exposed skin and histologically by diffuse granulomatous infiltrates composed of multinucleated giant cells, histiocytes and lymphocytes in the dermis along with phagocytosis of elastic fibers by multinucleated giant cells. We report a case of AEGCG in a 50-year-old woman and is highlighted for the classical clinical and histological findings of the disease and its rare co-existence with Hashimoto's thyroiditis. PMID:27057492
Portal annular pancreas: the pancreatic duct ring sign on MRCP.
Lath, Chinar O; Agrawal, Dilpesh S; Timins, Michael E; Wein, Melissa M
2015-12-01
Portal annular pancreas is a rare pancreatic variant in which the uncinate process of the pancreas extends and fuses to the dorsal surface of the body of the pancreas by surrounding the portal vein. It is asymptomatic, but it can be mistaken for a pancreatic head mass on imaging and could also have serious consequences during pancreatic surgery, if unrecognized. We report this case of a 53-year-old female patient who was diagnosed to have portal annular pancreas on the basis of an unusual course (ring appearance) of the main pancreatic duct on magnetic resonance cholangiopancreatography, not described earlier in the radiology literature. PMID:26649117
Portal annular pancreas: the pancreatic duct ring sign on MRCP
Directory of Open Access Journals (Sweden)
Chinar O. Lath, MD
2015-12-01
Full Text Available Portal annular pancreas is a rare pancreatic variant in which the uncinate process of the pancreas extends and fuses to the dorsal surface of the body of the pancreas by surrounding the portal vein. It is asymptomatic, but it can be mistaken for a pancreatic head mass on imaging and could also have serious consequences during pancreatic surgery, if unrecognized. We report this case of a 53-year-old female patient who was diagnosed to have portal annular pancreas on the basis of an unusual course (ring appearance of the main pancreatic duct on magnetic resonance cholangiopancreatography, not described earlier in the radiology literature.
Flow Visualisation of Annular Liquid Sheet Instability & Atomisation
Duke, Daniel; Soria, Julio
2012-01-01
Fluid dynamics videos of unstable thin annular liquid sheets are presented in this short paper. These videos are to be presented in the Gallery of Fluid Motion for the American Physical Society 65th Annual Meeting of the Division of Fluid Dynamics in San Diego, CA, 18-20 November 2012. An annular sheet of thickness h=1mm and mean radius R=18.9mm is subjected to aerodynamic axial shear from co-flowing air at various shear rates on both the inner and outer surface at a liquid sheet Reynolds Number of Re=500.
DEFF Research Database (Denmark)
Sandoval, Santiago; Vezzaro, Luca; Bertrand-Krajewski, Jean-Luc
2016-01-01
solids (TSS) online measurements (year 2007, 2 minutes time-step, combined system, Ecully, Lyon, France). Results show up the potential of the method to fill gaps longer than 0.5 days, especially between 0.5 days and 1 day (mean NSE > 0.6) in the flow rate time series. TSS results still perform very...... seeks to evaluate the potential of the Singular Spectrum Analysis (SSA), a time-series modelling/gap-filling method, to complete dry weather time series. The SSA method is tested by reconstructing 1000 artificial discontinuous time series, randomly generated from real flow rate and total suspended...