Build-up Model Research Articles

Flow Mathematic Model and Exact Solution of Swabbing Wells’ Fluid Level Build up

The fluid level of swabbing wells with packers or without packers is different from other wells’ when the swabbing wells are stopped swabbing, because the effect of gravity differentiation is obvious, which is used to calculate the sand face pressure. In the homogeny reservoir, flow mathematic model of build-up of fluid swabbing well in circular sealed stratum is built up under considering the well bore effect and skin factor. Then, the non-homogeneous equation’s exact solution in Laplace space of the model are acquired by using theory of Laplace transform and Bessel function ,then the chart of type curve and the matching of type curve are analyzed. Finally, the software of swabbing well’s fluid level build-up is developed which is used to calculate the formation parameters that are fitted the formation parameters calculated with other methods.

Model for radiation damage buildup in GaN

We propose a model that explains both saturation and a shift of the maximum of bulk disorder profiles in ion-implanted GaN. Our model is based on two main assumptions that (i) the advancing amorphous/crystalline interface acts as a perfect sink for mobile point defects generated in the crystal bulk and (ii) the diffusion length of mobile defects increases with increasing ion fluence due to saturation of defect sinks in the bulk.

Modeling the Build-Up of Organically Bound Tritium in Crops after Acute Tritium Exposure in Greenhouse’s Environment

The processes of tritium uptake, losses, transformation and organically bound tritium (OBT) build-up in crops such as potatoes, tomatoes, lettuce and wheat were studied in a set of experiments on crop’ short-term exposure to tritiated water (HTO) in a greenhouse. The crops were exposed at the stage of linear growth between blossoming and ripening. The results of experiments were used to develop a model of OBT build-up in crop’s storage organs.The model allows estimate tritium uptake, losses in crop’s leaves as well as its transformation in OBT and transport to storage organs of plants. The model parameters were obtained from the measured data for each crop’s type by using regression analysis. The model was validated against experiments. The model can be used to assess OBT activity in storage organs of crops upon short-term exposure in the atmosphere contaminated by HTO.

A Behavioral Approach To Derive The Cost Of Equity Capital For Small Closely Held Firms

The purpose of this research is to explore the theoretical structure that underlies the valuation process for small closely held firms. All discounted cash flow valuation models require an estimate of a firm’s weighted average cost of capital as well as the firm’s component cost of equity capital. The CAPM is frequently employed to measure the cost of equity capital for a publicly traded firm. A publicly held firm’s common stock price is determined in the capital markets and is readily available. The firm’s stock price can then be used to estimate its beta; a necessary input to the CAPM. Because there is no information about stock prices, the task of estimating the cost of equity for a closely held firm is more challenging. The build-up model is frequently used to calculate the cost of equity for the closely held firm. However there is much controversy over this model’s assumptions, reliability and validity. Specifically, this research critiques the build-up model identifying its advantages and its liabilities. The purpose of this work is to create discussion and stimulate economists to study and improve this important area. Additionally, this study offers a new economic model to estimate the cost of equity capital that is theoretically correct easy to understand

A One‐Dimensional Particle‐in‐Cell Model of Plasma Build‐Up in Vacuum Arcs

AbstractUnderstanding the mechanism of plasma build‐up in vacuum arcs is essential in many fields of physics. A one‐dimensional particle‐in‐cell computer simulation model is presented, which models the plasma developing from a field emitter tip under electrical breakdown conditions, taking into account the relevant physical phenomena. As a starting point, only an external electric field and an initial enhancement factor of the tip are assumed. General requirements for plasma formation have been identified and formulated in terms of the initial local field and a critical neutral density. The dependence of plasma build‐up on tip melting current, the evaporation rate of neutrals and external circuit time constant has been investigated for copper and simulations imply that arcing involves melting currents around 0.5–1 A/μm2, evaporation of neutrals to electron field emission ratios in the regime 0.01 – 0.05, plasma build‐up timescales in the order of ∼ 1 – 10 ns and two different regimes depending on initial conditions, one producing an arc plasma, the other one not. Also the influence of the initial field enhancement factor and the external electric field required for ignition has been explored, and results are consistent with the experimentally measured local field value of ∼ 10 GV/m for copper (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Model for localized buildup and thinning of metal due to electromigration

We present a model to account for the highly localized buildup and thinning of metal that has been observed during electromigration testing. It assumes variations in mobility along the line, rather than complete blockage. Using reasonable estimates for the parameters needed, it is possible to obtain a quantitative fit to previously observed data.

SUNSPOT ROTATION, FLARE ENERGETICS, AND FLUX ROPE HELICITY: THE HALLOWEEN FLARE ON 2003 OCTOBER 28

We study the X17 eruptive flare on 2003 October 28 using Michelson Doppler Imager observations of photospheric magnetic and velocity fields and TRACE 1600 A images of the flare in a three-dimensional model of energy buildup and release in NOAA 10486. The most dramatic feature of this active region is the 123° rotation of a large positive sunspot over 46 hr prior to the event. We apply a method for including such rotation in the framework of the minimum current corona model of the buildup of energy and helicity due to the observed motions. We distinguish between helicity and energy stored in the whole active region and that released in the flare itself. We find that while the rotation of a sunspot contributes significantly to the energy and helicity budgets of the whole active region, it makes only a minor contribution to that part of the region that flares. We conclude that in spite of the fast rotation, shearing motions alone store sufficient energy and helicity to account for the flare energetics and interplanetary coronal mass ejection helicity content within their observational uncertainties. Our analysis demonstrates that the relative importance of shearing and rotation in this flare depends critically on their location within the parent active region topology.

Modeling of dielectric charging in electrostatic MEMS switches

The most important failure mechanism for electrostatic MEMS switches is dielectric charging, which contributes to a significant reduction of the device lifetime. In this study the correlation between the dielectric properties and the switch lifetime is evaluated. The conduction mechanism and trapping kinetics for two types of PECVD SiN x are determined by I– V sweeps and constant-current injections from Metal–Insulator–Metal (MIM) capacitors. This type of procedure is used as a basis for modeling the charge build-up in a switch. Despite significant differences between the dielectrics, in terms of leakage current and trapping properties, the numerical model of charge build-up fits well with experimental data. We conclude that the switch lifetime can be correlated with the trapping properties of the dielectric itself.

Analytical model of the oxide layer build-up in complex lead-cooled systems

In order to support the R&D on protecting the structural materials against degradation in the heavy-metal-cooled fast-spectrum reactor systems, the model was developed for predicting the rate of the oxide layer build-up on the stainless steel surfaces in the reactor systems cooled by lead or lead-bismuth eutectics. After being integrated in the TRACE code which is a part of the FAST code system, the model was validated against available experimental data. The modified FAST code system can now be used for qualification of the oxygen control technology in the complex circuits of such systems as ELSY or XT-ADS.

FAST Code System: Review of Recent Developments and Near-Future Plans

The FAST code system is currently being developed and used at the Paul Scherrer Institut for static and transient analysis of the main Generation 4 fast-spectrum reactor concepts: sodium-, helium-, and gas-cooled fast reactors. The code system includes the ERANOS code system for static neutronics calculations, as well as coupled TRACE/PARCS/FRED for neutron kinetics, thermal hydraulic, and fuel transient analysis. The paper presents the status of the recent developments in neutronics (new 3D procedure for equilibrium cycle simulation and new transient cross section generation procedure), in thermal hydraulics and chemistry (equations-of-state for new coolants, two-phase flow models for sodium, and new model for oxide layer buildup in heavy-metal flow), and in fuel behavior (new model for the dispersed gas-cooled fast reactor fuel). Near-future plans for the further development of FAST are outlined.

An exergy application for analysis of buildings and HVAC systems

The paper presents an extended method for exergy analysis of buildings and Heating Ventilation Air Conditioning (HVAC) systems, according to an energy demand build-up model from the building side to the energy supply side. The HVAC systems comprise a thermal energy emission and control system, a thermal distribution system, an electricity distribution system and an energy conversion system. Energy and exergy that are required by a building and a HVAC system are posed into the external part and classified by different forms of energy carriers. The external part is out of the boundary of the study. The method is illustrated with an office building equipped with low-temperature heating and high-temperature cooling systems situated in the Netherlands. Thermal exergy and thermal energy demands of the building and thermal energy and thermal exergy losses occurring in the HVAC systems are discussed. The building and the HVAC systems to be considered meet standard Dutch energy performance regulations. Nevertheless their overall exergy efficiencies are low in both cases (17.15% and 6.81% subsequently). The exergy analysis also pinpoints that the thermal energy emission and control system and the energy conversion system are the main causes of the exergy inefficiencies in the heating and cooling cases, respectively.

Monte Carlo simulations of high-speed, time-gated microchannel-plate-based x-ray detectors: Saturation effects in dc and pulsed modes and detector dynamic range

We present here results of continued efforts to understand the performance of microchannel plate (MCP)-based, high-speed, gated, x-ray detectors. This work involves the continued improvement of a Monte Carlo simulation code to describe MCP performance coupled with experimental efforts to better characterize such detectors. Our goal is a quantitative description of MCP saturation behavior in both static and pulsed modes. A new model of charge buildup on the walls of the MCP channels is briefly described. The simulation results are compared to experimental data obtained with a short-pulse, high-intensity ultraviolet laser, and good agreement is found. These results indicate that a weak saturation can change the exponent of gain with voltage and that a strong saturation leads to a gain plateau. These results also demonstrate that the dynamic range of a MCP in pulsed mode has a value of between 10(2) and 10(3).

Mathematical modeling of first flush in highway storm runoff using genetic algorithm

A mechanistic model was developed to predict the highway runoff pollutographs during precipitation events. Pollutants were assumed to be in two phases, attached to the pavement surface and mobile in the runoff water. Detachment and reattachment of contaminants were considered as rate-limited processes and the detachment rate was assumed to be a function of flow velocity by a power expression. The build-up of pollutants on the surface during the dry period between the storm events was also included in the model. Using measured pollutographs from three highly urbanized highway sites in Los Angeles, California, a hybrid genetic algorithm was used to estimate the model parameters for four different constituents including total suspended solids, oil and grease, dissolved copper, and particulate copper. The model was then validated by predicting pollutographs for the same site for a different monitoring season. Results revealed that estimated model parameters were different for particle-associated and dissolved constituents. These findings suggest different mechanisms governing the detachment of particle-associated and dissolved constituents from the surface. The results have also indicated that there is a linear build-up of pollutants during the dry period and the removal of pollutants during dry periods was insignificant. From these findings, it has been concluded that either the removal rate during the dry period is small or it is not proportional to the concentration of pollutants accumulated on the surface. In general, the build-up contaminant concentrations from the build-up model followed the same trend. However, in some cases the estimated and measured pollutograph did not closely match that may be due to some unknown factors affecting the build-up rates in the current model.

Dynamics in Dye-Doped LC Systems in Presence of Trans-Cis Isomerism

The excitation as well as relaxation dynamics of dye-doped nematic liquid crystal cells has been explored both experimentally and theoretically. Overshoots in the build up of the probe signal diffracted from gratings written onto dye-doped liquid crystal systems have often been observed. The overshoot behaviour makes the accurate measurement of nonlinear optical (NLO) response magnitude difficult and ambiguous. Moreover, it complicates the understanding of the dynamics and the physics of the NLO processes. On the basis of the system with trans-cis isomerisation as a mechanism of the NLO effect the quantitative model has been built to describe the experimental results which we observe. The two unknown material parameters: diffusion coefficient and cis species lifetime are calculated from the relaxation data. A quantitative model of the signal build-up uses these parameters. The calculated dynamic behaviour based on this model correlates very well with the experimental data. The model is used to predict the performance of the system with various dopant diffusion properties.

A 1/f noise based research of radiation induced interface trap buildup process

Based on the two-step interface trap buildup model and the statistical thermodynamics mechanism of point defects in solids, a relation between the radiation induced increase of oxide hole-traps and the buildup of interface traps in MOSFET is proposed. Then, based on the correlation between pre-irradiation 1/f noise power spectral density and post-irradiation oxide-trap charge, a sim-empirical expression of pre-irradiation 1/f noise and post-irradiation interface traps buildup is established which agrees well with the experimental results. This model shows that the process of interface trap buildup was influenced by the increasing of oxide hole-traps that could dissociated hydrogen into proton under irradiation. So, the magnitude of pre-irradiation 1/f noise is directly proportional to post-irradiation interface-trap charge and sub-threshold slope. Our results not only proves that the 1/f noise can play a important role in MOSFET irradiation effects, but also proves a new nondestructive method to estimate MOSFET radiation response.

A two‐ejecta event associated with a two‐step geomagnetic storm

A new view on how large disturbances in the magnetosphere may be prolonged and intensified further emerges from a recently discovered interplanetary process: the collision/merger of interplanetary (IP) coronal mass ejections (ICMEs; ejecta) within 1 AU. As shown in a recent pilot study, the merging process changes IP parameters dramatically with respect to values in isolated ejecta. The resulting geoeffects of the coalesced (“complex”) ejecta reflect a superposition of IP triggers which may result in, for example, two‐step, major geomagnetic storms. In a case study, we isolate the effects on ring current enhancement when two coalescing ejecta reached Earth on 31 March 2001. The magnetosphere “senses” the presence of the two ejecta and responds with a reactivation of the ring current soon after it started to recover from the passage of the first ejection, giving rise to a double‐dip (DD) great storm (each min Dst < −250 nT). A drift‐loss global kinetic model of ring current buildup shows that in this case the major factor determining the intensity of the storm activity is the very high (up to ∼10 cm−3) plasma sheet density. The plasma sheet density, in turn, is found to correlate well with the very high solar wind density, suggesting the compression of the leading ejecta as the source of the hot, superdense plasma sheet in this case. This correlation is similar to that obtained in a previous investigation extending over several years, but the present case study extends the range of plasma sheet densities from ∼2 to ∼10 cm−3. Since the features of the ejecta interaction in this example are fairly general, we propose that interacting ejecta are a new, important IP source of DD major storms. Peculiarities in the behavior of the magnetopause current during these extreme events are briefly discussed in the light of recent work. In a brief discussion of a second example (21–23 October 2001), we suggest that by strengthening the leading shock, the ejecta merger may have added to the “shock‐driver gas” origin of DD geomagnetic storms by increasing the ability of the shock to compress preexisting Bz < 0 magnetic fields.

Estimating Pollutant Mass Accumulation on Highways during Dry Periods

For determining the accumulated pollutant mass on highways, two years of monitoring data were used from eight highway sites in southern California. Buildup over antecedent dry days was calculated from mass washed off from the following storm and retained pollutant mass. Mass accumulation rates were determined for total suspended solids (TSS), chemical oxygen demand (COD), oil and grease, total Kjeldahl nitrogen, and total phosphorus, and are reported in g∕ m2 -day . A revised buildup model is proposed using an alternative modeling approach to describe buildup during dry days between storms. The result shows that, between 1 and 10 antecedent dry days, the pollutant mass buildup rates are determined to be 0.544 g∕ m2 -day for TSS, 0.114 g∕ m2 -day for COD, and 0.0113 g∕ m2 -day for oil and grease. Buildup rates decline in subsequent periods rates decreased by 79% for TSS, 78% for COD, and 61% less for oil and grease in the following 10–70 day period.

A derived probability distribution approach to stormwater quality modeling

The closed-form analytical stormwater quality models are developed for simulating urban catchment pollutant buildup and washoff processes. By integrating the rainfall–runoff transformation with pollutant buildup and washoff functions, stormwater quality measures, such as the cumulative distribution functions (CDFs) of pollutant loads, the expected value of pollutant event mean concentrations (EMCs) and the average annual pollutant load can be derived. This paper presents methodologies and major procedures for the development of urban stormwater quality models based on derived probability distribution theory. In order to investigate the spatial variation in model parameters and its impact on stormwater pollutant buildup and washoff processes as well as pollutant loads to receiving waters, an extended form of the original rainfall–runoff transformation which is based on lumped runoff coefficient approach is proposed to differentiate runoff generation mechanisms between the impervious and pervious areas of the catchment. In addition, as a contrast to the aggregated pollutant buildup models formulated with a single lumped buildup parameter, the disaggregated form of the pollutant buildup model is proposed by introducing a number of physically-based parameters associated with pollutant buildup and washoff processes into the pollutant load models. The results from the case study indicate that analytical urban stormwater management model are capable of providing results in good agreement with the field measurements, and can be employed as alternatives to continuous simulation models in the evaluation of long-term stormwater quality measures.

Hollow Silica Spheres with an Ordered Pore Structure and Their Application in Controlled Release Studies

Herein we report the synthesis and characterization of hollow silica spheres with a narrow size distribution, uniform wall thickness, and a worm-like pore structure. The formation of these spheres was monitored by confocal laser scanning microscopy and dynamic light scattering. A model for the molecular build-up of these silica hollow spheres is derived from these data in combination with studies of the as-made particles by transmission electron microscopy, scanning electron microscopy, pore size analysis, thermogravimetric analysis, and solid-state nuclear magnetic resonance. We further demonstrate that these spheres can be used for the encapsulation and subsequent release of different dye molecules.

Effect of Temperature on the Buildup of Polyelectrolyte Multilayers

The effect of temperature on the buildup of polyelectrolyte multilayers consisting of poly(styrenesulfonate) (PSS), poly(diallyldimethylammonium) (PDADMA), and poly(allylamine) (PAH) was studied by using a quartz crystal microbalance. The increase of temperature in the deposition process was shown to have a considerable effect on the rate of the layer-by-layer buildup. The effect of temperature on the PDADMA/PSS deposition was found to be stronger than on the PAH/PSS deposition. The increasing temperature was found to extend the exponential buildup regime in all of the studied systems. A buildup model was created to simulate the buildup and to explain the effect of temperature. The model is based on the assumption that each deposition step leads to a quasi-equilibrium between the concentration of the polymer repeating unit in solution and the composition of the layer. According to the model, the layer-by-layer buildup is inherently exponential, becoming linear whenever diffusion is not fast enough to carry the polymer within the entire thickness of the film. This buildup model is discussed jointly with the earlier published three-zone model of the polyelectrolyte multilayers. The rate of the buildup is characterized by growth exponent beta. The temperature dependence of the growth exponent is discussed in connection with the thermodynamic parameters of the deposition.