Sink Model Research Articles

Comparison of calculated and experimental flow velocities upstream from the sampling cone of an inductively coupled plasma mass spectrometer

Experimentally-determined flow velocities in the 6 mm upstream from the sampling cone of an inductively coupled plasma mass spectrometer were compared with velocities determined from a computer simulation of the flow and those calculated from a modified hemispherical sink model. The measured values and those from the simulation agreed within experimental error, but differed from the values calculated from the modified hemispherical sink model by as much as 30%. An empirical alternative to the modified hemispherical sink model is presented that allows for accurate calculation of flow properties upstream from the sampling cone under a range of plasma conditions.

Steady State Productivity Equations for a Vertical Well in Anisotropic Sector Fault, Channel, and Rectangular Reservoirs

This paper presents steady state productivity equations for a fully penetrating vertical well in the following three anisotropic systems: (a) sector fault, (b) channel, and (c) rectangular reservoir using a uniform line sink model. The new equations, which are based on conformal mapping method, are simple, accurate, and easy to use in field practice. If the well is in a sector fault reservoir, the productivity is a function of the angle of the sector, wellbore location angle, off-vertex distance, and drainage radius. If the well is in a channel reservoir with two parallel impermeable lateral boundaries, well flow rate reaches a maximum value when the well is located in the middle of the channel width. If the well is in a rectangular reservoir with constant pressure lateral boundaries, a new equation is provided to calculate the productivity of the well arbitrarily located in the anisotropic reservoir for the case where the flow rate of an off-center well is bigger than that of a centered well. It is concluded that, for a vertical well, different steady state productivity equations should be used in different reservoir geometries.

Modeling the gas flow upstream and in the sampling nozzle of the inductively coupled plasma mass spectrometer via the Direct Simulation Monte Carlo algorithm

The Direct Simulation Monte Carlo algorithm has been applied to the flow of neutral argon gas through the first vacuum stage of the Inductively Coupled Plasma Mass Spectrometer. Good agreement is found between the simulation results and the equations of fluid dynamics, including the approximate hemispherical sink model of Douglas and French. The simulation reveals details of boundary layer formation in the nozzle, including a reduction in the total flow through the nozzle of about 15% from the ideal value calculated by Douglas and French.

Pressure Drop Equations for a Partially Penetrating Vertical Well in a Circular Cylinder Drainage Volume

Taking a partially penetrating vertical well as a uniform line sink in three‐dimensional space, by developing necessary mathematical analysis, this paper presents unsteady‐state pressure drop equations for an off‐center partially penetrating vertical well in a circular cylinder drainage volume with constant pressure at outer boundary. First, the point sink solution to the diffusivity equation is derived, then using superposition principle, pressure drop equations for a uniform line sink model are obtained. This paper also gives an equation to calculate pseudoskin factor due to partial penetration. The proposed equations provide fast analytical tools to evaluate the performance of a vertical well which is located arbitrarily in a circular cylinder drainage volume. It is concluded that the well off‐center distance has significant effect on well pressure drop behavior, but it does not have any effect on pseudoskin factor due to partial penetration. Because the outer boundary is at constant pressure, when producing time is sufficiently long, steady‐state is definitely reached. When well producing length is equal to payzone thickness, the pressure drop equations for a fully penetrating well are obtained.

CHARACTERIZING SOURCE–SINK DYNAMICS WITH GENETIC PARENTAGE ASSIGNMENTS

Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly with demographic methods, and indirect genetic methods are subject to a variety of assumptions that are difficult to meet or to apply to evolutionary timescales. Furthermore, such methods cannot be rigorously applied to high-gene-flow species. Here, we employ genetic parentage assignments in conjunction with demographic simulations to infer the level of immigration into a putative sink population. We use individual-based demographic models to estimate expected distributions of parent-offspring dyads under competing sink and closed-population models. By comparing the actual number of parent-offspring dyads (identified from multilocus genetic profiles) in a random sample of individuals taken from a population to expectations under these two contrasting demographic models, it is possible to estimate the rate of immigration and test hypotheses related to the role of immigration on population processes on an ecological timescale. The difference in the expected number of parent-offspring dyads between the two population models was greatest when immigration into the sink population was high, indicating that unlike traditional population genetic inference models, the highest degree of statistical power is achieved for the approach presented here when migration rates are high. We used the proposed genetic parentage approach to demonstrate that a threatened population of Marbled Murrelets (Braclhyrarmphus marmotus) appears to be supplemented by a low level of immigration (approximately 2-6% annually) from other populations.

High allozyme diversity and unidirectional linear migration patterns within a population of tetraploid Isoetes sinensis, a rare and endangered pteridophyte

Isoetes sinensis (Isoetaceae), an aquatic quillwort which occurs only in two fragmented sites of China as an allotetraploid, is critically endangered. Genetic variation among eight subpopulations of I. sinensis was examined in the Xin’an River (119°14′–15′E, 29°28′N) by using allozyme polymorphism. Eighteen loci of 10 enzyme systems were examined and used for the analysis of population genetic parameters. As expected for allotetraploids, fixed heterozygosity was found at four loci. A high level of genetic diversity was observed in the population, with mean number of alleles per loci of 1.8, and mean percentage of polymorphic loci of 55.6%, which were much higher than the average values in fern species. The genetic variation within each subpopulation was not positively correlated with its size, which may be explained by high gene flow ( Nm = 2.57), clonal reproduction and fixed heterozygosity of allopolyploid. The I. sinensis population contained high clonal diversity ( PD = 0.39, D = 0.95), indicating the successful seedling recruitment of the population. Significant positive relationship was detected between clonal diversity and the size of subpopulation. Partitioning the genetic diversity indicated that 91.1% of the genetic variation was within subpopulations and only 8.9% existed among subpopulations. The migration pattern of I. sinensis along the Xin’an River is best explained by a source–sink model, but with unidirectional gene flow among subpopulations underlined by hydrochoric force. The results were then discussed in relation to both in situ and ex situ conservation efforts of the population.

Physically Based Modelling of the Material and Gaseous Contaminant Interactions in Buildings: Models, Experimental Data and Future Developments

Abstract Although potentially having a significant influence on indoor air quality (IAQ), interactions between building materials and gaseous contaminants have often been neglected or crudely modelled in IAQ simulation tools. During the past 20 years, empirical source and sink models have progressively given way to physically based models; but confusion still remains on their applicability, as well as on the adequate experimental data to input for the model parameters. Thus, demonstration is first made that models relating macroscopically the room air phase and material concentrations through adsorption and desorption constants are not scientifically sound. Instead, elemental models combining diffusion equations and local sorption equilibria should be used. The compilation of sorption and diffusion data presented in the second part of this chapter underlines the fact that such data cannot be considered independently from the mass transport equations used to fit the measurements. As a result, a thorough analysis of diffusion processes in polymers and porous media is presented in order to define and relate the diffusion coefficients. Finally, the last part of the chapter discusses the way in which existing models could be extended to account for the contributions of temperature, multi-component mixtures, humidity and chemical transformations within materials. Still based on fundamental considerations, the proposed methodology consists of implementing new functionalities to describe the temperature dependence of the model parameters, elemental models representing the interactions between gaseous contaminants and water, as well as kinetic models coming from the fields of atmospheric and surface sciences.

The molecular pathophysiology of pseudoexfoliation glaucoma

This review summarizes recent observations and discoveries important for a current understanding of the clinical, molecular and genetic aspects of pseudoexfoliation glaucoma. Significant advances in our understanding of the molecular nature of the pseudoexfoliation material and pseudoexfoliation glaucoma have recently been made in the transcriptome, proteome, and genome levels. Differential gene expression studies have identified gene transcripts that are significantly downregulated and upregulated in the eyes of patients with pseudoexfoliation glaucoma relative to nonglaucomatous controls. Many of these differentially regulated genes are involved with extracellular matrix structure and metabolism and responses to stress and inflammation. Proteomic analysis of the pseudoexfoliation material similarly suggests that extracellular matrix and stress response proteins are associated with pseudoexfoliation glaucoma. Most recently, LOXL1 (which is involved with extracellular matrix formation and stability) has been discovered to be the first gene associated with a risk of developing pseudoexfoliation glaucoma. A proposed protein sink model parsimoniously accounts for the multitude of proteins known to be associated with pseudoexfoliation material and describes the orderly molecular formation of this disease causing material in the eye. Our understanding of pseudoexfoliation glaucoma has recently been significantly advanced by cutting edge molecular and genetic approaches to studying this sight threatening disease. An increased understanding of the molecular pathophysiology of pseudoexfoliation glaucoma will lead to improved management and diagnosis and new treatments for pseudoexfoliation glaucoma.

On the treatment of particulate organic matter sinking in large-scale models of marine biogeochemical cycles

Abstract. Various functions have been suggested and applied to represent the sedimentation and remineralisation of particulate organic matter (POM) in numerical ocean models. Here we investigate some representations commonly used in large-scale biogeochemical models: a constant sinking speed, a sinking speed increasing with depth, a spectrum of particles with different size and different size-dependent sinking velocities, and a model that assumes a power law particle size distribution everywhere in the water column. The analysis is carried out for an idealised one-dimensional water column, under stationary boundary conditions for surface POM. It focuses on the intrinsic assumptions of the respective sedimentation function and their effect on POM mass, mass flux, and remineralisation profiles. A constant and uniform sinking speed does not appear appropriate for simulations exceeding a few decades, as the sedimentation profile is not consistent with observed profiles. A spectrum of size classes, together with size-dependent sinking and constant remineralisation, causes the sinking speed of total POM to increase with depth. This increase is not strictly linear with depth. Its particular form will further depend on the size distribution of the POM ensemble at the surface. Assuming a power law particle size spectrum at the surface, this model results in unimodal size distributions in the ocean interior. For the size-dependent sinking model, we present an analytic integral over depth and size that can explain regional variations of remineralisation length scales in response to regional patterns in trophodynamic state.

Physically Based Modelling of the Material and Gaseous Contaminant Interactions in Buildings: Models, Experimental Data and Future Developments

Although potentially having a significant influence on indoor air quality (IAQ), interactions between building materials and gaseous contaminants have often been neglected or crudely modelled in IAQ simulation tools. During the past 20 years, empirical source and sink models have progressively given way to physically based models; but confusion still remains on their applicability, as well as on the adequate experimental data to input for the model parameters. Thus, demonstration is first made that models relating macroscopically the room air phase and material concentrations through adsorption and desorption constants are not scientifically sound. Instead, elemental models combining diffusion equations and local sorption equilibria should be used. The compilation of sorption and diffusion data presented in the second part of this chapter underlines the fact that such data cannot be considered independently from the mass transport equations used to fit the measurements. As a result, a thorough analysis of diffusion processes in polymers and porous media is presented in order to define and relate the diffusion coefficients. Finally, the last part of the chapter discusses the way in which existing models could be extended to account for the contributions of temperature, multi-component mixtures, humidity and chemical transformations within materials. Still based on fundamental considerations, the proposed methodology consists of implementing new functionalities to describe the temperature dependence of the model parameters, elemental models representing the interactions between gaseous contaminants and water, as well as kinetic models coming from the fields of atmospheric and surface sciences.

Serving Native American Students (New Directions for Student Services, #109) (review)

612 Journal of College Student Development nation as the necessary elements of a successful assessment plan. Moving from theory to practice can be a challenging, yet critical, process. Having carefully framed the discussion around concepts, ideas, and definitions, the author, using the Sink and Tuttle model, provides a useful methodology for assessing organizational performance. Student services staff will find this model applicable and useful for those interested in better understanding the effectiveness of their functional areas. To maximize the usefulness of the proposed model, the author suggests that “organizations have clearly defined strategic goals and intended outcomes: these are keys to good measurement of effectiveness” (p. 134). Assessing Organizational Performance in Higher Education is a useful tool for those who are seeking meaningful ways to evaluate the effectiveness of their organization. In addition, graduate students and entry-level staff will find this a worthy primer to understanding the complexity of organizations and the necessity for measurement.

Analysis of Forwarding Mechanisms on Fine-Grain Gradient Sinking Model in WSN

The communication efficiency of large-scale WSNs with high node density is highly related with specific forwarding strategy in complicated wireless environments. Thus, it is the key problem that how to use the characteristic of high-density to select appropriate forwarding nodes to relieve the load imbalance and improve the communication efficiency. In this paper, we first propose a Fine-grain Gradient Sinking (FGS) model and several data forwarding strategies based on this model. Then we give the criteria of communication efficiency and emphatically analyze the communication efficiency of various forwarding strategies. Simulation results show that forwarding strategies under FGS model can achieve higher communication efficiency, and the efficiency can be further elevated by introducing the statistics of packet receive rate during the forwarding process.

Estimation of Quartz Resonator Q and other Figures of Merit by an Energy Sink Method

An important determinant of the quality factor Q of a quartz resonator is the loss of energy from the electrode area to the base via the mountings. The acoustical characteristics of the plate resonator are changed when the plate is mounted onto a base substrate. The base substrate affects the frequency spectra of the plate resonator. A resonator with a high Q may not have a similarly high Q when mounted on a base. Hence, the base is an energy sink and the Q will be affected by the shape and size of this base. A lower bound Q will be obtained if the base is a semi-infinite base since it will absorb all acoustical energies radiated from the resonator. A scaled boundary finite element method is employed to model a semi-infinite base. The frequency spectra of the quartz resonator with and without the base are presented. In addition to the loss of energy via the base, there are other factors which affect the resonator Q, such as, for example, material dissipation, and damping at the interfaces of quartz and electrodes. The energy dissipation due to material damping increases with the resonant frequency and the reduction of resonator size; hence material damping becomes important in the current and future miniaturized resonators operating at very high frequencies. An energy sink model along with material dissipation would provide realistic Q, motional capacitance, motional resistance, and other figures of merit useful for designing resonators. The model could be used for evaluating resonator and mountings designs of microelectromechanical systems and miniaturized devices. The effect of the mountings, and plate and electrode geometries on the resonator Q and other electrical parameters are presented for AT-cut quartz resonators. Model results from the energy sink method were compared with experimental results and were found to be good.

Productivity equations for an off-center partially penetrating vertical well in an anisotropic reservoir

This paper presents steady state and pseudo-steady state productivity equations for an off-center partially penetrating vertical well in an anisotropic reservoir, using a uniform line sink model. This paper also gives equations for calculating pseudo skin factor due to partial penetration. Compared with the equations for partially penetrating wells in the literature, the new equations, which are based on three dimensional models, are simple and accurate. If the well is in steady state with a circular cylinder drainage volume, and if the top and bottom reservoir boundaries are impermeable, the radius of the cylindrical system and off-center distance appear in the productivity equations. If the reservoir has a gas cap or bottom water, the effects of the radius and off-center distance on productivity can be ignored. A new equation is provided to calculate the productivity of a partially penetrating vertical well arbitrarily located in the anisotropic reservoir with a box-shaped drainage volume under pseudo-steady state. A convenient expression to calculate the Dietz shape factor is also presented. It is concluded that, for a partially penetrating vertical well, different productivity equations should be used under different reservoir boundary conditions.

Mechanism and Analysis on Fine-Grain Gradient Sinking Model in Wireless Sensor Networks

Data sinking is one of the typical transmission patterns in WSN(wireless sensor network) . There is inherent unbalanced traffic load distribution in such funnel like transmission. A case in hop-based sinking(HBS) model is found more intricate than simple thought that inner nodes burden more forwarding tasks,showing the inverse direction within the same hop level comparing with global trend. With a simple weighted average mechanism,a continuous gradient parameter is introduced,which will be dedicated to instructing how to forward data to sink in place of hop count,namely fine-grain gradient sinking(FGS) . Through traffic analysis and detailed simulation,in FGS model the network turns out to be smoother on traffic load distribution and more efficient on data forwarding than that in HBS model.

EMC Computer Modeling Techniques for CPU Heat Sink Simulation

This paper presents finite-element frequency domain results for electromagnetic radiation emitted from high power microelectronic circuits connected to a heat sink. The heat sink model associated with one of the IEEE EMC challenging problems has been used to investigate three different grounding configurations. A new simulation model for the Intel P4 CPU heat sink is proposed and analyzed. A resonant frequency of 2.6 GHz with a reflection coefficient of 8.3 dB was found for the CPU heat sink. This is close to the IEEE and Bluetooth wireless communication system's operating frequency of 2.4 GHz. An optimal design of the CPU heat sink design should be performed in order to minimize the radiated emission from the CPU heat sink

Reply to Comment on ‘Effect of ionization on ion acoustic solitary waves in a collisional dusty plasma’ by J. Vranjes et al.

The main objective of the Comment made by J. Vranjes et al. is that the source–sink approach in studying physical phenomena, such as the ionization instability, is suspect. Also the term $(Q_{\rm i}-\nu_{\rm L} n_{\rm i})v_{\rm i}$ in the ion momentum conservation equation of the source–sink model used by [1] is improper.

A Thermal Model of a Forced-Cooled Heat Sink for Transient Temperature Calculations Employing a Circuit Simulator

∗Power semiconductors can be modeled as a thermal network of resistors and capacitors. The thermal boundary condition of such a model is typically defined as the heat sink surface temperature, which is assumed to be constant. In reality, the heat sink surface temperature underneath the power module is not exactly known. In this paper we show how to set up a thermal model of the heat sink in form of a RC thermal equivalent network that can be directly embedded in any circuit simulator. The proposed thermal heat sink model takes into account convection cooling, thermal hotspots on the heat sink base plate, thermal time constants of the heat sink, and thermal coupling between different power modules mounted onto the heat sink. Experimental results are given and show high accuracy of the heat sink model with temperature errors below 10%.

Land-use change and carbon sinks: Econometric estimation of the carbon sequestration supply function

If the United States chooses to implement a greenhouse gas reduction program, it would be necessary to decide whether to include carbon sequestration policies—such as those that promote forestation and discourage deforestation—as part of the domestic portfolio of compliance activities. We investigate the cost of forest-based carbon sequestration by analyzing econometrically micro-data on revealed landowner preferences, modeling six major private land uses in a comprehensive analysis of the contiguous United States. The econometric estimates are used to simulate landowner responses to sequestration policies. We treat key commodity prices as endogenous and predict carbon storage changes with a carbon sink model. Our estimated sequestration costs exceed those from previous engineering cost analyses and sectoral optimization models. Our estimated sequestration supply function is similar to the carbon abatement supply function from energy-based analyses, suggesting that forest-based carbon sequestration merits consideration in a cost-effective portfolio of domestic US climate change strategies.

Thermal Analysis of Heat Sink Models using CFD simulation

Thermal Analysis of Heat Sink Models using CFD simulation