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RPM-SIM-Based Analysis of Power Converter Applications in Renewable Energy Systems: Preprint (open access)

RPM-SIM-Based Analysis of Power Converter Applications in Renewable Energy Systems: Preprint

This paper briefly presents the RPM-SIM simulator and, in particular, its abilities to simulate and analyze renewable energy systems with power converters. This modular simulation system is used to study applications and cost-effective performance of renewable energy systems, analyze both static and dynamic performance, develop control strategies, and simulate autonomous renewable energy systems under different generation and load conditions (such as different wind speeds, temperature, insolation conditions, and load profiles).
Date: November 1, 2001
Creator: Bialasiewicz, J. T.; Muljadi, E. & Nix, R. G.
System: The UNT Digital Library
Status and Recent Results for EMSP Project No.70108 Effects of Fluid Distribution on Measured Geophysical Properties for Partially Saturated, Shallow Subsurface Conditions (open access)

Status and Recent Results for EMSP Project No.70108 Effects of Fluid Distribution on Measured Geophysical Properties for Partially Saturated, Shallow Subsurface Conditions

The objective of this report is to improve geophysical imaging of the vadose zone by developing improved methods for interpreting geophysical field data. The purpose of this EMSP project is to develop relationships between laboratory measured geophysical properties and porosity, saturation, soil composition, and fluid distribution, for partially saturated soils. Algorithms for relationships between soil composition, fluids, and geophysical measurements can provide new methods to interpret geophysical field data collected in the vadose zone at sites such as Hanford, WA.
Date: November 1, 2001
Creator: Berge, P. A.; Bonner, B. P.; Roberts, J. J.; Wildenschild, D.; Berryman, J. G. & Bertete-Aquirre, H.
System: The UNT Digital Library
Progress in Infrared Pyrometry Measurements of Shocked Solids (open access)

Progress in Infrared Pyrometry Measurements of Shocked Solids

Temperature measurement is one of the grand challenges still facing experimental shock physics. A shock experiment fundamentally measures E({sigma}{sub x}, {var_epsilon}{sub 11}) which is an incomplete equation of state since temperature (or entropy) remains unspecified. Ideally, one would like to experimentally determine a free energy F(T, {var_epsilon}{sub ij}) from which all other thermo-mechanical properties might be derived. In practice, temperature measurement would allow direct comparison with theory/simulation since T and {var_epsilon}{sub 11} are in most theories the underlying variables. Temperature is a sensitive measure of energy partitioning, knowledge of which would increase our understanding phase boundaries and thermally activated processes (such as chemical reactivity (including dissociation and ionization)). Temperature measurement would also allow a thermodynamically consistent coupling of hydrodynamic equations of state to the material's constitutive (deformation) behavior. The measurement of the temperature of a material that has undergone severe strains at small time-scales is extremely difficult, and we are developing a method using infrared reflectance and pyrometry. The emitted power from a warm surface is measured over a range of wavelengths using a multi-channel IR detector with a response time of {approx}0.1 {micro}s. Each channel of the detector passes the radiation from a selected wavelength interval into a detector. …
Date: November 5, 2001
Creator: Cazamias, J U; Hare, D E & Poulsen, P
System: The UNT Digital Library
Factors Affecting the Fuel Consumption of Plug-In Hybrid Electric Vehicles (open access)

Factors Affecting the Fuel Consumption of Plug-In Hybrid Electric Vehicles

Primary Factors that Impact the Fuel Consumption of Plug-In Hybrid Electric Vehicles RICHARD ‘BARNEY’ CARLSON, MATTHEW G. SHIRK Idaho National Laboratory 2525 N. Fremont Ave., Idaho Falls, ID 83415, USA richard.carlson@inl.gov Abstract Plug-in Hybrid Electric Vehicles (PHEV) have proven to significantly reduce petroleum consumption as compared to conventional internal combustion engine vehicles (ICE) by utilizing electrical energy for propulsion. Through extensive testing of PHEV’s, analysis has shown that the fuel consumption of PHEV’s is more significantly affected than conventional vehicles by either the driver’s input or by the environmental inputs around the vehicle. Six primary factors have been identified that significantly affect the fuel consumption of PHEV’s. In this paper, these primary factors are analyzed from on-road driving and charging data from over 200 PHEV’s throughout North America that include Hymotion Prius conversions and Hybrids Plus Escape conversions. The Idaho National Laboratory (INL) tests plug-in hybrid electric (PHEV) vehicles as part of its conduct of DOE’s Advanced Vehicle Testing Activity (AVTA). In collaboration with its 75 testing partners located in 23 states and Canada, INL has collected data on 191 PHEVs, comprised of 12 different PHEV models (by battery manufacturer). With more than 1 million PHEV test miles accumulated to …
Date: November 1, 2001
Creator: Carlson, Richard "Barney"; Shirk, Matthew G. & Geller, Benjamin M.
System: The UNT Digital Library
CHANGES IN MOISTURE, CARBON, NITROGEN, SULPHUR, VOLATILES, AND CALORIFIC VALUE OF MISCANTHUS DURING TORREFACTION (open access)

CHANGES IN MOISTURE, CARBON, NITROGEN, SULPHUR, VOLATILES, AND CALORIFIC VALUE OF MISCANTHUS DURING TORREFACTION

Torrefaction tests were carried out on miscanthus samples in order to understand the changes in chemical composition at temperatures of 250–350°C and residence times of 30–120 minutes. The raw material chemical composition was moisture content 7.97%, moisture-free carbon (C) 47.73%, hydrogen (H) 5.85%, nitrogen (N) 0.28%, sulphur (S) 0.02%, volatiles (V) 83.29% for volatiles, and moisture and ash-free (MAF) calorific value (CV) 8423 BTU/lb (19.59 MJ/kg). Torrefaction at temperatures of 250°C and residence time of 30 minutes resulted in a significant decrease in moisture by about 82.68%, but the other components, C, H, N, S, and V changed only marginally. Increasing the torrefaction temperature to 350°C and residence time to 120 minutes further reduced the moisture to a final value of 0.54% (a 93.2% reduction compared to original) and also resulted in a significant decrease in the other components, H, N, and V by 58.29%, 14.28%, and 70.45%, respectively. The carbon content at 350°C and 120 minutes increased by about 4% and sulfur values were below detection limits. The calorific values increased by about 5.59% at 250°C and 30 minutes, whereas at 350°C and 120 minutes, the increase was much greater (about 75.61%) and resulted in a maximum degree of …
Date: November 1, 2001
Creator: Tumuluru, Jaya Shankar; Boardman, Richard; Wright, Christopher & Heintzelman, John
System: The UNT Digital Library
Review of Methods Related to Assessing Human Performance in Nuclear Power Plant Control Room Simulations (open access)

Review of Methods Related to Assessing Human Performance in Nuclear Power Plant Control Room Simulations

With the increased use of digital systems in Nuclear Power Plant (NPP) control rooms comes a need to thoroughly understand the human performance issues associated with digital systems. A common way to evaluate human performance is to test operators and crews in NPP control room simulators. However, it is often challenging to characterize human performance in meaningful ways when measuring performance in NPP control room simulations. A review of the literature in NPP simulator studies reveals a variety of ways to measure human performance in NPP control room simulations including direct observation, automated computer logging, recordings from physiological equipment, self-report techniques, protocol analysis and structured debriefs, and application of model-based evaluation. These methods and the particular measures used are summarized and evaluated.
Date: November 1, 2001
Creator: Blanc, Katya L Le; Boring, Ronald L & Gertman, David I
System: The UNT Digital Library
Hot Wire Needle Probe for In-Pile Thermal Conductivity Detection (open access)

Hot Wire Needle Probe for In-Pile Thermal Conductivity Detection

Thermal conductivity is a key property of interest for both nuclear fuel and structural materials, and must be known for proper design, test, and application of new fuels and structural materials in nuclear reactors. Thermal conductivity is highly dependent on the physical structure, chemical composition, and the state of the material. Typically, thermal conductivity changes that occur during irradiation are measured out-of-pile by Post Irradiated Examination (PIE) using a “cook and look” approach in hot-cells. Repeatedly removing samples from a test reactor to make out-of-pile measurements is expensive, has the potential to disturb phenomena of interest, and only provides understanding of the sample's end state at the time each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for simulation design codes, the development of next generation reactors, and advanced fuels for existing nuclear plants. Being able to quickly characterize fuel thermal conductivity during irradiation can improve the fidelity of data, reduce costs of post-irradiation examinations, increase understanding of how fuels behave under irradiation, and confirm or improve existing thermal conductivity measurement techniques. This paper discusses advancements from Idaho National Laboratory (INL) / Utah State University (USU) examinations, including background information, governing …
Date: November 1, 2001
Creator: Daw, Joshua; Rempe, Joy; Condie, Keith; Knudson, Darrell; Wilkins, S. Curtis; Fox, Brandon S. et al.
System: The UNT Digital Library
Handheld Device for Simultaneous Monitoring of Fast Neutrons and Gamma Rays (open access)

Handheld Device for Simultaneous Monitoring of Fast Neutrons and Gamma Rays

Currently at the INEEL, a handheld device is being developed to measure fast neutrons and gamma rays using a single detector instead of a previous two detector system. The handheld detection system presented here uses a single 1/2 inch (diameter) by 1/2 inch (long) liquid scintillator detector (BC501). This means the detection system can be made smaller, lighter, less expensive, and is expected to be more sensitive than the original system. A smaller and lighter device makes it possible to be used in several applications such as customs inspection, border security, environmental radiation monitoring, and so on. The use of only one detector requires that the neutrons and gamma rays be distinguished by the shape of their pulses in the detector. Two methods of pulse shape discrimination (PSD) are: presented here, charge integration and crossover timing. Figures of merit were calculated for both methods for a threshold energy range of 50 to 600 keV. Results show that the crossover method gives much better PSD for electron energy of 100 keV and lower, whereas the charge integration method leads to better separation above 100 keV. However, the neutrons and gamma rays are totally separated for energies of 100 keV and above …
Date: November 1, 2001
Creator: Aryaeinejad, Rahmat; Reber, Edward Lawrence & Spencer, David Frazer
System: The UNT Digital Library
Characteristics of laser-driven electron acceleration invacuum (open access)

Characteristics of laser-driven electron acceleration invacuum

The interaction of free electrons with intense laser beamsin vacuum is studied using a 3D test particle simulation model thatsolves the relativistic Newton-Lorentz equations of motion inanalytically specified laser fields. Recently, a group of solutions wasfound for very intense laser fields that show interesting and unusualcharacteristics. In particular, it was found that an electron can becaptured within the high-intensity laser region, rather than expelledfrom it, and the captured electron can be accelerated to GeV energieswith acceleration gradients on the order of tens of GeV/cm. Thisphenomenon is termed the capture and acceleration scenario (CAS) and isstudied in detail in this paper. The maximum net energy exchange by theCAS mechanism is found to be approximately proportional to a 2_o, in theregime where a_o>100, where a_o = eE_o/m_ewc is a dimensionlessparameter specifying the magnitude of the laser field. The acceleratedGeV electron bunch is a macro-pulse, with duration equal or less thanthat of the laser pulse, which is composed of many micro-pulses that areperiodic at the laser frequency. The energy spectrum of the CAS electronbunch is presented. The dependence of the energy exchange in the CAS onvarious parameters, e.g., a 2_o (laser intensity), w_o (laser radius atfocus), tao (laser pulse duration), b_o (the impact …
Date: November 1, 2001
Creator: Wang, P. X.; Ho, Y. K.; Yuan, X. Q.; Kong, Q.; Sessler, A. M.; Esarey, E. et al.
System: The UNT Digital Library
Polymeric-Metallic Composite Membranes for High-Temperature Applications (open access)

Polymeric-Metallic Composite Membranes for High-Temperature Applications

Project Objective: Develop a polymeric based membrane that can withstand greater temperatures and pressures than current materials.
Date: November 9, 2001
Creator: Young, Jennifer S.; Jorgensen, Betty S.; Espinoza, Brent F.; Weimer, Marc & Jarvinen, Gordon D.
System: The UNT Digital Library
Selective Catalytic Oxidation of Hydrogen Sulfide to Elemental Sulfur from Coal-Derived Fuel Gases (open access)

Selective Catalytic Oxidation of Hydrogen Sulfide to Elemental Sulfur from Coal-Derived Fuel Gases

The development of low cost, highly efficient, desulfurization technology with integrated sulfur recovery remains a principle barrier issue for Vision 21 integrated gasification combined cycle (IGCC) power generation plants. In this plan, the U. S. Department of Energy will construct ultra-clean, modular, co-production IGCC power plants each with chemical products tailored to meet the demands of specific regional markets. The catalysts employed in these co-production modules, for example water-gas-shift and Fischer-Tropsch catalysts, are readily poisoned by hydrogen sulfide (H{sub 2}S), a sulfur contaminant, present in the coal-derived fuel gases. To prevent poisoning of these catalysts, the removal of H{sub 2}S down to the parts-per-billion level is necessary. Historically, research into the purification of coal-derived fuel gases has focused on dry technologies that offer the prospect of higher combined cycle efficiencies as well as improved thermal integration with co-production modules. Primarily, these concepts rely on a highly selective process separation step to remove low concentrations of H{sub 2}S present in the fuel gases and produce a concentrated stream of sulfur bearing effluent. This effluent must then undergo further processing to be converted to its final form, usually elemental sulfur. Ultimately, desulfurization of coal-derived fuel gases may cost as much as 15% …
Date: November 6, 2001
Creator: Gardner, Todd H.; Berry, David A.; Lyons, K. David; Beer, Stephen K. & Monahan, Michael J.
System: The UNT Digital Library
On the handling of atomic anisotropic displacement parameters (open access)

On the handling of atomic anisotropic displacement parameters

None
Date: November 12, 2001
Creator: Grosse-Kunstleve, Ralf W. & Adams, Paul D.
System: The UNT Digital Library
ADVANCED STEAM GENERATORS (open access)

ADVANCED STEAM GENERATORS

Concerns about climate change have encouraged significant interest in concepts for ultra-low or ''zero''-emissions power generation systems. In some proposed concepts, nitrogen is removed from the combustion air and replaced with another diluent such as carbon dioxide or steam. In this way, formation of nitrogen oxides is prevented, and the exhaust stream can be separated into concentrated CO{sub 2} and steam or water streams. The concentrated CO{sub 2} stream could then serve as input to a CO{sub 2} sequestration process or utilized in some other way. Some of these concepts are illustrated in Figure 1. This project is an investigation of one approach to ''zero'' emission power generation. Oxy-fuel combustion is used with steam as diluent in a power cycle proposed by Clean Energy Systems, Inc. (CES) [1,2]. In oxy-fuel combustion, air separation is used to produce nearly pure oxygen for combustion. In this particular concept, the combustion temperatures are moderated by steam as a diluent. An advantage of this technique is that water in the product stream can be condensed with relative ease, leaving a pure CO{sub 2} stream suitable for sequestration. Because most of the atmospheric nitrogen has been separated from the oxidant, the potential to form any …
Date: November 6, 2001
Creator: Richards, George A.; Casleton, Kent H.; Lewis, Robie E.; Rogers, William A.; Woike, Mark R. & Willis, Brian P.
System: The UNT Digital Library
Overview of NETL In-House Vision 21 Activities (open access)

Overview of NETL In-House Vision 21 Activities

The Office of Science and Technology at the National Energy Technology Laboratory, conducts research in support of Department of Energy's Fossil Energy Program. The research is funded through a variety of programs with each program focusing on a particular aspect of fossil energy. Since the Vision 21 Concept is based on the Advanced Power System Programs (Integrated Gasification Combined Cycle, Pressurized Fluid Bed, HIPPS, Advanced Turbine Systems, and Fuel Cells) it is not surprising that much of the research supports the Vision 21 Concept. The research is classified and presented according to ''enabling technologies'' and ''supporting technologies'' as defined by the Vision 21 Program. Enabling technology include fuel flexible gasification, fuel flexible combustion, hydrogen separation from fuel gas, advanced combustion systems, circulating fluid bed technology, and fuel cells. Supporting technologies include development of advanced materials, computer simulations, computation al fluid dynamics modeling, and advanced environmental control. An overview of Vision 21 related research is described, emphasizing recent accomplishments and capabilities.
Date: November 6, 2001
Creator: Wildman, David J.
System: The UNT Digital Library
Whole genome amplification - Review of applications and advances (open access)

Whole genome amplification - Review of applications and advances

The concept of Whole Genome Amplification is something that has arisen in the past few years as modifications to the polymerase chain reaction (PCR) have been adapted to replicate regions of genomes which are of biological interest. The applications here are many--forensics, embryonic disease diagnosis, bio terrorism genome detection, ''imoralization'' of clinical samples, microbial diversity, and genotyping. The key question is if DNA can be replicated a genome at a time without bias or non random distribution of the target. Several papers published in the last year and currently in preparation may lead to the conclusion that whole genome amplification may indeed be possible and therefore open up a new avenue to molecular biology.
Date: November 15, 2001
Creator: Hawkins, Trevor L.; Detter, J.C. & Richardson, Paul
System: The UNT Digital Library
Flow channeling and analysis of tracer tests in heterogeneous porous media (open access)

Flow channeling and analysis of tracer tests in heterogeneous porous media

Flow and solute transport through porous medium with strongly varying hydraulic conductivity are studied by numerical simulations. The heterogeneity of the porous medium is defined by {sigma} and {lambda}{prime}, which are, respectively, the standard deviation of natural log of permeability values and its correlation range {lambda} divided by transport distance L. The development of flow channeling as a function of these two parameters is demonstrated. The results show that for large heterogeneities, the flow is highly channelized and solute is transported through a few fast paths, and the corresponding breakthrough curves show a high peak at very early times, much shorter than the mean residence time. This effect was studied for a converging radial flow, to simulate tracer tests in a fracture zone or contact-thickness aquifer. It is shown that {sigma}{sup 2}{lambda}{prime} is an appropriate parameter to characterize the tracer dispersion and breakthrough curves. These results are used to study tracer breakthrough data from field experiments performed with nonsorbing tracers. A new procedure is proposed to analyze the results. From the moments of the residence-time distribution represented by the breakthrough curves, the heterogeneity of the porous medium, as characterized by {sigma}{sup 2}{lambda}{prime} and the mean residence time t{sub o}, may …
Date: November 3, 2001
Creator: Moreno, Luis & Tsang, Chin-Fu
System: The UNT Digital Library
Fuel Cell/Turbine Ultra High Efficiency Power System (open access)

Fuel Cell/Turbine Ultra High Efficiency Power System

FuelCell Energy, INC. (FCE) is currently involved in the design of ultra high efficiency power plants under a cooperative agreement (DE-FC26-00NT40) managed by the National Energy Technology Laboratory (NETL) as part of the DOE's Vision 21 program. Under this project, FCE is developing a fuel cell/turbine hybrid system that integrates the atmospheric pressure Direct FuelCell{reg_sign} (DFC{reg_sign}) with an unfired Brayton cycle utilizing indirect heat recovery from the power plant. Features of the DFC/T{trademark} system include: high efficiency, minimal emissions, simplicity in design, direct reforming internal to the fuel cell, no pressurization of the fuel cell, independent operating pressure of the fuel cell and turbine, and potential cost competitiveness with existing combined cycle power plants at much smaller sizes. Objectives of the Vision 21 Program include developing power plants that will generate electricity with net efficiencies approaching 75 percent (with natural gas), while producing sulfur and nitrogen oxide emissions of less than 0.01 lb/million BTU. These goals are significant improvements over conventional power plants, which are 35-60 percent efficient and produce emissions of 0.07 to 0.3 lb/million BTU of sulfur and nitrogen oxides. The nitrogen oxide and sulfur emissions from the DFC/T system are anticipated to be better than the Vision …
Date: November 6, 2001
Creator: Hossein, Ghezel-Ayagh
System: The UNT Digital Library
Virtual Simulation of Vision 21 Energy Plants (open access)

Virtual Simulation of Vision 21 Energy Plants

The Vision 21 Energy plants will be designed by combining several individual power, chemical, and fuel-conversion technologies. These independently developed technologies or technology modules can be interchanged and combined to form the complete Vision 21 plant that achieves the needed level of efficiency and environmental performance at affordable costs. The knowledge about each technology module must be captured in computer models so that the models can be linked together to simulate the entire Vision 21 power plant in a Virtual Simulation environment. Eventually the Virtual Simulation will find application in conceptual design, final design, plant operation and control, and operator training. In this project we take the first step towards developing such a Vision 21 Simulator. There are two main knowledge domains of a plant--the process domain (what is in the pipes), and the physical domain (the pipes and equipment that make up the plant). Over the past few decades, commercial software tools have been developed for each of these functions. However, there are three main problems that inhibit the design and operation of power plants: (1) Many of these tools, largely developed for chemicals and refining, have not been widely adopted in the power industry. (2) Tools are not …
Date: November 6, 2001
Creator: Syamlal, Madhava; Felix, Paul E.; Osawe, Maxwell O.; Fiveland, Woodrow A.; Sloan, David G.; Zitney, Stephen E. et al.
System: The UNT Digital Library
Durable Zinc Oxide-Based Regenerable Sorbents for Desulfurization of Syngas in a Fixed-Bed Reactor (open access)

Durable Zinc Oxide-Based Regenerable Sorbents for Desulfurization of Syngas in a Fixed-Bed Reactor

A fixed-bed regenerable desulfurization sorbent, identified as RVS-land developed by researchers at the U.S. Department of Energy's National Energy Technology Laboratory, was awarded the R&D 100 award in 2000 and is currently offered as a commercial product by Sued-Chemie Inc. An extensive testing program for this sorbent was undertaken which included tests at a wide range of temperatures, pressures and gas compositions both simulated and generated in an actual gasifier for sulfidation and regeneration. This testing has demonstrated that during these desulfurization tests, the RVS-1 sorbent maintained an effluent H2S concentration of <5 ppmv at temperatures from 260 to 600 C (500-1100 F) and pressures of 203-2026 kPa(2 to 20 atm) with a feed containing 1.2 vol% H{sub 2}S. The types of syngas tested ranged from an oxygen-blown Texaco gasifier to biomass-generated syngas. The RVS-1 sorbent has high crush strength and attrition resistance, which, unlike past sorbent formulations, does not decrease with extended testing at actual at operating conditions. The sulfur capacity of the sorbent is roughly 17 to 20 wt.% and also remains constant during extended testing (>25 cycles). In addition to H{sub 2}S, the RVS-1 sorbent has also demonstrated the ability to remove dimethyl sulfide and carbonyl sulfide …
Date: November 6, 2001
Creator: Siriwardane, Ranjani V.; Cicero, Daniel C. (U.S. Department of Energy, National Energy Technology Laboratory, Morgantown); Stiegel, Gary J.; Gupta, Raghubir P. (U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh) & Turk, Brian S. (Research Triangle Institute)
System: The UNT Digital Library
Development of Foster Wheeler's Vision 21 Partial Gasification Module (open access)

Development of Foster Wheeler's Vision 21 Partial Gasification Module

The US Department of Energy (DOE) has awarded Foster Wheeler Development Corporation a contract to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ({approx} 2500 to 2800F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. …
Date: November 6, 2001
Creator: Robertson, A.
System: The UNT Digital Library
Criticality and phase behavior in the restricted-primitive model electrolyte: Effect of ionic association (open access)

Criticality and phase behavior in the restricted-primitive model electrolyte: Effect of ionic association

Ion association is incorporated into the restricted-primitive model (RPM) electrolyte to account for the strong attraction between unlike ions. Two methods are investigated within the McMillan-Mayer framework: first is the binding mean-spherical approximation (BIMSA) based on the Wertheim Ornstein-Zernike integral equation formalism; and the second is the combination of the BIMSA with a simple interpolation scheme (SIS) based on the Wertheim thermodynamic perturbation theory. The latter gives a better description. Four different association constants are used to calculate the degree of dissociation, the critical point and the vapor-liquid coexistence curve. An increase in the association constant leads to a lower critical temperature and a higher critical density, and better agreement with computer simulations. When unlike ions are fully paired, corresponding to a charged hard dumbbell (CHDB) system, we obtain the best agreement with the most recent computer simulations of the RPM electrolyte.
Date: November 1, 2001
Creator: Jiang, Jianwen; Blum, Lesser; Bernard, Oliver & Prausnitz, John M.
System: The UNT Digital Library
Circulating Fluid-Bed Technology for Advanced Power Systems (open access)

Circulating Fluid-Bed Technology for Advanced Power Systems

Circulating fluid bed technology offers the advantages of a plug flow, yet well-mixed, and high throughput reactor for power plant applications. The ability to effectively scale these systems in size, geometry, and operating conditions is limited because of the extensive deviation from ideal dilute gas-solids flow behavior (Monazam et al., 2001; Li, 1994). Two fluid computations show promise of accurately simulating the hydrodynamics in the riser circulating fluid bed; however, validation tests for large vessels with materials of interest to the power industry are lacking (Guenther et al., 2002). There is little available data in reactors large enough so that geometry (i.e. entrance, exit, and wall) effects do not dominate the hydrodynamics, yet with sufficiently large particle sizes to allow sufficiently large grid sizes to allow accurate and timely hydrodynamic simulations. To meet this need experimental tests were undertaken with relatively large particles of narrow size distribution in a large enough unit to reduce the contributions of wall effects and light enough to avoid geometry effects. While computational fluid dynamic calculations are capable of generating detailed velocity and density profiles, it is believed that the validation and model development begins with the ability to simulate the global flow regime transitions. …
Date: November 6, 2001
Creator: Shadle, Lawrence J.; Ludlow, J. Christopher; Mei, Joseph S. & Guenther, Christopher
System: The UNT Digital Library
A practical approach to the interGroup protocols (open access)

A practical approach to the interGroup protocols

Existing reliable ordered group communication protocols have been developed for local-area networks and do not, in general, scale well to large numbers of nodes and wide-area networks. The InterGroup suite of protocols is a scalable group communication system that introduces an unusual approach to handling group membership, and supports a receiver-oriented selection of service. The protocols are intended for a wide-area network, with a large number of nodes, that has highly variable delays and a high message loss rate, such as the Internet. The levels of the message delivery service range from unreliable unordered to reliable timestamp ordered. We also present a secure group layer that builds on InterGroup to provide SSL-like security for groups.
Date: November 12, 2001
Creator: Berket, Karlo; Agarwal, Deborah A. & Chevassut, Olivier
System: The UNT Digital Library
Partitioning of clay colloids at air-water interfaces (open access)

Partitioning of clay colloids at air-water interfaces

None
Date: November 13, 2001
Creator: Wan, Jiamin & Tokunaga, Tetsu K.
System: The UNT Digital Library