bluuebunny/crossref_metadata_2025 huggingface dataset:
An NCME Instructional Module on Exploring the Logic of Tatsuoka's Rule‐Space Model for Test Development and Analysis
Authors: Gierl Mark J. , Leighton Jacqueline P. , Hunka Stephen M.
Published: October 2005

K. Tatsuoka's rule‐space model is a statistical method for classifying examinees' test item responses into a set of attribute‐mastery patterns associated with different cognitive skills. A fundamental assumption in the model resides in the idea that test items may be described by specific cognitive skills called attributes which can include distinct procedures, skills, or processes possessed by an examinee. The rule‐space model functions by collecting and ordering information about the attributes required to solve test items and then statistically classifying examinees' test item responses into a set of attribute‐mastery patterns, each one associated with a unique cognitive blueprint. The logic of Tatsuoka's rule‐space model, as it applies to test development and analysis, is examined an this module. Controversies and unresolved issues are also presented and discussed.
Incorporating the Testlet Concept in Test Score Analyses1
Authors: Lee Guemin , Brennan Robert L. , Frisbie David A.
Published: October 2005

How should we think about the concept of the testlet? How can testlets be better incorporated into test score analysis? Can there be a one‐item testlet?
Informed Test Component Weighting
Authors: Rudner Lawrence M.
Published: October 2005

How can we combine a multiple‐choice assessment with a performance assessment to yield a single score? What alternatives are there for weighting components of a test? What effect does reliability and validity have in component weighting?
An Investigation of Alternative Methods for Item Mapping in the National Assessment of Educational Progress
Authors: Zwick Rebecca , Senturk Deniz , Wang Joyce , Loomis Susan Cooper
Published: October 2005

What is item mapping and how does it aid test score interpretation? Which item mapping technique produces the most consistent results and most closely matches expert opinion?
East Meets West in Assessment Development: Western Technical Assistance to Eastern Needs. Part III. Reform of an Examination System: Shoulder to Shoulder in the Polish SMART Project
Authors: Annemarie de Knecht‐van Eekelen  , Bakker Steven , van Lent Gerben
Published: October 2005

This is Part III of a three part series describing the consultancy and training demands that are encountered in technical assistance projects in Central and Eastern Europe. Part I dealt with strategic issues for a successful delivery of “Western Technical Assistance to Eastern Needs.” Part II highlighted project management and co‐operation aspects in delivering support to the Romanian Assessment and Examination Service. In this part, we address training of Polish subject experts who were preparing to take on responsibility for a decentralized and strongly innovative final exam, the Matura.
Seeking Redemption for Our Psychometric Sins
Authors: Popham W. James
Published: October 2005

Many American children are currently receiving a reduced quality education because of the increasingly widespread misuse of educational tests. Employing a religious metaphor, the author argues that members of the educational measurement community are culpable, at least in part, for this calamity. During recent decades, our nation's assessment personnel have failed to speak out vigorously against the increasingly prevalent improper use of traditionally constructed achievement tests to appraise school quality. This absence of action, it is claimed, constitutes a nontrivial sin of omission. To secure absolution for that sin, it is contended that measurement specialists must promote widespread assessment literacy.
Multiple Measures: Alternative Design and Analysis Models
Authors: Henderson‐Montero Dianne , Julian Marc W. , Yen Wendy M.
Published: October 2005

The use of multiple measures is emphasized by legislation regulating the distribution of Title I funding to states, as well as by professional and industry standards regarding the use of test scores in high‐stakes decisions. There are a wide variety of methods with which multiple measures can be designed and analyzed, and these methods have different implications for conclusions that will be reached. Recognizing the complexities associated with the implementation of a multiple measures approach to system evaluation, this article provides an overview and discussion of alternative models that may be considered in an accountability system and their applicability relative to the goals of the system evaluation. The article concludes with an example of the use of multiple measures with regard to No Child Left Behind legislation.
Analyzing the Minority Gap in Achievement Scores: Issues for States and Federal Government
Authors: Miller G. Edward
Published: October 2005

The No Child Left Behind Act of 2001 requires that states demonstrate a reduction in the test score minority gap over time but does not specify what methodology states must use to demonstrate this. The Act also requires that a measure of Adequate Yearly Progress be established by each state expressed in terms of the percent of students who achieve a level of “proficiency” on the state examination. While the most common methods used by states for analyzing the minority gap in test scores over time are percent achieving a performance standard, mean scale scores, and effect sizes, the default method for analyzing the minority gap will likely be the percent achieving proficiency. This article considers some of the practical issues involved in using the percent achieving a performance standard, mean scale scores, and effect sizes to analyze the minority gap using Texas student performance on their in‐state assessment, National Assessment of Educational Progress (NAEP), and SAT. The intent of the article is to increase the understanding of policymakers and others on the issues of using the various statistics to analyze the minority gap.
Developing Measurement Theory for Classroom Assessment Purposes and Uses
Authors: Brookhart Susan M.
Published: October 2005

In many fields of inquiry, the need for new theoretical developments is often best seen in areas of strain, and strain is apparent in several areas in which the conventions of measurement theory do not quite “fit” classroom assessment. Three areas of strain are analyzed in order to suggest how theoretical development might focus directly on information quality in the classroom assessment context. This article describes the context dependence of classroom assessment, its inextricable relationship with instruction, and its simultaneous formative and summative functions. Thus a case is made for new theoretical developments in the area of measurement in the classroom.
SAT Validity for Linguistic Minorities at the University of California, Santa Barbara
Authors: Zwick Rebecca , Schlemer Lizabeth
Published: October 2005

The validity of the SAT as an admissions criterion for Latinos and Asian Americans who are not native English speakers was examined. The analyses, based on 1997 and 1998 UCSB freshmen, focused on the effectiveness of SAT scores and high school grade‐point average (HSGPA) in predicting college freshman grade‐point average (FGPA). When regression equations were estimated based on all students combined, some systematic prediction errors occurred. For language minorities, using only high school grades as a predictor led to predicted FGPAs that tended to exceed actual FGPAs, particularly for Latinos. Including SAT scores in the equation notably reduced prediction bias. Further analyses showed that, while HSGPA had the highest correlation with FGPA for most groups, SAT verbal score was the strongest predictor of FGPA for language minorities in 1998. An overriding conclusion is that combining data across language groups can obscure important test validity information.
Introduction to the Special Issue on Nebraska's Alternative Approach to Statewide Assessment
Authors: Bandalos Deborah L.
Published: October 2005

Nebraska's Standards‐based, Teacher‐led Assessment and Reporting System (STARS) is unique in its focus on locally developed, classroom‐based assessments in lieu of a state test. The purpose of this special issue is to introduce the STARS model and discuss the problems inherent in such a system. Other articles in this issue address issues of quality control and comparability of assessments, the development of teacher assessment literacy, and teachers' reactions to the implementation of STARS.
Modeling Passing Rates on a Computer‐Based Medical Licensing Examination: An Application of Survival Data Analysis
Authors: de Champlain André F. , Winward Marcia L. , Dillon Gerard F. , de Champlain Judy E.
Published: October 2005

The purpose of this article was to model United States Medical Licensing Examination (USMLE) Step 2 passing rates using the Cox Proportional Hazards Model, best known for its application in analyzing clinical trial data. The number of months it took to pass the computer‐based Step 2 examination was treated as the dependent variable in the model. Covariates in the model were: (a) medical school location (U.S. and Canadian or other), (b) primary language (English or other), and (c) gender. Preliminary findings indicate that examinees were nearly 2.7 times more likely to experience the event (pass Step 2) if they were U.S. or Canadian trained. Examinees with English as their primary language were 2.1 times more likely to pass Step 2, but gender had little impact. These findings are discussed more fully in light of past research and broader potential applications of survival analysis in educational measurement.
Professor Paul Horst's Legacy: A Differential Prediction Model for Effective Guidance in Course Selection
Authors: Clemans William V. , Lunneborg Clifford E. , Raju Nambury S.
Published: October 2005

The role of testing in determining college admissions and the impact of that testing on high school students are commanding increasing attention. There is emerging evidence that admissions decisions made solely on the basis of high school record can serve the college as well or better than decisions based, at least in part, on scores obtained on admissions tests. Further, though there is a recognized need for guidance, the tests in current use for admission provide limited information for helping students in making course selections that would make the best use of their abilities. This article reviews an alternative, long neglected and little known, for testing at the high school‐college interface that would meet this need. Testing to provide differential prediction of college performance, as proposed by Paul Horst, focuses on allowing students to make the best match between their achievements, interests, and goals with the undergraduate programs of study available to them.
A Fast Direct Solution Method for Nonlinear Equations in an Analytic Element Model
Authors: Haitjema Henk M.
Published: October 2005

The analytic element method, like the boundary integral equation method, gives rise to a system of equations with a fully populated coefficient matrix. For simple problems, these systems of equations are linear, and a direct solution method, such as Gauss elimination, offers the most efficient solution strategy. However, more realistic models of regional ground water flow involve nonlinear equations, particularly when including surface water and ground water interactions. The problem may still be solved by use of Gauss elimination, but it requires an iterative procedure with a reconstruction and decomposition of the coefficient matrix at every iteration step. The nonlinearities manifest themselves as changes in individual matrix coefficients and the elimination (or reintroduction) of several equations between one iteration and the other. The repeated matrix reconstruction and decomposition is computationally intense and may be avoided by use of the Sherman‐Morrison formula, which can be used to modify the original solution in accordance with (small) changes in the coefficient matrix. The computational efficiency of the Sherman‐Morrison formula decreases with increasing numbers of equations to be modified. In view of this, the Sherman‐Morrison formula is only used to remove equations from the original set of equations, while treating all other nonlinearities by use of an iterative refinement procedure.
Achieving Excellence in Practice: A Model for Continuing Education for Nurse Practitioners
Authors: Green Roger , Gorzka Patricia , Kodish Slavica
Published: October 2005

Purpose

To provide a continuing education (CE) model that will meet varied needs of nurse practitioners by incorporating the variable of years of experience in practice setting.

Data sources

An empirical study conducted over a period of approximately 10 months, from Fall 2002 to Spring 2003 in one of the southeastern states.

Conclusions

A model has been developed to plan and deliver CE education programs based on the changing CE needs of NPs as they gain experience and expertise.

Implications for practice

Results of this study may be used to guide providers to develop and offer CE programs based on the CE needs of NPs related to length of time in clinical practice, general issues of practice, and specialty practice area needs.
Knowledge, Perceptions, and Attitudes of Advanced Practice Nursing Students Regarding Medical Genetics
Authors: Maradiegue Ann , Edwards Quannetta T. , Seibert Diane , Macri Charles , Sitzer Lauren
Published: October 2005

Purpose

To describe the current medical genetic knowledge and perceptions of graduate advanced practice nursing (advanced practice nurse [APN]/nurse practitioner and nurse anesthetist) students using survey data for future integration of genetic topics, principles, and healthcare issues into curriculum.

Data sources

Survey data of APNs’ perceived knowledge of genetics and a review of the literature from past research studies of students and current articles from professional journals and organizations. Web sites were those of the National Coalition of Health Professions for Education in Genetics and National Institutes of Health, Human Genome Research Institute; professional organizations; and the authors’ professional, clinical, and educational experiences.

Conclusions

Most APN students perceived they had minimum knowledge and prior training regarding medical genetics. There is a need to integrate genetic concepts, principles, and medical conditions into advanced practice nursing curriculum and to provide clinical experiences in genetic conditions across the life span and throughout the health and illness spectrum. APN students have positive attitudes toward integrating genetics into graduate curricula. Potential methods for program integration include readings, small group discussion, standardized patients, and role‐play as measures to increase information.

Implications for practice

The National Coalition for Health Profession Education in Genetics, the American Nursing Association, and the American College of Nursing Education have recommended integration of genetics knowledge and skills into routine health care to provide effective interventions for individuals and families. However, previous research and data from this study have revealed that many nurses have minimal training in genetics. Advanced practice nurses must be knowledgeable on genetic principles, topics, and the ethical, legal, and social implications related to medical genetics to increase the ability to diagnose, prevent, and treat diseases and to provide effective care for individuals and families.
Health Care for the Homeless Assesses the Use of Adapted Clinical Practice Guidelines
Authors: Strehlow Aaron J. , Kline Susan , Zerger Suzanne , Zlotnick Cheryl , Proffitt Brenda
Published: October 2005

COLUMN EDITOR: Mary Jo Goolsby

This article describes a process of evaluating and adapting existing clinical practice guidelines (CPGs) for homeless individuals by different healthcare providers in multiple healthcare settings across the country. Data were collected using a standardized evaluation tool in nine sites across the United States. Clinicians completed an evaluation of the CPG after every use. Most clinicians used the CPG five times. Descriptive statistics were reported on the characteristics of the clinicians, and the utility of the guidelines and written comments. Clinicians had an average of 12 years of clinical experience, 8 years of which were specifically spent working with homeless individuals. Ninety‐one percent of the clinicians practiced in urban settings. The majority of clinicians felt the adapted guidelines met evaluation criteria. The major weaknesses reported the delineation of outreach and case management activities. Results did not vary by clinicians’ disciplines, years of experience, or any other indicators. Clients and clinicians providing primary care to homeless individuals may benefit from utilizing Health Care for the Homeless Clinicians’ Network adapted CPGs to assure quality, evidenced‐based care to a vulnerable population.
Barriers to Coronary Heart Disease Risk Modification in Women without Prior History of Coronary Heart Disease
Authors: Thanavaro Joanne L.
Published: October 2005

Purpose

To explore the extent to which women perceive barriers to coronary heart disease (CHD) risk modification and to determine if access to a nurse practitioner (NP) decreases perceived barriers to CHD risk modification.

Data sources

Surveys completed by 120 women between the ages of 35 and 60 years, with no known history of CHD. The barriers scale was used to examine women's perceived barriers to CHD risk modification.

Conclusions

Women with access to an NP had less perceived barriers to CHD risk modification.

Implications for practice

NPs are ideally suited to decrease the mortality and morbidity associated with CHD through education strategies and attention to individual barriers women face when attempting to incorporate CHD risk factor modification into their lifestyles.
Educational Options for Acute Care Nurse Practitioner Practice
Authors: Kleinpell Ruth M. , Perez Diego F. , McLaughlin Richard
Published: October 2005

Purpose

During the Acute Care Interest Group Forum held on June 18, 2005, at the American Academy of Nurse Practitioner's Conference, it was identified that information on educational options for acute care nurse practitioner (ACNP) practice was needed, particularly for NPs who may have had other educational preparation but who were now working in acute care practice settings. As a result, a workgroup was formed to compile information on educational options for ACNP practice, including post‐master's programs.

Data sources

Web site descriptions of ACNP programs (n= 70) and, as needed, phone calls to ACNP programs to obtain information on program offerings including post‐master's and distance‐learning options.

Conclusions

Educational options for ACNP practice include master's and post‐master's programs, along with national certification. A growing number of educational programs offer post‐master's options as well as distance‐learning formats for coursework.

Implications for practice

NPs interested in obtaining ACNP education, including those with other NP specialty education who are now working in acute care settings, have a number of choices for pursuing ACNP practice. NPs working in acute care need to ensure that their educational preparation meets the requirements set forth by the scope of standards for ACNP practice and national requirements and state regulations.
Numerical Analysis of Metallic Nanoparticle Synthesis Using RF Inductively Coupled Plasma Flows
Authors: Shigeta Masaya , Nishiyama Hideya
Published: October 2005

A thermal plasma flow is regarded as a multifunctional fluid with high energy density, high chemical reactivity, variable properties, and controllability by electromagnetic fields. Especially a radio frequency inductively coupled plasma (RF-ICP) flow has a large plasma volume, long chemical reaction time, and a high quenching rate. Besides, it is inherently clean because it is produced without internal electrodes. An RF-ICP flow is, therefore, considered to be very useful for nanoparticle synthesis. However, nanoparticle synthesis using an RF-ICP flow includes complicated phenomena with field interactions. In the present study, numerical analysis was conducted to investigate the synthesis of metallic nanoparticles using an advanced RF-ICP reactor. An advanced RF-ICP flow is generated by adding direct current (DC) discharge to a conventional RF-ICP flow in order to overcome the disadvantages of a conventional one. The objectives of the present work are to clarify the formation mechanism of metallic nanoparticles in advanced RF-ICP flow systems and to detect effective factors on required synthesis. A two-dimensional model as well as a one-dimensional model was introduced for nanoparticle growth to investigate effects of spatial distributions of thermofluid fields in RF-ICP flows on synthesized nanoparticles. In an advanced RF-ICP flow, a characteristic recirculation zone disappears due to a DC plasma jet. Larger numbers of nanoparticles with smaller size are produced by using an advanced RF-ICP flow. Thermofluid fields in RF-ICP flows can be controlled by applied coil frequency by means of skin effect. Larger numbers of nanoparticles with smaller size are produced near the central axis. Dispersion of particle size distributions can be suppressed by higher applied coil frequency through control of RF-ICP flows. Applied coil frequency can be a remarkably effective factor to control nanoparticle size distribution.
A Mixed-Mesh and New Angular Space Discretization Scheme of Discontinuous Finite Element Method for Three-Dimensional Radiative Transfer in Participating Media
Authors: Cui X. , Li B. Q.
Published: October 2005

This paper presents a discontinuous finite element method for the numerical solution of internal thermal radiation problems in three-dimensional (3D) geometries using an unstructured mesh of mixed elements. Mathematical formulation, numerical implementation, and computational details are given. The different domain discretization methods are presented, and a new angular space discretization is also given. Numerical examples are presented for 3D radiative transfer in emitting, absorbing, and scattering media. Computed results compare well with analytical solutions whenever available. The localized formulation intrinsic in discontinuous finite elements is considered particularly useful for computational radiation heat transfer in participating media.
Heterogeneous Nucleation With Artificial Cavities
Authors: Qi Yusen , Klausner James F.
Published: October 2005

Bubble incipience in artificial cavities manufactured from silicon has been studied using gas nucleation and pool boiling. Moderately wetting water and highly wetting ethanol have both been used as the bulk fluid with cylindrical cavities, as well as those with a triangle, square, and rectangle shape cross section. Nominal cavity sizes range from 8to60μm. The incipience conditions observed for water using both gas nucleation and pool boiling suggest that bubble initiation originates from a concave meniscus. Cornwell’s contact angle hysteresis theory for vapor-trapping cavities is used to explain the gas nucleation results. The pool boiling results are more difficult to explain. Using ethanol, cavities appeared to be completely flooded and were not activated using either gas nucleation or pool boiling. Using water and gas nucleation, cavities were almost always activated, provided the incipience criterion was satisfied; in contrast cavities in pool boiling with water activated with different superheats during different experiments. The difference in incipience behavior between gas nucleation and pool boiling with water is explained based on vapor-trapping and thermal suppression considerations. Based on limited experimental results, it appears that the backpressure does not influence gas bubble incipience, provided the pressure difference is the same. The experimental results presented affirm the theory of heterogeneous nucleation from vapor-trapping cavities provided contact angle hysteresis and vapor trapping are fully accounted for. However, the results also suggest that the theoretical considerations required for a deterministic model for incipience from vapor-trapping cavities during boiling is more complex than previously hypothesized.
Predicting Thermal Contact Resistance Between Molten Metal Droplets and a Solid Surface
Authors: Heichal Yoav , Chandra Sanjeev
Published: October 2005

Thermal contact resistance between molten metal droplets (aluminum alloy 380 and bismuth) and solid plates (steel and brass) was measured experimentally. The diameter of the droplets was 4mm, and droplet impact velocity ranged between 1 and 3m∕s. Substrate temperature was varied from 25to300°C and roughness from 0.06to5.0μm. Substrate temperature variation under impacting droplets was measured using fast temperature sensors that had a response time of 40ns and recorded substrate temperatures at five different radial locations under each droplet. Thermal contact resistance during the first few milliseconds of impact was obtained by matching measured surface temperature variation with an analytical solution of the one-dimensional transient heat conduction equation. An analytical model of the deformation of a free liquid surface in contact with a rough solid was used to calculate the true area of contact between them and, thereby, the thermal contact resistance. Test results agreed well with predictions from the analytical model. Thermal contact resistance values ranged from 10−7to3×10−6m2K∕W, increasing with surface roughness and decreasing with rising impact velocity.
Evaluation of an Alkaline Fuel Cell for Multifuel System
Authors: Verma A. , Jha A. K. , Basu S.
Published: October 2005

The performance of an alkaline fuel cell (AFC) is investigated using three different fuels, e.g., methanol, ethanol, and sodium borohydride. Pt∕C∕Ni was used as anode, whereas MnO2∕C∕Ni was used as standard (Electro-Chem-Technic, UK) cathode for all the fuels. Fresh mixture of electrolyte, potassium hydroxide (5M), and fuel (2M) was fed to AFC and withdrawn at a rate of 1ml∕min. The anode was prepared by dispersing platinum and activated carbon in Nafion® (DuPont USA) dispersion and placing it onto a carbon paper (Lydall, USA). Finally prepared anode material was pressed onto Ni mesh and sintered to produce the required anode. The maximum power density of 16.5mW∕cm2 is obtained at 28mA∕cm2 of current density for sodium borohydride at 25°C, whereas methanol produces 31.5mW∕cm2 of maximum power density at 44mA∕cm2 of current density at 60°C. The results obtained showed that the AFC could accept multifuels.
The Biased Laminar By-Pass Fluidic Flowmeter
Authors: Priestman Geoffrey H. , Boucher Robert F.
Published: October 2005

This paper demonstrates that the range of a fluidic flow meter can be significantly extended by connecting it in parallel with a fixed laminar by-pass resistance. Analysis shows how for any particular specification, there is an optimum combination of meter and by-pass which maximizes the flow range. Validation tests were done in air, using a fluidic target meter integrated into a housing with a laminar by-pass of parallel rectangular cross section passages formed between flat plates. Results obtained showed excellent agreement with analytical predictions, almost doubling the operating range for the typical specification chosen, a major advance in the context of the previous research aimed at extending meter range. In principle the concept should be applicable to any flowmeter having a suitable Eulerian pressure-flow characteristic.
A Quantitative Comparison of Delta Wing Vortices in the Near-Wake For Incompressible and Supersonic Free Streams
Authors: Wang Frank Y. , Milanovic Ivana M. , Zaman Khairul B. M. Q. , Povinelli Louis A.
Published: October 2005

When requiring quantitative data on delta wing vortices for design purposes, low-speed results have often been extrapolated to configurations intended for supersonic operation. This practice stems from a lack of database in high-speed flows due to measurement difficulties. In the present paper an attempt is made to examine this practice by comparing data from an incompressible flow experiment designed specifically to correspond to an earlier experiment in supersonic flows. The comparison is made for a 75° sweptback delta wing at angles of attack of 7° and 12°. For the incompressible flow, detailed flow-field properties including vorticity and turbulence characteristics are obtained by hot-wire and pressure probe surveys. The results are compared, wherever possible, with available data from the earlier Mach 2.49 experiment. The results indicate that quantitative similarities exist in the distributions of total pressure and swirl velocities. Qualitative similarities also exist in other properties, however, many differences are observed. The vortex core is smaller and rounded at low speed. At high speed, it is elongated in the spanwise direction near the trailing edge but goes through “axis switching” within a short distance downstream. The vortex is located farther outboard, i.e., the spacing between the two legs of the vortex pair is larger, at low speed. The axial velocity distribution within the core is significantly different in the two flow regimes. A “jet-like” profile, observed at low speed, either disappears or becomes “wake-like” at high speed. The axial velocity characteristics are examined in the light of an analytical model.
Modeling of Supercritical CO2 Flow Through Short Tube Orifices
Authors: Zhang Chun-Lu , Yang Liang
Published: October 2005

The transcritical cycle of carbon dioxide (CO2) is a promising alternative approach to heat pumps and automobile air conditioners. As an expansion device, the short tube orifice in a transcritical CO2 system usually receives supercritical fluid at the entrance and discharges a two-phase mixture at the exit. In this work, a two-fluid model (TFM) is developed for modeling the flow characteristics of supercritical CO2 through the short tube orifice. The deviations between the TFM predictions and the measured mass flow rates are within ±20%. Meanwhile, the TFM predicts reasonable pressure, temperature, and velocity distributions along the tube length. The small values of interphase temperature difference and velocity slip indicate that the nonequilibrium characteristics of the two-phase flow of CO2 in the short tube orifice are not significant. Consequently, the homogeneous equilibrium model reduced from the TFM gives a good prediction of the mass flow rate as well.
Extended Velocity–Enthalpy Relations for Wall-Bounded and Free Shear Layers
Authors: van Oudheusden B. W.
Published: October 2005

The relation between the velocity and the enthalpy in steady shear flow is expressed by the Crocco–Busemann relation, which states that for adiabatic conditions the total enthalpy remains constant throughout the shear layer when the Prandtl number is one. The subject of the present Technical Brief is the rational extension of this concept in case the Prandtl number differs from one. The comparison between wall-bounded and free shear flows is studied in particular, as well as the possible application of the concept in turbulent shear flow.
Experimental Methods for Hydrodynamic Characterization of a Very Large Water Tunnel
Authors: Park Joel T. , Cutbirth J. Michael , Brewer Wesley H.
Published: October 2005

The methodology for hydrodynamic characterization of a very large water tunnel is described. Results are presented for the U. S. Navy William B. Morgan Large Cavitation Channel in Memphis, Tennessee, the world’s largest water tunnel. Three key characteristics of tunnel velocity were measured: temporal stability̱, spatial uniformity̱, and turbulence̱. The velocity stability at a single point for run times greater than 2 h was measured as ±0.15% at the 95% confidence level for velocities from 0.5 to 18m∕s(1.6–59ft∕s). The spatial nonuniformity for the axial velocity component was ±0.34 to ±0.60% for velocities from 3 to 16m∕s(9.8–52ft∕s). The relative turbulence intensity was measured as 0.2–0.5% depending on tunnel velocity.
Level-Set Computations of Free Surface Rotational Flows
Authors: Colicchio Giuseppina , Landrini Maurizio , Chaplin John R.
Published: October 2005

A numerical method is developed for modeling the violent motion and fragmentation of an interface between two fluids. The flow field is described through the solution of the Navier-Stokes equations for both fluids (in this case water and air), and the interface is captured by a Level-Set function. Particular attention is given to modeling the interface, where most of the numerical approximations are made. Novel features are that the reintialization procedure has been redefined in cells crossed by the interface; the density has been smoothed across the interface using an exponential function to obtain an equally stiff variation of the density and of its inverse; and we have used an essentially non-oscillatory scheme with a limiter whose coefficients depend on the distance function at the interface. The results of the refined scheme have been compared with those of the basic scheme and with other numerical solvers, with favorable results. Besides the case of the vertical surface-piercing plate (for which new laboratory measurements were carried out) the numerical method is applied to problems involving a dam-break and wall-impact, the interaction of a vortex with a free surface, and the deformation of a cylindrical bubble. Promising agreement with other sources of data is found in every case.
Parallel DSMC Simulation of a Single Under-Expanded Free Orifice Jet From Transition to Near-Continuum Regime
Authors: Wu J.-S. , Chou S.-Y. , Lee U.-M. , Shao Y.-L. , Lian Y.-Y.
Published: October 2005

This paper describes the numerical analysis of the flow structure of a single underexpanded argon free jet issuing into a lower-pressure or vacuum environment using the parallel three-dimensional direct simulation Monte Carlo (DSMC) method employing dynamic domain decomposition. Unstructured and tetrahedral solution-based refined mesh depending on the local mean free path is used to improve the resolution of solution. Simulated Knudsen numbers of the stagnation conditions based on orifice diameter, Reynolds numbers based on the conditions at the orifice exit, and stagnation-to-background pressure ratios are in the range of 0.0005–0.1, 7–1472, and 5-∞, respectively, where “∞” represents vacuum condition in the background environment. Results show that centerline density decays in a rate proportional to the inverse of the square of the axial distance (z−2) from the orifice for all ranges of flow in the current study. The more rarefied the background condition is, the longer the z−2-regime is. In addition, a distinct flow structure, including barrel shock, Mach disk and jet boundary, is clearly identified as the Knudsen number reaches as low as 0.001. Predicted location and size of Mach disk in the near-continuum limit (Kn=0.001,0.0005) are found to be in reasonable agreement with experimental results in the continuum regime.
The Development Lengths of Laminar Pipe and Channel Flows
Authors: Durst F. , Ray S. , Ünsal B. , Bayoumi O. A.
Published: October 2005

The authors’ research work into fully developed pulsating and oscillating laminar pipe and channel flows raised questions regarding the development length of the corresponding steady flow. For this development length, i.e., the distance from the entrance of the pipe to the axial position where the flow reaches the parabolic velocity profile of the Hagen-Poiseuille flow, a wide range of contradictory data exists. This is shown through a short review of the existing literature. Superimposed diffusion and convection, together with order of magnitude considerations, suggest that the normalized development length can be expressed as L∕D=C0+C1Re and for Re→0 one obtains C0=0.619, whereas for Re→∞ one obtains C1=0.0567. This relationship is given only once in the literature and it is presumed to be valid for all Reynolds numbers. Numerical studies show that it is only valid for Re→0 and Re→∞. The development length of laminar, plane channel flow was also investigated. The authors obtained similar results to those for the pipe flow: L∕D=C0′+C1′; Re, where C0′=0.631 and C1′=0.044. Finally, correlations are given to express L∕D analytically for the entire Re range for both laminar pipe and channel flows.
Turbulent Mixing of Two Immiscible Fluids
Authors: Lemenand Thierry , Dupont Pascal , Della Valle Dominique , Peerhossaini Hassan
Published: October 2005

The emulsification process in a static mixer HEV (high-efficiency vortex) in turbulent flow is investigated. This new type of mixer generates coherent large-scale structures, enhancing momentum transfer in the bulk flow and hence providing favorable conditions for phase dispersion. We present a study of the single-phase flow that details the flow structure, based on LDV measurements, giving access on the scales of turbulence. In addition, we discuss the liquid-liquid dispersion of oil in water obtained at the exit of the mixer/emulsifier. The generation of the dispersion is characterized by the Sauter diameter and described via a size-distribution function. We are interested in a local turbulence analysis, particularly the spatial structure of the turbulence and the turbulence spectra, which give information about the turbulent dissipation rate. Finally, we discuss the emulsifier efficiency and compare the HEV performance with existing devices.
Skin Friction Correlation for Smooth and Rough Wall Turbulent Boundary Layers
Authors: Bergstrom D. J. , Akinlade O. G. , Tachie M. F.
Published: October 2005

In this paper, we propose a novel skin friction correlation for a zero pressure gradient turbulent boundary layer over surfaces with different roughness characteristics. The experimental data sets were obtained on a hydraulically smooth and ten different rough surfaces created from sand paper, perforated sheet, and woven wire mesh. The physical size and geometry of the roughness elements and freestream velocity were chosen to encompass both transitionally rough and fully rough flow regimes. The flow Reynolds number based on momentum thickness ranged from 3730 to 13,550. We propose a correlation that relates the skin friction, Cf, to the ratio of the displacement and boundary layer thicknesses, δ*∕δ, which is valid for both smooth and rough wall flows. The results indicate that the ratio Cf1∕2∕(δ*∕δ) is approximately constant, irrespective of the Reynolds number and surface condition.
QUANTUM MACROSTATISTICAL THEORY OF NONEQUILIBRIUM STEADY STATES
Authors: SEWELL GEOFFREY L.
Published: October 2005

We provide a general macrostatistical formulation of nonequilibrium steady states of reservoir driven quantum systems. This formulation is centered on the large scale properties of the locally conserved hydrodynamical observables, and our basic physical assumptions comprise (a) a chaoticity hypothesis for the nonconserved currents carried by these observables, (b) an extension of Onsager's regression hypothesis to fluctuations about nonequilibrium states, and (c) a certain mesoscopic local equilibrium hypothesis. On this basis, we obtain a picture wherein the fluctuations of the hydrodynamical variables about a nonequilibrium steady state execute a Gaussian Markov process of a generalized Onsager–Machlup type, which is completely determined by the position dependent transport coefficients and the equilibrium entropy function of the system. This picture reveals that the transport coefficients satisfy a generalized form of the Onsager reciprocity relations in the nonequilibrium situation and that the spatial correlations of the hydrodynamical observables are generically of long range. This last result constitutes a model-independent quantum mechanical generalization of that obtained for special classical stochastic systems and marks a striking difference between the steady nonequilibrium and equilibrium states, since it is only at critical points that the latter carry long range correlations.
SPIN-POLARIZED ATOMIC HYDROGEN IN THE STATIC FLUCTUATION APPROXIMATION
Authors: JOUDEH B. R. , AL-SUGHEIR M. K. , GHASSIB H. B.
Published: October 2005

In this paper we use the so-called static fluctuation approximation (SFA) to calculate the thermodynamic properties of spin-polarized atomic hydrogen. This approximation is based on the replacement of the square of the local-field operator with its mean value. A closed set of nonlinear integral equations is derived for neutral many-bosonic systems. This set is solved numerically by an iteration method for two triplet-state potentials: a Morse- and Silvera-type potentials. It is found that the mean internal energy per unit volume, the pressure, the entropy per unit volume, and the specific heat per unit volume increase with temperature and decrease with spin polarization in the low-temperature region (<8 mK ); whereas the condensate fraction increases with an applied magnetic field. It is also found that these quantities are nearly independent of spin polarization for high temperatures (>0.1 K ), and that they are independent of the number density up to 10-3Å-3 in the low-temperature region.
MODULATIONAL INSTABILITY IN NONLINEAR BI-INDUCTANCE TRANSMISSION LINE
Authors: KENGNE E. , CLETUS KUM K.
Published: October 2005

A nonlinear dissipative transmission line is considered and by performing the complex demodulation technique of the signal which allows, in particularly, to separate the right traveling and left traveling waves, we show that the amplitudes of these waves can be described by a complex coupled Ginzburg–Landau equations (CG-LE). The so-called phase winding solutions of the constructed CG-LE is analyzed. We also study the coherent structures in the obtained complex Ginzburg–Landau system. We show that the constructed CG-LE possesses nonlinear plane wave solutions and the modulational instability of these solutions is analyzed. The condition of the modulational instability is given in term of the coefficients of the constructed CG-LE and then in term of the wavenumber of the two right traveling and left traveling waves in the considered transmission line. The results obtained here show that the nonlinear plane wave solutions of the CG-LE under perturbation with zero wavenumber cannot be stable under modulation.
CLASSIFICATION, AUTOMORPHISM GROUPS AND CATEGORICAL STRUCTURE OF THE TWO-DIMENSIONAL REAL DIVISION ALGEBRAS
Authors: DIETERICH ERNST
Published: October 2005

The category of all 2-dimensional real division algebras is shown to split into four full subcategories, each of which is given by the natural action of a Coxeter group of type 𝔸1 or 𝔸2 on the set of all pairs of ellipses in ℝ2, which are centred in the origin and have reciprocal axis lengths. Cross-sections for the orbit sets of these group actions are being determined. They yield a classification of all 2-dimensional real division algebras. Moreover all morphisms between the objects in this classifying list are described, and thus an explicit and geometric picture of the category of all 2-dimensional real division algebras is obtained.

This elementary and self-contained exposition extends Darpö and Dieterich's recent description [14] of the category of all 2-dimensional commutative real division algebras, which in turn is based on Benkart, Britten and Osborn's investigation [4] of the isotopes of ℂ. It also supplements earlier contributions of Althoen and Kugler [2], Burdujan [9], Gottschling [25], Petersson [33], Hübner and Petersson [29], and Doković and Zhao [23] to the problem of classifying all 2-dimensional real division algebras.
DIXMIER'S PROBLEM 6 FOR SOMEWHAT COMMUTATIVE ALGEBRAS AND DIXMIER'S PROBLEM 3 FOR THE RING OF DIFFERENTIAL OPERATORS ON A SMOOTH IRREDUCIBLE AFFINE CURVE
Authors: BAVULA V. V.
Published: October 2005

In [6], J. Dixmier posed six problems for the Weyl algebra A1 over a field K of characteristic zero. Problems 3, 5,and 6 were solved respectively by Joseph and Stein [7]; the author [1]; and Joseph [7]. Problems 1, 2, and 4 are still open.

For an arbitrary algebra A, Dixmier's problem 6 is essentially aquestion: whether an inner derivation of the algebra A of the type ad f(a), a ∈ A, f(t) ∈ K[t], deg t(f(t)) > 1, has a nonzero eigenvalue. We prove that the answer is negative for many classes of algebras (e.g., rings of differential operators [Formula: see text] on smooth irreducible algebraic varieties, all prime factor algebras of the universal enveloping algebra [Formula: see text] of a completely solvable algebraic Lie algebra [Formula: see text]). This gives an affirmative answer (with a short proof) to an analogue of Dixmier's Problem 6 for certain algebras of small Gelfand–Kirillov dimension, e.g. the ring of differential operators [Formula: see text] on a smooth irreducible affine curve X, Usl(2), etc. (see [3] for details). In this paper an affirmative answer is given to an analogue of Dixmier's Problem 3 but for the ring [Formula: see text].
DEGENERATION-LIKE ORDERS IN TRIANGULATED CATEGORIES
Authors: JENSEN BERNT TORE , SU XIUPING , ZIMMERMANN ALEXANDER
Published: October 2005

In an earlier paper we defined a relation ≤Δ between objects of the derived category of bounded complexes of modules over a finite dimensional algebra over an algebraically closed field. This relation was shown to be equivalent to the topologically defined degeneration order in a certain space [Formula: see text] for derived categories. This space was defined as a natural generalization of varieties for modules. We remark that this relation ≤Δ is defined for any triangulated category and show that under some finiteness assumptions on the triangulated category ≤Δ is always a partial order.
ON THE RANKS OF THE CONWAY GROUPS Co2 AND Co3
Authors: ALI FARYAD , IBRAHIM MOHAMMED ALI FAYA
Published: October 2005

Let G be a finite group and X a conjugacy class of G. We denote rank(G:X) to be the minimum number of elements of X generating G. In the present article, we determine the ranks of the Conway groups Co2 and Co3. Computations were carried with the aid of computer algebra system 𝔾𝔸ℙ [18].
REGIONAL ATMOSPHERIC POLLUTION AND TRANSBOUNDARY AIR QUALITY MANAGEMENT
Authors: Bergin Michelle S. , West J. Jason , Keating Terry J. , Russell Armistead G.
Published: October 2005

▪ Abstract  The regional nature of several important air pollutants, which include acids, ozone, particulate matter, mercury, and persistent organics (POPs), is widely recognized by researchers and decision makers. Such pollutants are transported regionally over scales from about 100 to a few 1000s of kilometers, large enough to cross state, provincial, national, and even continental boundaries. Managing these regional pollutants requires overcoming political, economic, and cultural differences to establish cooperation between multiple jurisdictions, and it requires recognition of the linkages between pollutants and of impacts at different geographic scales. Here, regional dynamics of the pollutants are discussed, addressing them individually and as a tightly linked physical and chemical system. Collaborative efforts to characterize and manage regional pollution are presented, along with potential directions for future efforts.