bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of documentation in potential abusive head injury of infants in a Paediatric Emergency Department
Authors: Tingberg Björn , Falk Ann‐Charlotte , Flodmark Olof , Ygge Britt‐Marie
Published: April 2009

Aim: The aim is to evaluate medical record documentation regarding potential abusive head injury (AHI) in infants presenting to a Paediatric Emergency Department (ED) with certain primary complaints known to be associated with AHI.

Methods: A database search was performed to find all medical records over a period of one year relating to those children who had one AHI‐related primary complaint and who had had a CT head‐scan performed in conjunction with admission. Each medical record was reviewed, in order to assess whether potential abuse had been investigated and documented. Each CT‐scan image was re‐evaluated for missed indications of potential injuries attributable to AHI.

Results: Forty‐seven such medical records were found. Of these, 87% showed the diagnosis to be head injuries. The largest group of children was in the age group 0–3 months (38%). Of the children admitted to the Paediatric ED due to a head injury, 54% had a history deemed to raise suspicions of abuse but only five of them had had a documented investigation of child abuse. The re‐evaluation of the CT‐scans showed no missed cases.

Conclusion: In this study we found that among children with known risk factors for AHI, only a few had documentation regarding potential child abuse. The use of a standardized protocol could be helpful in the important work to help staff discover potential AHI.
Ontogenetic shifts in interactions of two dominant shrub species in a semi‐arid coastal sand dune system
Authors: Armas Cristina , Pugnaire Francisco I.
Published: March 2009

Question:How does the interaction between two dominant shrub species in a coastal sand dune community change during their life history? Does this interaction influence their population dynamics?

Location:A semiarid coastal sand dune system in southeast Spain.

Methods:For 3 years we monitored physiological status, growth and reproductive effort ofJuniperus phoeniceaandPistacia lentiscus, the dominant shrub species, growing either alone or in close spatial association. We also recorded adult mortality patterns and characterized seedling survival, soil properties and microclimate conditions beneath canopies and in bare ground.

Results and conclusions:There was a strong bi‐directional interaction between the two studied species, with a net balance that changed in sign with increasing plant development. While mature individuals facilitated the establishment of seedlings of both species, adult mortality patterns suggested asymmetric competition at later life stages. The interaction withPistacianegatively affected growth of juniper and contributed to its high mortality rates, while juniper had almost no effect on maturePistaciaindividuals. Physiological data suggested thatPistaciahad a competitive advantage over juniper, most likely because of differences in rooting patterns and tolerance to salinity, which may determine the source of water available for each species. Community dynamics are governed by facilitation at the seedling stage and shaped by differences in physiological traits in adult plants. Plant‐plant interactions, which are strongly affected by environmental gradients, are important drivers of community dynamics in this system.
Reliability and Failure Modes of Implant‐Supported Y‐TZP and MCR Three‐Unit Bridges
Authors: Bonfante Estevam Augusto , Coelho Paulo Guilherme , Navarro Jr Jose Manuel , Pegoraro Luiz Fernando , Bonfante Gerson , Thompson Van Purdy , Silva Nelson Renato Franç Alves
Published: March 2009

Purpose: Chipping within veneering porcelain has resulted in high clinical failure rates for implant‐supported zirconia (yttria‐tetragonal zirconia polycrystals [Y‐TZP]) bridges. This study evaluated the reliability and failure modes of mouth‐motion step‐stress fatigued implant‐supported Y‐TZP versus palladium‐silver alloy (PdAg) three‐unit bridges.

Materials and Methods: Implant‐abutment replicas were embedded in polymethylmethacrylate resin. Y‐TZP and PdAg frameworks, of similar design (n = 21 each), were fabricated, veneered, cemented (n = 3 each), and Hertzian contact‐tested to obtain ultimate failure load. In each framework group, 18 specimens were distributed across three step‐stress profiles and mouth‐motion cyclically loaded according to the profile on the lingual slope of the buccal cusp of the pontic.

Results: PdAg failures included competing flexural cracking at abutment and/or connector area and chipping, whereas Y‐TZP presented predominantly cohesive failure within veneering porcelain. Including all failure modes, the reliability (two‐sided at 90% confidence intervals) for a “mission” of 50,000 and 100,000 cycles at 300 N load was determined (Alta Pro, Reliasoft, Tucson, AZ, USA). No difference in reliability was observed between groups for a mission of 50,000. Reliability remained unchanged for a mission of 100,000 for PdAg, but significantly decreased for Y‐TZP.

Conclusions: Higher reliability was found for PdAg for a mission of 100,000 cycles at 300 N. Failure modes differed between materials.
Angio‐oedema in a Patient Treated with Etanercept for Rheumatoid Arthritis
Authors: Sendur Omer Faruk , Turan Yasemin , Berkit Isil Karatas , Tastaban Engin
Published: April 2009

Abstract:  In the treatment of rheumatoid arthritis, specific drugs targeting disease‐related proinflammatory cytokines such as tumour necrosis factor‐α have been observed to show a positive impact on the clinical course of the disease. One of these drugs, etanercept, is a recombinant soluble fusion protein of tumour necrosis factor‐α type 2 receptor. Although it has many well‐established side effects, up to date there has not been any report of angio‐oedema in the literature. Hence, we aimed to present clinical findings of a 59‐year‐old female patient who received etanercept for rheumatoid arthritis and developed angio‐oedema during treatment, and to the discuss side effects of the drug within the context of current literature.
How Do Copyrights Affect Economic Development and International Trade?
Authors: Smith Pamela J. , Da'ar Omar B. , Monroe Kevin H. , Nunez Fabricio X. , Tuttle Charlotte J.
Published: April 2009

This article analyzes the effects of copyrights on economic development and international trade. First, we apply an aggregate production function to examine the effects of “copyright‐related capital” (CRC) on development. This form of capital includes personal computers, servers, and bandwidth, which embody or transmit copyrighted materials. Second, we apply the gravity model of international trade to examine the effects of copyright policies on bilateral trade in core copyright industries. Third, we integrate the above frameworks to examine the two‐stage effects of copyrights on development, and then on trade. We analyze these relationships using cross‐sectional data for a large sample of countries. The findings show that a country's CRC contributes positively to its economic development. The findings also show that the relative harmonization of copyright policies between countries has a positive effect on bilateral trade in core copyright industries. Finally, the findings show evidence of a two‐stage process where a country's CRC contributes positively to its economic development (stage 1), which then contributes positively to its trade (stage 2).
Recent Developments in India's Plant Variety Protection, Seed Regulation and Linkages with UPOV's Proposed Membership
Authors: Ranjan Prabhash
Published: April 2009

The Agreement on Trade‐Related Aspects of Intellectual Property Rights of the World Trade Organization imposes an obligation on all member countries to protect plant varieties either by patents or by a sui generis regime or by a combination of both. India explored the sui generis option to provide protection to plant varieties. This legal regime recognizes the rights of commercial breeders and also grants a positive right to farmers and goes beyond the widely recognized international sui generis regime represented by the International Union for the Protection of Plant Varieties (UPOV). Notwithstanding this, India has made an application to join UPOV. However, with the present plant variety law, India's membership application to join UPOV may not be successful. The recent development of bringing the Seeds Bill, which dilutes farmers' rights provisions in the plant variety law, is important in this regard. The article argues that if the Seeds Bill is passed in its present form, it will dilute the beneficial provisions of the plant variety law and pave the way for India to join UPOV.
Prediction of Pairwise Gene Interaction Using Threshold Logic
Authors: Gowda Tejaswi , Vrudhula Sarma , Kim Seungchan
Published: March 2009

The two important problems of computational biology are the modeling of gene regulatory networks and the study of the network structure of complex biological systems. There is an increased use of mathematical and computational theory techniques to solve both these problems. The Boolean circuit model is one of the most popular modeling paradigms used to model gene regulatory networks. In this paper we try to make use of the properties of threshold logic (an alternative to Boolean logic to design digital circuits) to determine the network structure of gene systems. This approach uses the gene‐expression data from microarray experiments as input. The proposed method was first used to build the gene network for a set of genes, proteins, and other molecular components based onin silicodata. Then, the method was applied to a biological dataset to build the gene regulatory network for a core set of genes associated with melanoma. Some of the interactions found could be verified by earlier biological experiments reported in published literature. Other interactions that could not be validated by existing biological knowledge can provide insights into the investigation of bio‐chemical pathways associated with melanoma development.
Central Thalamic Deep‐Brain Stimulation in the Severely Injured Brain
Authors: Schiff Nicholas D.
Published: March 2009

This review outlines the scientific rationale supporting the potential use of deep‐brain electrical stimulation (DBS) in the central thalamus as a method to improve behavioral responsiveness following severe brain injury. Neurons within the central thalamus are selectively vulnerable to disconnection and dysfunction following severe brain injuries because of their unique geometry of cerebral connections. Because the central thalamus plays a key role in forebrain arousal regulation, impaired function of these cells has a broad impact. Prior clinical investigations, however, have targeted some components of the thalamus and related subcortical structures to improve behavioral responsiveness after severe brain injuries without providing evidence of sustained and clinically meaningful behavioral effects. Here important differences in conceptual framework, consideration of diagnostic categories for patient selection, and anticipated mechanisms of effect that distinguish earlier approaches and current studies are reviewed. As opposed to targeting chronically unresponsive patients, current efforts focus on identification of conscious patients with significant preservation of large‐scale integrative cerebral networks. The potential mechanisms and limitations of this evolving strategy are discussed, including the need to develop frameworks to calibrate patient selection to potential clinical benefits, range of potential effect size, and other present unknowns.
THE DETERMINANTS OF FINANCIAL DEVELOPMENT: INSTITUTIONS, OPENNESS AND FINANCIAL LIBERALISATION
Authors: Law Siong Hook , Habibullah Muzafar Shah
Published: March 2009

This paper provides new evidence that sheds light on the influence of institutional quality, trade openness and financial liberalisation on financial market development, using data from 27 economies (the G‐7, Europe, East Asia and Latin America) during 1980‐2001. The dynamic panel data analysis results demonstrate that real income per capita and institutional quality are statistically significant determinants of banking sector development and capital market development. The trade openness, however, is more prominent in promoting capital market development. In terms of financial liberalisation, the empirical results suggest that domestic financial sector reforms tend to promote banking sector development, whereas stock market liberalisation is potent in delivering stock market development. Nevertheless, the financial liberalisation programmes are more responsive in developed economies.
Self‐Assessment of Speaking Skills and Participation in a Foreign Language Class
Authors: De Saint Léger Diane
Published: March 2009

Abstract: This article investigates the ways in which learners' perception of themselves as second language (L2) speakers evolved over a 12‐week period. Thirty‐two students of the advanced French stream in a tertiary institution participated in this semester‐long study. Students self‐assessed their speaking skills and their level of participation in French oral tasks in weeks 4, 6, and 12, and set learning goals accordingly. Self‐perception evolved in a positive fashion over time, particularly in relation to fluency, vocabulary, and overall confidence in speaking in the L2. In addition, individual goal‐setting encouraged learners to take increased responsibility toward their own learning, although increased awareness did not necessarily lead to concrete actions to modify learning behavior. To conclude, this study highlights the potential pedagogical benefits of self‐assessment at both the cognitive and affective levels.
Horizontal cell feedback regulates calcium currents and intracellular calcium levels in rod photoreceptors of salamander and mouse retina
Authors: Babai Norbert , Thoreson Wallace B.
Published: March 2009

We tested whether horizontal cells (HCs) provide feedback that regulates the Ca2+ current (ICa) of rods in salamander and mouse retinas. In both species, hyperpolarizing HCs by puffing a glutamate antagonist, 6,7‐dinitro‐quinoxaline‐2,3‐dione (DNQX), onto HC processes caused a negative shift in the voltage dependence of rod ICa and increased its peak amplitude. Conversely, depolarizing HCs by puffing kainic acid (KA) into the outer plexiform layer (OPL) caused a positive voltage shift and decreased rod ICa. Experiments on salamander retina showed that these effects were blocked by addition of the pH buffer, Hepes. Intracellular calcium concentration ([Ca2+]i) was examined in rods by confocal microscopy after loading salamander and mouse retinal slices with Fluo‐4. Rods were depolarized to near the dark resting potential by bath application of high K+ solutions. Hyperpolarizing HCs with 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoylbenzo[f]quinoxaline (NBQX) enhanced high K+‐evoked Ca2+ increases whereas depolarizing HCs with KA inhibited Ca2+ increases. In both species these effects of NBQX and KA were blocked by addition of Hepes. Thus, like HC feedback in cones, changes in HC membrane potential modulate rod ICa thereby regulating rod [Ca2+]i at physiological voltages, in both mouse and salamander retinas. By countering the reduced synaptic output that accompanies hyperpolarization of rods to light, HC feedback will subtract spatially averaged luminance levels from the responses of individual rods to local changes. The finding that HC to rod feedback is present in both amphibian and mammalian species shows that this mechanism is highly conserved across vertebrate retinas.
Laminar Free Convection in a Vertical Channel With Asymmetrical Heating
Authors: Kazeminejad H.
Published: April 2009

A numerical investigation of laminar free convective heat transfer in a vertical channel with asymmetrical heating has been presented. Uniform wall temperatures are prescribed as thermal boundary conditions. The governing differential equations were solved by a finite volume method. The SIMPLER algorithm for pressure velocity coupling was adopted. A new iterative scheme based on mass balance at inlet and outlet has been used. By solving the flow as an elliptic problem, the effect of vertical diffusion of thermal energy, which was neglected in previous numerical studies, was taken into consideration. Variation of the mean velocity and average Nusselt number for Rayleigh number range of 10 to 103, channel aspect ratio range of 10 to 103 and Prandtl numbers of 0.72 and 5 are determined. For uniform wall temperature the average Nusselt number based on wall to ambient temperature difference and heat flux at different points are compared to the experimental results. The results revealed that the average Nusselt number from the thermally active surface in an asymmetric channel to be higher than from a comparable surface in a symmetric configuration, for fixed channel aspect ratio, at low values of Rayleigh number. There was no appreciable change in Nusselt number when Prandtl number was changed from 0.72 to 5. The minimum axial pressure for free convective flow of air is the highest for the symmetric heating condition.
The Skin Friction and Heat Transfer in a Laminar Plane Wall Jet That Evolves From a Uniform Velocity to Its Self-Similar Behavior
Authors: Issa Johnny , Ortega Alfonso
Published: April 2009

The plane, steady, laminar wall jet with a uniform velocity and temperature profiles at the jet exit is numerically investigated using a two-dimensional finite volume approach for a variety of Reynolds numbers and Prandtl number of 0.712 and 7. Between the jet exit and the downstream self-similar behavior, the flow exhibits a developing region that is not self-similar. The location of the dimensionless virtual origin is carefully investigated and expressed as a function of Reynolds number. The local skin friction coefficient is observed to converge to the analytical self-similar solution at downstream locations. Since no analytical solution exists for the temperature field in either the developing or self-similar regions of this problem, the thermal solution is investigated for both isothermal and isoflux boundary conditions at the wall. The local and overall skin friction coefficients, in addition to the local and overall Nusselt numbers, are reported as a function of Reynolds number, Prandtl number and the dimensionless location downstream of the jet exit.
Pool Boiling on Multiple Surfaces in Proximity
Authors: Ghariban Nasser , Rostami Ali
Published: April 2009

Information on the boiling heat transfer on a surface when affected by the presence of other surfaces is scares. Pool boiling heat transfer process on multiple surfaces in proximity has been investigated in this work. In particular, the boiling curve and the critical heat flux on a surface located in the heated plume of another surface is studied experimentally. The surfaces are made of two identical wires with known diameter positioned horizontally in a predetermined short distance from each other. Tests were performed by heating the wires up to the critical heat flux in a pool of stationary FC-72 fluid. The boiling curves were experimentally developed for a surface when it is located in the plume of another heated surface. Initial results indicate that the critical heat flux on such a surface drops more than 30% compared to a single isolated wire. The change may be attributed to the plume effects on the bubble formation and bubble dynamics of upper surface as well as the effects on the degree of subcooling in the immediate neighborhood of the test surface. The research focused on the effects of spacing and the degree of subcooling on the boiling and the critical heat flux of the upper surface which is affected by the natural convection and boiling plume of the lower surface. The results of this project are expected to expand the existing knowledge of boiling heat transfer, particularly when it is affected by the presence of other surfaces in the proximity.
Experimental Investigation of the Ice-Formation in a Planar Nozzle With Forced Convection Flow
Authors: Weigand B. , Zehner S. , Knapp A. , Braun R.
Published: April 2009

The present paper deals with the ice-formation in a planar nozzle with a convergence angle of 2.5 deg. First experiments have been carried out for different wall cooling parameters B in the range between 4 to 18 and for different flow rate Reynolds numbers in the range of 5000 < Re4h < 46000. For all these experiments only smooth ice-layers could be observed. However, in a cooled parallel plate channel or a diffuser, normally wavy ice-layers are observed for the parameter range reported above. This interesting result can be seen as a first justification for the hypothesis (which has been stated in literature) that the formation of wavy ice-layers is caused by flow laminarisation (due to the rapid growth in ice-layer thickness with increasing axial position from the inlet) and retransition to the fully turbulent state (after the ice-layer thickness reaches a nearly constant value). Thus, wavy ice-layers might be suppressed by superimposing flow acceleration.
Heat Transfer of Melting Nonadecane Spheres in Natural Convection of Water
Authors: Tanaka Yuta , Hishida Makoto , Tanaka Gaku
Published: April 2009

This paper deals with experimental and analytical heat transfer study of nonadecane spheres melting in natural convection of water. Experimental local and average heat transfer coefficients were obtained by analyzing photo images of the shape transformation of the nonadecane spheres. The relevant dimensionless parameters were varied in the ranges of 1.8×107 ≤ Grn·Prn ≤ 1.8×108 and 0.04 ≤ CnΔT/Ln ≤ 0.16. We found that (1) the melting nonadecane sphere was covered with thin nonadecane liquid film flowing upwards along the sphere to make a liquid cap on the top. The cap regularly repeated formation and splitting off, (2) on the lower hemisphere the experimental local heat transfer coefficients were slightly higher than the analytical ones and on the upper hemisphere the experimental local heat transfer coefficients were slightly lower than the analytical ones, and (3) the experimental average Nusselt number was correlated by Nu = 0.151 (Grn·Prn)0.257(CnΔT/Ln)0.117 that was in good agreement with the theoretical one.
A Non-Homogeneous Equilibrium Model for Convective Transport in Flowing Nanofluids
Authors: Buongiorno J.
Published: April 2009

A base fluid (e.g., water, ethanol, oil) in which nano-sized (1–100 nm) particles of a different material are dispersed, is known as a nanofluid. Nanofluids are attractive because the presence of the nanoparticles enhances energy transport considerably. As a result, nanofluids have higher thermal conductivity and single-phase heat transfer coefficients than their base fluids. In particular, the heat transfer coefficient increases appear to go beyond the mere thermal-conductivity effect, and cannot be predicted by traditional pure-fluid correlations such as Dittus-Boelter’s. In the nanofluid literature this behavior is generally attributed to thermal dispersion and intensified turbulence, brought about by nanoparticle motion. To test the validity of this assumption, we have considered seven slip mechanisms that can produce a relative velocity between the nanoparticles and the base fluid. These are inertia, Brownian diffusion, thermophoresis, diffusiophoresis, Magnus effect, fluid drainage and gravity. We concluded that, of these seven, only Brownian diffusion and thermophoresis are important slip mechanisms in nanofluids. Based on this finding, we developed a two-component four-equation non-homogeneous equilibrium model for mass, momentum and heat transport in nanofluids. A non-dimensional analysis of the equations suggests that energy transfer by nanoparticle dispersion is negligible, and thus cannot explain the abnormal heat transfer coefficient increases. Furthermore, a comparison of the nanoparticle and turbulent eddy scales clearly indicates that the nanoparticles move homogeneously with the fluid in the presence of turbulent eddies, so an effect on turbulence intensity is also doubtful.
Analysis of a Free Surface Film From a Controlled Liquid Impinging Jet Over a Rotating Disk Including Conjugate Effects, With and Without Evaporation
Authors: Rice Jeremy , Faghri Amir , Cetegen Baki M.
Published: April 2009

A detailed analysis of the liquid film characteristics and the accompanying heat transfer of a free surface controlled liquid impinging jet onto a rotating disk are presented. The computations were run on a two-dimensional axi-symmetric Eulerian mesh while the free surface was calculated with the volume of fluid method. Flow rates between 3 and 15 lpm with rotational speeds between 50 and 200 rpm are analyzed. The effects of inlet temperature on the film thickness and heat transfer are characterized as well as evaporative effects. The conjugate heating effect is modeled, and was found to effect the heat transfer results the most at both the inner and outer edges of the heated surface. The heat transfer was enhanced with both increasing flow rate and increasing rotational speeds. When evaporative effects were modeled, the evaporation was found to increase the heat transfer at the lower flow rates the most because of a fully developed thermal field that was achieved. The evaporative effects did not significantly enhance the heat transfer at the higher flow rates.
A New Computational Method for Free Surface Problems
Authors: Rice Jeremy , Faghri Amir
Published: April 2009

A new technique, called the surface velocity correction technique (SVC), is developed to track a free surface such as a liquid-vapor interface. SVC is a computationally inexpensive, and accurate method to capture interfacial fluid phenomena. This method uses a finite volume technique to discretize the governing equations, and a semi-Legrangian mesh to locate the interface between two fluids. The effectiveness of this technique is demonstrated through several classical examples and the results are also compared to both analytical and VOF solutions. The examples include: the shape of a meniscus in a capillary tube in mechanical equilibrium, the rise of a meniscus in a capillary tube, and the instability growth of a free flowing cylindrical column of fluid.
Influence of Ceramic Supports on Efficient Microwave Heating of Porous Dielectrics
Authors: Basak Tanmay , Aparna K. , Meenakshi A. , Balakrishnan A. R.
Published: April 2009

A detailed theoretical analysis has been carried out to study efficient heating of 1D porous dielectric samples due to microwaves. The heating effects are analyzed for two types of porous material: beef-air (b/a) and beef-oil (b/o) with and without ceramic supports (Al2O3 and SiC). Three test cases for porosity (φ) 0.3, 0.45 and 0.6, are considered. The effective dielectric properties are obtained using Fricke’s complex conductivity model with air and oil being the discontinuous media. The maxima in average power corresponding to resonances occur at various sample thicknesses for all porous materials with and without supports and two dominant resonance modes R1 and R2 are considered where the average power at R1 is larger than that at R2. It is observed that the maxima at R1 mode decreases significantly with porosity for samples with and without supports. It is interesting to observe that average power absorption is enhanced for samples (b/a and b/o) in presence of Al2O3 support whereas the average power is smaller with SiC support. The detailed analysis on spatial distribution of electric field, power and temperature illustrate that runaway heating is observed at the face which is not attached with support for b/a samples, and the intensity of thermal runaway is increased with porosity whereas the less thermal runaway is observed for b/o samples with all porosity regimes. The thermal runaway is less pronounced for SiC supports. The thermal runaway is also represented by ΔTb (temperature difference) vs time plot which illustrates that greater magnitudes of ΔTb occur with φ = 0.6 for b/a samples. In contrast, ΔTb vs time distribution is almost identical with porosity for b/o samples. Based on the analysis, it may be recommended that b/o samples with all porosity regimes would exhibit uniform heating rates with Al2O3 and SiC supports, whereas b/a samples may be heated with minimal thermal runaway heating corresponding to Al2O3 support at the left face.
Using Symbolic Calculation for Solving Natural Convection in a Narrow Horizontal Cylindrical Annulus
Authors: Mansour Kamyar
Published: April 2009

We consider the two-dimensional problem of steady natural convection in a narrow Horizontal Cylindrical annulus filled with viscous fluid due to a sine temperature variation on the outer and adiabatic conditions at the inner boundaries. The solution is expanded in powers of a single combined similarity parameter introduced by [1], which is the product of the Gap ratio to the power of four, and Rayleigh number and the series extended by means of symbolic calculation up to 16 terms. Analysis of these expansions allows the exact computation for arbitrarily accuracy up to 50000 figures. Although the range of the radius of convergence is almost zero but Pade approximation lead our result to be good even for much higher value of the similarity parameter.
Reduced Order Modeling of Steady Turbulent Convection Flows Using the POD
Authors: Rambo Jeffrey , Joshi Yogendra
Published: April 2009

In the characterization and design of complex distributed parameter thermo/fluid systems, detailed experimental measurements or fine numerical calculations often produce excessively large data sets, rendering more advance analyses inefficient or impossible. Acquiring the experimental or numerical data is usually a time consuming task, severely restricting the number and range of parameters and ultimately limiting the portion of the design space that can be explored. To develop low dimensional models, it is desirable to decompose the system response into a series of dominant physical modes that describe the system, while incurring a minimal loss of accuracy. The proper orthogonal decomposition (POD) has been successful in creating low dimensional dynamic models of turbulent flows and here its utility is extended to produce approximate solutions of steady, multi-parameter RANS simulations within predefined limits. The methodology is illustrated through the 2-dimensional analysis of an air-cooled data processing cabinet containing 10 individual servers, each with their own flow rate. The results indicate that a flux matching procedure can reduce the model size by 4 orders of magnitude while adequately describing the airflow transport properties within engineering accuracy. This low dimensional description of the flow inside the data processing cabinet can in turn be used to further explore the design space and efficiently optimize the system.
Spatially and Temporally Resolved Temperature Measurement of Laser Diode Arrays
Authors: Carter Jason , Snyder David
Published: April 2009

A method to determine the temperature of an operating laser diode is to measure the wavelength emitted by the array and use the linear relationship between wavelength and temperature to infer the temperature of the laser diode bar. A unique experimental method to measure spatially and temporally resolved wavelength emitted from a laser diode array has been developed and is used to determine local temperature transients. This approach involves the non-contact rastering of a 100μm aperture over the emitting surface of the array, passing the energy from a single emitter into a spectrograph. This paper describes the design and development of the spatially and temporally resolved wavelength measurement system that is unique to any system presented in the literature. Results from a validation study of this methodology based on a comparison of wavelength and intensity maps to well-established and calibrated time and spatially averaged LDA measurement techniques and IR images are presented. In turn, preliminary results from this system show that transient laser diode emitter behavior falls into a number of distinct categories. A system that can resolve localized heating of a laser diode array both spatially and temporally can provide a wealth of information about the thermal performance of these arrays: 1) precise mapping of array temperature and relative output power, 2) precise location of hot spots and accurate measurement of the magnitude of those hot spots, and 3) variations in thermal time constants that may predict the location of packaging defects along the heat flow path from the diode bar itself to the LDA heat sink.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.
Experimental Study on Ventilation Performance of Reefer Container Hold
Authors: Park I. S. , Park S. M. , Seol S. S. , Lee D. J.
Published: April 2009

The analysis of ventilation performance varying with the length and number of duct in scale-model of reefer container hold has studied experimentally. Most container ships have ventilation system of which ducts extended to the bottom for the purpose of efficient exhausting of condensing heat from refrigerator. However, the duct is so over-long which causes manufacturing troubles and costs higher. In this study, for the various types of duct, the flow visualizing test with smoke oil and normalized temperature rising analysis are performed. Keeping the notation of class for reefer container stowage, we concurrently saved the material and manufacturing costs. Finally, the ventilation performances of each system are compared with each other.
DNS of Three-Dimensional Unsteady Separated Flow and Heat Transfer Around a Downward Step
Authors: Sugawara Kazuaki , Kaihara Eiji , Yoshikawa Hiroyuki , Ota Terukazu
Published: April 2009

The direct numerical simulation methodology was employed to analyze the unsteady features of a three-dimensional separated flow and heat transfer around a downward step in a rectangular channel. Numerical calculations were carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The channel expansion ratio ER is 2.0 under a step aspect ratio of 36.0. It is found that the flow is steady upto Re = 500, but becomes sensibly unsteady at Re = 600 as accompanying a remarkable increase of the three-dimensionality of the flow and temperature fields. Nusselt number reaches its maximum in the reattachment flow region and also in the neighborhood of the side wall, and their locations depend greatly upon Re.
Three-Dimensional Linear Stability Analysis of Natural Convection in Horizontal Annuli
Authors: Petrone Giuseppe , Che´nier Eric , Lauriat Guy
Published: April 2009

Linear stability of two-dimensional natural convective flow in horizontal cylindrical annuli is performed for three-dimensional perturbations and radius ratios in the range 1.2 ≤ R ≤ 3. Flow transitions for moderate to large gap annuli which have not been reported before are thoroughly investigated. Then stability diagrams are obtained for finite and for infinite length annuli. The leading disturbances and thresholds values are found to agree well with experimental data and three-dimensional numerical solutions previously published.
Free Convection in Air-Filled Cavity With a Localized Heater From Below and Cooling Lateral Walls
Authors: Calcagni Barbara , Paroncini Massimo
Published: April 2009

The paper investigates the development of natural convection in air-filled square enclosure with a heat source flush mounted on the lower horizontal surface; the cavity is symmetrically cooled from the lateral walls. The experimental analysis has been carried out with the real time holographic interferometry that makes possible the investigation of the development of the convective phenomenon, and with the double exposure technique in order to obtain the temperature distribution inside the cavity at the steady-state. The experimental analysis allows the study of a limited range of Rayleigh numbers from about 1.63·104 to 2.8·105. On the contrary the numerical investigation makes possible to enlarge the analysis to a more wide range of Rayleigh numbers; thus the experimental analysis, has been integrated with the numerical results provided by the investigation with the commercial finite volume software Fluent 6.0. for Rayleigh number from 103 to 106. Different convective forms have been obtained depending on Ra, on the heat source length and on its position. The Nusselt number has been evaluated on the heater; graphs with relations between average Nu, Ra, the heat source length and its position are finally presented.
Influence of Some Parameters on Effective Thermal Conductivity of Nano-Porous Aerogel Super Insulator
Authors: Zhang Xinxin , Wei Gaosheng , Yu Fan
Published: April 2009

Based on the open-cell nano-porous structure features, a cubic array of nano-spheres unit cell model describing the coupled conduction of gas and solid in aerogel super insulator is developed. By one-dimensional heat conduction analysis in the unit cell, the effective thermal conductivity expression is obtained. The results show that the model matches well with the experimental data and nano-porous structure, nanometer size effect of solids as well as the very high specific surface area are the key factors make aerogel have very low thermal conductivity. There exists an optimal density value where the thermal conductivity of aerogel is minimum. Thermal radiative heat transfer is the dominating heat transfer mechanism of aerogel at an elevated temperature. It can decrease the thermal conductivity value of aerogel effectively at an elevated temperature by doping carbon or other matters which can strongly absorb infrared light at 3∼8 μm.
Thermal Conductivity of Core-Shell Nanostructures: From Nanowires to Nanocomposites
Authors: Yang Ronggui , Chen Gang , Dresselhaus Mildred S.
Published: April 2009

Core-shell heterostructures could potentially become the building blocks of nanotechnology for electronic and optoelectronic applications. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management such devices. In the mean time, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, a generic model is established to study phonon transport in core-shell nanowire structures in the longitudinal direction using the phonon Boltzmann equation. The model can be used to simulate a variety of nanostructures, including nanowires and nanocomposites by changing some of the input parameters. We first report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core - germanium shell and tubular silicon nanowires. When the scattering at the outer shell surface in the generic model is assumed to be totally specular, the core-shell nanostructure resembles a simulation unit cell of periodic two-dimensional (2-D) nanocomposites. Thermal conductivity of nanowire composites and cylindrical nanoporous material in longitudinal direction is thus predicted as a function of the size of the nanowires and nanopores, and the volumetric fraction of the constituent materials. Results of this study can be used to direct the development of high efficiency thermoelectric materials.
Effect of Oscillating Flow on Thermal Stratification in an Enclosure
Authors: Kim Sung Ki , Kim Seo Young
Published: April 2009

The present study aims at investigating the effect of oscillating flow on thermal stratification in a gas oven. To date, the fan convectors are common to reduce thermal stratification inside various types of oven. The impetus of the present study is to investigate the feasibility of flow oscillation to achieve more uniform distribution of air temperature within an oven. To produce the flow oscillation, an acoustic woofer is vertically installed on the back of a gas oven. The operating frequency of the acoustic woofer is varied from 30 to 60 Hz. Three-dimensional measurements of air temperature inside the oven are implemented to evaluate temperature uniformity. The experimental results show that the oscillating flow with a specific frequency enhances air mixing dramatically, which results in the attenuation of thermal stratification inside the oven. The actual baking of sponge cake also shows that the convector using the flow oscillation can provide better results compared to the conventional fan convectors.
Fluid Flow and Heat Transfer Analysis of Automotive Radiator Using CFD Tools
Authors: Malapure V. P. , Bhattacharya A. , Mitra Sushanta K.
Published: April 2009

This paper presents a three-dimensional numerical analysis of flow and heat transfer over plate fins in a compact heat exchanger used as a radiator in the automotive industry. The aim of this study is to predict the heat transfer and pressure drop in the radiator. FLUENT 6.1 is used for simulation. Several cases are simulated in order to investigate the coolant temperature drop, heat transfer coefficient for the coolant and the air side along with the corresponding pressure drop. It is observed that the heat transfer and pressure drop fairly agree with experimental data. It is also found that the fin temperature depends on the frontal air velocity and the coolant side heat transfer coefficient is in good agreement with classical Dittus–Boelter correlation. It is also found that the specific dissipation increases with the coolant and the air flow rates. This work can further be extended to perform optimization study for radiator design.
Chemically Etched Cryogenic Micro Structure Heat Exchanger
Authors: Jung Jeheon , Jeong Sangkwon
Published: April 2009

A tandem 4 K pulse tube refrigerator requires a recuperator to be fully accomplished. The recuperator should be a counter-flow heat exchanger which has micro heat-transfer structure like a regenerator of cryogenic refrigerators. However, the technology of such a heat exchanger is not well established yet. Hence, the development of a counter-flow compact heat exchanger with micro structure is demanded first in order to proceed to the recuperative 4 K pulse tube refrigerator. This paper describes the design, fabrication and preliminary performance test of such a heat exchanger. The stainless steel micro structure with approximately 0.1 mm characteristic length has been created by chemical etching. The parallel V-shape double-sided micro channels (chevron stucture) in the heat exchanger enable the flow to be three-dimensionally well mixed so that the heat transfer at low Reynolds number can be enhanced. The etched plates are stacked and bonded through a vacuum brazing process to compose a plate-type heat exchanger. The chemically etched micro-structure heat exchanger has thermal effectiveness of 97%.
The Determination of the Sensitivity of Heat Transfer Systems Using Global Sensitivity and Gaussian Processes
Authors: Emery A. F. , Bardot D.
Published: April 2009

A critical aspect of the design of systems or experiments is a sensitivity analysis to determine the effects of the different variables. This is usually done by representing the response by a Taylor series and evaluating the first order derivatives at a nominal operating point. When there is uncertainty about the operating point, the common approach is the construction of a response surface and Monte Carlo sampling based on the probability distribution of these uncertain variables. When there are many variables it is important to restrict the analysis to those variables to which the response is most sensitive. This can be conveniently done using Global sensitivity, that both defines the most critical variables and also quantifies the effects of interacting variables. This can be a computationally expensive process and for complex models is generally prohibitively expensive. A solution is the use of Gaussian processes that allows one to create a response surface using easy-to-evaluate functions. This paper describes the use of these ideas for a heat transfer problem.
A Mechanistic Condensation Model for a Passive Condenser System
Authors: Oh Seungmin , Revankar Shripad T.
Published: April 2009

An experimental study is conducted and a mechanistic model is developed to investigate the effect of noncondensable gas in a passive condenser system. A vertical condenser tube was submerged in a water pool where the heat from the condenser tube was removed through boiling heat transfer. Data was obtained for various process parameters such as inlet steam flow rate, noncondensable gas mass fraction, and system pressure. Degradation of the condensation with noncondensable gas was investigated, where condensation heat transfer coefficient and heat transfer rate decrease with the noncondensable gas. It was found that the condensation heat transfer rate is enhanced by increasing the inlet steam flow rate and the system pressure. A mechanistic condensation correlation is developed which contains the major heat transfer components in its functional relationships. The heat transfers for the film region and the gas region sensible heat were modeled with the modified Nusselt solution and the single phase heat transfer correlations, respectively. The gas region condensation was correlated with bulk noncondensable mass fraction, gas region Reynolds number, and Jakob number. New correlation was compared with available experimental data and models. Mean errors of the correlation were found to be 4.7% and 13.4% for the tube average and the local condensation heat transfer coefficient, respectively.
The Effect of Initial Charge on the Steady-State Operating Performance of a Capillary Assisted Thermosyphon
Authors: Tudor V. , Cerza M. , Smith A. N. , Conroy C. T.
Published: April 2009

The future capabilities of naval ships will be directly related to the electronic components used in advanced radar systems, fire control systems, electric propulsion and electric weapons. Modern electronics continue to grow in speed and functionality but shrink in size and mass, causing the power density to dramatically increase. Thermal management is becoming a major issue for the modern electronic Navy. An experimental investigation on the effect of liquid charge in a capillary assisted thermosyphon (CAT) loop for the shipboard cooling of electronics components has been conducted. The employed CAT loop differs from the capillary pumped loop or loop heat pipe system, in that the basic cooling loop is based on a thermosyphon. A wick structure located on the walls of the evaporator plate provides the capillary assistance needed to spread the working fluid (i.e. water) across the flat plate evaporator in the areas under the heat sources. This differs from a capillary pumped loop in that the wick structure does not produce a significant capillary pumping head from the liquid return to the vapor outlet side of the evaporator. The forced circulation in the CAT loop is caused by a gravity head between the condenser cold plate and the flat plate evaporator. The influence of the liquid charge on the CAT loop performance was studied for a fixed sink temperature and a range of heat inputs from 250W to 1000W. The initial liquid charge was varied from 50 ml to 200 ml (i.e. 16% to 24% evaporator fill ratio). The evaporator fill ratio was defined in this study as the ratio of the initial charge to the total volume of the evaporator. The condenser cold plate cooling water flow rate was set to 63.088 ml/sec. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperature, and initial charges. The experimental results obtained indicated that as heat input and the liquid charge increased or decreased above/below an optimum value, the operating temperature in the evaporator increased. The CAT loop flow dynamics also changed as a function of the initial liquid charge. Overall these effects did not hinder the thermal performance as measured by the internal operating temperature of the evaporator. An optimal charge was observed at an evaporator fill ratio of 40% (i.e. 125ml).