bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced Peak Atrial Systolic Mitral Annular Velocity Predicts the Development of Nonvalvular Atrial Fibrillation
Authors: Choi Jin‐Oh , Han Hyejin , Cho Soo Jin , Yang Ji Hyun , Song Bong Gun , Lee Sang Yeub , Kim Jung Hyuk , Lee Sang‐Chol , On Young Keun , Kim Jun Soo , Park Seung Woo
Published: April 2009

We investigated whether the echocardiographic parameters of the left atrium (LA) can predict the development of nonvalvular atrial fibrillation (AF). Among 14,062 patients (>20 years old) who underwent an echocardiographic examination were evaluated, 2,606 patients who underwent follow‐up ECG with an interval of >6 months were investigated. Newly developed AF was noted in 42 (1.6%) patients with follow‐up duration of 31.8 ± 8.9 months. Cox regression analysis revealed that a higher left atrial volume index (hazard ratio [HR]=1.06; 95% confidence interval [CI] 1.03–1.09, P < 0.001), relative wall thickness (RWT) of≥0.407 (HR=2.74, 95% CI 1.39–5.41, P=0.004), a reduced peak atrial systolic mitral annular velocity (HR=0.845, 95% CI 0.72–0.99, P=0.037), and an advanced age (HR=1.04, 95% CI 1.01–1.07, P=0.009) were independently related to the development of nonvalvular AF. Therefore, reduced A′, which is parameter of LA contractile function, might be an important predictor for the development of nonvalvular AF. (ECHOCARDIOGRAPHY, Volume 26, July 2009)
Discharge planning in mental health care: a systematic review of the recent literature
Authors: Steffen S. , Kösters M. , Becker T. , Puschner B.
Published: April 2009

Objective:  To determine and estimate the efficacy of discharge planning interventions in mental health care from in‐patient to out‐patient treatment on improving patient outcome, ensuring community tenure, and saving costs.

Method:  A systematic review and meta‐analysis identified studies through an electronic search on the basis of defined inclusion and exclusion criteria and extracted data.

Results:  Of eleven studies included, six were randomised controlled trials, three were controlled clinical trials, and two were cohort studies. The discharge planning strategies used varied widely, most were limited to preparation of discharge during in‐patient treatment. Pooled risk ratios were 0.66 (95% CI = 0.51 to 0.84; P < 0.001) for hospital readmission rate, and 1.25 (1.07 to 1.47; P < 0.001) for adherence to out‐patient treatment. Effect sizes (Hedge’s g) were −0.25 (−0.45 to −0.05; P = 0.02) for mental health outcome, and 0.11(−0.05 to 0.28; NS) for quality of life.

Conclusion:  Discharge planning interventions are effective in reducing rehospitalisation and in improving adherence to aftercare among people with mental disorders.
Mouse model of experimental periodontitis induced by Porphyromonas gingivalis/Fusobacterium nucleatum infection: bone loss and host response
Authors: Polak David , Wilensky Asaf , Shapira Lior , Halabi Amal , Goldstein Dita , Weiss Ervin I. , Houri‐Haddad Yael
Published: April 2009

Aim: To compare the effect of oral infection with Porphyromonas gingivalis or Fusobacterium nucleatum versus infection with both bacteria on mouse periodontal tissues, and to characterize the inflammatory response.

Materials and Methods: Mice were orally infected with P. gingivalis, F. nucleatum or both. At 42 days post‐infection, alveolar bone loss was quantified using micro‐computerized tomography. Tumour necrosis factor‐α (TNF‐α) and interleukin (IL)‐1β levels induced by the infection were quantified using the subcutaneous chamber model.

Results: Mice orally infected with F. nucleatum/P. gingivalis exhibited significantly more bone loss compared with that of mono‐infected and sham‐infected mice. F. nucleatum/P. gingivalis infection also increased the levels of TNF‐α and IL1β compared with the levels found in the mono‐infected groups.

Conclusions: Polymicrobial infection with P. gingivalis/F. nucleatum aggravates alveolar bone loss and induces a stronger inflammatory response compared with that observed upon infection with either bacterium alone. The results suggest that oral infection of mice with a mixture of P. gingivalis and F. nucleatum may be superior to mono‐infection models of experimental periodontitis.
Marathon of eponyms: 2 Bell palsy (idiopathic facial palsy)
Authors: Scully C , Langdon J , Evans J
Published: April 2009

The use of eponyms has long been contentious, but many remain in common use, as discussed elsewhere (Editorial: Oral Diseases. 2009: 15; 185–186). The use of eponyms in diseases of the head and neck is found mainly in specialties dealing with medically compromised individuals (paediatric dentistry, special care dentistry, oral and maxillofacial medicine, oral and maxillofacial pathology, oral and maxillofacial radiology and oral and maxillofacial surgery) and particularly by hospital‐centred practitioners. This series has selected some of the more recognised relevant eponymous conditions and presents them alphabetically. The information is based largely on data available from MEDLINE and a number of internet websites as noted below: the authors would welcome any corrections. This document summarises data about Bell paralysis.
Ceramic Inlays: A Case Presentation and Lessons Learned from the Literature
Authors: BOUSHELL LEE W. , RITTER ANDRÉ V.
Published: April 2009

Ceramic dental restorative materials offer an esthetic alternative to dental amalgam or gold. There is uncertainty relative to the longevity of ceramic inlay restorations. Recently published long‐term research studies reveal general clinical performance trends. These trends are discussed while presenting a ceramic inlay case. Successful clinical use of ceramic inlay materials is absolutely dependent on the creation of an uncompromised adhesive tooth/ceramic interface. Ceramic inlay restorations perform well in terms of long‐term retention, color match, and anatomic contour stability. These restorations all experience limited margin deterioration that does not predispose to marginal discoloration or secondary caries. Patients rarely suffer from postoperative sensitivity secondary to ceramic inlay placement.

Ceramic inlays fail predominantly as a result of crack propagation from material flaws leading to bulk fracture. Some superficial ceramic defects may be repaired with composite resin. Internal material flaws are minimized by industrial production of indirect pressable glass‐ceramic materials or ceramic blocks designed for computer‐aided design/computer‐assisted manufacturing (CAD/CAM). External surface flaws are limited by careful polishing techniques. Strategic placement of ceramic inlays in teeth that are not subject to heavy occlusal loading will result in more predictable long‐term performance. Preparation design to prevent flexure of ceramic inlay materials is essential.

CLINICAL SIGNIFICANCE

Use of ceramic inlays to restore defects in posterior teeth requires careful attention to detail. Placement of ceramic inlay materials in high‐stress areas may result in less predictable long‐term performance. Ceramic inlays are advantageous for restoring moderately sized defects when optimal control of restoration contours and esthetics is desired.
Advances in the understanding of chondrodermatitis nodularis chronica helices: the perichondrial vasculitis theory
Authors: Upile T. , Patel N.N. , Jerjes W. , Singh N.U. , Sandison A. , Michaels L.
Published: April 2009

Objectives:  Chondrodermatitis nodularis chronica helicis (CNCH) usually presents as a painful nodule affecting the pinna. The aetiology of the disease is unknown. Several theories have been suggested.

We suggest a possible explanation based upon pathophysiological treatment correlations to new histopathological evidence.

Design:  A detailed histopathological review of 16 confirmed cases of CNCH was undertaken by two pathologists, independently and together, using a qualitative grading of arteriolar narrowing.

Results:  Review of cases revealed arteriolar narrowing in perichondrium region of pinna most remote from arterial blood supply, i.e. helix. This has lead to ischaemic changes and death of the metabolically active underlying cartilage with necrosis and extrusion.

Conclusion:  This is the first report of specific perichondrial arteriolar changes as the possible cause of underlying cartilage necrosis resulting in CNCH.
Pathological validation of supracricoid partial laryngectomy in laryngeal cancer
Authors: Sun D.‐I. , Cho K.‐J. , Cho J.‐H. , Joo Y.‐H. , Jung C.‐K. , Kim M.‐S.
Published: April 2009

Objectives:  To validate pathologically whether supracricoid partial laryngectomy is an oncologically sound procedure in cases with invasion of the thyroid cartilage, paraglottic space, pre‐epiglottic space, anterior commissure, or subglottis.

Design:  A retrospective review of case notes was performed.

Setting:  Patients treated at a single institute in the Republic of Korea.

Participants:  Sixty‐three patients who underwent supracricoid partial laryngectomy for laryngeal squamous cell carcinoma between June 1994 and May 2005 who were followed for at least 2 years.

Main outcome measures:  Local control and overall survival rates. Pathological invasion of the thyroid cartilage, anterior commissure, pre‐epiglottic space, paraglottic space, or subglottis was also investigated as a cause of recurrence. Prognostic factors for local control and survival were evaluated with univariate and multivariate models.

Results:  Invasion of the anterior commissure, paraglottic space, thyroid cartilage, pre‐epiglottic space, or subglottis had no significant impact on the recurrence or overall survival rates. The presence of a positive resection margin was significantly associated with recurrence in the univariate and multivariate analyses (P = 0.026, 0.028, respectively). When considering the prognostic factors influencing survival, the univariate analysis showed that N stage, a positive resection margin and recurrence had significant influences on the overall survival rate (P = 0.010, 0.0004 and 0.000 respectively). In the multivariate analysis, only recurrence affected the survival rate (P = 0.002).

Conclusion:  Supracricoid partial laryngectomy can be used with oncological safety in selected cases of laryngeal cancer with invasion of the anterior commissure, thyroid cartilage, pre‐epiglottic space, paraglottic space, or subglottis.
Starting Out on the Right Foot: Negotiation Schemas When Cultures Collide
Authors: Adair Wendi L. , Taylor Masako S. , Tinsley Catherine H.
Published: April 2009

We investigate the intercultural negotiation schemas of 100 experienced Japanese and U.S. negotiators. Specifically, we examine the assumptions negotiators make about appropriate behavior when primed to negotiate with an intercultural (vs. intracultural) counterpart. We find that intercultural negotiation schemas clash on six of nine elements, meaning U.S. and Japanese negotiators have significantly different expectations about what it is like to negotiate with the other. This clash occurs not because negotiators stay anchored on their own cultural assumptions about negotiating, but rather because they try to adjust to their counterpart’s cultural assumptions about negotiating. But negotiators adjust their schemas by thinking about how their counterpart negotiates in an intracultural rather than intercultural setting. That is, they fail to account for the fact that their counterpart would also adjust expectations for the intercultural context. The phenomenon we uncover is one of schematic overcompensation, whereby negotiators’ intercultural schemas do not match because each negotiator expects the encounter to be just like the counterpart’s within‐culture negotiations. Our theory of schematic overcompensation receives some support, and negotiators’ perceived knowledge and experience with the other culture somewhat attenuates the phenomenon. Implications for negotiator cognition, intercultural negotiation, and global management are discussed.
Identification of Anguilla anguilla (L.) and Anguilla rostrata (Le Sueur) and their hybrids based on a diagnostic single nucleotide polymorphism in nuclear 18S rDNA
Authors: FRANKOWSKI JENS , BASTROP RALF
Published: April 2009

The variability of the nuclear 18S rDNA was examined for 10 species of freshwater eels: Anguilla anguilla, A. australis, A. dieffenbachii, A. japonica, A. marmorata, A. mossambica, A. nebulosa labiata, A. obscura, A. reinhardtii and A. rostrata. We observed that a single nucleotide polymorphism (SNP) separated A. anguilla and A. japonica from the remaining taxa. While this SNP marker may be used to identify hypothetical hybrids of A. japonica and sympatric eel species, we focused on Atlantic eels to evaluate the potential for this diagnostic chromosomal marker to discriminate between individuals of A. anguilla, A. rostrata and their hybrids.
A synopsis of Thai Nymphaeaceae
Authors: La‐ongsri Woranuch , Trisonthi Chusie , Balslev Henrik
Published: April 2009

A synopsis of Nymphaeaceae from Thailand was made by means of a literature search, consultation of herbarium specimens in several Thai and European herbaria, and a survey of 47 wetlands throughout Thailand. Nymphaeaceae phylogeny, habitats and reproductive ecology are reviewed. All species encountered were cultivated at Queen Sirikit Botanic Garden in Chiang Mai for further observations. Two species ofBarclaya(B. longifoliaandB. motleyi) the latter being represented by only a single herbarium specimen with uncertain origin, were encountered. InNymphaea,four native species, the day‐bloomingN. cyaneaandN. nouchali, and the night‐bloomingN. pubescensandN. rubra,were encountered. In addition, the day‐bloomingN. capensis,which has been introduced into Thailand, was found adventive at several localities.Barclayaspecies are restricted to pristine natural forest habitats, whereasNymphaeaspecies occur naturally in swamps and lakes, but are now found in many anthropogenic habitats.
Urinary bile acid sulfate levels in patients with hepatitis C virus‐related chronic liver diseases
Authors: Negoro Shinichiro , Tanaka Atsushi , Takikawa Hajime
Published: April 2009

Aim:  Urinary bile acids are mainly conjugated with sulfuric acid, and urinary sulfated bile acid (USBA) levels in hepatobiliary diseases have been reported. However, the relationship between USBA and fasting serum total bile acid (TBA) has not been studied in hepatobiliary diseases. In the present study, we measured USBA levels in patients with hepatitis C virus‐related chronic liver diseases, and the relationship between TBA and various laboratory tests was studied.

Methods:  USBA was measured using an automatic assay kit in 66 patients with chronic hepatitis and 28 patients with liver cirrhosis, and its relationship between TBA and various laboratory tests was studied.

Results:  The median USBA level was 10.7 µmol/g creatinine in patients with chronic hepatitis and 41.1 µmol/g creatinine in liver cirrhosis (P = 0.000). More patients with chronic hepatitis had elevated USBA levels (61%) compared to TBA level (39%) (P = 0.002). USBA level was well correlated with TBA (rs = 0.680), and negatively correlated with albumin (rs = −0.488), prothrombin time (rs = −0.385) and platelet counts (rs = −0.394). In patients with liver cirrhosis, USBA was significantly elevated in Child–Pugh class B compared to Child–Pugh class A (P = 0.036).

Conclusion:  Although the metabolic pathways of USBA and TBA are different, these levels correlated very well, and USBA is considered to be a useful indicator of hepatic function like TBA in patients with chronic hepatitis C.
Continuum Mesomechanical Finite Element Modeling in Materials Development: A State-of-the-Art Review
Authors: Mishnaevsky Leon L. , Schmauder Siegfried
Published: April 2009

Advanced finite element techniques for the simulation of materials behavior under mechanical loading are reviewed. Advantages, limitations and perspectives of different approaches are analyzed for the simulation of deformation, damage and fracture of materials taking into account their micro- and mesostructure. Development of simulation methods for different aspects of materials behavior (such as the unit cell approach, real structure simulation, cohesive zone model, etc) is described including the simple versions of the methods as well as the advanced, highly efficient models. Possibilities of using the finite element method in the development of new materials are analyzed. This review article contains 131 references.
Recent Advances in Liquid Sloshing Dynamics
Authors: Ibrahim R. A. , Pilipchuk V. N. , Ikeda T.
Published: April 2009

A liquid free surface in partially filled containers can experience a wide spectrum of motions such as planar, non-planar, rotational, quasi-periodic, chaotic, and disintegration. Civil engineers and seismologists have been studying liquid sloshing effects on large dams, oil tanks and elevated water towers under ground motion. Since the early 1960’s, the problem of liquid sloshing dynamics has been of major concern to aerospace engineers studying the influence of liquid propellant sloshing on the flight performance of jet vehicles. Since then, new areas of research activities have emerged. The modern theory of nonlinear dynamics has indeed promoted further studies and uncovered complex nonlinear phenomena. These include rotary sloshing, Faraday waves, nonlinear liquid sloshing interaction with elastic structures, internal resonance effects, stochastic sloshing dynamics, hydrodynamic sloshing impact dynamics, g-jitter under microgravity field, cross-waves, and spatial resonance. The dynamic stability of liquid gas tankers and ship cargo tankers, and liquid hydrodynamic impact loading are problems of current interest to the designers of such systems. This article will address the means of passive control of liquid sloshing and the use of liquid sloshing forces to control vibratory structures. Other important contributions include the development of digital computer codes to solve complex problems that were difficult to handle in the past. The purpose of this article is to review the research work developed in different applications. It will highlight the major achievements and results reported in the literature. Some early work will be cited very briefly in order to provide an updated bibliography of liquid sloshing dynamics. This review article contains 1,319 references.
Combustion Limits
Authors: Ju Yiguang , Maruta Kaoru , Niioka Takashi
Published: April 2009

Combustion limits and related flame behaviors are reviewed, especially with regard to fundamental problems. As for premixed flames, after a brief historical overview of research on the flammability limit, recent trends of research on planar propagating flames, curved propagating flames, flame balls, and stretched premixed flames are discussed, and then all types of flames are summarized. Finally, instability and dynamics near limits is discussed. With regard to combustion limits of counterflow diffusion flames and droplet flames, their instability is demonstrated, then an explanation of lifted flames and edge flames is presented. Suggestions for future work are also discussed in the concluding remarks. There are 166 references cited in this review article.
The Effect of Radiation and Turbulence on Heat Transport in Combustion in Porous Media
Authors: de Lemos Marcelo J. S.
Published: April 2009

Combustion in inert porous media has been extensively investigated due to the many engineering applications and demand for developing high efficiency power production devices. The growing use of efficient radiant burners can be encountered in the power and process industries and, as such, proper mathematical models of flow, heat and mass transfer in porous media under combustion can benefit the development of such engineering equipment. This paper proposes a new mathematical model for computing temperature and flow variables inside a porous burner. A new concept called “double-decomposition” is used to represent all transported variables. A set of governing equations is presented and the numerical solution method proposed is discussed. Computations are carried out for a test case considering a simple one-energy equation model and one-step reaction rates. Simulations are presented comparing the inclusion of turbulence and radiation transfer in the model. It is shown that for high Re flows, inclusion of turbulence is as important as modeling radiation for obtaining reliable temperature distribution within the porous material.
Wind Tunnel Measurements of Convective Heat Transfer With Droplet Impact on a Wind Turbine NACA63-421 Blade
Authors: Wang Xin , Naterer Greg , Bibeau Eric
Published: April 2009

Icing of wind turbine blades and sensors in cold climates can cause a significant decrease in turbine efficiency and power production, due to the altered blade aerodynamics and forced shutdowns. Various studies have developed innovative methods for de-icing of wind turbine blades and sensors. In this paper, experimental studies of heat transfer with water droplets on a NACA 63–421 airfoil are studied to simulate anti-icing conditions. Various liquid water contents (LWC) are investigated. The measurements can provide important characterization of heat convection between the airfoil surface and cold surrounding air just before icing accumulation. These experimental measurements can be used to develop better methods to reduce impact of wind turbine icing in cold weather climates. This study is intended to provide useful data to improve methods of anti-icing of wind turbines.
New Frontiers of Micro and Nano-Scale Thermophysical Properties Sensing
Authors: Nagasaka Yuji
Published: April 2009

The present keynote speech overviews new frontiers of sensing techniques for thermophysical properties in micro and nano-scale processes which are being developed at Keio. Especially, new optical sensing techniques to measure wide variety of thermophysical properties such as thermal diffusivity, thermal conductivity, viscosity, mass diffusion coefficient and surface tension of novel fluids and solids in micro and nano-scale are presented with an emphasis on their industrial applications. All of these new optical techniques have high spatial and temporal resolutions which have never been attained by other conventional measurement tools.
Numerical Analysis of the Effects of Solid Metal Fuel Particle Characteristics on the Combustion Process
Authors: Marino Thomas , Motevalli Vahid , Sondergaard Neal
Published: April 2009

Combustion using aluminum particles as fuel is an attractive energy source where high energy densities are desired. Very little experimental literature or computational results are available for metal combustion in high-pressure chambers, as most experimental and computational work has been done on chamber operating at near atmospheric pressures. This paper attempts to improve our understanding of metal-fueled combustion chambers at pressures above atmospheric. A numerical model of solid Aluminum fuel particle combustion is developed to investigate the effects of radiation and fuel particle size on the combustion process. Of specific interest are particle specific burn rate, residence time, combustion efficiency, coupled radiation effects, and flame characteristics. This computational model is applied to a linear-type dump combustor. The effects of a range of particle sizes are investigated using mono-dispersed and poly-dispersed particle distributions. Combustion efficiency and characterization of the combustion process are addressed by studying particle ignition delay, surface combustion time, and particle flame radiation intensity as a function of particle diameter and mass fraction. The computational results of this detailed theoretical combustor reveal fundamental physics relating particle sizes and distributions to the variables commonly used to define the effectiveness and performance of the combustion process. The computational models include nonisotropic turbulence models, empirically derived ignition criteria and reaction rates, as well as convective and radiant heat transfer. The numerical results were compared with test data with reasonable agreement.
Role of Artificial Intelligence (AI) in Thermal Science and Engineering
Authors: Yang Kwang-Tzu
Published: April 2009

The use of artificial intelligence methodologies in a variety of real-world applications has been around for some time. However, the application of such methodologies to thermal science and engineering is relatively new, but is receiving ever-increasing attention in the published literature since the mid 1990s. Such attention is due essentially to special requirements and needs of the field of thermal science and Engineering (TSE) in terms of its increasing complexity and the recognition that it is not feasible to approach many critical problems in this field by the use of traditional analysis. The purpose of the present brief review is to point out the recent advances in the artificial intelligence (AI) field and the successes of such methodologies to the current problems in thermal science and engineering. Some shortfalls and prospect for future applications will also be indicated.
Entropy Minimization in an Evaporating Thin Liquid Film in Capillary Tubes
Authors: Gorla Rama Subba Reddy , Nallappan Thamilselvan , Byrd Larry W. , Pratt David M.
Published: April 2009

An analysis has been provided for the entropy generated for the micro/nano scale heat and mass transfer in a capillary tube in terms of the gradients of velocity, temperature and concentration as well as the physical properties of the fluid. The heat and mass transfer rates are assumed to be uniform on the surface of the capillary tube. The optimum tube diameter that corresponds to the minimization of entropy generated and minimization of fluid flow resistance is about one millimeter. We have applied the method of thermodynamic optimization to capillary driven systems.
Combined Micro-Channel Heat Sink Optimization for Cooled Electronics
Authors: Bello-Ochende Tunde , Meyer Josua P.
Published: April 2009

This paper documents the geometric optimization of a three dimensional micro-channel heat sink with hydraulic diameter greater than 10μm. Two methods of analysis were used to perform the optimization; approximate relation using scale analysis and numerical method using a finite volume code. The micro-channel heat sink is treated as a combined unit. The effect of void fraction and pressure drop on the aspect ratio, hydraulic diameter and peak temperature on the micro-channel heat sink were investigated. The numerical simulation was carried out on a unit cell with volume of 0.9 mm3 and pressure differences between 10 kPa and 75 kPa. The optimal configurations obtained numerically were compared with those obtained from approximate relationship using scale analysis and the trends are found to be in good agreement.
Local Two-Phase Flow Heat Transfer in Plate Heat Exchangers
Authors: Kabelac Stephan , Freund Sebastian W.
Published: April 2009

Experimental results on quasi-local heat transfer coefficients for evaporation and condensation in PHEs related to vapor quality, mass flow rate and heat flux are presented in this paper. The data is obtained from a refrigeration cycle involving a PHE evaporator and a PHE condenser with a secondary fluid loop. The considered refrigerants are ammonia and R-134a. Evaporator and condenser are equipped with multiple thermocouples along the plates, which allow for the deduction of local heat flux and heat transfer coefficients on seven subsections of the plates. The data resolves for the first time the complete evaporation and condensation process along a plate channel and thus may contribute to the understanding of flow distribution and heat transfer mechanisms. The results show an increase of heat transfer coefficients with the vapor quality and the effects of mass flux and heat flux. The results conclude that parallel flow arrangement is advantageous for evaporation while counter flow enhances condensation heat transfer. Plates with low pitch angle chevron corrugations increase the evaporation. Comparisons with the limited available data from literature and various correlations indicate the need for further theoretical development. The data may be suitable for developing correlations of the thermo-hydraulic performance of plate evaporators and condensers as a function of flow, heat flux and plate parameters, which are not established in literature.
Numerical Prediction of Nitrogen Oxides in Radiant Porous Burner Flows
Authors: Tong Timothy W. , Abou-Ellail Mohsen M. , Li Yuan , Beshay Karam R.
Published: April 2009

The present paper is concerned with the numerical computation of flow, heat transfer and chemical reactions in porous burners. The porous solid matrix acts as a host for redistributing the thermal energy transferred to it from the hot reacting gases. Inside the porous matrix, heat is transferred down stream by conduction and radiation. This thermal energy is then transferred to the incoming cold fuel/air mixture to initiate the chemical reaction processes and thus stabilize the flame. One of the important features of porous burners is its presumed low levels of NO concentration. In the present work, the computed NOx is compared with experimental data and open premixed flames. In order to accurately compute the nitric oxide levels in porous burners, both prompt and thermal NOx mechanisms are included. In the present work, the porous burner species mass fraction source terms are computed from an ‘extended’ reaction mechanism, controlled by chemical kinetics of elementary reactions. The porous burner has mingled zones of porous/nonporous reacting flow, i.e., the porosity is not uniform over the entire domain. Finite-volume equations are obtained by formal integration over control volumes surrounding each grid node. Up-wind differencing is used to insure that the influence coefficients are always positive. Finite-difference equations are solved, iteratively, for velocity components, pressure correction, gas enthalpy, species mass fractions and solid matrix temperature. A non-uniform (80×80) computational grid is used. The grid used to solve the solid energy equation is extended inside the solid annular wall of the porous burner, to improve its modeling. A discrete-ordinate model with S4 quadrature is used for the computation of thermal radiation emitted from the solid matrix. The porous burner uses a premixed CH4-air mixture, while its radiating characteristics are required to be studied numerically under equivalence ratios 0.6 and 0.5. Twenty-five species are included, involving 75 elementary chemical reactions. The computed solid wall temperature profiles are compared with experimental data for similar porous burners. The obtained agreement is fairly good. Some reacting species, such as H2O, CO2, H2, NO and N2O increase steadily inside the reaction zone. However, unstable products, such as HO2, H2O2 and CH3, increase in the preheating zone to be depleted afterward.
Heat Transfer Enhancement Using Ferromagnetic Particle Laden Fluid and Oscillating Magnetic Fields
Authors: Murray Mark M.
Published: April 2009

A convective heat transfer enhancement technique and the experimental method used to quantify the improvement in heat transfer are introduced. The enhancement technique employs time varying magnetic fields produced in a pipe to cause the ferromagnetic particles of a particle laden fluid (mineral oil and iron filings) to be attracted to and released from the pipe wall. The magnetic field remains energized long enough to attract particles to the wall and allow the heat to be quickly transferred to the highly thermally conductive particles. The released particles utilize their large surface area when dispersed to efficiently transfer heat to the bulk fluid. The ferromagnetic particles act not only to advect heat into the bulk fluid, but they also disrupt the boundary layer, allowing cooler fluid to reach the high temperature pipe wall, increase thermal energy transfer directly to the fluid and contribute to the overall improvement in heat transfer rate. The experimental method utilized to quantify increased effectiveness of convective heat transfer uses an experimental apparatus designed to replicate an internally cooled fin. The pipe test section acts as an internally cooled fin whose surface temperature is measured with an IR camera. These temperature measurements are then utilized to calculate the convective heat transfer coefficient (h) of the fluid within the pipe. The enhancement technique demonstrated a 250% increases in heat transfer coefficient for the experimental parameters tested.
Prediction and Performance of Compact Latent Heat Recovery Heat Exchanger With Small Diameter Tubes
Authors: Osakabe Masahiro
Published: April 2009

The most part of energy losses in power system such as fuel cells is due to the heat released by the exhaust gas to atmosphere. The exhaust gas consists of non-condensable gas and steam with sensible and latent heat. As a lot of latent heat is included in the exhaust gas, its recovery is very important to improve the power system efficiency. Based on the previous basic studies, a thermal hydraulic prediction method for latent heat recovery exchangers was proposed. For the condensation of steam on heat transfer tubes, the modified Sherwood number taking account of the mass absorption effect on the wall was used. Two kinds of compact heat exchanger with staggered banks of bare tubes of 10.5 or 4mm in outer diameter was designed with the prediction method. The more compactness was obtained with the smaller tubes at a designed heat recovery. The thermal hydraulic behavior in the compact heat exchangers was experimentally studied with air-steam mixture gas. In the parametric experiments varying the steam mass concentration, the temperature distributions of cooling water and mixture gas were measured. The experimental results agreed well with the prediction proposed in this study and the more compactness with the smaller tubes was proved.
Investigation of Approximate Diffusion Models for the Prediction of Heterogeneous Combustion in Monolith Tubes
Authors: Kumar Ankan , Mazumder Sandip
Published: April 2009

In the case of heterogeneous reactions, diffusion is the only mechanism, locally, of transport of species to and from a surface. Thus, accurate prediction of diffusive transport is a prerequisite for accurate prediction of the operation of devices in which heterogeneous reactions occur. Three different diffusion models are examined from the standpoint of both accuracy and efficiency. Two of these models, namely the Dilute Approximation (DA) model and the Schmidt Number (SN) model, are approximate models, and are compared against a rigorous Multi-Component Diffusion (MCD) model derived from the Stefan-Maxwell equation. Both hydrogen-air and methane-air combustion in a monolith channel are studied. Inlet equivalence ratio, Reynolds number (flow rate), and wall temperature are considered as parameters. The results show that both the DA model and the SN model are accurate within 2% irrespective of the equivalence ratio or fuel—the worst accuracy being for hydrogen combustion. The DA model and the SN model produce almost identical results. In comparison to the MCD model, the DA model is approximately twice as computationally efficient, while the SN model is 3–4 times more efficient. The accuracy and efficiency of the SN model, in conjunction with its simplicity, makes it an attractive choice for the treatment of diffusion in catalytic combustion calculations.
An Analytical Model of External Streaming and Heat Transfer for a Levitated Flattened Liquid Drop
Authors: Lee Sungho , Sadhal S. S. , Rednikov Alexei Ye.
Published: April 2009

We present here the heat transfer and fluid flow analysis of an acoustically levitated flattened disk-shaped liquid drop. This work arises due to an interest in the non-contact measurement of the thermophysical properties of liquids. Such techniques have application to liquids in the undercooled state, i.e., the situation when a liquid stays in a fluidic state even when the temperature falls below the normal freezing point. This can happen when, for example, a liquid sample is held in a levitated state. Since such states are easily disrupted by measurement probes, non-contact methods are needed. We have employed a technique involving the use of acoustically levitated samples of the liquid. A thermal stimulus in the form of laser-heating causes thermocapillary motion with flow characteristics depending on the thermophysical properties of the liquid. In a gravity field, buoyancy is disruptive to this thermocapillary flow, masking it with the dominant natural convection. As one approach to minimizing the effects of buoyancy, the drop was flattened (by intense acoustic pressure) in the form of a horizontal disk, about 0.5 mm thick. As a result, with very little gravitational potential, with most of the buoyant flow suppressed, thermocapillary flow remained the dominant form of fluid motion within the drop. This flow field is visualizable and subsequent analysis for the inverse problem of the thermal property can be conducted. This calls for numerical calculations involving a heat transfer model for the flattened drop. With the presence of an acoustic field, the heat-transfer analysis requires information about the corresponding Biot number. In the presence of a high-frequency acoustic field, the steady streaming originates in a thin shear-wave layer, known as the Stokes layer, at a surface of the drop. The streaming develops into the main fluid, and is referred to as the outer streaming. Since the Stokes layer is asymptotically thin in comparison to the length scale of the problem, the outer streaming formally appears to be caused by an effective slip velocity at the boundary. The presence of the thin Stokes layer, and the slip condition at the interface, changes the character of the heat transfer mechanism which is inherently different from the traditional boundary layer. The current analysis consists of a detailed semi-analytical calculation of the flow field and the heat transfer characteristics of a levitated drop in the presence of an acoustic field.
Optimal Porosity of Fibrous Battings for Thermal Insulation
Authors: Fan Jintu , Du Ning , Wu Huijun
Published: April 2009

The porosity of fibrous porous materials is an important factor to the thermal insulating performance of the material. This paper considers both the optimal porosity of uniform fibrous battings and the optimal distribution of the porosity of non-uniform fibrous battings for thermal insulation. The former was determined by an approximate analytical solution and a numerical simulation by using Finite Volume Method, and the latter was studied by applying Simulated Annealing Method. The study showed that the optimal porosity of uniform fibrous porous materials is very much dependent on fiber emissivity, and fiber radius, but little influenced by the temperature difference of the boundaries. For non-uniform fibrous materials, there can be an optimal distribution of porosity, which can be predicted by applying the Simulated Annealing Method.
Molecular-Scale Reagent Transport-Induced Modification of Low Weber Number Droplet Impact Dynamics
Authors: Gatne Kalpak P. , Manglik Raj M. , Jog Milind A.
Published: April 2009

Effect of surfactant molecular mass transport on the normal impact and spreading of a droplet of its aqueous solution on dry horizontal substrates is investigated for a range of Weber numbers (We = 20 – 100). The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 4000 frames per second. Digital image-processing software was used to determine the drop spread and height of the liquid film on the surface from each frame. Experiments were performed with water and with two different aqueous solutions of Sodium Dodecyl Sulphate (SDS), one at its half critical micelle concentration (CMC) and another at twice CMC, on a hydrophilic surface (glass) and a hydrophobic surface (Teflon). It is seen that surfactant concentration, its dynamic surface tension behavior, and surface wettability govern the transient impact-spreading-recoil phenomena. A droplet of SDS solution exhibits higher maximum spread and weaker surface oscillations compared to a pure water drop colliding with the same velocity. On a hydrophobic (Teflon) surface, the drop rebound is inhibited by the presence of the surfactant. These effects are more pronounced at surfactant concentration of twice CMC compared to that at half CMC.
Theoretical Modeling and Experimental Measurements of Single Bubble Dynamics From a Submerged Orifice in a Liquid Pool
Authors: Kasimsetty S. K. , Subramani A. , Manglik R. M. , Jog M. A.
Published: April 2009

The dynamics of a single gas bubble, emanating from a submerged orifice in stagnant water has been explored both theoretically and experimentally. The mathematical model represents a fundamental balance of forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport, and the consequent motion of the gas-liquid interface. Theoretical solutions describe the dynamic bubble behavior (incipience, growth and necking) as it grows from a tip of a sub-millimeter-scale capillary orifice in an isothermal pool of water. These results are also found to be in excellent agreement with a set of experimental data that are obtained from optical high-speed micro-scale flow visualization. Variations in bubble shape, equivalent diameter, and growth times with capillary orifice diameter and air flow rates are outlined. These parametric trends suggest a two-regime ebullient transport: (a) a constant volume regime where the bubble diameter is not affected by the flow rate, and (b) a growing bubble regime where bubble size increases with flow rate.
The Effect of Flow-Duct Geometry on Solid Desiccant Dehumidification
Authors: Al-Sharqawi Hassan S. , Lior Noam
Published: April 2009

This study presents a comparative numerical solution of a conjugate-transient three-dimensional heat and mass transfer problem between a solid desiccant (silica gel) and a humid transient-laminar air stream in ducts with different cross sectional geometries: square, circular, and triangular. The problem is solved by using a finite control-volume method, and validated relative to available experimental data. The effects of the u velocity gradient normal to the wall (∂u/∂y) and the pressure drop (Δp) on the heat and mass transport for the three ducts are investigated. In duct flows, the results show that the average (∂u/∂y) for the triangular duct is 6.6% and 19.6% larger than that in the circular and square ducts, respectively; therefore, the triangular duct provides the largest convective heat and mass transport, and absorbs 11% and 42% more water than the circular and square ducts, respectively. At the same time, the average pressure drop for the triangular duct is 69% and 73.5% larger than the one for the square and circular ducts, respectively, which would result in higher fan power consumption. Using a figure of merit (Wr) that is a ratio of the required fan work to the dehumidification attained, the circular duct was found to be the best and the triangular the worst among the three geometries compared.
Modeling of Flooding Phenomena in Hydrophobic Gas Diffusion Layer of PEFC
Authors: Kudo Kazuhiko , Kuroda Akiyoshi , Takeoka Shougo , Shimazu Yosuke
Published: April 2009

The mechanism of liquid water removal, water vapor diffusion and oxygen diffusion in cathode side gas diffusion layer (GDL) of PEFC is studied by modeling the GDL as a hydrophobic flat plate with many straight holes with different diameters. As the results of the consideration using the model, following results are obtained. The spots where liquid water condensation is taken place between GDL-MEA gap are limited to the inlets of holes with larger diameters, and the condensed water is drained to air flow channel only through the larger holes. Other holes with smaller diameters are free of liquid water, and oxygen diffuses from the air flow channel to the catalyst surface through such holes. The reduction of output voltage of fuel cell due to the increase in the current density may be caused by the reduction of the oxygen concentration in GDL-MEA gap. The condensate tends to penetrate into larger holes instead of filling the gap of GDL and MEA.
Heat Conduction Across Corrugated Thermal Interface
Authors: Yang Bozhi , Liu Wenjun
Published: April 2009

This paper presents the analytical solution of the heat conduction across a corrugated thermal interface material with rectangular straight fin arrangement. Domain decomposition and eigenfunction expansion method were used to study the thermal diffusion in such geometry for the first time. The temperature field solved from the analytical method agrees well with FEM simulation. The total heat transfer rate across the corrugated interface and thermal boundary resistance were derived analytically also. Results have shown that the effective thermal resistance across the interface can be significantly reduced with the corrugated TIM geometry. The analytical solution in the paper can provide insight into geometry effect on the heat transfer enhancement, and is a very useful complement to experimental work and numerical simulation in designing high-performance corrugated thermal interface.
Flow Boiling Enhancement in Microchannels With Diffusion Bonded Wire Mesh
Authors: Wang Hailei , Peterson Richard
Published: April 2009

Flow boiling and heat transfer enhancement in four parallel microchannels using a dielectric working fluid, HFE 7000, was investigated. Each channel was 1000 μm wide and 510 μm high. A unique channel surface enhancement technique via diffusion bonding a layer of conductive fine wire mesh onto the heating wall was developed. According to the obtained flow boiling curves for both the bare and mesh channels, the amount of wall superheat was significantly reduced for the mesh channel at all stream-wise locations. This indicated that the nucleate boiling in the mesh channel was enhanced due to the increase of nucleation sites the mesh introduced. Both the nucleate boiling dominated and convective evaporation dominated regimes were identified. In addition, the overall trend for the flow boiling heat transfer coefficient, with respect to vapor quality, was increasing until the vapor quality reached approximately 0.4. The critical heat flux (CHF) for the mesh channel was also significantly higher than that of the bare channel in the low vapor quality region. Due to the fact of how the mesh was incorporated into the channels, no pressure drop penalty was identified for the mesh channels. Potential applications for this kind of mesh channel include high heat-flux electronic cooling systems and various energy conversion systems.
Thermal Conductivity of High Contrast Nanoparticle Composites
Authors: Tian Weixue , Yang Ronggui
Published: April 2009

In this paper, we investigated the thermal conductivity of three-dimensional nanocomposites composed of randomly distributed nanoparticles with large thermal conductivity differences in the constituents. Nanoparticles in composite materials fabricated by processes such as hot press or spark plasma sintering tend to be randomly distributed. For composites made of particles with high thermal conductivity contrast ratio, percolation theory predicts the existence of a continuous phase of high thermal conductivity material when its volumetric concentration reaches beyond the percolation threshold. Such a continuous phase can provide a low resistance pathway for phonon transport in the nanocomposites. Therefore, the thermal conductivity of the composites is expected to increase significantly with increasing concentration of the high thermal conductivity nanoparticles. However, when the characteristic size of the nanoparticles is comparable or smaller than the phonon mean free path, the interface between two materials causes phonon scattering and significant thermal resistance in the highly conductive phonon pathway. Such an additional thermal resistance can reduce the magnitude of the thermal conductivity improvement in the nanocomposites. In this study, the Monte Carlo simulation was employed to generate the nanoparticle random distribution and to simulate phonon transport in the nanocomposites. The effects of particle size, thermal conductivity contrast and interface characteristic on thermal conductivity of the nanocomposites are discussed.