bluuebunny/crossref_metadata_2025 huggingface dataset:
Taking young people as political actors seriously: opening the borders of political geography
Authors: Skelton Tracey
Published: April 2009

This article challenges the absence of young people from Political Geography. It shows how in many parts of the world young people are in an in‐between space politically and legally. This article suggests that the geographically divergent liminal positioning of young people within political–legal structures and institutional practices is what makes them extremely interesting political subjects. I argue for a deconstruction of the generally accepted binary of capital P Politics and lower case p politics. Using an illustration from a non‐Western geography, I argue that young people can do more than act politically in the interstices of this binary; they can in fact meld and blend both elements. Taking young people seriously may well create new definitions of the political and demonstrate other ways of conceptualising geopolitics and political geographies.
Peripheral and central sites of action for the non‐selective cannabinoid agonist WIN 55,212‐2 in a rat model of post‐operative pain
Authors: Zhu CZ , Mikusa JP , Fan Y , Hollingsworth PR , Pai M , Chandran P , Daza AV , Yao BB , Dart MJ , Meyer MD , Decker MW , Hsieh GC , Honore P
Published: April 2009

Background and purpose: Activation of cannabinoid (CB) receptors decreases nociceptive transmission in inflammatory or neuropathic pain states. However, the effects of CB receptor agonists in post‐operative pain remain to be investigated. Here, we characterized the anti‐allodynic effects of WIN 55,212‐2 (WIN) in a rat model of post‐operative pain.

Experimental approach: WIN 55,212‐2 was characterized in radioligand binding andin vitrofunctional assays at rat and human CB1and CB2receptors. Analgesic activity and site(s) of action of WIN were assessed in the skin incision‐induced post‐operative pain model in rats; receptor specificity was investigated using selective CB1and CB2receptor antagonists.

Key results: WIN 55,212‐2 exhibited non‐selective affinity and agonist efficacy at human and rat CB1versus CB2receptors. Systemic administration of WIN decreased injury‐induced mechanical allodynia and these effects were reversed by pretreatment with a CB1receptor antagonist, but not with a CB2receptor antagonist, given by systemic, intrathecal and supraspinal routes. In addition, peripheral administration of both CB1and CB2antagonists blocked systemic WIN‐induced analgesic activity.

Conclusions and implications: Both CB1and CB2receptors were involved in the peripheral anti‐allodynic effect of systemic WIN in a pre‐clinical model of post‐operative pain. In contrast, the centrally mediated anti‐allodynic activity of systemic WIN is mostly due to the activation of CB1but not CB2receptors at both the spinal cord and brain levels. However, the increased potency of WIN following i.c.v. administration suggests that its main site of action is at CB1receptors in the brain.

British Journal of Pharmacology(2009)157,645–655; doi:10.1111/j.1476‐5381.2009.00184.x; published online 3 April 2009
The ‘New Terrorism’: Revolution or Evolution?
Authors: Field Antony
Published: April 2009

It is essential to understand the concept of the ‘new terrorism’, since it has fostered a paradigm shift in the way that academics, policy makers and counter-terrorism professionals conceive of the contemporary threat. Capturing the notion that there has been a revolutionary change in the nature of terrorism, it now plays a pre-eminent role in shaping counter-terrorism policy. However, despite the attractive simplicity of the concept, there are good reasons to question the assumption that the actual behaviour of terrorist groups has fundamentally altered. Indeed, an analysis of the history of terrorism shows that many of the supposed hallmarks of the ‘new terrorism’ have been seen in the past. As a consequence, the concept of the ‘new terrorism’ should be viewed with some scepticism, as it unduly exaggerates the unprecedented nature of the contemporary terrorist threat and needlessly leads policy makers to reject the relevance of historical counter-terrorism lessons.
Bacterial Culture and DNA Checkerboard for the Detection of Internal Contamination in Dental Implants
Authors: Barbosa Rodrigo Edson Santos , Do Nascimento Cássio , Issa João Paulo Mardegan , Watanabe Evandro , Ito Izabel Yoko , De Albuquerque Junior Rubens Ferreira
Published: April 2009

Purpose: The aim of this in vitro study was to evaluate the bacterial leakage along the implant–abutment interface by the conventional bacterial culture and DNA Checkerboard hybridization method.

Materials and Methods: Twenty Branemark‐compatible implants with a 3.75‐mm diameter and external hexagonal platform were randomly placed in two groups of ten implant–abutment assemblies each. One group was used to analyze bacterial counts by DNA Checkerboard hybridization and the other by a conventional bacterial culture. Suspensions of Fusobacterium nucleatum (3 μl) were injected into the grooved internal cylinders of each implant assembly, and the abutment was connected by a 32 Ncm torque. The combined implant–abutments were individually placed in tubes containing the CaSaB culture medium and incubated in a bacteriological constant temperature oven for 14 days. The samples were observed daily as to the presence of turbidity, and after the designated time the microorganisms were collected from the implant interiors and analyzed by the two methods.

Results: After 14 days, six implant–abutment assemblies showed turbidity. Both methods indicated reduced microorganism counts in samples from the interior of the implant–abutment assemblies after incubation in the culture medium; however, the number of counts of F. nucleatum was higher by the DNA Checkerboard method when compared to the group analyzed by conventional bacterial cultures (p < 0.05).

Conclusion: The DNA Checkerboard method was shown to be more sensitive than conventional cultures in the detection of microorganisms.
Issuing of blood components dispensed in syringes and bar code–based pretransfusion check at the bedside for pediatric patients
Authors: Ohsaka Akimichi , Abe Katsumi , Nakamura Yuki , Ohsawa Toshiya , Sugita Shio
Published: April 2009

BACKGROUND: The pretransfusion check at the bedside is the most critical step for the prevention of mistransfusion in pediatric patients, as well as in adults. The objective of this study was to assess whether a bar code–based patient–blood unit identification system could be applied to the pretransfusion check at the bedside for the issuing of blood dispensed in syringes.

STUDY DESIGN AND METHODS: The issuing of blood components dispensed in syringes and the bar code–based pretransfusion check at the bedside were initiated for pediatric patients in May 2003. The number of blood components transfused to pediatric patients and rate of compliance with electronic bedside verification for blood dispensed in syringes were determined. Several variables in blood samples that were freshly collected, irradiated, split into 20‐mL aliquots, and stored in syringes at 4°C were measured.

RESULTS: Between May 2003 and April 2007, a total of 3957 blood components (10% of all transfusions) were administered to pediatric patients without a single mistransfusion, of which 871 (22%) were issued by dispensing in syringes. The compliance rate with electronic bedside verification for blood dispensed in syringes was 99%. The supernatant potassium concentrations and extracellular free hemoglobin in blood samples stored in syringes at 4°C for 24 hours were 14 ± 1.3 mmol/L and less than 0.3 g/L, respectively, and these were considered to be acceptable for transfusion to pediatric patients.

CONCLUSION: The bar code–based identification system that we used was fully applicable to the pretransfusion check at the bedside for blood dispensed in syringes.
Predicting the future of species diversity: macroecological theory, climate change, and direct tests of alternative forecasting methods
Authors: Algar Adam C. , Kharouba Heather M. , Young Eric R. , Kerr Jeremy T.
Published: April 2009

Accurate predictions of future shifts in species diversity in response to global change are critical if useful conservation strategies are to be developed. The most widely used prediction method is to model individual species niches from point observations and project these models forward using future climate scenarios. The resulting changes in individual ranges are then summed to predict diversity changes; multiple models can be combined to produce ensemble forecasts. Predictions based on environment‐richness regressions are rarer. However, richness regression models, based on macroecological diversity theory, have a long track record of making reliable spatial predictions of diversity patterns. If these empirical theories capture true functional relationships between environment and diversity, then they should make consistent predictions through time as well as space and could complement individual species‐based predictions. Here, we use climate change throughout the 20th century to directly test the ability of these different approaches to predict shifts of Canadian butterfly diversity. We found that all approaches performed reasonably well, but the most accurate predictions were made using the single best richness‐environment regression model, after accounting for the effects of spatial autocorrelation. Spatially trained regression models based on macroecological theory accurately predict diversity shifts for large species assemblages. Global changes provide pseudo‐experimental tests of those macroecological theories that can then generate robust predictions of future conditions.
Expression of Six1 homeobox gene during development of the mouse submandibular salivary gland
Authors: McCoy EL , Kawakami K , Ford HL , Coletta RD
Published: April 2009

Background:  Members of the Six family of homeoproteins are expressed in numerous tissues during vertebrate embryogenesis, and are critical regulators of both cell proliferation and survival. Here we report the temporal and spatial expression of Six1 during maturation of the mouse submandibular salivary gland (SSG) from embryonic day 18.5 (E18.5) to postnatal day 28. Additionally, we examine the role of Six1 during SSG development using Six1‐deficient mice.

Methods:  Six1 expression was assessed by reverse transcription‐polymerase chain reaction, Western blot, and immunofluorescence. Proliferation was measured by bromodeoxyuridine (BrdU) incorporation index, and apoptosis was evaluated by TUNEL assay.

Results:  Six1 mRNA and protein levels are high in the epithelial SSG cells at E18.5 and decrease progressively in the postnatal maturing SSG. Although SSGs from Six1−/− embryos are significantly smaller than wild type SSGs, the histological structures of the SSG acini and ducts are similar. Six1−/− salivary epithelial cells exhibit an intrinsic defect in cell proliferation accompanied by a significant reduction in the Six1 target gene cyclin A1, previously shown to be a critical mediator of Six1‐induced proliferation.

Conclusion:  Our results suggest that the reduction in size of Six1−/− SSGs is result of a decrease in cell proliferation during development/maturation.
Foetal and congenital talipes: interventions and outcome
Authors: Swamy Ravi , Reichert Bernd , Lincoln Karen , Lal Mithilesh
Published: April 2009

Aim: Talipes is a congenital anomaly that can be corrected conservatively or surgically. Despite advances in management, a proportion of pregnancies still result in termination. We therefore aimed to establish the birth prevalence, interventions and outcome of talipes in our population.

Methods: Cases with foetal talipes were identified from the ultrasound register at the James Cook University Hospital between 1990 and 2006. Infants with congenital talipes between 1998 and 2006 were identified from the physiotherapy database. Management details were obtained from case records.

Results: A total of 46 cases with foetal talipes were identified among 75 933 pregnancies. Of the 34 live‐born infants, 24 (70.5%) required surgery to correct the talipes. Congenital talipes was found in 69 infants, giving a birth prevalence of 2 per 1000 live births. Sixteen (72.7%) infants with an antenatal diagnosis required surgical correction. Infants with an antenatal diagnosis were at an increased risk of requiring surgery (relative risk [RR]= 1.6).

Conclusion: Surgical management was required in more than two‐thirds of babies with foetal talipes. Conservative management was successful in the majority of the babies without an antenatal diagnosis. Infants with an antenatal diagnosis are 1.6 times as likely to need surgical correction as infants without an antenatal diagnosis.
Effect of MK‐886 on Ca2+Level and Viability in PC3 Human Prostate Cancer Cells
Authors: Huang Jong‐Khing , Huang Chorng‐Chih , Lu Ti , Chang Hong‐Tai , Lin Ko‐Long , Tsai Jeng‐Yu , Liao Wei‐Chuan , Chien Jau‐Min , Jan Chung‐Ren
Published: April 2009

Abstract:3‐[1‐(p‐chlorobenzyl)‐5‐(isopropyl)‐3‐tert‐butylthioindol‐2‐yl]‐2, 2‐dimethylpropanoic acid (MK‐886) is widely used for inhibition of leucotriene synthesis inin vitrostudies, however, many of its other effects have been reported. The present study investigated the effect of MK‐886 on cytosolic‐free Ca2+concentrations ([Ca2+]i) and viability in human PC3 prostate cancer cells. [Ca2+]iin suspended cells was measured by using fura‐2. MK‐886 at concentrations of 1 µM and above increased [Ca2+]iin a concentration‐dependent manner with an EC50value of 20 µM. The Ca2+signal was reduced partly by removing extracellular Ca2+. MK‐886 evoked Mn2+quenching of fura‐2 fluorescence, implicating Ca2+entry. MK‐886‐induced Ca2+influx was inhibited by store‐operated Ca2+entry inhibitors nifedipine, econazole and SKF96365. In Ca2+‐free medium, after pre‐treatment with 10 µM MK‐886, 1 µM thapsigargin (an endoplasmic reticulum Ca2+pump inhibitor)‐induced [Ca2+]irises were abolished; and conversely, thapsigargin pre‐treatment abolished MK‐886‐induced [Ca2+]irises. Inhibition of phospholipase C with U73122 did not alter MK‐886‐induced [Ca2+]irises. MK‐886 at concentrations of 1–100 µM concentration‐dependently decreased cell viability with an IC50value of 60 µM. The cytotoxic effect of MK‐886 was not inhibited by pre‐chelating cytosolic Ca2+with BAPTA/AM. Together, in PC3 cells, MK‐886 induced [Ca2+]irises by causing phospholipase C‐independent Ca2+release from the endoplasmic reticulum; and Ca2+influx via store‐operated Ca2+channels. Independently, MK‐886 was cytotoxic to cells in a Ca2+‐independent manner.
Multilateralizing TRIPs‐Plus Agreements: Is the US Strategy a Failure?
Authors: Morin Jean‐Frédéric
Published: April 2009

This article examines the current wave of US bilateral agreements with respect to their strategic and political value at the plurilateral level. The US government has explicitly recognized its objective of leveraging bilateral agreements in order to influence regional and multilateral negotiations. Although it may be too early to assess the full effectiveness of this US strategy, the article argues that there are clear signs that the exploitation of bilateral agreements will not independently achieve the goal of strengthening plurilateral patent norms. This finding is supported by an assessment of six potential roads from bilateralism to plurilateralism: chain reaction, pressure for inclusion, coalition building, emulation, legal interpretation and adherence. The assertion that bilateral trade deals have a huge impact on international patent law making, made both by proponents and critics of the Agreement on Trade‐Related Aspects of Intellectual Property Rights‐Plus, is unsubstantiated. The author concludes that the US Government Accountability Office and Congress are justified in questioning whether the negotiation of these bilateral agreements, at least in the realm of intellectual property law, is a wise investment of US Trade Representative's resources.
Reforms Towards Intellectual Property‐Based Economic Development in Malaysia
Authors: Gee Lim Heng , Azmi Ida Madieha , Alavi Rokiah
Published: April 2009

It has been constantly asserted that the intellectual property (IP) system is an effective way to enhance creativity, technological innovations, trade and competitiveness. Others, however, maintain that the IP system may not necessarily be the most effective and appropriate way to fuel the economy. This article investigates the role that IP plays in the economic development of Malaysia from 1986 to 2006. In particular, the article examines the impact of IP‐based reforms, which includes not only the IP laws but other IP‐related policies with a view to determine how these policies contribute to economic development in Malaysia. For this purpose, the article starts with a brief summary of important IP‐related policies. Then the article proceeds with an analysis of trends in IP applications such as patent, trademark and industrial design application. Using data such as numbers of IP filing and grant, this article suggests ways in which the reforms in IP‐related policies could have supported growth or could have directly influenced trends in IP application in Malaysia. The article further examines the growth of IP applications in four industrial sectors in Malaysia, i.e. automobiles, information technology, pharmaceuticals, and information and communications technology.
Modeling of Indoor Air Quality and Comfort in the Tombs of Valley of the Kings
Authors: Abdel-Aziz Omar A. A. , Khalil Essam E.
Published: April 2009

Airflow characteristics in ventilated and airconditioned spaces play an important role to attain comfort and hygiene conditions. This paper utilizes a 3D Computational Fluid Dynamics (CFD) model to assess the airflow characteristics in ventilated and air-conditioned archeological tombs of Egyptian Kings in the Valley of the Kings in Luxor, Egypt. It was found that the optimum airside design system can be attained, if the airflow is directed to pass all the enclosure areas before being extraction with careful selection of near wall velocities to avoid any wear or abrasion of the tomb-wall paintings. In this model conditioned air is allowed to enter the tomb from its entrance with a large area of admission in order to maintain low air velocity while extraction points are distributed along the tomb axis. The mode of evaluation should assess the airflow characteristics in any tomb passage according to its position in the enclosure and the thermal pattern and air quality. The Governing Equations are numerically solved in a three dimensional grid configurations at more than 500000 nodes. The paper addresses the various modeling aspects and constraints and suggests solutions that are viable and do not affect the tomb construction, interior nor sustainability.
Transient Stability and Convection in Impulsively Heated Porous Layers
Authors: Kohl M. J. , Kristofferson M. , Kulacki F. A.
Published: April 2009

Experiments are reported on initial instability and convection in a porous medium impulsively heated from below. The porous medium comprises either water or a water-glycerin solution and randomly stacked glass spheres in an insulated cylinder of height-to-diameter ratio of 1.9. Heating is accomplished with a constant flux lower surface and a constant temperature upper surface. Results include measurement of the initial transition to convection, overall heat transfer coefficient over a range of Rayleigh-Darcy numbers, and temperature profiles. Time-averaged temperature profiles suggest the existence of a unicellular flow over the range of Rayleigh numbers of the present experiments. The critical Rayleigh number for the onset of convection is obtained in terms of a length scale normalized to the thermal penetration depth as Rac = 83/(1.08η−0.08η2) for 0.02 < η < 0.18. Steady convection in terms of the Nusselt and Rayleigh numbers is represented by a new correlation form, Nu=0.047Ra0.91Pr0.11μμ00.72, where Ra is the Rayleigh-Darcy number, 400 < Ra < 5000, and the viscosity ratio is found sufficient to account for strongly temperature-dependent viscosity.
Transient Thermal and Structural Analysis of the Liquid Rocket Turbopump Turbine
Authors: Yoon S. H. , Jeon S. M. , Kim J.
Published: April 2009

A turbopump unit is a key component of the liquid rocket engine assembly. Generally operated by an impulse-type turbine with supersonic hot gas for a gas generator cycle engine, it pressurizes liquid oxygen and fuel to attain high specific impulse. The turbine is exposed to hot gas while rotating at a high speed and experiences severe thermal and mechanical loads during the operation. Its structural integrity must be assured through thermal and structural analyses of the turbine. To investigate non-steady heat transfer characteristics from the hot gas to the turbine blade, the heat transfer of supersonic hot gas flow to the complicated turbine blade geometry is solved through a three-dimensional CFD analysis. The distribution of gas temperature, pressure and velocity on the blade surface are obtained by the CFD analysis with appropriate convection heat transfer coefficients to be used for the structural analysis of the turbine rotor. The thermal stress due to material expansion and mechanical stress due to centrifugal loads are considered in the analysis. The three-dimensional transient stress distributions of the turbine blades, shroud, and disk are obtained by a finite element analysis. Finally, the overall results are examined to evaluate the strength safety of the turbine.
Heat Sink Capabilities and Limitations: A Hierarchical Evaluation of Leading Thermal Technologies
Authors: Garner Scott D.
Published: April 2009

This paper discusses the pros, cons and performance capabilities of a variety of thermal solutions including: conductive heat sinks, heat pipe assisted heat sinks, and pumped single solutions. The goal of the paper is to map performance regimes for various thermal solutions that will quickly allow thermal designers to select the appropriate technology for their requirements. The paper presents current technologies in a progressive manner discussing performance capabilities and limitations. Although innovative designs exist in every class of sink that push the capabilities of the technology there are basic limitations that define the overall performance envelops, and thus the need to move up the performance heirarchy to the next performance level. The limitations to conductive heat sinks are addressed and correlated to the industries transition to heat pipe assisted heat sinks starting with notebooks and currently progressing into the desktop segment. A brief section addresses solid metal conductive heat sinks with discussions focused on the physical limitation set by conduction which limits overall heat sink volume which in turn can be correlated to a maximum power that can be dissipated in standard commercial applications. The analysis presented and conclusions will be correlated to CPU power and the markets adoption of heat pipe assisted heat sinks. A more extensive section is devoted to heat pipe assisted heat sinks their pros, cons and physical limitations. A similar analysis as discussed in the first section of the paper outlines the anticipated transition points for pumped single phase solutions.   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.
Spectral Emissivity Measurements of Single Mineral Phases and Ash Deposits
Authors: Bohnes S. , Scherer V. , Linka S. , Neuroth M. , Bru¨ggemann H.
Published: April 2009

The spectral and total emissivity of particulate ash deposits of different chemical composition which originate from lignite and hard coal fired boilers from Alstom Power and RWE Power were investigated with a spectral radiometer. Furthermore the emittance of all major single phases present in ashes and slag have been determined. The single phases under consideration were SiO2, Al2O3, FeO, Fe2O3, CaO and MgO. The results on SiO2, Al2O3 and MgO have already been presented by Linka in 2003 [6] and therefore the focus is on FeO, Fe2O3 and CaO in the current paper. A spectral radiometer measures the emittance as a function of temperature and wavelength. The temperature varies from 600 to 1200°C in steps of 50K. The wavelength range from 1 to 15 μm has been examined. The measurements confirm the dependency of the spectral emittance on the chemical composition. Especially the content of either FeO or Fe2O3 or CaO influences the emittance of ashes and slag. The single phase samples of FeO and Fe2O3 show a temperature dependence of the emittance in the wavelength range between 1 and 6 μm. The same character of emittance appears in samples with high fractions of FeO or Fe2O3. CaO shows no temperature dependency in the complete range of wavelengths.
The Research on Exergy Transfer of Forced Convective Heat Transfer Through a Duct With Constant Wall Temperature
Authors: Wu Shuang-Ying , Chen Yan , Li You-Rong , Zeng Dan-Ling
Published: April 2009

Based on the first and second thermodynamic laws, a new systematic approach to study in detail the exergy transfer processes of forced convective heat transfer through a duct with constant wall temperature for fully developed turbulent flow is introduced. Some definition formula of the local and mean convective exergy transfer coefficient, convective exergy resistance, exergy flux and exergy-transfer Nusselt number etc have been provided and their new generalized expressions are derived. By reference to smooth duct, the numerical results of exergy transfer are obtained, the effect of Reynolds number and different cross-sectional position in the duct on exergy transfer process is analyzed. In addition, a comparison of the results of exergy transfer with that of energy transfer is also discussed.
Thermal Hydraulics and Thermal Radiation for Ultra High Temperature Gas-Cooled Nuclear Reactor With Pebble Type Fuel
Authors: Fumizawa Motoo
Published: April 2009

This report presents the results of thermal-hydraulic analysis for the Ultra High Temperature Reactor Experiment (UHTREX) as well as the modular Gas Turbine High Temperature Reactor 300 MWth (HTGR-GT300) loaded with Pebble Type Fuel. A thermal-hydraulic computer code was developed that was named PEBTEMP. In order to compare the present PBR case with UHTREX, a calculation for HTGR-GT300 was carried out in the similar conditions with UHTREX i.e. the inlet coolant temperature of 871°C, system pressure of 3.45 MPa and power density of 1.3 W/cm3. The hot channel factor of 1.0, 1.1, 1.2, and 1.3 are chosen for the present calculation. As the result, the fuel temperature for the present PBR case is extremely low when compared to the UHTREX case. The evaluated temperature is compared to the data of conventional optical high temperature camera using the principle of the thermal radiation flux dependence upon surface temperature. Therefore, the present PBR system design will be named as NUHTREX i.e. New UHTREX. The evaluated temperature is compared to the data of conventional optical high temperature camera using the principle of the thermal radiation flux dependence upon surface temperature.
Large-Scale Quantum Chemical Molecular Dynamics Simulations on the Formation Dynamics of Hydrogen by the Chemical Reactions of Water
Authors: Kubo Momoji , Sasaki Yumiko , Chiba Keiko , Qiang Pei , Rajjak Abdul , Tsuboi Hideyuki , Koyama Michihisa , Broclawik Ewa , Akutsu Kazuyoshi , Hirota Masahiro , Kitada Masayoshi , Hirata Hajime , Miyamoto Akira
Published: April 2009

We have successfully simulated the chemical reaction dynamics of water molecules on various Si surfaces by using our new tight-binding quantum chemical molecular dynamics method. The formation dynamics of hydrogen molecules from water molecules on Si nano-particle was observed at 300 K. Especially, we found that the surface termination of Si nano-particle strongly influences the chemical reactions of water molecules and the non-terminated Si surface is the active site for the hydrogen generation. Moreover, we suggest that nano-space of the SiO2/Si interface is more active site for the hydrogen generation.
Molecular Dynamics Simulation of Phonon Transport in EDIP Silicon
Authors: Sun Lin , Murthy Jayathi Y.
Published: April 2009

In this paper, molecular dynamics (MD) simulation is employed to compute thermal conductivity, dispersion curves and single mode relaxation times for bulk silicon. A newly-developed environment-dependent interatomic potential (EDIP) is used in our simulations. Using the Green-Kubo method, simulations of bulk silicon thermal conductivity are conducted using 216 to 4096 atoms. The effect of domain size is explored for different temperatures. Thermal conductivity predictions are found to converge to a bulk value for simulations containing 1000 atoms or more, even though the domain is much smaller than the phonon mean free path. A domain-size independent thermal conductivity is computed for temperatures ranging from 300 K to 1000 K and is shown to compare reasonably well with experimental data without the need for correction factors. The MD results are analyzed to obtain phonon dispersion curves along the [100] direction. Dispersion curves are also obtained using EDIP under a harmonic approximation and the classical dynamical matrix approach. The two sets of curves agree reasonably well. Furthermore, single mode phonon relaxation times are computed from the MD simulations. The trend can be curve-fit by third or fourth-order polynomials.
Analysis of Developing and Fully Developed Turbulent Flow and Heat Transfer in a Square-Sectioned U-Bend Duct
Authors: Etemad Sassan , Sunde´n Bengt
Published: April 2009

Turbulent flow and thermal field were predicted in a square-sectioned 180° bend at a Reynolds number of 56000. Suga’s low-Re cubic k-ε model [5–6] and the RSM [7–8] were used. The results were compared to experimental data [1]. Identical inlet boundary conditions were used in both cases. The inlet length impact on the flow-heat transfer in the bend was investigated. The velocities are higher near the inner wall and lower near the outer wall when a short inlet section is used. As the inlet length increases, the boundary layer grows thicker and the pressure-driven secondary vortex near the side wall becomes stronger. This vortex contributes significantly to the mixing process and heat transfer. It also alters the velocity distribution to a higher velocity near the outer wall and a lower velocity near the inner wall. When using a very long inlet length the vortex grows so strong that it generates a second counter-rotating vortex which isolates the fluid near the inner wall and prevents from further mixing. Consequently the local Nusselt number decreases. Both models reproduced the experimental data fairly well. Suga’s model performed better and converged without problems. It is believed that Suga’s model would be more suitable for industrial applications.
Modelling Heat Transfer Performance of a Thin Bi-Porous Evaporator for a Heat Pipe
Authors: Vadnjal Aleksander , Catton Ivan
Published: April 2009

The evaporator of a heat exchanger is made with a porous, capillary, structure. In the past researchers [7] noticed that the heat flux limits of a bi-porous capillary structure is much greater than that of a mono-porous capillary structure and will be the focus of this work. There are three distinct stages in the heat transfer process in a bi-porous wick. Each of the stages is explored in turn. In the first stage, heat is transferred from the wall across the saturated wick by pure conduction to the evaporating front located on the top of the bi-porous wick. When the boiling limit is reached, bubbles begin to nucleate and the second stage begins. The boiling becomes more and more intensive as the heat flux is increased until all of the liquid from big pores is evaporated, and only small pores remain wetted with liquid. The point reached here is called the capillary limit, which is basically the limit at which the capillary forces are still sufficient to provide the liquid for evaporation into the big pores. The modelling of the different thermal physical processes determining heat transfer within each of the three stages for a bi-porous heat wick are modelled and significant improvement in achievable heat flux is observed. Comparison with experiment is found to be reasonable. Optimal selection of the bi-porous wick characteristics is shown to yield very high heat fluxes.
Critical Heat Flux (CHF) and Cold-Flow Pressure Drop Investigations of R-11 in a Vertical Uniformly Heated 5 x 5 Rod Bundle
Authors: Salahudidin Asif , Khan Jamil A. , Smith L. David , Wilbur Chris L.
Published: April 2009

Experimental and numerical investigations were performed to determine the critical heat flux (CHF) and pressure drop in a vertical uniformly heated 5×5 rod bundle. R-11 is used as the working fluid due to its low latent heat, low critical pressure and well known properties. The experimental investigation was performed at the Westinghouse Nuclear Fuel PWR Product Technologies Test Laboratory in Columbia, South Carolina. Two types of grid designs were tested with Bundle-1 and Bundle-2 respectively. The matrix of DNB test parameters (water equivalent conditions shown in parentheses) includes exit pressure: 317–445 psia (1800–2400), inlet mass flux: 1.725–3.400 Mlbm/hr-ft2 (1.5–2.5 Mlbm/hr-ft2) and inlet temperature: 170–305°F (320–590 Mlbm/hr-ft2). Nominal R-11 conditions for the cold test are 165 psia, and 80°F±10°F. The experimental results were validated using a nuclear thermal hydraulic code VIPRE-01, MOD-02.1. The EPRI-1 correlation was being used to have a gross understanding of the CHF in the Bundles. Subsequently an empirical correlation USC11F was developed with Bundle-1 CHF database which compares favorably with experimental CHF for both the grid designs. Overall mean ratios of experimental to predicted CHF of 0.9984 and 0.9948 with standard deviations of 0.0265 and 0.0338 were obtained for Bundle-1 and Bundle-2 respectively. The predicted cold flow pressure drops also reproduced the experimental values closely. At lower mass flux a slight overprediction was encountered due to the dependability of mixing grid loss coefficient on Reynold’s number.
Directional Solidification of Metal Matrix Particulate Composite Materials
Authors: Ma Yuan , Zheng Lili
Published: April 2009

Metal matrix particulate composites (MMPCs) are made of a continuous metallic matrix and discontinuous reinforcing particles. An efficient solidification model for MMPCs is developed in this paper. The molten metal is considered as a continuous multi-component medium, while the particles are treated as a discrete Lagrangian entity that exchanges mass, momentum and energy with the melt. The particle entrapment model is developed to determine the possibility of the particles to interact with the interface. The forces acting on particles in front of an advancing solidification interface are quantified for particle engulfment and pushing (PEP), and this model is incorporated into the computational scheme for simulating particle dynamic distributions. The integrated numerical model is applied to Al alloy growth with ZrO2 particle inclusions in the directional solidification. The results show that particle movement and distribution are gready affected by the two-phase liquid flow pattern and intensity. The effect of particle size and solidification velocity on PEP and final particle distribution in the solid matrix are also determined.
Investigation of the Accuracy and Spatial Resolution of Scanning Thermal Microscopy (SThM) Technique
Authors: Lo Hsinyi , Liu Wenjun , Asheghi Mehdi
Published: April 2009

Scanning Thermal Microscopy (SThM) employs a thermocouple as the scanning sensor to capture thermal images with sub-micron spatial resolution. After nearly two decades of research and development in this area, many outstanding issues/questions related to the accuracy and resolution of SThM technique has remained either unanswered or at best ambiguously defined. The present work uses numerical simulation for heat conduction in a combined SThM probe and device to obtain temperature distributions in various heated nanostructures. The limits of accuracy and spatial resolution of the SThM technique for heated metal bridges are estimated using a probe with 100 nm thermocouple junction as the temperature sensor. It is concluded mat large errors in temperature measurements should be expected for small devices that are fabricated on poor thermal conductivity substrates. There is no clear and unique definition for the spatial resolution of the SThM technique as it may change for different device configuration and substrates. It appears that the finite dimensions of the probe and contact area impose a limit on the spatial resolution of the SThM, which is strongly influenced by temperature gradients across the device under test.
Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling
Authors: Yang J. , Cheung F. B. , Rempe J. L. , Suh K. Y. , Kim S. B.
Published: April 2009

Four types of steady-state boiling experiments were conducted to investigate the efficacy of two distinctly different heat transfer enhancement methods for external reactor vessel cooling under severe accident conditions. One method involved the use of a thin vessel coating and the other involved the use of an enhanced insulation structure. By comparing the results obtained in the four types of experiments, the separate and integral effect of vessel coating and insulation structure were determined. Correlation equations were obtained for the nucleate boiling heat transfer and the critical heat flux. It was found that both enhancement methods were quite effective. Depending on the angular location, the local critical heat flux could be enhanced by 1.4 to 2.5 times using vessel coating alone whereas it could be enhanced by 1.8 to 3.0 times using an enhanced insulation structure alone. When both vessel coating and insulation structure were used simultaneously, the integral effect on the enhancement was found much less than the product of the two separate effects, indicating possible competing mechanisms (i.e., interference) between the two enhancement methods.
Modeling and Simulation of Physical Vapor Deposition/Etching Plasmas
Authors: Kelkar Umesh , Sundarrajan Arvind , Gung Tza-Jing , Hammond Ned , Bhatnagar Ajay , Fu Xinyu , Perrin Mark , Forster John , Gopalraja Prabu , Fu Jianming
Published: April 2009

A new physical vapor deposition source is developed to meet the challenges of barrier deposition for sub 100nm devices. The source employs multi-step process to deposit thin, conformal and uniform barrier films. This paper describes reactor scale modeling and simulation of deposition and etching plasmas used for barrier deposition. The modeling and simulation in tandem with experimental data demonstrate that the chamber can be used to independently control the particle fluxes as per the requirements of the deposition and etching steps. The simulation results were qualitatively used to optimize the ion flux uniformity by altering the magnetic fields near the wafer.
The Effects of the Distance Between Nozzle and Substrate on Cold Gas Dynamic Spray Process
Authors: Li Longjian , Cui Wenzhi , Chen Qinghua , Jen Tien-Chien , Liao Quan
Published: April 2009

In this paper, numerical simulations were performed for the gas-particle two phase flow in the cold gas dynamic spray process to investigate the acceleration of micro- and nanoparticles with diameters ranging from 100nm to 50μm. Nitrogen (N2) and Helium (He) were chosen as the carrier gas, respectively. The acceleration of carrier gas to particles in the De-Laval-Type supersonic nozzle was strongly dependent on the characteristics of flow field, as well as the densities and the size of the particles. Two kind of particles Copper (Cu) and Platinum (Pt) were chosen as the spraying materials. The computed results showed that the flow structures of the carrier gas were very different for different gas and different spraying distance, which resulted in consequently different accelerating features. The cone-shape weak shocks (compression waves) occurred at the exit of divergent section, and the bow-shaped strong shock wave was found right before the substrate, which played a resistance role to the particles and prevented the smaller particles from approaching on the substrate.
Finite Element Analysis of Carbon Foams With Randomly Distributed Spherical Pores
Authors: Druma Adriana , Alam Khairul , Druma Calin
Published: April 2009

Carbon foams have potential applications in thermal management of electronics and aerospace industries due to their low density and high thermal conductivity. These foams have open or closed pores that are approximately spherical. This paper presents a finite element analysis of the thermomechanical properties of carbon foams with randomly distributed spherical pores. The results are presented in nondimensional form and compared with theoretical and finite element analysis values obtained for cellular foams. The effect of pore distribution on the effective thermal conductivity of foams is also presented.
CFD in Design and Development of Heat Exchangers
Authors: Sunden Bengt
Published: April 2009

This paper gives a brief summary of CFD (computational fluid dynamics) methods and turbulence modeling for applications in the design, research and development of heat exchangers. Some examples are shown to demonstrate how CFD methods can be used as engineering tools. Nevertheless, limitations and shortcomings as well as need for further research are highlighted.
Three-Dimensional Modeling of Laser Sintering of a Two-Component Metal Powder Layer on Top of Sintered Layers
Authors: Chen Tiebing , Zhang Yuwen
Published: April 2009

A three-dimensional numerical model of Selective Laser Sintering (SLS) of the metal powders for a single scan line induced by a moving laser beam interacted with a loose powder layer on top of the sintered metal layers is presented. The problem is modeled using a temperature-transforming model and the partial shrinkage induced by melting is accounted for. The heat losses at the top surface due to the natural convection and radiation are taken into account. The liquid flow of the molten low melting point metal powders, which is driven by capillary and gravity forces, is also considered and formulated by using Darcy’s law. The effects of the dominant processing parameters, such as the moving heat source intensity, scanning velocity and number of the existing sintered layers underneath are investigated. A parametric study is performed and the best combination of the processing parameters is recommended.
Heat Transfer Across Ball Bearings in Vacuum
Authors: Takeuchi Yoshimi R. , Dickey James T. , Demsky Steven M. , Eby Matthew A.
Published: April 2009

Accurate spacecraft bearing temperature predictions often require both system and bearing level heat source and thermal conductance information. Bearing thermal conductance data is usually the most significant unknown in the development of the thermal model and little has been published in open literature on the subject. Consequently experiments have been conducted at The Aerospace Corporation to address this topic, with special attention given to applications such as high-speed momentum and flywheels. An experiment was designed to measure thermal conductance across a single bearing under both static and dynamic states. This paper will describe the test results for an angular-contact ball bearing under controlled inner race rotational speed, axial load, and thermal conditions. Tests were conducted on both dry and Nye Pennzane SHF2001 synthetic oil lubricated bearings. Test data showed that thermal conductance is sensitive to a complex interdependent set of variables including maximum run-in speed, axial load and temperature. A basic physical understanding of the heat transfer mechanism across a bearing was developed based on experimental results.
Numerical Simulation of Jet Diffusion Flames With Radiative Heat Transfer Modeling
Authors: Baburic´ Mario , Tatschl Reinhard , Duic´ Neven
Published: April 2009

Beside appropriate turbulence and combustion modeling, the problem of an accurate prediction of turbulent diffusion flames usually requires accurate radiative heat transfer predictions as well. In this paper it is shown that the inclusion of radiation modeling into the overall numerical simulation is important if accurate temperature profiles are needed. Two different jet diffusion flame configurations are simulated in this work — a diluted hydrogen jet flame (80% H2 and 20% He by volume) [1–4], and a piloted methane jet diffusion flame (flame D) [5, 6]. The predictions are compared to experimental data. Radiation is modeled by a conservative discrete transfer radiation method (DTRM) [7, 8]. Turbulence is modeled by a classical k-ε and by a hybrid procedure, as proposed in [9]. Combustion modeling is based on the stationary laminar flamelet model (SLFM) [10], where the combustion/turbulence interaction is accomplished via the presumed β probability density function (β-PDF).
The Experimental Study on High Temperature Air Combustion and CF4 Decomposition
Authors: Jia L. , Ma S.
Published: April 2009

For the purpose of decomposing the processing gases CF4 from semiconductor manufacturers, ceramic honeycomb regenerative burner system is suggested by using the principle of HTAC. A simulated high temperature air combustion furnace has been used to determine the features of HTAC flames and the results of the decomposition of CF4. The preheat air temperature of it is above 900 °C. The exhaust gas released into the atmosphere is lower than 150 °C. Moreover, the efficiency of recovery of waste heat is higher than 70%, the NOx level in exhaust gas is less than 300 mg/m3 and the distribution of temperature in the furnace is nearly uniform. The factors influencing heat transfer, temperature profile in chamber and NOx emission were discussed. Also some CF4 can be decomposed in this system. Experimental results indicated that the destruction removal efficiency (DRE) of CF4 increases with the increasing of concentration of H2O in some scale, and will not keep climbing when the concentration reach a point. DRE of CF4 decreases with the decreasing of concentration of CF4 under condition of other factors unchanged.
Post Extrusion Cooling of Multilayer Polymer Sheet on Chilled Rolls
Authors: Ansari Ajmal I.
Published: April 2009

To meet the stringent emission and environmental regulations, polymer sheet with as many as six layers is required for thermoformed fuel tanks used in the automotive industry. The 10 mm to 12 mm thick sheet is made using an extrusion process. Typically each polymer layer has its own hopper, screw, barrel, nozzle and extruder. During manufacturing, polymer layers are fused together within the tool and the multilayer polymer sheet leaves the extruder in a viscoelastic state. The multilayer sheet is initially cooled by passing it over chilled rolls. The final cooling of the sheet is done via natural convection to the ambient air while the sheet is transported to the cutting station at the end of the line. The cooling of the sheet on the chilled and polished rolls has a direct influence on the quality of the sheet as well as the scrap. The conductive heat transfer is primarily responsible for the cooling while the sheet is on the chilled roll. It is desired to have the smooth sheet exterior surfaces with constant thickness of each polymer layer in the cross section. Due to the numerous materials in the cross section, and associated variability of material properties, it becomes a challenging task to meet these requirements. This paper discusses the problem of the smoothness of the exterior surfaces of the extruded sheet. The “dimpled” or “orange peel” surface finish is observed to be linked to the cooling of the sheet on the chilled rolls. Experimental data and simulation results are presented that relate the formation of dimples to the local cooling rate. The variability of thermal contact resistance between the sheet surface and the chill rolls also appear to be another variable that contributes to the dimpled surface.