bluuebunny/crossref_metadata_2025 huggingface dataset:
Intelligent Regime Recognition in Upward Vertical Gas-Liquid Two Phase Flow Using Neural Network Techniques
Authors: Ghanbarzadeh Soheil , Hanafizadeh Pedram , Saidi Mohammad Hassan , Boozarjomehry Ramin Bozorgmehry
Published: March 2011

In order to safe design and optimize performance of some industrial systems, it’s often needed to categorize two-phase flow into different regimes. In each flow regime, flow conditions have similar geometric and hydrodynamic characteristics. Traditionally, flow regime identification was carried out by flow visualization or instrumental indicators. In this research3 kind of neural networks have been used to predict system characteristic and flow regime, and results of them were compared: radial basis function neural networks, self organized and Multilayer perceptrons (supervised) neural networks. The data bank contains experimental pressure signalfor a wide range of operational conditions in which upward two phase air/water flows pass to through a vertical pipe of 5cm diameter under adiabatic condition. Two methods of signal processing were applied to these pressure signals, one is FFT (Fast Fourier Transform) analysis and the other is PDF (Probability Density Function) joint with wavelet denoising. In this work, from signals of 15 fast response pressure transducers, 2 have been selected to be used as feed of neural networks. The results show that obtained flow regimes are in good agreement with experimental data and observation.
Heat Transfer Experiments of Ethylene Glycol-Water Mixture in Multi-Port Serpentine Meso-Channel Heat Exchanger Slab
Authors: Khan Mesbah G. , Fartaj Amir
Published: March 2011

In past few years, narrow diameter flow passages (≤3 mm) have attracted huge research attentions due to their several advantageous features over conventional tubes (≥6 mm) especially from the view points of higher heat transfer, lesser weight, and smaller device size. Several classifications of narrow channels, based on sizes, are proposed in the open literature from mini to meso and micro (3 mm to 100 μm). The meso- and micro-channels have not yet entered into the HVAC and automotive heat exchanger industries to the expected potentials to take the above-mentioned advantages. The reasons may be the limited availability of experimental data on pressure drop and heat transfer and the lack of consolidated design correlations as compared to what is established for compact heat exchangers. While a number of studies available on standalone single straight channels, works on multi-channel slab similar to those used as typical thermal heat exchanger core elements are inadequate, especially the research on multichannel serpentine slab are limited in the open literature. The 50% ethylene glycol and water mixture is widely used in heat exchanger industry as a heat transfer fluid. Studies of pressure drop and heat transfer on this commercially important fluid using narrow tube multi-channel slab is scarce and the availability of experimental data is rare in the open literature. Conducting research on various shapes of meso- and micro-channel heat exchanger cores using a variety working fluids are a definite needs as recommended and consistently urged in ongoing research publications in this promising area. Under present long-term project, an automated dynamic single-phase experimental infrastructure has been developed to carryout the fluid flow and heat transfer research in meso- and micro-channel test specimens and prototype microchannel heat exchanger using a variety of working fluids in air-to-liquid crossflow orientation. In the series, experiments have been conducted on 50% ethylene glycol and water solution in a serpentine meso-channel slab having 68 individual channels of 1 mm hydraulic diameter to obtain the heat transfer data and the general pressure drop nature of the test fluid. Current paper presents the heat transfer characteristics of ethylene glycol-water mixture and the Reynolds number effects on pressure drop, heat transfer rate, test specimen NTU and effectiveness, overall thermal resistance, and the Nusselt number.
Hot-Water Layer, Heat-Loss Characteristics of an Open-Pool-Type Research Reactor for Reducing the Pool Top Radiation Level
Authors: Park Young-Chul
Published: March 2011

During an open-pool-type research reactor operation, it is necessary to access the pool top area for un/loading irradiation test pieces by a required irradiation period. However, when the reactor pool top radiation level exceeds the limit of radiation level by the rising of reactor chimney water contaminated by radioactivity due to a natural convection of the pool water, access the reactor pool top area is denied due to the high radiation level. In the case of HANARO, a hot-water layer (HWL, hereinafter) is maintained below a depth of 1.2 m from the top of the reactor pool in order to reduce the radiation level of the reactor pool top area. After a normal operation of the HWL, the pool top radiation level is safely maintained below the limit of the pool top radiation level. For studying more the characteristics of the HWL under a reactor coolant downward flow condition, The HWL heat loss is calculated based on the HANARO HWL calculation model. The HWL heat loss characteristics were reviewed by variations of the HWL temperature, reactor core coolant flow direction, and reactor power. It was confirmed through the results that the HWL heat loss under a reactor coolant downward flow condition was increased by about 20% to 60% over that under a reactor coolant upward flow condition, as per the HWL temperature variation. It was the reason that the HWL bottom convection heat loss was increased by the higher flow rate under a reactor coolant downward flow condition than that under a reactor coolant in an upward flow condition.
Pool Boiling Heat Transfer and Bubble Dynamics Over Plain and Enhanced Microchannels
Authors: Cooke Dwight , Kandlikar Satish G.
Published: March 2011

Pool boiling is of interest in high heat flux applications because of its potential for removing large amount of heat resulting from the latent heat of evaporation and little pressure drop penalty for circulating coolant through the system. However, the heat transfer performance of pool boiling systems is not adequate to match the cooling ability provided by enhanced microchannels operating under single-phase conditions. The objective of this work is to evaluate the pool boiling performance of structured surface features etched on a silicon chip. The performance is normalized with respect to a plain chip. This investigation also focuses on the bubble dynamics on plain and structured microchannel surfaces under various heat fluxes in an effort to understand the underlying heat transfer mechanism. This work is expected to lead to improved enhancement features for extending the pool boiling option to meet the high heat flux removal demands in electronic cooling applications.
Fluid Mechanics of Deformable Aortic Prostheses
Authors: de Tullio Marco D. , Verzicco Roberto , Afferrante Luciano , Pascazio Giuseppe
Published: March 2011

The simultaneous replacement of a diseased aortic valve, aortic root and ascending aorta with a composite graft equipped with a prosthetic valve is a nowadays standard surgical approach in which the Valsalva sinuses of the aortic root are sacrificed and the coronary arteries are reconnected directly to the graft (Bentall procedure). In practice, two different polyethylene terephthalate (Dacron) prostheses are largely used by surgeons: a standard straight graft and a graft with a bulged portion that better reproduces the aortic root anatomy (Valsalva graft). The aim of the present investigation is to study the effect of the graft geometry, with its pseudo-sinuses, on the the flowfield, with particular attention to the coronary entry-flow, and on the stress concentration at the level of coronary-root anastomoses during the cardiac cycle. A bi-leaflet mechanical valve with curved leaflets is considered, attached to the two different prostheses. Two cylindrical channels, reproducing the very early coronary vasculature are connected to the grafts. An accurate three-dimensional numerical method, based on the immersed boundary technique, is proposed to study the flow inside deformable geometries. Direct numerical simulations of the flow inside the prostheses under physiological pulsatile inflow conditions are presented. The dynamics of the leaflets (considered rigid) is obtained by a fully-coupled fluid-structure-interaction approach, while a weak-coupled approach is employed for the deforming roots, in order to reduce the computational cost, using optimized solvers for both the fluid and structural problems. The Dacron material is modeled as orthotropic, with an inversion of the material properties in longitudinal and circumferential direction for the skirt region of the Valsalva prosthesis. Coronary perfusion is reproduced modulating in time the porosity, and thus the resistance, of the coronary channels. The results indicate that while the pseudo-sinuses do not significantly influence the coronary entry-flow, their presence allows for smaller levels of stresses at the level of coronary-root anastomoses, potentially reducing post-operative complications.
Thermoacoustic-Stirling Heat Pump for Domestic Applications
Authors: Vanapalli Srinivas , Tijani M. E. H. , Spoelstra Simon
Published: March 2011

Domestic heating contributes to a significant amount of energy usage in the Netherlands. Due to scare energy resources, attention to develop new and efficient technologies is increasing. At ECN, a burner driven heat pump employing thermoacoustic technology is being developed for possible applications in households and offices. The desired temperature lift is from 10 °C to 80 °C. As a first step the heat pump is driven by a linear motor. Measurements and performance analysis of the heat pump are presented in this paper. The heat pump has a coefficient of performance which is the ratio of heat produced to the work input of 1.38 when operating between 10 °C to 80 °C. The performance relative to maximum possible Carnot value is 26.5%.
Acoustically Levitated Nanofluid Droplet Vaporization
Authors: Tijerino Erick , Saha Abhishek , Kumar Ranganathan , Basu Saptarshi
Published: March 2011

The presence of nanometer size particles within an evaporating water droplet, affects the heat transfer and temperature distribution within the droplet. Levitating the droplet acoustically allows the study of this phenomenon without the heat transfer interference that occurs with the use of other techniques, such as capillary suspension [1]. In addition to the heat transfer effects, the remaining particle after the water in the droplet is completely evaporated, agglomerate together to form bowl shaped and ring shaped structures. The suspended droplet was heated using a Carbon Dioxide Laser. The process has been imaged in-situ with an Infrared (IR) camera, registering the temperature profile around the droplet surface. A high speed camera simultaneously captured the formation of nanoparticle structures. The experiments were conducted for a range of 0.1% to 5% nanosilica volume concentration solutions. Scanning Electron Microscopy was performed on the remaining structures to observe the inner portion and the outer surface of the formed structures.
Uncertainty Analysis Becoming Common Practice in Safety Assessment
Authors: Glaeser Horst G.
Published: March 2011

During the recent years an increasing interest in computational reactor safety analysis is to replace the conservative evaluation model calculations by best estimate calculations supplemented by uncertainty analysis of the code results. The evaluation of the margin to acceptance criteria, e.g. the maximum fuel rod clad temperature, should be based on the upper limit of the calculated uncertainty range. For example, due to power increase, licensing limits are approached. Therefore, regulators are looking closer on the way, how calculations are performed to meet these acceptance criteria. Methods have been developed and presented to quantify the uncertainty of computer code results. They are briefly presented in this paper. The present overview considers the international situation of development of uncertainty evaluation of computer code results and their application in licensing. Best estimate analysis plus uncertainty evaluation is used in licensing up to now in approximately seven countries. Demonstrations of applying uncertainty methods have been performed in nine additional countries at least. Most organizations use statistical methods. One statistical method is the GRS method proposing ordered statistics. Several demonstrations to apply the GRS method have been performed by GRS for courses of events in the nuclear steam supply system, calculating experiments as well as nuclear power plants. The method has also been applied for post test calculations of containment behavior, as well as severe accidents. One of the most important conclusions is that care must be exercised in determining ranges and probability distributions of the uncertain input parameters.
Modeling Jones’ Reduced Chemical Mechanism of Methane Combustion With Artificial Neural Network
Authors: Mehdizadeh Nasser S. , Sinaei Payam , Nichkoohi Ali L.
Published: March 2011

The present work reports a way of using Artificial Neural Networks for modeling and integrating the governing chemical kinetics differential equations of Jones’ reduced chemical mechanism for methane combustion. The chemical mechanism is applicable to both diffusion and premixed laminar flames. A feed-forward multi-layer neural network is incorporated as neural network architecture. In order to find sets of input-output data, for adapting the neural network’s synaptic weights in the training phase, a thermochemical analysis is embedded to find the chemical species mole fractions. An analysis of computational performance along with a comparison between the neural network approach and other conventional methods, used to represent the chemistry, are presented and the ability of neural networks for representing a non-linear chemical system is illustrated.
A Computational Model for Hydraulic Labyrinth Seals
Authors: Bouderlique Re´mi , Guibault Franc¸ois , Garon Andre´ , Vu Thi
Published: March 2011

Every Francis turbine has a thin gap between rotating and non-rotating parts, which prevents contact between the two units. Although necessary, hydraulic seals create energetic losses: some fluid does not flow through the runner (leakage loss) and exerts a torque on the rotor (friction loss). Only analytical and empirical prediction methods of a seal efficiency had been developed before 1980. Numerical methods are now used to predict seals performance. However, most of the studies known to the authors deal with gas labyrinth seals and use the k–ε turbulence model. In hydraulic seals, since the viscous losses in the boundary layer influence the leakage loss, low Reynolds turbulence models appear more appropriate. Our study aims to implement an accurate model to predict losses in labyrinth seals using a low Reynolds model, and validate it using experimental results. The issues of the mesh and boundary conditions are addressed. The commercial code ANSYS CFX 12 is used.
Analysis of a Bubble Deformation Process in a Microcapsule for Developing Drug Delivery Systems Using Underwater Shock Waves
Authors: Tamagawa Masaaki
Published: March 2011

This paper describes development of microcapsule using underwater shock waves, especially (1) the trial of making smaller microcapsules including a bubble for shock wave drug delivery systems, and analysis of a bubble deformation process to have higher efficiency of disintegration by shock wave, and (2) the effects of gradient of cytokine concentration on neutrophile motion in liquid by observing the concentration transport process with adding cytokine for developing drug delivery systems.
Characterization of Low Reynolds Number Wind Turbine Aerodynamics by BEM Theory and PIV Measurements
Authors: Villegas Vaquero A. , Cheng Y. , del Campo V. , Di´ez F. J.
Published: March 2011

In this study, low Reynolds number wind turbine aerodynamics was considered. The overall goal was to characterize the flow in order to optimize the power output of the system. First, BEMT theory (Blade Element Momentum Theory) was formulated for this flow where Prandtl’s tip- and hub-loss corrections were included, as well as Glauert’s thrust coefficient correction. The theory was validated with experimental data from National Renewable Energy Laboratory (NREL) for larger scale wind turbines. Also, a physical model of a low Reynolds number horizontal-axis wind turbine (HAWT) was built. Particle Image Velocimetry (PIV) was used to calculate the velocity field around the HAWT. This allowed for planar measurements of the velocity field at different location in the wake of the rotor. The measurements were performed in a water channel allowing for better control of PIV seeding and improved flow visualization. PIV results allowed observation of the velocity field and vorticity field in the wake of the rotor. This data is currently being compared to BEMT theory suggesting good agreement.
Thermal Hydraulics Structural Uncertainty Analysis: Approaches and Challenges
Authors: Pourgol-Mohamad Mohammad
Published: March 2011

Model uncertainty is a relatively new topic of discussion in TH code calculations, despite being often the major contributor to the overall uncertainty and a challenging practice in uncertainty analysis. The Integrated thermal-hydraulics uncertainty analysis (IMTHUA) methodology, developed by the authors, treats the TH code structural uncertainties (generally known as model uncertainty) explicitly by treating internal sub-model uncertainties, and by propagating such model uncertainties in the code calculations, including uncertainties about input parameters. This paper presents systematic model uncertainty of thermal-hydraulics system codes as part of IMTHUA methodology. The objective is to demonstrate effectiveness and practicality of the methodology on complex thermal-hydraulics system codes calculations and discuss the challenges dealing with these types of uncertainty sources. TH codes are an assembly of models and correlations for simulation of physical phenomena and behavior of system parameters in temporal domain. In some cases, there are alternative sub-models, or several different correlations for calculation of a specific phenomenon of interest. There are also “user options” for choosing one of several models or correlations in performing a specific code computation. Dynamic characteristics of TH calculations add more complexity to the code calculation, meaning for example, that specific code models and correlations invoked are sequence-dependent, and based certain (dynamic) conditions being satisfied. Structural uncertainty assessment (model uncertainty) for a single model will be discussed by considering “correction factor”, “bias”, and also through Bayesian sub-model output updating with available experimental evidence. In case of multiple alternative models, several techniques including dynamic model switching, user controlled model selection, model mixing, will be discussed. This paper discusses the challenges in treatment of the structural uncertainties in Thermal-Hydraulics system codes. Subjectivity and dependency on expert judgment in some of the solutions leaves some concerns on context of such systematic solutions to utilize imperfect and partially relevant data and information.
A Parametric Investigation of Operating Limits in Heat Pipes Using Novel Metal Foams as Wicks
Authors: Shirazy Mahmood R. S. , Fre´chette Luc G.
Published: March 2011

A parametric investigation has been performed to study the different operating limits of heat pipes employing a novel type of metal foam as wick for chip cooling applications. These foams have a unique spherical pore cluster microstructure with very high surface to volume ratio compared to traditional metal foams and exhibit higher operating limits in preliminary tests of heat pipes, suggesting high cooling rates for microelectronics. In the first part of this parametric study, widely used correlations are applied to calculate the five types of heat transfer limits (capillary, boiling, viscous, entrainment and sonic) as a function of temperature, type of foam, and porosity. Results show that the dominant limit is mostly the capillary limit, but for 50 pore-per-inch (PPI) foam, the boiling limit will be dominant. Also, 50 and 60 PPI foams have higher heat transfer limits than sintered copper powder. In the second part of this study, thermodynamic steady state modeling of a flat heat pipe has been done to study the effect of the different parameters on the dominant limit (capillary). A dimensionless number has been proposed to evaluate the balance between the pressure loss in the vapor and liquid phases as an additional design guideline to improve the capillary limit in flat heat pipes.
Development of a High Performance Francis Turbine for Runner Replacement Using a CFD-Based Design System
Authors: Roh Hyung-Woon , Suh Sang-Ho , Jung Jong-hyun , Oh SuegYoung
Published: March 2011

Recently, Korean Government is encouraging to propagate the small hydro-electric power in renewable energy development policy as the “Low CO2 Green Growth” policy. However, turbines in the Korea Water Resources Corporation (below K-water) operated at an average of 10% less than well-designed turbines due to the design weakness or the inferior manufacturing techniques for the small hydropower facilities. Thus, maintenance fees increased because the cavitations had excessively occurred on the main parts of turbines such as the runner, guide vane and Stator, the life cycles of turbines were reduced and the frequency breakdowns were increased. In order to improve the efficiency the CFD-based design system is applied to the Francis turbine replacement project with Korea Fluid Machinery Association (below KFMA) and K-water. Therefore, the inversed design technique and the fully turbulent 3-dimensional flow simulations are performed for both the existing and new turbines at design and off design conditions. As a result, the runner is optimized to the greatest extent with a possible minimum cost under the geometrical constraints of the existing machine. The performances of the new design are verified by extensive model tests and the guarantees have all been successfully met.
The Effect of Nanoscale Surface Modification on Boiling Heat Transfer and Critical Heat Flux
Authors: Kim Moo Hwan
Published: March 2011

Recently, there were lots of researches about enormous CHF enhancement with the nanofluid in pool boiling and flow boiling. It is supposed the deposition of nanoparticles on the heated surface is one of main reasons. In a real application, nanofluid has a lot of problems to be used as the working fluid because of sedimentation and aggregation. The artificial surfaces on silicon and metal were developed to have the similar effect with nanoparticles deposited on the surface. The modified surface showed the enormous ability to increase CHF in pool boiling. Furthermore, under flow boiling, it had also good results to increase CHF. In these studies, we concluded that wetting ability of surface; e.g. wettability and liquid spreading ability (hydrophilic property of surface) was a key parameter to increase CHF under both pool and flow boiling. In addition, using wettability difference of surface; e.g. hydrophilic and hydrophobic, we conducted some tests of BHT (boiling heat transfer) enhancement using the oxide silicon which have micro-sized hydrophobic islands on hydrophilic surface. By using both of these techniques, we propose an optimized surface to increase both CHF and BHT. Also, the fuel surface of nuclear power plants is modified to have same effect and the results shows a good enhancement of CHF, too.
Model Development for Fluid Structure Interaction in the Slip Regime
Authors: van Rij Jennifer , Harman Todd , Ameel Tim
Published: March 2011

While many microscale systems are subject to both rarefaction and fluid-structure-interaction (FSI) effects, most commercial algorithms cannot model both, if either, of these for general applications. This study modifies the momentum and thermal energy exchange models of an existing, continuum based, multifield, compressible, unsteady, Eulerian-Lagrangian FSI algorithm, such that the equivalent of first-order slip velocity and temperature jump boundary conditions are achieved at fluid-solid surfaces, which may move with time. Following the development and implementation of the slip flow momentum and energy exchange models, several basic configurations are considered and compared to established data to verify the resulting algorithm’s capabilities.
TITRAM Fast Transient Licensing Analysis Methodology for Kuosheng BWR/6
Authors: Tang Jan-Ru , Jien Hon-Chin , Chiu Yang-Kai , Wang Cheng-Der , Chian Julian S. C.
Published: March 2011

This paper presents the TITRAM (TPC/INER Transient Analysis Method) methodology for the fast transient analysis of Kuosheng Nuclear Power Station (KSNPS) with two units of General Electric (GE) designed BWR/6 (Boiling Water Reactor). The purpose of this work is to provide a technical basis of Taiwan Power Company (TPC)/Institute of Nuclear Energy Research (INER)’s qualification to perform plant specific licensing safety analyses for the Final Safety Analysis Report (FSAR) basis system fast transients, and related plant operational transient analyses for the Kuosheng plant. The major task of qualifying TITRAM as a licensing method for BWR transient analysis is to adequately quantify its analysis uncertainty. A similar approach as the CSAU (Code Scaling, Applicability, and Uncertainty Evaluation) methodology developed by the USNRC (United States Nuclear Regulatory Commission) was adopted. The CSAU methodology could be characterized as three significant processes, namely code applicability, transient scenario specification and uncertainty evaluation based on Phenomena Identification and Ranking. The applicability of the TITRAM code package primarily using the SIMULATE-3 and RETRAN-3D codes are demonstrated with analyses of integral plant tests such as Peach Bottom Turbine Trip Test and plant startup tests of KSNPS. A Phenomena Identification and Ranking Table (PIRT) with uncertainty values for each identified parameter to cover 95% of possible values are established for the selected KSNPS fast transients. The experience from BWR organizations in the nuclear industry is used as a guide in construction of the PIRT. Sensitivity studies and associated statistical analyses are performed to determine the overall uncertainty of fast transient analysis with TITRAM based on the KSNPS Analysis Nominal Model. Finally, the Licensing Model is established for future licensing applications.
Better Estimate Analysis for Use in Emergency Operating Procedure During a Loss of Coolant Accident
Authors: Speyer Daniel M. , Chang Jong E. , Irani Ardesar
Published: March 2011

Emergency Operating Procedures (EOPs) [1] provide prioritized response strategies that guide the operator in management of emergency transients. A desirable attribute of EOPs is optimal recovery from the transient. To achieve this, it is necessary to develop more realistic criteria rather than criteria based on traditional licensing analysis methods. One such application is evaluating measured core makeup flow during the recirculation phase of a Loss of Coolant Accident (LOCA) with adverse containment environment. During the recirculation phase of a LOCA, the adequacy of the internal recirculated water flow (from the containment sump) is confirmed by individual loop measured injection flows satisfying EOP criteria. Of particular concern is the flow split in the loop emergency cooling injection lines and the potentially large instrument uncertainty associated with measuring low flow rates. In the event one of the injection lines spills to containment (and possibly without a line spilling), traditional analysis methods based criteria would suggest adequate makeup flow may not be confirmed, and consequently the EOPs would prescribe external recirculation, which is not the preferred mode. In the present paper the EOP criteria for post LOCA core cooling flow is developed — using better estimate methods. Several (significantly) less restrictive analysis assumptions were identified and a new/materially different approach from that used in the past was taken. As result a more robust flow criterion was obtained — simpler and permitting about 0.019 m3/s [300 gpm] less flow.
Sampling Based Uncertainty Analysis of 10% Hot Leg Break LOCA in LSTF
Authors: Sengupta Samiran , Dubey S. K. , Rao R. S. , Gupta S. K. , Raina V. K.
Published: March 2011

This paper describes the uncertainty analysis carried out for 10% Hot leg break LOCA of Large Scale Test Facility as a part of IAEA Coordinated Research Project on “Evaluation of Uncertainty in Best Estimate Accident Analysis”. The best estimate code used for this analysis is RELAP5/MOD3.2. Initially the nodalisation of the test facility for carrying out the analysis is qualified for both steady state and transient level by systematically applying the procedures lead by Uncertainty Methodology based on Accuracy Extrapolation developed at University of Pisa. Subsequently the uncertainty analysis is carried out using sampling based Monte Carlo approach, which involves the generation and extrapolation of a mapping from uncertain inputs to the uncertain analysis results. The major steps followed in this methodology mainly includes screening sensitivity analysis for input parameters, design matrix generation using Latin Hypercube Sampling, representation of uncertainty analysis results based on best estimate thermal hydraulic code runs and importance /sensitivity analysis using regression analysis. The steps followed have been described in details in this paper.
Numerical Investigation of Turbulent Models in the Development and Establishment of Turbulent Flows With Flow Conditioners
Authors: Laribi Boualem , Wauters Pierre , Youcefi Abdelkader
Published: March 2011

The accuracy in measuring flow of fluids such as gas and oil has a great importance for the Algerian economy. The flows of fluids in non-standard conditions, presence of disturbances, in which there are flow meters in pipes, make a very important error. International standards ISO 5167 and AGA3 stipulate that the meter is installed in a fully developed flow. This article describes a numerical investigation of development and establishment of flows in the presence of a double bend 90° in perpendicular planes as a perturbation. The software used was code Fluent where different turbulence models are tested to better simulate and view the effectiveness of models in the description of the flow of fluid compared to flow behaviour cited in the standards and the experimental results. The numerical experimentation is done with air in a pipe of 100mm diameter at a Reynolds number 105. The numerical analysis is based on solving Navier-Stokes equation system with several turbulent models, k-ε, k-ω, RSM and its variants.
Numerical Investigation of Contribution of Three Flow Conditioners in the Development and Establishment of Turbulent Flows
Authors: Laribi Boualem , Wauters Pierre , Youcefi Abdelkader
Published: March 2011

This numerical study is a comparative study of the development and establishment of turbulent flows through three flow conditioners namely Laws perforated plate, the Etoile and the tube bundle. They are installed in a circular pipe with a disturbance generated by a 90° double bend out of plane which causes a very strong swirl of the fluid. The analysis is done with the code Fluent in which the Navier-Stokes equations describe a three-dimensional incompressible flow with the Reynolds stress model (RSM) as a closure system. This article focuses on the effectiveness of the three packers to produce the condition of fully developed velocity profile. The results are compared to references profiles cited in the literature and experimental results. The flow is simulated with air at Reynolds number of 105 in 100mm pipe diameter. The velocity profiles are compared with the profile obtained by the universal law of power 1/7th.
Numerical Investigations of Passive Scalar Transport in Turbulent Taylor-Couette Flows: Code Validation
Authors: Salhi Yacine , Si-Ahmed El-Khider , Degrez Ge´rard , Legrand Jack , Aloui Fethi
Published: March 2011

The highly turbulent flow occurring inside (electro)chemical reactors requires accurate simulation of scalar mixing if CFD methods are to be used with confidence in design. This has motivated the present paper, which describes the implementation of a passive scalar transport equation into a hybrid spectral/finite-element code. For this purpose, direct numerical simulations (DNS) and Large Eddy Simulation (LES) have been performed to study the effects of the gravitational and the centrifugal potentials on the stability of incompressible Taylor-Couette flow. The flow is confined between two concentric cylinders and only the inner cylinder is allowed to rotate while the outer one is at rest. The Navier-Stokes equations and the uncoupled convection–diffusion–reaction (CDR) equation are solved using a code named SFELES which consists on spectral development in one direction combined with a finite element discretisation in the two remaining directions. The performance of the LES code is validated against published DNS data for a channel flow for the velocity and scalar statistics with good agreement between the current LES predictions and DNS data.
Two-dimensional III-V nucleation on Si for nonlinear optics
Authors: Lin Angie C. , Harris James S. , Fejer M. M.
Published: March 2011

The nucleation of AlGaP and GaP on offcut (100) Si was studied by molecular beam epitaxy for the purpose of improving GaP films on Si. Atomic force microscopy and high-resolution transmission electron microscopy were used to characterize film quality. Significant reduction in surface rms roughness and antiphase domain annihilation within 30 nm of the III-V/Si interface was observed when using AlGaP as a nucleation layer. This technique was optimized for development of orientation-patterned GaP on Si for nonlinear optics but could also be applied to III-V integration on Si.
Netting Neutrophils Are Major Inducers of Type I IFN Production in Pediatric Systemic Lupus Erythematosus
Authors: Garcia-Romo Gina S. , Caielli Simone , Vega Barbara , Connolly John , Allantaz Florence , Xu Zhaohui , Punaro Marilynn , Baisch Jeanine , Guiducci Cristiana , Coffman Robert L. , Barrat Franck J. , Banchereau Jacques , Pascual Virginia
Published: March 2011

In systemic lupus erythematosus, neutrophil extracellular traps activate plasmacytoid dendritic cells to produce type I interferon.
Nanodiamond Therapeutic Delivery Agents Mediate Enhanced Chemoresistant Tumor Treatment
Authors: Chow Edward K. , Zhang Xue-Qing , Chen Mark , Lam Robert , Robinson Erik , Huang Houjin , Schaffer Daniel , Osawa Eiji , Goga Andrei , Ho Dean
Published: March 2011

Nanodiamond-based drug delivery significantly enhanced treatment efficacy and safety in multiple chemoresistant cancer models.
Dodging Drug-Resistant Cancer with Diamonds
Authors: Merkel Timothy J. , DeSimone Joseph M.
Published: March 2011

Nanodiamond-drug conjugates show antitumor activity in mouse models of chemoresistant breast and liver cancer.
Dissecting the Immune Cell Mayhem That Drives Lupus Pathogenesis
Authors: Craft Joseph E.
Published: March 2011

Three studies suggest that rational combinatorial targeting of the pathogenic mechanisms in lupus may be a winning therapeutic strategy.
This Changes Everything, Twice!
Authors: Hong David S.
Published: March 2011

Two small molecule drugs that target the mTOR and VEGF/PDGF pathways are highly effective in treating pancreatic neuroendocrine tumors.
Enabling Technology Gives the Brain a Hand
Authors: Wang Wei
Published: March 2011

Electrocorticographic signals enable brain–computer communication in a paralyzed stroke patient.
Target Practice
Authors: Nyendak Melissa
Published: March 2011

An inhibitor of RNA degradation inhibits growth of drug-resistant
Staphylococcus aureus
, pinpointing a new process for antibacterial targeting.
The Neutralization Breadth of HIV-1 Develops Incrementally over Four Years and Is Associated with CD4
+
T Cell Decline and High Viral Load during Acute Infection
Authors: Gray Elin S. , Madiga Maphuti C. , Hermanus Tandile , Moore Penny L. , Wibmer Constantinos Kurt , Tumba Nancy L. , Werner Lise , Mlisana Koleka , Sibeko Sengeziwe , Williamson Carolyn , Abdool Karim Salim S. , Morris Lynn ,   and the CAPRISA002 Study Team
Published: March 2011

An understanding of how broadly neutralizing activity develops in HIV-1-infected individuals is needed to guide vaccine design and immunization strategies. Here we used a large panel of 44 HIV-1 envelope variants (subtypes A, B, and C) to evaluate the presence of broadly neutralizing antibodies in serum samples obtained 3 years after seroconversion from 40 women enrolled in the CAPRISA 002 acute infection cohort. Seven of 40 participants had serum antibodies that neutralized more than 40% of viruses tested and were considered to have neutralization breadth. Among the samples with breadth, CAP257 serum neutralized 82% (36/44 variants) of the panel, while CAP256 serum neutralized 77% (33/43 variants) of the panel. Analysis of longitudinal samples showed that breadth developed gradually starting from year 2, with the number of viruses neutralized as well as the antibody titer increasing over time. Interestingly, neutralization breadth peaked at 4 years postinfection, with no increase thereafter. The extent of cross-neutralizing activity correlated with CD4
+
T cell decline, viral load, and CD4
+
T cell count at 6 months postinfection but not at later time points, suggesting that early events set the stage for the development of breadth. However, in a multivariate analysis, CD4 decline was the major driver of this association, as viral load was not an independent predictor of breadth. Mapping of the epitopes targeted by cross-neutralizing antibodies revealed that in one individual these antibodies recognized the membrane-proximal external region (MPER), while in two other individuals, cross-neutralizing activity was adsorbed by monomeric gp120 and targeted epitopes that involved the N-linked glycan at position 332 in the C3 region. Serum antibodies from the other four participants targeted quaternary epitopes, at least 2 of which were PG9/16-like and depended on the N160 and/or L165 residue in the V2 region. These data indicate that fewer than 20% of HIV-1 subtype C-infected individuals develop antibodies with cross-neutralizing activity after 3 years of infection and that these antibodies target different regions of the HIV-1 envelope, including as yet uncharacterized epitopes.
Electroacupuncture on a Patient with Pacemaker: A Case Report
Authors: Vasilakos Dimitrios G , Fyntanidou Barbara P
Published: March 2011

Electroacupuncture (EA) is commonly used for pain relief, with good results even in persistent chronic pain. However, published reports suggest that EA should not be used in patients who have pacemaker, since there is a theoretical risk of malfunction of the pacemaker. The case is described of a 50-year-old female patient, who has had severe low back pain resistant both to conventional and unconventional treatment methods. The only treatment that seemed to have some positive effect, but of extremely short duration, was acupuncture. Her condition deteriorated considerably, and after due consideration she was treated with EA. Even after the first EA treatment, the patient's condition improved. Since then, she has received many EA courses during the past 2 years without any complications or side effects. The results of this case study suggest that EA might be a safe alternative for patients with a pacemaker, confirming the current recommendations on use. Every patient should be considered with care, individually.
The attitudes of relatives to autopsy: a misconception
Authors: Tsitsikas Dimitris A , Brothwell Morag , Chin Aleong Jo-Anne , Lister Andrew T
Published: March 2011

Aim

Hospital autopsy rates have been falling steadily over recent decades. One factor that has been implicated in this decline is the perception that the general public views postmortem examinations unfavourably and that this often makes clinicians reluctant to discuss autopsy with families and seek their consent. The aim of this study was to test this assumption.

Objectives/methods

In the division of lymphoid malignancies at St Bartholomew's Hospital, we suggested autopsy and discussed it in depth with the families of all the patients who died in hospital in an 8-month period in order to assess whether the autopsy rate could be increased by improving the approach to the relatives.

Results

Consent for a postmortem examination was requested in 18 of 23 cases and granted in 16 cases, giving a consent rate of 89%, and an overall rate of autopsy of 69.5%.

Conclusion

The attitude of the general public is positive overall, and translates into high autopsy rates when the value of the examination is presented honestly and the details of the procedure are adequately explained.
Granulomatous mastitis: the histological differentials
Authors: Lacambra Maribel , Thai Tu Anh , Lam Christopher C F , Yu Alex M C , Pham Huong Thien , Tran Phuong Viet The , Law Bonita K B , Van Nguyen Thanh , Pham Dung Xuan , Tse Gary M
Published: March 2011

Background

The management of granulomatous mastitis depends on the causative factor, and accurate diagnosis in distinguishing between idiopathic granulomatous mastitis (IGM) and tuberculous mastitis (TBM) is indispensable. This is particularly problematic in the cases of granulomatous mastitis in which the microbiological studies are negative. In this study, in a large cohort, the histological features for IGM and TBM were compared.

Methods

The histopathology files from the two participating hospitals were searched for cases of granulomatous inflammation of the breast over an 8-year period. The parameters assessed included age of patient, lesional size, systemic and local symptoms, and histological findings of inflammatory cells, granulomas, necrosis, multinucleated giant cells, fibrosis and calcifications.

Results

29 cases of IGM and 33 cases of TBM were included in this study. A significant difference was seen between the two groups with regard to patient age (t=2.52, p<0.05) and lesional size (t=−5.56, p<0.01). TBM occurred in a significantly younger population, and demonstrated larger lesional sizes than IGM. There was no difference between the number of cases showing mass, local and systemic symptoms. Comparing the different histological features, the TBM group showed significantly more fibrosis, eosinophils and necrosis, whereas the IGM group showed significantly more plasma cells. Taking all the cases together as one group to evaluate the relationship between the histological parameters, there was significant positive correlation between eosinophils and fibrosis (rs=0.39, p<0.01), and negative correlation between vague and well-formed granulomas (rs=−0.38, p<0.01).

Conclusion

TBM was more likely to occur in younger patients, with a larger clinical mass at presentation. Histologically, TBM tends to show more eosinophils and necrosis, and IGM is associated with more plasma cells. The characteristics of the granulomas and giant cells were not distinguishing features.
Microbiological findings in sudden unexpected death in infancy: comparison of immediate postmortem sampling in casualty departments and at autopsy
Authors: Pryce Jeremy W , Roberts Sebastian E A , Weber Martin A , Klein Nigel J , Ashworth Michael T , Sebire Neil J
Published: March 2011

Aim

Sudden unexpected death in infancy (SUDI) represents the commonest presentation of post-neonatal infant death in the UK. This audit reviews current practice in the investigation of SUDI deaths, with particular regard to the practice of microbiological sampling in emergency departments (ED) compared with samples obtained at the time of autopsy for establishing the cause of death, as suggested by current guidelines.

Methods

Coronial autopsies performed for the indication of SUDI over a 4-year period at a single specialist centre were reviewed with particular regard to the findings of microbiological investigations performed in ED compared with those performed at the time of autopsy.

Results

Of 229 SUDI postmortems performed during the period, there were 136 cases in which both bacteriological samples taken in ED and at autopsy were available, including 109 with blood cultures taken at both time points. 66 cases had sterile blood cultures in ED of which 37 (56%) showed positive microbiological growth from autopsy samples including nine (14%) cases with group II pathogens. Group II pathogens were identified from ED samples in six (6%) of the total cases; all but two cases ofStaphylococcus aureuswere not detected at autopsy.

Conclusion

Blood cultures obtained at autopsy are associated with a significantly higher rate of positive microbial cultures compared with blood samples taken in life. Most represent easily identified postmortem translocation or overgrowth rather than infection as the cause of death. No cases with a final infective cause of death would have been missed if ED sampling had not been performed.
REDUCTION OF THE RESONANCE ERROR — PART 1: APPROXIMATION OF HOMOGENIZED COEFFICIENTS
Authors: GLORIA ANTOINE
Published: March 2011

This paper is concerned with the approximation of effective coefficients in homogenization of linear elliptic equations. One common drawback among numerical homogenization methods is the presence of the so-called resonance error, which roughly speaking is a function of the ratio ε/η, where η is a typical macroscopic length scale and ε is the typical size of the heterogeneities. In the present work, we propose an alternative for the computation of homogenized coefficients (or more generally a modified cell-problem), which is a first brick in the design of effective numerical homogenization methods. We show that this approach drastically reduces the resonance error in some standard cases.
HOMOGENIZATION IN GRADIENT PLASTICITY
Authors: HANKE HAUKE
Published: March 2011

This paper yields a two-scale homogenization result for a rate-independent elasto-plastic system. The presented model is a generalization of the classical model of linearized elasto-plasticity with hardening, which is extended by a gradient term of the plastic variables. The associated stored elastic energy density has periodically oscillating coefficients, where the period is scaled by ε > 0. The additional gradient term of the plastic variables z is contained in the elastic energy with a prefactor εγ(γ ≥ 0). We derive different limiting models for ε → 0 in dependence of γ. For γ > 1, the limiting model is the two-scale model derived in Ref. 17, where no gradient term was present. For γ = 1, the gradient term of the plastic variable survives on the microscopic cell problem, while for γ ∈ [0,1) the limit model is defined in terms of a plastic variable without microscopic fluctuation. The latter model can be simplified to a purely macroscopic elasto-plasticity model by homogenization of the elastic part.
REGULARIZATION SCHEMES FOR DEGENERATE RICHARDS EQUATIONS AND OUTFLOW CONDITIONS
Authors: POP IULIU SORIN , SCHWEIZER BEN
Published: March 2011

We analyze regularization schemes for the Richards equation and a time discrete numerical approximation. The original equations can be doubly degenerate, therefore they may exhibit fast and slow diffusion. In addition, we treat outflow conditions that model an interface separating the porous medium from a free flow domain. In both situations we provide a regularization with a non-degenerate equation and standard boundary conditions, and discuss the convergence rates of the approximations.