bluuebunny/crossref_metadata_2025 huggingface dataset:
Melatonin inhibits arsenite‐induced peripheral neurotoxicity
Authors: Lin Anya M. Y. , Feng S. F. , Chao P. L. , Yang C. H.
Published: August 2008

Abstract:  In this study, the effect of melatonin on sodium arsenite (arsenite)‐induced peripheral neurotoxicity was investigated using dorsal root ganglion (DRG) explants. After 24‐hr incubation, arsenite (30 μm) consistently elevated the expression of heat shock protein 70 and haeme oxygenase‐1, two well‐known stress proteins, in the treated DRG explants. Co‐incubation with melatonin (4 and 20 mm) concentration‐dependently attenuated arsenite‐induced elevation in stress proteins. Furthermore, melatonin inhibited arsenite‐induced phosphorylation of p38 and DNA fragmentation. Inhibition by melatonin of arsenite‐induced apoptosis was mediated via inactivating both endoplasmic reticulum (ER) and mitochondrial pathways. In the ER pathway, melatonin suppressed arsenite‐induced elevation in activating transcription factor‐6 and CCAAT/enhancer‐binding protein homologous protein in the nuclear fraction of the treated DRG explants. Moreover, melatonin attenuated arsenite‐induced activation of caspase 12, an ER‐specific enzyme. In the mitochondrial pathway, arsenite‐induced increases in Bcl‐2 levels and cytosolic cytochrome c were reduced by melatonin. At the same time, melatonin inhibited arsenite‐induced activation of caspase 3 in the treated DRG explants. Compared with glutathione and N‐acetyl cysteine, melatonin was more potent than either in inhibiting arsenite‐induced elevation in stress proteins. Taken together, our study demonstrates that melatonin is protective against arsenite‐induced neurotoxicity in DRG explants. In addition, melatonin prevented arsenite‐induced apoptosis via suppression of ER and mitochondrial activation. Our data suggest that melatonin is potentially a therapy for arsenite‐induced peripheral neuropathy.
Production and detoxification of H2O2 in lettuce plants exposed to selenium
Authors: Ríos J.J. , Blasco B. , Cervilla L.M. , Rosales M.A. , Sanchez‐Rodriguez E. , Romero L. , Ruiz J.M.
Published: August 2008

Selenium is considered an essential element for animals. Despite that it has not been demonstrated to be essential for higher plants, it has been attributed with a protective role against reactive oxygen species in plants subjected to stress. In this study, lettuce plants (Lactuca sativa cv. Philipus) received different application rates (5, 10, 20, 40, 60, 80 and 120 μM) of selenite or selenate, with the aim of testing the effect of Se on the production and detoxification of H2O2 in non‐stressed plants. The results indicate that the form selenate is less toxic than selenite; that is, the plants tolerated and responded positively to this element, and even increasing in growth up to a rate of 40 μM for the form selenate. On the contrary, the application of selenite triggered a higher foliar concentration of H2O2 and a higher induction of lipid peroxidation [malondialdehyde content and lipoxygenase activity] in comparison to that observed after the selenate application. Also, the plants treated with selenate induced higher increases in enzymes that detoxify H2O2, especially ascorbate peroxidase and glutathione (GSH) peroxidase, as well as an increase in the foliar concentration of antioxidant compounds such as ascorbate and GSH. These data indicate that an application of selenate at low rates can be used to prevent the induction in plants of the antioxidant system, thereby improving stress resistance.
Meeting patient needs in the hospital setting— are written nutrition education resources too hard to understand?
Authors: PERKINS Louise , COHEN Jennifer
Published: August 2008

Aims:  To determine the readability of written nutrition education resources currently used in the Nutrition and Dietetics Department in a large teaching hospital and assess whether these resources are of an appropriate readability level for the target population.

Methods:  Dietitians in the department (n = 17) were interviewed to identify resources in use. Readability analysis of current resources (n = 235) followed, using the Simplified Measure of Gobbledegook (SMOG). The SMOG scores were compared with census data for the average reading ability of the target population based on the number of school years completed.

Results:  The readability level for the resources ranged from 6 to 15. The mean was 10.4 ± 1.89 (n = 235). This compared with a reading ability in the target population of between years 6 and 8. This discrepancy suggests that the resources may be too complex and are unlikely to be well understood by the target population.

Conclusions:  In the time‐poor clinical environment where there is reliance on written nutrition resources to support and reinforce education messages, it is pertinent to pay more attention to readability level. Written resources are unlikely to be effective if they are too complex. It is therefore suggested that dietitians consider the readability when developing and reviewing written nutrition education resources to ensure best‐quality patient care. The results of this project suggest that the SMOG index is a useful method to use for this purpose as it is widely available, easy to use and expedient in implementation.
New Zealand children's dietary intakes during school hours
Authors: REGAN Asher , PARNELL Winsome , GRAY Andrew , WILSON Noela
Published: August 2008

Aim:  To describe the dietary habits of New Zealand schoolchildren during school hours.

Methods:  The present study was a secondary analysis of New Zealand's national nutrition survey of schoolchildren (2002 National Children's Nutrition Survey). It includes a subset of 2247 children aged 5–14 years, surveyed to recall a school day. A 24‐hour dietary recall was collected in the home of the child. Food or beverage consumption during the morning (9:00 a.m.−11:59 a.m.) and at lunch time (12:00 noon−2:00 p.m.) was based on whether energy intake during these times was above zero. Foods consumed and nutrient intakes during these two time periods were ascertained.

Results:  Approximately 80% of children consumed some food or beverage during the morning and over 90% during lunch time. Older children were less likely than younger children to consume foods or beverages during lunch time. Snack foods, fruit and biscuits were the food groups most consumed during the morning, while sandwiches and fruit were the most popular foods during lunch time. Children obtained approximately one‐third of their daily nutrient intakes during school hours. Food and nutrient intakes differed by ethnicity both during the morning and at lunch time.

Conclusions:  Children's food consumption at school could be improved—particularly morning snack quality. Encouraging healthier selections sourced from home is vital as well as ensuring that healthy options are available for purchase, and Pacific children need the most encouragement to choose wisely.
Antibacterial Activity against E. coli O157:H7, Physical Properties, and Storage Stability of Novel Carvacrol‐Containing Edible Tomato Films
Authors: Du W.‐X. , Olsen C.W. , Avena‐Bustillos R.J. , McHugh T.H. , Levin C.E. , Friedman Mendel
Published: August 2008

ABSTRACT:  Edible films containing plant antimicrobials are gaining importance as potential treatment to extend product shelf life and reduce risk of pathogen growth on contaminated food surfaces. The main objective of the present study was to evaluate the antimicrobial activities, storage stabilities, and physical–chemical–mechanica1 properties of novel edible films made from tomatoes containing carvacrol, the main constituent of oregano oil. The antimicrobial activities against E. coli O157:H7 and the stability of carvacrol were evaluated during the preparation and storage of tomato‐based films made by 2 different casting methods, continuous casting and batch casting. Antimicrobial assays of tomato films indicated that optimum antimicrobial effects occurred with carvacrol levels of approximately 0.75% added to tomato purees before film preparation. HPLC analysis of the films indicated that the carvacrol concentrations and bactericidal effect of the films remained unchanged over the storage period of up to 98 d at 5 and 25 °C. Carvacrol addition to the tomato puree used to prepare the films increased water vapor permeability of tomato films. The continuous method for casting of the films appears more suitable for large‐scale use than the batch method. This 1st report on tomato‐based edible antimicrobial tomato films suggests that these films have the potential to prevent adverse effects of contaminated food and promote human health associated with the consumption of tomatoes.
Characterization of Asparagus Lignin by HPLC
Authors: Jaramillo‐Carmona S. , Fuentes‐Alventosa J.M. , Rodríguez‐Gutiérrez G. , Waldron K.W. , Smith A.C. , Guillén‐Bejarano R. , Fernández‐Bolaños J. , Jiménez‐Araujo A. , Rodríguez‐Arcos R.
Published: August 2008

ABSTRACT:  Lignin is the cell wall component most frequently associated with hardening. Its characterization and quantification are very important to understand the biochemical modifications related to the changes in texture of vegetables such as asparagus (Asparagus officinalis), in which this organoleptic attribute is a very important quality factor. In this study, asparagus lignin from the basal sections of fresh and stored spears was analyzed using 2 methods, the traditional (Klason lignin) and the recently developed derivatization, followed by reductive cleavage (DFRC) method. The latter is a simple and reproducible technique for lignin characterization based on a degradation procedure that produces analyzable monomers and dimers by cleaving α‐ and β‐aryl ethers in lignins. The primary monomers derived from DFRC degradation of lignins are essentially p‐coumaryl peracetate, coniferyl peracetate, and sinapyl peracetate. To evaluate the efficiency of the DFRC method, our investigations have been carried on distinct sample types, including wood (data not shown), straw, and asparagus samples. The results have confirmed that lignin composition is affected by plant nature. It has been found that whereas wood samples mostly contain coniferyl units, plant foods, such as straw and asparagus, contain both coniferyl and guaiacyl units.
High Performance Recuperator With Oblique Wavy Walls
Authors: Morimoto Kenichi , Suzuki Yuji , Kasagi Nobuhide
Published: August 2008

A series of numerical simulation of the flow and heat transfer in modeled counterflow heat exchangers with oblique wavy walls has been made toward optimal shape design of recuperators. The effects of oblique angles and amplitudes of the wavy walls are systematically evaluated, and the heat transfer and pressure loss characteristics are investigated. It is found that counter-rotating streamwise vortices are induced by the wavy walls, and the flow field has been drastically modified due to the intense secondary flow. By using the optimum set of oblique angle and wave amplitude, significant heat transfer enhancement has been achieved at the cost of relatively small pressure loss, and the j∕f factor becomes much larger than that of straight square duct or conventional compact recuperators. When thermal coupling of hot and cold fluid passages is considered, the heat transfer is found to be strongly dependent on the arrangement of counterflow passages. The total heat transfer surface area required for a given pumping power and heat transfer rate can be reduced by more than 60% if compared to the straight square duct.
Modeling
of Convective Cooling of a Rotating Disk by Partially Confined Liquid Jet
Impingement
Authors: Lallave Jorge
C. , Rahman Muhammad
M.
Published: August 2008

This paper presents the results of the numerical simulation of conjugate heat transfer during a semiconfined liquid jet impingement on a uniformly heated spinning solid disk of finite thickness and radius. This study considered various disk materials, namely, aluminum, copper, silver, Constantan, and silicon; covering a range of Reynolds number (220–900), Ekman number (7.08×10−5–∞), nozzle-to-target spacing (β=0.25–1.0), disk thicknesses to nozzle diameter ratio (b∕dn=0.25–1.67), and Prandtl number (1.29–124.44) using ammonia (NH3), water (H2O), flouroinert (FC-77), and oil (MIL-7808) as working fluids. The solid to fluid thermal conductivity ratio was 36.91–2222. A higher thermal conductivity plate material maintained a more uniform interface temperature distribution. A higher Reynolds number increased the local heat transfer coefficient. The rotational rate also increased the local heat transfer coefficient under most conditions.
The Solution of Transient Radiative Transfer With Collimated Incident Serial Pulse in a Plane-Parallel Medium by the DRESOR Method
Authors: Cheng Qiang , Zhou Huai-Chun , Huang Zhi-Feng , Yu Yong-Lin , Huang De-Xiu
Published: August 2008

A time-dependent distribution of ratios of energy scattered by the medium or reflected by the boundary surfaces (DRESOR) method was proposed to solve the transient radiative transfer in a one-dimensional slab. This slab is filled with an absorbing, scattering, and nonemitting medium and exposed to a collimated, incident serial pulse with different pulse shapes and pulse widths. The time-dependent DRESOR values, representing the temporal response of an instantaneous, incident pulse with unit energy and the same incident direction as that for the serial pulse, were proposed and calculated by the Monte Carlo method. The temporal radiative intensity inside the medium with high directional resolution can be obtained from the time-dependent DRESOR values. The transient incident radiation results obtained by the DRESOR method were compared to those obtained with the Monte Carlo method, and good agreements were achieved. Influences of the pulse shape and width, reflectivity of the boundary, scattering albedo, optical thickness, and anisotropic scattering on the transient radiative transfer, especially the temporal response along different directions, were investigated.
Assessment of the Single-Mixture Gas Assumption for the Correlated K-Distribution Fictitious Gas Method in H2O–CO2–CO Mixture at High Temperature
Authors: Caliot C. , Flamant G. , Hafi M. El , Maoult Y. Le
Published: August 2008

This paper deals with the comparison of spectral narrow band models based on the correlated-K (CK) approach in the specific area of remote sensing of plume signatures. The CK models chosen may or may not include the fictitious gas (FG) idea and the single-mixture-gas assumption (SMG). The accuracy of the CK and the CK-SMG as well as the CKFG and CKFG-SMG models are compared, and the influence of the SMG assumption is inferred. The errors induced by each model are compared in a sensitivity study involving the plume thickness and the atmospheric path length as parameters. This study is conducted in two remote-sensing situations with different absolute pressures at sea level (105Pa) and at high altitude (16.6km, 104Pa). The comparisons are done on the basis of the error obtained for the integrated intensity while leaving a line of sight that is computed in three common spectral bands: 2000–2500cm−1, 3450–3850cm−1, and 3850–4150cm−1. In most situations, the SMG assumption induces negligible differences. Furthermore, compared to the CKFG model, the CKFG-SMG model results in a reduction of the computational time by a factor of 2.
Experiments in Single-Phase Natural Circulation Miniloops With Different Working Fluids and Geometries
Authors: Garibaldi Pietro , Misale Mario
Published: August 2008

The aim of this work is to analyze experimentally the influence of geometrical parameters and fluid properties on the thermal performances of rectangular single-phase natural circulation miniloops, which could be used for cooling of electronic devices. The present paper analyzes two experimental campaigns performed on two rectangular miniloops (ML1 and ML2), characterized by different heights, when two working fluids (water and FC43) are employed. The temperature trends are measured for different combinations of miniloop inclination and power, and the associated fluid velocities are calculated by means of an enthalpy balance. The experimental data are compared with Vijayan’s model, developed for large scale loops in steady-state conditions, corrected with a parameter that takes into account the loop inclination. The dynamical behavior is always stable. The time of the initial transient is long at high miniloop inclination (close to horizontal) and at low power, while the temperature overshoot grows up with increasing power and inclination. Results show that at the same power the velocity of FC43 is almost twice than that of water, but the thermal performances are worse because FC43 is characterized by low specific heat. Moreover, the velocities of the tallest miniloop are the lowest, probably because the enhancement of shear stresses overcomes the increase in buoyancy forces. For both fluids, the velocity grows almost linearly with power. Experimental data show a good agreement with the modified Vijayan’s model.
Modeling the Natural Convection Heat Transfer and Dryout Heat Flux in a Porous Debris Bed
Authors: Sinha R. , Nayak A. K. , Sehgal B. R.
Published: August 2008

An empirical model for natural convection heat transfer for film-boiling condition has been developed for volumetrically heated particulate debris beds when flooded with water at the top of the bed. The model has been derived from the quenching data generated in the POMECO facility located at KTH, Stockholm. A dryout model is also developed for countercurrent flooding limiting condition when the heat generating saturated debris bed is flooded with water from the top. The model is in good agreement with the experimental data over a wide range of particle size and porosity as compared to the existing models. The implication of the models with respect to quenching of porous debris bed formed during postulated severe accident condition is discussed.
Influence of Curvature and Pressure Gradient on Turbulent Wake
Development in Curved Channels
Authors: Schobeiri M. T.
Published: August 2008

The development of steady wake flow downstream of a cylindrical rod within a curved channel under the influence of positive, negative, and zero streamwise pressure gradients is theoretically and experimentally investigated. The measured asymmetric wake quantities, such as the mean velocity, turbulent fluctuations in longitudinal and lateral directions, and the turbulent shear stress, are transformed from the probe coordinate system into the curvilinear wake coordinate system. For the transformed nondimensionalized velocity defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on the experimental observations and using the transformed equations of motion and continuity, a theoretical framework that generally describes a two-dimensional curvilinear steady wake flow is developed. The theory treats the straight wake flow as a special case for which the curvature radius approaches infinity. A comparison of the developed theory with our own experimental results and with the re-evaluated experimental data from the literature establishes the general validity of the theory.
Distributions of Pressure, Velocity, and Void Fraction for One-Dimensional Gas-Liquid Bubbly Flow in Horizontal Pipes
Authors: Tran Phu D.
Published: August 2008

A homogeneous model for prediction of the longitudinal distributions of pressure, velocity, and void fraction for two-phase bubbly flow in horizontal pipes is presented. The mixture flow is described by a system of two nondimensional ordinary differential equations that can be integrated numerically to yield the distributions of the flow variables along the pipe. The viscosity of the two-phase mixture is assumed to vary with the void fraction according to a polynomial form. Experimental data were obtained for a range of air-water bubbly flow in a horizontal pipe. Prediction of pressure distributions along the pipe compares favorably with experimental data, while prediction of void fraction distributions can be achieved with moderate accuracy.
LES Study of the Influence of a Train-Nose Shape on the Flow Structures Under Cross-Wind Conditions
Authors: Hemida Hassan , Krajnović Siniša
Published: August 2008

Cross-wind flows around two simplified high-speed trains with different nose shapes are studied using large-eddy simulation (LES) with the standard Smagorinsky model. The Reynolds number is 3×105 based on the height of the train and the freestream velocity. The cross section and the length of the two train models are identical while one model has a nose length twice that of the other. The three-dimensional effects of the nose on the flow structures in the wake and on the aerodynamic quantities such as lift and side force coefficients, flow patterns, local pressure coefficient, and wake frequencies are investigated. The short-nose train simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear-layer instabilities. Prediction of vortex shedding, flow patterns in the train surface, and time-averaged pressure distribution obtained from the long-nose train simulation are in good agreement with the available experimental data.
Two-Dimensional Simulation of the Collapse of Vapor Bubbles Near a Wall
Authors: Jing Luo , Jian Li , Guangneng Dong
Published: August 2008

In order to investigate the erosion extent and mode of cavitation in different states by the commercial code FLUENT and evaluate the reliability of the software, the collapse processes of a vapor bubble, which was near or on the wall under the conditions in the stationary water or the high speed water, were simulated by the numerical calculation by using a 2D model. The results are in accordance with results presented by other researchers, so the simulation may testify to the validation of the code. We suppose that a bevel jet, which is generated contrary to the flow direction when the bubble collapses in high speed flow, may cause the ripple and fish-scale pit damage found on the transition parts of many hydraulic systems.
Droplet and Bubble Dynamics in Saturated FC-72 Spray Cooling on a Smooth Surface
Authors: Chen Ruey-Hung , Tan David S. , Lin Kuo-Chi , Chow Louis C. , Griffin Alison R. , Rini Daniel P.
Published: August 2008

Droplet and bubble dynamics and nucleate heat transfer in saturated FC-72 spray cooling were studied using a simulation model. The spray cooling system simulated consists of three droplet fluxes impinging on a smooth heater, where secondary nuclei outnumber the surface nuclei. Using the experimentally observed bubble growth rate on a smooth diamond heater, submodels were assumed based on physical reasoning for the number of secondary nuclei entrained by the impinging droplets, bubble puncturing by the impinging droplets, bubble merging, and the spatial distribution of secondary nuclei. The predicted nucleate heat transfer was in agreement with experimental findings. Dynamic aspects of the droplets and bubbles, which had been difficult to observe experimentally, and their ability in enhancing nucleate heat transfer were then discussed based on the results of the simulation. These aspects include bubble merging, bubble puncturing by impinging droplets, secondary nucleation, bubble size distribution, and bubble diameter at puncture. Simply increasing the number of secondary nuclei is not as effective in enhancing nucleate heat transfer as when it is also combined with increased bubble puncturing frequency by the impinging droplets. For heat transfer enhancement, it is desirable to have as many small bubbles and as high a bubble density as possible.
An Experimental Procedure for Determining Both the Density and Flow Rate From Pressure Drop Measurements in a Cylindrical Pipe
Authors: Michaux Ghislain , Vauquelin Olivier , Gauger Elsa
Published: August 2008

An experimental procedure was developed for determining both the density and flow rate of a gas from measurements of pressure drops caused by an abrupt flow area contraction in a cylindrical pipe. Experiments were carried out by varying the density and flow rate of a light gas mixture of air and helium, spanning a Reynolds number range from 0.2×104 to 3.4×104. From experimental results, a procedure was then proposed for evaluating the density from pressure change measurements in the scope of light gas extraction experiments.
Laminarization of Internal Flows Under the Combined Effect of Strong Curvature and Rotation
Authors: Guleren K. M. , Afgan I. , Turan A.
Published: August 2008

The laminarization phenomenon for the flow under the combined effect of strong curvature and rotation is discussed based on numerical predictions of large-eddy simulation (LES). Initially, the laminarization process is presented for the fully developed flow inside a spanwise rotating straight square duct. LES predictions over a wide range of rotation numbers (Ro=0–5) show that the turbulent kinetic energy decreases monotonically apart from 0.2<Ro<0.5. Subsequently, a spanwise rotating U-duct flow is considered with Ro=±0.2. The interaction of curvature and Coriolis induced secondary flows enhances the turbulence for the negative rotating case, whereas this interaction ensues strong laminarization for the positive rotating case. Finally, the laminarization is presented in the impeller of a typical centrifugal compressor, rotating at a speed of Ω=1862rpm(Ro=0.6). The resulting LES predictions are observed to be better than those of Reynolds-averaged Navier-Stokes (RANS) in the regions where turbulence is significant. However, for the regions dominated by strong laminarization, RANS results are seen to approach those of LES and experiments.
Analytical Prediction of Flow Field in Magnetohydrodynamic-Based Microfluidic Devices
Authors: Kabbani Hussameddine S. , Mack Martin J. , Joo Sang W. , Qian Shizhi
Published: August 2008

A new approximate solution for the velocity profile of steady incompressible magnetohydrodynamic (MHD) flows in a rectangular microchannel driven by the Lorentz force is proposed. Mean velocity and mass flow rate in a channel, subsequently derived, can be used efficiently for many MHD-based microfluidic applications, including the design of a MHD-based microfluidic network without resorting to costly full-scale computational fluid dynamics. The closed-form solutions, provided for both direct-current (dc) and alternating-current (ac) electric and magnetic fields, are in simple forms, without any series or functions to evaluate, and so can be readily used for inverse or control problems associated with MHD-based lab-on-a-chip (LOC) devices. Extensive comparisons with previous analytical, computational, and experimental results are performed, and summarized in the present study. The proposed solutions are shown to agree better with existing experimental and computational reports than previous approximations and are to be used in a broad range of MHD-based LOC applications with both dc and ac fields with required accuracy.
Experimental Study of a Curved Rotating Heat Pipe
Authors: Jankowski T. A. , Prenger F. C. , Razani A.
Published: August 2008

A curved rotating heat pipe for use in motor and generator applications is studied experimentally. The heat pipe is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is close to the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. The curved rotating heat pipe allows for a direct coupling of the rotating condenser section to an on-axis stationary refrigeration system, while allowing the revolving evaporator section to intercept off-axis heat sources in the rotating machine. An experimental rotating heat pipe test apparatus was built and operated. The test data indicate that the working fluid continued to circulate, resulting in heat transfer with a high effective thermal conductivity, with the curved rotating heat pipe operating under the influence of centrifugal accelerations approaching 400g. Furthermore, the experimental results were used to validate a heat pipe thermal model that can be used in the design of rotating machines that rely on the curved rotating heat pipe as part of the thermal management system.
Flow Boiling in Minichannels Under Normal, Hyper-, and Microgravity: Local Heat Transfer Analysis Using Inverse Methods
Authors: Luciani Sébastien , Brutin David , Le Niliot Christophe , Rahli Ouamar , Tadrist Lounès
Published: August 2008

Boiling in microchannels is a very efficient mode of heat transfer since high heat and mass transfer coefficients are achieved. Here, the objective is to provide basic knowledge on the systems of biphasic cooling in mini- and microchannels during hyper- and microgravity. The experimental activities are performed in the frame of the MAP Boiling project founded by ESA. Analysis using inverse methods allows us to estimate local flow boiling heat transfers in the minichannels. To observe the influence of gravity level on the fluid flow and to take data measurements, an experimental setup is designed with two identical channels: one for the visualization and the other one for the data acquisition. These two devices enable us to study the influence of gravity on the temperature and pressure measurements. The two minichannels are modeled as a rectangular rod made up of three materials: a layer of polycarbonate (λ=0.2Wm−1K−1) used as an insulator, a cement rod (λ=0.83Wm−1K−1) instrumented with 21 K-type thermocouples, and in the middle a layer of Inconel® (λ=10.8Wm−1K−1) in which the minichannel is engraved. Pressure and temperature measurements are carried out simultaneously at various levels of the minichannel. Above the channel, we have a set of temperature and pressure gauges and inside the cement rods, five heating wires provide a power of 11W. The K-type thermocouple sensors enable us to acquire the temperature in various locations (x, y, and z) of the device. With these temperatures and the knowledge of the boundary conditions, we are able to solve the problem using inverse methods and obtain local heat fluxes and local surface temperatures on several locations. The experiments are conducted with HFE-7100 as this fluid has a low boiling temperature at the cabin pressure on Board A300. We applied for each experiment a constant heat flux (Qw=33kWm−2) for the PF52 campaigns (Parabolic Flights). The mass flow rate varies in the range of 1<Qm<4gs−1 and the fluid saturation temperature (Tsat) is 54°C at Psat=820mbars.
On the Effect of Temperature on Tightening Characteristics of Gaskets
Authors: Bartonicek Jaroslav , Schaaf Manfred , Schoeckle Friedrich
Published: August 2008

To study the effect of temperature on the tightening characteristics of gaskets, leak rate tests were performed using a servo-hydraulic test equipment (short term temperature exposure). According to the tests the tightening behaviour of gaskets made of fibre based sheet material improved with temperature due to additional deformation of the gaskets during the test. In tests with camprofile gaskets with graphite layers there was no significant additional deformation of the gasket thus the leak rates showed no difference between room temperature and elevated temperature. Regarding long term exposure to temperature it is expected that with a lot of gasket materials the leak rates increase after a certain aging period. It is too expensive to study these effects with complex servo-hydraulic test rigs. Therefore a more simple test rig was developed that can be loaded in hydraulic test rigs (to determine leak rate vs. gasket stress curves) and that can be exposed to temperature in an oven or by a special heating device.
The Suitability of Various Gasket Types for Heat Exchanger Service
Authors: Brown Warren
Published: August 2008

This paper describes two important factors that must be considered during the selection of heat exchanger gaskets for petroleum refinery service. These factors are the assessment of the expected level of gasket stress relaxation and the ability of the gasket to resist the radial shear mode of gasket failure. The latest techniques for obtaining the necessary data to evaluate the gasket being considered are detailed. A summary of some generic results of recent tests, for some of the most commonly employed gasket types, is also presented.
Dynamic Characteristics of Structures With Bolted Joint
Authors: Aoki Shigeru
Published: August 2008

Bolted joints are widely used for pressure vessels and piping system. Many studies on strength of bolted joint are carried out. However, few studies on dynamic characteristics of structure with bolted joint are carried out. In this paper, the effect of bolted joints on dynamic characteristics of structure is examined. First, the damping ratio and the natural frequency of specimens with some types of bolted joints are measured. Obtained results are compared with those for the specimen without bolted joint. It is found that damping ratio increases and the natural frequency becomes lower. Next, the effect of bolted joint on random vibration response of structure using simplified model is examined. Standard deviation of acceleration response of structure with bolted joint is lower than that of structure without bolted joint.
FEM Stress Analysis and Sealing Performance in Pipe Flange Connections With Gaskets Subjected to Internal Pressure and External Bending Moment
Authors: Sawa Toshiyuki , Matsumoto Mitsuhiro
Published: August 2008

This paper deals with the characteristics of a pipe flange connection with a compressed asbestos sheet gasket (JIS) subjected to an internal pressure and a bending moment. The contact gasket stress distributions at the interfaces between pipe flanges and a gasket are calculated by the elasto-plastic finite element method taking account a hysteresis and a non-linearity in the stress-strain curve of the compressed asbestos sheet gasket. In addition, measurements of a change in axial bolt force and leakage test were conducted using an actual pipe flange connection with the gasket subjected to the internal pressure and the bending moment. The new gasket constants are calculated by using the results of the leakage test and the calculated average contact gasket stress. The values of the new gasket constants obtained by the present study are in a fairly good agreement with those from ROTT (PVRC). It is found that the value of the tightness parameter is increased as the bending moment is increased. This is because the average contact gasket stress under the bending moment is increased, while it is decreased under the internal pressure.
Design of Compact Flange Joints
Authors: Kirkemo Finn
Published: August 2008

In the past 10–15 years, flange joints designed for metal-to-metal face contact with self seating and pressure activated seal rings have been used extensively in high-pressure applications in industrial piping, pressure vessels, pipelines, risers and associated equipment. These flange joints are generally much smaller and lighter, with smaller bolts, than equally rated standard gasketed flange joints, and are often called compact flange joints. This paper provides all necessary information to design compact flange joints for pressure and external loads and made from any suitable material. The paper includes design methods for design of the seal ring, flange and bolts in addition to assembly guidelines. Weld neck flanges, where the hub is of uniform thickness are discussed in detail. Similar method as presented has been applied to design compact flange joints with great success for many years.
Stress Analysis and the Sealing Performance Evaluation of Pipe Flange Connection With Spiral Wound Gaskets Under Internal Pressure
Authors: Sawa Toshiyuki , Ogata Naofumi
Published: August 2008

This paper deals with the stress analysis of a pipe flange connection with a spiral wound gasket using the elasto-plastic finite element method taking account the hysteresis and the non-linearity in the stress-strain curve of the spiral wound gasket, when an intemal pressure is applied to the pipe flange connections with the different nominal diameters from 2″ to 20″. The effects of the nominal diameter of the pipe flange on the contact stress distributions at the interfaces are examined. Leakage tests of the pipe flange connections with 3″ and 20″ nominal diameters were conducted and measurement of the axial bolt force was also performed. The results by the finite element analysis are fairly consistent with the experimental results concerning the variation in the axial bolt force. By using the contact stress distributions and the results of the leakage test, the new gasket constants are evaluated. As a result, it is found that the variations in the contact stress distributions are substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated.
Bolt Preload Control for Bolted Flange Joint
Authors: Tsuji Hirokazu , Nakano Makoto
Published: August 2008

Tightening method for flange joints proposed by ASME PCC-1 specifies that bolts are tightened by the cross-pattern sequence and tightening torque is raised with several steps. On the other hand, new tightening method has been proposed by Japan BFC committee, in which bolts are tightened in the clockwise-pattern sequence and tightening torque is 100% of the target torque in all steps after an install step with some snug torque. Tightening tests using flanges with various nominal sizes, performed in this study, show that the new tightening method achieves comparable uniformity in bolt preloads and in flange alignment with ASME PCC-1 procedure. This new tightening method is able to reduce both the work volume in the tightening operation and the possibility of human errors like missing the tightening order in it. Step-like increment of the bolt tension under the repeated tightening with small increment of the tightening torque is also discussed. Experimental results show that continuous control of the bolt tension by the repeated tightening is impossible. The step-like increment of the bolt tension is observed in the tightening process of the actual bolted flange joints so that the excessive iteration of the repeated tightening round hardly improves the uniformity of the bolt preloads.
Requirements for Numerical Flange Calculations According to the German Nuclear Code
Authors: Kauer Robert
Published: August 2008

In Europe as well as in other countries a lot of effort is invested into developing new codes and standards for bolted joints under various loading conditions. The standardization of gasket factors and the improvement of calculation methods with respect to these factors characterize the last couple of years in this area. In Germany the nuclear code (KTA) is also influenced by this development. So, the leak rate dependency of gasket factors and the results of a research program on metal-to-metal contact type flanges were introduced into the new approach of the code for Class 2 and 3 components. Herein flange calculations can be performed for various flange types, floating type and metal-to-metal contact type. Generally, the calculations to be performed can be separated into a design step and the proof of sufficient tightness and strength of flange, bolts and gasket for the various operating conditions according to the chosen bolting method. In this step the stiffness of all components (flanges, bolts and gasket) and its influence on the mechanical behavior of the entire system is considered. Besides, influences caused by thermal effects, e.g. different thermal expansion between the flanges and the bolts, or seating effects in the gasket must be regarded. In cases, where the allowable stress values are not satisfied by performing code calculations or in cases, where the applicability of the code is not given, e.g. due to geometric facts, Finite-Element analyses often replace code calculations to show code compliance. Therefore, numerical Finite-Element analyses, performed according to a special code, e.g. KTA, must also fulfill the requirements of the code with respect to considered load cases, bolting condition, allowable stresses etc., to get an adequate testimony for a certain flange joint. In this paper certain methods for numerical calculations will be presented and compared to the results of the code for various flange types and dimensions.
Evaluation of Microstructure and Residual Stress on Bi-Material Welded Part
Authors: Kim Jong-Sung , Lee Seung-Gun , Jin Tae-Eun
Published: August 2008

To perform a more realistic integrity evaluation for the bi-material welded part of NPP (nuclear power plant) components, it is necessary to evaluate the microstructure and residual stress considering the actual welding process such as multi-pass welding and PWHT (post weld heat treatment). This paper proposes an integrated assessment methodology systematically developed for microstructure and residual stress on welds utilizing thermodynamics, diffusion theory, and finite element method and validation experiments. Also, the metallurgical microstructure and residual stress of the bi-material welds are evaluated by application of this systematic methodology.
Application of 3D Finite Element Modelling to Repair Weld Simulation in Industrial Applications
Authors: Vinas George , Dauda Tamba , Moyes Nicola , Laird Alan
Published: August 2008

The Finite Element Method (FEM) has been implemented in 3D to predict welding residual stresses in repair welds. The analysis has been used to achieve more accurate residual stress predictions for the weld at the cost of long computation times. The use of this CPU intensive approach has been facilitated by the advent of ever-faster computer processors being made more accessible to the engineering community. The same technique has also been used with coarser meshes involving simplified welding sequences where a number of weld passes are “lumped” together to reduce the simulation time. The authors argue that this latter approach can be very useful in predicting the more global component response — in cases where 2D model symmetries are not applicable — and for rapid identification of problem areas where finer simulations would be prohibitive. The authors show an example of a residual stress prediction for a letterbox repair obtained using the FEM. Good agreement between this prediction and experimental measurements is shown. The FEM simulation technique has been used to predict residual stress formation during the welding process and subsequent service loading of the component. This analysis shows the residual stress field relaxation following “shakedown”. The component under service conditions is subjected to pressure loading and a small amount of bending stress. Based on recent residual stress experimental programmes conducted at Mitsui Babcock Energy Limited (MBEL), the authors provide a brief discussion on the ways in which various experimental techniques have been used to verify welding residual stress predictions from FE. The authors argue that just as there has been an interest in the field to measure residual stresses in the highly stressed regions of a weld, it is equally important to measure stresses in areas of relatively low stress to confirm that stresses do indeed die out away from welds. It is in the latter case where some experimental techniques cannot perform as well as other simple, well proven, strain measurement techniques.
Temperature and Residual Stress Fields in an Austenitic Circumferential Pipe Weld
Authors: Bonn Ruthard , Metzner Klaus , Kockelmann H. , Roos E. , Stumpfrock L.
Published: August 2008

The main target of a research programme “experimental and numerical analyses on the residual stress field in the area of circumferential welds in austenitic pipe welds”, sponsored by Technische Vereinigung der Großkraftwerksbetreiber e. V. (VGB) and carried out at MPA Stuttgart, was the validation of the numerical calculation for the quantitative determination of residual stress fields in austenitic circumferential pipe welds. In addition, the influence of operational stresses as well as the impact of the pressure test on the residual stress state had to be examined. By using the TIG orbital welding technique, circumferential welds (Material X 10 CrNiNb 18 9 (1.4550, corresponding to TP 347) were produced (geometric dimensions 255.4 mm I.D. × 8.8 mm wall) with welding boundary conditions and weld parameters (number of weld layers and weld built-up, seam volume, heat input) which are representative for pipings in power plants. Deformation and temperature measurements accompanying the welding, as well as the experimentally determined (X-ray diffraction) welding residual stress distribution, served as the basis for the verification of numeric temperature and residual stress field calculations. The material model on which the calculations were founded was developed by experimental weld simulations in the thermo-mechanical test rig GLEEBLE 2000 for the determination of the material behaviour at different temperatures and elasto-plastic deformation. The numeric calculations were carried out with the Finite Element program ABAQUS. The comparison of the calculation results with the experimental findings confirms the proven validation of the developed numerical calculation models for the quantitative determination of residual stresses in austenitic circumferential pipings. The investigation gives a well-founded insight into the complex thermo-mechanical processes during welding, not known to this extent from literature previously.
Mathematical Expression for the Prediction of Penetration in V-Groove Joints for Aluminum 6063-T5
Authors: Payares Mari´a Carolina , Mun˜oz-Escalona Patricia , Almenara Minerva Dorta
Published: August 2008

In order to understand the mechanism of weld bead formation, a relationship between arc welding parameters and weld bead geometry must be established. This relationship is also necessary to forecast penetration variables allowing to optimize welding parameters for particular applications. However, establishing this relationship is a rather difficult problem due to the large number of parameters involved in the process along with the complexity of the process itself. In this regard, many investigators have performed experiments in aluminum using the GMAW processes in an effort to predict weld joint penetration behavior. Other researchers have also study the influence of the welding speed, arc current and arc voltage on the penetration. However, in spite of all this effort, a defined pattern to predict the influence of these parameters on the weld joint penetration for aluminum has not been established. The result of this research is an empirical expression for the prediction of penetration in V-groove joints of aluminum 6063-T5 using the GMAW technique. Also, the influence of these variables on the weld penetration is studied, providing with new evidence in aluminum welding.