bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERMITTENT HYPOXIA CONDITIONING PREVENTS OXIDATIVE BRAIN INJURY IN ETHANOL WITHDRAWN RATS
Authors: Jung Marianna E. , Mallet Robert T. , Fred Downey H. , Wilson Andrew M. , Metzger Daniel , Brown Nastassia D. , Simpkins James W.
Published: June 2008

Cyclic bouts of intermittent, normobaric hypoxia (IH) have been found to protect the central nervous system from ischemic and excitotoxic injury. We investigated whether IH mitigates oxidative brain injury in male rats subjected to ethanol intoxication and abrupt ethanol withdrawal (EW). We assessed the effects of IH on superoxide generation, protein oxidation, and mitochondrial membrane swelling and rupture as a marker of mitochondrial permeability transition pore (PTP) opening. Male rats consumed dextrin control diet or 6.5% ethanol diet for 5 weeks. During the last 20 days of the diet, rats were treated with repetitive (5‐8/day), brief (5‐10 min) periods of hypoxia (9.5‐10% inspired O2) separated by 4 min exposures to room air. Cerebellum, cortex and hippocampus were biopsied at the end of the ethanol diet or at 24 hours of EW. Superoxide and protein carbonyl contents in tissue homogenates and rate of absorbance decline at 540 nm in mitochondrial suspensions were measured as indicators of oxidative stress, protein oxidation and PTP opening, respectively. EW increased superoxide and protein carbonyl contents and accelerated PTP opening in all three brain areas in a manner that was ameliorated by IH. These results suggest that antecedent IH conditioning during chronic ethanol consumption attenuates subsequent oxidative damage to the brain in ethanol withdrawn rats. (supported by NIAAA/AA013864, NIAAA/AA015982, NCCAM/AT003598).
Quality Improvement Toward Decreasing High‐Risk Medications for Older Veteran Outpatients
Authors: Zillich Alan J. , Shay Kenneth , Hyduke Barbara , Emmendorfer Thomas R. , Mellow Alan M. , Counsell Steven R. , Supiano Mark A. , Woodbridge Peter , Reeves Pamela
Published: June 2008

OBJECTIVES: To examine the effectiveness of a quality improvement program to decrease prescribing of high‐risk medications.

DESIGN: Single cohort, pre‐ and postintervention.

SETTING: Regional network of Department of Veterans Affairs medical facilities.

PARTICIPANTS: Outpatient veterans aged 65 and older who received one or more high‐risk medications and the prescribing clinicians.

INTERVENTION: A two‐stage intervention was implemented. First, a real‐time warning message to prescribers appeared whenever one of the high‐risk drugs was ordered; second, a personally addressed letter from the Chief Medical Officer asking prescribers to consider discontinuing the high‐risk medication along with a copy of the Beers criteria article, a list of suggested alternatives to high‐risk medications, and a list of older patients receiving the high‐risk medications who had upcoming appointments with these prescribers.

MEASUREMENTS: The primary outcome was the absence of prescribed high‐risk medications for all patients in the cohort during the postintervention period. For a subgroup of the cohort whose prescribers received the second‐stage intervention, an additional outcome was the absence of prescribed high‐risk medications within the subgroup.

RESULTS: Two thousand seven hundred fifty‐three unique patients were identified in the cohort; 1,396 (50.7%) had high‐risk medications discontinued, resulting in a significant decrease in the number of patients prescribed high‐risk medications from the preintervention period to the postintervention period (P<.001). Of the 801 patients in the subgroup, 72.0% (n=577) had high‐risk medications discontinued (P<.001).

CONCLUSION: This multimethod intervention significantly decreased prescribing of high‐risk medications to older patients. Further studies are needed to confirm the findings.
A Survey of Background Levels of Explosives and Related Compounds in the Environment*
Authors: Lahoda Kristy G. , Collin Olivier L. , Mathis John A. , LeClair Holly E. , Wise Steven H. , McCord Bruce R.
Published: June 2008

Abstract:  In this paper, swabings from various public areas in 28 different cities throughout the United States were collected. A wide variety of objects were tested, ranging from park benches and telephones to sign posts and mailboxes. Inorganic anions and cations common in low explosives were detected simultaneously using capillary zone electrophoresis. Organic high explosives including nitroaromatics, nitramines, and nitrate esters were detected using gas chromatography with a pulsed‐discharge electron capture detector. Confirmation of selected results was performed by ion chromatography and negative ion chemical ionization GC/MS. In general the results provide two major conclusions: (i) with the exception of nitrate, most low explosive oxidizers are rare in the environment; (ii) no organic explosives or significant interferences to these explosives were detected.
The gp130/STAT3 signaling pathway mediates β‐adrenergic receptor‐induced atrial natriuretic factor expression in cardiomyocytes
Authors: Zhang Hui , Feng Wei , Liao Wenqiang , Ma Xiaowei , Han Qide , Zhang Youyi
Published: June 2008

β‐Adrenergic receptor (β‐AR)‐induced cardiac remodeling is closely linked with the re‐expression of the atrial natriuretic factor (ANF) gene. However, the exact molecular mechanism of this response remains elusive. Here, we demonstrate that the β‐AR agonist isoproterenol potently evokes the tyrosine phosphorylation of STAT3 and increases its transcriptional activity in an extracellularly regulated kinase 1/2 and glycoprotein (gp)130 signaling‐dependent manner in rat cardiomyocytes. Interestingly, both specific silencing of signal transducers and activators of transcription 3 (STAT3) expression by lentivirus‐mediated RNA interference and antagonism of gp130 signaling lead to significant inhibition of isoproterenol‐stimulated ANF expression. Together, these results indicate that gp130/STAT3 signaling has an essential role in ANF expression by β‐AR stimulation.
Thermal stability of homologous functional units of Helix pomatia hemocyanin does not correlate with carbohydrate content
Authors: Yesilyurt Betül T. , Gielens Constant , Meersman Filip
Published: June 2008

The thermal stability of the eight functional units of β‐hemocyanin of the gastropodan mollusc Helix pomatia was investigated by FTIR spectroscopy. Molluscan hemocyanin functional units have a molecular mass of approximately 50 kDa and generally contain three disulfide bridges: two in the mainly α‐helical N‐terminal domain and one in the C‐terminal β‐sheet domain. They show more than 50% sequence homology and it is assumed that they adopt a similar conformation. However, the functional units of H. pomatiaβ‐hemocyanin, designated HpH‐a to HpH‐h, differ considerably in their carbohydrate content (0–18 wt%). Most functional units are exceptionally stable with a melting temperature in the range 77–83 °C. Two functional units, HpH‐b and HpH‐c, however, have a reduced stability with melting temperature values of 73 °C and 64 °C, respectively. Although the most glycosylated functional unit (HpH‐g) has the highest temperature stability, there is no linear correlation between the degree of glycosylation of the functional units and the unfolding temperature. This is ascribed to variations in secondary structure as well as in glycan attachment sites. Moreover, the disulfide bonds might play an important role in the conformational stability of the functional units. Sequence comparison of molluscan hemocyanins suggests that the less stable functional units, HpH‐b and HpH‐c, similar to most of their paralogous counterparts, lack the disulfide bond in the C‐terminal domain.
Stochastic Transfer Function Model and Neural Networks to Estimate Soil Moisture1
Authors: Ramírez‐Beltran Nazario D. , Castro Joan Manuel , Harmsen Eric , Vásquez Ramón
Published: June 2008

Abstract:  A practical methodology is proposed to estimate the three‐dimensional variability of soil moisture based on a stochastic transfer function model, which is an approximation of the Richard’s equation. Satellite, radar and in situ observations are the major sources of information to develop a model that represents the dynamic water content in the soil. The soil‐moisture observations were collected from 17 stations located in Puerto Rico (PR), and a sequential quadratic programming algorithm was used to estimate the parameters of the transfer function (TF) at each station. Soil texture information, terrain elevation, vegetation index, surface temperature, and accumulated rainfall for every grid cell were input into a self‐organized artificial neural network to identify similarities on terrain spatial variability and to determine the TF that best resembles the properties of a particular grid point. Soil moisture observed at 20 cm depth, soil texture, and cumulative rainfall were also used to train a feedforward artificial neural network to estimate soil moisture at 5, 10, 50, and 100 cm depth. A validation procedure was implemented to measure the horizontal and vertical estimation accuracy of soil moisture. Validation results from spatial and temporal variation of volumetric water content (vwc) showed that the proposed algorithm estimated soil moisture with a root mean squared error (RMSE) of 2.31% vwc, and the vertical profile shows a RMSE of 2.50% vwc. The algorithm estimates soil moisture in an hourly basis at 1 km spatial resolution, and up to 1 m depth, and was successfully applied under PR climate conditions.
Submacular fluid after encircling buckle surgery for inferior macula‐off retinal detachment in young patients
Authors: Abouzeid Hana , Becker Klio , Holz Frank G. , Wolfensberger Thomas J.
Published: June 2008

Purpose:  Characterization of persistent diffuse subretinal fluid using optical coherence tomography (OCT) after successful encircling buckle surgery for inferior macula‐off retinal detachment in young patients.

Methods:  Institutional retrospective review of six young patients (mean age 31 ± 6 years; five female, one male) with spontaneous inferior rhegmatogenous macula‐off retinal detachment. All patients were treated with encircling buckle surgery and five out of six underwent additional external drainage of subretinal fluid. Mean follow‐up was 37 ± 25 months (range 17–75 months) and included complete ophthalmic and OCT examination.

Results:  At 6 months, 100% of patients showed persistence of subretinal fluid on OCT. Four patients had diffuse fluid accumulation, whereas two patients showed a ‘bleb‐like’ accumulation of fluid. This fluid was present independent of whether or not patients had been treated with external fluid drainage. Subretinal fluid only started to disappear on OCT between 6 and more than 12 months after surgery.

Conclusion:  Young patients with inferior macula‐off retinal detachments and a marginally liquefied vitreous may show persisting postoperative subclinical fluid under the macula for longer periods of time than described previously.
An Enhanced Quality Evaluation System for Continuous Manufacturing Processes, Part 1: Theory
Authors: Dooley K. J. , Kapoor S. G.
Published: June 2008

A quality evaluation system is presented which gives enhanced information about the nature of quality changes in continuous manufacturing processes. The system monitors a quality characteristic of the process via stochastic time series models and detects shifts in the process mean, variance, and dynamic parameters. A rule base classifies the type of change that occurred, and change magnitude and time of occurrence are estimated. Part 1 of the work addresses the theoretical issues concerning the statistics used by the rule base and their behavior under various process changes. The characteristics of the cusum chart, autocorrelation chart, and Chi-Square test are derived with respect to each of the possible change mechanisms.
Analysis and Modeling of Laser Measurement System Performance for Wood Surface
Authors: Yoo S. M. , Dornfeld D. A. , Lemaster R. L.
Published: June 2008

An attempt was made to characterize roughness using a laser and an optical detector which outputs precise information about the roughness change. The performance of the laser detector system is evaluated by modeling the sensor system and using a sinusoidal profile model as a simulated rough surface. The influence of surface roughness and sensor structure on the system performance is studied. The profile is also reproduced for comparison with the actual profile. A wood surface was chosen to be the test surface because of its unusual reflectivity. A two-dimensional profile analysis was made to find a relationship between the roughness and some characteristic parameter values of the detected profile.
A Comparison of Statistical and AI Approaches to the Selection of Process Parameters in Intelligent Machining
Authors: Chryssolouris G. , Guillot M.
Published: June 2008

This paper presents an approach for the selection of a set of process parameters for use in machining control. The approach is aimed at providing a range of parameters within which machining operations can be optimized. Because of the complexity and somewhat unpredictable nature of the machining process, this approach combines process modelling with rule-based techniques. Modelling correlates process state variables such as surface roughness or chip merit mark to process parameters such as feed rate, cutting speed, and tool rake angle. The modelling techniques considered in this paper include multiple regression analysis, group method of data handling (GMDH), and neural network. A rule-based module determines the final operational range of control parameters based on user information and modelling predictions. The different modelling techniques have been evaluated using data from orthogonal cutting.
Boring by Plug-Type Rotary Cutting Tool
Authors: Yamaguchi K. , Nakamura T. , Kato S.
Published: June 2008

A new boring process is introduced and machining properties are examined. In this process, a drilled hole is finished with a plug-type rotary cutting tool which has a ring-like cutting edge. The plug-type rotary cutting tool is forced into the hole while rotating about the central axis. The effects of the tool rotation on cutting forces and surface finish are experimentally examined, and a practical tool which has a burnishing guide just behind the cutting edge is designed. The machining accuracy of this tool is compared with that of a chucking reamer. Test results show that the inside diameter of the hole finished by the plug-type tool is accurate and stable, even if the tool has an eccentricity.
Update on High-Speed Milling Dynamics
Authors: Smith S. , Tlusty J.
Published: June 2008

As spindle speeds and power have increased, the possibility of using the stability lobe phenomena to substantially increase the metal removal rate has become more attractive, and selection of optimum spindle speeds has become an important consideration. It is shown that, for many milling operations, it is desirable to set the tooth frequency equal to the natural frequency. At this spindle speed, the development of resonant forced vibration is actually inhibited by regeneration of waviness. An algorithm is presented for automatically selecting the optimum spindle speed based on the cutting force signal.
A Computer-Aided Cooling-Line Design System for Injection Molds
Authors: Turng L. S. , Wang K. K.
Published: June 2008

This paper presents a methodology for analyzing the heat-transfer process during the injection molding of plastics as an aid to mold design. A numerical scheme using the Boundary Element Method (BEM) with “zonal” approach has been developed to solve the quasi-steady temperature field and its normal derivative over the entire surface of the mold plates including the cavity wall as well as parting surface. In order to obtain a solution for the temperature field, a cycle-averaged heat-transfer coefficient is introduced from a transient heat-conduction analysis and applied as the boundary condition at the cavity surface. The numerical predictions as compared with the experimental data have shown that the cycle-averaged solution used in this study gives a reasonable representation of the transient temperature variation over the cavity surface. Based on the numerical predictions, the mold designer will be able to design a proper cooling-system for a mold to achieve better part quality and high productivity through more uniform cooling and shorter cycle time, respectively.
Life Prediction for Unstable Shell Growth in Rails
Authors: Farris T. N. , Keer L. M. , Steele R. K.
Published: June 2008

The growth rate of the relatively benign shell type defects such as horizontal cracks found in the head of railroad rails is calculated. The effect of the residual stresses acting in the vicinity of the shell on the growth rate is significant. The results can be combined with a stability analysis of the tendency of the horizontal defects to turn into a vertical detail fracture to determine the time required for such a transition. Load reversals can cause the shell defect to grow to a length where it has lost its tendency to grow out of the plane. For this case the time required for the horizontal crack to reach the fast fatigue growth rate regime is calculated. The results allow the effect of the shell growth behavior on rail service life to be discussed.
On the Effects of a Built-Up Edge on Acoustic Emission in Metal Cutting
Authors: Hutton D. V. , Yu Qinghuan
Published: June 2008

Experimental evidence is presented which indicates that the presence of a built-up edge can significantly affect the generation of acoustic emission in metal cutting. Results for machining SAE 1018 and 4140 steels show that the built-up edge can mask the generally accepted AE-cutting speed relation when cutting tools having small rake angles are used. Under cutting conditions conducive to development of a built-up edge, it is shown that increased acoustic emission is generated as a result of increased effective rake angle and corresponding increase of shear angle in the primary deformation zone. Three distinct types of built-up edge have been observed and classified as immature, periodic, or developed, according to effect on acoustic emission.
Effects of Geometric and Process Parameters on Drill Transverse Vibrations
Authors: Tekinalp O. , Ulsoy A. Galip
Published: June 2008

Finite element solutions are used to analyze the effects of geometric and process parameters on the drill bit transverse vibrations. The effects of cross sectional geometry, of the flute helix angle, the drill rotational speed, and the thrust force generated during drilling on the drill transverse frequencies are investigated. Simulation results also show the transient vibrations of a drill bit under transverse cutting forces at the drill tip.
Sensor Integration Using Neural Networks for Intelligent Tool Condition Monitoring
Authors: Rangwala S. , Dornfeld D.
Published: June 2008

A framework for intelligent sensors in unmanned machining is proposed. In the absence of human operators, the process monitoring function has to be performed with sensors and associated decision-making systems which are able to interpret incoming sensor information and decide on the appropriate control action. In this paper, neural networks are used to integrate information from multiple sensors (acoustic emission and force) in order to recognize the occurrence of tool wear in a turning operation. The superior learning and noise suppression abilities of these networks enable high success rates for recognizing tool wear under a range of machining conditions. The parallel computation ability of these networks offers the potential for constructing intelligent sensor systems that are able to learn, perform sensor fusion, recognize process abnormalities, and initiate control actions in real-time manufacturing environments.
Evaluation of Parameters in a Fluid Cutting Equation
Authors: Whiting C. E. , Graham E. E. , Ghorashi B.
Published: June 2008

The application of a high speed jet of water for cutting solid materials has gained general industrial acceptance, but as yet no method exists for prediction of the depth of cut based on documented material properties. Extensive experimental data for the cutting of woods, plastics, and lead have been obtained and applied to equations developed by Hashish and duPlessis [1], [2] resulting in correlations for two key parameters in Hashish’s equations; the coherent core length and the damping coefficient. This has led to a general method for predicting the depth of a water jet cut that requires no prior experimental data. Using only basic physical properties of a solid material, the depth of cut can be predicted for a given set of operating conditions including feed rate, nozzle diameter, standoff distance, and pressure.
Numerical and Experimental Investigations of Deep Drawing of Metal Sheets
Authors: Saran M. J. , Schedin E. , Samuelsson A. , Melander A. , Gustafsson C.
Published: June 2008

Results of a comprehensive study on deep drawing are presented. The numerical results are based on finite element procedure developed for simulation of arbitrarily shaped, 3-D forming operations. The elastic-plastic material description with Hill’s anisotropic model is employed allowing for elastic effects, unloading, and multistage processes. By applying a proper computational model of large strain and large rotation plasticity, reliable results were obtained even using relatively simple material and friction laws. Predicted values of the press force, strain distributions, and flange reduction are compared with the corresponding results from axisymmetric deep draw experiments for a wide range of materials used in real forming applications including a deep drawing quality steel, brass, high strength steel, stainless steel, and aluminum. The parametric study shows the sensitivity of the solution on material parameter variations. Presented results can be considered as a set of benchmark problems.
Image Decomposition by Data Dependent Systems
Authors: Pandit S. M. , Weber C. R.
Published: June 2008

This paper presents a new digital image processing approach called image decomposition. This approach is based on a recently developed system modeling, prediction, and analysis methodology called Data Dependent Systems (DDS). DDS is an innovative approach to the application and interpretation of the well known stochastic Autoregressive Moving Average (ARMA) models. The Green’s function form of these models provides a modal decomposition of the image data with boundary features captured in the model residuals and regional feature dynamics captured by the components of the Green’s function. This approach is unique in that it provides a method for image representation and scene identification which is not dependent on geometric descriptions.
On-Line Detection of Drill Wear
Authors: Liu T. I. , Wu S. M.
Published: June 2008

An on-line system for drill wear detection has been developed by using a sensor fusion strategy. Both acceleration and thrust signals were analyzed. Flank wear area was used to evaluate drill wear states. The drill wear area was measured by a vision system and classified into two groups: usable and worn-out. The wear prediction model was obtained by a two-category linear classifier. On-line detection tests indicate that the prediction model has over a 90 percent success rate.
Diagnosis of the Tapping Process by Information Measure and Probability Voting Approach
Authors: Chen Y. B. , Sha J. L. , Wu S. M.
Published: June 2008

A new method for the diagnosis of the tapping process using the information measure and multiple probability voting scheme is proposed. Considering the features of short cutting-duration and the large uncertainties existing in a tapping process, a set of indices based on the time-domain statistical analysis has been formed. These indices have then been evaluated and ranked using an algorithm that calculates the information gain of each index about the tapping process. The final classification decision can be made by a voting scheme based on the conditional probability functions for multiple indices. Furthermore, the information gains estimated in the index evolution process can be used as a weighting function during voting to improve efficiency and reliability. From a tapping test, which includes five different tapping conditions, a success rate of 95 percent has been achieved.
An Efficient 2-D Finite Element Procedure for Isothermal Phase Changes
Authors: Chandrasekar S. , Wang S. , Yang H. T. Y.
Published: June 2008

An efficient finite element procedure is developed for the temperature and stress analyses of two-dimensional isothermal phase transformation problems such as solidification, melting, and solid-to-solid transformations, etc. This procedure uses adaptive remeshing along the element boundaries to track the discontinuities in the temperature gradient, the enthalpy, and the material properties, which exists across the phase transformation interface. The thermal stresses and the transient temperature distribution developed during solidification are calculated using this for several example problems. They are compared with the numerical and analytical solutions obtained for these problems by earlier investigators in order to demonstrate the efficiency and accuracy of this method, for the analysis of solidification problems, as well as its limitations.
The Mean Flow Structure on the Symmetry Plane of a Turbulent Junction Vortex
Authors: Pierce F. J. , Tree I. K.
Published: June 2008

The mean flow structure on the symmetry plane of a turbulent junction vortex is documented. A two-channel, two-color LDV system allowed nonintrusive measurements of the two velocity components on the symmetry plane. Extensive measurements were made in and around the separation point and within the junction vortex system, both very close to the floor and to the leading edge of the body generating the vortex system. Real-time smoke visualizations confirmed a region of strongly time-variant flow with large changes in the scale and position of the principal vortex structure. The extensive velocity field data are correlated with high quality surface visualizations and surface pressure measurements. The mean velocity measurements show one large well-defined vortex structure and one singular saddle point of separation on the symmetry plane. The transverse vorticity field computed from the extensive velocity field suggests a very strong but small second, counter rotating vortex located in the extreme corner formed by the floor and leading edge of the body. The surface flow visualization suggests only one clear separation line. The single pair of counter rotating vortices revealed by these detailed LDV velocity measurements is in agreement with two independent studies which used multiple orifice pressure probes. This measured two vortex model is not in agreement with the frequently pictured four vortex flow model, inferred from surface flow visualizations, showing two pairs of counter rotating vortices.
An Improved k-ε Model for Boundary Layer Flows
Authors: Nagano Y. , Tagawa M.
Published: June 2008

An improvement of the k-ε model has been made in conjunction with an accurate prediction of the near-wall limiting behavior of turbulence and the final period of the decay law of free turbulence. The present improved k-ε model has been extended to predict the effects of adverse pressure gradients on shear layers, which most previously proposed models failed to do correctly. The proposed model was tested by application to a turbulent pipe flow, a flat plate boundary layer, a relaminarizing flow, and a diffuser flow with a strong adverse pressure gradient. Agreement with the experiments was generally very satisfactory.
Prediction of Flows With Strong Curvature and Pressure Gradient Using the k–ε Turbulence Model
Authors: De Henau V. , Raithby G. D. , Thompson B. E.
Published: June 2008

The k–ε turbulence model of Launder and Spalding has found widespread application in the computation of fluid flows. Under conditions of strong adverse pressure gradient or strong streamline curvature, the accuracy of the model is known to decrease. The present paper adds to the available case studies involving these types of flows by providing predictions for two problems. In the first problem, Simpson’s flow, an adverse pressure gradient induces the flow along a planar surface to separate. The second problem is unseparated flow over an airfoil. In addition to predictions using the standard k–ε model, results are reported from another k–ε model by Hanjalic and Launder, that has been modified to account for adverse pressure gradients.
Numerical Simulation of Turbulent Shear Flow in an Isothermal Heat Exchanger Model
Authors: Zhang C. , Sousa A. C. M.
Published: June 2008

Numerical predictions of fluid flow are reported for the isothermal, two-dimensional, axisymmetric flow in a disk-doughnut heat exchanger. The system consists of alternating and equi-spaced doughnut and disk baffles located in a pipe with water flowing in a turbulent regime. The two-equation (k–ε) turbulence model as proposed by Nagano and Hishida is modified to accommodate disc and doughnut baffles. The governing equations for steady-state flow are solved in primitive variable form using segregated pressure correction linked algorithm. Predictions are critically evaluated against available data for mean quantities.
Experimental Investigations of Annular Liquid Curtains
Authors: Kihm K. D. , Chigier N. A.
Published: June 2008

Experiments have been performed to study the dynamics of vertical annular liquid curtains. Using a high and a low speed photographic recording technique, different modes of curtain formation have been visualized: (a) nonpressurized curtain, (b) pressurized steady curtain, (c) pressurized oscillating curtain, and (d) punctured curtain. The velocity of the liquid was measured by an argon-ion laser Doppler velocimeter, and results were compared with free falling motion. The convergence length of the curtain was measured as a function of the pressure differential for different Froude and Weber numbers, and for different nozzle gap widths. The experimental data agree well with existing theoretical predictions for steady curtains. For harmonically oscillating curtains, the average values of minimum and maximum convergence lengths show fairly good agreement with the theory.
Statistical Analysis of Turbulent Two-Phase Pipe Flow
Authors: Wang S. K. , Lee S. J. , Jones O. C. , Lahey R. T.
Published: June 2008

The statistical characteristics of turbulent two-phase pipe flow have been evaluated. In particular, the autocorrelation functions and the power spectral density functions of the axial turbulence fluctuations in the liquid phase were determined. The high frequency content of the power spectrum in bubbly two-phase pipe flow was found to be significantly larger than in single-phase pipe flow and, in agreement with previous studies of homogeneous two-phase flows (Lance et al., 1983), diminished asymptotically with a characteristic −8/3 slope at high frequency. The power spectrum and the autocorrelation functions in two-phase pipe flow, although distinctively different from those in single-phase pipe flow, were insensitive to the local void fraction and the mean liquid velocity when plotted against wave number and spatial separation, respectively. Finally, the dissipation scale, determined from the shape of the autocorrelation function, indicated that the turbulent dissipation rate in two-phase pipe flow was significantly greater than that in single-phase pipe flow.
A Reinterpretation of the Results of the Moby Dick Experiments in Terms of the Nonequilibrium Model
Authors: Bilicki Z. , Kestin J. , Pratt M. M.
Published: June 2008

The topological pattern of the set of measured pressure distributions included in the Moby Dick series of experiments on critical flow through a slender channel provided with a throat does not agree with that expected on the basis of the rigorous mathematical theory which predicts the appearance of a singular point, most likely, of a saddle point at or near the throat. This is considered to be paradoxical. The paper provides an alternative interpretation of these results. The Moby Dick experiments have clearly demonstrated the profound influence of the existence of metastable conditions near the flash point. For this reason, among others, the paper undertakes a re-evaluation of some of the Moby Dick results in terms of the nonequilibrium model first suggested by L. J. F. Broer in 1958 for use in flows of chemically reacting gases. Since the Moby Dick data contain measurements of the distribution α(z) of void fractions, it becomes possible to calculate local relaxation times, θ[α(z)], and so to close the system of differential equations of the model. Extensive numerical calculations reproduce the measured pressure distributions with an error of 6–10 percent at most. More importantly, the topological features of the calculated pressures, Pth(z), turn out to be identical with the measured ones, Pex(z). The most important, and totally unexpected, result is that the flow in the Moby Dick channel remained subcritical everywhere. In particular, the channel was not choked at the throat. Since the mass-flow rates were independent of back-pressure, it is concluded that the flows were choked at or near the exit. The paper advances additional reasons for the feasibility of this alternative interpretation, but emphasizes and re-emphasizes its provisional nature.
Teaching Design and Automation Principles Through a National Robotics Competition
Authors: Verma Alok K.
Published: June 2008

An innovative method for teaching senior project course has been discussed. The method involves use of seniors as mentors for a team of high school students participating in a national robotic competition. The experience offered students an opportunity to lead teams during design and fabrication of various components of the robot while meeting specific deadlines. Students learnt the principles of design and automation while teaching their high school counterparts.
Recovering Acoustic and Elastic Parameters From Travel Times
Authors: Uhlmann Gunther , Hansen So¨nke
Published: June 2008

The relation between travel times and waves in anisotropic media is explained using the geometrical optics method in a phase space setting. This approach also covers caustics and multiple arrivals. We than consider the question of whether one can determine an anisotropic index of refraction by measuring travel times. We show that this is indeed the case if the index of refraction satisfies some additional assumptions.
Surface Roughness Effects on Circular Cylinders at High Reynolds Numbers
Authors: Eaddy M. , Melbourne W. H. , Sheridan J.
Published: June 2008

The problem of flow-induced vibration has been studied extensively. However, much of this research has focused on the smooth cylinder to gain an understanding of the mechanisms that cause vortex-induced vibration. In this paper results of an investigation of the effect of surface roughness on the cross-wind forces are presented. Measurements of the sectional RMS fluctuating lift forces and the axial correlation of the pressures for Reynolds numbers from 1 × 105 to 1.4 × 106 are given. It was found that surface roughness significantly increased the axial correlation of the pressures to similar values found at high subcritical Reynolds numbers. There was little effect of the surface roughness on the sectional lift forces. The improved correlation of the vortex shedding means rough cylinders will be subject to larger cross-wind forces and an increased possibility of vortex-induced vibration compared to smooth cylinders.
The Effect of Sound on Vortex Shedding From Single and Tandem Cylinders
Authors: Hall Joseph W. , Ziada Samir , Weaver David S.
Published: June 2008

A single cylinder and two tandem cylinders configurations with longitudinal pitch ratios L/D = 1.75 and 2.5 were rigidly mounted in an open circuit windtunnel and a sound field was applied so that the acoustic particle velocity was normal to both the cylinder axis and the mean flow velocity. Tests were performed for a Reynolds number range of 5000 < ReD < 24000. The effect of sound on the vortex shedding was investigated by instrumenting the cylinders with pressure taps and hot-wire probes. These tests show that applied sound can entrain and shift the natural vortex shedding frequency to the frequency of excitation and produce nonlinearities in the wake. The lock-in envelope for the tandem cylinders is considerably larger than for the single cylinder. The lock-in range for the smaller tandem cylinder spacing (L/D = 1.75) was broader still than either the single cylinder, or the L/D = 2.5 tandem cylinder case.
Vortex-Induced Vibrations of a Flexible Cylinder in a Slowly Varying Flow: Experimental Results
Authors: Lague¨ Fre´de´ric , Laneville Andre´
Published: June 2008

This paper deals with a wind tunnel simulation of the vortex-induced vibrations of a long flexible cylinder in cross-flow when the flow velocity varies periodically with different low frequencies and different flow velocity amplitude. The experimental set-up consists of a flexible tube suspended at the nodes of its first free-free mode of vibration. In order to modulate the wind velocity, the fan rpm of the wind tunnel is controlled: this simulation allows the excursions and incursions in the region of lock-in as well as the periodical crossing of the critical curve separating the 2S and 2P modes of vortex shedding. The additional objective of the simulation is to reproduce more closely the behavior of aerial conductor in the fields and exposed to large scale and low frequency “turbulence”. The results show that the amplitude of vibrations of the flexible tube is modulated with the frequency of the periodic wind fluctuations: it can range from a simple beating to chaotic fluctuations superimposed to a mean. The amplitude of vibrations, when compared to the case of steady wind velocity, may decrease or increase according to the range of the wind mean velocity. Modulation taking different shapes is observed: it may adopt a wave form made of “sharp” peaks or “smooth” periodic oscillations or a combination of the two; sometimes it may be of chaotic form. A link is established between the “sharp” peaks, the occurrence of bifurcations, the presence of the two modes of vortex shedding and the critical curve. The instantaneous amplitude of vibrations is observed to exceed that measured under steady flow conditions.
Vortex Forces on an Oscillating Cylinder
Authors: Carberry J. , Sheridan J. , Rockwell D.
Published: June 2008

The characteristic wake states of a cylinder undergoing forced sinusoidal oscillations transverse to the free-stream are studied by simultaneously measuring the structure of the near wake and the forces on the cylinder. The wake exhibits two distinctly different wake states. The transition between these states corresponds to a large discontinuous change in the phase of both the total and vortex forces on the cylinder, as well as the mode and phase of vortex shedding. Over the range of flow and oscillation parameters studied the vortex lift and drag phases collapse towards values that depend primarily on wake state. This is in contrast with the phase of the total lift force, which varied significantly with both A/D and Re.
Critical Velocity for Bending Vibration of a Cantilever Cruciform Cylinder
Authors: Watanabe Masanobu , Hagiwara Tsuyoshi
Published: June 2008

Tip amplitudes of an isolated cantilever cruciform cylinder were measured, varying flow velocity approaching the cylinder and flow angles with 0° and 45° to a water test channel in order to investigate the vibration behavior and critical velocity for bending vibration. Flow velocity varied from about 0.4 m/s to 3.3 m/s, which corresponds to from 0.4 to 3.0 in reduced form using wing length of cruciform cylinder and from 1.6×104 to 1.4×105 in Reynolds number. The amplitudes were measured using strain gauges installed at the cylinder. In the case of 45°, it was observed that the amplitudes increased drastically in two regions. One region was from 0.65 to 1.0 in reduced velocity and oscillating direction is drag direction; the other was from 1.0 to 1.6 and oscillating direction is lift direction. On the other hand, such large amplitude vibration was not observed in the case of 0°. According to previous study on Strouhal number of vortex shedding from a cruciform cylinder, Strouhal numbers are 0.2 and 0.9. Therefore, this large amplitude vibration is not thought to be due to the resonance with the vortex shedding.
Two Staggered Elastic Cylinders in a Cross Flow
Authors: Su Zhongdi , Liu Yang , So Ronald M. C.
Published: June 2008

Two staggered elastic cylinders in a cross flow have been numerically studied. The inclined angles change from 0° to 90° at 15° degree interval while the spacing ratio is maintained at 1.5. The two cylinders are mounted at the ends and are free to move under the action of the unsteady flow-induced forces. The present approach solves the flow field using a finite element method and models the cylinder motions using a two-degree-of-freedom structural dynamics model. Two different cases are considered; one is the rigid case where the cylinders are still, and the other is the elastic case where the cylinders undergo oscillations. Good agreement for the rigid case is obtained between the present 2-D calculations and the previously published data. The investigation also examines the influence of the inclined angle on the vibrations of the cylinders and their spectral analysis.
Helical Flow of a Viscoplastic Material Through the Developing Region of Annular Spaces
Authors: Loureiro Bruno V. , Nieckele Angela O. , Souza Mendes Paulo R.
Published: June 2008

The laminar helical flow of a viscoplastic (or highly shear-thinning) material through the developing region of concentric annular spaces was examined. This physical situation is important in a variety of applications, including the flow of drilling muds through petroleum wells. The velocity, pressure and viscosity fields were obtained by solving the mass- and momentum-conservation equations via a finite-volume method. The Generalized Newtonian Liquid model was adopted as constitutive equation. The Carreau model was employed as viscosity function, whose parameters were obtained via a least-squares to fit to data obtained for a viscoplastic material. Solutions are presented for a wide range of Reynolds and Taylor numbers, within the subcritical regime.
Direct Simulation of Electrorheological Suspensions Subjected to Spatially Nonuniform Electric Field
Authors: Kadaksham J. , Singh P. , Aubry N.
Published: June 2008

A numerical method based on the distributed Lagrange Multiplier method (DLM) [2,8] is developed for direct simulations of electrorheological (ER) liquids subjected to spatially varying electric fields. The flow inside particle boundaries is constrained to be rigid body motion by the distributed Lagrange multiplier method. The point-dipole approximation [6] is used to model the electrostatic forces acting on the polarized particles. The code is verified by performing a convergence study that shows that the results are independent of mesh and time step sizes. In a spatially nonuniform electric field the particles move to the regions where the magnitude of electric field is locally maximum when the particle permittivity is greater than that of the liquid. On the other hand, when the particle permittivity is smaller than that of the liquid the particles move to the regions of local minimum of electric field.
The Gas Penetration Through Viscoelastic Fluids With Shear-Thinning Viscosity in a Tube
Authors: Yamamoto Takehiro , Suga Takanori , Nakamura Kiyoji , Mori Noriyasu
Published: June 2008

The gas penetration of a long bubble through a viscoelastic fluid in a tube was studied. Experiments were carried out for two Newtonian and five polymeric solutions to investigate the relation between the coating film thickness and rheological properties of the test fluids. The polymeric solutions are viscoelastic fluids having shear-thinning viscosity. A bubble of air was injected into a tube filled with a test fluid to form hydrodynamic coating on a tube wall. The film thickness was evaluated by hydrodynamic fractional coverage m. The fractional coverage was characterized using the capillary number Ca and the Weissenberg number Wi. For viscoelastic fluids, Ca and Wi were evaluated considering the shear-thinning viscosity. Two kinds of representative shear rate were used for the evaluation of Ca and Wi. The dependence of m on Ca in viscoelastic fluids was different from that of the Newtonian case. The film was thinner than that of the Newtonian case at the same Ca when Wi was small, i.e. the viscous property was dominant. The shear-thinning viscosity had a role to make the film thin. On the other hand, the film tended to be thicker than the corresponding Newtonian results at large Wi because of normal stress effect.
Experimental Investigation of the Influence of External Vibrations on Coriolis Mass Flow Meters
Authors: Cheesewright Robert , Clark Colin
Published: June 2008

The Coriolis flow meter is basically a vibrating tube device; it is therefore potentially susceptible to disruption by external vibrations transmitted from the environment in which the meter is mounted. The paper reports the findings from a carefully structured experimental study in which the results of both analysis and numerical simulation studies were used to guide the choice of vibration frequencies and the directions and the spatial distributions of the vibrations. The total of eight different meters from five different manufacturers covered a wide range of meter geometries and drive frequencies. In addition to comparisons of the flow rates indicated by the meters with independent measures of the flow rate, all the tests involved the recording of raw signals from the displacement sensors so that the effects of using different techniques to extract the phase relationship between these signals could be investigated. All the tests were performed using cold (room temperature) water as the working fluid. The results of the study show that vibrations at the meter drive frequency caused errors in all meters. Vibrations at other frequencies also caused errors in several meters but these errors appear to be due to the algorithm (implemented in the meter electronics) used to extract the phase difference (the measurand) between the sensor signals. However, the complete study suggests that, by suitable choices of meter mechanical design and of the algorithm used to determine the phase difference, it is possible to make a meter which is unaffected by vibrations at any frequency other than the meter drive frequency (provided only that the meter tube motion produced by the vibration is smaller than that produced by the meter drive). For vibrations at the drive frequency the results show that (in general agreement with the analytical and numerical studies) the magnitude of the error depends on the phase relationship between the imposed vibration and the meter drive. Errors also depend on the spatial distribution of the vibration (e.g. the error is different for the same amplitude of vibration applied uniformly to a meter and applied to one end only of the meter). Methods for reducing drive frequency errors are discussed but it is concluded that it may not be possible to eliminate these errors completely.