bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporation of ZP1 into perivitelline membrane after in vivo treatment with exogenous ZP1 in Japanese quail (Coturnix japonica)
Authors: Kinoshita Mihoko , Mizui Kaori , Ishiguro Tsukasa , Ohtsuki Mamoru , Kansaku Norio , Ogawa Hiroshi , Tsukada Akira , Sato Tsukasa , Sasanami Tomohiro
Published: June 2008

In birds, the egg envelope surrounding the oocyte prior to ovulation is called the perivitelline membrane and it plays important roles in fertilization. In a previous study we demonstrated that one of the components of the perivitelline membrane, ZP3, which is secreted from the ovarian granulosa cells, specifically interacts with ZP1, another constituent that is synthesized in the liver of Japanese quail. In the present study, we investigated whether ZP1 injected exogenously into the blood possesses the ability to reconstruct the perivitelline membrane of Japanese quail. When ZP1 purified from the serum of laying quail was injected into other female birds, the signal of this exogenous ZP1 was detected in the perivitelline membrane. In addition, we revealed, by means of ligand blot analysis, that serum ZP1 interacts with both ZP1 and ZP3 of the perivitelline membrane. By contrast, when ZP1 derived from the perivitelline membrane was administered, it failed to become incorporated into the perivitelline membrane. Interestingly, serum ZP1 recovered from other Galliformes, including chicken and guinea fowl, could be incorporated into the quail perivitelline membrane, but the degree of interaction between quail ZP3 and ZP1 of the vitelline membrane of laid eggs from chicken and guinea fowl appeared to be weak. These results demonstrate that exogenous ZP1 purified from the serum, but not ZP1 from the perivitelline membrane, can become incorporated into the perivitelline membrane upon injection into other types of female birds. To our knowledge, this is the first demonstration that the egg envelope component, when exogenously administered to animals, can reconstruct the egg envelope in vivo.
Inhibition of Oxidant‐Induced Biochemical Changes of Pork Myofibrillar Protein by Hydrolyzed Potato Protein
Authors: Wang L.L. , Xiong Y.L.
Published: June 2008

ABSTRACT:  The objective of the study was to investigate the role of hydrolyzed potato protein (HPP) in protecting myofibril protein isolate (MPI) from oxidative modification. MPI prepared from pork muscle was suspended (30 mg protein/mL) in 15 mM piperazine‐N, N‐bis(2‐ethane sulfonic acid) buffer (pH 6.0) with 0, 0.3, 0.75, and 1.5 mg/mL of antioxidative HPP (1‐h Alcalase hydrolysate). Oxidation was induced by incubating the protein suspensions at 4 °C for 24 h with (1) an iron‐catalyzed oxidizing system (IOS: 0.01 mM FeCl3, 0.1 mM ascorbic acid, and 1.0 mM H2O2) and (2) a metmyoglobin‐oxidizing system (MOS: 0.1 mM metmyoglobin and 0.1 mM H2O2). Changes in oxidized MPI were measured as thiobarbituric acid‐reactive substances (TBARS), protein carbonyl content, Ca‐ and K‐ATPase activities, and ultraviolet (UV) spectra. Oxidation increased the production of TBARS and protein carbonyls by 2.9‐ and 0.24‐fold in IOS and 5.6‐ and 2.2‐fold in MOS, respectively. The 2 oxidizing systems altered the Ca‐ and K‐ATPase activities and exposed hydrophobic groups buried in MPI. The presence of HPP reduced the extent of MPI oxidation in all physicochemical categories tested. Therefore, HPP may be used as a potential functional ingredient in meat products to enhance their oxidative stability.
Core‐Shell Biopolymer Nanoparticles Produced by Electrostatic Deposition of Beet Pectin onto Heat‐Denatured β‐Lactoglobulin Aggregates
Authors: Santipanichwong R. , Suphantharika M. , Weiss J. , McClements D.J.
Published: June 2008

ABSTRACT:  The purpose of this study was to produce and characterize core‐shell biopolymer particles based on electrostatic deposition of an anionic polysaccharide (beet pectin) onto amphoteric protein aggregates (heat‐denatured β‐lactoglobulin [β‐lg]). Initially, the optimum conditions for forming stable protein particles were established by thermal treatment (80 °C for 15 min) of 0.5 wt%β‐lg solutions at different pH values (3 to 7). After heating, stable submicron‐sized (d= 100 to 300 nm) protein aggregates could be formed in the pH range from 5.6 to 6. Core‐shell biopolymer particles were formed by mixing a suspension of protein aggregates (formed by heating at pH 5.8) with a beet pectin solution at pH 7 and then adjusting the pH to values where the beet pectin is adsorbed (< pH 6). The impact of pH (3 to 7) and salt concentration (0 to 250 mM NaCl) on the properties of the core‐shell biopolymer particles formed was then established. The biopolymer particles were stable to aggregation from pH 4 to 6, but aggregated at lower pH values because they had a relatively small ζ‐potential. The biopolymer particles remained intact and stable to aggregation up to 250 mM NaCl at pH 4, indicating that they had good salt stability. The core‐shell biopolymer particles prepared in this study may be useful for encapsulation and delivery of bioactive food components or as substitutes for lipid droplets.
Sclerosing Wegener’s granulomatosis in the orbit
Authors: Ostri Christoffer , Heegaard Steffen , Prause Jan Ulrik
Published: June 2008

Purpose:  To report three cases of sclerosing Wegener’s granulomatosis in the orbit and to compare the histopathological morphology with those of other types of sclerosing orbital inflammation.

Methods:  We analysed the clinical data along with histopathological specimens from orbital biopsies and from two enucleated eyes.

Results:  All three patients had longstanding inflammation in the orbit and involvement of the paranasal sinuses. Proptosis, impaired ocular motility and reduced visual acuity dominated the clinical picture. All histopathological specimens featured granulomatous inflammation, tissue necrosis, vasculitis and widespread dense fibrosis. In certain areas of all specimens the fibrous tissue was arranged in characteristic concentric, onionskin‐like whorls of collagen around obliterated small blood vessels.

Conclusions:  Wegener’s granulomatosis may lead to orbital fibrosis and sclerosis. The stromal changes and cellular infiltrate resemble the non‐specific orbital inflammation previously termed orbital pseudotumour. We present the first ‘onionskin’ lesions in association with Wegener’s granulomatosis in the orbit. This latter morphology may represent an abnormal fibrotic reaction in inflammatory tissue.
Corneal and conjunctival findings after mitomycin C application in pterygium surgery: an in‐vivo confocal microscopy study
Authors: Zhivov Andrey , Beck Ria , Guthoff Rudolf F.
Published: June 2008

Purpose:  To perform a qualitative assessment of the topical side‐effects of mitomycin C on cornea after pterygium surgery.

Methods:  In‐vivo confocal microscopy (Heidelberg Retina Tomograph II in combination with the Rostock Cornea Module) was performed in 10 patients with unilateral primary pterygium. Mitomycin C 0.02% was applied topically to seven eyes for 5 min intraoperatively and twice daily for 5 days postoperatively. Three eyes underwent surgery without application of cytostatic agent. Patient follow‐up was 1 month.

Results:  After application of mitomycin C, complete epithelialization of the operated zone was found 2 weeks after surgery. In‐vivo confocal microscopy revealed signs of superficial punctate keratitis for 2 weeks in the central cornea only after application of mitomycin C. The presence of epithelial and stromal oedema in this group was noted for up to 2 weeks in the central cornea and for up to 4 weeks in the operated zone. In the control group, complete epithelialization was found after 1 week; there were no signs of oedema after 1 week in the central cornea or after 2 weeks in the operated zone. Leucocyte infiltration and increased Langerhans cell density were noted in both groups in the operated and central zones. Analysis of the conjunctiva revealed a decrease in goblet cell density following cytostatic application.

Conclusion:  Local application of mitomycin C delays corneal epithelialization, and prolongs postoperative epithelial and stromal oedema in both the centre and periphery. Moreover, signs of punctate keratitis were noted 2 weeks after surgery in central intact cornea. Nevertheless, in‐vivo confocal microscopy shows that these changes are reversible 4 weeks after application of mitomycin C 0.02%.
Outcome indicators for vitrectomy in Terson syndrome
Authors: Garweg Justus G. , Koerner Fritz
Published: June 2008

Purpose:  There is no general agreement on the best indication and timing of vitrectomy in patients suffering from Terson syndrome. Therefore, we reviewed our cases in order to assess factors interfering with the functional outcome and complication rates after vitrectomy.

Methods:  In this retrospective consecutive case series, the records from all patients undergoing vitrectomy for Terson syndrome between 1975 and 2005 were evaluated.

Results:  Thirty‐seven patients (45 eyes) were identified, 36 of whom (44 corresponding eyes) were eligible. The best‐corrected visual acuity (BCVA) at first and last presentation was 0.07 ± 0.12 and 0.72 ± 0.31, respectively. Thirty‐five eyes (79.5%) achieved a postoperative BCVA of ≥ 0.5; 26 (59.1%) eyes achieved a postoperative BCVA of ≥ 0.8. Patients operated on within 90 days of vitreous haemorrhage achieved a better final BCVA than those with a longer latency (BCVA of 0.87 ± 0.27 compared to 0.66 ± 0.31; P = 0.03). Patients younger than 45 years of age achieved a better final BCVA than older patients (0.85 ± 0.24 compared to 0.60 ± 0.33; P = 0.006). Retinal detachment developed in four patients between 6 and 27 months after surgery. Seven patients (16%) required epiretinal membrane peeling and seven cataract surgery.

Conclusion:  Ninety‐eight per cent of our patients experienced a rapid and persisting visual recovery after removal of a vitreous haemorrhage caused by Terson syndrome. A shorter time between occurrence of vitreous haemorrhage and surgery as well as a younger patient age are predictive of a better outcome. Generally, the surgical risk is low, but complications (namely retinal detachment) may occur late after surgery.
Detrimental effect of preservatives in eyedrops: implications for the treatment of glaucoma
Authors: Baudouin Christophe
Published: June 2008

Antiglaucoma medications are often associated with ocular adverse reactions such as dry eye, and burning or stinging sensations. These undesirable effects may lead to treatment discontinuation and reduced quality of life in patients with glaucoma. Antiglaucoma medications usually contain benzalkonium chloride (BAK) as a preservative. Animal studies, in vitro studies and in vivo experiments have demonstrated various adverse effects of BAK. Clinical studies have also shown an increased incidence of adverse events with BAK and have demonstrated that the withdrawal of preservatives reduces these effects. Collectively, these data suggest that preservative‐free antiglaucoma treatments have clinically relevant benefits for patients.
Improved Methods for the Prediction of Chatter in Turning, Part 2: Determination of Cutting Process Parameters
Authors: Minis I. E. , Magrab E. B. , Pandelidis I. O.
Published: June 2008

The dynamics of the metal cutting process are identified by a new and simple experimental method that permits the direct determination of the cutting transfer functions from input-output measurements. A specially designed stiff force dynamometer rigidly mounted to the machine tool’s turret is used for the measurement of the cutting force. An external force is applied to the base plate of the dynamometer in such a way that the meaurements of both the tool’s displacement and the corresponding cutting force are uncoupled from the influence of the machine tool structure’s dynamics. The cutting transfer functions are obtained in the vicinity of the structure’s first resonance, under a wide range of cutting conditions.
Improved Methods for the Prediction of Chatter in Turning, Part 3: A Generalized Linear Theory
Authors: Minis I. E. , Magrab E. B. , Pandelidis I. O.
Published: June 2008

The linear theory of chatter has been generalized to any machining configuration without a priori assumptions on either the direction of the cutting force or the modal directions of the machine tool structure. Furthermore, the effects of the tool’s orientation on the stability of the machining system are directly expressed by its closed loop characteristic equation. Using experimental measurements for the dynamics of both the machine tool structure and the cutting process obtained previously under actual cutting conditions, the proposed theory is applied to two cases of orthogonal turning. The resulting predictions of the critical depth of cut are in excellent agreement with the measurements of actual chatter for a wide range of cutting conditions.
Dimensional and Surface Roughness Controls in a Turning Operation
Authors: Shiraishi M. , Sato S.
Published: June 2008

Dimensional and surface roughness controls in turning have been achieved by a newly developed measuring system based on an optical technique. The aim of these controls are not only to keep a size deflection within a given tolerance but also to make a smoother surface by removing local irregularities during machining. The control strategy is focused on a Rmax value because of the simplicity of the control system design. The dimensional control is implemented with a reference diameter level of 1/2 Rmax roughness by the regular cutting tool, while in the roughness control a compensatory flat bite tool is used to remove surface irregularities. To begin with the dimensional control is achieved, then the roughness control is followed immediately after the dimensional correction. The control results demonstrate an improvement of surface roughness together with dimensional assurance.
Investigation of Clamp Design for Temporary Attachment to Metal Pipe
Authors: Johnson J. A. , Henderson J. M.
Published: June 2008

A comparative study of different configurations of locator pads used to attach a portable piping lathe to a section of steel pipe was performed. The axial force exerted by adjustment screws attached to the locator pads was determined experimentally. The minimum axial force required to restrain relative motion between the lathe and the pipe during a worst case operating condition was used as a criterion to determine the effectiveness of a particular contact pad. Six different geometric variations and two different materials were investigated and it was found that aluminum, in a simple configuration, provided the best clamping capability.
Tool Face Temperatures in High Speed Milling
Authors: Lezanski P. , Shaw M. C.
Published: June 2008

While it is now generally understood that in continuous chip forming processes such as turning, there is no magic high speed above which tool temperature decreases and tool life increases with increased cutting speed. However, it has been suggested that this may not be the case in intermittent cutting operations such as face milling. It is argued that in such an operation, the tool temperature oscillates between an ambient value at the beginning of a cut and a maximum value at the end of a cut. As cutting speed is increased, the cutting time per cut will decrease and hence the fractional approach to the equilibrium value. Thus, even though the equilibrium temperature will increase with cutting speed, it is conceivable that the maximum temperature at the end of a cut will decrease. This possibility has been tested experimentally using the chip-tool thermocouple technique to record temperature vs time curves for a variety of cutting conditions. In no case was the exit temperature found to decrease with increase in cutting speed.
Limit Cycle Predictions of a Nonlinear Journal-Bearing System
Authors: Crooijmans M. T. M. , Brouwers H. J. H. , van Campen D. H. , de Kraker A.
Published: June 2008

An analysis is presented of the self-excited vibrations of a journal carried in a cylindrical fluid film bearing. Using linear stability theory, the values of the system parameters at the point of loss of stability are determined. These values agree well with those of previous investigators. Solutions of the nonlinear system equations are obtained by time discretization and by an arc-continuation method for solving the obtained nonlinear algebraic equations. In this way periodic solutions of the nonlinear equations of motion are calculated as a function of the system parameters. The behavior of the journal can be explained by the results of these calculations.
On the Design and Construction of Direct-Drive Robots
Authors: Kazerooni H. , Kim S.
Published: June 2008

In this research, a statically-balanced direct-drive manipulator is designed and constructed to achieve improved dynamic behavior for compliance control [10, 11, 12]. The manipulator mechanism, incorporating a four-bar linkage, is designed so that its functional parts are balanced in all positions without the addition of counterweights. The motors are never loaded by gravity. As a result, smaller motors with less torque can be used to achieve higher speed, accuracy, and repeatability in fine manipulation tasks. The robot is powered by high-torque AC synchronous motors. The mechanism is comprised of graphite-epoxy and AA7075T6 aluminum materials. The manipulator is controlled by a parallel processor computer.
Delamination During Drilling in Composite Laminates
Authors: Ho-Cheng H. , Dharan C. K. H.
Published: June 2008

Delamination is the major concern during drilling of composite laminates. Delamination, in addition to reducing the structural integrity of the laminate, also results in poor assembly tolerance and has the potential for long-term performance deterioration. Drilling-induced delamination occurs both at the entrance and at the exit planes. This paper presents an analysis of delamination during drilling. The analysis uses a fracture mechanics approach in which the opening-mode delamination fracture toughness, a material parameter, is used with a plate model of the laminate. The analysis predicts an optimal thrust force (defined as the minimum force above which delamination is initiated) as a function of drilled hole depth. Good agreement is achieved with data obtained from drilling carbon fiber-epoxy laminates. An advantage of the model is that it can predict varying degrees of delamination for other materials, such as glass fiber-epoxy, and for hybrid composites. In addition, the optimal thrust force for no delamination can be used to control a drilling machine with thrust force feedback for maximizing productivity.
The Effect of Hardness on Residual Stresses in Orthogonal Machining of AISI 4340 Steel
Authors: Wu D. W. , Matsumoto Y.
Published: June 2008

Residual stress remaining in machined parts can be detrimental. Previous experimental evidence shows that hardness has a significant effect on its formation. Yet, no satisfactory explanation is available for the causes of such a phenomenon. This work seeks to understand the mechanism of residual stress formation and explain the effect of hardness on it. The analysis is based on the existence of several measurable factors that influence the stress field in the work-material during the cutting process. The sensitivity of these factors to hardness allows establishment of relationships between the hardness and the material loading cycle. The results of the analysis indicate that the residual stress pattern is correlated most strongly to the orientation of the primary deformation zone in metal cutting. This correlation provides a good explanation for the role of the material hardness on the residual stress formation.
An Approximate Model to Calculate Foldover and Strains During Cold Upsetting of Cylinders Part I: Formulation and Evaluation of the Foldover Model
Authors: Ettouney O. M. , Stelson K. A.
Published: June 2008

In this paper, a new approximate model to calculate foldover of a cylinder undergoing nonuniform compression test (simple upsetting) is presented. The model is formulated using constant-volume equations and workpiece geometry. In addition to foldover, the model can be used to calculate equatorial-axial strains. This eliminates the need for inscribing grids (when determining forming-limit diagrams) on the cylinder’s free surface to find these strains. Combined with friction-calibration curves (prepared using finite-element analysis) that relate foldover to friction, the model enables one to estimate the friction coefficient. This eliminates the need for a separate test (e.g., the ring test) to determine friction or evaluate type of lubrication to be used. When compared to finite-element results and experiments, the new model showed excellent results in calculating foldover, strains, and friction coefficient.
Mechanics of Kinking in Cables
Authors: Dwivedi J. P. , Das Talukder N. K. , Mahmood N. A.
Published: June 2008

Kinks or loops are formed in cables, subjected initially to torque and tension, in underwater and other applications due to a critical combination of torque and tension, resulting from sudden slackening of the cable. Subsequent reduction in slackness tightens the kink often resulting in failure of the cable. In the following paper the mechanics of kink formation is dealt with and the critical tension-torque relationship established. From the analysis presented, kink length is also evaluated.
Tool Life in Oblique Cutting as a Function of Computed Flank Contact Temperature
Authors: Venuvinod P. K. , Lau W. S. , Rubenstein C.
Published: June 2008

The steps by which a tool life analysis applicable to orthogonal cutting can be extended to accommodate tool obliquity are detailed. By following these, a relation between tool-life, T, tool obliquity, λ, and a representative tool flank wear land contact temperature, θfs, is obtained. A method is then described by which θfs in oblique cutting can be computed. This is based on a recently developed procedure for estimating temperatures of obliquely moving heat sources on the rake face combined with the influence of constriction resistance occurring at the discrete contact points within the flank contact area. In this way, from a knowledge of the T − θfs relation applicable to a given tool/workpiece combination cut orthogonally, tool lives at different tool obliquities are predicted and are shown to agree quite well with experimentally determined values. Finally, a comprehensive tool life expression independent of cutting parameters and of tool geometry is proposed and is verified using data obtained by cutting mild steel with H.S.S. tools.
Finite Element Prediction of Chip Geometry and Tool/Workpiece Temperature Distributions in Orthogonal Metal Cutting
Authors: Strenkowski J. S. , Moon Kyoung-Jin
Published: June 2008

An Eulerian finite element model is presented that simulates orthogonal metal cutting. The model predicts chip geometry and temperature distribution in the workpiece, chip, and tool without the need for empirical cutting data. With the capability to predict chip geometry, the tool-chip contact length can also be found. Characteristics of the flow field in the vicinity of the tool can also be determined, such as the material velocity, and the stress and strain-rate distributions. It was found that the shear stress occurs over a finite region in front of the tool, rather than a single shear plane. Cutting experiments were performed for aluminum alloy 6061-T6 to validate the model. Good correlation with the model was found based on tool forces and average tool-chip interface temperature measurements.
Measurement and Analysis of Heat Transfer and Friction During Hot Forging
Authors: Burte P. R. , Im Yong-Taek , Altan T. , Semiatin S. L.
Published: June 2008

An investigation of heat transfer and friction during hot forging has been performed using experimental and analytical techniques. The interface heat transfer coefficient was measured in experiments in which two flat H-13 tool steel dies were heated to different initial temperatures and brought together under varying pressure levels, or the two dies were heated to the same temperature and used to upset aluminum alloy 2024-0 rings under both isothermal as well as nonisothermal conditions. The coupling between heat transfer and friction during hot forging has been studied by analysis of data from the ring experiments and the generation of heat transfer coefficient and friction shear factor calibration curves derived from finite element simulations. By this means, the effects of forging pressure, deformation rate, and lubrication on the heat transfer coefficient and the friction shear factor were established. It was shown that, for the geometry studied, the value of the friction shear factor is independent of the heat transfer coefficient and vice versa, at least to a first order.
Optimum Choice of Robot Actuators
Authors: Chedmail P. , Gautier M.
Published: June 2008

The object of this paper is to present a method for the optimum choice of robot actuators. The modelling of the system takes into account the inertia of the links and actuators, and viscous and Coulomb friction effects. The thermal model of the actuators is included in the model. The optimum actuators set is that corresponding to the minimization of the global mass of all the actuators with respect to the maximum pulse torque and maximum temperature constraints for each one. Under specified conditions, the solution of this problem is obtained by exploring a manufacturer’s data base of actuators which contains the inertial, electrical, and thermal characteristics. An application of our approach on a SCARA robot type is given in the paper.
A Discrete Data Base Multiple Objective Optimization of Milling Operation Through Geometric Programming
Authors: Jha N. K.
Published: June 2008

The optimum process planning of the milling operation has been attempted through multiple objectives. A multiple objective function based on cost of production and rate of production in milling operations has been developed. The unified objective function thus developed serves as true arbiter balancing the values and objectives of local or individual objective functions. Most of the machine settings are discrete in nature and this has been considered in computerized production planning of milling. The complete approach has been demonstrated through an example.
The Influence of the Wall on Flow Through Pipes Packed With Spheres
Authors: Fand R. M. , Thinakaran R.
Published: June 2008

This paper presents the results of an experimental investigation that is a sequel to a previously published study of the flow of fluids through porous media whose matrices are composed of randomly packed spheres. The objective of the previous study was to accurately determine the ranges of the Reynolds number for which Darcy, Forchheimer and turbulent flow occur, and also the values of the controlling flow parameters—namely, the Kozeny-Carman constant for Darcy flow and the Ergun constants for Forchheimer and turbulent flow—for porous beds that are infinite in extent; that is, practically speaking, for sufficiently large values of the dimension ratio, D/d, where D is a measure of the extent of the bed and d is the diameter of a single spherical particle of which the porous matrix is composed. The porous media studied in the previous and present experiments were confined within circular cylinders (pipes), for which the dimension D is taken to be the diameter of the confining cylinder. The previous study showed that the flow parameters are substantially independent of the dimension ration for D/d ≥ 40. For D/d < 40, the so-called “wall effect” becomes significant, and the flow parameters become functionally dependent upon this ratio. The present paper presents simple empirical equations that express the porosity and the flow parameters as functions of D/d for 1.4 ≤ D/d < 40. Transitions from one type to another were found to be independent of D/d and occur at values of the Reynolds number identical to those reported in the previous study.
Simulation of Vortex-Shedding Flow About a Circular Cylinder at High Reynolds Numbers
Authors: Song Charles C. S. , Yuan Mingshun
Published: June 2008

Vortex shedding over a circular cylinder is modeled based on the weakly compressible flow equations with a simple subgrid scale turbulence model and a simple hybrid boundary condition. An explicit finite volume method is used. A subcritical and a supercritical case are computed. It is shown that the large-scale vortex-shedding phenomenon, the primary vortices, and the related oscillatory lift and drag can be calculated fairly well with a grid system coarser than the boundary layer thickness. The secondary vortices and the related higher frequency oscillations are also calculated by using somewhat finer grids.
Streak Characteristics and Behavior Near Wall and Interface in Open Channel Flows
Authors: Rashidi M. , Banerjee S.
Published: June 2008

Turbulent structures near the boundaries (solid wall and gas-liquid interface) have been studied in open channel flows. Experiments with no shear, countercurrent shear, and cocurrent shear at the gas-liquid interfaces were conducted. Results indicate that near the sheared interfaces, the mean nondimensional span wise streak-spacing, lambda+, appears to be essentially invariant with shear Reynolds number, exhibiting consistent values of lambda+ ≈ 100 at y1+ = 5, while increasing with distance from the interface. Observation of the streaks near the interface indicates that the process of streak merging is active even for y1+ < 5. Further studies show that the low-speed streaks frequently occur as regions between longitudinal vortices separated by Deltaz+≈ 50 near the boundaries. These vortices generally originate from the boundaries at an angle of about 20–25 deg (for y+ <20), then lift up or eject chaotically at an angle of about 40–50 deg (for y+ >20). Based on these observations, a conceptual mechanism of streak breakdown near the sheared boundaries has been provided.
Impingement of Under-Expanded Jets on a Flat Plate
Authors: Iwamoto J.
Published: June 2008

When an under-expanded sonic jet impinges on a perpendicular flat plate, a shock wave forms just in front of the plate and some interesting phenomena can occur in the flow field between the shock and the plate. In this paper, experimental and numerical results on the flow pattern of this impinging jet are presented. In the experiments the flow field was visualized using shadow-photography and Mach-Zehnder interferometry. In the numerical calculations, the two-step Lax-Wendroff scheme was applied, assuming inviscid, axially symmetric flow. Some of the pressure distributions on the plate show that the maximum pressure does not occur at the center of the plate and that a region of reversed flow exists near the center of the plate.
Navier-Stokes Flow Analysis for Hydraulic Turbine Draft Tubes
Authors: Vu T. C. , Shyy W.
Published: June 2008

Three-dimensional turbulent viscous flow analyses for hydraulic turbine elbow draft tubes are performed by solving Reynolds averaged Navier-Stokes equations closed with a two-equation turbulence model. The predicted pressure recovery factor and flow behavior in the draft tube with a wide range of swirling flows at the inlet agree well with experimental data. During the validation of the Navier-Stokes flow analysis, particular attention was paid to the effect of grid size on the accuracy of the numerical result and the importance of accurately specifying the inlet flow condition.
Velocity Measurements on the Forward Portion of a Cylinder
Authors: Paxson D. E. , Mayle R. E.
Published: June 2008

Velocity measurements in the laminar boundary layer around the forward portion of a circular cylinder are presented. These results are compared to Blasius’ theory for laminar flow around a cylinder using a free-stream velocity distribution obtained from static pressure measurements on the cylinder. Even though the flow is periodically unsteady as a result of vortex shedding from the cylinder, it is found that the agreement is excellent.
Block Cycle Fatigue Life Simulation and Correlation With Test for an Automotive Hood Latch-Supporting Component
Authors: Liao Gene Y.
Published: June 2008

This paper describes the durability analysis procedure and fatigue life simulation of an automotive hood latch-supporting component under block cycle loads. The first step is to apply linear stress analysis to identify the regions with high possibility of failure. The bent cove section of the latch support and the upper bolt-edge on a tie bar connecting to the latch support are determined as the critical regions. The strain-life/signed von Mises stress approach is then used to perform the fatigue analysis at these critical regions. The predicted fatigue life is about 3 times of the experimental one. However, the experiment shows that a crack appears exactly at the bent cove section of the latch support as simulation predicted. This project also serves as a case study to the students in predicting fatigue failure of a real industrial part.
Outlet Pressure Influence on Flow Through an Arterial Branch
Authors: Tadjfar Mehran , Himeno Ryutaro
Published: June 2008

Many researchers use CFD to study the mechanics of blood flow in the human vascular system. The emphasis is shifting from averaged, idealized geometric models into realistic patient-specific models taken from MRI images or other advanced imaging techniques (Taylor et al. 1998). In order to use the results of CFD for clinical diagnoses or surgical planning, one needs to have fairly accurate representation of the given patient’s vascular system or at least in the region of interest. This involves fairly smooth geometrical model of the region and an accurate description of the inlet and outlet flow conditions. Here, we study the influence of the outlet pressure of the daughter tubes on the flow in an arterial branch. The branch model used is an accurate grid representation of a realistic MRI-based aortic branch (Fig. 1).
Mode Competition in a Flexible Cylindrical Riser
Authors: Marcollo Hayden , Hinwood Jon B.
Published: June 2008

The Vortex-Induced-Vibration (VIV) of a riser in a simplified shear flow is investigated in a series of experiments carried out in a large flume. In the experimental program the VIV from two different flow speed regions were forced to compete to determine the relative importance of underlying fluid and structure parameters.
Added Mass Variation and Van der Pol Models Applied to Vortex-Induced Vibrations
Authors: Fujarra Andre´ L. C. , Pesce Celso P.
Published: June 2008

Vortex Induced Vibrations (VIV) experiments in water, conducted with flexible or elastically mounted rigid cylinders, under low values of mass-damping parameter, often reveal a large lock-in range, presenting a flat response region just after the amplitude curve peak. Previous phenomenological models, which treat the vortex wake dynamics with nonlinear oscillators of the Van der Pol type, are unable to predict this flat response region. The present paper re-addresses the phenomenological approach and shows that a consistent interpretation of a relevant hydrodynamic parameter, written as functions of reduced velocity, namely the added-mass, plays an essential role in improving analytical results.
Interactions Between Vortex-Induced Vibration of a Spring-Supported Cylinder and Fluid Flow in a Narrow Channel
Authors: Nakano Masahito , Maruyama Shinichi , Mihira Hideyuki , Yoshizawa Masatsugu
Published: June 2008

This paper studies the nonlinear interactions between vortex-induced vibration of a spring-supported circular cylinder and the unsteady fluid flow in a narrow channel. The analytical model consists of two-dimensional incompressible viscous flow in a narrow channel at low Reynolds number, and the spring-supported cylinder that can move perpendicular to the wall of the channel. The marker-and-cell (MAC) method is used to calculate numerically the simultaneous equations governing the interaction between the motion of the cylinder and the unsteady fluid flow. Furthermore the numerical results are confirmed by experiments presented herein.
Numerical Simulations of the Flow-Induced Vibrations of Tethered Bluff Bodies
Authors: Pregnalato C. J. , Ryan K. , Thompson M. C. , Hourigan K.
Published: June 2008

One of the most basic examples of fluid-structure interaction is provided by a tethered cylinder or sphere in a fluid flow. The tendency of a tethered sphere to oscillate when excited by waves is a well-known phenomenon and it has only recently been found that the same system will act in a similar fashion when exposed to a uniform flow at moderate Reynolds numbers, with a transverse peak-to-peak amplitude of approximately two diameters over a wide range of velocities. The present paper presents results of DNS of the flow past a tethered cylinder. The coupled Navier-Stokes equations and the equations of motion of the cylinder are solved using a spectral element method. The fluid forces acting on the cylinder as well as the tension in the tether are computed and used to determine the resulting motion of the object. It is found that the mean amplitude response is greatest at high reduced velocities, i.e. when the cylinder is oscillating predominantly transverse to the fluid flow. Furthermore, the oscillation frequency is found to correspond to the vortex shedding frequency of a stationary cylinder, except at high reduced velocities. This is in contrast to a tethered sphere in which the oscillation frequency does not correspond to either the vortex shedding frequency or the natural frequency. Visualizations of the vortex structures in the wake reveal the mechanisms behind the motion of the cylinder, and suggest that the induced oscillations are highly significant in the prediction of cylinder response in a steady flow.
On a Circular Cylinder in a Uniform Planar Shear Flow at Subcritical Reynolds Number
Authors: Sumner D. , Akosile O. O.
Published: June 2008

An experimental investigation was conducted of a circular cylinder immersed in a uniform planar shear flow, where the approach velocity varies across the diameter of the cylinder. The study was motivated by some apparent discrepancies between numerical and experimental studies of the flow, and the general lack of experimental data, particularly in the subcritical Reynolds number regime. Of interest was the direction and origin of the steady mean lift force experienced by the cylinder, which has been the subject of contradictory results in the literature, and for which measurements have rarely been reported. The circular cylinder was tested at Reynolds numbers from Re = 4.0×104 − 9.0×104, and the dimensionless shear parameter ranged from K = 0.02 − 0.07, which corresponded to a flow with low to moderate shear. The results showed that low to moderate shear has no appreciable influence on the Strouhal number, but has the effect of lowering the mean drag coefficient. The circular cylinder develops a small steady mean lift force directed towards the low-velocity side, which is attributed to an asymmetric mean static pressure distribution on its surface. The reduction in the mean drag force, however, cannot be attributed solely to this asymmetry.
Reynolds Number Dependence of the Flow Structure Behind Two Side-by-Side Cylinders
Authors: Xu S. J. , Zhou Y. , So R. M. C.
Published: June 2008

The wake structure of two side-by-side cylinders was experimentally investigated using flow visualization and hotwire techniques. The investigation was focused on the asymmetrical flow regime, i.e., T/d = 1.2 – 1.6, where T is the center-to-center cylinder spacing and d is the cylinder diameter. Experiments were conducted in both water and wind tunnels at a Reynolds number (Re) range of 150 – 14300. It has been found that, as Re increases, the flow structure behind the cylinders would change from one single vortex street to two streets with one narrow and one wide, for the same T/d. The one-street flow structure is dominated by one frequency ƒ0* = ƒ0d/U∞ ≈ 0.09, where ƒ0 is the dominant frequency and U∞ is the free-stream velocity. On the other hand, two frequencies, ƒ0* ≈ 0.3 and 0.09, characterized the two-street flow structure. These are associated with the narrow and wide street frequency, respectively. It is further observed that the critical Re, at which transition from single to two streets occurs, increases as T/d decreases. The present finding help clarify previous scattered reports for 1.2 < T/d < 1.5: detection of one dominant frequency by some but two by others.
Numerical Study of Oscillatory Flow Past a Pair of Cylinders at Low Reynolds and Keulegan-Carpenter Numbers
Authors: Anagnostopoulos P. , Koutras A. , Seitanis S. A.
Published: June 2008

The results of a numerical study of the viscous oscillating flow around a pair of circular cylinders are presented herein, for a constant frequency parameter, β, equal to 50, and Keulegan-Carpenter numbers, KC, ranging between 0.2 and 10. The cylinders were placed side-by-side to the oncoming flow, for a pitch to diameter ratio, P/D, equal to 1.2. The finite-element method was employed for the solution of the Navier-Stokes equations, in the formulation where the stream function and the vorticity are the field variables. The streamlines and vorticity contours generated from the solution were used for the flow visualization. At low values of the Keulegan-Carpenter number the flow remains symmetrical with respect to the horizontal axis of symmetry of the domain. As the Keulegan-Carpenter number is increased asymmetries appear in the flow, which are eventually amplified and lead finally to more complicated vortex-shedding patterns. These asymmetries generate an aperiodic flow configuration at consecutive cycles, which becomes almost chaotic as KC grows larger. For the various Keulegan-Carpenter numbers examined the traces of the hydrodynamic forces are presented, and the r.m.s. values of the hydrodynamic forces and the coefficients of the in-line force were evaluated.
An Experimental Investigation of Staggered Circular Cylinders in a Uniform Planar Shear Flow
Authors: Akosile O. O. , Sumner D.
Published: June 2008

Two circular cylinders of equal diameter, arranged in staggered configurations of P/D = 1.125 and 1.25, were immersed in a uniform planar shear flow, at Re = 5.0×104 and a dimensionless shear parameter of K = 0.05. The mean aerodynamic forces and the vortex shedding frequencies were measured for the upstream and downstream cylinders at each P/D. Under uniform, no-shear flow conditions, K = 0, the flow field of the cylinder group is similar to a single bluff body. As the incidence angle is varied from α = 0° to 90°, the forces on each cylinder undergo discontinuous changes, or attain local minimum or maximum values, at several critical incidence angles. At small α, the Strouhal number is greater than that of a single, isolated circular cylinder, whereas at high α the Strouhal number is lower than the single-cylinder value. The effects of shear, K = 0.05, on the aerodynamic forces were different depending on whether the downstream cylinder was situated at a higher or lower centreline velocity compared to the upstream cylinder. The planar shear flow had its greatest influence when the cylinders were in a nearly side-by-side arrangement. This indicated that the effect of shear was mostly on the flow through the gap between the cylinders. The lift coefficient data were mostly unchanged by the shear flow, the drag coefficient data were lowered, and there were shifts in the critical incidence angles. The influence of shear on vortex shedding was less pronounced, but there was a small reduction in Strouhal number compared to the no-shear case.
Characterisation of Long Chain Branching (LCB) in Polyolefins and Elastomers Using Large Amplitude Oscillatory Shear (LAOS) and Fourier Transform Rheology Using Harmonics of the Stress Signal
Authors: Burhin Henri G.
Published: June 2008

It is difficult, if not impossible to quantify LCB in polymers using rheological test methods only. Most of the reported rheological methods are affected by polymer characteristics other than LCB (Molecular weight Distribution (MWD), polymer microstructure, polymer type etc…). Poly-Propylene samples having different level of LCB produced by reactive extrusion with Per-Oxi-Dicarbonate have been characterised at strain ratios between 2.5 and 10. Stress signal distortion has been found to be sensitive only to the presence and level of LCB and not to Average Molecular Weight (AMW) and MWD. Quantification of the signal distortion was performed using Fourier transform rheology. As linear visco-elasticity equations are not applicable to LAOS, the approach of Giacomin and Dealy was applied. This considers the stress signal as a Fourier series and enables the calculation of G′n and G″n. LCB has a strong effect on both G′n and G″n, on their ratio and especially on G′ from the first harmonic (G′1). Repeatability data (CV) on G′1 and G″1 shows excellent sensitivity (<1%). The technique has been successfully applied to commercially available elastomers (BR and EPDM) enabling comparisons based on LCB level irrespectively of the AMW and MWD. Rapid graphical differentiation between linear and non linear polymers is achieved with stress/strain rate curves (Lissajou figure). The development of this technique provides polymer suppliers and their customers the ability to rapidly assess variations in Long Chain Branching, essential for incoming material and/or production control.
Heat Transfer to Two-Phase: Air, Viscoelastic Fluid Flows Over a Hot Cylinder
Authors: Rao B. K.
Published: June 2008

Over a range of 70 < Rea < 9600, 7 < Pra < 130, 0 < ∃ < 0.12 and 0.7 < n < 1, circumferential wall temperatures for air-water and air-aqueous polymer (viscoelastic) solution flows over a horizontal cylinder were measured experimentally. The 2.5-cm-diameter and 7.5-cm-length cylinder was heated by passing direct electric current through it. The peripherally averaged heat transfer coefficient for relatively dilute viscoelastic-air solutions, at any fixed flow rate of liquid phase, increases with ∃. Such increase is more pronounced at lower flow rates of liquid phase. For relatively more elastic solutions, the two-phase heat transfer decreases with increasing ∃. Such reduction is more pronounced at higher flow rates of liquid phase. A new correlation is proposed for predicting the Nusselt number for air-viscoelastic fluid flows over a heated cylinder in cross flow.
Measurements of the Cavitation Threshold of Soils Under Dynamic Stressing by Pulses of Tension
Authors: Williams P. Rhodri , Williams Rhodri L.
Published: June 2008

This paper reports the first measurements of the effective tensile strength (or ‘cavitation threshold’), Fc, of degassed samples of a commercial ‘multigrade’ oil over a range of temperatures, T, representative of those encountered under its normal operating conditions (in the range 20°C ≤ T ≤ 140°C). Also reported are the values of Fc obtained for Newtonian silicon oils over a range of shear viscosities. In the experimental apparatus used in this work, samples of liquid are subjected to dynamic stressing involving a rapid pressure-tension cycle (this being a feature of conditions experienced by a lubricant within a dynamically-loaded journal bearing). Moreover, the method used herein to estimate Fc avoids reliance upon direct measurements of substantial dynamic negative pressures using transducers which are designed for use in the range of positive pressures.