bluuebunny/crossref_metadata_2025 huggingface dataset:
Administration of Procyanidins from Grape Seeds Reduces Serum Uric Acid Levels and Decreases Hepatic Xanthine Dehydrogenase/Oxidase Activities in Oxonate‐Treated Mice
Authors: Wang Ying , Zhu Ji Xiao , Kong Ling Dong , Yang Cheng , Cheng Christopher Hon Ki , Zhang Xin
Published: May 2004

Abstract: In this study we have investigated the effects of administration of procyanidins from grape seeds on serum uric acid levels in a model of hyperuricaemia in mice pretreated with oxonate, as well as the xanthine dehydrogenase and xanthine oxidase activities in mouse liver in vivo. The procyanidins, when orally administered to the oxonate‐pretreated hyperuricaemic mice, were able to elicit a dose‐dependent hypouricaemic effect. At a dose of 400 mg/kg for 3 days, the serum urate levels of the oxonate‐pretreated mice were not different from the normal mice. In addition, the hepatic activities of xanthine dehydrogenase and xanthine oxidase in the procyanidins‐treated mice were found to decrease significantly. However, the hypouricaemic effects observed in the experimental animals did not seem to parallel the changes in xanthine dehydrogenase and xanthine oxidase activities, implying that the procyanidins might be acting via other mechanisms apart from simple inhibition of enzyme activities. Furthermore, the procyanidin‐treated animals exhibited normal growth while the allopurinol‐treated animals exhibited some retarded growth. These results demonstrated for the first time that the procyanidins from grape seeds possess in vivo urate‐lowering activities. The potential application of these natural compounds in the treatment of hyperuricaemia is discussed.
(±) Epibatidine Increases Acetylcholine Release Partly through an Action on Muscarinic Receptors
Authors: Kommalage Mahinda , Höglund A. Urban
Published: May 2004

Abstract: Epibatidine has been used in a wide dose range and was found to produce both nociceptive and antinociceptive effects. The different effects were partly explained by an action on multiple nicotinic receptor systems. The present study investigated the possibility that part of the action of intraspinally or subcutaneously administered (±) epibatidine, is mediated through an action on muscarinic receptors. Radioligand receptor assays were performed using homogenates of rat spinal cord and muscarinic M1–M5 receptors expressed in Sf9 cells. The intraspinal acetylcholine releasing effect of intraspinally and subcutaneously administered (±) epibatidine was studied with and without with atropine pretreatment. (±) Epibatidine has affinity for muscarinic receptors both in spinal cord tissue and expressed in Sf9 cells. The intraspinal administration of 160 μM (±) epibatidine produced an increase in acetylcholine release that was reduced by pretreatment with 100 μM atropine. Subcutaneous administration of 30 μg/kg (±) epibatidine produced an increase in intraspinal acetylcholine release that was not inhibited by 5 mg/kg subcutaneous atropine pretreatment. We conclude that (±) epibatidine, in μM concentrations, is a partial muscarinic receptor agonist that may interact with spinal muscarinic receptors to increase acetylcholine release. Epibatidine induced spinal acetylcholine release observed after subcutaneous administration appears not to be mediated via muscarinic receptor. The dual action on both nicotinic receptors and muscarinic receptors may explain the potent analgesic effect observed after epibatidine administration.
Cellular Potassium Ion Deprivation Enhances Apoptosis Induced by Cisplatin
Authors: Marklund Linda , Andersson Britta , Behnam‐Motlagh Parviz , Sandström Per‐Erik , Henriksson Roger , Grankvist Kjell
Published: May 2004

Abstract: The anticancer drug cisplatin induces cell death by apoptosis. Apoptosis is dependent on cellular loss of potassium ions (K+). We have recently shown that the antifungal drug amphotericin B (enhancing K+ efflux), combined with the Na+, K+, 2Cl−‐cotransport blocker bumetanide (decreasing K+ influx), augmented cisplatin‐induced apoptosis in vitro. We therefore quantified K+ fluxes with the K+ analogue rubidium (86Rb+) in cisplatin‐induced apoptosis of mesothelioma cells treated with bumetanide and amphotericin B. Bumetanide combined with amphotericin B enhanced cisplatin‐induced apoptosis by a pronounced initial reduction of K+ influx due (in addition to Na+, K+, 2Cl−‐cotransport inhibition) also to Na+, K+, ATPase pump inhibition. As 86Rb+ efflux was initially preserved, combination of the drugs would lead to net K+ loss. Combinations of K+ flux modulators leading to cellular potassium ion deprivation thus augments cisplatin‐induced apoptosis and could therefore possibly be used to enhance the antitumour efficacy of cisplatin treatment.
Fexofenadine does Not Affect Omeprazole Pharmacokinetics: Both are putative P‐Glycoprotein Substrates
Authors: Takahata Takenori , Yasui‐Furukori Norio , Yoshiya Gen , Uno Tsukasa , Sugawara Kazunobu , Tateishi Tomonori
Published: May 2004

Abstract: An in vitro study has recently suggested that a proton pump inhibitor, omeprazole, is a modest substrate of P‐glycoprotein. Several studies have shown P‐glycoprotein is involved in the absorption and excretion of fexofenadine. Therefore, we examined the effect of fexofenadine on the pharmacokinetics of omeprazole. Eight healthy volunteers participated in this study. They received a single oral dose of 40 mg omeprazole before and after 60 mg fexofenadine (10 doses over 6 days). Blood samplings were performed up to 8 hr after each dosing. Plasma concentrations of omeprazole and its two metabolites were quantified with high‐performance liquid chromatography. In addition, the effect of fexofenadine on P‐glycoprotein function was examined by flow cytometry using rhodamine 123 and CD56‐positive lymphocytes. Comparison of the pharmacokinetic parameters of omeprazole before and after fexofenadine revealed that there were no differences in peak concentration, time to peak concentration, area under the time concentration curve up to 8 hr, and elimination half‐life. There were also no differences in these pharmacokinetic parameters for the two metabolites of omeprazole. Flow cytometric analysis revealed that fexofenadine did not inhibit the efflux of rhodamine 123. This study indicated that there was probably no drug interaction between omeprazole and fexofenadine, which might be due to less contribution of P‐glycoprotein to omeprazole absorption, insufficient inhibitory effect of fexofenadine on P‐glycoprotein, or the involvement of other transporters such as organic anion transporting polypeptides.
The baroreflex is counteracted by autoregulation, thereby preventing circulatory instability
Authors: Burattini Roberto , Borgdorff Piet , Westerhof Nico
Published: May 2004

The aims of this study were (a) to apply in the animal with intact baroreflex a two‐point method for estimation of overall, effective open‐loop gain, G0e, which results from the combined action of baroregulation and total systemic autoregulation on peripheral resistance; (b) to predict specific baroreflex gain by correcting the effective gain for the autoregulation gain; and (c) to discuss why the effective gain is usually as low as 1–2 units. G0e was estimated from two measurements of both cardiac output, Q, and mean systemic arterial pressure, P: one in the reference state (set‐point) and the other in a steady‐state reached 1–3 min after a small cardiac output perturbation. In anaesthetized cats and dogs a cardiac output perturbation was accomplished by partial occlusion of the inferior vena cava and by cardiac pacing, respectively. Average (±s.e.m.) estimates of G0e were 1.4 ± 0.2 (n= 8) in the cat and 1.5 ± 0.4 (n= 5) in the dog. The specific baroreflex open‐loop gain, G0b, found after correction for total systemic autoregulation, was 3.3 ± 0.4 in the cat and 2.8 ± 0.8 in the dog. A model‐based analysis showed that, with G0e as low as 1.4, the closed‐loop response of P to a stepwise perturbation in Q results in damped oscillations that disappear in about 1 min. The amplitude and duration of these oscillations, which have a frequency of about 0.1 Hz, increase with increasing G0e and cause instability when G0e is about 3. We conclude that autoregulation reduces the effectiveness of baroreflex gain by about 55%, thereby preventing instability of blood pressure response.
The effects of breathing 5% CO2 on human cardiovascular responses and tolerance to orthostatic stress
Authors: Howden Reuben , Lightfoot J. Timothy , Brown Stephen J. , Swaine Ian L.
Published: May 2004

Breathing carbon dioxide (CO2) is known to induce hypercapnic acidosis and to affect chemoreceptor regulation of the cardiovascular system. However, there is limited information in the literature regarding the effects of breathing CO2 upon tolerance to orthostatic stress where cardiovascular regulation is challenged. The purpose of this study was to investigate the effect of breathing 5% CO2 on presyncopal tolerance to lower body negative pressure (LBNP). Nine subjects (five males and four females; average ±s.d. age 21.9 ± 0.9 years, height 172.4 ± 9.7 cm, mass 70.3 ± 7.1 kg) volunteered to participate in this study. Orthostatic tolerance was determined by exposing subjects to LBNP until the onset of presyncopal signs and symptoms on two occasions each separated by approximately 1 week. On one occasion investigations were carried out while subjects were breathing room air and on the other while subjects were breathing air containing 5% CO2, inducing hypercapnia and stimulating systemic chemoreceptors. During hypercapnic conditions, as compared with normocapnia, there were significant increases (P < 0.05) in minute ventilation, end‐tidal CO2 and estimated arterial PCO2. Furthermore, under hypercapnic conditions there was an increase in orthostatic tolerance, peak heart rate and time to peak heart rate during LBNP. The LBNP‐induced increase in calf circumference was significantly attenuated at −50 mmHg of LBNP in addition to a further 22.3% reduction in stroke volume under hypercapnic conditions. In conclusion, these results suggest that the possible protective element of presyncope was delayed during hypercapnia at the expense of further reductions in stroke volume. This delayed presyncopal response may have been associated with increases in cerebral blood flow (CBF) induced by the increased arterial PCO2.
Effect of metabolic cage housing on immunoglobulin A and corticosterone excretion in faeces and urine of young male rats
Authors: Eriksson Emma , Royo Felix , Lyberg Karin , Carlsson Hans‐Erik , Hau Jann
Published: May 2004

Six 8‐week‐old Sprague‐Dawley rats were studied for 9 days divided into three periods of 3 days each: before transferral to metabolism cages, during metabolic cage housing and after return to their home cages. Faeces were collected daily when the animals were housed in their home cages and every 6 h when the animals were housed in metabolic cages during which time urine was also collected every 6 h. The rate of weight gain was slightly reduced during the 3 days in metabolic cages and the animals produced significantly larger amounts of faeces when housed in metabolic cages than when housed in their home cages. The total faecal excretion of corticosterone (nanograms excreted per hour per kilogram body weight) and immunoglobulin A (IgA) (milligrams excreted per hour per kg body weight) quantified by enzyme‐linked immunosorbent assays (ELISAs) exhibited a clear diurnal rhythm in the metabolic cage. Urinary excretions of corticosterone and IgA also followed a clear diurnal cycle. The mean daily amounts of corticosterone excreted were not significantly affected by cage change and by housing in metabolic cages. However, the excretion of faecal IgA was significantly reduced during the 3 days after the period in metabolic cages. Taken together the results indicate that metabolic cage housing is mildly stressful for young adult male rats.
Plastic Localization Revisited
Authors: Marante Maria Eugenia , Flo´rez-Lo´pez Julio
Published: May 2004

This brief note describes an alternative approach for the demonstration of the localization criterion. In the new approach, the criterion is not obtained in terms of the gradient jump, but in terms of the plastic multiplier jump. The new demonstration is as simple as the classic criterion in the loading/loading conditions, but much simpler in the loading/unloading case. It is the opinion of the authors that this alternative approach is more convenient for pedagogical purposes.
A Ritz Model of Unsteady Oil-Film Forces for Nonlinear Dynamic Rotor-Bearing System
Authors: Zheng Tiesheng , Yang Shuhua , Xiao Zhonghui , Zhang Wen
Published: May 2004

Based on the free boundary theory and variational method, this paper presents a Ritz method to compute the instantaneous hydrodynamic forces of a real bearing subject to any perturbed motions of the rotor. The given method manipulates the cavitation region by simply introducing a parameter to match the free boundary condition and, as a result, a very simple approximate formula of oil-film pressure were obtained leading to great saving of computing time. The numerical examples show the high accuracy of the proposed formulas. This oil-film force model is also used to analyze the nonlinear dynamics of a rigid unbalanced rotor with elliptical bearing support. The results well agree with those of the oil-film force model computed by the finite element method and the computing time is saved greatly.
Analysis of a Rocking and Walking Punch—Part I: Initial Transient and Steady State
Authors: Mugadu A. , Sackfield A. , Hills D. A.
Published: May 2004

A rigid, square-ended punch resting on a incompressible half-plane, and subjected to a constant shearing force, together with a normal force, constant in magntiude, but moving backwards and forwards over the face, is studied. The shearing force is insufficient to cause sliding, but the presence of a slip region which migrates in from each contact edge as the punch rocks back and forth may permit a steady rigid-body motion to occur. The conditions for this are found, both for the early transient problem, starting from complete adhesion, and in the steady state.
Analysis of a Rocking and Walking Punch—Part II: General Numerical Solution Using Quadratic Programming
Authors: Nowell D.
Published: May 2004

This paper pursues a numerical approach to the solution of the contact problem of a rigid punch on an incompressible half-plane, subjected to a shearing force together with a normal force which may be offset from the centerline of the punch. A piecewise-linear representation of the shear tractions is employed and quadratic programming techniques are used to solve the problem. This method enables an arbitrary load history to be followed. Results are presented which show excellent agreement with other solutions to the special cases of monotonic and steady-state cyclic loading. It is shown that the traction distribution reaches a steady-state cycle after only a few cycles of loading. The existence of an interesting stick-slip regime, where a central zone of slip is bordered by two stick regions is highlighted.
Advances in Polynomial Continuation for Solving Problems in Kinematics
Authors: Sommese Andrew J. , Verschelde Jan , Wampler Charles W.
Published: May 2004

For many mechanical systems, including nearly all robotic manipulators, the set of possible configurations that the links may assume can be described by a system of polynomial equations. Thus, solving such systems is central to many problems in analyzing the motion of a mechanism or in designing a mechanism to achieve a desired motion. This paper describes techniques, based on polynomial continuation, for numerically solving such systems. Whereas in the past, these techniques were focused on finding isolated roots, we now address the treatment of systems having higher-dimensional solution sets. Special attention is given to cases of exceptional mechanisms, which have a higher degree of freedom of motion than predicted by their mobility. In fact, such mechanisms often have several disjoint assembly modes, and the degree of freedom of motion is not necessarily the same in each mode. Our algorithms identify all such assembly modes, determine their dimension and degree, and give sample points on each.
Adaptive Slicing for a Multi-Axis Laser Aided Manufacturing Process
Authors: Zhang Jun , Liou Frank
Published: May 2004

An adaptive slicing algorithm which can generate optimal slices to achieve deposition without support structures for five-axis hybrid layered manufacturing is presented in this paper. Different from current adaptive slicing, this technique varies not only in layer thickness but also in slicing direction. The Laser Aided Manufacturing Process (LAMP), a five axis system combined material additive and removal process which was developed at the University of Missouri-Rolla, is used as an example. The multiple-degree-of-freedom system allows LAMP to build a part with minimum support structure. However, an automated method for path planning of such a system is necessary. Two techniques have been adapted to build the overhang between two adjacent layers: transition wall and surface tension. This paper addresses the critical slicing algorithm based on the above two techniques. The slicing direction is determined by a marching algorithm which is based on the surface normals of points on the side surface of the current slice.
Application of Workspace Generation Techniques to Determine the Unconstrained Motion of Parallel Manipulators
Authors: Voglewede Philip , Ebert-Uphoff Imme
Published: May 2004

Due to clearances in their passive joints, parallel manipulators always exhibit some unconstrained motion at the end effector. The amount of unconstrained motion depends on the pose of the manipulator and can increase significantly at or near singular configurations. This paper shows precisely how much unconstrained end effector motion exists at the end effector for a large class of parallel manipulators, namely those with passive revolute and/or spherical joints, if all the joint clearances are known. This includes the planar 3R_RR, and, in approximation the Gough-Stewart and the Hexa manipulators. For the analysis, the passive joints are assumed to be revolute or spherical because these are the simplest cases. However, the general framework also applies to other joint types, although leading to more complex calculations. For most manipulators, determining the amount of end effector motion can be transformed to a workspace generation problem. Therefore, general workspace generation techniques can be utilized.
Sequential Optimization and Reliability Assessment Method for Efficient Probabilistic Design
Authors: Du Xiaoping , Chen Wei
Published: May 2004

Probabilistic design, such as reliability-based design and robust design, offers tools for making reliable decisions with the consideration of uncertainty associated with design variables/parameters and simulation models. Since a probabilistic optimization often involves a double-loop procedure for the overall optimization and iterative probabilistic assessment, the computational demand is extremely high. In this paper, the sequential optimization and reliability assessment (SORA) is developed to improve the efficiency of probabilistic optimization. The SORA method employs a single-loop strategy with a serial of cycles of deterministic optimization and reliability assessment. In each cycle, optimization and reliability assessment are decoupled from each other; the reliability assessment is only conducted after the deterministic optimization to verify constraint feasibility under uncertainty. The key to the proposed method is to shift the boundaries of violated constraints (with low reliability) to the feasible direction based on the reliability information obtained in the previous cycle. The design is quickly improved from cycle to cycle and the computational efficiency is improved significantly. Two engineering applications, the reliability-based design for vehicle crashworthiness of side impact and the integrated reliability and robust design of a speed reducer, are presented to demonstrate the effectiveness of the SORA method.
Lagrangian Formulation of Rotating Beam With Active Constrained Layer Damping in Time Domain Analysis
Authors: Fung E. H. K. , Zou J. Q. , Lee H. W. J.
Published: May 2004

In this paper, Lagrangian formulation of a horizontal rotating beam with active constrained layer damping (ACLD) treatment is presented. The problem is approached by the Rayleigh-Ritz method. By assuming modal functions as the displacement shape functions and using effective damping model of the visco-elastic material (VEM) layer, the number of degrees of freedom of the system is greatly reduced. The damping of the visco-elastic material is characterized by a shear (storage) modulus and a loss factor. Also the dynamic behavior of the rotating ACLD beam is analyzed in the time domain. The effects of control gains, shear modulus and loss factor of the VEM on the dynamic response are also investigated.
Singularity Loci of a Special Class of Spherical 3-DOF Parallel Mechanisms With Prismatic Actuators
Authors: Wang Jing , Gosselin Cle´ment M.
Published: May 2004

In this paper, the singularity loci of a special class of spherical 3-DOF parallel manipulators with prismatic actuators are studied. Concise analytical expressions describing the singularity loci are obtained in the joint and in the Cartesian spaces by using the expression of the determinant of the Jacobian matrix and the inverse kinematics of the manipulators. It is well known that there exist three different types of singularities for parallel manipulators, each having a different physical interpretation. In general, the singularity of type II is located inside the Cartesian workspace and leads to the instability of the end-effector. Therefore, it is important to be able to identify the configurations associated with this type of singularity and to find their locus in the space of all configurations. For the class of manipulators studied here, the six general cases and the five special cases of singularities are discussed. It is shown that the singularity loci in the Cartesian space (defined by the three Euler angles) are six independent planes. In the joint space (defined by the length of the three input links), the singularity loci are quadric surfaces, such as hyperboloid, sphere or a degenerated line or a degenerated circle. In addition, the three-dimensional graphical representations of the singular configurations in each of the general and special cases are illustrated. The description of the singular configurations provided here has great significance for robot trajectory planning and control.
The Three-Dimensional Analog of the Classical Two-Dimensional Truss System
Authors: Christensen Richard M.
Published: May 2004

The octet-truss lattice system of Fuller and examined by Deshpande, Fleck and Ashby is here reasoned to be the most fundamental form for a three-dimensional truss system, placing it as the three-dimensional analog of the classical two-dimensional truss system. Useful applications may be possible from nanometer scales up to space station scales, in addition to the usual scales of interest in materials science.
Peeling in Bimaterial Beams: The Peeling Moment and Its Relation to the Differential Rigidity
Authors: Moore Thomas D. , Jarvis John L.
Published: May 2004

Two-layer beams (i.e., bimaterials) under thermomechanical stress are prone to peeling or delamination at the free edges. The self-equilibrating peeling stress gives rise to a peeling moment Mp close to the free ends. A simple and exact formula for Mp is presented in which the sign of Mp indicates whether the beam is prone or resistant to delamination. The effect on both the sign and magnitude of Mp of the flexural rigidities of both layers is examined. As the stiffness of one layer becomes dominant, the magnitude of the differential rigidity converges to one-half the thickness of the opposite layer.
Triple Coordinate Transforms for Prediction of Falling Cylinder Through the Water Column
Authors: Chu, Peter C. , Fan, Chenwu , Evans, and Ashley D. , Gilles Anthony
Published: May 2004

Triple coordinate systems are introduced to predict translation and orientation of falling rigid cylinder through the water column: earth-fixed coordinate (E-coordinate), cylinder’s main-axis following coordinate (M-coordinate), and hydrodynamic force following coordinate (F-coordinate). Use of the triple coordinate systems and the transforms among them leads to the simplification of the dynamical system. The body and buoyancy forces and their moments are easily calculated using the E-coordinate system. The hydrodynamic forces (such as the drag and lift forces) and their moments are easily computed using the F-coordinate. The cylinder’s moments of gyration are simply represented using the M-coordinate. Data collected from a cylinder-drop experiment at the Naval Postgraduate School swimming pool in June 2001 show great potential of using the triple coordinate transforms.
Determination of Loads in an Inextensible Network According to Geometry of Its Wrinkles
Authors: Luo Cheng
Published: May 2004

This note derives an analytical relationship for an inextensible network when it buckles. According to the relationship, the applied compressive force can be determined according to the maximum absolute values of deflection and angle of deflection in the network’s wrinkles.
Vibration and Stability of Frictional Sliding of Two Elastic Bodies
With a Wavy Contact Interface
Authors: Nosonovsky Mikhail , Adams George G.
Published: May 2004

The stability of steady sliding, with Amontons-Coulomb friction, of two elastic bodies with a rough contact interface is analyzed. The bodies are modeled as elastic half-spaces, one of which has a periodic wavy surface. The steady-state solution yields a periodic set of contact and separation zones, but the stability analysis requires consideration of dynamic effects. By considering a spatial Fourier decomposition of the vibration modes, the dynamic problem is reduced to a singular integral equation for determining the eigenvectors (modes) and eigenvalues (frequencies). A pure imaginary root for an eigenvalue corresponds to a standing wave confined to the interface, while a positive/negative real part of the eigenvalue indicates instability/dissipation. A complex eigenvector indicates a complex mode of vibration. Two types of modes are considered—periodic symmetric modes with period equal to the surface waviness period and periodic antisymmetric modes with the period equal to twice the surface waviness. The singular integral equation is solved by reducing it to a system of linear algebraic equations using a Jacobi polynomial series and a collocation method. For the limit of zero friction it can be demonstrated analytically that the problem is self-adjoint and the eigenvalues, if they exist, are pure imaginary (no energy dissipation). These roots are found for a wide range of material properties and ratios of separation to contact zones lengths. For the limiting case of complete contact, the solution found corresponds to a superposition of two slip waves (generalized Rayleigh waves) traveling in opposite directions and forming a standing wave. With increasing separation zone length, the vibration frequency decreases from the slip wave frequency to the smaller surface wave frequency of the two bodies. With a nonzero separation zone, solutions can exist for material combinations which do not allow slip waves. For nonzero friction and sliding velocities, unstable solutions are found. The degree of instability is proportional to the product of the friction coefficient and the sliding velocity. These instabilities may contribute to the formation of friction-induced vibrations at high sliding speeds.
Two-Dimensional Analysis of an Elastic Layer Coupled to a Viscous Fluid
Authors: Seok Jongwon , Kim Andrew T. , Cale Timothy S. , Tichy John A.
Published: May 2004

A two-dimensional elastohydrodynamic analysis is performed on a system consisting of a viscous fluid flowing between a sliding soft layer of finite thickness and a tilted flat plate. The behavior of a soft layer subject to a distributed contact pressure is described in detail. Green’s functions are obtained for each Fourier coefficient of the distributed applied pressure, utilizing the additive property of linear elasticity theory. The resulting equations are numerically evaluated for some typical cases. As a function of the contact dimension, calculations are performed for the critical thickness of the layer beyond which the deformed shape essentially resembles that of the layer having an infinite thickness, in the case of a uniformly applied pressure. We also investigate the effect of layer thickness on the hydrodynamics, which illustrates that conditions in which the infinite half-space assumptions can be justified are highly limited. The findings of this paper have direct application to the modeling of chemical mechanical planarization (CMP).
Dynamics of a Hyperelastic Gas-Filled Spherical Shell in a Viscous Fluid
Authors: Allen J. S. , Rashid M. M.
Published: May 2004

The dynamical response of a gas-filled, spherical elastic shell immersed in a viscous fluid is of interest in a number of different scientific and technological contexts. In this article, this problem is formulated and studied numerically, within a purely mechanical setting. For spherically symmetric motions, a neo-Hookean shell material, and an incompressible surrounding fluid, the equation of motion can be obtained through an integration in the radial coordinate. The resulting nonlinear initial-value problem must be integrated numerically. An interesting feature of the system response is the possibility of a departure from bounded oscillation for large-amplitude far-field forcing. The amplitude at which this departure occurs is found to be highly dependent on the forcing frequency. A stability map in the forcing frequency/amplitude plane is an important result of this study.
Free Attitude Motions of a Spinning Body With Substantial Mass Loss
Authors: Eke Fidelis O. , Mao Tai-Chien , Morris Michael J.
Published: May 2004

This paper explores the various analytical links between the free attitude motions of spinning bodies of the rocket type, and the system’s parameters. The system is modeled as an axisymmetric body with substantial mass loss, and special attention is paid to the presence of a nozzle on the system. It is found that the nozzle expansion ratio can have an important influence on attitude motion, the higher this ratio the better behaved the system.
Synthesis and Analysis of a Group of 3-Degree-of-Freedom Partially Decoupled Parallel Manipulators
Authors: Jin Qiong , Yang Ting-Li
Published: May 2004

The kinematics decoupling for parallel manipulators is studied in this paper. Based on the topological structure characteristics of parallel mechanisms, the internal relationship between kinematics decoupling and basic kinematics chains is revealed, and the basic principle for structural synthesis of topologically decoupled mechanisms is put forward. Using this theory, a group of 3 degree-of-freedom (DOF) partially decoupled manipulators are synthesized. The expected kinematic outputs of these manipulators are 1-DOF translation and 2-DOF rotation, and motions along or about undesired directions do not exist. The kinematics analysis of a newly synthesized manipulator is discussed and the results indicate that the decoupling property of these architectures makes possible reaching real time control and path planning of parallel manipulators.
RedesignIT—A Model-Based Tool for Managing Design Changes
Authors: Ollinger Gabriel Aguirre , Stahovich Thomas F.
Published: May 2004

RedesignIT is a computer program that uses model-based reasoning to generate and evaluate proposals of redesign plans for engineered devices. These proposals describe how the design parameters could be changed to achieve a specified performance goal. Equally important, the program proposes complementary modifications that may be necessary to counteract the undesirable side effects of the primary changes. RedesignIT is intended for use during the first stages of a redesign project, when engineers need to make a quick, yet accurate assessment of the overall effects of a particular design change. The program uses qualitative device models, which allow it to compute redesign plans efficiently. With its ability to predict the collateral, and probably undesirable, effects of a design change, the program is well suited to aid product designers in deciding on the feasibility of introducing design changes to a product.
Hierarchical Parallel Processes of Genetic Algorithms for Design Optimization of Large-Scale Products
Authors: Yoshimura Masataka , Izui Kazuhiro
Published: May 2004

A large-scale machine system often has a general hierarchical structure. For hierarchical structures, optimization is difficult because many local optima almost always arise, however genetic algorithms that have a hierarchical genotype can be applied to treat such problems directly. Relations between the structural components are analyzed and this information is used to partition the hierarchical structure. Partitioning large-scale problems into sub-problems that can be solved using parallel processed GAs increases the efficiency of the optimization search. The optimization of large-scale systems then becomes possible due to information sharing of Pareto optimum solutions for the sub-problems.
Decomposition-Based Assembly Synthesis for Structural Modularity
Authors: Cetin O. L. , Saitou K.
Published: May 2004

A method for modular design of structural products such as automotive bodies is presented where two structural products are simultaneously decomposed to components considering the structural performances of each structure and the component sharing between two structures. The problem is posed as an optimization to minimize the reduction of structural strength due to the introduction of spot-weld joints and the number of redundant joints, while maximizing the manufacturability of the component and component sharing between two structures. As an extension to our previous work, this paper focuses on the simultaneous decomposition of two 3D beam-based structures. The major extensions include 1) a new, realistic definition of feasible joining angles based on the local geometry of joining components, 2) a component manufacturability evaluation that eliminates the need of specifying the number of components prior to decomposition and 3) a multi-objective optimization formulation that allows an effective exploration of trade-offs among different criteria. A case study on the simplified, 3D beam models of automotive bodies is presented to demonstrate the developed method.
An Approach to the Determination of Spur Gear Tooth Root Fillet
Authors: Math V. B. , Chand Satish
Published: May 2004

The purpose of this paper is to present an approach for the determination of geometry of spur gear tooth root fillet. An equation is developed to determine the point of tangency of involute profile and root fillet on the base circle for a spur gear without undercutting and the point of intersection of root fillet and involute profile above the base circle for an undercut gear. Generation using a hob or rack type cutter with protuberance (increase in tooth thickness at the tip of the hob tooth) is also discussed.
Effects of Over-Torque on Stress Relief in Conical Threaded Connections
Authors: Baragetti S. , Terranova A.
Published: May 2004

The analysis of the stress state induced by the make-up torque of tapered threaded connections is very important for the improvement of both the static and the fatigue resistance of such connections. Make-up torque induces a nonuniform stress state; in the same way, the axial load induced by the make-up torque is distributed in a nonuniform way along the sections of the coupled elements of the connections. The most important consequence is the overloading at the first threads engaged, which has to be summed to the stress concentration in the core section due to the notch effect. The aim of this paper is to analyze the stress and strain fields induced by make-up torque in tapered threaded connections; in particular, the purpose is to investigate the effects of the application of over-torque before putting the connections into service (stress relief due to over-torque before nominal make-up torque application). The evaluation of the local stress state and of stress relief, with a good level of precision, was performed by using finite element models in order to assess the percentage of load carried by each thread after the application of the make-up torque and further axial tensile or compressive loads. Numerical results confirmed the favorable thread load distribution induced by overloading. Experimental tests carried out on full-scale connections, used in the oil and gas industry for the joining of pipes, confirmed the numerical results.
Estimation of Equivalent Permeability in Magnetorheological Fluid Considering Cluster Formation of Particles
Authors: Shiraishi Toshihiko , Morishita Shin , Gavin Henri P.
Published: May 2004

This paper describes a simulation method for the equivalent magnetic permeability of mangetorheological (MR) fluids considering cluster formation of suspended particles. The cluster formation under a magnetic field is simulated by cellular automata (CA). Simulated cluster structures are qualitatively equivalent to those observed experimentally. Considering this structure, magnetic permeability analysis is conducted on a representative MR fluid by the finite element method. The equivalent permeability in the MR fluid was obtained from the average magnetic flux density and field. The time evolution of the magnetic characteristics of the MR fluid is shown to correspond to the time evolution of cluster formation.
The Short-Time Impulse Response of Euler-Bernoulli Beams
Authors: Chatterjee Anindya
Published: May 2004

We study an undamped, simply supported, Euler-Bernoulli beam given an instantaneous impulse at a point G, far from its ends. The standard modal solution obscures interesting mathematical features of the initial response, which are studied here using dimensional analysis, an averaging procedure of Zener, a similarity solution for an infinite beam, asymptotics, heuristics, and numerics. Results obtained include short-time asymptotic estimates for various dynamic quantities, as well as a numerical demonstration of fractal behavior in the response. The leading order displacement of G is proportional to t. The first correction involves small amplitudes and fast oscillations: something like t3/2 cost−1. The initial displacement of points away from G is something like t cost−1. For small t, the deformed shape at points x far from G is oscillatory with decreasing amplitude, something like x−2 cosx2. The impulse at G does not cause impulsive support reactions, but support forces immediately afterwards have large amplitudes and fast oscillations that depend on inner details of the impulse: for an impulse applied over a time period ε, the ensuing support forces are of Oε−1/2. Finally, the displacement of G as a function of time shows structure at all scales, and is nondifferentiable at infinitely many points.
Flow Separation Within the Engine Inlet of an Uninhabited Combat Air Vehicle (UCAV)
Authors: Brear Michael J. , Warfield Zachary , Mangus John F. , Braddom Steve , Paduano James D. , Philhower Jeffry S.
Published: May 2004

This paper discusses the structure of the flow within the engine inlet of an uninhabited combat air vehicle (UCAV). The UCAV features a top-mounted, serpentine inlet leading to an engine buried within the fuselage. The performance of the inlet is found to depend strongly on a flow separation that occurs within the inlet. Both the time-averaged and the unsteady structure of this separation is studied, and an argument relating the inlet performance to the behavior of this separation is suggested. The results presented in this paper also suggest that there are considerable aerodynamic limitations to further shortening or narrowing of the inlet. Since there are substantial, system level benefits from using a smaller inlet, the case for separated flow control therefore appears clear.
Effects of Periodic Inflow Unsteadiness on the Time-Averaged Velocity Field and Pressure Recovery of a Diffusing Bend With Strong Curvature
Authors: Yaras M. I. , Orsi P.
Published: May 2004

This study examines the effects of periodic inflow unsteadiness on the flow development through fishtail-shaped diffusers utilized on small gas-turbine engines. In this application, periodic unsteadiness is caused by a jet-wake type of flow discharging from each passage of the centrifugal compressor impeller. The study consists of detailed measurements in a large-scale fishtail diffuser rig with a geometry that is typical of those used in small gas-turbine engines. Measurements of the transient velocity field have been performed at five cross-sectional planes throughout the diffuser using a miniature hot-wire probe with four wires. These measurements involve frequencies of inflow unsteadiness corresponding to design as well as off-design operating conditions. Results indicate significant effects of inflow unsteadiness at the low end of the tested frequencies on the time-averaged streamwise and cross-flow velocity fields in the diffuser. This is shown to translate into a notable impact on the pressure recovery. In addition to providing insight into the physics of this flow, the experimental results presented here constitute a detailed and accurate data set that can be used to validate computational-fluid-dynamics algorithms for this type of flow.
Decomposition-Based Assembly Synthesis for Maximum Structural Strength and Modularity
Authors: Cetin O. L. , Saitou K.
Published: May 2004

This study presents a systematic decomposition process to carry out assembly synthesis as a tool during the conceptual design phase of a product. Two configurations obtained by structural topology optimization are decomposed automatically into assemblies consisting of multiple members with simpler geometries. Generating topology graphs for both products, the search for an optimal decomposition can then be posed as a graph partitioning problem. Considering the complexity and the corresponding computational overhead of the problem, a steady-state genetic algorithm is employed as the optimization method. The final objective function attempts to find a solution that brings about two structures with maximum structural strength, maximum assemblability, and one or more components that can be shared by both products. The software implementation is carried out and a bicycle frame design problem is solved using the procedure. It is observed that the algorithm manages to find an acceptable solution, allowing the commonality of one component in both end products and still maintaining a good structural strength and assemblability.
Mesh Phasing Relationships in Planetary and Epicyclic Gears
Authors: Parker R. G. , Lin J.
Published: May 2004

The multiple tooth meshes in planetary and epicyclic gears have varying numbers of teeth in contact under operating speed, and these numbers of teeth all fluctuate at the same mesh frequency. All sun-planet meshes have the same shape and periodicity of variation of numbers of teeth in contact at the multiple meshes, but these variations are, in general, not in phase with each other. The same is true for the ring-planet meshes. Additionally, there is a phase difference between the sun-planet and ring-planet meshes. This work sets out a complete analytical description of each of these mesh phase relationships. Mesh phasing has a dramatic impact on the static and dynamic behavior of planetary and epicyclic gears. This work provides the necessary relationships to properly incorporate mesh phasing in analytical models.
Kinematic Calibration for Redundantly Actuated Parallel Mechanisms
Authors: Jeong Jay il , Kang Dongsoo , Cho Young Man , Kim Jongwon
Published: May 2004

We present a new kinematic calibration algorithm for redundantly actuated parallel mechanisms, and illustrate the algorithm with a case study of a planar seven-element 2-degree-of-freedom (DOF) mechanism with three actuators. To calibrate a nonredundantly actuated parallel mechanism, one can find actual kinematic parameters by means of geometrical constraint of the mechanism’s kinematic structure and measurement values. However, the calibration algorithm for a nonredundant case does not apply for a redundantly actuated parallel mechanism, because the angle error of the actuating joint varies with position and the geometrical constraint fails to be consistent. Such change of joint angle error comes from constraint torque variation with each kinematic pose (meaning position and orientation). To calibrate a redundant parallel mechanism, one therefore has to consider constraint torque equilibrium and the relationship of constraint torque to torsional deflection, in addition to geometric constraint. In this paper, we develop the calibration algorithm for a redundantly actuated parallel mechanism using these three relationships, and formulate cost functions for an optimization algorithm. As a case study, we executed the calibration of a 2-DOF parallel mechanism using the developed algorithm. Coordinate values of tool plate were measured using a laser ball bar and the actual kinematic parameters were identified with a new cost function of the optimization algorithm. Experimental results showed that the accuracy of the tool plate improved by 82% after kinematic calibration in a redundant actuation case.
A Boundary-Blending Method for the Parametrization of 2D Surfaces With Highly Irregular Boundaries
Authors: Chuang Jui-Jen , Yang Daniel C. H.
Published: May 2004

In this paper three methods are used to generate boundary-conformed parametrization of 2D surfaces. They include two conventional approaches, the Coons method and the Laplace method, and a new method, called “boundary-blending method.” In this new method, unidirectional 2D parametrization is achieved based on the geometric information of the given boundary curves. A dual offsetting procedure is adopted. The geometric properties considered for offsettings include position, curvature, and normal of the two facing parent curves. The algorithm contains two adjustable parameters that enable fine-tuning of this parametrization. This unidirectional process can be easily extended to bi-directional parametrization via superposition to include both boundary pairs. Examples show that this algorithm leads to reasonable smooth blending of the boundaries, and the dual process achieves seamless converging at the middle. It is more robust than the Coons method with regard to parametrization anomalies and relieves the relatively large uneven grid distribution problem experienced in the Laplace method. We believe that this method provides a useful alternative for the 2D boundary-conformed parametrization problems.
Workspace Optimization of 3-Legged UPU and UPS Parallel Platforms With Joint Constraints
Authors: Badescu Mircea , Mavroidis Constantinos
Published: May 2004

In this paper the workspace optimization of 3-legged translational UPU and orientational UPS parallel platforms under joint constraints is performed. The workspace of both platforms is parametrized using several design parameters that span a large range of values. In this paper both the unconstrained and the constrained workspaces (i.e., workspace with joint limits) are used. For the workspace of each design configuration three performance indices are calculated using a Monte Carlo method: a) the workspace volume; b) the average of the inverse of the condition number and c) a Global Condition Index which is a combination of the other indices. Plots of each performance index as a function of the design parameters are generated and optimal values for these design parameters are determined. For the optimal design, it is shown that by introducing joint limits, the global isotropy of the parallel platforms is improved at the cost of workspace reduction.