bluuebunny/crossref_metadata_2025 huggingface dataset:
Using different physical activity measurements in eight European countries. Results of the European Physical Activity Surveillance System (EUPASS) time series survey
Authors: Rütten A , Ziemainz H , Schena F , Stahl T , Stiggelbout M , Auweele Y Vanden , Vuillemin A , Welshman J
Published: June 2003

Objectives:

The European Physical Activity Surveillance System (EUPASS) research project compared several physical activity (PA) measures (including the International Physical Activity Questionnaire (IPAQ)) in a time series survey in eight countries of the European Union. The present paper describes first results provided by the different instruments regarding PA participation, frequency and duration, both at the European and national levels. The purpose of the present study is to explore and compare the specific quality and usefulness of different indicators rather than to provide valid and reliable prevalence data. Thus, the main focus is on discussion of the methodological implications of the results presented.

Methods:

A time series survey based on computer-aided telephone interviewing (CATI) was carried out in eight European countries over a six-month period. The study provided for about 100 realised interviews per month in each country (i.e. ~600 per country). Descriptive statistical analysis was used to: (1) report IPAQ results on vigorous, moderate and light PA and sitting, as well as on the overall measure of calories expenditure (MET min−1), in the different countries; (2) compare these results with national PA indicators tested in EUPASS; and (3) compare IPAQ results with other European studies.

Results:

First, the scores for the different PA categories as well as for the overall measure of calories expenditure provided by the IPAQ appeared rather high compared with previous studies and public health recommendations. Second, the different PA measurements used in EUPASS provided completely different results. For example, national indicators used in Germany and The Netherlands to date neither corresponded in absolute values (e.g. means of PA or sitting) nor correlated with the IPAQ in any significant way. Third, comparing EU countries, the ranking for vigorous, moderate and light activities by use of the IPAQ differed from that of other European studies. For example, in the present analysis, German respondents generally showed higher scores for PA than the Finns and the Dutch, while, in contrast, findings from other studies ranked Finland before The Netherlands and Germany.

Conclusions:

The present analysis highlights some methodological implications of the IPAQ instrument. Among other things, differences in overall scores for PA as well as in the ranking of nations between the present results using IPAQ and other measures and studies may partly be due to the concepts of PA behind the measurements. Further analysis should investigate if the range of PA-related categories provided by the IPAQ is fully appropriate to measure all relevant daily activities; it may also consider the public health implications of mixing up different contexts of PA (e.g. work, leisure-time, transportation) in the IPAQ short version.
Ca2+-dependent Binding and Activation of Dormant Ezrin by Dimeric S100P
Authors: Koltzscher Max , Neumann Claudia , König Simone , Gerke Volker
Published: June 2003

S100 proteins are EF hand type Ca2+binding proteins thought to function in stimulus-response coupling by binding to and thereby regulating cellular targets in a Ca2+-dependent manner. To isolate such target(s) of the S100P protein we devised an affinity chromatography approach that selects for S100 protein ligands requiring the biologically active S100 dimer for interaction. Hereby we identify ezrin, a membrane/F-actin cross-linking protein, as a dimer-specific S100P ligand. S100P-ezrin complex formation is Ca2+dependent and most likely occurs within cells because both proteins colocalize at the plasma membrane after growth factor or Ca2+ionophore stimulation. The S100P binding site is located in the N-terminal domain of ezrin and is accessible for interaction in dormant ezrin, in which binding sites for F-actin and transmembrane proteins are masked through an association between the N- and C-terminal domains. Interestingly, S100P binding unmasks the F-actin binding site, thereby at least partially activating the ezrin molecule. This identifies S100P as a novel activator of ezrin and indicates that activation of ezrin's cross-linking function can occur directly in response to Ca2+transients.
RNA Polymerase III Transcripts and the PTB Protein Are Essential for the Integrity of the Perinucleolar Compartment
Authors: Wang Chen , Politz Joan C. , Pederson Thoru , Huang Sui
Published: June 2003

The perinucleolar compartment (PNC) is a nuclear substructure present in transformed cells. The PNC is defined by high concentrations of certain RNA binding proteins and a subset of small RNAs transcribed by RNA polymerase III (pol III), including the signal recognition particle RNA and an Alu RNA as reported here. To determine if the PNC is dependent on pol III transcription, HeLa cells were microinjected with the selective pol III inhibitor, Tagetin. This resulted in disassembly of the PNC, whereas inhibition of pol I by cycloheximide or pol II by α-amanitin did not significantly affect the PNC. However, overexpression of one of the PNC-associated RNAs from a pol II promoter followed by injection of Tagetin blocked the Tagetin-induced PNC disassembly, demonstrating that it is the RNA rather than pol III activity that is important for the PNC integrity. To elucidate the role of the PNC-associated protein PTB, its synthesis was inhibited by siRNA. This resulted in a reduction of the number of PNC-containing cells and the PNC size. Together, these findings suggest, as a working model, that PNCs may be involved in the metabolism of specific pol III transcripts in the transformed state and that PTB is one of the key elements mediating this process.
Survey of the nutritional content of meat products on sale in Scotland from butchers’ shops and multiple retailers
Authors: Matthews Kim , Blades Mabel , Strong Maureen
Published: June 2003

In response to concerns over the role of meat products in the Scottish diet, a study of the nutritional analysis of a range of meat products for sale in Scotland was carried out. The nutritional analysis of products was compared with that in the composition of foods (Royal Society of Chemistry and Ministry of Agriculture, Fisheries, and Food). This indicated a probable reduction in the fat content of some products, such as sausage‐rolls and burgers. It is concluded that more information could be conveyed to consumers on the nutritional value of meat products to enable informed choices to be made based on the value of products in a balanced diet.
Effect of acha (Digitaria exilis staph.) grain flours on the physical and sensory quality of biscuit
Authors: Ayo J.A. , Nkama I.
Published: June 2003

Acha (Digitaria exilis staph.) grain was purchased locally from Jos central market in Plateau State of Nigeria. The grain was washed, destoned, oven (cabinet)‐dried, dry milled, sieved and used as acha grain flour to substitute for wheat flour for the production of biscuit. The physical (spread ratio, break strength, weight) and sensory (colour, taste, odour, texture) qualities of the biscuit were determined. The spread ratio increases (5.95 to 7.33), while the bread strength decreases (1.97 to 1.49) with the increase in the acha grain flour percentage. The effects were generally significant at above 30 per cent substitution (p≤0.05).
Reference collections, reference services, and the change from text to technology
Authors: Sowards Steven W.
Published: June 2003

The transition from printed to digital versions of reference works has important consequences not only for those materials as collections of resources, but also for the ways in which libraries select and use those materials. Users are attracted by the benefits of online tools: remote access, around the clock access, access to multiple copies, and improved searching features. Librarians are aware of the drawbacks: the absence of some content, technical complexity, higher costs, and risks that arise when leased access replaces ownership. Database purchasing decisions may bypass the expertise of subject bibliographers, while aggregators, consortia and grant‐makers play new roles in defining the content of library collections. The technical and mechanical problems associated with databases present new challenges to reference desk staff, and introduce systems staff as partners. Successful engagement with change includes an appreciation of users’ expectations, and a positive attitude.
Culture’s complications: the problem of global data collection in a world of difference
Authors: Hamilton Stuart
Published: June 2003

This paper specifically refers to the problems of data collection within a PhD project where the research is on a global scale. While it can be difficult to collect adequate amounts of data in some subject areas, the area of research covered – libraries and barriers to accessing information resources on the Internet – is overflowing with information sources due to the global scale of the project and the capability of the Internet to provide vast amounts of topical information, especially in a subject area related to itself. The data collection process is further complicated by the variety of disciplines that need to be drawn on in order to create a firm theoretical framework for a study of this scale. This paper looks at the effects of these problems on the data collection process and the attempts made by the author to select a research methodology that will enable analytic generalisation within the theoretical structure.
Raising issues of salaries and status for library/information professionals
Authors: Ashcroft Linda
Published: June 2003

Focuses on the issue of raising the profile and status of librarians, with emphasis on higher salaries and recognition through pay equity. Considers the issues taken up by Mitch Freedman, President of the American Library Association (ALA) and his Campaign for America’s Librarians. Expresses viewpoints on salary issues for librarians/information professionals in the context of the USA and UK, drawn both from an impassioned speech delivered by Mitch Freedman and from the findings of a pay and status survey conducted by The Chartered Institute of Library and Information Professionals (CILIP) and CILIP’s consequent response.
Pb‐free solder bumping for flip chip package by electroplating
Authors: Hwang Hyeon , Hong Soon‐Min , Jung Jae‐Pil , Kang Choon‐Sik
Published: June 2003

Sn‐Pb and Sn‐Ag bumps (130 μm diameter, 250 μm pitch) made using an electroplating process were studied. As a preliminary experiment, the effects of current density and plating time on the Sn‐Pb and Sn‐Ag deposits were investigated. The morphology and composition of the plated surface were examined using scanning electron microscopy. The shape and thickness of the solder bumps were also compared. Bump shear testing was performed to measure the adhesion strength between the solder bumps and the under bump metallurgy. In electroplating, the Sn‐Ag plating thickness was proportional to the current density, while plated Sn‐Pb thickness saturated above the limiting current density. The optimal conditions for solder bump fabrication were found at 6 A/dm2 for 3 h in the case of Sn‐Pb bump plating and 6 A/dm2 for 1 h for the Sn‐Ag bump plating. The bump shear strength for Sn‐Ag was found to be higher than that of Sn‐Pb.
Process characterization of PCB assembly using 0201 packages with lead‐free solder
Authors: Geiger David , Mattsson Fredrik , Shangguan Dongkai , Ong MT , Wong Patrick , Wang Mei , Castello Todd , Yi Sammy
Published: June 2003

0201 assembly plays a very important role in the continuing miniaturization of electronics products. After a systematic study using Sn‐Pb solder paste on pad design, machine evaluation, component qualification, and process optimisation, this study focused on the PCB assembly process for 0201 packages using Sn‐Ag‐Cu solder paste. The post‐reflow solder defects for a range of different spacings were examined for the different solder pastes.
A novel measurement technique for stencil printed solder paste
Authors: Dusˇek Milosˇ , Hunt Christopher
Published: June 2003

The printing process is the most critical step in surface mount assembly. To control and monitor printing, complex instrumentation is available for measuring the print consistency. This paper describes a novel robust method, which introduces critical variables defining print quality. Conventional measurement methods include only the volume and average height of solder paste. The limitations of using just these parameters are discussed and a new method is introduced. In our novel approach, the matrix is levelled first to take account of any tilt in the plane of the substrate surface. Then pseudo‐virtual object parameters are calculated. Major attributes of the proposed measurement method is its insensitivity to both the specific location of the printed deposit and the location of a specific defect. This algorithm, coupled with variables defined in the analysis package, delivers a new and flexible approach to the printed media.
Study of under bump metallisation barrier layer for lead‐free solder
Authors: Chan K.C. , Zhong Z.W. , Ong K.W.
Published: June 2003

The elimination of lead from solders for flip‐chip attachment has necessitated many new studies on the reliability of the resultant systems. There are many lead‐free solder material systems. However, most of them contain a large proportion of tin. The tin in the solder reacts with the copper layer present in some types of under bump metallisation (UBM) depleting the UBM of copper, and thereby causing loss of adhesion and a weak interface. In this work, the relative reliability of Cr/Cu/Cu and Cr/Cu/Cu/Ni UBM systems was studied. The UBM systems were deposited with an electroplated Sn‐3.5Ag lead‐free solder alloy. The results conclusively showed that the Cr/Cu/Cu/Ni UBM system is a better choice for the Sn‐3.5Ag lead‐free solder. In the Cr/Cu/Cu/Ni UBM system, the thickness of the nickel layer was found to be an important parameter. Multiple reflow and high temperature storage test results showed that serious depletion of the UBM layer could occur if the UBM layers were not optimised. The thermo‐mechanical reliability of Ni‐based UBM bumps showed promising results up to 1,500 temperature cycling.
Interaction kinetics between PBGA solder balls and Au/Ni/Cu metallisation during laser reflow bumping
Authors: Tian Yanhong , Wang Chunqing , Zhang Xiaodong , Liu Deming
Published: June 2003

In this paper, the interaction kinetics between eutectic PbSn solder and Au/Ni/Cu metallisation of plastic ball grid array packages during laser reflow bumping were investigated. The effects of processing variables, including laser reflow power and time, on the morphology of the intermetallic compounds formed at the solder/pad interface were studied by scanning electron microscopy and energy dispersive X‐ray spectrometry. Furthermore, dissolution and diffusion of Au and Sn inside the solder bump within the duration of the laser heating was analysed by Auger electron spectroscopy (AES). The results reveal that the morphology of the intermetallic compounds was strongly influenced by the laser input energy. The AES results showed that Au atoms dissolved rapidly into the solder after the solder was melted.
The Elastic-Viscoelastic Correspondence Principle for Functionally Graded Materials, Revisited
Authors: Mukherjee S. , Paulino Glaucio H.
Published: June 2003

Paulino and Jin [Paulino, G. H., and Jin, Z.-H., 2001, “Correspondence Principle in Viscoelastic Functionally Graded Materials,” ASME J. Appl. Mech., 68, pp. 129–132], have recently shown that the viscoelastic correspondence principle remains valid for a linearly isotropic viscoelastic functionally graded material with separable relaxation (or creep) functions in space and time. This paper revisits this issue by addressing some subtle points regarding this result and examines the reasons behind the success or failure of the correspondence principle for viscoelastic functionally graded materials. For the inseparable class of nonhomogeneous materials, the correspondence principle fails because of an inconsistency between the replacements of the moduli and of their derivatives. A simple but informative one-dimensional example, involving an exponentially graded material, is used to further clarify these reasons.
Drilling in Bone: Modeling Heat Generation and Temperature Distribution
Authors: Davidson Sean R. H. , James David F.
Published: June 2003

Thermo-mechanical equations were developed from machining theory to predict heat generation due to drilling and were coupled with a heat transfer FEM simulation to predict the temperature rise and thermal injury in bone during a drilling operation. The rotational speed, feed rate, drill geometry and bone material properties were varied in a parametric analysis to determine the importance of each on temperature rise and therefore on thermal damage. It was found that drill speed, feed rate and drill diameter had the most significant thermal impact while changes in drill helix angle, point angle and bone thermal properties had relatively little effect.
Bending of Cord Composite Laminate Cylindrical Shells
Authors: Paris A. J. , Costello G. A.
Published: June 2003

A theory for the bending of cord composite laminate cylindrical shells is developed. The extension-twist coupling of the cords is taken into account. The general case of a circular cylindrical shell with cord plies at various angles to the shell axis is considered. The differential equations for the displacements are derived. These equations are solved analytically in closed form for a shell subjected to axisymmetric loading and no in-plane tractions. The results of the current study are compared with the commonly used Gough-Tangorra and Akasaka-Hirano solutions.
A Fluid/Solid Model for Predicting Slender Body Deflection in a Moving Fluid
Authors: Mollendorf J. C. , Felske J. D. , Samimy S. , Pendergast D. R.
Published: June 2003

An analytical solution is presented for the steady-periodic shape variation of a thin elastic beam subject to fluid mechanic forces and driven by the motion imposed on its ends. The general solution is applicable to such problems as swim fins and aerodynamic flutter, with the proper choice of boundary conditions. The general results are exemplified here by using specific boundary conditions that mimic the motion of swim fins. The calculated instantaneous shape, position, slopes, and lateral velocities of the fin are compared with corresponding measurements taken from underwater video of fins worn by divers swimming at a controlled speed. The analysis revealed new swim technique parameters that characterize the heel slope and its phase with respect to the heel motion. The calculated power, thrust, and Froude efficiency are presented in terms of these parameters.
Local Solutions in Potential Theory and Linear Elasticity Using Monte Carlo Methods
Authors: Kulkarni S. S. , Mukherjee S. , Grigoriu M. D.
Published: June 2003

A numerical method called the boundary walk method is described in this paper. The boundary walk method is a local method in the sense that it directly gives the solution at the point of interest. It is based on a global integral representation of the unknown solution in the form of potentials, followed by evaluating the integrals in the resulting series solutions using Monte Carlo simulation. The boundary walk method has been applied to solve interior problems in potential theory with either Dirichlet or Neumann boundary conditions. It has also been applied to solve interior problems in linear elasticity with either displacement or traction boundary conditions. Weakly singular integral formulations in linear elasticity, to which the boundary walk method has been applied, are also derived. Finally, numerical results, which are computed by applying the boundary walk method to solve some two-dimensional problems over convex domains in potential theory and linear elasticity, are presented. These solutions are compared with the known analytical solutions (when available) or with solutions from the standard boundary element method.
On the Eshelby’s Inclusion Problem for Ellipsoids With Nonuniform Dilatational Gaussian and Exponential Eigenstrains
Authors: Sharma P. , Sharma R.
Published: June 2003

This work investigates the three-dimensional elastic state of inclusions in which the prescribed stress-free transformation strains or eigenstrains are spatially nonuniform and distributed either in a Gaussian, or an exponential manner. The prescribed eigenstrain distributions are taken to be dilatational. Typical research in the micromechanics of inclusions and inhomogeneities has dealt, by and large, with spatially uniform eigenstrains and, to some limited degree, with polynomial distributions. Solutions to Eshelby’s inclusion problem, where eigenstrains are Gaussian and exponential in nature, do not exist. Such eigenstrain distributions arise naturally due to highly localized point-source type heating (typical in electronic chips), due to compositional differences, and those due to diffusion related mechanisms among others. The current paper provides such a solution for ellipsoidal shaped inclusions located in an infinite isotropic elastic matrix. It is shown, similar to the much-discussed uniform eigenstrain problem, that the elastic state is completely determined in closed form save for some simple one-dimensional integrals that are evaluated trivially using numerical quadrature. For the specialized case of a spherical shape, solutions in terms of known functions are derived and numerical results are presented. The elastic state both within and outside the inclusion is investigated. For the specific case of a sphere, the elastic strain energies are given in terms of simple formulas. Some applications of the current work in various areas such as electronics, micromechanics of composites, and material science are also discussed.
Multiscale, Multiphenomena Modeling and Simulation at the Nanoscale: On Constructing Reduced-Order Models for Nonlinear Dynamical Systems With Many Degrees-of-Freedom
Authors: Dowell E. H. , Tang D.
Published: June 2003

The large number of degrees-of-freedom of finite difference, finite element, or molecular dynamics models for complex systems is often a significant barrier to both efficient computation and increased understanding of the relevant phenomena. Thus there is a benefit to constructing reduced-order models with many fewer degrees-of-freedom that retain the same accuracy as the original model. Constructing reduced-order models for linear dynamical systems relies substantially on the existence of global modes such as eigenmodes where a relatively small number of these modes may be sufficient to describe the response of the total system. For systems with very many degrees-of-freedom that arise from spatial discretization of partial differential equation models, computing the eigenmodes themselves may be the major challenge. In such cases the use of alternative modal models based upon proper orthogonal decomposition or singular value decomposition have proven very useful. In the present paper another facet of reduced-order modeling is examined, i.e., the effects of “local” nonlinearity at the nanoscale. The focus is on nanoscale devices where it will be shown that a combination of global modal and local discrete coordinates may be most effective in constructing reduced-order models from both a conceptual and computational perspective. Such reduced-order models offer the possibility of reducing computational model size and cost by several orders of magnitude.
An Economic Design Change Method
Authors: Roser Christoph , Kazmer David , Rinderle James
Published: June 2003

New product design as well as design revision to remedy defects is complicated by an inability to precisely predict product performance. Designers often find that they are confident about the performance of some design alternatives and uncertain about others. Similarly, alternative design changes may differ substantially in uncertainty, potential impact, and cost. This paper describes a method for including the effects of uncertainty in the evaluation of economic benefits of various design change options. The results indicate that the most profitable change option sequence depends not only on relative costs but also on the relative degree of uncertainty and on the magnitude of the potential design defects. The method demonstrates how design change alternatives can be compared using the engineering design of a beam. Finally, the validity of some common engineering change heuristics are discussed relative to their associated, quantitatively determined limits.
The Computation of All 4R Serial Spherical Wrists With an Isotropic Architecture
Authors: Chablat Damien , Angeles Jorge
Published: June 2003

A spherical wrist of the serial type with n revolute (R) joints is said to be isotropic if it can attain a posture whereby the singular values of its Jacobian matrix are all equal to n/3. What isotropy brings about is robustness to manufacturing, assembly, and measurement errors, thereby guaranteeing a maximum orientation accuracy. In this paper we investigate the existence of redundant isotropic architectures, which should add to the dexterity of the wrist under design by virtue of its extra degree of freedom. The problem formulation, for n=4, leads to a system of eight quadratic equations with eight unknowns. The Bezout number of this system is thus 28=256, its BKK bound being 192. However, the actual number of solutions is shown to be 32. We list all solutions of the foregoing algebraic problem. All these solutions are real, but distinct solutions do not necessarily lead to distinct manipulators. Upon discarding those algebraic solutions that yield no new wrists, we end up with exactly eight distinct architectures, the eight corresponding manipulators being displayed at their isotropic postures.
Optimal Kinematic Design of Spatial Parallel Manipulators: Application to Linear Delta Robot
Authors: Stock Michael , Miller Karol
Published: June 2003

An optimal kinematic design method suited for parallel manipulators is developed. The kinematic optimization process yields a design that delivers the best compromise between manipulability and a new performance index, space utilization. It is shown that the exhaustive search minimization algorithm is effective for as many as four independent design variables and presents a viable alternative to advanced nonlinear programming methods. The proposed kinematic optimization method is applied to the Linear Delta: a three degree of freedom translational manipulator. The kinematics of the Linear Delta are solved via the polynomial method. The mobility, workspace and manipulability characteristics are examined. It is shown that the Linear Delta’s manipulability generally exhibits relatively little variation when compared to space utilization. The tendency exists for the solution to converge on a zero workspace size architecture when manipulability is optimized alone. The inclusion of the space utilization index in the cost function is crucial for obtaining realistic design candidates.
Robustness Evaluation for Compliant Assembly Systems
Authors: Hu S. J. , Webbink R. , Lee J. , Long Y.
Published: June 2003

A new method for evaluating the robustness of compliant assembly systems is developed based on previously developed variation simulation models. This method can be used for selecting a robust assembly system at product/process development stage. Examples are presented to illustrate the proposed method.
Freeform Skeletal Shape Optimization of Compliant Mechanisms
Authors: Xu Dong , Ananthasuresh G. K.
Published: June 2003

Compliant mechanisms are elastic continua used to transmit or transform force and motion mechanically. The topology optimization methods developed for compliant mechanisms also give the shape for a chosen parameterization of the design domain with a fixed mesh. However, in these methods, the shapes of the flexible segments in the resulting optimal solutions are restricted either by the type or the resolution of the design parameterization. This limitation is overcome in this paper by focusing on optimizing the skeletal shape of the compliant segments in a given topology. It is accomplished by identifying such segments in the topology and representing them using Bezier curves. The vertices of the Bezier control polygon are used to parameterize the shape-design space. Uniform parameter steps of the Bezier curves naturally enable adaptive finite element discretization of the segments as their shapes change. Practical constraints such as avoiding intersections with other segments, self-intersections, and restrictions on the available space and material, are incorporated into the formulation. A multi-criteria function from our prior work is used as the objective. Analytical sensitivity analysis for the objective and constraints is presented and is used in the numerical optimization. Examples are included to illustrate the shape optimization method.
A Family of 3-DOF Translational Parallel Manipulators1
Authors: Carricato Marco , Parenti-Castelli Vincenzo
Published: June 2003

This article addresses parallel manipulators with fewer than six degrees of freedom, whose use may prove valuable in those applications in which a higher mobility is uncalled for. In particular, a family of 3-dof manipulators containing only revolute joints or at the most revolute and prismatic ones is studied. Design and assembly conditions sufficient to provide the travelling platform with a pure translational motion are determined and two sub-families that fulfill the imposed constraint are found: one is already known in the literature, while the other is original. The new architecture does not exhibit rotation singularities, i.e., configurations in which the platform gains rotational degrees of freedom. A geometric interpretation of the translation singularities is provided.
A New Photoelastic Investigation of the Dynamic Bending Stress of Spur Gears
Authors: Wang Ming-Jong
Published: June 2003

In this paper, the maximum tensile bending stress (MTBS) and the critical point in the root fillet of spur gear tooth during transmission are determined by a digital photoelastic system involving real time imaging. The behavioral characteristics of the bending stresses of the gear tooth are analyzed at different rotation speeds, transmitted torques, and contact points. Then, the dynamic effects, the various critical points and the maximum tensile bending stresses are compared experimentally and theoretically, and discussed. Finally, the best approaches for determining the maximum bending stress and its position in the root fillet of spur gear tooth are recommended.
Kinematic Analysis of a Novel Translational Platform
Authors: Callegari Massimo , Tarantini Matteo
Published: June 2003

A new three-d.o.f. parallel mechanism, with 3-RPC topology, is presented in the paper and its kinematics is studied. The proposed architecture, if proper geometrical conditions are satisfied, has an overconstrained structure which allows motions of pure translation. The simple structure of the mechanism allows finding closed-form solutions for both inverse and direct position kinematics; the differential analysis has been developed as well, by deriving a symbolic expression for the Jacobian matrix. Then, some design considerations are exposed to keep the singular points out of the working space of the mechanism and all the isotropic configurations are eventually identified.
A Method for Representing the Configuration and Analyzing the Motion of Complex Cable-Pulley Systems
Authors: Hong Dennis W. , Cipra Raymond J.
Published: June 2003

In this paper a systematic way of representing complex cable-pulley mechanism configurations and a method to analyze their motion is presented. This technique can also be used as an aid for synthesis. The cable-pulley system model that is being considered is planar and composed of three basic elements which are pulleys, blocks, and cables. A configuration table is used to identify the constraint equations by systematically defining the connections between the cables, pulleys, and blocks. The basic strategy is to use the constraint equations to generate the relationship between each variable and a subset of the variables identified as the inputs. A row reduction process on the system of constraint equations identifies the number of inputs and ultimately generates the relationships of each variable to the input(s). Results with different input variables can be easily obtained by a simple column interchange process. Examples are given to illustrate the procedure.
Strategies for Modeling Friction in Gear Dynamics
Authors: Vaishya Manish , Singh Rajendra
Published: June 2003

Sliding friction between meshing teeth is one of the primary excitations for noise and vibration in geared systems. Yet, there exist very limited studies on this topic. This paper proposes new modeling strategies for incorporating friction in the dynamic analysis of a gear pair. First, some tribological issues are discussed for estimation of the friction forces under different operating conditions. Second, modeling procedures and results are compared for linear time-invariant, linear time-varying and non-linear time-varying formulations. Criteria such as energy balance, system complexity and desired solution methodology are discussed. Finally, sample results from the various analyses along with their benefits and limitations are examined.
Influence of Idler on Transmission Error in Synchronous Belt Drives (Under Transmission Force)
Authors: Makita Kenichi , Kagotani Masanori , Ueda Hiroyuki , Koyama Tomio
Published: June 2003

Synchronous belt drives are widely used in various machines in order to transmit rotation accurately and synchronously. In these machines, idlers are commonly used to increase the angle of contact on the pulley and to avoid obstacles. However, the generating source of the transmission error under a transmission force with an idler remains unclear. In the present study, transmission error over a period of one pitch of the pulley was investigated both theoretically and experimentally for a synchronous belt drive attached an idler when a transmission force acted on the belt span. The experimental results agree closely with the computed results. The transmission error is greatly affected by change in the meshing state in the incomplete meshing sections. The idler position at which the transmission error is reduced exists even if the transmission torque increases. In addition, transmission error is reduced when the helix angle is increased.
Position Analysis of a New Family of 3-DOF Translational Parallel Manipulators*
Authors: Carricato Marco , Parenti-Castelli Vincenzo
Published: June 2003

This article presents the position analysis of a new family of 3-limbed 3-dof parallel manipulators, whose output links exhibit a motion of pure translation with respect to the base. Each limb contains four passive revolute joints and an active prismatic pair, which can be mounted anywhere along the kinematic chain or replaced by a fifth revolute one. A univariate polynomial has been found that solves the direct position problem wherever the actuators are placed. The inverse analysis has been carried out in closed-form for all possible locations of the actuated joints. Finally, numerical examples are provided.
Identifying Modular and Integrative Systems and Their Impact on Design Team Interactions
Authors: Sosa Manuel E. , Eppinger Steven D. , Rowles Craig M.
Published: June 2003

The typical approach to developing complex products is to decompose the product into systems, and these into components. We introduce a new notion of system modularity based upon the way components share design interfaces across systems. Modular systems are those whose design interfaces with other systems are clustered among physically adjacent systems, whereas integrative systems are those whose interfaces are physically distributed or functionally integrative across all or most other systems. Our research method allows us to study how system modularity impacts design team interactions. Our approach is illustrated by analyzing the development of an aircraft engine.
Under-Actuated Kinematic Structures for Miniature Climbing Robots
Authors: Minor Mark A. , Mukherjee Ranjan
Published: June 2003

This paper presents two biped designs for miniature climbing robots. The designs use under-actuation to satisfy space and weight constraints. In the first design, one actuator provides steering and another two propel the robot in a cartwheel style gait. The cartwheel gait is quite effective but space required for the maneuver precludes certain applications. The limitation is overcome in the second design, which uses under-actuation to provide two different forms of locomotion. It uses a crawling stride in confined environments and a faster pivoting gait in open environments. Such adaptability is achieved without increasing the number of actuators. Both robots have been built and have successfully demonstrated their mobility and maneuverability.
Mathematical Model and Surface Deviation of Helipoid Gears Cut by Shaper Cutters
Authors: Wu Jun-Long , Liu Chia-Chang , Tsay Chung-Biau , Nagata Shigeyoshi
Published: June 2003

Crossed-axis helical gears and hypoid gears are two conventional crossed-axis power transmission devices. Helipoid gears, a novel gear proposed herein, possess the merits of the crossed-axis helical and hypoid gears. A mathematical model of the proposed helipoid gear cut by shapers is also derived according to the cutting mechanism and the theory of gearing. The investigation shows that the tooth surface varies with the number of teeth of the shaper. Computer graphs of the helipoid gear are presented according to the developed gear mathematical model, and the tooth surface deviations due to the number of teeth of the shaper are also investigated.
Damage Identification of a Gear Transmission Using Vibration Signatures
Authors: Choy F. K. , Mugler D. H. , Zhou J.
Published: June 2003

Important advancements in preventive maintenance of rotor-craft gear transmission systems are currently being sought for the development of an accurate machine health diagnostic system. Such a diagnostic system would use vibration or acoustic signals from the gear transmission system for (1) rapid on-line evaluation of gear wear or damage status, and (2) prediction of remaining gear life. Such health diagnostic capabilities would be essential for effective machine event/life management and advance warning before critical component failures. This paper demonstrates the use of vibration signature analysis procedures for health monitoring and diagnostics of a gear transmission system. The procedures used in this paper include

(i) the numerical simulation of the dynamics of a gear transmission system with single and multiple tooth damage,

(ii) the application of the Wigner-Ville Distribution (WVD) and the Wavelet transform in damage identification and quantification of damaged tooth based on the numerically generated vibration signal, and

(iii) the application of both WVD and the Wavelet transform on experimental data at various stage of gear failure obtained from an accelerated gear damage test rig. This paper demonstrates that the developed signature analysis procedure can successfully detect faulty gears in both numerically simulated and experimental tested transmission system. General conclusions on identification and quantification of gear tooth damage are drawn based on the results of this study.
Kinematic Condition Analysis of Three-DOF Pure Translational Parallel Manipulators
Authors: Kim Doik , Chung Wan Kyun
Published: June 2003

Several 3-DOF pure translational parallel manipulators have been reported recently. However, kinematic conditions of such translational parallel manipulators have not been studied deeply. Most previously reported translational parallel manipulators were analyzed by considering constraints on the motion of an independent leg. In addition to the constraints of independent legs, the effect of the constraints on an overall mechanism are analyzed in this paper. The overall kinematic constraints are explained by introducing the restriction of motion, which is a constraint that prohibits a manipulator from moving in a certain region or direction, instantaneously. By introducing it, kinematic constraints can be embedded explicitly in the formulation of rate kinematics, and by analyzing it, constraints for a desired motion can be found. This paper derives constraints for pure translational motion in a systematic way. Necessary and sufficient conditions are suggested and several translational parallel manipulators with their kinematic features are provided.
Computational Fluid Dynamics Performance Estimation of Turbo Booster Vacuum Pump
Authors: Cheng H.-P. , Chen , C.-J. , Cheng , P.-W.
Published: June 2003

The CFD performance estimation of turbo booster vacuum pump shows the axial vortex and back flow is evident when the mass flow rate is increased. The pressure is increased from the pump inlet to the outlet for the low mass flow rate cases. But for high mass flow rate cases, the pressure is increased until the region near the end of the rotor then decreased. The calculated inlet pressure, compression ratio, and pumping speed is increased, decreased, and decreased, respectively, when the mass flow rate is increased. The pumping speed is increased when the rotor speed is increased.
Oxidation Effect on the Monosized Droplets Generation of the Liquid Metal Jet
Authors: Lai Wei-Hsiang , Chen Chia-Chin
Published: June 2003

The oxide formation on the surface of the molten metal jet was shown to have a drastic effect on the droplet formation process according to the description of some publication. Thus, the main objective of this research is to investigate the influence of oxygen concentration on the breakup and the monosized droplets generation of molten metal jet (Sn63 Pb37 alloy). The breakup phenomena of molten metal jet can be approximately divided into three regimes. They are “breakup regime” for oxygen concentration below C1, “transition regime” for oxgyen concentration between C1 and C2, and “breakup failing regime” for oxygen concentration beyond C2, respectively.
The Shear Layers of a Two-Dimensional Jet Excited by Flexible Wires
Authors: Yu Ming-huei , Liao Yi-chun , Tseng Chung-ho
Published: June 2003

A two-dimensional air jet, heated at a density ratio of 0.8, under external forcing by flexible wires is investigated experimentally. In each shear layer of the hot jet flow, a wire of diameter 0.23 mm (0.015 jet width) is flexibly mounted along the spanwise direction. By flow visualization, temperature measurements, and spectral analysis, the study demonstrates that the wires have quite different effects on the jet flow depending on that the wires are motionless or vibrating in the flow, and the shear layers of the heated plane jet can be manipulated by means of flexible wires.
Large Eddy Simulation of Flow in a Stirred Tank
Authors: Yoon H. S. , Balachandar S. , Ha M. Y. , Kar K.
Published: June 2003

Here we report on results obtained from large eddy simulations of flow inside a stirred tank performed using a spectral multidomain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius. Stereoscopic PIV measurements along with a theoretical model are used in defining the impeller-induced flow as a superposition of circumferential, jet and tip-vortex pair components. Both time-independent (fixed inflow) and time-dependent (oscillatory inflow) impeller-induced flows were considered. In both cases, the improved impeller-induced inflow allowed for the development of tip-vortex pairs in the interior of the tank. At Rem=4000 considered here, the flow in the interior of the tank naturally evolves to a time-dependent turbulent state. The jet component of the impeller-induced flow becomes unstable and shows signs of both sinuous and varicose behavior. The vortex pairs are anchored near the blades, but as they extend outwards into the tank their backbones exhibit time-dependent fluctuation. The instability of the jet is intimately connected with the fluctuation of the tip-vortex system. The time-averaged location of the vortex backbone compares well with previous measurements. The radial profile of θ-averaged radial velocity along the midplane is a good sensitive measure for evaluating the computed results. It is observed that computed flow from the 20 deg oscillatory impeller-induced inflow model compares well with the corresponding experimental measurements on the r-z plane.
The Spatial Stability of Natural Convection Flow on Inclined Plates
Authors: Tumin Anatoli
Published: June 2003

The spatial stability of a natural convection flow on upward-facing, heated, inclined plates is revisited. The eigenvalue problem is solved numerically employing two methods: the collocation method with Chebyshev polynomials and the fourth-order Runge-Kutta method. Two modes, traveling waves and stationary longitudinal vortices, are considered. Previous theoretical models indicated that nonparallel effects of the mean flow are significant for the vortex instability mode, but most of them ignored the fact that the eigenfunctions are dependent on the streamwise coordinate as well. In the present work, the method of multiple scales is applied to take the nonparallel flow effects into consideration. The results demonstrate the stabilizing character of the nonparallel flow effects. The vortex instability mode is also considered within the scope of partial differential equations. The results demonstrate dependence of the neutral point on the initial conditions but, farther downstream, the results collapse onto one curve. The marching method is compared with the quasi-parallel normal mode analysis and with theoretical results including correction to nonparallel flow effects. The marching method provides better agreement of theoretical and experimental growth rates.
Sensitivity Evaluation of a Transport-Based Turbulent Cavitation Model
Authors: Vaidyanathan Rajkumar , Senocak Inanc , Wu Jiongyang , Shyy Wei
Published: June 2003

A sensitivity analysis is done for turbulent cavitating flows using a pressure-based Navier-Stokes solver coupled with a phase volume fraction transport model and nonequilibrium k-ε turbulence closure. Four modeling parameters are assessed, namely, Cε1 and Cε2, which directly influence the production and destruction of the dissipation of turbulence kinetic energy, and Cdest and Cprod, which regulate the evaporation and condensation of the phases. Response surface methodology along with design of experiments is used for the sensitivity studies. The difference between the computational and experimental results is used to judge the model fidelity. Under noncavitating conditions, the best selections of Cε1 and Cε2 exhibit a linear combination with multiple optima. Using this information, cavitating flows around an axisymmetric geometry with a hemispherical fore-body and the NACA66(MOD) foil section are assessed. Analysis of the cavitating model has identified favorable combinations of Cdest and Cprod. The selected model parameters are found to work well for different geometries with different cavitation numbers for attached cavity. It is also confirmed that the cavitation model parameters employed in the literature are within the range identified in the present study.