bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of tin‐lead balled BGAs soldered with lead‐free solder paste
Authors: Tapani Nurmi Sami , Olavi Ristolainen Eero
Published: October 2002

This paper will describe tests of the interconnect reliability of BGA components with tin‐lead bumps soldered with lead‐free solder paste during temperature cycling. Tin‐lead BGA components soldered with tin‐lead solder paste and lead‐free BGA components soldered with lead‐free solder paste were used as a reference. The lead‐free solder used was eutectic tin‐silver‐copper. Two kinds of surface finishes were used on the printed circuit boards (PCB), an immersion gold over electroless nickel and an organic solderability preservative. The test PCBs were temperature‐cycled for 2500 cycles in the range of −40°C to +125°C and they were continuously electrically monitored during the cycling. The results of the temperature cycling test showed that lead‐ containing BGA components soldered with lead‐free solder paste don't show any serious reliability risks and can actually withstand temperature cycling stresses better than entirely lead‐free BGA assemblies.
Critical success factors for SPC implementation in UK small and medium enterprises: some key findings from a survey
Authors: Rungasamy Selvan , Antony Jiju , Ghosh Sid
Published: October 2002

There is no doubt that quality has become a major feature in the survival plan of many organisations today. Statistical process control (SPC) is a powerful technique for monitoring, managing, analysing and improving the process performance through the use of statistical methods. In this paper, the implementation of SPC is examined and analysed, based on a survey of 33 manufacturing small and medium enterprises (SMEs). The results presented here are focused on 12 critical success factors (CSFs) identified from the literature. The results of the analysis have shown that the critical success factors, in order of importance, are: management commitment, process prioritisation, control charting, teamwork, measurement system evaluation and so on. Moreover, this research has revealed that the least important factor is the use of pilot study in SMEs.
The innovation challenges of proactive cannibalisation and discontinuous technology
Authors: Cravens David W. , Piercy Nigel F. , Low George S.
Published: October 2002

Innovation is central to modern competition and yet many executives are wary of the risks of cannibalisation of their existing product and service sales through inappropriate innovation. However, the impact of discontinuous technological change is fundamental, and the risks to established companies from not innovating to compete with disruptive technologies are substantial. Many of the arguments which tended towards avoiding cannibalisation are increasingly invalid as a basis for strategic decisions. We propose a framework of proactive cannibalisation that responds to changing customer value, as part of the process for building appropriate innovation strategies for the new competitive and technological environment faced by companies. We provide a framework for managers to evaluate the drivers of successful innovations in developing their strategies.
Nerves for smart clothing – optical fibre sensors and their responses
Authors: Tao Xiaoming
Published: October 2002

Deals with the optical responses of fibre Bragg grating (FBG) sensors under different modes of deformation. It derives both the polarisation states and reflection spectra of FBGs based on coupled mode equations by considering the deformation perturbations. It conducts numeric simulations, finds that the experimental results agree well with the simulated ones for normal germano‐silicate FBGs under different individual modes of deformations.
Significant impacts and environmental risks generated by coal extraction in Romania
Authors: Radulescu Monica , Buia Grigore
Published: October 2002

The paper presents a sequential approach regarding the environmental management in the coal basin of the Jiu Valley. Mining activity in the Jiu Valley has an important impact both in environmental and socio‐economic terms. The main problem these days is identifying the correct and significant impacts of the mining activity, defining also the ways to mitigate and monitor the process associated with coal extraction. Romania, a country experiencing a lack of tradition regarding very strict environmental legislation, has made important efforts in focusing, identifying and possibly resolving the environmental problems associated with mining activity, particularly coal mining in the Jiu Valley. The paper also presents some western European regulations adapted to the specific conditions in a country with a transitory state of the economy.
New methods for human reliability analysis
Authors: Bley Dennis
Published: October 2002

A wide variety of methods for human reliability analysis have been developed. A major thrust has been to quantify the chance of human error within probabilistic risk analysis. However, when compared with human unsafe acts in real events (especially human actions that lead to serious accidents), current analyses appear deficient. The character of the real events is decidedly different than the results of analysis. New, second generation methods have been developed in recent years (CREAM, ATHEANA, MERMOS and others). These methods view the context in which the human must operate as a critical element. Search schemes have been developed to identify potentially challenging contexts (often beyond those normally considered in risk analysis). New methods for quantification are evolving.
On safety risks during underground coalmine closure
Authors: Michaylov Michael
Published: October 2002

This paper discusses the dynamics of safety risks during the first period of coalmine closure and suggests an approach for general and detailed assessment of risks using data from statistical analyses and expert estimation of frequency rise and origination of new risks, specific for the period of closure. Conclusions and considerations are supported by data about real mining sites in the period of planning their closure.
Mentoring school governance and management
Authors: Macpherson Reynold J.S. , McKillop Ann
Published: October 2002

The aim of the research project reported here was to evaluate the process and outcomes of the in‐depth training programme provided to primary and secondary schools’ boards of trustees by the Far North Rural Education Assistance Programme (REAP) in New Zealand. Practical research questions were developed from an analysis of the policy context and programme contracts. The international research literature on mentoring and effective support programmes was then examined. Data were collected using four methods: documentary analysis; case studies of eight selected school communities; a survey of all members of 24 participating boards’ of trustees; and a focus group interview of programme consultants. Construct validity, multiple data types and sources, reasonable survey response rates, bias control strategies and triangulation permitted tentative conclusions and provisional recommendations to be drawn. It was found that the REAP scheme was valued for three main reasons; it built governance capacity in school communities; delivered “free”, appropriately‐scaled, culturally sensitive and customized support on‐site; and it improved the ability of schools to self‐manage improvements. It was also found that the Far North REAP Office played a key role in conceptualizing, developing, brokering and managing these board mentoring services, and developed a model of brokerage that might be usefully replicated through the Ministry of Education’s contracting processes.
European retail journals: a bibliometric analysis
Authors: Findlay Anne , Sparks Leigh
Published: October 2002

The 1990s have seen a major expansion in both the interest in retailing as an academic research subject and in the availability of European retail academic journals. Using a bibliometric approach, this paper investigates the development of published academic retail research in these journals. It identifies different emphases within the retail journals and retail research. Overall, however, retailing is identified increasingly as a synthetic rather than an interdisciplinary subject. A gulf between the direction that European scholars and US scholars are following is considered.
Woman and information systems development: not just a pretty (inter)face?
Authors: Woodfield Ruth
Published: October 2002

The paper reviews literature that claims that for the first two decades of its existence, the computer industry was insular, esoteric and disproportionately populated by men. It cites feminist and industry commentary that claims that these sub‐cultural features have had a negative impact on information systems (IS∥ development, and that because they possess more rounded profiles ‐‐ typically possessing both social as well as technical skills ‐‐ the advent of more women into the sector would lead to improvements in design and golden opportunities for female developers. The paper discusses qualitative interview data elicited from developers designed to assess the likelihood of these predictions holding true. Specifically, it discusses the common‐sense discourses deployed to represent male and female workers’ social and technical skills. It concludes that the processes whereby both types of skills are recognised are highly complex and that such processes often privilege male workers and their competencies, so that we should remain sceptical of any over‐optimistic predictions that a shift in the quantities of women undertaking IS work will automatically lead to a shift in the qualitative nature of such systems and the contexts within which they are produced.
Political scenarios: the future of the North Cyprus tourism industry
Authors: Altinay Levent , Altinay Mehmet , Bicak Hasan Ali
Published: October 2002

The North Cyprus tourism industry has been sensitive to the political instability on the island, which has arisen from the political problems between the Turkish and Greek Cypriots. Economic integration with Turkey and federation with the Greek Cypriots are considered to be two alternative political solutions. This paper evaluates the possible impacts of these two political scenarios on the tourism industry of North Cyprus by using semi‐structured interviews with experts and senior managers. Findings suggest that although economic integration has already been implemented to an extent, it has not contributed to the development of the tourism industry of North Cyprus as hoped. A federal solution to the Cyprus problem is expected to have a more favourable impact on the tourism industry of North Cyprus. Thus, long‐term benefits of the North Cyprus tourism industry lie with a federal solution to the Cyprus problem.
Unique training: the mood indicator is an employee’s tool
Authors: Wildes Vivienne J.
Published: October 2002

Unique training methods help to attract and retain career minded hospitality service professionals at The Inn at Little Washington, one of America’s top rated inns and restaurants. Professional development is discussed as it relates to teaching servers how to “read the customer” and to create teamwork. The mood indicator is explained as an example of providing employees with a tool to make the dining experience exceptional.
Effect of outlet positions and various turbulence models on mixing in a single and multi strand tundish
Authors: Jha Pradeep K. , Dash Sukanta K.
Published: October 2002

The Navier‐Stokes equation and the species continuity equation have been solved numerically in a boundary fitted coordinate system comprising the geometry of a large scale industrial size tundish. The solution of the species continuity equation predicts the time evolution of the concentration of a tracer at the outlet of a single strand bare tundish. The numerical prediction of the tracer concentration has been made with three different turbulence models; (a standard k‐ε, a k‐ε RNG and a Low Re number Lam‐Bremhorst model) which favorably compares with that of the experimental observation for a single strand bare tundish. It has been found that the overall comparison of k‐ε model with that of the experiment is better than the other two turbulence models as far as gross quantities like mean residence time and ratio of mixed to dead volume are concerned. However, it has been found that the initial transient development of the tracer concentration is best predicted by the Lam‐Bremhorst model and then by the RNG model. The k‐ε model predicts the tracer concentration much better than the other two models after the initial transience (t>40 per cent of mean residence time) and the RNG model lies in between the k‐ε and the Lam‐Bremhorst one. The numerical study has been extended to a multi strand tundish (having 6 outlets) where the effect of outlet positions on the ratio of mix to dead volume has been studied with the help of the above three turbulence models. It has been found that all the three turbulence models show a peak value for the ratio of mix to dead volume (a mixing parameter) when the outlets are placed 200 mm away from the wall (position‐2) thus signifying an optimum location for the outlets to get highest mixing in a given multi strand tundish.
New directions in managing women’s trade union careers: online learning
Authors: Kirton Gill , Greene Anne‐marie
Published: October 2002

This article is concerned with strategies for managing the careers of women who work in paid positions in the union movement. Recently there has been some debate about the positive potential offered by the use of ICTs in a variety of areas of trade union activity. We link this to debates about the role of trade union education in developing women’s careers within trade unions by exploring the experiences of participants on a recent British Trades Union Congress (TUC) online course for women. The study suggests that the potentialities of ICTs in this sphere of trade union activity are mediated by a number of gendered constraints.
Corporate governance and the development of global capital markets
Authors: Davies Howard
Published: October 2002

In this article, drawn from a speech Howard Davies made to the Securities regulatory Commission in China, the author contrasts the efforts which are being made in developing economies like China with the more established regulatory regimes like those of the UK and the USA. He argues that good corporate governance brings greater investment but there are important disciplines which ensure the strength of corporate governance and which must be firm but evolving to ensure success.
Corporate treasurers: an ally to treasure
Authors: Raeburn Richard
Published: October 2002

The author argues that in difficult times for risk and corporate governance the corporate treasurer is increasingly the most valuable source of information for non‐executive directors. Risk is at the heart of the work of the corporate treasurer. This is particularly true in financial services industries.
Unbundling the local network and the incentives for broadband investment
Authors: Sandbach Jonathan , Durnell Chris
Published: October 2002

The US government is considering removing regulations on ILECs (incumbent local exchange carriers) with respect to local access services, through the implementation of legislation. These regulations imposed through the US 1996 Telecommunication Act, include local network unbundling and TELRIC pricing, and, in our view, set the correct economic incentives for efficient investment in the telecommunications industry, and industries using telecommunication services. Critics argue that unbundling requirements and TELRIC pricing are negatively affecting investment incentives of the ILECs. This paper uses empirical data to study the causes of varying degrees of DSL take‐up in Western Europe and the US. The analysis shows that, rather than disincentivising incumbent investment, local network unbundling actually provides a competitive stimulus for incumbents to achieve higher rates of take‐up for their own DSL services. Any departure from unbundling and TELRIC prices would protect ILECs against competition in downstream services, and dampen incentives for efficient service provision.
Definitions and frameworks for environmental sustainability in higher education
Authors: Wright Tarah S.A.
Published: October 2002

This paper reviews definitions and frameworks for sustainability in higher education by examining a set of major national and international declarations and institutional policies related to environmental sustainability in universities. It identifies emerging themes and priorities, and discusses how these declarations and policies are affecting various institutions in how they frame the central task of becoming sustainable and how they perceive their own commitment to sustainability.
The perception and administrative effect of Internet usage in Jordanian university libraries
Authors: Razeq Mustafa Younis Abdul
Published: October 2002

Reviews the extent of Internet utilisation in Jordanian university libraries. Discusses: its use, benefits, services, and applications; the effect on acquisitions, the libraries’ organisational structure, administration, cost, and services; problems and solutions. The study investigated 13 libraries linked to the Internet. They employ it for technical functions, information services, and Web pages. Head librarians perceive the Internet as a supplement to libraries’ collections, as a substitute for databases on CD‐ROMs, and a way of saving on subscription charges for printed journals, but not as a replacement for printed books. They perceive the Internet’s main administrative effect is on staff’s satisfaction, motives, speed and ease of services, users’ satisfaction, and turnouts, but it has the least effect on libraries’ budgets. Lack of experience, misconceptions about the Internet, misuse of Web sites, information inauthenticity, censorship, copyright, insufficient high quality terminals, and language problems are, inter alia, prime reasons limiting the optimal use of the Internet.
Versatile cloning system for construction of multimeric proteins for use in atomic force microscopy
Authors: Steward Annette , Toca‐Herrera José Luis , Clarke Jane
Published: October 2002

This manuscript introduces a versatile system for construction of multimeric proteins to be used as substrates for atomic force microscopy. The construction makes use of a cassette system that allows modules to be cut and ligated in any combination in eight different positions. The modules can be sequenced in situ after construction. A three‐module fragment can be produced that is of a size amenable to structural and biophysical analysis to check the effect of placing a protein into a multimeric construct. We show that if the parent titin modules are retained in a construct, they can act both as linkers and as an internal standard for the force measurements. Proteins that cannot be expressed solubly in an eight‐module homopolymer have been expressed and subject to force measurements using this system.
Structural and dynamic properties of water around acetylcholinesterase
Authors: Henchman Richard H. , McCammon J. Andrew
Published: October 2002

Structural and dynamic properties of water molecules around acetylcholinesterase are examined from a 10‐nsec molecular dynamics simulation to help understand how the protein alters water properties. Water structure is broken down into hydration sites constructed from the water density <3.6 Å from the protein surface. These sites are characterized according to occupancy, number of water neighbors, hydrogen bonds, dipole moment, and residence time. The site description provides a convenient means to describe the extent and localization of these properties. Determining the network of paths that waters follow from site to site and measuring the rate of flow of waters from the sites to the bulk make it possible to quantitatively study the time scales and paths that water molecules follow as they move around the protein.
Fourier–Jacobi Type Spherical Functions for PJ‐Principal Series Representations of Sp(2, R)
Authors: Hirano Miki
Published: October 2002

The paper studies a generalized spherical function, or a generalized Whittaker model for generalized principal series representations of G=Sp(2, R) induced from the Jacobi maximal parabolic subgroup PJ, which is called the Fourier–Jacobi type. In particular, a multiplicity theorem and an explicit formula via the Meijer G‐functions for this function are given.
Intersections of Symbolic Powers of Prime Ideals
Authors: Sather-Wagstaff Keri Ann
Published: October 2002

Let (R,m) be a local ring with prime ideals p and q such that . If R is regular and contains a field, and dim(R/p)+dim(R/q)=dim(R), then it is proved that p(m) ∩ q(n) ⊆ mm+n for all positive integers m and n. This is proved using a generalization of Serre's Intersection Theorem which is applied to a hypersurface R/fR. The generalization gives conditions that guarantee that Serre's bound on the intersection dimension (R/p)+(R/q)⩽dim(R) holds when R is nonregular.
Antibound States and Exponentially Decaying Sturm–Liouville Potentials
Authors: Eastham M. S. P.
Published: October 2002

We consider the Sturm–Liouville equation

y″(x)+{λ−q(x)}y(x)=0 (0⩽x<∞) (1.1)

with a boundary condition at x = 0 which can be either the Dirichlet condition

y(0)=0 (1.2)

or the Neumann condition

y′(0)=0 (1.3)

As usual, λ is the complex spectral parameter with 0 ⩽ arg λ < 2π, and the potential q is real‐valued and locally integrable in [0, ∞).
Toe flexor muscle spindle discharge and stretch modulation during locomotor activity in the decerebrate cat
Authors: Murphy P. R. , Pearson K. G. , Stein R. B.
Published: October 2002

In order to investigate the nature (i.e. static or dynamic) of fusimotor drive to the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) muscles during locomotion we recorded Ia and group II muscle spindle afferent responses to sinusoidal stretch (0.25 and 1 mm amplitude, respectively, 4–5 Hz) in a decerebrate cat preparation. FHL Ia and group II afferents generally had increased discharge rates and decreased modulation to stretch throughout the step cycle, compared to rest, suggesting raised static γ drive at all locomotor phases. Although the modulation of Ia afferents was reduced during locomotion, most (13 of 18) showed a clear increasing trend during homonymous muscle activity (extension). This was consistent with phasic dynamic γ drive to FHL spindles linked with α drive. In agreement with previous reports, FHL gave a single burst of EMG activity during the step cycle while FDL α drive had two components. One was related to extension while the other comprised a brief burst around the end of this phase. Typically FDL Ia and group II afferents also had elevated firing rates and reduced modulation at all locomotor phases, again implicating static γ drive. Half the afferents (seven Ia, three group II) showed increased discharge during extension, suggesting phasic static γ drive. There was no γ drive associated with the late FDL α burst. In conclusion, the γ drives to FHL and FDL differed during locomotion. FHL, which has the α drive of a classic extensor, received γ drive that closely resembled other extensors. The γ drive of FDL, which exhibits both extensor and flexor α synergies, did not match either muscle type. These observations are compatible with the view that fusimotor drive varies in different muscles during locomotion according to the prevailing sensorimotor requirements.
Dynamic Condensation and Synthesis of Unsymmetric Structural Systems
Authors: Rao G. Visweswara
Published: October 2002

In this paper model reduction of an unsymmetric and damped structural system is presented using a two-sided dynamic condensation technique. The method is an iterative one and essentially utilizes orthonormalized complex eigenvectors of the unsymmetric system. The eigensolution of the reduced order model with specified master degrees-of-freedom is obtained by Lanczos algorithm. The model reduction procedure is further utilized in substructure synthesis and eigenvalue analysis of large size unsymmetric systems. Application of the condensation technique is illustrated via two example problems of rotor bearing systems.
Nonlinear-Time-Dependent Analysis of Micro Via-In-Pad Substrates for Solder Bumped Flip Chip Applications
Authors: Lau John H. , Lee S. W. Ricky , Pan Stephen H. , Chang Chris
Published: October 2002

An elasto-plastic-creep analysis of a low-cost micro via-in-pad (VIP) substrate for supporting a solder bumped flip chip in a chip scale package (CSP) format which is soldered onto a printed circuit board (PCB) is presented in this study. Emphasis is placed on the design, materials, and reliability of the micro VIP substrate and of the micro VIP CSP solder joints on PCB. The solder is assumed to obey Norton’s creep law. Cross-sections of samples are examined for a better understanding of the solder bump, CSP substrate redistribution, micro VIP, and solder joint. Also, the thermal cycling test results of the micro VIP CSP PCB assembly is presented.
Effective Local Flexural Stiffness of Ball Grid Array Assemblies
Authors: Lee Jung-Chuan , Rassaian Mostafa
Published: October 2002

Parts on the circuit board serve as reinforcements and produce local stiffness, which influences the deflection of the assembly under vibration. The curvature of the circuit board, combined with material properties, produces stresses that lead to the high-cycle fatigue failure of interconnecting soldering joints. Use of a conventional finite element method (FEM)—referred to as “h-method”—for circuit board analysis is cost prohibitive, as numerous parts, each containing many soldering joints, would need to be analyzed for a typical board. Instead, a direct-stress analysis method—referred to as the multi-domain method (MDM)—can be used to calculate effective local stiffness of ball grid array assemblies. The fast and accurate MDM is based on nested multi-field displacement superposition and is similar in concept to p-type FEM. It is similar to conventional FEM only in its use of the Rayleigh-Ritz methodology. The computational advantages of MDM over conventional FEM for computing thermal stresses caused by thermal coefficient mismatch have been documented previously. In present work, the use of MDM as a direct-stress analysis method to extract the effective local stiffness of ball grid-array assemblies for determining high-cycle fatigue life has been extended. This method simulates a three-point bend test for flexural stiffness calculation. It demonstrates that the force-deflection relationship at the center of the system can be accurately achieved with proper constraints at the ends. The flexural stiffness is then calculated on the basis of beam theory. This calculation produces numerical results for various part-board connections, both with and without underfill. The accuracy of the formulation is examined for layered assembly. The results for long-layered beam theory agree with those based on layered beam theory.
Vibration Analysis Based Modeling and Defect Recognition for Flip-Chip Solder-Joint Inspection
Authors: Liu Sheng , Ume I. Charles
Published: October 2002

A novel approach for flip-chip solder joint quality inspection based on vibration analysis is presented. Traditional solder joint inspection methods have their limitations when applied to flip chips. The vibration detection method is a new approach which has advantages such as being non-contact, non-destructive, accurate, fast and applicable for in-line inspection or during process development. In this technique, a flip chip was modeled as a thick plate supported by solder bumps. Changes in solder joint quality produce different flip chip vibration responses, and also change its natural vibration frequencies. In this paper, the vibration frequencies of a flip chip on a ceramic substrate were calculated using the finite element method. Based on vibration analysis, a laser ultrasound and interferometric system was developed for flip chip solder joint quality inspection. In this system, chips with good solder joints can be distinguished from chips with bad joints using their vibration responses and frequencies. Data analysis and defect recognition methods were developed and tested. Results indicate this approach offers great promise for solder bump inspection in flip chip, BGA, and chip scale packages.
Hygro-Mechanical Durability of Underfilled Flip-Chip-on-Board (FCOB) Interconnects
Authors: Okura J. H. , Dasgupta A. , Caers J. F. J. M.
Published: October 2002

The effect of constant temperature and humidity environments on the durability of interconnects in underfilled Flip-Chip-on-Board (FCOB) assemblies is investigated in this study. Polymeric underfills, used to enhance thermomechanical durability of the interconnects, are found to create new failure modes due to hygromechanical swelling. Based on experimental observations, the failure mechanism is hypothesized to be cracking of intermetallics, which have weakened due to thermal aging. Pseudo 3-D finite element analyses are conducted to quantify the moisture absorption and diffusion through the polymeric underfill, and the resulting hygromechanical viscoplastic stress history. The simulations are combined with accelerated aging tests to assess in-service durability in hot, humid environments. Model predictions are compared with results of accelerated life tests available in the literature.
Analysis of Eddy Current Data Using a Probabilistic Neural Network (PNN)
Authors: Au-Yang M. K. , Griffith J. C.
Published: October 2002

To characterize flaws caused by intergranular attack (IGA) in steam generator tubes, the Babcock & Wilcox (B&W) Owners’ Group sponsored a program to study different techniques to determine the depth of flaws based on eddy current data obtained from Bobbin coil probes. Techniques based on multiple regression analysis, neural network regression, and artificial intelligence have been reported elsewhere. This report summarizes the results based on application of a probabilistic neural network (PNN) to classify the flaws into groups of different depths. As a starter, only two classes were selected: Class 1 contained flaws with actual maximum depths below 40% through-wall; Class 2 contained flaws with depths above 40% through-wall. Classification was based on the Bobbin coil peak voltage and the corresponding phase angle data at the three different excitation frequencies of 600, 400, and 200 kHz. The results were compared with results from destructive examination. The study showed that best results were obtained when only the peak voltages were used to train the neural network. Based on this approach, the network classified the flaws correctly 72% of the time. Two methods of improving the network performance are proposed.
Designing a Control and Containment Device for Cradle-Mounted, Axial-Actuated Swash Plates
Authors: Manring Noah D.
Published: October 2002

Many axial-piston pumps utilize a swash plate for regulating discharge flow. In this research, the required control and containment forces are examined for a cradle-mounted, axial-actuated swash plate. These forces are described in closed-form for providing the designer with information that is necessary for sizing these critical components within the pump. In this research, it is shown that a proper design of the control device may be used to load the cradle bearings equally during high-pressure operation. While previous research has shown that a transverse-actuated swash plate will tend to dislocate itself from the cradle during high speed and low pressure operation, this research shows that an axial-actuated swash-plate tends to keep the swash-plate well seated within the cradle during all operating conditions. The information presented here is generalized for typical characteristics of swash plates that are used within the industry and is therefore useful for analyzing existing designs as well as new ones.
Enhanced Measurement of Residual Stress by Speckle Correlation Interferometry and Local Heat Treating for Low Stress Levels
Authors: Pechersky Martin J. , Vikram Chandra S.
Published: October 2002

The measurement of residual stresses by laser annealing and electronic speckle pattern interferometry has been successful for moderate to high stress levels. However, for lower stress levels, say less than 80% of yield, submicrometer deformations are encountered that result in subfringe interferograms. Subfringe measurements are not a serious problem with modern optical procedures such as phase shifting interferometry. However, such subfringes are comparable to noise levels resulting from air turbulence, environmental thermal variations, and so forth. Stress relief from local heating is also subject to theoretical lower stress limits that result from the competing effect of thermal expansion in the case of tensile stresses. Thus, for both practical and fundamental reasons the technique was modified such that several fringes will result at lower stress levels. These experimental techniques are shown to substantially expand the stress measurement range for this technique.
Laser-Optic Evaluation for Bond Quality of Polymeric Medical Tubing
Authors: Harms Kent D. , Suh C. Steve
Published: October 2002

A noncontact, laser-optic based laser ultrasonic technique referred to as the thermo-acousto-photonic nondestructive evaluation (TAP-NDE) was utilized to investigate bond integrity and localized stiffening due to an attached wire stent on small-diameter polymeric medical tubing. Laser-generated interrogating ultrasonic waves in the tubing were detected by use of a fiber-tip interferometer (FTI) and a continuous wave HeNe laser. The time-frequency analysis of the generated dispersive waves was performed using the Gabor wavelet transform (GWT) that effectively decomposed the digitized waveguide mode enabling identification of defect characteristic frequency tendencies. Three different bond defects were evaluated: tensile pull, needle puncture, and crease. These induced flaws represent possible manufacturing defects such as de-bond, potential leak sources, and geometry irregularities. The frequency tendencies were found to uniquely identify each bond defect. Frequency tendencies were also found to uniquely identify localized stiffening due to an attached wire stent proving that this technique can unambiguously identify propagation modes from among nonpropagation modes or vibrations. These findings demonstrate the utility of TAP-NDE and the GWT for quality inspection of small-diameter polymeric medical tubing.
A Control-Oriented CVT Model With Nonzero Belt Mass
Authors: Pfiffner Rolf , Guzzella Lino , Onder Chris H.
Published: October 2002

A new model for the dynamics of the mechanical part of a belt CVT (Continuously Variable Transmission) is presented. The model takes into account the mass of the belt, assuming it to be uniformly distributed over its length. The model can therefore be used as a benchmark for FE models, which focus on every element of the belt or chain, as well as for much simpler models that neglect the belt mass or imply significant simplifications in the respective kinematics. Although a nonholonomic system has to be investigated, the result is surprisingly simple, i.e., an algebraic solution is provided that is not much more complicated than the solutions derived with more stringent assumptions. The equations of motion derived here are especially suitable for use in control applications.
Identification of Armax Models With Time Dependent Coefficients
Authors: Mrad R. Ben , Farag E.
Published: October 2002

A method that uses input/output measurements is developed for the estimation of the coefficients of stochastic Time-varying AutoRegressive Moving Average with eXogeneous imputs (TARMAX) models. The TARMAX coefficients are expressed as linear combinations of a set of pre-selected functions. The model coefficients estimation method is fully based on linear operations, does not require initial guess values and is suitable for micro-computer implementation. The good performance of the estimation method is verified through numerical examples. A TARMAX model is also used to capture the dynamics of a detailed highly nonlinear model of an automobile hydraulic active suspension system. The TARMAX model is used to relate a desired force provided by a corner processor to the actual force generated by the hydraulic actuator. The TARMAX model is shown to provide good signal prediction ability.
An Approach for Product Line Design Selection Under Uncertainty and Competition
Authors: Li Hui , Azarm Shapour
Published: October 2002

An approach in product line design is presented in which a line of products is selected while accounting for their market potential. In this approach, the product line design selection is viewed as a selection problem with two main stages: design alternative generation and product line design evaluation and selection. The focus of this paper is on the product line design evaluation and selection stage. Issues considered include a large variety of customers’ preferences, market competitions, multiple business goals, uncertainties in several factors that are used for evaluating the design alternatives, and commonality among the alternatives in a product line. Because of the combinatorial nature of the problem, a genetic algorithm is used in the evaluation stage. Product line design selection of a cordless screwdriver is used as a demonstration example. The emphasis in the example is more on the approach and not in the details of the example per se.
Scission and Healing in a Spinning Elastomeric Cylinder at Elevated Temperature
Authors: Wineman A. S. , Shaw J. A.
Published: October 2002

When an elastomeric material is subject to sufficiently high temperature, macromolecular network junctions can undergo time-dependent scission and re-crosslinking (healing). The material system then consists of molecular networks with different reference states. A constitutive framework, based on the experimental work of Tobolsky, is used to determine the evolution of deformation of a solid rubber cylinder spinning at constant angular velocity at an elevated temperature. Responses based on underlying neo-Hookean, Mooney-Rivlin, and Arruda-Boyce models, were solved numerically and compared. Different amounts of healing were studied for each case. For neo-Hookean molecular networks, there may be a critical finite time when the radius grows infinitely fast and the cylinder “blows up.” This time depends on the angular velocity and the rate of re-cross linking. In addition, no solution was possible for angular velocities above a critical value, even without the effects of scission. Such anomalous behavior does not occur for Mooney-Rivlin or Arruda-Boyce network response.
Smart Optimization of Machine Systems Using Hierarchical Genotype Representations
Authors: Yoshimura Masataka , Izui Kazuhiro
Published: October 2002

Design problems for machine products are generally hierarchically expressed. With conventional product optimization methods, however, it is difficult to concurrently optimize all design variables of portions within such hierarchical structures. This paper proposes a design optimization method using genetic algorithms containing hierarchical genotype representations, so that the hierarchical structures of machine system designs are exactly expressed through genotype coding, and optimization can be concurrently conducted for all of the hierarchical structures. Crossover and mutation operations for manipulating the hierarchical genotype representations are also developed. The proposed method is applied to a machine-tool structural design and a 2 DOF robot arm design to demonstrate its effectiveness.
Could Shock Tests Adequately Mimic Drop Test Conditions?
Authors: Suhir E.
Published: October 2002

Drop tests are often substituted in qualification or life testing of microelectronic and optoelectronic products by shock tests. The existing (e.g., Telcordia) qualification specifications require that a short term load of the given magnitude and duration (say, an “external” acceleration with the maximum value of 500 g, acting for 0.001 s) is applied to the support structure of the product under test. The natural frequencies of vibration are not taken into account. The objective of our study is to develop simple analytical (“mathematical”) predictive models for the evaluation of the dynamic response of a structural element in a microelectronic or an optoelectronic product/package to an impact load occurring as a result of drop or shock tests. We use the developed models to find out if a shock tester could be “tuned” in such a way that the shock tests adequately mimic drop test conditions. We suggest that the maximum induced curvature and the maximum induced acceleration be used as suitable characteristics of the dynamic response of a structural element to an impact load. Indeed, the maximum curvatures determine the level of the bending stresses, and the maximum accelerations are supposedly responsible for the functional (electronic or photonic) performance of the product. We use the case of an elongated rectangular simply supported plate as an illustration of the suggested concept. We show that in order to adequately mimic drop test conditions, the shock test loading should be as close as possible to an instantaneous impulse, and that the duration of the shock load should be established based on the lowest (fundamental) natural frequency of vibrations. We show also that, for practical purposes, it is sufficient to consider the fundamental mode of vibrations only, and that the shock load does not have to be shorter than, say, half the quarter of the fundamental period. We demonstrate that, if the loading is not short enough, the induced curvatures and accelerations can exceed significantly the curvatures and accelerations in drop test conditions. Certainly, the results of such shock tests will be misleading. After the appropriate duration of the shock impulse is established, the time dependence and the maximum value of the imposed (“external”) acceleration in shock tests should be determined, depending on the most likely drop height, in order to adequately mimic drop test conditions. We demonstrate that the application of a probabilistic approach can be helpful in understanding the mechanical behavior and to ensure high short- and long-term reliability of an electronic or photonic device that might be or will be subjected to an accidental or expected impact loading. We conclude that although it is possible to “tune” the shock tester, so that the drop test conditions are adequately reproduced, actual drop tests should be conducted, whenever possible. The results of the analysis can be helpful in physical design and qualification testing of microelectronic and photonic products, experiencing dynamic loads of short duration.
On-Board Reforming Effects on the Performance of Proton Exchange Membrane (PEM) Fuel Cell Vehicles
Authors: Boettner Daisie D. , Paganelli Gino , Guezennec Yann G. , Rizzoni Giorgio , Moran Michael J.
Published: October 2002

This paper incorporates a methanol reformer model with a proton exchange membrane (PEM) fuel cell system model for automotive applications. The reformer model and fuel cell system model have been integrated into a vehicle performance simulator that determines fuel economy and other performance features. Fuel cell vehicle fuel economy using on-board methanol reforming is compared with fuel economy using direct-hydrogen fueling. The overall performance using reforming is significantly less than in a direct-hydrogen fuel cell vehicle.
Wind Stress Over Waves: Effects of Sea Roughness and Atmospheric Stability
Authors: Myrhaug Dag , Slaattelid Olav H.
Published: October 2002

The paper considers the effects of sea roughness and atmospheric stability on the sea surface wind stress over waves, which are in local equilibrium with the wind, by using the logarithmic boundary layer profile including a stability function, as well as adopting some commonly used sea surface roughness formulations. The engineering relevance of the results is also discussed.
The Isotropic Ellipsoidal Inclusion With a Polynomial Distribution of Eigenstrain
Authors: Rahman M.
Published: October 2002

We consider the problem of determining the elastic field in an infinite elastic solid induced by an ellipsoidal inclusion with a distribution of eigenstrains. The particular type of distribution considered in the article is characterized by a polynomial in the Cartesian coordinates of the points of the inclusion. Eshelby showed that in such a situation the induced strain field within the inclusion is also characterized by a polynomial of the same order. However, the explicit expression for this polynomial seems to have not yet been reported in the literature. The present study fills this gap.
Characterization of the crotalus durissus terrificus venom by atomic force microscopy
Authors: Baranauskas Vitor , Dourado Doroty Mesquita , Jingguo Zhao , da Cruz-Höfling Maria Alice
Published: October 2002

Atomic force microscopy was used to study the morphology of crude venom from the South American rattlesnake crotalus durissus terrificus. The results indicate that the crystallized crude venom has a high surface roughness with pores of diameters around 100 nm. Coiled filamentary structures of diameters of about 200 nm and lengths greater than 1000 nm, and large concave structures of diameter around 1000 nm, have also been observed dispersed over the main solid surface of the venom. Such structures may be related to aggregates of toxic enzymes or to bacteria or both. The coiled filamentary structures appear to be entangled on the pores of the venom surface in contrast to the large concave structures, which appear not to be bonded to the principal crystallized surface.
Gallium nitride: Method of defect characterization by wet oxidation in an oxalic acid electrolytic cell
Authors: Sundararajan Sri Priya , Crouse David , Lo Yu-Hwa
Published: October 2002

A method is suggested to characterize the defect density of a given gallium nitride film, through anodic etching. We report that oxalic acid etches gallium nitride, at room temperature and pressure in an electrolytic cell. Etching is theorized to proceed by attacking those points where planar defects and threading dislocations terminate on the GaN surface. The effect of varying electrolysis voltage on the etch pit density of the porous gallium nitride thus formed is investigated. Etch pit densities on the order of 4×1010 pits/cm2 were measured. The use of etch pit density to estimate defect density of a given GaN film is discussed.
Impact of pitting defect on 0.25 μm standard random access memory
Authors: Chiu C. M. , Yen T. F. , Chiu K-F.
Published: October 2002

Pittings are originated from crystal originate particles. It is difficult to avoid pittings by improving in-line processes. We have measured the amount of defects in both Czochralski (CZ) and epitaxial (EPI) wafers, which were processed by active area etching. For CZ wafers, 27% of total defects were found to be pittings, but only 5.9% for EPI wafers. These pittings may result from the crystal growth and could be further enhanced by dry etching and wet cleaning processes. Standard 0.25 μm standard random access memory (SRAM) fabrication processes were performed on both types of wafers, and electrical tests were carried out to verify the influence of pittings on the device performance. It was found that pittings induced greater leakage current between two adjacent p transistors, which may be due to local thinning at pitting location within the isolation region. However, the pitting induced leakage current was still in an acceptable level, and therefore these pittings with the size as large as 0.2 μm did not have a significant impact on device performance of 0.25 μm SRAM.