bluuebunny/crossref_metadata_2025 huggingface dataset:
Convective Heat Transfer Distribution on the Surface of an Electronic Package
Authors: Wirtz R. A. , Mathur Ashok
Published: April 2008

Measurements of the distribution of convective heat transfer over the five exposed faces of a low profile electronic package are described. The package, of square planform and length-to-height ratio, L/a = 6, is part of a regular array of such elements attached to one wall of a low aspect ratio channel. The coolant is air, and experiments are described for the Reynolds number range, 3000<Re<7000. The average heat transfer coefficient for the top face is found to be nearly equal to the overall average heat transfer coefficient for the element. The average heat transfer coefficient for the upstream face and two side faces are higher than the overall average by approximately 30–40 percent and 20–30 percent, respectively while that for the downstream face is 20–30 percent less than the overall average. Furthermore, the distribution in local heat transfer coefficient over the five surfaces of the element is approximately independent of variations in Reynolds number.
The Effects of Adhesive Nonlinearity on Thermal Stress in Layered Components
Authors: Yin Wan-Lee , Dale James L.
Published: April 2008

Interlaminar stresses near the free edge of a multi-layered structure under thermal and mechanical loads are significantly affected by nonlinear and inelastic material properties. Most previous studies of the subject ignored such effects and obtained singular or extremely severe and localized stress fields in boundary regions based strictly on the assumption of linearly elastic stress-strain relation. In the present paper, a variational method, using approximate stress functions and the principle of complementary energy, is developed to study the thermal stress in a three-layer beam including a thin, compliant, non-linearly elastic middle layer. It is found that the elastic softening behavior of the thin layer results in dispersion of the interlaminar stresses and widening of the boundary region. Hence the use of toughened, compliant bonding layers may produce a beneficial effect by alleviating local concentration of interlaminar stresses.
Elastic Analysis of Flip-Chip Solder Joints Undergoing Thermal Excursions
Authors: Conway H. D. , Bo̸rgesen P. , Li C.-Y.
Published: April 2008

An elastic analysis is developed to provide estimates of the stresses in area array solder joints during thermal excursions. The analysis provides a rapid quantitative evaluation of the important stresses during elastic deformation, and may serve as a basis for the qualitative understanding of the loading of interconnects during thermal and power cycles.
Thermal Model of a PC
Authors: Linton Ronald L. , Agonafer D.
Published: April 2008

This paper presents an alternative approach to modeling box cooling in electronic packages. A finite-control-volume simulation code is used to simulate an IBM desktop Personal Computer. Only the geometry, the overall air flow rate, the turbulent viscosity and the power dissipations from each card must be specified. The simulation code predicts the flow distribution inside the PC, the convection coefficients, the turbulence effects, and the temperatures. Predicted component temperatures were compared to measured values.
Natural Convection Heat Transfer From an Array of Rectangular Protrusions in an Enclosure Filled With Dielectric Liquid
Authors: Joshi Y. , Kelleher M. D. , Powell M. , Torres E. I.
Published: April 2008

An experimental investigation of natural convection liquid immersion cooling of a three by three array of rectangular protrusions in an enclosure is presented. The heated elements geometrically simulated 20 pin dual-inline electronic packages and were mounted on a plexiglass substrate, which formed one vertical wall of a dielectric liquid filled rectangular enclosure. The remaining vertical boundaries of the enclosure were insulated, while the top and bottom were maintained at prescribed temperatures using individual heat exchanger plates. Protrusion surface temperatures in steady state are reported for a range of power dissipation levels for three fluorinert liquids spanning a Prandtl number range from about 20 to 1400. The influence of enclosure top and bottom surface boundary conditions and its width on element temperatures is investigated. Non-dimensional heat transfer results are empirically correlated. Changes in component temperatures due to partial powering of the array are also measured.
Thermal Fatigue Damage in the Solder Joints of Leadless Chip Resistors
Authors: Govila R. K. , Jih E. , Pao Y.-H. , Larner C.
Published: April 2008

Leadless chip resistors (LCR) made by two different manufacturers and surface mounted on glass/epoxy printed circuit board (PCB) were subjected to thermal cycling between −55°C to 125°C in order to induce thermal fatigue failure/damage. The test units were subjected to a maximum of 250 thermal cycles. Solder joints in both types of LCRs were examined in scanning electron microscope and a relative comparison of the extent of fatigue damage is presented. The failure mechanism is associated with cracking in the eutectic compostion Sn/Pb solder initiated at the stress concentration sites. A nonlinear, time-dependent finite element modeling analysis has been performed to determine critical stress concentration sites in the solder joint. Key parameters leading to the initiation of solder damage are identified, and recommendations are made to improve the design in terms of solder configuration such as the radius of corner of the alumina substrate and the standoff height.
Critical Accumulated Strain Energy (Case) Failure Criterion for Thermal Cycling Fatigue of Solder Joints
Authors: Pan Tsung-Yu
Published: April 2008

In the automotive and computer industries, a perennial challenge has been to design an adequate and efficient accelerated thermal cycling test which would correspond to field service conditions. Failures, induced in both thermal cycle testing and field service, are characterized by thermal fatigue behavior. Several fatigue models have been proposed, none of these models take into account all of the many parameters of the test or service environment. In thermal cycling, for example, the temperature range, ramp rate, hold time, and stepped heating and cooling are known to influence the number of cycles to failure. In this study, a critical accumulated strain energy (CASE) failure criterion is proposed to correlate the fatigue life to both the plastic and creep strain energies, which accumulate in solder joints during the thermal cycling. This criterion suggests that solder joints fail as the strain energy accumulates and reaches a critical value. By using finite element analysis with a “ladder” procedure, both time-independent plastic strain energy and time-dependent creep strain energy are quantified. These are related to fatigue life by the equation: C = N*f (Ep + 0.13Ec), where C is the critical strain energy density, Nf is the fatigue life, Ep and Ec are plastic and creep strain energy density accumulation per cycle, respectively, for the eutectic Sn-Pb solders. By analyzing Hall and Sherry’s thermal cycling data (Hall and Sherry, 1986), it is found that creep is the predominant factor in deciding fatigue life. Creep accounts for 51 to 97 percent of the total accumulated strain energy, depending on the cycling profiles. This criterion is used to simulate crack propagation in a solder joint by analyzing the strain energy in small “domains” within the joint.
Effect of Flow Bypass on the Performance of Longitudinal Fin Heat Sinks
Authors: Wirtz R. A. , Chen Weiming , Zhou Ronghua
Published: April 2008

Heat transfer experiments are reported on the thermal performance of longitudinal fin heat sinks attached to an electronic package which is part of a regular array of packages undergoing forced convection air cooling. The effect of coolant bypass on the performance of the heat sink is assessed and performance correlations for reduced heat transfer due to this effect are developed. These correlations are used to develop design guidelines for optimal performance.
Fixed Wand Electronic Flame-Off for Ball Formation in the Wire Bonding Process
Authors: Qin Wei , Cohen Ira M. , Ayyaswamy P. S.
Published: April 2008

In the latest generation of wire bonders, the cycle is so short that the wand electrode is kept stationary and the electronic flame off (EFO) discharge is from the side of the wire. This is the discharge that heats and melts the wire causing roll up into a ball that is pressed down onto the chip to form a ball bond. The balls must be perfectly formed with defects in the few ppm range. In the first part of the paper, the fixed, conically shaped side wand and the improved ring wand design are studied by considering the electrostatic field before the breakdown. In the second part of the paper, discharge development starting from the initial electrostatic field between a wire and a ring wand up to the breakdown, and ionization growth in the gap between the electrodes are both examined by numerical simulations. In the computations, the conservation equations for ions and electrons and Poisson’s equation have been employed for the self-consistent electric field. Based on sensitivity to wire length and wire deflection, the results show that the ring wand is a better design than the conical side wand electrode for ball formation and wire bonding. Also, positive wire polarity is preferred over negative wire polarity.
Effects of Ceramic Ball-Grid-Array Package’s Manufacturing Variations on Solder Joint Reliability
Authors: Ju Teh-Hua , Lin Wei , Lee Y. C. , Liu Jay J.
Published: April 2008

The effects of manufacturing variations on the reliability of solder joints between a ceramic ball grid array (BGA) package and a printed wiring board (PWB) are investigated. Two cases are studied, namely, with and without spacers between the BGA package and the PWB to maintain the solder joint height. Manufacturing variations considered include changes in solder volume, joint height, and pad size. To evaluate the effect of manufacturing variations on reliability, every possible solder joint profile is first derived. The maximum strain is calculated next. Finally, the fatigue life is predicted. The calculations show that these manufacturing variations change the joint profile, and subsequently affect the fatigue life. Since the package is heavy, the use of spacers is necessary to control the solder joint height for reliable connections, and to maintain a large gap for cleaning. The solder joints formed with the use of spacers, may have convex, cylindrical or concave profiles. The concave solder joints are preferred, since they have long fatigue lives and are less sensitive to the manufacturing variations. For the convex solder joints, their fatigue lives are strongly affected by the joint height variation caused by package warpage and by the combined effects of solder volume and pad size.
Residual Stresses for In-Situ Deposition of Thin-Film High-Temperature Superconductors
Authors: Phelan P. E. , Ghasemi Nejhad M. N.
Published: April 2008

Residual stresses are caused by nonuniform thermal expansion and chemical shrinkage taking place during processing. For thin-film high-temperature superconductors, residual stresses result because of the thermal expansion mismatch between the film and substrate, and the introduction of oxygen into the film after in-situ deposition, which makes the unit cell dimensions change (chemical shrinkage) as the oxygen stoichiometry changes. Since both the reliability of the film—especially the bond between the film and substrate—and the film critical temperature are functions of the state of stress, it is important to understand how the residual stresses vary with processing conditions. Here, a three-dimensional residual stress analysis is carried out based on laminate theory, which assumes the lateral dimensions of the entire system to be much larger than its thickness. The normal residual stress components in the film, and the peeling stress at the film/substrate interface, are calculated. The results demonstrate the crucial role that chemical shrinkage plays in the formulation of residual stresses. A large portion of the stresses arises from the initial change of the unit cell dimensions due to changes in the film oxygen stoichiometry. Therefore, the processing temperature, and especially the initial oxygen pressure in the deposition chamber, are the key variables that impact the residual stresses.
Translation of Stress States Into Reliability Terms for Single Chip Ceramic Packages
Authors: Mirman Boris
Published: April 2008

This paper addresses the gap between optimistic and pessimistic analytical predictions of the reliability of microelectronic structures using the example of single chip ceramic packages. The necessity of structural (rather than material) characterization is emphasized. Equations for the probability of failure of a single chip ceramic package are presented.
A Solution Methodology for the Multiple Batch Surface Mount PCB Placement Sequence Problem
Authors: Huang Yu-Wen , Srihari K. , Adriance Jim , Westby George
Published: April 2008

The placement of surface mount components is a time consuming and critical task in the assembly of surface mount Printed Circuit Boards (PCBs). The focus of this research was the identification of “near optimal” solutions for the placement sequence identification problem. The factors considered include the placement machine and the specific PCB, the feeder space available, the need for tooling and nozzle changes, and the actual traveling path of the placement head. Expert (or knowledge based) systems were used as the solution method for this problem. The system developed can cope with single PCBs, panels, 180 deg offset boards (panels), and multiple PCB batches. The prototype knowledge based system developed in this research identifies solutions in (almost) realtime.
Two-Phase Electronic Cooling Using Mini-Channel and Micro-Channel Heat Sinks: Part 2—Flow Rate and Pressure Drop Constraints
Authors: Bowers M. B. , Mudawar I.
Published: April 2008

Increased rate of heat dissipation from electronic chips was explored by the application of flow boiling in mini-channel (D = 2.54 mm) and micro-channel (D = 510 μm) heat sinks with special emphasis on reducing pressure drop and coolant flow rate. A pressure drop model was developed that accounts for the single-phase inlet region, the single- and two-phase heated region, and the two-phase unheated outlet region. Inlet and outlet losses associated with the abrupt contraction and expansion, respectively, were also accounted for, and so were the effects of compressibility and flashing within the two-phase region. Overall, the major contributor to pressure drop was the acceleration caused by evaporation in the channels; however, compressibility effects proved significant for the micro-channel geometry. Based upon practical considerations such as pressure drop, erosion, choking, clogging, and manufacturing ease, the mini-channel geometry was determined to offer inherent advantages over the micro-channel geometry. The latter is preferred only in situations calling for dissipation of high heat fluxes where minimizing weight and liquid inventory is a must.
Effect of Pin Fin Density of the Thermal Performance of Unshrouded Pin Fin Heat Sinks
Authors: Azar Kaveh , Mandrone Carlo D.
Published: April 2008

An experimental investigation was conducted to examine the effect of pin fin density on thermal resistance of unshrouded pin fin heat sinks. Six heat sinks with different number of round pin fins were constructed. Heat sink thermal resistance was calculated by maintaining its base temperature constant. For these experiments, air flow varied from natural to high velocity forced convection. The results showed that thermal resistance did not decrease with increase of number of pin fins. An optimum number of pin fins existed beyond which thermal resistance actually increased. The study also showed that thermal resistance was a function of air velocity and governing flow pattern. Comparison of the heat transfer coefficient (h) and pin fin surface area showed that h decreased dramatically as surface area increased. The results showed that pin fin heat sinks with small number of pins had the best performance at low and moderate forced convection cooling.
Decoupling Convective and Conductive Heat Transfer Using the Adiabatic Heat Transfer Coefficient
Authors: Anderson Ann M.
Published: April 2008

In many heat transfer situations, such as those found in the electronics cooling field, more than a single mode of heat transfer occurs. For example, modules on a printed circuit board dissipate heat through convection to the air, through conduction to the board and through radiation to the surroundings. The adiabatic heat transfer coefficient, had, works well in such situations because it describes the change in wall temperature due to each incremental change in the convective heat transfer rate (due to conduction, radiation, or generation in the wall). The value of had is independent of the surface heat transfer distribution and can be used with the superposition method to interface between a convection solver and a conduction solver and “decouple” a conjugate heat transfer problem. If one uses the heat transfer coefficient based on the mean fluid temperature, hm, the problem is complicated because the value of hm is a function of the surface heat transfer distribution. This decoupling strategy is demonstrated through a series of numerical computations which solve the fully conjugate problem for laminar flow in a duct. These results are then compared to the decoupled solution. Excellent agreement between the fully conjugate and the decoupled solution is found for all cases when had and Tad are used to decouple the problem. Using hm and Tm can result in temperature prediction errors as large as 50 percent (for the cases studied here). The results show that when the Biot number (formulated as the resistance to axial wall conduction over the resistance to convection) is greater than 1.0 the adiabatic heat transfer coefficient should be used to decouple the problem. If the Biot number is below this value, h based on the mean temperature (for uniform surface temperature) can be used as the decoupler.
Some Effects of Water Immersion on the Mechanical Behavior of a Polyimide Film
Authors: Harper B. D. , Rao J. M.
Published: April 2008

Absorbed moisture is generally thought to have a plasticizing effect upon the mechanical behavior of polymers. This paper presents some experimental results illustrating the effects of water immersion upon the room temperature creep and stress-strain behavior of a polyimide film. It is shown that immersion in water results in antiplasticization as demonstrated by a significant increase in stiffness and decrease in time dependence. These effects were found to be reversible following thermal conditioning at 300°C.
MORSE POSITION OF KNOTS AND CLOSED INCOMPRESSIBLE SURFACES
Authors: OZAWA MAKOTO
Published: April 2008

In this paper, we study on knots and closed incompressible surfaces in the 3-sphere via Morse functions. We show that both knots and closed incompressible surfaces can be isotoped into a "related Morse position" simultaneously. As an application, we have the following results.

• Smallness of Montesinos tangles with length two and Kinoshita's theta curve.

• Classification of closed incompressible and meridionally incompressible surfaces in 2-bridge theta-curve and handcuff graph complements and the complements of links which admit Hopf tangle decompositions.
THE MINIMAL GENUS PROBLEM IN RULED MANIFOLDS
Authors: ZHAO XU-AN , GAO HONGZHU
Published: April 2008

In this paper, we consider the minimal genus problem in a ruled 4-manifold M. There are three key ingredients in the studying, the action of diffeomorphism group of M on H2(M,Z), the geometric construction of surfaces representing a cohomology class and the generalized adjunction formula. At first, we discuss the standard form (see Definition 1.1) of a class under the action of diffeomorphism group on H2(M,Z), we prove the uniqueness of the standard form. Then we construct some embedded surfaces representing the standard forms of some positive classes, the generalized adjunction formula is used to show that these surfaces realize the minimal genera.
INVARIANTS OF SURFACE LINKS IN ℝ4 VIA SKEIN RELATION
Authors: LEE SANG YOUL
Published: April 2008

Using Yoshikawa's surface diagram, we constructed new invariants of ambient isotopy classes of smoothly embedded closed surfaces in ℝ4 via a state-sum model similar to the Kauffman's state-sum model for the Jones polynomial for classical knots and links in ℝ3. It is shown that the invariants can also be defined by skein relation and thus they are calculated from Yoshikawa's surface diagrams recurrently. Some of the properties of the invariants are given and explicit computations for several surfaces are included.
TOWARD A CLASSIFICATION OF FINITE QUANDLES
Authors: EHRMAN G. , GURPINAR A. , THIBAULT M. , YETTER D. N.
Published: April 2008

This paper summarizes substantive new results derived by a student team (the first three authors) under the direction of the fourth author at the 2005 session of the KSU REU "Brainstorming and Barnstorming". The main results are a decomposition theorem for quandles in terms of an operation of "semidisjoint union" showing that all finite quandles canonically decompose via iterated semidisjoint unions into connected subquandles, and a structure theorem for finite connected quandles with prescribed inner automorphism group. The latter theorem suggests a new approach to the classification of finite connected quandles.
RAMAN APPROACH IN POROUS SILICON AT 1.5 μM
Authors: SIRLETO L. , FERRARA M. A. , RENDINA I. , JALALI B.
Published: April 2008

In the last years, the possibility of light generation and/or amplification in silicon, based on Raman emission, has achieved great results. However, some significant limitations, inherent to the physics of silicon, have been pointed out, too. In order to overcome these limitations, a possible option is to consider low dimensional silicon. Along this line of argument, an approach based on Raman scattering in porous silicon is presented. We prove two significant advantages with respect to silicon: the broadening of spontaneous Raman emission and the tuning of the Stokes shift. Finally, we discuss the prospect of Raman amplifier in porous silicon.
TUNING OF PHOTONIC CRYSTAL BAND PROPERTIES BY ATOMIC LAYER DEPOSITION
Authors: SUMMERS C. J. , GRAUGNARD E. , GAILLOT D. P. , YAMASHITA T. , NEFF C. W. , BLAIR J.
Published: April 2008

We report the application of atomic layer deposition to manipulate the dielectric architecture of conventional and superlattice two-dimensional photonic crystal waveguides fabricated in silicon. Conformal deposition of a second dielectric layer is shown to have a dramatic influence on the photonic band structure and produces unique effects that cannot be emulated in a single dielectric slab photonic crystal material. With additional dielectric coatings, a strong decrease in photonic band frequencies and change in band slope are observed, which for the lowest photonic states produces strong degeneracies. The capability, in principle, to tune the position of bands to within 0.005% accuracy, is demonstrated. Additionally, new features are observed when differential band shifts result in band-crossing and for which like polarizations activate perturbation mechanisms that result in local and strong band curvatures. The extremely strong band bending resulting from band-band interactions could have applications, in slow light devices, and provide a way to introduce non-linear effects into tunable photonic crystal structures.
ESTIMATION OF THE COUPLING POWER PARAMETER OF FUSED COUPLED FIBERS
Authors: SAKTIOTO  , ALI JALIL , FADHALI MOHAMMED , ZAINAL JASMAN
Published: April 2008

Fiber couplers are widely used in telecommunications and industry as passive splitting power devices. The effective power coupling and transmission from one fiber to another is mainly determined by both the coupling length and the coupling coefficient. The coupling length can be calculated directly but the coupling coefficient depends upon the refractive index and the separation fiber axis. After the fusion processes of two SMF-28e® couplers, the refractive index is unknown due to a change in the radius of the fiber (r cladd < 40 μ m and r core < 1.5 μ m ). The coupling coefficient range is obtained from a distribution of the coupling ratio and compared with the empirical formula, which also enables one to calculate the refractive index. In this experiment, the coupling coefficient in the range of 0.6–0.9/mm is calculated as a function of the separation fiber axis and the refractive index of the core and cladding. The result shows a good correlation between experimental results and theoretical calculation.
GEOMETRY OPTIMIZATION AND SECOND HARMONIC GENERATION IN PARA-NITROANILINE–DIMETHYL FORMAMIDE ADDUCT
Authors: DAS MALYAJ , TRIVEDI RASHMI , SEN PRANAY K. , KHATTAK B. Q. , SHANKAR P. RAM , PRASAD RAJENDRA , SEN PRATIMA
Published: April 2008

Para-nitroaniline(p- NA )–dimethyl formamide (DMF) adduct has been synthesized chemically. The formation of adduct is confirmed via UV, FTIR, CHN analyses and other techniques. The adduct formation takes place due to dipolar interaction and hydrogen bonding. The parent polar molecules, viz. p- NA and DMF, crystallize in symmetric forms and do not exhibit optical second harmonic generation (SHG). The adduct has been found to exhibit a considerable SHG efficiency and hence this confirms that the adduct crystallizes in a noncentrosymmetric form. These observations suggest a Λ-shaped structure of the molecule, which is further established theoretically via geometry optimization.
VARIATIONAL STABILITY OF SOCIAL NASH EQUILIBRIA
Authors: MORGAN JACQUELINE , SCALZO VINCENZO
Published: April 2008

New results on the variational stability of social Nash equilibria are obtained using the class of sequentially pseudocontinuous functions. This class of functions strictly includes the class of sequentially continuous functions and finds a natural motivation in the framework of Choice and Economic Theory since it characterizes the continuity of the preference relations on first countable topological spaces. We investigate the connections with previous results and we show that it is not possible to improve our results further on.
TECHNOLOGICAL LEADERSHIP AND SUSTAINABLE GROWTH IN A BILATERAL TRADE MODEL
Authors: CABO FRANCISCO , MARTÍN-HERRÁN GUIOMAR , MARTÍNEZ-GARCÍA MARÍA PILAR
Published: April 2008

This paper develops a trade model for a technologically leading country and a developing country that exploits a renewable natural resource. Technology diffuses from the technological leader to the developing country through foreign direct investment (FDI). Alternatively, innovative activities can also be carried out in the developing economy. We prove the existence and uniqueness of an equilibrium path along which both countries grow at the same rate, maintaining the natural-resource stock at a constant level. The saddle-point property for this equilibrium is proved and a sensitivity analysis is carried out. The steady-state growth rate and consumption under both scenarios are compared and the effect of resource abundance analyzed.
COMPARING SOLUTIONS IN JOINT IMPLEMENTATION PROJECTS
Authors: ZAKHAROV VICTOR , GAN'KOVA ANNA , DEMENTIEVA MARIA , NEITTAANMÄKI PEKKA
Published: April 2008

The problem of comparing TU-cooperative game values is introduced and analyzed. The proposed method is based on multicriteria methodology and the ASPID (Analysis and Synthesis of Parameters under Information Deficiency) technique (Hovanov and Kolary (1998)). The Shapley value and the nucleolus are compared despite a lack of information about coalitional preferences.
A NOTE ON ESSENTIAL EXTENSIONS OF SEMI-SIMPLE MODULES
Authors: ER NOYAN
Published: April 2008

In a series of recent papers, Beidar, Jain and Srivastava studied the question as to when a ring R with the property that essential extensions of semi-simple right R-modules are direct sums of quasi-injectives is right Noetherian. Beidar and Jain proved that it is, when R is commutative or right q.f.d. In this note we extend their results proving the following: A ring R with this property is right Noetherian iff for some n ∈ ℕ, R/socn(RR) has ascending chain condition on essential non-two-sided right ideals (in particular, when R/socn(RR) is right q.f.d. or commutative). Also shown is the following: A ring is a right Noetherian right V-ring iff modules with essential socle are quasi-continuous/quasi-injective.
A Comparison of Similarity Measures for Text Documents
Authors: Hariharan Shanmugasundaram , Srinivasan Rengaramanujam
Published: April 2008

Similarity is an important and widely used concept in many applications such as Document Summarisation, Question Answering, Information Retrieval, Document Clustering and Categorisation. This paper presents a comparison of various similarity measures in comparing the content of text documents. We have attempted to find the best measure suited for finding the document similarity for newspaper reports.
Knowledge-Based Expert System Development and Validation with Petri Nets
Authors: Tavana Madjid
Published: April 2008

Expert systems (ESs) are complex information systems that are expensive to build and difficult to validate. Numerous knowledge representation strategies such as rules, semantic networks, frames, objects and logical expressions are developed to provide high-level abstraction of a system. Rules are the most commonly used form of knowledge representation and they are derived from popular techniques such as decision trees and decision tables. Despite their huge popularity, decision trees and decision tables are static and cannot model the dynamic requirements of a system. In this study, we propose Petri Nets (PNs) for dynamic system representation and rule derivation. PNs with their graphical and precise nature and their firm mathematical foundation are especially useful for building ESs that exhibit a variety of situations, including: sequential execution, conflict, concurrency, synchronisation, merging, confusion, or prioritisation. We demonstrate the application of our methodology in the design and development of a medical diagnostic expert system.
Research on Evaluation Model of Organisational Knowledge Assets
Authors: Li Jun , Zhang Ling Ling , Shi Yong
Published: April 2008

Nowadays, valuation and measurement of knowledge assets has become a challenging problem for many organisations. This paper first introduces the concept of knowledge assets and presents some evaluation models of knowledge assets. Then, based on the methodology of the balanced scorecard, this paper proposes an index system which comprises quantitative indices and qualitative indices and financial indices and non-financial indices which are weighted by the analytical hierarchy process method to evaluate organisational knowledge assets. Thus, the status of organisational knowledge assets management can be estimated by a final score calculated by efficacy coefficient method and professional evaluation method in the model. At last, the paper gives a case study for this model's application. It is hoped that the information accrued from the case study, together with the evaluation model, will help to pave the way for organisations to evaluate their knowledge assets.
Adoption of Knowledge Management Technologies and Organisational Culture: An Exploratory Study
Authors: Cheng Eric Y. , Liu Yen Lin
Published: April 2008

Organisational culture is increasingly recognised as a major facilitator or barrier to leverage intellectual assets. Early works have shown that there are various technologies that support knowledge management (KM). This research presents an empirical study designed to explore and investigate the sophisticated relationships between organisational culture and the adoption of KM technologies. According to empirical studies, organisational culture could be decomposed into five dimensions: rational, group, development, hierarchical and ethical culture. On the other hand, the application of KM technologies can be categorised into five major categories: creation, storage/retrieval, transfer, application and platform technology. A random sample of 1000 largest companies in Taiwan was chosen as target organisations for this study. Among them, 121 completed survey responses were received, which yielding an effective response rate of 12.1%. The result of the correlation analysis indicates that storage/retrieval and platform technologies have positive relationships with all the cultures, while creation technologies are positively correlated with ethical, group and development cultures; and application technologies with development and hierarchical cultures. However, in general, organisational culture and KM technologies are weakly correlated. Moreover, though the majority of corporations started to recognise the value and importance of KM, there are only a few technologies such as database, email, intranet and Internet that were highly adopted and frequently used in KM activities. There exists a huge gap between recognising the importance of KM and enthusiastically adopting KM technologies. This study contributes to the understanding of how organisational culture affects and interacts with KM technologies and in what ways. It also demonstrates the current status of KM technology adoption in Taiwan's large corporations.
Inducing and Imaging Localized Passivity Breakdown in Aluminum Using an AFM Approach
Authors: Zavadil Kevin R.
Published: April 2008

The impact of localized polarization of aluminum in aqueous chloride is studied using in situ atomic force microscopy (AFM). The primary goal of this study is to determine whether nanostructural degradation in the form of passivity loss and pit initiation can be induced by applying potential pulses between a conductive AFM probe tip and an aluminum surface. Nanoscopic imaging of the mechanically compliant hydrous oxide on an Al(111) textured film with 0.5 wt.% Cu is demonstrated. A correlation is made between characteristic nanostructural changes observed for localized and macroscopic area polarization. Pit initiation proximity to the AFM tip is also demonstrated arguing for millisecond time periods as being sufficient to drive pit initiation within a targeted area. A significant degree of spatial variance in proximity is observed, which suggests a larger length scale, intrinsic susceptibility to pit initiation not dictated by known structural heterogeneity like grain boundary structure.
Electrochemically Controlled Corrosion Initiation and Propagation in AlMgSi alloys In-situ Monitored Using X-ray Microtomography
Authors: Eckermann Fabian , Suter Thomas , Uggowitzer Peter J. , Afseth Andreas , Stampanoni Marco , Marone Federica , Schmutz Patrik
Published: April 2008

An X-ray microtomography monitored, electrochemically controlled corrosion experiment with high spatial resolution was performed. A modified electrochemical microcell-setup was mounted on the sample holder of the synchrotron beamline. This setup enabled in-situ corrosion tomography at a small-defined volume combined with well-defined electrochemical control. Hence high spatial submicrometer resolution and early detection of single corrosion events were possible. Three heat treatments are investigated. I) 45min at 180{degree sign}C showing high intergranular corrosion susceptibility. Preferential initiation at intermetallics lying on grain boundaries was found with subsequent penetration into the material. Correlation of intermetallics and propagation path could not be found. II) 16h at 180{degree sign}C showing susceptibility to pitting. An exfoliation-like attack was found which attacks straight into the bulk with a width of approximate 2 um. III) 111h at 350{degree sign}C showing a high amount of large MgSi phase. intermetallics and MgSi are not initiation sites for corrosion propagation even though dissolution can occur.
Application of Synchrotron Radiation Photoemission Spectroscopy to Structure Analysis of Thin Corrosion Product Films on Hot-Dip Zn-Al Coatings
Authors: Nishihara Katsuhiro , Matsumoto Masamitsu , Kimoto Masanari , Kudo Takeo , Uchida Hitoshi , Haruyama Yuichi , Kanda Kazuhiro , Matsui Shinji
Published: April 2008

Structure of the corrosion product films, which formed on hot-dip Zn-0.2%Al, Zn-5%Al and Zn-55%Al coatings in the early stages of corrosion reaction under the presence of NaCl particles, have been investigated by means of photoemission spectroscopy using synchrotron radiation and Al-Kα radiation. As a result, it is found that the surface compound of initial oxide film on Zn-Al coating changes from zinc oxide to aluminum oxide with increasing Al content, and that the structure depends on Al content. Additionally, the dominant compound of 1 nm or less in depth from the surface of corrosion products is seen to be different from that of 4 nm or less in depth. The corrosion resistance of Zn-Al coating is considered to be attributed to the depth profile of corrosion products on coating.
Simulation of Solution Chemistry in Crevice Corrosion for Stainless Steel
Authors: Shinohara Tadashi , Fukaya Yuichi , Tahara Akira , Hosoya Yuji
Published: April 2008

The calculation model to simulate solution chemistry in crevice corrosion for stainless steel immersed in NaCl solution was studied by using mass transfer model and considering formation of complex ions. The calculation was conducted in consideration of metal ions complex ions, Cl-, Na+(i=5) and potential, φ. Distributions of concentrations of ions and electrode potential were obtained for Type 316 stainless steels in 3% NaCl solution at 80åC. It was confirmed that only the distribution of Cl- ion depended on the ratio of t - t1=[FeCl+]/([Fe2+]+[FeCl+]), t2=[CrCl2+]/([Cr3+]+[CrCl2+]) - because the diffusion coefficient of Cl-, D4(Cl-)=2×10-5cm2/s, is 4 times larger than those of metal and complex ions, for example D1(Fe2+)=5×10-6cm2/s. For Cl- ion, maximum value decreases down to 6.9mol/L from 10.2mol/L by considering complex ions. And almost all Fe and Cr form complex ions of FeCl+ and CrCl2+.
Effect of Stress on Hydrogen Distribution Around SCC Crack of SUS304 Stainless Steel
Authors: Masuda Hiyoyuki
Published: April 2008

A new SCC test method that enables the super Kelvin force microscope observation has been developed. The effect of applied stress on the surface potential distribution and hydrogen distribution near stress corrosion crack was studied on SUS304 stainless steel of 0.07mm in thickness by using this test method. There was a good relationship between the negative potential region and the hydrogen distribution examined by the Ag crystal decoration method. A crack was produced when the applied stress was high, while multi-branched crack was produced when the applied stress was low. The amount of hydrogen was large when the applied stress was low.
Human Fingerprint - Metal Interactions Studied Using a Scanning Kelvin Probe
Authors: Williams Geraint , McMurray H. N.
Published: April 2008

Human fingerprint friction ridge deposits induce local Volta potential variations on a range of technologically important metals including iron, copper, aluminium and brass, which can be spatially mapped at high resolution using a scanning Kelvin probe (SKP). Because the Volta potential patterns principally derive from a depassivation of the metal surface by inorganic salts in human sweat, fingerprints can be visualized by SKP even after exposure to high temperatures. This property is exploited in the use of SKP to visualize fingerprint patterns on items of forensic significance, such as fired cartridge cases, where the loss of organic fingerprint components upon firing typically renders conventional chemical development techniques ineffective.
Hydrocarbon based BPSH-BPS Multiblock Copolymers as Novel Proton Exchange Membranes
Authors: Roy Abhishek , Lee Hae-Seung , McGrath James E. E.
Published: April 2008

There have been growing evidences, both experimental and theoretical, that block copolymer systems with well-defined sulfonated regions may provide enhanced transport of protons, especially at low relative humidity. We have recently demonstrated a novel way to make nearly all hydrocarbon, hydrophobic-hydrophilic block copolymers. The chemical structure and chemical composition are very similar to BPSH copolymers. However the microstructure and the morphology are very different. This paper will try to unfold the structure property relationships of the multiblock copolymers for application as potential proton exchange membranes.
Preparation of the PVA/TiO2 nanocomposite polymer membranes by a sol-gel process for alkaline DMFC
Authors: Yang Chun-Chen , Lin Che-Tseng
Published: April 2008

The PVA/TiO2 nanocomposite polymer membrane was prepared by a sol-gel process. Glutaraldehyde (GA) and TiO2 particles were used as a crosslinker and the fillers for the composite polymer membrane in order to increase their ionic conductivities, thermal and mechanical stability properties and to enhance the dimension stability. The characteristic properties of the PVA/TiO2 nanocomposite polymer membranes were systematically studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and AC impedance spectroscopy. Alkaline DMFC, consisting of an air cathode electrode with MnO2/BP2000 (1:1) catalyst ink, an anode electrode with 4 mg cm-2 PtRu black coated on Ti-mesh, respectively, and the PVA/TiO2 nanocomposite polymer membrane based on titanium isopropylate (TTIP), was assembled and examined. It was revealed that the DMFC utilizing the PVA/TiO2 nanocomposite polymer membrane showed good electroc hemical performance at room temperature and ambient air. The maximum power density of alkaline DMFC in 4M KOH + 2M CH3OH solution is 11.47 mW cm-2 at ambient conditions.
Management of Pediatric Malaria: Role of Nutritional Interventions
Authors: Osei Akoto Kwame , Hamer Davidson H.
Published: April 2008

Malaria is a leading cause of morbidity and mortality among children, particularly in sub-Saharan Africa. Although substantial progress has been made in the treatment of pediatric malaria with artemisinin-based combination therapy, there remain many obstacles to the effective implementation of these highly efficacious new treatment options. Similarly, while effective tools are available for the prevention of malaria in children, scaling these up so that they have a clear impact on malaria-associated morbidity and mortality has presented significant challenges to public health officials. Host nutritional status influences the acquisition and potential severity of malaria infection. While there is substantial evidence that malaria contributes to impaired weight and height gain in children, the impact of undernutrition on malaria is complex. There is increasing evidence that supplementation with certain micronutrients may play a critical role in the prevention of malaria in young children. Micronutrient interventions such as zinc or vitamin A supplementation may help reduce the burden of disease due to malaria whereas others such as iron may exacerbate infection. Differences in study design, quality, intensity of malaria transmission, and other study site characteristics complicate the interpretation of the limited number of studies that have evaluated the impact of specific micronutrients for the treatment and prevention of malaria. There has only been one trial to evaluate the use of zinc as an adjunct in the treatment of malaria and it failed to demonstrate any benefit of zinc in this role. This article reviews the clinical management of malaria in children, interactions between malaria and nutritional status, and the potential role of micronutrient supplementation for the prevention of clinical malaria episodes in young children, with a particular focus on whether each nutrient supplement improves or worsens malaria outcomes.
Mechanisms, Risks, and New Treatment Options for Hyponatremia
Authors: Ghali Jalal K.
Published: April 2008

Hyponatremia is the most common electrolyte abnormality in hospitalized patients and is associated with increased mortality, morbidity, and longer hospital stays. Because patients with this disorder are often asymptomatic, hyponatremia is frequently undiagnosed and untreated. Serious neurologic complications may ensue when hyponatremia develops too rapidly or the serum sodium concentration ([Na+]) falls below 120 mEq/l. Hypotonic dilutional hyponatremia is the most common form of this disorder, which may present as euvolemic [e.g., due to failure to suppress secretion of arginine vasopressin (AVP)] or hypervolemic (due to edema-forming conditions such as heart failure). Hypovolemic hyponatremia is due to conditions promoting renal or extrarenal sodium loss. Because AVP, which is intimately involved in regulating osmolar homeostasis, is often elevated in patients with hypervolemic and euvolemic hyponatremia, treatments that directly target the effects of this hormone may provide a more predictable correction of serum [Na+] than those traditionally used. The AVP receptor antagonists (conivaptan, tolvaptan, lixivaptan, and satavaptan) are a new class of agents that have been shown to normalize serum [Na+] by promoting aquaresis – the electrolyte-sparing excretion of free water.
Less Benefit from Warfarin in Diabetics after Myocardial Infarction?
Authors: Smith Pål J. , Hurlen Mette , Abdelnoor Michael , Arnesen Harald
Published: April 2008

Objectives: To examine the impact of prognostic factors on the outcome of treatment with warfarin or aspirin after acute myocardial infarction. Methods: Patients from the Warfarin Aspirin Re-Infarction Study, assigned to treatment with warfarin (n = 1,216) or aspirin (n = 1,206) after myocardial infarction, were stratified according to important prognostic factors. Survival from the composite endpoint of death, myocardial infarction and thromboembolic stroke was estimated within each stratum by odds ratios (OR). The effect of therapy was then tested for heterogeneity across the two groups. Unadjusted analyses were complemented with regression analyses. Results: In diabetics the OR was 1.54 (95% CI 0.80–2.94) compared to 0.75 (95% CI 0.60–0.93) in nondiabetic patients. The latter difference was statistically significant when testing for heterogeneity, suggesting effect modification of warfarin by diabetes. After adjusting for confounders, diabetic patients who received warfarin had a 56% excess risk of an endpoint as compared with those receiving aspirin. By contrast, nondiabetic patients on warfarin had a 22% lower risk of an endpoint than those allocated to aspirin. Conclusions: The present data suggest less benefit from warfarin as compared to aspirin in diabetics. The mechanisms behind this remain in question.
Association of Fibrinogen and Fibrinogen Gene β148 and β854 Polymorphisms with Coronary Heart Disease
Authors: Sun Ai-jun , Ma Hui-li , Chen Xue-ying , Wang Ying , Fang Ye-ming , Ma Yong-li , Wang Ke-qiang , Zou Yun-zeng , Huang Wei , Ge Jun-bo
Published: April 2008

Background: The aim of this study was to observe the association between fibrinogen C148T, G854A polymorphisms and plasma fibrinogen levels in a large cohort of Chinese patients with coronary heart disease (CHD). Methods: Fibrinogen gene β148/β854 polymorphisms were screened and plasma fibrinogen levels and lipids were measured in patients with angiographically confirmed CHD (n = 836) and in controls without CHD (n = 418). Results: Age, sex, smoking, hypertension, diabetes mellitus, blood lipids and fibrinogen levels were related to CHD (all p < 0. 05) while the frequencies of fibrinogen β148 and β854 alleles, gene and genotypes between the two groups were similar (all p > 0.05). Conclusion: This study demonstrates that the plasma fibrinogen level, but not fibrinogen β148 and β854 genotypes, was associated with CHD in the Chinese population.