bluuebunny/crossref_metadata_2025 huggingface dataset:
A CRITICAL REMARK ON PLANCK'S MODEL OF BLACK-BODY
Authors: CARATI ANDREA , GALGANI LUIGI
Published: April 2004

We reexamine the model of matter–radiation interaction considered by Planck in his studies on the black-body problem, and point out that its consistency seems to be in doubt. The key point is that Planck's model deals in principle with a system of n material resonators interacting with the field, but in fact Planck actually deals with a single resonator, because he explicitly makes the assumption that the resonators act independently of each other, i.e. perform incoherent motions. We point out that it would be more appropriate to deal from the start with the dynamics of the complete system, and that, in view of the long range character of the electrodynamical forces, motions of a coherent or correlated type might thus be found to occur.
HOW REAL ARE QUANTONS?
Authors: CINI MARCELLO
Published: April 2004

In spite of the recent extraordinary progresses of experimental techniques it does not seem that, after more than seventy years from the birth of quantum mechanics, a unanimous consensus has been reached in the physicist's community on how to understand the "strange" properties of quantons, the wavelike/particlelike objects of the quantum world. In the first paragraph I will briefly recall some results on the problem of decoherence in large quantum systems, which at the same time may be viewed as an attempt of providing a "realistic" physical interpretation of the standard mathematical formulation of the theory. In the following ones I will present a derivation from first principles of the Wigner representation of quantum mechanics in phase space which eliminates altogether from the theory the Schrödinger waves and their questionable properties. This approach leads to the conclusion that the wave/particle duality has nothing to do with "probability waves", but is simply the manifestation of two complementary aspects (continuity vs. discontinuity) of an intrinsically nonlocal physical entity (the quantum field) which objectively exists in ordinary three dimensional space.
THE KAC LIMIT FOR DILUTED SPIN GLASSES
Authors: FRANZ SILVIO , TONINELLI FABIO LUCIO
Published: April 2004

We study diluted spin glass models in arbitrary dimension, where each spin interacts with a finite number of other spins chosen at random with a probability decaying to zero over some distance γ-1. For systems with pairwise interactions we show that the infinite-volume free energy converges to that of the mean-field Viana–Bray model,1 in the Kac limit γ→0. For p-spin like models we get only one bound: the free-energy is bounded from above by the one of the mean-field diluted p-spin.
Noyσ Und σoia In Offb 17
Authors: Schmidt Josef
Published: April 2004

Die apokalyptische Rätselzahl hat nicht nur die Funktion, die historische Rückschau des 13. Kapitels eindrucksvoll abzuschließen; sie ist auch im 17. Kapitel präsent. Dort repräsentiert sie die innere Mitte einer weiteren historischen Reflexion, die nun aber der künftigen Entwicklung des römischen Kaiserreiches gewidmet ist. Der Verfasser sieht die Zeit einer neuen Verfolgung am politischen Horizont heraufziehen und mahnt seine Leser zu illusionsloser Wachsamkeit. Der historische Standort des Verfassers ist die Zeit des Vespasian; sein geographischer Standort ist die Stadt Rom. Nicht nur die kryptische Geographie von Kapitel 17, sondern auch die des 11. Kapitels kann dem Areal dieser Stadt zugeordnet werden.
Sign Consumption in the 19th-Century Department Store
Authors: Parker Ken W.
Published: April 2004

The department stores of the 19th century continue to fascinate social theorists. This article will expand on the work of two such theorists, Laermans and Featherstone. Extending Laermans’ and Featherstone’s analysis, and applying the early work of Baudrillard, this article will assert that through the manipulation of visual merchandising, the 19th-century department store’s managers constructed a world of sign-consumption where goods were not only consumed for their use- or exchange-value, but also were consumed as signs of luxury, exoticism and excess. By asserting that highly developed forms of sign-consumption existed in the 19th century, this article challenges the view that symbolic consumption in spaces such as shopping malls is particular to the contemporary or postmodern age.
Houston, 2001
Authors: Fouad Nadya A. , McPherson Robert H. , Gerstein Larry , Blustein David L. , Elman Nancy , Helledy Kristin Ihle , Metz A. J.
Published: April 2004

This article presents an overview of the Houston 2001 National Counseling Psychology Conference. The authors discuss the context for the 4th National Counseling Psychology Conference, documentthe process of decision makingaboutthe conference, andexamine the content of the conference. The authors also examine a unique feature of the conference, the social action groups, discussing their philosophical underpinnings as well as how they were organized, what took place, and recommendations drawn from the groups. The authors evaluatethe outcomes of the Houston Conference andalso assess the conference within the context of the legacy of the three other counseling psychology conferences held at Northwestern University in 1951, in the Greyston Conference Center at Teachers College in 1964, and in Atlanta in 1987. Finally, the authors make recommendations for the field to move the conference’s initiatives forward and plan for future conferences.
Déjà Vu and Moving the Conversation
Authors: Galassi John P. , Akos Patrick
Published: April 2004

Romano and Kachgal argue for greater collaboration between counseling psychology and school counseling. Although their proposal has considerable merit, a variety of barriers to collaboration—including professional jealousies and turf, the lack of knowledge and interest of most counseling psychologists in schools, and the availability of benefits to sustain the partnership for all parties—must be addressed. We argue that adopting shared conceptual frameworks that return to and extend the roots of both disciplines is needed to foster and sustain the proposed partnership. Three conceptual models are presented.
Back to School for Counseling Psychology?
Authors: Lichtenberg James W. , Goodyear Rodney K.
Published: April 2004

Despite an early shared history with school counseling, counseling psychology has, over time, distanced itself from the schools. Current circumstances with regard to public education and questions about the relevance of counseling psychology’s graduate training programs within schools and colleges of education have resurrected consideration of a partnership between school counseling and counseling psychology. In this response, the authors question the motives and sincerity of counseling psychology’s embracing school counseling as a partner, as well as the feasibility of the proposed partnership.
Problem-Solving Appraisal in Counseling and With Different Populations
Authors: Lucas Margaretha S.
Published: April 2004

Heppner, Witty and Dixon have presented the development and theoretical base of the Problem Solving Inventory (PSI). They link it to numerous validity and reliability studies, with findings in predicted directions. This article expresses concerns about its use as a target in counseling and its applicability to individuals of the nonmajority culture.
Microbes and Us
Authors: Gee Ellen M.
Published: April 2004

This article provides an overview of microbes (viruses and pathogenic bacteria) in human history, with special focus on their emerging threat in societies that had appeared to have conquered them as significant takers of life. The relationship between microbes and mortality level is discussed, with reference to both developed and developing societies, which display different historical patterns regarding the timing and tempo of reductions in mortality due to microbes. An overview of the epidemiological transition theory - which has until recently guided current thinking about the mortality-microbe relationship - is presented in the light of current trends that counter its view of the diminishing role of microbes over time. Four factors leading to a re-examination of epidemiological theory’s optimism about the eventual control of microbes are identified. Consequences of microbe resurgence in the West, particularly in Canada, are discussed. Concerns about the Canadian reaction to microbes - which focuses upon individualist responses - and to threats to the health care system - which ignore public health - are raised.
Cultures of Intimacy and Care beyond ‘the Family’: Personal Life and Social Change in the Early 21st Century
Authors: Roseneil Sasha , Budgeon Shelley
Published: April 2004

The authors argue that if sociologists are to understand the current state, and likely future, of intimacy and care, we should decentre the ‘family’ and the heterosexual couple in our intellectual imaginaries. In the context of processes of individualization much that matters to people in terms of intimacy and care increasingly takes place beyond the ‘family’, between partners who are not living together ‘as family’, and within networks of friends. The first section of the article provides a critique of family sociology and the sociology of gender for the heteronormative frameworks within which they operate. It proposes an extension of the framework within which contemporary transformations in the realm of intimacy are to be analysed, and it suggests that there is a need for research focusing on the cultures of intimacy and care inhabited by those living at the cutting edge of social change. In the second part of the article, the authors draw upon their own research on the most ‘individualized’ sector of the population – adults who are not living with a partner. They explore contemporary cultures of intimacy and care among this group through a number of case studies, and argue that two interrelated processes characterize these cultures: centring on friendship, and decentring sexual relationships.
Programs and Strategies to Increase Latino Students’ Educational Attainment
Authors: Haro Roberto
Published: April 2004

This article presents strategies that Latino parents and Latino students need to know regarding preparing for and selecting the best undergraduate college or university for the career desired, especially if the choice involves engineering, mathematics, or the sciences. Access to pertinent information on preparation for admission to a college or a university of choice, and then how to negotiate the system to graduate in a timely manner with high grades, is discussed. Sources for advice on going to college can be located at community centers, public libraries, schools, and especially outreach programs and the internet. Moreover, the role of faculty and of academic-guidance personnel on most good campuses that are able to assist students to make informed decisions about career plans is provided. Whether a Latina or Latino student succeeds in going to graduate school involves having correct information, interacting and mentoring with supportive faculty, learning to use a computer with Internet capabilities, and completing a rigorous academic program.
Epilogue
Authors: Contreras A. Reynaldo
Published: April 2004

As we move into the 21st century, Latinos have become the largest minority group in American society. Consequently, we are shifting from a majority White/minority Black paradigm to a paradigm that will consider a broader spectrum of ethnic and racial diversity wherein Latinos will provide guidance in promoting inclusiveness as we address social change in the 21st century. The focus of this article is on the education of Latinos and on the efforts to address segregation while pursuing educational opportunities. It is concluded that maintaining any paradigm that promotes continued segregation of Latinos is inconsistent with the spirit if not the letter of the Brown v. Board of Education decision.
Brown at 50
Authors: Ilg Timothy J. , Massucci Joseph D. , Cattaro Gerald M.
Published: April 2004

In light of the elimination of busing to achieve racial integration and judicial reluctance to consider creative, new ways to provide integrated, high quality learning environments for poor and minority children, advocates of the principles established by Brown must no longer accept the public schools as the best hope for providing integrated schooling. Educators should seriously consider supporting Catholic schools as a viable option in effort to advance racial integration since absent immediate support, these models for integration might be lost for future generations.
Ensuring Equality of Educational Opportunity in the Digital Age
Authors: Morse Timothy E.
Published: April 2004

As the quintessential right-to-education case, Brown v. Board of Education, Topeka, (1954) addressed equality of educational opportunity for all students regardless of race. Recently, the term digital divide has been used primarily to highlight inequities between various social groups with respect to acquiring computers and accessing the Internet. Given how use of these technologies has permeatedour society, including our nation’s schools, all relevant aspects of the digital divide must be addressed if the spirit of Brown is to be realized. Hence, in this article, the multidimensional meaning of the term digital divide is discussed, as are (a) the effect of this phenomenon as it relates to equality of educational opportunity for all students and (b) ways to address it.
African Americans and Multicultural Education
Authors: Harris J. John , Brown Elinor L. , Ford Donna Y. , Richardson Jeanita W.
Published: April 2004

This article examines the root causes for the overrepresentation of African American students in special education classes and their under representation in gifted and talented programs in America’s public schools. The article (a) provides a historic overview of the legal struggles for educational equity, (b) examines key issues surrounding the academic status of African American students, (c) discusses multicultural education as a remedy, and (d) recommends an appropriate course of action for educators and policy makers.
Interlocking Interactions, the Diffusion of Innovations in Health Care
Authors: Fitzgerald Louise , Ferlie Ewan , Wood Martin , Hawkins Chris
Published: April 2004

This article aims to provide a reassessment of the processes of diffusion of innovations into organizations, based on new empirical data. The focus of the article is the latter stages of the diffusion process. The article draws on the results of two studies, which examined the diffusion of innovations in health care in the UK. These projects were a matched pair of qualitative studies, using purposeful selections of comparative case studies. The results demonstrate the ambiguous, contested nature of new scientific knowledge. The highly interactive nature of diffusion, with active adopters is illustrated. There is no evidence of a single adoption decision. The science is socially mediated. The features of context and of actors interlock to influence diffusion.
Psychosocial Studies and Psychology: Is a Critical Approach Emerging?
Authors: Frosh Stephen
Published: April 2004

This article describes a brand of ‘psychosocial studies’ that adopts a critical attitude towards psychology as a whole, yet remains rooted in an attempt to theorize the ‘psychological subject’. Principles for psychosocial studies work of this kind are discussed, arising out of the actual work of one academic centre within a university department of psychology. These principles are: concern with the human subject as a social entity; interest in the emergence of subjectivity in the social domain; interest in critique, defined as a concern with ideological issues in psychology; methodological pluralism, including an active assertion of the value of qualitative and theoretical research, as well as more traditional quantitative research; theoretical pluralism, including interest in discourses traditionally marginalized in academic psychology (e.g. psychoanalysis, systems theory, feminist theory, phenomenology); interest in inter- and transdisciplinary approaches to psychological theory and research; and interest in personal and social change, including psychotherapy. Some complicating issues relating to the process and content of this kind of work are also outlined.
A Typology of Negative Mentoring Experiences: A Multidimensional Scaling Study
Authors: Simon Shana A. , Eby Lillian T.
Published: April 2004

A typology of negative mentoring experiences was generated utilizing multidimensional scaling techniques. Similarity ratings were obtained on 16 negative mentoring experiences identified by previous research. Multidimensional scaling results supported a three-dimensional solution for the data. Based on both subjective and empirical interpretation strategies, it was determined that individuals consider outcome severity (minor versus serious), specificity (targeted versus diffuse), and mentor function (psychosocial versus career-related) when comparing negative mentoring experiences. Connections with theoretically related areas of social science research, as well as implications for theory-building, future research, and applied practice are discuss
Boundaries and Role Conflict When Work and Family are Colocated: A Communication Network and Symbolic Interaction Approach
Authors: Shumate Michelle , Fulk Janet
Published: April 2004

As virtual workplaces and homework programs become more common, workers often find themselves inhabiting multiple worlds and multiple roles simultaneously. For these individuals, boundary transitions are both more frequent and more challenging. This paper expands current theory on work-related boundary transitions by: (1) conceptualizing role conflict in the logic of dynamic communication networks, and (2) reconceptualizing ritual and routine behavior in boundary transitions as not simply aids to mental transitions but also as communicative and symbolic performance that is oriented toward other role senders. Underlying the framework is the concept of time-space paths (Giddens, 1979; Heidegger, 1996) as critical elements of role boundary identification and demarcation. This paper contributes to a better understanding of boundary issues for homeworkers by using a communication framework and emphasizing the agency that homeworkers have to mold others' expectations.
The Use of Questions in Organizational Consulting
Authors: Dillon J. T.
Published: April 2004

How do organizational consultants use questions as they go about their consulting work? Based on interviews with experienced consultants in France, this article reports their use of schemas or organized sets of questions that they pose to themselves as a guide to action in the moment of consulting, a usage interpreted on the principle of “questioning-in-action.” A comprehensive classification scheme is then introduced to accommodate the various questions that consultants ask about the various things involved in consulting. This scheme of categories and questions is used to analyze the actual questions that consultants are observed to ask, and then it is compared with other conceptual schemes and applied to one detailed consulting case in the literature. The findings are suggested as one means to enhance the understanding and practice of consulting.
Specific Factors Underlying Reemployment Self-Efficacy
Authors: Westaby James D. , Braithwaite Kenneth N.
Published: April 2004

This study compared two methods for assessing the specific factors underlying people’s reemployment self-efficacy (RSE). The first method used control belief measures, which assessed the specific factors perceived to make reemployment easy or difficult. The second method used motivational reason measures, which assessed the specific (nonhypothetical) factors people use to explain their overall RSE. Measures from both methods were applied to the same attribute categories, such as job availability, work qualifications, and job-listing information. An ethnically diverse sample of 815 unemployed individuals (mean age 37.2 years) registering for unemployment benefits in New York City participated. As hypothesized, results indicated that both control belief and motivational reason variables were related to RSE. In line with expectations, motivational reason variables explained substantial variance in RSE and scheduled interviews beyond that explained by the control belief variables. Moreover, the motivational reason method identified several variables influencing RSE that the control belief method was unable to identify as significant (e.g., having needed qualifications and job-listing knowledge). When results from both methods were presented to executive management at the New York City Department of Labor, motivational reason results had the strongest impact on subsequent policy decisions.
Organizational Reflections
Authors: Smith Kenwyn K. , Zane Nancie
Published: April 2004

This article explores the lessons extracted from the parallel processes enacted in the relationship between two consultant groups hired by Eastern (a large financial institution) to kick off a major culture change initiative. The inevitable conflicts between these two consulting groups, selected because they had very different missions and modes of operating, mirrored deeply impacted systemic tensions within Eastern, such as the desire to change and the wish to remain fundamentally unaltered. The consultants’ public struggles to overcome the obstacles to their collaboration helped Eastern surface several latent and intractable tensions threatening its culture change initiative. The processes highlighted here are pertinent whenever multiple organizations or groups attempt to assist a third institution.
Electron Beam Irradiation of Noncrosslinked LDPE–EVA Foam
Authors: Kim D. W. , Kim K. S.
Published: April 2004

The conventional cross-linking method using an electron beam for polyolefin foams is highly efficient, but the drawbacks are: costly equipment, nonuniform crosslinking, uneven dispersion of chemical foaming agents and additives, and relatively low gel content, which affect physical properties of the foam. In this paper, low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) were blended in an 80/20 ratio, and this noncrosslinked foam was exposed to various doses of electron beam irradiation in air. The foam was made using isobutane as the blowing agent. It has been found that foam with uniform cell structure was not achieved in the case of precrosslinked foam with more than 40% gel fraction. On the other hand, noncrosslinked foams are easily crosslinked to a gel content of about 57% with an electron beam irradiation under optimum conditions. The gel content of the postcrosslinked foams increases with increase in the irradiation dose, beam intensity, irradiation temperature and with the crosslinking coagent content. As derived from experimental studies, beam intensity seems to be the most essential parameter in regard to gel content homogeneity. Noticeable changes in mechanical properties, e.g. tensile strength, tear strength, compressive strength and hardness, were also observed. This paper also presents an experimental study on the manufacture of low-density open-cell foam.
Monitoring of Polyurethane Foam Cure
Authors: Jones Stephen A. , Scott Keith W. , Willoughby Bryan G. , Sheard Eric A.
Published: April 2004

The curing of polyurethane foam involves complex changes, changes from mobile liquid to rubbery, or even rigid, product are accompanied by changes in density and sample size. All these take place under conditions where there may be rapid changes in temperatures. The ability topro file and record such events has traditionally required skilled, often time-consuming observation. However, where non-foaming systems are concerned, technologists have had access to a variety of instrumentation that can monitor changes in viscosity or the development of elastic character. This facility is now available for foamed polyurethane, with a development of the Rapra Vibrating Needle Curemeter (VNC). The development involves the integration of the existing instrument with detectors for rise and exotherm. Continuous response/time plots are thus produced, a response for the development of viscoelastic properties being added to those for height and temperature. The result is a unique fingerprint for the cure which is amenable to storage and archiving. This paper will show the outputs for foaming PU systems and discuss some of the insights accessible with this powerful tool.
Automotive, Molded Viscoelastic Foams
Authors: Farkas Paul , Stanciu Romeo , Mendoza Liberato
Published: April 2004

An improved type ofmolded viscoelastic foam, Intellisense TM(Trademark of Woodbridge Foam Corporation), extends the effective operating range ofthe material from elevated temperatures to below 0 C, while maintaining the energy dissipation values at designed levels.

Until now, viscoelastic (VE) foams have not found a significant success in automotive interior/exterior applications due to an evident loss ofsome essential properties with changing conditions (e.g. diminished softness/ “friendliness” in contact with human body when used at low temperatures or reduced VE properties at high temperatures).

A viscoelastic behavior means a time-delayed and rate-dependent response to applied stress [Birley, A.W. et al. (1991). Physics of Plastics, pp. 260–261, Oxford University Press, New York, NY] and makes it desirable in parts designed for specific energy management (EM). However, to be acceptable for an application, the effectiveness of the foam response has to be in the expected usage temperature range of the final part. Systems formulated with a balanced mixture ofpolyols, some special additives, and modified isocyanates generated VE foams with the glass transition temperature (Tg) below 20 C. The observed loss ofviscoelasticity at elevated temperatures, common with prior-art foam of this type, is significantly reduced as well.

This novel approach to viscoelastic foams will benefit energy management automotive applications like head restraint, seat occupant safety, sound or vibration attenuation, etc. It is expected that this finding may extend the area of applicability beyond the car industry.
A Novel System Design for Continuous Processing of Plastic/Wood-Fiber Composite Foams with Improved Cell Morphology
Authors: Rizvi Ghaus M. , Pop-Iliev Remon , Parky Chul B.
Published: April 2004

It is believed that the moisture that is inherently present in nondried wood-fibers adversely affects the cell morphology of plastic/wood-fiber composite foams processed in extrusion. Based on this hypothesis, achieving a continuous extrusion-based production of fine-celled plastic/wood-fiber composite foams witha desirable quality would be strongly conditioned by the efficiency of the system designed for uninterrupted wood-fiber moisture elimination. This paper presents an innovative approachin addressing this problem by implementing the well-known cascade devolatilizing system in a chemical blowing agent (CBA) based production of plastic/wood-fiber composite foams. It comprises a moisture-evaporation tandem extrusion system equipped witha vent at the interconnection of the two extruders to serve for purging the moisture in the atmosphere. In order to check the performance of the newly developed system, an experimental study has been carried out for comparing the cell morphology and the volume expansion ratios of the foams obtained by processing identically formulated foamable plastic/wood-fiber composite mixtures using simultaneously the cascade devolatilizing tandem extrusion system and a corresponding single extruder withno vent. The experimental results revealed that the foams produced by using the cascade devolatilizing tandem system exhibited significantly improved cell morphologies and surface quality.
Foaming with Polymer Microspheres in Rotational Molding: The Effect of Coupling Agent
Authors: D’Agostino D. , Takács E. , Vlachopoulos J.
Published: April 2004

The use of polymer microspheres for producing fine-cellular foams is a new development in rotational molding. In previous studies, some reduction in mechanical properties has been found due to the immiscibility between the polymer shell and the matrix polymer. Coupling agents can act as a molecular bridge at this interface and can also affect bubble growth by altering the rheological properties of the matrix polymer as well as the microsphere shell material. The influence of different coupling agents on the melt properties of several resins was investigated, as well as the effect of these coupling agents on the mechanical properties of foamed rotationally molded parts.
Evaluation and Modeling of Injection-Molded Rigid Polypropylene Integral Foam
Authors: Müller Norbert , Ehrenstein Gottfried W.
Published: April 2004

Employing a modified injection-molding technology, where the mold is opened a short stroke after injection of the polymer melt, it is possible to manufacture plastic parts with a density reduction of 50% and more. For this processing approach, standard injection-molding equipment can be used. Together with an appropriate selection for the chemical foaming agent, most thermoplastic materials are suitable. The resulting moldings are a real lightweight design with compact skin layers and a foamed core fraction. To estimate the lightweight performance, bending specimens were investigated, and the gain in stiffness was visualized. By varying the thickness and the expansion degree, hints on the optimum foaming conditions were obtained. For engineering purpose, it is important to predict the performance of the integral foam molding during part design. A three- and a five-layer modeling approach were employed to represent the integral foam structure. Both ways were suitable to predict the stiffness enhancement, where already the three-layer representation is sufficient for primary design calculations. It became obvious that the foaming of thermoplastics with a breathing mold enables weight reduction up to 40% in flexion-loaded applications. Since the processing is still highly integrated, as it is the case with standard injection molding, and the cycle times do not increase significantly, the extra cost for the gain in stiffness almost reduces to the cost for foaming agent.
An Evaluation of the Thermal Conductivity of Extruded Polystyrene Foam Blown with HFC-134a or HCFC-142b
Authors: Vo Chau V. , Paquet Andrew N.
Published: April 2004

Insulation performance of extruded polystyrene (XPS) foams expanded with various halogenated blowing agents including HFC-134a or HCFC-142b was measured over time. Residual blowing agents were measured after aging up to 26 years. The diffusive transport properties of the blowing agents can be determined through the mathematical calculation of the heat transfer in the gas phase component of the foam thermal conductivity. These values are used in a Dow model which allows an accurate prediction of the long-term thermal resistance of extruded polystyrene foams blown with a variety of blowing agents including CFC-12, HCFC-142b, HCFC-22, HFC-134a, HFC-152a, and CO2. Excellent agreement was obtained between measured and predicted thermal conductivity values with samples stored in laboratory conditions, as well as samples extracted from field conditions, such as cellar and upside-down roof applications.

The results confirm the slow diffusion rate of CFC-12, HCFC-142b and HFC-134a through extruded polystyrene foam, and demonstrate that HFC-134a or HCFC-142b-blown extruded polystyrene (XPS) foams meet the requirement for applications requiring excellent long-term insulation performance. HCFC-22 and HFC-152a are fugitive blowing agents in XPS foams, and the thermal performance of foams made with these blowing agents reach the thermal performance of CO2-blown foams after a short aging period.
V.S. Naipaul, Chinua Achebe, Nobel Literature Prizes and African Writers as Cats, Dogs and Chameleons
Authors: lo Liyong Taban
Published: April 2004

Taban lo Liyong sent this comment on the award of the 2001 Nobel Prize for Literature to V.S. Naipaul, after reading’s the Journal’s Editorial on the subject (JCL 37, 1). It was, however, written prior to this and so bears no direct relationship to that Editorial. Nevertheless we hope it complements it as an African response to “Naipaul’s Nobel”.
Damage Tolerance of Thick-Section S-2 Glass Fabric Composites Subjected to Ballistic Impact Loading
Authors: Gillespie J. W. , Monib A. M. , Carlsson L. A.
Published: April 2004

The damage tolerance of thick S-2 glass-fabric reinforced polyester, vinylester, and epoxy matrix composite panels subjected to ballistic impact loading has been examined. The damage shape and size was examined using ultrasonic NDE. After inspection of the damage, residual compression strength of the impacted panels was measured. The hand laid-up glass-polyester composite suffered from a large damage size, and low strength in compression after ballistic impact (CABI). The glass-vinylester and glass-epoxy panels manufactured using the SCRIMP process showed small damage sizes and high residual strengths. Through-thickness stitching of glass-vinylester and glass-epoxy panels was found to reduce the impact damage size, but the difference was quite small and did not translate into a substantial strength increase. The performance of panels with a ceramic tile bonded at the impact site was also examined. Model predictions of the CABI strength based on compression failure at the net section are compared to measured data, and implications for design of damage tolerant materials are discussed.
A Postprocessing Approach to Determine Transverse Stresses in Geometrically Nonlinear Composite and Sandwich Structures
Authors: Lee Keejoo , Lee Sung W.
Published: April 2004

A postprocessing scheme is developed to accurately determine transverse stresses in composite and sandwich panels undergoing geometrically nonlinear deformations. Transverse stresses are recovered at a point of interest via a one-dimensional, equilibrium-based least-square finite element method that utilizes the in-plane stresses and shear forces obtained by a finite element analysis. Numerical results demonstrate that, with minimal addition of computational efforts, the present postprocessing approach can be used to enhance the accuracy of transverse stresses.
Fatigue Crack Propagation Behavior of Thermally Degraded SiCp/Al Composites
Authors: Ahn J. J. , Ochiai S.
Published: April 2004

Silicon carbide particle reinforced aluminum 6061 composites (SiCp/Al) with 5 and 10% SiC particle volume fractions as well as aluminum 6061 alloy (AA6061) were used to examine their fatigue crack propagation behavior after degraded by thermal cycling and isothermal exposure. Fracture surfaces were observed under a scanning electron microscope. Thermally cycled specimens (TC-SiCp/Al and TC-AA6061) were prepared through 100 thermal cyclings between 200 C and 300 C and isothermally exposed specimens (IE-SiCp/Al and IE-AA6061) was prepared by isothermal exposure at 300 C for 80 h. Difference of fatigue crack propagation behavior in the IE- and TC-AA6061 was small with increase of stress intensity factor range, iK even if da/dN of the both types of AA6061 were different at the initial stress intensity factor range. Fatigue crack propagation behavior of the IE-SiCp/Al was similar regardless of SiC particle volume fractions. While for the TC-SiCp/Al, fatigue crack propagation behavior was different in the SiC particle volume fractions and to the TC-AA6061. Besides, it notes that there was good relation between exponent m and coefficient C of the Paris equation regardless of thermal cycling and isothermal exposure and SiC particle volume fractions. The relation between m and C could be described as C 1/4 AΘm where constants A and B were 1.668 E-5 and 0.165, respectively.
Experimental Investigation of the Effect of Fiber-mat Architecture on the Unsaturated Flow in Liquid Composite Molding
Authors: Babu Baiju Z. , Pillai Krishna M.
Published: April 2004

In liquid composite molding technologies such as RTM, this study of the inlet-pressure history for the constant flow-rate 1-D flow experiment reveals that the measured pressure profile, which droop downwards as in earlier studies on the unsaturated flow, is at a variance with the linear pressure profile predicted by the physics used for state-of-the-art LCM mold filling simulations. The droop along with the error in the inlet-pressure predictions increase with an increase in the fibermat compression. The effect of fiber-mat architecture on the droop in the inletpressure profiles is studied and significant droops are observed for various stitched mats as compared to the woven mats. This study repudiates the long-held view that mere presence of cylindrical or elliptical tows in the woven or stitched fiber-mats automatically leads to the unsaturated flow characteristic of dual-scale porous media; rather the presence of continuous uninterrupted macrochannels along the flow direction for preferential channel-flow is found to be necessary for the appearance of a drooping inlet-pressure history characteristic of the unsaturated flow.
Porosity Reduction in the High-Speed Processing of Glass-Fiber Composites by Resin Transfer Molding (RTM)
Authors: Barraza Harry J. , Hamidib Youssef K. , Aktasb, Levent , O’Rear Edgar A. , Altan M. C.
Published: April 2004

High-speed processing is essential to achieve lower production cost in the fabrication of fiber-reinforced composites with the current liquid molding practices. A major consequence of increasing the resin injection velocity is the formation of defects such as voids and dry regions that decrease the load-bearing capability of the composite. Void formation mechanisms and analytical predictions of the detrimental effect of porosity on the structural integrity of molded parts have been studied extensively. In contrast, knowledge of void removal strategies is very limited. In this investigation, various postfill pressure levels were applied to disk-shaped random-mat glass/epoxy parts molded at high volumetric flow rates as a method to reduce their voidage content. Quantitative image analysis over cross-sections cut from these composites revealed that significant changes in porosity concentration take place with the postfill pressure. For instance, overall void content dropped more than 70% with the application of a postfill pressure as low as 300 kPa. Other important void morphometry characteristics such as void shape, size, and spatial distribution could also be manipulated by this method. As the packing pressure increases, large voids gradually disappear, and at the same time, the small circular voids are mobilized towards radial locations near the vents. In addition to this spatial voidage gradient in the radial direction, voidage gradient also exists through the specimen thickness. It seems that higher front velocities promote the appearance of secondary flow phenomena inside the mold cavity (e.g. microfountain flow), which may explain why more voids tend to concentrate at the surface of the specimen irrespective of the postfill pressure level reached inside the mold.
A Novel Method for Determining Interfacial Residual Stress in Fiberreinforced Composites
Authors: Xing Y. M. , Kishimoto S. , Tanaka Y. , Shinya N.
Published: April 2004

A method for measuring the residual stress at the interface in fiberreinforced composites is presented in this study. The residual strains (stresses) at the interface are released by pushing the fiber out. The released residual strains are measured using an electron moire technique, which can fabricate grids with frequencies up to 10,000 lines/mm on the composites surface so that a displacement sensitivity of 100nm can be achieved. This method can be applied to almost all fiber-reinforced composites, such as metal-matrix composites (MMCs) and fiberreinforced plastics (FRPs). It provides a new experimental technique for measuring interfacial residual stress in MMCs, and a unique method for FRPs. Measurements of the interfacial residual stresses in SiC/Ti-15-3 and boron/epoxy composites show the validity of the method.
Processability, Thermal, Mechanical, and Morphological Properties of Novolac Type-Epoxy Resin-Based Carbon-Carbon Composite
Authors: Ma Chen-Chi M. , Chen Chih-Yuan , Kuan Hsu-Chiang , Chang Wen-Chi
Published: April 2004

The objectives of this study are to investigate the feasibility of utilizing novolac type-epoxy resin to prepare carbon-carbon(C-C) composite and to study the properties of the composite. Different postcuring times, temperatures, and carbonization heat treatment temperatures were used to treat the novolac type-epoxy resin. The changes in the thermal, physical, and mechanical properties during the carbonization processing are also investigated. The results show that the matrix cured at a higher postcuring time and temperature possesses a significant weight loss on the postcure process and limits the weight loss on carbonization processing. Increasing the postcure time and temperature will improve the mechanical properties of composite after carbonization, however, higher postcure time and temperature will cause additional matrix and fabric damage. In the carbonization process, the mechanical properties and density of C-C composite decrease rapidly after 400 C. When heat treatment temperature is increased to 800 C, mechanical properties and density of composite will remain constant and then increase slightly.
Permeability-Porosity Relationship in RTM for Different Fiberglass and Natural Reinforcements
Authors: Rodriguez E. , Giacomelli F. , Vazquez A.
Published: April 2004

This study investigates the permeability-porosity relationship for glass and natural fiber mats. The estimation of the permeability-porosity relationship for glass mats is not new and has been investigated before by several authors, but in the present paper the same relationship was discovered for natural fibers. The experimental permeability values were fitted by the Carman-Kozeny equation with two fitting parameters: the Kozeny constant and the exponent of the porosity. The obtained permeability for the natural fiber mats shows higher values than glass fiber mat.
Transverse Failure in Thick S2-Glass/ Epoxy Fiber-Reinforced Composites
Authors: Vural M. , Ravichandran G.
Published: April 2004

The transverse mechanical and failure behavior of unidirectional S2-glass/epoxy composites are investigated and reported for a wide range of strain rates from 10-4to 10 4s-1under multiaxial compressive loading conditions. The effect of stress multiaxiality is explored using the confining sleeve technique to impose varying degrees of lateral confinement. The lateral confinement has been found to significantly increase both the maximum attainable stress level and the strain to failure. Scanning electron microscopy (SEM) observations on recovered specimens reveal that the transverse failure occurs within localized shear bands through multiple fiber–matrix interface failure at the micro-scale. Based on theorientation of shear bands a Mohr–Coulomb type failure criterion is suggested to represent the transverse failure of unidirectional S2-glass/epoxy composites.
Temporal Uncertainty Time Warp: An Implementation Based on Java and ActorFoundry
Authors: Beraldi Roberto , Nigro Libero , Orlando Antonino
Published: April 2004

This article describes temporal uncertainty time warp (TUTW), a distributed control engine designed for exploitation of temporal uncertainty (TU) in general optimistic simulations. Novel in TUTW is an event model in which time intervals are attached to events instead of classical punctual or “precise” time stamps. All of this complies with system specifications where the occurrence time of events cannot be known with complete certainty. TUTW is able to take advantage of TU by resolving events in such a way as to reduce the number of rollbacks. The simulator performance can thus be improved without necessarily compromising the accuracy of the results. An agent-based implementation of TUTW was achieved that enables simulations to be carried out over the Internet. The implementation depends on Java and the ActorFoundry middleware. The implementation is totally portable and simplifies configuration and control of a distributed simulation virtual computer that includes heterogeneous computing platforms. The article reports performance and accuracy results of TUTW applied to a large QNET simulation model.
Simulation of Graphical Models for Multiagent Probabilistic Inference
Authors: Xiang Y. , An X. , Cercone N.
Published: April 2004

Multiply-sectioned Bayesian networks (MSBNs) extend Bayesian networks to graphical models for multiagent probabilistic reasoning. The empirical study of algorithms for manipulations of MSBNs (e.g., verification, compilation, and inference) requires experimental MSBNs. As engineering MSBNs in large problem domains requires significant knowledge and engineering effort, the authors explore automatic simulation of MSBNs. Due to the large domain over which an MSBN is defined and a set of constraints to be satisfied, a generate-and-test approach toward simulation has a high rate of failure. The authors present an alternative approach that treats the simulation process as a sequence of decisions. They constrain the space of each decision so that backtracking is minimized and the outcome is always a legal MSBN. A suite of algorithms that implements this approach is presented, and experimental results are shown.
Simulation Methods for Optimal Experimental Design in Systems Biology
Authors: Faller D. , Klingmüller U. , Timmer J.
Published: April 2004

To obtain a systems-level understanding of a biological system, the authors conducted quantitative dynamic experiments from which the system structure and the parameters have to be deduced. Since biological systems have to cope with different environmental conditions, certain properties are often robust with respect to variations in some of the parameters. Hence, it is important to use optimal experimental design considerations in advance of the experiments to improve the information content of the measurements. Using the MAP-Kinase pathway as an example, the authors present a simulation study investigating the application of different optimality criteria. It is demonstrated that experimental design significantly improves the parameter estimation accuracy and also reveals difficulties in parameter estimation due to robustness.
Improving the Development Process for Eukaryotic Cell Cycle Models with a Modeling Support Environment
Authors: Allen Nicholas A. , Shaffer Clifford A. , Ramakrishnan Naren , Vass Marc T. , Watson Layne T.
Published: April 2004

Theoretical molecular biologists attempt to describe cellular processes and regulatory networks with continuous and discrete mathematical models. Previous practice has been to develop models largely by hand and then to validate them primarily by comparing time-series plots versus the observed experimental results. The authors report their experiences in designing and building a modeling support environment for cell cycle models. They describe improvements to the development process for molecular network models by (a) identifying the key elements of the existing modeling process, (b) incorporating simulation methodology into a revised modeling process, and (c) building and testing software that supports the revised modeling process.