220 research outputs found

    Physical and mechanical behavior of amorphous poly(arylene ether-co-imidazole)s and poly(arylene ether-co-imidazole) modified epoxies

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    Due to the high crosslink density of cured epoxy resins they generally lack damage tolerance. A significant amount of research has been expended to improve the toughness of epoxies. Research into the area of thermoplastic epoxy modifiers has begun to overcome some of the limitations of early methods of epoxy toughening (i.e. lower modulus and thermal stability).;This study examines the physical and mechanical properties of random poly(arylene ether-co-imidazole) (PAE-co-Is) and the characterization of epoxies modified with poly(arylene ether-co-imidazole)s.;Poly(arylene ether-co-imidazole)s exhibited the highest solubility in N,N,N{dollar}\rm\sp\prime,N\sp\prime,{dollar}-tetraglycidyl- 4,4{dollar}\sp\prime{dollar} diaminodiphenyl methane (TGMDA) based resins. The high molecular weight polymers caused significant decreases in melt flow behavior of the modified systems. Modification of TGMDA resins with PAE-co-Is significantly decreased the tetrahydrofuran sensitivity of the cured system and did not significantly affect the moisture absorption properties. One system modified with 10% w/w polymer exhibited increases in fracture toughness 1.7 times that of the unmodified system

    Institutional analysis of governmental involvement in housing : a preliminary exploration

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    This paper, one of a series resulting from institutional analysis of photovoltaic (PV) acceptance, provides a preliminary exploration of governmental acitvities in the housing sector. It is based on theoretical formulations and utilizes methods developed in an earlier paper in this series. The housing process is examined in terms of seven institutional functions -- finance, research, political, regulation, production, service, and socialization -- from a governmental perspective. It is concluded that the federal government is most active in providing for finance, research, and political functions. State and local governments tend to perform the bulk of the regulation functions, though recent trends show increased federal involvement in large-scale regulation, through such mechanisms as the Environmental Impact Statement. The production, service, and socialization functions tend to be performed as a result of the direct realization of the first four.Prepared under Dept. of Energy Contract no. EX-76-A-01-2295, Task order no.37

    Tobacco industry issues management organizations: Creating a global corporate network to undermine public health

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    <p>Abstract</p> <p>Background</p> <p>The global tobacco epidemic claims 5 million lives each year, facilitated by the ability of transnational tobacco companies to delay or thwart meaningful tobacco control worldwide. A series of cross-company tobacco industry "issues management organizations" has played an important role in coordinating and implementing common strategies to defeat tobacco control efforts at international, national, and regional levels. This study examines the development and enumerates the activities of these organizations and explores the implications of continuing industry cooperation for global public health.</p> <p>Methods</p> <p>Using a snowball sampling strategy, we collected documentary data from tobacco industry documents archives and assembled them into a chronologically organized case study.</p> <p>Results</p> <p>The International Committee on Smoking Issues (ICOSI) was formed in 1977 by seven tobacco company chief executives to create common anti-tobacco control strategies and build a global network of regional and national manufacturing associations. The organization's name subsequently changed to INFOTAB. The multinational companies built the organization rapidly: by 1984, it had 69 members operating in 57 countries. INFOTAB material, including position papers and "action kits" helped members challenge local tobacco control measures and maintain tobacco-friendly environments. In 1992 INFOTAB was replaced by two smaller organizations. The Tobacco Documentation Centre, which continues to operate, distributes smoking-related information and industry argumentation to members, some produced by cross-company committees. Agro-Tobacco Services, and now Hallmark Marketing Services, assists the INFOTAB-backed and industry supported International Tobacco Growers Association in advancing claims regarding the economic importance of tobacco in developing nations.</p> <p>Conclusion</p> <p>The massive scale and scope of this industry effort illustrate how corporate interests, when threatened by the globalization of public health, sidestep competitive concerns to coordinate their activities. The global network of national and regional manufacturing associations created and nurtured by INFOTAB remains active, particularly in relation to the recently negotiated global health treaty, the Framework Convention on Tobacco Control. Policymakers should be aware that although these associations claim to represent only national or regional interests, they are allied to and coordinated with a confederation of transnational tobacco companies seeking to protect profits by undermining public health.</p

    A Framework for Predicting the Optimal Price and Time to Sell a Home

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    Due to high barriers to conduct housing market research, many home sellers opt to go to the market with asymmetric information or invest large sums of money into hiring a professional. This research aims to reduce these inefficiencies by proposing a framework that provides sellers with a concrete recommendation on optimal time and price to sell a home to maximize financial gains. The core data used in this research is the NOVA Home Price dataset, which contains 34,973 house listings over multiple years in Northern Virginia. A pipeline of machine learning models, including a linear regression, random forest, XGboost and artificial neural network are trained and evaluated for performance on predicting home close prices. The final model employed is an ensemble of random forest and XGboost and is tested on both a holdout set of Northern Virginia data as well as real estate data scraped from Zillow to introduce some variance. To control for future economic trends, a long-short-term memory model is then trained using temporal data from the Federal Reserve. Finally, the algorithm distills the insights from the disparate models to provide recommendations on optimal time and price to go to market, as well as short-term investments to increase potential gains from sale. The study finds that home features coupled with macro-economic trends can offer home sellers strong recommendations on optimal time and price to list homes. This research is preliminary and should be used as a baseline for future studies

    Solar heating and cooling of housing : |b five institutional analysis case studies

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    This paper is one of a series resulting from institutional analysis of photovoltaic (PV) acceptance. The case studies reported here involve use of solar thermal technologies in various residential settings. All of the projects are part of the DOE-HUD Solar Heating and Cooling Demonstration Program. This program provides grants to developers to prompt them to use this innovation. Each of the five cases illustrates one or more institu- tional forces which influence the acceptance of solar energy in the resi- dential sector. Friends Community is an instance of developer involvement for reasons other than profit, and the way in which other factors (such as designers and consumers) react to such housing development. Reservoir Hills Solar Houses illustrates the process of entry by new development firms, the role of public agencies in encouraging various forms of housing and the problems of using product innovations without adequately developed industry support infrastructures. Project Solar for Indiana illustrates the import- ance of supporting institutional networks, in this case the homebuilders association, the state government and key individuals, who play mediating and legitimating roles in solar acceptance. Solar in California discusses public efforts at a city level -- Santa Clara, a county level -- San Diego, and the state level in what is generally regarded as the state most active in turning to forms of solar energy. Finally, PNM/AMREP illustrates the process of large development corporation decision making, and the manner in which an investor- owned utility is shifting its orientation of energy provision

    Do as I Say and Do as I Do: Teacher Educators’ Narratives about Urban Teaching

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    Teacher educators share much in common with their pre-service candidates, but neither group resembles the increasingly diverse PreK-12 student population in cities across the United States. In the words of Gary Howard (1999): How can you teach what you don’t know? A group of faculty members at a small, suburban liberal arts college decided to address this dilemma head-on by creating an urban teaching group. In addition to reading about and discussing important issues related to urban education and culturally responsive pedagogy, we participated in community mapping with early childhood candidates and were assigned to inner-city elementary classrooms. Across a tenweek term, we observed, tutored, and taught lessons under the supervision of cooperating teachers, many of whom were our own graduates. Through direct experience, reflection, and dialogue, we challenged our assumptions and examined the realities of teaching in an urban setting

    Modelos explicativos da memória prospectiva: uma revisão teórica

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    Neste artigo é apresentada uma revisão da literatura sobre os mecanismos cognitivos associados à memória prospectiva, organizados de acordo com a divisão das diferentes fases da recordação prospectiva (i.e., codificação, retenção e recuperação). Inicialmente, é apresentada a diversidade de dados da investigação que sustentam diferentes abordagens explicativas do fenômeno de recuperação de intenções, considerando a natureza automática ou estratégica da memória prospectiva. Em seguida, são salientadas as potenciais explicações sobre os mecanismos presentes durante o intervalo de retenção e na fase de codificação.(undefined
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