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排序方式: 共有265条查询结果,搜索用时 125 毫秒
91.
Authier Jerry; Gustafson Kay; Fix A. James; Daughton David 《Canadian Metallurgical Quarterly》1981,12(4):438
Evaluates the effectiveness of the psychoeducational model of treatment by examining social-skills training (SST), a subset of the model. The literature comparing SST with traditional insight-oriented therapy suggests that SST is equal to, and possibly superior in, effectiveness. Possible problems with social-skills training models, such as too narrowly defining the client's problems, expecting the approach to be a panacea, and the possible lack of generalizability, are elaborated. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
A model applicable to normal metal tunnel junctions is presented. This model, referred to herein as the stationary state model, is an extension of the extended basis function theory of Kleinman and Duke. Under the assumption that elastic tunneling is the dominant transport mechanism under static bias, we have extended the theory to include the case where there is an ac component of bias potential, and we have derived the fluctuation spectrum. In this approach structure eigenstates are used as the basis, allowing observables to be evaluated without recourse to the perturbation theory inherent in the transfer Hamiltonian model. Comparison is made to the appropriate results of the first order transfer Hamiltonian model, and it is found that there is close but not always exact agreement to lowest order in the tunneling exponential. The stationary state model should be accurate with large barrier transmission, as it includes all orders of the tunneling exponential. The model as presented here should be applicable to normal metal tunnel junctions, where elastic tunneling is the dominant transport mechanism (under static bias), up to infrared excitation frequencies. 相似文献
93.
At present, as in the past, the bulk of environmental radiation comes from natural sources, cosmic radiation, and natural radioactivity. The normal dose to man from natural sources ranges from about 60 to 250 mrads/year. Fallout from weapons testing has provided as much as 20 to 25 mrads/year during the early to mid-1960's. At present, medical uses provide 20 to 100 mrads/year to the average individual in the U.S. Radiation to the general population from nuclear power is insignificant at present. With the trend toward improved technology in the control and containment of radioactivity from nuclear facilities, future levels should not exceed those observed from fallout. Improvements in radiological procedures should materially reduce unnecessary exposure from this application. 相似文献
94.
The effect of ageing at different storage conditions on the microstructure and melting properties of two petroleum waxes,
petrolatum and microcrystalline wax, were investigated. The two waxes were stored for a maximum of 50 weeks at different temperatures.
Samples were analysed before storage and removed from storage and analysed after different storage times. The effect of storage
time and temperature was analysed with confocal laser scanning microscopy and modulated differential scanning calorimetry.
Some alteration in the microstructure occurred with longer storage time. The amount of fine and irregular structures seen
in the initial petrolatum samples decreased with storage time, and some shadowy, grey areas appeared. The microstructure of
the microcrystalline wax stored at 23 °C became more diffuse and more, shadowy, grey areas appeared with time compared to
samples stored at 50 °C. These showed coarser crystalline structures and fewer shadowy, grey areas. The results of confocal
laser scanning microscopy and modulated differential scanning calorimetry analyses indicated that recrystallization occurred
in both waxes during storage. The proposed recrystallization processes taking place during storage were most likely the same
in all samples, but the recrystallization occurred to a greater extent in the microcrystalline wax samples stored at 50 °C. 相似文献
95.
Ketterson Timothy U.; Glueckauf Robert L.; Blonder Lee X.; Gustafson David J.; Donovan Neila J.; Rodriquez Amy D.; Pekich Dan; Ley Christy; Gonzalez-Rothi Leslie J. 《Canadian Metallurgical Quarterly》2008,53(2):215
Objective: To perform a psychometric evaluation of the Functional Outcome Questionnaire for Aphasia (FOQ-A), a 32-item instrument designed to assess the extent to which a person who has had a stroke performs several important functional communication behaviors. Research Design: The FOQ-A was administered to family caregivers of persons with a history of left hemisphere stroke (N = 91) undergoing a comprehensive screening assessment to determine their eligibility for participation in research trials for novel stroke rehabilitation interventions. Results: Statistical analyses provided strong support for the internal consistency reliability and the convergent and discriminant validity of the FOQ-A. An exploratory factor analysis revealed a two-factor solution, Basic Verbal Expression and Conversational Response Skills. Conclusions: The present findings build on earlier evidence indicating that the FOQ-A has good psychometric properties and considerable promise as a measure of functional communication in aphasia rehabilitation. Future research will focus on the test-retest reliability, criterion-oriented validity, and predictive validity of the instrument. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
David Whitall W. Dean Hively Andrew K. Leight Laura L. McConnell Clifford P. Rice Gregory W. McCarty Anne Gustafson 《The Science of the total environment》2010,408(9):2096-7590
Restoration of the Chesapeake Bay, the largest estuary in the United States, is a national priority. Documentation of progress of this restoration effort is needed. A study was conducted to examine water quality in the Choptank River estuary, a tributary of the Chesapeake Bay that since 1998 has been classified as impaired waters under the Federal Clean Water Act. Multiple water quality parameters (salinity, temperature, dissolved oxygen, chlorophyll a) and analyte concentrations (nutrients, herbicide and herbicide degradation products, arsenic, and copper) were measured at seven sampling stations in the Choptank River estuary. Samples were collected under base flow conditions in the basin on thirteen dates between March 2005 and April 2008. As commonly observed, results indicate that agriculture is a primary source of nitrate in the estuary and that both agriculture and wastewater treatment plants are important sources of phosphorus. Concentrations of copper in the lower estuary consistently exceeded both chronic and acute water quality criteria, possibly due to use of copper in antifouling boat paint. Concentrations of copper in the upstream watersheds were low, indicating that agriculture is not a significant source of copper loading to the estuary. Concentrations of herbicides (atrazine, simazine, and metolachlor) peaked during early-summer, indicating a rapid surface-transport delivery pathway from agricultural areas, while their degradation products (CIAT, CEAT, MESA, and MOA) appeared to be delivered via groundwater transport. Some in-river processing of CEAT occurred, whereas MESA was conservative. Observed concentrations of herbicide residues did not approach established levels of concern for aquatic organisms. Results of this study highlight the importance of continued implementation of best management practices to improve water quality in the estuary. This work provides a baseline against which to compare future changes in water quality and may be used to design future monitoring programs needed to assess restoration strategy efficacy. 相似文献
97.
Peter A. Gustafson Anthony M. Waas 《International journal for numerical methods in engineering》2009,79(1):94-126
A bonded joint finite element (FE) for a symmetric double lap joint is developed that is capable of predicting field quantities in the lap region. The element is a hybrid method and incorporates features of classical analytical and numerical methods. The element stiffness and load vector formulations have unique, load dependent, non‐linear shape functions based on an analytical solution. The adaptive shape functions are formulated in terms of the dimensionless mechanical load fraction $(\bar{\bar{\phi}}_P)$ and total load $(\bar{\bar{\phi}}_{\rm {tot}})$ and are capable of predicting the thermal and mechanical load response. The bonded joint element has been implemented as a user element in the Abaqus® commercial FE code. A comparison of the stress predictions for the bonded joint element and a conventional 2D FE model is presented and are found to be in good agreement. Therefore, the element provides a computationally efficient and mesh‐independent stress prediction. The single element reproduces the analytical solution with minimal analyst input and can be easily incorporated into early design and sizing studies. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
98.
This study examines the financial feasibility of producing ethanol biofuel from sugar beets in central North Dakota. Under the Energy Independence and Security Act (EISA) of 2007, biofuel from sugar beets uniquely qualifies as an “advanced biofuel”. EISA mandates production of 21 billion gallons of advanced biofuels annually by 2022. A stochastic simulation financial model was calibrated with irrigated sugar beet data from central North Dakota to determine economic feasibility and risks of production for 0.038 hm3y−1 (or 10 MGY (Million Gallon per Year) and 0.076 hm3y−1 (or 20 MGY) ethanol plants. Study results indicate that feedstock costs, which include sugar beets and beet molasses, account for more than 70 percent of total production expenses. The estimated breakeven ethanol price for the 0.076 hm3y−1 plant is $400 m−3 ($1.52 per gallon) and $450 m−3 ($1.71 per gallon) for the 0.038 hm3y−1 plant. Breakeven prices for feedstocks are also estimated and show that the 0.076 hm3y−1 plant can tolerate greater ethanol and feedstock price risks than the 0.038 hm3y−1 plant. Our results also show that one of the most important factors that affect investment success is the price of ethanol. At an ethanol price of $484.21 m−3 ($1.84 per gallon), and assuming other factors remain unchanged, the estimated net present value (NPV) for the 0.076 hm3y−1 plant is $41.54 million. By comparison, the estimated NPV for the 0.038 hm3y−1 plant is only $8.30 million. Other factors such as changes in prices of co-products and utilities have a relatively minor effect on investment viability. 相似文献
99.
S. Savary S. Bregaglio L. Willocquet D. Gustafson D. Mason D’Croz A. Sparks N. Castilla A. Djurle C. Allinne Mamta Sharma V. Rossi L. Amorim A. Bergamin J. Yuen P. Esker Neil McRoberts J. Avelino E. Duveiller J. Koo K. Garrett 《Food Security》2017,9(2):311-327
The literature on the importance of plant pathogens sometimes emphasizes their possible role in historical food shortages and even in famines. Aside from such major crises, plant pathogens should also be seen as important reducers of crop performances, with impacts on system sustainability, from the ecological, agronomical, social, and economic standpoints – all contributing ultimately to affecting food security. These views need reconciliation in order to produce a clearer picture of the multidimensional effects of plant disease epidemics. Such a picture is needed for disease management today, but would also be useful for future policies. This article attempts to develop a framework that would enable assessment of the impacts of plant diseases, referred collectively to as crop health, on food security via its components. We have combined three different existing definitions of food security in order to develop a framework consisting of the following six components: (1) Availability. Primary production; (2) Availability. Import - Stockpiles; (3) Access. Physical and supply chain; (4) Access. Economic; (5) Stability of food availability; (6) Utility-Safety-Quality-Nutritive value. In this framework, components of food security are combined with three attributes of production situations: the nature of the considered crop (i.e. food- or non-food), the structure of farms (i.e. subsistence or commercial), and the structure of markets (i.e. weakly organized and local, to strongly organized and globalized). The resulting matrix: [Food security components] × [Attributes of production situations] provides a framework where the impacts of chronic, acute, and emerging plant disease epidemics on food security can be examined. We propose that, given the number of components and interactions at play, a systems modelling approach is required to address the functioning of food systems exposed to plant disease risks. This approach would have application in both the management of the current attrition of crop performances by plant diseases, and also of possible disease-induced shocks. Such an approach would also enable quantifying shifts in disease vulnerability of production situations, and therefore, of food systems, as a result of climate change, globalization, and evolving crop health. 相似文献
100.
This work deals with the synthesis of a new type of compatibilizer suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complimentary to hydroxyl. Polypropylene–phenol formaldehyde graft copolymers from thermoplastic phenol formaldehyde (PF) resins and functionalized polypropylene (f‐PP) were synthesized by reactive extrusion. The content of PF in the graft copolymer was determined by reaction variables like type and density of functionality on PP, molecular weight of PF, and viscosity ratio of f‐PP and PF. The results showed that the viscosity ratio is of primary importance for such reactive processing. Also, type and concentration of the functional groups were important variables. The glycidyl methacrylate functionality resulted in higher conversions than did PP‐g‐maleic anhydride within the available reaction times. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 347–354, 2000 相似文献