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991.
Recently, Douglas et al. [4] introduced a new, low-order, nonconforming rectangular element for scalar elliptic equations.
Here, we apply this element in the approximation of each component of the velocity in the stationary Stokes and Navier–Stokes
equations, along with a piecewise-constant element for the pressure. We obtain a stable element in both cases for which optimal
error estimates for the approximation of both the velocity and pressure in L
2 can be established, as well as one in a broken H
1-norm for the velocity.
Received: January 1999 / Accepted: April 1999 相似文献
992.
Agent technology has been considered as an important approach for developing distributed intelligent manufacturing systems. A number of researchers have attempted to apply agent technology to manufacturing enterprise integration, supply chain management, manufacturing planning, scheduling and control, materials handling, and holonic manufacturing systems. This paper gives a brief survey of some related projects in this area, and discusses some key issues in developing agent-based manufacturing systems such as agent technology for enterprise integration and supply chain management, agent encapsulation, system architectures, dynamic system reconfiguration, learning, design and manufacturability assessments, distributed dynamic scheduling, integration of planning and scheduling, concurrent scheduling and execution, factory control structures, potential tools and standards for developing agent-based manufacturing systems. An extensive annotated bibliography is provided. 相似文献
993.
Brener Nancy D.; McMahon Pamela M.; Warren Charles W.; Douglas Kathy A. 《Canadian Metallurgical Quarterly》1999,67(2):252
This study analyzed data from the 1995 National College Health Risk Behavior Survey (NCHRBS) to assess the prevalence of lifetime rape among female college students and to examine the association between rape and health-risk behaviors. The NCHRBS used a mail questionnaire to assess health-risk behaviors among a nationally representative sample of undergraduate students. Twenty percent of female students reported ever having been forced to have sexual intercourse, most often during adolescence. When analyses controlled for demographic characteristics, female students who had ever been raped were significantly more likely than those who had not to report a wide range of health-risk behaviors. These results highlight a need to improve rape prevention and treatment programs for female adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
J. D. Douglas J. E. Braun E. A. Groll D. R. Tree 《International Journal of Refrigeration》1999,22(2):647
This paper describes the development and application of a general purpose method for comparing alternative refrigerants. The method utilizes a single performance index based upon minimum cost for a simplified system operating with a given cooling capacity and efficiency. The cost-based method is an improvement over other methods for evaluating refrigerants in that it more appropriately considers the influence of both thermodynamic and transport properties on refrigerant choice and it allows consideration of additional costs associated with some replacements (e.g. safety features for flammable refrigerants). A computer model based upon this method was used to evaluate the performance of several leading R-22 replacement candidates for window air conditioners. Primarily, the cost differences between alternative refrigerants are associated with the heat exchangers and the refrigerant/oil requirements. The cost differences associated with different compressor displacement requirements were found to have a minor influence on overall cost differences. For the optimized systems, all of the alternatives had system costs that were within about 4% of those for R-22. Further, the differences between most of the alternative refrigerants were smaller than the uncertainties in the analysis. 相似文献
995.
Many changes in organizations are based on communication developments, the most prevalent of which currently is the expanding nature of electronic communication media. The use of electronic communications leads to changes in other areas. Manager and employee relationships rely on organizational structure, type of technology, group work and task, and employee empowerment and organizational attitude. This paper explores the communication changes by comparing components of the traditional, hierarchical organization with the modern, spherical or flat organization. A synthesis of the literature concerning this topic is presented. From this, a survey instrument was developed, and a pretest was run. The information presented here gives managers certain insights about the impact of new communication technologies on the evolving modern organization. © 相似文献
996.
Krishnamoorthy A.V. Ford J.E. Kiamilev F.E. Rozier R.G. Hunsche S. Goossen K.W. Tseng B. Walker J.A. Cunningham J.E. Jan W.Y. Nuss M.C. 《IEEE journal of selected topics in quantum electronics》1999,5(2):261-275
We present a single-chip asynchronous multiprocessor optoelectronic bit-sliced arrayed (AMOEBA) crossbar switch. The AMOEBA switch addresses the challenge to produce a large-scale, nonblocking packet switch through dense integration of photonic devices directly onto silicon VLSI circuits. Optoelectronic-VLSI technology is used to integrate the switch fabric, routing controller, packet buffers, line interface circuits, and optoelectronic conversion devices on a single chip. We show how free-space optical interconnects and wavelength-and-space-division-multiplex networking on single-mode fibers can provide switched interconnection between multiple nodes in a distributed computing environment. An optomechanical transceiver package accomplishes the free-space-to-fiber interfacing. We report the implementation and testing of the key components of a 16-channel AMOEBA prototype switch with a potential capacity of 12.8 Gb/s (or 800 Mb/s/channel), and capable of switching 16 million packets per second 相似文献
997.
998.
Eddaoudi Mohamed Li Hailian Reineke Theresa Fehr Michael Kelley Douglas Groy Thomas L. Yaghi O.M. 《Topics in Catalysis》1999,9(1-2):105-111
Metal-carboxylate clusters are ideally suited as secondary building units (SBU) for the assembly of extended open frameworks.
Examples extracted from the chemistry of the multidentate building block 1,4-benzenedicarboxylate (BDC) show that Zn(BDC)
clusters lead to the formation of rigid, stable and truly microporous metal-carboxylate networks. Gas sorption isotherms measured
for this class of materials show type (I) gas uptake that is analogous to those observed for zeolites and molecular sieves.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
999.
Rubber–rubber blends are used widely in industry, for example, in tire manufacture. It is often difficult to characterize interfaces in such rubber–rubber blends quantitatively because of the similarity in the chemical structure of the component rubbers. Here, a new method was suggested for the measurement of the weight fraction of the interface in rubber–rubber blends using modulated‐temperature differential scanning calorimetry (M‐TDSC). Quantitative analysis using the differential of the heat capacity, dCp/dT, versus the temperature signal from M‐TDSC allows the weight fraction of the interface to be calculated. As examples, polybutadiene rubber (BR)–natural rubber (NR), BR–styrene‐co‐butadiene rubber (SBR), SBR–NR, and nitrile rubber (NBR)–NR blend systems were analyzed. The interfacial content in these blends was obtained. SBR is partially miscible with BR. The cis‐structure content in BR has an obvious effect on the extent of mixing in the SBR–BR blends. With increasing styrene content in the SBR in the SBR–BR blends, the interface content decreases. NR is partially miscible with both BR and SBR. The NBR used in this research is essentially immiscible with NR. The maximum amount of interface was found to be at the 50:50 blend composition in BR–NR, SBR–BR, and SBR–NR systems. Quantitative analysis of interfaces in these blend systems is reported for the first time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1791–1798, 2000 相似文献
1000.
Certain lowland streams have experienced prehistorical and historical cycles of aggradation, occlusion, degradation, headward incision, and renewed aggradation. Historical cycles appear to be related to human activities. A case study is presented of the Yalobusha River in Mississippi with emphasis on the effects of blockage and removal on aquatic habitats and fish. The adjacent Skuna River, which was channelized and unblocked, was used in space for time substitution to infer effects of blockage removal on the Yalobusha. Variables describing physical aquatic habitat and fish were sampled from three groups of river reaches: unblocked channelized, channelized and blocked, and naturally sinuous. Fish collections were used to compute six indicators of ecological integrity. At baseflow, mean water depths were an order of magnitude lower in the unblocked channelized stream than for the others. In‐channel aquatic habitat volume per unit valley length was 5, 85, and 283 m3/m for the channelized, blocked channelized, and natural reaches, respectively. Mean values for all six ecological indicators were lowest for the channelized group. Species richness was greatest for the channelized blocked reach. The ecological indicators displayed gradients in response to the range of observed physical conditions. Management of corridors susceptible to the cycle described above should involve a blend of measures designed to conserve higher quality habitats. 相似文献