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81.
Stephen Kemmis 《Pedagogy, Culture & Society》1993,1(1):35-54
Educational evaluation may be understood in terms of what Michel Foucault describes as 'discursive practice', yet this perspective may lead to a kind of despair if evaluation technologies are seen as no more than an expression of 'the will to power'. The issue of evaluation technologies as 'machines' is not new to the evaluation literature, as the author's autobiographical reflections on his evaluation training and experience suggest. The Foucauldian view is counterposed here with the Habermasian notion of a 'science of social action', and explorations of the potential of Habermas's ideas in educational evaluation by the author and his colleagues. It is argued that Habermas's theory of communicative action offers humane, convivial and rational resources for the further development of the theory and practice of educational evaluation. 相似文献
82.
Roadmapping the Technological Future of Electricity 总被引:1,自引:0,他引:1
A future-scanning collaboration orchestrated by the Electric Power Research Institute has sought to illuminate the technologies whose development will be needed to attain the “2 percent” solution of improvements in economic productivity, energy efficiency and agricultural productivity necessary for global sustainability. 相似文献
83.
Davies Nigel Friday Adrian Wade Stephen P. Blair Gordon S. 《Mobile Networks and Applications》1998,3(2):143-156
Mobile computing environments increasingly consist of a range of supporting technologies offering a diverse set of capabilities
to applications and end-systems. Such environments are characterised by sudden and dramatic changes in the quality-of-service
(QoS) available to applications and users. Recent work has shown that distributed systems platforms can assist applications
to take advantage of these changes in QoS and, more specifically, facilitate applications to adapt to their environment. However,
the current state-of-the-art in these platforms reflects their fixed network origins through their choice of synchronous connection-oriented
communications paradigms. In this paper we argue that these paradigms are not well suited to operation in the emerging mobile
environments. Furthermore, we offer an alternative programming paradigm based on tuple spaces which, we believe, offers a
number of benefits within a mobile context. The paper presents the design, implementation and evaluation of a new platform
based on this paradigm.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
84.
David F. Bliss Robert M. Hilton Stephen Bachowski Joseph A. Adamski 《Journal of Electronic Materials》1991,20(12):967-971
We have used a combined magnetic liquid encapsulated Kyropoulos/Czochralski (MLEK/ MLEC) technique to produce twin-free indium
phosphide (InP) crystals. This technique has advantages over the standard LEC method used for commercial production of InP.
By stabilizing convective flows with a magnetic field and controlling the angle between solid and liquid, one can grow large
diameter twin-free (100) InP crystals; they are shaped with a flat top as is typical for Kyropoulos growth, and then pulled
from the magnetically stabilized melt as in Czochralski growth. This shaping method has the benefit of maximizing the number
of single crystal wafers which can be sliced from the boule. MLEK InP growth is distinguished from other methods such as LEC
and MLEC with respect to solid-liquid interface shape, dislocation density, and impurity distribution. This process has demonstrated
that twin-free InP (100) crystals can be consistently grown. 相似文献
85.
When polyimide is used as the insulating dielectric in multilevel-metal structures, a high contact resistance can result within
the interconnecting vias. This paper examines the particular case of oxygen plasma patterning of the polyimide using a photoresist
mask. Auger analysis in combination with compositional depth profiling was employed on a series of samples to measure surface
composition of etched vias in polyimide. Results show two effects which, together, can account for high contact resistance:
first, there is a thicker than normal aluminum oxide layer on the first level metal surface (due to exposure to the oxygen
plasma); second, there is a thin, etch-resistant carbonaceous film (due to redeposition of organic material during plasma
etching) that prevents oxide thinning through chemical means. It was found that by lowering the plasma pressure to 50 mTorr
near the end of the etch, the organic film can be removed. In the absence of the carbonaceous layer, the oxide can then be
chemically thinned to produce clean aluminum surfaces within the vias. 相似文献
86.
Development of the Utah Artificial Arm 总被引:2,自引:0,他引:2
Jacobson Stephen C. Knutti David F. Johnson Richard T. Sears Harold H. 《IEEE transactions on bio-medical engineering》1982,(4):249-269
The development of a practical multifunction, electronically controlled artificial arm is an extremely complex undertaking. Various technical factors such as the limited capability of man-made components, together with problems in the development of adequate control systems, impair the ultimate performance of any prosthesis. Also, nontechnical problems in clinical, marketing, and economic areas strongly influence the potential success of any system. Consequently, the realization of a practical system with the possibility of near-term application requires simultaneous and coordinated work by personnel in a number of normally unrelated areas of medicine and engineering. The opinions of engineers, physicians, amputees, industrial entities, and institutions responsible for funding the fitting of artificial limnbs must be understood and must influence the design process. This paper begins with a discussion of the natural limb and those design objectives and compromises which govern the development of its artificial counterpart Specific details of the Utah Arm are then reviewed, along with general comments regarding the area of prosthetic limb research and application. 相似文献
87.
The human undergoing rapid and sustained weight loss by very low calorie dieting (VLCD) derives the majority of daily energy
needs from adipose fatty acids. To evaluate the rates of metabolic utilization of individual fatty acids in humans, two groups
of adult women outpatients were studied during major weight loss by VLCD. The diets used were either food or formula, providing
the recommended dietary allowance for minerals and vitamins, with fat contents of 2–20 g/d. Group 1 consisted of 10 subjects
[initial body mass index (BMI) 32.7, 157% of ideal body weight (IBW)] with a mean loss of 17.7 kg in 3–5 months. Group 2 consisted
of 14 subjects (initial BMI 36.7, 167% of IBW) with a mean loss of 25.6 kg in 4–5 months. Adipose tissue biopsies were obtained
by needle aspiration from Group 1 before and after weight loss and from Group 2 before, at the midpoint, and after weight
loss. With weight loss in Group 1, the adipose tissue content of 18∶1ω9, 18∶2ω6, and 20∶4ω6 did not change, but 18∶3ω3 fell
(0.67 to 0.56 wt%, p<0.0001) as did 20∶5ω3 (0.08 to 0.05, p<0.01). Adipose tissue 22∶6ω3 rose from 0.03 to 0.07 (p<0.01).
In Group 2, only 18∶3ω3 showed a change, falling from 0.71 to 0.69 to 0.59 wt% across weight loss (p=0.03 by analysis of variance).
We conclude that the major fatty acids are oxidized in proportion to their composition in adipose triglyceride. The significant
reduction in the concentration of 18∶3ω3 during weight loss is unique among fatty acids. Its accelerated removal from adipose
tissue indicates either a preferential step in β-oxidation or a defined need during supplemented fasting which exceeds its
rate of provision from adipose stores.
This work was presented in part at the Annual Meeting of the American Society for Clinical Nutrition, Washington, D.C., 1988. 相似文献
88.
Prapaipan Chantikul Stephen J. Bennison Brian R. Lawn 《Journal of the American Ceramic Society》1990,73(8):2419-2427
An investigation of the interrelationships between strength, crack-resistance ( R -curve) characteristics, and grain size for alumina ceramics has been carried out. Results of identation-strength measurements on high-density aluminas with uniform grain structures in the size range 2 to 80 μm are presented. A theoretical fit to the data, obtained by adjusting parameters of a constitutive frictional-pullout relation in a grain-bridging model, allows determination of the critical microstructural parameters controlling the R -curve behavior of these aluminas. The primary role of grain size in the toughness characteristic is to determine the scale of grain pullout at the bridged interface. It is shown that the strength properties are a complex function of the bridged microstructure, governed at all but the finest grain sizes by the stabilizing effect of the R -curve. The analysis confirms the usual negative dependence of strength on grain size for natural flaws that are small relative to the grain size, but the dependence does not conform exactly to the −1/2 power predicted on the basis of classical "Griffith-Orowan" flaws. The analysis provides a self-consistent account of the well-documented transition from "Orowan" to "Petch" behavior. 相似文献
89.
Networks of phased array radars are generally able to provide better counter stealth target detection and classification. Each radar sensor (or node) generates information which requires transmission to a central authority that is able to evaluate the information. This requires a communications network to be established to allow transmission of information to and from any node. Each radar node is limited by range and degree and relies on the formation of a multi-hop network to facilitate these transmissions.This paper presents a model whereby the radar beam itself is used in the formation of a multi-hop network. The phased array’s multi-functional nature allows rapid switching between communications and radar function. A model of how the communication system could operate is presented, and an evolutionary optimisation algorithm based upon the concept of Pareto optimality is used for the topological design of the network. Finally, a simulation environment is presented to show the simulated performance of the communication model and designed networks. 相似文献
90.