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151.
The primary objective for modeling of machining processes is to develop a predictive capability of machining performance in order to facilitate effective planning of machining operations. This capability leads to faster implementation, higher performance, quality at a lower cost. This comes about due to improved selection of machining parameters, optimal fixture design and the avoidance of tool failure. The simulation system presented simultaneously considers the effect of cutter geometry, the cutter's initial position errors, workpiece geometry, machine tool dynamics, and workpiece/fixture system dynamics on the machining process.The integration of all of the above in one model provides an off-line tool to simulate and optimize the machining parameters and the fixture configuration cutting both lead and production time. The modular nature of the simulation system presented allows for the study of many different machining processes. The cutting forces in this system are modeled using a mechanistic approach. NURBS curves and surfaces are utilized for the geometric modeling and simulation of the machining process. While a finite element method is used to model and analyze the workpiece/fixture dynamics. Two case studies are presented to demonstrate the practical application of the presented simulation. The first case presents the optimization of the fixture configuration of a generic automotive component. While the second case presents the results of simulations performed on a novel mill/grind machining process. This process is a combination of face milling and grinding in one operation. Some simulated results are presented along with experimental validation. 相似文献
152.
Michael J. Kurtz Guenther Eichhorn Alberto Accomazzi Carolyn Grant Markus Demleitner Edwin Henneken Stephen S. Murray 《Information processing & management》2005,41(6):1395-1402
It has been shown (Lawrence, S. (2001). Online or invisible? Nature, 411, 521) that journal articles which have been posted without charge on the internet are more heavily cited than those which have not been. Using data from the NASA Astrophysics Data System (ads.harvard.edu) and from the ArXiv e-print archive at Cornell University (arXiv.org) we examine the causes of this effect. 相似文献
153.
154.
Swee‐Kin Loke June Tordoff Michael Winikoff Jenny McDonald Peter Vlugter Stephen Duffull 《British journal of educational technology : journal of the Council for Educational Technology》2011,42(5):865-874
Several scholars contend that learning with computer games and simulations results in students thinking more like professionals. Bearing this goal in mind, we investigated how a group of pharmacy students learnt with an in‐house developed computer simulation, SimPharm. Adopting situated cognition as our theoretical lens, we conducted a case study involving 20 undergraduate students to tease out how they made meaning of a clinical case differently in two different contexts: a typical paper‐based workshop and one enabled by SimPharm. The data collected included audio recordings of classroom discourse, focus group interviews and class observations. The findings identified differences in four areas: framing of the problem; problem‐solving steps and tools used; sources and meaning of feedback; and conceptualisation of the patient. These four areas can serve as axes along which future evaluations of educational simulations can be carried out based on their affordances. 相似文献
155.
School quality, child wellbeing and parents’ satisfaction 总被引:1,自引:0,他引:1
Child wellbeing at school and enjoyment of the learning environment are important economic outcomes, in particular because a growing body of research shows they are strongly linked to later educational attainments and labour market success. However, the standard working assumption in the economics of education is that parents choose schools on the basis of test-score performance, and concerns about child happiness are largely ignored. In this paper, we address this omission and investigate to what extent parents’ and children's views of their school are linked to test-score based performance, and to what extent parents’ judgements of school quality are linked to their child's happiness. To do so, we use information on stated attitudes from the Longitudinal Survey of Young People in England (LSYPE) matched to administrative records on pupil achievements in England. Our results suggest that test-score based measures of school quality tend to dominate parental satisfaction with the learning environment. However, school quality along this dimension is not strongly associated with pupil happiness and wellbeing at school. 相似文献
156.
157.
Regional investment in R&D, technological development and innovation is perceived as being strongly associated with productivity, growth and sustained international competitiveness. One policy instrument by which policy makers have attempted to create regional advantage has been the establishment of publicly funded research centres (PRCs). In this paper we develop a logic model for this type of regional intervention and examine the outputs and longer-term outcomes from a group of (18) publicly funded R&D centres. Our results suggest some positive regional impacts but also identify significant differences in terms of innovation, additionality and sustainability between university-based and company-based PRCs. University-based PRCs have higher levels of short-term additionality, demonstrate higher levels of organisational innovation but prove less sustainable. Company-based PRCs demonstrate more partial additionality in the short-term but ultimately prove more sustainable. 相似文献
158.
Stephen B. Adams 《Research Policy》2011,40(3):368-379
What are the respective roles of indigenous and exogenous factors in the development of high-tech regions? Entrepreneurs and their start-ups have dominated Silicon Valley's economy in recent decades, but a different dynamic was at work from 1940 to 1965, when the Valley emerged as a formidable high-tech region. In key industries (electronics, semiconductors, computers, and aerospace) that defined Silicon Valley as a high-tech cluster during that period, companies based elsewhere played critical roles in planting the organizations that would - through the innovations they made, the technical talent they attracted, and the start-ups they spun off - help make the Valley the world's most admired and emulated high-tech region. 相似文献
159.
Effect of post-match cold-water immersion on subsequent match running performance in junior soccer players during tournament play 总被引:2,自引:1,他引:1
In this study, we investigated the effects of two hydrotherapy interventions on match running performance and perceptual measures of fatigue and recovery during a 4-day soccer tournament. Twenty male junior soccer players were assigned to one of two treatment groups and undertook either cold-water immersion (5 × 1 min at 10 °C) or thermoneutral water immersion (5 × 1 min at 34 °C) after each match. High-intensity running distance (>15 km · h?1) and total distance covered, time spent in low (<80% maximum heart rate), moderate (80-90% maximum heart rate), and high (>90% maximum heart rate) heart rate zones, and rating of perceived exertion (RPE) were recorded for each match. Perceptions of general fatigue and leg soreness were recorded approximately 22 h after each match. There were decreases in both groups across the 4-day tournament for high-intensity running distance (P = 0.006, Cohen's d = 0.63), total distance run (P < 0.001, d = 0.90), time in high heart rate zone (P = 0.003, d = 0.90), and match RPE (P = 0.012, d = 0.52). Cold-water immersion was more effective than thermoneutral immersion for reducing the perception of leg soreness (P = 0.004, d = -0.92) and general fatigue (P = 0.007, d = -0.91), ameliorating the decrement in total distance run (P = 0.001, d = 0.55), and maintaining time in the moderate heart rate zone (P = 0.01, d = 1.06). In conclusion, cold-water immersion mediates the perceptions of fatigue and recovery and enhances the restoration of some match-related performance measures during a 4-day tournament. 相似文献
160.
Greene NP Greene ES Carbuhn AF Green JS Crouse SF 《Research quarterly for exercise and sport》2011,82(2):264-273
We compared cardiorespiratory responses to exercise on an underwater treadmill (UTM) and land treadmill (LTM) and derived an equation to estimate oxygen consumption (VO2) during UTM exercise. Fifty-five men and women completed one LTM and five UTM exercise sessions on separate days. The UTM sessions consisted of chest-deep immersion, with 0, 25, 50, 75, and 100% water-jet resistance. All session treadmill velocities increased every 3 min from 53.6 to 187.8 m x min(-1). Cardiorespiratory responses were similar between LTM and UTM when jet resistance for UTM was 50%. Using multiple regression analysis, weight-relative VO2 could be estimated as: VO2 (mLO2 c kg(-1) x min(-1)) = 0.19248 x height (cm) + 0.17422 x jet resistance (% max) + 0.14092 x velocity (m x min(-1)) -0.12794 x weight (kg)-27.82849, R2 = .82. Our data indicate that similar LTM and UTM cardiorespiratory responses are achievable, and we provide a reasonable estimate of UTM VO2. 相似文献