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11.
A hybrid two-stage flowshop scheduling problem was considered which involves m identical parallel machines at Stage 1 and a burn-in processor M at Stage 2, and the makespan was taken as the minimization objective. This scheduling problem is NP-hard in general. We divide it into eight subcases. Except for the following two subcases: (1) b≥ an, max{m, B} 〈 n; (2) a1 ≤ b ≤ an, m ≤ B 〈 n, for all other subcases, their NP-hardness was proved or pointed out, corresponding approximation algorithms were conducted and their worst-case performances were estimated. In all these approximation algorithms, the Multifit and PTAS algorithms were respectively used, as the jobs were scheduled in m identical parallel machines. 相似文献
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In Experiment 1, male rats were exposed to either aggressive (i.e., alpha) or nonaggressive conspecific colonies and tested 24 h later, with or without alpha odors, for freezing behavior and burying of a wall prod that had been the source of a brief electric shock. The results indicated that prior defeat experience and the presence of alpha odors alone during testing had no significant effects, but the combination of prior defeat and alpha-odor testing significantly decreased burying and increased freezing behavior. In Experiment 2, we examined the effects of noncontact exposure to a cat, as a predatory Stressor, during subsequent prod-shock tests involving the presence or absence of cat odors. Exposure to a cat failed to disrupt later prod burying and did not produce freezing. However, the presence of cat odors during testing significantly reduced the amount of defensive burying,without resulting in an increment in freezing. In Experiment 3, rats were given 1, 5, or 30 inescapable preshocks in the presence of either cat odors or a hedonically neutral citronella odor and were tested 24 h later for prod burying and freezing with or without these odors. Both the cat and the citronella odors resulted in a significant reduction in burying and an increase in freezing for rats given 5 and 30 preshocks and tested in the presence of these respective conditioned odors. For the groups that were given 5 preshocks, preshock and later testing in the presence of cat odors resulted in significantly less prod burying and more freezing than for rats that were preshocked and tested in the presence of citronella. The findings of these three ethoexperimental studies are discussed in terms of the learned-helplessness theory, the stress-coping-fear-defense (SCFD) theory, and the concept of selective CS-US associability. 相似文献
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Constructivist Metaphors of Learning Science 总被引:2,自引:1,他引:2
Based on an analysis of a fundamental distinction between metaphors of finding versus making for the obtaining of new knowledge, a number of constructivist positions in education are discussed and criticised, taking account of earlier criticism particularly by Suchting and by Matthews. Constructivist claims which are denied include the claim that we have no direct access to the world, and the claim that communication is inherently meaningless. What is valuable in constructivism, namely the insistence on active learning, on respect for the pupils own thinking, and on the high priority needed for ideas taught to make sense to pupils, together with the reminder that science is a human product, is important to retain without its additional and ill-founded philosophical baggage. 相似文献
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The paper presents findings from an evaluation of ‘industrial education’ subjects (wood, metal, electrical and power technology) in Kenyan academic secondary schools. As a project established in 35 schools with comprehensive aid agency (SIDA) support, these subjects do not suffer from lack of attraction to students or from low teacher morale. Exposure to them increases students' aspirations and expectations of ‘technical/practical’ work, but the problem is not lack of interest in such work, but rather scarce opportunity to realise such ambition, in a labour market where school leavers face great problems in finding a source of livelihood. Except for individual cases, exposure to these subjects does not seem to give students an advantage in the labour market, according to findings from a one-year follow-up. Further, doing well in general on the lower secondary examination does not confer any short-term labour market advantage either, suggesting that personal contacts rather than school credentials are decisive. We conclude policy makers need to recognise that pre-vocational subjects should be seen as part of general education rather than as a remedy for youth unemployment. 相似文献
16.
Jon Lauglo 《Prospects》1989,19(3):407-426
Working within a comparative perspective, has published on pre-vocational education and vocational training, the teaching profession, distribution of authority in education systems and university policy. 相似文献
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Jon Zabala Borja González-Albo Ana García-García Aurora Garrido-Domínguez José Ignacio Vidal-Liy Luis R. Álvarez-Díez Soledad Hernando-Tundidor Yara Mostazo-Fernández Teresa Abejón 《Learned Publishing》2023,36(2):205-216
This article analyses the review, acceptance and publication dates of a sample of 21,890 articles from 326 Ibero-American scientific journals from all subject areas and countries included in the Latindex Catalogue 2.0 and published between 2018 and 2020 (freely available as an open access dataset). The aim is to discover evaluation and publication times. The evaluation process takes a median of 110 days, the publication process, a median of 82 days, and the whole process, a median of 224 days. Statistical differences are found according to periodicity, subject areas, countries, existence of a printed version and article type (Call for Papers or General articles). From the data we find that the delay in publication is longer than publishers themselves report to the DOAJ. STEM areas present the most similarity in publication patterns, having a higher number of evaluation days (Ed) than publication days (Pd); Arts and Humanities present the opposite pattern, with a higher Pd than Ed. In the case of Social Sciences, the times are similar. General articles and Call for Papers articles differ in terms of Ed, but not Pd, indicating that Call for Papers revisions are faster. 相似文献
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10年前,几乎所有人都相信网球的未来将被会大力发球的巨人主宰,但现在卡洛维奇和埃斯纳都还是二流选手,这当中到底发生了什么?有人开玩笑说:男子网球有三条铁律。第一,所有时代的伟大选手都有一手漂亮的单反,第二,他们都有一个贤内助(米尔卡?但布里吉特也算吗?),第三,他们都有炮弹发球。这里面听起来比较靠谱的仅仅是发球,作为全世界最好的选手和全世界最高的选手费德勒和卡洛维奇,我们可以拿他们的二十项技术指标做比较,卡洛维奇只有一项技术指标可以超过费德勒,那就是发球,这就使得卡洛维奇有机会在任何时候和费德勒较量一番,这就像拳击手有致命的重拳,网球选手有发球,就有了机会。 相似文献