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Agricultural science and technology (S&T) is under great scrutiny. Reorientation towards more holistic approaches, including agroecology, has recently been backed by a global international assessment of agriculture S&T for development (IAASTD). Understanding the past and current trends of agricultural S&T is crucial if such recommendations are to be implemented. This paper shows how the concepts of technological paradigms and trajectories can help analyse the agricultural S&T landscape and dynamics. Genetic engineering and agroecology can be usefully analysed as two different technological paradigms, even though they have not been equally successful in influencing agricultural research. We used a Systems of Innovation (SI) approach to identify the determinants of innovation (the factors that influence research choices) within agricultural research systems. The influence of each determinant is systematically described (e.g. funding priorities, scientists’ cognitive and cultural routines etc.). As a result of their interactions, these determinants construct a technological regime and a lock-in situation that hinders the development of agroecological engineering. Issues linked to breaking out of this lock-in situation are finally discussed.  相似文献   
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在人工智能领域,辅助agent是一种能够帮助用户解决工作环境中特定任务的认知agent.本文将个人辅助agent应用于e-karning环境中,提出了一种具有记忆能力的辅助agent模型--MemoPELA,目的在于帮助学生和教师进行更好的教学活动.  相似文献   
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In this paper, we examine the factors that influence the reputation or prestige of universities. We first develop a model of university behaviour which indicates how the decisions made by university officials would be chosen in order to maximize their respective reputations. In doing so, we assume that reputation is enhanced by the quality of students produced, the caliber of research and the service provided to the community in terms of the provision of publicly funded education services. We argue that the relative weights placed on these intermediate outputs may vary by university type as well as the means of producing them. Using the results of the reputational survey – a ranking of the institution in terms of reputation – conducted as part of the Canadian magazine Maclean’s overall ranking exercise, we then estimate an Error Correction—Ordered Probit Model of the rankings of Canadian universities to determine the factors that influence the change in reputation or “prestige” of the university as viewed by the external community. We find evidence that the change in reputation of a university is based on what might be considered the appropriate “signals” that one might use in estimating the respective quality of the institution given the respective differences in mission.  相似文献   
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Black crusts formed on limestone built into the King's Gate represent the most important process in stone deterioration that is occurring in this part of the monumental complex of the Belgrade Fortress (Serbia). Of special importance is the association of salts (namely gypsum and syngenite). Syngenite is a common secondary deposit on granite monuments and on medieval stained glass (i.e., on K-containing materials). However, its appearance over calcareous substrates is not apparent, particularly in cases where cement mortar was not used for bounding. The origins of the potassium and sulphate ions required for syngenite formation are related to meteoritic water, which penetrates the soil above the arch of King's Gate. Water dissolves some soil components and becomes enriched with various ions before coming into contact with the limestone blocks. Enriched water contains two times more K+ and SO42? ions than pristine meteoritic water does. The source of the required ions is potassium-sulphate that is present in agricultural fertilisers that are used above the monument. The proposed mechanism for syngenite formation was additionally supported with laboratory experiment. The results of X-ray diffractometry and SEM-EDS analyses of limestone treated with potassium-sulphate solution and sulphuric acid suggest the possibility that the syngenite was formed over calcite:CaCO3 + K2SO4 + H2SO4  K2Ca(SO4)2 H2O + CO2↑However, the complex mechanisms of gypsum and syngenite formation under natural conditions (variable concentration of potassium and sulphate ions, intermediates phases, temperature changes, humidity, the amount of disposable water etc.) do not exclude the possibility of syngenite formation over gypsum.  相似文献   
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Bayesian structural equation modeling (BSEM) was used to investigate the latent structure of the Differential Ability Scales—Second Edition core battery using the standardization sample normative data for ages 7–17. Results revealed plausibility of a three‐factor model, consistent with publisher theory, expressed as either a higher‐order (HO) or a bifactor (BF) model. The results also revealed an alternative structure with the best model fit, a two‐factor BF model with Matrices (MA) and Sequential and Quantitative Reasoning (SQ) loading on g only with no respective group factor loading. This was only the second study to use BSEM to investigate the structure of a commercial ability test and the first to use a large normative sample and the specification of both approximate zero cross‐loadings and correlated residual terms. It is believed that the results produced from the current study will advance the field's understanding of not only the factor structure of the DAS‐II core battery but also the potential utility of BSEM in psychometric investigations of intelligence test structures.  相似文献   
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Taking a test on a passage one has just studied is known to enhance later retention of the passing contents. This study examined the effects of three types of initial test on later retention: a short-answer test, a multiple-choice test, and a full free-recall test. Questions on the first two of these tests covered only half of the passage contents. Later retention was compared for both initially tested content and un-tested content with that of a control group not initially tested on the passage at all. The subjects were 57 secondary school students who studied a brief history text before taking one of the initial tests. All were given retention tests 2 weeks later. The classical testing effect (enhanced retention due to initial testing) was shown to be influenced by the type of initial test used. Thus, a testing effect was evident in the case of the initial short-answer test, but not in the case of either of the other two tests. A depth-of-processing view is advanced in interpreting this finding. The testing effect was found not to generalize to untested content and in one condition (the initial multiple-choice test), retention of untested content was depressed.  相似文献   
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