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本文分析了蒋劲松先生题为"作为环境问题根源的实验科学传统初探"的报告中的两个主要论点:(1)实验室环境中得到的知识必然是地方性的知识,(2)大规模应用这种知识的企图是造成我们通常所谓的环境问题的重要根源之一.分析的结果是第一论点不成立,而第二论点的理由不充足.笔者对蒋先生的第二个论点在某种意义上表示赞同.为此本文最后提出一个在理解环境问题上的新维度:即从第三人称与进化论的视角来看环境问题. 相似文献
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预习是学习的重要环节与阶段,却常因学生不会预习或预习的低效率而流于形式。本文结合初中科学课前预习的实践研究,对如何采用"三管齐下"的策略,提高初中科学课前预习有效性进行了详尽的阐述。"三管齐下"指:(1)设计合理、科学的讲学稿,(2)布置适量、适度的预习作业,(3)改变授课方式等三个方面齐头并进,加强预习的方法指导,对预习的结果进行及时的检测,课堂上让学生有效的运用预习的成果。 相似文献
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机械系统的碰撞振动与控制 总被引：2，自引：0，他引：2
机械系统内部或边界间隙引起的碰撞振动是机械动力学的研究热点之一。该领域的近期研究成果有:(1)碰撞振动的间断和连续分析,包括稳定性分析、奇异性问题、擦边诱发分叉、非线性模态等研究,(2)碰撞振动控制,特别是不连续系统的控制方法和控制混沌碰撞振动,(3)碰撞振动分析的数值方法,(4)碰撞振动实验研究。 相似文献
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病毒性肝炎引起的黄疽与外科疾病造成的黄疸的处理原则和方法截然不同,为了正确与及时区分这两类性质迥异的黄疸,临床医师在鉴别黄疸病因时,应着重注意:(1)性别与年龄,(2)既往病史,(3)起病方式,(4)黄疸波动情况,(5)发热与腹痛,(6)粪、尿颜色,(7)皮肤瘙痒,(8)肝臭,(9)三个进行性,(10)三个分离,(11)腹部体征,(12)GOT/GPT比值,(13)AKP等三项指标,(14)PTT的维生素K纠正试验,(15)激素试验性治疗,(16)肝炎病毒的抗原抗体测定等。 相似文献
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本文作者根据我国理论生物物理学十年来发展的情况和当前国内外的研究现状。就理论生物物理学的发展提出了三点看法:(1)心脑功能、神经科学是生命科学非常重要的方面,它有很多重要前沿领域,需要开展多学科综合性研究,(2)理论学科的发展或主攻方向的确定要受关联学科发展水平与实验研究工作的积累所制约,(3)理论生物物理学是对实验生物物理而言,它应包括许多分支学科领域。在此基础上,作者进而提出了三点建议:(1)理论生物物理学的研究,有必要组织一个有关复杂系统或生命系统复杂性研究的重大课题,(2)为赶上国际生命前沿科学水平,在科学基金使用和管理上,将“气功原理”作为重点课题,(3)应特别重视“生物功能无损伤测定”HFSP,应立专题开展研究。 相似文献
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国家自然科学基金委员会成立近五年了。本文是唐敖庆教授在第六次全委会议上作的五年工作总结报告(摘要)。全文共四部分: 一、五年主要工作。开展了三个层次和七种项目类型的资助工作和接受委托承担的其它工作。二、五年基本成效。稳定了队伍,涌现了成果,培养了人才和调动了科技人员的积极性。三、基本经验:(1)有一个好的认识,(2)有比较明确的指导思想,(3)有“十六”字评审原则和一个好的专家评审系统,(4)有点面结合的资助工作格局,(5)有比较健全和适用的管理制度和办法,(6)有广泛接受社会监督、加强工作透明度的措施。四、今后的建议和希望:(1)争取科学基金事业规模尽快扩大,(2)开展科学基金工作的理论研究,进一步完善我国科学基金制,(3)重视和加强国际科技合作工作,(4)搞好国家重点实验室和开放实验室的评估工作,(5)加强机关建设工作。 相似文献
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《Information processing & management》2005,41(3):489-506
This paper presents a laboratory based evaluation study of cross-language information retrieval technologies, utilizing partially parallel test collections, NTCIR-2 (used together with NTCIR-1), where Japanese–English parallel document collections, parallel topic sets and their relevance judgments are available. These enable us to observe and compare monolingual retrieval processes in two languages as well as retrieval across languages. Our experiments focused on (1) the Rosetta stone question (whether a partially parallel collection helps in cross-language information access or not?) and (2) two aspects of retrieval difficulties namely “collection discrepancy” and “query discrepancy”. Japanese and English monolingual retrieval systems are combined by dictionary based query translation modules so that a symmetrical bilingual evaluation environment is implemented. 相似文献
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《Information processing & management》2022,59(2):102861
Integrating useful input information is essential to provide efficient recommendations to users. In this work, we focus on improving items ratings prediction by merging both multiple contexts and multiple criteria based research directions which were addressed separately in most existent literature. Throughout this article, Criteria refer to the items attributes, while Context denotes the circumstances in which the user uses an item. Our goal is to capture more fine grained preferences to improve items recommendation quality using users’ multiple criteria ratings under specific contextual situations. Therefore, we examine the recommenders’ data from the graph theory based perspective by representing three types of entities (users, contextual situations and criteria) as well as their relationships as a tripartite graph. Upon the assumption that contextually similar users tend to have similar interests for similar item criteria, we perform a high-order co-clustering on the tripartite graph for simultaneously partitioning the graph entities representing users in similar contextual situations and their evaluated item criteria. To predict cluster-based multi-criteria ratings, we introduce an improved rating prediction method that considers the dependency between users and their contextual situations, and also takes into account the correlation between criteria in the prediction process. The predicted multi-criteria ratings are finally aggregated into a single representative output corresponding to an overall item rating. To guide our investigation, we create a research hypothesis to provide insights about the tripartite graph partitioning and design clear and justified preliminary experiments including quantitative and qualitative analyzes to validate it. Further thorough experiments on the two available context-aware multi-criteria datasets, TripAdvisor and Educational, demonstrate that our proposal exhibits substantial improvements over alternative recommendations approaches. 相似文献
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Recommender systems learn from historical users’ feedback that is often non-uniformly distributed across items. As a consequence, these systems may end up suggesting popular items more than niche items progressively, even when the latter would be of interest for users. This can hamper several core qualities of the recommended lists (e.g., novelty, coverage, diversity), impacting on the future success of the underlying platform itself. In this paper, we formalize two novel metrics that quantify how much a recommender system equally treats items along the popularity tail. The first one encourages equal probability of being recommended across items, while the second one encourages true positive rates for items to be equal. We characterize the recommendations of representative algorithms by means of the proposed metrics, and we show that the item probability of being recommended and the item true positive rate are biased against the item popularity. To promote a more equal treatment of items along the popularity tail, we propose an in-processing approach aimed at minimizing the biased correlation between user-item relevance and item popularity. Extensive experiments show that, with small losses in accuracy, our popularity-mitigation approach leads to important gains in beyond-accuracy recommendation quality. 相似文献
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《Information processing & management》2023,60(5):103470
Previous federated recommender systems are based on traditional matrix factorization, which can improve personalized service but are vulnerable to gradient inference attacks. Most of them adopt model averaging to fit the data heterogeneity of federated recommender systems, requiring more training costs. To address privacy and efficiency, we propose an efficient federated item similarity model for the heterogeneous recommendation, called FedIS, which can train a global item-based collaborative filtering model to eliminate user feature dependencies. Specifically, we extend the neural item similarity model to the federated model, where each client only locally optimizes the shared item feature matrix. We then propose a fast-convergent federated aggregation method inspired by meta-learning to address heterogeneous user updates and accelerate the convergence of global training. Furthermore, we propose a two-stage perturbation method to protect both local training and transmission while reducing communication costs. Finally, extensive experiments on four real-world datasets validate that FedIS can provide more competitive performance on federated recommendations. Our proposed method also shows significant training efficiency with less performance degradation. 相似文献
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Past research into text retrieval methods for the Web has been restricted by the lack of a test collection capable of supporting experiments which are both realistic and reproducible. The 1.69 million document WT10g collection is proposed as a multi-purpose testbed for experiments with these attributes, in distributed IR, hyperlink algorithms and conventional ad hoc retrieval.WT10g was constructed by selecting from a superset of documents in such a way that desirable corpus properties were preserved or optimised. These properties include: a high degree of inter-server connectivity, integrity of server holdings, inclusion of documents related to a very wide spread of likely queries, and a realistic distribution of server holding sizes. We confirm that WT10g contains exploitable link information using a site (homepage) finding experiment. Our results show that, on this task, Okapi BM25 works better on propagated link anchor text than on full text.WT10g was used in TREC-9 and TREC-2000 and both topic relevance and homepage finding queries and judgments are available. 相似文献
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本教学设计在建构主义思想的指导下,结合探究式教学的特点,对"机械能守恒定律"这一节进行教学设计。首先,教师创设情境引出机械能,其次,通过单摆对照演示实验引导学生发现机械能可以守恒,通过理论探究引导学生推导机械能守恒定律以及机械能守恒条件,通过实验探究验证机械能守恒定律,最后,通过例题分析,引导学生深入理解、应用机械能守恒定律,完成对新知识的意义建构,并在此过程中提高学生的探究、应用能力。 相似文献
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《Information processing & management》2019,56(3):939-954
Recently, the high popularity of social networks accelerates the development of item recommendation. Integrating the influence diffusion of social networks in recommendation systems is a challenging task since topic distribution over users and items is latent and user topic interest may change over time. In this paper, we propose a dynamic generative model for item recommendation which captures the potential influence logs based on the community-level topic influence diffusion to infer the latent topic distribution over users and items. Our model enables tracking the time-varying distributions of topic interest and topic popularity over communities in social networks. A collapsed Gibbs sampling algorithm is proposed to train the model, and an improved diversification algorithm is proposed to obtain item diversified recommendation list. Extensive experiments are conducted to evaluate the effectiveness and efficiency of our method. The results validate our approach and show the superiority of our method compared with state-of-the-art diversified recommendation methods. 相似文献
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