Retrieving and classifying instances of source code plagiarism

Automatic detection of source code plagiarism is an important research field for both the commercial software industry and within the research community. Existing methods of plagiarism detection primarily involve exhaustive pairwise document comparison, which does not scale well for large software collections. To achieve scalability, we approach the problem from an information retrieval (IR) perspective. We retrieve a ranked list of candidate documents in response to a pseudo-query representation constructed from each source code document in the collection. The challenge in source code document retrieval is that the standard bag-of-words (BoW) representation model for such documents is likely to result in many false positives being retrieved, because of the use of identical programming language specific constructs and keywords. To address this problem, we make use of an abstract syntax tree (AST) representation of the source code documents. While the IR approach is efficient, it is essentially unsupervised in nature. To further improve its effectiveness, we apply a supervised classifier (pre-trained with features extracted from sample plagiarized source code pairs) on the top ranked retrieved documents. We report experiments on the SOCO-2014 dataset comprising 12K Java source files with almost 1M lines of code. Our experiments confirm that the AST based approach produces significantly better retrieval effectiveness than a standard BoW representation, i.e., the AST based approach is able to identify a higher number of plagiarized source code documents at top ranks in response to a query source code document. The supervised classifier, trained on features extracted from sample plagiarized source code pairs, is shown to effectively filter and thus further improve the ranked list of retrieved candidate plagiarized documents.     

如何在作文教学中培养学生的创造能力

作文教学是培养学生创造能力的重要途径,要做到以下几点:一、创造和谐、民主的学习环境,让学生主动学习;二、注重学生观察能力的培养;三、激发和培养学生的想象能力。     

把“愉快教学”引进英语课堂

要上好一节英语课,提高英语课堂教学质量,为学生创造一个轻松愉快的学习氛围,教师必须改变陈旧的教学模式,将愉快教学引进英语课堂。     

Wearable skin-like optoelectronic systems with suppression of motion artifacts for cuff-less continuous blood pressure monitor

According to the statistics of the World Health Organization, an estimated 17.9 million people die from cardiovascular diseases each year, representing 31% of all global deaths. Continuous non-invasive arterial pressure (CNAP) is essential for the management of cardiovascular diseases. However, it is difficult to achieve long-term CNAP monitoring with the daily use of current devices due to irritation of the skin as well as the lack of motion artifacts suppression. Here, we report a high-performance skin-like optoelectronic system integrated with ultra-thin flexible circuits to monitor CNAP. We introduce a theoretical model via the virtual work principle for predicting the precise blood pressure and suppressing motion artifacts, and propose optical difference in the frequency domain for stable optical measurements in terms of skin-like devices. We compare the results with the blood pressure acquired by invasive (intra-arterial) blood pressure monitoring for >1500 min in total on 44 subjects in an intensive care unit. The maximum absolute errors of diastolic and systolic blood pressure were ±7/±10 mm Hg, respectively, in immobilized, and ±10/±14 mm Hg, respectively, in walking scenarios. These strategies provide advanced blood pressure monitoring techniques, which would directly address an unmet clinical need or daily use for a highly vulnerable population.     

政府购买教育服务何以可能

我国政府购买教育服务的试行和有效实践,需要在理论上对教育服务何以可"购买"、政府何以要"购买"、政府在何处"购买"以及如何购买等问题进行深入思考,并形成科学的认识与判断,以帮助我们更清晰地认识政府购买教育服务所需的理论环境、政策环境和市场环境,为政府购买教育服务实践提供相应的理论支持与实践指导.     

浅谈通过化学实验实施学生的探究性学习

化学实验所具有的获知、激趣、求真、循理、育德的教育功能,决定了其是实施探究性学习的有效途径。中学化学教学中,通过化学实验来实施探究性学习必须创设真实的问题情境,并且充分发挥化学实验的探究功能。     

从封闭走向开放--研究生培养模式的重构与思考

当人们对我国现行研究生培养模式给予一定程度的关注时,往往会产生如下印象:即无论是研究生培养过程中所设置的课程体系、教学方式、师资组成,还是大学与科研机构的关系,与社会的结合程度,乃至于与外国同行的交往方式,均呈现出相当严重的封闭性.一定意义上,"封闭性"正暴露出我国研究生培养模式的症结所在.本文希望对研究生培养过程中存在的一系列现象进行剖析,将各种习以为常的现象"问题化",进而讨论可能的思考方向和可行的改革路径.     

高校思想政治理论课教育教学的态势分析

现阶段高校思想政治理论课的教育教学既存在优势也存在劣势,既拥有机遇也蕴涵威胁,优势、劣势、机遇、威胁这四个方面存在内在的关联,构成四种不同的矩阵--组合方式.基于四种不同的矩阵--组合分析,新形势下的思想政治理论课教育教学的改革对策是:发挥优势、把握机遇、抑制劣势、战胜威胁.     

试论我国中、高职农科专业课程衔接

实现中、高职教育农科专业课程的有效衔接,是推动农科职业教育步入良性发展轨道的客观要求.本文对当前我国中、高等职业教育农科专业课程开发的现状进行分析,指出课程内容重复、专业技能倒挂等问题,并对建立中、高等职业教育农科专业课程的有效衔接机制进行阐述.