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全文: "H2 Database"
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  • Miki ENOKI, Issei YOSHIDA, Masato OGUCHI
    IEICE Transactions on Information and Systems
    2017年 E100.D 巻 4 号 776-784
    発行日: 2017/04/01
    公開日: 2017/04/01
    ジャーナル フリー

    In Twitter-like services, countless messages are being posted in real-time every second all around the world. Timely knowledge about what kinds of information are diffusing in social media is quite important. For example, in emergency situations such as earthquakes, users provide instant information on their situation through social media. The collective intelligence of social media is useful as a means of information detection complementary to conventional observation. We have developed a system for monitoring and analyzing information diffusion data in real-time by tracking retweeted tweets. A tweet retweeted by many users indicates that they find the content interesting and impactful. Analysts who use this system can find tweets retweeted by many users and identify the key people who are retweeted frequently by many users or who have retweeted tweets about particular topics. However, bursting situations occur when thousands of social media messages are suddenly posted simultaneously, and the lack of machine resources to handle such situations lowers the system's query performance. Since our system is designed to be used interactively in real-time by many analysts, waiting more than one second for a query results is simply not acceptable. To maintain an acceptable query performance, we propose a capacity control method for filtering incoming tweets using extra attribute information from tweets themselves. Conventionally, there is a trade-off between the query performance and the accuracy of the analysis results. We show that the query performance is improved by our proposed method and that our method is better than the existing methods in terms of maintaining query accuracy.

  • Rizky Januar AKBAR, Takayuki OMORI, Katsuhisa MARUYAMA
    IEICE Transactions on Information and Systems
    2014年 E97.D 巻 5 号 1069-1083
    発行日: 2014/05/01
    公開日: 2014/05/01
    ジャーナル フリー
    Developers often face difficulties while using APIs. API usage patterns can aid them in using APIs efficiently, which are extracted from source code stored in software repositories. Previous approaches have mined repositories to extract API usage patterns by simply applying data mining techniques to the collection of method invocations of API objects. In these approaches, respective functional roles of invoked methods within API objects are ignored. The functional role represents what type of purpose each method actually achieves, and a method has a specific predefined order of invocation in accordance with its role. Therefore, the simple application of conventional mining techniques fails to produce API usage patterns that are helpful for code completion. This paper proposes an improved approach that extracts API usage patterns at a higher abstraction level rather than directly mining the actual method invocations. It embraces a multilevel sequential mining technique and uses categorization of method invocations based on their functional roles. We have implemented a mining tool and an extended Eclipse's code completion facility with extracted API usage patterns. Evaluation results of this tool show that our approach improves existing code completion.
  • 本藤 祐樹, 森泉 由恵, 臼井 達朗
    日本エネルギー学会誌
    2008年 87 巻 9 号 753-762
    発行日: 2008年
    公開日: 2008/10/06
    ジャーナル フリー
    This paper describes the results of life cycle environmental analysis of hydrogen energy systems. It is proposed that hydrogen can be produced from coke oven gas (COG), and then stored and distributed to consumption sites in the form of organic hydride (methylcyclohexane/toluene). In this study, such a hydrogen energy system is analyzed in terms of primary energy requirement and CO2 emission, with a special attention to the hydrogen distribution using organic hydride. The results show that energy requirement and CO2 emission at consumption sites (i.e. dehydrogenation reaction of methylcyclohexane, refining of hydrogen) account for a large percentage of the whole system. From the results, it is understood that this is a special characteristics of the organic hydrides option. It also implies that primary energy requirement for the organic hydride option is almost equivalent to the liquid hydrogen option, but it is lager than the compressed hydrogen option. Furthermore, improvement analysis is carried out focusing on the characteristics of organic hydride. The results reveal that CO2 emission from the whole system are considerably reduced if waste heat from fuel cells at consumption sites can be used as energy source for dehydrogenation reaction of methylcyclohexane.
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