MD5碰撞攻击中的充要条件集

通过分析MD5中非线性函数的性质以及模2³²减差分和异或差分的性质,证明了Liang Jie和Lai Xuejia 给出的产生MD5碰撞的充分条件集中的条件是保证第23～62步的差分路径满足的充要条件,给出了保证第63、64步的输出差分满足的充要条件集.利用得到的充要条件集,提出了对MD5的改进的碰撞攻击算法,该算法的平均计算复杂度约为已有碰撞攻击算法的0.718 7倍,并通过实验对该算法的改进效果进行了验证.     

An Adaptive Approach to Schema Classification for Data Warehouse Modeling

Data warehouse （DW） modeling is a complicated task, involving both knowledge of business processes and familiarity with operational information systems structure and behavior. Existing DW modeling techniques suffer from the following major drawbacks -- data-driven approach requires high levels of expertise and neglects the requirements of end users, while demand-driven approach lacks enterprise-wide vision and is regardless of existing models of underlying operational systems. In order to make up for those shortcomings, a method of classification of schema elements for DW modeling is proposed in this paper. We first put forward the vector space models for subjects and schema elements, then present an adaptive approach with self-tuning theory to construct context vectors of subjects, and finally classify the source schema elements into different subjects of the DW automatically. Benefited from the result of the schema elements classification, designers can model and construct a DW more easily.     

Web仓储系统的视图刷新方案

1 Web仓储的时新性标准 WWW的迅猛发展使其成为全球信息传递与共享日益重要的信息资源。Web仓储使用物化视图构建信息集成系统,是对Web信息进行充分利用的一种有效方法。Web仓储具有高稳定性,查询速度非常快,非常适合决策分析等需要对信息进行深度加工的应用。与使用虚视图方法进行集成的系统不同,Web仓储系统中的首要任务是物化视图的构建和维护,而视图刷新则是物化视图维护工作的主体。     

豆瓣酱加工过程中产生的危害物分析及控制措施研究

近年来,随着我国食品行业的不断创新与发展,豆瓣酱产业也随之呈现稳固上升的趋势,然而开放式的豆瓣制作环境和复杂繁长的制作工序也使得豆瓣酱在生产加工过程中存在某些食品安全隐患。本文探讨了豆瓣酱用料、制曲、发酵和贮藏等环节可能产生的危害物,如黄曲霉毒素B1、肉毒毒素、微生物、生物胺等,以及减少和控制这些有害物质的措施,为豆瓣酱生产过程中的安全控制提供有效借鉴。     

Web仓储中视图变化频率的自适应估测

物化视图的刷新是Web仓储进行系统维护的一项主要任务,而基础数据变化频率则是刷新方案中的重要因素.在已有文献中,研究者已经给出一些关于基础数据变化规律的算法和估测器.虽然这些估测器取得了不错的效果,然而他们却忽略了这些估测器都有一定的适用范围,超出这个范围则效果急剧下降.在此,基于泊松过程进行分析,对估测器的适用范围进行了讨论,根据估测结果的偏离值和有效性对估测公式进行参数调整,同时根据估测值的大小不断调整数据源的访问频率和次数,从而使数据源访问模式和估测器互相适应,使估测器在最佳估测范围内获得估测值.实验结果表明,与已有文献中的方法相比,新提出的自适应估测算法能够取得更好的效果.     

Contribution of morphological awareness to Chinese-English biliteracy acquisition.

This study is an investigation of the contribution of morphological awareness in Chinese-English biliteracy acquisition. Comparable tasks in Chinese and English were administered to test children's skills in morphological awareness, phonological awareness, oral vocabulary, word reading, and reading comprehension. The results showed that after the effect of Chinese-based predictors had been accounted for, English morphological awareness of compound structure still contributed to variance in both character reading and reading comprehension in Chinese. This finding indicates a cross-language morphological transfer in acquisition of two distinct writing systems. The transfer from English L2 to Chinese L1 is due to the bilingual children's rapidly increasing English L2 skills in their primary school years. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

桃江锰矿矿坑排水方案的探讨

针对矿山的水文地质和生产现状,提出了两套排水方案,通过方案对比,确定了最终的排水方案,并把该方案应用到矿山实际排水中,结果表明该方案合理可靠,在有效降低生产成本的前提下达到了理想的排水效果。     

黑豆山楂发酵乳稳定性的研究

通过对黑豆山楂发酵乳稳定性的研究，获得了重要的工艺参数和技术要点。实验结果表明，在均质温度60℃、均质压力25MPa下均质2次、杀菌温度85～95℃下，杀菌10～15min，在接种量为3％，温度42℃培养发酵3～4h、添加0．15％CMC、0．15％海藻酸钠和0．2％的单甘酯，所制得的产品均匀细腻，稳定性较好。     

Efficient Incremental Maintenance of Frequent Patterns with FP-Tree

Mining frequent patterns has been studied popularly in data mining area. However, little work has been done on mining patterns when the database has an influx of fresh data constantly. In these dynamic scenarios, efficient maintenance of the discovered patterns is crucial. Most existing methods need to scan the entire database repeatedly, which is an obvious disadvantage. In this paper, an efficient incremental mining algorithm, Incremental-Mining (IM), is proposed for maintenance of the frequent patterns when new incremental data come. Based on the frequent pattern tree (FP-tree) structure, IM gives a way to make the most of the things from the previous mining process, and requires scanning the original data once at most. Furthermore, IM can identify directly the differential set of frequent patterns, which may be more informative to users. Moreover, IM can deal with changing thresholds as well as changing data, thus provide a full maintenance scheme. IM has been implemented and the performance study shows it outperforms three other incremental algorithms: FUP, DB-tree and re-running frequent pattern growth (FP-growth).     

用有机硅聚合物制备高温结构陶瓷材料研究进展

回顾了用有机硅聚合物制备陶瓷历史,综述了工艺及材料性能,其中碳化硅、氮化硅等纤维,碳化硅、二氧化硅等薄膜已进入实用阶段;重点介绍了在高温1400－2000℃下长期稳定存在的块体材料研究进展和趋势。