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101.
102.
大学计算机基础课程是高校非计算机专业的一门公共基础课。它着力培养学生运用计算机技术分析问题、解决问题的意识和能力;培养学生的系统思维能力,提高大学生的信息素养。该文分析了目前大学计算机基础课程教学的存在的主要问题,针对问题,提出了一些改革性的建议。 相似文献
103.
We study single machine batch scheduling with release times. Our goal is to minimize the sum of weighted flow times (or completion times) and delivery costs. Since the problem is strongly $\mathcal{NP}$ -hard even with no delivery cost and identical weights for all jobs, an approximation algorithm is presented for the problem with identical weights. This uses the polynomial time solution we give for the preemptive version of the problem. We also present an evolutionary metaheuristic algorithm for the general case. Computational results show very small gaps between the results of the metaheuristic and the lower bound. 相似文献
104.
As probabilistic data management is becoming one of the main research focuses and keyword search is turning into a more popular query means, it is natural to think how to support keyword queries on probabilistic XML data. With regards to keyword query on deterministic XML documents, ELCA (Exclusive Lowest Common Ancestor) semantics allows more relevant fragments rooted at the ELCAs to appear as results and is more popular compared with other keyword query result semantics (such as SLCAs). In this paper, we investigate how to evaluate ELCA results for keyword queries on probabilistic XML documents. After defining probabilistic ELCA semantics in terms of possible world semantics, we propose an approach to compute ELCA probabilities without generating possible worlds. Then we develop an efficient stack-based algorithm that can find all probabilistic ELCA results and their ELCA probabilities for a given keyword query on a probabilistic XML document. Finally, we experimentally evaluate the proposed ELCA algorithm and compare it with its SLCA counterpart in aspects of result probability, time and space efficiency, and scalability. 相似文献
105.
Upflow anaerobic sludge bed reactors fed on glucose were used to investigate the effects of Ce(3+) on soluble microbial products (SMP) production, which is the majority of the residual chemical oxygen demand present in the effluent. It was found that Ce(3+) concentration of 0.05 mg/L had no significant effect on the amount of SMP production, whereas that of 1 mg/L led to the increase in SMP production. The molecular-weight distribution and carbohydrate analysis indicated that an increase in SMP production may be partly attributed to the release of extracellular polymeric substances (EPS) into the bulk solution resulted from cerium toxicity, and the nucleic acids analysis suggested that increased cell lysis also contributed to SMP accumulation in the presence of Ce(3+). The increase in SMP production in the presence of Ce(3+) is possibly a consequence of the release of EPS and increased cell lysis due to cerium toxicity. 相似文献
106.
XUE Rui 《中国科学:信息科学(英文版)》2013,(3):179-189
Key-privacy is a notion of security that is concerned with the key anonymity in public-key encryption.Some popular schemes keep key-privacy,while others do not.Key-privacy has been shown to be orthogonal to data-privacy within one cryptosystem.This paper investigates the relationship between keyprivacy and data-privacy in public-key encryption.We show that the existence of IK-CPA secure cryptosystems implies the existence of IE-CCA secure cryptosystems in the random oracle model.The main contributions include a novel construction of a family of injective one-way trapdoor functions directly based on any IK-CPA secure public-key cryptosystem in the random oracle model.This construction adopts a novel idea in the construction compared to the existing one.The latter was based on unapproximable trapdoor predicates.The novelty of the construction allows to show that the injective trapdoor functions are secure under correlated products with respect to uniform repetitional distribution.That further allows us to conclude,in the random oracle model,that the existence of IK-CPA secure public-key cryptosystems implies the existence of CCA secure cryptosystems by a result of Rosen and Segev. 相似文献
107.
通过对各种SIM卡技术的对比,说明了SIM卡不仅用于解决用户入网鉴权和加密问题,还在向着双面应用、非预置个人化信息、更小更薄、存储容量更大等方向发展。SIM卡技术的演进,推动着手机终端的发展,随着智能手机的普及,手机终端除具备通信功能外,还将具有银行卡、门禁卡、公交卡等多种个人化应用。 相似文献
108.
This paper focuses on the mechanism underlying the overall delay of a real-time video communication system from the time of capture at the encoder to the time of display at the decoder. A detailed analysis is presented to illustrate the delay problem. We then describe a statistically uniform intra-block refresh scheme for very low delay video communication. By scattering intra-blocks uniformly into continuous frames, the overall delay is significantly decreased, and object changes in the scene could be presented to the end user instantly. For comparison, the overall delay and the peak signal-to-noise ratio (PSNR) performance are tested. The experiment results show that an average of approximately 0.1 dB PSNR gain on average is obtained relative to random intra-macroblock refresh algorithm in H.264 JM, and the end-to-end delay performance is significantly improved. 相似文献
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