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11.
Intensity modulated radiation therapy (IMRT) is one of the most effective modalities for modern cancer treatment. The key to successful IMRT treatment hinges on the delivery of a two-dimensional discrete radiation intensity matrix using a device called a multileaf collimator (MLC). Mathematically, the delivery of an intensity matrix using an MLC can be viewed as the problem of representing a non-negative integral matrix (i.e., the intensity matrix) by a linear combination of certain special non-negative integral matrices called segments, where each such segment corresponds to one of the allowed states of the MLC. The problem of representing the intensity matrix with the minimum number of segments is known to be NP-complete. In this paper, we present two approximation algorithms for this matrix representation problem. To the best of our knowledge, these are the first algorithms to achieve non-trivial performance guarantees for multi-row intensity matrices. 相似文献
13.
Luan Yu Shi Yuhang Wu Wanyin Liu Zhiyao Chang Hai Cheng Jun 《Knowledge and Information Systems》2021,63(10):2791-2814
Knowledge and Information Systems - In the past decade, human activity recognition (HAR) has grown in popularity due to its applications in security and entertainment. As recent years have... 相似文献
14.
Large-scale data-intensive cloud computing with the MapReduce framework is becoming pervasive for the core business of many
academic, government, and industrial organizations. Hadoop, a state-of-the-art open source project, is by far the most successful
realization of MapReduce framework. While MapReduce is easy- to-use, efficient and reliable for data-intensive computations,
the excessive configuration parameters in Hadoop impose unexpected challenges on running various workloads with a Hadoop cluster
effectively. Consequently, developers who have less experience with the Hadoop configuration system may devote a significant
effort to write an application with poor performance, either because they have no idea how these configurations would influence
the performance, or because they are not even aware that these configurations exist. There is a pressing need for comprehensive
analysis and performance modeling to ease MapReduce application development and guide performance optimization under different
Hadoop configurations. In this paper, we propose a statistical analysis approach to identify the relationships among workload
characteristics, Hadoop configurations and workload performance. We apply principal component analysis and cluster analysis
to 45 different metrics, which derive relationships between workload characteristics and corresponding performance under different
Hadoop configurations. Regression models are also constructed that attempt to predict the performance of various workloads
under different Hadoop configurations. Several non-intuitive relationships between workload characteristics and performance
are revealed through our analysis and the experimental results demonstrate that our regression models accurately predict the
performance of MapReduce workloads under different Hadoop configurations. 相似文献
15.
Zhang Hongtao Cai Minghui Zhu Wanjun Sun Shenghui Yan Haile Yao Shengjie Luan Yikun Tang Shuai Hodgson P. D. 《Metallurgical and Materials Transactions A》2022,53(11):3869-3880
Metallurgical and Materials Transactions A - A cold-rolled low Al-added medium Mn steel was employed to investigate the low-temperature superplastic deformation at a relatively high initial strain... 相似文献
16.
电弧炉炼钢碳化硅白渣工艺的脱氧与脱硫 总被引:1,自引:0,他引:1
理论计算和实践表明,在电弧炉上采用碳化硅代替硅铁粉和碳粉的白渣还原工艺,可强化钢的脱氧和脱硫效果;提高电炉炼钢生产效率;降低吨钢电耗和生产成本。并指出,采用喷吹技术会进一步改善该工艺的炼钢技术经济效果。 相似文献
17.
3D C/SiC复合材料在复杂环境试验中性能演变的两重性 总被引:3,自引:0,他引:3
用减压化学气相浸渗法(LPCVI)制备2组3D C/SiC复合材料,其中一组具有不同厚度的PyC界面层,另一组PyC界面层厚度一定,但经过热处理.对C/SiC复合材料在复杂环境中性能演变的两重性,即确定性和随机性进行了研究.结果表明,残余强度及其波动性对评价材料的环境适应性和可靠性是必需的.界面层和涂层是对氧化环境最敏感的微结构控制单元.以敏感度排序,3种环境参数依次是温度、气氛和应力.气氛参数的排序是氧气、水和盐,应力参数的排序是疲劳/蠕变,蠕变和疲劳.应力通过增加涂层裂纹及宽度从而加速复合材料的性能演变.氧化物薄膜有利于涂层裂纹封填,水能促进这种封填,然而疲劳/蠕变应力会使涂层裂纹封填失效.因此包括有氧气、水、疲劳和蠕变的环境是所有环境中最恶劣的.为了使复合材料具有自适应性,PyC的厚度应为最优,以提高热处理的效果;需保持适中的涂层氧化速率,以提高近表面抗氧化性.而适中的氧化速率是由温度和氧化气体分压来控制的. 相似文献
18.
利用田间试验方法研究保护剂长残效除草剂解毒效应。不同保护剂对豆磺隆解毒效应有差异,作保灵解毒效应最明显,但在除草剂高残留量时解毒作用下降。作保灵对三种长残效除草剂都具有明显的解毒作用,作物的出苗率可恢复80%~100%。解毒效应顺序为油莱>白菜>甜菜。 相似文献
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