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Enhanced Efficiency of Metamorphic Triple Junction Solar Cells for Space Applications 被引量:1
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作者 王笃祥 宋明辉 +5 位作者 毕京锋 陈文浚 李森林 刘冠洲 李明阳 吴超瑜 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第6期126-130,共5页
Metamorphic In0.55Ga0.45P/In0.06Ga0.94As/Ge triple-junction (3J-MM) solar cells are grown on Ge (100) sub- strates via metal organic chemical vapor deposition. Epi-structural analyses such as high resolution x-ray... Metamorphic In0.55Ga0.45P/In0.06Ga0.94As/Ge triple-junction (3J-MM) solar cells are grown on Ge (100) sub- strates via metal organic chemical vapor deposition. Epi-structural analyses such as high resolution x-ray diffrac- tion, photoluminence, cathodoluminescence and HRTEM are employed and the results show that the high crystal quality of 3J-MM solar cells is obtained with low threading dislocation density of graded buffer (an average value of 6.8× 10^4/cm2). Benefitting from the optimized bandgap combination, under one sun, AM0 spectrum, 25℃ conditions, the conversion efficiency is achieved about 32%, 5% higher compared with the lattice-matched In0.49Ga0.51P/In0.01Ga0.99As/Ge triple junction (3J-LM) solar cell. Under 1-MeV electron irradiation test, the degradation of the EQE and I-V characteristics of 3J-MM solar cells is at the same level as the 33-LM solar cell. The end-of-life efficiency is -27.1%. Therefore, the metamorphic triple-junction solar cell may be a promising candidate for next-generation space multi-junction solar cells. 展开更多
关键词 GA MM As Enhanced efficiency of Metamorphic Triple Junction Solar Cells for space Applications
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Space- and time-efficient approach for virtual machine provisioning
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作者 胡博林 雷州 +1 位作者 许东 李建敦 《Journal of Shanghai University(English Edition)》 CAS 2011年第5期451-455,共5页
As a new promising paradigm, cloud computing can make good use of economics of scale and elastically deliver almost any IT related services on demand. Nevertheless, one of the key problems remaining in cloud computing... As a new promising paradigm, cloud computing can make good use of economics of scale and elastically deliver almost any IT related services on demand. Nevertheless, one of the key problems remaining in cloud computing is related to virtual machine images, which require a great amount of space/time to reposit/provision, especially with diverse requests from thousands of users simultaneously. In this paper, by using the splitting and eliminating redundant data techniques, a space and time efficient approach for virtual machines is proposed. The experiments demonstrate that, compared with existing solutions, our approach can conserve more disk space and speed up the provisioning of virtual machines. 展开更多
关键词 cloud computing space and time efficient on-demand provision rapid deployment
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A Comparative Study on Two Techniques of Reducing the Dimension of Text Feature Space
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作者 Yin Zhonghang, Wang Yongcheng, Cai Wei & Diao Qian School of Electronic & Information Technology, Shanghai Jiaotong University, Shanghai 200030, P.R.China 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2002年第1期87-92,共6页
With the development of large scale text processing, the dimension of text feature space has become larger and larger, which has added a lot of difficulties to natural language processing. How to reduce the dimension... With the development of large scale text processing, the dimension of text feature space has become larger and larger, which has added a lot of difficulties to natural language processing. How to reduce the dimension has become a practical problem in the field. Here we present two clustering methods, i.e. concept association and concept abstract, to achieve the goal. The first refers to the keyword clustering based on the co occurrence of 展开更多
关键词 in the same text and the second refers to that in the same category. Then we compare the difference between them. Our experiment results show that they are efficient to reduce the dimension of text feature space. Keywords: Text data mining
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Experimental and simulation optimization analysis of the Whipple shields against shaped charge 被引量:4
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作者 G.Hussain A.Hameed +2 位作者 I.Horsfall P.Barton A.Q.Malik 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2012年第3期877-884,共8页
Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed p... Occasionally, the Whipple shields are used for the protection of a space station and a satellite against the meteoroids and orbital debris. In the Whipple shields each layer of the shield depletes part of high speed projectile en- ergy either by breaking the projectile or absorbing its energy. Similarly, this investigation uses the Whipple shields against the shaped charge to protect the light armour such as infantry fighting vehicles with a little modification in their design. The unsteady multiple interactions of shaped charge jet with the Whipple shield package against the steady homogeneous target is scrutinized to optimize the shield thickness. Sim- ulations indicate that the shield thickness of 0.75 mm offers an optimum configuration against the shaped charge. Exper- iments also support this evidence. 展开更多
关键词 Whipple shield Mass efficiency - space effi-ciency Erosion. Pressure
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Analysing the effect of stand density and site conditions on structure and growth of oak species using Nelder trials along an environmental gradient:experimental design,evaluation methods,and results 被引量:1
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作者 Enno Uhl Peter Biber +8 位作者 Matthias Ulbricht Michael Heym Tamás Horváth Ferenc Lakatos Janós Gál Leonhard Steinacker Giustino Tonon Maurizio Ventura Hans Pretzsch 《Forest Ecosystems》 CSCD 2015年第3期243-261,共19页
Background: Most current approaches in forest science and practice require information about structure and growth of individual trees rather than- or in addition to- sum and mean values of growth and yield at forest s... Background: Most current approaches in forest science and practice require information about structure and growth of individual trees rather than- or in addition to- sum and mean values of growth and yield at forest stand level as provided by classic experimental designs. By inventing the wheel design, Nelder provided the possibility to turn to the individual tree as basic information unit. Such trials provide valuable insights into the dependency of growth on stand density at particular sites.Methods: Here, we present an extension of the original design and evaluation by Nelder.(i) We established Nelder wheels along an environmental gradient through Europe in atlantic climate in Belgium and Germany, Mediterranean climate in Italy, continental climate in Hungary as well as on high land climate in Mexico. Such disjunct Nelder wheels along an environmental gradient can be regarded and analysed as a two-factor design with the factors of site condition and stand density.(ii) We present an advanced statistical approach to evaluate density dependent growth dynamics of trees planted in form of the Nelder design, which considers spatio-temporal autocorrelation.(iii)We prove the usefulness of the methods in improving ecological theory concerning density related productivity,trade-offs between facilitation and competition, and allometric relations between size variables.Results: First evaluations based on remeasured Nelder wheels in oak(Quercus robur L.) show a size growth differentiation during the first observation period. In particular, height growth is accelerated under higher competition indicating facilitation effects. We detect furthermore a high variability in allometric relations.Conclusions: The proposed design, methods, and results are discussed regarding their impact on forest practice,model building, and ecological theory. We conclude that the extended Nelder approach is highly efficient in providing currently lacking individual tree level information. 展开更多
关键词 FACILITATION Long-term trial Nelder Single tree analyses space use efficiency Stress-gradient-hypothesis Tree allometry QUERCUS
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Eco-sustainability Assessment of Building Projects Based on Eco-footprint
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作者 CHEN Yan WANG Yanyu +2 位作者 WU Xianguo TENG Jiaying ZHONG Jinbin 《Journal of Landscape Research》 2017年第4期41-44,共4页
The life-cycle eco-footprint computing model of building projects was established in the study. It contained the eco-footprint in 4 aspects during the lifecycle: consumed energy, consumed resource, emitted carbon diox... The life-cycle eco-footprint computing model of building projects was established in the study. It contained the eco-footprint in 4 aspects during the lifecycle: consumed energy, consumed resource, emitted carbon dioxide and produced solid waste. Space efficiency of life-cycle eco-footprint index was proposed and used to assess the eco-sustainability of building projects. Then, the eco-footprint and ecosustainability of 4 different structure types(brick-concrete bungalow, multi-storey brick-concrete, multistorey steel-concrete, high-rise steel-concrete) for residential building in severely cold areas were investigated. The results indicated that: 1) Compared with bungalow, high-rise building with relatively smaller shape coefficient and window-wall ratio had higher eco-sustainability; 2) For the buildings with the same storey, shape coefficient and window-wall ratio, steel-concrete building had higher eco-sustainability than brickconcrete building; 3) High-rise steel-concrete structure had the greatest eco-sustainability during the 4 different bui lding structures, so it was more suitable to promote. 展开更多
关键词 Eco-footprint space efficiency Residential building
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MemSC: A Scan-Resistant and Compact Cache Replacement Framework for Memory-Based Key-Value Cache Systems 被引量:2
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作者 Mei Li Hong-Jun Zhang +1 位作者 Yan-Jun Wu Chen Zhao 《Journal of Computer Science & Technology》 SCIE EI CSCD 2017年第1期55-67,共13页
Memory-based key-value cache systems, such as Memcached and Redis, have become indispensable components of data center infrastructures and have been used to cache performance-critical data to avoid expensive back-end ... Memory-based key-value cache systems, such as Memcached and Redis, have become indispensable components of data center infrastructures and have been used to cache performance-critical data to avoid expensive back-end database accesses. As the memory is usually not large enough to hold all the items, cache replacement must be performed to evict some cached items to make room for the newly coming items when there is no free space. Many real-world workloads target small items and have frequent bursts of scans (a scan is a sequence of one-time access requests). The commonly used LRU policy does not work well under such workloads since LRU needs a large amount of metadata and tends to discard hot items with scans. Small decreases in hit ratio can result in large end-to-end losses in these systems. This paper presents MemSC, which is a scan-resistant and compact cache replacement framework for Memcached. MemSC assigns a multi-granularity reference flag for each item, which requires only a few bits (two bits are enough for general use) per item to support scanresistant cache replacement policies. To evaluate MemSC, we implement three representative cache replacement policies (MemSC-HM, MemSC-LH, and MemSC-LF) on MemSC and test them using various workloads. The experimental results show that MemSC outperforms prior techniques. Compared with the optimized LRU policy in Memcached, MemSC-LH reduces the cache miss ratio and the memory usage of the resulting system by up to 23% and 14% respectively. 展开更多
关键词 key-value cache system cache replacement scan resistance space efficiency
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