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1. chinaXiv:201803.00578 [pdf]

A Parallel Domain Decomposition Method for 3D Unsteady Incompressible Flows at High Reynolds Number

Rongliang Chen Yuqi Wu Zhengzheng Yan Yubo Zhao Xiao-Chuan Cai
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Direct numerical simulation of three-dimensional incompressible ows at high Reynolds number using the unsteady Navier-Stokes equations is challenging. In order to obtain accurate simulations, very #12;ne meshes are necessary, and such simulations are increasingly important for modern engineering practices, such as understanding the behavior around high speed trains, which is the target application of this research. To avoid the time step size constraint imposed by the CFL number and the #12;ne spacial mesh size, we investigate some fully implicit methods, and focus on how to solve the large nonlinear system of equations at each time step on large scale parallel computers. In most of the existing implicit Navier-Stokes solvers, segregated velocity and pressure treatment is employed. In this paper, we focus on the Newton-Krylov-Schwarz method for solving the mono-lithic nonlinear system arising from the fully coupled #12;nite element is cretizationof the Navier-Stokes equations on unstructured meshes. In the subdomain, LU or point-block ILU is used as the local solver. We test the algorithm for some three-dimensional complex unsteady ows, including ows passing a high speed train,on a supercomputer with thousands of processors. Numerical experiments show that the algorithm has superlinear scalability with over three thousand processors for problems with tens of millions of unknowns.

提交时间: 2018-03-15 点击量30下载量11 评论 0

2. chinaXiv:201803.00580 [pdf]


Yan Zhengzheng
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

对于城市大气环境模拟问题,高保真度往往意味着庞大的计算量,几何多尺度、高雷诺数等因素致使其求解非常具有挑战性,对计算机的硬件与算法都有极高的要求。寻求稳定、可扩展的高效并行数值算法以获取时效性强且可置信的数值结果是数值模拟的关键所在。基于国产大规模计算系统平台,本文通过对大规模非线性系统进行高效求解器和预处理技术的研究,提出一种可扩展并行Newton-Krylov-Schwarz算法。非线性方程采用非精确Newton方法进行求解,在每个Newton步,Jacobian系统通过基于区域分解方法的限制加性Schwarz 预 条件子处理,然后使用以GMRES方法为代表的Krylov子空间迭代法作为线性求解器进行求解。作为应用,我们对深圳地王大厦附近约一平方公里区域进行大气流场进行计算。数值结果显示,本文的算法在扩展至万核处理器平台时仍具有非常良好的可扩展并行性能,为未来对整个城市区域进行高精度(如网格分辨率达到米级,未知数个数达十亿量级)的大气环境模拟提供了一种可参考的算法。

提交时间: 2018-03-15 点击量27下载量9 评论 0

3. chinaXiv:201803.00581 [pdf]


Yan Zhengzheng
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等


提交时间: 2018-03-15 点击量23下载量8 评论 0

4. chinaXiv:201803.00012 [pdf]

Desiccation tolerance in bryophytes: the rehydration proteomes of Bryum argenteum provide insights into the resuscitation mechanism

GAO, Bei; ZHANG, Daoyuan; LI, Xiaoshuang; YANG, Honglan; LIANG, Yuqing; CHEN, Moxian; ZHANG, Yuanming; ZHANG, Jianhua; WOOD, Andrew
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Bryum argenteum Hedw. is a desiccation tolerant bryophyte and belongs to one of the most important components of the biological soil crusts (BSCs) found in the deserts of Central Asia. Limited information is available on rehydration-responsive proteins in desiccation tolerant plants. As a complement to our previous research analyzing the rehydration transcriptome, we present a parallel quantitative proteomic effort to study rehydration-responsive proteins. Bryophyte gametophores were desiccated (Dry) and rehydrated for 2 h (R2) and 24 h (R24). Proteins from Dry, R2 and R24 gametophores were labeled by isobaric tags for relative and absolute quantitation (iTRAQ) to determine the relative abundance of rehydration-responsive proteins. A total of 5503 non-redundant protein sequences were identified and 4772 (86.7%) protein sequences were annotated using Gene Ontology (GO) terms and Pfam classifications. Upon rehydration 239 proteins were elevated and 461 proteins were reduced as compared to the desiccated protein sample. Differentially up-regulated proteins were classified into a number of categories including reactive oxygen species scavenging enzymes, detoxifying enzymes, Late Embryogenesis Abundant (LEA) proteins, heat shock proteins, proteasome components and proteases, and photosynthesis and translation related proteins. Furthermore, the results of the correlation between transcriptome and proteome revealed the discordant changes in the expression between protein and mRNA.

提交时间: 2018-03-02 来自合作期刊:《Journal of Arid Land》 点击量567下载量214 评论 0

5. chinaXiv:201803.00001 [pdf]

Regional difference and dynamic mechanism of locality of the Chinese farming-pastoral ecotone based on geotagged photos from Panoramio

WANG, Fang; LI, Yixi; DONG, Ying; ZHU, Xiaohua
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Cross-regional locality research reflects the influences of natural environment and the human activities due to the abundant land types and the multiple landscape combinations in related regions. The Chinese farming-pastoral ecotone is a typical large-scale region but few studies were conducted. This research contributed to the understanding of cross-regional locality of the Chinese farming-pastoral ecotone from different scales, including national, sectional, and provincial administrative units by utilizing geotagged photos (GTPs) obtained from the Panoramio website. The major results were as follows: (1) the locality elements of the Chinese farming-pastoral ecotone included 52 free nodes classified into 8 types of scene attributes; (2) there were huge differences between locality elements of different regions, and there was a negative correlation between the similarity degree of elements of different provinces and their spatial distances; (3) the Chinese farming-pastoral ecotone could be divided into the northern, central and southern sections, whose localities had differences in element constitution, association structure and the strength of elements, system stability and the anti-interference capability; and (4) the evolution of the localities of the northern and central sections was mainly influenced by human activities, while the locality of southern section retained more natural features. On a theoretical level, this research aimed to establish the research methodology of locality from the perspective of open data on the web with strong operability and replicability. On a practical level, this research could enrich the structuring recognition of the locality of the Chinese farming-pastoral ecotone and the comprehension of its dynamic mechanism. The results provide a reference for locality differentiation protection and the development of a cross-regional scale.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量587下载量324 评论 0

6. chinaXiv:201803.00003 [pdf]

Planting density affected biomass and grain yield of maize for seed production in an arid region of Northwest China

JIANG, Xuelian; TONG, Ling; KANG, Shaozhong; LI, Fusheng; LI, Donghao; QIN, Yonghui; SHI, Rongchao; LI, Jianbing
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Field experiments were conducted from 2012 to 2015 in an arid region of Northwest China to investigate the effects of planting density on plant growth, yield, and water use efficiency (WUE) of maize for seed production. Five planting densities of 6.75, 8.25, 9.75, 11.25 and 12.75 plants/m2 were conducted in 2012, and a planting density of 14.25 plants/m2 was added from 2013 to 2015. Through comparison with the AquaCrop yield model, a modified model was developed to estimate the biomass accumulation and yield under different planting densities using adjustment coefficient for normalized biomass water productivity and harvest index. It was found that the modified yield model had a better performance and could generate results with higher determination coefficient and lower error. The results indicated that higher planting density increased the leaf area index and biomass accumulation, but decreased the biomass accumulation per plant. The total yield increased rapidly as planting density increased to 11.25 plants/m2, but only a slight increase was observed when the density was greater than 11.25 plants/m2. The WUE also reached the maximum when planting density was 11.25 plants/m2, which was the recommended planting density of maize for seed production in Northwest China.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量543下载量277 评论 0

7. chinaXiv:201803.00004 [pdf]

Variations of the thermal growing season during the period 1961–2015 in northern China

CUI, Linli; SHI, Jun; MA, Yue; LIU, Xiaochen
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated the differences under various definitions of thermal growing season and compared the trends of thermal growing season in different parts of China. Based on the daily mean air temperatures collected from 877 meteorological stations over northern China from 1961 to 2015, we investigated the variations of the thermal growing season parameters including the onset, ending and duration of the growing season using the methods of differential analysis, trend analysis, comparative analysis, and Kriging interpolation technique. Results indicate that the differences of the maximum values of those indices for the thermal growing season were significant, while they were insignificant for the mean values. For indices with the same length of the spells exceeding 5°C, frost criterion had a significant effect on the differences of the maximum values. The differences of the mean values between frost and non-frost indices were also slight, even smaller than those from the different lengths of the spells. Temporally, the starting date of the thermal growing season advanced by 10.0–11.0 days, while the ending dates delayed by 5.0–6.0 days during the period 1961–2015. Consequently, the duration of the thermal growing season was prolonged 15.0–16.0 days. Spatially, the advanced onset of the thermal growing season occurred in the southwestern, eastern, and northeastern parts of northern China, whereas the delayed ending of the thermal growing season appeared in the western part, and the length of the thermal growing season was prolonged significantly in the vast majority of northern China. The trend values of the thermal growing season were affected by altitude. The magnitude of the earlier onset of the thermal growing season decreased, and that of the later ending increased rapidly as the altitude increased, causing the magnitude of the prolonged growing season increased correspondingly. Comparing the applicability of selected indices and considering the impacts of frost on the definitions are important and necessary for determining the timing and length of the thermal growing season in northern China.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量572下载量309 评论 0

8. chinaXiv:201803.00005 [pdf]

Efficiency of soil and water conservation practices in different agro-ecological environments in the Upper Blue Nile Basin of Ethiopia

SULTAN, Dagnenet; TSUNEKAWA, Atsushi ; HAREGEWEYN, Nigussie ; ADGO, Enyew ; TSUBO, Mitsuru ; MESHESHA, Derege T ; MASUNAGA, Tsugiyuki ; AKLOG, Dagnachew ; FENTA, Ayele A ; EBABU, Kindiye
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

In developing countries such as Ethiopia, research to develop and promote soil and water conservation practices rarely addressed regional diversity. Using a water-balance approach in this study, we used runoff plots from three sites, each representing a different agro-ecological environment, e.g., high, mid and low in both elevation and rainfall, in the Upper Blue Nile Basin of Ethiopia to examine the runoff response and runoff conservation efficiency of a range of different soil and water conservation measures and their impacts on soil moisture. The plots at each site represented common land use types (cultivated vs. non-agricultural land use types) and slopes (gentle and steep). Seasonal runoff from control plots in the highlands ranged 214–560 versus 253–475 mm at midlands and 119–200 mm at lowlands. The three soil and water conservation techniques applied in cultivated land increased runoff conservation efficiency by 32% to 51%, depending on the site. At the moist subtropical site in a highland region, soil and water conservation increased soil moisture enough to potentially cause waterlogging, which was absent at the low-rainfall sites. Soil bunds combined with Vetiveria zizanioides grass in cultivated land and short trenches in grassland conserved the most runoff (51% and 55%, respectively). Runoff responses showed high spatial variation within and between land use types, causing high variation in soil and water conservation efficiency. Our results highlight the need to understand the role of the agro-ecological environment in the success of soil and water conservation measures to control runoff and hydrological dynamics. This understanding will support policy development to promote the adoption of suitable techniques that can be tested at other locations with similar soil, climatic, and topographic conditions.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量664下载量322 评论 0

9. chinaXiv:201803.00006 [pdf]

Forest recovery after clear-cutting in Chinese pine (Pinus tabuliformis) plantations of North China

DONG, Boqian; ZHAO, Kuangji; WANG, Zhibin; JIA, Zhongkui; XIA, Xinli
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

In Hebei Province of North China, forest was recovered with natural recruitment in plantations with large area of clear-cutting Chinese pine (Pinus tabuliformis). This study was aimed to demonstrate the dynamic characteristics of recruits during the natural recruitment. Both plot survey and the spatial point-pattern analysis were performed. Five developmental stages of natural recruitment were selected and studied, including 1 year before and 2, 5, 8, and 11 years after clear-cutting. Different slope aspects were also included. Natural recruitment was always dominated by Chinese pine with a proportion of higher than 90%. For plots of 1 year before clear-cutting on east- and north-facing slopes, recruit densities were 7886 and 5036 stems/hm2, the average heights were 0.78 (±0.85) and 1.06 (±1.15) m, and the average diameters at breast height (DBH) were 3.21 (±1.38) and 2.91 (±1.38) cm, respectively. After clear-cutting, recruit density was initially increased, then it was gradually declined with time; however, the variation of average DBH was contrary to that of recruit density. Both of them were no longer varied between 8 and 11 years after clear-cutting. The average height of recruits continued to increase after clear-cutting. For the plots of 11 years after clear-cutting on east- and north-facing slopes, average heights of recruits reached 2.00 (±1.14) and 2.24 (±1.20) m, respectively. The statuses of recruits on north-facing slopes were better than those on east-facing slopes after clear-cutting. Meanwhile, recruits on east-facing slopes were always aggregated at small scales, while spatial pattern of recruits varied with time on north-facing slopes. Moreover, forest was recovered more quickly by natural recruitment than by artificial afforestation after clear-cutting. The structural diversity was higher in naturally regenerated forests than in plantations of the same age. Our results demonstrated that clear-cutting of Chinese pine plantations recovered by natural recruitment has the potential to be an effective approach for establishing multifunctional forest.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量547下载量288 评论 0

10. chinaXiv:201803.00010 [pdf]

Model based decision support system for land use changes and socio-economic assessments

YU, Yang; CHEN, Xi; HUTTNER, Philipp; HINNENTHAL, Marie; BRIEDEN, Andreas; SUN, Lingxiao; DSE, ISMarkus
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等

Hydrological models are often linked with other models in cognate sciences to understand the interactions among climate, earth, water, ecosystem, and human society. This paper presents the development and implementation of a decision support system (DSS) that links the outputs of hydrological models with real-time decision making on social-economic assessments and land use management. Discharge and glacier geometry changes were simulated with hydrological model, water availability in semi-arid environments. Irrigation and ecological water were simulated by a new commercial software MIKE HYDRO. Groundwater was simulated by MODFLOW. All the outputs of theses hydrological models were taken as inputs into the DSS in three types of links: regression equations, stationary data inputs, or dynamic data inputs as the models running parallel in the simulation periods. The DSS integrates the hydrological data, geographic data, social and economic statistical data, and establishes the relationships with equations, conditional statements and fuzzy logics. The programming is realized in C++. The DSS has four remarkable features: (1) editable land use maps to assist decision-making; (2) conjunctive use of surface and groundwater resources; (3) interactions among water, earth, ecosystem, and humans; and (4) links with hydrological models. The overall goal of the DSS is to combine the outputs of scientific models, knowledge of experts, and perspectives of stakeholders, into a computer-based system, which allows sustainability impact assessment within regional planning; and to understand ecosystem services and integrate them into land and water management.

提交时间: 2018-02-28 来自合作期刊:《Journal of Arid Land》 点击量619下载量282 评论 0

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