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101.
为提高土壤水分数据同化结果的精度,将基于双集合卡尔曼滤波(Dual Ensemble Kalman Filter,DEnKF)的状态-参数估计方案与简单生物圈模型(simple biosphere model 2,SiB2)相结合,同时更新土壤水分和优化模型参数(土壤属性参数)。选用2008年6月1日~10月29日黑河上游阿柔冻融观测站为参考站,开展了同化表层土壤水分观测数据的实验。研究结果表明:DEnKF可同时优化土壤属性参数和改进土壤水分估计,该方法对表层土壤水分估计的精度0.04高于EnKF算法的精度0.05。当观测数据稀少时,DEnKF算法仍然可以得到较高精度的土壤水分估计,3层土壤水分的估计精度在0.02~0.05之间。 相似文献
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云计算应用正以势如破竹的态势进入到教育领域,云计算的推广有利于教育资源的共建共享,方便师生快捷地获取所需资源和服务,更高效地开展学习和科研工作.分析了现有网络资源的具体实际情况,利用云计算技术,探究资源整合的有效方式,整合校园网资源,探索适合于教师教学与科研、学生学习与成长,以及学校提升社会服务能力的校园私有云服务模式. 相似文献
104.
Jing-Shan Zhao Jian-Yi WangFulei Chu Zhi-Jing FengJian S. Dai 《Mechanism and Machine Theory》2011,46(7):998-1015
This paper proposes a foldable stair that can be deployed for use and folded for conservation and investigates the geometry and statics of the structure. It not only has the moving flexibility of a mechanism but also has the high stiffness and high strength of statically indeterminate structures. The primary linkage is a deployable scissor-like element which forms the staircase after expanding. This paper starts with the analysis of the geometry of planar four- and six-bar mechanisms and processes to synthesize the foldable stair and then investigates its statics. The paper further investigates redundant inner forces of every link based on the second Castigliano theorem, develops a foldable stair model, assembles and manufactures. Working experiments verify the theoretical results and the outstanding advantages over the general fixed stairs. 相似文献
105.
Toxic and Potent Chinese Materia Medica (T/PCMM) is a special and very important category of Chinese medicines. They have long been used in traditional medical practice and are being used more and more widely throughout the world in recent years. As there may be many fatal toxic effects caused by misusing or confusion of T/PCMM, their quality and safety control arouse increasing attention internationally. Researches on the accurate identification to ensure the safe use of T/PCMM are acquired; however, there are few reports on authentication. We are carrying out a series of studies on 31 T/PCMM originating from plants, animals, minerals, and secreta. In our previous studies, we proved that modern microscopic authentication is a simple, fast, effective, low cost, and less toxic method for identifying animal, seed, and flower T/PCMM. In the present study, we focused on the authentication of four kinds of mineral arsenicals, including orpiment (mainly containing As2S3), realgar (mainly containing As4S4), arsenolite, and arsenic trioxide (mainly containing As2O3). We examined the macroscopic and microscopic characteristics of the above minerals and found that they all can be easily identified and authenticated by using light microscopy coupled with polarized microscopy. Moreover, the authentication results for arsenolite and arsenic trioxide are confirmed by ICP‐MS analysis. We are sure that the morphological and microscopic characteristics indicated here are indispensable to establishing standards for these four mineral T/PCMMs. Microsc. Res. Tech. 74:1‐8, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
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针对片状颗粒厚度检测的实际需求,结合机器视觉、图像处理和嵌入式技术,设计与实现了一套基于高性能ARM11的微片状颗粒厚度检测系统。该系统以QT和S3C6410为软硬件平台,提出了利用轮廓提取和最小矩形边界框相结合的方法计算片状颗粒厚度。结果表明,该检测系统具有处理速度快,测量精度高和成本低廉等优点,满足了对颗粒厚度测量的需求。 相似文献
109.
Temperature is one of the most important environmental variables in stream ecosystems because it affects the growth, survival and distribution of stream biota. This study examined if the spatial variability of thermal regimes and 18 other environmental variables were associated with fish communities in watersheds throughout the Great Lakes Basin (GLB), Ontario. The thermal regimes were defined as regimes 1, 2 and 3 and had maximum water temperatures of 26.4, 28.4 and 23.5°C, and spring warming rates of 0.20, 0.12 and 0.10 °C d?1, respectively. The spatial variability of the thermal regimes (VTR) within the watersheds was summarized into four VTR groups: S1, S2, M23 and M123. Stream sites in S1 watersheds had temperatures characteristic of regime 1 whereas stream sites in S2 watersheds followed regime 2. M23 watersheds had sites with a mix of regimes 2 and 3 whereas M123 watersheds had all three thermal regimes at sites throughout watersheds. Canonical correspondence analysis (CCA) indicated that 16% of the variation in fish communities was related to the spatial VTR in the watersheds. Forward selection CCA indicated that elevation, the S1 VTR group, sparse forest cover, wetland area, base flow index (groundwater discharge potential), flow and industrial stress explained 42% of the variance in the fish communities. Simplified indicator species analysis (ISA) showed that different species could be used as indicators for each of the VTR groups. Human activities such as industrial development, deforestation, groundwater withdrawal and flow alteration all may affect the environmental variables related to stream fish communities. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
110.
传统的基于测量的Internet性能参数估计要求测量点是端到端路径的起点和终点,这一方面使得测量和估计带有很大盲目性,增加了网络流量;另一方面会导致测量方法难于实施,估计结果不准确。提出了基于分段测量的思想,对ITU-T定义的延迟、延迟变化、丢包率和错误率4个参数进行测量和估计。由于测量是分段进行的,每次测量值都可应用于多条端到端路径的性能参数估计,因此降低了盲目性并大大减少了网络流量。为验证本方法的性能,基于PlanetLab平台设计和实现了生成器、性能参数测量机和结果收集器。通过在全球的100多个节点上的部署和为期一个月的运行证明了该方法便于实施,并且具有较高的准确性。 相似文献